Patent Application
20240001296
The invention relates to a method to capture CO2 from the flue gases emitted intermittently from a power plant burning a synthetic fuel in power-to-fuel-to-power systems. The method is characterized by arranging a reservoir of Ca(OH)2 to feed a flow of such solids to a countercurrent carbonator located in the flue gas path of the power plant, separating the resulting carbonated solids from the CO2 depleted-gas, storing the carbonated solids in a reservoir of CaCO3 while the power plant is operating, calcining a steady flow of carbonated solids to produce CaO solids and CO2 when the power plant is not operating, hydrating the resulting CaO solids with water to replenish the reservoir of Ca(OH)2 and feeding the CO2 to the power-to-fuel system to manufacture and store the synthetic fuel burned when the power plant is operating.
Climate change mitigation is calling for radical changes in the energy systems required to achieve full decarbonisation by 2050. It is generally accepted that future electricity networks aimed at a very high penetration of renewable sources with intermittent power output (wind, solar, etc.) will need some kind of back-up power systems to cover those periods where there is no sufficient power supply to match demand. Carbonaceous synthetic fuels manufactured from CO2 and renewable hydrogen and/or electricity, are regarded as major candidates to store vast quantities of renewable energy in chemical form. Therefore, there is a growing interest on power-to-fuel-to-power processes, where renewable energy and pure CO2 are first converted to a suitable synthetic fuel containing carbon (methane, methanol, Fisher-Tropsch liquids, etc.) during long “energy charge periods” when there is availability of low-cost renewable energy. The resulting synthetic fuel containing carbon can then be easily transported and/or stored at very low cost. Peaks of power can be then generated using this synthetic fuel, by air-firing it in turbines during brief power “discharge periods”, when such power back-up is needed in the electricity network. Power discharge periods can occupy far less than 20% of the total hours in a year. With such a low capacity factor, and to avoid waste of capital, only low cost or amortized power equipment can be used during the brief power discharge periods, even if this comes with a certain sacrifice in energy conversion efficiencies. For example, open gas turbines of natural gas, or existing natural gas combined cycles, are already being used to back-up power in many countries with a high share of renewables in the electricity network. During the air-fired power discharge periods, flue gases with diluted CO2 (2-10 vol % depending on the fuel and combustion conditions in turbines) are emitted to the atmosphere. Capturing such CO2 represents an unsolved technical challenge, because existing technologies for CO2 capture from such diluted CO2 streams need to be designed for the maximum flow rate of flue gases (i.e. those emitted during pick power production). Since such existing capture technologies are capital intensive, they would be un-economic for the low capacity factors inherent in the power-to-fuel-to-power system described above. Therefore, the lack of CO2 capture technologies for power-to-fuel-to-power processes introduces a fundamental environmental problem for these processes: even when the energy to transform CO2 into synthetic fuel (power-to-fuel) is fully renewable, the system re-emits the carbon contained in the fuel to the atmosphere as CO2 in the fuel-to-power part of the cycle. Making the power-to-fuel-to-power system carbon neutral would require the closing of such carbon loop. For example, by making the pure CO2 entering the power-to-fuel-to-power system come from renewable sources (i.e. captured directly from the atmosphere or from biogenic sources). For the case of direct CO2 capture from air, this is known to be energy inefficient and costly because of the very low concentration of CO2 in air (about 400 ppm) compared to the CO2 concentration in flue gases noted above. The use of biofuels as a source of carbon introduce additional environmental constrains (i.e. linked to known limitations on land use to grow biomass for energy purposes).
