Refinery Hydrogen Applications

In principle, recovering hydrogen from the inert purge gas is an easy apphca-tion for membranes. However, as hydrogen is removed through the membrane, the remaining gas becomes enriched in hydrocarbons, and the dew point increases to 60 °C or more. To avoid condensation of hydrocarbons on the membrane, the gas should be heated to at least 60 °C. In practice, to provide a safety margin and to minimize plasticization of the membrane, the gas must be heated to 15-20 °C above the expected dew point, in other words to above 80 °C. 

In the past, the available membranes lost a significant fraction of their selectivity when operated at these high temperatures. They also became plasticized by absorbed heavy hydrocarbons in the feed gas. As a consequence, a number of early hydrogen-separation plants installed in refineries had reliability problems. The development of newer polyimide and polyaramide membranes that can safely operate at high temperatures has solved most of these problems and the market for membrane-based hydrogen-recovery processes in refineries is growing. 

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Refinery, hydrogen-rich applications (Refinery) - Grayson, Peng-Robinson, Redlich-Kwong-Soave. 

Non-power applications have been assessed on the basis of the typical characteristics of the SEWGS technology mentioned earlier. The applications that are being assessed are (i) distributed refinery hydrogen, (ii) refinery process hydrogen, (iii) refinery fuel gas, (iv) ammonia production, (v) coal to liquid chemicals and liquid fuels. The assessment made clear that these non-power applications cannot fully exploit the SEWGS characteristics, and therefore, these non-power applications are less obvious with likely lower economic benefits. 

During the 1970s, considerable research and developmental work was devoted to membranes. Many potential applications were identified, but commercialization was slow. In 1977, Monsanto demonstrated its first full scale membrane separator at Texas City, Texas, in a hydrogen/carbon monoxide ratio adjustment application (Burmaster and Carter, 1983). In 1979, Monsanto commercialized its hollow fiber membrane module as the Prism separator. From 1979 to 1982 Prism separators were evaluated in several refinery hydrogen purification applications (Bollinger et al., 1982). The success of these pilot tests established the commercial viability of gas separation with membranes. The first large scale commercial CO2 membrane separation project was the installation of two membrane separation facilities at the Sacroc tertiary oil recovery project in West Texas in 1983. Up to 80 MMscfd of gas has been processed in these facilities (Parro, 1984). 

When hydrogenation is carried out in a continuous process often so-called trickle-ttow reactors are used. Mass-tran.sfer limitations often occur. An elegant improvement is the application of extrudates with a noncircular cross section, which increa.ses the external surface without increasing the pressure drop. Trilohe and Quadrilohe shapes are generally used in oil-refinery processes and they might also be useful in fine chemicals production. 

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