RU2378519C2 - Thermal electric power station with reduced co2-content and method to produce electric power from coal fuel - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates to electric power station with reduced CO₂-content and method to produce electric power from coal fuel. Gaseous combustion products are additionally cooled and separated into low CO₂-content and high CO₂-content flows in CO₂-trap. Low CO₂-content flow is heated in expanded in turbine to generate electric power and, thereafter, low CO₂-content flow is discharged into ambient medium. Note here that high CO₂-content flow is separated into flow to be stored or discharged, and flow to be returned into combustion chamber. Note also that at least a fraction of high CO₂-content flow returned into combustion chamber is mixed with coal fuel to forced into combustion chamber together with coal fuel.

EFFECT: possibility to use CO₂ as fuel propulsor and to prevent fuel preignition.

11 cl, 6 dwg

Description

The invention relates to a method for generating electricity mainly from coal fuel, in which the gaseous products of combustion are separated into a stream with a high content of CO ₂ , which is sent, for example, for safe storage; and a low CO ₂ stream that is released into the environment. The invention also relates to a power plant implementing this method and to a power plant device.

The concentration of CO ₂ in the atmosphere over the past 150 years has increased by almost 30%, mainly due to the combustion of fossil fuels such as coal and hydrocarbons. The methane concentration doubled, and the concentration of nitrogen oxides increased by almost 15%. As a result of this, the atmospheric greenhouse effect intensified, which entailed the following phenomena.

The average temperature near the surface of the earth has increased by approximately 0.5 ° C over the past hundred years, and this trend has accelerated in the last decade.

Over the same period, rainfall increased by approximately 1%.

Sea level increased by 15-20 cm due to the melting of glaciers and due to the expansion of water when heated.

Growing amounts of greenhouse gas emissions are expected to continue to cause climate change. The temperature may rise neither more nor less to 0.6-2.5 ° C in the next 50 years. In scientific circles, there is a generally accepted opinion that the increasing use of fossil fuels with an exponential increase in the amount of CO ₂ emissions into the atmosphere has changed the natural balance of CO ₂ , and therefore is the direct cause of this phenomenon.

It is important to take immediate measures to stabilize the atmospheric CO ₂ content. This can be done if the CO ₂ generated by the thermal power plant is collected and stored securely. It is assumed that such a collection measure

_CO2 cost three quarters of the total cost of growth inhibition amount of CO ₂ emissions.

The gas emitted by thermal electric power to the atmosphere usually contains 4-10% CO ₂ by volume, with the lowest values usually in gas turbines and the highest in the case of using combustion chambers with cooling, for example, when generating steam.

The capture CO ₂ from CO ₂ containing gas by means of absorption is well known (see. E.g. EP 0551876). The CO ₂ -containing gas is contacted with an absorbent, which is usually an amine solution that absorbs CO ₂ from the gas. The amine solution is then regenerated by heating. But in this case, the absorption depends on the partial pressure of CO ₂ . If the partial pressure is too low, then a relatively small fraction of the total CO _{2 is} absorbed. Typically, the partial pressure of CO ₂ in gaseous products of combustion is relatively low, in the case of gas turbines it is usually 0.04 bar. The energy consumption in such a station is almost 3 times higher per unit weight of CO ₂ than in the case when the partial pressure of CO ₂ in the feed gas is 1.5 bar. The treatment plant becomes too expensive, and the degree of treatment and the size of the plant are limiting factors.

Therefore, design developments are aimed at increasing the partial pressure of CO ₂ . According to WO 00/48709, the pressure of gaseous products of combustion expanded in a gas turbine and cooled is re-increased. The pressurized gas is then brought into contact with the absorbent. In this way, the partial pressure of CO _{2 is} increased, for example, to 0.5 bar, and the cleaning becomes more efficient. A significant disadvantage of this method is that the partial pressure of oxygen in the gas also becomes high, for example, of the order of 1.5 bar, and the physical properties of amines are rapidly violated when the partial pressure of oxygen exceeds about 0.2 bar. In addition, this method requires expensive additional equipment.

Another possibility of increasing the partial pressure of CO ₂ is to separate the air. By separating the air entering the combustion equipment into oxygen and nitrogen, circulating CO ₂ can be used as a carrier gas (for gas turbines) or as cooling gas (for coal-fired boilers) in a gas turbine combined cycle or in coal-fired power plants , respectively. If there is no nitrogen to dilute the resulting CO ₂ , then the CO ₂ in the exhaust gas will have a relatively high partial pressure of up to about 1 bar. The excess CO ₂ generated by combustion can then be separated relatively simply so that the corresponding CO ₂ collection plant can be simplified. But the total cost of this system is becoming relatively high, because you need to have a powerful installation for oxygen, in addition to the power plant.

The production and burning of pure oxygen poses serious safety issues, besides the great demand for this material. For this, in all likelihood, the development of new turbines will also be required.

