Reversible chemisorption of carbon dioxide: simultaneous production of fuel-cell grade H2 and compressed CO2 from synthesis gas

Abstract

One vision of clean energy for the future is to produce hydrogen from coal in an ultra-clean plant. The conventional route consists of reacting the coal gasification product (after removal of trace impurities) with steam in a water gas shift (WGS) reactor to convert CO to CO 2 and H 2 , followed by purification of the effluent gas in a pressure swing adsorption (PSA) unit to produce a high purity hydrogen product. PSA processes can also be designed to produce a CO 2 by-product at ambient pressure. This work proposes a novel concept called "Thermal Swing Sorption Enhanced Reaction (TSSER)" which simultaneously carries out the WGS reaction and the removal of CO 2 from the reaction zone by using a CO 2 chemisorbent in a single unit operation. The concept directly produces a fuel-cell grade H 2 and compressed CO 2 as a by-product gas. Removal of CO 2 from the reaction zone circumvents the equilibrium limitations of the reversible WGS reaction and enhances its forward rate of reaction. Recently measured sorption-desorption characteristics of two novel, reversible CO 2 chemisorbents (K 2 CO 3 promoted hydrotalcite and Na 2 O promoted alumina) are reviewed and the simulated performance of the proposed TSSER concept using the promoted hydrotalcite as the chemisorbent is reported.

Monitoring Solid Oxide CO2 Capture Sorbents in Action

“…[1] Lee et al has recently studied two promising high temperature chemisorbents for the water-gas-shift-SER (WGS-SER), a K 2 CO 3 -promoted hydrotalcite and a Na 2 O-promoted alumina. [1,[4][5][6][7] The chemisorbents were originally developed by Air Products and Chemicals, Inc. to produce fuel-cell-grade hydrogen by steam methane reforming. [8][9][10][11] These chemisorbents offer (i) reversible sorption of CO 2 in the presence of steam, H 2 , and CO, (ii) relatively fast CO 2 sorption and desorption kinetics, (iii) moderate heats of sorption (~20-65 kJ mol À1 ), (iv) acceptable cyclic working capacity, (v) nearly infinite selectivity of CO 2 chemisorption over gases like CO, steam, N 2 , and CH 4 at 200-500 8C, and (vi) thermal stability under WGS reaction conditions.…”

Decentralized Production of Hydrogen for Residential PEM Fuel Cell from Piped Natural Gas by Low Temperature Steam - Methane Reforming Using a Novel Sorption Enhanced Reaction Concept

“…It should be mentioned here that the model was also used to simulate the performance of another rapid TSSER process designed for simultaneous production of fuel cell grade H 2 and a compressed CO 2 by-product stream to facilitate its sequestration from a synthesis gas produced by gasification of coal [55].…”

Design aspects of the cyclic hybrid adsorbent-membrane reactor (HAMR) system for hydrogen production

“…The HAMR system can be viewed as a membrane reactor (MR) under a PSA operation, potentially suitable for using in a scaled-down version of the SRM process. Conventional MR (Liu et al, 2002;Sanchez and Tsotsis, 2002;Karnik et al, 2003;Ma and Lund, 2003;Tosti et al, 2003;Basile et al, 2003;Drioli, 2004) and sorption-enhanced reactor (SER) technologies (Balasubramanian et al, 1999;Hufton et al, 1999;Waldron and Sircar, 2000;Ding and Alpay, 2000a, 2000bOrtiz and Harrison, 2001;Xiu et al, 2002aXiu et al, , 2002bXiu et al, , 2003aXiu et al, , 2003bXiu et al, , 2004Lee et al, 2007aLee et al, , 2007bLee et al, 2008a, 2008b) proposed in the literature, allow only one of the two SRM products (H 2 for the MR or CO 2 for the SER) to be removed. The ability of the HAMR to remove both products offers additional synergies, both in terms of reaction rate enhancement and product purification.…”