WO2023033682A1 - Method of concentrating carbon dioxide gas and device for carrying out same - Google Patents

Abstract

The invention relates to the field of environmental protection and can be used in vehicles, thermal power plants and industrial and other facilities for the purpose of capturing and sequestering carbon dioxide. In order to reduce costs, nitrogen is replaced in a fuel mixture by gaseous substances having a condensation temperature higher than or equal to the condensation temperature of carbon dioxide. In addition, exhaust gases are returned to the combustion chamber for reuse. Before the exhaust gases are returned, СО2 build-up is removed and spent oxygen and fuel are added in the required amount to form a fuel mixture. Fuel is fed from a source (1) to a combustion chamber (2), and oxygen О2 and carbon dioxide gas СО2 are fed into a mixer (3) from a collector (4). The mixture is combusted in the chamber (2) and the combustion products СО2 and Н2О pass into a combustion product separator (38) (see fig. 5). Н2О is condensed and removed. Of the remaining СО2, the excess is removed to the collector, and the leftover gas is returned to the chamber (2).

Description

METHOD FOR CARBON DIOXIDE CONCENTRATION AND DEVICE FOR ITS IMPLEMENTATION

The invention relates to the field of environmental protection and can be used in vehicles, in industrial, civil and other facilities to capture carbon dioxide, then carbon dioxide, or carbon dioxide, or CO2, followed by its decarbonization by burial or processing.

Climate change is one of the most pressing issues of our time. In order to save our planet's ecosystem, carbon dioxide emissions must be significantly reduced over the next ten years, in line with the goals of the Paris Climate Agreement, while continuing to meet the needs of an ever-growing population.

Carbon dioxide continues to build up in the atmosphere at a rate of about 40 gigatonnes per year. To achieve the goals set by the agreement, it will be necessary to reduce emissions - this is a necessary component of the "carbon neutrality" strategy in any country.

The main sources of carbon dioxide emissions into the atmosphere are thermal power plants, vehicles, aircraft and ships with thermal engines, the metallurgical and cement industries. The Intergovernmental Panel on Climate Change (IPCC) estimates that fossil fuel power plants and large industrial facilities account for up to 60% of global carbon dioxide emissions. Transport accounts for more than 20% of emissions.

Greenhouse gases, in addition to carbon dioxide, also include methane and nitrous oxide, which destroy the stratospheric ozone layer, which protects us from the harmful effects of ultraviolet sunlight. It accounts for about 6% of the radiative forcing of long-lived greenhouse gases. Nitrous oxide is 300 times more greenhouse gas than carbon dioxide.

SUBSTITUTE SHEETS (RULE 26) Removing greenhouse gases from heat engine emissions is currently expensive. Many developing countries, for this reason, continue to operate old thermal power plants and build new ones.

To reduce greenhouse gas emissions in these countries, methods should be applied to inexpensively extract carbon dioxide and nitrous oxide from the flue gases of thermal engines in power plants and transport. Along with developing industrialized countries, they also need to reduce the cost of methods for cleaning exhaust gases from various thermal engines that consume fossil hydrocarbon fuels.

The share of coal in the global fuel and energy balance is 42.8%, while that of gas is 18.5%. In many countries, the importance of coal for the power industry is much higher: in Poland - 95%, South Africa - 90%, Australia - 86%, China - 81%, England - 60%, Germany - 54%, USA - 52%, Japan - 30% . The use of coal for electricity generation in the world by 2030 will increase to 4.5 billion tons of standard fuel, and coal will remain the main source of electricity production.

Power plants are the first candidates for capturing CO2. The following capture technology options and applications are available. A way to efficiently capture CO2 is to create a concentrated high pressure CO2 stream that can be easily transported to a storage location. Although the entire gas stream containing low concentrations of CO2 can be transported and injected underground, energy costs and other associated costs generally make such an approach impractical. Therefore, for transportation and storage purposes, it is necessary to create an almost pure CO2 stream.

CO2 separation applications are already in operation today in large industrial plants, including those for natural gas processing and ammonia production. At present, CO2 is generally absorbed to clean up other industrial gas streams. Absorption is used for storage purposes in only a few cases; most often CO2 is emitted into the atmosphere. Capture processes have always been used to obtain commercially viable amounts of CO2 from flue gas streams resulting from combustion

SUBSTITUTE SHEETS (RULE 26) coal or natural gas. Today, however, large power plants (eg 500 MW) do not have any application for CO2 capture.

There are three main conceptual technologies for capturing CO2 from primary fossil fuels (coal, natural gas or oil), biomass, or mixtures of these fuels (see Intergovernmental Panel on Climate Change (IPCC) Carbon Dioxide Capture and Storage, 2005. , 66 pp. ISBN 92-9169-419-3, page 24):

1. Capture systems after combustion (see Patent RU 2676642 Cl BOID 53/02, publ. 01/09/2019, Bull. 1, or Patent RU 2689620 Cl BOID 53/14, publ. 16) separate CO2 from flue gases formed in the air as a result of primary fuel combustion. These systems typically use a liquid solvent to capture a small fraction of the CO2 (typically 3-15% by volume) present in the flue gas stream, in which the main constituent is nitrogen (from the air).