According to the document WO 2004/001301 combustion is performed at an elevated pressure, the combustion gases are cooled by generation of water vapor, combustion gases are separated in a stream rich in CO ₂ and flow with low CO ₂ and expand the flow with a low content of CO ₂ in turbine before discharge into the atmosphere. This refers to a gas-fired station, and the use of coal as fuel is not mentioned.

WO 2004/026445 discloses a method for separating gaseous products of combustion from a gas-fired thermal power plant into a stream with a high CO ₂ content and a stream with a low CO ₂ content. The gaseous combustion products of this station are used as oxygen-containing gas in a secondary combined power plant and in a gas separation unit.

The methods described herein generally relate to natural gas power plants. But at present, coal is being used more and more instead of natural gas for a thermal power plant. Coal thermal power per unit of electricity produce more CO ₂ than using natural gas station. In addition, coal is more affordable than natural gas, and it is cheaper.

The introduction of coal fuel, such as pulverized coal, into combustion chambers with high pressure is associated with technical difficulties. The use of air as a carrier for pulverized coal creates an explosive mixture, as a result of which combustion will begin even before entering the combustion chamber, and this circumstance can even lead to an explosion in the means of mixing air and coal, or in connecting lines, or in the combustion chamber. The use of an inert gas, such as nitrogen, is another option, but due to the need for nitrogen purification, the costs of the power plant itself will unacceptably increase. In addition, the introduction of nitrogen will increase the total gas flow and for this reason will reduce the partial pressure of CO ₂ in the gaseous products of combustion, and this will affect the performance for the separation of CO ₂ .

According to the so-called method of burning fuel in a fluidized bed under pressure, pulverized coal is mixed with water to obtain a pasty mixture, which is injected into the combustion chamber. Water-carbon paste is needed for pumping fluid and, thereby, to overcome the pressure in the boiler. Water will evaporate from the paste, as a result of which the efficiency will decrease. To set fire to a coal-water paste, it is necessary to use a fluidized-bed combustion chamber. This requires large and expensive equipment. In addition, the fluidized bed significantly reduces pressure by an order of 2 bar. As a result, the power of the downstream turbine is reduced.

Accordingly, it is necessary to provide a cost-effective way of generating electricity from coal fuel, according to which the gaseous products of combustion are separated into a stream with a high content of CO ₂ for storage, and into a stream with a low content of CO ₂ that can be discharged into the atmosphere.

According to a first aspect of the present invention, there is provided a method for generating electricity mainly from coal fuel, in which coal fuel and oxygen-containing gas are introduced into the combustion chamber and burned at elevated pressure, and the gaseous combustion products are cooled in the combustion chamber by generating steam to generate electricity; while the gaseous products of combustion are further cooled and separated into a stream with a high content

CO ₂ stream and the low CO ₂ in the CO ₂ capturing apparatus; a low CO ₂ stream is heated and expanded in a turbine to generate electricity, and then a low CO ₂ stream is discharged into the environment; moreover, a stream with a high content of CO _{2 is} divided into a stream for storage or for shipment and a stream returned to the combustion chamber, and at least part of the stream with a high content of CO ₂ returned to the combustion chamber is mixed with coal fuel and then the chamber is introduced combustion, while it is injected into the combustion chamber together with coal fuel.

Preferably, the low CO ₂ stream is heated by heat exchange from the gaseous products of combustion from the secondary gas-fired combustion chamber, and then the low CO ₂ stream is expanded in the turbine.

Preferably, the pressure in the combustion chamber is from 5 to 35 bar.

Preferably, the pressure is from 10 to 20 bar, more preferably from about 12 to 16 bar.

Preferably, the temperature of the combustion gases leaving the combustion chamber is reduced to a temperature below about 350 ° C. by generating steam.

Preferably, natural gas is introduced into the combustion chamber to facilitate combustion.

According to a second aspect of the present invention, there is provided a thermal power plant operating mainly on coal fuel, comprising a combustion chamber, means for introducing coal fuel and oxygen-containing gas into the combustion chamber, cooling means for cooling gaseous products of combustion in the combustion chamber, and means for separating gaseous products of combustion to a stream with a high CO ₂ content and a stream with a low CO ₂ content, a line for recycling part of the CO ₂ to the combustion chamber and a CO ₂ line for delivering the rest via current with a high content of CO ₂ for storage or for shipment, while the means for introducing coal fuel into the combustion chamber comprises a reservoir and a CO ₂ line for introducing CO ₂ into the reservoir, and an injector for introducing coal fuel together with CO ₂ from the reservoir into the combustion chamber.

Preferably, the cooling means are cooling coils inside the combustion chamber; moreover, the cooling coils are made with the possibility of cooling the gaseous products of combustion by generating steam.

