Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
  • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
  • B01D53/047—Pressure swing adsorption
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
  • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
  • B01D53/047—Pressure swing adsorption
  • B01D53/0476—Vacuum pressure swing adsorption
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
  • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
  • C10L3/08—Production of synthetic natural gas
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
  • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
  • C10L3/10—Working-up natural gas or synthetic natural gas
  • C10L3/101—Removal of contaminants
  • C10L3/105—Removal of contaminants of nitrogen
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/102—Carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
  • B01D2253/1085—Zeolites characterized by a silicon-aluminium ratio
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/10—Single element gases other than halogens
  • B01D2257/102—Nitrogen
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/702—Hydrocarbons
  • B01D2257/7022—Aliphatic hydrocarbons
  • B01D2257/7025—Methane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/414—Further details for adsorption processes and devices using different types of adsorbents
  • B01D2259/4141—Further details for adsorption processes and devices using different types of adsorbents within a single bed
  • B01D2259/4145—Further details for adsorption processes and devices using different types of adsorbents within a single bed arranged in series
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/10—Recycling of a stream within the process or apparatus to reuse elsewhere therein
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/26—Composting, fermenting or anaerobic digestion fuel components or materials from which fuels are prepared
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/46—Compressors or pumps
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/48—Expanders, e.g. throttles or flash tanks
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
  • C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
  • C10L2290/542—Adsorption of impurities during preparation or upgrading of a fuel

Definitions

• the present disclosure relates to processes and systems for the purification of feed gas containing methane, for example unmarketable sub-quality reserves and renewable feed gas, e.g., landfill gas.
• the present disclosure provides efficient processes and systems for separating methane from nitrogen to yield a highly purified methane that is suitable for transport in gas pipeline.
• Methods and systems disclosed herein allow high recovery, such as up to 95% or higher recovery, of methane from feed gases.
• Systems disclosed herein typically comprise at least two nitrogen rejection units (“NRUs”), referred to herein as a first NRU and a second NRU.
• each NRU is configured for methane adsorption.
• the first NRU can adsorb methane and produce a product methane stream.
• the first NRU can also purge a nitrogen-enriched purge stream which comprises methane, e.g., methane not adsorbed in the first NRU.
• the second NRU which is also configured to adsorb methane, can receive a methane-containing, nitrogen-enriched purge stream, such as produced from the first NRU. Methane adsorbed in the second NRU is then recycled through the first NRU, where it adsorbed for release into a product methane stream.
• PSA pressure swing adsorption
• Examples of such systems include those described in Section 5, in Group A numbered embodiments 13 to 24, and in Group B numbered embodiments 58 to 84 and 98 to 127.
• Methods of enriching for methane e.g., using the systems of the disclosure, can produce product methane streams comprising high percentages, such as up to 95% or higher, of the methane in feed gases. Examples of such methods include those described in Section 5, in Group A numbered embodiments 1 to 12, and in Group B numbered embodiments 1 to 57, 85 to 97, and 128 to 140.
• the present disclosure provides a pressure swing adsorption method to produce a high purity methane product stream from a pretreated landfill feed, comprising:
• NRU nitrogen rejection unit
• the present disclosure provides a pressure swing adsorption system to produce a high purity methane product stream from a pretreated landfill feed comprising:
• a first nitrogen rejection unit that contains a methane selective material and is in fluid communication with a pretreated landfill gas feed, such that the first NRU adsorbs methane and allows nitrogen to pass through to produce a purged stream, and that the adsorbed methane is then desorbed and recovered as a product stream to be removed in a separate outlet;
• a second nitrogen rejection unit that contains a methane selective material and is in fluid communication with the first NRU to receive the first purged waste stream, such that the second NRU adsorbs methane, and allows nitrogen to pass through, to produce a second purged stream; wherein the second NRU is also in separated fluid communication with the pretreated landfill feed inlet to said first NRU, such that the adsorbed methane within the second NRU is desorbed, recovered and sent to the first NRU together with said pretreated landfill gas.
