Power generation system for improving boiler flexibility by coupling low-carbon fuel

Abstract

The invention discloses a power generation system for improving the flexibility of a boiler by coupling low-carbon fuel, and relates to the technical field of peak shaving of coal-fired units. A flue gas branch is arranged between a denitration device and an air pre-heater, and a chemical heat storage device and a flue gas adjusting plate are arranged at the joint of the flue gas branch; a flue gas adjusting plate opens a flue gas branch, so that flue gas generated by a coal-fired boiler enters a chemical heat storage device and absorbs heat in a fixed bed reactor, generated synthesis gas is output to a synthesis gas storage tank to be stored after a product is treated by a gas-liquid separator, generated liquid is recycled through a reactant storage tank, and in a heat release mode, the chemical heat storage device is connected with the fixed bed reactor. And the synthesis gas stored in the synthesis gas storage tank is input into the coal-fired boiler for combustion to improve the output of the coal-fired boiler. By coupling the low-carbon fuel, the waste heat of the flue gas at the tail part of the boiler is fully utilized to prepare the synthesis gas during load reduction; when the load rises, the variable load rate of the unit is increased through the synthesis gas, meanwhile, the grade of flue gas waste heat is improved, and the flexibility and the high efficiency of the unit are cooperatively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of peak load regulation of coal-fired units, and in particular to a power generation system for coupling low-carbon fuel to enhance boiler flexibility. Background Art

[0002] By the end of 2023, the total installed capacity of renewable energy in China will have exceeded that of coal-fired power, and the proportion of renewable energy power generation will steadily increase. New energy generally has the characteristics of large volatility and strong randomness, so the electricity from new energy will bring more impact to the stability of the power grid in large-scale grid connection.

[0003] During the peak period of renewable energy generation, coal-fired units need to reduce their output, and renewable energy will take on the main power generation task. However, in the low-load operation range, coal-fired units are prone to a series of system economic and environmental problems such as low system efficiency, sharp increase in coal consumption per unit of power generation, low system economy, reduced boiler combustion stability under ultra-low load, and substandard inlet temperature of the desulfurization and denitrification system. It may even cause damage to the turbine tip blades, re-ignition of incompletely burned coal powder, and local overheating of the furnace, which threaten the safety of the unit. The demand for deep peak regulation requires coal-fired units to have a certain degree of flexibility, but coal-fired units under low load seriously deviate from the design conditions. The impact of the unit operating under abnormal conditions on the safety, environmental protection and economy of the unit cannot be ignored. The flexibility and efficiency of coal-fired units are interrelated, but there is a certain incompatibility.

[0004] The peak load regulation of coal-fired units coupled with energy storage systems can reduce the damage to the units caused by the deviation of peak load regulation from the design conditions, while enhancing the response rate of coal-fired units to changes in grid load. It is a feasible flexibility transformation plan. The energy storage technologies that can be coupled with coal-fired units mainly include heat storage technology, electrochemical energy storage, compressed air energy storage, flywheel energy storage and other technologies. Among them, heat storage technology is a low-cost technology that has been initially applied. The heat storage technology currently used is mainly sensible heat storage technology such as thermal storage tanks. Due to cost constraints, the scale of the energy storage system can only play a regulatory role and increase the response rate of coal-fired units to load changes, but it cannot solve the inefficiency problem of coal-fired units when operating at low loads. Summary of the invention

[0005] The purpose of the present invention is to provide a power generation system that couples low-carbon fuel to enhance the flexibility of the boiler, thereby enhancing the flexibility of the coal-fired unit, increasing the efficiency of the coal-fired unit during peak-shaving operation while increasing the low-load stable combustion capability of the boiler, and achieving quality improvement and efficiency enhancement of the thermal energy of the coal-fired unit.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a power generation system for coupling low-carbon fuel to improve boiler flexibility, including a denitration device, an air preheater, a flue gas branch arranged between the denitration device and the air preheater, a chemical heat storage device connected to the flue gas branch, and a flue gas regulating plate. The flue gas regulating plate is located in the tail flue of the boiler outlet, and is used to adjust the flue gas ratio flowing through the air preheater and the heat storage device. The chemical heat storage device includes a reactant storage tank, a fixed bed reactor, a gas-liquid separator and a synthesis gas storage tank. The reactant storage tank stores reactants and is connected to the fixed bed reactor. The reactants are low-carbon fuels. The chemical heat storage device is used in the heat storage mode. The flue gas regulating plate opens the flue gas branch so that the flue gas generated by the coal-fired boiler enters the chemical heat storage device and reacts in the fixed bed reactor to generate a product. After the product is processed by the gas-liquid separator, the generated synthesis gas is output to the synthesis gas storage tank for storage, and the generated liquid is recovered through the reactant storage tank. In the heat release mode, the synthesis gas stored in the synthesis gas storage tank is input into the coal-fired boiler for combustion to increase the output of the coal-fired boiler.