Preferably, the thermal power plant further comprises a steam turbine connected to a generator for generating electricity.

Preferably, the thermal power plant further comprises a gas-fired secondary combustion chamber for generating heat for heating the low CO ₂ stream and a turbine for expanding the heated low CO ₂ stream, which is then discharged into the environment.

Preferably, the turbine is connected to a generator for generating electricity.

Thus, according to a preferred embodiment, at least a portion of the high CO ₂ stream that is returned to the combustion chamber is mixed with coal fuel before being introduced into the combustion chamber, and introduced into the combustion chamber together with the coal fuel. The high CO ₂ -containing stream returned to the combustion chamber can be used to fluidize the fuel in the intermediate storage tanks so that the settled coal fuel does not interfere with the introduction into the combustion chamber. Also, a stream with a high CO ₂ content can be used as a carrier for fuel in order to force the fuel out of the tank into the combustion chamber.

The low CO ₃ stream is preferably heated by heat exchange with combustion gases from the secondary gas-burning combustion chamber, and then the low CO ₂ stream is expanded in the turbine. This is done in order to optimize the power generation by the power plant and to increase the part of the electricity that is generated by expanding this stream before it is released into the environment.

The pressure in the combustion chambers may be 5-35 bar, preferably 10-20 bar and most preferably about 12-60 bar. The absorption of CO ₂ in the CO ₂ capture device is more effective at elevated pressure than at reduced pressure. Combustion at elevated pressure delivers gaseous products of combustion at elevated pressure to the capture device without the use of energy-consuming compressors. If the combustion chamber is constantly almost completely filled with combustion, the mass flow rate of the flue gas to be cleaned is minimized, and therefore the concentration and partial pressure of CO ₂ increase as much as possible.

Preferably, the temperature of the gaseous products of combustion from the combustion chamber would be reduced to approximately 350 ° C. by generating water vapor. If the temperature of the gaseous products of combustion from the combustion chamber is maintained at a value of 350 ° C, then in equipment for the subsequent gas treatment, steel of ordinary quality can be used. A significant amount of energy is taken from the water vapor used to generate electricity.

According to one embodiment of the invention, natural gas is introduced into the combustion chamber to provide combustion. Combustion is more effective if it is promoted by natural gas.

According to a preferred embodiment of the invention, a secondary gas-fired combustion chamber is used to generate heat to heat the low CO ₂ stream; and a turbine for expanding the heated stream with a low CO ₂ content before it is discharged into the environment. Heating the stream before it is discharged into the environment gives the gas additional energy. As a result of this, power generation by expanding the low CO ₂ flow in the turbine becomes more efficient, thereby increasing the overall efficiency of the plant.

Preferably, the low CO ₂ flow expansion turbine is coupled to an electric generator for generating electricity.

According to a third aspect of the invention, there is provided an injector for coal fuel and oxygen-containing gas, which pumps them into the combustion chamber and comprises a central pipe for introducing a mixture of pulverized coal fuel and gaseous CO ₂ , around which injectors for oxygen-containing gas are mounted. The design of the injector with a central pipe for injecting coal and CO ₂ , around which the injectors of oxygen-containing gas are installed, provides quick and proper mixing of coal fuel and oxygen-containing gas. This quick and proper mixing of fuel and oxygen-containing gas ensures optimal combustion in the combustion chamber.

According to a preferred embodiment of the invention, the injector further comprises one or more injectors for injecting natural gas. The introduction of additional fuel in the form of natural gas can be used both to start combustion and to maintain combustion. The combustion of natural gas in the combustion chamber improves and optimizes the combustion of coal, since the additional heat provides the evaporation of lighter components of the fuel and more efficient combustion.

In the central tube, spiral ribs can be additionally made. The presence of spiral ribs determines the vortex movement of coal fuel and

CO ₂ in the central pipe. This movement further improves the mixing of coal fuel containing oxygen gas and any additionally introduced natural gas.

According to one embodiment of the invention, the gas injectors are oriented so that the gas rotates in the direction opposite to the movement of pulverized coal. The rotation of gas and pulverized coal in opposite directions provides optimal mixing of gas and pulverized coal.

Further, the present invention will be described in more detail with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of a preferred embodiment of the invention;

Figa is a longitudinal section of an injector according to the invention;

Fig.2b is a section along the line aa of Fig.2a;

Figure 3 is an exemplary fuel milling device and an intermediate fuel storage device according to the invention;

4 is a longitudinal section of a combined heat exchanger and a secondary combustion chamber for a power plant according to the invention;

5 is a block diagram of a device for intermediate storage of fuel and means of storage of CO ₂ ; and

6 is a block diagram of an exemplary CO ₂ capture device.

