SW16C
NEW CHEMICAL CONCEPTS FOR
UTILIZATION OF WASTE PLASTICS
An Analytical Investigation
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NEW CHEMICAL CONCEPTS FOR
UTILIZATION OF WASTE PLASTICS
This report (SW-l6c) was prepared for
the Federal solid waste management program
by M.E. BANKS, W.D. LUSK, and R.S. OTTINGER
TRW Systems Group, Redondo Beach, California
under Contract No. PH 86-68-206
Environmental Protection
Librai.v, n-^icn V
1 Hurth BacJror Drive
Chicago, Illinois 60606
U.S. ENVIRONMENTAL PROTECTION AGENCY
1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.25
Stock Number 5502-0044
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ENVIRONMENTAL PROTECTION AGENCY
An environmental protection publication
in the solid waste management series (SW-16c)
For sale by the Superintendent of Documents
U.S. Government Printing Office, Washington, D.C. 20402
Price xxx
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FOREWORD
A MAJOR EMPHASIS of the Solid Waste Disposal Act, Title II of Public
Law 89-272, October 20, 1965, was directed toward the conservation of
natural resources through the recovery and utilization of the potential
resources in solid wastes. Plastic wastes are a growing concern among the
variety of solid wastes produced in this country. These materials are
difficult to dispose of and are expected to serve an even larger role in the
future.
The Federal solid waste management program has decided to investigate
the possibility of reacting waste plastic with various reagents in a
high-temperature, gas-phase reactor in order to produce chemicals for
eventual commercial use. The first step in the overall study has involved the
computer simulation of the thermodynamics and kinetics of various
reaction systems. This has produced design parameters and economic data
for various systems. This report represents the results of Contract No. PH
86-68-206, which was prepared by TRW Systems Group, Redondo Beach,
California. The Federal solid waste management program was represented
by Dr. Daniel F. Bender during the implementation of the contract and the
preparation of the report.
-RICHARD D. VAUGHAN
Deputy Assistant Administrator
for Solid Waste Management
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CONTENTS
1. INTRODUCTION AND SUMMARY 1
2. TECHNICAL APPROACH 3
Phase I 3
Phase II 4
3. THERMODYNAMIC ANALYSES 4
TRW Chemical Analysis Program and Thermochemical Data Base 5
Equilibrium Product Distribution Analyses , 7
Thermal Decomposition Reaction Systems 7
Hydrogen Chloride Reaction Systems 7
Ammonia Reaction Systems 7
Water Reaction Systems 8
Air Reaction Systems 8
Chlorine Reaction Systems 8
Reaction Path Analyses 9
Thermal Decomposition Reaction Path Analysis 9
Air-Plastic Reaction Path Analysis 9
Chlorine Reaction Path Species Analysis 10
4. KINETIC ANALYSES 10
Thermal Decomposition Kinetic Analysis 11
Polystyrene 11
Polyethylene 12
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Polyvinyl Chloride 12
Thermal Decomposition Preliminary Reactor Designs 13
Waste Plastics/Chlorine Kinetic Analysis 13
Polystyrene . 13
Polyethylene and Polyvinyl Chloride 14
Waste Plastics/Steam Kinetic Analysis 14
Waste Plastics/Air Kinetic Analyses 15
5. PRELIMINARY DESIGN AND ECONOMIC ANALYSES 16
Waste Plastic/Nitrogen Processes "
Polystyrene/Nitrogen , 16
Polyethylene/Nitrogen 17
Polyvinyl Chloride/Nitrogen
Mixed Waste Plastics/Nitrogen 18
Waste Plastic/Air (Oxygen) Processes 18
Polystyrene/Air and Polyethylene/Air Systems 18
Polyvinyl Chloride/Air and Mixed Plastics/Air Systems . 19
Waste Plastic/Water Processes . • 1"
Polystyrene/Water 19
Polyethylene/Water 20
Polyvinyl Chloride/Water 20
Mixed Plastics/Water 20
6. CONCLUSIONS AND RECOMMENDATIONS 20
7. REFERENCES 23
8. BIBLIOGRAPHY
25
INDEX OF FIGURES
1. Generalized Technique for Chemical Process Development 29
2. Technical-Economic Analysis for Plastic/Coreactant Chemical Processes 30
3. Project Flow Diagram 31
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4. Thermal Decomposition: Major Products Analysis • .,...,...«. 32
5. Hydrogen Chloride: Major Product Analysis 33
6. Ammonia: Major Product Analysis 34
7. Water: Major Product Analysis 35
8. Air: Major Product Analysis 36
9. Chlorine: Major Product Analysis 37
10. Feasible Reaction Path Species, Thermal Decomposition, 773 K, 1 atm 38
11. Feasible Reaction Path Species, Air, 773 K, 1 atm, 70 Percent Plastic Material 39
12, Feasible Reaction Path Species, Chlorine, 773 K, 1 atm, 70 Percent Plastic Material ...... 40
13. Styrene Produced versus Solid Residence Time 41
14. Styrene Produced versus Solid Residence Time 42
15. Styrene Produced versus Solid Residence Time 43
16. Nitrogen Necessary per Gram of Styrene 44
17. Amount of Product versus Solid Residence Time 45
18. Amount of Product versus Solid Residence Time 46
19. Amount of Product versus Solid Residence Time . 47
20. Nitrogen Necessary per Gram of Product 48
21. HC1 Produced versus Solid Residence Time 49
22. HC1 Produced versus Solid Residence Time 50
23. Organic Product Formed versus Solid Residence Time 51
24. Organic Product Formed versus Solid Residence Time 52
25. HC1 and Organic Product Comparison at 723 K . 53
26. Semicontinuous Waste Plastics Reactor 54
27, Decomposition and Chlorination Reactor System 55
28. Amount of Products versus Residence Time 56
29. Grams of Trichloro Derivative Produced versus Residence Time 57
30. Semicontinuous Waste Plastics Reactor 58
31. Steam Consumption versus Residence Time for the Plastic Mixture 59
32. Steam Consumption versus Residence Time for the Plastic Mixture 60
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33. Waste Plastic Combustion Reactor 61
34. Proposed Process for the Decomposition of Polystyrene with Nitrogen as a Heat Carrier .... 62
35. Proposed Process for the Decomposition of Polyethylene with Nitrogen as a Heat Carrier .... 63
36. Proposed Process for the Decomposition of Polyvinyl Chloride with Nitrogen as a Heat
Carrier 64
37. Proposed Process for the Decomposition of a Mixture of Three Waste Plastics with
Nitrogen as a Heat Carrier 65
38. Proposed Process to React Polyvinyl Chloride or a Mixture of Waste Plastics with Air 66
39. Methane Production as a Function of Temperature 86
40. Computer Program Flow Diagram 107
INDEX OF TABLES
1. Polyethylene Thermal Decomposition 67
2. Polyvinyl Chloride Thermal Decomposition 68
3. Reactor Geometry for a Waste Plastic/Nitrogen Decomposition Reactor ..........69
4. Nitrogen Effect on Styrene-Chlorine Reaction—Second Reactor 70
5. Amount of Indicated Heat Source Necessary for the Specified Conversion ......... 71
6. Mixture Reaction Products 72
7. Reactor Geometry for a Waste Plastic/Water Decomposition Reactor 73
8. Waste Plastics/Air Adiabatic Reactor 74
9. Process Cost Summary: Polystyrene Decomposition with Nitrogen as a Heat Carrier 75
10. Process Cost Summary: Polyethylene Chloride Decomposition with Nitrogen as a Heat
Carrier 76
11. Process Cost Summary: Polyvinyl Chloride Decomposition with Nitrogen as a Heat
Source 77
12. Process Cost Summary: Mixed Plastics Decomposition with Nitrogen as a Heat Carrier 78
13. Process Cost Summary: Combustion with Air of Polystyrene or Polyethylene Waste 79
14. Process Cost Summary: Combustion with Air of Polyvinyl Chloride or Mixed Plastics
System BO
15. Process Cost Summary: Polystyrene Decomposition with Steam as a Heat Carrier . 81
16. Process Cost Summary: Polyethylene Decomposition with Steam as a Heat Carrier 82
17. Process Cost Summary: Polyvinyl Chloride Decomposition with Steam as a Heat Carrier .... 83
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18. Process Cost Summary: Mixed Plastics Decomposition with Steam as a Heat Carrier 84
19. Polyethylene Decomposition 87
20. Polyethylene/NH3 88
21. Polyethylene/H20 89
22. Polyethylene/Air 90
23. Polyethylene/Cl2 91
24. Polystyrene Decomposition 92
25. Polystyrene/NH3 93
26. Polystyrene/H20 94
27. Polystyrene/Air 95
28. Polystyrene/Cl2 96
29. System: Polyvinyl Chloride Decomposition 97
30. System: Polyvinyl Chloride/NH3 98
31. Polyvinyl Chloride/H20 99
32. Polyvinyl Chloride/Air 100
33. Polyvinyl Chloride/Cl2 101
34. Variables Used in Mathematical Model 112
35. Thermal Decomposition Differential Rate Equations 114
36. Waste Plastic(s)/Chlorine Differential Rate Equations 115
37. Decomposition Products/Chlorine Differential Rate Equations 116
38. Thermal Decomposition Products/Air Differential Rate Expressions 118
39. Waste Plastics (Solid)/Air Differential Rate Expressions 119
40. Predicted Results Compared with Experimental Results 120
41. Waste Plastics Kinetics Computer Program 122
42. Kinetic Rate Parameters 125
APPENDIX A: EQUILIBRIUM PRODUCT DISTRIBUTION 85
APPENDIX B: KINETIC MODELS AND PARAMETERS 106
APPENDIX C: ECONOMIC MODELS 126
APPENDIX D: ASSUMPTIONS MADE IN ECONOMIC ANALYSES 128
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NEW CHEMICAL CONCEPTS FOR
UTILIZATION OF WASTE PLASTICS
1. INTRODUCTION AND SUMMARY
In June 1968, TRW Systems Group, under
contract to the U.S. Department of Health,
Education, and Welfare's Bureau of Solid Waste
Management,* undertook a project to investigate
analytically the use of waste plastic materials for the
production of high-volume process chemicals. The
objectives of the analysis were as follows: to identify
waste plastic/coreactant reaction products with
potential commercial value; to identify waste
plastic/air combustion products that are potential air
pollutants; to conceive of and provide technical and
economic evaluations for chemical processes utilizing
waste plastics as raw materials; and to identify
potential R&D programs leading to the development
of commercially viable chemical processes.
The approach developed by TRW Systems Group
for this contract uses the first two phases of a
generalized technique for the development of
chemical processes. This technique starts with the
formulation of a process concept, followed by the
analysis of the proposed process using
technical-economic simulation models, laboratory
development of the process, pilot plant operation,
and commercialization (Figure 1). Throughout this
procedure management is provided information about
the technical and economic implications of various
results upon which they can base an informed,
intelligent decision for continuing the procedure. At
any stage, each of which calls for an increasingly large
investment, a proposed process concept is measured
against criteria based on earlier results. New
information on the technical and economic feasibility
is used to update the criteria for the next stage of
development.
In using the first two stages of the chemical
process development procedure, TRW Systems
analyzed the technical and economic aspects of a
wide variety of process concepts involving the use of
waste plastic materials. In order to provide a
maximum amount of information at minimum cost,
the analyses of the chemical systems of interest were
performed with literature information where available
and with estimates where direct information could
not be found. The technical-economic analysis was
divided into two phases as follows: phase I,
thermochemical equilibrium analyses; phase II,
reaction kinetic analyses and preliminary design and
economic analyses. Similar to the overall chemical
process development procedure, this division of the
technical-economic analysis into two phases with
different sections was designed to provide decision
points to project management where the number of
systems to be considered in the subsequent analyses
could be limited to those demonstrating technical
feasibility at the end of the previous analysis. This
approach converges on those systems demonstrating
both technical and economic feasibility for
laboratory investigation (Figure 2). The various
portions will now be described in detail.
"During this project, the Federal solid waste management program was a part of the U.S. Department of Health, Education,
and Welfare, although the program is now in the U.S. Environmental Protection Agency.
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The thermochemical equilibrium analysis (phase I)
was initiated with three thermoplastic materials,
polystyrene, polyethylene, and polyvinyl chloride,
together with five coreactants, ammonia, hydrogen
chloride, chlorine, steam, and air, plus heat without
air. The various plastic/coreactant systems were
examined in the gas phase by use of the TRW
chemical analysis program. The product distributions
resulting from the various systems under a wide range
of reactant mixture, pressure, and temperature
conditions were used for the identification of
commercially important products. The systems in
which no significant quantities of commercial-quality
products were predicted were eliminated at this stage
of the analysis. This procedure eliminated the
following two coreactants from further
consideration: ammonia, which has a very high
tendency to decompose; and hydrogen chloride,
which shows no tendency to react with plastics to
form anything other than itself. A general approach
developed by TRW Systems for this study was used
to determine thermochemically feasible reaction
paths for the remaining chemical systems. This
second treatment considerably narrowed the range of
reaction intermediates to be considered in the
reaction kinetic analysis.
The management information generated in the
thermochemical equilibrium analysis was used first to
limit the number of chemical systems to be
considered in subsequent analyses and second to
determine the scope of the reaction kinetic analysis,
that is, the number of species to be considered, the
products desired, and the approximate operating
conditions. The reaction kinetic analysis (phase II,
part 1), which employed mathematical
representations of the rate relationships of the various
reactions occurring in the chemical system of interest,
was used to determine the product distribution-time
history of that system. The models and the
parameters contained therein were derived from
current theory and the literature. Where information
was not available, estimating techniques were used to
provide the necessary data. The models were
formulated for the computer and used to analyze the
systems of interest.
On the basis of reaction kinetic analysis it was
possible to eliminate the plastics/chlorine system
from further consideration, since it was not possible
to identify conditions producing a commercially
attractive product mix. Steam was also eliminated as
a reactant although it was retained as a heat carrier.
The parameters resulting from the reaction kinetic
analysis, including residence times, flow rates, reactor
sizing, and heat requirements, were provided to the
subsequent analyses.
The data resulting from the reaction kinetic
analysis were used to perform the final phase of the
technical-economic analysis, preliminary design and
economic analysis (phase II, part 2). The objective of
this final analysis was to provide information about
the economic behavior of the proposed chemical
process. The analysis was based on the development
of a preliminary process design corresponding to the
material and energy relationships of the major process
components. The various components of the process
system were sized by use of data from the reaction
kinetic analysis. The operating costs were then
derived in terms of depreciation, utilities costs, and
labor and used to define an "upgrading cost" per unit
of product or raw material. This information is to be
used by management together with other data, such
as market analyses, to select the processes to be
continued into the laboratory development phase.
The following chapters present the approaches,
methods, and results of the various phases of the
technical-economic analyses performed on waste
plastic utilization systems. Chapter 2 presents the
general approach and analytical tools employed by
TRW Systems Group. The determination of the
equilibrium species distributions and reaction path
analyses may be found in chapter 3. Chapters 4 and 5
present the kinetic analyses and preliminary design
and economic analyses, respectively. These results
provide the basis for the conclusions and
recommendations of chapter 6. The conclusions and
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recommendations include not only the proposed
selection of processes for further application, but also
other implications, for air pollution, for example, of
the results of the TRW analysis.
2. TECHNICAL APPROACH
The technical approach taken by TRW Systems in
meeting the project objectives consisted of two
interrelated phases described in this chapter (Figure
3).
Phase I
Phase I of the theoretical study of waste plastics
utilization employed the TRW-developed chemical
analysis program (CAP). Cap is a thermochemical
equilibrium computer program used to provide the
following information:
1. The equilibrium product distribution of the
chemical reactions of plastics with selected chemical
reactants under various conditions
2. The potential air and water pollutants
associated with each chemical system
3. The thermodynamically feasible reaction paths
from the reaction of plastic materials with selected
reagents to produce desirable end products
The approach for the first part of phase I was to
apply thermochemical principles to determine the
behavior of plastics/chemical agent reaction systems.
The following three plastics representative of the
families of plastics expected to have large-scale future
consumer usage were investigated in the program:
polyethylene, polystyrene, and polyvinyl chloride.
Chemical agents to react with these plastics, such as
oxygen (air), and steam, hydrogen chloride, chlorine,
and ammonia, were selected on the basis of cost,
availability, and possible reactivity with the selected
plastics. The TRW thermochemical equilibrium
program computed the distribution of chemical
species produced at equilibrium from specified
reactants as a function of temperature, pressure, and
reactant composition. The program is capable of
describing systems containing gases, pure liquids, pure
solids, and solutions. It requires as inputs only the
chemical formulas, entropies, and enthalpies of the
reaction products. Given the selected plastics and
chemical agents, possible reaction products were
selected, and the necessary thermodynamic data for
these products obtained. For the waste plastics
analysis, only a small number of chemical elements
are involved in the possible products as follows:
carbon, hydrogen, oxygen, nitrogen, and chlorine.
