484 results about "Adsorption desorption" patented technology

An autonomous water source (AWS) for extracting water from ambient air and delivering it to a plant to support growth. The system is based on an adsorption-desorption-condensation (ADC) cycle using a sorption material to extract moisture from ambient air and condensing the water vapor driven off from the sorption material by subsequent heating and followed by condensation. Liquid condensate produced in this process on the condenser is collected and delivered by gravity to a plant to reduce thermal stress and to support growth. The invention provides a sustainable source of irrigation water for agriculture and forestry, including areas where no water resources exist or are not economically viable. It can be tailored in size, and therefore, output capacity, reflecting the desired water requirements of a particular application, and can be used to replace most agricultural situations now reliant on surface water drip feed systems. The device is simple, rugged, invulnerable to rain, snow, and freezing conditions, and can be designed to last for many years without service as there are few moving parts and power required for operation is provided by sunlight.

The invention discloses an adsorption-desorption-seepage experiment system for loaded coal containing gas under the condition of varying temperatures. The experiment system comprises a tank body used for holding constant-temperature water bath. A triaxial pressure chamber is arranged in the tank body; a coal chamber is arranged in the triaxial pressure chamber; a coal sample is installed in the coal chamber; a foil gauge is adhered onto the coal sample and is connected with a dynamic strain meter; one end of the coal chamber is provided with an opening, and a pressure head is mounted in the opening and connected with a pressure unit; the coal chamber is communicated with a vacuum pipeline and a high pressure gas-transmission pipeline; and a confining pressure pipeline used for conveying hydraulic oil is communicated with a cavity between the coal chamber and the triaxial pressure chamber. The adsorption-desorption-seepage experiment system for loaded coal containing gas under the condition of varying temperatures in the invention has the advantages of a simple structure, convenient operation, reasonable design, high experiment precision and a low price.

The invention discloses a water-gas two-phase adsorption-desorption-seepage experimental system and method for loaded coal containing methane. The water-gas two-phase adsorption-desorption-seepage experimental system for loaded coal containing methane comprises a pressure loading part, wherein the pressure loading part comprises a tank body for containing a constant-temperature water bath, a reference pot and a coal sample holder are arranged in the tank body, the gas inlet of the reference pot is connected with a high-pressure methane delivery pipeline, the gas outlet of the reference pot is connected with the gas inlet of the coal sample holder through a connecting pipeline, and the gas outlet of the coal sample holder is connected with a water-gas separation device. The water-gas two-phase seepage experimental method for loaded coal containing methane is carried out on the basis of the experimental system. By changing different loading conditions, loading paths and experimental temperatures, adsorption-desorption experiments and methane seepage experiments for the loaded coal containing methane under the conditions of different solid-gas thermal coupling can be realized, and water-gas two-phase seepage experiments and methane adsorption-desorption experiments under the condition of different moisture contents also can be realized.

The invention discloses a shale gas reservoir gas diffusion coefficient experiment test method. According to a method, a one-dimensional diffusion mathematic model is built by monitoring pressure attenuation data in a shale plunger rock sample under effective stress conditions of methane gas with a certain initial pressure in a constant-temperature closed system with the micro-pore structure and the gas existence state of a shale reservoir as bases, the diffusion coefficient of the gas (methane) in shale is calculated, and the diffusion mass-transfer capacity of the gas (methane) in the shale is quantitatively assessed. In the experiment testing process, the diffusion process of gas in the shale gas reservoir can be effectively simulated, and influences of effective stress, gas adsorption / desorption and other factors on the diffusion coefficient are reflected. Besides, the method can overcome influences of gas free expansion stage data in a traditional adsorption / desorption method on the diffusion coefficient. The method can assess the diffusion mass-transfer capacity of the gas in the shale and provide experiment support for researches in the aspects of shale gas reservoir productivity models, productivity prediction and the like.