In a modern pulverized coal or natural gas combined cycle power plant, current post-combustion recovery systems typically use an organic solvent such as monoethanolamine.

The disadvantage of this method is that the concentration of carbon dioxide in the combustion products (flue gases) does not increase, and this saves the complexity of separating CO2 from nitrogen coming from the air during fuel oxidation. Capture is the most costly and most energy intensive step of the entire process.

2. Pre-combustion capture systems treat the primary fuel in a reactor with an air or oxygen saturated stream to create a mixture consisting primarily of carbon monoxide and hydrogen (“syngas”). Additional hydrogen along with CO2 is formed by the reaction of carbon monoxide with the stream in the secondary reactor. The resulting mixture of hydrogen and CO2 can then be separated into a CO2 gas stream and a hydrogen stream.

The disadvantage of this method is that the initial stages of fuel conversion are more complex and expensive compared to post-combustion systems. Weight and size characteristics of the installation,

SUBSTITUTE SHEETS (RULE 26) implementing the method, do not allow them to be widely used in transport. The concentration of CO2 is not enough - in practice 15-60% by volume after drying the gases.

3. Combustion systems with a reduced proportion of inert gases and an increased proportion of oxidizer. Able to increase the concentration of CO2 over 99%, after drying the gases.

Oxygen-enriched combustion systems use oxygen instead of air to burn the primary fuel to produce flue gas, which consists mainly of water vapor and carbon dioxide. The water vapor is then removed by cooling and compressing the gas stream. A mixture of gases highly enriched in carbon dioxide remains.

Combustion of oxygen-enriched fuel requires separation of oxygen from air at the beginning of the process chain, while most modern designs assume the use of oxygen with a purity of 95-99%. Oxygen-enriched combustion systems are in the demonstration phase. Research is being carried out on the use of oxygen-enriched fuel systems in gas turbine systems, but the conceptual development of such applications is still at the research stage, since oxygen enrichment leads to an unacceptable increase in the temperature of the working processes.

In view of the temperature limitations of the method, it can be applied so far only to external combustion heat engines. For this reason, the device of this type of heat engines contains an atmospheric air separator, an external combustion chamber in which oxygen of a high degree of purification (95-99%) is used, a mechanism for converting heat into mechanical energy, a device for separating carbon dioxide-enriched combustion products and its accumulation.

In the case of internal combustion engines, the combustion of fuel in pure oxygen leads to too high a flame temperature, so in practice the products of combustion of fuel in oxygen are diluted by mixing with CO2 from the flue gases. Due to the fact that the recirculated CO2 is not added before, but after the combustion of the fuel, high-temperature combustion zones remain, which do not allow the use of this

SUBSTITUTE SHEETS (RULE 26) method in reciprocating internal combustion engines due to the impossibility of implementing separate combustion in oxygen and cooling the combustion products with cold CO2. Therefore, the mixing of combustion products with recirculated CO2 has so far been implemented only on experimental and demonstration gas turbines, in which the presence of flame tubes in the combustion chamber ensures the separation of fuel combustion processes in oxygen and cooling of the combustion products by mixing with recirculated CO2.

Modern post- or pre-combustion capture systems for power plants can capture 85-95% of the CO2 generated. Higher capture efficiencies are possible, although separators are becoming much larger, more energy intensive and more expensive. Trapping and compression require approximately 10-40% more energy than a similar setup without trapping, depending on the type of system in question. Due to the associated carbon dioxide emissions, the net amount of CO2 captured is approximately 80-90%.

In analogues, there is a problem of separation of CO2 and nitrogen in the combustion products, because nitrogen has a large proportion in the combustion products, which makes it difficult to separate them. In existing methods, energy consumption varies from 1 to 10 GJ per ton, depending on the concentration of carbon dioxide at the inlet.

The exhaust gases of piston-type internal combustion engines contain 12-17% CO2, and gas turbine-type engines contain 3-5% carbon dioxide. Therefore, the separation of low concentration CO2 from this mass of air, for example, by cryogenic distillation, leads to excess energy consumption for cooling nitrogen and oxygen in the air to the temperature of CO2 condensation into a liquid. Other methods are also energy intensive due to the low concentration of carbon dioxide.

An attempt to solve this problem is a way to increase the concentration of CO2 by separating oxygen from the air and supplying it to the combustion chamber with a minimum amount of residual gases, which leads to a multiple increase in the proportion of CO2 in the combustion products.

