Hydrogen from waste refinery gases

Commercial application of these principles has been made for separating hydrogen from waste refinery gases in shell-and-tube devices which resemble in part the common heat exchanger. However, in this use the polymeric-fiber tubes are only 30 jum OD, and there are 50 million of them in a shell roughly 0.4 m in diameter [6]. 

The most promising new membrane-based vapor separation applications include (i) separation of higher hydrocarbons (C2+) from methane for dewpoint and heating value control of natural gas, (ii) recovery of hydrogen and/or hydrocarbons from petroleum refinery waste gases, and (iii) separation of olefins (ethylene or propylene) from polyolefin polymerization purge gas streams. In all of these applications, the higher hydrocarbons are the minor components in the feed gas. To minimize... 

The phenomenon of surface diffusion, demonstrated by Barter and Strachan (1955) may be used to advantage for the separation of some hydrogen-hydrocarbon mixtures (Sircar, 1993b). Thus, thin microporous carbon membranes (<5 pm), supported by macroporous sheets of graphite assembled into a plate and frame membrane module, were able to separate H2 at 63% recovery from a refinery waste gas. The feed was passed at high pressure over the membrane unit which preferentially adsorbed the hydrocarbons and facilitated surface diffusion of these species through the membrane to the low pressure side of the module. Adsorption, accompanied by surface diffusion through a thin microporous membrane, thus offers possible future applications. 

Certain refinery wastewater streams are treated separately, prior to the wastewater treatment plant, to remove contaminants that would not easily be treated after mixing with other wastewater. One such waste stream is the sour water drained from distillation reflux drums. Sour water contains dissolved hydrogen sulfide and other organic sulfur compounds and ammonia which are stripped in a tower with gas or steam before being discharged to the wastewater treatment plant. 

Light hydrocarbons from nitrogen or hydrogen Reactor purge gas, petrochemical process streams, refinery waste gas Application is expanding rapidly... 

Sulfur is quite versatile it can be used as an agricultural insecticide or as a raw material for making sulfuric acid, as shown in Figure 2.12. To make sulfur, acid gas (hydrogen sulfide, sulfur dioxide, and carbon dioxide) from the various refinery amine units is collected and fed to a sulfur plant. In a typical sulfur plant, the acid gas is fed to a reaction furnace. The hydrogen sulfide is first partially burned at 2,500° F (1,370° C) and 15 psia (103 kPa) in the reaction furnace to form sulfur dioxide next, it is passed through a waste heat boiler and then passed over catalyst beds at 500°F (260° C) and 15 psia (103 kPa) in the converters. Sulfur is condensed from the effluent of successive converters and solidified in pits. 

When this plant was being considered for construction, a search was made for an adequate source of electrolytic hydrogen. None was found. However, many sources of refinery waste gas, considered not worth recovery, were found. This waste gas consists of hydrogen gas with impurities ranging from 5-18 of assorted hydrocarbons. A typical analysis is given in Table I. 

Recovery of heavy hydrocarbons or liquefied petroleum gas (LPG) from refinery purge or fuel gas is significantly more profitable than using these components as waste fuel. If the gas contains hydrogen, it can also be recovered. This application is a long-standing area of research pilot plants for the process are installed. This could become a significant market. 

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