[0007] Wherein, the gas-liquid separator includes a product inlet, a synthesis gas outlet and an unreacted product outlet. The gas-liquid separator inputs the product of the fixed bed reactor reaction through the product inlet and then separates the product into solid and liquid through heat exchange in a heat exchanger, outputs the gas generated by the solid-liquid separation to the synthesis gas storage tank through the synthesis gas outlet for storage, and outputs the liquid generated by the solid-liquid separation to the reactant storage tank through the unreacted product outlet and through the unreacted liquid loop for recovery.

[0008] Wherein, the heat exchanger is a tubular heat exchanger or a plate heat exchanger, which is used to perform heat exchange on the product to achieve solid-liquid separation and to preheat the reactants before they enter the fixed bed reactor.

[0009] Among them, it also includes a synthesis gas preheater connected to the outlet of the synthesis gas storage tank and a reactant preheater arranged on the reactant storage tank and the fixed bed reactor. The synthesis gas preheater is used to preheat the synthesis gas output from the synthesis gas storage tank so that the synthesis gas reaches the combustion preheating temperature before being output to the furnace of the coal-fired boiler through the burner nozzle for combustion. The reactant preheater is used to preheat the reactants of the fixed bed reactor or to preheat the reactants output from the reactant storage tank to the fixed bed reactor through a material pump before reaching the fixed bed reactor. The heat exchanger is connected to the reactant preheater and the synthesis gas preheater for exchanging heat with the reactant preheater and the synthesis gas preheater.

[0010] Among them, it also includes a fixed bed temperature sensor arranged in the fixed bed reactor, a synthesis gas temperature sensor arranged in the synthesis gas preheater, and a reactant temperature sensor arranged in the reactant preheater. The fixed bed temperature sensor is used to detect the inlet temperature value and the outlet temperature value of the fixed bed reactor, the synthesis gas temperature sensor is used to detect the temperature value of the synthesis gas preheater before and after preheating the synthesis gas, and the reactant temperature sensor is used to detect the temperature value of the reactant before and after preheating by the reactant preheater. The controller is connected to the fixed bed reactor, the synthesis gas preheater, and the reactant preheater, and controls the operating parameters of the flue gas regulating plate, the operating parameters of the fixed bed reactor, the operating parameters of the synthesis gas preheater, and the operating parameters of the reactant preheater according to the operating parameters of the corresponding equipment and the current equipment operating mode.

[0011] Among them, it also includes a first valve arranged between the reactant storage tank and the feed pump, a second valve arranged between the feed pump and the heat exchanger, a third valve arranged between the heat exchanger and the gas-liquid separator, a fourth valve arranged between the gas-liquid separator and the synthesis gas storage tank, a fifth valve arranged between the synthesis gas storage tank and the synthesis gas preheater, a sixth valve arranged between the synthesis gas preheater and the burner nozzle, a seventh valve arranged between the flue gas adjustment plate and the synthesis gas preheater, and an eighth valve arranged between the flue gas adjustment plate and the fixed bed reactor.

[0012] The invention also includes a granular packed bed catalyst layer arranged in the fixed bed reactor, wherein the bed porosity of the granular packed bed catalyst layer is 0.4-0.8, and the granular packed bed catalyst layer is CuO, ZnO and Al 2 O 3 The granular stacked bed catalyst layer is composed of a mixture, wherein the mass proportion of CuO in the granular stacked bed catalyst layer is 55% to 65%, the mass proportion of ZnO is 28% to 32%, and the mass proportion of Al 2 O 3 The quality accounts for 8%~12%.

[0013] Wherein, it also includes a pressurizing device arranged in the synthesis gas storage tank, which is used to pressurize the synthesis gas output from the synthesis gas outlet to a predetermined pressure and then store it in the synthesis gas storage tank.

[0014] The synthesis gas is hydrogen, the low-carbon fuel reactant is a low-carbon fuel that undergoes a reforming reaction in a temperature range of 150-350° C., and the low-carbon fuel includes at least one of methanol, ethanol and propanol.

[0015] Wherein, the fixed bed reactor is a spiral coil fixed bed reactor, a vertical cylindrical fixed bed reactor or a horizontal cylindrical fixed bed reactor.

