System for separating co2 from a co2-containing offgas

Abstract

System (1) for separating CO2 from a CO2-containing offgas (2) from an industrial plant (3), wherein the system (1) comprises an offgas recirculation circuit (4) connectable to the industrial plant (3), an ammonia synthesis plant (5), an air fractionation plant (6) for fractionating air into oxygen (7) and nitrogen (8), and a fertilizer production plant (9), wherein the offgas recirculation circuit (4) is designed to enrich a first portion (A1) of the offgas (2) with the oxygen (7) and feed it to the industrial plant (3), and to feed a second portion (A2) of the offgas (2) to the fertilizer production plant (9), and wherein the ammonia synthesis plant (5) is designed to synthesize ammonia (11) from the nitrogen (8) and hydrogen (10), and wherein the fertilizer production plant (9) is designed to produce plant fertilizer (12) from the CO2 present in the second portion (A2) of the offgas (2) and the ammonia (11).

Description

[0001] System for separating CO2 from a CCh-containing exhaust gas

[0002] The invention relates to a system for separating CO2 from a CCh-containing exhaust gas of a technical plant according to claim 1, and a method for separating CO2 from a CCh-containing exhaust gas of a technical plant according to claim 13.

[0003] Progressive global warming and climate change represent one of the greatest challenges worldwide. A key factor in this development is the emission of carbon dioxide from industrial processes and the combustion of fossil fuels. As recently as the 1980s, a comfortable climate prevailed with a carbon dioxide concentration of approximately 340–360 ppm in the atmosphere. However, this value has increased significantly in the following decades. Consequently, several agreements, such as the Kyoto Protocol and the Paris Agreement, have been ratified in recent decades, aiming to reduce global carbon dioxide emissions and thus counteract progressive climate change.From the Kyoto Protocol of 1997, which entered into force in 2005, to the Paris Climate Agreement – ​​COP 21 – where 195 countries in 2015 made a legally binding commitment to limit the global temperature increase to 1.5°C if possible, and in any case well below 2°C compared to the pre-industrial era, no reduction in global CO2 emissions was achieved by 2024; rather, the increase was merely reduced or stabilized. While improvements can be achieved through more efficient industrial processes and the conversion of building heating systems to renewable energy sources, for example, it is foreseeable that these activities alone will not lead to the necessary reductions in CO2 emissions required to achieve the global climate goals.Various mechanisms for CO2 capture are known in the art, generally referred to as "Carbon Capture and Storage" technologies, abbreviated CCS technologies. These involve extracting CO2 from the atmosphere or from the exhaust gas of a technical process and then injecting it, for example, under high pressure into rock. Particularly when used in industrial plants where natural gas is burned, extracted, or used, these methods can achieve CO2 neutrality, as the captured CO2 can be returned to the cavities from which the natural gas was extracted. If, in all existing natural gas fields, CO2 with a mass of 0.75 kg / m³ were used instead of the extracted natural gas... 3 CO2, which is approximately 2.6 times heavier with a mass of 1.977 kg / m³ 3 Even if stored and brought to the same volume, with the same pressure and temperature, this is not enough to stabilize the world's climate.

[0004] The reason for this is that burning 1 kg of natural gas with approximately 75% carbon produces 2.75 kg of CO2. Thus, burning natural gas produces roughly the same amount of CO2 as can be stored in the natural gas field from which the gas was originally extracted. However, to meet the climate goals of the Paris Agreement, the Intergovernmental Panel on Climate Change (IPCC) stipulates that only 420 gigatons of CO2 may be emitted by 2040, with emissions then set to reach zero. Currently, however, approximately 40 gigatons of CO2 are emitted annually, resulting in an increase in the carbon dioxide (C) concentration in the atmosphere of about 5 ppm per year. Consequently, from 2025 onwards, with a prevailing CO2 concentration of approximately 430 ppm per year, only about 28 gigatons of CO2 may be emitted annually, a reduction of approximately 30%. If the 2°C target is achieved in 2040, then the CO2 concentration in the atmosphere will reach approximately 480 ppm.According to IPCC model calculations, the concentration of carbon chlorine (CCh) in the atmosphere will decrease from 100% to 15%–40% within 1000 years. If this is the case, the CCh concentration of the 1980s will be reached in 166 to 345 years, i.e., between the years 2191 and 2370. Even if 100% of usable energy were to be generated from renewable sources by 2025, this would take 108 to 225 years, meaning that the CCh concentration in the atmosphere of the 1980s would not be reached until between 2133 and 2250.