After all the necessary information was collected
and placed on the program input tapes, the analysis
was conducted as follows: (1) by calculating rapidly
and inexpensively the product distribution for a
broad range of initial compositions and temperature
and pressure conditions; and (2) by examining the
outputs for economically significant product
concentrations and potentially harmful air or water
pollutants. Further calculations were made to
determine quantitatively the effects of the reaction
conditions on the concentrations of important
products.
The second part of phase I applied the
thermochemical computer program to determine the
thermodynamically feasible reaction paths. In the
equilibrium analysis performed during the first part
of phase I, the reactant systems were essentially
reduced to an elemental composition and recombined
into the products according to thermodynamic
principles describing equilibrium. It was then
necessary to determine if an actual chemical reaction
path could be described, that is, whether or not some
required intermediate reaction step was likely to
occur thermodynamically.
The thermochemical equilibrium program was
applied to reaction path analysis simply by limiting
the number of products considered at each stage to
those that were possible intermediates for the next
stage. For example, the polyethylene/chlorine
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coreactant system predicted benzene, methane,
hydrogen, and hydrogen chloride as the principal
equilibrium products. The first stage of the reaction
path analysis eliminated these from consideration and
found ethane, propane, and toluene as the next most
feasible intermediates. A subsequent deletion found
ethylene, pentadiene, butane, and other products as
the next higher feasible intermediate stage. Following
this stage, ethylene was predicted. In sum, the
feasible reaction path was scoped from ethylene to
the final equilibrium products through two reaction
stages.
Phase II
Phase II of the theoretical study employed
mathematical models for describing the various
time-dependent characteristics of plastics-containing
chemical reaction systems. The information generated
with the models included the following: (1)
quantitative data describing the time dependence of
various steps in the reaction path; (2) quantitative
descriptions of product distribution as a function of
time and temperature; (3) parametric functions
relating cost factors such as plastics pretreatment,
reactants used with the plastics, value of products,
and reactor design and control capabilities.
The first task of phase II was the formulation of
the general physical and chemical properties of waste
plastics and the waste plastics reaction chemistry into
a chemical model. This was followed by the synthesis
of a mathematical model that restated the chemistry
model in analytical expressions. The mathematical
model was translated into an equivalent computer
model that described the time-dependent
characteristics of each plastic containing chemical
reaction system.
The second task of phase II was the application of
the mathematical models developed under phase II
(part 1) to the analysis of the selected reaction
systems. The analysis of the reacting systems required
the knowledge of (1) the reaction paths and chemical
reaction equations for each step in the reaction path
(phase I), (2) the parameters describing the various
chemical and physical reaction rates at each step, (3)
the pressure, and the temperature environment
throughout the reactor, and (4) the flow velocity (or
residence time) in the reactor. As mentioned already,
only those reactions that appeared important from
either an economic or pollution viewpoint were
analyzed with the simulation models. The reaction
rate parameters required to complete the description
of the reactions were taken from the available
literature. Where data were not available in the
literature, they were estimated from data on similar
systems or calculated by use of theoretical-empirical
techniques.
The temperature environment and the flow rates
through the reactors are parameters that were varied
to determine the effects on the reaction
corresponding to the desirable product distributions
investigated under phase I. These conditions were
varied to assess the effects on product distribution in
the kinetically controlled systems. The data resulting
from the variations of parameters provided the
necessary information on the dependence of the
reaction on residence time in the reactor.
Finally, the data resulting from these analyses
were interpreted to develop relationships describing
disposal costs in terms of the reactants used with the
plastics, the value of the products, the complexity of
the reactor and process, and the control capability
requirements.
3. THERMODYNAMIC ANALYSES
The objectives of the analyses of the waste plastic
systems equilibrium were to determine the following:
the thermal decomposition equilibrium products for
polystyrene, polyethylene, and polyvinyl chloride;
the equilibrium reaction products formed by
combustion of waste plastics with air; the potential
pollution products of waste plastic reactions; the
useful products resulting from the reactions of waste
plastics with other chemical materials; and the
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feasible reaction paths for each system in order to
scope kinetic analysis. The approach taken by TRW
Systems Group to reach these objectives includes
application of the chemical analysis program (CAP)
computer program. This program is capable of
calculating possible reaction products and reaction
paths by determining the thermodynamic equilibrium
of each system. The principal purpose of the CAP
application is to eliminate from further consideration
those systems that will not yield useful products. In
addition, CAP is used to determine for each
coreactant system the products that may form. The
specific methods of and results for each CAP
application are presented in what follows.
TRW Chemical Analysis Program
and Thermo chemical Data Base
Determination of theoretically expected
thermochemical equilibrium product and of reaction
path species distribution requires appropriate
thermochemical data for each potential product. In
addition, a mathematical model is required to
combine these data in order to ascertain the
equilibrium quantities of each product. The data and
model are used under various conditions of
temperature, pressure, and reactant combination to
stimulate each equilibrium chemical system and
reaction stage.
The mathematical model necessary to compute
these equilibrium product distributions is embodied
in the TRW chemical analysis program. This program
is capable of simultaneously considering a maximum
of 200 gaseous products together with a maximum of
20 condensed species. The basic variables considered
by the program are the partial pressures of the
elemental gases, such as monatomic hydrogen gas,
monatomic carbon gas, and the total moles of gas in
the system. These variables are used to solve a system
of simultaneous equations, including mass balances
for each element and a pressure match. The
concentrations of the other species in the system .are
computed from the partial pressure of the elemental
gas. The program requires curvefit coefficients (a
ninth-order orthogonal polynomial is used) for the
standard enthalpy and standard entropy of each
species as a function of temperature. These data are
used by the program to determine standard free
energies from which equilibrium constants are
computed for reactions of the type
aA + bB + cC + .... A0 Bu C- ....
These constants are used in the mass balance
relationships to provide the appropriate weighting
factors to each elemental gas.
The program is capable of providing equilibrium
calculations for a complete set of thermodynamic
constraints input as pairs, as follows: constant
pressure, energy; temperature, volume; temperature,
enthalpy; temperature, entropy; temperature, energy;
volume, enthalpy; volume, entropy; enthalpy, energy;
and entropy, energy. The program accepts the weight
percents of the various reactants together with their
molecular formulas and enthalpies of formation.
Other data, such as T and P, are input corresponding
to the constraints. The quantities of each element
(100 g total system being assumed) are computed and
species corresponding to the combinations of
elements selected from the thermochemical data tape.
The mass balances are set up for each element and the
equilibrium compositions computed under the
stipulated thermochemical constraints.
The equilibrium distribution is computed only
among the species selected from the thermochemical
data tape. Under the normal operating mode, data for
all listed potential products of the reactant elements
are selected from the species tape. The program is,
however, designed to accept specifications on the
product list considered, allowing specific deletions
and selections of potential products. The classes of
problems that can be analyzed are, therefore,
expanded to include competitive reaction analysis as
well as general system equilibrium.
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The proper use of the mathematical model
requires accurate data describing the thermdchemical
behavior of the various species considered as resulting
from the reaction of the starting materials. The
thermochemical data required by the TRW chemical
analysis program for the waste plastic systems are the
enthalpy and entropy as a function of temperature.
These data are used not only to compute the
necessary equilibrium constants but also to provide
the information necessary to satisfy the
thermochemical constraints.
The primary data base used by the TRW chemical
analysis program was provided by the JANAF
thermochemical tables prepared by the Dow
Chemical Corporation. These data include
information on a broad range of chemical species
containing a very representative selection of the
common elements. The JANAF tables emphasize
species that could be significant in chemical rocket
exhausts. Since rocket conditions are very severe,
complex organic molecules are unlikely and are not
included.
In order to perform an adequate equilibrium
product distribution analysis, it was necessary to
develop a thermochemical data set containing
additional species representative of the products
expected under the less severe conditions
characteristic of industrial reactors. The JANAF
tables include the potential products methane,
acetylene, ethylene, ethylene oxide, formaldehyde,
and the various methyl chlorides among the organics;
no higher organics are represented. Data for classes of
compounds were required to represent the products
expected with the waste plastics coreactants. The
classes are the following:
(1) higher saturates, e.g., ethane;
(2) higher unsaturates, e.g., propylene;
(3) alcohols;
(4) glycols;
(5) higher aldehydes, e.g., acetaldehyde;
(6) ketones;
(7) ethers;
(8) higher chlorides, e.g., ethyl chloride;
(9) amines;
(10) higher epoxides, e.g., propylene oxide;
(11) aromatics.
Data for the first two classes were available from a
compilation prepared by the American Petroleum
Institute Project (API) 44.2 The thermochemical data
selected were limited to compounds having six
carbons in the case of aliphatics and nine carbons in
the case of aromatics since higher molecular weight
materials are not found in significant quantities under
the conditions planned for study.
Heat capacity (CP) data for some of the alcohols,
glycols, aldehydes, chlorides, and epoxides were
available from the recent compilations prepared by R.
W. Gallant and published in Hydrocarbon
Processing.-1'^ In order to compute the necessary
enthalpy and entropy data as a function of
temperature, data for the enthalpy of formation
(H°f 298) and entropy at 25 C (S°298) are combined
with the heat capacity data. These data were obtained
from the literature when available. ^' Data not
available from these sources were estimated with the
techniques of S. W. Benson. •* A computer program
was written for the TRW time-sharing system to
compute the appropriate enthalpies and entropies
from the heat capacity, heat of formation, and
reference entropy data.
Data for the ketones, ethers, amines and certain
compounds of interest in the other classes were not
available in compiled sources; therefore, the
technique of S. W. Benson was again used to estimate
heat capacity as well as heat of formation and
reference entropy. ^ Whenever possible, computed
data were compared with individual data available in
the literature. The estimated data were used together
with the time-sharing program to generate the
necessary entropies and enthalpies.
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Equilibrium Product Distribution Analyses
The purpose of the equilibrium product
distribution analyses is to provide a sound
thermochemical basis for the determination of the
species resulting from the reaction of waste plastic
materials with various coreactants. Three plastic
materials, polyethylene, polystyrene, and polyvinyl
chloride, were considered with five coreactants,
hydrogen chloride, ammonia, water, air, and chlorine,
as well as with no coreactants (thermal
decomposition). In the following sections the
products resulting with each coreactant are discussed
with emphasis on the general characteristics of the
reaction systems. The numerical results for each
system and the equilibrium chemical species
considered were summarized (Appendix A).
Thermal Decomposition Reaction Systems. The
equilibrium product distributions resulting from each
of the three plastic systems were examined at two
pressures, 68 and 1 atm, and three temperatures,
1,472, 1,073, and 773 K. Thermal decomposition
provides a basis for comparison of the effects of the
coreactants on the product distribution. The primary
products produced at equilibrium for the three plastic
types vary with carbon-hydrogen ratio in the original
plastic material (Figure 4). The relative amounts of
the various products naturally vary also as a function
of temperature and pressure—the amounts of the
unsaturated aliphatics increasing as temperature
increases and decreasing with increasing pressure.
Benzene appears to be particularly favored in the
polystyrene and polyvinyl chloride systems. The
polystyrene (CgHg)n is stoichiometric to benzene,
and the polyvinyl chloride (CH2CHCl)n is also
stoichiometric to benzene if hydrogen chloride is
formed. Under the temperature and pressure
conditions considered, the polyethylene system
indicated a tendency toward dehydrogenation to
acetylene and benzene. At temperatures lower than
those examined in the analysis, it would be expected
that ethylene would become the most favored
decomposition product.
Hydrogen Chloride Reaction System. The set of
pressure-temperature conditions used for the thermal
decomposition was the basis of comparison for the
subsequent analyses. The hydrogen chloride system
represented the first coreactant analysis. For the
analysis, reactant concentrations were chosen such
that complete reaction would not result in large
excesses of the initial materials since excesses tend
greatly to promote kinetic rather than equilibrium
effects. The concentrations selected were 70 weight
percent polymer/30 percent coreactant, 50 percent
polymer/50 percent coreactant, and 20 percent
polymer/80 percent coreactant.
The hydrogen chloride systems analyses indicated
that hydrogen chloride does not react significantly
under the conditions examined, primarily because of
the favoring of equilibrium toward the aromatic
compounds (Figure 5). The product distribution is,
therefore, essentially the same as is seen in the
thermal decomposition analysis. It is possible,
therefore, to eliminate this system from specific
consideration.
Ammonia Reaction Systems. The ammonia
systems were examined to indicate whether arnine
compounds were feasible products from waste plastic
reactions. Under equilibrium conditions at the
compositions, pressures, and temperatures selected,
the analysis showed that ammonia formation
equilibrium
N2 + 3H2 2NH3
was completely reversed supplying free hydrogen to
the system (Figure 6). The hydrogen released from
the ammonia severely decreased the concentrations of
the unsaturated compounds, both aliphatic and
aromatic. The most significant organic reaction
product under these conditions is methane.
The production of methane from the waste
plastics/ammonia systems is not an economically
significant result. Ammonia is prepared commercially
by a process including the partial oxidation of
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methane or other saturated hydrocarbon with air to
produce hydrogen and nitrogen, which are further
reacted to give ammonia. The results of the ammonia
equilibrium analysis further indicate that direct
hydrogenation would also be economically limited
since the hydrogen is produced from similar
reactions.
Water Reaction Systems. The water (steam)
coreactant systems were investigated primarily to
determine whether partially oxidized compounds,
e.g., alcohols, were potential products of waste
plastics utilization. The equilibrium product
distributions were computed under the previously
stated environmental and compositional conditions.
Partially oxygenated product types represented in the
calculations included alcohols, glycols, ethers,
aldehydes, and ketones in addition to the various
carbon oxides.
Under the conditions studied, no significant
quantities of the various oxyorganic compounds were
found in the major product distributions (Figure 7).
The analyses indicated, however, the potential of a
steam reforming reaction system's producing carbon
monoxide and hydrogen with the waste plastics. A
steam-fed catalytic reactor could eliminate the bulk
plastic and produce reducing gas products. Recovery
equipment would be necessary to collect the
hydrogen chloride generated by the polyvinyl
chloride system.
Air Reaction Systems. The steam reaction system
represents a relatively inexpensive reactant that when
combined with waste plastics might have economic
potential as a disposal technique. The air reaction
system described in this section also uses a very
inexpensive reactant. The purposes of this analysis
were twofold. First, the systems were examined to
indicate conditions that limit the formation of
products, representing a potential air pollution
hazard. These analyses are concentrated on a current
technology used in many places to eliminate bulk
waste, substituting a potential pollution problem for
the immediate bulk waste disposal problem.
Commercially significant products for these
systems are absent in the temperature-pressure and
composition ranges examined (Figure 8). The primary
products are the expected combustion products;
however, certain potential pollutants are indicated in
the analyses. In the fuel-rich combustion range
examined, the equilibrium analyses show significant
quantities of hydrogen cyanide gas, HCN, present in
all the plastics systems. Temperatures higher than
those examined show a further preference for this
product. This would indicate that the reactor
(combustor) design used for the burning of plastic
materials must include specific provision for the
adequate mixing of the reactants eliminating hot
spots in fuel-rich zones.
A second potential pollutant whose quantity is
dependent only upon the original quantity of plastics
is hydrogen chloride gas, HCl, produced from
polyvinyl chloride. Its presence indicates that plastics
combustion equipment must have provision for the
recovery of this gas, which certainly is comparable
with the sulfur oxides in potential corrosive effects
on biological, metallic, and other systems exposed to
it.
Chlorine Reaction Systems. Chlorine gas
represents a relatively expensive reactant but one
whose reactivity was considered likely to produce
economically significant products. Organic chlorides
have found a wide variety of commercial applications.
The chlorine/plastics systems were examined in
equilibrium under the usual conditions in order to
predict the product mix obtained (Figure 9). As was
expected, significant quantities of chloro-organic
products were predicted under equilibrium
conditions. The simulation of the chemical-kinetic
behavior of these systems defined conditions that
allowed chlorine to produce several different chlorine
derivatives.
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Reaction Path Analyses
The purpose of this analysis was to determine the
general types of possible thermodynamically feasible
intermediate species for each chemical reaction. The
resulting information from this analysis was used to
scope the chemical-kinetics model. A separate
analysis from that of the equilibrium results reported
earlier is necessary since its data are calculated by
reducing the reactant system to elements and
recombining them into products according to
equilibrium thermodynamic principles. Calculations
of this type give no hint about the possible reaction
paths and species to consider. Possible intermediate
species at a given step are identified by rerunning the
equilibrium program and deleting all major
equilibrium products found by the previous run.