[0016] The power generation system for coupling low-carbon fuel to improve boiler flexibility provided by the embodiment of the present invention has the following advantages compared with the prior art:

[0017] The power generation system provided by the embodiment of the present invention for coupling low-carbon fuel to improve the flexibility of the boiler is provided by setting a flue gas branch between the denitrification device and the air preheater, and setting a chemical heat storage device and a flue gas regulating plate at the connection of the flue gas branch. In the heat storage mode, the flue gas regulating plate opens the flue gas branch so that the flue gas generated by the coal-fired boiler enters the chemical heat storage device and reacts in the fixed bed reactor to generate a product. After the product is processed by the gas-liquid separator, the generated synthesis gas is output to the synthesis gas storage tank for storage, and the generated liquid is recovered through the reactant storage tank. In the heat release mode, the synthesis gas stored in the synthesis gas storage tank is input into the coal-fired boiler for combustion to improve the output of the coal-fired boiler. By coupling low-carbon fuels, when reducing the load, the flue gas waste heat in the tail flue of the boiler is fully utilized to produce synthesis gas; when increasing the load, the synthesis gas is used to increase the load change rate of the unit, while the flue gas waste heat is used to improve the quality, thereby synergistically improving the flexibility and efficiency of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of an embodiment of a power generation system for improving boiler flexibility by coupling low-carbon fuels provided in an embodiment of the present invention;

[0020] Among them, 1-reactant storage tank, 2-feed pump, 3-fixed bed reactor, 4-waste heat recovery device, 5-gas-liquid separator, 6-synthesis gas storage tank, 7-synthesis gas preheater, 8-synthesis gas nozzle, 9-coal-fired boiler, 10-three flue gas regulating dampers, 11-unreacted liquid loop; 12-first valve, 21-second valve, 31-third valve, 41-fourth valve, 51-fifth valve, 61-sixth valve, 71-seventh valve, 81-eighth valve. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of an embodiment of a power generation system for coupling low-carbon fuel to enhance boiler flexibility provided in an embodiment of the present invention.

[0023] In a specific embodiment, the power generation system for coupling low-carbon fuel to improve boiler flexibility includes a denitration device, an air preheater, a flue gas branch arranged between the denitration device and the air preheater, a chemical heat storage device connected to the flue gas branch, and a flue gas conditioning plate 10. The flue gas regulating plate 10 is located in the tail flue of the boiler outlet, and is used to adjust the flue gas ratio flowing through the air preheater and the heat storage device. The chemical heat storage device includes a reactant storage tank 1, a fixed bed reactor 3, a gas-liquid separator 5 and a synthesis gas storage tank 6. The reactant storage tank 1 stores reactants and is connected to the fixed bed reactor 3. The reactants are low-carbon fuels. The chemical heat storage device is used in the heat storage mode. The flue gas regulating plate 10 opens the flue gas branch so that the flue gas generated by the coal-fired boiler 9 enters the chemical heat storage device and reacts in the fixed bed reactor 3 to generate a product. After the product is processed by the gas-liquid separator 5, the generated synthesis gas is output to the synthesis gas storage tank 6 for storage, and the generated liquid is recovered through the reactant storage tank 1. In the heat release mode, the synthesis gas stored in the synthesis gas storage tank 6 is input into the coal-fired boiler 9 for combustion to increase the output of the coal-fired boiler 9.

[0024] By setting a flue gas branch between the denitrification device and the air preheater, and setting a chemical heat storage device and a flue gas regulating plate 10 at the connection of the flue gas branch, in the heat storage mode, the flue gas regulating plate 10 opens the flue gas branch so that the flue gas generated by the coal-fired boiler 9 enters the chemical heat storage device and reacts in the fixed bed reactor 3 to generate a product. After the product is processed by the gas-liquid separator 5, the generated synthesis gas is output to the synthesis gas storage tank 6 for storage, and the generated liquid is recovered through the reactant storage tank 1. In the heat release mode, the synthesis gas stored in the synthesis gas storage tank 6 is input into the coal-fired boiler 9 for combustion to increase the output of the coal-fired boiler 9. By coupling low-carbon fuels, the flue gas waste heat in the tail flue of the boiler is fully utilized to produce synthesis gas when the load is reduced; when the load is increased, the synthesis gas is used to increase the load change rate of the unit, and the flue gas waste heat is used to improve the quality, which synergistically improves the flexibility and efficiency of the unit.

[0025] In the present application, the product is separated into gas and liquid through the gas-liquid separator 5, and the generated synthesis gas is separated from the unreacted reactants. The specific structure is not limited. In one embodiment, the gas-liquid separator 5 includes a product inlet, a synthesis gas outlet and an unreacted product outlet. The gas-liquid separator 5 inputs the product of the fixed bed reactor 3 through the product inlet and then performs solid-liquid separation of the product through heat exchange by a heat exchanger, and outputs the gas generated by the solid-liquid separation to the synthesis gas storage tank 6 through the synthesis gas outlet for storage, and outputs the liquid generated by the solid-liquid separation to the reactant storage tank 1 through the unreacted product outlet and through the unreacted liquid loop 11 for recovery.

