PT103615B - SEPARATION COLUMN AND ADSORPTION PROCESS WITH PRESSURE MODULATION FOR GAS PURIFICATION - Google Patents

Abstract

This invention relates to a novel type of separation column and ADSORPTION PROCESSES OF THE ADSORPTION TYPE WITH PRESSURE SWING ADSORPTION, AS WELL AS ITS USE FOR THE PURIFICATION OF GASES, SO, THE PRESENT INVENTION CONSISTS OF OBTAINING OF A SEPARATION COLUMN WITH TWO LAYERS OF ADSORVENT MATERIAL BEING CONSTITUTED BY MATERIAL WITH DIFFERENT CHARACTERISTICS WITH REGARD TO ITS FUNCTIONS. IN PARTICULAR THE FIRST LAYER MAKES A KINETIC SEPARATION, WHILE THE SECOND LAYER MAKES A SEPARATION BY BALANCE DIFFERENCE OF BACKGROUND OF THE INVENTION The process of adsorption with pressure modulation consists in performing separation cycles with the use of one or a plurality of said separation columns mentioned above, each being constituted by said one of said cyclic seals OF SEPARATION FOR FIVE STEPS. THIS PROCESS ALLOWS TO REMOVE CARBON DIOXIDE (CO 2) A METHANE (CH4) RICH CHAIN, PREFERENTIALLY FOR PRODUCING METHANE WITH HIGH FUELS WITH VARIOUS INDUSTRIAL APPLICATIONS FROM THE CHEMICAL INDUSTRY OF GASES, AS FOR THE OBTAINMENT OF FUELS, PURIFICATION OF METHANE FOR USE AS A REAGENT IN THE CHEMICAL INDUSTRY AND FOR REMOVAL OF CARBON DIOCIDE IN THE TRANSPORTATION OF NATURAL GAS IN GAS PIPES.

Description

DESCRIPTION

SEPARATION COLUMN AND PRESSURE MODULATING ADSORPTION PROCESS FOR GAS PURIFICATION

Technical field of the invention

This invention relates to a novel type of separation column and Pressure Swing Adsorption (PSA) type adsorption processes as well as their use for gas purification.

This process allows the removal of carbon dioxide (CO ₂ ) from a methane rich stream (CH ₄ ), preferably to produce fuel grade methane, its main application being the purification of biogas and landfill gas streams to produce methane grade. fuel for use in cars, preferably in public transport. Other applications of this invention are methane purification for use as a reagent in the chemical industry and for the removal of carbon dioxide in the transportation of natural gas in pipelines.

Summary of the Invention

The present invention consists in obtaining a separation column with two layers of adsorbent material, with distinct characteristics, the first layer consisting of microporous material, with pores of size between 4Â ° and 5.5Â ° and with kinetic separation functions, while whereas the second layer consisting of microporous materials, preferably based on high surface area inorganic materials, with micropores larger than 6Å, performs the separation by adsorption equilibrium difference. This layer acts as a containment barrier for C0 _2.

The pressure-modulated adsorption process consists of performing separation cycles using one or more of the above-mentioned separation columns, each of which consists of five stages of separation cycles. This process allows to remove carbon dioxide (CO2) from a methane rich stream (CH ₄ ), preferably to produce fuel grade methane with various industrial applications from the gas chemical industry, such as for obtaining fuels, methane purification for its reagent use in the chemical industry and for carbon dioxide removal in the transport of natural gas in pipelines.

Background of the Invention

There are different sources of methane use that are currently or may be used to obtain automotive fuels. Namely, this invention contemplates two methane-rich streams with high concentrations of carbon dioxide from landfill gas and biogas. This process can also be applied to streams of natural gas contaminated with large amounts of CO2.

Natural gas exists underground and is often contaminated with CO2. This gas must be purified for use as a fuel or for injection into a pipeline. The process described in this invention would be useful in small or medium flow cases since for high gas flows the amine absorption processes are more economically competitive (Appl et al., 1982).