[0005] One disadvantage of existing CO2 capture systems is that they are far too inefficient and, moreover, treat CO2 as a waste product, sometimes attempting to store it permanently at great energy expense. This results in high energy demand and, furthermore, the storage of CO2 necessitates further environmental interventions.

[0006] The aim of the present invention is to provide a system and a method for separating CO2 from a CCh-containing exhaust gas of a technical plant, which practically separates all of the CO2 and also significantly improves the removal of CO2 from the atmosphere.

[0007] This is achieved by a system according to the invention having the features of claim 1 and a method according to the invention having the features of claim 13.

[0008] The system according to the invention for separating CO2 from a CCh-containing exhaust gas of a technical plant comprises an exhaust gas recirculation circuit connectable to the technical plant. Furthermore, the system according to the invention comprises an ammonia synthesis plant, an air separation plant for separating air into oxygen and nitrogen, and a fertilizer production plant. The air separation plant is configured to supply the oxygen to the exhaust gas recirculation circuit and the nitrogen to the ammonia synthesis plant and, optionally, to other applications. Within the framework of the system according to the invention, the exhaust gas recirculation circuit is configured to enrich a first portion of the exhaust gas from the technical plant with oxygen supplied to the exhaust gas recirculation circuit by the air separation plant and to return this enriched portion to the technical plant.This process recycles the first portion of the exhaust gas, which can then be used as a substitute for air in the operation of the technical system. According to the invention, a second portion of the exhaust gas is fed into the fertilizer production plant.

[0009] The ammonia synthesis plant is also designed to synthesize ammonia from the nitrogen supplied by the air separation plant and the hydrogen supplied from the ammonia synthesis plant, and to supply this synthesized ammonia to the fertilizer production plant. The fertilizer production plant subsequently produces plant fertilizer, or nitrogen fertilizer, from at least the CO2 contained in the second part of the exhaust gas and the ammonia supplied by the ammonia synthesis plant.

[0010] This achieves the advantage that the system according to the invention avoids any CO2 emissions into the environment, and the CO2 does not need to be stored geologically using technical means and at high energy expenditure. Furthermore, the use of the plant fertilizer increases plant growth, thereby removing additional CO2 from the atmosphere. This further improves the overall CO2 emissions balance of the system according to the invention. The system according to the invention is also suitable for retrofitting to any existing technical plant, which can drastically improve the CO2 balance of existing plants. Moreover, the system according to the invention has no significant impact on the operation of the existing technical plant.In the case of application of the system according to the invention to newly constructed facilities, a further advantage of the system is that environmental impact assessment procedures are significantly simplified due to the reduced CO2 and pollutant emissions, and the duration of the assessment is shortened. Furthermore, the use of the plant fertilizer produced by the system according to the invention, for example in agriculture, results in additional plant growth, meaning that 20 to 30 times the amount of CO2 can be bound compared to conventional carbon capture and storage methods.

[0011] According to a preferred embodiment, the system according to the invention emits no CO2 and absolutely no air pollutants. Furthermore, any fuel used to operate the technical system is utilized more efficiently than is usual in the prior art. A major advantage of the system according to the invention lies in the production of plant fertilizer, specifically nitrogen fertilizer or synthetic fertilizer, which is produced at least from the CO2 and the added ammonia (NH3).

[0012] According to one embodiment of the system according to the invention, the fertilizer production plant is designed to produce plant fertilizer in the form of urea. Urea is produced from the CO2 contained in the second part of the exhaust gas and the ammonia supplied by the ammonia synthesis plant, and is a nitrogen fertilizer.

[0013] According to a preferred embodiment of the system according to the invention, the fertilizer production plant is configured to produce plant fertilizer from water contained in the second part of the exhaust gas and / or supplied to the fertilizer production plant, as well as from the CO2 contained in the second part of the exhaust gas and the ammonia supplied by the ammonia synthesis plant. The fertilizer production plant is preferably configured to produce plant fertilizer in the form of NH4HCO3. NH4HCO3, also known as ammonium bicarbonate, is particularly suitable for use as a nitrogen fertilizer. In this process, NH4HCO3 is produced by the fertilizer production plant from water contained in the second part of the exhaust gas and / or supplied to the fertilizer production plant, as well as from the CO2 contained in the second part of the exhaust gas and the ammonia supplied by the ammonia synthesis plant.

