Method and apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification

Abstract

Title of the invention: Method and apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification In a method for capturing CO2, a flow (1) containing CO2 and at least one other component is separated by pressure swing adsorption (PSA) producing a CO2-enriched fluid (5) at a first pressure and a CO2-depleted fluid (3) at a second pressure, higher than the first pressure, the CO2-enriched fluid is compressed in a compressor (C1) generating heat of compression and producing a compressed fluid at a pressure between 15 and 40 bar abs, the compressed fluid is sent to a partial condensation separation unit which produces a CO2-enriched flow, the CO2-depleted fluid is expanded in a turbine (T1) to produce an expanded fluid, the compressor, the turbine and a motor (M) being mechanically connected in an integrated machine,so that the turbine as well as the engine drive the compressor. Abstract figure: Fig. 1,

Description

Title of the invention: Method and apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification

[0001] The present invention relates to a method for capturing CO2 with separation by partial condensation and / or distillation and / or solidification. It also relates to a start-up method for such a method and a CO2 capture apparatus.

[0002] Methods for capturing CO2 from flue gases with low CO2 contents, for example at most 40% CO2, by separation by partial condensation and / or distillation and / or solidification require the use of a flue gas pre-concentration step. This step optionally includes compression, passage through an adsorption separation apparatus, for example a PSA or a permeation separation apparatus. The apparatus generates a CO2-enriched fluid at a first pressure (called in English "Tail Gas") and a CO2-depleted fluid at a second pressure, higher than the first pressure. The CO2-depleted fluid is expanded in order to recover energy while the CO2-enriched fluid is compressed in order to be separated and purified by partial condensation and / or distillation and / or solidification.

[0003] The present invention relates to the integration of compression and expansion technologies possibly with heat recovery in a clever manner.

[0004] State of the art Machines having both at least one compression stage and at least one expansion stage are well established. These machines include, among other things, a machine comprising an engine and an expansion turbine braked by a compressor known in English as a "compander". These systems are used to compress and recover energy from gases generated by various processes, such as PTA applications. They are very efficient and can significantly reduce the energy consumption required for gas compression, resulting in significant cost savings.

[0006] The integration of these machines into CO2 capture technologies is also documented. In this case, the expansion turbine braked by a compressor comprises a compressor part which compresses the fumes (downstream of a washing and filtration stage), driven at least partially by the turbine of the machine on the product of a PSA.

[0007] FR2890575 shows in [Fig. 1] that it is known to drive the compressor of the fumes intended for an adsorption device by a turbine which expands depleted gas in CO2 produced by this adsorption device. The gas to be expanded is heated upstream of the expansion.

[0008] Problems solved by the invention

[0009] An aim of the invention is to achieve a pressure at the outlet of the tail gas compressor of an adsorption unit that is higher than what the turbine coupled to the compressor is capable of supplying in terms of energy. One solution is the use of a compressor on the tail gas of the adsorption unit partially driven by at least one turbine on the high-pressure gas of this same adsorption unit, the additional power being provided by an electric motor or a turbine expanding another fluid.

[0010] In addition, it is often considered to reheat the gas before its expansion in the at least one turbine in order to avoid excessively cold temperatures at its outlet. The heat source initially considered is the smoke compressor, via a hot water loop or via gas / gas exchangers (smoke / PSA product). The desired temperatures are typically in the order of 80°C to 130°C. If the flow rate treated by the at least one turbine is very different during the start-up stage or during operation at lower load while it is close to the nominal on the compressor side (>80% load to avoid pumping problems ("surge" in English), in this case there is an imbalance between the heat extracted from the compressor and the consumer that is the turbines.This heat must then be extracted by another means involving oversizing the hot water / cold water exchanger (coming from the cold water network) evacuating the excess heat from the hot water loop in normal operation.

[0011] In normal operation, the integration of heat on the expansion turbine braked by a compressor which compresses the fumes imposes constraints on the upstream system (washing). It is important not to cool the fumes too much before their compression in order to obtain the target hot water temperature (in the case of using a hot loop) or to obtain the target gas temperature (in the case of using gas / gas exchange). Since cooling before the compressor is often the consequence of climatic conditions, it is then necessary to limit it when the air temperatures are too low, thus depriving oneself of a potential gain on the energy of compressing the fumes (colder compression and more water to compress).