A system is known in which, in order to lower the temperature around the combustion zone of fuel in oxygen and prevent the destruction of the combustion chamber,

SUBSTITUTE SHEETS (RULE 26) the combustion zone is surrounded by CO2 fluid - carbon dioxide, which is in a special form of the state of aggregation of matter. , NC), Palmer; Miles R.(Chapel Hill, NC), “System and Method for High Efficiency Power Generation Using a Carbon Dioxide Circulating Working Fluid.” USA Patent 8,959,887 B2, 24 February 2015).

The prototype implements a recuperable high-pressure Brayton cycle using a working fluid in the form of a supercritical fluid CO2 with a gas-oxygen fuel combustion mode.

In the prototype carbon dioxide is in the supercritical state. When applied to substances in this state, a special term is used - supercritical fluid (from the English word fluid, that is, "able to flow"). In modern literature, the abbreviated designation of supercritical fluids is SCF. Supercritical fluids are a form of aggregate state of matter, different from both liquid and gaseous. Supercritical fluids are a cross between a liquid and a gas. They can compress like gases (ordinary liquids are practically incompressible) and, at the same time, are able to dissolve solids, which is not characteristic of gases.

This cycle begins with combustion in the combustion chamber of gaseous fuel with oxygen and a hot working fluid in the form of recycled supercritical CO2. At the same time, in the combustion zone in the presence of SCF-CO2. should be the maximum concentration of oxygen. Combustion in the presence of SCF-CO2 serves the dual purpose of lowering the temperature of the combustion flame to an acceptable level and diluting the combustion products so that the working fluid of the cycle is predominantly CO2. The pressure in the combustion chamber can be up to about 30 MPa and the combustion feedstock is about 95% recycled CO2 by weight.

The combustor provides high pressure exhaust which can be fed into a turbo expander operating at a high pressure drop. The exhaust mixture comes out of the expander in the form of subcritical CO2, mainly mixed with water obtained by combustion. This liquid enters the economizer heat exchanger, which cools the outlet

SUBSTITUTE SHEETS (RULE 26) expander to a temperature below 65 ° C against the flow of CO2, which is returned to the combustion chamber. After leaving the economizer heat exchanger, the expander exhaust is additionally cooled to a temperature close to ambient temperature using a central cooling system, which allows liquid water to be removed from the working fluid.

The remaining working body of almost pure CO2 then passes to the stage of compression and pumping. The compression system consists of a conventional intercooled centrifugal compressor with an inlet pressure below the CO2 critical pressure. The working fluid in the form of CO2 is compressed and then cooled to a temperature close to the ambient temperature in the aftercooler of the compressor. At this stage, the combination of compression and cooling of the working fluid makes it possible to achieve a density in excess of 500 kg/m ³ . In this state, the CO2 stream can be pumped to the required high combustion pressure using a multi-stage centrifugal pump. Finally, the high pressure working fluid is sent back through the economizer heat exchanger to be reheated and returned to the combustion chamber.

The pure CO2 product obtained by adding fuel and oxygen to the combustion chamber is removed from the high pressure stream; at this point CO2 is a high pressure, high purity product, ready to be sequestered or disposed of without the need for further compression.

In the prototype, the system provides a flow of combustion products containing CO2 at a pressure of at least about 8 MPa and a temperature of at least about 800 ° C, which, with high efficiency, solves the problem of eliminating losses in typical CO2 removal systems for its compression for injection into the pipeline, although it creates difficulties due to excessive pressure of the working fluid associated with high temperature. In terms of temperature and power intensity, the combustion chamber of the prototype is similar to rocket jet engines, which affects the working life, reliability and cost of its manufacture.

The combustion chamber, like the turbine of the system, is therefore atypical, not standard - for the new system, Toshiba has designed a special turbine and a special combustion chamber, corresponding to the unique physical conditions.

SUBSTITUTE SHEETS (RULE 26) Thus, the technology cannot be applied at existing, typical power plants as a result of their modernization, just as, for example, through the modernization of coal-fired thermal power plants, more efficient stations with combined cycle plants with an efficiency of up to 65% are created. The fleet of old operating thermal power plants cannot be transferred to the new technology - it is required to create new thermal power plants and liquidate old, but efficient stations. This is a significant drawback of the prototype, preventing the implementation of this technology in poor developing countries.

The disadvantages include the fact that supercritical carbon dioxide is a very strong solvent. Due to the extreme temperatures and pressures under which it is used, very stringent requirements are placed on the materials of construction. It is reported that one of the most resistant alloys of titanium, nickel, chromium and aluminum, in contact with supercritical CO2 at a temperature of 750 ° C, thins by 1-2 microns per year). This means that such thermal power plants may encounter still unknown problems during operation (see Aleksey Batyr. Supercritical approach. Energy science.