Significant products are formed from
polyethylene, polystyrene, and polyvinyl chloride by
reacting them thermally and with the coreactants air
and chlorine. These system paths and their possible
intermediates were studied, and the results are now
reported.
Thermal Decomposition Reaction Path Analysis.
The polystyrene thermal decomposition equilibrium
results indicate that benzene is in equilibrium with
styrene at 1,073 K and 1 atm pressure. This
equilibrium mixture represents a minimum of the
relative system's free energy, or in other words the
most probable distribution of species at equilibrium.
When benzene is not allowed to form, the reaction
yielded a new product distribution (Figure 10), which
represents a higher system's free energy. This result
may be interpreted to mean that these products are
similar to the actual intermediates in the benzene
from polystyrene reaction. The possible intermediates
include toluene, the cis-trans 1-phenyl-l-propylene
and the ortho-meta-para methyl-styrene.
Polyethylene equilibrium results, like polystyrene
results, predict conversion of the given plastic to
benzene at 773 K and 1 atm. The feasible reaction
intermediates are, however, for the most part
different (Figure 10). Toluene is the only species that
appears in both cases. In addition to toluene, the
feasible intermediates include ethane, propane,
e t h y 1 - b e n z ene , and ortho-meta-para
dimethyl-benzene.
The major coproducts of the thermal
decomposition of polyvinyl chloride at 773 K and 1
atm pressure are benzene and hydrogen chloride. This
is similar to the polystyrene and polyethylene
decomposition, except that no hydrogen chloride can
be formed in the first two systems. The polyvinyl
chloride decomposition path analysis consisted of
two equilibrium runs, the first excluding benzene
from forming. The results of this run indicate that
chlorine-substituted ethylenes and toluene are
formed. A second run deleting these as possible
products yielded ethyl benzene as the next level of
feasible product.
Air-Plastic Reaction Path Analysis. The reaction
path analyses for the determination of feasible
intermediate species for the air-plastic reactions are
presented in this section. As in the thermal
decomposition equilibrium analysis and reaction path
analysis, benzene is one of the major coproducts
formed from the three waste plastics (773 K, 1 atm,
and with 70 percent plastic material and 30 percent
air by weight). In addition to benzene, carbon
monoxide, carbon dioxide, and methane are formed
at equilibrium from the polystyrene-air system. When
these products are not allowed to form in the
polystyrene system, toluene appears to be the next
most feasible product. After all previous products are
deleted, the styrene monomer is the most feasible
species (Figure 11).
Polyethylene-air reaction equilibrium products
include hydrogen as well as those products found in
the polystyrene-air reaction system under similar
conditions. Although the equilibrium results are
similar, a number of differences are found in the
distribution of feasible intermediate species. In
addition to toluene, which is found in both systems,
propane, ethylbenzene, and ortho-meta-para-dimethyl
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benzene are formed. When these are excluded,
propylene, ethanal, and dimethyl ketone are found to
comprise the next level of feasible products (Figure
11).
The polyvinyl chloride equilibrium products are
similarly distributed to those previously listed except
that in place of hydrogen, hydrogen chloride is
formed. The first level of feasible products includes
toluene and styrene. After deletion of these products,
ortho-meta-para methyl-styrenes and xylenes, and
ethanal become feasible products (Figure 11).
Chlorine Reaction Path Species Analysis. Reacting
polystyrene with chlorine at 773 K, 1 atm, and 70
percent plastic to 30 percent chlorine (on a weight
basis) results in the reaction products benzene and
tetrachloroethylene with hydrogen chloride as a
coproduct (Figure 12). The styrene monomer
comprises a secondary level of feasible materials when
the previous product formations are suppressed. After
styrene, the next level of feasible products includes
toluene and tetrachloroethane.
The polyethylene reaction path equilibrium
analysis identified benzene, methane, and hydrogen
along with hydrogen chloride as the major products.
These were formed at 773 K, 1 atm, and 70 percent
polyethylene by weight. After suppression of the
products, a rerun of the chemical equilibrium
program predicted ethane, propane, and toluene as
the next set of feasible intermediates. A second
product suppression and rerun yielded 1,4
pentadiene; 1,3 butadiene; ethylene; and butane as
feasible intermediate products.
The final path analysis studied polyvinyl chloride
and chlorine reacting at 773 K and 1 atm pressure
with a mixture of 70 percent by weight polyvinyl
chloride to chlorine. The final equilibrium mixture
under these conditions gave methane, benzene,
tetrachloroethylene, and hydrogen chloride as
products. Feasible intermediate products included
toluene, the three isomers of dichloroethylene,
isomers of tetrachloroethane, and ortho-meta-para
dimethylbenzene. A rerun of the equilibrium program
gave styrene as a feasible intermediate after all
previous major products were suppressed (Figure 12).
4. KINETIC ANALYSES
Phase I of the waste utilization program was based
on the application of a TRW-developed
thermochemical equilibrium computer program. This
program determined equilibrium reaction species
concentrations resulting from chemical reactions of
plastics in various environments. In addition, the
program selected thermochemically feasible reaction
paths from the total number possible. The kinetic
analysis expanded the phase I equilibrium data base
by determining residence times, flow rates, reactor
sizing, and heat requirements for each system.
Emphasis of the kinetic analysis was placed on
identifying reaction systems of an economic potential
that would lead to the development of commercially
attractive chemical processes. The primary purpose of
the kinetic analysis is to provide time-dependent data
resulting in a consistent characterization of each
system.
The information compiled from phase I and from
the literature was used to delineate those reactions
and reaction mechanisms that would yield the
identified final products. The reactions were
combined with a heat and material balance to
complete the chemical-kinetics model. In some cases,
the rate parameters, and the enthalpy and heat
capacity data for the models were not obtainable. For
these, the data were estimated by methods developed
by Benson. 15 This information resulted in the
formulation of mathematical models describing the
time and temperature behavior of chemically reacting
waste plastic systems.
Following the formulation stage, the models were
programmed into equivalent computer programs
capable of simulating a broad range of operating
conditions. The resulting computer programs were
used to simulate the process unit operations for
determining technical-economic characteristics of the
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total system. The results of these analyses are
interpreted in terms of the following: cost factors
associated with various reaction processes,
performance criteria necessary for research on new
reaction process concepts, and the design of chemical
reactors capable of providing desired product
distributions.
The results of the polystyrene, polyethylene, and
polyvinyl chloride thermal decomposition kinetic
analyses using nitrogen gas as the heat source are
presented now, followed by the waste
plastics/chlorine gas coreactant analyses and the
coreactant system analyses of the three waste plastics
with water and with air.
Thermal Decomposition Kinetic Analysis
The approach for the kinetic analysis of thermally
decomposing polystyrene, polyethylene, and
polyvinyl chloride waste plastics consisted of the
following: (1) determining the physical and chemical
properties of the reactants, (2) determining the
decomposition mechanism, (3) formulating a
chemical model, (4) translating the chemical model
into a mathematical model, (5) programming the
mathematical model into an equivalent computer
program, and (6) simulating each reaction system
under various reaction conditions. The results are
presented as concentrations of reaction products and
nitrogen gas (heat source) as a function of time. From
these data the reactor geometry and heat
requirements were defined.
Polystyrene. The kinetic behavior of a chemical
system is strongly dependent upon the physical and
chemical properties of the reactants. In order to treat
realistically these time-dependent characteristics of
the polystyrene decomposition reaction, the
following physical and chemical properties of waste
polystyrene were postulated from information
reported in the literature: (1) polystyrene waste
plastic contains thermally active sites ("weak links"),
which are randomly distributed within each molecule;
(2) waste polystyrene is heterogeneous with respect
to initial chain size; (3) the reactant plastic can be
characterized by an initial "most probable" molecular
weight distribution; (4) plastic fed to the reactor is
selected at random, that is, no distinction is made on
the basis of degree of polymerization, molecular
weight, etc; (5) it is homogeneous with respect to
monomer type, i.e., polystyrene only.
Initially, the decomposition of commercial
polystyrene occurs by a random mechanism owing to
weak links formed in the polymerization reaction.
When a weak link is broken, a number of monomers
are split off. This phase continues until the weak links
are exhausted. During this rapid initial period,
inhibitors are produced to give rise to an induction
period that is very pronounced at 625 K and below.
Above 675 K the induction period is not
experimentally evident for either unfractionated or
fractionated samples.
A depolymerization reaction occurs at the end of
the induction period by the following mechanism:
chain end initiation reaction, transfer reactions,
propagation reaction, termination reaction. Transfer
reactions are at a trace level for temperatures between
700 and 1,000 K, which means high styrene
monomer yield with 100 percent selectivity.
This chemical model was reformulated in terms of
a mathematical model that describes the
time-dependent or kinetic behavior of waste plastic
chemical reactions. It is composed primarily of
systems of interdependent ordinary differential
equations. For waste plastic thermal degradation
models, these equations describe the rates of product
formation as a function of time and distance within a
chemical reactor. Usually, these equations can be
solved numerically only by high-speed computing
machines. It is for this reason that the waste plastic
mathematical models are coded into equivalent
computer programs. The computer programs are
written in a general format in order to facilitate
conversion from one set of differential equations
describing polystyrene into another set describing
either polyethylene or polyvinyl chloride.
11
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The grams of styrene produced per gram of
polystyrene as a function of the solid residence time
(that is, the residence time of the solid waste plastic
material) were computed for a broad range of
temperatures (Figures 13, 14, and 15). As expected,
the higher the temperature the faster the rate;
however, the increase in rate must be balanced against
heat requirements. The heat necessary to maintain an
isothermal reactor is supplied by hot nitrogen gas that
is preheated to 1,500 K. At 92 percent conversion the
reactor requires a total of 15.5 g of nitrogen per gram
of styrene when the initial nitrogen is 1,500 K. This
may be compared with 82.0 g of nitrogen per gram of
styrene at 1,000 K initial nitrogen temperature. The
quantity of nitrogen (at 1,500 K) required per gram
of styrene produced increases with reactor
temperature at fixed conversion (Figure 16). The
economies in nitrogen gas at the higher conversion are
due to the fixed amount of nitrogen (1,500 K)
required to bring the waste plastic from ambient
temperature to reactor temperature.
The reactor residence time-heat requirement
tradeoffs, the required conversion, and the physical
properties of unreacted waste plastic dictate the
necessary solid residence time and as such the total
volume. From this, an economical reactor system and
associated process were designed and used to estimate
the costs for processing each pound of waste
polystyrene.
Polyethylene. As expected in a kinetic study, the
physical/chemical properties of waste polyethylene
are important in characterizing its time-dependent
nature. Spectroscopic investigations show that
polyethylene is not strictly a straight polymethylene
chain but contains methyl, carbonyl, and peroxide
groups. Moreover, it has been determined that
polyethylene is branched with one branch point
present on the average for every 50 carbon atoms.
Additional physical properties of waste polyethylene
are equivalent to the ones listed for polystyrene. The
decomposition reaction mechanism for polyethylene
proceeds, however, in a different fashion from that of
polystyrene. Polystyrene degrades into monomer
styrene between 700 and 1,000 K. Reaction products
resulting from polyethylene contain little monomer
but primarily paraffins with as many as 50 carbon
atoms, depending on the temperature. The
degradation reaction for temperatures between 660
and 710 K appears to be of zero order over a large
range of percent weight loss. The mechanism
probably consists of splitting off large molecular
fragments in rapid succession once the chain is
initiated.
After the chemical and mathematical models were
derived, the necessary simulation model was
programmed and an analysis was completed that
characterized the system. The quantity of product
produced versus residence time with a polymer of
822 average degrees of polymerization varies strongly
with temperature (Figures 17 and 18). Temperatures
between 685 and 710 K were found to be practical
reactor temperatures, heat input requirements and
residence times being considered. Complicating the
analysis is the fact that the rate was found to be
affected by the average degree of polymerization
(ADP). Inasmuch as it is impossible to determine
waste polyethylene ADP a priori, its effect must be
considered parametrically in designing the reactor.
The effect of ADP over a range of 571 to 3,000 units
was examined in the present study (Figure 19). As in
the polystyrene analysis, the heat versus rate or
conversion was studied for the reaction design (Figure
20). The product distribution for a polyethylene
thermal degradation system was calculated at 710 K
(Table 1). The relative concentrations of species are
approximately constant at each conversion.
Polyvinyl Chloride. Polyvinyl chloride is
essentially a linear polymer of "head to tail"
configuration. A small amount of branching is present
composed probably of carbon and chlorine atoms.
The general properties of waste polyvinyl chloride
material are the same as those presented for
polystyrene.
The thermal degradation of polyvinyl chloride is
primarily a dehydrochlorination reaction. After a
short initial period, hydrogen chloride is evolved
under a mechanism of approximately 3/2 order in the
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fraction of undegraded units. Following hydrogen
chloride evolution, a secondary decomposition occurs
that yields numerous organic products (Table 2). The
effects of temperature on the hydrogen chloride and
on the hydrocarbon reaction were examined to
determine feasible reaction conditions (Figures 21,
through 24). The net result is that the reaction is
commercially feasible above 675 K. The hydrogen
chloride and hydrocarbon product evolution was
examined as a function of solid residence time
(Figure 25), 723 K being selected as the nominal case.
Here the hydrogen chloride is the predominant
product at all residence times. The overall reaction is
exothermic owing to the predominance of the
exothermic hydrogen chloride stage over the
endothermic organic evolution stage. As such, no
nitrogen is required after the initial 1.2 g/g of waste
plastic polymer necessary to raise the temperature
from 300 to 723 K.
Thermal Decomposition Preliminary Reactor
Designs. The thermal decomposition reactor
mathematical models were based on engineering
design of a semicontinuous moving-bed reactor. The
reactors are to be operated isothermally by supplying
"hot" nitrogen gas at various points within the
reactor. Waste plastic is fed continuously from above.
Any unreacted material is removed in a batch fashion
by switching to auxiliary reactors.
Resulting data from the reactor models are used to
develop relationships describing plastic-processing
costs as a function of coreactants, value of reaction
products, capital costs and operating costs. A
schematic diagram of the designed plastic thermal
decomposition reactor was prepared (Figure 26), and
the specific dimensions of the reactor for each of the
decomposition systems were summarized (Table 3).
Waste Plastics/Chlorine Kinetic Analysis
Polystyrene. This section describes the results of
the polystyrene/chlorine kinetic analysis. Reactions
of polystyrene waste plastic and chlorine gas were
kinetically simulated with two different reactor
configurations. The first configuration consisted of a
two-stage reactor; the first reactor used hot nitrogen
gas to decompose the polymer thermally, followed by
a second reactor that reacted the monomer with
chlorine gas (Figure 27). The second configuration
consisted of a single reactor using chlorine gas
reactant as the heat carrier. This reactor is equivalent
to the thermal decomposition reactor presented
earlier (Figure 26).
Kinetic results of the first-configuration second
reactor indicated that the monomer/chlorine
reactions proceed slowly in the presence of excess
nitrogen. .A modification to this configuration was
proposed whereby nitrogen was removed before the
second reactor. Subsequent analyses calculated more
favorable kinetics. In addition, the volume of the
second reactor without nitrogen was found to be
approximately 3 percent that of an equivalent reactor
with nitrogen at equal conversions. The product
analysis of the second reactor (Table 4) and the
product produced per gram reactant (Figure 28) were
calculated for both systems (with and without
nitrogen at 900 K).
The second configuration consisted of a single
reactor where polystyrene reacts with chlorine gas
directly. Here chlorine acts as the heat source as well
as the coreactant. The kinetic analysis of this reactor
indicated an almost total conversion of waste
polystyrene gas phase products to hydrogen chloride
and heavily chlorinated styrene with some
chlorinated toluene and methane derivatives.
From a kinetic or reaction control standpoint, the
practical system would be the first configuration,
where chlorine gas is reacted with styrene monomer
after the nitrogen-waste plastic decomposition
reaction (first reactor) and after nitrogen removal.
Further analyses of this two-stage reactor indicated
that increasing chlorine/styrene ratio (or
temperature) favors formation of (ortho, meta, para)
1,2 dichloro-ethyl chlorobenzene over 1,2
dichloro-ethyl benzene as the major product (Figure
29). Both systems were found to be impractical from
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an economic and product yield point of view (see
what follows).
Polyethylene and Polyvinyl Chloride. Kinetic
analyses similar to the polystyrene/chlorine analysis
were completed for polyethylene and polyvinyl
chloride waste plastics reacting with chlorine. Both
waste plastic systems were modeled with the two
configurations already described.
