Combined method and apparatus for CO2 capture and energy storage

Abstract

Title: Combined CO2 Capture and Energy Storage Process and Apparatus. In an energy storage process, a waste gas (1) is compressed, and the compressed waste gas (5) is sent to a separation unit (CO2 PSA) for separation by adsorption, producing a CO2-enriched flow (7) and a CO2-depleted flow (9). During a first period, the CO2-depleted flow (9) is stored in liquid form, and during a second period, the stored liquid is vaporized and expanded in a turbine (T). Figure: Fig. 1

Description

Title of the invention: Combined method and apparatus for CO2 capture and energy storage

[0001] The present invention relates to a method and a combined apparatus for CO2 capture and energy storage.

[0002] Carbon dioxide capture and storage is one of the only solutions to reduce carbon dioxide emissions from certain industries (e.g. cement works, steelworks, etc.)

[0003] Technologies that do not use a solvent to capture carbon dioxide, such as Cryocap ® FG processes (with CO2 PSA and low temperature separation by partial condensation and / or distillation), cold membrane processes (with low temperature permeation separation and low temperature separation or potassium carbonate chemical absorption processes) mainly use electricity as an energy source.

[0004] In order to avoid indirect emissions, it is desirable to use electricity from renewable sources which are inherently intermittent in most cases. This intermittency makes it necessary to enter into an energy purchase agreement which is oversized (compared to the average needs of the process) to minimize periods of renewable shortage.

[0005] An object of the invention is to provide energy storage in a carbon dioxide capture process involving the compression of a waste gas. The capture process may be adsorption, permeation, potassium carbonate separation or may involve several types of separation (for example those described above.)

[0006] It is generally known to store energy using batteries for short-term (and reduced power) storage.

[0007] Liquefied air storage (or LAES) is an alternative technology for long-term energy storage that is penalized by its efficiency, which is around 50% when there is no waste heat source available. This technology is described in "Storage of Electrical Energy using Supercritical Liquid Air" by E.M. Smith, Proc. Instn. Mech. Engrs. Vol. 191 27 / 77, 1977.

[0008] In carbon dioxide capture processes, for example by adsorption, permeation or absorption using potassium carbonate, two flows are produced: a low pressure flow enriched in CO2 and a high pressure flow depleted in CO2.

[0009] It is known from FR2497119A to expand the flow depleted in a component of a PSA, after heating, in a turbine to recover energy, by coupling the turbine to the compressor supplying the PSA. The amount of energy recovered by the turbine from the high-pressure flow depleted in CO2 is equivalent to between 50 and 70% of the energy that would be required to compress this flow in a centrifugal compressor (which is explained by irreversibilities during the compression stage and the expansion stage).

[0010] It is also possible to couple the turbine of the capture unit (PSA tail gas compressor or cycle compressor)

[0011] According to the invention, it is planned to use this CO2-depleted flow for an energy storage process, in order to improve the round trip efficiency (RTE) by at least 10%.

[0012] The use of this CO2-depleted flow as a liquid to be stored has particular advantages:

[0013] -its liquefaction temperature is lower than that of air.

[0014] According to the invention, a combined method of CO2 capture and energy storage is provided in which a. A residual gas containing between 10 and 45% mol CO2 on a dry basis, or even between 15 and 25% mol CO2 on a dry basis, and nitrogen is compressed to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs. b. The compressed residual gas is sent to a separation unit to separate it by adsorption and / or permeation and / or absorption producing a flow at a first pressure enriched in CO2 relative to the compressed residual gas and a flow at a second pressure lower than the first pressure depleted in CO2 containing less than 5 mol% CO2, preferably between 1 and 3 mol% CO2 and more than 80 mol% nitrogen, or even more than 90 mol% nitrogen and preferably at most 12 mol% oxygen c. The CO2-enriched flow is separated to produce a CO2-rich product, possibly by partial condensation and / or distillation and / or solidification and

[0015] i) During a first period

[0016] At least a portion of the CO2-depleted flow is liquefied in a liquefaction unit, where preferably only the at least a portion of the depleted flow is liquefied, and the at least a liquefied portion is stored in a thermally insulated storage in liquid form and

[0017] ii) During a second period

[0018] Liquid is withdrawn from storage, pressurized by pumping to a pressure greater than 100 bar abs, or even greater than 120 bar abs and at least part of the pressurized liquid is vaporized, heated and expanded in a turbine to produce mechanical and / or electrical energy, without having been sent to a combustion stage.

