EPA-650/2-74-004
January 1974
Environmental Protection Technology Series
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EPA-650/2-74-004
IRON FOUNDRY CUPOLA
RECUPERATIVE EMISSION
CONTROL DEMONSTRATION
DESIGN MANUAL
by
Joseph F. Coursey
Flynn and Emrich Co.
3001 Grantley Avenue
Baltimore, Maryland 21215
Contract No. 68-02-0286
ROAPNo. 21ARO-02
Program Element No. 1AB013
EPA Project Officer: Robert C. McCrillis
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
January 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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ABSTRACT
The utilization of the heat in exhaust gases from an iron
foundry cupola melting operation has long been an objective of
the industry. Unfavorable economics and technical limitations,
however, have limited development and employment of cupola
waste heat devices to a relatively few installations. The
recent laws requiring air pollution control on cupolas have
resulted in major capital expenditures in cupola melting
facilities. This required control, together with the recent
energy shortages, has lead to renewed interest in waste heat
recovery methods.
This demonstration, utilizing a dry media heat exchanger
for producing hot blast air for cupola melting, will test the
technical feasibility of this type of heat exchange unit as
well as the validity of the economic assumptions that indicate
a savings in fuel, air pollution equipment costs, and a net
reduction in operating costs. This Design Manual describes the
system, provides estimates of the gross economic benefits, pre-
sents the capital cost of the system, and briefly describes
operation of the system to date.
This report was submitted in partial fulfillment of
Contract Number 68-02-0286 by Flynn and Emrich Company under
the sponsorship of the Environmental Protection Agency.
iii
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ACKNOWLEDGMENTS
The conception and design of the air pollution control
system and the heat exchanger are those of Combustion Equipment
Associates, Inc., 555 Madison Avenue, New York, New York 10306.
Much of the technical data and information used for the drawings
in this report were supplied by Mr. Paul J. Vandenhoeck of C.E.A.
The conception and design of the cupola are those of
R. & R. Zoller Industries, Inc., Beltsville, Ohio 44815.
Mr. Robert H. Zoller supplied the information concerning the
design of the cupola.
Mr. Robert C. McCrillis of the Office of Research and
Development, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711 is the Project Officer.
1v
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CONTENTS
Page
Abstract ill
Acknowledgments iv
List of Figures vi
Sections
I Conclusions 1
II Introduction 3
III Description of System 7
IV Projected Operating Economics 27
V Installed Cost 37
VI System Start-Up 39
VII Conversion Factors 43
VIII References 44
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FIGURES
No. Page
1 Flow Schematic (15 ton per hour model test case) 6
2 General Arrangement. Plan View 9
3 General Arrangement, Main Elevation 10
4 General Arrangement, After Double Cyclone 11
5 View of Charge Turntable, Double Cyclones,
ID Fan, and Water Tank 13
6 View of Cupola, Vertical Quench, and Heat
Exchanger 14
7 View of Cupola, Heat Exchanger, Double
Cyclones, and ID Fan 15
8 View of Cyclones, ID Fan, and Site of Future
Baghouse 16
9 Cupola and Water Tank Layout 17
10 Water Cooled Cupola 18
11 Water Tank 19
12 Cupola Top 20
13 One Group of Two Cyclones, General Arrangement 22
14 Dry Media Heat Exchanger Schematic 23
v1
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SECTION I
CONCLUSIONS
Installation of the new Internally water-cooled cupola and
the associated recuperative emission control system commenced in
mid-1971. Hot metal was initially produced in July 1972. All
operations to date have been with the heat exchanger bypassed,
due to unsatisfactory performance of the original retention tray
design during model tests. Installation of the redesigned trays
is now complete with on-line operation of the heat exchanger
projected for early January 1974, following installation of a
larger 10 fan and resolution of problems in the water spray temperature
control system.
Early operation of the new water-cooled cupola indicated an
inadequate slag layer, which serves as the refractory, around and
between the cooling tubes. Increased coolant flow, together with
revised slag chemistry (to increase eutectic temperature), has not
provided an adequate solution.
Installed cost for the complete system Including the cupola
will be about $342,000. Installed cost for the recuperative emission
control system alone will be about $171,000.
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Estimates have been made of the gross economic benefits to
be derived by recouping the waste heat In the cupola exhaust.
When used solely for hot blast, coke savings of over 20 percent
are projected. At a nominal operating condition, coke savings
of approximately 10 percent are projected; In addition, there
will be nearly 3.5 million Btu/hr* of surplus energy available
In the form of clean hot air.
*A list of factors for conversion from non-metric to metric
units is provided in Section VII of this report for the
convenience of the reader.
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SECTION II
INTRODUCTION
Flynn and Emrich Co., a medium-sized gray iron foundry
located within metropolitan Baltimore, was confronted In early
1970 with planning to meet the State of Maryland air pollution
regulations for Its melting facility. The Company soon recognized
a problem that exists today, common to all foundries; i.e., air
pollution systems are presently being installed on cupolas in the
United States at a complete economic loss to the installers.
