EPA-650/2-74-021
March 1974
Environmental Protection Technology Series
PRO?*'-
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EPA-650/2-74-021
EFFICIENCIES IN POWER
GENERATION
by
T. R. Blackwood and W. H. Hedley
Monsanto Research Corporation
Dayton Laboratory
1515 Nicholas Road
Dayton, Ohio 45407
Contract No. 68-02-1320
Task 7
ROAP No. 21ADE-29
Program Element No. 1AB013
Task Officer: C. J. Chatlynne
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
.. March 1974
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This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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TABLE OF CONTENTS
Page
I. SUMMARY 1
II. INTRODUCTION 3
III. SUMMARY OF EFFICIENCIES (TaL.le) 5
IV. DISCUSSION OF POWER SOURCES* 7
A. DIRECT USE OF FUELS 7
1. Convertional boiler 8
a. Boiler only (la) 8
b. Overall process (Ib) 9
2. Conventional boiler with flue lri
gas cleaning (2)
3. Pressurized fluid bed combustor (3) 1?
4. Atmospheric fluid bed combustor (4) 14
B. COAL CONVERSION TO CLEANER FUEL 16
1. Low Btu gas generator 16
a. Cold cleaning (5a)
b. Hot cleaning (5b)
2. High Btu gas generator (6) 18
3. Coal liquefaction (7) 19
4. Conversion of coal to methanol 21
and methanol fuels (8)
C. FUEL CLEANING METHODS 23
1. Coal cleaning plant (9) 23
2. Chemical coal cleaning systems (1) 24
3. Residual oil desulfurization (11) 25
4. Chemically active fluid bed (12) 25
D.- POWER PRODUCING MACHINERY 26
1. Steam turbine (13) 26
2. Gas turbine (14) 28
3. Combined cycle (15) 29
* Numbers in parentheses refer to topic numbers
in Table 1, "Summary of Efficiencies".
iii
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Page
E. SPECIAL ENERGY CONVERSION METHODS 30
1. Nuclear steam plants (16) 31
2. Feher cycle (17) 32
3. Potassium topping cycle (18) 33
4. Bottoming cycle (19) 34
5. Magnetohydrodynamlcs (MHD) (20) 34
P. PORTABLE POWER SOURCES 36
1. Fuel cells (21) 37
2. Automotive (22) 39
3. Diesel (23) 40
V. REFERENCES In
iv
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LIST OF FIGURES
Page
1. Conventional Boiler 8
2. Overall Steam Boiler 10
3- Conventional Steam Boiler Overall Heat Balance 11
4. Pressurized Fluid Bed Boiler 13
5. Atmospheric Fluidized Bed Boiler 15
6. Low Etu Gas Generator 18
7. High Btu Gas Generator 19
8. Coal Liquefaction 20
9. (a) Coal to Methanol 22
(b) Methyl Fuel Process 22
10. Physical Cleaning of Coal 23
11. Chemical Coal Cleaning 24
12. Residual Oil Desulfurization 25
13. Chemically Active Fluid Bed 26
14. Steam Turbine 2?
15. Gas Turbine 29
16. Combined Cycle System 30
17. Nuclear Reactor 31
18. Feher Cycle 32
19. Topping Cycle Applied to Steam Boiler 33
20. Bottoming Cycle 3^
21. (a) MHD Steam Cycle 35
(b) MHD Air Turbine Cycle 35
22. (a) Hydrogen Fuel Cell Methanol 38
(b) Hydrogen Fuel Cell Using Coal 38
(c) Pratt and Whitney Fuel Cell System 38
•v
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I. SUMMARY
Herein is assembled an introduction to some important aspects
of the energy conservation problem with respect to polluticr.
abatement and alternate fuel processing technology. Many cf
the topics have been researched and developed with energy con-
version as the prime goal. Other studies have not addressed
this subject but have been more concerned with the efficiency
of pollution control.
Prom this investigation, we conclude that more exploration of
the topics is needed, especially the fuel conversion processes.
These appear to be poor choices for coal substitutes in electric
energy production.
It is recommended that further investigations be conducted in
the following areas:
1. Low and high Btu gasification of coal as a substitute
for natural gas.
2. Coal cleaning for sulfur and ash removal.
3. Higher turbine inlet temperature.
4. Magnetohydrodynamics flue gas cleaning and insulator
developments.
5. High-temperature gas-cooled nuclear reactor-
6. Topping and bottoming cycles. Materials for use in
these cycles need to be developed.
7. Coal conversion to methanol fuels.
t
Certain areas show little promise in the near future as power
generators. These are:
1. Fuel cells for utility use
2. Internal combustion engine
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II. INTRODUCTION
An important consideration in the use of fuels for power genera-
tion has always been the efficiency of conversion. It enters
directly into the economics of the process as a cost factor.
Utility companies as compared to industrial users are notori-
ously conservative with a Btu of energy. This has mainly teen
due to the economic trade-offs made in design and ultimate use
of the input energy. Rising fuel costs and environmental pres-
sure have replenished interest in heat cycle and energy con-
version techniques which make use of this input.
Since the early 1960's, energy consumption has risen faster than
the GNP. Thermal efficiency of large fossil fuel electric gener-
ators has declined and nuclear energy seems to cost more each
day. Any environmental control techniques have been crude and
have generally required the addition of more power consuming
equipment and cleaner fuels. All of these factors have contri-
buted to the realization for many Americans that our energy
resources are not inexhaustible. However, air quality criteria
must not be relaxed. Thus, cleaner fuels and air pollution
control techniques must continue to develop but in an overall
conservation light (ecology, energy, economics).
This report is an introductory view of 23 ways of using or con-
verting energy. The thermodynamic limiting, present and future
(1990) efficiencies are compared in tabular form in Table 1. In
all cases, .the efficiency is concerned with energy input versus
output. Thermodynamic limits are referenced to 70°F, 1 atnu,
unless otherwise stated. In some cases, practical limits are
more meaningful and are used in lieu of a detailed thermodynamic
analysis. This was done to expidite the study and provide the
necessary overview of the topics. Limiting factors in thermc-
dynamic or practically obtainable efficiencies are discussed in
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Section IV. Through the use of the topic numbers, reference is
made back to Table 1. The numbers in parentheses following the
discussion heading in Section IV are these topic numbers.
Following the comparisons given, combinations of systems may be
evaluated for overall efficiency. Here are five very general
rules to apply when making comparisons.