Biogas and landfill gas are gaseous mixtures that come from anaerobic decomposition of organic matter. Typically the composition of landfill gas and biogas is 70-30% methane, 25-60% carbon dioxide, sulfuric acid and other contaminants and is further saturated with water vapor at room temperature. The composition of biogas (mainly the quantity and quality of contaminants) varies depending on the source and biogas production conditions. Due to the high degree of toxicity and flammability, and more recently the control of greenhouse gas emissions, landfill gas and biogas cannot be emitted directly into the atmosphere. The most frequent solution is gas flaring. The first use of landfill gas, as well as biogas, was the use of flare heat for local and occasional uses. This was followed by electric power generation and heat recovery (combined cycles). There are currently three different alternatives with proven economic interest: fuel production, chemical generation and the most widely used are the combined heat and power cycles. With the recent rise in fuel prices, methane production as a fuel becomes a highly cost-effective option, and moreover produces a fossil fuel-like fuel with high throughput and lower CO2 emissions. The PSA process described in this invention is applicable to flow rates in all biogas and landfill gas sources.

To produce combustible methane from biogas it is necessary to remove contaminants (mainly sulfur compounds and water), and then CO2 (Knaebel and Reinhold, 2003). The process to be studied in this paper is based on the hypothesis that all contaminants have been removed and focuses on binary CH4 / CO2 separation.

Landfill gas purification for pipeline injection is already used in the United States. Biogas purification for fuel production is already used in Sweden and France for bus and car power. Biogas fuel production can help to comply with European Commission measure 2003/30 / EG where a value of 5.75% biofuels has been set for 2010.

There are different industrial processes for removing CO2 from biogas streams. Many of the technologies applicable to this mixture have been imported from the natural gas industry and adapted to lower pressures. The most widely used technologies are CO2 absorption in water, CO2 absorption in amines, membranes and adsorption processes (Hagen et al., 2001). This invention specifically addresses a novel configuration of adsorbents within the PSA unit column (s) as well as a novel configuration of steps for selective CO2 removal.

A previous study on biogas separation using a difference separation adsorbent on adsorption kinetics (CMS 3K carbon molecular sieve) indicated that with a four-step cycle a purity greater than 98% can be obtained (Cavenati et al. 2005) with 60% methane recoveries. The four-step cycle consisted of pressurization, feed, counter-current evacuation and back-current product purge and the results obtained by simulation were confirmed with experimental data in a laboratory unit. Recent studies using a carbon molecular sieve CMS 3A) show that other research groups have obtained similar results in this separation (Bae et al., 2006). Further studies in our laboratory (results not yet published) indicated that using the same adsorbent (CMS 3K) can increase methane recovery to 80% (98% purity) by modifying the PSA cycle. A new step was included in the cycle, which was then a five-step cycle consisting of: pressurization, feed, co-current depressurization to an intermediate pressure, back-current evacuation and back-current purge.

Also found in the literature are patent documents that use adsorbents with high kinetic selectivity to remove CO2 for methane purification. Examples of these adsorbents are clinoptilolites (Seery, 1998), titanosilicates (Dolan and Mitariten, 2003) DDR-type membrane zeolites (Fujita et al., 2006) and carbon molecular sieves (Masahiro and Kazuo, 1995).

The main problem with PSA processes using kinetic adsorbents (including carbon molecular sieves) is their low productivity. In the case of CMS 3K adsorbent the productivity is around 3.5 mol CH4 / hour.kg adsorbent. The low productivity of these PSA processes is due to the low utilization of the total adsorbent capacity (usually less than 50%) and CO2 concentration profiles are widely dispersed within each column forcing to stop feeding long before adsorbent saturation. to avoid contamination of the product at concentrations higher than two or three percent depending on the desired methane specifications. Another problem with kinetic adsorbents is that in the methane purge step the adsorbed CO2 cannot be displaced, which is why this step is ineffective. Methane is not significantly adsorbed to the micropores of the kinetic adsorbents over a PSA cycle.

The first PSA units used materials that adsorbed large amounts of CO2 and little CH4 and therefore the separation was made by difference in the adsorption equilibria. Examples of such adsorbents are: activated carbon (Sircar et al., 1988; Davis, et al., 1992; Sircar, 1986), 13X zeolite (Sircar, et al., 1988), silica gel (Dolan and Mitariten, 2003) and organo-metallic compounds (Muller et al., 2005).

For comparison purposes, in our laboratory studies of this separation were performed with an adsorbent with high selectivity of CO2 adsorption equilibrium: 13X zeolite. These studies were performed using pure compound adsorption data and a proven mathematical model for the separation of these gases (Cavenati et al., 2006).

For this particular case, the total productivity of the PSA unit was around 2 mol CH4 / hour.kg adsorbent. The low productivity is caused by the low utilization of the total adsorbent capacity due to the great difficulties of CO2 desorption and the large amount of methane retained by the zeolite in the pressurization step.

