Improvements in or relating to the synthesis of urea

摘要

Urea is prepared by the carbon dioxideammonia synthesis in an apparatus at least one part of which, which is subjected to attack by the hot reaction components or products under pressure, is constructed of or protected by a layer of a copper alloy containing from 3 to 11 per cent of aluminium, with or without one or more further elements the total quantity of which does not exceed 5 per cent. The specified further elements are silicon, nickel, vanadium, chromium, lead, titanium, iron and manganese. The preferred alloys contain little or no iron; when iron and manganese are present, the quantity of iron present should preferably not exceed that of the manganese. The parts of the apparatus which may be constructed or protected by the alloys include the autoclave and valves or pipes through which the reactants or product pass under pressure at temperatures exceeding 130 DEG C. Numerous specific alloys are described (see Group II).ALSO:At least part of the apparatus used in the synthesis of urea from carbon dioxide and ammonia which is subject to attack by the hot reaction components or products under pressure is constructed of or protected by a layer of an aluminium bronze consisting of a copper alloy containing from 3 to 11 per cent of aluminium, with or without one or more further elements the total quantity of which does not exceed 5 per cent. The specified further elements are silicon, nickel, vanadium, chromium, lead, titanium, iron and manganese. Preferably the alloys should contain little or no iron. The parts of the apparatus which may be constructed of or protected by the alloys include the autoclave and pipes and valves through which the reactarts or products pass under pressure at above 130 DEG C. Numerous specific alloys are mentioned (see Group II).ALSO:Aluminium bronzes consist of a copper alloy containing 3-11 per cent of aluminium with or without other elements, e.g. iron, manganese, nickel, chromium, vanadium, lead, titanium and silicon, the total quantity of which does not exceed 5 per cent. The alloys, which are utilizable in the manufacture of urea-synthesis apparatus (see Group IV(b), are preferably poor in iron content and when both iron and manganese are present, the quantity of iron should preferably not exceed that of the manganese. Preferred alloys are those containing 8-10 per cent Al, up to 1 per cent Mn, not more than 0.4 per cent Fe and less than 0.3 per cent of other elements, e.g. Cr, Va, Ti and/or Si, the balance being copper and the percentage ratio of Fe:Mn not exceeding 1:2, including those containing 9-10 per cent Al, 0.2-0.6 per cent Mn, 0.05-0.25 per cent Fe, the percentage ratio of Fe:Mn preferably being between 0.1:1 and 0.45:1, and preferably a total quantity of 0.01-0.1 of Si, Va, Cr and/or Ti. Other alloys mentioned contain 6-8 per cent Al and 1.5-3 per cent Fe or 9-10 per cent Al and 2.75-3.75 per cent Fe, in each case there being at most 0.5 per cent of other elements, the balance being copper.