As is known, increasing the compression ratio is the most direct way to increase the total output power of a system using the Brayton cycle, which is implemented in the system adopted as a prototype. However, in order to obtain compressed CO2 suitable for pumping into the pipeline, it is not necessary to use a combustion chamber with a pressure of about 300 bar, since the condensation of carbon dioxide is also possible due to its cooling, followed by the recovery of the spent cold, moreover, due to the free heat of the exhaust gases. in an absorption refrigerator.

The purpose of this invention is to increase the concentration of carbon dioxide and, as a consequence, reduce the cost of separating it from other components of the exhaust gases.

This goal is achieved by burning hydrocarbon fuel in the combustion chamber, supplying oxygen with an admixture of nitrogen and a recirculating working fluid, and the resulting water vapor and carbon dioxide are separated from the combustion products and removed, according to this statement, deplete nitrogen and at the same time nitrogen

SUBSTITUTE SHEETS (RULE 26) replaced by the addition of a recirculating working fluid, mixed with oxygen up to the combustion chamber and having a gaseous state, which, either individually or as a mixture of gases, is carbon dioxide, water vapor, hydrocarbons or derivatives of hydrocarbons, or other substances that have a temperature condensation above the condensation temperature of carbon dioxide. In this case, the enrichment is performed either proportionally, or with an excess, or with a deficiency.

When carbon dioxide is supplied, water and the increase in carbon dioxide from the burnt fuel are removed, and the remaining carbon dioxide is returned to the supplied gas mixture.

As a substitute for nitrogen, in addition to carbon dioxide, water vapor, hydrocarbons or derivatives of hydrocarbons, or other substances that have a dew point equal to or higher than the dew point of carbon dioxide can be used. The above components can be used either singly or as a mixture.

When a nitrogen substitute is supplied in the form of carbon dioxide, the combustion products with a nitrogen substitute are cooled to the water condensation temperature. The water is then removed to produce a carbon dioxide concentrate, from which the carbon dioxide gain from the burnt fuel is removed, after which the remaining carbon dioxide is returned to the combustion chamber.

When a nitrogen substitute is supplied in the form of steam, the combustion products with a nitrogen substitute are cooled to the water condensation temperature. The remaining carbon dioxide with impurities and the increase in water are separated and removed, after which the water in the form of steam is returned to the combustion chamber.

When a nitrogen substitute is supplied in the form of hydrocarbons, for example, alkanes, alkenes, alkynes, alkadienes, cycloalkanes, the products of fuel combustion and its hydration, hydrogenation and pyrolysis, such as, for example, ethylene and propylene, with nitrogen substitutes, are cooled to their condensation temperature , and the remaining carbon dioxide with impurities and water is removed, after which the hydrocarbons separated from the synthesis products, for example, ethylene and propylene, are returned to the combustion chamber in the form of gas or steam, along with a new portion of hydrocarbons that compensate for the loss.

SUBSTITUTE SHEETS (RULE 26) When a nitrogen substitute is supplied in the form of hydrocarbon derivatives, for example, alcohols such as ethanol and methanol, the products of fuel combustion, its dehydration, dehydrogenation, pyrolysis, such as, for example, ethylene and 1,3-butadiene, are cooled to their condensation temperature, and the remaining carbon dioxide with impurities and water is removed. After that, derivatives of hydrocarbons, minus synthesis products, for example, such as ethylene and 1,3-butadiene, are returned to the combustion chamber in the form of gas or steam, along with a new portion of derivatives of hydrocarbons that compensate for the loss.

When a nitrogen substitute is supplied in the form of other substances that have a condensation temperature higher than the carbon dioxide condensation temperature, the combustion products with nitrogen substitutes are cooled until the substitutes pass into the condensed phase, and the remaining gas phase in the form of carbon dioxide with impurities is removed. In this case, the nitrogen substitute is returned to the combustion chamber in the form of gas or steam, and the removed carbon dioxide is condensed in the air separator heat exchanger, for example, due to the evaporation of cryogenic nitrogen and oxygen.

The proposed method is implemented in a device for concentrating carbon dioxide, containing a fuel supply system, a combustion chamber, an air separator into oxygen and nitrogen, an oxygen supply system to the combustion chamber and a nitrogen removal system in a depot for storage, a separator for combustion products and a depot for their storage with channels transportation, a gas accumulator (working fluid) that replaces nitrogen and a system for supplying it to the combustion chamber, a transportation channel in the form of a branch to the combustion chamber, according to this statement, an oxygen mixer with a recirculating working fluid is installed at the inlet of the combustion chamber. Both of these devices can be placed either in a piston engine, or in a gas turbine engine of a combined cycle plant, or in furnace units, such as, for example, metallurgical blast furnaces or cement kilns.

The device for concentrating carbon dioxide may be provided with a valve to control the amount of supply in the conveyance channel, or in the branch channel, or in both channels, or in all the conveyance and branch channels simultaneously.