[0019] According to other optional aspects:

[0020] -the CO2-depleted flow is purified to reduce its CO2 content and possibly at least one other impurity likely to liquefy at the storage temperature, the purified flow is liquefied and stored at a cryogenic temperature.

[0021] -the CO2-depleted stream is washed at a temperature below 0°C to remove at least one component heavier than CO2, such as at least one NOx.

[0022] -the CO2-depleted flow is washed at a temperature below 0°C with liquid CO2, possibly produced by step c).

[0023] -compression heat from the compressor is used to heat the stored liquid from step e).

[0024] -the compressor compresses the waste gas with at least one adiabatic compression step.

[0025] -during the first period, no liquid is drawn from storage.

[0026] -during the second period, no portion of the CO2-depleted flow is used as a cycle fluid in a refrigeration cycle to liquefy a fluid and no portion of the depleted flow is liquefied.

[0027] -during the first period, electricity from a renewable source is sent to a motor of the compressor and during the second period, electricity from a non-renewable source is sent to a motor of the compressor.

[0028] -heat is transferred to the liquid to be vaporized through heat storage means, such as molten salts, gravels, quartz.

[0029] -heat from the waste gas upstream of the compressor is used to vaporize the stored liquid, for example by storing the heat during the first period and transferring it to the liquid to be vaporized during the second period.

[0030] -the CO2-depleted flow is at a pressure of at least 5 bar abs and at least another portion of the CO2-depleted flow is expanded in at least one turbine to liquefy the portion of the CO2-depleted flow from step i).

[0031] -at least a portion of the CO2-depleted flow is liquefied without having been compressed.

[0032] -the part of the flow depleted in CO2 is liquefied, preferably without having been compressed and another part of the flow depleted in CO2 is compressed in a compressor and expanded in at least one turbine.

[0033] - heat of compression of the compressor and / or of a compressor of the CO2-rich gaseous product and / or of a compressor of the CO2-enriched flow and / or of a compressor of a portion of the CO2-depleted flow is stored during the first period and transferred to the liquid to be vaporized during the second period.

[0034] -the compressed waste gas contains water and is dried upstream of the separation unit.

[0035] -heat generated by a source of the waste gas is used to vaporize the stored liquid, for example by storing this heat during the first period and transferring it to the liquid to be vaporized during the second period.

[0036] -the waste gas comes from a source which is a power plant, for example biomass.

[0037] According to another aspect of the invention, there is provided a combined CO2 capture and energy storage apparatus comprising a. A compressor for compressing a residual gas containing between 10 and 45% mol CO2 on a dry basis, or even between 15 and 25% mol CO2 on a dry basis, and nitrogen to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs b. A unit for separation by adsorption and / or permeation and / or absorption, a pipe for sending the compressed residual gas from the compressor to the separation unit to separate it by adsorption and / or permeation and / or absorption producing a flow at a first pressure enriched in CO2 relative to the compressed residual gas and a flow at a second pressure lower than the first pressure depleted in CO2 containing less than 5 mol% CO2, preferably between 1 and 3 mol% CO2 and more than 80 mol% nitrogen, or even more than 90 mol% nitrogen and preferably at most 12 mol% oxygen c. A second separation unit, possibly by partial condensation and / or distillation and / or solidification, a pipe for sending the CO2-enriched flow to the second separation unit to produce a CO2-rich product, and d. A liquefaction unit, a conduit for sending at least a portion of the CO2-depleted flow to liquefy in the liquefaction unit, and a thermally insulated storage for storing the at least a liquefied portion in liquid form, a conduit for withdrawing liquid from the storage, a pump for pressurizing the withdrawn liquid, a turbine, a heat exchanger, a conduit for sending the pressurized liquid from the pump to the heat exchanger to vaporize it, a conduit for sending the vaporized liquid to the turbine to expand to produce mechanical and / or electrical energy, without having been sent to a combustion stage and means for stopping the sending of liquid to the storage and for stopping the sending of liquid from the storage to the pump.

