Energy Policy 30 (2002) 865–883
A Chinese cokemaking process-flow model for energy and
environmental analyses
Karen R. Polenskea,*, Francis C. McMichaelb
b
a
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 9-535, Cambridge, MA 02139, USA
Blenko Professor of Environmental Engineering, Department of Civil and Environmental Engineering, Porter Hall 123G, Carnegie Mellon University,
Pittsburgh, PA 15213, USA
Abstract
The purpose of this paper is to describe the design of a process-flow model that will improve our understanding of the industrial
energy use, efficiency, and pollution in the cokemaking sector in the People’s Republic of China (China). We use a modified version
of the input–output process model (IOPM), developed by Lin and Polenske. By modifying the design of the IOPM model for use in
the cokemaking sector, we have made three key contributions. First, the end result of our design is a generic energy process-flow
model that can be easily adapted for use in conducting energy and environmental analyses of cokemaking in China and other
countries as well as examining other industrial processes in other sectors. Second, as we constructed our design framework, we have
identified the key differences in energy use and pollution generation among three generic cokemaking technologies in China. Third,
we have determined the crucial issues, such as changes in iron and steel making technologies, plant location, and world coal and
coke trade, that may affect the cokemaking sector in China in the next decade. Our research is a micro-level examination of the
production processes and input–output structure of three alternative types of cokemaking technologies (modified indigenous, small
machinery, and nonrecovery) in use in Shanxi Province, China, in the year 2000. r 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Environment; Process-flow; Energy-efficient technologies
1. Introduction
Policy makers can use a number of tools to improve
their understanding of the industrial energy use,
efficiency, and pollution in the cokemaking sector in
the People’s Republic of China (China). The cokemaking input–output process-flow model (hereafter IOPM)
we design here should help serve that purpose. To design
the model and to illustrate its use, we focus especially on
the cokemaking plants in Shanxi Province, which is the
region where the greatest amount of coke is produced in
China.
We use a modified version of the IOPM that was
developed by Lin and Polenske (1998), to examine these
types of plants. By adapting the IOPM for examination
of the cokemaking sector in the Province, we make three
key contributions. First, the end result of our design is a
generic energy and environmental process-flow model
*Corresponding author. Tel.: +1-617-253-6881; fax: +1-617-2532654.
E-mail address: [email protected] (K.R. Polenske).
that can be easily adapted for studying other heavy
energy-using and polluting sectors, such as cement
making, brick making, and ironmaking. Second, as we
construct our design framework, we identify the key
differences in energy use and pollution generation
among the following three generic cokemaking technologies that were in use in the Province in the late 1990s:
(1) advanced modified indigenous, (2) small machinery,
and (3) nonrecovery. Third, we determine the crucial
issues that may affect the cokemaking sector in China in
the next decade. These include changes in ironmaking
technologies, plant location, and world coal and coke
trade.
Our research is a micro-level examination of the
production processes and input–output structure of
these three alternative types of cokemaking plants in
existence in Shanxi Province, China, in the late 1990s.
We will refer to these as three generic cokemaking
plants, although some of the data upon which they are
based are from over 20 different types of cokemaking
ovens. First, we provide some general background
information for the coke sector; second, we describe
0301-4215/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 3 0 1 - 4 2 1 5 ( 0 1 ) 0 0 1 4 7 - 1
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K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
the basic IOPM model for the coke sector and how it
compares with previous process models; third, we
extend the IOPM for use by cokemaking plant managers
and policy makers in China for structural analyses,
energy process-flow analyses, and environmental management.
We focus on cokemaking because it is one of the two
largest coal-using sectors in China, which together with
the United States, produces about 50% of the total coal
mined in the world (US Bureau of the Census, 1997). We
focus on Shanxi Province, which produces more than
25% of total coal production in China, and coke plants
use a major portion of the total coal produced in the
Province. In addition, seven of the eight top polluting
cities in China are in Shanxi Province and many of
these, such as Linfen, are major coke-producing areas in
the Province. We analyze coke-production technologies
used by the township and village enterprises (TVEs),
which are currently the major producers of coke in
Shanxi Province. Because of the systematic way we
designed the cokemaking IOPM, it can be used for coke
plants both in the TVE and state-owned enterprise
(SOE) sectors. SOEs are more energy efficient, but less
economically efficient, than TVEs (Polenske and
McMichael, 2000). By making relatively straightforward
adaptations of the model, policymakers also can use it
for cokemaking or other sectors elsewhere in China or
other countries.
During 1998–1999, Chinese colleagues working with
us on an Alliance for Global Sustainability (AGS)
project collected (directly from cokemaking plants in
Shanxi Province) some of the detailed data we present
later in the paper. We combined those data with
published data from Chinese statistical yearbooks,
interviews with plant officials at selected plants during
three field missions to the Province, and other relevant
sources to construct and test the IOPM presented later.
2. Background to the study
Coke is a critical intermediate product in the foundry
and metallurgical coke supply (production) chains that
extend from the coal mines to the cokemaking plants to
the durable-goods manufacturers, such as automobiles
and other goods made of steel (Polenske, 2001). In many
cases, the coke supply chain extends to the port of
export, as both foundry and metallurgical coke are
traded throughout the world. Because over 80% of
China’s coke and a majority of the world coke produced
are metallurgical coke, we focus on the production of
metallurgical coke for iron making, which is made from
the blending of various kinds of bituminous coal to
make strong cokes for use in large-size (in height) blast
furnaces (Paxton, 1982). Of the coke produced in China,
almost 75% is used in making iron and steel.
Given this supply chain, at least four major (sometimes interconnected) factors could influence the future
of cokemaking in China: (1) world coal, coke, iron, and
steel production, (2) new ironmaking, steelmaking, and
automobile-production technologies, (3) imposition and
enforcement of environmental regulations, and (4) new
cokemaking technologies. After discussing these factors
briefly, we present the IOPM that should help policy
makers determine the appropriate cokemaking technology to use, given their goals and priorities.
2.1. World coal, coke, iron, and steel production
Since the early 1970s, the location of world coal, coke,
and iron and steel production has shifted dramatically.
The world production of coal has remained remarkably
stable at approximately 5 billion (short tons) from 1986
through 1998, after steadily rising from 3.4 million tons
in 1973 (US Bureau of the Census, 1987, 1990, 1997),
despite a significant shift in the spatial distribution of
the production. By 1995, only 20 countries produced
96% of the coal, whereas in 1986, those countries
produced 64% of the world total (US Bureau of the
Census, 1986–1997). Both the United States and China
have increased their share, representing 23.3% and
23.6%, respectively, of the world total in 1999 versus
17.7% and 19.6% in 1986 (www.eia.doe.gov/emeu/
international/coal.html; www.iea.org/statist/index.htm)
(International Energy Association)). Together, they now
represent almost 50% of the total production.
The second major spatial shift is in the production of
coke, with China now being a major producer. Coke
production in China increased from 23 million tons in
1970 to 73 million tons in 1990, representing 3% and
11%, respectively, of total world production to almost
140 million tons by 1997 (Ministry of Coal Industry,
1998).1 The other principal world coke producer is the
former Union of Soviet Socialist Republics (USSR),
which produced 75 million tons in 1970 (12% of world
production) and 80 million tons in 1990 (14%). In the
United States, coke production decreased from 65
million tons in 1970 (11%) to 23.8 million tons in 1995
(5%) and to 20.8 million tons in 2000 (www.eia.doe.gov/cneaf/coal/quarterly/html/t2p01p1.html; Ministry
of Coal Industry, 1998; Agarawal et al., 1996a, b),
and US coke consumption decreased from 66 million
tons in 1973 to 24.5 million tons in 1995 (www.eia.doe.gov (Energy Information Administration); US
Bureau of the Census, 1997, p. 708). The gap between
production and consumption caused a large net import
of coke into the United States in 1995 of 1.1 million
short tons, with 40% of the imports coming from
1
This is probably an underestimate of the total production, because
the production of most so-called ‘‘indigenous’’ coke in China may not
be included in the number.
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
China and 53% from Japan (US Bureau of the Census,
1997).
The third major spatial shift is in the production of
iron and steel. Currently, the Pacific Basin accounts for
30% of the world steel production, and by 2005, the
Asia/Pacific area is projected to have up to 45% of the
world steel production (www.iea.org/statist/index.htm
Brichaut, 1996). As one of the largest consumers of
coke, the iron and steel sector can change the
international trade flows of coal and coke through
the major plant relocations currently taking place.