An exemplary embodiment of a natural gas and coal-fired thermal power plant is shown in FIG. Coal and, if necessary, limestone are introduced into the coal mill 12 through line 10 of coal and line 11 of limestone, respectively. Coal and, if necessary, limestone are ground to a state of a ground mixture in a coal mill 12 to particle sizes corresponding to the supply to the combustion chamber.

The milled coal and, if necessary, limestone are conveyed by conveyor 13 to the intermediate storage means 14. The intermediate storage means 14 in the illustrated embodiment includes two or more storages, each of which acts as a dispenser. For continuous operation of the combustion chamber, it is necessary to have two or more storages.

Each intermediate storage has an inlet valve 15, a reservoir 16 and an output valve 17. In addition, each storage has one or more CO ₂ inputs, which is supplied via the CO _{2 line} 18. The ground mixture from the coal mill is delivered to the intermediate storage device and at a time poured into one tank. The inlet valve 15 for the filling tank 16 is opened, and the outlet valve 17 is closed. During or after filling the reservoir 16, air is preferably removed from the reservoir using CO ₂ from the CO _{2 line} 18 to eliminate the occurrence of a hazardous mixture of air and coal dust.

CO _{2 is} regulated by valve 19 for CO ₂ . After filling the tank and removing air from the tank, the inlet valve 15 is closed. Before introducing the mixture from the tank into the combustion chamber 25, CO ₂ is introduced into the tank so that the pressure in the tank becomes higher than the combustion pressure, for example: 0.5-1 bar, 0.7 bar or higher.

According to one embodiment of the invention, the CO ₂ inlets in the tank are arranged so that the mixture in the tank is at least partially fluidized by the incoming CO ₂ stream. The outlet valve 17 is then opened, and the mixture goes to the injector 21 via line 20. The mixture is introduced into the combustion chamber 25 by the injector 21 together with CO ₂ , compressed oxygen-containing gas from the air line 23 and, in addition, natural gas from the line 2. Injector 21 more described in detail below with reference to Figure 2. Gas from line 22 is used to facilitate combustion in the combustion chamber and to control combustion therein.

The oxygen-containing gas may be air, oxygen-rich air, or oxygen. In this description and in the claims, the terms “oxygen-containing gas” and “air” are used synonymously for this gas.

Combustion in the combustion chamber 25 occurs at elevated pressure, for example from 5 to 25 bar, more preferably from about 10 to about 20 bar, and most preferably about 15 bar.

A solid in the combustion chamber, such as a non-combustible residue of coal and calcium sulfate in a binder of sulfur compounds in the gaseous products of combustion, is collected at the bottom of the combustion chamber and is removed via the solids removal line 24.

The combustion chamber 25 described above is currently the preferred chamber. But it will be clear to a person skilled in the art that other designs and operating principles are possible. The combustion chamber design described above can be replaced, for example, with a fluidized-bed combustion chamber.

A significant amount of heat generated by combustion is removed from the combustion chamber by generating steam in cooling coils 9 in the combustion chamber. Heat is mostly removed from the top of the combustion chamber in order to lower the temperature of the combustion gases leaving the combustion chamber 25 along the line 35 of the combustion gases.

Water vapor generated in the cooling coil 9 is removed from the combustion chamber via a steam line 26 and expanded in the turbine 28 to generate electricity in the generator 27. The expanded steam flows through line 29 to the condenser 30, where the expanded gas is cooled and condensed. Water condensate is pumped out by pump 31 and preheated by heat exchange in heater 32, then water is again introduced via line 33 into cooling coil 9 in combustion chamber 25. It should be noted that this scheme can be much more complicated. The cooling coil can be divided into two or more cooling coils, each of which will participate in the heating of one or more steam turbines.

Exiting combustion chamber 25, gaseous products of combustion through line 35 of gaseous products of combustion preferably have a temperature of about 350 ° C. or lower. A temperature below 350 ° C in gaseous products of combustion from the combustion chamber allows the use of relatively inexpensive steel used in the construction of lines and technological equipment, and reduce the cost of their construction.

The gaseous products of combustion in line 35 contain dust from the combustion chamber. This dust can be harmful for the further processing of gaseous products of combustion. Accordingly, the dust must be removed in the dust removal device 36, which contains sequentially installed cyclones or filters 38.

The dust extractor 36 may also contain more than two parallel lines, each of which will have several cyclones or filters in series. This device may contain more than two parallel lines. For continuous operation of the dust extractor, one or more parallel lines can be closed for cleaning and maintenance if at least one of the parallel lines is always open and working.

The inlet side of one of the parallel lines may be closed by the preceding valve 34, while the other side of the parallel lines may be closed by the subsequent valve 40. Dust trapped in the cyclones and / or filters is removed through the dust extraction lines 39.