[0014] According to one embodiment of the system according to the invention, the second portion of the exhaust gas is split into CO2 and water before being fed into the fertilizer production plant. This is preferably done by condensing the water. This allows the amount of water supplied to the fertilizer production plant to be regulated. Preferably, water is either removed from or added to the second portion of the exhaust gas before it is fed into the fertilizer production plant.

[0015] Preferably, the technical plant is a production plant fueled by carbon-containing primary energy carriers, such as a thermal power plant, a cement plant, a pulp and paper plant, a chemical plant, or a steel plant. These types of plants emit particularly large quantities of CO2, making the use of the system according to the invention especially effective.

[0016] According to one embodiment of the system according to the invention, the first portion of the exhaust gas comprises 70–80% of the total exhaust gas from the technical plant. This allows the majority of the exhaust gas to be reused as process gas or nitrogen substitute for the technical plant, thus reducing CO2 emissions into the environment. The fertilizer production plant is preferably designed to produce plant fertilizer in the form of NH4HCO3. NH4HCO3, also known as ammonium bicarbonate, is a nitrogen fertilizer.

[0017] Preferably, the exhaust gas recirculation circuit includes at least one recirculating fan and / or a heat exchanger. This improves the energy efficiency of the system according to the invention.

[0018] According to the preferred embodiment of the system according to the invention, the system comprises the technical plant, wherein the technical plant is preferably a thermal power plant, and the ammonia synthesis plant and / or the air separation plant is supplied with electricity by the thermal power plant. This allows the ammonia synthesis to be carried out energy self-sufficiently.

[0019] In the inventive process for separating CO2 from CO2-containing exhaust gas of a technical plant, a first portion of the exhaust gas from the technical plant is enriched with oxygen supplied by an air separation plant in an exhaust gas recirculation circuit and preferably fed back to the technical plant as a substitute for air. A second portion of the exhaust gas from the technical plant is fed to a fertilizer production plant, and ammonia is synthesized by means of an ammonia synthesis plant from nitrogen supplied to the ammonia synthesis plant by the air separation plant and hydrogen supplied to the ammonia synthesis plant. This synthesized ammonia is fed to the fertilizer production plant, and plant fertilizer or nitrogen fertilizer is produced by means of the fertilizer production plant from at least the second portion of the exhaust gas and the ammonia supplied by the ammonia synthesis plant.

[0020] According to one embodiment of the inventive method, plant fertilizer or nitrogen fertilizer is produced by means of the fertilizer production plant from water contained in the second part of the exhaust gas and / or supplied to the fertilizer production plant, as well as from the CO2 contained in the second part of the exhaust gas and the ammonia supplied by the ammonia synthesis plant.

[0021] According to one embodiment of the inventive method, water is added to the second portion of the exhaust gas before it is fed into the fertilizer production plant. This improves the efficiency of fertilizer production.

[0022] Preferably, 70-80% of the total exhaust gas from the technical plant is fed into the exhaust gas recirculation loop as the first portion of the exhaust gas. This replaces the atmospheric carbon dioxide and makes a large part of the exhaust gas usable again as process gas for the technical plant, virtually reducing CO2 emissions to the environment.

[0023] According to one embodiment of the process according to the invention, plant fertilizer in the form of NH4HCO3 is produced in the fertilizer production plant. NH4HCO3, also known as ammonium bicarbonate, is particularly suitable for use as a nitrogen fertilizer.

[0024] According to a further embodiment of the inventive method, the fertilizer production plant produces plant fertilizer in the form of urea. Urea (CO(NH2)2) is a nitrogen fertilizer.

[0025] The system according to the invention, the method according to the invention, as well as alternative and preferred embodiments are explained in more detail below with reference to the figure.

[0026] Figure 1 shows a process diagram of a system and a method according to the invention.