• FIG. 1 is a schematic view of an exemplary system and a method to produce a pipeline stream of methane from a landfill gas feed comprising two nitrogen rejection units.
• the present disclosure relates to processes and systems for the purification of feed gas containing methane.
• Methods and systems disclosed herein allow high recovery, such as up to 95% or higher recovery, of methane from feed gases.
• This high recovery can increase the value of otherwise unmarketable gases and/or renewable gases, such as landfill gases.
• This high recovery can also benefit the environment by capturing methane (a highly potent greenhouse gas, with an average radiative forcing over a 100-year time frame estimated to be 20-fold to 80-fold higher than CO2) for renewable energy or other purposes.
• the present disclosure relates to methods of enriching methane from a feed gas comprising nitrogen and methane, comprising adsorbing methane from a feed gas on a first adsorbent bed comprising a first adsorbent in a first NRU to produce a first nitrogen-enriched purged stream enriched in nitrogen and comprising methane; adsorbing methane from the first nitrogen-enriched purged stream on a second adsorbent bed comprising a second adsorbent in a second NRU to produce a second nitrogen- enriched purged stream; and recycling methane adsorbed in the second NRU to the first NRU.
• Methane adsorbed by the first NRU can be desorbed to yield a methane product stream, which can provide 95% or higher recovery of methane from the feed gas.
• the present disclosure relates to systems for enriching methane, comprising two NRUs.
• the systems can be pressure swing adsorption (PSA) systems comprising a first NRU that contains a first adsorbent bed comprising a first adsorbent and is in fluid communication with an inlet for a feed gas comprising nitrogen and methane, such that the first NRU adsorbs methane, allows nitrogen to pass through to produce a first nitrogen-enriched purged stream, and is configured to desorb adsorbed methane and remove desorbed methane as a product stream; and a second NRU that contains a second adsorbent bed comprising a second adsorbent and is in fluid communication with the first NRU to receive the first nitrogen-enriched purged stream, such that the second NRU adsorbs methane and allows nitrogen to pass through, to produce a second nitrogen-enriched purged stream; and the second NRU is configured to desorb adsorbed me
• PSA pressure swing adsorption
• the systems can comprise a first NRU that rejects nitrogen using adsorption, membrane separation, or cryogenic separation and is in fluid communication with an inlet for a feed gas comprising nitrogen and methane, such that the first NRU enriches nitrogen in a first rejected stream and enriches methane in a methane product stream; and a second NRU that contains an adsorbent bed comprising an adsorbent and is in fluid communication with the first NRU to receive the first rejected stream, such that the second NRU adsorbs methane and allows nitrogen to pass through, to produce a second rejected stream; wherein the second NRU is configured to desorb adsorbed methane and recycle desorbed methane as a methane-enriched stream to the first NRU.
• the present disclosure relates to a pressure swing adsorption method to produce a high purity methane product stream from a pretreated landfill feed, comprising:
• NRU nitrogen rejection unit
• the present disclosure relates to a pressure swing adsorption system to produce a high purity methane product stream from a pretreated landfill feed comprising:
• a first nitrogen rejection unit that contains a methane selective material and is in fluid communication with a pretreated landfill gas feed, such that the first NRU adsorbs methane and allows nitrogen to pass through to produce a purged stream, and that the adsorbed methane is then desorbed and recovered as a product stream to be removed in a separate outlet;
• a second nitrogen rejection unit that contains a methane selective material and is in fluid communication with the first NRU to receive the first purged waste stream, such that the second NRU adsorbs methane, and allows nitrogen and other hydrocarbons to pass through, to produce a second purged stream; wherein the second NRU is also in separated fluid communication with the pretreated landfill feed inlet to said first NRU, such that the adsorbed methane within the second NRU is desorbed, recovered and sent to the first NRU together with said pretreated landfill gas.
• Natural gas streams frequently contain components smaller than nitrogen, such as water vapor, carbon dioxide, and hydrogen sulfide.
• the gas stream to be treated in accordance with embodiments herein can have these contaminants removed prior to treatment of the feed gas stream in accordance with the process and systems of this disclosure.
