Peak shaving system and method of calcium-based material for circulating fluidized bed coal-fired power plant

Abstract

The invention belongs to the technical field of coal-fired power generation, and particularly relates to a peak shaving system and method for a circulating fluidized bed coal-fired power plant with a calcium-based material. The peak shaving system comprises a circulating fluidized bed boiler, a heat exchange pipeline is arranged in the circulating fluidized bed boiler, and one end of the heat exchange pipeline is connected with an inlet of a gas-solid separation device through a pipeline; the other end of the heat exchange pipeline is connected with discharge ports of a limestone / carbide slag mixing storage tank, a CaO storage tank, a CO2 storage tank and a water storage tank through pipelines, and a gas outlet of the gas-solid separation device is connected with a feed port of the CO2 storage tank through a pipeline; and a solid outlet of the gas-solid separation device is connected with feed ports of the limestone / carbide slag mixing storage tank and the CaO storage tank through a pipeline with a three-way valve. According to the invention, the calcium cycle energy storage with reversible conversion between CaO and CaCO3 / Ca (OH) 2 is utilized, and the calcium cycle energy storage technology with low cost, high energy storage density and long energy storage time is combined with the traditional coal-fired power generation technology, so that the load regulation speed and the load regulation depth of the thermal power generating unit are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-fired power generation, and in particular relates to a peak-shaving system and method for a circulating fluidized bed coal-fired power plant using a calcium-based material. Background Art

[0002] With the substantial increase in installed capacity of new energy sources in recent years, deep and rapid peak regulation of thermal power units plays an important role in ensuring the stability of the power system.

[0003] In order to meet the needs of my country for deep peak regulation of thermal power units and save the use of fossil energy, many studies are devoted to the use of clean energy for deep peak regulation. Patent CN111322602A proposes that when the circulating fluidized bed boiler is under pressure, all fans and coal feeders are stopped, and the heat storage capacity of the boiler is used to continue to heat the feed water. The steam separated by the separator is reheated and supplied to the steam turbine after reaching the rated parameters. It can ensure that the steam turbine can still drive the generator to run stably at the rated speed of 3000r / min within a certain period of time, realize 0-100% full load section deep peak regulation, ensure that the boiler is stopped without stopping, and meet the peak regulation requirements of the power grid. Patent CN111853749A invented a method of combining molten salt energy storage technology with traditional coal-fired power supply technology, which is suitable for boiler units that participate in deep peak regulation requirements. It uses the heat storage and heat release flexibility of the heat storage system to break through the limitations of peak regulation of thermal power units and meet the requirements of deep peak regulation of thermal power units. Patent CN110529209A proposes to set up a solar thermal heater and a hot water storage tank system in the thermal power unit system. In the non-peak-shaving period, the solar thermal heater is used to heat the circulating water of the heat network. The insufficient heating part can be extracted from the exhaust steam of the intermediate pressure cylinder of the unit, and the cold water of the heat network is heated by the heat network heat exchanger. The heated water is stored in the hot water storage tank. In the period when deep peak-shaving is required, the hot water in the hot water storage tank is supplied to the primary network system of the heat network to achieve deep peak-shaving, while reducing the power generation load and ensuring the continuous and stable operation of the unit. It saves the energy consumption of the unit operation and effectively alleviates the dilemma of clearing energy consumption. Most of the above patents use sensible heat storage in thermal energy storage for peak load regulation, which uses materials with high heat capacity, such as water, molten salt, etc. However, compared with thermochemical energy storage, sensible heat storage has low energy density and low long-term storage utilization rate of energy. Thermochemical energy storage (TCES) technology of calcium-based materials (such as limestone CaCO3 and carbide slag Ca(OH)2) is considered to be one of the promising energy storage technologies. At present, there is no report on the method of using thermochemical energy storage for deep peak load regulation. Summary of the invention

[0004] In view of the above problems, the present invention provides a peak-shaving system and method for a circulating fluidized bed coal-fired power plant using a calcium-based material.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The calcium-based material is used in a peak-shaving system of a circulating fluidized bed coal-fired power plant, including a circulating fluidized bed boiler. A heat exchange pipeline is arranged inside the circulating fluidized bed boiler, one end of the heat exchange pipeline is connected to the inlet of a gas-solid separation device through a pipeline, and the other end of the heat exchange pipeline is connected to the discharge ports of a limestone / carbide slag mixed storage tank, a CaO storage tank, a CO2 storage tank and a water storage tank through a pipeline. A No. 1 regulating valve, a No. 2 regulating valve, a No. 3 regulating valve and a No. 4 regulating valve are respectively arranged on the discharge port pipelines of the limestone / carbide slag mixed storage tank, the CaO storage tank, the CO2 storage tank and the water storage tank, the gas outlet of the gas-solid separation device is connected to the feed port of the CO2 storage tank through a pipeline, and the solid outlet of the gas-solid separation device is connected to the feed ports of the limestone / carbide slag mixed storage tank and the CaO storage tank through a pipeline with a three-way valve.