From the dust extraction device, dust-free gaseous products of combustion enter line 41 to a selective catalytic reduction unit for substantial reduction of NOx formed in the combustion chamber. In this installation 42 selective catalytic reduction (ICR) NOx can be removed using NH ₃ according to the following reaction: 3NO + 2NH ₃ = 2.5N ₂ + 3H ₂ O. This purification is effective up to 90% at atmospheric pressure, but it is believed that can be improved at operating pressures above 10 bar. Therefore, it is possible to purify NOx to a residual content of 5 ppm or lower. Using heat exchangers, the gas can be given a temperature that is optimal for this process. Other NOx purification methods can also be used without NH ₃ . The NH ₃ method has the disadvantage that some NH ₃ “skips”.

The purified gas leaves the IQW through line 3 and is cooled in the heat exchanger 44. From the heat exchanger 44, the gas enters the condenser 47 on line 46. The gas is further cooled in the condenser and the water condensate is removed from the gas. Gas from the condenser enters the CO ₂ capture unit 49 on line 48.

Alternatively, a scrubber can be installed in front of the condenser. In an optional scrubber, the gas is saturated with water vapor and the gas is cooled by countercurrent contact with water at appropriate temperatures. The scrubber can use chemicals to oxidize and / or absorb containing NOx, SOx, other acids or gases, or particulate residues in the flue gas stream. This chemical can be “leaked” NH ₃ from the ICV system, which gives an alkaline solution, or a special chemical with alkaline and / or oxidizing properties. In the latter case, the scrubber can completely replace the installation of 42 IKV.

Flue gas cleaning is essential to reduce the formation of heat-resistant salts in an absorbing CO ₂ absorbent, to reduce the deterioration over time of CO ₂ uptake.

The CO ₂ capture unit typically comprises an absorber in which the flue gas flows countercurrently to an absorbent such as an amine, hot carbonate, or a physical absorbent. The amount of CO ₂ in the flue gas is usually reduced by 90-99% in the absorber, and then the flue gas leaves the absorber as a stream with a low CO ₂ content. The absorbent with absorbed CO ₂ (saturated absorbent) is heated in a solvent / solvent heat exchanger and regenerated in a stripper. The regenerated solvent is cooled in the heat exchanger of the "solvent / solvent", is cooled in the aftercooler and is recycled to the absorption column CO _2, the CO ₂ is removed from the stripper as stream saturated with CO _2. 6 shows an exemplary CO ₂ capture device. The specific design of the device will depend on the type of solvent used.

The CO ₂ capture device 49 can be any device that will separate partially purified gaseous products of combustion into a stream with a high CO ₂ content exiting the device via a CO _{2 line} 51 and a low CO ₂ stream exiting the device from a line 50. In line 51, a stream with a high CO ₂ content is compressed to a pressure of about 100 bar in a compressor 52 powered by an electric motor 53. A portion of the compressed stream with a high CO ₂ content exits the compressor through line 51 and is returned as a CO ₂ source for means 14 between weft storage. The remaining CO _{2 is} compressed further and removed from the station by

CO ₂ lines 55.

The effluent from device 49 capturing the CO ₂ stream with a high content of CO ₂ in line 50 enters the humidifier, where the gas is heated and saturated with water, which then flows through line 57 to heat exchanger 44 where the gas low in CO ₂ is heated by the hot gas in line 43. Preferably, air or other appropriate gas is introduced into line 57 (or 50) through line 73 of air to compensate for the mass of CO ₂ that has been removed from the gaseous products of combustion, and therefore the heat capacity of the low CO ₂ stream is approximately the same as heat capacity of gaseous products of combustion in line 43. Air is introduced into the system through an air intake 70 and is compressed by a compressor 71 operating from an electric motor 72. Alternatively, a certain amount of air from a compressor 78 can be allowed to bypass the combustion chamber 25 and subsequent equipment and introduced into line 50 or line 57 (not shown in FIG. 1).

The low-CO ₂ heated stream exits the heat exchanger 44 via line 58 and enters the heat exchanger 59, where the low CO ₂ stream is heated from the gaseous products of combustion entering the heat exchanger through line 82 from the secondary combustion chamber 81. The secondary combustion chamber 81 burns natural gas, which enters from the inlet line 80. Oxygen for combustion in the secondary combustion chamber 81 is introduced into the secondary combustion chamber via line 87.

The cooled gas from the heat exchanger 59 leaves it through line 86, which goes into line 41 to remove CO ₂ . Part of the gas in line 86 can be taken in line 83 and returned to line 82 using a fan 84 and line 85. Returning to line 83 is used to increase the mass flow of heated gas through heat exchanger 59 from line 82. If the heat exchanger is made of a material that can withstand high temperature, up to 2000 ° C, then recirculation is not needed.

The low CO ₂ heated stream exiting heat exchanger 59 via line 60 expands in turbine 61. The expanded low CO ₂ content stream from turbine 61 via line 62 is further cooled in heat exchangers 63, and then the gas stream is released into the atmosphere via line 64 The heat exchanger (s) 63 may be identical to the heater 32 and heat the cooling coils in the combustion chamber, and the energy of the expanded stream with a low CO ₂ content is used to heat the water in the heater 32.