• Methods and systems to pre-treat feed gas (e.g., landfill gas) to remove these contaminants are well known in the art.
• the feed gas e.g., landfill gas
• the feed gas is first treated and produced at 100 psig, to contain about 70% by volume of methane; less than 2% by volume, such as less than 1 % by volume of water vapor; less than 10% by volume, such as less than 2% by volume of carbon dioxide; and less than below 1 ,000 ppm, such as less than 10 ppm by volume of H 2 S.
• pretreatment of the feed gas can comprise compression (e.g., to 200 psig), removal of volatile organic compounds (VOCs) by adsorbent-based systems, removal of CO 2 by membrane separation, or any two or all three thereof.
• compression e.g., to 200 psig
• VOCs volatile organic compounds
• the amount of nitrogen present in the feed gas stream is not critical in carrying out embodiments herein and can be as low as 5 mol percent to as high as about 35 mol percent. Typically, the nitrogen content is in the range of 5 to 20 mol percent.
• the first NRU unit at first cycle achieves at least 85% by volume recovery of the methane from desorbing and recovering the methane within the methane selective adsorbent, and the % by volume will increase to at least a pipeline quality of 95% by volume of methane, after further enrichment of the feed gas mixed with the desorbed methane from the second NRU.
• the purged stream from the first NRU will produce a rejected nitrogen rich stream with about 15 to 50% by volume CH 4 and 20% to 50% by volume N 2 .
• the concentration of the rejected nitrogen is dependent on the amount of nitrogen in the feed gas and the recovery rate of methane in the first stage NRU.
• a co-current depressurization step is introduced into the first NRU and the second NRU units to desorb methane.
• the first nitrogen-enriched purged stream is optionally compressed and sent to the second NRU that contains a CH 4 selective adsorbent to treat the first nitrogen-enriched purged stream to adsorb the CH 4 , while letting the nitrogen pass through the adsorbent bed to be purged.
• this second NRU, or High Recovery NRU Module (“HRM”) does not aim to produce pipeline quality gas, rather it enriches methane to an increased purity at less than pipeline quality (enriched as compared to the NRU reject stream).
• the adsorbed CH 4 in the second NRU is then regenerated in a PSA cycle, wherein the CH 4 is desorbed at about 80% by volume.
• the desorbed CH 4 is optionally compressed, and recycled back to the feed for the first NRU, to achieve a product stream of CH 4 of at least 95%, such as at least 97% by volume from the first NRU.
• the N 2 in the purged feed stream from the first NRU passes through the bed of the CH 4 selective adsorbent in the second NRU and becomes a final rejected or purged nitrogen stream, containing less than 10, such as less than 5% by volume of methane.
• Separation of nitrogen from methane can be performed using one or more techniques of combinations of techniques. In some embodiments, separation of nitrogen from methane involves fractional distillation at low temperature and (usually) high pressure, i.e. cryogenics. Since nitrogen has a lower boiling point than methane and the other hydrocarbons present in natural gas, it may be removed as a gas on liquefying the remaining constituents, which are then revaporized.
• separation of nitrogen from methane can comprise one or more of selective diffusion through a series of organic membranes, formation of lithium nitride by treatment with lithium amalgam, absorption of the nitrogen in liquid ammonia or in liquid sulfur dioxide.
• separation of nitrogen from methane can be achieved using membrane separation technology.
• separation of nitrogen from methane comprises pressure swing adsorption (“PSA”) systems that use nitrogen specific adsorbents to remove nitrogen.
• PSA pressure swing adsorption
• separation of nitrogen from methane comprises selective adsorption of the methane and higher hydrocarbons on an adsorbent such as activated charcoal.
• Adsorbents such as activated charcoal that more strongly adsorb methane than nitrogen ⁇ i.e., are selective for methane over nitrogen) are sometimes termed “equilibrium absorbents.”
• the adsorbed gases are then desorbed to yield a gas reduced in of nitrogen.
