An assessment for the viability of recovering heat from a smoke extract system

Abstract

Over the course of industrial manufacturing, additional heat within the extract systems is usually released into the atmosphere and its intrinsic energy is wasted. This paper investigated a cold abatement smoke extract system for a fire testing wall furnace to determine the viability in recovering heat from the hot smoke. Three scenarios were investigated: 1) the extract system was closed and only 300°C smoke was present; 2) the system took in ambient air around the furnace and heat recovery occurred at 80°C in smoky air; 3) the smoke had been removed from the air and the temperature was 60°C. It was found that there was a significant build-up of soot on Scenarios 1 & 2 with a build-up rate of 0.25 μm/s which totalled 2.7 mm of soot after a three-hour test. The soot had a low heat transfer rate and therefore acted as an insulator on the heat exchanger which reduced the efficiency significantly of it over time. Due to this loss in efficiency, it was more viable to recover heat in Scenario 3 at 60°C in clean air than it was to recover heat at 300°C or 80°C in smoky air. The results show that having clean air was more important than a higher temperature when it came from recovering heat from a cold abatement system for a fire testing furnace. This paper contributes to reveal the possibilities of harnessing the “waste heat” for use in other applications in the vicinity of the manufacturing processes, such as heating water within a central heating plant, domestic hot water or electricity generation, or re-cycled within the industrial plant itself.