1. When combining two energy convertors where the one
uses the energy of the other as total input, the
efficiencies (in terms of a fraction) are multiplicative
2. When combining a system which operates in series with
another energy extraction system, the overall efficiency
is derived from the equation:
nQ = HI + (1-ni) ri2
where n = overall efficiency (in fraction form)
o
where m, ri2 = system No. 1 and 2 efficiency (in
fractions)
3. When fuels other than those for which the equipment
was evaluated are substituted, losses or gains in
efficiency may result from thermodynamic considerations.
Comparison of these losses when applying a system will
be necessary.
4. The form of the power output is important since any
conversion will require energy.
5. Whenever combinations are made additional system
components may be necessary to close the loop. With
this in mind, the calculations will represent approxi-
mations to typical installations.
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III. SUMMARY OF EFFICIENCIES
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Table 1
EFFICIENCIES IM POWER GENERATION
Topic
No.
Ib
2
3
4
5a
5b
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
2 la
21b
21c
21d
21e
22
23
Equipment
Conventional
Sub-critical Boiler
Conventional Boiler
Process (overall)
Conventional Boiler
with Flue Gas Cleaning
Pressurized Fluid Bed
Combustor
Atmospheric Fluid Bed
Combuator
Low Btu Oas Generator
(Cold Cleaning)
Low Btu Gas Generator
(Hot Cleaning)
High Btu Gas Generator
Coal Llqulfactlon
Conversion of Coal
to Methanol Fuels
Cnal Cleaning Plant
Chemical Coal Cleaning
Systems
Residual Oil
Desulfurlzation
Chemically Active
Fluid Bed
Steam Turbine
Oas Turbine
Combined Cycle
(Oaa and Steam)
Nuclear Steam Plants
Peher Cycle
Potassium Topping0
Bottoming Cycle0
Magnetohydrodynamics
Hydrogen Fuel Cell
Natural Qas Fuel
Cell
Methanol Fuel Cell
Hydrogen Fuel Cell from
Converted Methanol
Hydrogen Fuel Cell from
Converted Coal
Automotive (I-C Engine)
Diesel
processes have yet to be
Present
(1974)
88
40
36
a88
a86
75
aao
"65
"75
a50
90
"91
93
76
45
30
42
33
"IB
a!6
"12
*50
a70
50
°48
28
»45
41
48
app lied
Efficiency
Projected"
(1990)
95
50
48
90
B8
86
92
75
76
60
95
95
99
81
54
42
59
43
42
20
14
60
70
55
48
46
52
37
48
(<)
Thennodynaml c
Limit
99
60
60
99
99
96
98
77
99*
77
100
100
99
89
68
83
95
72
82
45
50
82
83
93
96
77
60
58
66
to any commercial extent. Thi
40"
Btu/lb Fuel
-12,1(00
-12,400
-45,700
-45,700
-14,848
-4,150
-3,890
-780
-8,700
-12,400
-51,030
-24,200
9,444
-12,000
-13,460
Btu/lb Fuel
-12,500
-12,500
-47,500
-46,500
-19,194
-4,150
-4,350
-1,145
-10,500
-200 Hev
-12,500
-61,470
-26,100
- 9,769
-20,570
-20,395
The values given for present
e carbon "nvdro^nT'lnlhi861;^ "lst*upe °f the fee<1 material or for elemental components
e bec"se"oftheTomolexitlor YE???0" Droce"- 3<""e ™lues °f »0 and 4H are not obtaln-
lless faoUrSeco0mfp^iesorPlThesey «««£?£"£ ^l*-! Processes would be mean-
AC and
P°"er
efficiency can be cal-
"b - "t
a
6 « Binary efficiency (fraction)
t - Topping or bottoming efficiency (fraction)
s - Power cycle efficiency (fraction)
d. Thermodynamlc Uniting efficiencies are related to 70°F and 1 atm.
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IV. DISCUSSION OF POWER SOURCES
Classifying equipment by a single efficiency number can be con-
fusing and misleading. The power conversion and extraction
systems referenced in Table 1, require definition and further
discussion to minimize this. Generally, a range of efficiencies
exists for each topic as opposed to the single stated value.
Economic pressure can also favor a lower efficiency due to
either low fuel cost or low capital requirements. These aspects
are not discussed in any depth since the report purpose is to
provide more of a scientific comparison. For comparison ease,
the equipment topics are broken into six distinct categories:
Direct fuel use
Coal conversion
Fuel cleaning
Power producing machinery
Special energy conversions
Portable power sources
A. DIRECT USE OF FUELS
Coal, oil and gas are the convential fuels in common use today.
The gas may be natural or man-made such as the coke-oven gases
used by the British during World War II. With the exception of
most natural gas, these fuels result in significant pollution
when burned. However, there are two distinct concepts for
utilizing these fuels while protecting the environment. These
are:
1. Conventional boilers using flue gas cleaning
2. Pressurized and atmospheric fluid bed combustors
For reference, the conventional boiler without flue gas cleaning
is discussed as a separate topic since this represents the
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majority of present day power generation.
1. Conventional Boiler
The state-of-the-art of conventional boilers is well advanced
with economics dominating the energy conversion. The boiler is
generally very efficient with most overall losses in efficiency
on the steam side of the power production. These two topics are
discussed separately, (la) and (13) and as a combination (Ib).
a. Boiler only (la)
The conventional sub-critical boiler is represented by a common
pulverized-coal steam boiler operating below the critical
throttle pressure (3500 psia). Its efficiency is given in terms
of its ability to convert coal to steam Btu's (see Figure 1).
Coal-
Boiler
Heat
Exchanger
1
Air Heater
Super Heated
Steam
Boiler
Feed
Air (70°F)
Flue Gas
180-300°F
Figure 1 Conventional Boiler
Presently, boiler efficiencies range from 85-90%. The major
losses are classified roughly as follows:
(1) Heating of excess air for combustion
(2) Incomplete fuel combustion
8
2,
2,
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(3) Heating of moisture in coal and air 4.0$
(4) Dry gas losses (240°F) 4.0$
As the year 1990 approaches, improvements in the efficiencies
will come with the use of physically or chemically cleaned coal.
