Abstract: A reactor tube for thermally cracking or reforming hydrocarbons comprising a tube member made of Fe-Cr-Ni heat resisting material and a covering layer of self-fluxing alloy fusing to the inner surface of the tube member, the covering layer made of heat resisting material free from Ni or with a low Ni content. The tube member is manufactured by centrifugal casting, and the covering layer is formed by applying the self-fluxing alloy powder by scattering with or without thermit agent or spraying the alloy to the inner surface of the tube member.

Abstract: A reactor tube for thermally cracking or reforming hydrocarbons comprising an outer tube member made of Ni-containing heat resisting material and having enhanced mechanical strength with a large wall thickness, and an inner tube member of small wall thickness fitted in the outer tube member and made of heat resisting material free from Ni or with a low Ni content. The inner and outer tube members have been subjected to a diffusion treatment with a thin coating of Ni-P solid solution provided at the junction therebetween and thereby bonded together.

Abstract: A reactor tube for thermally cracking or reforming of hydrocarbons wherein a reacting layer contacting hydrocarbons is made of heat resisting steel comprising, in terms of % by weight, 0.3 to 1.5% C, up to 3% Si, 6 to 15% Mn, 20 to 30% Cr, up to 3% Nb, up to 0.15% N, the balance being substantially Fe and a covering layer which covers the said reacting layer is made of Fe-Cr-Ni heat resisting steel and is fused to the reacting layer at their boundary.

Abstract: In the process for urea synthesis, an effluent from a reactor 2 containing urea, ammonium carbamate, excess ammonia and water is introduced in a first heater 3 to separate excess ammonia and to decompose ammonium carbamate, thereby separating them from the liquid phase; then the liquid effluent from the first heater 3 is introduced in a second heater 6 to separate the remaining excess ammonia and to decompose ammonium carbamate in the presence of starting carbon dioxide used as stripping gas, thereby separating them from the liquid phase; the liquid effluent from the second heater 6 is introduced into a urea solution purification step in which pressure is lower than in the above step; and the separated gaseous effluents from the first and the second heaters are returned into the reactor.

Abstract: In a urea synthesis process, the reaction product from the reaction vessel is flowed in series through high pressure, medium pressure and low pressure decomposing and stripping devices to decompose ammonium carbamate to NH.sub.3 gas, CO.sub.2 gas and water vapor, and to remove those gases and unreacted starting materials from the aqueous urea solution. CO.sub.2 gas is used as the stripping gas in the decomposing and stripping devices.

Abstract: A process for manufacturing methanol is disclosed, wherein the pressure in the step of preparation of the synthesis gas is selected equal to the pressure in the step of preparation of methanol from the synthesis gas. The operation efficiency of the process is maintained by recycling the methanol-free recycle stream to the reaction zone for methanol synthesis notwithstanding the lower pressure in the step of methanol synthesis.

Abstract: The tail gas from the urea synthesis plant is rendered non-explosive by adding thereto a purge gas that is obtained from the ammonia synthesis plant that is usually installed closed to the urea synthesis plant and used for synthesis of ammonia used as starting material for the urea synthesis.