自驱动湿热烟气全热回收系统的适用性

Applicability of self-driven humid and hot flue gas waste heat recovery system

摘要:

燃气燃烧产生的烟气具有温度高、含湿量大的特点,虽然可以采用溴化锂吸收式热泵技术对湿热烟气中的显热和潜热热量进行回收,但仍需要外部驱动热源. 为解决现有吸收式热泵系统的热回收能力与经济性较差的问题,以传统溴化锂吸收式热泵机组为基础,通过与分级式烟气换热器相结合,构建了一种可实现自驱动运行的湿热烟气全热回收系统.建立了系统热力模型和适用性模型,并研究了主要参数对系统热力性能和适用性的影响规律.结果表明:在烟气进口温度为550 ℃、入口含湿量为120 g/kg(a)的条件下,系统最大热回收效率为11.6%,热回收净收益平衡期的极小值为5.2 a;当热回收率、净收益平衡期的预期值分别为10%和5.5 a时,二次水出口温度的适用范围为55 ℃~64 ℃.自驱动系统在烟气进口温度较高、含湿量较低时的节能扩大系数极大值为29.7%,表明此时的自驱动系统相对于直接换热方案的节能效果最为显著.

Abstract:

The flue gas produced by gas combustion has the characteristics of high temperature and high moisture content. The lithium bromide absorption heat pump can recover the sensible and latent heat in the flue gas, but it still requires an external driving heat source. To solve the problems of poor heat recovery capacity and low economic efficiency of such systems, this paper proposes a self-driven humid and hot flue gas waste heat recovery system. The system combines a graded flue gas heat exchanger with traditional lithium bromide absorption heat pump. The thermal model and applicability model of the system were established, and the influence of main parameters on the thermal performance and applicability of the system was analyzed. Results show that under the conditions of flue gas inlet temperature of 550 ℃ and inlet moisture content of 120 g/kg(a), the maximum heat recovery efficiency of the system was 11.6 %, and the minimum value of the heat recovery net income balance period was 5.2 a. When the expected values of the heat recovery ratio and the net income balance period were 10% and 5.5 a respectively, the applicable range of the secondary water outlet temperature was 55 ℃~64 ℃. The maximum value of the energy-saving expansion coefficient of the self-driven system was 29.7%, when the flue gas inlet temperature was high and the inlet moisture content was low, indicating that the self-driven system at this time has the most significant energy-saving capacity in contrast with the direct heat exchange scheme.