The temperature of the gases at the top of the cupola stack
Is in the 1600 to 2200°F range; whereas, the cleaned exhaust
gases will be 550°F or lower. This represents an energy loss
on the order of 1.5 to 3.0 million Btu/ton of Iron produced.
A considerable potential for cost reduction exists if this
energy, which is normally a total loss, could be economically
converted to useful form.
Flynn and Emrich, with limited capital resources, became
firmly convinced that utilization of this potential was necessary
for the Company to stay in business. Thus, an intense study of
alternative solutions that could result in reducing the cost of
air pollution control was initiated. After a review of many
proposals, Flynn and Emrich selected a Combustion Equipment
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Associates, Inc. concept as the most viable potential solution
to the problem. The keystone to the ultimate success of the
system is the dry media heat exchanger and its potential to:
(1) make available free waste heat in the form of clean hot air;
(2) permit the use of low cost fabric material 1n the baghouse;
and (3) minimize the volume of gases to be cleaned and, hence,
the cost of the emission control system.
On June 30, 1972, Flynn and Emrich sinned a contract (68-02-
0286) with the Environmental Protection Agency, to cover a 1 year
emission testing and system evaluation program to be performed
on their integrated cupola recuperative emission control system.
From the data gathered, Flynn and Emrich will be able to establish
potential emission control enhancement and cost reduction, component
degradation, wear points, maintenance requirements, system reliability,
and optimum operating procedures. The data gathered will be used to
123
verify the mathematical model of the system provided by EPA. ' *
Using the validated model (sized to suit the varied melting depart-
ments encountered in the domestic iron foundry industry), Flynn and
Emrich will then project the system's performance.
This Design Manual, submitted as partial fulfillment of the
contract requirements, describes the system in detail and provides
estimates of the gross economic benefits to be derived by recover-
ing the waste heat. Capital cost of the system and of each principal
component is also presented. The concluding section briefly
describes operation of the system to date. The final report, to be
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issued at the conclusion of the 1 year test program, will include a
complete listing of the data and the analytical procedures employed
including a full description of the mathematical model. Most
importantly, it will contain an indepth discussion of the application
of the test results to the domestic iron foundry industry.
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GAS VOLUME
63,500 dm
AT 2000 °F
NEGATIVE PRESSURE
0.3 in. WC
DUST, 309 Ib/hr
CUPOLA
STACK
AFTERBURNER^
9000 CFH 4
FEED RATE
METAL 15 ton/hr
COKE 2.0 ton/hr
COMBUSTION AIR
5520 sclm
6AS VOLUME
35,400 dm
AT540°F
FIVE PRESSURE
5.0 in. WC
DUST
280 Ib/hr
IAS VOLUME \
54,300 clmi \_
AT 1550 °F
DUST
18 Ib hr
— WATER
^_660 gal/mm
.BLAST RATE
17,000 dm
AT920°F
GAS VOLUME
34,600 dm
AT 550°F
DUST
95 Ib/hr
NEGATIVE PRESSURE
AT FAN INLET
12 in. WC
WATER
5218 Ib/hr
DUST
11 Ib/hr
HEAT EXCHANGER
BLOWER
32 oz PRESSURE
8000 sclm
DUST'
94.6 Ib/hr
COLD BLAST
BLOWER
Odm
Figure 1. Flow schematic (15 ton pet hout model test case).
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SECTION III
DESCRIPTION OF SYSTEM
The subject of study in this contract Is the Integrated
cupola melting emission control system recently put into oper-
ation by Flynn and Emrich in Baltimore, Maryland. The unique
features of this system are a dry media heat exchanger and an
internally water-cooled cupola. Figure 1, a flow schematic of
the system, depicts the components and presents a hypothetical
operating point. The values shown for the various parameters
were derived by the mathematical model as a test case; they do
not represent actual operating data. In this test case, the
cupola is producing molten Iron at the design maximum rate of
15 tons per hour (tph). With a blast air temperature of 920°F
and no oxygen enrichment, the metal to coke ratio required is
7.5 to 1. The carbon monoxide rich gases emanating from the
charge are mixed with air insplrated through the charge door.
All combustibles are then burned in the afterburner (cupola
stack) which is piloted by a gas fired burner. The total flow
exiting the afterburner is 63,500 cfm at a temperature of
2000°F. The hot gas then flows into the downcomer where the
temperature is reduced to 1550°F. It then enters the upper
compartment of the heat exchanger and, after giving up heat to
the circulating media, exits at 860°F, is further cooled to 540°F
in a second water quench, and finally exits to atmosphere after
removal of particulates in the cyclones and baghouse.
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In the lower compartment of the heat exchanger, the circula-
ting media gives up its stored energy to the clean air being
supplied by the heat exchanger (hot blast) blower. The blast
air exits the heat exchanger at 1000°F, passes through a small
cyclone to remove any entrained media and continues on to the
cupola. Even at this condition of maximum hot blast utilization,
however, the heat exchanger is supplying about 14 percent more
air than can be used by the cupola. This excess air (2517 cfm
at 958°F) would be available for other uses such as heated plant
makeup air, core oven heating, etc. As the blast air temperature
requirement is relaxed, a greater proportion of the heat exchanger
output becomes available for other uses. As Is discussed in detail
in Section IV, Flynn and Emrich anticipates that, under typical
operating conditions of 10 tph melt rate and 600°F blast air, the
cupola will require less than one-half the heat exchanger output.