The air for the combustion chamber 25 and the secondary combustion chamber 81 in the illustrated embodiment is introduced into the system through the air intake 75. The air in the air intake 75 is preferably compressed in a two-stage compressor having two compressors 76 and 78 and an intermediate cooler 77. Compressed gas leaves the compressor 78 through line 79 and is divided into two streams: into the air line 23, which goes to the injector 21, and into the second air line 87, which goes into the secondary combustion chamber 81. The overflow in the compressors 76, 78 and / or the turbine 61 is shown as an overflow line 88. Compressors in the illustrated embodiment are located on shaft 66, common to both compressors 76, 78, turbine 61 and electric generator 65. Alternatively, a two-stage compressor 76, 78 (not shown) and a two-stage turbine 61 (low pressure stage and high pressure stage) can be used - not shown — wherein the low pressure turbine drives the low pressure compressor 76, and the high pressure turbine drives the high pressure compressor 78 and the generator 65.

Figure 2a shows a cross section along the length of the combustion chamber and a preferred embodiment of the injector 21. The injector 21 is mounted on a cuff 101 welded to the wall of the combustion chamber. The injector is inserted into the cuff 101 and attached to the cuff by a mounting plate 100. The injector comprises a central pipe 102 for injecting coal, air injectors 103 and gas injectors 104 mounted around the central pipe. The cuff 101 is preferably cooled by air from the air inlet 109 circulating in the cooling jacket 106 located around the cuff. The air heated by cooling the cuff in the cooling jacket preferably flows through line 107, enters the air injectors 103, and is supplied to the combustion chamber.

A mixture of coal, CO ₂ and, if necessary, limestone, enters the injector 20 via line 21, enters the central pipe 102. This mixture is blown through the pipe due to the increased pressure of CO ₂ and introduced into the combustion chamber. According to the drawing, air is injected into the combustion chamber by nozzles, and the Venturi effect created by the nozzles will cause additional entrainment of the material from the central pipe into the combustion chamber.

The hot and burning gas-coal mixture from the injector 21 can adversely affect the wall of the combustion chamber and the heating coils 9. In order to avoid damage to the walls of the combustion chamber and the heating coils 9, a reflection plate 111 is installed opposite the injector 21 to reduce the rate of remaining unburnt particles and to avoid or to reduce damage to the inner wall of the combustion chamber. The reflector is preferably cooled by CO ₂ delivered through a gas line 110 circulating through the cooling channels 112 on the rear side of the reflector plate. Typically, one reflector plate is mounted on each injector if more than one injector is installed on the wall of the combustion chamber. Alternatively, the reflector may be in the form of a truncated cone with holes for injectors.

Figure 2b shows a cross section along line AA of Figure 2a. Around the central pipe 102, air injectors 103 are mounted. Gas injectors for injecting natural gas into the injectors through a gas line 22 are disposed, according to an example injector, inside one or more air injectors. Spiral ribs 105 on the inner wall of the central pipe cause the rotation of the coal mixture and, accordingly, the formation of turbulence in the combustion chamber. Turbulence is essential to ensure proper mixing of the injected coal, gas and air, necessary to create optimal combustion conditions.

Figure 3 shows a combination mill and intermediate storage device 14. Coal and limestone are transported via a conveyor 10, 11, 13 to a funnel 150 leading to the mill 12. The funnel 150 has inner shields 151 to reduce the coal / limestone feed rate to the mill 12. A reduced feed rate will optimally reduce the air intake rate. Mill 12 preferably contains several mills; moreover, the incoming coal and limestone are first included in the mill, and then in the fine grinding mill to ensure the desired particle size.

The mill and the bottom of the funnel are preferably cleaned with CO ₂ from the purification line 152 in order to reduce the amount of oxygen or air brought in with coal and limestone, since the mixture of coal dust and oxygen can be explosive. The flow of CO ₂ in the purification line is regulated by valve 153.

After the mill, the dust consisting of coal and limestone is fed vertically by an Archimedean screw 13 into the reservoir 16. The valve 15, installed between the conveyor 13 and the reservoir 16, is used to close the reservoir when it is filled with coal and limestone dust. When the reservoir 16 will need to be emptied into the combustion chamber, the valve 15 is closed, CO ₂ is introduced into the reservoir tank from the top via line 154 CO _2, controlled by a valve 155, and / or CO ₂ line 157 controlled by a valve 158. The introduction of CO ₂ or by line 154, or line 157 increases the pressure in the tank. The pressure in the tank rises to a pressure exceeding the pressure in the combustion chamber. The pressure in the reservoir is preferably 0.5-1 bar higher than the pressure in the combustion chamber. The introduction of CO ₂ through line 157 near the bottom of the tank will at least partially fluidize the contents of the tank. The valve 17 in line 20 will then be opened, and a mixture of CO ₂ , coal dust and limestone will be forced to enter through line 20 through the injector 21 into the combustion chamber, as described previously. After emptying the reservoir 16, the valve 17 is closed again, the valve 15 is opened, and the reservoir is again filled with dust, as mentioned above.

