摘要:
A continuous process is described for contacting an olefins-containing feed gas stream, which has been freed of CO.sub.2 and sulfur compounds, compressed, cooled, and dried, with a solvent in an intercooled and reboiled demethanizing absorber to produce a rich solvent bottom stream containing ethylene and heavier hydrocarbons and an absorber overhead stream which is fed to a methane absorber which recovers a hydrogen product stream as overhead and produces a rich solvent stream as bottoms. When recovering up to 50% of the incoming hydrogen, this rich solvent stream from the methane absorber is fed to the demethanizing absorber, but when recovering from 20% to 100% of the incoming hydrogen, this rich solvent stream is recycled in part to the demethanizing absorber and in part is fed to a methane stripper which sends its bottoms to the methane absorber and its overhead to an auto refrigerated recovery unit which removes H.sub.2, CH.sub.4, and CO as a fuel gas product and produces an ethylene and heavier stream. The rich solvent stream from the demethanizing absorber is separated in a solvent regenerator into an overhead stream of ethylene and heavier hydrocarbons and a bottom lean solvent stream for recycle to the methane absorber and then to the demethanizing absorber. The bottom stream of the recovery unit and the overhead stream of the solvent regenerator are combined to form an ethylene and heavier product stream.
摘要:
A continuous process is described for contacting an olefins-containing feed gas stream, freed of CO.sub.2 and sulfur compounds, in a front-end heat-pumped depropanizer to remove the C.sub.4+ compounds, selectively hydrogenating the overhead stream to significantly reduce the acetylene and diolefins content, dehydrating the reactor effluent to remove traces of moisture, feeding the dehydrated stream to an intercooled and reboiled demethanizing absorber to produce a rich solvent containing ethylene and heavier hydrocarbons, feeding the absorber overhead stream to an auto refrigerated recovery unit to remove hydrogen, methane, and CO as overhead to a fuel gas system, separating the rich solvent in a solvent regenerator into an overhead stream of ethylene and heavier hydrocarbons and a bottom lean solvent stream for recycle to the demethanizing absorber, combining the overhead of the solvent regenerator with the bottoms of the demethanizer in the auto refrigerated recovery unit, and feeding the combined stream to a deethanizer which produces an overhead stream that is split into ethylene as product and ethane for recycling to the cracker.
摘要:
The Mehra process, for selectively extracting C.sub.2 + hydrocarbons from a raw natural gas stream to produce a residue gas stream meeting pipeline specifications and a natural gas liquid product, is improved by providing a process for purifying the liquid product. This improved process comprises injecting a stream of methanol into the stream of flashed gases from at least the final flashing stage. The injection preferably occurs prior to condensing the flashed gases and must occur prior to reaching the temperature of hydrate formation. The natural gas liquid product from the demethanizing (stripping) column is then allowed to separate into two phases in a surge vessel. The lower layer of methanol/water/physical solvent is removed, the methanol is recovered for recycling to the flashed gases. The upper layer is decanted as purified natural gas liquid product which meets specifications for gumming compounds if the raw natural gas stream is entirely sweet. If, however, the raw stream is sour or has even small quantities of acidic components, such as CO.sub.2, the purified natural gas liquid product is further sweetened with, for example, an aqueous amine treatment.
摘要:
An absorption process for separating a feed gas stream having components with a spectrum of volatilities including volatile (light) components, intermediate volatility components, and least volatile (heavy) components. The disclosed process includes the steps of: (1) contacting the feed gas stream with a liquid lean solvent stream in an absorber to produce a light product gas stream that is composed of predominantly light components and a rich solvent stream containing most of the intermediate and heavy components; (2) flashing the rich solvent stream at reduced pressure in a flash zone to produce an intermediate product gas stream composed predominantly of intermediate components and a lean solvent stream; (3) conveying the lean solvent stream from the flashing zone to the absorber, wherein the lean solvent is composed predominantly of heavy components taken from the feed; the process does not use an external lean solvent. The process is particularly useful for rejecting nitrogen from natural gas and for recovering hydrogen from refinery and petrochemical process off-gases.
摘要:
A continuous process is disclosed for separating components of a hydrocarbon gas stream which are selected from the group consisting of methane, ethane, higher saturated hydrocarbons, and mixtures thereof by countercurrently contacting the hydrocarbon gas stream with a physical solvent selected from the group consisting of:(1) paraffinic solvents having molecular weights ranging from 75 to 140 and UOP characterization factors ranging from 12.0 to 13.5, these factors being independent of the aromatic content of the paraffinic solvents,(2) naphthenic solvents having molecular weights ranging from 75 to 130 and UOP characterization factors ranging from 10.5 to 12.0, these factors being independent of the aromatic content of the naphthenic solvents, and(3) benzene and toluene,to produce an overhead stream which is rich in methane and a rich solvent bottoms stream and then recovering the lean physical solvent and a C.sub.2 + hydrocarbons product from the rich solvent bottoms stream and recycling the recovered solvent stream to the contacting step.