Thus, spatial shifts in production and consumption of
coal, coke, and iron and steel are important to
understanding what future there is for coke production
in China.
2.2. New ironmaking and/or steelmaking and automobile
production technologies
The development of new ironmaking and steelmaking
technologies that either do not require the use of coke or
that require use of far less coke than at present are
affecting the demand for coke. Wakelin (1999), Considine et al. (1993), and Rosenberg (1982) discuss three
options that iron and steel producers in a given country,
especially in Europe and in the United States, may
employ to reduce or eliminate the use of domestic coke:
(1) Adopt processes that require no coke, (2) adopt
processes that require less coke than before, and/or (3)
import coke from other countries.
In some direct steelmaking processes, no coke is
required (Normille, 1991). The introduction of electricarc furnaces (EAFs), for example, has caused a major
reduction in coke demand. EAFs use scrap iron and
steel and do not use any coke directly. Today, they
produce over 40% of the US raw steel (www.steel.org/
mt/roadmap/roadmap.htm).
In other processes, pulverized coal injection (PCI)
allows the coal-to-coke ratio to be dramatically
decreased, because every pound of pulverized coal used
replaces about one pound of coke. Since the mid 1970s,
innovations in ironmaking have allowed the average US
coke rate (tons (t) of coke consumed per ton of blastfurnace iron produced) to decrease from 0.61 t coke/1 t
iron to 0.43 t coke/1 t iron (www.steel.org/mt/roadmap/
roadmap.htm). In addition, automobile producers are
replacing steel with other materials, such as plastics,
which reduces the demand for coke.
2.3. Imposition and enforcement of environmental
regulations
Environmental abatement measures and the use or
discharge of the by-products, such as coal-gas, tar, and
chemical products also affect the overall production
and consumption of the coke. The United States and
867
China are imposing new and more stringent environmental regulations than 20 years ago. As of November
15, 1993, US coke producers, for example, had to
choose one of two tracks, with the end goal being that
all batteries at a facility must meet a residual-risk
standard (RRS) based on minimizing the risk to public
health in the surrounding community. On January 1,
1998, each facility had to reach the lowest achievable
emissions rate (LAER), and on January 1, 2010, even
more severe restrictions will be imposed until 2020
when the facility must be in full compliance with the
RRS. The purpose of the RRS is to control risks to
public health from exposure to hazardous or toxic
substances.
Under the 1990 amendments to the Clean Air Act, the
US Environmental Protection Agency (EPA) was
required by December 31, 1995, to issue standards for
a Maximum Achievable Control Technology (MACT)
for all US coke batteries (www.epa.gov/epahome/
laws.htm). A MACT has the lowest achievable pollution
emissions.2
For the last half century in the United States, byproduct cokemaking has been the normal practice. The
US by-product plants collect or process the chemicals
usually to control environmental emissions rather
than to provide a source of revenue. The most recently
constructed US coke plants, however, convert coal
into coke and fuels with no recovery of the chemical
byproducts. This is called ‘‘nonrecovery’’ cokemaking, even though heat is usually recovered for use in
electricity generation. Nonrecovery plants currently
have fewer environmental problems than byproduct
plants and, as noted above, are now designated by
the EPA as MACT. By-products (volatiles, tars,
chemicals, etc.) are burned in the nonrecovery oven,
rather than being recovered, and the flue gas is cleaned
of sulfur dioxide and particulate matter prior to being
vented.
‘‘Meeting a standard’’ means that the coke-oven
battery must be below the standard number of allowable
occurrences of pollution (e.g., percentage of leaking
doors, lids, and off-takes during a given time period and
restrictions on charging times), as set by the relevant
MACT and/or LAER standard (Environmental Quality
Management, Inc., 1991). According to Considine et al.,
1993, p. 16), ‘‘ydoors are the single largest source of
leaks.’’ At Clairton Works, for example, each year 70%
of the doors are sent to an on-site door-repair shop, with
each repair taking about 32.5 h (Bagsarian, 1998, p. 4).
The need for these repairs increases as the coke batteries
2
‘‘The 1990 Amendments to the Clean Air Act name the Sun Coke
non-recovery [cokemaking] technology as a Maximum Achievable
Control Technology (MACT), the standard that any new coke plants
built in the US must meet’’ (www.33metalproducing.com). The new
Indiana Harbor nonrecovery coke plant meets the MACT (Polenske,
1999a; Westbrook, 1999).
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K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
age. In the United States, the average battery life is
considered to be 35 years, but recent advances in repair
and maintenance have made it possible that 40% of the
batteries are over 30 years old and 25% are over 40
years old (Bagsarian, 1998). When the LAER standard
is not met, the facility must be rebuilt, either by
retrofitting existing ovens or rebuilding the coke ovens,
or the plant must be shutdown by 2003. Several facilities
have been closed, such as the LTV one in Pittsburgh,
which closed in 1998, because rebuilding the plant would
have cost $400-$500 million (Hogan and Koelble, 1997;
www.newsteel.com).
China is also imposing environmental regulations on
cokemaking (SEPA, 1999), although the enforcement
of the regulations is not as strict as in the United States.
In 1996, the State government in China issued a
directive that all indigenous cokemaking ovens had to
be closed by 1998. By 1999, a new set of regulations
had been imposed in which most modified indigenous
plants also had to be closed, with a dispensation
being given until 2003–2004 for those that produce
town gas (Polenske, 1999b). Enforcement of regulations is a problem, however, partly because peasants
from towns and villages produce coke throughout the
countryside; many of these local facilities may be far
off a main highway along roads that most enforcement
officials may not bother to travel. In August 1998, our
research team conducted a survey of TVE cokemaking
plants and found that 7% of the plants surveyed in
Shanxi Province were indigenous despite the 1996
regulation to close all indigenous plants (Chen et al.,
1999). This is probably because cokemaking pays well
in China and is an important source of income for
many peasants.
The Chinese have emission regulations for air
pollutants for ‘‘‘nonmechanized’’ and ‘‘mechanized
ovens.’’ The regulations vary for coke ovens of different
vintages and for three types of ambient air-quality areas.
New coke ovens (whether nonmechanized or mechanized) are not permitted to be built at all in the most strict
(Class One) areas, so that the standards apply only to
Class Two and Class Three areas. Emission standards
are given for particulate matter, sulfur dioxide, benzo(a)pyrene, while a Ringleman blackness standard of
less than 1 applies to all areas. (SEPA, 1999).
There are also national water-discharge standards for
cokemaking, which limit the volume of wastewater per
ton of coke produced to 3 m3 in water-short regions and
to 4 m3 in regions with adequate water resources. The
wastewater regulations set limits for pH, suspended
solids, cyanide, chemical oxygen demand, oils, hexavalent chromium, ammonia-nitrogen, and zinc.3 (SEPA,
1999).
3
pH, or hydrogen potential, a shorthand term used when specifying
the hydrogen-ion (acid) concentration in a solution.
Cokemaking plants in China and the United States
face three options as environmental regulations become
stricter and are enforced. First, a coke plant manager
can rebuild or retrofit the ovens, but this is a costly
proposition in either country. Second, the firm can build
a new plant with some of the latest technologies, but this
is even costlier, as noted above. Third, the plant can
close. As we describe our process-flow model later in this
paper, we will show how such a model can aid analysts
in China in determining the trade-offs in the different
options by examining the environmental-employmentinvestment-energy use for the byproduct, nonrecovery,
and other ovens.
2.4. New cokemaking technologies
In the United States, as noted above, the primary new
technology competing with the byproduct oven is the socalled nonrecovery coke oven. We say ‘‘so-called’’
because heat is recovered at some of the facilities.
As of the spring of 2002, there are however only two
nonrecovery facilities in the United States, both of
which are run by Sun Coke and have a total capacity of
about 2.0 million tons. These are the only new US
coke plants built since the mid 1980s (Westbrook, 1999,
p. 25).
Other technologies that are being tested in Europe
and Japan include (1) a two-stage process of gasification
and then formation of briquettes, developed by Coal
Technologies Corporation, (2) a combo reactor that has
enlarged coking chambers, and (3) a low-temperature
continuous cokemaking facility being developed in
Japan. As far as we know, none of these last three
technologies are used in China as of 2002. The
nonrecovery technology is being used in at least two
coke plants in Shanxi Province, China.
3. The input–output process model
To help users understand the various components of
the input–output process model, we first quickly review
predecessors to our model. Then, we specify the main
features of cokemaking in China, such as location and
sizes of the plant and the organizational structure of the
plants. Finally, we describe the model and review the
inputs and outputs that are associated with alternative
technologies.
