Abstract:

Considerable amount of energy provided for drying processes is rejected to the environment with the moisture in the discharged moist gas, which results in a significant energy inefficiency of the drying processes. In this paper, a new double-stage open absorption heat pump system has been proposed to recover the latent heat of the moist gas and produce high-temperature output, especially in the forms of steam, which is more practical for industrial application and more easier to store. A mathematical model was constructed to analyze the performance of the system. It was demonstrated that the secondary generator pressure p_g2 had to be optimized to get a high energy-saving rate (RES), but heat recovery rate (η) of moist gas decreased with the increase of p_g2. The optimized p_g2 was 81.78 kPa when pressure of driven steam supplied to generators (p_dsg) supplied to generators was above 750 kPa. The η increased with the increase of p_dsg, and the highest η could achieve 49.5%. It was also found that the RES achieved from 16.47% to 60.3% when p_dsg was from 550 to 850 kPa, which means that when 1 kg paper product was produced 60% of energy consumption could be saved.

Key words: double-stage, open absorption, heat pump, waste heat recovery, mathematical modeling

摘要：

烘干过程广泛应用于造纸、木材、食品加工、化工等行业,并排放大量湿空气,造成能量极大浪费、能源利用效率极低等问题。提出了一种新型两级开式吸收热泵系统,用于回收烘干排气的潜热,并输出高温蒸汽;高温蒸汽直接回用于烘干过程,大大节约了能源并提高了能源利用效率。新系统也可用于回收其他来源的湿空气的潜热。结合造纸烘干过程,对新系统建立了热力学模型以分析其性能,并与传统闭式吸收式热泵系统性能进行了比较。结果表明新系统可产生满足烘干需求的高温蒸汽,回收烘干排气约50%的废热,降低造纸烘干过程能耗达60%以上。在给定工况下新系统的COP根据发生热源温度的不同可达1.204~1.995,而闭式热泵系统的COP最高仅可达1.409。

关键词: 两级, 开式吸收, 热泵, 废热回收, 数学模拟