Process for capturing CO2 from a gas stream

Abstract

The present invention relates to a process for capturing carbon dioxide from a gas stream. The gas stream is contacted with solid adsorbent particles in an adsorption zone. The adsorption zone has at least two beds of fluidized solid adsorbent particles, and the solid adsorbent particles are flowing downwards from bed to bed. The solid adsorbent particles comprise 15 to 75 weight % of organic amine compounds. The gas stream entering the adsorption zone has a dew point which is at least 5 C. below the forward flow temperature of the coolest cooling medium in the adsorption zone. Carbon dioxide enriched solid adsorbent particles are heated, and then regenerated. The desorption zone has at least two beds of fluidized solid adsorbent particles, and the stripping gas is steam. The regenerated particles are cooled and recycled to the adsorption zone.

Claims

1. A process for capturing carbon dioxide from a gas stream, the process comprising the steps of: (a) contacting the gas stream with solid adsorbent particles in an adsorption zone, wherein the adsorption zone has at least two beds of fluidized solid adsorbent particles, and wherein the solid adsorbent particles are flowing downwards from bed to bed, and wherein the gas stream is flowing upwards, and wherein the adsorption zone has at least one internal cooling means in each of the beds of fluidized solid absorbent particles, and wherein the solid adsorbent particles comprise 15 to 75 weight % of organic amine compounds, based on the total weight of the adsorbent particles, and wherein the gas stream entering the adsorption zone, at the pressure at which it enters the adsorption zone, has a dew point which is at least 5 C., below the forward flow temperature of the cooling medium in the internal cooling means having the lowest forward flow temperature in the adsorption zone; (b) passing carbon dioxide enriched solid adsorbent particles obtained in step (a) to a riser zone (I) with a riser gas (I); (c) heating at least a part of the carbon dioxide enriched solid adsorbent particles in the riser zone (I), optionally by means of direct or indirect heat exchange with carbon dioxide depleted solid adsorbent particles in the riser zone (II) of step (f); (d) separating the heated carbon dioxide enriched solid adsorbent particles from the riser gas (I) at the end of the riser zone (I) in a separating device; (e) regenerating at least a part of the carbon dioxide enriched solid absorbent particles obtained in step (d) in a desorption zone, wherein the desorption zone has at least two beds of fluidized solid adsorbent particles, and wherein the solid adsorbent particles are flowing downwards from bed to bed and a stripping gas is flowing upwards, and wherein the stripping gas comprises at least 50 volume % steam; wherein the desorption zone has at least one internal heating means in each of the beds of fluidized solid absorbent particles; (f) passing carbon dioxide depleted solid adsorbent particles obtained in step (e) to a riser zone (II) with a riser gas (II); (g) cooling at least a part of the carbon dioxide depleted solid absorbent particles in riser zone (II), optionally by means of direct or indirect heat exchange with carbon dioxide enriched solid adsorbent particles in the riser zone (I) of step (b); (h) separating the carbon dioxide depleted solid adsorbent particles from the riser gas (II) at the end of the riser zone (II) in a separating device; and (i) recycling at least 50% of the carbon dioxide depleted solid adsorbent particles obtained in step (h) to the adsorption zone.

2. The process according to claim 1, wherein the beds of fluidized solid adsorbent particles in the adsorption zone and/or in the desorption zone are present above sieve plates and/or nozzle plates, and wherein the sieve plates and/or nozzle plates comprise overflow weirs and downcomers.

3. The process according to claim 1, wherein in step (b) a gas comprising at least 80 vol % CO2, is used as riser gas in the riser zone (I), and/or wherein in step (f) a gas comprising at most 5 vol % CO2 is used as riser gas in the riser zone (II); wherein the gas comprising at most 5 vol % CO2 comprises carbon dioxide depleted gas obtained in step a), or a mixture of steam and carbon dioxide depleted gas obtained in step a).

4. The process according to claim 1, wherein at least 80% of the carbon dioxide depleted solid adsorbent particles obtained in step (h) are recycled to the adsorption zone in step (i).

5. The process according to claim 1, wherein fresh solid adsorbent particles are added to the adsorption zone.

6. The process according to claim 1, wherein the gas stream used in step a) comprises in the range of from 0.1 to 70 vol % carbon dioxide.

7. The process according to claim 1, wherein the solid adsorbent particles comprising 15 to 75 weight % of organic amine compounds comprise a carrier material and one or more types of organic amine compounds.

8. The process according to claim 7, wherein the solid adsorbent particles comprise one or more primary, secondary and/or tertiary organic amine compounds chosen from the group of monoethanol amine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA) and methyldiethanolamine (MDEA) and diethyl-monoethanolamine (DEMEA).

9. The process according to claim 7, wherein the solid adsorbent particles comprise one or more polyethylene amines chosen from the group of diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA) and polyethyleneimine (PEI).

10. The process according to claim 9, wherein the solid adsorbent particles comprise PEI, or PEI and (3-aminopropyl)triethoxysilane (APTES).

11. The process according to claim 6, wherein the carrier material is selected from the group consisting of porous metal oxides, activated carbons, zeolites, metal-organic frameworks, zeolitic-imidazolate frameworks, and polymers, and polymethyl methacrylate (PMA).

12. The process according to claim 11, wherein the carrier material is selected from the group consisting of silica, alumina, titania, zirconia, magnesium oxide, amorphous silica-aluminas (ASA), and combinations thereof.

13. The process according to claim 1, wherein the solid adsorbent particles have an average pore volume in the range of from 0.9 to 1.8 g/ml, a bulk density in the range of from 0.3 to 0.7 g/ml, an average particle diameter in the range of from 100 to 800 micrometer, and an average total surface area in the range of from 250 to 1000 m2/g.

