Method and system for co2 capture with separation via partial condensation and / or distillation and / or solidification

Abstract

The invention relates to a method for capturing CO2, wherein a stream (1) containing CO2 and at least one other component is separated by pressure swing adsorption (PSA), producing a fluid (5) enriched in CO2 at a first pressure and a fluid (3) depleted in CO2 at a second pressure, higher than the first pressure, wherein the CO2-enriched fluid is compressed in a compressor (C1), which generates compression heat and produces a compressed fluid at a pressure between 15 and 40 bar abs, wherein the compressed fluid is sent to a unit for separation via partial condensation, which produces a CO2-enriched flow, wherein the CO2-depleted fluid is expanded in two turbines (T1, T2) to produce an expanded fluid, and wherein the compression heat is used to heat the fluid upstream of each turbine.

Description

[0001] Method and apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification

[0002] 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.

[0003] Processes 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 preconcentration step. This step possibly includes compression, passage through an adsorption separation device, for example a PSA or a permeation separation device. The device generates a CO2-enriched fluid at a first pressure (called "Tail Gas") and a CO2-depleted fluid at a second pressure, higher than the first pressure. The CO2-depleted fluid is expanded to recover energy while the CO2-enriched fluid is compressed to be separated and purified by partial condensation and / or distillation and / or solidification.

[0004] The present invention relates to the integration of compression and expansion technologies possibly with heat recovery in a clever way.

[0005] State of the art

[0006] Machines with 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.

[0007] The integration of these machines into CO2 capture technologies is also documented. In this case, the compressor-braked expansion turbine includes a compressor part that compresses the fumes (downstream of a washing and filtration stage), driven at least partially by the machine's turbine on the product of a PSA.

[0008] FR2890575 shows in Figure 1 that it is known to drive the flue gas compressor intended for an adsorption device by a turbine which expands CO2-depleted gas produced by this adsorption device. The gas to be expanded is heated upstream of the expansion.

[0009] Problems solved by the invention

[0010] An aim of the invention is to mechanically and thermally integrate the compression of the tail gas of an adsorption unit and the expansion of the CO2-depleted gas produced by the adsorption unit, and used after expansion in an evaporative tower. This configuration imposes temperature levels to be respected and the invention proposes a clever integration making it possible to minimize the electrical power necessary to drive the compressor and which is not provided by the expansion of the CO2-depleted gas.

[0011] For mechanical coupling, the turbine(s) expanding the CO2-depleted gas are mechanically linked to the tail gas compressor. Depending on the pressure to be achieved at the compressor outlet, the power provided by expansion is less than that required for compression. An electric motor (or steam turbine) provides the missing power.

[0012] Heating the CO2-depleted gas before expanding it maximizes the energy recovered in the turbine(s). The higher the gas temperature, the greater the energy recovered. Furthermore, we want to achieve a temperature above 0°C at the expansion outlet but close to 0°C (typically below 10°C, preferably below 5°C): it must be above 0°C to avoid freezing the water in the tower but not too high to maximize the generation of cold in this tower. These constraints impose a temperature to be reached for the CO2-depleted gas before expansion depending on the pressure available before expansion (the pressure after expansion being close to atmospheric pressure). The higher the pressure, the higher the required temperature will be. For example, for a pressure of 8 bara, the required temperature is typically between 140°C and 190°C depending on the efficiency of the turbine.

[0013] The invention consists of recovering heat at the tail gas compressor: to do this, the water that cools the gas between the compression stages is heated by this same gas. This hot water can then reheat the CO2-depleted gas before expansion. However, the temperature reached at the compression stage outlet is typically between 80°C and 120°C, which is not sufficient compared to the constraints of expansion. One solution would have been to have successive compression stages without intermediate cooling, but this would significantly penalize the compressor's power consumption (because we are moving even further away from the ideal case of isothermal compression).The solution is therefore to double the turbines and introduce intermediate reheating: in this way, the temperature required to heat the gas is lower (typically between 70°C and 120°C), while respecting the same temperature constraints at the expansion outlet (between 0°C and 5°C). These lower temperatures can be achieved by heat recovery units placed between the compression stages. The intermediate pressure and temperature between the two turbines become parameters that can also be adjusted to respect the temperature constraints. This pressure is typically between 2.5 bara and 4.5 bara.

