GB1426564A - Removing ammonia from gases - Google Patents

Abstract

1426564 Removing ammonia from gases SIMON-CARVES Ltd 21 Feb 1973 [7 June 1972] 8527/73 Heading C1A [Also in Division C5] Ammonia is removed from gases, and converted to innocuous products by washing the gas in a saturator with an inorganic acid, and then burning the ammonium salt solution obtain with the addition of a suitable fuel, at a temperature such that nitrogen, water vapour, and the acid or its anhydride occur as combustion products, and at least the acid or its anhydride is recycled to the washing stage after suitable cooling. The gas to be treated, preferably coke oven gas which may be obtained from the collecting main of the ovens, after only moderate cooling and thus still containing its tar constituents, is passed directly, as shown in Fig. 1, via line 11 into spray saturator 10 and leaves via line 12. The inorganic acid, preferably sulphuric, but may be HCl or sulphurous, is atomized through nozzles 13 and 17 and drawn off at the base via line 14. Part is recycled via pump 15 and line 16, and the remainder is passed through line 18 to reactor 19. The feed through line 18 is as concentrated as possible. A fuel, e.g. part of the treated gas, is fed through line 20 together with combustion air through line 21. The resultant combustion products are cooled in heat exchanger 23 to a point slightly above the dew point. The acid content of the vapours is removed in unit 25 and recycled to the scrubbing tower. The residual gas may then be discharged via line 26. The acid may be picked up in unit 25 by means of water, part of which may be introduced from the top of the unit, or a small amount of alkaline solution (Fig. 3, not shown) may be introduced through the top of the column. The small amount of salt solution so formed may be fed into the acid circulation or fed separately into the furnace 19, and the resulting oxides separated, dissolved in water and reused. The combustion products discharged from furnace 19 may be used for raising steam (Fig. 2, not shown) and then passed directly back to the saturator. A catalytic material having as active constituent a metal of Groups V to VIII of the periodic table according to Mendeleev may be introduced into the solution of the ammonium salt, when conditions in the furnace 19 can be adjusted so that there is an oxygen deficiency and reducing conditions obtain and the catalyst is discharged as a fine metallic dust together with some oxide. The metallic dusts pass either directly back to the saturator or to the acid recovery plant where they are dissolved in the scrubbing acid and re-used.