SUBSTITUTE SHEETS (RULE 26) The device for concentrating carbon dioxide may be provided with a heat exchanger in which the evaporation of nitrogen and/or oxygen is used to condense the carbon dioxide released from the combustion products.

In the version for road transport, the device for concentrating carbon dioxide can be made with a cryogenic air separator into liquid oxygen and gaseous nitrogen, using a reserve of cryogenic nitrogen.

Excess components are removed through the transportation channels after the branch, and through the branch, the nitrogen substitute completes the circuit of the cycle, entering the combustion chamber.

Conveyance channels and branches, equipped with valves for regulating the supply of products, allow you to maintain the operation of the combustion chamber in an optimal mode and effectively remove accumulated carbon dioxide.

By pre-mixing oxygen and nitrogen-replacing gas, oxy-fuel combustion is avoided, which creates high temperature loads on the combustion chamber.

In the future, the proposed solution is explained by drawings, in which: Fig.1 - structurally shows the method when carbon dioxide (CO2) replaces nitrogen; Fig.2 - structurally shows the method when water (HgO) replaces nitrogen;

Fig.3 - structurally shows the method when hydrocarbons (HC) replace nitrogen;

Fig.4 - structurally shows the method when alcohols replace nitrogen;

Fig.5 - a block diagram of a device for concentrating carbon dioxide is presented.

In the figures, the designated positions have the following meanings: 1 - fuel source C ; 2 - combustion chamber; 3 - mixer, for example, Og and COg; 4 - oxygen accumulator Og; 5 - exhaust gas separator; 6 - water storage HgO; 7 - CO2 accumulator; 8 - nitrogen accumulator N2; 9 - source of carbon dioxide CO2; 10 - depot for excess carbon dioxide COg; And - a mixer of oxygen Og and water NgO; 12 - source of water HgO; 13 - source of fuel CH4 and HC; 14 - HC and Og mixer; 15 - source of hydrocarbons HC; 16 - separator HgO, HC, HC*,COg; 17 - separator of hydrocarbons HC and HC*; 18 - depot of hydrocarbons HC; 19 - CH4 fuel source and alcohols; 20 - alcohol mixer

SUBSTITUTE SHEETS (RULE 26) and oxygen Og; 21 - source of alcohols; 22 - flue gas separator for water NgO, Alcohols, HC*, COg; 23 - separator of Alcohols and hydrocarbons HC*; 24 - cylinders for water HgO, or hydrocarbons HC, or Alcohols, or carbon dioxide COg; 25 - valve for regulating the amount of CO2 supply for discharge into depot 27; 28 - valve for regulating the amount of excess water supply HgO; 29 - valve for regulating the amount of water supply HgO returned through the branch to the combustion chamber 2; 30 - depot for dumping excess water; 31 - valve for regulating the amount of supply of hydrocarbon HC to the depot; 32 - valve for regulating the amount of supply of hydrocarbon in the branch for returning to the combustion chamber 2; 33 - depot for dumping excess hydrocarbon HC; 34 - valve for regulating the amount of alcohol supply to the depot; 35 - valve for regulating the amount of alcohol supply to the branch for return to the combustion chamber 2; 36 - depot for dumping excess alcohol; 37 - depot for the accumulation of nitrogen N2 obtained from the air; 38 - separator of combustion and synthesis products.

The working fluid in the form of CO2, or NgO, or HC, or Alcohols in mixer 3 is mixed with oxygen O2 (see Fig.5).

The device for concentrating carbon dioxide according to the proposed method works as follows.

From source 1, fuel is supplied to combustion chamber 2, and oxygen Og and carbon dioxide CO2 are supplied to mixer 3 from accumulator 4. In chamber 2, this mixture burns out and the combustion products pass into the exhaust gas separator 5 (cM.Fig.l) or the combustion and synthesis separator 38 (Fig.5). In the separator 5, two H2O fractions are formed, which pass into the water accumulator 6 and are removed from the cycle, and CO2, which passes into the carbon dioxide accumulator 7 (cM.Fig.l). The main flow of carbon dioxide moves to the source of carbon dioxide 9, and its excess is withdrawn to the depot 10 for excess carbon dioxide CO2.

Through the transport channels 9, 12, 15 and 21, H2O, HC, CO2 and Alcohols exit the separator 38.

By shutting off the flow control valves 25, 28, 31, 34, they limit the discharge into depots 27, 30, 33, 36 of Alcohols, H2O, HC and CO. And the valves 26, 29.32, 35 control the amount of flow in the branches to return to the combustion chamber 2.

SUBSTITUTE SHEETS (RULE 26) On Fig. Figures 2,3,4 show the cycles of work with H2O, HC and Alcohols, respectively.

