WSP10254 - Laserfiche WebLink

Home Browse Search

"~ (') -:,\,J ....-1 <..i r' ~.. AQUATRAIN April 1983 Section 3. The AQUATRAIN Project RELATED TECIINOLOGIES--SALINE WATER AND COAL For practical energy production purposes, saline water collected and delivered by AQUATRAIN could be beneficially used for powerplant cooling through the use of saline water cooling towers (see figure 2). These cooling towers use a heat exchanger system designed such that saline water can be circulated through a secondary cooling loop. The primary freshwater cooling loop and the saline water cooling loop are separated by thin plastic sheets so that no mixing of freshwater and saline water occurs. The resultant wastewater (120,000 milligrams per liter salt concentration) would be put into approved brine evaporation ponds or desert dry lakes. The coal currently being considered for AQUATRAIN is subbituminous "C" of approximately 10,000-11,000 BTU per pound, 16-percent moisture, 5-6 percent ash, and 0.5 percent sulfur. Ultra or deep cleaning _thods to remove all or part of the coal contaminants (moisture, ash, sulfur) are being developed by private industry and government sponsored projects. These methods raise the coal's heat content to more than 13,000 BTU per pound, as well as substantially lowering the cost of emission control equipment and offering more economical Shipping. Coal with higher sulfur and ash content could also be used in powerplants by utilizing fluidized-bed combustion techniques (see figure 3). Several fluidized-bed designs are available or under development. In general, all fluidized-bed combustors generate steam from coal via a heat exchanger. In a fluidized-bed system, a mix of crushed coal and limestone or dolomite is constantly agitated from below by pressurized air jets. The mix responds in the manner of a boiling liquid, hence "fluidized". The ignited mix burns at 1500 to 17000 F-- one half the te~rature of conventional coal-fired steam generating systems. The bed's lower operating temperature and controlled combustion substantially reduce generation of nitrous oxides. The mix is in constant contact with the coiled metal tubes of the heat exchanger, and heat is transferred five to ten times more efficiently than in present systems. The limestone or dolomite, in addition to transferring heat, absorbs sulfur and can eliainate sulfur dioxide eaissions. The resulting sulfurous ash has been successfully used as a soil conditioner. Also, fluidized-bed systems cost less to build than conventional coal combustors and allow use of any grade of crushed, unwashed coal. Ready availability of high-quality coal and/or coal products, economically transported by AQUATRAIN, will help spur full development of saline water cooling towers, fluidized beds, and other beneficial coal-fired power generation techniques. 10