Increasing the capacity of a recovery boiler by withdrawing some of the exhaust gases from the furnace section

Abstract

Waste liquor from cellulose pulp processes is used in a recovery boiler to recover energy and chemicals. The recovery boiler includes a furnace section in which heat and exhaust gases are generated, and heat recovery surfaces downstream of the furnace section in a path of exhaust gas movement. Waste liquor is injected into the furnace section of the recovery boiler at a first location, and the exhaust gases produced are divided into at least first and second streams. The first stream is passed into association with the heat recovery surfaces of the recovery boiler and then discharged, while the second stream is withdrawn from the recovery boiler at a second location between the first location and the heat recovery surfaces. The withdrawn second stream is positively cooled exteriorly of the recovery boiler preferably utilizing a circulating bed cooler. An electric precipitator removes particulates from the first exhaust gas stream downstream of the heat recovery surfaces, and from the second gas stream downstream of the cooler. The second gas stream is preferably removed from the furnace section between a tertiary air inlet and a nose, and third, fourth, or even more, exhaust gas streams are preferably also removed from the furnace section between the first location and the heat recovery surfaces. Utilizing the invention the capacity of an existing recovery boiler can be inexpensively and effectively increased.

Dependencies are inferred from the claim text.