[0012] Furthermore, in the case of heat recovery from flue gas compression, the heat exchangers are large and made of high-quality materials (risk of corrosion due to humid flue gases and high temperatures). It should also be noted that heat recovery is negatively affected by the condensation of water from the flue gases.

[0013] FR2890575 shows that it is known to drive the compressor of a gas enriched in CO2 from an adsorption device by the turbine which expands CO2-depleted gas produced by this adsorption device. The gas to be expanded is heated upstream of the expansion.

[0014] For example, the configuration proposed in [Fig. 3] according to the present invention may consist of integrating the turbines on a CO2-depleted fluid at a second (high) pressure (approximately 5 to 15 bara) with the compressor treating the CO2-enriched fluid at a first (low) pressure (CO2-enriched gas at atmospheric pressure), the two fluids being at ambient temperature (approximately 5 to 35°C).

[0015] In this configuration, the start-up of the turbines can be completely independent of the start-up of the flue gas compressor, allowing the use of the compressed flue gas for the generation of fresh water (without passing through the turbines). In general, this configuration allows for better start-up sequencing; the units to be started are operational in the order of the process.

[0016] A secondary aim of the invention is to provide heat transfer between the CO2-enriched gas compressor and the at least one turbine that drives this compressor. Indeed, since the at least one turbine is started at the same time as the CO2-enriched gas compressor, the heat producers and consumers are operated simultaneously. In normal operation, heat can be transferred in the same way.

[0017] Other advantages of this configuration are: • Stability of operating parameters: the PSA temperature is relatively fixed (because it results from the temperature of the dryers), this induces stability of the temperature of the CO2-enriched gas and therefore of the temperature of the hot water recovered by the “compander” on the CO2-enriched gas. It is no longer necessary to degrade the operation of the scrubber upstream of the flue gas compressor, thus allowing significant savings in compression energy. • Use of standard materials: there is no risk of condensation, which allows the use of inexpensive materials for heat recovery units. • Better heat recovery: since the CO2-enriched gas is dry, water condensation no longer poses a problem during heat recovery. • Possibility of reaching high pressures and therefore improving the CO2 yield of partial condensation and / or distillation and / or solidification, without the use of an additional compressor with a dedicated motor

[0018] According to an object of the invention, there is provided a method for capturing CO2 with se- preparation by partial condensation and / or distillation and / or solidification in which: i. A flow containing CO2 and at least one other component, for example nitrogen, is separated by pressure swing adsorption or permeation producing a fluid enriched in CO2 and depleted in the at least one other component relative to the flow at a first pressure and a fluid depleted in CO2 and enriched in the at least one other component relative to the flow at a second pressure, higher than the first pressure ii. The CO2-enriched fluid is compressed in at least one compressor generating heat of compression and producing a compressed fluid at a pressure between 15 and 40 bar abs, or even between 20 and 30 bar abs iii. The compressed fluid is sent to a separation unit by partial condensation and / or distillation and / or solidification which produces a CO2-enriched stream compared to the CO2-enriched fluid iv. The CO2-depleted fluid is heated and expanded in at least one turbine to produce an expanded fluid, which serves as a product or source of cold for cooling water and v. The at least one compressor, the at least one turbine and a motor and / or another turbine expanding a fluid other than the CO2-depleted fluid being mechanically connected in an integrated machine, such that the at least one turbine as well as the motor and / or the other turbine drive the at least one compressor.

