Process for solid-phase extraction of substances from gas mixtures

Abstract

A process for solid-phase extraction of at least one substance contained in a gas mixture (11), such as NO2, N2O, SO2, H2S, or CO2, - A step (20) of cooling a gas mixture containing a substance that directly transitions from the gas phase to the solid phase at low temperatures; - A parallel process in which hydrocarbon snow (250) is generated in a series of ejectors (350), -A step of dispersing this hydrocarbon snow in a tower (450) through which a gas mixture containing the anti-sublimation substance circulates, at a temperature lower than the triple point of the substance to be anti-sublimated; - A process of sublimating solid hydrocarbon particles that cause anti-sublimation of substances contained in a gas mixture; A process comprising the step of recovering a solid-phase substance (5) at the bottom of a tower into a dual storage device (51, 52) which operates alternately in recovery mode or discharge mode for the solid substance.

Description

Technical Field

[0001] The present invention relates to the anti-sublimation of substances such as nitrogen oxides (N2O, NO2), SO2, H2S, or carbon dioxide (CO2) contained in a gas mixture mainly containing gases (such as CH4, N2, O2, H2, etc.) that are very far from their triple points by the sublimation of hydrocarbon snow injected into the circulating gas mixture.

[0002] Here, anti-sublimation means that a substance such as carbon dioxide directly solidifies from its gaseous state to its solid state at a temperature lower than its triple point temperature. For example, reference can be made to the literature Pan et al. CO2 capture by antisublimation process and its technical economic analysis, doi.org / 10.1002 / ghg.1313. References can also be made to European Patent No. 2464436 (Armines, 2015), European Patent No. 1979072 (GDF, 2010), International Publication No. 2010 / 012658 (Alstom, 2010), and International Publication No. 2010076464 (Air Liquide, 2010).

[0003] In the latest technology anti-sublimation carbon dioxide recovery device, CO2 accumulates in solid form on the finned tube heat exchanger.

[0004] European Patent No. 1355716 (B1) (Armines, 2005) describes a process for extracting carbon dioxide from flue gas generated by the combustion of hydrocarbons. The process includes a step of cooling the flue gas at a pressure substantially equal to atmospheric pressure and a temperature at which carbon dioxide directly transitions to the solid state by anti-sublimation, followed by a step of melting the carbon dioxide in a sealed chamber, where the pressure and temperature in the chamber change to the triple point of carbon dioxide.

[0005] The implementation of the process described in European Patent No. 1355716(B1) requires a very large exchange surface area when the flow rate of the gas being treated is high.

[0006] International Publication No. 2011 / 097043 (Exxonmobil, 2011) describes the use of a cold liquid to separate solidifiable gaseous components from a process gas flux. The cold liquid may be an oxygen-containing hydrocarbon such as isopentane, isohexane, isoalkenes, mixtures thereof, alcohols, and alcohol mixtures. The cold liquid is brought into contact with the gas flow to be treated in a spray tower or bubble tower.

[0007] The implementation of the process described in International Publication No. 2011 / 097043 requires additional separation between the liquid and the solid. Objective of the present invention

[0008] One of the objectives of the present invention is to enable denitrification, desulfurization, and decarbonization of gas mixtures such as flue gas or process gas that contain gases (such as CH4, N2, O2, and H2) that are very far from the triple point at various concentrations.

[0009] Another object of the present invention is nitrogen oxides (NO X ), sulfur oxides (SO X This involves limiting emissions of greenhouse gases such as carbon dioxide (CO2), as well as other harmful substances.

[0010] Another objective of the present invention is to enable the decarbonization of the atmosphere.

