Mathematical simulation of the flue-gas recovery system for coal-fired boilers based on the direct-contact heat exchanger

In China, coal-fired boilers and coal-fired combined heat and power plants (CHP) are primary heat sources for district heating, and there is severe heat loss due to flue gas flowing out at a high temperature level. This paper introduces an approach to regather the exhausted heat contained in the coal-fired flue gas based on direct-contact heat exchanger and absorption heat pumps (DAHP). This paper has established a mathematical model for the DAHP system and validated the model with experimental data, and the overall performance evaluation of the DAHP system were conducted, including energy consumption, environmental and economic feasibility. The results showed that the thermal efficiency is 104.5% (evaluated by lower caloric value), emissions significantly decrease and large amount of condensed water is regathered.