POLLUTION POTENTIALS OF COAL GASIFICATION PLANTS
Stanley L. Klemetson, Assistant Professor
Department of Civil Engineering
North Dakota State University
Fargo, North Dakota 58102
INTRODUCTION
Since the time that natural gas and oil replaced coal as a major source of power, our
needs for energy have continued to rise.   However, domestic production of natural gas is
on the decline, and this has created an energy crisis in the United States.   While some of
our needs for natural gas will be met with imported products, the production of synthetic
natural gas (SNG) by the coal gasification process is also being considered as a part of the
solution.   This would allow the production of a clean fuel from a pollutirig fuel such as
coal.   A primary concern is that the treatment and/or conversion process that generates
the clean fuel does not itself become a major pollution source.   While the potential pollutants can be expressed in any or all of the three possible states of air emissions, solid
wastes and liquid effluents, all of them ultimately contribute to the wastewater effluents
of the plant and its site.
Energy production utilizing a coal gasification process to produce a high-Btu SNG with
a heating value of about 970 Btu/scf will become a reality in the United States within the
next few years.   The enactment of increasingly stringent environmental legislation requires
that information be made available on the types of wastes to be generated, the environmental effects of these wastes, and the best available treatment technology.   Since coal
gasification plants are net consumers of water, it is also important to assess the wastes
from the standpoint of water reuse potential.   The proposed plants will be operating under
widely different climatic conditions, and this could have a significant effect on the choice
of wastewater treatment processes.
A variety of processes have been developed to produce both high-Btu and low-Btu SNG
(Table 1).   Each of the gasification processes has a different configuration of unit operations, but the resulting wastewater effluents are somewhat similar.   Since the Lurgi gasification process is currently available and is being planned for several areas in the northern
Great Plains region of the United States, this paper has been limited to this process and to
North Dakota lignite coal.   However, much of the information will be applicable to the
other processes also.
The purpose of this paper is:   (a) to discuss the Lurgi gasification unit operations and
potential sources of wastewater effluents, (b) to assess the pollutants present in the feed
coals, (c) to review the characteristics of selected process streams and waste effluents, (d)
to review the available treatment technologies, and (e) to assess the effects of climatic
conditions on these treatment methods.
LURGI GASIFICATION PROCESS
The Lurgi coal gasification plants planned for construction in the United States are
being designed to produce about 250 x 106 scfd of medium- to high-Btu SNG that will
yield about 970 Btu/scf.   The average consumption of coal in these plants is about 1000
to 1500 tons per hour, and the average annual usage of raw water is about 17,500 ac-ft.
The plants will be required to meet strict air, solid waste and water pollution regulations,
and will be expected to practice conservation by a reasonable water reuse program.
The complexity of the coal gasification process requires that major (Operations be described in terms of modules that will allow for the analysis of process streams and emissions.   A list of the modules and their typical effluents is shown in Table II, and a simplified block diagram of the Lurgi gasification plant processes and effluent sources is shown
in Figure 1.   The various process and effluent   streams have been left off for clarity.
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