3.1. Predecessors to the cokemaking IOPM model
An input–output model is a systematic economic
analytical tool that analysts can use to compare
alternative cokemaking technologies. In designing the
cokemaking IOPM, we determine the inputs of materials, energy, capital, and labor that are purchased to
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
operate a coke plant. The principal material input is
coal. Coke is the main output of cokemaking, but,
depending upon the technology used, byproducts, such
as tars, ammonia, light oils, aromatic chemicals (like
benzene, toulene, xylene, and naphthalene), phenolics,
and coke-oven gas also result. For example, in
byproduct cokemaking in China, about 60–75% of the
coal mass becomes coke, and the remaining 25–40%
becomes volatile chemicals and tars and coke-oven gas
(Chen, 2000).
Lin and Polenske (1998) developed the original IOPM
model to investigate the energy-intensity of steel
making. One key reason to use the IOPM is to help
policymakers know how alternative technologies will
affect the energy intensity (energy consumption per unit
of output) of a sector. Some analysts have investigated
the energy-intensity issues in China and other countries
(e.g., Garbaccio et al., 1999; Levine et al., 1991; Lin and
Polenske, 1995; Polenske and Lin, 1993; and Sinton and
Levine, 1993; Sinton et al., 1996). Even so, few analysts
have investigated the factors in China causing the
dramatic decline in energy intensity (about 50%
between 1978 and 1998), its differences across regions,
and the implications on technological change. We
developed the cokemaking IOPM to help understand
the energy-intensity implications of alternative cokemaking technologies.
Previously, Russell and Vaughan (1976) conducted a
pioneering study of the US steel industry in which they
introduced a linear-programming approach to trace the
economic and environmental consequences of alternative steelmaking technologies. They examined details for
the US by-product cokemaking technologies as part of
their overall assessment of steelmaking. Early processflow models were based upon principles outlined in
Dorfman et al. (1958) and developed for ironmaking
and steelmaking and for energy flows (Sakamoto et al.,
1999; Marakovits, 1994; and Considine et al., 1993).4
Lupis and McMichael (1999) extended the Lin-Polenske IOPM (1998) to assess the costs of a simple threeprocess system of cokemaking, ironmaking, and steelmaking. They included three main products (coke, pig
iron, and steel), seven purchased inputs (iron ore, coal,
scrap steel, fluxes (materials that change the fluidity or
viscosity of the liquid), air, oxygen, and make-up water
(water added to make up for that evaporated in the
quenching), ten by-products and wastes (coke-oven gas,
blast-furnace gas, basic oxygen-furnace gas, slag, tar,
ammonia liquor, dust and fumes, evaporated water,
purged wastewater (water released from the system) to
stream or sewer, purged solids (in wastewater), and five
primary inputs (process capital, environmental capital,
4
Marakovits and Considine (1996) provide a summary of the
ironmaking and steelmaking process-flow models that preceded theirs,
which we do not repeat here.
869
process labor, environmental labor, and other charges).
Their process-flow model uses a mass balance with some
use of environmental-emission factors. The authors
included a vector of prices for inputs and outputs to
calculate the net costs or revenues of selected production
schemes as well and the total costs of the entire system
and individual process units.
In this paper, we modify the Lin-Polenske IOPM to
examine the various processes of cokemaking and the
alternative technologies in use in Shanxi Province,
China. Next, we discuss differences in the rationale for
and organization of cokemaking in China and the West.
We then explain three different aspects of the model: (1)
inputs (mainly coal) into cokemaking, (2) technologies
available, and (3) coke and by-product outputs of the
cokemaking process.
3.2. Rationale for and organizational structure of
cokemaking in China
China plans to grow a cokemaking industry that will
not only support a domestic iron and steelmaking
industry and an automobile and other consumerdurable industry, but will also export coke to other
countries. To accomplish these goals, four factors are
important in determining the inputs to cokemaking: (1)
location of the plant, (2) size of the plant, (3)
organizational structure of the plant, (4) alternative
cokemaking technologies available.
In the West, most metallurgical coke plants are
located contiguous to the ironmaking facility, and some,
such as the nonrecovery cokemaking plant in Vansant,
Virginia, are close to the coal mines. In Shanxi Province,
China, with the rapid growth of township and village
enterprise cokemaking since the early 1980s, most of the
cokemaking plants are neither near the mine nor the
ironmaking plants. Rather, the plant is usually established in the town or village where the peasant who sets
up the plant lives. Coal frequently is transported 50–
100 km to the cokemaking plant; then, the coke sometimes is transported even longer distances to the
ironmaking plant or to ports for export (Polenske,
1999b).
The size of the plants also differs in the West versus in
China. In the United States, the largest cokemaking
facility (Clairton Works in Pittsburgh, Pennsylvania)
produces up to five million short tons of coke annually
and accounts for approximately 20% of the total
metallurgical coke produced in the country. Twelve of
twenty-three cokemaking facilities in the United States
have an annual capacity greater than 1 million short
tons. These facilities are able to reap economies of scale
in terms of using less coal, electricity, water, and other
inputs per unit of output than smaller-size plants. In
Shanxi Province, most facilities are very small and are
scattered throughout the countryside. Although their
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K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
dispersed location enhances the employment opportunities for the peasants, it creates a need for an extensive
transportation infrastructure. In the late 1990s, the
largest TVE plants produce about 300,000–600,000 t
(metric) of coke annually, although at least one TVE
produces about 1 million tons. Of the 37 SOEs, the eight
largest together account for less than 40% of the total
coke produced in the Province (Chen et al., 1999).
Chinese cokemaking is organized in two ways. The
first way, which is increasing in importance, is comprised of many local, generally small, facilities operated
as township and village enterprises (TVEs). Although
classified in the statistics as TVEs, they may be jointly
owned by the peasant with a town or village, privately
owned, or have other diverse ownership structures other
than state ownership (Chen et al., 1999). The second
way is comprised of usually large facilities run under
state ownership, identified as state-owned enterprises
(SOEs). TVEs tend to select technologies that permit
smaller-scale operation and are less capital intensive
than the SOEs. Until the late 1990s, most TVEs in China
operated the so-called ‘‘indigenous’’ or ‘‘modified
indigenous’’ ovens (Li et al., 1995). Indigenous cokemaking is similar to beehive cokemaking in the United
States, which has been abandoned since the 1950s
partially due to strict US environmental emission
standards. Compared to the TVEs, the SOEs in China
use more capital-intensive cokemaking technologies,
commonly called ‘‘machinery ovens,’’ which have basic
vertical slot-oven geometries of chemical byproduct
ovens.5
Both in China and the United States, cokemaking is
done in batches. Continuous production of coke is
achieved with many ovens staged to operate in sequence.
To maintain the physical integrity of oven materials and
brickwork, it is customary to keep the ovens always
warm; otherwise, the extreme variations of oven
temperatures lead to failure of the oven materials.
Building a larger oven or adding more ovens may
achieve increased capacity. A group of ovens that are
operated concurrently is called a coke battery. A facility
(plant) is described by counting the number of ovens
and the number of batteries. For the smallest facility, a
battery may consist of three ovens, while large facilities
may have as many as 100 ovens in a single battery.
Analysts can use the IOPM to help with a technical
issue concerning the selection of an economically viable
size of a coke oven, or to design the size of a coke oven
that is the most energy efficient or one that has the least
environmental impact.
5
Cokemaking analysts describe the different ovens as indigenous
and machinery ovens, or small, medium, and large, or simple and
modified, or byproduct and nonrecovery. We will use these terms,
when necessary, to identify specific facilities. Mostly, however, we
classify the Chinese technology options in terms of their specific inputs
and outputs.
3.3. Alternative cokemaking technologies
Technology choices in cokemaking involve finding
ways to change or control the yield of coke, chemicals,
energy, and wastes. Removing tars, ammonia, light oils,
aromatic chemicals (like benzene, toulene, xylene, and
naphthalene), and phenolics makes the coke-oven gas
easier to burn and transport. If these materials are not
removed from the raw coke gas, they create maintenance problems by condensing in pipelines and burner
nozzles. In the best of circumstances, these recovered
chemicals may generate revenue. In the worst of
circumstances, the recovered materials form liquid and
solid-waste materials that require special handling and
containment.
Coal for making coke ideally has different properties
than coal burned for making steam and electricity and is
referred to as ‘‘coking coal,’’ which is lower in ash and
sulfur content than noncoking (thermal) coal. Both in
China and the United States, most of the coal used in
cokemaking is washed. Cleaning and preparing coal for
cokemaking includes some changes in both the physical
form and the chemical composition of the coal. By
reducing the size of the raw coal, the producer can
separate ash and inorganic sulfur from the coal.