Much of the effort expended during the test and evaluation
program will be aimed at defining the performance parameters of
the system over the full range of cupola operation. Additionally,
complete records of operating and maintenance costs and system
operability and reliability will be maintained.
Figures 2 through 4 are general arrangement drawings of the
Flynn and Emrich installation. The fact that the new system had
to be compatible with the existing charge and hot metal handling
systems and in addition could not interfere with operation of the
8
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FOR THIS AREA SEE FIG 4.
ID FAN
EXHAUST
DUCT
ID FAN
AND MOTOR
NORTH
HAT URAL GAS BURNER COLD BLAST
COLD BLAST DUCT /Bt-olM_
/ / HOT BLAST
) ) / BLOWER
»
6ft-10 in.
HEAT
EXCHANGER
EXHAUST
DUCT
81f(-2m.-
VERTICAL HEAT
EXCHANGER
DVPASS
DUCT
PANEL
NOTE: FOR ELEVATIONS
SEE FIGURES 3 and 4
4-posmow
CHARGE
TURNTABLE
Figure 2. General arrangement, plan view.
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CUPOLA
VERTICAL
QUENCH
CT HEAT
HEAT EXCHANGER
EXCHANGER EXHAUST DUCT
BYPASS DUCT
NOTE- FOR PLAN VIEW. SEE FIGURE 2"
FOR ELEVATION AFTER DOUBLE
CYCLONE, SEE FIGURE 4
DOUBLE
CYCLONE
HOT BLAST
CYCLONE COLO BLAST HOT BLAST
BLOWER BLOWER
4-POSITION
CHARGE
TURNTABLE
Figure 3 General anangement, mam elevation.
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NOTE: FOR PLAN VIEW.SEE
FIGURE 2; FOR MAIN
ELEVATION, SEE FIGURE 3.
DOUBLE J
CYCLONE''
5 It 3-1/2 in.
PLAN VIEW
ELEVATION
35 ft 2-3/8 in.
•DOUBLE
CYCLONE
EXHAUST
-4 ft ID
ID FAN
EXHAUST
DUCT
SIDE VIEW ELEVATION
Figure 4. General arrangement, after double cyclone.
11
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old cupola during installation, was the major design constraint.
The photographs presented in Figures 5 through 8 further define
the relationship of the various components. Each of the principal
components is discussed in some detail in the following paragraphs.
The 4-position charge turntable, consisting of four charging
buckets and associated positioning controls, is used for dumping
the charge onto a loading conveyor. This vibrating conveyor is
designed to transport material from the charge buckets to the
charging door where it is fed into the cupola.
The internally water-cooled cupola (Figures 9 through 11)
melts the charges producing gray iron of the desired chemistry
and also a significant volume of hot contaminated gases.
Carbon monoxide and hydrogen gases, as well as any other
combustible compounds produced within and above the charge bed,
pass into a gas-fired afterburner section (Figure 12) for
complete oxidation, exiting from the afterburner at a temperature
ranging from 1600 to 2200°F. Water is injected into these gases
in the vertical quench section to limit the gas temperature into
the heat exchanger to 1550°F.
At this point, a bypass arrangement permits either a portion
or all of the exhaust gases to enter the upper section of the
fluidized-bed heat exchanger. The remainder of the exhaust gases
12
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DOUBLE
CYCLONES
EXHAUST
4-POSIT10N
CHARGE
TURNTABLE
(4TH NOT VISIBLE)
Figure 5. View of charge turntable, double cyclones, ID fan, and water tank.
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VERTICAL
QUENCH
DUCT
HEAT
EXCHANGER
;EXHAUST DUCT
Figure 6. View of cupola, vertical quench, and heat exchanger.
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CYCLONE
EXHAUST
CT
CHARGE
CONVEYOR
INCLINE
Figure 7. View of cupola, heat exchanger, double cyclones, and ID fan.
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DOUBLE
CYCLONE
EXHAUST
FUTURE
l_BAGHOUSE_j
Figure 8. View of cyclones, ID fan, and site of future baghouse.
16
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CORE
ROOM
?p^ 3
PRESENT
"CUPOLA
-€ft5i
in. ENGLE CUPOLA
(SEE FIGURE 10)
WATER TANK
FOR CUPOLA
(SEE FIGURE 11)
MULLER AREA
Figure 9. Cupola and water tank layout.
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WIND BOX
AIR INTAKE
COOLING
WATER
TUBES
(48)
Figure 10, Water cooled cupola.
18
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STACK
6 in. PIPE
WATER
OUTLET- :^>
WATER
WATER
OUTLET-
WATER
INLET.
WATER
OUTLET
Figure 11 Water tank.
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ELEVATION S3 ft 2-1/8 in.
4-1/2 in
REFRACTORY
9 in.
REFRACTORY
12 in.
REFRACTORY
79-1/2 in.
ROLLED BAR
T
ELEVATION 0 ft 0 in.
Figure 12. Cupola top.
