Graded pressurized oxygen-enriched combustion boiler coupled supercritical carbon dioxide circulation thermodynamic system

Abstract

The invention provides a staged pressurized oxygen-enriched combustion boiler coupling supercritical carbon dioxide circulation thermodynamic system, and belongs to the technical field of thermodynamic systems. The present invention comprises: an air molecule system for generating oxygen; the combustion subsystem is used for performing staged pressurized oxygen-enriched combustion on the oxygen generated by the air molecule system to generate heat and flue gas, one part of the flue gas is used as backflow flue gas to blow pulverized coal, and the other part of the flue gas enters the CO2 compression and purification subsystem to be deeply purified to generate high-purity CO2 gas; the CO2 compression and purification subsystem is used for deeply purifying the flue gas generated by the combustion subsystem to obtain high-purity CO2, and a CO2 working medium is compressed to a critical state and compressed to storage and transportation pressure; and a supercritical carbon dioxide working medium in the circulation subsystem absorbs the heat generated by the combustion subsystem and then generates power. The power generation efficiency of the system can reach 49.08% by coupling staged pressurized oxygen-enriched combustion with supercritical carbon dioxide circulation.

Description

Technical Field

[0001] The invention relates to the technical field of thermal systems, and in particular to a staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system. Background Art

[0002] Terminology explanation:

[0003] SPOC: Staged, Pressurized Oxy-Combustion: Gophan et al. proposed a new concept of staged oxygen-enriched combustion: through staged combustion of fuel, excess oxygen is used for dilution in the first stage, and the excess oxygen in the next few stages and the flue gas produced by the previous stage are used for dilution to control the combustion temperature and heat flux. In the new staged combustion system, the fuel is delivered to each stage of the combustion chamber in approximately equal proportions, and all O 2 The combustion products of the first combustion chamber are mixed with oxygen and then passed into the second combustion chamber to burn with the pulverized coal again. This process continues until the fourth combustion chamber. In the final combustion chamber, almost all the oxygen in the 2 is consumed, completing the staged combustion of coal. It is worth pointing out that in the staged combustion system, the combustion heat is mainly transferred to the circulation through radiation, and the outlet flue gas temperature of each stage combustion chamber is reduced to about 700℃. Figure 1 .

[0004] sCO 2 :supercritical Carbon dioxide, sCO 2 Supercritical carbon dioxide: Carbon dioxide fluid (supercritical fluid) maintained above the critical temperature and critical pressure has both gaseous and liquid properties.

[0005] Dual carbon: carbon peak and carbon neutrality;

[0006] ASU: Air Separation Unit, a device for separating and purifying nitrogen, oxygen, argon, etc. in the air. In the present invention, it refers to the air molecular system;

[0007] CPU: CO 2 Compression and Purification Unit, a carbon dioxide compression and purification unit, converts CO in the flue gas of coal-fired power plants into 2 Purification and storage device, used to reduce carbon emissions from power plants, in this invention, refers to CO 2 Compression purification subsystem;

[0008] LCOE: Levelized Cost of Energy, the levelized cost per kilowatt-hour, is the power generation cost calculated by leveling the cost and power generation during the project life cycle, that is, the present value of cost during the life cycle / the present value of power generation during the life cycle.

[0009] Under the background of global dual carbon, thermal power plants must also undertake the task of carbon emission reduction. Oxygen-enriched combustion technology is one of the most promising near-zero emission technologies for coal combustion. However, oxygen-enriched combustion requires air separation to produce oxygen and post-combustion carbon capture. These two parts consume a lot of energy, resulting in a significant decrease in the efficiency of the entire power plant. It is imperative to find a more efficient system. The efficiency of coal-fired power plants using oxygen-enriched combustion is improved mainly by: improving the circulation efficiency on the circulation side and adopting a more efficient combustion method on the boiler side. At present, steam coal-fired power plants improve their circulation efficiency mainly by improving the circulation steam parameters: supercritical units and ultra-supercritical units have been developed, and the circulation efficiency has been greatly improved. In recent years, domestic and foreign scholars have studied the use of more efficient sCO 2 The cycle is used in coal-fired power plants to further improve efficiency, and research has shown that sCO 2 The use of sCO in coal-fired power plants has obvious efficiency advantages. On the boiler side, Gophan et al. proposed a new combustion method: staged pressurized oxygen-enriched combustion, which can improve system efficiency and has economic advantages. 2 The SPOC system with better efficiency and economy is coupled with the cycle, and the SPOC pulverized coal boiler coupled with sCO 2 New thermal system.