[0027] The system 1 according to the invention for separating CO2 from a CCh-containing exhaust gas 2 of a technical plant 3 is shown in Figure 1. The technical plant 3 is shown in the lower left of Figure 1. The technical plant 3 generates the CCh-containing exhaust gas 2, for example, by the combustion of carbon-containing primary energy carriers CP such as natural gas, coal, biomass, and others. The technical plant 3 can thus be a production plant fueled with carbon-containing primary energy carriers CP, which produces a product P. This includes, for example, thermal power plants for electricity generation. However, the technical plant 3 can also be any other technical plant 3 in whose operation CCh-containing exhaust gas 2 is produced. Cement plants or steel plants are examples of such plants. Carbon-containing primary energy carriers CP can include, for example, coal, oils, gases, oil shale, fracked gas, biomass, charcoal, or mixtures thereof.Other technical installations 3 can be, for example, combined heat and power plants for heating, cooling, process heat, seawater desalination plants, plants in the chemical industry, glass industry, pulp and paper industry, plastics industry, petroleum industry, etc. Further technical installations 3 in the operation of which CO2-containing exhaust gas 2 is produced will be apparent to those skilled in the art from these exemplary references. The system 1 according to the invention, shown in Figure 1, comprises an exhaust gas recirculation circuit 4 connectable to the technical installation, an ammonia synthesis plant 5, an air separation plant 6 for separating air into oxygen 7 and nitrogen s, and a fertilizer production plant 9. According to an embodiment of the system 1 according to the invention, the system 1 can also comprise the technical installation 3 itself.

[0028] The exhaust gas recirculation circuit 4 is designed to enrich a first portion of the exhaust gas 2 from the technical plant 3 with oxygen 7 supplied to the exhaust gas recirculation circuit 4 from the air separation plant 6 and to supply it to the technical plant 3, and to supply a second portion of the exhaust gas 2 from the technical plant 3 to the fertilizer production plant 9. Preferably, the first portion of the exhaust gas comprises 70–80% of the total exhaust gas 2 from the technical plant 3. This achieves a particularly high recirculation of the exhaust gas 2, and no nitrogen 8 is required for the operation of the technical plant 3. This makes more nitrogen 8 available for the operation of the remaining components of the system 1 according to the invention, in particular for the ammonia synthesis plant 5.The ammonia synthesis plant 5 is designed to synthesize ammonia 11 from the required nitrogen 8 supplied to the ammonia synthesis plant 5 by the air separation plant 6 and the hydrogen 10 supplied to the ammonia synthesis plant 5, and to supply it to the fertilizer production plant 9. The fertilizer production plant 9 of the inventive system 1 is also designed to produce plant fertilizer 12, at least from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0029] If the technical plant 3 is designed as a thermal power plant, in an advantageous embodiment the ammonia synthesis plant 5 can be supplied with electricity from the thermal power plant with lower losses and at a lower cost. Alternatively and / or additionally, the air separation plant 6 can also be supplied with electricity from the thermal power plant with lower losses and at a lower cost. This allows the system according to the invention to operate energy-autonomously. In addition, in the event of an overproduction of the very pure nitrogen 8, the nitrogen can be diverted from system 1 and supplied to a nitrogen utilization plant NA. Preferably, the fertilizer production plant 9 is designed to produce plant fertilizer 12 or nitrogen fertilizer in the form of urea. Here, the urea is preferably produced by the fertilizer production plant 9 from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5.This process produces water, which should preferably be drained away.

[0030] Preferably, the fertilizer production plant 9 of the system 1 according to the invention is configured to produce plant fertilizer 12 or nitrogen fertilizer from water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5. To provide the hydrogen 10, the system 1 according to the invention can additionally include a hydrogen production plant 12. Hydrogen 10 can be produced, for example, by electrolysis, thermolysis, pyrolysis, from waste wood, refuse, and other processes known to those skilled in the art. Within the framework of the system 1 according to the invention, the fertilizer production plant 9 is configured to produce plant fertilizer 12 or nitrogen fertilizer from the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0031] As shown in Figure 1, the second fraction A2 of the exhaust gas 2 can be split into CO2 and water 14 before being fed into the fertilizer production plant 9. This can be done in an exhaust gas conditioning plant 16. This results in a stream 15 of CO2 and water 14, preferably liquid water 14, that is essentially purified of water 14 or water vapor. This allows for precise preconditioning. Furthermore, as also shown in Figure 1, water 14 can be added to the second fraction A2 of the exhaust gas 2 before it is fed into the fertilizer production plant 9. This is indicated by a small arrow in Figure 1. This has the advantage that the amount of water 14 relative to CO2 supplied to the fertilizer production plant 9 can be precisely controlled. Preferably, the water 14 is added in liquid form.Any addition of water to the second component A2 of the exhaust gas 2 can also be carried out via the exhaust gas conditioning system 16. If the technical system 3 uses a carbon-containing primary energy carrier, the amount of water 14 present in the exhaust gas 2 of the technical system depends on the proportion of hydrogen in the carbon-containing primary energy carrier and its water content.