20
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which are not diverted through the heat exchanger, as well as
the cooled heat exchanger outlet gases, continue on to a pair
of dry cyclones (Figure 13), which remove about 70 percent (by
weight) of the total dust emissions, and finally are delivered
to the baghouse to be installed after the design parameters
are established based on the operation of the heat exchanger.
The initial purpose of the heat exchanger is to utilize
the available thermal energy from a portion of the exhaust
gases to preheat blast air for the cupola from ambient tempera-
ture to as high as 1000°F. Controlled recirculation of the bed
material through the hot gas section and cool air compartment
maintains the desired internal operation of the heat exchanger.
Appropriate ambient bleed air controls are provided to supply
proper mixing ratios with the heated air for final control to
the desired blast air temperature. The heat energy supplied to
the cupola in the blast air reduces the quantity of coke required,
thus effecting substantial fuel savings.
Basically, the heat exchanger (Figure 14) consists of a hot
flue gas section, a separate clean air compartment and heat
transfer media in the form of fine-mesh ceramic particles. These
particles are transported by air in an enclosed central duct to
the upper or exit area of the flue gas compartment. Trays, with
specified openings, are used to build up layers of fluidized-bed
material with controllable retention time to permit the desired
21
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-j LOUT LET
• i ii
INLET
• 5 ft 6-3/4 m.-*
WEIGHT 8400 Ib
Figure 13. One group of two cyclones, general arrangement.
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CUPOLA EXHAUST
OUTLET
MEDIA DEFLECTION CONE
CUPOLA EXHAUST
INLET
FLOW FEEDER PIPE
(6 TOTAL)
HOT BLAST
AIR OUTLET
TRAY CONTROL
MEDIA NOZZLE
O* hi* I i ini i mi i_i » •
I CONTROL BLOWER
PERFORATED TRAY CONE
6 TOTAL PER TRAY LEVEL
30% OPEN, 1 in. DIAMETER HOLES
HOPPER MEDIA
DEPTH CONTROL
AIR SUPPLY FROM
CONTROL AIR BLOWER
TRAY PRESSURE
DROP CONTROL
AIR SUPPLY FROM
CONTROL AIR BLOWER
HOT BLAST
AIR INLET
AIR
•" MEDIA
TRANSPORT FAN
Figure 14. Dry media heat exchanger schematic.
23
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heat exchange to occur. Upward countercurrent flow of exhaust
gases through holes in the trays not only fluidize the bed but
permit controlled release of fluidized media downward through
the holes and on to successive trays.
After absorbing heat from the hot flue gases, the media is
collected in a surge hopper, which maintains sufficient bed
height to provide an isolation seal between flue gas and ambient
air compartments. Particle flow regulators control the flow of
heated bed materials into the clean air section of the heat
exchanger, which is furnished with a similar arrangment of
retention trays. After yielding up its stored heat energy to
ambient air, the media is collected in a storage compartment
which feeds another particle flow regulator. This regulator
controls the flow rate at which the media is transported up
through the center duct to the flue gas compartment, thereby
starting another cycle of heat removal and recuperation.
The combination of energy waste and additional equipment
cost to dispose of it makes the development of more efficient
heat exchangers for the foundry industry essential. Unlike
conventional equipment, the efficiency of the circulating media
heat exchanger is not related to the amount of the stationary
surface area required to develop the desired efficiency. The
cost of conventional systems 1s proportional to the surface area
required. The surface area in turn increases rapidly with each
24
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percentage increase of desired heat recovery efficiency. On the
other hand, the cost of a circulating media heat exchanger is
fixed by the amount of gases to be handled. The efficiency is
related only to the energy required to maintain the media in
contact with the gases. The desired heat recovery is, therefore,
a function of operating cost rather than fixed capital cost. The
Flynn and Emrich heat exchanger should be capable of obtaining
85 percent heat recovery. Obtaining this type of efficiency with
a conventional air to air stationary surface system would be
completely uneconomical for all but the largest foundries. Also,
previous applications of conventional heat exchangers to recoup
cupola waste heat have met with little success due in part to the
fouling of the heat exchange surface by the dust in the gases.
Some attempts have been made to clean the gases prior to combustion
of the CO. However, this approach requires zero leakage, particu-
larly with induced draft systems, to preclude the formation of an
explosive mixture.
In addition, unlike conventional tube-type heat exchangers,
the circulating media serves only as a heat transfer medium and
not as both heat transfer surface and structural member. This
permits the selection of materials such as ceramics to allow the
unit to operate at substantially higher temperatures.
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The electrical control system 1s necessarily more complex
than would be found on a cupola equipped with a standard air
pollution control system; however, because every effort was made
to automate It, the current skill level of cupola operators Is
sufficient to operate the new system. Likewise, the controls
and Instrumentation, while adding to the maintenance load, do
not add new technology to the current skills of foundry mainten-
ance personnel.