[0010] The closest existing technologies are: SPOC boiler coupled steam circulation system, conventional boiler coupled supercritical carbon dioxide circulation system, both of which have the problem of low efficiency. Summary of the invention

[0011] In view of this, in order to solve the problem of low efficiency in the prior art, on the one hand, the present invention provides a staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system. By coupling the staged pressurized oxygen-enriched combustion with the supercritical carbon dioxide cycle, the power generation efficiency of the system can reach 49.08%, which is higher than the prior art.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system, comprising:

[0014] Empty molecular system for generating oxygen;

[0015] The combustion subsystem is used to perform oxygen enrichment combustion on the oxygen generated by the air molecular system to generate heat and flue gas, a part of the flue gas is used as the reflux flue gas to blow the coal powder, and the other part of the flue gas enters the CO 2 The compression and purification subsystem produces high-purity CO 2 gas;

[0016] CO 2 The compression and purification subsystem is used to deeply purify the flue gas generated by the combustion subsystem to obtain high-purity CO 2 , CO 2 The working fluid is compressed to a critical state and then compressed to storage and transportation pressure by a compressor;

[0017] The supercritical carbon dioxide working fluid in the circulation subsystem absorbs the heat generated by the combustion subsystem to generate electricity.

[0018] Preferably, the air molecule system is a three-tower air separation system.

[0019] Preferably, the air is compressed by a compressor, cooled to a critical temperature by a heat exchanger, and then divided into three streams and enter three distillation towers, namely, high, medium and low distillation towers;

[0020] When the saturated oxygen-nitrogen mixed gas passes through the oxygen-nitrogen mixed liquid with a lower temperature than it, the high-boiling point oxygen in the gas phase partially condenses into liquid, releasing the latent heat of condensation. At the same time, the low-boiling point nitrogen in the liquid phase absorbs heat and evaporates. After multiple partial condensations and partial evaporations, the nitrogen component in the gas phase becomes more concentrated as it moves upward, and the oxygen component in the liquid phase becomes more concentrated as it moves downward, thus achieving the purpose of oxygen-nitrogen separation.

[0021] Preferably, oxygen with a purity of 95.5% is finally obtained.

[0022] Preferably, the oxygen generated by the air molecule system is compressed in multiple stages, and then heated by the waste heat utilization device - oxygen heater before entering the multi-stage boiler of the combustion subsystem for combustion;

[0023] All the oxygen is directly introduced into the primary boiler, and the pulverized coal is sent into the boiler by the reflux flue gas for combustion;

[0024] The combustion products and excess oxygen from the first boiler enter the second boiler, and the process is repeated until the last boiler, where the combustion process ends.

[0025] The boiler transfers heat to the circulation subsystem through radiation heat exchange.

[0026] Preferably, the multi-stage boiler is four boilers, and the pulverized coal is fed into the four boilers for combustion in a ratio of 24:26:24:26.

[0027] Preferably, the last stage boiler outlet enters the economizer to reduce the temperature and then transfers the heat to the circulation subsystem. The flue gas after the economizer outlet enters the waste heat utilization equipment, dust collector and direct contact condenser in sequence for preliminary purification and removal of SO 2 After the initial purification, part of the flue gas is used as the reflux flue gas to blow the coal powder, and part of it enters the CO 2 Compression purification subsystem for deep purification.

[0028] Preferably, the flue gas after preliminary purification enters the CO 2 After dehydration in the compression purification subsystem, the dry flue gas after dehydration is partially condensed, and then the gas-liquid mixture enters the primary flash tank, N 2 , O 2 Volatilizes into steam, CO 2 Remaining in the liquid, the flue gas is separated into CO-rich 2 Logistics and CO 2 Logistics, CO2-rich 2 The stream is cooled and then enriched with CO in a secondary flash tank 2 The flow is separated again into CO-poor 2 Steam and CO-rich 2 Liquid flow, CO lean 2 The steam stream is discharged as exhaust gas, rich in CO 2 The liquid stream is compressed and then mixed with the CO in the primary flash tank. 2 The liquid streams are mixed and the resulting high-purity CO 2 The working fluid is compressed to a critical state and then compressed to storage and transportation pressure.