[0032] According to one embodiment of the system 1 according to the invention, the fertilizer production plant 9 is configured to produce plant fertilizer in the form of NH4HCO3. NH4HCO3, also known as ammonium bicarbonate, baking soda, or ammonium carbonate, can be used as a nitrogen fertilizer for plants. The plant fertilizer 12 is produced by the fertilizer production plant 9 preferably from water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2, and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0033] According to an embodiment of the system 1 according to the invention, the fertilizer production plant 9 is designed to produce urea (CO(NH2)2) from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5, and / or to produce NH4HCO3 from water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0034] According to an advantageous embodiment of the system 1 according to the invention, the exhaust gas recirculation circuit 4 has at least one recirculating fan 17 and / or a heat exchanger 18. Furthermore, another recirculating fan 17 can also be provided in the stream 15 containing CO2 that is essentially purified of water 14 or water vapor. The pressure is preferably increased to approximately 1 bar by means of the recirculating fan 17. A heat exchanger 18 can also be provided in the channel for the water 14 separated from the second fraction A2 of the exhaust gas 2, and / or upstream or downstream of the recirculating fan 17 in the stream 15. A further heat exchanger 18 can be arranged to increase the temperature of the oxygen 7 before it is introduced into the exhaust gas recirculation circuit 4. In addition, a heat exchanger 18 can be provided for preconditioning the carbon-containing primary energy carriers CP.Within the framework of the system 1 according to the invention, coolers 19 can also be provided to cool the nitrogen 8 before it is fed to the ammonia synthesis plant 5, and / or to cool the water 14 and / or the stream 15 of CO2 before it is fed to the fertilizer production plant 9. The coolers 19 and / or the heat exchangers 18 can improve the overall energy balance of the system 1 according to the invention by using the waste heat, for example, for preconditioning the carbon-containing primary energy carriers CP. According to a further embodiment, the second component A2 of the exhaust gas 2 can also be passed through an exhaust gas cleaning system (not shown in Figure 1) before being fed to the fertilizer production plant. The exhaust gas cleaning system is preferably designed to remove impurities such as argon, nitrogen, etc., from the second component A2 of the exhaust gas 2. This can improve the quality of the produced plant fertilizer.

[0035] The system 1 according to the invention can additionally comprise a buffer storage tank not shown in Figure 1, wherein the second portion A2 of the exhaust gas 2 is temporarily stored, preferably at least partially, in the buffer storage tank before being fed to the fertilizer production plant 9. Furthermore, the system 1 according to the invention can additionally or alternatively comprise a carbon capture and storage tank not shown in Figure 1, wherein the second portion A2 of the exhaust gas 2 is preferably temporarily stored, at least partially, in the capture and storage tank before being fed to the fertilizer production plant 9.

[0036] The inventive process for separating CO2 from a CCh-containing exhaust gas 2 of a technical plant 3 is preferably carried out using the system 1 described above. Here, the first portion Al of the exhaust gas 2 from the technical plant 3 is enriched with oxygen 7 provided by the air separation plant 6 in the exhaust gas recirculation circuit 4 and fed to the technical plant 3. The second portion A2 of the exhaust gas 2 from the technical plant 3 is fed to the fertilizer production plant 9. Using the ammonia synthesis plant 5, ammonia 11 is synthesized from nitrogen 8 provided by the air separation plant 9 and hydrogen 10 supplied to the ammonia synthesis plant 5. This synthesized ammonia 11 is fed to the fertilizer production plant 9. By means of the fertilizer production plant 9, at least from the CO2 contained in the second part A2 of the exhaust gas 2, and the ammonia 11 supplied by the ammonia synthesis plant 5, plant fertilizer 12 is produced.Preferably, the fertilizer production plant 9 produces plant fertilizer 12 in the form of urea. In this process, the plant fertilizer 12 in the form of urea is preferably produced by the fertilizer production plant 9 from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied to the fertilizer production plant 9 by the ammonia synthesis plant 5. Water is produced in this process, which is preferably removed.