These will burn more completely, use less excess air, and have a
lower moisture content. This should add about 6% to the present
efficiency. Use of cleaner fuels should lower the final flue gas
temperature, adding significantly to the efficiency. In 1990,
the efficiency of conventional boilers is expected to be 90-96$,
depending upon the coal quality. Losses would then be:
(1) Heating of excess air for combustion 1.0%
(2) Incomplete fuel combustion 1.0%
(3) Heating of moisture in coal and air 1.052
(4) Final flue gas temperature 2.05?
The boiler process is well established and improvements are
constantly being made. R&D programs are minimal; most improve-
ments are made progressively as new full scale units are built
and tested.
AG and AH in Table 1 are calculated based on a coal that is
assumed to have 12,500 Btu/lb heating value and a hydrogen-to-
carbon ratio of 0.9- If there were no losses, 99% of this
value could be converted to steam energy. This is the limiting
thermodynamic efficiency.
b. Overall process (Ib)
Overall, a."conventional boiler process" would include the
steam turbine and other components necessary to produce electric-
ity. The present average operating efficiency of this type of
process for the entire U.S. is 31%, but the most modern plants
achieve 40$.3 The Linden generating station of the .New Jersey
Public Service Electric and Gas Co. reportedly has achieved a 49*
2
efficiency. This was a record obtained using very low condenser
temperatures and selling process steam.
9
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A generator efficiency of 98$ has been assumed in calculating
the overall efficiency.
The conventional boiler process is shown in Figure 2. Figure 3
gives an overall heat balance.
Coal
Boiler
i 1
Heat
Exchanger
.
"— Air
" Heater
Steam
Turbine
— finnnrnfnr
Air(70°F)
•- Flue Gas
180-300°F
— kW
Figure 2. Overall Steam Boiler
The overall boiler process may be improved through the addition
of topping and bottoming cycles . Advancement of materials
technology to meet the severe steam conditions is needed.
Use of higher temperature boilers does not seem likely without
oxygen enrichment. R&D efforts appear more worthwhile in
other areas such as described in Section I (summary).
2. Conventional boilerjwith flue^ gas clejaning_(2_)
When flue gas cleaning is added to a boiler, the efficiency
will go down. The removal of sulfur oxides and fly-ash consumes
power which reduces the net power available. For particulate
control, the reduction is 1-3% of the net power. For dry SOX
control systems the reduction is about 2% of the power input
(thermal),15
10
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.'fir.
G«»,o'u. lood, 7JJ38 kw
Turfaina ™>t h*ot rait, 7,970 Btu pv k-
r
t
~1
il lASOblMrh. .
8|7 ~~u~'»
Us i
^i. SI s
^ »*J ir, p* -, ' V -, ;- -
'.«0> 1 "" 1*80
< TUfb-Fl« vOly.
S«om ^ "\
I — *~ — vJV~"*
1
1 .no.e,^
,
*- _/T»
1
1 ^...ao.^.
1 II" ,- ui.«, ~
I I
V*
Iniercooler and abv
loir egcdor
Gland iteam l*ok lou condenMr^
Figure 3. Conventional Steam Boiler
Overall Heat Balance
Capacity: 66 Megawatts
(courtesy. Steam Div.3 Westinghouse Electric Corp.)
11
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A wet scrubbing system not including product recovery would use
3? of the net energy produced by the boiler. Product recovery
or reagent regeneration, such as in the Wellman-Lord or
Molten Carbonate processes, can require 10? or more additional
power. If steam reheat of the scrubber gases is involved,
1-2? of the heat available would be consumed. Given a
boiler with the following characteristics,
100 MW input (in the form of coal)
88 MW input to steam (88? boiler efficiency)
40 MW generator output
then the losses due to flue gas cleaning would be:
1.60 MW for wet scrubber (4? of net power)
1.32 MW for steam reheat (1.5? of steam input)
0.80 MW for particulate cleaning (2? of net power)
3-72 Total Losses
This reduces the overall efficiency to about 36?. The lower
losses shown in Table 1 for 1990 result from expected improve-
ments in scrubber design. The use of lower energy levels for
cleaning will come with increased process confidence.
Summaries of on-going R&D in this area are plentiful; however,
these do not directly address the efficiency problem. A
major concern of the utilities is the power and cost required
for pollution abatement. At best, sulfur oxide control systems
will run $20-25/kW and cost over one mill/kW-hr to operate.
This is exclusive of particulate control, which is also expected
to increase power consumption.
3. Pressurized fluid bed combustor (3)
This type of combustor is shown in Figure 4. The fluid bed
12
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•o
Lime
Coal
Sulphate, Ash
^ fc^
120 MW
Generator
Steam
Turbine
25 MW
Generator
Air
Compressor
Turbine
Figure 4. Pressurized Fluid Bed Boiler
(courtesy, Westinghouse Research Laboratories
NTIS Publication PB211494)
13
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is used to increase heat transfer and promote sulfur removal.
Increased pressure results in lower losses to the combustion
gas and moisture.
By raising the pressure, less excess air is needed at higher
pressures. In fluidized bed combustors, the bed temperature
must be near l650°F. Raising the temperature will increase the
combustion efficiency but bed life is seriously shortened. The
major losses in efficiency are:
(1) Dry gas losses at 275°? 3-9%
(2) Hydrogen and water in the coal 4.1$
(3) Incomplete combustion 1.51
(4) Design factor and other losses 1.8$
The efficiency-limiting factors are basically the same as for
the conventional boiler, with the added restriction of bed
temperature. Although the boiler efficiency is reduced, the
sulfur is removed from the gas stream. Present R&D activity by
Pope, Evans & Robbins, Foster Wheeler, Oak Ridge National
Laboratories, Westinghouse Research Laboratories, and the EPA
Office of Air Programs is expected to yield pressurized fluid
14
bed boilers by 1982. Design factor losses should eventually be
be reduced, raising the efficiency to about 90$ in 1990.
4. Atmospheric fluid bed combustor (4)
Figure 5 shows the atmospheric fluid bed in a typical system
configuration. Although it resembles a conventional steam
boiler plant, the boiler size is reduced because of better
heat transfer of the fluid bed. Losses are about the same as
for a pressurized bed. Dry gas and moisture losses are
increased due to the lower combustion temperatures. (in a
pressurized bed, these are compensated for by the increased
pressure.) Losses are:
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Induced Drafl Fan
Economizer
Particulate Removal
Evaporator
Superheater
Evaporator
Forced Draft
Fan
•o
Feed Water Pump
Stack
Figure 5. Atmospheric Fluidized Bed Boiler
(courtesy, Westinghouse Research Laboratories
NTIS Publication PB 211494)
15
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(1) Dry gas losses (275°F) ^-3%
(2) Hydrogen and moisture in coal 5-1$
(3) Incomplete combustion 2.^%
(4) Design factor and other losses 1.8$
As atmospheric fluid beds develop, design factor and combustion
losses should go down, giving about 88$ efficiency by 1990.