• Other molecules having smaller molecular dimensions than nitrogen e.g., carbon dioxide, oxygen, water, small organic molecules and hydrocarbons other than methane, and/or carbon monoxide, will also tend to remain in the nitrogen stream and will tend not to be adsorbed with the methane and higher hydrocarbons.
• Adsorption/desorption systems require a change in conditions to desorb an adsorbed material.
• Adsorption/desorption systems include, but are not necessarily limited to, pressure swing adsorption (PSA), thermal swing adsorption, displacement purge, and non-adsorbable purge/partial pressure reduction.
• PSA pressure swing adsorption
• thermal swing adsorption thermal swing adsorption
• displacement purge displacement purge
• non-adsorbable purge/partial pressure reduction Use of equilibrium absorbents in PSA is sometimes referred to herein as “equilibrium PSA.”
• first NRUs and second NRUs such as dimensions, shape, and volume, number of adsorbent beds in each NRU, and number of adsorbent layers in each adsorbent bed, and bed and layer dimensions, shapes, and volumes can each independently be selected based on the feed gases, the desired throughputs, and other parameters.
• a nitrogen removal system 100 is operable to remove nitrogen from a methane-containing pretreated landfill feed 101 entering through a feed conduit 102.
• the feed from 102 enters a first NRU adsorption unit 104 that contains a methane selective bed (/.e., an adsorbent bed comprising an adsorbent that preferentially adsorbs methane over nitrogen, with such adsorbents described in more detail elsewhere herein).
• Methane is then desorbed, recovered, and sent out of unit 104 as a product stream 108 via a product conduit 106.
• Product stream 108 contains at least 90% by volume methane, such as over 95% by volume methane and less than 10%, such as less than 5% by volume of nitrogen and carbon dioxide.
• a nitrogen rich, low methane purged stream is produced from unit 104, and this nitrogen-enriched purged stream is optionally compressed via compressor 110 and send to a second nitrogen rejection unit 112 via conduit 114, wherein the second nitrogen rejection module 112 contains a methane selective adsorbent bed that adsorbs methane, purges a purified N 2 waste stream 116 from the second NRU 112 unit via conduit 118.
• the final purged nitrogen waste stream contains at least 75% by volume, such as at least 90% by volume of nitrogen.
• a recycled methane stream is desorbed and recovered from the adsorbent bed of the second NRU, optionally compressed in a compressor 120, and recycled to feed conduit 102 via recycled conduit 122.
• the recycled methane stream contains no more than 70% by volume of methane.
• the methane selective adsorbent bed employed in adsorption units 104 and 112 can comprise from the same or similar methane adsorbing material, such that the adsorbent beds have characteristics in which methane has an equilibrium adsorption amount greater than that of nitrogen. Thus, units 104 and 112 adsorb methane preferentially over nitrogen.
• adsorbent materials can be used: activated carbon, zeolite such as crystalline aluminosilicate zeolite (e.g., 13X) or a high aluminum X zeolite having a silicon-to- aluminum ratio of about one (/.e., 1 :1 ⁇ 25% or 1 :1 ⁇ 10%), or an amorphous adsorbent (e.g., silica gel or carbon), or the like having an average pore diameter of 4.5 - 15 A as determined by the MP method and an adsorbed quantity of methane at a temperature of 298 K of 20 Ncc/g or greater at atmospheric pressure can be used.
• Appiicable adsorbents include molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• adsorbent beds in the adsorption units 104 and 112 can comprise multiple layers, such as from two to ten layers, such as of different materials described above. In some embodiments, adsorbent beds comprise two layers. In some embodiments, adsorbent beds comprise three layers. In some embodiments, adsorbent beds comprise 4-10 layers or subranges thereof.
• the layers can be disposed in any orientation, e.g., vertically (stacked together) or horizontally.
• the layers can be disposed such that multiple layers are disposed between an inlet to the adsorption unit 104 or 112 and an outlet for a purge stream, product stream, or recycle stream. For example, if an inlet is at the bottom of a unit and an outlet is at the top of the unit, the layers can be vertically oriented.
• the layers can be discrete (/.e., one adsorbent material per layer), or can be gradients from a region of one substantially pure adsorbent material to another.