[0026] By setting a product inlet, a synthesis gas outlet and an unreacted product outlet, after the reactants are input from the product inlet, the heat of the reactants is absorbed by the heat exchanger to reduce the temperature. On the one hand, the heat is recovered, and on the other hand, the unreacted reactants are converted from gaseous to liquid. At the same time, the generated synthesis gas is in gaseous state, thereby realizing the separation of gas and liquid. The synthesis gas is output to the synthesis gas storage tank 6 through the synthesis gas outlet for storage, and the liquid unreacted product is output to the reactant storage tank 1 through the unreacted liquid loop 11 for recovery. Since the gas-liquid separation is realized, the synthesis gas storage tank 6 only stores the synthesis gas, thereby improving the storage degree and the safety of subsequent use. At the same time, the temperature of the synthesis gas is reduced, which can reduce the storage pressure, improve the storage efficiency and safety, and the unreacted reactants can be recycled, thereby improving the utilization efficiency.

[0027] The specific structure of the gas-liquid separator 5 is not limited in the present application, and includes but is not limited to the above-mentioned structure.

[0028] The structure of the heat exchanger is not limited in the present application. The heat exchanger is a tubular heat exchanger or a plate heat exchanger, or a heat exchanger of other structures. The heat exchange medium therein is not limited in the present application. It can be a gaseous heat exchange medium or a liquid heat exchange medium. The heat exchanger achieves solid-liquid separation by exchanging heat with the product and preliminarily preheats the reactants before entering the fixed bed reactor 3.

[0029] In order to further improve the heat utilization efficiency and subsequent utilization efficiency, in one embodiment, the power generation system coupled with low-carbon fuel to enhance boiler flexibility also includes a synthesis gas preheater 7 connected to the outlet of the synthesis gas storage tank 6 and a reactant preheater arranged at the reactant storage tank 1 and the fixed bed reactor 3. The synthesis gas preheater 7 is used to preheat the synthesis gas output from the synthesis gas storage tank 6 so that the synthesis gas reaches the combustion preheating temperature before being output to the furnace of the coal-fired boiler 9 through the burner nozzle for combustion. The reactant preheater is used to preheat the reactants of the fixed bed reactor 3 or to preheat the reactants output from the reactant storage tank 1 to the fixed bed reactor 3 through a material pump before reaching the fixed bed reactor 3. The heat exchanger is connected to the reactant preheater and the synthesis gas preheater 7 for heat exchange with the reactant preheater and the synthesis gas preheater 7.

[0030] By means of the synthesis gas preheater 7 and the reactant preheater, the synthesis gas is preheated to a predetermined temperature before combustion or the reactant reacts. In subsequent use, the reactants do not need to be heated for a long time, which can improve the reaction efficiency and reaction stability, or ensure that the synthesis gas burns stably during the combustion process, thereby improving the efficiency and safety of the equipment.

[0031] The present application does not limit the structure, heat source, etc. of the synthesis gas preheater 7 and the reactant preheater. The heat source can be obtained through a heat exchanger, directly from the flue gas of a boiler, from other sources, or by using multiple sources.

[0032] In order to strengthen the precise management of equipment and improve the operating efficiency and reliability of equipment, in one embodiment, the power generation system coupled with low-carbon fuel to enhance the flexibility of the boiler also includes a fixed bed temperature sensor arranged in the fixed bed reactor 3, a synthesis gas temperature sensor arranged in the synthesis gas preheater 7, and a reactant temperature sensor arranged in the reactant preheater. The fixed bed temperature sensor is used to detect the inlet temperature value and the outlet temperature value of the fixed bed reactor 3, the synthesis gas temperature sensor is used to detect the temperature value of the synthesis gas preheater 7 before and after preheating the synthesis gas, and the reactant temperature sensor is used to detect the temperature value of the reactant before and after preheating by the reactant preheater. The controller is connected to the fixed bed reactor 3, the synthesis gas preheater 7, and the reactant preheater, and controls the operating parameters of the flue gas regulating plate 10, the operating parameters of the fixed bed reactor 3, the operating parameters of the synthesis gas preheater 7, and the operating parameters of the reactant preheater according to the operating parameters of the corresponding equipment and the current equipment operating mode.

[0033] By setting a fixed bed temperature sensor in the fixed bed reactor 3, setting a synthesis gas temperature sensor in the synthesis gas preheater 7 and setting a reactant temperature sensor in the reactant preheater, its operating status information can be obtained in real time to judge whether it is operating normally, such as whether the inlet temperature and outlet temperature of the fixed bed reactor 3 meet the standards, whether the preheating of the preheater meets the standards, etc., to judge whether a fault occurs and realize rapid maintenance of the equipment. At the same time, the operating parameters of the equipment can also be adjusted accordingly to improve the operating efficiency, such as improving the heat recovery efficiency of the flue gas and improving the reaction efficiency of the fixed bed reactor 3.

[0034] The present application includes but is not limited to the above-mentioned temperature sensor installation positions, and the present application does not limit the type and quantity of the temperature sensors.