The invention discloses a loaded coal rock constant pressure gas adsorption desorption testing system and a method thereof. The system comprises a gravity constant pressure device, a vacuum pump, a high pressure gas cylinder, a constant pressure gas tank, a sample tank, a gravity constant hydraulic device and a hand pump. The method can be used for carrying out following gas adsorption and desorption tests on a coal sample under different external loading pressures and different gas pressures: 1) studying the change of absorption characteristics caused by the damage of coal rocks under different loading effects, and studying the change rules of adsorption constant, adsorption quantity and the like with the load; 2) studying the gas desorption process of coal rocks containing gas under different loading situations; 3) studying the adsorption process and adsorption constant of coal rocks containing gas with different particle sizes under constant gas pressure; 4) studying gas desorptionprocess and rules of coal rocks containing gas with different particle sizes under different atmosphere pressures; and 5) studying the creep mechanical properties of the coal rocks containing gas in gas adsorption and desorption process.

The invention relates to an air purification medium unit, an air purification device and an air purification method. The air purification medium unit comprises an upstream filtering unit, a middlestream adsorption-desorption unit, and a downstream photocatalysis unit. Meanwhile, with the air purification medium unit, the air purification device is designed and a set of the air purification method is formed. By aiming at characteristics of light catalysis and an adsorption method, the adsorption method is combined with photocatalysis, so that activated carbon and activated carbon fiber adsorption and desorption-TiO2 (titanium dioxide) photocatalysis technology becomes an air purification technology with high efficiency and long service life. On the one hand, the activated carbon or the activated carbon fiber is desorbed to be regenerated in situ, thereby reducing the original replacement cycle of a filter element; and on the other hand, the activated carbon or the active carbon fiber is desorbed to provide a high-concentration reaction environment for the photocatalysis of TiO2, so as to accelerate the reaction rate.

The invention discloses a dynamic and static combined loading rock test machine and test method used for multiphase coupling. The machine comprises a visual confining pressure loading chamber module, air pressure control modules, a dynamic loading module and constant volume modules; and the loading chamber of the visual confining pressure loading chamber module is a steel cylinder structure with a square outside and a circular inside, three surfaces of the loading chamber has windows, high borosilicate glass is embedded in every window to realize the visualization of the test process, an opening in one surface of the loading chamber is provided with a rear door which is convenient to replace and take a test piece, and various monitoring devices are arranged in the loading chamber and are led out through sensor lead wires of a baseboard to realize real-time monitoring of all physical-mechanical parameters of the test piece in the test process. The machine has the advantages of small size, simple structure, convenience in dismounting, and realization of accurate, quantitative and visual monitoring of the adsorption-desorption characteristic of a coal rock standard test piece in different load forms and coupling form and the permeability and the damage dilatancy process of gas-containing coal body in different loading stages.

The invention relates to a supercritical-state gas adsorption desorption apparatus and an application method thereof. The apparatus is capable of simulating gas isothermal pressurization absorption, isothermal pressure-reduction desorption and isotope fractionation experiments under stratum conditions. The apparatus comprises a gas feed system, a pressurization system, a vacuumization system, a gas adsorption desorption system, a gas acquisition and analysis system, and a data acquisition and processing system. The apparatus is capable of realizing isothermal pressurization absorption and isothermal pressure-reduction desorption experiments, the sampling point quantity is more and is controllable according to experiment requirements, the adsorption and desorption trends are relatively well reflected, also the temperature in the experiment process is controllable, the oil bath temperature is set according to experiment requirement, relatively similar effect compared with actual stratum conditions is realized, shale gas exploitation is simulated through an isothermal pressure-reduction process, so that the stratum-condition maximum gas desorption amount is calculated. Operation in the experiment process is simple and safe, and error caused by human factors is reduced by acquiring data through the data acquisition and processing system. The apparatus is widely applicable to gas adsorption and desorption experiment processes.

The invention provides a measuring method for an isothermal adsorption / desorption curve of coaly shale. The measuring method mainly comprises the following steps of: placing a coaly shale specimen into a true triaxial core clamping system; setting an initial measuring state of the specimen according to the actual stratigraphic condition; carrying out an adsorption / desorption experiment on the specimen after the volume of a free pore is calibrated; respectively measuring and recording a cumulative flow value of gas at an inlet end or outlet end and a balanced system pressure value according to a high-precise gas mass flow meter at the inlet end or outlet end and a system pressure sensor; calculating to obtain the volume of the absorbed gas; and then, drawing the isothermal adsorption / desorption curve of the coaly shale specimen. By using the measuring method, influences of a strain field, a temperature field and the like to the adsorption / desorption of gas on the surface of the coaly shale can be truly reflected, experiments carried out under the influence of single factor and experiments carried out under the coupled action of multiple factors can be achieved, and the measured adsorption / desorption curve can be used for truly representing the adsorption / desorption characteristic for gas in an actual coaly shale reservoir.

