| 摘要 |
660,113. Gas separation. DIRECTIE VAN DE STAATSMIJNEN IN LIMBURG. Dec. 18, 1947 [Feb. 22, 1944], No. 33512/47. Class 8 (ii). In a process for the separation of a gaseous mixture e.g. coke oven gas by fractional condensation in a rectification column 10, Fig. 7 under superatmospheric pressure, say thirty atmospheres and cooling the mixtures in countercurrent heat exchange relation with the separated ethylene, methane, carbonmonoxide nitrogen and hydrogen in exchangers 2, 4, 7 whilst vaporizing by expanding at a valve 17 part of the separated methane to a pressure intermediate one and thirty atmospheres and further expanding this vaporized methane at a turbine 18 and also vaporizing the remaining methane by expanding it to one atmosphere at a valve 16, the proportion of the methane chosen for expansion at the valve 17 and the expansion pressure are such that at every point of the temperature trajectory traversed by the gaseous and liquified fractions a surplus of cold remains on that part of the trajectory of the gases below the vaporization temperature at least equal to the deficit of cold on the trajectory above this temperature, and that the minimum value of the hypothetical work necessary to transfer the cold obtained by such vaporization is at least 90 per cent of the maximum. The cold needed for the cooling of the coke oven gas mixture from-90 to -190‹C is shown by the complete line in Fig. 8, and the cold set free by returning fractions is shown by the broken line. The area bounded by the curves between any two temperatures gives the cold deficit or surplus according to the relative positions of the curves. Thus between -90 and -160‹C; i.e., during the liquifaction of the ethylene and part of the methane there is a cold deficit of 104À8-366À6, i.e., 471À4 calories per molecule of gas, which is compensated by a surplus of 474À2 calories per molecule due to vaporization of methane between 160 and 177‹C. Cold needed for condensation of gas below 177‹ is obtained from an outside source e.g., liquid nitrogen at high pressure expanded at a valve 13. The optimim pressure to which the methane is expanded at the valve 17 is seven atmospheres. U.S.A. Specification 2,122,238 is referred to. |
