Effects of geometric and heat transfer parameters on adsorption-desorption characteristics of CO_2-activated carbon pair

摘要

A comprehensive 2-D transient heat and mass transfer analysis is carried out to identify the best reactor configuration in terms of better charge and discharge characteristics for a CO_2-activated carbon (Maxsorb Ⅲ)-based sorption systems. Reactors with different aspect ratios (AR) ranging from 0.35 to 7.8 are analysed for a wide range of convective heat transfer coefficient (h), constant pressure charging, and discharging cases. Effects of external cooling/heating fluid temperature, convective heat transfer coefficient (h), operating pressures are studied for both the charging (1-100 bar) and discharging (65-110 bar) cases. The adsorption cell with AR=7.8 showed the best performance for CO_2 adsorption/desorption in a fixed charge/discharge time of 300s. For charging at 100 bar pressure, the reactor with AR= 7.8 resulted in an increment of 23.34% in CO_2 uptake and reduction in maximum bed temperature by 27 K compared to that of the reactor with AR=0.35. For h = 700 and 500 W/m~2 K, the reactor with AR = 7.8 adsorbs 1300 g and desorbs 832 g of CO_2/kg of adsorbent at 100 bar and 65 bar for external cooling and heating fluid temperature of 293 K and 800 K, respectively. The study concludes that better discharge performance can be attained by proper selection of AR even at a lower heating fluid temperature as the reactor with AR = 7.8 at 600 K can desorb 46 to 131 g of extra CO_2 w.r.t. all ARs at 800 K. The proposed reactor configurations are supposed to play a vital role in designing of adsorption-based green refrigeration and carbon capture systems.