[0038] The invention will be described in more detail with reference to the figure where:

[0039] [Fig-1] represents a method according to the invention.

[0040] A waste gas 1 is produced by a cement plant, a lime manufacturing unit, a steel mill, a combustion, for example oxycombustion or another source, such as a power plant, for example a biomass power plant.

[0041] This waste gas may be generated at a relatively high temperature and the source of the waste gas may generate waste heat. It may therefore be necessary to cool the waste gas before compression and possibly before washing in a washing column, if present, upstream of compression.

[0042] The residual gas 1 containing between 10 and 45% mol CO2 on a dry basis, or even between 15 and 25% mol CO2 on a dry basis as well as nitrogen, is washed in the washing column Q with water and / or an alkaline liquid to reduce its NOx and / or SOx content producing condensates PC. Then the purified gas 3 is compressed in a compressor C, cooled in a cooler RI and then cooled by water in the coolers R2, R3 to condense the water W that it contains. This water W is partially eliminated in the separator S and then in the dryers D. The dried residual gas 5 is sent to a first CO2 PSA separation unit operating by adsorption and / or permeation and / or absorption.The unit operates for example by a Cryocap ® FG process using pressure swing adsorption or by a cold membrane process (with low temperature permeation separation as described in US8911535, US8734569 or US8617292) or by a potassium carbonate chemical absorption process.

[0043] It will be understood that the washing column Q and the dryers D are not necessarily present, for example only if the waste gas contains the compounds which they are intended to remove.

[0044] The CO2 PSA unit produces a CO2-enriched and nitrogen-depleted flow 7 relative to the treated residual gas 5 under a first pressure and a CO2-depleted and nitrogen-enriched flow 9 under a second pressure of at least 2 bar abs, preferably equal to at least 5 bar abs, lower than the first pressure, this CO2-depleted flow 9 containing less than 5 mol% CO2, preferably between 1 and 3 mol% CO2. The CO2-depleted flow contains between 3 and 12 mol% oxygen and between 83 and 96 mol% nitrogen.

[0045] The CO2-enriched flow is sent, possibly after compression, to a second separation unit CC, operating for example by partial condensation and / or distillation and / or solidification, producing a CO2-rich flow 11 in gaseous and / or liquid and / or solid form and a dry gas with a reduced CO2 content which is used to regenerate the dryers D, if these operate by adsorption. The gas 13 having recovered the water from the dryers D is sent downstream of the cooler RL

[0046] The CO2-depleted flow 9 is optionally purified in a purification unit I to remove impurities that it contains, for example at least part of the CO2 remaining, at least one hydrocarbon, at least one NOx.

[0047] On the other hand, it is possible to do without the purification unit if the PSA producing flow rate 9 is adjusted to stop CO2 and other impurities at very low levels.

[0048] Then, during a first period, at least a portion of the CO2-depleted flow 9 is liquefied in a liquefaction unit L and stored in a storage and thermally insulated in liquid form. In this case, the depleted flow 9 must be purified upstream to remove the remaining CO2 (residual content to be achieved of the order of a few ppm CO2) that it contains and any other component likely to solidify at the storage operating temperature which is a cryogenic temperature. The at least a portion of the CO2-depleted flow is at a pressure of at least 2 bar abs, preferably more than 5 bar abs. and a portion 9a of the flow 9 can be compressed in a compressor C1, cooled and then expanded in a turbine T1 to produce the frigories necessary for liquefaction.

[0049] Storage st can be under pressure (vacuum insulated) or at atmospheric pressure (flat bottom storage).

[0050] During a second period, liquid 15 is drawn from the storage st, pressurized by pumping in a pump P up to a pressure greater than 100 bars abs, or even greater than 120 bars abs and at least part of the pressurized liquid is vaporized, heated in the element CS and / or HS and expanded in a turbine T to produce mechanical and / or electrical energy.

