Abstract:

Taking the Kalina cycle driven by the low temperature flue gas waste heat as the research object, net work (W_net) and levelized energy cost (LEC) versus outlet temperature of flue gas (T_go) were analyzed from the perspective of thermo-economics under variations of the pinch point temperature difference of evaporator (ΔT_e), evaporation pressure (p_e) and basic ammonia mass fraction (x). Considering the corrosion of low temperature flue gas, the necessity and reasonability of limiting T_go at its minimum allowed discharge temperature were studied. Results showed that the system existed an optimal outlet temperature of flue gas (T_go,opt) and evaporation pressure (p_e,opt) for LEC, while T_go,opt was associated with the pinch point temperature difference of evaporator (ΔT_e), p_e and x. For W_net, it only existed p_e,opt and W_net decreased approximately linearly with the increase of T_go. The economic factors affected directly the optimal operation parameters of the system. The economic factors and low temperature flue gas corrosion problem should be considered comprehensively to choose the appropriate operation parameters in view of different heat source conditions.

Key words: Kalina cycle, waste heat power generation, low temperature flue gas, recovery, thermodynamics, economics

摘要：

以低温烟气余热发电Kalina循环为研究对象，基于热经济学原理，在不同的蒸发器换热端差ΔT_e、蒸发压力p_e和基本氨水质量分数x下，研究了烟气出口温度T_go的变化对系统的净输出功W_net与平准化电能成本LEC的影响。考虑到低温烟气的腐蚀性，分析了固定烟气出口温度为最低允许排烟温度的必要性和合理性。研究结果表明，存在最佳烟气出口温度T_go,opt和蒸发压力p_e,opt使系统的LEC最小；且T_go,opt与ΔT_e、p_e和x有关。对于W_net，只存在p_e,opt使系统W_net最大；W_net随T_go的增加近似线性减少。经济因素会直接影响到系统的最佳运行参数；在选择循环的运行参数时，应针对不同的热源条件，综合考虑系统的经济性与低温烟气腐蚀性问题。

关键词: Kalina循环, 余热发电, 低温烟气, 回收, 热力学, 经济