[0019] According to other optional features: • at least part of the compression heat is used to heat the CO2-depleted fluid upstream of an expansion stage in the turbine. • the flow contains at most 40% mol of CO2. • at least one heat exchanger recovers heat within the compressor. • at least one heater upstream of the turbine or between expansion stages heats the fluid to be expanded. • a heat exchanger serves both as a heat exchanger to recover heat within the compressor and as a heater for the expansion fluid. • heat is transferred from the at least one recovery heat exchanger to the at least one heater via a closed circuit of intermediate fluid, for example water or oil. • the closed circuit includes means for dividing the intermediate fluid to send a flow of the intermediate fluid to each of the heaters upstream of each expansion stage. • the closed circuit includes means for dividing the intermediate fluid to send an intermediate fluid flow to each of the coolers. • the closed circuit transfers heat to at least one heat consumer other than the turbine. • the compressed fluid is compressed in the at least one compressor in a booster to a pressure higher than that at which the flow leaves the at least one compressor, before separating the flow by partial condensation and / or distillation and / or solidification. • the compressed flow in the at least one compressor is compressed in a booster to a pressure higher than that at which the flow leaves the at least one compressor, before separating the flow by partial condensation forming a gas enriched in the at least one component and a liquid enriched in CO2. • the CO2-depleted fluid expanded in the turbine is used to cool water used to cool the flow containing CO2 and at least one other component, for example nitrogen, upstream of the separation by pressure swing adsorption or by permeation, the flow containing cooled CO2 then being dried in a dryer and sent to step i).

[0020] According to another object of the invention, there is provided a method for starting a CO2 capture process with separation by partial condensation and / or distillation and / or solidification as described above in which the compressor and the at least one turbine as well as the engine and / or the other turbine are started at the same time.

[0021] According to another object of the invention, there is provided a CO2 capture apparatus with separation by partial condensation and / or distillation and / or solidification comprising a pressure modulation or permeation adsorption unit in which a flow containing CO2 and at least one other component, for example nitrogen, is separated by producing a fluid enriched in CO2 and depleted in the at least one other component relative to the flow at a first pressure and a fluid depleted in CO2 and enriched in the at least one other component relative to the flow at a second pressure, higher than the first pressure, at least one compressor for compressing the CO2-enriched fluid generating heat of compression and producing a compressed fluid at a pressure between 15 and 40 bar abs, or even between 20 and 30 bar abs, a unit for separation by partial condensation and / or distillation and / or solidification,means for sending the compressed fluid to the separation unit by partial condensation and / or distillation and / or solidification to produce a CO2-enriched stream relative to the CO2-enriched fluid, means for heating the CO2-depleted fluid, at least one turbine, means for sending the heated CO2-depleted fluid to expand in the at least one turbine to produce an expanded fluid, serving as a product or for cooling water, the at least one turbine as well as a motor and / or a , another turbine expanding a fluid other than the CO2-depleted fluid being mechanically connected in an integrated machine, such that the at least one turbine as well as the engine and / or the other turbine are capable of driving the at least one compressor.

[0022] The invention will be described in more detail with reference to the figures where:

[0023] [Fig-1] represents a method according to the invention.

[0024] [Fig.2] represents another method according to the invention.

[0025] [Fig.3] represents another method according to the invention.

[0026] [Fig.4] represents another method according to the invention.

[0027] [Fig. 1] represents a process for capturing CO2 with separation by partial condensation and / or distillation and / or solidification with pre-concentration of fumes containing at most 40% of CO2 by pressure swing adsorption. Here fumes are described but it will be understood that the invention applies to any flow of CO2 comprising at least one other lighter or heavier component.

[0028] The fumes 1, possibly compressed in a compressor (not shown) and dried, are separated in the PSA adsorption unit forming a fluid 5 enriched in CO2 at a first pressure (called in English "Tail Gas") and a fluid 3 depleted in CO2 at a second pressure, higher than the first pressure. The second (high) pressure can be between approximately 5 and 15 bara), the first (low) pressure is atmospheric pressure), the two fluids 3, 5 being at ambient temperature (approximately 5 to 35°C).

[0029] The fluid 3 depleted in CO2 and depleted in the at least one other component, for example nitrogen, is heated by the heater H and then expanded in a turbine TL. The expanded gas 3 can be a product of the process. The CO2-enriched fluid 5 is compressed in a compressor C1 until, coupled to the turbine T1 and the engine M, forming a single machine with the compressor C1. The fluid leaves the compressor C1 at a third pressure P between 15 and 40 bar abs, or even between 20 and 30 bar abs. This gas is cooled in a cooler R, preferably compressed to a fourth pressure higher than the third pressure P in a booster (not shown) and then separated and purified by partial condensation and / or distillation and / or solidification. The partial condensation forms at least one gas enriched in the at least one component and at least one liquid enriched in CO2 in one or more stages.