[0011] Another object of the present invention is to enable solid-phase extraction of any substance having a triple point temperature higher than that of hydrocarbons when injected in the form of snow into a gas stream containing these substances. [Modes for carrying out the invention]

[0012] For these purposes, according to a first embodiment, a process is provided for solid-phase extraction of at least one substance contained in a gas mixture, such as NO2, N2O, SO2, H2S, or CO2, the process is - A process of cooling a gas mixture containing a substance that directly transitions from the gas phase to the solid phase at low temperatures; A parallel process for generating hydrocarbon snow in a series of ejectors, The process involves dispersing this hydrocarbon snow in a tower through which a gas mixture containing the anti-sublimation substance circulates, at a temperature lower than the triple point of the substance to be anti-sublimated; A process of sublimating solid hydrocarbon particles that cause anti-sublimation of substances contained in a gas mixture;

[0013] The process includes recovering a solid-phase material in a dual storage device at the bottom of a tower, which operates alternately in recovery mode or solid material discharge mode.

[0014] Advantageously, the hydrocarbon snow production process includes mixing liquid hydrocarbons with a propellant gas at a temperature below the triple point of hydrocarbons.

[0015] Advantageously, a treated gas mixture is obtained that does not contain at least one substance such as NO2, N2O, SO2, H2S, or CO2, and this treated gas mixture is used to form at least a portion of the propulsion gas.

[0016] Advantageously, the process of dispersing hydrocarbon snow is carried out in a cyclone-type tower.

[0017] Advantageously, the process includes a step of recovering the cold energy of the treated gas mixture from which the solid-phase extracted substance has been removed.

[0018] Advantageously, the process includes a step of condensing hydrocarbon vapor, which is then advantageously passed through an activated carbon filter.

[0019] Advantageously, the process includes a step of discarding a treated gas mixture from which most of the solid-phase extracted substances such as NO2, N2O, SO2, H2S, or CO2 have been removed.

[0020] In some embodiments, the triple point of the hydrocarbon is less than -95 °C.

[0021] In some embodiments, the hydrocarbon is selected from the group consisting of pentane (CAS 109-66-0), hexane (CAS 110-54-3), isopentane (2-methylbutane CAS 78-78-4), isohexane (2-methylpentane CAS 107-83-5), 2,3-dimethylbutane (CAS 79-29-8), 2,2-dimethylbutane (CAS 75-83-2), and 3-methylpentane (CAS 96-14-0).

[0022] Advantageously, the substance extracted from the gas mixture is carbon dioxide CO2.

[0023] In some embodiments, the gas mixture to be treated is flue gas or process gas.

[0024] Advantageously, a plurality of cyclone-shaped separation towers are arranged in series to perform progressive decarbonization.

[0025] In some embodiments, the substance extracted from the gas mixture is recovered in the solid phase and conveyed.

[0026] In other embodiments, the extracted substance(s) is recovered in the solid phase and then liquefied with cold thermal energy recovery by sublimation and melting.

[0027] In other embodiments, the extracted substance(s) is recovered in the solid phase and then liquefied and vaporized with cold thermal energy recovery.

[0028] Therefore, the process enables the recovery of large quantities of solid CO2 with high energy efficiency, and furthermore, in the two storage volumes, the CO2 can then be recovered and transported in solid form, or in liquid form with pressurized and cold energy recovery, or even in a gaseous phase with heat recovery.

[0029] Other objects and advantages of the present invention will become apparent in light of the description of embodiments made below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0030] [Figure 1] This figure shows the process of solid condensation of substances at temperatures below the triple point, particularly the process of solid condensation of carbon dioxide via the sublimation of hydrocarbon snow. [Figure 2] This is a schematic diagram of a type of ejector that mixes a flow of decarbonized flue gas, which is at a temperature below the triple point of hydrocarbons, with liquid hydrocarbons, which are at a temperature close to the triple point. [Figure 3] This figure shows a cyclone-type tower for CO2 anti-sublimation by injecting hydrocarbon snow.

[0031] Description of the Embodiment The following table shows the triple point temperatures and pressures for several substances that can be extracted in solid phase from gas mixtures whose other components are CH4, N2, O2, and H2. JPEG2026525730000001.jpg44169

[0032] In the remainder of the following explanation, the substance extracted is carbon dioxide.