Improvements are expected in the sulfur removal system and
economic areas, but efficiency will be limited by the losses
given as (1) and (2) above. The best route to improvement of
the efficiency would be use of cleaner coal.
On-going R&D is conducted by the same organizations as for
pressurized fluid bed combustors. Pluidized bed boiler concepts
and design criteria are very closely related whether they are
at atmospheric or elevated pressures. Hence, the research work
in this area is not very different than that described in the
previous section. The problems to overcome are very similar,
regardless of the pressure.
B. COAL CONVERSION TO CLEANER FUEL
As an alternative to combustion of the coa!3 it may be processed
to a cleaner fuel. Gas, oil and many other fluids may be pro-
duced from coal. Four coal conversion subjects are addressed
in this section.
1. Low Btu_gas generator_(5a & 5b)
Coal converted to CO at 110°C, such as in the COGAS process
(Figure 6) was evaluated in reference 6. Low Btu gas generators
produce fuel with a heating value typically of 100-300 Btu/cu. ft.
The majority of the gas is usually CO. Transformation of carbon
to carbon monoxide can be very efficient. From thermodynamic
considerations, 98% of the Btu content can be conserved. However,
16
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the efficiency is limited by more important factors than thermo-
dynamics. These are:
(1) Energy consumed in gas production 3%
(2) Losses due to moisture and inerts 6%
in coal and ash
(3) Losses due to heat exchange and 6%
excess air
(4) Losses due to hydrogen enrichment 3%
necessary for the reaction
(5) Gas cleaning (not including thermo- 3%
dynamic loss of 2%}
Most experts7,8,9 agree that 80% efficiency is realistic for this
process with a 5% penalty for cold cleaning. The Institute of
Gas Technology is getting about 85$ in their pilot process, but
this is believed to be on a hot cleaning basis. A cold cleaning
gas generator could be applied today at about 75% efficiency.
Hot cleaning is expected in the mid 1980's along with process
improvements to boost performance to about 92$.
The following is a list of on-going R&D efforts and commercially
available units for low Btu gasification:
(1) Lurgi (moving bed)
(2) Wellman-Galusha (moving bed)
(3) General Electric (moving bed)
(4) Winkler (fluid bed)
(5) Synthane (fluid bed)
(6) CO Acceptor (fluid bed)
(7) Westinghouse (fluid bed)
(8) IGT (fluid bed)
(9) Battelle (fluid bed)
(10) Bi-Gas (entrainment)
(11) Combustion Engineering and Con Ed (entrainment)
(12) Pittsburgh & Midway Coal (entrainment)
(13) Koppers-Totzek
17
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(1*0 Texaco (entrainment)
(15) ATGAS (molten iron)
(16) Kellogg (molten carbonate)
(17) Atomics International (molten carbonate)
Generally, higher temperatures and gas rates would improve each
of these processes.
Coal
Low BTU
Gasifier
CO + H2
Ash and Sulfur
Figure 6. Low Btu Gas Generator
2. High Btu gas generator (6)
In high Btu gas generation, the ultimate product is usually a
methane-grade gas similar to natural gas. It is suitable for use
in pipelines and has a heating value typically of 900-1000
Btu/cu.ft. For definition purposes, a high Btu gas is defined as
having more than 400 Btu/cu.ft. This is not rigid but includes
all gasification which is not considered as low Btu.
Research into this process category is an on-going concern of
many investigators. Commercially, the Lurgi and Koppers-Totzek
processes are established in other countries. Some of the more
common methods are the same as for low Btu gasification. The
limitations are the same as with low Btu gas with additional
i
energy consumed in the gas production and cleaning steps. The
Synthane process is believed to offer efficiencies of about 75%
when it is developed.8 Analysis of a design study for producing
900 Btu/scf gas shows that 77% would be a limiting efficiency.11
18
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Our personal contacts indicate that 65% could be achieved in tne
near future.8*9 Although high Btu gasifiers are not used in
this country, they are expected to be developed and in use by
1990.14 At that time, efficiencies of 75% should be achievable.
The prime limiting factor on efficiency is the amount of energy
required to convert the carbon (coal) to a synthesis gas and
ultimately to a methane-type product (see Figure 7), Because
of this, production of pipeline quality (high Btu) gas will be
discouraged compared to the low Btu gas for many years.
Coal
CO + H2
Ash and Sulfur
Figure 7. High Btu Gas Generator
3. Coal liquefaction (7)
Coal liquefaction is the process by which coal is transformed to
a liquid hydrocarbon. The prime method is to treat the coal
with hydrogen. This removes the sulfur as H2S and gives a
high H/C ratio liquid product as shown in Figure 8. Some
liquefaction processes also produce light oils, gases, and even
gasoline. One process was selected for evaluation (hydrodesul-
furization of coal).13 Depending upon the operating pressure,
yields of 0.8 and 0.86 Ib fuel oil/lb coal gave energy effici-
encies of 97 and 99%, respectively. The other limiting factors
that reduce the efficiency dramatically are specific to each
process. Losses are expected to be about 20$ of the available
energy.9
19
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Current R&D effort is based mainly in four processes. These
are:
(1) FMC's COED process
(2) H-Coal process of Hydrocarbon Research
(3) Bureau of Mines Hydrodesulfurization
(4) Pittsburgh and Midway's Solvent-refined
coal process
Areas with continued problems that could be improved by apply-
ing current technology are:
(1) High pressures
(2) Catalyst life
(3) High hydrogen consumption
When liquefaction becomes commercial in the mid 1980's3 it
should be 75$ efficient.9
, H2S and Light
Hydrogen ^ ^ Hydrocarbons
Reactor
Coal
Liquified Product
Ash
Figure 8. Coal Liquefaction
20
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4 . Conversion of coal to methanol and methanol fuels (8)
Another alternative in the liquefaction of coal is production
of methanol from synthesis gas. Coal may be converted to a
low Btu gas (CO + H2) using Fisher-Tropsch (F-T) technology.