26
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SECTION IV
PROJECTED OPERATING ECONOMICS
The melt facility being studied at Flynn and Emrlch has a
solid media heat exchanger in the exhaust gas system between the
cupola stack and the pollution control device. If this heat
exchanger performs as anticipated, it will deliver 8,000 scfm
of air at 1000°F at the maximum melt rate (15 tons per hour)
of the cupola and 5000 scfm of air at 1000°F at the minimum
(7-1/2 tons per hour). The most obvious use for some of this
energy is as preheated blast air for the cupola. This would
allow a substantial reduction in the use of coke in the
cupola, thereby providing a fuel cost savings. The reduction
in coke will yield two additional benefits: (1) coke is a major
contributor to the air pollution problem both during its manu-
facture and its consumption in the cupola; and (2) there is a
well-publicized national shortage of metallurgical coal and coke.
Since the demands of the cupola will be in the order of
4500 to 5000 scfm of air at 500-700°F (less than half of the
capacity of the heat exchanger), there will be considerable
heat energy available for other uses. The system to be installed
at Flynn and Emrich includes only the equipment necessary for the
conversion of waste heat to preheat blast air for the cupola.
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Another function of the heat exchanger 1s to reduce the
volume of the exhaust gases to be cleaned, relative to standard
air pollution control systems. This reduction In volume occurs
because the gas temperatures are lowered In the heat exchanger
rather than through air dilution or water quench. This permits
the air pollution control equipment, 1n this case cyclones and
a baghouse, to be smaller In size (less cfm) than would otherwise
be required and, therefore, contributes to savings 1n the total
system Installation and operating costs.
Substantiation of the fuel savings, development of data to
permit evaluation of other savings by the utilization of the
remainder of the heat available, and demonstration of an Integrated
melting air pollution control system are the major thrust of this
study.
Some of the possibilities for waste heat utilization, In
addition to the hot blast arrangement, would Include:
1. Heated make-up air for the plant.
2. Heat for core ovens.
3. Heat for sand temperature control in sand mixing.
4. Absorption refrigeration.
Another aspect of waste heat utilization from the heat
exchanger, one which certainly merits investigation within this
program, would be the storage of heat energy for use during off-
28
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melting hours. This could be accomplished by the use of a material
such as Dowtherm, which would be heated by excess air from the
heat exchanger and stored in an insulated reservoir. It would
appear possible to store this liquid at temperatures near 800°F
and to circulate it to ovens or other points in the plant as
required. Use of this procedure would enable foundries to achieve
long-term use of waste heat generated from a short melt time.
The cupola will use a recirculating water system for
refractory cooling. The heated water from this system might be
used for the following purposes:
1. Office and plant heating.
2. Hot water supply for showers.
3. Low pressure steam.
The major consideration in the decision to install this
system was the anticipated cupola fuel savings made possible by
the use of the heat exchanger. Data and calculations in support
of this decision are shown below.
In a cold blast cupola all of the heat required to preheat,
melt, and superheat the metal and to satisfy the demand of
radiation losses, water decomposition, slag melting, calcining,
etc., is furnished by the combustion of the fuel, coke.
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In a hot blast cupola part of these heat requirements are
supplied by the sensible heat of the hot blast.
The calculation of the savings In coke made possible by
heat supplied from the hot blast, however, is not one of a
simple substitution of the Btu's in the blast air for a constant
Btu value for coke. This is the case since part of the heat
of combustion is removed from the cupola as a result of carbon
dioxide (COg) being reduced to carbon monoxide (CO) in the
reduction zones of the cupola. The lower the percentage of
C02 converted, the greater is the quantity of heat available
for effective use. The C02 content of the effluent gas may be
taken as a fairly reliable indication of these conditions.
Table 1. HEAT AVAILABLE FOR MELTING
trriuent
Gas
% C02
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
% CO
23.1
21.5
19.8
18.2
16.5
14.8
13.2
11.6
9.9
8.3
Heat developed,
Btu/lb of carbon
6716
7114
7533
7961
8431
8910
9409
9930
10490
11064
Heat developed, ^ Btu/lb of
coke (coke @ 90% carbon)
6039
6403
6780
7165
7588
8019
8468
8937
9441
9958
30
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Table 1 shows that the heat available from the coke varies
appreciably with the CO/(£2 ratio and that an anticipated coke
savings calculation requires an estimation of this ratio. A
cupola operating at a low metal-to-coke ratio (I.e., using
relatively large amounts of coke and thus melting slower) will
have a higher percentage CO formation with less heat developed
per pound of coke. Conversely, a cupola using less coke and
melting faster will have a lower percentage CO formation and be
receiving greater Btu output per pound of coke.
Thus a replacement of a given amount of the heat require-
ment, by heat from the heat exchanger hot blast, will replace
different amounts of coke, depending on the melting conditions
and rate in the cupola.
A few sample calculations will demonstrate this.
Case I. Maximum melt rate = 15 ton/hr.
Maximum heat exchanger output = 8000 scfm @ 1000°F.
Total heat available from the heat exchanger:
HE = air vol x sp wt x sp ht x temp diff
HE = 8000 x 0.0749 x 0.242 (1000 - 70)
= 134,856 Btu/min.
Since at the maximum melt rate, minimum CO is produced, the
coke is replaced at the estimated rate of 9,441 Btu per pound.