[0007] Furthermore, two calcium oxide powder channels are provided at the lower part of the circulating fluidized bed boiler for spraying calcium oxide powder into the bed material of the circulating fluidized bed boiler. The calcium oxide powder channels are provided near the coal feeding port at the lower part of the circulating fluidized bed boiler.

[0008] Calcium-based materials are used in peak-shaving methods for circulating fluidized bed coal-fired power plants, including rapid variable load regulation; near-zero ultra-long deep peak-shaving; SO2 control and coal coking inhibition during near-zero deep peak-shaving;

[0009] The specific steps of the rapid load regulation are as follows: when the circulating fluidized bed boiler needs to reduce the load quickly, open the No. 1 regulating valve and the No. 3 regulating valve, and transport the powder mixture in the limestone / carbide slag mixed storage tank to the heat exchange pipe in the boiler through the CO2 gas flow in the CO2 storage tank, and decompose the powder mixture in the heat exchange pipe by the high temperature in the circulating fluidized bed boiler, and use the endothermic decomposition reaction of the limestone and carbide slag to quickly take away the heat in the furnace, so as to accelerate the load reduction, and the decomposed limestone and carbide slag are converted into CaO, and a large amount of chemical The solid powder can enter the gas-solid separation device along with the CO2 gas flow, and enter the corresponding CaO storage tank and CO2 storage tank respectively after separation by the gas-solid separation device; when the circulating fluidized bed boiler needs to increase the load quickly, open the No. 2 regulating valve, the No. 3 regulating valve and the No. 4 regulating valve, and transport the CaO powder in the CaO storage tank to the heat exchange pipe in the boiler through the CO2 gas flow in the CO2 storage tank, and at the same time introduce the water in the water storage tank into the heat exchange pipe, and release heat by the combination reaction of CaO and water and CaO and CO2, increase the heat in the furnace, and accelerate the load increase;

[0010] The specific steps of the near-zero ultra-long deep peak regulation are: when it is necessary to utilize the heat storage of the circulating fluidized bed boiler to maintain near-zero load operation, stop all fans and coal feeders, stop delivering fuel to the circulating fluidized bed boiler, open the No. 2 regulating valve, the No. 3 regulating valve and the No. 4 regulating valve, and deliver the CaO powder in the CaO storage tank to the heat exchange pipe in the boiler through the CO2 gas flow in the CO2 storage tank, and at the same time introduce the water in the water storage tank into the heat exchange pipe, and release heat by the combination reaction of CaO and water and CaO and CO2, increase the heat in the furnace, and prolong the time for the bed temperature to drop to the safe ignition boundary, so as to achieve the purpose of prolonging the maintenance time of the near-zero deep regulation;

[0011] The control of SO2 and the inhibition of coal coking during the near-zero depth peak regulation process specifically include the following steps: before the near-zero depth peak regulation of the circulating fluidized bed boiler, during the preparation process for high-parameter heat storage, the calcium oxide powder channel is started, and in the process of increasing the bed pressure, CaO powder is sprayed into the circulating fluidized bed boiler through the calcium oxide powder channel, so that the CaO powder is mixed with the coal transported by the coal feeder to the circulating fluidized bed boiler. The presence of CaO powder can greatly reduce the contact area between coals and reduce the risk of coal coking in the high-temperature furnace. In addition, after the circulating fluidized bed boiler is maintained at near-zero load for an extremely long time, a large amount of SO2 will be instantaneously generated during the ignition process. At this time, at a relatively low bed temperature, the highly active CaO will come into contact with SO2 for the first time to achieve the purpose of desulfurization.

[0012] Furthermore, the mixing ratio of limestone and carbide slag in the limestone / carbide slag mixing tank is 1:2-3. By mixing carbide slag and limestone, on the one hand, the H2O produced when carbide slag and limestone are simultaneously decomposed at high temperature is utilized to improve the reaction activity of calcium oxide after the decomposition of limestone. On the other hand, the lower decomposition temperature of carbide slag is utilized to improve the system's adaptability to rapid load regulation at low temperatures.