The cokemaking technology used to convert coal into
coke, gas, and other coal-chemical products determines
the final size distribution of the coke. The physical size
of coke is related to its role in deep-bed blast furnaces.
For use in the blast furnace, the operator requires fistsized pieces of coke in order to provide the permeability
and porosity that permit the mass flow of air and other
blast-furnace gases to pass through the burden of blastfurnace materials. Large pieces of coke also must
support the physical weight of several meters of depth
of other furnace materials above them. The size of the
coke is not a measure of its strength. Foundry coke, for
example, is typically larger in size than metallurgical
coke, but foundry coke does not have to be as strong,
because it is used in foundry cupola furnaces, which are
less tall than blast furnaces and therefore have to
support less burden.
Coal can be converted into coke by several technologies. Analysts can use the cokemaking IOPM to
evaluate each technology in terms of mass, energy, and
economic efficiency. Nominally, about 75% of the mass
of the coal is converted into coke; and, about 85% of the
energy of the input coal is contained in the coke. It goes
without saying that coke has a higher unit price than
coal. The details of the mass and energy balances for
each cokemaking technology determine the energy and
the pollution obtained from the coal. For example, if
25% of the mass of coal is not converted into coke, it is
found in the by-products of cokemakingFthe cokeoven gas, the coke chemicals, and the wastes. In early
cokemaking, these materials were discharged into the
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
environment (air, water, and land). This is the kind of
environmental impact that any country wants to avoid
today.
When plant managers collect and utilize these
materials, they improve the mass and energy efficiencies.
They may also collect revenue from the sale of the
byproducts and reduce harmful environmental emissions. In China, a few managers have made an
important improvement over the earliest cokemaking
technologies by designing ovens that capture some of
the coke oven gas and recycle it back to the oven for
combustion heating, i.e., they use nonrecovery coke
ovens. Sanjia Cokemaking Corporation, for example,
runs one major nonrecovery coke plant in Jiexiu, Shanxi
Province; however, this facility does not capture the
energy for making electricity.6
Coke has desirable physical and chemical properties.
It is both a fuel and a chemical-reducing agent. Both
roles are important in the blast furnace for converting
iron oxides to iron metal. Although fine coke, called
coke breeze, is not suitable for direct use in a blast
furnace, it can be agglomerated or bound in some
fashion to make larger particles for use in the furnaces.
Fine coke may be a suitable feed material for burning
directly, or it may be further processed to make an
activated carbon.
For our study, we distinguish between technologies
that recover coke and fuel gas and chemicals (used for
byproduct ovens) and technologies that recover coke
and fuel gas only (used for nonrecovery ovens). The
most primitive technology (in China, these are the socalled ‘‘indigenous coke ovens’’) that recovers only coke
is unacceptable today, because of its enormous negative
environmental effects (Li et al., 1995).
Regardless of the technology used, incandescent coke
from the ovens must be cooled to ambient temperatures
for storage or transport. Cooling is normally done with
direct contact with water, which evaporates in the
cooling process. This is called a consumptive use of
water and means that a continuous source of new water
is required. About 1000 liters of water are used to cool a
ton of hot coke if quenching is done externally to the
coke ovens, as is the practice for by-product or
machinery ovens. Less water is used for quenching in
indigenous and nonrecovery ovens in China because the
water is applied directly to the coke in the oven. During
quenching, some water is evaporated, and the excess
water is collected and recycled. The recycled water has
coal fines, which must be separated and handled or
disposed. If the waste water is blended with natural
waters for quenching, the volatile organic materials are
transferred from the wastewater to the atmosphere
surrounding the quench tower. In some advanced
6
As noted earlier, the United States has two nonrecovery coke ovens
built by Sun Coke, both of which have heat recovery.
871
modified indigenous coke processes, a worker adds the
quench water to the oven, and the evaporated water is
exhausted near the ground. In the byproduct plants,
coke is ‘‘pushed’’ from the slot ovens into a quenching
(railroad) car and transported to the quenching tower,
which is designed to exhaust the steam (evaporated
water) through a stack elevated above ground level.
The managers’ choice of an appropriate cokemaking
technology depends upon a number of additional
factors. One factor is the availability or nonavailability
of markets for byproducts and fuel gas from the
cokemaking. Another key policy issue they confront is
the choice between generating revenue from byproducts
or incurring additional waste-disposal problems. Additional variations occur among the key cokemaking
technologies in terms of the capital costs and labor
requirements, including the skills of workers, which
differ among those workers whose jobs are to tend the
different types of ovens and those workers who have the
administrative jobs needed to run the plant. Occupational health and safety exposures also differ from plant
to plant.
4. Modeling issues concerning cokemaking
We designed the cokemaking IOPM to use in
comparing the economic, energy-use, and environmental performance of alternative cokemaking technologies
in China. Many data issues arose as we collected the
information.
For the technology comparisons, for example, we are
especially concerned with the environmental costs,
which we could only approximate. Given the lack of
detailed information about specific environmental control technologies in China, we use US environmentalcost ratios (10–20%) for the process-technology environmental costs. We would require more detailed
information if we were to define the costs accurately.
Additional difficult issues arise from the relative
importance of capital and operational expenditures in
controlling emissions. Environmental costs are generally
higher when plant personnel are retrofitting controls,
than when they are making choices early in the design of
a process technology. Some design choices can change
environmental impacts and costs in major ways. For
example, quenching coke with water, which then
evaporates, has very different environmental and
economic effects than dry quenching (with nitrogen),
which is often used to capture the heat for other
purposes. In indigenous and nonrecovery coke ovens,
the workers apply the quench water in the kiln reactor in
which the coal is coked. For machinery coke ovens,
workers quench coke with water in a facility, called a
quenching tower, external to the ovens, producing
evaporated water and volatiles with vapor pressures
872
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
close to that of water and releasing fine coke particles,
called ‘‘breeze’’.7 Dry quenching uses no water and has
minimal air emissions, but it is a more complicated and
capital-expensive process than wet quenching.
All those working with cokemaking must give critical
attention to air emissions from cokemaking ovens and
by-product chemical plants, because coke-plant air
emissions have been identified and classified by the
International Agency for Research on Cancer (IARC)
as a human carcinogen. Studies in Allegheny County in
the United States by the University of Pittsburgh School
of Public Health found that top-side coke-oven workers
have a risk of lung, trachea, and bronchus cancer seven
times larger than the risk for non-oven production
workers (Wu et al., 1998; Constantino et al., 1995;
Redmond, 1983; Redmond and Mazumbar, 1993). The
risk to highly exposed workers on and around the ovens
varies with their location on the site. In the United
States in the 1970s, Graham and Holtgrave (1989) found
that two-thirds of the primary sources of emissions from
coke batteries were from charging (putting coal into the
ovens) and one-third from pushing the finished coke
from the ovens into the quenching car.
We are interested in the changes in Chinese cokemaking technologies and how they affect the releases of
volatile products to the atmosphere. The United States
Environmental Protection Agency (USEPA) prefers not
to measure (thus regulate) concentrations of particulate
matter directly from coke-oven charging lids, coke-oven
doors, or by-product coke-oven gas offtakes. Proposed
regulatory schemes set limits on the fraction of these
locations that are observed to have visible leaks; for
example, a USEPA standard requires the following: less
than 10% PLD (percent leaking doors), less than 3 PLL
(percent leaking lids), less than 6% PLO (percent
leaking offtakes), and less than 16 seconds of visible
emissions per charge. Plants can achieve these limits in
several ways, such as technology requiring capital
investment in hoods and ventilation control or operation and maintenance schemes using various kinds of
sealants applied as needed. Costs vary considerably as
does the effectiveness of these measures. Coke-oven
workers wearing personal respirators cut down on their
own exposure, but not on the exposure to the community at large. If regulatory officials are not to squander
money, time, and effort, they should regulate coke-oven
emissions with occupational and non-occupational
exposures in mind. (Graham and Holtgrave, 1989).
An additional issue is that to determine the amount of
cleaning of the raw coke-oven gas required, the plant
manager must determine how the gas will be burned and
how far the gas must be transported through pipes
before it is burned. The length of transport affects the
7
The incandescent coke is pushed from the oven into a quenching
car, which is then moved to the quenching tower.
degree of gas cooling and the concomitant formation of
condensation products that may result in plugging of the
pipes and nozzles, creating major maintenance problems.
