Adsorption behaviour of molecular sieve and activated carbon for CO2 adsorption at cold temperatures

Abstract

At present, insufficient works have provided insights into the application of adsorption to remove CO2 in flue gas below room temperatures under ambient pressure. In this work, the effects of temperature, CO2 partial pressure and moisture on dynamic adsorption characteristics for CO2 are conducted for various adsorbents. Based on our findings, lower the adsorbing temperature can drastically enhance the adsorption of carbon dioxide over molecular sieves and activated carbon. Among various adsorbents, 13X molecular sieve shows highest adsorption capacity. With a concentration of 10% CO2 in flue gas, the specific adsorption capacity of CO2 over 13X molecular sieve is 0.11, 2.54 and 5.38 mmol/g at 80 °C, 0 °C and − 80 °C, respectively. In addition, the partial pressure of CO2 also has a significant impact on the adsorption capacity. With the increment of the concentration of CO2 from 1% to 10% under 0 °C, the specific capacity of 13X molecular sieve increases from 1.212 mmol/g to 2.538 mmol/g. Water vapor in flue gas can not only reduce the specific adsorption capacity of CO2 due to competing adsorption, but also increase the heat penalty of molecular sieve regeneration due to the water adsorption. An overall analysis is conducted on the energy penalty of capture 1 ton CO2 at various adsorption temperatures between − 80 °C and 80 °C, considering both the heat penalty of molecular sieve regeneration as well as the energy penalty for cooling the adsorber. It is found that the lowest energy penalty is about 2.01 GJ/ton CO2 when the adsorption is conducted at 0 °C.