[0035] In order to further improve the control efficiency and control reliability, in one embodiment, the power generation system for coupling low-carbon fuel to enhance boiler flexibility also includes a first valve 12 arranged between the reactant storage tank 1 and the feed pump 2, and a second valve 21 arranged between the feed pump 2 and the heat exchanger, and a third valve 31 arranged between the heat exchanger and the gas-liquid separator 5, and a fourth valve 41 arranged between the gas-liquid separator 5 and the synthesis gas storage tank 6, and a fifth valve 51 arranged between the synthesis gas storage tank 6 and the synthesis gas preheater 7, and a sixth valve 61 arranged between the synthesis gas preheater 7 and the burner nozzle, and a seventh valve 71 arranged between the flue gas adjustment plate 10 and the synthesis gas preheater 7, and an eighth valve 81 arranged between the flue gas adjustment plate 10 and the fixed bed reactor 3.

[0036] By setting valves on the corresponding pipelines and outlets, the requirements for the sealing of the equipment outlet itself are reduced, and the occurrence of gas reflux and the like is also avoided. For example, a valve is set at the outlet of the feed pump 2 to avoid the reflux of materials entering the reactor due to their higher temperature and air pressure, thereby improving the control efficiency and safety of use, and also protecting the relevant equipment and pipelines. The type of valve is not limited in this application, and generally, PLC control is used for automatic control, or other controllers are used for control.

[0037] In order to further improve the reaction efficiency of the reactor, in one embodiment, the power generation system for coupling low-carbon fuel to improve boiler flexibility also includes a granular stacked bed catalyst layer arranged in the fixed bed reactor 3, the bed porosity of the granular stacked bed catalyst layer is 0.4-0.8, and the granular stacked bed catalyst layer is CuO, ZnO and Al 2 O 3The granular stacked bed catalyst layer is composed of a mixture, wherein the mass proportion of CuO in the granular stacked bed catalyst layer is 55% to 65%, the mass proportion of ZnO is 28% to 32%, and the mass proportion of Al 2 O 3 The quality accounts for 8%~12%.

[0038] By providing a granular stacked bed catalyst layer, the contact area between the reaction gas and the catalyst can be increased, thereby improving the reaction efficiency and the stability of the reaction.

[0039] The present application includes but is not limited to the use of the above-mentioned CuO, ZnO and Al 2 O 3 The mixed granular stacked bed catalyst layer has no limitation on the ratio of the components, and other materials can also be used as catalysts.

[0040] In order to further improve the storage efficiency of synthesis gas, in one embodiment, the power generation system coupled with low-carbon fuel to enhance boiler flexibility also includes a pressurizing device arranged in the synthesis gas storage tank 6, which is used to pressurize the synthesis gas output from the synthesis gas outlet to a predetermined pressure and then store it in the synthesis gas storage tank 6.

[0041] The synthesis gas output from the synthesis gas outlet is pressurized to a predetermined pressure by a pressurizing device and then stored in the synthesis gas storage tank 6, which can increase the storage capacity of the synthesis gas and reduce the space occupied. The storage temperature, storage pressure, etc. of the synthesis gas are not limited in the present application, and the type of the pressurizing device is not limited. The pressurizing device can pressurize the synthesis gas to a predetermined pressure for storage at one time, or can store it after multiple pressurizations. The present application does not limit this.

[0042] The type of synthesis gas and the type of reactants are not limited in the present application. The synthesis gas is hydrogen, and the low-carbon fuel is a low-carbon fuel that undergoes a reforming reaction in the temperature range of 150-350°C. The low-carbon fuel includes at least one of methanol, ethanol and propanol, and other types of low-carbon fuels can also be used.

[0043] The type and size of the fixed bed reactor 3 are not limited in the present application. The fixed bed reactor 3 is a spiral coil type fixed bed reactor 3, a vertical cylindrical fixed bed reactor 3 or a horizontal cylindrical fixed bed reactor 3, or other types of fixed bed reactors 3.

[0044] In one embodiment, the power generation system for coupling low-carbon fuel to improve boiler flexibility mainly includes a boiler and a heat storage system. The boiler is a pulverized coal boiler. The difference from the common pulverized coal boiler is that the flue gas baffle and the burner are modified accordingly. The flue gas baffle is a three-flue flue gas baffle, which can be adjusted to allow the flue gas to flow to the heat storage system; the burner has an additional synthesis gas pipeline, which can burn the synthesis gas generated by the heat storage system. The flue gas adjustment plate 10 is located above the air preheater to control the proportion of the flue gas flowing to the primary air preheater, the secondary air preheater and the heat storage system.