[0014] In this way, the two machines can be thermally integrated while respecting the constraints on the temperature of the CO2-depleted gas at the expansion outlet.

[0015] Heat recovery can be done by gas / gas heat exchangers but this has several disadvantages:

[0016] • Size of exchangers

[0017] • Control of compression stage inlet temperatures

[0018] • Management of excess heat

[0019] For these reasons, integration using an intermediate fluid is necessary (typically water or oil for example). This closed circuit allows the exchanger to be introduced upstream of a turbine which has several functions:

[0020] • It allows to minimize the temperature of the fluid arriving at the heat recovery unit which allows to minimize the power consumed by the compressor.

[0021] • It dissipates the excess heat produced by the compressor. Depending on the ratio between the power of the turbines and the power of the compressors, this excess can be more or less significant. This excess heat can then also be used by other heat consumers.

[0022] Depending on the amount of heat required by the turbines and the required temperature level, it is possible to adjust the number of heat recovery units, or even to have successive compression stages to generate more usable heat.

[0023] 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.

[0024] In addition, it is often considered to reheat the gas before expansion in the at least one turbine in order to avoid excessively cold temperatures at its outlet (above 0°C). The heat source initially considered is the flue gas compressor, via a hot water loop or via gas / gas exchangers (flue gas / 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, 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.

[0025] 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 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 flue gas compression (colder compression and more water to compress).

[0026] 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.

[0027] FR2890575 shows that it is known to drive the compressor of a CO2-enriched gas coming 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.

[0028] According to the invention, a closed circuit transfers compression heat from compressors to the turbines that drive these compressors.

[0029] For example, the configuration proposed in Figure 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), both fluids being at ambient temperature (approximately 5 to 35°C). 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. Transferring heat between the CO2-enriched gas compressors and the turbines that drive this compressor has several advantages.Indeed, since 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.

[0030] Other advantages of this configuration are:

[0031] • 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.

[0032] • 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.

[0033] • 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

[0034] According to an object of the invention, there is provided a method for capturing CO2 with separation 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 by permeation producing a fluid enriched in CO2 and depleted in the at least one other component compared to the flow at a first pressure and a fluid depleted in CO2 and enriched in the at least one other component compared 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 relative to the CO2-enriched fluid. iv) The CO2-depleted fluid is heated and expanded in at least two turbines to produce an expanded fluid, used as a product or source of cold or to cool water. 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, so that the at least one turbine as well as the motor and / or the other turbine drive the at least one compressor, vi) At least part of the heat of compression is used to heat the CO2-depleted fluid upstream of an expansion step in each turbine. vii) At least one heat exchanger recovers heat within the compressor.(viii) At least two heaters between expansion stages heat the fluid to be expanded. (ix) Heat is transferred from the at least one recovery heat exchanger to the at least two heaters via a closed circuit of intermediate fluid, for example water or oil and (x) The closed circuit includes means for dividing the intermediate fluid and sends a different flow rate of the intermediate fluid to each of the heaters upstream of each expansion stage and a different flow rate of the intermediate fluid to each of the coolers.

[0035] According to other optional aspects:

[0036] • a heat exchanger serves both as a heat exchanger to recover heat within the compressor and as a heater for the expansion fluid.

[0037] • the closed circuit includes means for dividing the intermediate fluid to send a flow of the intermediate fluid to each of the coolers.

[0038] • the closed circuit transfers heat to at least one heat consumer other than the turbine.

[0039] • 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 forming a gas enriched in the at least one component and a liquid enriched in CO2.

[0040] • the CO2-depleted fluid expanded in the at least two turbines is used to cool water.

[0041] • the CO2-depleted fluid expanded in the at least two turbines 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).

