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<br />"..... <br />en <br />w <br />.!::. <br /> <br />coal ash and gangue. Sample analyses are shown in Appendices A and B. The <br /> <br />concentration of pollutants depends on the coal type and on the process. If <br /> <br />we take chemical o~Jgen demand, COD. as the first measure of pollutant level, <br /> <br />the Synthane and Lurgi processes using subbituminous coals and the Hygas <br /> <br />process using a lignite have the dirtiest water. <br /> <br />Less polluted is the Hygas <br /> <br />wastewater when a bituminous coal is used. Least polluted is the condensate <br />from the entrained flow Koppers gasifier. <br />The level of contamination, to a first approximation, decreases when the <br />coal rank increases and when the reactor temperature increases. However, <br />reactor residence time and configuration also enter into the picture. A great <br />deal of variation in Synthane wastewater has been obtained by changing the <br />7 <br />point of injection of steam and oxygen . <br />For all except the highest tempe:ature gasifiers, p:ocess condensate is <br />much the most troublesome wastewater in the plant. As can be seen from the <br />analyses in ~~e appendix, the water is usually foul. It cont3ins large <br />quantieies of ammonia and carbon dioxide. In gasi!ying wes~ern, low sulfur <br />coals, ~e wastewater will, fortunately, be low in hydrogen sulfide. <br />Conde~sate can be high in phenols and high in o~"er oxygen demand. Since <br />phenol exerts about 2 1b biochemical oxygen demand per 1 1b phenol, or 2.4 lb <br />chemical oxygen demand per 1 lb phenol, it can be calculated that phenols <br />represent in the range of half of the BOD and below one quarter of the ceo. <br />The organic matter, in addition to phenol, contains fatty acids and other <br />compounds which are mostly biodegradable8,9 <br />In most processes foul condensate wastewater is so contaminated ~~at its <br />~elease to the environment in any form is unacceptable a Apart from the prohibi~ive <br />cost of evaporation ponds for so large a flo~, ammonia and volatile organic <br />matter will cause serious air pollution if this water is stored. Therefore, <br />release of ~treated condensate wastewater is, for the purposes of this study, <br />taken not to be a permitted option, Rather, the water must first be treated <br />for removal of ~onia and organic matter. In all but a few plants ,where <br />treatment of condensate wastewater is required, the treatment will be such as <br />~o fit :he water for make~p to a cooling system instead of for disposal to a <br />river. This is because a circulating cooling systa~ can accept considerably more <br />organic material and ammonia than effluent guidelines, under PL92-S00, are apt <br />to permit for discharge to a river~ Furthermore, treated process condensate, <br /> <br />29 <br />