All components shown in the figures contain residual nitrogen. Its fractional content is determined by the quality of the air separator and is usually a small percentage - up to 3% of oxygen. Therefore, due to the low content of residual nitrogen, it is not indicated in the figures, although it is present. The resulting excess is separated by condensation of carbon dioxide and removed from the circuit. Also on the figures, the designations HC are introduced - hydrocarbons, hydrocarbons, and HC* - modified HC in the combustion chamber under the influence of temperature, pressure, catalysts.

Thus, to solve the problem, as proposed in this application, a replacement for nitrogen is selected, such that the gas replacing nitrogen should have a dew point close to the dew point of carbon dioxide, preferably higher.

Such substances can be water, alcohols and other derivatives of hydrocarbons, certain groups of hydrocarbons, and, finally, carbon dioxide itself. The list of suitable substitutes is longer, but many substances are currently not passed for environmental or economic reasons - for example, the thermally very stable hydrogen bromide, other bromine compounds or bromine itself, as well as some fluorocarbons, monoethanolamine and its analogues.

Thus, in order to achieve the result in the form of an increase in the proportion of carbon dioxide in the separated combustion products, it is proposed, after air separation, to replace the removed nitrogen with carbon dioxide, water, alcohols and other derivatives of hydrocarbons, hydrocarbons - propane, butane, etc., which should be mixed in the combustion chamber with oxygen at a standard concentration of 21% by volume, with deviations from this concentration upwards or downwards, set by the technological needs of the operation of gas turbines and reciprocating internal combustion engines. For repeated use of a nitrogen substitute, circulation of the working fluid is necessary.

In order to reduce the cost of removing CO2 formed during fuel combustion in the fuel mixture, in whole or in part, nitrogen is replaced with carbon dioxide. In this case, exhaust gases are used, which are returned to the engine.

SUBSTITUTE SHEETS (RULE 26) Before returning, the increase in CO2 is removed from them and the spent oxygen is added in the required amount. In the engine, fuel is added to the gases, forming a fuel mixture.

Thus, the composition of the fuel mixture burned further in the engine is a mixture of CO2, oxygen, fuel particles and non-combustible gases (N2, H2O, Ar). In the fuel mixture, the proportion of CO2 exceeds the proportion of oxygen, and the proportion of oxygen exceeds the proportion of other non-combustible gases, which, after combustion of the mixture, maximizes the concentration of CO2 in the exhaust gases, and thus reduces the cost of cleaning exhaust gases from the proportion of CO2 and other gases that obtained as a result of the oxidation of hydrocarbon fuels.

With this method, there is no increase in the temperature of the burning mixture to extreme values for parts of heat engines, as when using an increased concentration of oxygen in the fuel mixture.

The proposed method makes it possible to maximize the CO2 content in the exhaust gases of reciprocating internal combustion engines and gas turbines, since it does not increase the temperature of the working process to unacceptable values.

The method can be used at thermal power plants, ships, railway, road and air transport, which will reduce emissions not only of CO2, but also of another greenhouse gas - N2O, which is 300 times more dangerous than CO2.

Not all vehicles implementing the proposed method are able to place units for separating air into oxygen and nitrogen in order to supply Og to a closed CO2 flow (from the combustion chamber back to the combustion chamber). Therefore, for such vehicles, instead of a plant for the separation of oxygen from the air, a stock of ready-made liquid Og stored in Dewar vessels is used.

The cost of one ton of Og in mass production is 40-60 dollars, which is economically acceptable, since it adds about 1 cent to the cost of 1 liter of spent fuel. Exhaust gas (combustion products), after purification from water vapor, is technically pure CO2.

If there is an additional supply of liquid nitrogen, as well as water consumed for pre-cooling of exhaust gases (up to

SUBSTITUTE SHEETS (RULE 26) temperature of about 35°C), carbon dioxide is frozen to a liquid state and placed in the vehicle storage tank, and liquid oxygen passes into the gas phase and enters the engine as part of the fuel mixture. Nitrogen and water evaporate and are released into the atmosphere.

At filling stations, vehicles unload accumulated liquid CO2 and fill up with water and liquid oxygen and nitrogen.

Solid carbon dioxide (dry ice) can be transported to the place of long-term storage or sequestration in thermostatic tanks at atmospheric pressure, which reduces the material consumption and cost of containers. Moving solid carbon dioxide from a low-pressure zone to a high-pressure zone is much simpler than pumping gaseous carbon dioxide into a pressure vessel, the required value of which reaches 70 bar.

The most economical way to transport carbon dioxide is considered to be pipeline and sea transport. In order to introduce CO2 into the pipeline, it is necessary to increase its pressure to 60-70 bar. Due to the evaporation of oxygen entering the engine from a cryogenic air separator, as well as due to the evaporation of part of the nitrogen, carbon dioxide is liquefied in heat exchangers with little or no increase in pressure. Then, with negligible costs, it, like a liquid, is injected into a pipeline or vessel with compressed CO2, where it evaporates and turns into a gas with the required pressure.