The results of these analyses were analogous to the
results reported in the previous section, where the
two-reactor configuration was found to be favored
from a process control standpoint. Various mixtures
of hydrocarbons and chlorinated hydrocarbons could
be produced by varying feed concentrations of
nitrogen and chlorine. The second configuration
(single reactor) gave hydrogen chloride as the major
product for both plastics. In addition, the mixed-feed
alkane-alkene stream of polyethylene produced a
mixture of carbon tetrachloride, hexachloroethane,
etc., whereas chlorinated toluene and styrene, along
with carbon tetrachloride, hexachloroethane, etc.,
were produced from the polyvinyl chloride
decomposition stream.
The general usefulness of the waste
plastic/chlorine system is limited by the fact that
chlorine reactions are not very selective. All types of
alkane hydrogens are attacked with almost equal
probability. Introduction of one chlorine atom does
not appreciably affect the replacement rate of a
second or third, etc., hydrogen atom. The net result is
that all possible products are obtained when the
reaction is chlorine limited. Excess chlorine replaces
all available alkane hydrogens at a very rapid rate.
In summary, kinetic analyses of the three waste
plastic/chlorine coreactant systems demonstrated the
usefulness of the two-reactor configuration from a
control or final product standpoint. From an
economic point of view, however, this configuration
is unfavorable, since it requires the heating of waste
plastic to the decomposition temperature followed by
cooling to remove part or all of the nitrogen.
Subsequently, the stream must be reheated to react
with chlorine. Most importantly, the value of the
final chlorinated products (including upgrading costs)
is less than the value of the thermal decomposition
products. Commercially, it would be possible to
hydrolyze the mixed chlorides to produce mixed
alcohols. Reactions with ammonia would yield
amines and with sodium hydrosulfide would yield
mercaptans and sulfides. For reactions such as these
to be commercially rewarding, a market for these
chemicals would have to be identified.
Waste Plastics I Steam Kinetic Analysis
Presented in this section are the results of the
kinetic analyses of polystyrene/steam,
polyethylene/steam, and polyvinyl chloride/steam
digestion systems. The objective of these studies was
to determine the feasibility of using steam-fed
reactors to eliminate bulk waste plastics and supply
products valuable for fuel. Results indicate processes
could be designed for thermal decomposition using
steam that would be more economical than
corresponding waste plastics/nitrogen thermal
decomposition systems.
Waste plastics/steam digestion systems were
analyzed with use of equilibrium thermodynamics in
phase I of the waste plastics utilization study. The
purpose was to determine whether partially oxidized
compounds such as alcohols, glycols, ethers,
aldehydes, and ketones were potential products.
Results of phase I showed that no significant
quantities of these chemicals will be found under the
conditions studied. They did, however, indicate the
potential of steam-reforming reaction systems'
producing carbon monoxide and hydrogen. These
reforming systems were not kinetically simulated,
since the reactor would require a catalyst
development that would be outside the scope of this
study. A system without catalysis was, however,
modeled that would thermally decompose the bulk
plastics with steam as the heat source.
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The analyses of the waste plastic/steam systems
without catalysts gave kinetic results similar to those
of the waste plastics/nitrogen systems in that the
product distributions were essentially the same for
each system. There are however, advantages in using
steam as a source of heat in place of nitrogen. This is
due to the larger heat capacity of steam as compared
with nitrogen, which reduces the carrier gas
concentrations, and hence, the reactor gas volume.
For example, the polyvinyl chloride decomposition
reactor operating isothermally at 723 K requires 0.9
mole of nitrogen at 1,500 K as compared with 0.7
mole of steam at 1,500 K. A nitrogen/steam
comparison was calculated for a variety of thermal
decomposition systems and conditions (Table 5).
A fourth waste plastic/steam system was simulated
wherein an equal-weight mixture of polystyrene,
polyethylene, and polyvinyl chloride was fed to the
reactor. The product distribution (Table 6), the
reactor design (Figure 30), the geometries (Table 7),
and steam (as a heat carrier) requirements (Figures 31
and 32) were calculated for the composite feed
system as necessary for the economic analysis.
Waste Plastics/Air Kinetic Analyses
The phase I equilibrium analysis and reaction path
analysis indicated the possibility of reacting waste
polystyrene, polyethylene, and polyvinyl chloride
with air. From the point of view of the technologic
and economic importance of hydrocarbon oxidation,
the air oxidation of waste plastics was considered an
important system for analysis. The utilization of
oxidized waste plastics could be important in two
separate applications as follows: partial oxidation to
synthesize important industrial compounds, and
complete oxidation to produce energy. In this light,
the waste plastics/air reactor systems were modeled
for an adiabatic reactor and an isothermal reactor
with two configurations.
The adiabatic reactor system was simulated to
determine the value of using waste plastic materials as
a source of energy. Four separate systems were
simulated as follows: polystyrene/air,
polyethylene/air, polyvinyl chloride/air, and an
equal-weight mixture of the three plastics with air.
The system consisted of an adiabatic reactor with
plastic material and air input at ambient temperature
(298 K). A preliminary kinetic analysis indicated the
lack of usefulness of rate data (by itself) for
determining reactor geometry.
For the waste plastic systems considered, the
observed products are very near equilibrium for any
reasonable reactor geometry. For this reason, the
complete simulation model was not formulated.
Rather, the preliminary kinetic analysis was expanded
by use of the CAP program to determine reactor heat
requirements. These requirements along with
estimated heat transfer coefficients allowed the
determination of a heat transfer area. As is customary
with combustion reactors, the preliminary reactor
design and estimated costs are based on this surface
area. A preliminary reactor design was prepared for
the waste plastic/air system (Figure 33), and the
product distribution, reactor exit temperature, and
air input were calculated for the four systems (Table
8). Polystyrene and polyethylene yielded heat value
products; polyvinyl chloride and the mixture yielded
heat value products and hydrogen chloride.
The isothermal reactor was modeled in two
separate configurations. The first configuration
consisted of a single reactor using air as the heat
source as well as the reactant. The second
configuration consisted of two reactors; the first
reactor thermally decomposes waste plastics into
products, using nitrogen or steam as the heat source.
Following this reactor, a second reactor is used to
react the decomposition products with air under mild
conditions. The first configuration was found to be
impractical from a reaction control standpoint. In
addition to the all but uncontrollable heat transfer
problems, local hot spots encourage the formation of
air pollutants such as hydrogen cyanide. The second
isothermal configuration was found controllable and
without pollutants, but owing to the thermal
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decomposition product mix, the partially oxidized
product mix from the second reactor was found
commercially unattractive.
In summation, the isothermal reactor
configurations were found to be commercially
unattractive. The polystyrene and polyethylene
adiabatic reactors were found to be commercially
feasible for energy production. Polyvinyl chloride and
the waste plastic adiabatic reactors were found to
yield hydrogen chloride and heat.
5. PRELIMINARY DESIGN
AND ECONOMIC ANALYSES
The objective of this portion of the investigation
was to provide information regarding the economic
potential of proposed chemical processes for waste
plastics utilization. The analyses were based on
preliminary process designs accomplished by use of
chemical engineering principles together with material
and energy relationships supplied by reaction kinetic
analyses.
Three of the originally proposed coreactants
survived the screening and evaluation phase following
the chemical reaction analyses. Specifically, those
coreactants were nitrogen, air (oxygen), and water
(steam). The results of the economic analyses for
waste plastic/nitrogen systems, wherein the nitrogen
is used as a heat carrier for the thermal
decomposition of polystyrene, polyethylene,
polyvinyl chloride, and a mixture of equal portions of
all three, are given in what follows. In the next
section, the economic analyses for the four waste
plastic/air (oxygen) systems are presented. In those
analyses, air was used as a source of oxygen for
combusting the selected waste plastics. Finally, the
economic analyses for the waste plastic/water (steam)
systems are discussed. In those cases, water, rather
than nitrogen, was used as a source of heat for the
thermal degradation of waste plastics.
Waste Plastic/Nitrogen Processes
The first process concept analyzed for the
utilization of waste plastics involved using hot
nitrogen to decompose thermally the selected waste
plastics in a semicontinuous moving-bed reactor,
followed by recovery of the reactor effluent and
separation of the useful products. This section
presents the results of economic analyses
accomplished for proposed processes to decompose
polystyrene, polyethylene, polyvinyl chloride, and a
mixture of equal portions of all three. The economics
for each waste plastics utilization system are
presented in what follows.
Polystyrene/Nitrogen. This first proposed process
for waste polystyrene utilization was based on the
thermal degradation of scrap polystyrene to form
pure styrene monomer (Figure 34).
The degradation is accomplished in a sfainless steel
reactor at 600 C in the presence of nitrogen, which is
used to carry the heat required for the endothermic
styrene-producing reactions. Nitrogen at 1,230 C is
fed to the reactor through a number of inlets so that
the temperature will remain constant throughout. A
lower cost system might be based on the direct use of
burner product gases to provide the heat and
eliminate the need for the gas-gas heat exchanger.
This configuration, however, was not considered for
the economic analyses, since the effect of the oxygen
carried in the heating gas would first have to be
determined. The costs presented herein are therefore
probably higher than what could be determined
following laboratory development.
After leaving the reactor, the gaseous reaction
products are cooled to 250 C by heat exchange with
the nitrogen recycle from the refrigeration step and
then sent to the secondary heat exchanger, where the
reaction products are further cooled with water to 50
C. Refrigeration is used to cool the stream to 20 C,
removing all but 0.6 percent of the styrene monomer
from the gaseous nitrogen. The stream is then sent to
16
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a phase separator, and an inhibitor is added to the
liquid monomer before it is pumped to the product
storage tank.
The nitrogen leaving the refrigerator is recycled to
the direct fired heater, cooling the effluent reactor
gases on the way. In the direct fired heater step,
make-up nitrogen is added to the recycle nitrogen
stream (now at 460 C) and heated up to 1,230 C by
means of oil/gas combination burners.
Overall capital and operating costs were estimated
with the aid of computer subprograms written for the
process as well as of modified existing subprograms.
When the installed process equipment costs and
hourly operating costs were summarized (Table 9) for
a plant designed to process 12.5 million Ib of scrap
polystyrene per year, it was found that at current
market values, the plant would gross a cost-price
differential of 6.1 cents/lb of pure polystyrene
processed. No estimate was made for potential waste
plastic separation costs although a good part of the
cost-price differential might be applied thereto.
A similar- analysis was performed with use of
nitrogen at 730 C to heat the polystyrene feed. It was
found that the reduced temperature necessitated
increasing the size of many pieces of the process
equipment by a factor of five with no increase in
production. Increasing the size of pieces of process
equipment would have a detrimental effect on the
process economics, and hence, the higher temperature
was used in modeling and costing the proposed
process.
Polyethylene/Nitrogen. The first proposed process
for waste polyethylene utilization was based on the
thermal degradation of scrap polyethylene to form
useful hydrocarbons (Figure 35).
Nitrogen, used as an inert heat carrier, is preheated
to 1,230 C in a direct fired heater using oil/gas
combination burners. The hot nitrogen stream is then
fed to the semicontinuous stainless steel reactor,
where thermal degradation of the polyethylene is
accomplished at a constant temperature of 440 C.
The reactions are only slightly endothermic, most of
the heat carried by the nitrogen being used to elevate
the temperature of the polyethylene feed.
After leaving the reactor, the gaseous reaction
products are cooled to 110 C by heat exchange with
cold water and then sent to the secondary heat
exchanger (condenser), where the stream is further
cooled to 45 C (again with cold water). Phase
separation is used to separate the hydrocarbons that
have condensed from those that are still gaseous. Fuel
credit was taken for the effluent gaseous stream and
gasoline credit was taken for the condensed
hydrocarbon stream.
Overall capital and operating costs were estimated
by use of computer subprograms written for the
polystyrene process as well as of subprograms created
specifically for this process. The installed process
equipment cost and hourly operating costs were
summarized (Table 10) for a plant designed to
process 12.5 million Ib of scrap polyethylene per
year, including contingencies and contractor's fee.
Even with the credits taken for all products and with
the separation costs ignored, the process was found to
be uneconomical, and it was concluded that the
process should be compared to other disposal
techniques to determine its overall value.
Polyvinyl Chloride/Nitrogen. The first proposed
process for waste polyvinyl chloride utilization was
based on the thermal degradation of scrap polyvinyl
chloride with nitrogen to yield hydrogen chloride as
the major product, hydrocarbon streams receiving
fuel and gasoline credit (Figure 36).
Nitrogen, used as an inert heat carrier, is preheated
to 1,230 C in a direct fired heater using oil/gas
combination burners. The hot nitrogen stream is fed
to the semicontinuous stainless steel reactor, where
thermal degradation of the polyvinyl chloride is
accomplished at a constant temperature of 450 C.
The overall system is exothermic, the heat carried by
the nitrogen being used to elevate the temperature of
the polyvinyl chloride feed.
17
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After leaving the reactor, the gaseous reaction
products are sent to the scrubbing system, which is
capable of removing 99 percent of the hydrogen
chloride from the reactor effluent. •* The scrubber
process allows recovery of the hydrogen chloride
either as acid, at 18 Baume, or, with the aid of a
simple stripping system, as anhydrous hydrogen
chloride.
The installed process equipment cost and hourly
operating costs were summarized (Table 11) for a
plant designed to process 12.5 million Ib of scrap
polyvinyl chloride per year, including contingencies
and contractor's fee. At current market values there is
no gross cost-price differential for the processing of
pure polyvinyl chloride, and this indicates that
further information is required for determining the
potential profitability of this process.
Mixed Waste Plastics/Nitrogen. This proposed
process involves the thermal decomposition of a
mixture of equal portions of polystyrene,
polyethylene, and polyvinyl chloride, using hot
nitrogen (Figure 37).
Nitrogen, again used as an inert heat carrier, is
preheated to 1,230 C in a direct fired heater using
oil/gas combination burners. The hot nitrogen is fed
to the semicontinuous stainless steel reactor, where
thermal degradation of the waste plastics mixture is
accomplished at a constant temperature of 600 C.
After leaving the reactor, the gaseous
decomposition products are cooled by heat exchange,
incoming nitrogen being sent to the direct fired
heater for preheating. The stream temperature is then
lowered to 90 C with a water spray quench that
removes the hydrogen chloride and water from the
stream. The condensed hydrogen chloride/water
stream is sent to a phase separator for recovery of
heavy hydrocarbons for gasoline credit and then on
to a hydrogen chloride distillation column.
The gaseous stream leaving the quench is cooled to
50 C with a cold water heat exchanger, sent to a
phase separator to remove fuel grade organics, and
then refrigerated to 20 C, which removes all but 0.6
percent of the styrene monomer from the gas stream.
The condensed styrene stream is further purified in a
vacuum finishing column, treated with an inhibitor,
and sent to storage.
When the installed process equipment costs and
hourly operating costs for a plant designed to treat
12.5 million Ib of mixed waste plastics per year were
summarized (Table 12), with contingencies and
contractor's fee included in the plant costs, it was
found that the gross cost-price differential for the
mixed plastic-heat system is approximately -0.1
cents/lb of plastics processed, credits based on
current market values being used. This again indicated
that further research is required for determining
profitability.
Waste Plastic/Air (Oxygen) Processes
The second method studied for waste plastics
utilization proposes reacting (combusting) the
specified plastics with oxygen (air). Presented in this
section are the results of analyses performed for the
four waste plastic/oxygen (air) systems. Specifically,
the waste plastics treated are polystyrene,
polyethylene, polyvinyl chloride, and a mixture of
equal portions of all three. The economics for each
system of waste plastic disposal will now be
discussed.
Polystyrene /Air and Polyethylene/Air Systems.
The proposed process for reacting polystyrene or
polyethylene with air is based on controlled
combustion of the plastic in an air (oxygen)
environment. Once combustion is initiated, the
reaction is perpetuated by continuous addition of
plastic.
Economic analysis of the polystyrene/air and
polyethylene/air systems indicates that a plant
designed to process 12.5 million Ib of scrap
polystyrene or polyethylene per year would yield
about 1.5 million Btu of recoverable heat per hour.
18
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The process cost summary for either a polystyrene/air
or polyethylene/air system (Table 13) indicates that
the relatively small amount of heat liberated by either
system would probably not justify the purchase of
process equipment to make use of it to produce
steam. The alternative to steam production would be
to consider the polystyrene or polyethylene to be a
general fuel, fit for burning as a source of heat with a
process value of $0.25 per million Btu. Contingencies
and contractor's fee were included in the installed
boiler unit cost.
Polyvinyl Chloride/Air and Mixed Plastics/Air
Systems. The polyvinyl chloride/air and mixed
plastics/air systems were considered together since
the combustion products of the two systems are
nearly identical and require the same process for
recovering usable process heat and valuable hydrogen
chloride.
The proposed process for reacting polyvinyl
chloride or mixed plastics with air was based on
controlled combustion of the plastic in air to yield
hydrogen chloride (Figure 38).