• a discrete layer may include some portion of an adsorbent material from an adjoining layer, arising from interactions between the layers during initial loading and/or during operation of the unit.
• the masses and/or volumes of each of multiple layers in adsorption units 104 and 112 can be the same or can vary.
• an adsorbent bed comprises two layers
• the mass and/or volume ratio of the layers can be in a range from 1 :9 to 9:1 .
• the mass and/or volume ratio of the two layers is 1 :1 ⁇ 20% or 1 :1 ⁇ 10%.
• the mass and/or volume ratio of the layers can be in a range from 1 :1 :18 to 1:18:1 to 18:1 :1.
• the mass and/or volume ratio of the three layers is 1 :1 :1 ⁇ 20% or 1 :1:1 ⁇ 10%.
• the layers can be arranged so that each pair of adjacent layers comprises or consists of different materials, e.g., a first material in a first layer and a second material in a second, adjacent layer.
• the third layer can comprise or consist of a third material or the first material, and the like holds for a fourth layer, fifth layer, etc., if such are included.
• the first NRU and/or the second NRU comprise(s) one, two, three or more (e.g., 4 to 10) adsorbent beds.
• the first NRU and/or the second NRU comprise(s) one adsorbent bed.
• the first NRU and/or the second NRU comprise(s) two adsorbent beds.
• the first NRU and/or the second NRU comprise(s) three adsorbent beds.
• the first NRU and/or the second NRU comprise(s) from 4 to 10 adsorbent beds.
• Multiple adsorbent beds in a single NRU can be the same or differ in number of adsorbent layers, adsorbent material(s) used, and/or other parameters. Multiple adsorbent beds within a single NRU can be used for a common subprocess, e.g., multiple adsorbent beds in the first NRU can be used for adsorbing methane, passing a nitrogen-enriched purge stream to the second NRU, and desorbing methane to a product stream. Adsorbent beds can perform different aspects of a subprocess at different times. Continuing the example, the first adsorbent bed of the first NRU can adsorb methane and pass a nitrogen-enriched purge stream, while an additional adsorbent bed of the first NRU can desorb methane to a product stream.
• adsorbents in the adsorption units 104 and 112 can be the same or can be different.
• adsorption performed in adsorption units 104 and 112 can be performed by any known adsorption process such as, for example, pressure swing adsorption (PSA), thermal swing, displacement purge, or nonadsorbable purge (/.e., partial pressure reduction).
• PSA pressure swing adsorption
• thermal swing displacement purge
• nonadsorbable purge /.e., partial pressure reduction
• embodiments herein can be advantageously performed using a pressure swing cycle. Pressure swing cycles are well known in the art.
• adsorption in units 104 and 112 can be “equilibrium” PSA that takes advantage of the higher adsorption capacity of methane over nitrogen.
• the temperature within the units can be maintained in the range of from about 40°F to about 140°F, such as 70°F to 120T.
• the adsorption pressure in the NRU can be maintained in the range of from about one psia to about 200 psia, such as from five to 80 psia.
• the adsorption pressure in NRUs, such as units 104 and 112 can be from 20 psia to 200 psia.
• Desorption can be at any pressure less than the adsorption pressure, e.g., a pressure from the pressure of the feed gas down to vacuum or near-vacuum, e.g., 1 psia.
• the first nitrogen-enriched purged stream from the first NRU (e.g., unit 104) can be produced by co-current depressurization.
• methane can be desorbed in the first NRU (e.g., unit 104) by counter-current depressurization.
• NRUs can adsorb or desorb methane or other materials independently of one another, e.g., a first NRU can adsorb methane at a time when a second NRU is desorbing methane.
• the adsorption capacities of units 104 and 112 can vary depending on the nitrogen content of the feed gas.
• the adsorption capacities can be optimized by adjusting adsorption cycle times, pressure of feed gas and/or recycled methane streams, or other parameters of the process.
• the units 104 and 112 can be skid-mounted, thus providing easy mobility to and between gas processing locations.
