Verfahren zur Gewinnung von Ammoniak aus Kokereigasen

摘要

A method of recovering NH3 from coke-oven gases comprises introducing the gases by pipe 10 to a primary cooler 11, and cooling with an ammonia-liquor spray, conducting the gases from the top of 11 by pipe 15 to the bottom of absorber 16 where the gases ascend countercurrent to a scrubbing solution of ammonia and phosphoric acid supplied to the top of the absorber by pipe 17, delivering the ammonia liquor issuing from the bottom of 11 to a still 13 for steam rectification, and conducting the enriched solution and the condensed vapours from the still 13, via vessel 20 and pipe 23 to a stripping column 24. The acid contaminants e.g. H2S, HCN, CO2, and phenol, in the ammonia-water vapour emerging from the stripper 24 may be removed by washing the vapour with an aqueous solution of a strong alkali e.g. sodium, calcium, or magnesium hydroxide, also oils such as benzene, naphthalene, and pyridine may be removed by decanting. The ammonia and phosphoric acid solution may be represented by the formula (NH4)nH3-nPO4; thus the solution just prior to stripping contains 40% salts of average composition (NH4)1.9H1.1 PO4. The absorber may be a two- or three-stage spray tower and the stripping column may be a bubble-tray tower containing ten or more trays.ALSO:A method of recovering NH3 from coke-oven gases comprises introducing the gases by pipe 10 to a primary cooler 11, and cooling with an ammonia-liquor spray, conducting the gases from the top of 11 by pipe 15 to the bottom of absorber 16 where the gases ascend counter-current to a scrubbing solution of ammonia and phosphoric acid supplied to the top of the absorber by pipe 17, delivering the ammonia liquor issuing from the bottom of 11 to a still 13 for steam rectification, and conducting the enriched solution and the condensed vapours from the still 13, via vessel 20 and pipe 23 to a stripping column 24. The acid contaminants, e.g. H2S, HCN, CO2, and phenol, in the ammonia-water vapour emerging from the stripper 24 may be removed by washing the vapour with an aqueous solution of a strong alkali, e.g. sodium, calcium, or magnesium hydroxide, also oils such as benzene, naphthalene, and pyridine may be removed by decanting. The ammonia and phosphoric acid solution may be represented by the formula (NH4)nH3-nPO4; thus the solution jus prior to stripping contains 40% salts of average composition (NH4)1.9H1.1PO4. The absorber may be a two- or three-stage spray tower and the stripping column may be a bubble-tray tower containing ten or more trays.