Relevant for the process is EP13382033, that discloses a flexible system of power generation integrating a flexible CO2 capture method using CaO as regenerable sorbent of CO2. The flexibility to adapt to a variable flue gas flows is achieved by using a high temperature silo of CaO, that supplies this material to the carbonator in order to match the flow of CO2 in the flue gas and form CaCO3. The resulting CaCO3 is stored in a low temperature silo, waiting for calcination in an oxy-fired calciner to generate a rich CO2 stream of gas. This is a gas with a CO2 concentration above 95% vol (dry) in similar oxy-combustion calcination systems, and it can be considered suitable for effective purification before CO2 compression for storage or use. By operating the calciner in steady state mode, it is possible to design the calciner smaller than what would be the case for a standard calcium looping system operating in steady state, thereby reducing the cost of the overall system when operating with low capacity factors (Criado et al., Calcium looping CO2 capture systems for back-up power plants. Energy & Environmental Science, 2017, 10, 1994-2004). However, the system of EP13382033 is designed with the objective to achieve the highest possible energy conversion efficiencies, by recovering energy from the high temperature solids in additional steam cycles. Also, the need for high temperature solid storage in these systems is likely to make technically more difficult the solid handling operations and therefore will increase the capital cost, because special equipment to store and handle those high temperature solids would be needed. Operating at lower temperatures would be also challenging because the particles of CaO are known to yield too modest carbonation conversions for practical purposes at temperatures below 600° C. (Criado et al. “Effect of carbonation temperature on the CO2 carrying capacity of CaO”. I&EC Research, 27, 12595-12599, 2018). The need for capital intensive equipment such as large-scale steam cycles and high temperature silos will increase the capital cost and would make this flexible capture solution non-competitive under very low capacity factors (0.05 to 0.2) expected in future greenfield power-to-fuel-to-power systems.
Also relevant is U.S. Pat. No. 9,610,537B2, where a carbonator reactor is disclosed that includes multiple cyclones reactors connected in a tower as to achieve a countercurrent gas-solid contact mode, with the solids increasing their carbonate conversion when moving down through the different cyclone reactors and the gas decreasing the CO2 content as it moves up through the different cyclone reactors. The operation of such device is similar to commercial suspension preheaters in cement plants, where the total residence time of the solids is known to be around 10 seconds per cyclone reactor, when operating with the fine particle size characteristics (i.e. dp<50 micron) of cement raw meals.
On the other hand, Ca(OH)2 particles are known to react much faster with CO2 in a wider temperature range between 300-700° C. Ca(OH)2 has been proposed as an alternative sorbent of CO2 in calcium looping systems. U.S. Pat. No. 8,512,661B2 presents the state of the art of this category of calcium looping processes for the efficient capture of CO2 and sulphur from combustion flue gas streams and gasification gas mixtures, using regenerable and recyclable Ca(OH)2 sorbents obtained by hydration of CaO at high temperatures. In particular, U.S. Pat. No. 8,512,661B2 discloses an advanced method of CO2 capture by integrating a carbonation-calcination process in a conventional coal fired power plant, comprising a carbonator to remove the CO2 from the flue gas by reacting it with Ca(OH)2; separating a gas-solid mixture from said carbonator to form a lean-CO2 flue gas and a carbonated solid stream; calcining said carbonated solid stream to form a concentrated CO2 stream and a calcined sorbent stream; directing said calcined sorbent stream to a hydrator fed with preheated steam; hydrating said sorbent stream in said hydrator to form hydrated solids containing Ca(OH)2; and directing said hydrated solids to said carbonator for the Ca(OH)2 to react with the flue gas at temperatures between 500 to 700° C. It must be noted however that the process of U.S. Pat. No. 8,512,661 B2 is not generally accepted as it is not free from technical constrains that can make it costly and energy inefficient: the lower enthalpy of carbonation of Ca(OH)2 (−74 kJ/mol) compared to CaO (−178 kJ/mol) reduces the possibilities to recover energy from carbonation and demand for high levels of energy recovery during hydration (inherently less energy efficient because hydration takes place at lower temperatures than carbonation). The high requirements of water for the hydration can also be a barrier depending on location. In general, these problems are exacerbated because the system is designed to operate in highly steady state mode, where the CO2 flow is steadily captured in the carbonator from the flue gases and steadily released in concentrated form from the calciner. This means that all the pieces of equipment in the system (carbonator, calciner, hydrator, energy recovery equipment, solid handling, etc.) must be dimensioned proportionally to the power output of the main plant. Therefore, as discussed above for other existing CO2 capture technologies, such an advanced calcium looping system, with all main pieces of equipment designed for the maximum power output of the power plant, will likely be un-economic for the low capacity factors characteristic of intermittently operated power-to-fuel-to-power systems, characterised by a low capacity factor (0.05 to 0.2) of all the equipment operated during the periods of maximum power output.