[0029] Preferably, the circulation process of the circulation subsystem is as follows:

[0030] Supercritical carbon dioxide enters the first-stage heater to absorb heat, and after the working fluid absorbs heat, it enters the first-stage turbine to do work, and then enters the second-stage heater and the third-stage heater to absorb heat, and enters the second-stage turbine and the third-stage turbine to do work. After the fluid exits the turbine, it enters the high-temperature regenerator to exchange heat with the cold side fluid, and then enters the low-temperature regenerator to exchange heat with the cold side fluid. Subsequently, part of the fluid is compressed by the re-compressor and merges with the fluid from the outlet of the low-temperature regenerator to enter the high-temperature regenerator, and the other part of the fluid is cooled by the cooler. After compression by the main compressor, cooling by the second-stage cooler, and compression by the second-stage main compressor, part of the fluid enters the low-temperature regenerator for heating, and the other part of the working fluid enters the fourth-stage heater for heating. Most of the heated fluid enters the high-temperature regenerator to absorb heat, and the other part enters the economizer for heating.

[0031] Preferably, the power generation efficiency reaches 49.08%.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system provided by the present invention can achieve a power generation efficiency of 49.08% by coupling staged pressurized oxygen-enriched combustion with a supercritical carbon dioxide cycle, which is higher than the prior art. Compared with the prior art, the present invention is more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a conceptual diagram of staged pressurization and oxygen-rich combustion;

[0035] Figure 2 It is the overall flow chart of the present invention;

[0036] Figure 3 It is a flow chart of a three-tower air separation system;

[0037] Figure 4 This is the layout diagram of the boiler heating surface in the combustion subsystem;

[0038] Figure 5 For CO 2 Flow chart of compression and purification subsystem;

[0039] Figure 6 It is the flow chart of the loop subsystem;

[0040] Figure 7 It is the circulation flow chart of the working fluid in the circulation subsystem;

[0041] In the figure, MC1-MC2 are the first-stage and second-stage main compressors respectively, RC is the recompressor, Cooler1 is the first-stage cooler, Cooler2 is the second-stage cooler, LTR is the low-temperature regenerator, HTR is the high-temperature regenerator, T1-T3 are the first-stage, second-stage and third-stage turbines respectively, H1-H4 are the first-stage, second-stage, third-stage and fourth-stage heaters respectively, ECO is the economizer, and DCC is the direct contact condenser. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "primary", "secondary", and "quaternary" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] like Figure 1-7 As shown, the present invention provides a staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system, comprising:

[0046] Empty molecular system for generating oxygen;

[0047] The combustion subsystem is used to perform oxygen enrichment combustion on the oxygen generated by the air molecular system to generate heat and flue gas, a part of the flue gas is used as the reflux flue gas to blow the coal powder, and the other part of the flue gas enters the CO 2 The compression and purification subsystem produces high-purity CO 2 gas;

[0048] CO 2 The compression and purification subsystem is used to deeply purify the flue gas generated by the combustion subsystem to obtain high-purity CO 2 , CO 2 The working fluid is compressed to a critical state and then compressed to storage and transportation pressure by a compressor;

[0049] The supercritical carbon dioxide working medium in the circulation subsystem absorbs the heat generated by the combustion subsystem to generate electricity. The supercritical carbon dioxide working medium circulates in a closed loop in the circulation subsystem.

[0050] A specific embodiment of the present invention is as follows Figure 2As shown in the overall system flow chart, air passes through the three-tower air separation system (low temperature) to obtain high-concentration oxygen (concentration of 95.5%), which is compressed to an operating pressure of 1.6 MPa and then introduced into the furnace (inconel625 nickel-based alloy steel is selected as the cooling wall of the entire furnace) to mix with coal powder for staged pressurized oxygen-enriched combustion. Most of the heat generated by combustion is transferred to sCO by radiation. 2 Working fluid, high temperature and high pressure sCO after absorbing heat 2 Enters the turbine to do work (high temperature and high pressure sCO 2 The flue gas produced by combustion is initially purified and then a part of it is fed into the coal feeder as power gas to deliver powder (coal powder), and the other part is compressed and purified by the CPU to obtain high-purity CO 2 Compression, storage and transportation. The waste heat utilization equipment includes oxygen heater, flue gas heater and four-stage heater (H4).

