沼气水洗技术中解吸工艺对提纯性能的影响分析与优化

Analysis and optimization of the purification performance depending on the desorption process in biogas water scrubbing technology

以中试规模的25 Nm^(3)/h沼气压力水洗提纯实验系统为基础,耦合填料吸收塔/填料解吸塔和填料吸收塔/旋转解吸床两种工艺,研究解吸工艺对提纯性能的影响以及强化解吸的优化对比。塔/塔系统实验结果表明,当鼓风量Q_(a)从0增至20 Nm3/h时,吸收塔的分离效率快速上升(产品气CO_(2)体积分数y_(2)至3%以下)而后趋向稳定,权衡效率与能耗下Q_(a)与进气流量G的优化比值在3~4之间。在压力为0.85~1.15 MPa、温度为10~25℃、液气比1∶8~1∶5、进气CO_(2)体积分数为35%~50%及进气流量为15~30 Nm^(3)/h条件下,分析了解吸对分离性能的影响程度及机理,发现当进水CO_(2)摩尔分数达0.0001时相对纯贫液的传质单元数N_(OG)上升幅度在15.7%~42.8%之间。通过塔/床系统实验得出当转速增至840 r/min时,y_(2)快速下降至2.02%而后趋向稳定,而当转速超过1120 r/min时塔/床系统比塔/塔系统的分离性能要优。

This study focuses on the influence of the desorption process and enhanced desorption optimization for biogas upgrading using pressure water scrubbing technology.Two systems based on a packed absorption tower/packed desorption tower and a packed absorption tower/rotating desorption bed were included in a pilot-scale(25 Nm^(3)/h)test device.In the tower/tower system the separation efficiency of the absorption tower rose rapidly(with CO_(2) concentration in the product gas y_(2) below 3%)along with the air blast flow Q_(a) from 0 to 20 Nm^(3)/h and then tended to be stable.The optimal ratio of air blast flow Q_(a) and intake gas flow G was in the range 3 to 4 when balancing efficiency and energy consumption.The effect of desorption on the separation performance was analyzed under the conditions of pressure p 0.85-1.15 MPa,temperature T 10-25℃,liquid-gas volume ratio L/G 1∶8-1∶5,gas intake CO_(2) concentration y135%-50%,and intake gas flow G 15-30 Nm^(3)/h.When the CO_(2) molar content in the intake water reached 0.0001,the increase in the number of transfer units NOG was in the range 15.7%-42.8%relative to the pure lean liquid.The CO_(2) concentration in the product gas y_(2) decreased rapidly to 2.02%as the rotation speed exceeded 840 r/min and then tended to be stable in the tower/bed system.When the rotation speed was over 1120 r/min,the tower/bed system afforded higher separation efficiency than the tower/tower system.