A gas processing system for recovering methane gas from a landfill includes a high pressure main absorber plus a relatively low pressure one. The low pressure absorber receives a gas stream from an equally low pressure flash tank. This low pressure gas stream consists mostly of carbon dioxide and methane. The methane would normally be lost due to the high cost of recompressing the carbon dioxide, but by running this mixture of carbon dioxide and methane through the low pressure absorber with a slip stream of cold absorbent, a large portion of the carbon dioxide can be removed with negligible methane losses. The remaining methane can be recycled through the high pressure main absorber without having to recompress the removed portion of carbon dioxide.

A system for recovering methane from a biogas comprises a pressure swing adsorption (PSA) unit, a biogas inlet, a gas mixer and a surge tank. The PSA unit recovers methane from the biogas and directs one fraction of the recovered methane toward a product gas outlet. The PSA unit directs another fraction of the recovered methane toward a recycling line and directs remaining gases to an exhaust. The biogas inlet receives biogas from a biogas source. The gas mixer is fluidly connected to the biogas inlet, to the recycling line and to the PSA unit, forms a combination of the biogas received at the biogas inlet and of the recycled methane, and supplies the combination to the PSA unit for methane recovery. The surge tank is in one of the recycling line or in an exhaust line and reduces a pressure in the PSA unit to improve methane recovery efficiency.

Biomass (e.g., plant biomass, animal biomass, and municipal waste biomass) is processed to produce useful products, such as fuels. For example, systems are described that can use feedstock materials, such as cellulosic and/or lignocellulosic materials, to produce ethanol and/or butanol, e.g., by fermentation.

A method is described for removing carbon dioxide during Liquid Natural Gas production from natural gas at gas pressure letdown stations. The above method removes carbon dioxide from a Liquid Natural Gas production stream by using hydrocarbon fractions taken from a gas for consumption stream as a carbon dioxide stripping adsorption agent for a stripping column used to remove carbon dioxide.

The present invention concerns an improved process for a process for the treatment of biomass, comprising (a) subjecting biomass to hydrothermal treatment in a hydrothermal reactor by immersing the biomass in a treatment liquid, wherein an effluent drained from step (b) or (c) is used as treatment liquid; (b) draining the liquid from the reactor via a liquid outlet to obtain a liquor and simultaneously or subsequently introducing another washing liquid into the reactor, wherein the washing liquid is pre-heated to a temperature 30? C. below operational temperature of step (a) or higher before being introduced into the reactor, (c) draining the reactor to obtain washed hydrothermally treated biomass and an effluent, wherein at least one of step (a) and (b) is performed at a temperature in the range of 100-250? C. The invention further concerns a solid fuel and a liquor obtained by the process according to the invention, as well as a hydrothermal treatment facility to operate the process according to the invention.

A system and method for treating gas to fuel turbines by passing raw gas through an inlet pressure reducing valve to adjust the gas pressure and through a scrubber to capture liquids from the gas. Next, the gas is passed through a compressor to bring it to a pressure above that required by an inlet of a turbine and then to a post-compression aerial cooler that cools the gas to a temperature lower than a required dewpoint at fuel delivery pressure. Next, natural gas liquids are removed from the gas by passing it through a separator. A first portion of the cooled compressed gas is sent through a gas-to-gas heat exchanger, creating heated compressed gas, and a second portion of the cooled compressed gas passes through a backpressure valve. The heated compressed gas is blended with the second portion to create a fuel gas stream with a desired delivery temperature.

A compound of the general formula (I) ##STR00001##
in which R.sub.1, R.sub.2 and R.sub.3 are independently selected from C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.4 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; each R.sub.5 is independently selected from hydrogen, C.sub.1-4-alkyl and C.sub.1-4-hydroxyalkyl; m is 2, 3, 4 or 5; n is 2, 3, 4 or 5; and o is an integer from 0 to 10. A preferred compound of the formula (I) is 2-(2-tert-butylaminoethoxy)ethylamine. Absorbents comprising a compound of the formula (I) have rapid absorption of carbon dioxide from fluid streams and are also suitable for processes for the simultaneous removal of H.sub.2S and CO.sub.2, where given H.sub.2S limits have to be observed but complete removal of CO.sub.2 is not required.

The present invention discloses a process for the dissociation of natural gas hydrates comprises injecting additives or hydrate dissociation promoters into the system at the hydrate dissociation temperatures ranging from 283-293 K in conjunction with or without first depressurizing the system to pressures (50%-75%) below the hydrate equilibrium pressure and such leading to the recovery of methane or natural gases.

Biogas containing H.sub.2S and CO.sub.2 is upgraded by removing H.sub.2S using PTSA and CO.sub.2 using two stages of gas separation membranes. The first stage permeate may optionally be used a regeneration gas stream. The second stage permeate may optionally be used a cool down gas stream. The PTSA unit includes two or more adsorbent beds each selective for water, VOCs, and H.sub.2S over CO.sub.2 and for H.sub.2S over methane.

Described herein are catalysts and methods for converting waste biogas (e.g., a mixture of carbon dioxide and methane) into useful products. In some embodiments, the biogas is converted into a highly purified methane, that can be further processed to generate fuel products, including recycled natural gas (RNG) and liquid fuels. The described catalysts and methods may be advantageous over conventional methods, including by reducing catalyst costs, decreasing temperature requirements and/or providing higher purity products by reducing carbon dioxide and carbon monoxide in product streams.