PROCESS FOR CONCURRENTLY TREATING PROCESS WASTE WATERS AND FLUE GASES FROM AMMONIA SYNTHESIS

摘要

1480657 Treatment of waste water and flue gas SUMITOMO CHEMICAL CO Ltd 3 Feb 1975 [11 April 1974] 4574/75 Headings C1A and ClC Waste water containing ammoniacal nitrogen and organic materials and flue gases containing NO x discharged from an ammonia synthesis gas manufacturing plant in which hydrocarbons are reformed with steam are treated to render them innocuous by removing the ammoniacal nitrogen and the organic material in gaseous form from the waste water, selectively decomposing the organic material in the presence of a catalyst at a temperature of 120-400‹ C., mixing the resulting gases with the flue gases so that the mixture contains NH 3 in an amount of 0À3-10 moles per mole of NO x and effecting the reduction of the NO + by bringing the mixture into contact with a second catalyst at a temperature of 150-700‹ C. Any NH 3 remaining may be removed by oxidizing the product gases in the presence of a third catalyst. The waste water may be stripped with superheated steam, hot air or a portion of the flue gases and the gases formed are passed at a space velocity of 500-50,000 hr-1 over a catalyst which may be iron, nickel, chromium, zinc or copper or oxides or complex oxides thereof. If O 2 is a component of the mixture, the reaction is carried out at 120-250‹ C. whereas if O 2 is absent the reaction is preferably carried out at 150-400‹ C. The gases are then mixed with flue gases, further NH 3 being added if necessary to achieve the required molar ratio which is preferably between 0À7 and 5 moles per mole of NO x . The gases are preferably passed at rate of 2,000- 100,000 hr-1 and a temperature of 150-500‹ C. over a second catalyst which may be a noble metal, e.g. Pt, Pd, a metal oxide, e.g. of Cu, V, Mo or W or a complex metal oxide such as an Fe-Cr, CuCr, or a Mn-Cr. Preferred catalysts are complex oxides containing V and one or more of Cu, Zn, Sn, Pb, Ti, P, Cr, Co, Ni, W or Mo or containing Cr and one or more of Ni, Co, Zn, Mo, W, Sn, P or Ti. If the gases contain excess ammonia, they are preferably passed at a rate of 2,000-100,000 hr-1 and a temperature of 150-700‹ C. over a catalyst which is a chromium oxide, a complex oxide of Cr with Fe, Mg or one or more of Sn, Sb, V, Co, P, Zn, Ni, Pi, Mo or W.