The composition of this gas is perfect for methanol synthesis,
as shown in Figure 9a. An important side reaction is the
production of methane and water, which is emphasized in high
Btu gas manufacture. Grade AAA methanol may be produced by
this scheme but at a maximum efficiency of
Figure 9b describes another process of liquefaction of coal
to produce "methyl fuel".27 Here the catalyst is promoted to
produce higher alcohols which give a higher available energy
than methanol alone. It has been estimated by promoters of
this process than 133 to 272 gallons of this fuel can be
produced from a ton of coal.28 This corresponds to a 34 to
69% energy efficiency. We find that about 11% of the energy
could be available as a thermodynamic limit. Concensus values
are reported in Table i.21*>29
Limiting factors which have not been quantified in prior studies
on methanol fuels are as follows:
(1) Energy required to run gasifier and converters
(2) Energy input to Glaus unit and strippers
(3) Losses of available energy as C02
(4) Energy required to produce reactants, steam
or oxygen.
These facto'rs may be significant and could reduce the operating
efficiency from the maximum expected value. Estimates have
been made which indicate efficiencies as low "as 25 to 30% for
methanol fuel production when these energy inputs are accounted
for on a theoretical basis. Thus, a great deal of study is
necessary in this field to determine the extent, of these limi-
tations in the production of methanol fuels from coal.
21
-------
Coal *~
Oxygen / ^
-------
C. FUEL CLEANING METHODS
Certain fuels can be used directly to produce power in conven-
tional equipment if the pollutants are removed prior to combus-
tion. Examples are coal, residual oil and low Btu gas.
1. Coal cleaning plant (9)
Physical cleaning of the ash and separable pyrites from coal has
been well established (Figure 10). Present efficiencies run
from 60 to 95%9 depending upon the type of coal, how it is mined,
and the economic value of the products. If economics warrant,
coal could be cleaned with little loss. There is no applicable
thermodynamic limit.9 Losses may be expected in:
(1) The heating value of the non-organic
sulfur removed
(2) The coal physically bound to the pyrites
that are removed
It is not reasonable to expect that physical coal cleaning
efficiency will improve beyond 95%- No major R&D programs are
under way, although electrostatic/electromagnetic methods are
constantly being evaluated and improved.
Coal
Cleaned Coal
and
"Organic Sulfur
(Various Forms)
Pyrites
Figure 10. Physical Cleaning of Coal
23
-------
2. Chemical coal cleaning systems (10)
In chemical coal cleaning a solvent Is used to supplement
physical coal cleaning of the pyritic sulfur. It is possible to
remove virtually all of this sulfur and some of the organic
sulfur this way (see Figure 11). In terms of energy, losses
are confined to:
(1) heat requirements 5%
(2) sulfur combustion value
-------
The R&D effort described in reference 12 best exemplifies some
of the better efficiencies obtained thus far in chemical coal
cleaning.
3- Residual oil desulfurization (11)
Crude oil has been treated catalytically for years to remove
sulfur and improve quality. With the use of high sulfur Middle
East crudes, this process has gained more prominence recently
and may be applied to residual oils. Figure 12 is a schematic
of a typical residual oil desulfurization unit. Between 92 and
94$ of the potential energy is conserved, with 96% being the
limit according to one source.16 Data from the Gulf HDS process
indicates that 99+% of the energy can be conserved when applied
to a petroleum operation.22 R&D efforts are concentrated on
improving catalysts since the state-of-the-art with regard to
energy conservation is well-established.
•Sulfur and Light Ends as H2S
Residual Oil-
Reactor
Hydrogen
Fuel Oils
t
Heavy Ends
Figure 12. Residual Oil Desulfurization
4. Chemically active fluid bed (12)
A chemically active fluid bed combustor suffers heat losses from
solid chemical addition, but offers an economical way to clean
and burn low Btu gas. Losses are expected as follows:
-------
(1) Chemical reaction and absorption 3%
(2) Unburned CO 2%
(3) Unaccounted for and radiation 1.5%
(1) Sensible heat (350°P flue gas) 6.5%
Process improvements should reduce some of these losses. Efficien-
cies as high as 86% should be achievable by 1990- Comparison to
fluid bed operation indicates that the performance is quite simi-
lar. Thermcdynamic performance is that envisioned for CO combus-
tion (low-Btu gas). Figure 13 is a diagram of this process. One
method of improving this process is proper selection of the gas
composition, which could improve thermodynamic performance.
•Caustic Solids
CO Rich Gas_
with Impurities
Fluid Bed
roooi
Clean Flue Gas
Impurities
Heat Extraction
Figure 13. Chemically Active Fluid Bed
D. POWER PRODUCING MACHINERY
To extract electrical power from a hot gas conventionally requires
a conversion of heat to rotating mechanical energy. Steam and gas
turbines are the work horses of the power industry in this respect
They may also be combined to give better conversion efficiencies.
1. Steam turbine(13)
Presently, the better steam turbines operate at efficiencies of
45%. Unavoidable losses occur due to the cycle itself. These
26
-------
are:
(1) Condenser heat rejection - residual heat
is lost to the sink when the steam is
condensed.
(2) Turbogenerator losses - mechanical and
electrical losses are inherent in design.
(3) Radiation losses - other than nonrecoverable
heat dissipation.
While the efficiency of the steam turbine may be increased
by using higher inlet pressures and temperatures, most boilers
operate just over 1000°F for best overall plant economy with
boiler gas temperatures of 2000°F. AG and AH were selected for
1000°P and 1200 psia throttle steam pressure. A Carnot cycle
limiting efficiency of 63% corresponds to these conditions but
does not take into account the effect of reheat. An increase
of ^4 to 5$ can result from this. Figure 14 schematically de-
fines the section of a steam boiler defined as the steam tur-
bine. Figure 3 gives a typical steam turbine heat balance
with an efficiency of 42.7$.