[0033] The detailed examples for CO2 shown below also apply to other substances that have a higher triple point temperature than hydrocarbons injected as snow in a gaseous stream, particularly the substances listed in the table above (NO2, N2O, SO2, H2S).

[0034] As recalled, anti-sublimation is a direct transition from the gas phase to the solid phase.

[0035] Carbon dioxide (CO2) has a triple point at a pressure of 520 kPa and a temperature of -56.6°C, which means that when carbon dioxide is cooled at a pressure below 520 kPa, anti-sublimation occurs at a temperature dependent on its partial pressure.

[0036] To recover CO2 contained directly from flue gas or gaseous emissions from industrial processes (e.g., cement plants, steel industries) or means of transport (e.g., ships), or from the air, the partial pressure of CO2 in the gas mixture corresponds to its molar concentration, and this concentration determines the initiation temperature of anti-sublimation.

[0037] Examples of temperatures are shown in the table below, and these were calculated using the solid-gas equilibrium equation defined by the NIST (National Institute of Standards and Technology)-Refprop10 software, which is globally recognized by the thermodynamic research community. JPEG2026525730000002.jpg8089

[0038] The CO2 concentration in biogas ranges from 25% to 50%, in cement plants and the steel industry it ranges from 5% to 35%, in combustion flue gas of gas turbines it ranges from 3% to 10%, and in flue gas of large ships it ranges from 4% to 5%. The carbon dioxide concentration in the air is generally 400 ppm, or 0.04%.

[0039] An outlet concentration is defined for each inlet concentration, and is generally set to ensure a CO2 recovery efficiency of 90%. That is, if the inlet concentration is 15%, the outlet concentration is 1.5%.

[0040] In this example, the start temperature for anti-sublimation is -99°C, and the exit temperature is -119°C.

[0041] In this process, the sublimation of hydrocarbon snow at atmospheric pressure enables the anti-sublimation of substances having triple points higher than the triple point of hydrocarbons.

[0042] The CO2 present in the gas mixture being processed has a variable CO2 concentration, and carbon dioxide is anti-sublimated at a variable temperature of -90°C to -150°C, while other gases in the gas mixture are, for example, nitrogen, oxygen, argon, hydrogen, or methane.

[0043] The flow rates processed in cement plants or steel plants, and also in gas-fired power plants, are between 100,000 and 3,000,000 Nm³. 3 The range is / h. For these large flow rates, the flow rate of solid CO2 can be in the range of 10 to 100 tons / hour. NO X and SO X The flow rate is on the order of several tons.

[0044] To handle such flow rates, CO2 capture systems must be robust, feature simple and energy-efficient controls, and have a relatively small footprint.

[0045] Advantageously, to reduce energy consumption, this process operates at near atmospheric pressure.

[0046] In this process, the flow rate of a gas mixture containing carbon dioxide (or any anti-sublimation substance such as SO2, H2S, NO2, N2O) is advantageously circulated within a separation tower where a hydrocarbon-type cryogenic solid circulates in the form of snow.

[0047] Sublimation of hydrocarbon snow at a given temperature results in the anti-sublimation of substances extracted from gas mixtures, particularly CO2.

[0048] This CO2 anti-sublimation tower advantageously has the form of a cyclone-type tower to facilitate the separation of CO2 snow enriched with sublimated hydrocarbons from the gas mixture to be decarbonized.

[0049] Substances that become cryogenic snow at -90°C to -160°C and are sublimable are, advantageously, hydrocarbons having a triple point lower than the anti-sublimation temperature of other substances extracted from CO2 or gas mixtures.

[0050] When these molecules are in the gas phase, it is advantageous to condense them, especially at around 20°C and atmospheric pressure.

[0051] Therefore, by controlling this process at atmospheric pressure, the need to compress the large flow rate of the gas mixture being processed is avoided, resulting in significant energy savings compared to any process that requires compression of the gas mixture being decarbonized.