There are also in the literature examples of PSA units composed of different layers of adsorbents,

particularly for the separation of different mixtures gaseous. applications PSA with columns using

Layered adsorbents were recorded for methane reformed output streams (Golden and Weist,

2004), separation of water and CO2 from a gas stream (Deng et al., 2001; Little and Spektor, 2005). In all of the references mentioned, each of the different adsorbent layers is intended to remove a specific component from a multi-component gas mixture. Another type of PSA process with different layers of different adsorbents may be the separation of water from a stream of air or natural gas or N2 / O2 (Lu, et al., 2003). In this example, layers of different adsorbents are used for the sole purpose of removing water from a gaseous stream, and this type of configuration allows for increased process productivity. In the example of water removal, the layers are distributed according to a suitable combination of adsorption properties: first a high capacity activated carbon layer at high relative humidity, then a silica gel layer to remove another large part to lower concentrations. at 1% and finally a zeolite layer to eliminate water content to a few parts per million (ppm). In this example, all adsorbents strongly adsorb water and the process is controlled by the adsorption equilibrium of this compound in the different materials.

In the above mentioned processes the layering of adsorbents was aimed at the selective removal of several components individually (one adsorbent to remove each contaminant).

Another application, having layered adsorbents for removal of a single contaminant gas, utilizes a first adsorbent with higher adsorption capacity followed by a smaller adsorbent, preferably without kinetic limitations.

The main difference of the present invention with respect to the already known and mentioned processes is the existence of two different types of adsorbents together and their innovative arrangement: a first adsorbent, with less effective adsorption capacity (either by lower capacity or by diffusional limitations). ), followed by another adsorbent, with higher effective capacity and microporous structure, allowing a fast diffusion of all components, acting as a containment barrier.

At the same time, the PSA process using this type of speaker proves to be more effective and productive.

General Description of the Invention The object of the present invention aims to improve the performance and productivity of Pressure Swing Adsorption (PSA) pressure modulation adsorption units using kinetic adsorbents. The increased productivity of these units helps reduce installation and operating costs.

This invention can be applied to binary separations where there is a single contaminant gas and a single product gas, performed by pressure modulation adsorption process. Specifically, we will discuss the application of this process to CH ₄ - C0 ₂ currents. This mixture is found in natural gas streams and biogas streams, including landfill gas. The product obtained may be used as a fuel (high purity methane), but the process may also be used in other applications. This process will be used to remove CO ₂ contents from 5% to 85% and preferably from 30% to 45%. The process operates between -10 ° C and 100 ° C, but preferably between 25 ° C and 55 ° C. The pressure-modulated adsorption process presented herein consists of one or more columns arranged for continuous or discontinuous operation. Discontinuous operations are characterized by buffer buffer tanks coupled to the PSA system.

The adsorbent materials within the columns are arranged in two layers: a first adsorbent layer with kinetic selectivity for the contaminant gas preferably where the product gas has very slow adsorption kinetics and a second layer of adsorbent material with equilibrium selectivity. where the contaminant gas is more adsorbed than the product gas. The first adsorbent layer must be the first to come into contact with the gas to be purified.

The novelty of this invention lies in the arrangement of two adsorbent layers within a single column in a single column or multiple column pressure modulation adsorption process for removal of a contaminating gas (CO ₂ ) from a product gas (CH ₄ ). The layered arrangement proposed in this invention enables the separation of CO ₂ with the efficiency of a kinetic separation but increases process productivity due to the existence of a containment layer of a larger material existing only at the end of the column. Within the field of invention, the biggest novelty is the unconventional arrangement of a smaller capacity adsorber that acts by kinetic separation followed by a larger capacity adsorber that acts by difference in adsorption equilibria.

The first layer containing the first adsorbent is intended to remove large amounts of CO ₂ from the mixture. Examples of kinetic adsorbents that can be applied to this layer are all materials having micropores of approximately 4 angstroms: carbon molecular sieves, natural zeolites and 4A zeolite, decadodecasil 3R DDR zeolites, ITQ (Institute of Chemical Technology) zeolites, clinoptilolites and titanosilicates . This qualification also includes other chemically or physically modified zeolites to adjust the micropores to a value close to 4 angstroms.

