Waste Heat Recovery of Biomass Based Industrial Boilers by Using Stirling Engine

Abstract

Industrial boilers by using biomass for electricity generation have received significant attention recent years. However, during the process, a significant fraction of thermal energy is often lost to the environment as flue gas. The exhaust flue gas heat loss which ranges from 150-180°C has led to discovery of importance of recovering the waste heat of the flue gas to overcome the reliance on fossil fuel. Stirling engine as an external combustion engine with high efficiencies and able to use any of heat source is the best candidate to recover waste heat of the exhausted gas by converting it into power. Nevertheless, Stirling engine shows a drastic decline in performance when connected to a low temperature heat source. For this reason, CFD simulation test was performed to design an initial computational model of Stirling engine for low temperature heat waste recovery. The CFD model was validated with the experiment model and shows 4.3% of deviation. The validated model then connected to a lower temperature. It shows that when the heat source is 400K, the work done by the engine is 8.4J compared to when heat source 775K the work done is 17.0 J. The computational model can be used to evaluate method in heat transfer enhancement from low temperature heat source for low temperature waste heat recovery of biomass based industrial boilers by using Stirling engine.