Air and chlorinated waste plastics are fed to the
semicontinuous stainless steel reactor, where
combustion is accomplished at a constant
temperature of 930 C for the polyvinyl chloride/air
system and 1,600 C for the mixed plastics/air system.
Both systems are exothermic and self-perpetuating.
From this point in the process, the steps taken to
recover the hydrogen chloride are the same as those
described in the economic analysis of the process for
thermal degradation of polyvinyl chloride. After
leaving the reactor, the gaseous reaction products are
sent to the scrubbing system which is capable of
removing 99 percent of the hydrogen chloride
contained in the reactor effluent. The scrubber
process allows recovery of the hydrogen chloride
either as acid, at 18 Baume, or, with the aid of a
simple stripping system, as anhydrous hydrogen
chloride.
The installed process equipment cost and hourly
operating costs, including contingencies and
contractor's fee, were summarized (Table 14) for a
plant designed to process yearly 12.5 million Ib of
scrap polyvinyl chloride or a blend of equal portions
of polystyrene, polyethylene, and polyvinyl chloride.
The gross cost-price differential per pound of
polyvinyl chloride reacted is 0.7 cents/(credit).
Waste Plastic/Water Processes
The third coreactant system investigated in this
analysis involves the use of water (steam) as a heat
carrier in the thermal degradation of the waste
plastics. The chemical reaction analyses for the waste
plastic/water systems without catalysts produced
results similar to those of the waste plastic/nitrogen
systems in that the distributions of reactor products
were essentially the same. Since water has a larger
heat capacity than nitrogen has, the volume of steam
required in each system is significantly less than the
amount of nitrogen required for the waste
plastic/nitrogen reaction systems. This property of
water (steam) results in the size reduction of some
process equipment and hence reduces the overall
process cost. The results of economic analyses
completed for each of the four waste plastic/water
coreactant systems are now discussed.
Polystyrene/Water. This process proposes the
direct substitution of water (steam) for nitrogen in
the polystyrene/nitrogen process (Figure 34).
Low-pressure steam is fed to the direct fired heater
(furnace), where its temperature is raised to 1,230 C.
The steam is then fed to the reactor in the same
manner as nitrogen is fed in the polystyrene/nitrogen
process already described.
With the steam for nitrogen substitution, this
process is analogous to the rest of the process for
polystyrene/nitrogen. The installed process
equipment cost and hourly operating costs for a plant
designed to process 12.5 million Ib of waste
polystyrene per year (1,580 Ib/hr), including
19
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contingencies and contractor's fee, were summarized
(Table 15). The gross cost-price differential was
found to be 6.1 cents/lb of feed.
Polyethylene/Water. The proposed process for
reacting polyethylene with water again involves the
substitution of steam for nitrogen (Figure 35). The
remarks in the previous section concerning the
preparation of steam also apply here. The process
costs were summarized (Table 16), and the byproduct
credits are reflected in the cost-price differential of
-0.6 cents/lb of feed.
Polyvinyl Chloride I Water, The substitution of
steam for nitrogen in the degradation of plastic is
again the essence of this proposed process. Steam is
preheated and sent to the reactor in the same manner
as described for the polystyrene/water system.
Since the reaction products for this process are
essentially the same as those for the polyvinyl
chloride/nitrogen system (Figure 36), the reactor
effluent is treated in exactly the same manner. The
process cost summary was seen to vary only slightly,
owing to the similarities of the two processes (Table
17).
Mixed Plastics/Water. This process is again
analogous to its mixed plastics/nitrogen counterpart.
Low-pressure steam is sent through the direct fired
heater (furnace) and heated to 1,230 C prior to being
sent to the reactor. The reactor effluent would not be
first cooled by the incoming nitrogen, but the rest of
the process is the same as the process to decompose a
mixture of waste plastics with hot nitrogen, as
already described (Figure 37). The economic analysis
indicated that the gross cost-price differential for this
proposed process would be 0.3 cents/lb of feed
(Table 18).
6. CONCLUSIONS AND RECOMMENDATIONS
The present study has successfully demonstrated
the value of computer-based simulation and analysis
of proposed chemical processes. The information
resulting from the analyses provides HEW
management with an evaluation of a large number of
chemical process concepts for the use of waste
plastics as raw materials for the production of
commercially valuable process chemicals. In addition
to these direct results, the project has also provided
information applicable to other related process
techniques that might be applied to waste disposal as
well as to the assessment of potential air pollution
problems resulting from the incineration of waste
plastic materials.
The chemical process development technique was
used to analyze 18 separate concepts for the use of
various plastics as raw materials in the production of
commercially valuable process chemicals. The various
stages of the analysis have provided the information
required for narrowing the concepts to those that
should be continued into the laboratory development
phase of the chemical process development technique
as follows: polystyrene-thermal decomposition,
polyvinyl chloride-thermal decomposition, mixed
plastics-thermal decomposition, and mixed
plastics-combustion with air. The individual
characteristics of the various systems to be examined
in the laboratory development phase are now
presented.
The polystyrene-thermal decomposition system
produces styrene by using an inert gas as a heat
source. The particular information required from the
laboratory is related to the design of an efficient
reactor system capable of volatilizing a maximum
amount of the plastic materials. Process variables to
be examined include initial solid particle size, heating
gas temperature-volume tradeoffs, heating gas duct
locations, reactor design, solid residence times,
heating gas (the direct use of combustion products in
place of nitrogen or steam reduces the costs
considerably), and separation of styrene from the
heating gas.
The polyvinyl chloride-thermal decomposition
system produces a hydrocarbon mixture and
hydrogen chloride. The parameters to be examined
-------
include those listed already, plus the identification of
reactor conditions leading to a more desirable
hydrocarbon mixture. The separation of the various
components of the reactor effluent stream must also
be examined in detail.
The mixed plastic-thermal decomposition system
eliminates a major economic shortcoming of the first
two separate processes in that it does not require a
prereaction separation of the plastic materials. The
laboratory development, however, is more complex
since it would require the examination of both the
individual systems and the mixed system. The depth
of the examination of the individual systems would
be less than that required for the first two. The
information described earlier would still be required
for the mixed system, but the individual system
examinations would limit the regions examined.
The mixed plastics combustion with air system is
essentially a chemical processing approach to a
commonly used waste disposal technique. The
laboratory development would be primarily
concerned with the design and testing of efficient
combusters and with the separation of the effluent
hydrogen chloride from the combustion products.
This system is of particular importance since it has
been indicated throughout the analysis that specific
measures are required to prevent hydrogen chloride
pollution resulting from the incineration of polyvinyl
chloride and other chlorinated organics.
The contract effort provides, in addition to the
laboratory development recommendations already
mentioned, a more general set of chemical
engineering guidelines applicable to the scope of
research and development programs related to waste
disposal. The approach used in this study has
identified materials that appear to have little or no
value in the gas phase reaction of
organic-chemical-based waste systems. These
coreactants, hydrogen chloride and ammonia, should
be considered for further research and development
effort only where specific reaction technology is
previously known. It has further been demonstrated
that chlorine gas is highly nonselective in reactions
with mixed organic systems while, of course, it still
has great value in individual process systems. The lack
of selectivity greatly limits its value for using waste in
the production of marketable organic chlorides. The
contract effort has also indicated that future R&D
efforts relative to incineration should be concerned
both with the design of efficient combustion
reactions and with the recovery of valuable and
noxious combustion effluents such as hydrogen
chloride from chlorocarbons and hydrogen fluoride
from fluorocarbons. Finally, the economic analyses
have consistently indicated that labor is an important
cost factor in both the utilization and the disposal by
combustion of waste materials. The labor costs and
capital costs per pound of product would be reduced
significantly in large plant sizes. This indicates that
strong consideration should be given to the
establishment of a network of regional waste
treatment plants not only for economic reasons but
also for prevention of a considerable pollution
problem.
The use of waste materials for the production of
process chemicals has demonstrated both economic
and technical feasibility under appropriate conditions
(partial or complete separation and large plant size).
Further R&D efforts in this general area should
concentrate on the further examination of the waste
plastics systems that appear promising and on the
technical-economic analysis of concepts related to
other specific waste constituents such as cellulosics.
Simultaneously, concepts involving stage-by-stage
preprocessing and separation techniques should also
be examined.
21
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July 1960.
Valko, L. Kinetic study of thermal dehydrochlorination of poly(vinyl chloride)
in the presence of oxygen. Part II. Correlations of derived equations with
experimental results. Journal of Polymer Science, Part C: Polymer
Symposia, No. 16(Part l):545-554, 1967.
Venn, R. G. A. Physical degradation of polyethylene due to oxidation. Plastics
Institute, Transactions and Journal, 35(118):601-605, Aug. 1967.
Vidotto, G. A. Crosato-Arnaldi, and G. Talamini. Determination of transfer to
monomer in the vinyl chloride polymerization. Makromolekulare Chemie,
114:217-225, May 1968.
Wall, L. A., and J. H. Flynn. Degradation of polymers. Rubber Chemistry and
Technology. 35:1157-1221, 1962.
Wall, L. A. Polymer decomposition. Part 1. Thermodynamics, mechanisms, and
energetics. Part 2. Energetics of polymer decompositions. SPE [Society of
Plastics Engineers] Journal, 16(8):810-814, Aug. 1960; 16(9):1031-1035,
Sept. 1960.
Wall, L. A., S. Straus, J. H. Flynn, D. Mclntyre, and R. Simha. The thermal
degradation mechanisms of polystyrene. Journal of Physical Chemistry,
70(l):53-62, Jan. 1966.
Williams, J. L., and K. J. Cleereman. The general physical properties of
polystyrene. In Boundy, R. H., and R. F. Boyer, eds. Styrene. Its
polymers, copolymers and derivatives. New York, Reinhold Publishing
Corporation, 1952. (American Chemical Society Monograph Series), p.
448-516.
Wunderlich, B., and C. M. Cormier. Heat of fusion of polyethylene. Journal of
Polymer Science, Part A-2: Polymer Physics, 5(5):987-988, Sept. 1967.
28
-------
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o -i- -i-
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c o >>
-C S=i—
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29
-------
Initially
Considered
Thermochemical
Equilibrium
Results
Reaction
Kinetic
Results
Preliminary
Design and
Economi c
Results
Polystyrene
Polyethylene
Polyvinyl Chloride
Hydrogen Chloride, Air, Chlorine, Ammonia, Water, Heat
CHEMICAL SYSTEMS REMAINING
Polystyrene
Polyethylene
Polyvinyl Chloride
Air Chlorine Water Heat
Polystyrene
CHEMICAL SYSTEMS REMAINING
Polyethylene
Polyvinyl Chloride
Air
System
Polyvinyl chloride - Air
Polystyrene - Heat
Polyvinyl Chloride - Heat
Heat
(Steam or
Carrier)
Product
Heat - HC1
Styrene monomer
HC1 - Hydrocarbon
Recommended
For
Laboratory
Development
Mixed Plastics - Air
Polystyrene - Heat
Polyvinyl Chloride - Heat
Mixed Plastics - Heat
to give HC1 and Heat
to give Styrene
to give HC1 - Hydrocarbon Mixture
to give HC1, Styrene and Hydrocarbons
Figure 2. Technical-economic analysis for plastic/coreactant
chemical processes. The analysis effort converges on those processes
demonstrating both technical and economic feasibility for laboratory
investigation.
30
-------
rnase l
\
Selected Plastics /
and Reactants /
Pha
Thermoc
Ana
AReac
Prod
X
se I >^Polli
hemical , S c™n,
lysis
\hermochemically Feasible/
Reaction Paths /
Phas
Inte
Re pc
^
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e I
rim
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iew ^x^
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Paths /
^Cnt<
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\
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emical Kinetic /
Model /
Pros±in9 y
Chemical Kinetic
Analysis
\Kinetically Feasible /
Systems /
\Eco
D
nomi c /
ata /
\Economic Description /
Laboratory Criteria /
Final
Report
y^
Figure 3. Project flow diagram. Step-by-step diagram of the
approach applied to this study.
31
-------
Polyethylene
Polystyrene
Polyvinyl Chloride
C,
6 6
CH,
C6H6
ri^r
c. DO
HC1
C6H6
C2H2
Figure 4. Thermal decomposition: major products analysis.
species favored depend on the plastic's carbon-hydrogen ratio.
Product
32
-------
Polyethylene
HC1
- HC1
Polystyrene
Polyvinyl Chloride
C6H6
CH,
HC1
C6H6
^^ H,-
c. bo
C2H2
HC1
-C6H6
£.r-
00
C2H2
Figure 5. Hydrogen chloride: major product analysis. The addition
of hydrogen chloride to the plastics system does not lead to the formation
of chlorinated addition products under the conditions examined.
33
-------
Polyethylene
NH.
Polystyrene
Polyvinyl Chloride
CH,
C6H6
CH,
C6H6
HC1
CH
Figure 6. Ammonia: major product analysis. Ammonia is decomposed to
nitrogen and hydrogen under the equilibrium conditions examined.
34
-------
Polyethylene
H20
Polystyrene
H,
CO
CO,
CO
CH
co
Polyvinyl Chloride
HC1
H2
CH4
CO
COo
Figure 7. Water: major product analysis. Under the reaction
conditions examined, the major products of the reactions between the
plastics and water included no oxyorganic compounds.
35
-------
'CO
Polyethylene
Air
Polystyrene
Polyvinyl Chloride
'CO,
>H2°
'HCN
'CO
• CO,
L
.Ho
•HCN
•HC1
•CO
-C0
•HCN
Figure 8. Air: major product analysis. As was the case with
water, no oxyorganfc compounds were favored under the conditions examined.
36
-------
Polyethylene
Cl.
Polystyrene
Polyvinyl Chloride
HC1
CH,
C6H6
cci2cci2
HC1
C6H6
cci2cci2
CC1
Figure 9. Chlorine: major product analysis. Under the equilibrium
conditions examined, the plastics/chlorine systems favored the formation
of various chlorinated organic compounds.
37
-------
J
LU
1—
oo
oo
u_
0
oc
LU
LU
LU
LU
DC
u_
LU
I — i
| —
_J
POLYSTYRENE POLYETHYLENE POLYVINYL C
-(CHCHo)- -(CH0CH0)- -(CHC1CH7)-
• z n 1 Z -n i^n
C6H5
CH3C6H5
trans CH3CHCHC6H5
cis CH3CHCHC6H5
OirtflO Liriotj^iH/ drlCjiio
•mc.4-f\ PU |° T4 PUPT4
iiic L d Vjn.o^/-n/ 'onL'n.r)
J Q t|. ^
„._„._ PTJ P 13 PTJ PT4
L/ciLcl V^ilnL//:!!/ LfilLirlo
i O A ^
Cl
pri ptr , upl
L«rl_L»rirt / nU-L
CH3CH2CH3 | C2H5C6H5
CH3C6H5
CU C1 U UP 1
on.[-L//-n[- rivfj.
ortho CH3C6H4CH3 CH3C6H5
meta CH3C6H4CH3 CHC1CC12
para CH3C6H4CH3 CC12CC12
( C6H6 ( CH4 ( C6H6
) CHoCHCcHc I Cf,R{. 1 HC1
LU
Figure 10. Feasible reaction path species, thermal decomposition,
773 K, 1 atm. The compounds in the higher relative free-energy ranges
are found in significant quantities at equilibrium only when the lower
energy products are deleted from consideration. (Polystyrene at
1,073 K in place of 773 K.)
38
-------
I
SYSTEM
u_
o
s
LU
•z.
LU
LU
LU
Lu
LU
I — i
1—
t
_J
LU
POLYSTYRENE POLYETHYLENE POLYVINYL CHLORIDE
-(CHCH2)- -(CH2CH2)- - CHCH2 -
CH2CHC6H5
CH3C6H5
CH4
CO
co2
C6H6
CH2CHCH3
CH3COCH3
CH3CHO
323
C2H5C6H5
CH0C.~Hr
Job
ortho CH3CgH4CH3
1
ortho CH3CgH4CH3
meta CH.,CgH4CH3
para CH3CgH4CH3
ortho CH3CgH4CHCH2
meta CnnC,-n.CHCHp
para CH3CgH4CHCH2
CH3CHO
HC1
~« 4. -, f*U C 14 PU
meia on.-)"/-n/ion->
JUT- J
para CH3CgH4CH3
CH4
CH3C6H5
CHpCrlC/-H|-
HC1
CO
co2
C6H6
H2
CO
co2
CH4
C6H6
wn
Figure 11. Feasible reaction path species, air, 773 K, 1 atm, 70
percent plastic material. Deletion of the normal combustion products
from consideration leads to product distributions similar to those from
thermal decomposition. Deletion of these compounds gives some oxyorganic
products.