The second layer containing the second adsorbent will be used to remove smaller amounts of CO ₂ using much less adsorbent. The inclusion of this adsorbent layer acts as a CO ₂ containment barrier and constitutes the main modification to the PSA process. This allows CO _{2 to} take longer to exit and therefore the feed step can purify more mixing, increasing unit productivity.

The adsorbent to be used in the second layer should be a material that can adsorb much more CO ₂ than CH ₄ , ie materials where the separation is by differences in gas adsorption equilibria. Preferably adsorbents should be used where diffusibility of both gases is rapid. These materials are usually all high surface area inorganic materials with micropores larger than 6 angstroms. Examples of such materials are: 13X zeolite and Y zeolite, mordenites, activated carbon, aluminas, silica gel and other mesoporous silica matrix materials. Examples of use can be activated carbons and high surface area also activated carbons with surface modifications to increase the adsorption capacity of C0 _2.

Each column goes through five steps before completing a cycle. These steps are a) feeding at high pressure with the gas to be separated; b) depressurization to an intermediate pressure; c) countercurrent evacuation; d) countercurrent purge; and e) countercurrent pressurization.

1) Feeding: the gas mixture is fed by the bottom of the column being trapped C0 ₂ and methane withdrawn from the top high pressure. This step just before the C0 ₂ coming out the top of the column reach a concentration greater than specified for fuel grade methane.

2) Intermediate depressurization: Without supply, the column is depressurised to a pressure lower than that used in the supply, preferably to an intermediate pressure in a range between 20 and 600 kPa. It is intended to decrease the amount of methane retained in the gas phase and thereby increase its recovery. This methane may be recompressed or used to pressurize other column (s) or possibly in the purge step. The diffusivity of C0 ₂ adsorbed onto the adsorbent kinetic is slow and therefore only begins to desorb but not in large quantities. This step must be quickly completed.

3) Countercurrent Evacuation: The column outlet is closed and then the column is connected to a line with lower pressure. The minimum system pressure is reached at evacuation, preferably within a range of 100 to 1kPa total pressure. This pressure may be lower than atmospheric pressure if the adsorbent is regenerable only under these conditions. At this stage some methane is lost which must be burned before it is emitted into the atmosphere.

4) Countercurrent product purge: a part of the product or the outlet of the depressurization step is introduced into the column at the top and the outlet is, together with the outlet of the evacuation step, a secondary process stream that can be used to obtain power. In this step the pressure is also the minimum system pressure, preferably within a range of 200 to 1 kPa of total column pressure, and the purpose of this step is to move the existing CO ₂ at the end of the column in order to give greater use to the bed in the column. feeding step.

5) Pressurization: With part of the product and gas from the depressurization step, the column pressure is increased from minimum pressure to maximum pressure, between 1 and 200 kPa to 250 and 2000 kPa total pressure, preferably between 200 and 1500 kPa, and more preferably between 400 and 800 kPa. Once this pressure value is reached, you can start the supply step and restart a new cycle.

Brief Description of the Figures

Figure 1 shows the layered arrangement of a column of

LPSA (Layered Pressure Swing Adsorption) where:

(D represents the product - ch ₄ purified; (2) represents the layer in adsorbent in separation per differences in balances in adsorption; (3) represents the layer in adsorbent in separation per

differences in adsorption kinetics;

(4) represents the column feed: CH ₄ -C0 ₂

Detailed Description of the Invention

1. Preparation of the separation columns

In order to separate carbon dioxide from methane-rich streams first, a column with the two adsorbent layers to be used in the process is required.

The first layer should contain kinetic adsorbents that are the first to come into contact with the C0 _2. Examples of such adsorbents are clinoptilolites, decadodecasil 3R DDR zeolites, titanosilicates, carbon molecular sieves, and Li and K modified LTA zeolites.

The second layer should contain an adsorbent with a large capacity to retain C0 ₂ and it is desirable that the diffusion of both gases is fast. Examples of such adsorbents are 13X zeolite and Y zeolite, activated carbon, aluminas, silica gel and other mesoporous silica matrix materials.

The amount of material used in each layer is directly related to the desired specifications in the product. Usually the second adsorbent layer occupies between 5 and 50% of the total column volume.

