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Process control using membranes to adjust the stoichiometry of steam methane reforming synthesis gas for feed gas in gas-to-liquids production

IP.com Disclosure Number: IPCOM000182980D
Publication Date: 2009-May-11
Document File: 5 page(s) / 333K

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The IP.com Prior Art Database

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Process control using membranes to adjust the stoichiometry of steam methane reforming synthesis gas for feed gas in gas-to-liquids production

Steam methane reformers (SMR) make a synthesis gas or syngas with a H2:CO ratio of greater than 5:1, far in excess of the 2:1 ratio required for feed gas by typical gas-to-liquid (GTL) operations. This makes it infeasible as a direct feed to a GTL process since the excess H2 would build up to impractical levels in a recycle loop required for a reasonable carbon conversion and would also alter the selectivity to undesired lighter products. Large land based GTL plants use autothermal reformers due to economy of scale that give a syngas much closer to the desired 2:1 ratio.  However, increases in oil prices and product values make smaller gas monetization volumes practical, particularly for offshore associated gas reserves.  On this scale, steam methane reformers become attractive since there is no expensive oxygen plant and related safety concerns in an offshore environment are eliminated. Membranes selective to hydrogen are widely used in industry for hydrogen recovery. New high temperature ceramic-based membranes produce H2 at high purity. These are typically used to recover hydrogen for hydrotreating and fuel cells and so are designed for maximum recovery in the 75-85% range. This is done by setting the permeate back pressure controller at the minimum possible value that gives the largest differential pressure driving force. A typical control scheme is shown in Figure 1. In a typical scheme for produ...