WATER MANAGEMENT IN COAL GASIFICATION PROJECTS
(LURGI PROCESS)
Sid Thomson, Manager
Fluor Engineers and Constructors, Inc.
Irvine, California 92730
INTRODUCTION
The design and construction of coal gasification plants are becoming increasingly
important in meeting the world's energy demands.   The maximum utilization of water
is one of the most important factors that must be considered in the design of these
facilities.   This is especially true in the arid areas of the western United States where
the large coal deposits are contained.   This requirement essentially dictates a zero
effluent discharge to the receiving stream.
An effective water management program includes:   (a) water balances for variations
in ambient and operating conditions; (b) comprehensive studies on raw water treatment
and effluent treatment; (c) recognition of applicable environmental regulations; and
(d) evaluation of the economics with sufficient consideration given to maintenance and
operating costs.
Failure to properly address any of these points during the design of a coal gasification facility will have a significant impact on the viability of the project.
Primarily, this paper will describe a method of establishing a water balance using a
typical 275 million standard cubic feet per day (MMSCFD) coal gasification plant as an
example.
WATER LOSSES IN A COAL GASIFICATION PLANT
Evaporation from the Cooling Towers
Theoretically, a plant could be designed to utilize all the heat generated, thereby
eliminating the necessity of heat removal in cooling towers or air coolers.      Unfortunately,
inherent inefficiencies in equipment items during the transfer of heat from one medium
to another make the application of this theory impracticable. The evaporative losses
from cooling towers can be reduced by decreasing the heat load to the cooling tower.
This is accomplished by the use of additional process heat exchangers and the utilization of air coolers rather than cooling water exchangers.   Cost-beneficial considerations
usually dictate the amount of heat removed by the cooling tower operation.
Evaporation from Ash Quench and Moisture Adsorbed by the Ash
The ash quenching operation provides a convenient method for disposing of effluent
streams which contain large quantities of both suspended and dissolved solids.   Blow-
downs from water treating, cooling towers, and waste treating are utilized for ash
quenching.   The water adsorbed by the ash and the water evaporated in the quenching
operation constitute a net loss of water.   Recycle of the excess water from the ash
pond to ash quench is practiced to minimize the total water losses.
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