From the previous review of the state of the art, it can be concluded that there is an unsolved problem when it comes to have an energy cost-effective method for CO2 capture from the flue gases emitted intermittently from power-to-fuel-to-power plants. They generate their maximum power output intermittently during fuel-to-power modes and emit CO2 in flue gases that are currently unabated. They generate no flue gases during the power-to-fuel mode, and they require a steady flow of CO2 during such period. Ideally, the system would be carbon neutral if the carbon flow could be made to flow in circular mode by capturing the CO2 during the brief and intermittent stages of fuel-to-power and feeding the captured CO2 to the long power-to-fuel stages. To avoid waste of capital in such a system with such closed carbon loop, it would be beneficial to have a CO2 capture method requiring very low specific capital cost for the equipment that is used only during the brief periods of operation of the fuel-to-power plant, consistent with capacity factors of 0.05-0.2. In contrast, higher energy requirements and higher specific capital cost for the equipment could be allowed during the stages related to pure CO2 generation, when energy will be available at much lower cost and the capacity factors will take high values between 0.95 and 0.8.
The present invention discloses a novel and alternative solution for the closure of such carbon loop in power-to-fuel-to-power systems, by designing a flexible capture system that uses low cost Ca(OH)2 materials at suitable temperatures and conditions to maximise the CO2 capture efficiency while minimising the energy consumption and cost of the CO2 capture device that treats the flow of flue gases emitted during the fuel-to-power part of the cycle. The system is able to capture the CO2 from the flue gases emitted during the brief power discharge periods and supply it as a steady flow of pure CO2 to the power-to-fuel system. The method is especially designed to capture CO2 from the flue gas emitted from a turbine when burning with air a synthetic fuel containing carbon (methane, methanol, diethyl ether, Fisher-Tropsch liquids, etc.). The turbine will typically operate in the fuel-to-power part of a power-to-fuel-to-power system, conceived to provide energy storage service in future energy systems with high penetration of renewables.
Thus, a first aspect of the present invention is related to a method to capture CO2 from a flue gas (2) emitted intermittently by a fuel turbine (34) of a power-to-fuel-to-power system (100) when firing with air a carbonaceous synthetic fuel contained in a tank (33), comprising the following steps:
The advantages of the present invention is to capture CO2 from the flue gases emitted intermittently from power-to-fuel-to-power systems when operating in fuel-to-power mode (i.e. with low capacity factors between 0.05 and 0.2) and return the captured CO2 in pure form to the power-to-fuel system, thereby producing a carbon-neutral system, where the loop of carbon is closed. It is therefore critical in the process to use two large scale reservoirs of solids, one for Ca(OH)2 and one for CaCO3, because this is the way to effectively decouple the short duration CO2 capture step in a) and b) (characterised by a large molar flow of Ca(OH)2 matching the large molar flow of CO2 contained in the turbine flue gases) from the long periods of time available to carry out the steps c), d) and e), that correspond to periods of time where the turbine is not operating.
A further advantage of these two solid reservoirs is that they serve as stable and easy storage at large scale of the CO2 used in power-to-fuel-to-power energy storage systems with a closed carbon loop: the molar density of CaCO3 (25 kmol/m3) is very close to the molar density in cryogenic storage tanks of CO2. Also, due to the high enthalpy of calcination of CaCO3 (ΔH=+178 kJ/mol), the large-scale storage of CaCO3 allows for a more adequate use of the energy needed for the sorbent regeneration step, by operating in time periods when energy is more readily available for such energy demanding sorbent regeneration process. The oxy-calcination can thus take place when the energy cost is low (i.e. coinciding with the energy charging periods where power and CO2 are converted to fuel in the power-to-fuel-to-power system).
A further technical advantage introduced by the two reservoirs of Ca(OH)2 and CaCO3 refers to the possibility to use a small calciner (as well as all devices linked to the scale of the calciner such as the air separation unit and hydrator) compared to the scale of the carbonator, as the calciner treats gas and solid flows between 2 and 20 times lower than those in the carbonator.
Due to the low capacity factors for the capture devices and other equipment in a) and b), it is very important that such capture devices and equipment have very low specific capital cost and can adapt well to treat the gases directly at the flue gas conditions of the combustion turbine. Therefore, the process is best suited to treat flue gases at 550-700° C. from existing turbine, that are cooled down to a lower temperature (450° C.-550° C.) to exploit the benefits of operating the carbonator at said lower temperatures, overcoming equilibrium limitations for high CO2 capture efficiencies by carbonation. These low temperatures of carbonation will also facilitate the use of a simpler solid handling and simpler gas-solid separation equipment (i.e. bag filters).