[0042] • the CO2-depleted fluid expanded in the two turbines is used to cool water in a water cooling tower by direct contact.

[0043] • the CO2-depleted fluid expanded in the two turbines used to cool the water is at a temperature equal to or less than 10°C but greater than 0°C.

[0044] • the CO2-depleted fluid expanded in the at least two turbines used to cool the water is at a temperature below 5°C. 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-modulated or permeation adsorption unit in which a flow containing CO2 and at least one other component, for example nitrogen, is separated, 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 partial condensation and / or distillation and / or solidification separation unit (CPU), means for sending the compressed fluid to the partial condensation and / or distillation and / or solidification separation unit to produce a CO2-enriched stream relative to the CO2-enriched fluid, means for heating the CO2-depleted fluid, at least two turbines, means for sending the heated CO2-depleted fluid to expand in the at least two turbines to produce an expanded fluid, serving as a product or for cooling water, the at least two turbines and also a motor 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 two turbines as well as the motor and / or the other turbine are capable of driving the at least one compressor, a heater upstream of each turbine,at least one heat exchanger connected to recover heat within the at least one compressor, a closed circuit of intermediate fluid, for example water or oil, the closed circuit comprising means for dividing the intermediate fluid and means for sending a different flow rate of the intermediate fluid to each of the heaters upstream of each turbine, the closed circuit being connected to transfer at least part of the heat of compression to heat the CO2-depleted fluid upstream of the expansion in each turbine.,

[0045] According to other optional aspects, the apparatus comprises:

[0046] • - means for cooling water and means for bringing the CO2-depleted fluid expanded in the at least two turbines to the means for cooling the water. • the means for cooling water are a direct contact water cooling tower.

[0047] • the means for cooling water are connected to cool the flow containing CO2 and at least one other component upstream of the pressure swing adsorption or permeation unit.

[0048] • means of adjusting the pressure of the expanded gas in a turbine in order to obtain a desired temperature at the turbine outlet.

[0049] • means of adjusting the temperature of the expanded gas in a turbine in order to obtain a desired temperature at the turbine outlet.

[0050] • the means for dividing the intermediate fluid are connected to send a different flow of the intermediate fluid to each of the coolers.

[0051] • According to another aspect of the invention, there is provided a method for capturing CO2 with separation 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 by permeation producing a fluid enriched in CO2 and depleted in the at least one other component compared to the flow at a first pressure and a fluid depleted in CO2 and enriched in the at least one other component compared 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 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, serving 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, so that the at least one turbine as well as the motor and / or the other turbine drive the at least one compressor. According to other optional features:,

[0052] • at least part of the compression heat is used to heat the CO2-depleted fluid upstream of an expansion stage in the turbine.

[0053] • the flow contains at most 40% mol of CO2.

[0054] • at least one heat exchanger recovers heat within the compressor.

[0055] • at least one heater upstream of the turbine or between expansion stages heats the fluid to be expanded.

[0056] • a heat exchanger serves both as a heat exchanger to recover heat within the compressor and as a heater for the expansion fluid.

[0057] • 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.

[0058] • 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.

[0059] • the closed circuit includes means for dividing the intermediate fluid to send a flow of the intermediate fluid to each of the coolers.

[0060] • the closed circuit transfers heat to at least one heat consumer other than the turbine.

[0061] • 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.

[0062] • 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.

[0063] • 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). 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.

[0064] 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 and a motor 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 and the motor and / or the other turbine are capable of driving the at least one compressor.,

[0065] The invention will be described in more detail with reference to the figures where: [FIG.1] represents a comparative method.

[0066] [FIG.2] represents another comparative process.

[0067] [FIG.3] represents a method according to the invention.

[0068] [FIG.4] represents another method according to the invention.

[0069] [FIG.1] represents a CO2 capture process with separation by partial condensation and / or distillation and / or solidification with pre-concentration of fumes containing at most 40% CO2 by pressure swing adsorption. Here fumes are described. The invention applies to any CO2 flow comprising at least one other lighter or heavier component.

