Vapor-phase ammonia-injection process

In the vapor-phase ammonia-injection process, water (or steam) and gaseous ammonia are injected into the stack gas while the gas is at some temperature (>160°F) above the decomposition temperatiure of ammonium sulfite, the principal product (140° to 158°F) (2). After the water is vaporized and the reactants are thoroughly mixed, the gas is cooled below 140°F and the finely divided salt particles separate from the gas as a smoke or fume dp = 0.01-1.0/un). The entrained solids, salt particles, and fly ash are then recovered concurrently. 

A vapor-phase ammmonia-injection process for SO2 removal is being developed at the Morgantown Energy Research Center. In laboratory research with simulated stack gas containing 4200 ppm SO2 (equivalent to 6.0% sulfur in coal), essentially complete removal of SO2 from the gas phase was effected by ammonia injection (i). Preliminary work has since proceeded with a small pilot-scale installation in which the sulfur products from the vapor-phase reaction are removed in a water scrubber. This paper presents additional data from the laboratory work and the pilot-scale installation. 

Although small quantities of sour water may be disposed of by injection into deep wells or by adding to the plant waste water disposal system, these are not viable options for most plants. Normally the sour water is either processed in a sour water stripper (SWS), which produces a vapor phase containing both ammonia and acid gases, or it is selectively stripped in a two-colunon system such as the Chevron WWT process, which produces separate ammonia and hydrogen sulflde-rich gas streams. 

The materials of constmction of the radiant coil are highly heat-resistant steel alloys, such as Sicromal containing 25% Cr, 20% Ni, and 2% Si. Triethyi phosphate [78-40-0] catalyst is injected into the acetic acid vapor. Ammonia [7664-41-7] is added to the gas mixture leaving the furnace to neutralize the catalyst and thus prevent ketene and water from recombining. The cmde ketene obtained from this process contains water, acetic acid, acetic anhydride, and 7 vol % other gases (mainly carbon monoxide [630-08-0][124-38-9] ethylene /74-< 3 -/7, and methane /74-< 2-<7/). The gas mixture is chilled to less than 100°C to remove water, unconverted acetic acid, and the acetic anhydride formed as a Hquid phase (52,53). 

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