39
-------
POLYSTYRENE
-(CHCH2)F
POLYETHYLENE
—(CH2CH2)—
POLYVINYL CHLORIDE
Cl
' SYSTEM
u_
O
>-
CD
QL
UJ
•z.
UJ
UJ
UJ
o:
u.
UJ
>
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1—
«=C
UJ
C£.
CHC1CHC12 '
CH3C6H5
(
\
C5H8
CH2CHCHCH2 CH2CHCgH5
C2H4
CH9CHCH9CHCH?
£_!-•-.
CHC12CHC12
CH3C6H5
CHpCHC/-Hr
C6H6
cci2cci2
HC1
CH3CH3 <
CHoCHo^n-
323
PU P U
CH3C6H5
(isomers) C9H9C'
C, L.
CH0CcHr:
o b o
CHC12CHC12
ortho CH3C6H4CH
meta CH-X.H.CH.,
OUT1 %3
para CH3CgH4CH3
C6H6
CH,
H2
HC1
HC1
C6H6
cci2cci2
CHA
Figure 12. Feasible reaction path species, chlorine, 773 K, 1 atm,
70 percent plastic material. Many different chlorinated products are
favored following the deletion of the lowest energy products.
40
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46
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53
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WASTE
PLASTICS
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UNREACTED WASTE PLASTIC
Figure 26. Semlcontinuous waste plastics reactor. The dimensions
specific to each of the plastic systems are given in Table 3.
54
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57
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WASTE
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Figure 30. Semicontinuous waste plastics reactor. Thermal
decomposition of mixed plastics system.
58
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OXIDATION PRODUCTS
TO A HEAT EXCHANGER
WASTE
PLASTICS
AIR
Figure 33. Waste plastic combustion reactor. Solid plastics are
burned with air for the production of heat energy.
61
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TABLE 1
POLYETHYLENE THERMAL DECOMPOSITION (710 K REACTOR
TEMPERATURE, 3,000-sec RESIDENCE TIME, 1.0 g/sec
POLYETHYLENE FEED)
COMPONENT
C2H4
C2H6
C3H4
C3H6
C3H8
C4H8
C4H10
C5H8
C5Hi0
C5Hl2
C6H10
C6H12
C6Hl4
C7H14
C7Hi6
j'1N2 ~ 1'500
N2 } T = 1,000 K
(10+2) g/sec
1.8
5.5
0.15
3.25
9.60
19.90
15.85
0.35
7.65
6.40
0.40
3.95
1.65
0.30
0.60
191.00
520.40
Unreacted polyethylene
22.65
67
-------
TABLE 2
POLYVINYL CHLORIDE THERMAL DECOMPOSITION (723 K REACTOR
TEMPERATURE, 255-sec RESIDENCE TIME, 1 g/sec POLYVINYL
CHLORIDE)
COMPONENT
HC1
C2H4
C2H6
C3H6
C3H8
C4Hg
C4H10
C5H10
C5Hl2
C6H6
C6H12
C6H14
C7Hg
C8H8
C2H4C12
H2
CH4
fT = 1,500 K
3 2
N2 )
IT = 1,000 K
V 2
Unreacted polyvinyl chloride
(10+2) g/sec
51.00
7.18
3.71
1.28
1.97
4.16
2.12
3.63
1.13
5.67
0.83
0.91
3.02
1.29
1.44
0.23
1.44
127.62
344.90
9.00
68
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TABLE 4
NITROGEN EFFECT ON STYRENE-CHLORINE
REACTION-SECOND REACTOR (900 K REACTOR TEMPERATURE,
1.25 atme, 0.68 g/sec CHLORINE FEED, 1.00 g/sec
STYRENE FEED, 25 sec RESIDENCE TIME)
Species
C12
HC1
0 g/sec N2
(g/sec)
0.023
0.098
1.66 g/sec
(g/sec)
0.211
0.073
N2
CH=CH,
CHC1CH Cl
0.207
0.866
0.397
0.664
(o,m,
CH=CH
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y Cl 0.348
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s/
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70
-------
TABLE 5
AMOUNT OF INDICATED HEAT SOURCE*
NECESSARY FOR THE SPECIFIED CONVERSION
Polystyrene,
Converted
823 K
(%) 55
50
25
Nitrogen
(g)
9.35
9.13
7.96
Steam
(g)
4.47
4.38
3.82
Polyvinyl Chloride, 673 K
Converted
Polyethylene
ADP 822
Converted
(%) 90
75
50
, 685 K
(%) 75
50
1.14
1.04
1.00
1.75
1.51
0.58
0.55
0.53
0.86
0.74
* 1,500 K heat source temperature, 1 g plastic.
71
-------
TABLE 6
MIXTURE REACTION PRODUCTS AT 700 K AND 4,400 sec SOLID
RESIDENCE TIME. BASIS: 1 g OF MIXTURE, WITH EQUAL
PARTS (BY WEIGHT) OF POLYVINYL CHLORIDE, POLYETHYLENE,
AND POLYSTYRENE.
Product
CH4
C2H4
C2H6
C3H4
C3H6
C3H8
C4H8
C4H10
C5H8
C5H10
C5H12
g (xlO3)
1.00
32.73
31.35
0.49
14.99
37.79
78.68
58.39
1.22
37.96
24.77
Polyvinyl chloride 14.56
Polystyrene 298.52
Polyethylene 88.17
Product
C.H
6 6
C6H10
C6H12
C6H14
C7H8
C7H14
C7H16
C8H8
C2HC12
H2
HC1
Steam (1,500
g (xlO3)
21.40
1.23
15.64
8.71
11.42
0.98
1.96
39.47
5.52
0.99
175.92
K)
Required 1045.30
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TABLE 8
WASTE PLASTICS/AIR ADIABATIC REACTOR*
Mixture (Equal
Products Polyvinyl Parts by Weight
(g) Chloride Polyethylene Polystyrene of the three)
C02 1.41 3.06
CO traces 0.06
H20 0.30 1.27
N2 12.00 13.19
NO traces 0.06
02 2.12 0.34
HC1 0.55
C12 0.04
Others traces 0.02
Temperature
out of 1,200 K 2,130 K
reactor
Weight of
Air input 15.40 16.99
3.19 2.69
0.08 < 0.01
0.66 0.77
11.74 12.85
0.06 0.05
0.34 0.01
0.18
traces
0.02 0.01
2,200 K 1,870 K
15.10 16.55
* All data based on 1 g of plastic.
74
-------
TABLE 9
PROCESS COST SUMMARY. POLYSTYRENE DECOMPOSITION
WITH NITROGEN AS A HEAT CARRIER. INSTALLED UNIT
COST: $219,000
Summary $/hr
Utilities 0.90
Raw materials 1.40
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 5.50
Total 17.30
Waste polystyrene-processing 1.1 C/lb feed
cost
Product credit:
styrene 7.2 £/lb feed
Net credit 6.1 C/lb feed
75
-------
TABLE 10
PROCESS COST SUMMARY: POLYETHYLENE DECOMPOSITION
WITH NITROGEN AS A HEAT CARRIER. INSTALLED UNIT
COST: $199,000
Summary $/hr
Utilities 1.50
Raw materials 5.30
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 5.05
Total 21.35
Waste polyethylene-
processing cost 1.8 C/lb feed
Product credits:
Gasoline stream and
fuel gas 0.5 £/lb feed
Net expense 1.3 C/lb feed
76
-------
TABLE 11
PROCESS COST SUMMARY: POLYVINYL CHLORIDE
DECOMPOSITION WITH NITROGEN AS A HEAT SOURCE.
INSTALLATION UNIT COST: $464,000.
Summary $/hr
Utilities 7.80
Raw materials 19.70
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 11 70
Total 48.70
Waste polyvinyl chloride-
processing cost 3.1 C/lb feed
Product credits:
organic stream and HCl acid 3.1 £/lb feed
Net expense 0 C/lb feed
77
-------
TABLE 12
PROCESS COST SUMMARY: MIXED PLASTICS DECOMPOSITION
WITH NITROGEN AS A HEAT CARRIER. INSTALLED UNIT
COST: $307,000
Summary $/hr
Utilities 3.35
Raw materials 7.90
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 7.75
Total 28.50
Waste mixed plastics-
processing cost 1.8 £/lb feed
Product credits:
styrene, HCl acid, gasoline
stream 1.7 C/lb feed
New expense 0.1 £/lb feed
78
-------
TABLE 13
PROCESS COST SUMMARY: COMBUSTION WITH AIR OF
POLYSTYRENE OR POLYETHYLENE WASTE. INSTALLED
BOILER UNIT: $13,000
Summary $/hr
Utilities* (0.40)
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 0.35
Total 9.45
Waste polystyrene or
polyethylene disposal cost 0.6 £/lb feed
*Includes credit for process heat generated.
79
-------
TABLE 14
PROCESS COST SUMMARY: COMBUSTION WITH AIR OF
POLYVINYL CHLORIDE OR MIXED PLASTICS SYSTEM.
INSTALLED PLANT COST: $395,000.
Summary
$/hr
Utilities and raw materials
Labor with 100% overhead
Depreciation, maintenance,
taxes, etc. (20% of
capital annually)
Chlorinated plastic-
processing cost
Product credit:
hydrochloric acid
Net credit
Total
18.00
9.50
9.85
37.35
2.4 C/lb feed
3.1 C/lb PVC feed
0.7 C/lb feed*
*Calculated on the basis of pure PVC feed.
80
-------
TABLE 15
PROCESS COST SUMMARY: POLYSTYRENE DECOMPOSITION
WITH STEAM AS A HEAT CARRIER. INSTALLED UNIT
COST $183,000.
Summary $/hr
Utilities 2.20
Raw materials 1.40
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 4.60
Total 17.70
Waste polystyrene-processing
cost 1.1 C/lb feed
Product credit:
styrene 7.2 <=/lb feed
Net credit 6.1 C/lb feed
81
-------
TABLE 16
PROCESS COST SUMMARY: POLYETHYLENE DECOMPOSITION
WITH STEAM AS A HEAT CARRIER. INSTALLED UNIT
COST $151,000.
Summary $/hr
Utilities 2.50
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 3.80
Total 15.80
Waste polyethylene-processing
cost 1.0 «/lb feed
Product credits:
gasoline stream and fuel
gas 0.4 £/lb feed
Net expense 0.6 £/lb feed
82
-------
TABLE 17
PROCESS COST SUMMARY: POLYVINYL CHLORIDE
DECOMPOSITION WITH STEAM AS A HEAT CARRIER.
INSTALLED UNIT COST: $436,000.
Summary $/hr
Utilities 7.80
Raw materials 7.20
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 11. 00
Total 35.50
Waste polyvinyl chloride-
processing cost 2.3 C/lb feed
Product credits:
organic stream and HC1
acid 3.1 C/lb feed
Net credit 0.8 $/lb feed
83
-------
TABLE 18
PROCESS COST SUMMARY: MIXED PLASTICS
DECOMPOSITION WITH STEAM AS A HEAT CARRIER.
INSTALLED UNIT COST: $282,000.
Summary $/hr
Utilities 3.65
Raw materials 1.40
Labor with 100% overhead 9.50
Depreciation, maintenance,
taxes, etc. (20% of
capital annually) 7.15
Total 21.70
Waste plastic disposal cost 1.4 <=/lb
Product credits:
styrene 0.3
HC1 (18 B) 1.0
gasoline stream 0.4
Total 1.7 £/lb feed
Waste plastic-processing cost 1.4 C/lb feed
Product credits:
styrene, HCl acid, gasoline
stream 1.7 C/lb feed
Net- credit 0.3 C/lb feed
84
-------
APPENDIX A
EQUILIBRIUM PRODUCT DISTRIBUTION
The quantities presented in this appendix represent the results of the
equilibrium product distributions and analyses described in chapter 3. The values
tabulated are the moles of each particular product per unit monomer of plastic.
The values are presented as a function of temperature, pressure, and initial
composition (weight percent polymer in the reacting system).
The tabular form used is convenient for the preparation of plots, as is
illustrated in Figure 39, where methane production is presented as a function of
temperature for the polyethylene decomposition. The data format used in the
tables is an exponential form, i.e., X.XX-Y is equivalent to X.XXX * 10~\ Zero
indicates a number of moles less than 1 * 10" . A complete list of the species
considered in the equilibrium analysis is included in this appendix.
85
-------
86
-------
TABLE 19
POLYETHYLENE DECOMPOSITION. COMPOSITION AS A FUNCTION OF
TEMPERATURE, PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
100
T (C) psia
2,400 1,000
14.7
2,000 1,000
14.7
1,600 1,000
14.7
1,200 1.000
14.7
800 1,000
14.7
500 1,000
14.7
C6H6
0
0
0
0
0
0
1.90-1
2.62-1
1.66-1
2.32-1
1.29-1
2.04-1
C2H4
1.19-2
1.64-4
4.44-2
7.88-4
1.62-1
6.32-3
2.08-2
1.73-2
1.83-2
2.88-3
0
0
CH4
1.95-2
2.86-4
8.01-2
1.50-3
2.86-1
1.45-2
4.84-1
1.56-1
6.72-1
5.32-1
6.27-1
6.51-1
CH2CH
C6H5
9.53-1
1.01
8.29-1
9.97-1
4.06-1
9.70-1
9.70-1
7.44-1
3.22-2
1.92-1
1.85-3
1.20-2
87
-------
TABLE 20
POLYETHYLENE/NH3 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C) psia
1,200 1,
14
70 800 1,
14
500 1,
14
1,200 1,
14
50 800 1,
14
500 1,
14
1,200 1,
000
.696
000
.696
000
.696
000
.696
000
.696
000
.696
000
14.696
20 800 1,
000
14.696
500 1,
000
14.696
CH
9.
2.
1.
1.
1.
1.
1.
4.
1.
1.
1.
1.
1,
9,
2.
2.
2.
2.
4
81-1
90-1
30
07
34
35
57
42-1
98
71
99
99
99
63-1
01
01
01
,01
C6H6
1.23-1
2.08-1
8.65-2
1.46-1
6.53-2
9.95-2
3.93-2
1.56-1
0
4.29-2
0
0
0
2.58-2
0
0
0
0
H2
5.
1.
7.
4.
4.
2.
1.
2.
4.
05-
59
91-
45-
1
2
1
65-3
92-
03
75
69-
2
1
8.87-1
4.
4.
7.
9.
7.
7.
6.
7.