[0037] Preferably, fertilizer 12 is produced by means of the fertilizer production plant 9 from the water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2, and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0038] Preferably, in the exhaust gas recirculation circuit 4, the first portion Al of the exhaust gas 2 of the technical system 3 is cooled to a temperature above the condensation temperature of the water, preferably < 90°C, so that the water remains in vapor form before it is brought to the required combustion chamber pressure of, for example, a few hundred 100 bar in the subsequent compressor 17 and then preheated again to, for example, 300 to 400°C, for example, in a heat exchanger not explicitly shown in Figure 1.

[0039] According to one embodiment of the system 1 according to the invention, the second portion A2 of the exhaust gas 2 is cooled in the heat exchanger 16 to such an extent that the water 14 condenses and is discharged in liquid form. The pressure drops to 0.3 to 0.4 bar. As a result, the CO2 is essentially pure and contains essentially only the trace gases N2, O2, Ar, etc. Thus, a stream 15 of CO2 and water 14, essentially purified of water 14 or water vapor, is present. Preferably, the pressure of the stream 15 is increased again to approximately 1 bar by the compressor 17, whereby the temperature rises to over 100°C. The heat exchanger 18 raises the temperature to the level required for the fertilizer converter.

[0040] In the production of NH4HCO3, the stoichiometric amount of water required according to the amount of CO2 is preferably supplied to the fertilizer production plant 9. However, depending on the fuel used, water can also be discharged from the technical plant 3. In the case of ammonium nitrate production, preferably twice the amount of ammonia per kg of CO2 is required as with baking powder or NH4HCO3. In this case, preferably no water is required; instead, water is produced according to CO2 + 2 NFF -> CO(NH2)2 + H2O.

[0041] According to one embodiment of the process according to the invention, water 14 is added to the second fraction A2 of the exhaust gas 2 before it is fed to the fertilizer production plant 9. Preferably, 70-80% of the total exhaust gas 2 from the technical plant 3 is fed to the exhaust gas recirculation circuit 4 as the first fraction Al of the exhaust gas 2. This allows the majority of the exhaust gas 2 to be reused as process gas or air substitute for the technical plant 3, and further reduces the release of CO2 into the environment. According to one embodiment of the process according to the invention, plant fertilizer 12 or nitrogen fertilizer in the form of NH4HCO3 is produced in the fertilizer production plant 9. NH4HCO3, also known as ammonium bicarbonate, is a nitrogen fertilizer.Preferably, in the fertilizer production plant 9 NH4HCO3, plant fertilizer 12 or nitrogen fertilizer is produced from the water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2, and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0042] According to one embodiment of the process according to the invention, urea is produced in the fertilizer production plant 9 from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5 and / or from water contained in the second part A2 of the exhaust gas 2 and / or supplied to the fertilizer production plant 9, as well as from the CO2 contained in the second part A2 of the exhaust gas 2 and the ammonia 11 supplied by the ammonia synthesis plant 5.

[0043] The system 1 according to the invention preferably emits practically no air pollutants and no CO2 and has a better fuel efficiency. According to a preferred embodiment of the system 1 according to the invention, the oxidation of a fuel containing C, H2, and H2O produces an exhaust gas 2 with a high H2O and CO2 content. According to one embodiment of the system and the process according to the invention, CO2 and H2O, together with NH3, are produced from this exhaust gas by cooling and condensation in the plant fertilizer 12 NH4HCO3, which is also known as baking soda, ammonium carbonate, or teschemacherite. The trace gases SO2 and NO are also produced. xA plant fertilizer 12 can also be produced from P₂O₅ with H₂O and NH₃, thus eliminating the need for REA and DENOX plants. According to a preferred embodiment, plant fertilizer 12 can also be produced from SO₂, NO, NO₂, and / or P₂O₅ contained in the exhaust gas 2. Although the plant fertilizer 12 produced from NO₂ is explosive, the amount produced is so small due to the low N₂ content (1–3% instead of >70% N₂) of the oxidizing agent and the low combustion chamber temperature that the nitrogen fertilizer is harmless. Preferably, the amount of plant fertilizer 12 produced per MWh of fuel heat is almost independent of the type of fuel in the case of thermal combustion in the technical plant 3.With the help of relatively small quantities of plant fertilizer 12, significant additional amounts of biomass grow when it is used. This biomass removes as much CO2 from the atmosphere as 20 to 30 similar technical plants 3 would emit, even taking into account N2O emissions and the fact that 100% of the CO2 from the nitrogen fertilizer is emitted into the atmosphere if these plants were not equipped with the system 1 according to the invention. The amount of CO2 removed from the atmosphere is therefore highly dependent on the type of fertilized biomass, the soil quality, and the climate. If a disused steam power plant with a capacity of approximately 250 MW is equipped with a system 1 according to the invention and then put back into operation—whether using gas, oil, coal, or other carbon-containing fuels as primary energy sources—a country the size of Austria could be made CO2-free by 2030, provided it meets the COP21 targets.If we do not meet the COP21 requirements, a power plant capacity of approximately 500MW is needed.

