Patent ID: 9598742
Date: 2017-03-21
CPC Classifications: C21B,C21C,F23J,F23L,F27D,Y02E,Y02P

Claim:
1. A method of extracting heat from a flue gas stream including acidic material and flue gas particulates using an air preheater equipped with a flue gas inlet, a flue gas outlet and a plurality of heat exchange surfaces, the method comprising: a. receiving a flue gas stream into the air preheater through the flue gas inlet of the air preheater; b. determining a mass flow rate of acid material entrained in the flue gas stream; c. determining a mass flow rate of alkaline particles to be injected into the flue gas stream to neutralize the entrained acidic material to obtain a determined mass flow rate; d. injecting at the determined mass flow rate alkaline particles with a bi-modal size distribution into the flue gas stream upstream of the air preheater for mixing of the alkaline particles with the flue gas stream before entering the air preheater; e. measuring a pressure drop across the air preheater from the flue gas inlet to the flue gas outlet; f. comparing the measured pressure drop to at least one predetermined threshold to obtain a determined degree of accumulation of flue gas particulates; and g. adjusting, based upon a mass rate of alkaline particles and the measured pressure drop, the bi-modal size distribution of the alkaline particles to be injected into the flue gas stream, to reduce accumulation of flue gas particulates on the heat exchange elements, to reduce fouling and corrosion of the air preheater, and to increase thermal efficiency of the air preheater.