Oil shale retorting at superatmospheric pressures - with hydrostatic sealing at both ends of the retort

摘要

The process is an improvement of the known (e.g. from US 3361644) solids-upflow, gas-downflow retorting technique in which the crushed shale is fed upwards through a vertical retort by a reciprocating feed piston, the bed continuously exchanging heat with a downflowing, high specific heat hydrocarbon recycle gas, The improvement comprises carrying out the process at superatmospheric pressures (pr f. 5-50 psig), the pressure being maintained by a hydrostatic sealing arrangement through which solids are fed into and removed from the retort. Specifically, an elongated, upwardly extending feed conduit is provided which communicates at its lower end with the cylinder in which the feed pump reciprocates, and with the liquid reservoir of oil which accumulates at the bottom of the retort. Pref. a low-pour-point, relatively light fraction of the shale oil product is continuously recycled to the feed conduit to maintain an inventory of oil in it, filling the conduit to the level established by the retort pressure and excluding high-pour-point oil from the shale feed conduit. Operating the process under pressure drastically reduces the volume of recycle gas required, providing savings in recycle gas compressor facilities and improving heat exchange efficiencies.