[0070] 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 room temperature (approximately 5 to 35°C).

[0071] 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 T1. The expanded gas 3 may 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.

[0072] The heat of compression accumulated in cooler R is at least partially transferred to heater H. Cooler R and heater H can be formed by a single heat exchanger or alternatively a closed circuit of an intermediate fluid can perform the heat transfer. An engine M can provide energy for 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 compressor O1, a generator can produce electricity to be exported.

[0073] Otherwise the engine can be replaced by at least one other turbine, which expands a gas other than the CO2-depleted fluid 3.

[0074] [FIG. 2] differs from [FIG. 1] 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. [FIG. 3] is a variant of [FIG. 1] in which the compressor comprises four stages C1, C2, C3, C4 and the turbine comprises two expansion stages T1, T2.

[0075] 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.

[0076] Gas 5 is compressed in compression stages C1, C2 without cooling between them, cooled by cooler R1, compressed in stage C3, cooled by cooler R2, compressed in stage C4 and cooled in cooler R3 before being sent to separation by partial condensation and / or distillation and / or solidification.

[0077] 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 R1, R2, R2. The heated fluids are mixed and divided into three flows W4, W5, W6. The optional flow W6 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.

[0078] Thus the fluid circuit transfers at least part of the compression heat generated in C1, C2, C3, C4 to the turbine T1, T2. The gas expanded in the turbines T1, T2 in series is sent to a tower TR to cool CCW water sent to the top of the tower. Each expansion stage T1, T2 is preheated in the heaters H1, H2 by a different flow rate from the closed cycle in order to reach a temperature high enough not to freeze the water cooled in the tower T by the gas from the last of the turbines.

[0079] The intermediate pressure between the two turbines T1, T2 is a parameter that can also be adjusted to meet temperature constraints. This pressure is typically between 2.5 bara and 4.5 bara.

[0080] The fluid, for example water, which heats the heater H1 upstream of the turbine T1 causes the gas to expand to between 80°C and 100°C. Without the reheating upstream of the turbines T1, T2, the expanded gas leaving the second turbine would be between -50°C and -15°C, depending on the expansion ratio. By choosing the fluid flow rates, the temperature of the expanded gas in the second turbine can be set to be greater than 0°C and at most equal to 10°C, preferably less than 5°C.

[0081] Means of adjusting the pressure and / or temperature of the expanded gas in a turbine make it possible to obtain a desired temperature at the outlet of the turbine T2.

[0082] [FIG.4] represents another method according to the invention which is a more complete version of [FIG.3]. 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 C and cooled by the cooler R, corresponding to the compressors C1, C2, C3, C4 and coolers R1, R2, R3 of [FIG.3]. 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.

[0083] The CO2-depleted fluid 3 expanded in the at least one turbine T, for example two turbines T1, T2, see [FIG.3] can be used for a purpose other than that of [FIG.3]. Here it is used to cool water used to cool flow 1 (flue gas) containing CO2 and at least one other component, for example nitrogen, upstream of the separation by pressure swing adsorption (PSA) or by permeation (M 1 ). The heat exchange with the water and flow 1 can be direct or indirect and requires preheating of the gas to be expanded to avoid freezing the water. The cooled flow 1 containing CO2 is then dried in the dryer D and sent to the PSA or to the membrane M1 for separation.

Claims

Claims 1. Method for capturing CO2 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 (M1) producing a fluid (5) enriched in CO2 and depleted in the at least one other component relative to the flow (1) at a first pressure and a fluid (3) depleted in CO2 and enriched in the 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 (C1, C2, C3, C4) generating heat of compression and producing a compressed fluid at a pressure between 15 and 40 bar abs,or 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 two turbines (T 1 , T2) to produce an expanded fluid, serving as a product or source of cold or for cooling water v) The at least one compressor, the at least two turbines and 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 drive the at least one compressor, vi) at least part of the compression heat is used to heat the CO2-depleted fluid (3) upstream of an expansion step in each turbine (T 1 , T2), vii) at least one heat exchanger (R, R1, R2,R3) recovers heat within the compressor, viii) at least two heaters (H, H1, H2) between expansion stages (T1, T2) heat the fluid to be expanded (3), ix) heat is transferred from the at least one recovery heat exchanger (R, R1, R2, R3) to the at least two heaters (H, H1, H2) via a closed circuit of intermediate fluid (W), for example water or oil and x) the closed circuit comprises means for dividing the intermediate fluid (W) and sends a different flow rate (W4, W5, W6) of the intermediate fluid to each of the heaters (H1, H2) upstream of each expansion stage (T1, T2).