2. Development of the separation process

The separation process takes place in five-step cycles each. Each of these steps involves the following steps: a) feeding at high pressure with the gas to be separated; b) depressurization to an intermediate pressure;

c) countercurrent evacuation; d) countercurrent purge; and e) countercurrent pressurization.

a) Feed: The gas mixture is fed from the bottom of the column with CO ₂ retained and methane removed from the top at high pressure. This step is operated at high pressures between 200 and 1500 kPa, preferably between 400 and 800 kPa. This step ends before CO ₂ exiting the top of the column reaches a concentration higher than specified to obtain combustible methane;

b) Intermediate depressurization: without supply, the column is depressurised to a lower pressure than used

in food. It is intended decrease the amount in retained methane in the gas phase and so increase your recovery. This methane may be recompressed or used for pressurize others) column (s) or

eventually in the purge stage. This step must be quickly completed;

c) Countercurrent evacuation: the column outlet is closed and then the column is connected to a line with lower pressure. The minimum system pressure is reached at evacuation. This pressure may be lower than atmospheric pressure if the adsorbent is regenerable and only under such conditions. At this stage some methane is lost which must be burned before it is emitted into the atmosphere.

d) Countercurrent product purge: a part of the product or outlet of the depressurization step is introduced into the column at the top and the outlet is, together with the outlet of the evacuation step, a secondary process stream that can be used to obtain power. In this step the pressure is also the minimum system pressure.

e) Pressurization: With part of the product and gas from the depressurization step, the column pressure is increased from the minimum pressure to the maximum pressure.

Once this pressure value is reached, you can start the supply step and restart a new cycle.

This cycle is intended to use the column described in this invention to remove a specific component (CO2) and then regenerate said column for reuse. This process is used to process gas mixtures at temperatures between 20 and 70 ° C and total pressures between 250 and

2000 kPa. When the process is used continuously the cyclic steady state behavior is achieved, where the desired performance objectives must be achieved. A PSA process consisting of one or more columns can be used with this type of cycles. In a multiple column unit the current from the depressurization step can be used to equalize the pressure from another column to decrease the energy consumption of the unit.

Application Examples

EXAMPLE 1: CH ₄ -CO ₂ carbon molecular sieve separation CMS 3K.

The initial CH ₄ -CO ₂ separation study was performed with a CMS 3K kinetic adsorbent where CH ₄ diffusion is very slow. We simulate a five step PSA process (feed, intermediate depressurization, back current evacuation, back current product purge and back current pressurization). The flow rate to be treated is on the order of 1000 Nm ³ / h (under conditions of 298 K and 101.3 kPa) with a CH ₄ content of 55%. To treat this current a PSA with two columns of 4,667m in length and 0.4667m radius with a porosity of 0.33 was used. The feed was done at a pressure of 600 and 800 kPa and the evacuation and purge at 10 kPa. Simulations with different intermediate pressures were performed. The results obtained can be seen in Table 1.

Table 1. Simulation results of a PSA process using a CMS 3K kinetic adsorbent.

Test Qalim huh t-play t-evac P alim p - ¹ - inter Purity Recover Productivity SLPM s s s kPa kPa CH ₄ % ration life of ch ₄ % molCH ₄ / h.

kg THE 16666.7 135 0 160 600 200 99.1 53.1 2.63 1 16666.7 135 10 160 600 200 97.2 85.7 4.33 2 16666.7 135 10 160 800 200 97.3 85.6 4.32 3 16666.7 135 10 160 800 250 97.8 81.5 4.09 4 16666.7 130 10 140 800 250 97.9 80.8 4.05 5th 16000 130 10 140 800 250 98.1 79.7 3.83

Pressurization step: 70s; purge step: 50s.

This example serves as a basis for comparing the results obtained with a kinetic adsorbent.

EXAMPLE 2: CH ₄ -CO ₂ separation with LPSA: CMS 3K followed by 13X zeolite.

In this example we used a kinetic adsorbent CMS 3K followed by zeolite 13X, known by its great adsorption capacity C0 _2.

For comparison of results, we used a PSA unit with two columns of 4,667m in length and 0.4667m radius. The process also has 5 steps (feed, intermediate depressurization, back current evacuation, back current product purge and feed pressurization has always been 10 kPa evacuation. The arrangement for the first current adsorbent to purify is CMS against -chain). The 800 kPa pressure and the adsorbent pressure was made to come into contact with 3K followed by the 13X zeolite.