[0051] The combustion system is coupled with the circulation subsystem, and the boiler heating surface layout is shown in Figure 4 The entire boiler heating surface is divided into four parts: part 1, part 2, part 3, and part 4. The first-level working fluid first enters the heating surface part 3 for heating. After being heated to 570°C, it enters the heating surface part 4 to obtain the second-level working fluid, and then enters the turbine to do work. Figure 4 2-6 (secondary to sixth-level working fluid) repeat the heating and working process.

[0052] The above system according to the present invention is described below by way of example in conjunction with the accompanying drawings of the specific specification, as follows:

[0053] like Figure 3 As shown, in the present invention, the air molecule system is preferably a three-tower air separation system. The air is compressed by a compressor (preferably compressed to 5.5MPa), then cooled to the critical temperature by a heat exchanger (preferably two heat exchangers), and then divided into three streams and enter the high, medium and low distillation towers respectively. The same process occurs in the three towers.

[0054] When the saturated oxygen-nitrogen mixed gas (rising in the tower) passes through the oxygen-nitrogen mixed liquid with a lower temperature than it (descending in the tower), the high-boiling-point oxygen in the gas phase is partially condensed into liquid, releasing the condensation latent heat. At the same time, the low-boiling-point nitrogen in the liquid phase absorbs heat and evaporates. After multiple partial condensations and partial evaporations, the nitrogen component in the gas phase becomes more concentrated as it goes up, and the oxygen component in the liquid phase becomes more concentrated as it goes down, achieving the purpose of oxygen-nitrogen separation. Finally, oxygen with a purity of preferably 95.5% is obtained.

[0055] like Figure 5As shown, in the present invention, the oxygen generated by the air molecule system is compressed in multiple stages, and then heated by the waste heat utilization device - oxygen heater, and then enters the multi-stage boiler of the combustion subsystem for combustion;

[0056] All the oxygen is directly introduced into the primary boiler, and the pulverized coal is sent into the boiler by the reflux flue gas for combustion;

[0057] The combustion products and excess oxygen from the first boiler enter the second boiler, and the process is repeated until the last boiler, where the combustion process ends.

[0058] The boiler transfers heat to the circulation subsystem through radiation heat exchange.

[0059] like Figure 2 As shown, in the present invention, the multi-stage boiler is four boilers, which are named as primary, secondary, tertiary and quaternary boilers respectively, and the pulverized coal is fed into the four boilers for combustion in a ratio of 24:26:24:26 respectively.

[0060] In the present invention, the flue gas at the last boiler outlet enters the economizer to reduce the temperature and then transfers the heat to the circulation subsystem. The flue gas at the economizer outlet enters the waste heat utilization equipment, the dust collector and the direct contact condenser in sequence to initially purify and remove SO 2 After the initial purification, part of the flue gas is used as the reflux flue gas to blow the coal powder, and part of it enters the CO 2 Compression purification subsystem for deep purification. Figure 2-4 As shown, a specific process of the above-mentioned space molecule system and combustion subsystem is as follows:

[0061] The combustion subsystem preferably adopts the staged pressurized combustion technology in the article "Process design and performance analysis of a Staged, Pressurized Oxy-Combustion (SPOC) power plant for carbon capture". 95.5% of the oxygen obtained in the air molecule system is compressed in multiple stages to reach 1.6MPa, 128°C, and then heated to 325°C by the waste heat utilization equipment-oxygen heater before entering the combustion system. All the oxygen is directly introduced into the first-stage boiler, and the pulverized coal is sent to four boilers for combustion by the return flue gas in a ratio of 24:26:24:26. ​​The return flue gas is first heated to 115°C by the waste heat utilization equipment-flue gas heater. The combustion products and excess oxygen of the first-stage boiler enter the second-stage boiler, and this process is repeated until the fourth-stage boiler, and the combustion process is completed. The boiler transfers heat to the cycle through radiation heat exchange. The flue gas temperature at the outlet of each boiler is 700℃. After the outlet of the fourth boiler, it enters the economizer to reduce the temperature to 330℃ and transfers the heat to the cycle. After the outlet of the economizer, the flue gas enters the waste heat utilization equipment (including H4, flue gas heater and oxygen heater) to reduce the temperature to 130℃, and then enters the dust collector for dust removal and then passes through the direct contact condenser (DCC) for preliminary purification to remove SO 2 and NOx and is cooled to 25°C again. The flue gas after preliminary purification is compressed to 3Mpa and 43°C, part of which is used as reflux flue gas to blow coal powder, and part of which enters CO 2 Compression purification subsystem for deep purification.