[0044] The dimensions of the air separation plant 6 are preferably determined based on the type of fuel and its heat output, the purity of the O2, and the excess O2 required for complete combustion. The very pure N2 produced in the air separation plant 6 can be used primarily, but not predominantly, for NH3 production and sold on the market depending on the prevailing conditions. Any unused N2 can be used to cool H2O condensate before it is heated to the permissible temperature and released into the atmosphere. The O2 from the air separation plant 6 can preferably be used to cool the H2O condensate and is preferably brought to the desired temperature before oxidation by means of a heat exchanger system.

[0045] In the oxidation chamber of a combustion process within the technical system, O2 is preferably mixed with recirculated exhaust gas as a substitute for air. Particularly in existing primary systems, it is important to note that CO2 and H2O are more radiant than N2, meaning that a lower combustion chamber temperature is sufficient for the same heat output. The temperature in the oxidation chamber and the amount of recirculated exhaust gas allow for some degree of design flexibility, depending on the system's construction.

[0046] The processing of carbon-containing materials depends heavily on the type, consistency, and varying environmental conditions, according to one implementation variant. The aim is to achieve rapid and complete oxidation and to improve the utilization of low-temperature heat by introducing it into the oxidation chamber. Generally, oxygen ingress is achieved by increasing the surface area, and the reaction rate is increased by raising the material temperature, although safety aspects such as spontaneous combustion must be considered. For liquid fuels, it is preferable to improve pumpability and atomization by increasing the temperature. For gaseous fuels, the preferred objective is to generate the oxidation chamber pressure and to heat the primary energy carrier. When drawing natural gas from the high-pressure network, the condensation heat of the exhaust gas (< 90°C) can be converted into electrical energy with almost 100% efficiency.

[0047] The exhaust gas 2 produced during the oxidation of a carbon-containing primary energy carrier can be recycled using the system 1 according to the invention, depending on the temperature of the oxidation components and the desired temperature in the oxidation chamber. Exhaust gas temperatures above or below 300°C are typical at the exit of the technical system 3. Since the outlet pressure is lower than the inlet pressure to the technical system 3, a compressor can be used. Under typical conditions, it can be advantageous to cool the exhaust gas 2 to reduce the compressor power requirement. The heat extracted from the exhaust gas 2 can be used in the process, for district heating, for seawater desalination, or within the process according to the invention itself, or can be used to a large extent for reheating the first portion of the exhaust gas 2. Preferably, the exhaust gas 2 released from the oxidation is cooled to such an extent that the H₂O it contains condenses.This is usually done at slightly below 90°C. Preferably, the components NH3, H2O, CO2, but also the trace gases SO2, NO, can be used. X , P2O5 in the fertilizer production plant 9 in an exothermic process preferably at temperatures below 38°C the plant fertilizer 12 or nitrogen fertilizer is produced.

Claims

Patent claims:

1. System (1) for separating CO2 from a CCh-containing exhaust gas (2) of a technical plant (3), wherein the system (1) comprises an exhaust gas recirculation circuit (4) connectable to the technical plant (3), an ammonia synthesis plant (5), an air separation plant (6) for separating air into oxygen (7) and nitrogen (8), and a fertilizer production plant (9), wherein the air separation plant (6) is configured to supply the oxygen (7) to the exhaust gas recirculation circuit (4) and the nitrogen (8) to the ammonia synthesis plant (5), and wherein the exhaust gas recirculation circuit (4) is configured to enrich a first fraction (Al) of the exhaust gas (2) with the oxygen (7) supplied by the air separation plant (6) and supply it to the technical plant (3), and to supply a second fraction (A2) of the exhaust gas (2) to the fertilizer production plant (9), wherein the ammonia synthesis plant (5) is trained toto synthesize ammonia (11) from the nitrogen (8) supplied by the air separation plant (6) and the hydrogen (10) supplied to the ammonia synthesis plant (5) and to supply it to the fertilizer production plant (9), wherein the fertilizer production plant (9) is configured to produce plant fertilizer (12) at least from the CO2 contained in the second part (A2) of the exhaust gas (2) and the ammonia (11) supplied by the ammonia synthesis plant (5).