Also, contrary to what happens in the United States,
where coke is typically made to be used onsite or close
by the cokemaking facility, in Shanxi Province, the
cokemaking plants are frequently neither close to the
coal mine, nor close to the iron and steel mills or other
end users. A producer who transports coke to external
(outside the region or even country) users may find that
the user imposes special coke-strength requirements on
the sale.
Finally, regardless of the technology, converting coal
to coke releases water of composition. Cokemaking
analysts study two kinds of water problems. First,
cokemaking generates wastewater that is salty like
seawater and contains a large quantity of organic
chemicals and dissolved inorganic salts. Each ton of
coal converted to coke produces about 100 liters of
wastewater. If this water condenses from the raw gas,
plants must control the resulting major wastewater
stream; later, we refer to this condensate as ammonia
liquor. This process water, separated from coke-oven
gas to improve its combustion properties, is a difficult
wastewater to treat to meet environmental standards for
discharging to natural waters (rivers and lakes).
Second, water is consumed in the quenching of hot
coke, with the heat being removed as the water
evaporates into the atmosphere. In the United States,
some plants use process water for quenching in order to
eliminate its discharge to surface waters. This practice
transfers pollutants from being a threat to the water to
being a concern for the atmosphere. Each manager must
choose which media (water or air) to pollute, depending
upon the effects on the cost of environmental control for
a facility as well as its impact on the nearby community.
5. Spreadsheet model for cokemaking
Spreadsheets offer flexibility and simplicity in modeling costs, mass flows, and environmental emissions for
cokemaking. By using this form of technical-cost
modeling, we can link processes and separate parameters that are common to processes by a process-flow
diagram.
Our spreadsheet model guides us in collecting
information about alternative technologies. It helps us
to build a process-flow diagram (e.g., Fig. 1) for linking
the cokemaking unit operations and identifying key
points to support alternative decisions to deal with
byproduct recovery or energy recovery. We can easily
see when choices are made to shift pollutant emissions
from water to air, etc. This systematic approach to
understanding the topology of cokemaking technologies
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
873
RAW
COAL
WASH
REFUSE
COAL WASHING
CLEAN
COAL
BYPRODUCT
COKE
OVEN
EXTERNAL
QUENCH
OF HOT COKE
QUENCH
WATER
EVAPORATED
QUENCH
WATER
COKE
COMBUSTION
GAS
RAW
COG
TAR AND
BYPRODUCT
CHEMICAL
RECOVERY
TAR,
ETC.
COKE-OVEN
GAS (COG)
COKE
BREEZE
Fig. 1. Process flows for a byproduct coke enterprise.
provides a basis for communicating among industry
personnel, environmental regulators, planning officials,
and the public. Our approach gives us qualitative and
quantitative results. The accuracy of the quantitative
results is affected by how well we have modeled the
system as well as the accuracy of our numerical data.
To show the process flow for each cokemaking
technology, we describe a mass balance that equates
the output of coke, coke chemicals, and coke-oven gas
to the input of coal and other feedstocks. We account
for some important, yet very small (less than a percent
of the total process flows), environmental emissions in
terms of empirical emission coefficients.
Our cokemaking IOPM represents a Chinese (TVE)
coal-based cokemaking enterprise that has facilities for
coal washing (one for steam coal and one for
metallurgical coal), producer-gas generation, electricity
production, and three types of coke ovens: small
machinery, modified indigenous, and nonrecovery.8
These seven facilities are listed in Table 1 with the
assumptions about the technology, economics, and
environment for the seven facilities that we model in
our cokemaking enterprise. The important processes in
cokemaking are the ovens, the quenching of the hot
coke, and the processing of the hot, raw coke-oven gas.
By developing the model hierarchically, we can isolate
the major differences among the technologies. We first
identify the key capital facilities: coal cleaning, coke
ovens, coke quenching, coke-oven gas processing for
chemical or heat recovery, combustion-gas processing,
etc. We also include facilities for generating electricity
and producer gasFa low-heat content fuel gas substitutable (for economic reasons) for coke-oven gas for
heating ovens, as part of our coal enterprise.9
Using information from Chen’s empirical case studies
(Chen, 2000), we describe the capital (investment) costs
of each technology in terms of capital cost per unit of
annual production.10 For illustration, we summarize the
8
Differences exist between Chinese and Western names given to
alternative cokemaking technologies. In the West, managers commonly use ‘‘byproduct recovery’’ to mean collection and separation of
chemicals (gases, liquids, and solids) from raw (unprocessed) cokeoven gas, and they use ‘‘nonrecovery’’ to mean a technology that does
not recover a mass of chemicals, but does recover energy by
combusting the chemicals in the raw coke-oven gas.
9
Producer gas is cheaper if it is made from coal-washing plant
refuse, but because of its carbon-monoxide content, its use in a town
rather than an industrial plant is less desirable.
10
In July of 2000, the two authors revisited the coke plants and
verified the numbers Chen recorded and made a few modifications in
his numbers.
874
Table 1
Assumptions for process-flow cokemaking model
Process characteristics (assumptions)
Clean coal requirement
Ash content of raw coal
Ash content of clean coal
Ash content of washer refuse
Sulfur content of raw coal
Sulfur content of clean coal
Sulfur content of washer refuse
Fraction of sulfur in clean coal to coke
Fraction of sulfur in clean coal to COG
Fraction of sulfur in clean coal to byproducts
Heat content of clean coal
Thermal efficiency of power plant
S to flue gas/S in clean coal
Electricity consumption
Coke oven gas production
Tar recovery
Ammonia liquor production
Ammonium sulfate production
Bottom ash from clean coal input ash
Fly ash from clean coal input ash
Process wastewater generation
Quench water consumption
Coke breeze production from external quench
Capital investment
Unit for capital investment
Labor
Labor rate
Environmental capital/process capital
Environmental labor/process labor
SO2 scrubber removal efficiency
t coal/t coke
Percent
Percent
Percent
Percent
Percent
Percent
Percent
Percent
Percent
MJ/kg
J electricity/J input
tS/tS
kWh/t input
m3/t coal
l/t coal
l/t coal
kg/t coal
Percent
Percent
l/t coal
l/t coke
t breeze/t coke
RMB/annual unit
Annual unit
Person years
RMB/person year
Fraction
Fraction
Percent
Steam coal
washer
Metallurgical
coal
washer
Producer gas
generator
Steam coal
power
plant
Small machinery
coke ovens
(1)
(2)
(3)
(4)
(5)
1.32
25
10
65
2
2
2
(7)
1.32
60
30
10
60
30
10
30
300
10
120
10
15
300
5
60
10
300
1000
0.1
800
t/year
400
12,000
0.05
0.05
600
600
90
t/year
300
12,000
0.05
0.05
45
t/year
300
12,000
0.05
0.05
24
0.33
1
50
10
100
60
t/year
200
12,000
0.05
0.05
1.35
Nonrecovery
coke ovens
15
7
65
1
1
1
24
50
Advanced
modified
indigenous
coke ovens
(6)
60
t/year
200
12,000
0.05
0.05
0.3
m3/year
300
12,000
0.05
0.05
70
30
913,242
MkWh/year
400
12,000
0.05
0.05
65
COG=coke-oven gas; j=joule; kg=kilogram; kWh=kilowatt hour; m3=cubic meters; RMB=renminbi; S=sulfur; SO2=sulfur dioxide; t=ton.
Sources: Chen Hao. 2000. ‘‘Technological Evaluation and Policy Analysis for cokemaking’’, Cambridge, MA, Technology and Policy Program.
Master’s thesis. Field missions to Shanxi Province by the Multiregional Planning Staff, MIT, July 1999 and 2000, December 1999.
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
Units
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
economic model assumptions by comparing three
alternative Chinese cokemaking technologies for (1)
small machinery, (2) advanced-modified indigenous, and
(3) non-recovery (Table 1, columns 5–7). As Chen (2000)
collected these data during case studies of Chinese
cokemaking technologies, he obtained annual costs and
revenues, but he did not explicitly separate environmental control costs from cokemaking costs.
In Table 1, we list the production factors and other
assumptions used in making the model calculations. For
example, the capital cost of cokemaking technologies in
China ranges from 45 to 800 renminbi (RMB) per
annual ton of coke produced, depending on the level of
chemicals or heat recovered. We assign a 5% environmental capital and labor cost for all facilities for
illustrative purposes only. Our hypothetical facility is
profitable including this level of additional control costs.
We also identify variable costs for each of the major
purchased inputs, such as coal, electricity, and labor.