The results of the different simulations can be seen in Table 2. The objective is to place a high adsorbent CO ₂ adsorbent at the end of the bed that can also be purged using methane (the effectiveness of the CMS 3K purge is low due to CH ₄ diffusivity in the adsorbent micropores). This makes it possible to make better use of the 3K CMS layer and the last 13X zeolite layer acts as a containment barrier for CO ₂ . From these simulations we can confirm that the productivity of the LPSA unit is much higher than using only a CMS 3K type kinetic adsorbent.

Table 2. Simulation results of an LPSA process using a CMS 3K kinetic adsorbent followed by a separation adsorber by differences in adsorption equilibria (13X zeolite).

Test Z13X / CMS3K Qalim SLPM Talim s have s t evac s P inter kPa Purity CH ₄ % CH ₄ % recovery MolCH _{4 /} h.kg productivity I ^a Zeolite 16000 130 10 140 250 97.0 47.8 2.20 3rd ^to 9th 16000 130 10 140 250 95.3 49.3 2.31 5 ^b 0.111 16000 130 10 140 250 99.2 48.8 2.31 6 ^d 0.111 22000 130 10 140 250 98.3 76.8 5.03 7 ^C 0.25 22000 130 10 140 250 99.8 50.1 3.22 78 ^d 0.25 30000 130 10 140 250 96.7 83.7 7.55 80 ^d 0.429 30000 130 10 140 250 98.7 74.8 6.58

Pressurization step: 70s; Purge Step: 50s ^to Purge Flow: 5000 SLPM.

^b Pressurization flow rate: 10000 SLPM.

^c Feed rate: 22000 SLPM. Pressurization flow rate: 16000 SLPM.

^d Pressurization flow rate: 16000 SLPM.

REFERENCES

Appl, M .; Wagner, U .; Henrici, HJ; Kuessner, K .; Volkamer, K .; Fuerst, E. Removal of CO ₂ and H ₂ S and / or COS from Gases Containing these Constituents. US 4,336,233, 1982. Cavenati, S .; Grande, CA and Rodrigues, AE Upgrade of Methane from Landfill Gas by Pressure Swing Adsorption, Energy & Fuels, 2005, 19, 2545-2555.

Cavenati, S .; Grande, CA; Rodrigues, AE Separation of CH ₄ / CO ₂ / N ₂ Mixtures by Layered Pressure Swing Adsorption for Upgrade of Natural Gas. Chem. Eng. Sci., 2006, 61, 38933906.

Davis, Μ. M; Gray, R.L. J .; Patei, K. Process for the Purification of Natural Gas. United States Patent, US 5,174,796, 1992.

Deng, S .; Kumar, R .; Bulow, M .; Fitch, F. R .; Ojo, A. F .; Gittleman, C.S. Air Purification Process. United States Patent, US 6,238,460, 2001.

Dolan, WB; Mitariten, MJ CO ₂ Rejection from Natural Gas. United States Patent US 2003/0047071, 2003.

Dolan, W. B .; Mitariten, M. U. Heavy Hydrocarbon Recovery from Pressure Swing Adsorption Unit Tail Gas. United States Patent, US 6,610,124.

Fujita, S .; Himeno, S .; Suzuki, K .; Method for Concentrating Methane from Sewage Sludge and Methane Storage Equipment. European Patent, EP 1,647,531, Al.

Golden, T. C .; Weist, E.L. J. Layered Adsorption Zone for Hydrogen Production Swing Adsorption. United States Patent, US 6814787, 2004.

Hagen, M .; Polman, E .; Jensen, J. K .; Myken, A .; Jonsson, O .; Dahl, A. Adding Gas from Biomass to the Gas Grid, Swedish Gas Center, Report SGC 118, 2001.

Kim, M-B .; Bae, Y-S .; Choi, D. K .; Lee, C-H. Kinetic Separation of Landfill Gas by Two Bed Pressure Swing Adsorption Process Packed with Molecular Carbon Sieve: Nonisothermal Operation. Ind. Eng. Chem. Res. 2006, 45, 5050-5058.

Little, W. A .; Spektor, S. Device and Method for Removing Water and Carbon Dioxide from a Gas Mixture Using Pressure Swing Adsorption. World Patent, WO 2005/089237 A2, 2005.

Lu, Y .; Doong, S-J .; Bulow, M. Pressure-Swing Adsorption Using Layered Adsorbent Beds with Different Adsorption Properties I- Results of Process Simulations. Adsorption, 2003, 9, 337-347.

Knaebel, K. S .; Reinhold, Η. E. Landfill Gas: From Rubbish to Resource. Adsorption 2003, 9, 87-94.