[0052] The following table shows the triple point temperature and pressure (Pa), as well as the condensation pressure (kPa) at 20°C, for hydrocarbons that can produce cryogenic snow. JPEG2026525730000003.jpg91135

[0053] The advantages of the properties of these fluid hydrocarbons are as follows:

[0054] Firstly, their latent heat of sublimation is comparable to that of CO2, i.e., approximately 570 kJ / kg.

[0055] Secondly, after sublimation, these hydrocarbon vapors are condensed at atmospheric pressure for reuse.

[0056] By sequentially anti-sublimating these hydrocarbons, it is possible to anti-sublimate substances found in flue gas, namely NO2, N2O, SO2, H2S, and CO2, at a temperature dependent on their partial pressure in the gas mixture, and the gas mixture complementarily contains gases far from the triple point, such as CH4, N2, O2, Ar, and H2.

[0057] The solidification of these substances, primarily CO2, i.e., anti-sublimation condensation, occurs through direct contact with hydrocarbon snow. For CO2 anti-sublimation, pentane or isopentane is preferably used, corresponding to final CO2 anti-sublimation temperatures of -126.5°C to -122°C, respectively, for desired residual concentrations in the decarbonization of flue gas, i.e., preferably on the order of 0.5% to 1%.

[0058] To decarbonize air to 100 ppm, the anti-sublimation temperature for CO2 is favorably -148°C, and therefore, for example, isopentane snow needs to be used.

[0059] Advantageously, multiple solid condensation towers can be connected in series depending on the CO2 content in the flue gas and the flow rate of the flue gas.

[0060] For example, a volume concentration of 15% and a flow rate of 100,000 Nm³ 3 In the case of / h, the mass of CO2 recovered when the concentration decreases from 15% to 1.5% is approximately 26 tons / hour. In this case, it is desirable to divide this recovery into three parts, that is, to install three CO2 solid condensation towers with progressively lower temperatures, for example, -105°C, -115°C, and -125°C.

[0061] First, refer to Figure 1.

[0062] In step 10, the flow rate of the gas mixture 11 to be decarbonized is supplied, for example, by a booster compressor 100.

[0063] In step 20, the flow rate of the gas mixture 11 is cooled in the heat exchanger 200 to just above the CO2 anti-sublimation temperature at near atmospheric pressure, depending on its concentration in the gas mixture 11.

[0064] In step 30, the liquid hydrocarbon 25 recovered from step 70 is cooled in a heat exchanger 300 to a temperature very close to the triple point of the hydrocarbon 25.

[0065] The liquid hydrocarbon 25 is injected into the ejector 350 by the pump 325.

[0066] Step 35 includes mixing the propulsion gas with the liquid hydrocarbon 25 in a series of ejectors 350, preferably as part of the flow rate of a decarbonized gas mixture 155.

[0067] Because the temperature of the propulsion gas 155 is lower than the triple point of the hydrocarbon 25, and due to the pressure drop effect caused by injecting the propulsion gas 155 into the ejector 350, the hydrocarbon 25 transitions from the liquid phase to the solid phase, and this hydrocarbon snow 250 is injected by the ejector 350 into the flow rate of the decarbonized gas mixture 11.

[0068] Step 40 includes injecting hydrocarbon snow 250 from the side into the gas mixture 11 to be decarbonized using an ejector 350, the injection taking place in one or more towers 450 arranged in series, preferably in the form of a cyclone.

[0069] Step 45 includes sublimating the hydrocarbon snow 250 at a temperature lower than the triple point at the minimum concentration of CO2, for example, -126.5°C for 0.5%, resulting in anti-sublimation of CO2 within one or more columns 450, preferably in the form of a cyclone, where at the outlet, the decarbonized gas mixture 12 and the CO2 snow separated by the cyclone shape of the separation column 450 are formed.

[0070] The density at this temperature is approximately 1550 kg / m³. 3The solid CO2 is carried towards the walls of the cyclone-shaped tower by vortex motion, and as a result, its density at this temperature is typically about 2.5 kg / m³. 3 It is separated from the gas mixture.