[0045] The heat storage system includes: a reactant storage tank 1, a first valve 12, a feed pump 2, a second valve 21, a fixed bed reactor 3, a waste heat recovery device 4, a third valve 31, a gas-liquid separator 5, a fourth valve 41, a synthesis gas storage tank 6, a fifth valve 51, a synthesis gas preheater 7, a sixth valve 61, a seventh valve 71 and an eighth valve 81. The reactant storage tank 1 is a liquid storage tank, in which a methanol aqueous solution configured in a certain proportion is placed, and the molar ratio of methanol to water is not greater than 1.

[0046] The fixed bed reactor 3 may be Figure 1 The spiral coil fixed bed reactor 3 shown in the figure can also be made into a reactor with other structures such as a vertical cylinder or a horizontal cylinder. The reaction catalyst required for methanol wet reforming is configured in the reactor, which is generally a copper-based catalyst with good catalytic activity, but the catalyst temperature of the reactor needs to be controlled not to exceed 350°C for a long time. The waste heat recovery device 4 is a tubular or plate heat exchanger, which exchanges heat between the reaction product and the unreacted reactant, and plays the role of preheating the unreacted product and cooling the product. The gas-liquid separator 5 is a gas and liquid separation device, which condenses the incompletely converted methanol and water after the reaction and returns them to the reactant storage tank 1, while the condensed synthesis gas is input into the synthesis gas storage tank 6. The synthesis gas storage tank 6 is a gas storage tank and needs to meet certain explosion-proof requirements. A pressurizing device is configured in front of the synthesis gas storage tank 6 to make full use of the storage capacity of the storage tank.

[0047] The chemical reaction equation for methanol wet reforming is:

[0048] ;

[0049] Under the design conditions, taking the reaction at normal pressure as an example, 1 mol CO 2 The heat released by cooling 3 mol of hydrogen from 300°C to room temperature 25°C is 35.4 kJ, which can convert 1 mol of CH 3 OH and 1 mol H 2 O is heated from 25°C to 64.7°C. Therefore, the temperature of the reactants passing through the waste heat recovery device 4 is still far below 150°C, and there is sufficient heat exchange temperature difference to absorb the heat in the flue gas.

[0050] When the heat storage system is not in operation, all valves are closed. The smoke damper only adjusts the smoke ratio on the primary and secondary air sides, and the damper on the heat storage system side is fully closed.

[0051] When the system is in a high-load state and needs to reduce the load, the first valve 12 and the second valve 21 are opened in advance, the feed pump 2 starts working, the third valve 31 and the fourth valve 41 are opened, and the reactants pass through the feed pump 2 and enter the fixed bed reactor 3, the waste heat recovery device 4 and the gas-liquid separator 5 in turn, and then return to the reactant storage tank 1 through the unreacted liquid loop 11. At this time, there is no high-temperature flue gas flowing through the reactor, and the temperature in the reactor has not reached the reaction temperature, so the reactants will not react, and only the reactants establish a cycle. This is to avoid the high-temperature flue gas suddenly entering the fixed bed reactor 3 at the beginning of the load reduction, causing the reactor to overheat and damage the internal catalyst. When the system starts to reduce the load, adjust the flue gas damper and open the eighth valve 81, so that the flue gas enters the energy storage system and starts to prepare hydrogen-rich low-carbon fuel. Methanol and water vapor react to generate hydrogen and carbon dioxide. The product passes through the gas-liquid separator 5, is condensed to remove the liquid, and then enters the gas storage tank.

[0052] When the system is in a low-load state and needs to increase the load, open the seventh valve 71 and adjust the flue gas damper so that the high-temperature flue gas first flows through the synthesis gas preheater 7 and meets a certain preheating temperature. Then open the fifth valve 51 and the sixth valve 61 to allow the synthesis gas to enter the synthesis gas nozzle 8 inside the furnace. This is to prevent the synthesis gas from entering the furnace without being heated by the synthesis gas preheater 7. The low initial temperature has an adverse effect on the stable combustion of the flame inside the furnace under low load. After being fully preheated, the synthesis gas enters the furnace and has a higher initial temperature, which is conducive to the stable combustion of the furnace. The introduction of synthesis gas into the furnace can fully increase the furnace temperature and increase the load increase rate of the boiler. When the predetermined load is reached, the supply of synthesis gas is gradually reduced, and the supply of pulverized coal is increased until the supply of synthesis gas is completely stopped. The fuel in the furnace is completely provided by pulverized coal. Then completely close the flue gas damper on the heat storage system side.

[0053] When the boiler is in the startup stage and the furnace temperature needs to be increased, the fifth valve 51 and the sixth valve 61 are opened to allow the synthesis gas to directly enter the furnace to heat the furnace to a predetermined temperature. Synthesis gas has a low ignition point and is easy to ignite. Synthesis gas has good fluidity, is easy to control and adjust, does not require too many preparation steps, and can be prepared by recovering the waste heat of the tail flue, which has great advantages.