For the technologies we investigated in Shanxi Province,
the cost of the coal may range from 20% to 80% of the
total annualized cost of production. We include other
875
variable costs, like water consumed in quenching and
electricity to run pumps, or if we believe that they
represent a small fraction of the total cost, we neglect
them. Although we include labor requirements as an
important variable cost, we are also interested in
measuring the employment opportunities or lack of
opportunities for each technology.
Before introducing the process-flow materials balance, we provide prices for the inputs (outputs) to
(from) the enterprise (Table 2). We illustrate how the
model can be used by introducing the process-flow
materials balance for a fictitious enterprise with seven
facilities that produces 789 million kWh of electricity,
580,000 t of coke per year (180 small machinery ovens,
200 modified indigenous ovens, and 200 nonrecovery
ovens), 180 million cubic meters of coke-oven gas, and a
number of byproducts and pollutants (Table 3, last
column). Each row describes the production (positive
number) and the consumption (negative number) of a
commodity (main product, byproduct, or waste). The
process-flow balance contains three key production
sections: main products, purchased inputs, and
Table 2
Prices for cokemaking enterprise inputs and outputs
Inputs and outputs
Units
1. Clean steam coal
2. Clean metallurgical coal
3. Producer gas
4. Electricity
5. Coke from small machinery plant
6. Coke from advanced modified indigenous plant
7. Coke from nonrecovery ovens
8. Raw steam coal
9. Raw metallurgical coal
10. Water
11. Steam coal washer refuse
12. Metallurgical coal washer refuse
13. Bottom ash
14. Power plant fly ash
15. Coke breeze from quench
16. SO2 to atmosphere [social cost]
17. S to coke oven gas to atm [social cost]
18. COG
19. COG to underfire ovens
20. Tar and pitch
21. Ammonium sulfate
22. Ammonia liquor
23. Process capital investment-capital recovery
factor (CRF)
24. Process labor
25. Environmental capital investment-CRF
26. Environmental control labor
RMB/t
RMB/t
RMB/m3
RMB/kWh
RMB/t
RMB/t
RMB/t
RMB/t
RMB/t
RMB/m3
RMB/t
RMB/t
RMB/t
RMB/t
RMB/t
RMB/t
RMB/t
RMB/m3
RMB/m3
RMB/l
RMB/kg
RMB/l
Per year
a
RMB/person year
Per year
RMB/person year
Value
150.00
180.00
0.08
0.20
360.00
360.00
360.00
100.00
120.00
0.40
10.00
12.00
(8.00)
(8.00)
25.00
(1.00)
(1.00)
0.30
0.30
40.00
0.50
(0.01)
0.20
12,000.00
0.20
12,000.00
a
Value in US$
$18.75
$22.50
$0.01
$0.03
$45.00
$45.00
$45.00
$12.50
$15.00
$0.05
$1.25
$1.50
($1.00)
($1.00)
$3.13
($0.13)
($0.13)
$0.04
$0.04
$5.00
$0.06
($0.00)
Assumptions
Assume 1.5 times raw coal price
Assume 1.5 times raw coal price
Assume 25% of COG price
Assume 2 times clean coal price
Assume 2 times clean coal price
Assume 2 times clean coal price
Assume 10% of raw coal price
Assume 10% of raw coal price
$1500.00
$1500.00
8 renminbi (RMB)=B$1 US.
atm=atmosphere; COG=coke-oven gas; CRF=capital recovery factors; kg=kilogram; kWh=kilowatt hours; S=sulfur; SO2=sulfur dioxide.
Parentheses equal negative values.
Sources: Chen Hao. 2000. ‘‘Technological Evaluation and Policy Analysis for Cokemaking’’, Cambridge, MA, Technology and Policy Program,
Master’s thesis.
Field missions to Shanxi Province by the Multiregional Planning Staff, MIT, July 1999 and 2000, December 1999.
876
Table 3
Cokemaking enterprise process-flow model
Product/input
Main products
[A matrix]
1.
2.
6.
7.
Purchased products
[B matrix]
8.
9.
10.
Byproducts and
wastes [C matrix]
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
Clean steam coal
Clean metallurgical
coal
Producer gas
Electricity
CokeFsmall
machinery plant
CokeFadvanced
modified indigenous
plant
CokeFnonrecovery
ovens
Units
kt/year
kt/year
Mm3/year
MkWh/year
kt/year
Steam coal
washer
Metallurgical
coal
washer
Producer gas
generator
Steam coal
power plant
[100 MWe]
Small
machinery
coke ovens
(1)
(2)
(3)
(4)
(5)
394
(46)
56
(3)
876
kt/year
kt/year
m3/year
Steam coal
washer refuse
Metallurgical
coal washer refuse
Bottom ash
Power plant fly ash
Coke breeze
from quench
SO2 to atmosphere
S to coke oven gas
COG production
COG to
underfire ovens
SO2 to atm from
combusted COG
Tar and pitch
Ammonium sulfate
Ammonia liquor
kt/year
(264)
(56)
(6)
180
(3)
(2)
200
kt/year
kt/year
kt/year
kt/year
kt/year
kt/year
Mm3/year
Mm3/year
200
(540)
0
0
Y3
Y4
Y5
0
789
180
Y6
200
Y7
200
(540)
(926)
(346,800)
(146)
Zc1
0
(128)
Zc2
0
Zc3
Zc4
Zc5
206
12
20
Zc6
Zc7
Zc8
Zc9
6
6
180
(117)
(26,400)
128
Y1
Y2
Zb1
Zb2
Zb3
(926)
146
Final
output
[Z]
(270)
kt/year
Symbol
(7)
(264)
kt/year
Raw steam coal
Raw metallurgical coal
Water
Nonrecovery
coke
ovens
(394)
798
(27)
Advanced
modified
indigenous
coke ovens
(6)
178
(162,000)
(158,400)
28
12
20
6
4
1
60
(18)
1
60
(57)
1
60
(42)
kt/year
0
1
1
l/year
kg/year
l/year
2640
2640
31,680
1350
16,200
Zc10
1
Zc11
Zc12
Zc13
3990
2640
47,880
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
3.
4.
5.
Detailed
Product/input
(105)
Main products [Xa vector]
27.
Abbreviations: k=thousand; M=million; for other abbreviations, see Table 2.
Sources: Chen Hao. 2000. ‘‘Technological Evaluation and Policy Analysis for Cokemaking’’, Cambridge, MA, Technology and Policy Program, Master’s Thesis.
Field missions to Shanxi Province by the Multiregional Planning Staff, MIT, July 1999 and 2000, December 1999.
394
798
56
876
180
200
200
Zd4
(15)
(15)
(20)
(20)
(15)
(10)
Person years
(10)
(2100)
(52,966)
Zd2
Zd3
(300)
(450)
(300)
(900)
(400)
(7200)
(400)
(40,000)
(300)
(840)
(200)
(2394)
(200)
(1182)
Person years
kRMB
25.
26.
Primary inputs
[D matrix]
24.
Process capital
investment
Process labor
Environmental
capital investment
Environmental
control labor
kRMB
(23,640)
(47,880)
(16,800)
(800,000)
(144,000)
(18,000)
(9000)
Zd1
(105,9320)
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
877
byproducts and wastes. The fourth section, primary
inputs, represents financial costs, such as investment
capital costs and labor. The last line shows the total
output for each of the seven facilities. Thus, this balance
sheet provides information on the investment, labor,
and maintenance costs plus costs of purchased coal and
utility costs. It also provides estimates of revenues from
coke, chemical by-products, and generated steam and
electricity. Both costs and revenues are expressed in
yuan per annual ton of coke.11
The columns pertain to the seven main facilities at the
plant: (1) steam coal washer, (2) metallurgical coal washer,
(3) producer-gas generator, (4) steam coal-fired electric
power plant, and (5–7) three types of ovens used at the
hypothetical plant. In any column, the positive entries
represent outputs of a facility, and the negative entries are
the inputs. We identify all entries in terms of appropriate
physical units. Although sometimes (to clarify the mass
balance), analysts use this kind of table to present all
entries in common units, we did not do that here.
We can also view Table 3 as a statistical account of
the flows in the enterprise and of the inputs used and the
outputs generated in each facility. For example, the first
line in the main products section shows that the washer
produced 394,000 t of clean steam coal, which were
consumed by the electric power plant. The first column
shows that 27 million kWh of electricity and 540,000 t of
raw steam coal were consumed by the washer to produce
394,000 t of clean steam coal and 146,000 t of coal washer
refuse. The steam coal washer required a capital investment
of 23,640,000 RMB and used 200 person-years of labor.