A channelized sorbent material comprises porous sorbent particles characterized by an average pore diameter. Each sorbent particle has at least one interior channel of an average transverse dimension (i.e. transverse diameter) that is at least ten times larger than the average pore diameter of the porous sorbent particle. The interior channel may constitute a single cylindrical through-bore in the sorbent particle, or alternatively, an array of intersecting or non-intersecting channels. The porous sorbent particles preferably comprise bead activated carbon particles. Such channelized sorbent material is particular useful as sorbent media in an adsorption-desorption apparatus for storage and dispensing of a sorbable fluid.

The invention provides a novel adsorption and desorption experiment device and a novel adsorption and desorption experiment method. The device mainly consists of a reference cylinder, a sample cylinder, a confining pressure pump, a booster pump, an air compressor, an intermediate container, a constant temperature system, a pressure sensor and a computer, wherein the sample cylinder mainly consists of a sample chamber, a confining pressure chamber, a left adjustable plug, a right adjustable plug, a barrel, a sealing ring, a screen mesh and a leather sheath; the confining pressure chamber is defined by the barrel and the leather sheath; the sample chamber is defined by the leather sheath and the adjustable plugs; the sample chamber is connected with the reference cylinder; the reference cylinder, the sample cylinder and the pressure sensor are arranged in the constant temperature system; the confining pressure chamber is connected with the confining pressure pump, and the confining pressure pump is used for increasing the confining pressure of the confining pressure chamber, so that the real stratum conditions can be simulated; the sample cylinder is provided with the two adjustable plugs, one adjustable plug is provided with the screen mesh on the top, and the other adjustable plug is not provided with the screen mesh, so that two rock samples including standard rock samples (having length of 5cm and diameter of 2.5cm) or rock sample powder (with 60-80 meshes) can be arranged in the sample cylinder. The device and the method have the advantages that the principle is reliable, and the device is simple in structure and simple and safe to operate; the real stratum environment can be simulated, and temperature and pressure conditions of different reservoir stratums as well as the methane adsorption and desorption law of the rock samples can be determined, so that reasonable experimental data can be provided for shale gas occurrence form research and reserve calculation.

The invention relates to a gas adsorption and desorption test apparatus, which comprises an inflation system, a degassing system, a gas adsorption and desorption system and a temperature control system. The gas adsorption and desorption test apparatus with a simple structure is used for determining the adsorption constant and the ultimate gas desorption quantity of coal, can determine the parameters such as the quantity of lost gas, the drilling cuttings desorption index, the diffusion coefficient and the like under the conditions of different temperature, different pressure, different degree of metamorphism and different particle sizes, and is suitable for a test of particles of coal gas adsorption and desorption laws. The gas adsorption and desorption test apparatus can simulate the underground reservoir environment, can simultaneously conduct gas adsorption and desorption tests of four groups of different particle sizes of cuttings coal samples at different temperatures, can conduct isothermal adsorption tests and gas diffusion tests, and can directly determine the gas adsorption loss amount and the ultimate gas desorption quantity. The gas adsorption and desorption test apparatus can simultaneously conduct multiple groups of gas adsorption and diffusion tests and effectively increase the test efficiency, and the determining precision is high.

The invention relates to regenerative, solid sorbents for adsorbing carbon dioxide from a gas mixture, including air, with the sorbent including a modified polyamine and a solid support. The modified polyamine is the reaction product of an amine and an epoxide. The sorbent provides structural integrity, as well as high selectivity and increased capacity for efficiently capturing carbon dioxide from gas mixtures, including the air. The sorbent is regenerative, and can be used through multiple cycles of adsorption-desorption.

An apparatus and process for thermally-linked adsorption-desorption. The process involves (a) at least one pair of adjacent sorbent beds, referenced herein as first and second sorbent beds, each pair of adjacent beds being thermally-linked one to the other through a thermally conductive wall; wherein each sorbent bed comprises a heat conductive foam, such as a reticulated metallic foam or sponge, having a sorbent coated thereon; then (b) alternating a flowstream between the beds such that at least one bed operates in adsorption cycle to remove target compound(s) from the flowstream with generation of heat of adsorption, which is conductively transferred away from the first bed towards the second bed, while operating the second bed in desorption cycle to remove the adsorbed target compound(s).

