Efficient utilization of hydrogen in a hydrocracking system is obtained by recovering in a first gas-liquid separation zone hydrogen by gas-liquid separation of hydrocrackate at a pressure of at least about 75 percent of the pressure in the hydrocracking zone, and recovering in a second gas-liquid separation zone hydrogen from the separated liquid phase from the first gas-liquid separation zone, said second gas-liquid separation zone being at a pressure less than 75 percent of the pressure in the first gas-liquid separation zone and at conditions sufficient to provide a separated vapor phase containing at least about 50 volume percent of hydrogen and having a hydrogen partial pressure of at least about 20 atmospheres. At least a portion of the separated vapor phase from the second gas-liquid separation zone is contacted with the feed side of a polymeric membrane exhibiting a high selectivity to the permeation of hydrogen as compared to the permeation of methane. The opposite side, i.e., permeate side, of the membrane is maintained at a pressure sufficiently below the pressure on the feed side of the membrane such that the ratio of the total pressure on the feed side to total pressure on the permeate side of the membrane is at least about 3:1 to permeate hydrogen to the permeate side of the membrane and provide a hydrogen permeate having a concentration of hydrogen greater than the concentration of hydrogen in the separated vapor phase contacting the membrane. At least a portion of the hydrogen permeate is recycled to the hydrocracking zone. Thus, the second gas-liquid separation zone co-acts with the polymeric membrane separation to provide a highly useable, recovered hydrogen stream in the hydrocracking system.
In the purification of gas streams by contact with a permeable membrane selective for the separation of desired components from impurities, harmful gas stream components are removed by means of a pressure swing adsorption system prior to passage of said gas streams to the permeable membrane. Where the harmful components nevertheless comprise valuable components of said gas streams, the purified portion of said gas stream, either the permeate or the non-permeate from said membrane, is used to supply purge gas to the pressure swing adsorption system for desorption and recovery of said harmful components together with said desired components purified upon contact with said membrane. Where said harmful components are not valuable components of said gas streams, the impurity portion of said gas stream, either permeate or non-permeate from said membrane, is used to supply purge gas to said pressure swing adsorption system for desorption and discard of said impurities and said harmful components from the gas purification operation.
An ultrathin film composed substantially of silicon-containing polyurea comprising polyaddition bonded units derived from (A) at least one polyamine selected from the group consisting of silicon-containing polyamines and hydrocarbon-type polyamines, each of said polyamines containing at least two primary or secondary amino groups in the molecule, and (B) at least one polyisocyanate compound selected from the group consisting of silicon-containing polyisocyanates and hydrocarbon-type polyisocyanates, each of said polyisocyanates having at least two isocyanate groups in the molecular chains; provided that when the polyisocyanate compound is the hydrocarbon-type polyisocyanate alone, at least one of the selected polyamines is a silicon-containing polyamine containing at least one terminal amino group in the molecule. A composite structure composed of a microporous supporting film and the ultrathin film supported thereon is useful for the production of a gaseous mixture containing a specified gas in a high concentration from a mixture of two or more gases including said specified gas, and is prepared by subjecting the polyamine and the polyisocyante compound to interfacial polyaddition reaction on a microporous supporting film to form an ultrathin film composed substantially of a silicon-containing polyurea on the microporous supporting film.
Disclosed is a method and apparatus for separating and stabilizing a hydrotreater effluent into a stabilized liquid product and a dry gas product. The hydrotreater effluent is expanded in a first expansion drum from a high pressure to an intermediate pressure, evolving both gaseous and liquid phase components. The gaseous phase components are withdrawn as the gas product and the liquid phase components are further processed. The liquid phase components are further expanded in a second expansion drum, evolving further gas products which are compressed, cooled and returned to the first expansion drum. The second expansion drum liquid phase can comprise the liquid product output or can be further treated by an additional expansion stage.
Membrane or pressure swing adsorption systems are used for air separation, with the crude nitrogen stream obtained thereby passing to a catalytic combustion system for reaction of residual oxygen with hydrogen to produce a high purity nitrogen product. Excess hydrogen in the nitrogen product is minimized by controlling the amount of hydrogen employed based on the instantaneous crude nitrogen flow and purity, and adjusting hydrogen ingestion in response to nitrogen product purity feedback. Plant flow rate tracking control limits maximum rates of flow change to ensure stable operation.
Process and apparatus for separation of hydrogen, methane, and higher hydrocarbons from gas feed stock. For example, such feedstock is fed to a gas-liquid separator, the resulting gas is treated in a gas-gas membrane separator, the residue is separated in a second gas-liquid separator, and the permeate is separated in a second gas-gas membrane separator; the process may be repeated until the desired effluent specificity is achieved.
