A process and an apparatus are disclosed for the recovery of components from a hydrocarbon gas stream which is divided into first and second streams. The first stream is cooled, expanded to lower pressure, and supplied to a fractionation tower. The second stream is cooled and separated into vapor and liquid streams. The vapor stream is divided into two portions. A first portion is cooled, expanded to tower pressure, and supplied to the tower at an upper mid-column feed position. The second portion and the liquid stream are expanded to tower pressure and supplied to the tower. After heating, compressing, and cooling, a portion of the tower overhead vapor is cooled, expanded, and supplied to the tower at the top feed position. The quantities and temperatures of the feeds to the tower maintain the overhead temperature of the tower whereby the major portion of the desired components is recovered.

A system for liquefying a gas includes a liquefaction heat exchanger having a feed gas inlet adapted to receive a feed gas and a liquefied gas outlet through which the liquefied gas exits after the gas is liquefied in the liquefying passage of the heat exchanger by heat exchange with a primary refrigeration passage. A mixed refrigerant compressor system is configured to provide refrigerant to the primary refrigeration passage. An expander separator is in communication with the liquefied gas outlet of the liquefaction heat exchanger, and a cold gas line is in fluid communication with the expander separator. A cold recovery heat exchanger receives cold vapor from the cold gas line and liquid refrigerant from the mixed refrigerant compressor system so that the refrigerant is cooled using the cold vapor.

Various illustrative embodiments of a system and process for recovering high-quality biomethane and carbon dioxide product streams from biogas sources and utilizing or sequestering the product streams are provided. The system and process synergistically yield a biomethane product which meets gas pipeline quality specifications and a carbon dioxide product of a quality and form that allows for its transport and sequestration or utilization and reduction in greenhouse gas emissions. The system and process result in improved access to gas pipelines for products, an improvement in the carbon intensity rating of the methane fuel, and improvements in generation of credits related to reductions in emissions of greenhouse gases.

A system and method for removing nitrogen from natural gas using two fractionating columns, that may be stacked, and a plurality of separators and heat exchangers, with horsepower requirements that are 50-80% of requirements for prior art systems. The fractionating columns operate at different pressures. A feed stream is separated with a vapor portion feeding the first column to produce a first column bottoms stream that is split into multiple portions at different pressures and first column overhead stream that is split or separated into two portions at least one of which is subcooled prior to feeding the top of the second column. Optional heat exchange between first column and second column streams provides first column reflux and reboil heat for a second column ascending vapor stream. Three sales gas streams are produced, each at a different pressure.

A process for the separation of nitrogen from a feed stream containing at least methane and nitrogen, with a methane content between 4 and 12% mol. consists of at least the following steps: separation of the feed stream by means of a rubbery-type membrane to produce a permeate enriched in methane at a pressure greater than 2 bara and a non-permeate which is a nitrogen-enriched residue gas at a pressure greater than 2 bara and processing of the high-pressure residue gas in a cryogenic separation unit to produce a methane rich liquid and a nitrogen-enriched gas wherein the pressure of the membrane permeate is controlled as a function of the nitrogen concentration in the nitrogen-enriched gas.

A system and method for producing an LNG product stream to provide fuel to generators, as an alternative to diesel, to power drilling and other equipment. Using sales gas from a natural gas/NGL plant containing less than 95% methane as a feed stream, production of LNG having 95% or more methane in quantities of 100,000 GPD or more LNG product are achievable with the system and method. The system and method preferably combine use of strategic heat exchange between the feed and a nitrogen-methane flash vapor stream and other streams within the LNG processing system without requiring heat exchange with process streams in the natural gas/NGL plant and a rectifier column that uses an internal knockback condenser and does not require a reboiler to remove heavier components from the sales gas feed.

A method to recover hydrocarbonfractions from refineries gas streams involves a pre-cooled heat refinery fuel gas stream mixed with a pre-cooled and expanded supply of natural gas stream in an inline mixer to condense and recover at least C.sub.3.sup.+ fractions upstream of a fractionator. The temperature of the gas stream entering the fractionator may be monitored downstream of the in-line mixer. The pre-cooled stream of high pressure natural gas is sufficiently cooled by flowing through a gas expander that, when mixed with the pre-cooled refinery fuel gas, the resulting temperature causes condensation of heavier hydrocarbon fractions before entering the fractionator. A further cooled, pressure expanded natural gas reflux stream is temperature controlled to maintain fractionator overhead temperature. The fractionator bottoms temperature may be controlled by a circulating reboiler stream.

Described herein are methods and systems for producing liquefied natural gas (LNG) from a methane-containing synthetic gas (MCSG). An MCSG feed stream may be cooled and partially liquefied using one or more heat exchanger units. A first phase separator and a second phase separator in downstream fluid flow communication with the first phase separator may be used to separate the partially liquefied MCSG stream into a first residue gas stream and first and second feed streams, the first and second feed streams then being fed into a distillation column to produce an LNG stream and a second residue gas stream.

A system for melting contaminant-laden solids that have been separated from a hydrocarbon-containing vapor stream in a hydrocarbon distillation tower, comprising at least one plate positioned where the solids form within the hydrocarbon distillation tower, hollow tubing forming an integral part of each of the at least one plate, and a heating medium disposed to flow through the hollow tubing at a higher temperature than a temperature of the solids to at least partially melt the solids.

A process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C.sub.2 (or C.sub.3) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the tower overhead vapor is directed to an absorbing means and a heat and mass transfer means inside a processing assembly. A portion of the outlet vapor from the processing assembly is compressed to higher pressure, cooled and substantially condensed in a heat exchange means inside the processing assembly, then expanded to lower pressure and supplied to the heat and mass transfer means to provide cooling. Condensed liquid from the absorbing means is fed to the tower.