14. The process according to claim 1, wherein step (a) is carried out at a temperature in the range of from 67 to 140 C.

15. The process according to claim 2, wherein the forward flow temperature of the cooling medium in the internal cooling means having the lowest forward flow temperature in the adsorption zone is at least 5 C., below the average temperature in the bed of fluidized solid adsorbent particles which comprises this internal cooling means.

Description

FIGS. 1 and 3

(1) The present invention will be further illustrated with reference to the drawings, wherein:

(2) FIG. 1 shows a schematic diagram of an embodiment of a device that can be used for a process according to the invention;

(3) FIG. 2 shows a line-up that can be used for a process according to the invention including heat integration.

(4) FIG. 3 shows the temperature profile of the desorption zone and the adsorption zone under two types of stripping gas.

(5) FIG. 1 shows a schematic diagram of an embodiment of a device that can be used for a process according to the invention. The device shown contains an adsorber, a desorber, two risers and two particle separators. A feed gas enters at the bottom of the adsorber, and a strip gas enters at the bottom of the desorber. Solid adsorber particles flow over overflow weirs and move down from fluidized bed to fluidized bed in the adsorber as well as in the desorber.

(6) FIG. 2 shows a line-up that can be used for a process according to the invention including heat integration. When applying the process of the invention, use may be made of heat integration. This can be done through heat exchange between hot stream(s) and cold stream(s) directly or indirectly, or with additional equipment, e.g. through the application of heat pumps. FIG. 2 shows the application of a lean rich heat exchanger between the two risers. An additional working fluid may be used for this heat exchange.

Examples A and FIG. 3

(7) The apparatus used in the examples A for a process according to the invention is characterized as follows. The adsorption zone has an internal diameter of 150 mm and comprises 5 staged fluidized beds; the desorption zone has an internal diameter of 110 mm and comprises of 5 staged fluidized beds.

(8) In all cases the weir height of the fluidized beds was 60 mm. The two risers have an internal diameter of 25 mm.

(9) The silica carrier comprises spherical particles with an average particle diameter (d50) of about 300 micrometer and a pore volume of 1.1 ml/g and is impregnated with PEI to arrive at a 50% PEI loading.

(10) In one experiment, a dry gas stream entered the adsorption zone. FIG. 3 shows the temperature profile of the desorption zone and the adsorption zone under two types of stripping gas. The temperature of both types of stripping gas when entering the desorption zone was the same.

(11) When the stripping gas was nitrogen, the temperature of the desorption zone was higher than the temperature of the adsorption zone. When the stripping gas was switched from nitrogen to steam, the temperature in the adsorption zone slightly decreased, and the temperature in de desorption zone was significantly increased. This is exemplified by the data for Examples A with a dry gas stream in FIG. 3.

(12) In another experiment, the gas stream entering the adsorption zone in step (a) contained some moisture; it had a dew point of more than 5 C. below the forward flow temperature of the cooling medium in the internal cooling means having the lowest forward flow temperature in the adsorption zone. When the stripping gas was switched from nitrogen to steam, the temperature in the adsorption zone slightly decreased, and the temperature in de desorption zone was significantly increased.

(13) As discussed above, in the section about heat integration, it was found that the combination of the specific dew point range for the gas stream entering the adsorption zone in step (a), and the steam regeneration of step (e) resulted in an advanced heat integration. An internal heat displacement between the adsorption zone and the desorption zone was observed.

(14) In yet another experiment, the gas stream entering the adsorption zone in step (a) contained too much moisture. Lumps of catalyst particles formed on the cooling coils in the adsorption zone due to condensation of water on the cooling coils.

(15) Hence, drying of flue gas is often desired in order to avoid catalyst lump formation in the adsorption zone. It was now found that is not necessary to dry flue gas completely; this saves energy. Furthermore, a gas with the specific dew point range shows an advanced heat integration.

(16) Further, it was found that the overall performance was higher when steam was used as stripping gas as compared to the use of nitrogen as stripping gas.

Examples B and Table

(17) The apparatus used in the examples B for a process according to the invention is characterized as follows. The adsorption zone has an internal diameter of 150 mm and comprises 5 staged fluidized beds; the desorption zone has an internal diameter of 110 mm and comprises of 5 staged fluidized beds.

(18) In all cases the weir height of the fluidized beds was 60 mm. The two risers have an internal diameter of 25 mm.

(19) The silica carrier comprises spherical particles with an average particle diameter (d50) of about 300 micrometer and a pore volume of 1.1 ml/g and is impregnated with PEI to arrive at a 50% PEI loading.

(20) A dried gas stream entered the adsorption zone. In the desorption zone nitrogen was used as stripping gas.

(21) Examples B show that high capture efficiencies can be achieved with the process of the present invention; see the Table below.

(22) TABLE-US-00001 TABLE Total Solid Temp top Temp bottom CO2 gas CO2 recycle bed in bed in Capture CO2 Exp feed conc. rate adsorber desorber efficiency captured nr (Nm3/h) (v %) (kg/h) (deg C.) (deg C.) (%) (kg/d) 3.1 15.8 5 18 79 116 78 30 3.3 15.8 5 25 75 110 90 34 2.1 15.8 5 33 77 107 96 37 2.3 32 5 33 82 107 56 43 4.2 15.8 10 25 89 109 58 44

(23) The results of Example B show that increasing the solid recycle rate improves the CO2 capture efficiency (example 3.1, 3.3 and 2.1). Increasing the total gas feed results in a decreased capture efficiency (example 2.1 and 2.3). Increasing the concentration of CO2 in the feed gas also decreases the capture efficiency (example 3.3 and 4.2).