Waste heat recovery enhancement in the CO2 chemical absorption process by hydrophobic-hydrophilic composite ceramic membranes

Abstract

A novel ceramic composite membrane configuration was proposed to improve the waste heat recovery performance from stripped gas in the CO2 chemical absorption process. Tubular hydrophobic and hydrophilic ceramic membranes were serially assembled to form a single composite membrane. The stripped gas and bypassed CO2-rich solvent flowed countercurrent on both sides of the composite membrane. The waste heat recovery performance from the stripped gas was investigated under eight membrane configurations using: hydrophobic, hydrophilic, and Janus membranes (i.e., with hydrophilic inner-surface and hydrophobic outer-surface, and viceversa). Results showed that when the stripped gas enters the hydrophobic segment, the waste heat recovery performance increases to a plateau and then decreases with an increasing length of the hydrophobic segment. When the length ratio of the hydrophobic segment was 25%, a maximum waste heat recovery performance was achieved. Similarly, an increase in the hydrophobicity of the hydrophobic segment caused an increase in waste heat recovery performance, in which the optimal water contact angle (CA) was 137.35°. As a result of the abovementioned conditions, a 7.44%–25.15% higher waste heat recovery of the composite membrane was achieved compared to commercial hydrophilic membranes.