[0030] The heat of compression accumulated in the cooler R is at least partially transferred to the heater H. The cooler R and the heater H can be constituted by a single heat exchanger or otherwise a closed circuit of an intermediate fluid can carry out the heat transfer. An engine M can provide energy for the compressor C1 if that generated by the turbine is not sufficient. On the contrary, if the energy generated by the turbine is greater than that required by the compressor C1, a generator can produce electricity to be exported.

[0031] Otherwise the engine can be replaced by at least one other turbine, which expands a gas other than the fluid depleted in CO2 3.

[0032] [Fig.2] differs from [Fig.l] in that the adsorption unit is replaced by a permeation unit whose permeate 3 is the CO2-depleted fluid and whose residue 5 is the CO2-enriched fluid.

[0033] [Fig.3] is a variant of [Fig.l] in which the compressor comprises four stages C1, C2, C3, C4 and the turbine comprises two expansion stages Tl, T2.

[0034] Gas 3 is reheated in heater H1, expanded in expansion step T1, reheated in heater H2, expanded in expansion step T2 and then forms a product of the process.

[0035] The gas 5 is compressed in the compression stages C1, C2 without cooling between them, cooled by the cooler R1, compressed in the stage C3, cooled by the cooler R2, compressed in the stage C4 and cooled in the cooler R3 before being sent to separation by partial condensation and / or distillation and / or solidification.

[0036] A closed circuit of intermediate fluid W, for example water or oil, is divided into three flows W1, W2, W3, each of which is sent to cool a cooler RI, R2, R2. The heated fluids are mixed and divided into three flows W4, W5, W6. The flow W6, optional, is sent to heat a heat consumer U independent of the process. The flows W4, W5 are each sent to one of the heaters H1, H2. The cooled flows W4, W5, W6 are mixed, cooled by a refrigerant flow CW, for example cooling water, and return to a pump P which circulates the fluid. The closed circuit obviously includes a fluid inlet to compensate for losses.

[0037] Thus the fluid circuit transfers at least part of the compression heat generated in C1, C2, C3, C4 to the turbine T1, T2.

[0038] [Fig.4] represents another method according to the invention which is a more complete version of [Fig.l]. Flue gases G are compressed in a compressor GC, dried in a dryer D and sent as gas 1 containing at most 40 mol% CO2 to the PSA. A partial condensation and / or distillation and / or solidification separation unit CPU is used to separate the gas 5 compressed in the compressor C1 and cooled by the cooler R. The partial condensation forms at least one gas enriched in the at least one component and at least one liquid enriched in CO2 in one or more stages.

[0039] The CO2-depleted fluid 3 expanded in the at least one turbine T1, T2 can be used to cool water used to cool the flow 1 (flue gases) containing CO2 and at least one other component, for example nitrogen, upstream of the separation by pressure swing adsorption (PSA) or by permeation (M1). The heat exchange with the water and the flow 1 can be direct or indirect. The cooled flow 1 containing CO2 is then dried in dryer D and sent to the PSA or membrane M1 for separation.

Claims

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2.

3. Claims CO2 capture process with separation by partial condensation and / or distillation and / or solidification in which: i. A flow (1) containing CO2 and at least one other component, for example nitrogen, is separated by pressure swing adsorption (PSA) or by permeation (Ml) producing a fluid (5) enriched in CO2 and depleted in at least one other component relative to the flow (1) at a first pressure and a fluid (3) depleted in CO2 and enriched in at least one other component relative to the flow (1) at a second pressure, higher than the first pressure ii. The CO2-enriched fluid is compressed in at least one compressor (Cl, C2, C3, C4) generating compression heat and producing a compressed fluid at a pressure between 15 and 40 bar abs, or even between 20 and 30 bar abs. iii. The compressed fluid is sent to a partial condensation and / or distillation and / or solidification separation unit (CPU) which produces a CO2-enriched stream compared to the CO2-enriched fluid iv. The CO2-depleted fluid is heated and expanded in at least one turbine (T1, T2) to produce an expanded fluid, used as a product or source of cold or to cool water and v. The at least one compressor, the at least one turbine and a motor (M) and / or another turbine expanding a fluid other than the CO2-depleted fluid being mechanically connected in an integrated machine, such that the at least one turbine as well as the motor and / or the other turbine drive the at least one compressor. Method according to claim 1 in which at least part of the compression heat is used to heat the CO2-depleted fluid (3) upstream of an expansion step in the turbine (T1, T2). Method according to one of the preceding claims in which at least one heat exchanger (R, RI, R2, R3) recovers heat within the compressor.