Figure 4 shows a combined secondary combustion chamber and a heat exchanger 200 instead of the secondary combustion chamber 81, the heat exchanger 59 and the lines connecting them. From the point of view of heat engineering, this combination is more efficient and eliminates or reduces the need for connecting lines.

Air and natural gas are introduced through the air line 203 and the gas line 202, respectively, into the combustion chamber 201. CO ₂ is introduced from the CO _{2 line} 204 along the cooling jacket 205 to cool the upper part of the combustion chamber, and then it enters the combustion chamber to control the composition of the gas in the combustion chamber. Burning gas in the combustion chamber is forced down into the combustion chamber and through openings 206 near the bottom of the combustion chamber. Warm flue gas from the combustion chamber circulates in the flue gas chamber located around the combustion chamber. The hot flue gas in the flue gas chamber is cooled by heat exchange from a low CO ₂ stream from line 58 entering the device through an inlet 212. A low CO ₂ stream is circulated in the circulation space between the outer wall of the flue gas chamber 207 and the heat exchanger housing 210.

The flue gas from the secondary combustion chamber 201 exits this device through the flue gas outlet 208 and enters line 86. The low CO ₂ heated stream exits this device through the exchanger outlet 213 to line 60. Air introduced into the air line 203 are preferably preheated by heat transfer from the low CO ₂ stream while introducing air into the air inlet of the jacket 216 that surrounds at least a portion of the heat exchanger housing 210. Heated air is removed through the air outlet 217 and output to the air line 203.

This combined combustion chamber and heat exchanger provides a more compact combustion chamber design. A significant temperature difference on the wall separating the combustion chamber and the heat exchanger of this device necessitates a relatively small heat exchange area.

5 shows an embodiment of an intermediate storage means 14 having a CO ₂ storage means 250. The means 250 comprises a _CO2 storage tank 255 CO ₂ compressor 259, the motor-263, the dust filter 252 and connecting lines 257 and 261, and several valves 253, 254, 258, 260 and 262, flow regulating system. The CO ₂ storage means 250 is configured to overlap from the intermediate storage means 14 with an additional valve 251.

When pressurized CO ₂ in the reservoir 255 fills one of the reservoirs 16, 16 ′ or 16 ″, the valve connected to the reservoir 16, i.e., 248, 248 ″ or 248 ″, opens. Then, valves 256 and 262 open so that gas from reservoir 255 goes along lines 257, 261 and 249, 249 'or 249'. When the flow from reservoir 255 to reservoir 16, 16 'or 16''is interrupted due to a decrease in pressure difference, valve 256 closes, valves 254, 260 and 258 open, and CO ₂ from reservoir 255 is compressed by compressor 259 so that the pressure in reservoir 255 reached almost atmospheric pressure. All valves 253, 254, 256, 258, 260, 262, and 248 then close.

To direct excess CO ₂ from reservoir 16, 16 'and 16''to reservoir 255, the corresponding valve 248, 248' or 248 '' opens. Then, CO ₂ can pass through the filter 252 from the reservoir 16, 16 'or 16''into the reservoir 255 by opening the valves 253 and 254. As soon as the flow decreases due to a decrease in the pressure difference between the reservoirs, the valve 254 closes, the valves 260, 258 and 256 will open and gas from reservoir 16, 16 'or 16''will be compressed and fed into reservoir 255 for temporary storage. When tank pressure 16, 16 'and 16''reaches almost atmospheric pressure, all valves 248, 248' and 248 '', 253, 254, 256, 258, 260 and 262 will close.

It will be obvious to a person skilled in the art that CO ₂ can be introduced into the reservoir 16 and removed from it via any CO ₂ lines into the reservoir, for example, along lines 154, 157 or 18; and that line 249 is indicated for purposes of explanation only and may be any line mentioned, for example, alone or in combination with others.

6 shows an exemplary and somewhat simplified CO ₂ capture device 49. Cooled gaseous products of combustion enter the device 49 via line 48 and enter the absorber 300 near its bottom. The cleaned gaseous products of combustion exit the absorber 300 via line 50 near the top of the absorber. An absorbent, such as an amine or a hot carbonate solution, is introduced into the absorber through line 301 near the top of the absorber, and the absorbent exits the absorber as a saturated absorbent (high CO ₂ content) through line 302 near the bottom of the absorber. Opposite flows of the gas to be cleaned and the absorbent through the absorber provide optimal conditions for the absorption of CO ₂ .

