以中低温余热为热源的LNG冷能利用流程改进

在火用分析的基础上，提出了一个同时回收中低温余热和LNG冷量的新流程。该流程是氮气Brayton循环、天然气直接膨胀和氨水混合物Rankine循环的联合。流程中以中低温余热为热源，并将LNG冷量分为低温级的潜热冷量和高温级的显热冷量两级，氮气Brayton循环回收LNG低温级的潜热冷量，氨水混合物Rankine循环回收LNG高温级的显热冷量，实现了能量的梯级利用，有效提高了LNG冷能利用的火用效率。采用Aspen Plus软件对新流程和传统的Brayton循环在相同的热源温度下分别进行了模拟计算。结果表明，新流程在循环最高温度为350 ℃时，火用效率达到了58.24%。

A NEWLY-DEVELOPED PROCESS FOR LNG COLD ENERGY UTILIZATION BASED ON MIDDLE-LOW-TEMPERATURE WASTE HEAT RECOVERY

A new process for the recovery of middle low temperature waste heat and LNG cold energy was proposed on the basis of exergy analysis. It consists of nitrogen Brayton cycle, nature gas direct expansion and ammonia water Rankine cycle. In the new process, middle low temperature waste heat is used as heat source and LNG cold energy is divided into the low temperature latent cold energy and the high temperature sensible cold heat. Nitrogen Brayton cycle recovers low temperature latent LNG cold energy, while the ammonia water Rankine cycle recovers the high temperature sensible LNG cold heat, whereby the graded use of energy can be realized. The exergy efficiency of LNG cold energy utilization can be effectively improved. Analog calculation is carried out with Aspen Plus software on the new process and the traditional Brayton cycle at the same heat source temperature. The results show that exergy efficiency reaches 58.24 percent when the peak temperature is 350 ℃.