Patent GB-142874-A (GB)
Title: Improvements in the manufacture of mixtures of hydrogen and nitrogen
IPC: C01B3/16
Filed: 1917-11-28
Abstract: 142,874. Harger, J. Nov. 28, 1917. Hydrogen; nitrogen.-In making mixtures of hydrogen and nitrogen for preparing ammonia by the Haber process, a mixture of air, oxygen and steam, or of air and steam, is passed through coke in a gas producer heated to 650-850‹ C. at a rapid rate to avoid formation of much carbon monoxide. The resulting gas is treated to remove sulphur compounds, oxygen, water, &c. and to transform carbon-monoxide to carbon dioxide which is removed by treatment with ammonia. If necessary, hydrogen may be added to bring the mixture to the requisite composition. The coke is prepared by carbonizing coal which has been washed to remove iron pyrites and mixed with iron oxide and calcium carbonate or other sulphur retainer, in a preliminary producer A. Air is introduced through openings D, and the gas withdrawn at E is purified and used for heating and power purposes. The hot coke is fed into the main producer B formed of a casing of sheet iron with a lining of hollow glazed bricks or silica, in which passages are formed for pre-heating the gases. Owing to the low temperature used and the rapid current of gas, the ash does not clinker, and much of it is carried by the gas into a separate settling chamber (not shown). The hot gases are passed over limestone, magnesia or magnesium limestone in a vessel K, heated to about 700‹ C. to remove sulphur compounds, are treated to remove dust and tar, and mixed with steam and passed over suitable known catalysts such as iron oxide at about 450‹ C. to convert carbon monoxide into carbon dioxide with formation of hydrogen and to convert carbon disulphide into sulphuretted hydrogen which is removed by passage over iron oxide or by other means. The gases are mixed with air and passed over a low temperature catalyst, as described in Specification 127,609, to transform the residual carbon monoxide into carbon dioxide, and are compressed to 5-15 atmospheres to separate water which is passed through a heat exchanger and formed into steam at ordinary pressure and used in the earlier part of the process. Carbon dioxide is removed by treating the gases in towers O<1>, O<2>, with water and ammonia from the Haber plant or from another source. The ammonium bicarbonate formed is treated with sodium chloride to form sodium bicarbonate, or is passed over calcium sulphate to form ammonium sulphate. The towers may contain calcium sulphate to form ammonium sulphate directly. The gases are passed through a tower O<3> containing packing, water, and iron or copper to remove oxygen, and are compressed as R to 100-150 atmospheres. The water which separates is used to wash in tower T, the circulating gases in the Haber plants to remove the last traces of ammonia. The gases are mixed with the circulating gases, washed with water, dried by passage through strong caustic soda or potash solution, and over solid caustic potash or sodium wire. The final trace of carbon monoxide may be removed by adding oxygen and passing over a low temperature catalyst as described in Specification 127,609, the carbon dioxide formed being removed by adding the gas to the catalysed gases under pressure before removal of ammonia.