Thus, a preferred embodiment of the method of the present invention provides the flue gas (2) from the fuel turbine at a temperature of between 550° C. and 700° C. is cooled down to a temperature of between 450° C. and 550° C. before entering the countercurrent carbonator (22).
Operating the countercarbonator at an optimum temperature of 450-550° C., for the equilibrium to allow a very high capture efficiency, while ensuring a fast carbonation reaction rate (i.e. a maximum carbonation conversion, Xmax, achieved in just 30 seconds of gas-solid contact time). Furthermore, such gas-solid contact time in the order of 30 seconds are achievable in a Ca(OH)2 carbonator involving three gas-solid cyclone separating stages, as it is the case in suspension preheaters of a cement plant or in CaO carbonators described in the state of the art. Therefore, it has been determined an operating window for the carbonation reaction of Ca(OH)2 to progress at sufficient rate and up to a sufficient maximum carbonation conversion that depends on carbonation temperature.
In a more preferred embodiment of the method, the process is adapted to a combined cycle power plant with a standard configuration of gas turbine and heat recovery steam generator (HRSG).
The term “heat recovery steam generators” as used herein refers to a system design to recover the heat from the flue gas leaving the fuel turbine to produce steam to generate power in a steam cycle.
A first section of the HRSG is used to cool the flue gases from the turbine to 450° C.-550° C. and then using a second section of the HRSG to recover energy from the flue gases leaving the carbonator at 450-550° C., wherein the equilibrium partial pressures of CO2 are as low as 0.0027 vol % and 0.075 vol %, respectively.
In another preferred embodiment of the present method the molar ratio between the large flow of Ca(OH)2 and the minor flow of CaCO3 is between 5 and 20. Thus, the system works as a back-up power system, with time fractions in fuel-to-power mode between 0.05 and 0.2, the capacity factors of the capture devices will also be between 0.05 and 0.2.
A further embodiment of the present invention provides the oxy-fired calciner (25) is supplied by renewable energy such us biomass, renewable electricity or a mixture of H2 and ½O2 from water hydrolysis from renewable electricity.
Regarding the closure of the overall carbon loop in the overall power-to-fuel-to-power carbon loop, some losses of carbon are unavoidable in such carbon loop as CO2 capture efficiencies over 90% in the carbonator would require uneconomically large reactors and other losses of carbon may be present in the power-to-fuel-to-power process. Therefore, a make-up flow of natural limestone, of between 1/10 and 1/20 of the total CaCO3 entering the calciner, is arranged to be fed to the oxy-fired calciner and to maintain the necessary flow of carbon between the power-to-fuel-to-power process and the capture system. This necessarily results in a purge of CaO from the overall system, that could be used in the lime or cement industry. Preferably, the purge of solid material can be in the form of Ca(OH)2 instead of CaO, so that the Ca(OH)2 can be safely disposed and recarbonated in contact with atmosphere. When CaCO3 is formed from purged Ca(OH)2 and CO2 from ambient air, it can be claimed that the overall system disclosed in this invention is carbon neutral.
Therefore, in another preferred embodiment of the method, between 1/10 and 1/20 of the Ca(OH)2 is purged and dispossed to recarbonate in contact with atmosphere.
In another preferred embodiment, when the synthetic fuel containing carbon manufactured in (32) is synthetic natural gas and the fuel turbine (34) firing such fuel is part of a natural gas combined cycle, a preferred embodiment of the method involves the feeding of the flue gas leaving the gas turbine (2) into a first heat exchanger section of the heat recovery steam generator (30) of a natural gas combined cycle to produce a cooled flue gas flow containing CO2 (16); feeding a large flow of Ca(OH)2 solids (1) from the first reservoir (21) with the cooled flue gas flow (16) to a countercurrent carbonator (22) forming CaCO3 containing solids (3); separating the CaCO3 containing solids (3) from the lean-CO2 flue gas (4) to store the solids in the second large reservoir of solids (24) and; feeding the lean CO2 flue gas (4) into a second heat exchanger section of the heat recovery steam generator (31) and release a low temperature lean CO2 flue gas (17) into the atmosphere.