36-1
69-1
93
44
80
91
90
,90
88
-------
TABLE 21
POLYETHYLENE/HoO COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C)
1,200
70 800
500
1,200
800
50
500
1,200
800
20
500
psia
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
CH4
9.16-1
2.57-1
1.24-1
9.95-1
1.22
1.29-1
5.09
2.63-1
1.19
4.69-1
1.47
1.30
9.63-3
0
7.32-1
2.24-3
1.40
8.24
CO
6.64-1
6.65-1
6.18-1
6.65-1
1.33-1
5.70-1
1.46
1.55
4.82
1.51
1.62-2
1.72-1
1.50
1.50
4.67-1
1.14
9.95-3
1.31-1
co2
3.61-4
0
2.25-2
0
2.66-1
4.80-2
2.46-2
0
3.15-1
1.03-2
5.07-1
5.18-1
5.06-1
5.05-1
8.09-1
8.64-1
6.02-1
1.05
H2
5.76-1
1.59-1
8.43-2
4.96-1
4.50-3
3.63-2
2.46
2.91
7.25-1
2.59
8.62-2
5.91-1
4.49
4.52
2.62
4.88
4.31-1
2.59
89
-------
TABLE 22
POLYETHYLENE/AIR COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C) psia CH4 CO C02 H2
HCN
1,200 1,000 5.04-1 1.75-1 0 2.83-1 1.93-2
14.696 1.43-1 1.74-1 0 8.51-1 8.36-2
800 1,000 6.74-1 1.72-1 1.24-3 4.28-2 5.07-4
70 14.696 5.55-1 1.74-1 0 2.44-1 2.24-3
500 1,000 6.75 6.61-2 5.41-2 2.37-3 0
14.696 7.07-1 1.69-1 2.84-3 1.59-2 0
1,200 1,000 5.33-1 4.06-1 0 3.58-1 3.24
14.696 1.34-1 4.06-1 0 9.83-1 1.40-1
800 1,000 7.45-1 3.97-1 4.62-3 5.66-2 8.47-4
50 14.696 5.89-1 4.08-1 0 3.11-1 3.74-3
500 1,000 7.28-1 1.27-1 1.39-1 3.00-3 0
14.696 7.79-1 3.85-1 1.05-2 2.09-2 0
1,200 1,000 3.54-1 1.62 3.43-3 6.62-3 -1.83-2
14.696 7.64-2 1.64 0 0 1.79-1
800 1,000 7.32-1 1.01 2.61-1 1.04-1 0
20 14.696 3.70-1 1.64 1.90-3 1.35-3 1.62-3
500 1,000 9.89-1 3.21-1 6.59-1 3.14-3 0
14.696 8.78-1 6.53-1 4.77-1 3.17-2 0
90
-------
TABLE 23
POLYETHYLENE/C12 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
70
50
20
T (C) psia
1,200 1,000
14.696
800 1,000
14.696
500 1,000
14.696
1,200 1,000
14.696
800 1,000
14.696
500 1,000
14.696
1,200 1,000
14.696
800 1,000
14.696
500 1,000
14.696
CH4
3.84-1
1.14-1
5.08-1
4.26-1
5.16-1
4.77-1
2.61-1
6.76-2
3.63-1
2.93-1
3.69-1
3.89-1
C H
2 6
2.77-1
1.14-1
2.64-1
2.68-1
2.69-1
2.69-1
C6H6
2.09-1
2.67-1
1.87-1
2.50-1
1.50-1
2.23-1
2.34-1
2.72-1
2.16-1
2.72-1
1.80-1
2.50-1
CC1 CC1
2 2
0
0
1.87-1
1.90-1
1.82-1
1.90-1
HC1
3.37-1
3.38-1
3.37-1
3.38-1
3.37-1
3.38-1
7.86-1
7.88-1
7.86-1
7.87-1
7.86-1
7.89-1
HC1
2.21
3.06
2.39
2.39
2.39
2.39
91
-------
TABLE 24
POLYSTYRENE DECOMPOSITION, COMPOSITION AS A FUNCTION OF
TEMPERATURE, PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
100
T(C)
1,200
800
500
psia
1,000
14.7
1,000
14.7
1,000
C2H2
8.98-3
1.62-1
0
3.36-4
0
C6H6
1.19
1.25
1.29
1.32
1.33
C"^ H f\ CHC*/-
1.03-1
2.59-2
3.10-2
7.81-3
5.18-3
H5
92
-------
TABLE 25
POLYSTYRENE/NH3 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
70
50
20
T (C) psia
1,200 1,000
14.7
800 1,000
14.7
500 1,000
14.7
1,200 1,000
14.7
800 1,000
14.7
500 1,000
14.7
1,200 1,000
14.7
800 1,000
14.7
500 1,000
14.7
CH4
1.85
5.43-1
2.44
2.04
2.49
2.57
4.27
1.19
5.78
4.67
6.03
6.01
7.96
3.48
8.08
8.08
8.09
8.08
C6H6
7.88-1
1.00-1
7.02
9.48-1
5.58-1
8.37-1
4.41-1
7.68-1
2.79-1
5.26-1
2.06-1
3.07-1
0
1.59-1
0
0
0
0
H2
9.82-1
3.05
1.46-1
8.49-1
8.44-3
5.46-2
2.51
7.25
3.92-1
2.14
2.32-2
1.45-1
2.50+1
3.17+1
2.46+1
2.50+1
2.18+1
2.49+1
93
-------
TABLE 26
POLYSTYRENE/H20 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C) psia
1,200 1,
14
70 800 1,
14
500 1,
1,200 1,
14
50 800 1,
14
500 1,
14
1,200 1,
14
20 800 1,
14
500 1,
000
.7
000
.7
000
000
.7
000
.7
000
.7
000
.7
000
.7
000
14.7
CH
1.
4.
2.
1.
2.
2.
8.
3.
2.
4.
4.
2.
0
2.
7.
4.
2.
4
70
67-1
30
87
05
27
25-1
94-1
24
84
43
88-2
47
13-3
71
84
CO
2.
2.
2.
2.
5.
5.
5.
2.
5.
5.
1.
5.
5.
1.
4.
4.
5.
co2
48
49
36
48
21-1
68
78
85
74
20-1
54
87
89
98
46
97-2
39-1
1
0
€
0
9
2
0
1
1
2
2
2
2
3
3
3
4
.25-3
.18
.82-1
.48-2
.20
.53-2
.62
.02
.20
.19
.64
.61
.32
.68
H2
1
2
1
8
7
5
7
1
5
3
7
1
1
8
1
1
8
.03
.97
.57-1
.92-1
.25-3
.16
.38
.36
.28
.45-2
.34-1
.42+1
.43+1
.38
.57+1
.29
.28
94
-------
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p^
rH
CTl
CM
rH
0
O
o
^
rH
O
o
in
^
i
in
,
rH
rH
1
0
r-H
rH
CM
1
CO
CTl
in
rH
rH
CTl
CM
m
in
m
CO
00
rH
p^
•
*^
rH
95
-------
TABLE 28
POLYSTYRENE/C12 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C)
1,200
70 800
500
1,200
50 800
500
1,200
20 800
500
psia
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
1,000
14.7
cci4
2.18-1
1.34-4
2.75-4
0
2.56-3
4.42-4
5.46-1
2.13-3
8.61-4
1.69-4
7.04-3
1.40-3
2.25-1
6.94-1
5.22-3
1.02-3
4.22-2
8.42-3
C6H6
1.16
1.25
1.24
1.26
1.26
1.26
1.12
7.45-1
1.14
1.17
1.16
1.17
8.81-1
2.82-3
6.70-1
6.83-1
6.84-1
6.83-1
CC12CC12
0
0
2.07-1
2.07-1
2.05-1
2.07-1
0
0
4.78-1
4.84-1
4.72-1
4.84-1
0
0
1.94
1.96
1.90
1.96
HC1
3.20-1
1.25
4.19-1
4.19-1
4.17-1
4.19-1
5.94-1
2.88
9.69-1
9.79-1
9.63-1
9.79
2.26
7.87
3.94
3.95
3.89
3.94
96
-------
TABLE 29
SYSTEM: POLYVINYL CHLORIDE DECOMPOSITION, COMPOSITION AS
A FUNCTION OF TEMPERATURE, PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W T (C) psia C2H2 C2H6 CH2CHCH5 HC1
1,200 1,000 5.82-3 3.08-1 1.69-2 9.98-1
14.7 9.88-2 2.95-1 3.84-3 1.00
100 800 1,000 0 3.25-1 4.90-3 1.00-0
14.7 2.12-4 3.31-1 1.23-3 9.98-1
500 1,000 0 3.31-1 8.13-4 9.98-1
14.7 0 3.33-1 2.01-4 9,98-1
97
-------
TABLE 30
SYSTEM: POLYVINYL CHLORIDE/NH3. EQUILIBRIUM COMPOSITION AS
A FUNCTION OF TEMPERATURE, PRESSURE, AND INITIAL COMPOSITION
(moles products/unit monomer)
Percent
polymer
W/W
70
50
20
T (C)
1,200
800
500
1,200
800
500
1,200
800
500
psia
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
CH4
1.052
2.691-1
1.443
1.154
1.553-1
1.541
1.911
5.735-1
1.999
1.985
2.000
2.000
1.982
1.172
2.000
1.999
2.000
2.000
H2
7.207-1
1.929
1.974-1
6.201-1
7.002-3
4.378-2
2.602
4.600
2.478
2.507
2.251
2.500
1.899+1
2.023+1
1.874+1
1.902+1
1.650+1
1.897+1
HC1
9.983-1
9.996-1
9.989-1
9.999-1
9.995-1
9.997-1
9.995-1
9.998-1
1.000
9.964-1
1.000
9.999-1
9.997-1
1.000
9.999-1
9.999-1
9.998-1
1.000
98
-------
TABLE 31
POLYVINYL CHLORIDE/H20 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
70
50
20
T (C)
1,200
800
500
1,200
800
500
1,200
800
500
psia
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
CH4
5.211-1
1.80-1
9.469-1
5.179-1
1.219
1.084
2.317-2
0
7.630-1
6.826-3
1.197
8.820-1
0
0
1.998-1
0
1.046
2.409-1
CO
1.465
1.486
7.60-1
1.478-1
9.448-2
4.702-1
1.710
1.738
5.569-1
1.516
1.576-2
1.701-1
9.569-1
9.574-1
4.382-1
5.606-1
1.218-2
1.185-1
H2
1.424
1.946
4.404-1
1.447
1.834-2
2.569-1
3.197
3.262
1.389
3.457
1.949-1
1.302
4.042
4.042
3.763
4.438-1
8.020-1
3.917
H20
1.158-2
0
1.502-1
2.643-3
2.563-2
6.206-2
1.226
1.208
1.553
9.982-1
1.879
1.403
1.083+1
1.083+1
1.072+1
1.044+1
1.198+1
1.048+1
HC1
9.996
9.998-1
9.996-1
9.997-1
9.996-1
1.000
9.998-1
1.000
1.000
9.997-1
1.000
1.000
9.999-1
9.999-1
1.000
9.999-1
9.999-1
1.000
99
-------
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cn
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cn
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100
-------
TABLE 33
POLYVINYL CHLORIDE/C12 COMPOSITION AS A FUNCTION OF TEMPERATURE,
PRESSURE, AND INITIAL COMPOSITION
Percent
polymer
W/W
70
50
20
T (C)
1,200
800
500
1,200
800
500
1,200
800
500
psia
1,000
14.696
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
1,000
14.696
CC14
1.31-1
2.02-3
0
3.50-3
7.34-4
3.18-1
1.81-2
1.01-3
0
8.18-3
1.63-3
1.32
1.01
4.32-1
1.95-1
5.24-1
5.18-1
C6H6
2.86-1
1.75-1
2.90-1
2.90-1
2.91-1
2.56-1
4.13-2
2.30-1
2.34-1
2.34-1
2.35-1
9.13-2
0
0
0
0
0
CC12CC12
0
0
1.23-1
1.18-1
1.25-1
0
0
2.84-1
2.88-1
2.78-1
2.88-1
0
0
7.83-1
9.02-1
7.33-1
7.40-1
HC1
1.13
1.71
1.25
1.25
1.25
1.32
2.57
1.58
1.58
1.58
1.58
2.32
2.97
3.00
3.00
2.99
3.00
101
-------
SPECIES CONSIDERED IN EQUILIBRIUM ANALYSIS
carbon
graphite
carbon charged +1
carbon charged +2
carbon charged -1
diatomic carbon charged +1
diatomic carbon charged -1
methyl ion +1
carbon monoxide charged +1
carbon dioxide charged +1
carbon dioxide charged -1
cyanide ion -1
carbon hydroxide ion +1
diatomic carbon
(C3) carbon, trimeric
(C4) carbon, tetratomic
(C5) carbon pentatomic
CCH radical
methylidyne
methylene
methyl
ethylene
acetylene
methane
ethylene oxide
carbon monoxide
carbon dioxide
CCO radical
carbon suboxide
cyano (CN)
CNN radical
NCN radical
cyanogen
carbon subnitride
carbon monochloride
carbon dichloride
carbon trichloride
carbon tetrachloride
CHC13
CH2C12
CH3C1
carbonyl monochloride
carbonyl chloride
ethane
propane
N-butane
N-pentane
N-heyane
iso-butane
isopentane
neo-pentane
102
-------
2-methyl-pentane
3-methyl-pentane
2,2-dimethyl butane
2,3-dimethyl butane
cycle pentane
methyl cyclopentane
ethyl cyclopentane
cyclohexane
methyl cyclohexane
ethyl cyclohexane
propylene
1-butene
2-butene (cis)
2-butene (trans)
1-pentane
2-penene (cis)
2-pentene (trans)
2-methyl, 1-butene
3-methyl, 1-butene
2-methyl, 2-butene
propadiene
1, 2-butadiene
1, 3-butadiene
cyclopentane
cyclohexene
propyne
1-butyne
2-butyne
1-pentyne
2-pentyne
3-methyl, 1-butene
benzene
methyl benzene
ethyl benzene
1, 2-dimethyl benzene
1, 3-dimethyl benzene
1, 4-dimethyl benzene
phenyl ethene
cis-1-phenyl, 1-propene
trans-1-phenyl, 1-propene
(2-methyl phenyl) ethene
(3-methyl phenyl) ethene
(4-methyl phenyl) ethene
1-chloro ethene
dichloro ethene
1,2,2 trichloro ethene
tetrachloro ethene
1-chloro propane
1, 2-dichloro propane
chloro ethane
1, 2dichloro ethane
1-propanol
1-butanol
ethanol
methanol
103
-------
2-butanol
2-methyl, 1-propanol
1-pentanol
1-hexanol
3-hydroxy, 1-propene
1, 2-epoxy butane
1, 2-epoxy propane propylene oxide
3-chloro, 1,2 epoxy propane
1, 2 ethandiol
2 (2 hydroxy ethoxy) ethanol
1, 2 propandiol
2, 3-dihydroxy propanol
3-(3-hydroxy propoxy) propanol
trans-1, 2-dichlora ethene
cis-1, 2-dichloro ethene
1,1,1-trichloroethane
1,1,2,2-tetrachloroethane
butanal
propanal
ethanal
methoxymethane
ethoxyethane
propoxypropane
methoxyethane
methoxypropane
ethoxypropane
2-methoxypropane
2-ethoxypropane
2-(2-propoxy) propane
2-propanone
3-pentanone
4-heptanone
2-butanone
3,3-dimethyl, 2-butanone
1-chlorohexane
1 chloropentane
1 chlorobutane
2-chlorohexane
2-chloropentane
2-chlorobutane
2, chloropropane
3-chlorohexane
3-chloropentane
ami nome thane
aminoethane
1-aminopropane
1-aminobutane
1-aminopentane
1-ami nohexane
2-aminopropane
2-aminobutane
2-aminopentane
chlorine, monotomic
chlorine, monotomic charged + (unipositive ion)
chlorine, monotomic charged - (uninegative ion)
104
-------
chlorine
chlorine monoxide
chlorine dioxide
dichlorine monoxide
cyanogen chloride
hydrogen monatomic
proton (H-f)
hydrogen uninegative ion
hydronium unipositive ion
hydrogen
hydroperoxyl
water
hydrogen peroxide
hydrogen chloride
hydrogen oxychloride
formyl
formaldehyde
hydrogen cyanide
nitroxyl
nitrous acid cis & trans
nitric acid
hydrogen isocyanate
nitrogen monotomic
" " unipositive ion
" " dipositive ion
" " tripositive ion
nitrogen diatomic unipositive ion
uninegative ion
nitric oxide unipositive ion
nitrogen diatomic
imidogen (NH)
amidogen (NH_)
ammonia
hydrazine gas, liquid, solid
nitrogen tetraoxide gas, liquid solid
nitric oxide
nitrogen dioxide uninegative ion
nitrogen trioxide
dinitrogen monoxide
dinitrogen trioxide
dinitrogen pentoxide
nitrosyl chloride
nitryl chloride
ammonium chloride crystal
ammonium perchlorate crystal
oxygen monatomic
oxygen unipositive ion
oxygen uninegative ion
oxygen diatomic uninegative
hydroxyl unipositive ion
hydroxyl uninegative ion
oxygen monatomic 2+
3 +
oxygen diatomic
oxygen triatomic
hydroxyl
105
-------
-------
APPENDIX B
KINETIC MODELS AND PARAMETERS
Presented in this section is a brief description-of the mathematical models,
computer models, and estimated rate data employed in the waste plastics kinetic
analysis.
107
-------
To 1
Set All
Variab1es=0
i
r
Read
Data
Print
Case No.
Ibs/yr
Calculate Rate
Constant Mass
Distributions
Initial Enthalpy
Calculate Heat
Required (N£ gas)
to Bring Waste
Plastic Mass to
Reaction Temperature
Figure 40. Computer program flow diagram.
