The gas that leaves the carbonate absorber at about 160°F is heated to 600°F by heat exchange with the process gas in two exchangers, E-110 and E-106, before entering methanation reactor R-105. Here, any remaining oxides of carbon are catalytically converted to methane over a nickel-alumina catalyst. The exit gas, the product hydrogen, is used to partially preheat the feed before being cooled to 20-30°F above ambient temperature. A small quantity of water is condensed and removed before the gas is sent to the battery limit for use. Operating conditions of methanation reactor are shown in Table 5-4.
Figure 5-3 shows the chemical reactions involved in H2 manufacture. Tables 5-5 to 5-8 show process yield, utility consumption and feed/ product qualities.
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