The invention discloses a method for calculating a non-steady state yield of a volume fractured horizontal well of a shale gas reservoir. The method comprises the following steps of dividing the reservoir into a volume fractured region and a non-transformed matrix region, and collecting basic parameters of the volume fractured region, the non-transformed matrix region and the horizontal well, wherein the volume fractured region is Darcy flow, and the non-transformed matrix region is Knudson flow; according to a mass conservation law, establishing a steady-state yield formula of the volume fractured horizontal well of the shale gas reservoir; based on a pressure propagation formula, the steady-state yield formula and a matter balance equation, calculating the non-steady state yield of the volume fractured horizontal well of the shale gas reservoir by applying a continuous quasi-steady method; and repeating the previous step, and performing calculation to obtain the non-steady state yield of the volume fractured horizontal well of the shale gas reservoir. The method fully considers a process that a pressure is propagated to a boundary gradually in a production process of the volume fractured horizontal well of the shale gas reservoir, different seepage laws of shale gas in a volume transformation region and the non-transformed matrix region, and adsorption and desorption effects of the shale gas, so that actual conditions are better met.

A channelized sorbent material comprises porous sorbent particles characterized by an average pore diameter. Each sorbent particle has at least one interior channel of an average transverse dimension (i.e. transverse diameter) that is at least ten times larger than the average pore diameter of the porous sorbent particle. The interior channel may constitute a single cylindrical through-bore in the sorbent particle, or alternatively, an array of intersecting or non-intersecting channels. The porous sorbent particles preferably comprise bead activated carbon particles. Such channelized sorbent material is particular useful as sorbent media in an adsorption-desorption apparatus for storage and dispensing of a sorbable fluid.

An autonomous water source (AWS) for extracting water from ambient air and delivering it to a plant to support growth. The system is based on an adsorption-desorption-condensation (ADC) cycle using a sorption material to extract moisture from ambient air and condensing the water vapor driven off from the sorption material by subsequent heating and followed by condensation. Liquid condensate produced in this process on the condenser is collected and delivered by gravity to a plant to reduce thermal stress and to support growth. The invention provides a sustainable source of irrigation water for agriculture and forestry, including areas where no water resources exist or are not economically viable. It can be tailored in size, and therefore, output capacity, reflecting the desired water requirements of a particular application, and can be used to replace most agricultural situations now reliant on surface water drip feed systems. The device is simple, rugged, invulnerable to rain, snow, and freezing conditions, and can be designed to last for many years without service as there are few moving parts and power required for operation is provided by sunlight.

A process is disclosed for preparing biomass particles for thermolytic or enzymatic conversion whereby the biomass particles baying a moisture content of at least 20% are subjected to flash heating. The flash heating may be preceded by one or more adsorption / desorption cycles with water or steam. A swelling aid may be added during the adsorption part of an adsorption / desorption cycle.

An autonomous water source for extracting water from ambient air and delivering it to a plant to support growth. The system is based on an adsorption-desorption-condensation cycle using a sorption material to extract moisture from ambient air and condensing the water vapor driven off from the sorption material by subsequent heating and followed by condensation. Liquid condensate produced in this process on the condenser is collected and delivered by gravity to a plant to reduce thermal stress and to support growth. The invention provides a sustainable source of irrigation water for agriculture and forestry, including areas where no water resources exist or are not economically viable. It can be tailored in size, and therefore, output capacity, reflecting the desired water requirements of a particular application, and can be used to replace most agricultural situations now reliant on surface water drip feed systems. The device is simple, rugged, invulnerable to rain, snow, and freezing conditions, and can be designed to last for many years without service as there are few moving parts and power required for operation is provided by sunlight.