• FIG. 1 shows two units 104 and 112. Systems comprising a series of three or more units are contemplated, wherein all but a final unit provide a nitrogen-enriched stream to subsequent units, a final unit purges a purified N 2 waste stream, and all but a first unit recycle methane to the first unit.
• a pressure swing adsorption method to produce a high purity methane product stream from a pretreated landfill feed comprising: a) Sending a pretreated landfill feed containing at least 70% by volume of methane to a first nitrogen rejection unit (“NRU”) containing a methane selective material to adsorb methane and to produce a purged stream enriched in nitrogen; b) Desorbing said methane within said first NRU in a PSA cycle to produce a product stream of methane; c) Sending said purged stream to a second NRU containing a methane selective material to adsorb methane, and to produce a second purged stream; d) Desorbing said methane from the second NRU in a PSA cycle to be recycled back to said pretreated landfill feed for said first NRU, to enrich said product stream to contain at least 95% by volume of methane.
• NRU nitrogen rejection unit
• methane selective adsorbent of steps a) and c) is selected from the group consisting of a high aluminum X having a silicon-to- aluminum ratio of about 1, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon and a combination of two or more thereof.
• landfill feed comprises about 80% by volume of methane, less than 2% by volume of water vapor, less than 10% by volume of carbon dioxide, and less than below 1 ,000 ppm by volume of H2S.
• a pressure swing adsorption system to produce a high purity methane product stream from a pretreated landfill feed comprising: a) A first nitrogen rejection unit (“NRU”) that contains a methane selective material and is in fluid communication with a pretreated landfill gas feed, such that said first NRU adsorbs methane and allows nitrogen to pass through to produce a first purged stream, and that said adsorbed methane is then desorbed and recovered as a product stream to be removed in a separate outlet; b) A second nitrogen rejection unit that contains a methane selective material and is in fluid communication with said first NRU to receive said first purged waste stream, such that said second NRU adsorbs methane, and allows nitrogen and other hydrocarbons to pass through, to produce a second purged stream; wherein said second NRU is also in separated fluid communication with said pretreated landfill feed inlet to said first NRU, such that said adsorbed methane within said second NRU is desorbed, recovered and sent to said first NRU together with said
• methane selective adsorbent of steps a) and b) is selected from the group consisting of a high aluminum X having a silicon-to- aluminum ratio of about 1, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon and a combination of two or more thereof.
• landfill feed comprises about 80% by volume of methane, less than 2% by volume of water vapor, less than 10% by volume of carbon dioxide, and less than below 1 ,000 ppm by volume of H2S.
• landfill gas feed comprises about 80% by volume of methane, less than 2% by volume of water vapor, less than 10% by volume of carbon dioxide, and less than below 1 ,000 ppm by volume of H2S.
• a pressure swing adsorption system to produce a high purity methane product stream from a pretreated landfill feed comprising: a) A first nitrogen rejection unit (“NRU”) that rejects nitrogen using adsorption, membrane or cryogenic technology and is in fluid communication with a pretreated landfill gas feed, such that said first nitrogen rejection unit enriches nitrogen in a rejected stream and enriches methane in a methane product stream; b) A second nitrogen rejection unit that contains a methane selective material and is in fluid communication with said first NRU to receive said first waste stream, such that said second NRU adsorbs methane, and allows nitrogen and other hydrocarbons to pass through, to produce a second waste stream; wherein said second NRU is also in separated fluid communication with said pretreated landfill feed inlet to said first NRU, such that said adsorbed methane within said second NRU is desorbed
• the second set of numbered embodiments (the “Group B numbered embodiments”) is as follows:
• a method of enriching methane from a feed gas comprising nitrogen and methane comprising:
• recycling methane comprises:
• desorbing methane in the first NRU comprises counter-current depressurization.
• first adsorbent and the second adsorbent are each independently selected from a high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• pelleted activated carbon or a combination of two or more thereof.
• first adsorbent and the second adsorbent are each independently selected from molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• pelleted activated carbon or a combination of two or more thereof.