2. System according to claim 1, characterized in that the fertilizer production plant (9) is designed to produce plant fertilizer (12) from water contained in the second part (A2) of the exhaust gas (2) and / or supplied to the fertilizer production plant (9), as well as from the CO2 contained in the second part (A2) of the exhaust gas (2), and the ammonia (11) supplied by the ammonia synthesis plant (5).

3. System (1) according to one of claims 1 or 2, characterized in that the second part (A2) of the exhaust gas (2) is split into CC and water (14) before being fed to the fertilizer production plant (9).

4. System (1) according to one of claims 1 to 3, characterized in that water (14) is added to the second part (A2) of the exhaust gas (2) before it is fed to the fertilizer production plant (9).

5. System (1) according to one of claims 1 to 4, characterized in that the system comprises the technical plant (3), and the technical plant (3) is a production plant fueled with carbon-containing primary energy carriers (CP).

6. System (1) according to claim 5, characterized in that the technical installation (3) is a thermal power plant.

7. System (1) according to claim 5, characterized in that the technical plant (3) is a cement plant, a steel plant, a chemical plant, a paper mill or a pulp mill.

8. System (1) according to one of claims 1 to 7, characterized in that the first part (Al) of the exhaust gas (2) comprises 70 - 80% of the total exhaust gas (2) of the technical system (3).

9. System (1) according to claim 2, characterized in that the fertilizer production plant (9) is designed to produce plant fertilizer (12) in the form of NH4HCO3.

10. System (1) according to claim 1, characterized in that the fertilizer production plant (9) is designed to produce plant fertilizer (12) in the form of urea.

11. System (1) according to one of claims 1 to 10, characterized in that the exhaust gas recirculation circuit (4) has at least one recirculation fan (17) and / or a heat exchanger (18).

12. System (1) according to claim 6, characterized in that the ammonia synthesis plant (5) and / or the air separation plant (6) is supplied with electricity by the thermal power plant.

13. A process for separating CO2 from a CCh-containing exhaust gas (2) of a technical plant (3), wherein a first portion (Al) of the exhaust gas (2) is enriched in an exhaust gas recirculation circuit (4) with oxygen (7) supplied to the exhaust gas recirculation circuit (4) from an air separation plant (6) and supplied to the technical plant (3), and a second portion (A2) of the exhaust gas (2) of the technical plant (3) is supplied to a fertilizer production plant (9), and wherein ammonia (11) is synthesized by means of an ammonia synthesis plant (5) from nitrogen (8) supplied to the ammonia synthesis plant (5) from the air separation plant (6) and hydrogen (10) supplied to the ammonia synthesis plant (5), which is supplied to the fertilizer production plant (9), and wherein, by means of the fertilizer production plant (9), at least from the second portion (A2) of the exhaust gas (2) contained CO2, and the plant fertilizer (12) is produced from the ammonia (11) supplied by the ammonia synthesis plant (5).

14. Method according to claim 13, characterized in that plant fertilizer (12) is produced by means of the fertilizer production plant (9) from water contained in the second part (A2) of the exhaust gas (2) and / or supplied to the fertilizer production plant (9), as well as from the CO2 contained in the second part (A2) of the exhaust gas (2), and the ammonia (11) supplied by the ammonia synthesis plant (5).

15. Method according to one of claims 13 or 14, characterized in that water (14) is added to the second part (A2) of the exhaust gas (2) before it is fed to the fertilizer production plant (9).

16. Method according to one of claims 13 to 15, characterized in that 70-80% of the total exhaust gas (2) of the technical system (3) is supplied as a first fraction (Al) of the exhaust gas (2) to the exhaust gas recirculation circuit (4).

17. Method according to claim 14, characterized in that the fertilizer production plant (9) produces plant fertilizer (12) in the form of NH4HCO3.

18. Method according to claim 13, characterized in that the fertilizer production plant (9) produces plant fertilizer (12) in the form of urea.

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