[0054] When the boiler is at an extremely low load and it is difficult to stabilize combustion inside the boiler, the fifth valve 51 and the sixth valve 61 are opened to allow the synthesis gas to directly enter the furnace and mix with the pulverized coal for combustion. Synthesis gas is equivalent to increasing the content of volatile matter inside the pulverized coal, making the pulverized coal easier to burn. The addition of synthesis gas can replace or reduce the fuel oil added for stable combustion in the boiler, which has better economic efficiency.

[0055] The above technical solution has the following beneficial effects:

[0056] It not only improves the flexibility of coal-fired units and achieves the effect of energy storage, but also fully improves the quality and efficiency of low-grade waste heat and increases the overall efficiency of the units at low load.

[0057] A system that improves the flexibility and efficiency of low-carbon fuels. When the boiler needs to reduce its load, the low-carbon fuel reforming reaction can absorb the waste heat of the boiler and reduce the boiler load. When the boiler reaches an ultra-low load and stable combustion is difficult, the synthesis gas can be input into the burner, which is equivalent to increasing the volatile content of coal, which is conducive to stable combustion of the boiler;

[0058] When the boiler is started or under ultra-low load, synthesis gas can be used to reduce or completely replace the amount of fuel injection and reduce the number of oil injections, thereby reducing the amount of fuel used in the power plant and achieving a cleaner and lower-carbon power generation process.

[0059] In short, by coupling low-carbon fuels, the waste heat of the flue gas in the tail flue of the boiler can be fully utilized to produce synthesis gas when the load is reduced; when the load is increased, the synthesis gas is used to increase the load change rate of the unit, while the waste heat of the flue gas can be used to improve the quality, thereby increasing the efficiency of the unit.

[0060] At the same time, with the continuous increase in renewable energy installed capacity, the proportion of green hydrogen and green methanol produced by abundant wind and solar power will increase, and the production cost of green low-carbon fuels will be further reduced. The prepared green low-carbon fuels can be used as peak load regulators in thermal power units to improve the variable load capacity and variable load depth of thermal power units, while improving the quality of waste heat during the variable load process, maintaining the efficiency of the overall system, and achieving both flexibility and efficiency, which is more conducive to increasing the amount of new energy grid-connected power generation and increasing the grid's ability to absorb new energy.

[0061] In summary, the power generation system coupled with low-carbon fuel to improve the flexibility of the boiler provided by the embodiment of the present invention is provided by setting a flue gas branch between the denitrification device and the air preheater, and setting a chemical heat storage device and a flue gas regulating plate at the connection of the flue gas branch. In the heat storage mode, the flue gas regulating plate opens the flue gas branch so that the flue gas generated by the coal-fired boiler enters the chemical heat storage device and reacts in the fixed bed reactor to generate a product. After the product is processed by the gas-liquid separator, the generated synthesis gas is output to the synthesis gas storage tank for storage, and the generated liquid is recovered through the reactant storage tank. In the heat release mode, the synthesis gas stored in the synthesis gas storage tank is input into the coal-fired boiler for combustion to improve the output of the coal-fired boiler. By coupling low-carbon fuels, when reducing the load, the flue gas waste heat in the tail flue of the boiler is fully utilized to produce synthesis gas; when increasing the load, the synthesis gas is used to increase the load change rate of the unit, while the flue gas waste heat is used to improve the quality, thereby synergistically improving the flexibility and efficiency of the unit.

[0062] The above is a detailed introduction to the power generation system for coupling low-carbon fuel to enhance boiler flexibility provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A power generation system that couples low-carbon fuel to improve boiler flexibility, characterized in that: The invention comprises a denitration device, an air preheater, a flue gas branch arranged between the denitration device and the air preheater, a chemical heat storage device and a flue gas regulating plate connected to the flue gas branch, wherein the flue gas regulating plate is located in the tail flue of the boiler outlet and is used to adjust the flue gas ratio flowing through the air preheater and the heat storage device, the chemical heat storage device comprises a reactant storage tank, a fixed bed reactor, a gas-liquid separator and a synthesis gas storage tank, the reactant storage tank stores reactants and is connected to the fixed bed reactor, the reactants are low-carbon fuels, the chemical heat storage device is used for, in a heat storage mode, the flue gas regulating plate opens the flue gas branch so that the flue gas generated by the coal-fired boiler enters the chemical heat storage device and reacts in the fixed bed reactor to generate a product, the product is processed by the gas-liquid separator and the generated synthesis gas is output to the synthesis gas storage tank for storage, the generated liquid is recovered through the reactant storage tank, and in an exothermic mode, the synthesis gas stored in the synthesis gas storage tank is input into the coal-fired boiler for combustion to increase the output of the coal-fired boiler.