[0071] Step 50 includes recovering solid CO25 at the lower part of the tower, preferably in the form of a cyclone.

[0072] Steps 51 and 52, which involve storing solid CO25, are performed alternately. When the level in storage unit 510 reaches the maximum threshold, flap 511 closes and flap 521 of storage unit 520 opens (these flaps are shown in Figure 3). CO2 is discharged from each of storage units 510 and 520, either in solid form or in liquid form with energy recovery.

[0073] Step 60 includes transferring cold energy from the flow rate of the decarbonized mixture 15 to the mixture 11 to be decarbonized using a heat exchanger 200 during step 20 in order to reduce energy consumption.

[0074] Step 70 includes condensing the hydrocarbons 25 contained in the decarbonized gas mixture 15 in a gas-liquid separation heat exchanger 700 at approximately 20°C in order to reuse the hydrocarbons 25.

[0075] To limit the hydrocarbon content 25 in the decarbonized gas mixture 15 to less than 1 ppm, a renewable activated carbon filter may be advantageously installed downstream of the hydrocarbon condenser 700.

[0076] Step 80 includes condensing the hydrocarbon 25 and then distributing the decarbonized flow 150 at a flow rate of 15 for subsequent use or returning it to the atmosphere.

[0077] Step 90 includes compressing a decarbonized and hydrocarbon-free flow 155 by a compression system 900 and favorably converting it into a propulsion flow 155 for the ejector.

[0078] Step 65 includes cooling the flow rate 155 in the heat exchanger 650 to a temperature below the triple point of hydrocarbons, thereby completing the recirculation of the flow rate 155.

[0079] The result of all these processes is the decarbonization of the gas mixture flow rate, accompanied by the recovery of CO2 in the solid phase.

[0080] The result may be denitrification or desulfurization of the gas mixture, accompanied by the recovery of SO2 from H2S, or NO2 and N2O in a solid phase.

[0081] Refer to Figure 2, which is a cross-sectional view of a type of ejector, and its operation for generating hydrocarbon ice is as follows:

[0082] The propulsion gas is preferably a mixture of decarbonized and hydrocarbon-free gases 155, which is injected into the ejector 350 via an injection nozzle 355.

[0083] The near-sonic velocity of this gas at the outlet of the injection nozzle 355 creates a pressure drop effect, drawing in the hydrocarbon 25 through the supply manifold 345.

[0084] The resulting vacuum, combined with the temperature of the propellant gas 155 which is lower than the triple point of hydrocarbons 25, leads to the formation of hydrocarbon snow 250 within the mixing chamber 360.

[0085] The throttling section 365 at the outlet of the ejector 350 effectively increases the injection speed and the dispersion of the snow 250.

[0086] Refer to Figure 3, which is a three-dimensional representation of the cyclone-shaped tower 450.

[0087] The decarbonized mixture 11 flows into the tower 450 from the side via the manifold 451 at an angle that generates vortex motion, which rotates clockwise as shown in Figure 3.

[0088] Along the wall of the tower 450, an ejector crown 350 is installed to project hydrocarbon ice 25 at a temperature lower than the triple point temperature corresponding to the desired final concentration for decarbonizing the gas mixture 11.

[0089] The CO2 contained in mixture 11 transitions from the gas phase to the solid phase as an anti-sublimation change caused by the sublimation of hydrocarbon snow 25.

[0090] The solid CO25 falls to the bottom of the tower 450, where it is collected in the storage unit 510 or 520, depending on whether the flap 511 or 521 is open.

[0091] The opening or closing of flaps 511 or 521 is caused by level sensors 512 for storage unit 510 and 522 for storage unit 520, respectively. When level sensor 512 indicates that tank 510 is full of solid CO25, it generates a signal to open flap 521 and close flap 511, and the opposite operation is performed for level sensor 522.