[0013] Furthermore, the water added to the heat exchange pipe in the rapid variable load regulation and near-zero ultra-long deep peak regulation is mixed with CaO in the form of water mist to react, so as to improve the efficiency of the CaO hydration exothermic reaction and prevent the problem of low reaction efficiency caused by insufficient liquid-solid contact.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The present invention utilizes the calcium cycle energy storage of the reversible conversion between CaO and CaCO3 / Ca(OH)2, combines the calcium cycle energy storage technology with low cost, high energy storage density and long energy storage time with the traditional coal-fired power generation technology, effectively improves the load regulation speed and load regulation depth of the thermal power unit, and provides a technical path for the sustainable development of the circulating fluidized bed power plant;

[0016] The present invention mixes carbide slag and limestone and introduces them into a heat exchange pipe for reaction. On the one hand, H2O generated when carbide slag and limestone are decomposed at high temperature is used to improve the reaction activity of calcium oxide after limestone decomposition. On the other hand, the lower decomposition temperature of carbide slag is used to improve the adaptability of the system to rapid load change regulation at low temperature.

[0017] The present invention selects CO2 as the conveying gas flow. CO2 is not only used as the conveying gas flow, but also participates in the reaction as a reactant. The chemical reaction includes the combination of CaO and CO2 to release heat, which is used to quickly increase the load. In addition, CO2 is easy to compress and store as the conveying gas flow, and can be taken as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention;

[0019] In the figure, there are circulating fluidized bed boiler 1, heat exchange pipe 2, gas-solid separation device 3, limestone / carbide slag mixed storage tank 4, CaO storage tank 5, CO2 storage tank 6, water storage tank 7, No. 1 regulating valve 8, No. 2 regulating valve 9, No. 3 regulating valve 10, No. 4 regulating valve 11, and calcium oxide powder channel 12. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical solution of the present invention, the present invention is further described below through embodiments.

[0021] like Figure 1 As shown, the calcium-based material is used in a peak-shaving system of a circulating fluidized bed coal-fired power plant, including a circulating fluidized bed boiler 1, wherein a heat exchange pipe 2 is arranged inside the circulating fluidized bed boiler 1, one end of the heat exchange pipe 2 is connected to the inlet of a gas-solid separation device 3 through a pipeline, and the other end of the heat exchange pipe 2 is connected to the discharge ports of a limestone / carbide slag mixed storage tank 4, a CaO storage tank 5, a CO2 storage tank 6 and a water storage tank 7 through a pipeline, and a No. 1 regulating valve 8, a No. 2 regulating valve 9, a No. 3 regulating valve 10 and a No. 4 regulating valve 11 are respectively arranged on the discharge port pipelines of the limestone / carbide slag mixed storage tank 4, the CaO storage tank 5, the CO2 storage tank 6 and the water storage tank 7, the gas outlet of the gas-solid separation device 3 is connected to the feed port of the CO2 storage tank 6 through a pipeline, and the solid outlet of the gas-solid separation device 3 is connected to the feed ports of the limestone / carbide slag mixed storage tank 4 and the CaO storage tank 5 through a pipeline with a three-way valve.

[0022] Two calcium oxide powder channels 12 are provided at the lower part of the circulating fluidized bed boiler 1 for spraying calcium oxide powder into the bed material of the circulating fluidized bed boiler 1 . The calcium oxide powder channels 12 are provided close to the coal feeding port at the lower part of the circulating fluidized bed boiler 1 .

[0023] Calcium-based materials are used in peak-shaving methods for circulating fluidized bed coal-fired power plants, including rapid variable load regulation; near-zero ultra-long deep peak-shaving; SO2 control and coal coking inhibition during near-zero deep peak-shaving;

[0024] The specific steps of the rapid load change regulation are as follows: when the circulating fluidized bed boiler 1 needs to reduce the load quickly, open the No. 1 regulating valve 8 and the No. 3 regulating valve 10, and transport the powder mixture in the limestone / carbide slag mixed storage tank 4 to the heat exchange pipe 2 in the boiler through the CO2 gas flow in the CO2 storage tank 6, and decompose the powder mixture in the heat exchange pipe 2 by the high temperature in the circulating fluidized bed boiler 1, and use the endothermic decomposition reaction of the limestone and carbide slag to quickly take away the heat in the furnace, so as to accelerate the load reduction, and the decomposed limestone and carbide slag are converted into CaO, and a large amount of chemical energy is stored, and As the CO2 gas flow enters the gas-solid separation device 3, it enters the corresponding CaO storage tank 5 and CO2 storage tank 6 after separation by the gas-solid separation device 3; when the circulating fluidized bed boiler 1 needs to increase the load quickly, open the No. 2 regulating valve 9, the No. 3 regulating valve 10 and the No. 4 regulating valve 11, and transport the CaO powder in the CaO storage tank to the heat exchange pipe 2 in the boiler through the CO2 gas flow in the CO2 storage tank 6, and at the same time, introduce the water in the water storage tank 7 into the heat exchange pipe 2, and use the heat release of the chemical reaction of CaO and water and CaO and CO2 to increase the heat in the furnace, which plays a role in accelerating the load increase;