Masahiro, I .; Kazuo, H. Method for Removing Carbon Dioxide from Mixed Gas and Alternative Natural Gas Generating Device Using the Method. World Patent, WO95526804.

Muller, U .; Hesse, M .; Putter, H .; Schubert, M .; Mirsch, D. Adsorptive Anreicherung von Methan in Methan-haltigen Gasmischen. European Patent EP 1674555, 2005.

Seery, M. W .; Bulk Separation of Carbon Dioxide from Methane Using Natural Clinoptilolite. World Patent, WO 98/58726, 1998.

Sircar, S .; Kock, W. R. Adsorptive Separation of Methane and Carbon Dioxide Gas Mixtures. European Patent EP 0193716, 1986.

Sircar, S .; Kumar, R .; Koch, W. R .; Vansloun, J. Recovery of Methane from Landfill Gas. United States Patent 4,770,676, 1988.

Sircar, S .; Kock, W. R. Adsorptive Separation of Gas Mixtures. European Patent EP 0257493, 1988

Claims (13)

1. Gas purification separation column, consisting of two layers of adsorbent material, as follows: The. the first layer, between 50 and 95% of the total column volume, consisting of a microporous material with pores of between 4 ° and 5.5 ° and adsorbent with kinetic selectivity for the contaminant gas and with slow adsorption kinetics; and B. the second layer, between 5 and 50% of the total column volume, consisting of microporous materials, preferably based on high surface area inorganic materials, with larger micropores 6® is adsorbent with a higher adsorption capacity for the contaminant gas than for the product gas, this second layer forming a containment barrier for the contaminant gas at the end of the column. Gas purification separating column according to the preceding claim, characterized in that the first layer consists of carbon molecular sieves, natural zeolites and 4A zeolites, LTA-modified LTA zeolites, DDR zeolites, ITQ zeolites , clinoptilotites or titan silicates. Gas purification separation column according to any one of the preceding claims, characterized in that the second layer consists of 13X zeolite, Y zeolite, mordenites, activated carbon, aluminas, silica gel, and other porous materials. silica matrix or activated carbon with superficial modifications. 4. Pressure-modulating adsorption process for gas purification, characterized in that each cycle is carried out in five steps which comprise: a) feeding at least one column containing the two layers of adsorbent material at high pressure with the gas to be separated; b) depressurizing the mixture to an intermediate pressure within a range of from 20 to 600 kPa; c) countercurrent evacuation; d) purge with countercurrent product; and e) countercurrent pressurization within a range of 200 to 1500 kPa, preferably between 400 and 800 kPa. Process according to the preceding claim, characterized in that the supply pressure is within a interval 400 and 800 in between kPa. 200 and 1500 kPa, preferably between 6. Process, in wake up with claims 4-5, featured by intermediate depressurization of column up to a pressure lower than the supply pressure. Method according to Claim 4-6, characterized in that the countercurrent evacuation is carried out with the column outlet closed, and then the column is connected to a line with lower pressure within a range of 100 to 1kPa total pressure. . Process according to Claim 4-7, characterized in that the counter-current product purge is carried out by introducing all or only part of the product and is carried out at minimum system pressure, ie within a range of 200 to 1 kPa of total column pressure. Pressure-modulating adsorption process for gas purification according to Claim 5,8, characterized in that the pressurization is carried out with all or part of the product and the gas from the depressurization and the column pressure is increased. from minimum pressure to maximum pressure, ie from 1 to 200 kPa to 250 to 2000 kPa total pressure. Pressure modulating adsorption process for gas purification according to claims 4 9, characterized in that it is carried out continuously by using multiple separating columns and starting a new cycle upon reaching the maximum pressure value referred to in the preceding claim. Pressure modulating adsorption process for gas purification according to claims 4 10, characterized in that it is developed in continuous or individual cycles. Use of the separation column as described in claims 1-3 by the process described in claims 4-11, characterized in that it is applicable to the purification of CH ₄ -CO ₂ mixtures. Use of the separation column according to the preceding claim, characterized in that it is applicable for the removal of CO ₂ from CH ₄ -CO ₂ streams in natural gas, biogas and landfill gas. 14. Use of the separation column, according to the preceding claim, characterized by being applicable in the removal of C0 ₂ CH ₄ CO ₂ streams which C0 ₂ molar fractions may vary from 0.15 to 0.85, preferably between 0:45 and 0.55.