The saturated absorbent in line 302 is heated in the heat exchanger 303 from the regenerated (depleted) absorbent, and then the saturated absorbent enters the stripper 305 near its top. The temperature in the stripper is higher and the pressure is lower than in the absorber 300, as a result of which CO ₂ is released from the absorbent. The CO ₂ released from the absorbent is removed from the stripper via line 306 CO ₂ . The CO ₂ in line 306 is cooled in the partial reflux condenser 307, moisture is removed from the high CO ₂ stream exiting the CO ₂ capture device through line 51. The moisture condensed in the partial reflux condenser 307 is returned to the stripper via line 308 hot irrigation.

The desorbate is taken near the bottom of the stripper 305 via line 301. The desorbate in line 301 is cooled in the heat exchanger 303 and in the cooler 311, and then it enters the absorber 300. A portion of the desorbate can be taken in the heating circuit 309, where it is heated in the reboiler 310, and then heated the desorbate is reintroduced into stripper 305.

In the exemplary station of FIG. 1, the basic values of temperature, pressure and mass flow can be as follows:

Table 1 Pressure, temperature, mass flow and productivity for different devices / in different locations at a 400 MW station No. Pressure (bar) Temperature (° C) Mass flow (kg / s) Mfr. (MW) 13 1.013 thirty 21 (coal) 22 twenty fifteen 2,3 23 16 300 300 26 300 600 272 27 428 35 16 350 323 46 120-130 48 40-90 55 one hundred thirty 78 58 fifteen 330 385 60 fifteen 850 385 65 80 73 16 145 fifty 75 1.013 fifteen 400 80 twenty fifteen 5 82 870 86 fifteen 330 90 87 16 300 85 88 16 300 fifteen

It will be apparent to those skilled in the art that said heat exchangers, turbines, compressors, and the like. can be two or more devices connected in parallel and / or in series. In those cases where two or more parallels are mentioned, their number may differ from the number indicated in the exemplary embodiment of the invention.

Claims (11)

1. A method of generating electricity mainly from coal fuel, in which coal fuel and oxygen-containing gas are introduced into the combustion chamber and burned at elevated pressure and the gaseous combustion products are cooled in the combustion chamber by generating steam to generate electricity, while the gaseous combustion products are additionally cooled and separated into a high CO ₂ stream and a low CO ₂ stream
device capturing CO ₂ poor stream containing CO ₂ is heated and expanded in a turbine to generate electricity, and then flow with a low content of CO ₂ discharged into the environment, wherein the flow of high CO ₂ is separated at stream for storage or shipment and to the stream returned to the combustion chamber, and at least a portion of the high CO ₂ stream returned to the combustion chamber is mixed with coal fuel and then introduced into the combustion chamber, while it is injected into the combustion chamber together with coal fuel. 2. The method according to claim 1, wherein the low CO ₂ stream is heated by heat exchange from the gaseous products of combustion from the secondary gas-fired combustion chamber, and then the low CO ₂ stream is expanded in the turbine. 3. The method according to claim 1 or 2, wherein the pressure in the combustion chamber is from 5 to 35 bar. 4. The method according to claim 3, wherein the pressure is from 10 to 20 bar, more preferably from about 12 to 16 bar. 5. The method according to claim 1, wherein the temperature of the gaseous products of combustion leaving the combustion chamber is reduced to a temperature below about 350 ° C due to the generation of steam. 6. The method according to claim 1, wherein the natural gas is introduced into the combustion chamber to facilitate combustion. 7. Thermal power plant, operating mainly on coal fuel, containing a combustion chamber, means for introducing coal fuel and oxygen-containing gas into the combustion chamber, cooling means for cooling gaseous products of combustion in the combustion chamber, and means for separating gaseous products of combustion into a high flow CO ₂ content and a stream of low CO ₂ content, a line for recirculating a portion of CO ₂ in the combustion chamber and a _CO2 line for delivering the rest of the stream rich in CO ₂ for storage or otgr narrow, while the means for introducing coal fuel into the combustion chamber contains a reservoir and CO ₂ a line for introducing CO ₂ into the reservoir, and an injector for introducing coal fuel together with CO ₂ from the reservoir into the combustion chamber. 8. The thermal power station of claim 7, wherein the cooling means is cooling coils inside the combustion chamber, the cooling coils being configured to cool gaseous products of combustion by generating steam. 9. The thermal power station of claim 8, further comprising a steam turbine connected to a generator to generate electricity. 10. The thermal power station of claim 7, further comprising a gas-fired secondary combustion chamber for generating heat to heat the low CO ₂ stream and a turbine to expand the heated low CO ₂ stream, which is then discharged into the environment. 11. The thermal power station of claim 10, wherein the turbine is connected to a generator to generate electricity.

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