In matrix form, Table 3 provides the information for
the 10 components required for a cokemaking version of
the Lin-Polenske IOPM:
A=matrix summarizing the production and consumption of the main products,
B=matrix describing the consumption of purchased
products,
C=matrix describing the generation of byproducts
and wastes.
D=matrix describing the consumption of primary
inputs,
X a =line matrix or vector giving for each main
process the corresponding main productoutput,
Y =vector giving the final output of main products,
Z a =vector giving the total demand for purchased
products,
Z b =vector giving the total demand for purchased
products,
Z c =vector giving the total discharge of by-products
and wastes.
Z d =vector giving the total consumption of primary
inputs.
11
In 2001, 1 yuan=8.2 US dollars; renminbi (RMB) is another term
used for yuan.
878
Product/input
1. Main products
2. [a matrix]
3.
4.
5.
6.
7.
Detailed product/input
Steam coal
washer
Metallurgical
coal washer
Producer gas
generator
Steam coal
power plant
[100 MWe]
Small machinery
coke ovens
(1)
(2)
(3)
(4)
(5)
Clean steam coal
Clean metallurgical coal
Producer gas
Electricity
Coke from small machinery plant
Coke from advanced modified indigenous plant
Coke from nonrecovery ovens
1.000
0.000
0.000
(0.069)
0.000
0.000
0.000
0.000
1.000
0.000
(0.058)
0.000
0.000
0.000
0.000
0.000
1.000
(0.054)
0.000
0.000
0.000
(0.450)
0.000
0.000
1.000
0.000
0.000
0.000
8. Purchased products
9. [b matrix]
10.
Raw steam coal
Raw metallurgical coal
Water
(1.371)
0.000
0.000
0.000
(1.160)
0.000
0.000
0.000
0.000
11. Byproducts and wastes
12 [c matrix]
13.
14
15.
16.
17.
18.
19.
20.
21.
22.
23.
Steam coal washer refuse
Metallurgical coal washer refuse
Bottom ash
Power plant fly ash
Coke breeze from quench
SO2 to atmosphere
S to coke oven gas
COG production
COG to underfire ovens
SO2 to atm from combusted COG
Tar and pitch
Ammonium sulfate
Ammonia liquor
0.371
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.160
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
(2.607)
(2.286)
3.179
0.000
0.000
0.000
0.075
0.000
0.000
0.000
0.000
0.000
0.000
Advanced
modified
indigenous
coke ovens
(6)
Nonrecovery c
oke ovens
(7)
0.000
(1.467)
(0.311)
(0.033)
1.000
0.000
0.000
0.000
(1.350)
0.000
(0.015)
0.000
1.000
0.000
0.000
(1.320)
0.000
(0.010)
0.000
0.000
1.000
0.000
0.000
0.000
0.000
0.000
(146.667)
0.000
0.000
(810.000)
0.000
0.000
(792.000)
0.000
0.000
0.032
0.014
0.000
0.006
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.111
0.000
0.004
0.333
(0.100)
0.001
14.667
14.667
176.000
0.000
0.000
0.000
0.000
0.000
0.000
0.004
0.300
(0.285)
0.004
6.750
0.000
81.000
0.000
0.000
0.000
0.000
0.000
0.000
0.004
0.300
(0.210)
0.003
0.000
0.000
0.000
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
Table 4
Cokemaking process-flow direct inputs
24. Primary inputs
25. [d matrix]
26.
27.
Process capital investment
Process labor
Environmental capital investment
Environmental control labor
[P transpose]* [a]=profit per gross main product
[b]
[c]
[d]
[P transpose]* [a]*[a inverse]=profit per final main product
[b]
[c]
[d]
(60.000)
(0.508)
(3.000)
(0.025)
(60.000)
(0.251)
(3.000)
(0.013)
(300.000)
(5.357)
(15.000)
(0.268)
(913.242)
(0.457)
(45.662)
(0.023)
(82,281)
126,217
111,131
99,518
128,168
5350
35,392
(75,390)
128,624
143,871
149,227
176,171
394
798
56
876
180
200
Clean steam coal
Clean metallurgical coal
Producer gas
Electricity
Coke from small machinery plant
Coke from advanced
modified indigenous plant
200 Coke from nonrecovery ovens
Profit in million RMB
192.46
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
Clean steam coal
Clean metallurgical coal
Producer gas
Electricity
Coke from small machinery plant
Coke from advanced
modified indigenous plant
200 Coke from nonrecovery ovens
Profit in million RMB
192.46
(45.000)
(1.500)
(2.250)
(0.075)
27,977
Total output [X ]
0
0
0
789
180
200
(90.000)
(1.500)
(4.500)
(0.075)
(3464)
Source: Calculated from Table 3 by dividing each element in a given column by the total output of the plant. Abbreviations refer to Table 3.
Final demand [Y ]
(800.000)
(2.222)
(40.000)
(0.111)
879
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
880
When we divide each element in a column in Table 3
by the output of the main product of the process
corresponding to that column, we obtain the ‘‘directinput-coefficients’’ matrices (Table 4). The elements of
the new matrices [a], [b], [c], and [d] are related to the
elements of the matrices [A], [B], [C], and [D] by the
relations:
facility within a plant and the interrelationships among
the facilities that comprise this type of coal-using
enterprise. We can readily modify the relationships
and modules for the individual facilities to represent
other types of coal-using enterprises.
aij ¼ Aij =Xj ; bij ¼ Bij =Xj ;
dij ¼ Dij =Xj ;
6. Discussion of model results and limitations
cij ¼ Cij =Xj ;
ð1Þ
where the subscripts i and j of an element identify,
respectively, the row and column of its matrix. Each
coefficient shows the amount of input required or
output produced per unit of a production process, and
thus each column shows the input–output structure of a
facility. For example, the producer-gas generator
column in Table 3 indicates that 1 million cubic meters
of producer gas consumes 0.054 million kWh of
electricity, 2.607 103 t of steam coal washer refuse
and 2.286 103 t of metallurgical coal refuse, and
discharges 3.179 103 t of bottom ash, while consuming
300,000 RMB of investment capital and 5.357 personyears of labor (excluding estimates for environmental
control).
The final demands and outputs are related to the
matrices [a], [b], [c] and [d] by the following relations:
½a½X ¼ ½Y ;
¼ ½Zc ;
½b½X ¼ ½Z b ;
½c½X ½d½X ¼ ½Z d ;
ð2Þ
where [X ] is the transposed column matrix [vector] of
the line vector [X a ] whose elements are the main
products for each facility.
Eq. (2) may be transformed by using the inverse
matrix [a1 ] into the following relations:
½X ¼ ½a1 ½Y ; ½Zb ¼ ½b½a1 ½Y ; ½Z c ¼ ½c½a1 ½Y ;
½Zd ¼ ½d½a1 ½Y ;
ð3Þ
where, per unit of main product final output:
*
*
*
*
[a1 ] is the total main product output,
[b][a1 ] is the total purchased input requirement,
[c] [a1 ] is the total byproduct and waste discharge,
and
[d][a1 ] is the total primary input requirement.
The matrices are shown in Table 5. Each coefficient in
the table describes the total input required, both directly
and indirectly, to generate one unit of main product.
For example, each coefficient in the raw steam coal row
in Table 5 is larger than the corresponding number in
the same row in Table 4 of direct input coefficients. The
difference between the two numbers indicates the
amount of raw steam coal required indirectly for each
of the seven processes.
As is shown by Tables 1–5, the cokemaking processflow model provides a great deal of information for each
To each unit of output (elements of the vectors [Y ],
[Zb ], [Zc ], and [Z d ]) can be associated a revenue (positive
number) or a cost (negative number), thus revenue and
price vectors [Py ], [Pb ], [Pc ], and [Pd ]. An analyst
calculates the profit of the enterprise by taking the inner
product of the two vectors:
Profit ¼ ½P transpose½Z
ð4Þ
As shown in Lupis and McMichael (1999), we can
also calculate the profit per unit of gross output of main
product, which readily provides the change in profit
associated with a change in the total production of one
of the main products.
Profit ¼ ½P transpose
a½X b
c
d
ð5Þ
By transforming ½X ¼ ½a1 ½Y ; we can calculate the
profit per unit of final main product output, or
determine the change in the profit associated with a
variation in the amount of main product sold to the final
customers.