[0025] The specific steps of the near-zero ultra-long deep peak regulation are: when it is necessary to utilize the heat storage of the circulating fluidized bed boiler 1 to maintain near-zero load operation, stop all fans and coal feeders, stop delivering fuel to the circulating fluidized bed boiler 1, open the No. 2 regulating valve 9, the No. 3 regulating valve 10 and the No. 4 regulating valve 11, and deliver the CaO powder in the CaO storage tank to the heat exchange pipe 2 in the boiler through the CO2 gas flow in the CO2 storage tank 6, and at the same time introduce the water in the water storage tank 7 into the heat exchange pipe 2, and release heat by the chemical reaction of CaO and water and CaO and CO2, increase the heat in the furnace, and prolong the time for the bed temperature to drop to the safe ignition boundary, so as to achieve the purpose of prolonging the maintenance time of the near-zero deep regulation;

[0026] The mixing ratio of limestone and carbide slag in the limestone / carbide slag mixing storage tank 4 is 1:2-3. By mixing carbide slag and limestone, on the one hand, the H2O produced when carbide slag and limestone are decomposed at high temperature is used to improve the reaction activity of calcium oxide after limestone decomposition. On the other hand, the lower decomposition temperature of carbide slag is used to improve the adaptability of the system to rapid variable load regulation at low temperature. In the rapid variable load regulation and near-zero ultra-long depth peak regulation, the water added to the heat exchange pipe 2 is mixed with CaO in the form of water mist to improve the efficiency of the CaO hydration exothermic reaction and prevent the problem of low reaction efficiency caused by insufficient liquid-solid contact.

[0027] The control of SO2 and the suppression of coal coking during the near-zero depth peak regulation process are specifically carried out as follows: before the near-zero depth peak regulation of the circulating fluidized bed boiler 1, during the preparation process for high-parameter heat storage, the calcium oxide powder channel 12 is started, and in the process of increasing the bed pressure, CaO powder is sprayed into the circulating fluidized bed boiler 1 through the calcium oxide powder channel 12, so that the CaO powder is mixed with the coal transported by the coal feeder to the circulating fluidized bed boiler 1. The presence of CaO powder can greatly reduce the contact area between coals and reduce the risk of coal coking in the high-temperature furnace; in addition, after the circulating fluidized bed boiler 1 is maintained at near-zero load for an extremely long time, a large amount of SO2 will be instantaneously generated during the ignition process. At this time, at a relatively low bed temperature, the highly active CaO will come into contact with SO2 for the first time to achieve the purpose of desulfurization.

[0028] The above shows and describes the main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0029] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. The calcium-based material is used in a peak load regulation system of a circulating fluidized bed coal-fired power plant, comprising a circulating fluidized bed boiler (1), characterized in that: A heat exchange pipe (2) is arranged inside the circulating fluidized bed boiler (1), one end of the heat exchange pipe (2) is connected to the inlet of the gas-solid separation device (3) through a pipeline, and the other end of the heat exchange pipe (2) is connected to the discharge ports of the limestone / carbide slag mixed storage tank (4), the CaO storage tank (5), the CO2 storage tank (6) and the water storage tank (7) through a pipeline. A No. 1 regulating valve (8), a No. 2 regulating valve (9), a No. 3 regulating valve (10) and a No. 4 regulating valve (11) are respectively arranged on the discharge port pipelines of the limestone / carbide slag mixed storage tank (4), the CaO storage tank (5), the CO2 storage tank (6) and the water storage tank (7), the gas outlet of the gas-solid separation device (3) is connected to the feed port of the CO2 storage tank (6) through a pipeline, and the solid outlet of the gas-solid separation device (3) is connected to the feed port of the limestone / carbide slag mixed storage tank (4) and the CaO storage tank (5) through a pipeline with a three-way valve.

2. The calcium-based material according to claim 1 is used in a peak load regulation system of a circulating fluidized bed coal-fired power plant, characterized in that: Two calcium oxide powder channels (12) are arranged at the bottom of the circulating fluidized bed boiler (1) for spraying calcium oxide powder into the bed material of the circulating fluidized bed boiler (1). The calcium oxide powder channels (12) are arranged close to the coal feeding port at the bottom of the circulating fluidized bed boiler (1).

