GB1408560A - Process for the production of hydrogenrich gas - Google Patents

Abstract

1408560 Hydrogen rich gas SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 24 Nov 1972 [26 Nov 1971] 54987/71 Heading C5E A hydrogen-rich gas stream is produced by partial combustion of a fuel in a substantially hollow combustion chamber, whereby a crude gas predominantly containing hydrogen and carbon monoxide and also containing entrained soot and other particulate matter is obtained, the crude gas is cooled in a waste heat boiler to not below 200‹ C. and at substantially the same temperature is passed into a zone for the catalytic shift conversion of carbon monoxide and steam to carbon dioxide and hydrogen, in which zone the gases pass through one or more reactors comprising a housing having therein at least one elongated open gas channel with a gas inlet at one end and a gas outlet at the other end and having one or more walls providing thereon or therein or therebehind a cataylst freely accessible to the gas passing through the gas channel(s), and the emanating gases are purified. The soot may be kept in the gas during the conversion and the gas is purified subsequent to the conversion by the removal of water vapour, soot and sour gases, such as carbon dioxide, hydrogen sulphide and carbonyl sulphide. The conversion may be carried out in two or more reactors with intermediate cooling of the gases in between the reactors. A temperature difference between the inlet and outlet of the or each conversion reactor of less than 200‹ C. may be maintained, with an inlet temperature of the conversion zone, reactor or reactors of 210‹ to 450‹ C., and the gases leaving each reactor at below 500‹ C. The partial combustion is carried out at atmospheric or superatmospheric pressure, the conversion being carried out at substantially the same pressure. The pressure in the conversion reactors may differ from and be less than the pressure in the partial combustion chamber and/or the pressure in the waste heat boiler. Water and/or water vapour is injected into the gas prior to the conversion in the first reactor, and between the reactors when there is a number of separate reactors. Water and/or water vapour is introduced into the combustion chamber, such that the amount of water vapour in the gas that is ultimately available for the conversion is enlarged, more water and/or water vapour being introduced than required for a thermal shift conversion of the carbon monoxide at above 900‹ C. in and/or upstream of the waste heat boiler, e.g. into the downstream part of the chamber so that the crude gas enters the waste heat boiler at not less than 900‹ C. A connection or carburettor is provided between the combustion chamber and the waste heat boiler of such cross-section as to increase the residence time of the gases at high temperature whereby the yield of the thermal shift is augmented. Water and/or steam may be injected into the gas in the connection or carburettor. For each 100 Kg fuel that has been partially combusted, 60 to 140 Kg water or 100 to 200 Kg steam, or an equivalent combination of water and steam is introduced into the lower part of the combustion chamber. The soot is partially removed from the crude gas in between the waste heat boiler and the conversion zone by washing it at an elevated temperature with hot oil whereby a slurry of soot in oil is obtained, e.g. fuel oil is used and the slurry is used as at least part of the feed for the partial combustion, or by passing the gas from the waste heat boiler through one or more cyclones and the removed soot recycled for partial combustion, a small amount of liquid, e.g. fuel oil, water or the aqueous soot slurry obtained by a waterwash of the gas subsequent to the conversion, is injected in the underflow or in the conical portion near the apex of the cyclone or cyclones to take up the soot and obtain a concentrated suspension of soot in liquid. Each reactor in the conversion zone may comprise a plurality of substantially parallel open elongated gas channels, catalyst being present between each pair of two adjacent gas channels in catalyst chambers which are separated from the gas channels by gas-permeable channel walls. The reactor internals may comprise a plurality of gauze sheets which are spaced apart and supported by spacing means, alternately leaving the space between two adjacent sheets at opposite ends open to form a gas channel and secluding the space between each one of the sheets and its next adjacent sheet to form a catalyst chamber to be filled with particulate catalyst material; or a plurality of substantially parallel rows of ceramic tiles comprising the catalyst and spaced apart to form substantially open elongated gas channels therebetween, the tiles forming the catalyst-comprising channel walls; or one or more blocks or elements provided with open elongated gas channels, the blocks being made of inert base material and solid catalyst. The catalyst is sulphur-resistant and comprises one or more refractory oxides, e.g. alumina, magnesia, chrome oxide, iron oxide or a mixture thereof, as the carrier and one or more metals from Groups VI to VIII of the Periodic System, e.g. cobalt, molybdenum and/or nickel, as the active agent, which metals are either used as such or as their sulphides. The catalyst may comprise about 3À5% by wt. nickel and about 8% by wt. molybdenum based on alumina. The partial pressure of the hydrogen sulphide in the gas leaving the water heat boiler may be 0À1 to 0À7 atmospheres. The soot remaining in the gas subsequent to the conversion is removed by water wash and a dilute aqueous soot slurry is obtained which may be passed on to a pelletizer when the soot is agglomerated by means of hydrocarbons and the agglomerates are separated and taken up in a fuel oil which is recycled to the combustion zone, or the dilute slurry or part thereof may be introduced directly into the combustion zone or combined with the relatively concentrated aqueous soot slurry obtained from the cyclone(s). The gases may then be further cooled and freed from undesirable components. All or at least a major amount of water is recycled in the process. The water wash to remove soot after the conversion constitutes the first of two cooling stages, the remaining water vapour being removed from the gas as clean water in the second cooling stage.