To Stack
Hot Gas
from Burners
Figure
Steam Turbine
27
-------
2. Gas turbine (1*1)
The gas turbine, shown in Figure 15, generally uses an inter-
cooler and regenerator to improve the basic Brayton cycle. The
thermodynamic efficiency of the Brayton cycle can be expressed
as follows:
1-k
e = 1 - (Pi/P2) k
where e = efficiency
k = ratio of heat capacities (Cp/Cv)
PI = lower pressure
?2 = upper pressure
Based upon present technology, gas inlet temperatures of 1800°F
with an outlet of 1130°F gives an efficiency of 30$. A steady
improvement in design is expected to give ^2% by 1990. This is
based upon 2600°F inlet and 1300°F outlet temperatures. The
efficiency of a gas turbine is directly related to its inlet
temperature and various techniques are available to increase this
temperature. Research into the use of ceramics for gas turbines
is widespread. Although applications may be difficult in large
turbines, this is a viable means for increasing the operating
temperature. Studies of metal creep and corrosion resistance
could well uncover a material that would also withstand higher
temperature. It is expected that inlet temperatures of 2600°F
can be reached by 1982 with an aggressive R&D effort. Another
possible route to improvement is to increase the turbine pressure
ratio at the higher temperatures. For a pressure ratio of 16,
the limiting efficiency is 55%.
The gas turbine must be supplemented by another heat cycle to
economically extract the energy. The thermodynamic limit on
efficiency is 83$ for a gasified coal product of about 400 Btu/cu.
ft.
28
-------
Realistically, the gas turbine output is about 1100°P.5 Thus,
it is usually combined with some other means of heat extraction
(i.e., a steam boiler).
FUEL
AIR
POWER TURBINE
ELECTRIC GENERATOR
Figure 15. Gas Turbine
3. Combined cycle (.15)
In the combined gas and steam turbine cycle an improvement in
overall efficiency results from supplemental use of gas turbine
energy (see Figure 16). This method is limited by the efficiencies
of the steam and gas side. In addition to the basic limits of
each component, these two systems are used in series to extract
the available energy- Referring to Table 1, the gas turbine is
capable of removing 30% (197*0 of the energy. Since the
corresponding turbine exit gas temperature would be 1130°F
the steam cycle efficiency would be much lower. A steam-side
efficiency of 17? would be expected, giving a combined cycle
efficiency of ^2%. As the inlet turbine temperature rises the
exit temperature will also go up. This leads to higher steam
efficiencies. Based upon a gas exit temperature of 1300°F, the
steam efficiency is 30%.
29
-------
FUEL
AIR
POWER TURBINE
ELECTRIC GENERATOR
ELECTRIC GENERATOR
PUMP
Figure 16. Combined Cycle System
E. SPECIAL ENERGY CONVERSION METHODS
In addition to the methods of producing power discussed in
the previous sections, there are other alternatives. Further
energy extraction from either the hot gases or heat rejection
(condenser, etc.) can come from the use of topping or bottoming
cycles. Electrical energy can be extracted directly from the
hot gas with magnetohydrodynamics. Nuclear reactors are still
another source of energy using special fuels. Most of these
processes are viable alternatives in improving the efficiency
of power generation.
30
-------
1. Nuclear steam plants (16)
There are three basic types of nuclear steam plants. These ^::-e
schematically shown in Figure 17- The pressurized and boiling;
water reactors are 32 to 33% efficient in the newest plants.'
The high temperature gas-cooled reactors are about 39% efficient.
Efficiency is limited by:
(1) The upper sink temperature
(2) Lower condenser temperature
(3) Reactor safety considerations
The heat input to the steam cycle can be virtually 1005? of that
released by the reactor. Thus, the efficiency limitation would
be on the steam side. R&D into improving and upgrading nuclear
plants is a primary concern of the AEC. Most R&D effort has
been placed on lowering reactor cost and improving safety. The
closed loop nature of nuclear power provides high heat efficiency
The use o'f steam in nuclear power plants will limit the attain-
able efficiency. Considerable R&D is being focused on other
energy transfer media to lift this limitation.
Heat
Exchanger
or Reactor
Figure 17- Nuclear Reactor
31
-------
2. Feher cycle (17)
The Feher cycle is similar to the Brayton cycle except that it
operates entirely in the supercritical pressure region. Work-
ing fluids such as carbon dioxide are used in a closed-loop
cycle for energy extraction. Real gas effects are important in
this range. At present this process has only been able to give
about ±8% efficiency.6
The thermodynamic limit would be the same as for the Brayton
cycle. By keeping the pressure high, the turbine inlet temper-
ature can be kept at lower, achievable temperatures. Figure 18
gives the overall system concept. Achievable efficiency is
limited by turbine inlet temperatures only. No technological
breakthrough is needed to achieve a working machine.23 The
Department of Defense is developing units for portable and
special purpose applications. At turbine inlet temperatures of
1400°F, efficiencies of k2% are achievable.23
Supercritical
Discharge
Pressure
Heat Source
Figure 18. Feher Cycle
32
-------
3. Potassium topping cycle (18)
Topping of a steam cycle is represented in Figure 19- Efficiency
is limited by Carnot cycle limitations which come from high
temperature material problems. At 2200°F, the thermodynamic
limiting efficiency is about 45$. Materials for high temperature
and corrosion free service are needed to extend the usefulness
of topping. The turbine presently has an intrinsic design limit
value of 1500°F on the blades.5
This gives an efficiency of l6$.6 If inlet temperature could
be raised to 1800°F, the efficiency would increase to 20$.e
Potassium topping has gained attention due to improvements in
liquid metal technology. At present, developments in corrosion
resistance beyond 1600°F are necessary to extend use of this
method.6 Columbium addition to stainless steel is thought to
offer protection up to 2200°F. With the present decline in
aerospace activity, R&D in this technology has been curtailed
and only minor programs remain.
Fuel
*- Flue Gas
from Economizer
Figure 19. Topping Cycle Applied to Steam Boiler
33
-------
4. Bottoming cycle (19)
The bottoming cycle is best approximated by a Rankine cycle, as
shown in Figure 20. The limiting temperature available for the
heat source would be 600°P, so efficiency is limited to 50%.
Depending upon the fluid, the efficiency varies from 10 to I6%6
for practical cases.
f
Waste
Heat
Source
Figure 20. Bottoming Cycle
The limiting factors are:
(1)
(2)
(3)
Heat source temperature
Inlet turbine pressure
"Wetting" characteristics of working fluid
(4) Critical temperature of working fluid
Further investigation of this cycle should uncover a better
fluid. The technology of the cycle exists, but application
has been unwarranted in the past by economics.
5. Magnetohydrodynamlcs (MHD) (20)
MHD may be used to produce dc electricity in -a variety of ways.