[0062] like Figure 5 As shown, the CO provided by the present invention 2 Flow chart of compression purification subsystem. The flue gas after preliminary purification (3Mpa, 43℃ flue gas) enters CO 2 After dehydration in the compression purification subsystem (preferably using molecular sieve dehydration to reduce the water content in the flue gas to 20ppm), the dehydrated dry flue gas is partially condensed (preferably partially condensed in a heat exchanger), and then the gas-liquid mixture enters the primary flash tank. In the primary flash tank, due to the difference in boiling point, N 2 , O 2 Volatilizes into steam, CO 2 Remaining in the liquid, the flue gas is separated into CO-rich 2 Logistics and CO 2 Logistics, CO2-rich 2 Logistics cooling (preferably CO rich 2 The flow enters the secondary heat exchanger for further cooling) and then is enriched with CO in the secondary flash tank. 2 The flow is separated again into CO-poor 2 Steam and CO-rich 2Liquid flow, CO lean 2 The steam stream is discharged as exhaust gas, rich in CO 2 The liquid stream is compressed and then mixed with the CO in the primary flash tank. 2 The liquid streams are mixed and the resulting high-purity CO 2 The working fluid is compressed to a critical state and then compressed to storage and transportation pressure (preferably using CO 2 The compressor compresses to the storage and transportation pressure of 11MPa).

[0063] It should be noted that the high-purity CO 2 The supercritical carbon dioxide produced by compressing the working fluid to a critical state can also supplement the supercritical carbon dioxide in the circulation subsystem according to actual needs, and can also be used for other purposes or sold on the market, without any special requirements.

[0064] like Figure 4 , 6 -7, in the present invention, the circulation process of the circulation subsystem is as follows:

[0065] Supercritical carbon dioxide enters heater 1 (H1) at point 1 to absorb heat. After absorbing heat, the working fluid obtains state point 2 and enters turbine 1 (T1) to do work. Then, it enters heaters 2 and 3 (H2 and H3) to absorb heat in processes 3-4 and 5-6 respectively. It enters turbines 2 and 3 (T2 and T3) to do work in processes 4-5 and 6-7. After the fluid 7 exits the turbine, it enters the high temperature recuperator (High Temperature Recuperator, HTR) to exchange heat with the cold side fluid to point 8. The fluid at point 8 enters the low temperature recuperator (Low Temperature Recuperator, LTR) to exchange heat with the cold side fluid to point 9. A part of the fluid after point 9 is compressed by the re-compressor (Re-compressor, RC) and merges with the cold side fluid from the low temperature recuperator to enter the high temperature recuperator. The other part of the fluid is cooled by the cooler (Cooler) to point 10. It is compressed by the main compressor (Main Compressor, MC) 1, cooled by the cooler 2, and compressed by the main compressor 2 to obtain point 13, and then enters the low temperature recuperator. A portion of the working fluid at point 13 is diverted into H4 for heating and then to point 14, and a portion of the working fluid at point 14 is diverted into the economizer (Economizer, ECO) for heating to point 1.

[0066] H1 corresponds to parts 3 and 4, H2 corresponds to part 1, and H3 corresponds to part 2. Figure 7 All Arabic numerals 1-14 in the table refer to the working fluid, and Figure 4 , 6 -7 The Arabic numerals correspond one to one.

[0067] The layout of the circulation subsystem is as follows Figure 6As shown, the selection of cycle parameters is shown in the following Table 1.