In another preferred embodiment where such heat recovery steam generators are not available, as it is the case in back-up power plants using open cycle gas turbines, the cooling of the flue gas leaving the gas turbine (2) before contacting the Ca(OH)2 flow (1) takes place by mixing with the flue gas (2) with an air flow (18) at ambient temperature to produce the cooled flue gas flow stream (16) entering the carbonator (22). A compromise needs to be found for the addition of this cooling air: there is no benefit in cooling the flue gas below 450° C., where the equilibrium partial pressure of CO2 is already as low 0.0027 vol %, allowing theoretical capture efficiencies higher than 99%. Carbonation rates measured under these low temperatures remain very high but there are new experimental results indicating that maximum carbonation conversion of the solids will be lower. Therefore, a temperature window of operation of the carbonator between 450-550° C. seems to be a good compromise to ensure high capture efficiencies in very short gas-solid contact times and sufficient utilisation of the solids for carbonation.
In any of the preferred embodiments, leakage and inneficiencies, in particular in the CO2 absorption stages by carbonation of Ca(OH)2 taking place in (22), will demand for a make-up flow of carbon to the system. In the proposed methods, this is between 0.005 and 0.025 (defined as the ratio between the molar flow of CO2 entering with the make-up flow (12) and the molar flow of CO2 contained in the flue gas leaving the fuel turbine (2)) because this has to balance the capture efficiencies of the carbonator of around 90% and the brief periods of time at which the carbonator is operating (capacity factors between 0.05 and 0.2).
A second aspect of the invention is a system according to the method described before for capturing CO2 from a flue gas (2) emitted intermittently by a fuel turbine (34) when firing with air a carbonaceous synthetic fuel contained in a tank (33) characterized in that it comprises
In a preferred embodiment of the system it further comprises a heat recovery steam generator of a combined cycle (30) configured to cooling flue gases from the turbine (2) in a first section of said heat recovery (30) and configured to cooling the flue gases leaving the carbonator (4) in a second section of the same heat recovery steam generator (31).
In another preferred embodiment of the system it further comprises a means of supply configured to supplying the oxy-fired calciner (25) by renewable energy such us biomass, renewable electricity or a mixture of H2 and ½O2 from water hydrolysis from renewable electricity.
In another preferred embodiment of the system it further comprises a means of purge configured to purging between 1/10 and 1/20 of the Ca(OH)2 from the first reservoir (21).
In another preferred embodiment of the system it further comprises a first heat exchanger section of the heat recovery steam generator (30) configured to produce a cooled flue gas flow containing CO2 (16); feeding a large flow of Ca(OH)2 solids (1) from the first reservoir (21) with the cooled flue gas flow (16) to a countercurrent carbonator (22) forming CaCO3 containing solids (3); separating the CaCO3 containing solids (3) from the lean-CO2 flue gas (4) to store the solids in the second large reservoir of solids (24) and; feeding the lean CO2 flue gas (4) into a second heat exchanger section of the heat recovery steam generator (31) and release a low temperature lean CO2 flue gas (17) into the atmosphere, when the synthetic fuel containing carbon manufactured in (32) is synthetic natural gas and the fuel turbine (34) firing such fuel is part of a natural gas combined cycle.
In another preferred embodiment of the system it further comprises a means of cooling configured to achieve the mixing of the flue gas (2) with an air flow (18) at ambient temperature to produce the cooled flue gas flow stream (16) entering the carbonator (22). This preferred embodiment is useful when heat recovery steam generators are not available in the fuel-to-power part of the system, as it is the case in back-up power plants using open cycle gas turbines. The cooling of the flue gas leaving the gas turbine (2) before contacting of the Ca(OH)2 flow (1) takes place when mixing with the air flow (18) at ambient temperature.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of the present invention. Throughout the description and claims the word “comprise” and its variations are not intended to exclude other technical features, additives, components, or steps. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples, drawings and sequence listing are provided by way of illustration and are not intended to be limiting of the present invention.
The particular example of design of the method disclosed in this patent is presented below, with reference to the notation of
The countercurrent carbonator (22) is composed of three cyclone reactors. The CO2 capture efficiency in the countercurrent carbonator (22) is 0.95 and the CO2 volume fraction of the flue gas is reduced up to 0.002 before being emitted to the atmosphere. The sorbent conversion and the composition of the gas and solid streams leaving each cyclone reactor has been calculated by assuming an effective reaction time in each reactor cyclone of 4 seconds. The average concentration of CO2 between the inlet and the outlet of the individual cyclone reactors is found by iteration until the carbon mass balance is fulfilled (carbon disappeared from the gas phase must equal the carbonate formed in the solid phase). This can be done by calculating solid conversion using the Avrami equation, that has been fitted to the experimental data of
According to the data presented in
Consequently, cooling the flue gas below 450° C., where the equilibrium partial pressure of CO2 is already as low 0.0027 vol %, allows theoretical capture efficiencies higher than 99%. Carbonation rates measured under these low temperatures remain very high (
According to scheme depicted in
The flue gas discharged from the first cyclone reactor (36) at a temperature of 536° C. with a CO2 volume fraction of 0.0386 is mixed with a stream of solids coming from the third cyclone reactor (38) at a temperature of 577° C. and a carbonate content of 0.357 to react in the second cyclone reactor (37). After reacting, the partially carbonated solids are discharged from the second cyclone reactor (37) at a temperature of 552° C. with a carbonate conversion of 0.410.
