OCR Text |
Show Heat Recovery It is often economically attractive to recover heat produced by the combustion process, especially in applications where the waste stream has little or no heating value necessitating the use of large amounts of fuel. To recover some of the energy expended, a waste heat boiler is used downstream of the final stage to generate steam. Generally, a portion of the cooled flue gas out of the boiler is used for quenching the products of combustion in the second stage. Because this minimizes the heat lost with the flue gases, the amount of heat recovered may be as high as 85 percenL Additionally, for higher-pressure boilers, an economizer is used to cool the flue gases funher. The lower the flue gas temperature, the lower the quantity of flue gas needed for quenching. Depending on the application, a watertube or a firetube boiler may be used. LOWNOx EFFLUENT ~STACK RE-OXIDAnON CHAMBER REDUCTION FURNACE COMBUSTlON AIR BLOWER NITROGEN-BEARING WASTE STREAM Figure 2 - Vertical System O RE-OXIDAnON AIR BLOWER ,~~~"'tt -QUENCH WATER GUNS 4 |