The method is implemented using a device that can be used as a module or a group of modules connected to existing thermal power plants, container ships and other types of water transport, diesel locomotives of railways, automobile container ships, aircraft and airships. Modules for trucks include Dewar vessels for storing cryogenic reserves of Og, N2 and COg, as well as water tanks for pre-cooling combustion products by evaporation of water.

Modules for railway diesel locomotives contain devices for cryogenic air separation, which simplifies the solution of the CO2 freezing problem. At the same time, diesel locomotives with modules become mobile distribution points for cryogenic oxygen and nitrogen for refueling centers for trucks and cars.

Modules for heavy-duty water transport, for example, for container ships and dry cargo ships, have weight and size characteristics,

SUBSTITUTE SHEETS (RULE 26) allowing to accumulate CO2 for a long time in large volumes. In some ports, terminals are installed to receive accumulated CO2 and pump it into pipelines transporting CO2 to disposal sites. It is advisable to discharge the accumulated CO2 not only in the ports of loading and unloading, but also on the routes of ships, thanks to specialized ships.

The device includes an oxygen generator from atmospheric air, for example, a cryogenic one, in the form of a turboexpander, an evaporator of liquid oxygen and nitrogen with a heat exchanger for converting carbon dioxide into liquid or ice, a water evaporator with a heat exchanger for cooling exhaust gases to room temperature and separating water vapor, storage tank cryogenic CO2, fuel storage device, CO2 recirculation pipeline system, for the relatively easy transport option - Og, N2 and water accumulators.

Reaction formula:

7C0g + 2Og + CH ₄ => 8COg + 2HgO (1)

After cleaning the exhaust gases from water and removing a unit of CO2, the remainder is 7C0g, as at the beginning of the cycle.

Heavy hydrocarbons in the form of gas or vapor are used as a substitute for nitrogen in the gas-fuel mixture. In reciprocating internal combustion engines, the mixture consists of 80% or more heavy hydrocarbons, with a corresponding proportion of oxygen of 20% or less. In gas turbines in the flame tubes, the ratio of hydrocarbons and oxygen is used as 80 to 20, and at the exit from the flame tubes on the way to the turbine blades, the exhaust gas is diluted with a portion of hydrocarbons, which is 3-4 times larger than the initial portion of the gas-fuel mixture.

The exhaust gas after the turbine is cooled to a temperature below 100°C and above 0°C, purified from water, compressed at a constant temperature to the temperature of formation of the liquid fraction of most hydrocarbons and separated into a liquid fraction of heavy hydrocarbons and into gaseous CO2 mixed with the gaseous part of hydrocarbons .

A mixture of gases from CO2 and hydrocarbons is subjected to further compression and cooling until the formation of a liquid phase of CO2 and gaseous residues of the decomposition products of heavy hydrocarbons into light hydrocarbons. Liquid CO2 is sent to the accumulator, and heavy hydrocarbons, after being cleaned from

SUBSTITUTE SHEETS (RULE 26) solid fractions, together with gaseous decomposition products of heavy hydrocarbons, are used to form a new gas-fuel mixture. The cycle is repeated.

The purpose of the proposed method is to stop the carbonization of the atmosphere by capturing emissions from the combustion of fossil fuels. In this case, the method does not affect the decrease in the level of previously accumulated technogenic carbon dioxide. However, the proposed method is also a way to remove carbon dioxide from the atmosphere, when instead of fossil fuels, biofuels obtained from renewable bioresources are burned. In this case, technogenic carbon is removed from the atmosphere and the main goal of decarbonization of nature is achieved.

When using biofuels in the proposed method, the concept of removing CO2 from the atmosphere, known as BECCS, is implemented.

The idea behind BECCS is carbon sequestration by plants; burning plants for energy; capturing carbon in the chimney; and carbon storage underground. The idea behind BECCS is to capture carbon with trees; boom trees for energy; capture carbon at the smokestack; and bury carbon underground. URL: http://carbon.ycombinator.com/.

The best implementation is a device for concentrating carbon dioxide in flue gases from piston-type heat engines in thermal power plants, marine and rail transport, which, as is well known, operate on Otto, Diesel, Trinkler, Atkinson or Miller thermodynamic cycles.

The device contains a combustion chamber, a pipeline system for recirculating CO2 (branch from the channel for transporting CO2), from the combustion chamber to the combustion chamber as a gas replacing nitrogen, a gas accumulator - circulating (circulating) CO2, an oxygen supply system to the combustion chamber, a fuel supply system to the chamber combustion, modules in the form of a cryogenic oxygen generator from atmospheric air in the form of a turbo-expander, an evaporator of liquid oxygen and nitrogen with a heat exchanger for converting the increase in carbon dioxide into liquid or ice, a frozen CO2 accumulator, a water evaporator with a heat exchanger for cooling exhaust gases to room temperature and

SUBSTITUTE SHEETS (RULE 26) water vapor separation, fuel storage device, CO2 supply control valves, in the transportation channel and in the branch channel.