摘要:
A gas-liquid extractive stripping process is disclosed which uses at least one preferential physical solvent in at least one solvent loop, each loop passing through at least two unit operations: extractive-stripping and distillation. At least the first extractive-stripping operation may additionally comprise a rectification section on top of the extraction section. Three products are made from streams of thermally cracked gases or refinery gases: a hydrogen-rich gas stream, a methane-rich gas stream, and a C.sub.2 =+ hydrocarbons stream which is the feed stream for the conventional fractionation train of an olefins manufacturing facility. Ethylene can be economically produced from the C.sub.2 =+ hydrocarbons product stream at a recovery of at least 99.5% and a purity of at least 99.9%.
摘要:
A stream of natural gas, which is rich in C.sub.5 + hydrocarbons and may be wet or dry or sweet or sour, is extracted in two stages with a physical solvent. In the first stage, a major portion of the solvent, containing up to an equilibrium amount of C.sub.5 + hydrocarbons, removes substantially all of the water and the C.sub.2 + hydrocarbons. In the second stage, the partially stripped natural gas is countercurrently extracted with a lean-and-dry minor portion of the solvent which contains less than 1% by weight of water and less than 1% by volume of hydrocarbons. The residue natural gas, which is then sent to a pipeline, contains less than 7 pounds of water per million standard cubic feet. The rich solvent is flashed to atmospheric pressure in at least two stages, forming a methane-rich vapor portion which is suitably recycled to the first extraction, a methane-poor vapor portion, and a flashed solvent containing up to equilibrium amounts of C.sub.5 + hydrocarbons. The methane-poor vapor portion is compressed, cooled, and condensed to form a liquid stream which is selectively stripped of C.sub.1, C.sub.1 +C.sub. 2, C.sub.1 +C.sub.2 +C.sub.3 or C.sub.1 +C.sub.2 +C.sub.3 +C.sub.4 to form a liquid hydrocarbon product of selected composition based on market economics. A slipstream of the flashed solvent, containing the amount of water picked up from the natural gas stream and amounting to less than 25% by weight of the flashed solvent, is all that needs to be regenerated to form the lean-and-dry minor portion.
摘要:
A continuous process for selective countercurrent extraction of C.sub.2 + hydrocarbons from a natural gas stream with a physical solvent while at pipeline pressures to produce a residue natural gas stream meeting pipeline specifications and a liquid hydrocarbon product having a composition which can be readily adjusted to any selected degree in accordance with market conditions so that profitability of the extraction operation can be maximized at all times. The rich solvent is let down in pressure through successive flashing stages to produce a liquid product, and the stripped solvent is recirculated to the extraction step. The versatility of the process is achieved by using the following steps, in order of importance: (1) selectively varying the flow rate of the solvent with respect to the flow rate of the natural gas stream; (2) selectively varying the flashing pressure for one or more successive flashing stages; (3) recycling the flashed C.sub.1 + undesirable gases to the extraction step; and (4) rejecting selected components of the liquid product in a stripping column for the liquid hydrocarbon product by: (a) selectively varying the pressure in the column, and (b) selectively varying the temperature at the bottom of the column. The rejected components are also recycled to the extraction step and are C.sub.1, C.sub.1 +C.sub.2, C.sub.1 +C.sub.2 +C.sub.3, or C.sub.1 +C.sub.2 +C.sub.3 +C.sub.4. If water is present in significant quantities, the solvent is regenerated before recycling it to the extraction step.
摘要:
A process for rejecting reactor byproduct from the polymerization reactor in an olefins polymerization process wherein reactor waste gas stream(s) comprising unreacted monomers, reactor byproduct and light components are treated in an absorption process to additionally recover the monomers. The absorption process comprises contacting the reactor waste gas stream(s) with an absorption solvent in an absorption zone to produce a gas stream comprising the light components, and a liquid stream comprising the absorption solvent, absorbed reactor byproduct and absorbed monomers. The liquid stream is fractionated in a distillation column to produce a distillation column bottoms stream that is the absorption solvent which is conveyed to the absorption zone, and an overhead stream comprising the monomers and reactor byproduct which is further fractionated in a splitter column to reject the reactor byproduct as a bottoms stream. The recovered monomers from the splitter overhead can be conveyed to the reactor. In a preferred embodiment, the absorption solvent consists essentially of components derived from the reactor waste gas stream(s) so that no external solvent is required.
摘要:
An absorption process for separating a feed gas stream having components with a spectrum of volatilities including volatile (light) components, intermediate volatility components, and least volatile (heavy) components. The disclosed process includes the steps of: (1) contacting the feed gas stream with an internally generated liquid lean solvent stream in an absorber to produce a light product gas stream that is composed of predominantly light components and a rich solvent stream containing most of the intermediate and heavy components; (2) flashing the rich solvent stream at reduced pressure in a flash zone to produce an intermediate product gas stream composed predominantly of intermediate components and a lean solvent stream; (3) conveying the lean solvent stream from the flashing zone to the absorber, wherein the lean solvent is composed predominantly of heavy components supplied from the feed; the process does not use an external lean solvent. The process is particularly useful for rejecting nitrogen from natural gas and for recovering hydrogen from refinery and petrochemical process offgases.