液化天然气冷能发电效益分析

Efficiency of power generation by LNG cold energy

通过分析LNG的温焓、温熵特性和不同压力下的可用能,揭示LNG冷能发电循环效率最大化原则和影响可用能利用率因素。同时对实际有机朗肯+直接膨胀复合循环进行参数计算,分析循环在不同压力下的LNG冷源条件下的效率及变化特点,并与不可逆卡诺循环和普通朗肯循环进行比较。结果表明,各种循环都存在一个最佳LNG冷能利用温度,使得循环性能最佳,而且随着LNG汽化压力的增大,循环效率呈下降趋势。在LNG汽化压力较高的情况下,回收直接膨胀功使得复合循环的效率及可用能利用率明显优于普通有机朗肯循环。

In this paper, a comparative study for the practical power generation from LNG cold energy with the Organic Ran- kine Cycle （ORC） ＋ Direct Expansion （DE） combined cycle, the ordinary ORC and the irreversible Carnot cycle was performed. The optimized LNG cold energy utilization temperature for obtaining the highest efficiency of power generation was revealed and the characteristics of the enthalpy and entropy as well as the availability for the LNG cold sinks with different pressures were studied. The results showed that the optimized LNG utilization temperature exists and increases with the LNG vaporizing pressure, while the power output by unit LNG and the availability efficiency are reduced accordingly. For applying the higher LNG vaporizing pressure, the efficiency of the combined cycle is considerably superior to the ordinary Rankine cycle, due to the recovery of power from the direct expansion.