3. A peak shaving method for a circulating fluidized bed coal-fired power plant using the calcium-based material of the peak shaving system according to claim 2, characterized in that: Including fast variable load regulation; near-zero ultra-long deep peak regulation; control of SO2 and suppression of coal coking during near-zero deep peak regulation; The specific steps of the rapid load change regulation are as follows: when the circulating fluidized bed boiler (1) needs to reduce the load quickly, the first regulating valve (8) and the third regulating valve (10) are opened, and the powder mixture in the limestone / carbide slag mixed storage tank (4) is transported to the heat exchange pipe (2) in the boiler through the CO2 gas flow in the CO2 storage tank (6); the powder mixture in the heat exchange pipe (2) is decomposed by the high temperature in the circulating fluidized bed boiler (1); the heat in the furnace is quickly taken away by the endothermic decomposition reaction of the limestone and carbide slag, which plays a role in accelerating the load reduction; the decomposed limestone and carbide slag are converted into CaO, and a large amount of chemical energy is stored, and is discharged along with the CO2. 2 airflow enters the gas-solid separation device (3), and after separation in the gas-solid separation device (3), enters the corresponding CaO storage tank (5) and CO2 storage tank (6) respectively; when the circulating fluidized bed boiler (1) needs to increase the load quickly, the second regulating valve (9), the third regulating valve (10) and the fourth regulating valve (11) are opened, and the CaO powder in the CaO storage tank is transported to the heat exchange pipe (2) in the boiler through the CO2 airflow in the CO2 storage tank (6), and at the same time, the water in the water storage tank (7) is introduced into the heat exchange pipe (2), and the heat in the furnace is increased by the heat release of the chemical reaction between CaO and water and between CaO and CO2, so as to accelerate the load increase; The specific steps of the near-zero ultra-long deep peak regulation are as follows: when it is necessary to utilize the heat storage of the circulating fluidized bed boiler (1) to maintain near-zero load operation, stop all fans and coal feeders, stop delivering fuel to the circulating fluidized bed boiler (1), open the No. 2 regulating valve (9), the No. 3 regulating valve (10) and the No. 4 regulating valve (11), and deliver the CaO powder in the CaO storage tank to the heat exchange pipe (2) in the boiler through the CO2 gas flow in the CO2 storage tank (6), and at the same time introduce the water in the water storage tank (7) into the heat exchange pipe (2), so as to increase the heat in the furnace by means of the heat release of the chemical reaction between CaO and water and between CaO and CO2, and prolong the time for the bed temperature to drop to the safe ignition boundary, thereby achieving the purpose of prolonging the maintenance time of the near-zero deep regulation; The control of SO2 and the suppression of coal coking during the near-zero depth peak regulation process specifically include the following steps: before the circulating fluidized bed boiler (1) performs near-zero depth peak regulation, during the preparation process for high-parameter heat storage, the calcium oxide powder channel (12) is started; during the process of increasing the bed pressure, CaO powder is sprayed into the circulating fluidized bed boiler (1) through the calcium oxide powder channel (12), so that the CaO powder is mixed with the coal transported by the coal feeder into the circulating fluidized bed boiler (1); the presence of the CaO powder can significantly reduce the contact area between coals and reduce the risk of coal coking in the high-temperature furnace; in addition, after the circulating fluidized bed boiler (1) is maintained at near-zero load for an extremely long time, a large amount of SO2 will be instantaneously generated during the ignition process; at this time, at a relatively low bed temperature, the highly active CaO will come into contact with the SO2 in the first place, thereby achieving the purpose of desulfurization.

4. The peak-shaving method of a circulating fluidized bed coal-fired power plant using the calcium-based material according to claim 3 is characterized in that: The mixing ratio of limestone and carbide slag in the limestone / carbide slag mixing tank (4) is 1:2-3. By mixing carbide slag and limestone, on the one hand, the H2O produced when carbide slag and limestone are decomposed simultaneously at high temperature is utilized to improve the reaction activity of calcium oxide after the decomposition of limestone. On the other hand, the lower decomposition temperature of carbide slag is utilized to improve the adaptability of the system to rapid load regulation at low temperature.

5. The peak-shaving method of using the calcium-based material in a circulating fluidized bed coal-fired power plant according to claim 3 is characterized in that: In the rapid variable load regulation and near-zero ultra-long deep peak regulation, the water added to the heat exchange pipe (2) is mixed with CaO in the form of water mist to react, so as to improve the efficiency of the CaO hydration exothermic reaction and prevent the problem of low reaction efficiency caused by insufficient liquid-solid contact.

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