[0068] Table 1 Cycle parameters

[0069]

[0070]

[0071] In the above-mentioned staged pressurized oxygen-enriched combustion boiler coupled with supercritical carbon dioxide cycle thermal system provided by the present invention, the boiler heating surface is arranged as follows Figure 4 As shown, the four boilers use the same heating surface layout, and the heating surface parameters are shown in the following table

[0072] Table 2 Heating surface parameters

[0073]

[0074]

[0075] Note: The above-mentioned first-level boiler, second-level boiler, third-level boiler and fourth-level boiler correspond to Figure 2 Boiler 1, boiler 2, boiler 3 and boiler 4 in the embodiment.

[0076] The above-mentioned staged pressurized oxygen-enriched combustion boiler coupled with the supercritical carbon dioxide cycle thermal system provided by the present invention has a power generation efficiency of 49.08%.

[0077] The technical solution of the present invention is clearly described in detail below in conjunction with specific embodiments.

[0078] Example 1

[0079] The above-mentioned staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system provided by the present invention is adopted, and its parameters are selected from the above-mentioned preferred parameters.

[0080] Comparative Example 1

[0081] The concept of staged pressurized oxygen-enriched boiler proposed in the paper "Process design and performance analysis of a Staged, Pressurized Oxy-Combustion (SPOC) power plant for carbon capture" was adopted, and the staged pressurized oxygen-enriched boiler was combined with the steam Rankine cycle to generate electricity. A 550MW unit was built. Considering the energy consumption of air separation oxygen production and CO 2 The efficiency of capturing energy consumption is 36.7%, which is the highest level among all oxygen-enriched combustion system steam cycle power generation systems. The efficiency of this system reaches 39.7%, which is 3% higher than that of the reference.

[0082] Comparative Example 2

[0083] The paper "Economic comparison between sCO2 power cycle and water-steamRankine cycle for coal-fired power generation system" gives a 1000MW atmospheric pressure air coal-fired boiler coupled with a supercritical carbon dioxide cycle power generation system. The net power generation efficiency of the system is 49.01%. When the energy consumption of air separation oxygen production and carbon dioxide capture is not considered in this paper, the system power generation efficiency reaches 49.08%, which is slightly higher than the reference.

[0084] In comparison, the article "Design and Economic Analysis of a 660MW Supercritical Carbon Dioxide Coal-fired Unit Boiler" presents a 660MW atmospheric pressure air coal-fired boiler coupled with a supercritical carbon dioxide cycle power generation system. The net power generation efficiency of the system is 47.12%, which is 1.96% lower than the efficiency of the system in this article when the energy consumption of air separation for oxygen production and carbon dioxide capture is not considered, which is quite impressive.

[0085] Comparative Example 3 (economical aspect)

[0086] The article “Boiler Design and Economic Analysis of 660MW Supercritical CO2 Coal-fired Unit” gives the levelized cost of electricity (LCOE) of 660MW conventional steam cycle unit as 0.609 yuan / kwh and the LCOE of supercritical CO2 unit as 0.540 yuan / kwh. The cost calculation in the literature does not involve the power consumption of air separation oxygen production and carbon dioxide capture. The LCOE of this system is 0.574 after considering the power consumption of air separation oxygen production and carbon dioxide capture, which is more economical than the steam cycle unit. The LCOE of this system when considering the sale of carbon dioxide is 0.536 yuan / kwh, which is still slightly lower than the LCOE of 0.540 yuan / kwh of the supercritical CO2 unit in the literature.

[0087] In summary, the above-mentioned staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system provided by the present invention has the technical effects of high efficiency and good economy, and its efficiency and economic benefits are significantly improved compared with the coal-fired power plant in the prior art.

[0088] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system, characterized in that: include: Empty molecular system for producing oxygen; The combustion subsystem is used to perform staged pressurization and oxygen-enriched combustion on the oxygen generated by the air molecule system to generate heat and flue gas, a part of the flue gas is used as reflux flue gas to blow the coal powder, and the other part of the flue gas enters the CO2 compression and purification subsystem for deep purification to produce high-purity CO2 gas; The CO2 compression and purification subsystem is used to deeply purify the flue gas generated by the combustion subsystem to obtain high-purity CO2. The CO2 working medium is compressed to a critical state and then compressed to a storage and transportation pressure by a compressor; The supercritical carbon dioxide working fluid in the circulation subsystem absorbs the heat generated by the combustion subsystem to generate electricity.

