Comparison and Optimization of Low Temperature Flue Gas Power Generation Systems in Iron and Steel Enterprises

To make use of the flue gas waste heat at 200 to 450 ℃ from iron and steel works with a high efficiency,simulated and calculated were the thermal efficiency,exergy efficiency and power generation capacity of the working medium in unit mass of an organic Rankine cycle(ORC) and a steam-organic combined dual Rankine cycle(S-ORC) by using the software EES.Through a comparison of the performance of various power generation systems,the measures for optimizing the low temperature power generation systems were investigated.To further utilize the exhaust steam waste heat from the turbines of an ORC system,a cascade organic Rankine cycle was designed for heat sources at 300 ℃ and above.When the performance of various power generation systems is taken into account in a comprehensive way,it has been concluded that for flue gases at 200 to 300 ℃,an ORC power generation system can be adopted with R141b serving as the working medium,for flue gases at 300 to 450 ℃,a CORC power generation system can be adopted.Due to the thermal efficiency,exergy efficiency and power of a steam organic Rankine cycle being higher than those of the traditional steam Rankine cycle and such a cycle capable of effectively lowering the negative pressure of the working medium in the condenser,for heat sources at a temperature higher than 450 ℃,a steam organic Rankine cycle can be used to replace the traditional steam Rankine cycle.