[0051] The expansion turbine supplied by the heated gas 17 is a turbine expanding the heated gas 17 itself and does not expand the gas produced by a combustion chamber supplied by the heated gas 17.

[0052] The energy generated by the turbine T powered by the heated gas 17 can power the motor of a compressor of the device in the form of electricity. The electricity can otherwise be sent to the network or used on site.

[0053] The expanded gas V coming from the turbine T is sent to the air.

[0054] During the first period, electricity from a renewable source is sent to a motor of the compressor C and during the second period, electricity from a non-renewable source is sent to a motor of the compressor C. Preferably, during the first period, only electricity from a renewable source is sent to a motor of the compressor C. Preferably, during the second period, electricity from a non-renewable source is sent to a motor of the compressor C.

[0055] The heat for heating the storage liquid st during the second period may come from the compressor of the residual gas (flue gas), which may comprise at least one adiabatic stage and / or from a compressor of the gaseous CO2 produced by the second separation unit and / or from a compressor of the CO2-enriched flow intended for the second separation unit.

[0056] The heat for heating the liquid 15 of the storage st during the second period may come from the waste gas 3 upstream of the waste gas compressor and possibly upstream of the washing column or the source of the waste gas 1.

[0057] In any case, it is possible to store the heat coming from at least one of these sources during the first period and to send from the element CS, HS where the heat is stored to vaporize the liquid during the second period. To do this, it is recommended to use heat storage means, such as gravel beds, quartz CS or molten salts HS.

[0058] Preferably, during the first period, no liquid is withdrawn from the storage st.

[0059] Preferably, during the second period no part of the CO2-depleted flow 9 is liquefied.

[0060] In this second period, the depleted CO2 flow 9 can be recycled to be treated in the first CO2 PSA separation unit.

Claims

Claims

1. A combined CO2 capture and energy storage method wherein a. A residual gas (1) containing between 10 and 45% mol CO2 on a dry basis, or even between 15 and 25% mol CO2 on a dry basis, and nitrogen is compressed to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs. b. The compressed residual gas (5) is sent to a separation unit (CO2 PSA) to separate it by adsorption and / or permeation and / or absorption producing a flow (7) at a first pressure enriched in CO2 relative to the compressed residual gas and a flow (9) at a second pressure lower than the first pressure depleted in CO2 containing less than 5 mol% CO2, preferably between 1 and 3 mol% CO2 and more than 80 mol% nitrogen, or even more than 90 mol% nitrogen and preferably at most 12 mol% oxygen c. The CO2-enriched flow is separated to produce a CO2-rich product (11), possibly by partial condensation and / or distillation and / or solidification and i) During a first period At least a portion of the CO2-depleted flow (9) is liquefied in a liquefaction unit (L), where preferably only the at least a portion of the depleted flow is liquefied, and the at least a liquefied portion is stored in a thermally insulated storage (st) in liquid form and ii) During a second period Liquid (15) is withdrawn from storage, pressurized by pumping to a pressure greater than 100 bar abs, or even greater than 120 bar abs and at least a portion (17) of the pressurized liquid is vaporized, heated and expanded in a turbine (T) to produce mechanical and / or electrical energy, without having been sent to a combustion stage.

2. Method according to claim 1 in which the CO2-depleted flow (9) is purified (I) to reduce its CO2 content and possibly at least one other impurity capable of liquefying at the temperature of the storage, the purified flow is liquefied and stored at cryogenic temperature.

3. A method according to claim 1 or 2 wherein the CO2-depleted stream (1) is scrubbed (Q) at a temperature below 0°C to remove at least one component heavier than CO2, such as at least one NOx.

4. A method according to claim 3 wherein the CO2-depleted stream (9) is washed at a temperature below 0°C with liquid CO2, optionally produced by step c).

5. A method according to one of the preceding claims wherein compression heat from the compressor (c) is used to heat the stored liquid (15) from step e).

6. Method according to one of the preceding claims in which the compressor (C) compresses the waste gas (3) with at least one adiabatic compression step.