The flue gas discharged from the second cyclone reactor (37) at a temperature of 552° C. with a CO2 volume fraction of 0.034 is mixed with a flow of Ca(OH)s solids (1) at 350° C. to react in the third cyclone reactor (38). After that, the flue gas leaving the third cyclone reactor (38) is cooled down in the second heat exchanger section of the heat recovery steam generator (31) to a temperature of 105° C., by extracting 73.6 MWth from the gases before being emitted to the atmosphere (17). This results in a leakage of just 0.009 kmol/s of CO2 into the atmosphere.
In order to regenerate the Ca(OH)2, a flow of CaCO3 containing solids (5) of 2.77 kg/s is fed from the second solid reservoir (24) into an oxy-fired calciner (25). Also, a flow of 0.10 kg/s of fresh limestone (12) at 20° C. is fed into the oxy-fired calciner (25) to compensate the CO2 leakage in the lean CO2 flue gas emitted to the atmosphere (17) during discharging periods and to close the carbon loop. In order to ensure a full calcination of the CaCO3, the oxy-fired calciner (25) operates at temperatures between 875-950° C. (the adiabatic heat balance in the calciner is closed at 910° C. for the conditions of this particular example). This results into a heat demand in the calciner of 8.1 MWth for calcining the CaCO3 and heating up the stream of solids entering the calciner (5 and 12). In this specific example, the heat demand is fulfilled by feeding a flow of fuel (10) of 0.06 kg H2/s and a flow of oxygen (11) of 0.46 kg O2/s. The gases and solids leaving the oxy-fired calciner (25) are separated in a second solids separation device (26) to produce a rich CO2 stream (14) and CaO solids (6). The rich CO2 stream (14) is sent to a purification unit (29) to produce a pure CO2 stream (7) of 0.021 kmol/s that is fed into the manufacturing plant of synthetic fuel (32). On the other hand, the CaO solids (6) are sent to a hydrator reactor (27) where they react with a stream of 0.43 kg/s of H2O (8) to produce 0.037 kmol/s of Ca(OH)2 at a temperature of 350° C. Then, a stream of Ca(OH)2 solids (9) of 0.047 kmol/s is diverted to the first reservoir (21) while a stream of Ca(OH)2 solids (13) of 0.001 kmol/s is sent for disposal.
In another particular configuration of this example, biomass can be used as fuel (10) to fulfil the heat demand in the oxy-fired calciner (25). This results into an input of carbon into the loop that avoids the need of feeding a make-up flow (12) of natural limestone into the system. For the case described above, there is a biomass with a calorific value of 20 MJ/kg, a carbon content of 50 wt % and an oxygen requirements of 1.5 kg O2/kg biomass, a flow of fuel (10) of 0.41 kg/s and a flow oxygen of 0.61 kg O2/s of oxygen (11) are fed into the oxy-fired calciner (25) to fulfil the heat demand. After separation in the second solids separation device (26), the rich CO2 stream (14) containing 0.036 kmolCO2/s is sent to a to a purification unit (29) to produce a pure CO2 stream (7) of 0.021 kmol/s that is fed into the manufacturing plant of synthetic fuel (32) and a second stream of pure CO2 (15) of 0.016 kmolCO2/s. There are other opportunities to reduce the heat demand in the oxy-fired calciner by preheating the stream of solids entering the reactor (5 and 12) using the rich-CO2 flue gas (14) and to increase the carbonator temperature by preheating of the Ca(OH)2 solids (1) using the flue gas (4) leaving the countercurrent carbonator reactor (22) are not discussed. It will be obvious for a skilled in the art to take benefit from these method alternatives.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20383113.6 | Dec 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/086120 | 12/16/2021 | WO |