The invention relates to a preparation method of (Lactobacillus planetarium subsp.plantarum)Zhang-LL and its listeria monocytogene-resistant bacteriocin. The preparation method is suitable for preservation and fresh-keeping of meat and meat products, milk and milk products, fruits and vegetable, and instant foods. The (Lactobacillus planetarium subsp.plantarum)Zhang-LL (CGMCC No.6936) is selected from bacon on the Fujian farmer's market. A bacteriocin production broth is obtained by fermentation of a Zhang-LL strain, and the Zhang-LL strain bacteriocin is extracted and purified by a pH-dependent adsorption-desorption method, a cation exchange chromatography and a reversed phase high-performance liquid chromatography so that titer is improved by 32 times and purity is improved by 36.65 times. The bacteriocin can inhibit a plurality of food-borne pathogenic bacteria such as listeria monocytogenes, has high bacteriostatic activity, good heat, acid and base stability, can be degraded by human protease and is a natural and safe biological preservative. The preparation method has the advantages of simple processes, stability, high efficiency, source convenience, low cost and industrial production feasibility.

Provided are a servo measuring testing system and method for coal sample gas adsorption and desorption. The system comprises a gas supply device, a vacuumizing device, a gas adsorption device, a gas desorption measurement device and an electric control device; the gas supply device comprises a high-pressure gas tank and a gasing tank; the vacuumizing device comprises a vacuum pump and a vacuum meter; the gas adsorption device comprises a coal sample tank, and the gas desorption measurement device comprises a water storage container, a water collection container, an electronic balance, a servo motor, a fixed support and a water guide pipe. According to the servo measuring testing system and method for coal sample gas adsorption and desorption, volume measurement of desorbed gas is converted into volume measurement of liquid water, test operation is easy and convenient, test data is accurate, and real-time precise automatic collection and real-time display of the test data are achieved; in addition, it is guaranteed that the gas desorbed from a coal sample is under the condition of one atmospheric pressure, and a more reliable data basis is provided for researching the coal-mass gas adsorption and desorption rule.

An energy storage device comprising a negative electrode plate having a negative electrode active material layer of a carbonaceous composite material formed on a negative electrode collector, a positive electrode plate having a positive electrode active material layer capable of inserting and releasing lithium ions and a non-faradic reaction layer capable of accumulating and releasing electric charges upon physical adsorption-desorption of ions on the surface layer of the positive electrode active material layer and an insulator layer for electrically insulating the positive electrode plate from the negative electrode plate, the insulator layer being capable of permeating only mobile ions. The carbonaceous composite material comprises particles of graphite and / or amorphous carbon and activated charcoal, and the particles of the graphite and / or amorphous carbon and particles of the activated charcoal are united.

A process for extracting arasaponin from notoginseng features that the strong-polarity macroreticular adsorption resin and the "adsorption-desorption" technology are used.

This disclosure involves an adsorption-desorption material, e.g., crosslinked polyvinyl-amine material having an Mw from about 500 to about 1×106, total pore volume from about 0.2 cc / g to about 2.0 cc / g, and a CO2 adsorption capacity of at least about 0.2 millimoles per gram of crosslinked material, and / or linear polyvinyl-amine material having an Mw from about 160 to about 1×106, total pore volume from about 0.2 cc / g to about 2.0 cc / g, and a CO2 adsorption capacity of at least about 0.2 millimoles per gram of linear material. This disclosure also involves processes for preparing the crosslinked polyvinyl-amine materials and linear polyvinyl-amine materials, as well as selective removal of CO2 and / or other acid gases from a gaseous stream using the polyvinyl-amine materials.

The present invention relates to an adsorbent obtained by using porous hybrid inorganic-organic materials that have high surface area, and have pore with the size of molecules or nanometers. More specifically, the present invention relates to a water adsorbent showing facile adsorption-desorption even below 100° C., having high adsorption capacity, and having high desorption capacity when it is heated up to the temperature below 100° C. The adsorbent of the present invention can be applied to a humidifier, dehumidifier, cooler and heater. The present invention also relates to a technology to control humidity using the adsorbent.

The invention discloses a true-triaxial coal and gas adsorption-desorption and outburst test device system. The true-triaxial coal and gas adsorption desorption and outburst test device system comprises a cylindrical coal sample chamber structure which is formed by sequentially connecting a plurality of cylindrical units, wherein a plurality of pressure and temperature sensors are uniformly arranged on the outer circumference of each cylindrical unit, four loading devices are symmetrically arranged on the outer circumference of each cylindrical unit, the loading devices stretch into an inner cavity of each cylindrical unit along the radial direction of the cylindrical unit to be connected with loading plates, and lateral stress is applied to briquette coal in the inner cavity of each cylindrical unit by the loading plate; two ends of the cylindrical coal sample structure are respectively provided with a counterforce cover, a surface-type inflating loading disc with the inner side surface being communicated with the inner cavity of the cylindrical coal sample chamber structure is arranged in the counterforce cover on one end and is used for applying the axial pressure, a coal and gas outburst opening is formed in the other end, and an instantaneous release mechanism is arranged in the coal and gas outburst opening. The invention also discloses a test method utilizing the device. By adopting the test device and the test method, the adsorption-desorption characteristics of briquette coal to the gas and the gas outburst mechanism under the condition of different ground stress and different gas pressure can be researched.