2. Method according to claim 1 in which a heat exchanger serves both as a heat exchanger (R, R1, R2, R3) to recover heat within the compressor and as a heater (H, H1, H2) of the expansion fluid.

3. Method according to claim 1 or 2 in which 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).

4. Method according to one of claims 1 to 3 in which the closed circuit (W, W6) transfers heat to at least one heat consumer (C) other than the turbine.

5. Method according to one of the preceding claims, in which the compressed fluid is compressed in the at least one compressor (C1, C1, 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) forming a gas enriched in the at least one component and a liquid enriched in CO2.

6. Method according to one of the preceding claims in which the CO2-depleted fluid (3) expanded in the at least two turbines (T1, T2) is used to cool water (CCW).

7. Method according to claim 6 - in which the CO2-depleted fluid (3) expanded in the at least two turbines (T 1 , 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 (M1), the flow containing cooled CO2 then being dried in a dryer (D) and sent to step i).

8. Method according to claim 6 wherein the CO2-depleted fluid (3) expanded in the at least two turbines (T1, T2) is used to cool water in a water cooling tower (TR) (CCW) by direct contact.

9.

9. Method according to one of claims 6 to 8 in which the CO2-depleted fluid (3) expanded in the at least two turbines (T 1 , T2) used to cool the water (CCW) is at a temperature equal to or less than 10°C but greater than 0°C.

10. Method according to claim 9 in which the CO2-depleted fluid (3) expanded in the at least two turbines (T 1 , T2) used to cool the water (CCW) is at a temperature below 5°C.

11. Apparatus for capturing CO2 with separation by partial condensation and / or distillation and / or solidification comprising a pressure swing adsorption (PSA) or permeation unit (M1) 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 two turbines (T1, T2), means for sending the heated CO2-depleted fluid to expand in the at least two turbines to produce an expanded fluid, serving as a product or for cooling water (CCW), the at least two turbines 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 two turbines as well as the motor and / or the other turbine are capable of driving the at least one compressor, a heater (H1, H2) upstream of each turbine, at least one heat exchanger (R, R1, R2, R3) connected to recover heat within the at least one compressor,a closed circuit of intermediate fluid (W), for example water or oil, the closed circuit comprising means for dividing the intermediate fluid (W) and means for sending a different flow rate (W4, W5, W6) of the intermediate fluid to each of the heaters (H1, H2) upstream of each turbine (T1, T2), the closed circuit being connected to transfer at least part of the heat, compression to heat the CO2-depleted fluid (3) upstream of the expansion in each turbine (T 1 , T2).

12. Apparatus according to claim 11 comprising means for cooling water and means for supplying the CO2-depleted fluid expanded in the at least two turbines to the means for cooling the water.

13. Apparatus according to claim 12 wherein the means for cooling water is a direct contact water cooling tower.

14. Apparatus according to claim 12 wherein the means for cooling water are connected to cool the flow containing CO2 and at least one other component upstream of the pressure swing adsorption (PSA) or permeation unit (M1).

15. Apparatus according to one of claims 11 to 14 comprising means for adjusting the pressure of the expanded gas in a turbine in order to obtain a desired temperature at the outlet of the turbine.

16. Apparatus according to one of claims 11 to 13 in which the means for dividing the intermediate fluid (W) are connected to send a different flow rate of the intermediate fluid (W1, W2, W3) to each of the coolers (R, R1, R2, R3).

Images