Returning to the fictitious TVE coal-based enterprise,
we can examine the results in terms of the assumed
production factors in Table 1. In our highly simplified
model, we have not analyzed any environmental control
technologies directly. Cokemaking technologies might
be compared environmentally and economically on the
yield of coke from a unit of coal input. Using less coal
for a unit of coke output is viewed as good from both
viewpoints. Cokemaking with the byproduct ovens
where workers externally quench the hot coke consumes
more water for quenching than the other coke processes
where workers quench the hot coke inside the ovens.
Quenching in the oven obviates the need for capital
investment in quench towers, but may have other
undesirable features like increased oven maintenance.
Purchased water is used to makeup for the losses of
evaporated water in quenching. Process wastewater,
called ammonia liquor, is generated in the small
machinery and the advanced modified indigenous coke
plants. Any water generated in the nonrecovery coke
ovens is unaccounted for in the model. Ammonia liquor
is assigned a negative price, reflecting that it is a cost
Table 5
Total input coefficient cokemaking process-flow model
Input/product
Metallurgical
coal washer
Producer gas
generator
Steam coal
power plant
[100 MWe]
(1)
(2)
(3)
(4)
1.032
0.000
0.000
0.071
0.000
0.000
0.000
(1.414)
0.000
0.000
0.382
0.000
0.002
0.001
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
(126.481)
(0.556)
(6.324)
(0.028)
0.027
1.000
0.000
0.059
0.000
0.000
0.000
(0.037)
(1.160)
0.000
0.010
0.160
0.002
0.001
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
(115.922)
(0.291)
(5.796)
(0.015)
0.025
0.000
1.000
0.055
0.000
0.000
0.000
(0.034)
0.000
0.000
(2.598)
(2.286)
3.180
0.001
0.000
0.000
0.075
0.000
0.000
0.000
0.000
0.000
0.000
(351.971)
(5.395)
(17.599)
(0.270)
0.464
0.000
0.000
1.032
0.000
0.000
0.000
(0.636)
0.000
0.000
0.172
0.000
0.033
0.014
0.000
0.006
0.000
0.000
0.000
0.000
0.000
0.000
0.000
(970.130)
(0.707)
(48.506)
(0.035)
Small
machinery
coke
ovens
(5)
Advanced
modified
indigenous coke
ovens
(6)
Nonrecovery
coke ovens
0.062
1.467
0.311
0.139
1.000
0.000
0.000
(0.086)
(1.702)
(146.667)
(0.788)
(0.476)
0.993
0.002
0.111
0.001
0.027
0.333
(0.100)
0.001
14.667
14.667
176.000
(1111.859)
(4.352)
(55.593)
(0.218)
0.043
1.350
0.000
0.096
0.000
1.000
0.000
(0.059)
(1.567)
(810.000)
0.016
0.217
0.003
0.001
0.000
0.001
0.004
0.300
(0.285)
0.004
6.750
0.000
81.000
(261.047)
(1.904)
(13.052)
(0.095)
0.040
1.320
0.000
0.089
0.000
0.000
1.000
(0.055)
(1.532)
(792.000)
0.015
0.212
0.003
0.001
0.000
0.001
0.004
0.300
(0.210)
0.003
0.000
0.000
0.000
(207.719)
(1.892)
(10.386)
(0.095)
(7)
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
1. Clean steam coal [a inverse]
2. Clean metallurgical coal
3. Producer gas
4. Electricity
5. Coke from small machinery plant
6. Coke from advanced modified indigenous plant
7. Coke from nonrecovery ovens
8. Raw steam coal [b]*[a inverse]
9. Raw metallurgical coal
10. Water
11. Steam coal washer refuse [c]*[a inverse]
12. Metallurgical coal washer refuse
13. Bottom ash
14. Power plant fly ash
15. Coke breeze from quench
16. SO2 to atmosphere
17. S to coke oven gas
18. COG production
19. COG to underfire ovens
20. SO2 to atm from combusted COG
21. Tar and pitch
22. Ammonium sulfate
23. Ammonia liquor
24 Process capital investment [d]*[a inverse]
25. Process labor
26. Environmental capital investment
27. Environmental control labor
Steam coal
washer
Source: Calculated from Table 4 by inverting the matrices.
881
882
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
that would change depending on the level of treatment
provided.
We list coke-oven gas as a byproduct, but this gas
presents several concerns. On the one hand, it is a
valuable fuel gas, having a heat value about one-half of
natural gas. On the other hand, coke ovens generate
more gas than they consume for heating coke. In China,
the excess gas may be used as an industrial fuel gas or as
town gas, and the level of gas cleaning and purification
(i.e., the level of sulfur) varies with the intended use of
the gas. We have assumed that 30% of the sulfur in the
coal fed to the coke ovens ends up in the coke-oven gas.
The technology chosen to remove sulfur depends on the
form of the sulfur in the gas. Unburned coke-oven gas
has sulfur in a reduced form like H2S; after combustion
the sulfur is oxidized to the form of SO2. The decision to
remove the sulfur or not to remove it involves technical
and regulatory issues. This model draws attention to the
different forms of sulfur and the path that sulfur traces
through the enterprise.
With the assumed values for processes and costs, our
model for the base case shows that, overall, the
enterprise is profitable, despite different profits for each
of the seven facilities. Expressing the profit vector using
Eq. (5), we find that the overall system makes an annual
profit of about 192 million RMB (Table 4). Separating
this profit for each of the seven facilities, we get the
following results for a final demand vector, Y ¼ 0 clean
steam coal, 0 clean metallurgical coal, 0 producer gas,
789 MkWh, 180 kt small-machinery coke, 200 kt of
advanced-modified-indigenous coke, and 200 kt of nonrecovery coke:
*
*
*
*
*
*
*
Steam coal washerFloss of 19.6 103 RMB per
kiloton of clean steam coal.
Metallurgical coal washerFloss of 20.2 103 RMB
per kiloton of clean metallurgical coal.
Producer gas generatorFloss of 28.1 103 RMB per
M cubic meters of producer gas.
Power plantFa gain of 146,000 RMB per M kWh.
Small-machinery coke ovensFa gain of 104,000
RMB per kiloton of coke.
Advanced-modified-indigenous coke ovensFa gain
of 127,000 RMB per kiloton of coke.
Nonrecovery coke ovensFa gain of 127,000 RMB
per kiloton of coke.
The negatives represent losses and imply that at the
prices assumed for washed coal and producer gas,
marginal increases in production of these commodities
would lose money. On the other hand, marginal
increases in the production of electricity and coke
proved to be beneficial. More experimentation with
the assumptions will provide insight about the strengths
and weaknesses of the model.
7. Conclusion
We have illustrated how the cokemaking IOPM can
be used to determine the economic (investment cost,
labor cost, material input costs, and revenues) and
specific energy (coal and electricity) requirements, as
well as the environmental tradeoffs of using alternative
cokemaking technologies. Plant managers, government
officials, and/or academic researchers can use the IOPM
to determine the effect that a particular technology,
environmental, energy, labor, and investment policies
may have on the individual plants and regional and
national economy. As an example, policy discussions are
now occurring in Shanxi Province concerning the use of
new by-product ovens versus new nonrecovery ovens.
By using the cokemaking process-flow model the
environmental policy analysts will know the amount of
pollution to be expected if a given amount of coke is
produced by each proposed facility. The economic
planning commission analysts could use the same model
to determine the amount of coal, electricity, water, and
other inputs the alternative technologies would require.
Thus, for China, it is a useful tool to study the economic
and environmental impacts of the closing of indigenous
and most modified indigenous plants and to help
policymakers determine which cokemaking technologies
to support with investment funds and other incentives.
Our cokemaking IOPM is sufficiently generic to be
used not only for cokemaking in Shanxi Province,
China, but also for other regions in China. In addition,
coke managers and economic and environmental
analysts in India, the United States, or any other
cokemaking country can assemble the relevant data for
their own countries and use the model. In addition, with
only minor adjustments, we can adapt our process-flow
model for use in other sectors of any economy. We
believe this model will prove to be a very valuable
addition to the toolbox of models already available.
Acknowledgements
The authors appreciate the many plant managers and
local officials in Shanxi Province who provided and
helped us verify the numbers presented here. The
numbers were originally collected during field missions
to the Province in 1998–2000 by Chen Hao (2000) for his
master’s thesis at MIT and were verified by Professors
Polenske and McMichael during their July 2000 field
trip. We also thank an external reviewer and Monica
Pinhanez who provided useful editorial comments.
Funding for this research is from the Alliance for
Global Sustainability grant number 198.11m-f and NSF
grant number INT 9970425.
K.R. Polenske, F.C. McMichael / Energy Policy 30 (2002) 865–883
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