• first adsorbent bed and/or the second adsorbent bed independently comprises two or more layers each comprising or consisting of high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), or pelleted activated carbon.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• a pressure swing adsorption (PSA) system for enriching methane e.g., suitable for performing the method of any one of embodiments 1 to 57; comprising:
• a first nitrogen rejection unit (“NRU”) that contains a first adsorbent bed comprising a first adsorbent and is in fluid communication with an inlet for a feed gas comprising nitrogen and methane, such that the first NRU adsorbs methane, allows nitrogen to pass through to produce a first nitrogen-enriched purged stream, and is configured to desorb adsorbed methane and remove desorbed methane as a product stream; and
• NRU first nitrogen rejection unit
• a second NRU that contains a second adsorbent bed comprising a second adsorbent and is in fluid communication with the first NRU to receive the first nitrogen-enriched purged stream, such that the second NRU adsorbs methane and allows nitrogen to pass through, to produce a second nitrogen-enriched purged stream; and the second NRU is configured to desorb adsorbed methane and recycle desorbed methane as a methane-enriched stream to the first NRU.
• first adsorbent and the second adsorbent each independently selected from high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• pelleted activated carbon or a combination of two or more thereof.
• first adsorbent and the second adsorbent are each independently selected from molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• pelleted activated carbon or a combination of two or more thereof.
• first adsorbent bed and/or the second adsorbent bed independently comprises from 4-10 layers of materials or subranges thereof.
• first adsorbent bed and/or the second adsorbent bed independently comprises two or more layers each comprising or consisting of high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), or pelleted activated carbon.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• a method for enriching methane comprising using the system of any one of embodiments 58 to 84 to enrich methane in a feed gas comprising nitrogen and methane.
• a system for enriching methane e.g., suitable for performing the method of any one of embodiments 1 to 57, comprising:
• NRU first nitrogen rejection unit
• a second NRU that contains an adsorbent bed comprising an adsorbent and is in fluid communication with the first NRU to receive the first rejected stream, such that the second NRU adsorbs methane and allows nitrogen to pass through, to produce a second rejected stream; wherein the second NRU is configured to desorb adsorbed methane and recycle desorbed methane as a methane-enriched stream to the first NRU.
• each adsorbent is selective for methane over nitrogen.
• each adsorbent is independently selected from high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• pelleted activated carbon or a combination of two or more thereof.
• each adsorbent is independently selected from molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), pelleted activated carbon, or a combination of two or more thereof.
• each adsorbent individually comprises or consists of molecular sieved activated carbon (“MSC”).
• each adsorbent individually comprises or consists of crushed activated carbon (“AC-1”).
• each adsorbent individually comprises or consists of granular activated carbon (“AC-2”).
• each adsorbent individually comprises or consists of pelleted activated carbon.
• each adsorbent bed independently comprises more than one layer of materials.
• each adsorbent bed independently comprises two layers of materials.
• each adsorbent bed independently comprises three layers of materials.
• each adsorbent bed independently comprises from 4-10 layers of materials or subranges thereof.
• each adsorbent bed independently comprises two or more layers each comprising or consisting of high aluminum X zeolite, zeolite 13X, carbon or silica gel, molecular sieved activated carbon (“MSC”), crushed activated carbon (“AC-1”), granular activated carbon (“AC-2”), or pelleted activated carbon.
• MSC molecular sieved activated carbon
• AC-1 crushed activated carbon
• AC-2 granular activated carbon
• a method for enriching methane comprising using the system of any one of embodiments 98 to 127 to enrich methane in a feed gas comprising nitrogen and methane.
• Table 1 compares the Material Balances of a process using a system comprising only one NRU to the Material Balances of a process using a system comprising two NRUs, with the second NRU being a High Recovery Module (HRM), such as the system set forth in FIG. 1.
• HRM High Recovery Module
• the CH4 recovery rate of the first NRU is the CH4 product flow divided by the feed CH4 flow or 707.8 SCFM divided by 786.4 SCFM or 90%.
• the added CH4 recovery by the use of the High Recovery Module is thus 761 SCFM divided by 786.4 SCFM or 96.8% CH4 recovery.

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• 2023
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