31
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Thus 134.856 _ 14.28 Ib of coke/min may be replaced
9,441 " if all the heat exchanger output is
supplied to the cupola.
Case II. Intermediate melt rate = 10 ton/hr.
Heat exchanger output = 6000 scfm 0 1000°F.
HE = 6000 x 0.0749 x 0.242 (1000 - 70)
HE = 101,142 Btu/min.
At an intermediate melt rate, a nominal CO formation is
assumed and coke is replaced at the rate of 8,019 Btu/per pound.
Thus 101.142 _ 12.61 Ib of coke/min may be replaced
8,019 " if all the heat exchanger output is
supplied to the cupola.
Case III. Minimum melt rate = 7-1/2 ton/hr.
Minimum heat exchanger output = 5000 scfm @ 1000°F.
HE = 5000 x 0.0749 x 0.242 (1000 - 70)
HE = 84,285 Btu/min.
At minimum melt rate, maximum CO is produced; therefore, coke
is replaced at the rate of 6,403 Btu per pound.
Thus 84,285 = 13.17 Ib of coke/min may be replaced
6,403 " if all the heat exchanger output is
supplied to the cupola.
The above calculations are oversimplifications and rough
approximations at best; however, they do show that as the heat
exchanger output drops due to a lower melt rate (lower volume of
exhaust air being available to the heat exchanger), the cupola
melting efficiency (expressed by the Btu's developed per pound
of coke) also drops. This offsetting characteristic of the
32
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melt-heat exchanger system thus allows an assumption of a constant
coke replacement per hour of melt. On the basis of this review,
Flynn and Emrich decided to use an expected coke saving of 12
pounds per minute for 1000°F blast air (regardless of the melt
rate) in the decision to purchase the heat exchanger.
With a nominal melt rate of 10 tons per hour and a metal-to-
coke ratio of 6 to 1, coke usage without hot blast would be 333 Ib
of coke per ton (2000 Ib) of iron melted, or 3333 Ib of coke per
hour. Using the hot blast to maximum capacity, the coke consumption
would be reduced to 261 Ib of coke per ton of iron melted, or
2610 Ib of coke per hour (approximately 7.7 to 1 metal-to-coke
ratio). This represents a savings of 72 Ib of coke per ton of
iron melted, or 720 Ib of coke per hour. The calculation is as
follows:
60 min (1 hr) of melt x coke savings of 12 Ib per minute =
720 Ib of coke saved per hour.
?0°tons/hr = 72 lb of coke saved per ton melted<
This represents a 21-1/2 percent savings in coke, a gross
savings of $2.11 per ton of iron melted, or $21.12 per hour of
melt at the current (Fall 1972) delivered coke price of $58.68
per ton. The net savings, of course, depend on the operating cost
of the heat exchanger which will be established over the 1-year
test program.
33
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The above determinations assume full utilization of the heat
exchanger capacity for use as cupola hot blast. Actual production
requirements are not expected to allow the full capacity to be used
for melting; heat will be available for use in other foundry appli-
cations. The calculations below show the potential utility cost
savings for excess heat not used for the hot blast.
Utility Savings
1. Assume an average of 101,142 Btu per minute available from
the heat exchanger; that is, the output of the heat exchanger
expected during a nominal 10 ton/hr melt rate.
2. Natural gas rates for Flynn and Emrich are:
$0.1438 per 100 cu ft considering all usage; and
$0.097 per 100 cu ft in lowest rate block charged.
3. Electric rates for Flynn and Emrich are:
$0.0282 per KWH, including demand, considering all usage; and
$0.0146 per KWH in lowest rate block charged.
Natural Gas
1 cu ft of natural gas = 1020 Btu; therefore
Thus, the total output of the heat exchanger 1s equivalent to 99.16
cu ft of natural gas per minute. This equates to a potential
savings of:
"-16 x^° x °-1438 = $8.56/hr, using average gas cost; or
"-16 x° x °'097 = $5.77/hr, using minimum gas cost.
34
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Electricity
1 KWH of electricity = 3,413 Btu; therefore
101.142 Btu/min _ ?q ,, wu/mtn
3,413 Btu/KWH ' Z9'63 KWH/min-
Thus, the total output of the heat exchanger is equivalent to
29.63 KWH of electricity per minute. This equates to a potential
savings of:
29.63 x 60 x 0.0282 = $50.13/hr, using average electricity
cost; or
29.63 x 60 x 0.0146 = $25.96/hr, using minimum electricity
cost.
Thus, the total heat exchanger output from a 10 ton per hour
melt rate could represent a heat source equivalent to approxi-
mately 6000 cu ft of natura-l gas per hour, or 1775 KWH of
electricity per hour.
A coke and utility savings combination, typical of what is
actually expected in production for a 10 ton/hr melt rate, could
be as follows:
Typical cupola use of the heat exchanger, as determined by
the cupola operator to meet production requirements, might be:
4,500 scfm at 600°F.
HEC = 4,500 x 0.0749 x 0.242 (600-70)
HEC = 43,230 Btu/min to the cupola
= 5.39 Ib of coke/min replaced by the hot blast
5.39 x 60 x jrg§§= $9.49/hr in coke savings.
