Hydrophobic activated carbon for elevated-temperature pressure swing adsorption
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Hydrophobic activated carbon for elevated‑temperature pressure swing adsorption Peixuan Hao1,2 · Yixiang Shi1,2 · Shuang Li1,2 · Ningsheng Cai1,2 Received: 21 August 2019 / Revised: 1 February 2020 / Accepted: 13 March 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Elevated temperature pressure swing adsorption is a newly developed gas purification technology, wherein the product gas recovery rate can be significantly improved by adding a steam rinse and purge. Furthermore, high temperature industrial syngas can be directly purified at elevated temperatures, so the temperature variation during purification process is not as large as that in Selexol, Rectisol or some other methods, which benefits to the simplification of heat management and improvement of energy efficiency. At working temperatures of approximately 200 °C, activated carbon is considered to be a promising adsorbent. Nevertheless, activated carbon also adsorbs large amounts of steam during rinse and purge, which affects its adsorption capacity. Herein, hydrophobic activated carbon was synthesized by impregnation and characterized, achieving a contact angle with a water droplet of up to 134°. When exposed to wet air, the weight increase of the hydrophobic adsorbent was 0.3%, whereas it was approximately 12% for the commercial activated carbon, which can be mainly attributed to vapor adsorption. The CO2 adsorption capacity was tested under humid conditions at 200 °C on a fixed bed. The effect of steam on the hydrophobic adsorbent was much smaller than that on the commercial adsorbent. The working capacity decreased from 0.091 to 0.009 mmol/g when the commercial activated carbon was operated under steam at 1 atm, whereas the hydrophobic material exhibited a stable and desired working capacity at the same condition, which was around 0.05 mmol/g. Steam rinse and purge were demonstrated to be feasible for the hydrophobic adsorbent and the introducing of steam rinse could not only compensate for the deterioration of adsorption capacity resulting from impregnation, but further improve the purification efficiency. Keywords Hydrophobic activated carbon · Pressure swing adsorption · Steam rinse · Steam purge
1 Introduction Pressure swing adsorption (PSA) is a promising technique for gas separation because of its excellent flexibility and has been widely used for syngas purification, air separation, and CO2 capture (Sircar and Golden 2000; Yin et al. 2008; Luberti et al. 2014; Khunpolgrang et al. 2015; Voldsund et al. 2016). Conventional PSA techniques usually operate at lower temperatures ( 99% (Zhu et al. 2018). The working temperature of Mg–Al hydrotalcite is usually 300–450 °C because at lower temperatures, its adsorption capacity and kinetic performance deteriorate sharply. Thus, for low temperature syngas (approximately 200 °C) purification or pre-combustion CO2 capture, activated carbon is a better adsorbent than hydrotalcite. TDA (Alptekin 2012) constructed a pilot scale ET-PSA system to capture CO2 as part of an
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