实验测试了丙酮在不同温度、真空度和饱和吸附量的活性炭上脱附的出口浓度。结果表明:脱附真空度越大,脱附初始吸附容量越大,但脱附速率相应变小;吸附剂微孔内的毛细管现象作用和脱附过程中的传热传质耦合影响使脱附浓度曲线表现出真空浓缩区、快速衰减区和缓慢衰减区3个阶段,特别在脱附压力低于60kPa时,脱附出口浓度开始出现较长时间的反弹和维持,然后才缓慢下降。通过理论分析和建立脱附过程的耦合模型,数值模拟了丙酮在活性炭上的脱附,实验和理论分析发现脱附引起温度变化不大,相应由于温度变化所引起的传质系数变化以及浓度变化都不大;耦合影响的传质系数在脱附过程的不同阶段对浓度曲线影响程度不一样;分段求取传质系数和轴向扩散系数可以使数值计算结果很好地与实验数据吻合;对于同一初始吸附容量,脱附时丙酮分压越大其传质系数k越大;轴向扩散系数在真空脱附时不宜忽略。
The outlet concentration of acetone desorption from activated carbon was measured under different conditions, such as different temperature, different vacuum and different saturation adsorption quantity. The experimental data show that larger desorption vacuum and initial adsorption quantity of desorption lead to smaller desorption rate. For the effect of capillarity of micropore on the adsorbent and the couple of the heat and mass transfer in the process of desorption, the change of the desorption concentration underwent three phases, which were vacuum concentration, rapid attenuation and slow attenuation. Especially when the pressure of desorption is lower than 60 kPa, the outlet concentration begian to rebound and maintain for a longer time, and then it decrease slowly. In order to study the discipline of the couple of heat and mass transfer of desorption, the heat-and-mass-coupled model was established and the outlet concentration of acetone desorption on activated carbon was simulated. Through experimental and theoretic analysis, it was found that the temperature of desorption change a little, and accordingly, the changes of the coefficient of mass transfer and the concentration caussed by temperature are small. The influence of the coefficient of mass transfer on concentration is various in different phases of desorption and choosing different coefficient of mass transfer or coefficient of axial diffusion made the calculated value of simulation fit the experimental data well. For the same initial adsorption quantity, the greater the partial pressure of acetone is, the larger the coefficient of mass transfer is. The omission of the coefficient of axial diffusion of desorption is not suitable.