35
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The remaining capacity of the heat exchanger would be:
101,142 Btu/min capacity at 10 ton/hr melt rate
- 43,230 Btu/min used by cupola
57,912 Btu/min is available for other uses.
53i413 Btu^KUH " 16'97 KWH/min of electricity
or
5?'J20 Btu/cu"ft = 56'78 cu ft/min of natural *"•
Thus, the potential savings of utilities would be:
16.97 x 60 x 0.0282 = 28.71/hr, using average electricity costs
16.97 x 60 x 0.0146 = 14.87/hr, using minimum electricity costs
or
56.78 x 60 x 0.1438
100
56.78 x 60 x 0.097
= $4.99/hr, using average gas cost
= $3.33/hr, using minimum gas cost.
The combined potential gross savings achieved by using the
heat exchanger would be: $9.49/hr in coke savings plus one of,
or some combination of both, the above utility savings.
36
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SECTION V
INSTALLED COST
The entire Installation of the new melt facility with pollution
control and the heat exchanger at Flynn and Emrich is expected to
cost about $342,000 as outlined below.
1. Basic cupola emission control system $115,000
(not including baghouse to be added later)
2. Cupola 52,000
3. Charging equipment 85,000
4. Foundation work 34,000
5. Heat exchanger 56,000
Total 342,000
Since the existing cupola at Flynn and Emrich was fully
depreciated and the charging system was a high cost maintenance
problem, it was decided that this older equipment would not
warrant an investment of this magnitude. Thus, the pollution
control equipment and heat exchanger alone represent about a
$171,000 investment which could have been made on an existing
melting system in another foundry with a more modern charging
facility.
The heat exchanger cost of $56,000 represents a turn-key
installed cost. Combustion Equipment Associates estimated
37
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approximately $2,000 of this total cost could be allocated for
erection and installation of the heat exchanger.
38
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SECTION VI
SYSTEM START-UP
The new cupola emission control system started up in July
1972. Initially, it operated intermittently, with major pro-
duction demands met by the old cupola. Debugging of the new
system has now progressed to the point where 100 percent of
production demand is being met with the new system. All
operations to date, however, have been with the heat exchanger
bypassed. This has been due to the fact that Combustion Equip-
ment Associates found during scale model tests that the original
retention tray design did not provide sufficient gas flow area.
Several redesign/prototype-testing cycles were required before
a satisfactory design was developed. It is now anticipated that
installation of the heat exchanger trays will be completed and
the unit on-line by early January 1974.
Perhaps the most vexing problem, outside of the heat exchanger,
concerns the refractory practice employed in the new cupola. The
cupola melt zone employs internal water cooling, rather than the
more conventional brick lining. The cooling unit consists of a
number of vertical tubes arranged around the inner diameter of
the shell. In operation, the rate of cooling should be such that
a continuous layer of solidified slag is maintained at all times
between and around these tubes. Initial operation of the cupola
39
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showed, however, that there was little or no slag buildup; and
that the cooling tubes were continuously exposed to molten iron.
This exposure caused severe erosion of the tubes which would
have resulted in an unacceptably short tube life.
In December 1972, the cooling unit was replaced with one
containing more tubes at a reduced spacing. Although this
resulted in a substantial improvement, portions of the tubes
were still exposed to molten iron.
Chemical analysis of the slag from the new cupola indicated
that it had a lower eutectic temperature, relative to the slag
from the old brick-lined cupola, even though the same limestone
was used in both. Since the new cupola slag exhibited a lower
silicon content, it was felt that the addition of silicon to the
charge, to simulate the silicon contributed by the bricks in the
old cupola, would increase the eutectic temperature and thus
improve operation.
Initial tests with the revised slag chemistry, using old
cores for silicon addition, were inconclusive. It was, therefore,
decided to continue the revised chemistry and, in addition,
increase the capacity of the cooling water circulating pump
capacity from 550 to 780 gpm which could be done without changing
the pump body. At the same time, the trough refractory was
40
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replaced because It did not appear to be compatible with the
revised slag chemistry.
The combination of increased cooling water flow and a higher
eutectic temperature slag appeared to have completely solved the
problem. After an initial period of trouble-free operation, however,
minor water leaks started to develop. Finally, following the
occurence of a major water leak and in light of the fact that
increased production demands left little leeway for experimentation,
the water cooling unit was removed and the cupola converted to a
conventional brick lined furnace. It is anticipated that further
attempts to make the water cooling unit work satisfactorily will
be made when time permits. Other cupola operators have achieved
reliable operation on identical cupolas.
It should be noted that there is no technical basis for
assuming that the recuperative system will not function equally
as well with the conventional brick-lined cupola. The decision
to employ water cooling rather than conventional refractory
practice was based on: (1) projected savings in maintenance
costs resulting from the elimination of the need for daily
refractory repair; and (2) potential cost benefits derived from
utilizing the energy in the cooling water as a source of energy
in the foundry. This energy is normally lost through radiative
loss.