The device is assembled by connecting the operating unit to the combustion chamber and the above modules - by connecting to the intake and exhaust systems. For example, an existing thermal power plant with a reciprocating internal combustion engine that consumes natural gas is equipped with modules for supplying a gas-fuel mixture containing carbon dioxide replacing nitrogen to the combustion chamber and modules for separating CO2 from turbine flue gases.

With an electric power of 55 MW, the thermal power of such a power plant is 100 MW, with an efficiency of about 55%, which, for example, is provided by Wartsila plants. The average specific heat of combustion of natural gas is 45.2 MJ/kg, which gives a rounded fuel consumption of 2.2 kg/s. Accordingly, the maximum oxygen consumption, taking into account the excess, does not exceed 8.8 kg/s. When producing oxygen with a volume of more than 1000 m ³ /h (1429 kg/h), it is advantageous to use cryogenic air separators. In large air separators, the electricity consumption is 0.3 kWh/m ³ oxygen or 0.21 kWh/kg. With a flow rate of 8.8 kg/s, the energy costs are 1.847 kWh or 6.65 MJ/s, which gives 12% of the station's power generator. At the same time, when implementing the method at a plant using a trigeneration scheme, the cold produced by the heat of the exhaust gases, without a significant reduction in efficiency, can be used to condense CO2 into liquid or ice.

The device operates without the use of ultra-high temperatures and pressures. Instead of the supercritical fluid CO2 (the fourth aggregate state of matter), the working fluid in the gaseous state is used as a recirculating working fluid.

SUBSTITUTE SHEETS (RULE 26)

Claims

CLAIM E A method of concentrating carbon dioxide, which consists in burning hydrocarbon fuel in a combustion chamber, supplying oxygen with an admixture of nitrogen and a recirculated working fluid, and the resulting water vapor and carbon dioxide are isolated and removed from the combustion products, characterized in that nitrogen is depleted and at the same time, nitrogen is replaced by the addition of a recirculating working fluid, mixed with oxygen up to the combustion chamber and having a gaseous state, which, either individually or as a mixture of gases, is carbon dioxide, water vapor, hydrocarbons or derivatives of hydrocarbons or other substances having a temperature condensation equal to or higher than the condensation temperature of carbon dioxide: when carbon dioxide is supplied, water and the increase in carbon dioxide from the burned fuel are removed, and the rest of the carbon dioxide is returned to the supplied gas mixture; when steam is supplied from the products of combustion and steam reforming of fuel, for example, hydrogen, water and carbon dioxide growth are removed, and then water in the form of steam is returned to the supplied gas mixture, with compensation for the loss of water as a result of fuel conversion, so that the amount of circulating water is kept constant; when supplying hydrocarbons, for example, alkanes, alkenes, alkynes, alkadienes, cycloalkanes, water and carbon dioxide growth are removed from the products of fuel combustion and hydration, hydrogenation and pyrolysis, such as, for example, ethylene and propylene, and the remainder of the hydrocarbons is returned to the feed mixture gases, together with a new portion of fuel, in such a way that the amount of circulating hydrocarbons and/or their derivatives is maintained necessary for the operation of the combustion chamber; when supplying derivatives of hydrocarbons, for example, alcohols, such as ethanol and methanol, from the products of combustion of fuel and dehydration, dehydrogenation, pyrolysis, such as, for example, ethylene and 1,3-butadiene, water and an increase in carbon dioxide, and the remainder of hydrocarbon derivatives are removed is returned to the supplied gas mixture together with a new portion of fuel, in such a way that the amount of circulating hydrocarbons and/or their derivatives is maintained necessary for the operation of the combustion chamber. SUBSTITUTE SHEETS (RULE 26) 2. A device for concentrating carbon dioxide, containing a fuel supply system, a combustion chamber, an oxygen supply system to the combustion chamber and a nitrogen removal system in a depot for storage, a separator for combustion products and a depot for their storage with transportation channels, a gas accumulator that replaces nitrogen and a system its supply to the combustion chamber, a transportation channel in the form of a branch to the combustion chamber, characterized in that an oxygen mixer with a recirculating working fluid is installed at the inlet of the combustion chamber and both devices are placed in a piston engine, or a gas turbine engine of a combined-cycle plant, or in furnace units. 3. A device for concentrating carbon dioxide according to i.2, characterized in that it is equipped with a supply control valve in the transportation channel. 4. A device for concentrating carbon dioxide according to claim 3, characterized in that it is equipped with a supply control valve in the branch channel. SUBSTITUTE SHEETS (RULE 26)