It is expected that commercially available units will first be
used with steam power plants by 1980. In this case the steam
cycle supplements the MHD channel output. An efficiency of 50$
should be achieved with the MHD air turbine cycle shown in
34
-------
Figure 21(b). For central station use, the dc output is believe-
to be better than ac output3 and eliminates the necessity for
power conversion. Major limitations in efficiency are:
(1) Preheat temperature of combustion air
(2) Magnetic field strength
SUPPL.
MHO STEAM
POWER POWER
STEAM TURBINE
INVERTER
COAL
CLEAN STACK
CONDENSER WATER GAS
RECOVERED SEED
SULFURIC ACID
NITRIC ACID
Figure 21(a). MHD Steam Cycle
MHO POWER
CLEAN STACK
GAS
CHEMICAL RECOVERY
OF FIXED NITROGEN
AND SULFUR^
RECOVERED SEED
Figure 21(b). MHD Air Turbine Cycle
35
SULFURIC AC!D
NiTRIC ACID
-------
For a MHD station operating around 5 Teslas (1 Tesla = 10,000
gauss) with a preheat temperature of 3000°F, efficiencies of 60%
may be achieved in a binary cycle such as Figure 21(a).
Typical losses from MHD are:23
(1) Burner heat 2.5%
(2) Dry gas at 300°F 8.5*
(3) Expansion and contraction 4.0$
(4) Other process 2.0%
Thermodynamically, a regenerative Brayton cycle would have a
limiting efficiency of about 82%. However, the binary MHD
cycle efficiency will be reduced because of the steam cycle;
65% is considered a practical limiting efficiency.17 Use of
Rankine cycles could make this achievable by the year 2000.
R&D by Avco has been continuing since the early 1950's. Major
present-day efforts are primarily concerned with seed recovery,
high temperature combustion, air pollutants, and superconducting
magnets.
F. PORTABLE POWER SOURCES
Fuel cells and internal combustion and diesel engines are use-
ful portable power souces for electricity or motive power. They
are not as bulky as other power equipment and can provide power
whenever needed. Although the efficiency may not compare to
other sources, in many cases they represent the only feasible
alternative for power production. Fuel cells are generally so
efficient that the power industries interest is economic as well
as conservation oriented.
36
-------
1. Fuel cells (21)
Attempts have been made to use fuel cells for central power
stations with little success. Although the efficiency is gener-
ally high, their cost is too high and durability too low for
today's utility market. Since an individual fuel cell produces
about one volt, the number of possible trouble points in a unit
big enough to give reasonable outputs is staggering. A natural
gas fuel cell has been successfully used for small homes and for
portable power generation.3 Hydrogen/oxygen cells are routinely
used in space with effciencies as high as 90% (non-condensing)
methanol has been widely investigated as a fuel cell by a variety
of researchers.20
Limiting factors are all practical problems since under controlled
conditions 80-99% of the thermodynamic energy can be recovered.
Direct methanol fuel cells lose excessive fuel to carbonate form-
ation and evaporation in most applications. Thus they have lower
efficiencies than hydrogen cells even though the thermodynamic
limit is higher. This is caused by oxidation at the anode and
cathodic corrosion. This leads to low over-voltages and low
current densities.
Several substance can be used to extract hydrogen for a fuel
cell from water (see figure 22(a) and 22(b)). Examples are coal
and methanol. They may also contain substantial amount of
hydrogen which can be liberated. Methanol can be reformed accord-
ing to the following endothermic reaction:
4,
CH3OH + H20 -»• 3H2
Energy efficiency of this reaction has been demonstrated to be
36%.25 Since economics do not favor this method of producing
hydrogen, very little has been done with it since about 1950.
An efficiency of 60% was used for 1990 and supposed economic
37
-------
OJ
CO
H20 ..„._».
Gasification
•C02 H- H2
Figure 22(a) Hydrogen Fuel Cell Methanol
CH3UH ».
H20 ^
Reformer
^C02 H
h H2— »-
Fuel Cell
Figure 22(b) Hydrogen Fuel Cell Using Coal
kW
kW
Coal
H20
Gasification
CH,
Reformer
— »-C02 + H2 -»-
Fuel Cell
kW
Figure 22(c) Pratt and Whitney Fuel Cell System
-------
interest in this path. Coal may also be used to produce hydr
from water through a similar reaction:
C + 2H20 •*• C02 + 2H2
This is a low Btu gasification process which operates at lower
efficiency due to the greater amount of hydrogen produced. The
limiting efficiency is 77-5$ for the conversion. In both cases
the hydrogen is used to produce electricity in the fuel cell.
The reforming and fuel cell efficiencies are multiplicative.
Pratt & Whitney and a group of utilities have studied the techni-
cal feasibility of using fuel cells for peaking power but progress
has been slow in overcoming mechanical failures.3 When developed
the Pratt & Whitney system is expected to be similar to that shown
in Figure 22(c).26 Westinghouse and the Office of Coal Research
ran out of funds in developing a coal-energized fuel cell system
in the early 1970's. Fuel cells may be applied to major power
generation to a limited extent, but probably not until after
1990.
2. Automotive (22)
The internal combustion (I-C) engine is best approximated by the
Otto cycle. The thermodynamic efficiency is a function of the
compression ratio only. Reduction of this efficiency from thermo-
dynamic is a function of the variable specific heats, dissocia-
tion, and heat loss. For a typical 9:1 compression ratio engine,
(100$ theoretical air) the efficiency is presently ^l^.1 When
this same engine is used to drive a typical American-made auto-
mobile, (16 mpg), the efficiency drops to 8$,23 but efficiencies
as high as 28$ have also been recorded. Major limiting factors
are:
39
-------
(1) Vehicle weight
(2) Air drag
(3) Idling losses
(4) Drive line drag and losses
Vehicle redesign with emphasis on loss factors (1) and (2)
should improve the efficiency. These are expected to be counter-
acted by lower compression ratios and air usage necessary to meet
emission control requirements. The I-C engine is not expected
to survive beyond 1990.21 It will probably be replaced with
diesel or turbine engines, or electric motors.
3. Diesel (23)
Diesel engines operate at higher compression ratios and compress
the combustion air prior to fuel injection. As in the Otto
cycle (I-C engine) the efficiency can be obtained from the known
compression ratio. A 15:1 ratio was selected for determinations
in this study. The vehicle efficiency is much lower and the
limiting factors are the same as for the automobile. No R&D
programs aimed at improvement of this engine are known.