41
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Several relatively minor problems have also arisen since
start-up. Principal among these is the higher than anticipated
ID fan power requirement. With the existing 100 hp motor-fan
combination the maximum draft possible is not sufficient to
entirely contain the cupola emissions nor to maintain satisfactory
internal operation of the heat exchanger. A larger fan and motor
(150 hp) have been ordered which, when installed, should prove an
adequate solution.
In summary, start-up of the system has not been without
problems. However, considering the complexity of the system and
the fact that it is a first-of-a-kind installation, the problems
encountered, at least to date, have not been unusually stubborn
or difficult to solve.
The major events for the remainder of the project are:
Heat exchanger on-line - January 1, 1974
Start 1-year test and
evaluation program - February 1, 1974
Complete 1-year test and
evaluation program - Januarv 31, 1975
Issue final report - April 30, 1975
42
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SECTION VII
CONVERSION FACTORS
Environmental Protection Agency policy is to express all
measurements in agency documents in metric units. When imple-
menting this practice will result in undue cost or lack of
clarity, conversion factors are provided for the non-metric units
used in a report. Generally, this report uses British units of
measure. For conversion to the metric system, use the following
conversions:
To convert from
Btu/lb-F
Btu/min
Btu/ton
cfm
°F
ft
gal.
gpm
hp
in.we
Ib
Ib/ft3
oz
psig
To
J/kg-C
U
J/kg
nvVsec
°C
m
1
I/sec
U
N/m2
kg
kg/m3
N/m2
N/m2
Multiply by
4184.
17.573
2324.444
.0004719
5/9 (°F-32)
.3048
3.785
0.0631
745.7
248.84
0.454
16.018
430.922
6,894.757
43
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SECTION VIII
REFERENCES
1. Iron Foundry Cupola - Recuperator Demonstration Conceptual
Test Program Definition. Catalytic, Inc., 1515 Mockingbird
Lane, Charlotte, N.C. 28209. Contract 68-02-0241, Task 1,
Final Report (Unpublished). Environmental Protection Agency,
Research Triangle Park, N.C. 27711, January 1972, 40 p.
2. Catalytic Cupola - Regenerator System Model VIA Pacer.
Catalytic, Inc., 1515 Mockingbird Lane, Charlotte, N.C. 28209.
Contract 68-02-0241, Task 12, Final Report (Unpublished).
Environmental Protection Agency, Research Triangle Park,
N.C. 27711, August 1972, 101 p.
3. Ranck, B. A. Modification of Catalytic Computer Data List
for PACER Program. York Research Corp., Stamford, Ct.
Contract 68-02-0286, Subcontractor's Interim Report (Unpub-
lished). Environmental Protection Agency, Research Triangle
Park, N.C. 27711. October 1972, 98 p.
44
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BIBLIOGRAPHIC DATA
SHEET
1. Report No
S.NJccipient's Accession No.
4. I uli. .ind Subtitle
Iron Foundry Cupola Recuperative Emission Control
De m ons t r at i on—Des i gn Manual
'5. Report Date
January 1974
6.
7. Auihor(s)
Joseph F. Coursey
8- Performing Organization Kept.
No.
9. Performing Ori;:ini^aiiun N.iniL ind Addri.ss
Flynn and Emrich Co.
3001 Grant ley Avenue
Baltimore, Maryland 21215
10. Pron-H/Task/Work Unit No.
ROAP 21ARO-02
11. Contract/Gram No.
68-02-0286
12. Sponsoring Orcani/.iiuMi \aine and Address
EPA, Office of Research and Development
NERC-RTP, Cont rol Systems Laboratory
Research Triangle Park, NC 27711
13. I ypc of Report & Period
Covered
Design Manual
14.
15 "supple nu nt i
Nori
16. \hs nets ijine manuai describes a demonstration, utilizing a dry media heat exchange!
for producing hot blast air for cupola melting, to test both the technical feasibility
of this type of heat exchange unit and the validity of the economic assumptions that
indicate a savings in fuel, air pollution control equipment costs, and a net reduction
in operating costs. It describes the system, provides estimates of the gross economic
benefits, presents the capital cost of the system, and briefly describes operation of
the system to date. The use of exhaust gas heat from an iron foundry cupola has long
been an objective of the industry. Unfavorable economics and technical limitations,
however, have limited development and employment of cupola waste heat devices to a
relatively few installations. Recent laws requiring air pollution control on cupolas
have resulted in major capital expenditures in cupola melting facilities. This required
control and recent energy shortages have led to renewed interest in such devices.
17. K<-\ Words jnd Document Analysis 17a Descriptors
Air Pollution
Iron and Steel Industry
Foundries
Furnace Cupolas
Cast Iron
Capitalized Costs
Operating Costs
Heat
Afterburners
17h Idt ntit iers,'0p< n Tndcd Terms
Air Pollution Control
Stationary Sources
Iron Melting
Energy Conservation
Particulates
17c. COSAII Tie Id/Group \3B , 13H
Cyclone Separators
Heat Exchangers
18. Av.nlability Statement
Unlimited
19. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
Page
UNCLASSIFIED
21. No. of Pages
51
22. Price
rORM NTIS T5 (REV 3-721
THIS FORM MAY BE REPRODUCED
45
•"iCOMM-OC I4B92-P72
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