2. The power generation system for improving boiler flexibility by coupling low-carbon fuel as claimed in claim 1, characterized in that: The gas-liquid separator includes a product inlet, a synthesis gas outlet and an unreacted product outlet. The gas-liquid separator inputs the product of the fixed bed reactor reaction through the product inlet and then separates the product into solid and liquid through heat exchange through a heat exchanger, outputs the gas generated by the solid-liquid separation through the synthesis gas outlet to the synthesis gas storage tank for storage, and outputs the liquid generated by the solid-liquid separation through the unreacted product outlet and through an unreacted liquid loop to the reactant storage tank for recovery.

3. The power generation system for coupling low-carbon fuel to improve boiler flexibility as claimed in claim 2, characterized in that: The heat exchanger is a tubular heat exchanger or a plate heat exchanger, which is used to perform heat exchange on the product to achieve solid-liquid separation and to preheat the reactants before they enter the fixed bed reactor.

4. The power generation system for increasing boiler flexibility by coupling low-carbon fuel as claimed in claim 3, characterized in that: It also includes a synthesis gas preheater connected to the outlet of the synthesis gas storage tank and a reactant preheater arranged on the reactant storage tank and the fixed bed reactor. The synthesis gas preheater is used to preheat the synthesis gas output from the synthesis gas storage tank so that the synthesis gas reaches the combustion preheating temperature before being output to the furnace of the coal-fired boiler through the burner nozzle for combustion. The reactant preheater is used to preheat the reactants of the fixed bed reactor or to preheat the reactants output from the reactant storage tank to the fixed bed reactor through a material pump before reaching the fixed bed reactor. The heat exchanger is connected to the reactant preheater and the synthesis gas preheater for exchanging heat with the reactant preheater and the synthesis gas preheater.

5. The power generation system for coupling low-carbon fuel to improve boiler flexibility as claimed in claim 4, characterized in that: It also includes a fixed bed temperature sensor arranged in the fixed bed reactor, a synthesis gas temperature sensor arranged in the synthesis gas preheater, and a reactant temperature sensor arranged in the reactant preheater. The fixed bed temperature sensor is used to detect the inlet temperature value and the outlet temperature value of the fixed bed reactor, the synthesis gas temperature sensor is used to detect the temperature value of the synthesis gas preheater before and after preheating the synthesis gas, and the reactant temperature sensor is used to detect the temperature value of the reactant before and after preheating by the reactant preheater. The controller is connected to the fixed bed reactor, the synthesis gas preheater, and the reactant preheater, and controls the operating parameters of the flue gas regulating plate, the operating parameters of the fixed bed reactor, the operating parameters of the synthesis gas preheater, and the operating parameters of the reactant preheater according to the operating parameters of the corresponding equipment and the current equipment operating mode.

6. The power generation system for increasing boiler flexibility by coupling low-carbon fuel as claimed in claim 5, characterized in that: It also includes a first valve arranged between the reactant storage tank and the feed pump, a second valve arranged between the feed pump and the heat exchanger, a third valve arranged between the heat exchanger and the gas-liquid separator, a fourth valve arranged between the gas-liquid separator and the synthesis gas storage tank, a fifth valve arranged between the synthesis gas storage tank and the synthesis gas preheater, a sixth valve arranged between the synthesis gas preheater and the burner nozzle, a seventh valve arranged between the flue gas adjustment plate and the synthesis gas preheater, and an eighth valve arranged between the flue gas adjustment plate and the fixed bed reactor.

7. The power generation system for coupling low-carbon fuel to improve boiler flexibility as claimed in claim 1, characterized in that: It also includes a granular packed bed catalyst layer arranged in the fixed bed reactor, the bed porosity of the granular packed bed catalyst layer is 0.4~0.8, the granular packed bed catalyst layer is a granular packed bed catalyst layer composed of a mixture of CuO, ZnO and Al2O3, the mass proportion of CuO in the granular packed bed catalyst layer is 55%~65%, the mass proportion of ZnO is 28%~32%, and the mass proportion of Al2O3 is 8%~12%.

8. The power generation system for improving boiler flexibility by coupling low-carbon fuel as claimed in claim 1, characterized in that: It also includes a pressurizing device disposed in the synthesis gas storage tank, which is used to pressurize the synthesis gas output from the synthesis gas outlet to a predetermined pressure and then store it in the synthesis gas storage tank.

9. The power generation system for improving boiler flexibility by coupling low-carbon fuels as claimed in any one of claims 1 to 8, characterized in that: The synthesis gas is hydrogen, and the low-carbon fuel is a low-carbon fuel that undergoes a reforming reaction in a temperature range of 150-350° C. The low-carbon fuel includes at least one of methanol, ethanol and propanol.

10. The power generation system for increasing boiler flexibility by coupling low-carbon fuel as claimed in claim 9, characterized in that: The fixed bed reactor is a spiral coil fixed bed reactor, a vertical cylinder fixed bed reactor or a horizontal cylinder fixed bed reactor.

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