7. Method according to one of the preceding claims in which during the first period, no liquid is withdrawn from the storage (st).

8. A method according to any preceding claim wherein during the second period, no portion of the CO2-depleted flow (9a) is used as a cycle fluid in a refrigeration cycle to liquefy a fluid and no portion of the depleted flow (9) is liquefied.

9. Method according to one of the preceding claims in which during the first period, electricity from a renewable source is sent to a motor of the compressor (C) and during the second period, electricity from a non-renewable source is sent to a motor of the compressor.

10. Method according to one of the preceding claims in which heat is transferred to the liquid to be vaporized (15) through heat storage means (CS, HS), such as molten salts, gravels, quartz.

11. A method according to any preceding claim wherein heat from the waste gas upstream of the compressor (C) is used to vaporize the stored liquid (15), for example by storing the heat during the first period and transferring it to the liquid to be vaporized during the second period.

12. Method according to one of the preceding claims in which the CO2-depleted flow (9) is at a pressure of at least 5 bar abs and at least another part of the CO2-depleted flow is expanded in at least one turbine (Tl) to liquefy the part of the CO2-depleted flow from step i).

13. Method according to one of the preceding claims in which at least part of the CO2-depleted flow (9) is liquefied without having been compressed.

14. Method according to one of the preceding claims in which the part of the flow depleted in CO2 (9) is liquefied, preferably without having been compressed and another part of the flow depleted in CO2 is compressed in a compressor (Cl) and expanded in at least one turbine (Tl).

15. Method according to one of the preceding claims in which heat of compression of the compressor (C) and / or of a compressor of the gaseous product (11) rich in CO2 and / or of a compressor of the flow enriched in CO2 (7) and / or of a compressor (Cl) of a part of the flow depleted in CO2 (9) is stored during the first period and transferred to the liquid to be vaporized during the second period.

16. Method according to one of the preceding claims in which the compressed waste gas (3) contains water and is dried S, D) upstream of the separation unit (CO2 PSA).

17. A method according to any preceding claim wherein heat generated by a source of the waste gas (1) is used to vaporize the stored liquid, for example by storing this heat during the first period and transferring it to the liquid to be vaporized (15) during the second period.

18. Method according to one of the preceding claims in which the waste gas (1) comes from a source which is a power plant, for example biomass.

19. Combined CO2 capture and energy storage apparatus comprising a. A compressor (c) for compressing a waste gas (1) containing between 10 and 45 mol% CO2 on a dry basis, or even between 15 and 25 mol% CO2 on a dry basis, and nitrogen to a pressure greater than 2 bar abs, preferably greater than 5 bar abs or even greater than 7 bar abs b. An adsorption and / or permeation and / or absorption (CO2 PSA) separation unit, a conduit for sending the compressed waste gas from the compressor to the separation unit to separate it by adsorption and / or permeation and / or absorption producing a flow (7) at a first pressure enriched in CO2 relative to the compressed residual gas and a flow (9) at a second pressure lower than the first pressure depleted in CO2 containing less than 5 mol% CO2, preferably between 1 and 3 mol% CO2 and more than 80 mol% nitrogen, or even more than 90 mol% nitrogen and preferably at most 12 mol% oxygen c. A second separation unit (CC) possibly by partial condensation and / or distillation and / or solidification, a pipe for sending the CO2-enriched flow (7) to the second separation unit to produce a CO2-rich product, and d. A liquefaction unit (L), a pipe for sending at least a portion of the CO2-depleted flow (9) to liquefy in the liquefaction unit, and a thermally insulated storage (st) for storing the at least a liquefied portion in liquid form, a pipe for withdrawing liquid from the storage, a pump for pressurizing the withdrawn liquid, a turbine, a heat exchanger, a pipe for sending the pressurized liquid from the pump (p) to the heat exchanger (HS, CS) to vaporize it, a pipe for sending the vaporized liquid (17) to the turbine (T) to expand to produce mechanical and / or electrical energy, without having been sent to a combustion step and means for stopping the sending of liquid to the storage and for stopping the sending of liquid from the storage to the pump.

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