-------
V. REFERENCES
1. Marks, L. S. and Baumeister, T. S.; "Standard Handbook for
Mechanical Engineers;" pages 9-24, 9-142
2. Shields, Carl D.; "Boilers;" F. W. Dodge; New York, New
York, 1961; pages 509, 503
3. Schurr, Sam H.; "Energy Research Needs;" NTIS PB 207516;
Washington, D. C., 1971; pages VI-12, VI-14
4. Union Oil Products; "Fossil Fuel Boilers in S02 Removal
Processes;" Company literature handout, and personal
communication
5. Hedley, W. H.; "Effect of Gas Turbine Efficiency and Fuel
Cost on Cost of Producing Electric Power;" Monsanto
Research Corporation, August, 1973; EPA Contract 68-02-1320,
Task 2
6. Robson, Giramonti, Lewis, and Gruber; "Technical Economic
Feasibility of Advanced Power Cycles and Methods of Pro-
ducing Fuels;" United Aircraft Research Laboratory; Decem-
ber, 1970; NAPCA Contract CPA-22-69-H4; pages 110, 160,
212, 218, 230
7. Personal Communication - Bruce Hinchel, Environmental
Protection Agency
8. Personal Communication - Jack Huebler, Institute of Gas
Technology
9. Personal Communication - Kelley Janes, Environmental
Protection Agency
41
-------
10. Personal Communication - A. Glen Slider, M. W. Kellogg
Company
11. Lummus, C. E.; "Coal to Gas Prototype Pilot Plant;" U. S.
Bureau of Mines, Bruceton, Pennsylvania; October 13, 1973;
Contract HO 110989; page III-5
12. Hamersma, Koutsoukos, Kraft, Meyers, Ogle, and Van Nice;
"Chemical Desulfurization of Coal: Report of Bench-Scale
Developments;" TRW Systems; Volume 1 PB 221-405; February,
1973
13. Akhta, Friedman, and Yavorsky; "Low Sulfur Fuel Oil from
Coal;" Bureau of Mines Progress Report 35; July, 1971
14. "Second Round Delphi Questionnaire;" Monsanto Research
Corporation; November, 1973; EPA Contract 68-02-1320,
Task 3
15. "Evaluation of Fluid Bed Combustors;" Westinghouse Re-
search; PB 211-494, Volume 1; August, 1971
16. Personal Communication - Richard DeVierman, Universal Oil
Products
17- Personal Communication - F. A. Hals, AVCO Everett
Laboratory
18. Sutton, G.; "Direct Energy Conversion;" McGraw-Hill Book
Company; New York, New York, 1966; pages 4l, 207
19. Mitchell, W.; "Fuel Cells;" Academic Press; New York,
New York, 1966; page 176
-------
20. Liebhafsky, H. J. and Cairns, E.; "Fuel Cells and Fuel
Batteries;" John Wiley and Sons, New York, New York,
1968; page 452
21. Personal Communication - J. T. Hepp, Consultant
22. Personal Communication - G. F. Ondish, Gulf Research
and Development Co.
23. "The U.S. Energy Problem," ITC report C645 to the
National Science Foundation, Inter Technology Corp.,
Volume II: Appendices, November, 1971
24. Harris, W- D. and Davidson, R. R., "Methanol from Coal
Can Be Competitive with Gasoline", Oil and Gas Journal,
December 17, 1973, Pg 70. Personal Communications.
25. Kirk, R. E., and Othmer, D. F., "Encyclopedia of
Chemical Technology," Vol. 7, The Interscience Encyclo-
pedia Inc., New York, 1952
26. "Why Utilities Are Backing the Fuel Cell", Business
We k, January 12, 1974: page 28c
27- Jones, F. L. and Vorres, K. S., "Clean Fuels from Coal -
an Alternative to SNG," 1973 American Chemical Society
Annual Meeting, Division of Fuel Chemistry, August 1973
28. Persona.1 Communication - Joe Schons, Vulcan-Cincinnati.
29. Hammond, 0., M.I.T. unpublished Seminar notes,
January 1974.
-------
TECHNICAL REPORT DATA
(Please rcail ImunifiHHUi on ilie reverse before c
| EPA-650/2-74-021
4 TITL.L -V\DSL'STITLE
Efficiencies in Po^er Generation
IT. A.UTHORIS)
T.R. Blacixwood and W. H. Hedley
3. RECII'll. NTS ACCbSSION-NO.
5. REI'OHT DATE
March 1.974
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
MRC-DA-404
. PERFORMING OPSANIZATION NAME AND ADDRESS
Monsanto Research Corporation
Dayton Laboratory
131S r,icliola3 ixoad, Dayton, Ohio 454u/
10. PROGRAM ELEMENT NO.
1AB01S: RGAP 21ADE-29
11. CONTRACT/GRANT NO.
68-02-1320 (Task 7)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA. Office of Research and Development
IxEKC-RTP, Control Systems Laboratory
Research Triangle Park, North Carolina ?77U
13. TYPE OF REPORT AND PERIOD COVERED
Final, 11/73 - 2/74
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT T!ae rSpOr£ introduces 23 different ways of using or converting energy. It
provides a tabular comparison of the thermodynamic limiting; present and. future
(1990) efficiencies. It includes a brief discussion of efficiency limiting factors ,
possible general routes for process improvement, and relevent on-going research
and development. The report concludes that more study is required in several of the
following (alphabetically listed) areas: atmospheric fluid-bed combustion, automotive,
bottoming cycle, chemical coal cleaning systems, chemically active fluid-bed comb-
ustion, coal cleaning plants, coal liquefaction, combined cycle (gas and steam),
conventional boilers, conventional boilers plus flue gas cleaning, conversion of coal
to methanol, diesel, Feher cycle, fuel cells, gas turbines, high-Btu gas generation,
low-Btu gas generation, magnetohydrodynamics, nuclear power plants, potassium
topping cycle, pressurized fluid-bed combustion, residual oil desulfurization, and
steam turbines.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Held/Group
Air Pollution
Power
Energy
Uti li zation
Conversion
Thermodynamics
Liquefaction
Boilers
Flue Gases
Fluidized Bed
Processing
Nuclear Power Plants
Gas Generators
Des ulfur ization
Pollution Control
Combined Cycle
13B
10A
20M
18E
10B
18L
13. DISTRIBUTION STATEMENT
19. SECURITY CLASS {This Report}
Unclassified
Unlimited
21. NO. OF PAGES
47
20. SECURITY CLASS {Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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