4. Method according to one of the preceding claims in which at least one heater (H, H1, H2) upstream of the turbine (T1, T2) or between expansion stages heats the fluid to be expanded (3).

5. Method according to claims 2, 3 and 4 in which a heat exchanger serves both as a heat exchanger (R, RI, R2, R3) to recover heat within the compressor and as a heater (H, Hl, H2) of the expansion fluid.

6. A method according to claim 2, 3 and 4 wherein heat is transferred from the at least one recovery heat exchanger (R, RI, R2, R3) to the at least one heater (H, Hl, H2) via a closed circuit of intermediate fluid (W), for example water or oil.

7. A method according to claim 6 wherein the closed circuit comprises means for dividing the intermediate fluid (W) to send a flow (W4, W5, W6) of the intermediate fluid to each of the heaters (H1, H2) upstream of each expansion stage (T1, T2).

8. A method according to claim 6 or 7 wherein the closed circuit comprises means for dividing the intermediate fluid to send a flow of the intermediate fluid (W1, W2, W3) to each of the coolers (R, R1, R2, R3).

9. Method according to one of claims 6 to 8 in which the closed circuit (W, W6) transfers heat to at least one heat consumer (C) other than the turbine.

10. Method according to one of the preceding claims in which the compressed fluid is compressed in the at least one compressor (Cl, Cl, C2, C3, C4) in a booster to a pressure higher than that at which the flow leaves the at least one compressor, before separating the flow by partial condensation and / or distillation and / or solidification (CPU).

11. Method according to claim 10 in which the compressed flow in the at least one compressor (Cl) is compressed in a booster to a pressure higher than that at which the flow leaves the at least one compressor, before separating the flow by partial condensation forming a gas enriched in the at least one component and a liquid enriched in CO2.

12. Method according to one of the preceding claims in which the CO2-depleted fluid (3) expanded in the at least one turbine (T1, T2) is used to cool water used to cool the flow (1) containing CO2 and at least one other component, for example nitrogen, upstream of the separation by pressure swing adsorption (PSA) or by permeation (Ml), the flow containing cooled CO2 then being dried in a dryer (D) and sent to step i).

13. Method for starting a CO2 capture process with separation by partial condensation and / or distillation and / or solidification according to one of the preceding claims in which the compressor (Cl) and the at least one turbine (Tl, T2) as well as the engine (M) and / or the other turbine are started at the same time.

14. Apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification comprising a pressure swing adsorption (PSA) or permeation unit (Ml) in which a flow containing CO2 and at least one other component, for example nitrogen, is separated, producing a fluid (5) enriched in CO2 and depleted in the at least one other component relative to the flow at a first pressure and a fluid (3) depleted in CO2 and enriched in the at least one other component relative to the flow at a second pressure, higher than the first pressure, at least one compressor (C1, C2, C3, C4) for compressing the CO2-enriched fluid generating heat of compression and producing a compressed fluid at a pressure between 15 and 40 bar abs, or even between 20 and 30 bar abs, a unit for separation by partial condensation and / or distillation and / or solidification (CPU),means for sending the compressed fluid to the separation unit by partial condensation and / or distillation and / or solidification to produce a CO2-enriched stream relative to the CO2-enriched fluid, means for heating the CO2-depleted fluid, at least one turbine (T1, T2), means for sending the heated CO2-depleted fluid to expand in the at least one turbine to produce an expanded fluid, serving as a product or for cooling water, the at least one turbine and also a motor (M) and / or another turbine expanding a fluid other than the CO2-depleted fluid being mechanically connected in an integrated machine, so that the at least one turbine as well as the motor and / or the other turbine are capable of driving the at least one compressor.,

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