Ammonia Plants based on Heavy Hydrocarbons

The hot gas contains soot, formed because of insufficient mixing of the reactants, and fly ash. A waste-heat boiler, a proprietary item of the Shell process, raises 100 bar steam and cools the gas to 340 °C. Soot is removed from the raw gas in a two-stage water wash. Older installation used an elaborate technique to remove the soot from the water by extraction with naphtha and light oil to form soot pellets which could be burnt or recycled to the feed oil. In newer installations the carbon-water slurry is filtered off in automatic filters, and the moist filter cake is subjected to a controlled oxidation in a multiple-hearth furnace. 

A selective Rectisol unit with methanol of about - 30 °C as solvent is used to remove H2S and COS (together with some C02) to less than 0.1%. The removed sulfur-rich 

Partia( oxidation CO shift-conversion Recfisoi scrubbing unit scrubbing box NH -loop 

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