108
-------
Figure 40. Computer program flow diagram (continued)
Print
Variables
If
Reactor
Distance (Z)
<. Reactor
Length
If
Zero Order
Reaction Stage
of Mechanism
If
Reactor
Distance (Z)
<_ Reactor
Length
Calculate Zero
Order and First
Order Reaction
Concentrations
If
Distance
at Print
Point
Integrate Empirical
Expansion Describing
Final Reaction Stage
109
-------
Figure 40. Computer program flow diagram (continued)
Execute
Subroutine
Out
No
Execute
Subroutine
Out
If
Specified
Waste Plastic
Material
Remains
no
-------
Figure 40. Computer program flow diagram (continued),
SUBR0UTINE 0UT
Calculate
Required
Heat
Calculate
Heat Carrier
Gas Require-
ments
Calculate
Solid and
Gas Residence
Time
ill
-------
Figure 40. Computer program flow diagram (continued)
Print
Output
Return
112
-------
TABLE 34
VARIABLES USED IN MATHEMATICAL MODEL
M = original polymer feed (gr sec •-)
MHC1 = original HC1 feed (gr sec"1)
M = original polymer involved in random degradation
(gr.sec"1)
M = original polymer involved in zero order degradation
(gr.sec"1)
Mn = original polymer involved in final stage of
degradation (gr.sec"1)
N = total mass of gas product (gr.sec"1)
n = mass of gas product due to random reaction (gr.sec"1)
n = mass of gas product due to zero order reaction
Z (gr.sec"1)
nr = mass of gas product due to final stages of reaction
(gr.sec"1)
nHCl = mass of HC1 product (gr.sec"1)
nO = moles of styrene product (moles.sec"1)
nl = moles of (ortho,meta,para) V 2 (moles.aec-l)
C]
I
n2 = moles of // \^ CHC1CH2CL (moles.sec-i)
/ CHC1CH2CL
n3 = moles of (ortho,meta,para) / A (moles.sec"1)
Cl_ = moles of Cl_ (moles.sec"1)
nR-H = moles aliphatic material (moles.sec"1)
Z = distance along reactor (cm)
ADP = average degree of polymerization
k,, = random rate constant (related to sec"1)
113
-------
TABLE 34 (continued)
k = zero order rate constant (related to sec )
z
p = density of waste plastic at z (gr . cm~^)
p0 = density of unreacted waste plastic (gr . cm~3)
f\
V = void space of reactor (cmz)
t = time (sec)
MW = molecular weight (gr . gr-mole )
A = cross sectional area of reactor (cm )
T = Temperature (K)
114
-------
TABLE 35
THERMAL DECOMPOSITION DIFFERENTIAL RATE EQUATIONS*
(i) dN =rdnr+ dnz j- dn ~i . / M ,
are Lair" 3t~ ' airJ (ADP-MW '
dn
(2)
(3)
(4)
(5)
(6)
r = k • M
dt r r
dn
z = k
dt
•? - k COS ( nj)
dt z z • M^
dz M dp
dt \- (1-V) dt
dn" d)1' ^,4- U
]_ = j dt whi
dz dt ' dz
- 2HC1) 3/2
MHCI
* It was assumed that the three plastics underwent thermal
decomposition by a three-stage mechanism as follows: (1)
an initial random degradation reaction (2) a zero order
reaction, and (3) a final stage characterized by an empirical
expression.
+ Applicable to polyvinyl chloride system.
115
-------
TABLE 36
WASTE PLASTIC(S)/CIDIFFERENTIAL RATE EQUATIONS
= &L
ut dt dt ADP-MW
dn
(2) —£ = M . k
dt r r
(3) t_ = k cos (T» n^)
dt r 2 ' M,
(4) dz = ( M ) . d
dt A-(1-V) d
(5) dnj = dnj dt where j=r or ^?
dz dt ' dz
(6)* dnHCl = dt • MHC1 • kHCl (1 - nHCl) 3/2
dz dz MHC1
* Applicable to polyvinyl chloride system.
116
-------
TABLE 37
DECOMPOSITION PRODUCTS/CI DIFFERENTIAL RATE EQUATIONS*
2
(1) dnO
dt
V
(2) ^1 = n
dt 2
(3) dnz = n |n k - n k ]
dF~ Cl, 0 A 2 ET
(4) dn3 =
dt
dncl
(5) 2 =
dt
Cl.
+ n2kD = nR-H
(6) dnHCl =
dt
nicl2
n2ko
(7) dnRH =
dt
RH
*Reactions
(a)
CHCH2
^ CHC1CH2C1
(b)
//\\ CHCH2 + C12
CHC1CH2C1
Cl
Cl
(c)
CHCH
^ CHCH2
Cl
+ HC1
(d)
Cl
+ Cl
CHC1CH2C1
+ HC1
Cl
117
-------
TABLE 37 (continued)
(e) R-H + Cl- -*• R-C1 + HC1 where R equals various
saturated and unsaturated hydrocarbons with various
degrees of Cl substituting.
118
-------
TABLE 38
THERMAL DECOMPOSITION PRODUCTS/AIR
DIFFERENTIAL RATE EXPRESSIONS*
(1)+ d
(2)+ d
(^c=cC)
dt
0
dt
~ kl (R-H)
0
*d(xc%)
dt
(o2)
= k(
B
(>>C<) (OH)
d(C02) ^ d(H20) ^ k, (
dt dt
* The differential rate expressions were not programmed into
equivalent computer programs. As such, these above rate
expressions were used to characterize the systems.
+ The preliminary kinetic analysis equations are (see
reference 1) the following:
(A) R + 02 £ H02 + ^C=c(
(B) HO + RH -» HO H + R
(C) M + HO -» 20H + M
O
(D) Jb=c' + HO -> OH + ^C-CX
(E) /C=C^ + OH + O -» HO - ^p-C7 - O-O
O
. > ' \> \ ' \
(F) EO-C-C-0-O + C=C -» ^-C + XC=O + HO~CH2
(G) RH + 20 ~» R + 2H O + CO
J ^ £* &,
119
-------
TABLE 39
WASTE PLASTICS (SOLID)/AIR DIFFERENTIAL RATE EXPRESSIONS
(1)* N. = K ' M
dt
~i - k^ (R-H)(02)
dt
0
dt dt
= kl
dt dt
2
C 2
* Oxidation opcurs in a random reaction to yield intermediate
gas products from the solid waste material.
+ See note 2 on Table 38.
120
-------
TABLE 40
PREDICTED RESULTS COMPARED WITH EXPERIMENTAL RESULTS
STY RENE
Based on 1.
Calculated
970 K @ 2.5 min
Styrene 0.81
Toluene and
ethylbenzene
Residue 0.19
gr/sec polystyrene feed
(17)
Experimental
898 K
g 0.74 g
Trace "
g 0.26 "
POLYETHYLENE
Based on 1
Calculated
710 K @ 50 min
C2H 0.018 g
C2H 0.055 g
C3H 0.0015 g
C3H6 0.0325 g
C_HQ 0.0960 g
J o
C4Hg 0.1990 g
C4H1Q 0.1585 g
C5Hg 0.0035 g
C5H1Q 0.0765 g
C5H12 0.0640 g
C6H10 0.0040 g
C6H12 0.0395 g
C6H14 0.0165 g
C7H1 0.0030 g
C?H16 0.0060 g
Unreacted 0.2265 g
gr/sec polyethylene feed
(18)
Experimental
702 K @ 30 min
0.016 g
0.048 g
—
0.028 g
0.085 g
0.177 g
0.144 g
0.003 g
0.068 g
0.057 g
0.003 g
0.035 g
0.014 g
0.002 g
0.005 g
0.373 g
121
-------
TABLE 40 (continued)
POLYVINYL CHLORIDE
Based on 1 gr/cc polyvinyl
Calculated
723 K @ 4.25 rain
HCl
H2
CH4
C2H6
C2H4
C6H6
C7H8
Other
Residue
0.510
0.0023
0.0144
0.0371
0.0718
0.0567
0.0302
0.1875
0.0900
g
g
g
g
g
g
g
g
g
(19'
Experimentalx '
873 K with H
0.555
0.0006
0.0100
0.0069
0.0052
0.0560
0.0067
0.0630
g
g
g
g
g
g
g
g
g
122
-------
r-i rv re xt xt
C O C C C
LT u"> vC r— cu cr
C C C C C C
C <— cv co xt IA ^O r— CCG^
r-CCCCCCCCC
t—• rv CV' rvj cvi cv cvj cv cv cv
<3 CC
rv rv rv rr; xl LT\
C C c c c c
rf1 m fT, r" ro m
f— cc O C- O *—' cv r<~! xl LT
C. C C r-^ ,— C C CCC
re (T m re rr, xt xt xt x} xt
O
CC
o.
oo
o
UJ
CO
00
o
oo
Q_
LL
C
C
00
1—
LL1
Z
LL
Z
LL i£
CV 00
1— _)
> CL
i LU
C r-
H- 0 1
I/;
< 2 00
LU LU CC
C£ C _J
RIABLES CASE.LBSYRP
4 16* RAD** 2
8?.06*TMRR)/PRS
<< r— i x_
> • II
r^ . i
H-HO
z
OE+ 1 1*EXP ( -44700. /{TVPR* 1.9872 6) )
.
rvi
n
rxj
LU
1—
<
rs
CV
r-
CC
a-
i — i
or
Q.
s:
i —
c
c
r~-
1
CL
X
LL'
i — 1
LU
.
^j-
II
a:
m
1 —
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00
1
C
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AMMA*POLYIM
1. -GAMMA )*POLYIM*.722?22?
OLYIM-MASSRO-MASSZH
O —• CL
II II II
0 C C
a: rxj _i
OO l/> OO
t/) 00 00
0
1 «
« 0
r-l II
' ' 1
II 00
LU CL
S CJD
•-> Z
I- UJ
p_5*(TMPR**3-2.7F+6) ) )+] 9. 0/1 04. 14
0.24 + fS.3E-4-;=TMPR-r-5.623E-5*TMPR**2-1.5066F-8*TMPR**3
IT rr-
xt II
I — >-
OC t-
. 00
, — i 27
— • z
•it LU
.001*(-60023.+7.084*TMPR+.001337*THPR**2 )
. 001* (-60023. +7. 084*TMP!\i+.00 1337 *TM PN**? )
T
N*( ENGPST-.1 82 ) /( FNMN2N-FNMIV2R )
P IABLFS
T
MHKCL
8H8*( 104.] 4*ENGPST-FMMSTY)
*7*vnin
MHKCL/. 25198
MHKCL-nEMKCL
KCL/ ( ENMM2M-FMMM2R )
IN
C8H8 + N2 )*vnLMHL/( vnL*Z )
,/SPCVFL
OLYIN-104.14*C«H8
H8/ ( M2 + C8H8 )
M2+C8H8 )
CC^i-1 > O M II LL II II LL 2 II II II O *"-
CL 2 CL i rv _' — ! c£ n. _i C + rv < ^ >- n r\>
rvirvfxjir2i— ^oo-ai-o n rv z LL >-H i— (— o^X II
ZSTr- || C«C.2X_!XZ'— II OOOO_JCCCV
22Q.rvcvo:_jLLi2C2ijjrvrvcv'CLU.'C'_;z
LLIU-i'x-l2XCLCCCLL'>LLCZZXlACr:CLLLI-L
123
-------
-a
z
1 — 1 1 —
>- z
DEN=POLSTY*DFNS I/PQI
GRMSEC = C8H8*104. 1.4
IF BUG FO I THEN PR
IM,POLSTY,C8H8,H20,FNHKCL,EI
= C
1— 00
oo s:
RINT VARIABLES ZtRF
,C8H8R,C8H8LTDEN,GR
END BLOCK
Q- rx!
cc
3^
co
o
•if
'+ LT MASSRO+MASSZO-POL YIN*0,
,-! C C
« o o
.4- (x in
c
r-i O C
-x- t- t-
X
ICC
cc _J LU
LU O X
cc H- M h-
0 LU
CJ5 1-1
o
0
in
cr
o>
cr
O
i—
0
o
UJ
00
_)
LU
_J
CO
I
cc
(_:
•if
sf-
1 — 1
»
sf
c
•X-
•
rv
x»
0-
in
. — i
sf
r-4
t
rr
00
a
o
-*
rxj
RFJOIM
BLOCK DERS
DC8H8L=TIME*RATE
t — t
c
in
LZ ,C8H8L TDC8H8L
LU
C
DPZ*104.14)
END BLOCK
INTEGRATION DERS,Z,
INTEGRATE DERS
in
O
in
•i:-
c
T=POLSTY
C8H8=C8H8+C8H8L
IF Z-ZPT-f.5*DFLZ GF
i—
Q.
THEN ZPT=ZPRNT+2
EXECUTE nin
sf
o
in
c
i—
c
o z
UJ C
00 — 5
_! LU
LU CC
124
-------
-a
OJ
<
c c >-H ex m -j r^ *o r~ or o o
•—•-CCOCCCCCOi-l
1^1^-0000000000 CO ODOCOCOO
IP
c\.
2
>-
—1
c
CL
I
cc
X
oo
u
oo
X
CO
I
O
00
IT
o
ITl
O
o
OC
o
I
OC
I
oo
o
ii
oo
T
00
o
-::- o
-4-
,-( UJ
II UJ
V 2:
o o
UJ
I LL
HOC
O C
CD C)
UJ C t- r-(
oo -; _)
_r UJ O
c
U- C Z
O (T- <
•-H (r i—
tp (r <
125
-------
TABLE 42
KINETIC RATE PARAMETERS
A (
'base
mole
1
•sec
E (Kcal/mole)
• Thermal decomposition
Polystyrene
Random RXN
Zero order
Polyethylene
Random RXN
Zero order
RXN
RXN
1.
4.
92
33
t
f
x
x
10
10
12
9
44.
44.
*
*
7
7
Polyvinyl chloride
Random RXN
Zero order
HC1 RXN
RXN
§
4.
1.
1.
8
9
9
X
X
X
10
10
10
10
9
9
44.
44.
33.
2
2
0
• Plastic (solid) /C12
Polystyrene
Polyethylene
Polyvinyl chloride
• Decomposition
RXN A
RXN B
RXN C
RXN D
RXN E
• Decomposition
RXN 1
RXN 2
RXN 3
• Waste plastic
Polystyrene
Polyethylene
(g)/ci2
(g)/air
(solid)/air
Polyvinyl chloride
§
§
i
§
§
§
§
§
§
§
§
3.
1.
5.
3.
2.
4.
4.
1.
2
1
3.
2
1
2
4
9
0
2
1
0
0
0
2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
10
10
10
10
10
10
10
10
10
8
5
5
6
Q
u
8
1015
10
10
y
9
Q
10-
10
/
32.
31.
30.
17.
17.
23.
23.
1.
10,
43.
9.
40.
44.
44.
2
0
0
0
0
5
5
0
00
0
0
7
7
7
* E = 27586. + 46.853 x ADP.
f A = EXP (42.4 + 0.1445 x
t A'= 4 x 102 x A.
§ Units in sec"1 (pressure units).
126
-------
APPENDIX C
ECONOMIC MODELS
This appendix contains brief descriptions of some of the computer models
(subroutines) used in the economic analyses of chemical systems for waste
plastic utilization. These subroutines are called by the main program when
needed and were written to calculate the capital and operating costs' associated
with that specific piece of equipment.
Subroutine COMPRS
Subroutine COMPRS calculates the actual brake horsepower required to drive
a compressor. A mechanical efficiency of 94 percent and a compression
efficiency of 83.5 percent were assumed. The intake and exit volumes are
calculated based on stream composition, entrance and exit temperatures, and the
input-output pressure ratio. Subroutine ECON is then called to determine the
more economical type of compressor, the installed cost of the compressor, and
the operating cost in dollars per hour.
Subroutine ECON
Subroutine ECON determines which type of compressor is more economical,
centrifugal or reciprocating. The subroutine calculates the capital cost of each
type of compressor for the brake horsepower required and the operating cost per
hour based on which source of power is chosen, steam or electricity. The
resultant costs for each type of compressor are compared and the smaller of the
two is chosen.
127
-------
Subroutine SEPAR
Subroutine SEPAR calculates the minimum required volume of a vapor-liquid
gravity settling tank. As the vapor passes upward through the tank, particles with
terminal velocities equal to or greater than the vertical velocity of the vapor
stream will be removed. A particle terminal velocity of 1 ft/sec was assumed to
exist in the settler, and a tank height of 10 ft was assigned. The subroutine then
calculates the area required to decrease the vapor velocity to 1 ft/sec. The
installed cost of the vessel is determined as a function of vessel capacity.
Subroutine REF
Subroutine REF calculates the brake horsepower required to refrigerate the
product to the desired temperature. Based on the change in enthalpy, the type
of power specified for driving the refrigerator, and the materials involved, the
installed cost is determined.
Subroutine EXCH
Subroutine EXCH calculates the square feet of heat exchanger required based
on the heat load in Btu per hour, and the inlet and exit temperatures. The
capital cost is then calculated from the area required and the operating pressure.
Subroutine PUMP
Subroutine PUMP calculates the gallons of liquid per minute that must be
moved by a process pump. The capital cost is then calculated as a function of
flow (gal/min).
Subroutine BCCOL
Subroutine BCCOL calculates the minimum allowable diameter of a
bubble-cap distillation column. A column must have sufficient cross sectional
area to handle the rising gases without excessive carryover of liquid from one
tray to another. The vapor velocity
where: PT , *Q = density of liquid and vapor, respectively.
128
-------
APPENDIX D
ASSUMPTIONS MADE IN ECONOMIC ANALYSES
Utilities
Cooling water
Electrical power
Fuel Gas
Boiler water
Steam
2
-------
Environmental Protection Agencj
Libra*/ Ifag .'cr; 7
1 fi c>v t ]f\ V/&0. - -" Drive
rniv^gj, Illinois 60606
-------
-------
U.S. ENVIRONMENTAL PROTECTION AGENCY
------- |