PREHEATING BOILER BLAST AIR WITH EXHAUST GASES IN COOLING THEM BELOW THE DEW POINT

It has been suggested that, before being fed into the boiler′s air heater, blast air be preheated in a condensation surface heat exchanger with natural combustion products cooled below the dew point. A thermal calculation has been made of a condensation heat exchanger installed behind a BKZ-420-140 NGM power boiler, which has made it possible to determine for different values of the temperature of ambient air: the heating power of the heat exchanger, the consumption of exhaust gases for preheating boiler blast air provided they are cooled below the dew point, the share of exhaust gases delivered to the heat exchanger, consumption of the steam condensate from gas fuel combustion products, the temperature, moisture content, and dew point of the exhaust gases on exit from the boiler unit, the increase in the boiler′s combustion effi ciency due to the work of the condensation heat exchanger, the coeffi cient of heat transfer from the gases to the wall and from the wall to the air being heated, and the heat-exchange coeffi cient. It has been established that the share of the exhaust gases supplied to the heat exchanger for preheating the blast air of a BKZ-420-140 NGM boiler with cooling them below the dew point, depending on the ambient air temperature, is 3.9–20.7% and 7.6–24.4% of their amount in heating the air to 20 and 30^o C respectively. A calculation has been made of economic effi ciency due to preheating the blast air of the BKZ-420-140 NGM boiler at the Samara Heat and Electric Power Plant of the Samara Branch of the PJSC (Public Joint-Stock Company) "T Plus" in the condensation heat exchanger installed behind it.
   
Author:  S. K. Ziganshina and A. A. Kudinov
Keywords:  boiler, combustion products, heat exchanger, dew point, steam condensate, effi ciency
Page:  1142