This invention relates to a method for preparing straw cellulose by adsorption-enzymolysis with cellulose. The method comprises: (1) steam-exploding straw, drying, mixing with cellulose solution, performing adsorption-desorption at -4-0 deg.C, and performing solid-liquid separation to obtain supernatant and cellulose-adsorbed steam-exploded straw; (2) performing enzymolysis on the straw at 40-50 deg.C for 48-72 h; (3) repeating adsorption-desorption and enzymolysis for 1-4 times. The cellulase consumption is 6 IU / g substrate, and the productivity of reducing sugar is 17.70-27.07 mg / IU cellulase. The method also has such advantages as short enzymolysis time, low energy consumption and recoverable cellulose.

The invention relates to a combined technique of separating and recycling VOCS (volatile organic compounds) from industrial waste gas by adsorption-desorption-rectification-pervaporation, which comprises the following steps: drying, cooling and filtering the industrial waste gas containing the VOCS, then conveying into a plurality of adsorption-desorption groups to carry out adsorption-desorption operation, uniformly spraying through upper parts of adsorption-desorption devices by saturated vapor with the pressure at 0.15-0.5MPa, heating GAC (granular active carbon) or ACF (active carbon fiber) to desorb the adsorbed VOCS; after finishing the desorption, entering the next adsorption, using the VOCS-containing saturated vapor desorbed by the vapor in a pervaporation membrane for separation and heat supply. The combined technique provided by the invention forms an impact and enclosed circulation to sufficiently recycle the VOCS from the waste gas. The VOCS-containing saturated vapor desorbed by the saturated vapor contains large amount of latent heat and sensible heat, and the sensible heat of residual liquid on the bottom of a rectification tower is utilized sufficiently.

The invention discloses an assembly line system in which the service life of lithium ion sieve adsorbents is prolonged and an operating method. The system is an adsorption-desorption assembly line composed of a plurality of adsorption towers connected in series and communicated end to end. Each adsorption tower comprises the lithium ion sieve adsorbents with which the adsorption tower is filled, a pump arranged at an inlet of the adsorption tower, a first valve for controlling the inlet of the adsorption tower and a second valve for controlling an outlet of the adsorption tower. According to the assembly line system, the working state of the lithium ion sieve adsorbents is switched in time in an assembly line rotating mode according to the adsorption saturation degree of the lithium ion sieve adsorbents, the service life of the adsorbents can be prolonged on the premise that the microstructures of the adsorbents are not improved, the adsorption and transferring quantity of lithium elements in the whole life cycle is increased, production cost is reduced, and the efficiency-cost ratio is increased. By means of the assembly line system and the operating method, the lithium ion sieve adsorbents and the adsorption-desorption technology thereof can be easily applied to the occasions in which the concentration of the lithium elements is low, and the resource use rate in the lithium mineral resource exploiting process and the waste lithium battery recycling process is increased.

The invention relates to an experimental method applicable to a test of the adsorption-desorption deformation of a coal body under high temperature and high pressure. The experimental method is carried out by using a test system applicable to the adsorption-desorption deformation of a coal body under high temperature and high pressure, and the test system applicable to the adsorption-desorption deformation of a coal body under high temperature and high pressure comprises a vacuumizing system, a gas injection system, an adsorption-desorption deformation test system, and a gas metering system; the vacuumizing system comprises a vacuum pump and a vacuum container, the air inlet of the vacuum pump is connected to the air outlet of the vacuum container through a first air pipe, a first stop valve is arranged on the first air pipe, and the air inlet of the vacuum container is connected to a second air pipe. To sum up, the experimental method has the advantages of convenience in operation, low workload, quick and accurate measurement and high experimental performance, and provides experiment and theoretical research for adsorption-desorption volumetric deformation in the process of coal bed methane extraction.