2. According to claim 1, a staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system is characterized in that: The air molecule system is a three-tower air separation system.

3. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 2 is characterized in that: The air is compressed by the compressor, cooled to the critical temperature by the heat exchanger, and then divided into three streams and enters the high, medium and low distillation towers respectively; When the saturated oxygen-nitrogen mixed gas passes through the oxygen-nitrogen mixed liquid with a lower temperature than it, the high-boiling point oxygen in the gas phase partially condenses into liquid, releasing the latent heat of condensation. At the same time, the low-boiling point nitrogen in the liquid phase absorbs heat and evaporates. After multiple partial condensations and partial evaporations, the nitrogen component in the gas phase becomes more concentrated as it moves upward, and the oxygen component in the liquid phase becomes more concentrated as it moves downward, thus achieving the purpose of oxygen-nitrogen separation.

4. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 3 is characterized in that: Finally, oxygen with a purity of 95.5% is obtained.

5. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 1, characterized in that: The oxygen generated by the air molecule system is compressed in multiple stages, and then heated by the waste heat utilization device - oxygen heater, and then enters the multi-stage boiler of the combustion subsystem for combustion; All the oxygen is directly introduced into the primary boiler, and the pulverized coal is sent into the boiler by the reflux flue gas for combustion; The combustion products and excess oxygen from the first boiler enter the second boiler, and the process is repeated until the last boiler, where the combustion process ends. The boiler transfers heat to the circulation subsystem through radiation heat exchange.

6. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 5, characterized in that: The multi-stage boiler consists of four boilers, and the pulverized coal is fed into the four boilers for combustion in a ratio of 24:26:24:

26.

7. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 5, characterized in that: After the outlet of the last stage boiler, the flue gas enters the economizer to reduce the temperature and then transfers the heat to the circulation subsystem. After the outlet of the economizer, the flue gas enters the waste heat utilization equipment, dust collector and direct contact condenser in sequence for preliminary purification to remove SO2 and NOx and is cooled again. Part of the flue gas after preliminary purification is used as reflux flue gas to blow coal powder, and part enters the CO2 compression purification subsystem for deep purification.

8. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 7, characterized in that: The flue gas after preliminary purification enters the CO2 compression and purification subsystem for dehydration, and then the dehydrated dry flue gas is partially condensed, and then the gas-liquid mixture enters the primary flash tank, N2 and O2 evaporate into the steam, CO2 remains in the liquid, and the flue gas is separated into CO2-rich logistics and CO2-containing logistics. The CO2-rich logistics is cooled, and then the CO2-rich logistics is separated again into CO2-lean vapor flow and CO2-rich liquid flow in the secondary flash tank. The CO2-lean vapor flow is discharged as waste gas, and the CO2-rich liquid flow is compressed and mixed with the CO2 liquid flow of the primary flash tank. Finally, the obtained high-purity CO2 working fluid is compressed to the critical state, and then compressed to the storage and transportation pressure.

9. The staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claim 1, characterized in that: The cyclic process of the cyclic subsystem is as follows: Supercritical carbon dioxide enters the first-stage heater to absorb heat, and after the working fluid absorbs heat, it enters the first-stage turbine to do work, and then enters the second-stage heater and the third-stage heater to absorb heat, and enters the second-stage turbine and the third-stage turbine to do work. After the fluid exits the turbine, it enters the high-temperature regenerator to exchange heat with the cold side fluid, and then enters the low-temperature regenerator to exchange heat with the cold side fluid. Subsequently, part of the fluid is compressed by the re-compressor and merges with the fluid from the outlet of the low-temperature regenerator to enter the high-temperature regenerator, and the other part of the fluid is cooled by the cooler. After compression by the main compressor, cooling by the second-stage cooler, and compression by the second-stage main compressor, part of the fluid enters the low-temperature regenerator for heating, and the other part of the working fluid enters the fourth-stage heater for heating. Most of the heated fluid enters the high-temperature regenerator to absorb heat, and the other part enters the economizer for heating.

10. A staged pressurized oxygen-enriched combustion boiler coupled with a supercritical carbon dioxide cycle thermal system according to claims 1-9, characterized in that: The power generation efficiency reaches 49.08%.

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