PROCESS FOR UTILIZING LOW CALORIFIC VALUE OFF-GASES AND SIMULTANEOUS DEODORIZATION THEREOF

摘要

Abstract of the DisclosureA process is disclosed in which any off-gas generated in a waste-water treatment plant, which off-gas has a low calorific (or BTU) value aboutone-tenth of that of natural gas, and usually even less, may be profitablyburned in a multiple hearth furnace if the off-gas is first wet-scrubbed to atemperature below about 90°F, then pre-heated by passing it through the centershaft of a multiple hearth furnace, before the pre-heated gas is burned. Suchcooling of the off-gas by wet-scrubbing has the effect of lowering the moisturecontent of the wet-scrubbed gas sufficiently so that it may be advantageouslypre-heated in the center shaft of the furnace and recycled to the hearths toassist in the combustion of sludge. In addition to providing desirable savingsin auxiliary fuel usage, wet-scrubbed off-gas is unexpectedly cleansed of asufficient amount of its corrosive components so as to permit ducting the wet-scrubbed gas in mild steel or cast iron equipment. Further, burning an odorousgas conveniently deodorizes it. The greater operating efficiency thus achievedprovides more economical operation of a wastewater treatment facility. Theprocess is most profitably utilizied with decant tank off-gas which is generatedin an amount about equal to the normal cooling gas capacity of the furnaco'scenter shaft, and which decant tank off-gas is about equal to the volume ofcombustion air which would be required to burn the sludge.