[0092] The decarbonized gas mixture 12 flows out of the tower 450 through the manifold 452 in a vortex motion, and the direction of this vortex is opposite to the direction of the vortex of the carbonized gas mixture 11, which is being decarbonized in contact with the hydrocarbon snow 25.

[0093] Various solid CO2 management options are available.

[0094] In some embodiments, CO2 is transferred in solid phase from storage units 510 and 520 and introduced into a mobile storage unit for the purpose of transporting it in solid phase.

[0095] In some embodiments, the CO2 is transferred to a chamber where the cold energy generated by sublimation and melting is recovered. The CO2 may also be transferred to a tank or powder pipeline so as to be transported at a pressure in the range of 600 kPa to 2 MPa and a temperature in the range of -50°C to -20°C.

[0096] In some embodiments, liquid CO2 can also be vaporized for use in processes carried out near a CO2 capture facility.

Claims

1. NO contained in the gas mixture (11) ２ , N ２ O, SO ２ , H ２ S, or CO ２ A process for solid-phase extraction of at least one substance such as, - A step (20) of cooling a gas mixture (11) containing a substance that directly transitions from the gas phase to the solid phase at low temperatures; - A parallel process in which hydrocarbon snow (250) is generated in a series of ejectors (350), The process involves dispersing the hydrocarbon snow (250) in a tower (450) through which a gas mixture (11) containing the substance to be anti-sublimated circulates, at a temperature lower than the triple point of the substance to be anti-sublimated; A step of sublimating the solid particles of hydrocarbons that cause anti-sublimation of the substance contained in the gas mixture (11); A process comprising the step of recovering a solid substance (5) at the bottom of the tower (450) into a dual storage device (51, 52) which operates alternately in recovery mode or discharge mode for the solid substance (5).

2. The process according to claim 1, characterized in that the hydrocarbon snow generation step (250) includes a step (35) of mixing liquid hydrocarbon (25) with propellant gas at a temperature lower than the triple point temperature of the hydrocarbon (25).

3. The process according to claim 1 or 2, characterized in that the step of dispersing the hydrocarbon snow (250) is carried out in a cyclone-type tower (450).

4. The process according to any one of claims 1 to 3, characterized in that the solid-phase extracted substance (5) includes a step of recovering the cold energy of the removed treated gas mixture (12).

5. The process according to any one of claims 1 to 4, comprising a step of condensing hydrocarbon vapor (70), and preferably a step of passing it through an activated carbon filter.

6. NO ２ , N ２ O, SO ２ , H ２ S, or CO ２ A process according to any one of claims 1 to 5, characterized by comprising the step of discarding a treated gas mixture (12) from which most of the solid-phase extracted substances such as have been removed.

7. The process according to any one of claims 2 to 6, characterized in that the triple point of the hydrocarbon (25) is less than -95°C.

8. The process according to any one of claims 2 to 6, characterized in that the hydrocarbon (25) is selected from the group consisting of pentane, hexane, isopentane, isohexane, 2,3-dimethylbutane, 2,2-dimethylbutane, and 3-methylpentane.

9. The substance extracted from the gas mixture (11) is carbon dioxide (CO2). ２ The process according to any one of claims 1 to 8, characterized in that it is the process described above.

10. The process according to any one of claims 1 to 9, characterized in that the gas mixture (11) is either a flue gas or a process gas.

11. The process according to any one of claims 1 to 10, characterized in that a plurality of cyclone-shaped separation towers are arranged in series to carry out gradual decarbonization.

12. The process according to any one of claims 1 to 11, characterized in that the substance extracted from the gas mixture (11) is recovered in solid phase and transported.

13. The process according to any one of claims 1 to 11, characterized in that the extracted substance is recovered in a solid phase and then liquefied with the recovery of cold energy due to sublimation and melting.

14. The process according to any one of claims 1 to 11, characterized in that the extracted substance is recovered in a solid phase, then liquefied with the recovery of thermal energy, and further vaporized.

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