Combined heat and power generation system based on coupling of steam energy accumulator and ejector and steam supply method

Abstract

The invention belongs to the related technical field of industrial steam supply, and discloses a combined heat and power generation system based on coupling of a steam energy accumulator and an ejector and a steam supply method. The combined heat and power generation system comprises a coal-fired boiler, a first fused salt steam heat exchanger, a steam energy accumulator, a first control valve, a steam ejector, a second fused salt steam heat exchanger, a first fused salt pump, a cold fused salt storage tank, a second control valve, a second fused salt pump, a hot fused salt storage tank and a third control valve. According to the combined heat and power generation system, the steam energy accumulator and the steam ejector are cooperatively coupled, so that the system can stably output industrial steam meeting parameter requirements under different operation load conditions, flexible operation of the combined heat and power generation system is guaranteed on the premise of not interrupting industrial steam consumption, and the service life of the combined heat and power generation system is prolonged. The invention further provides an efficient and stable industrial steam supply method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field related to industrial steam supply, and more particularly, to a combined heat and power system based on coupling of steam accumulator and ejector and a steam supply method. BACKGROUND

[0002] With the development of energy systems towards low-carbon and high-proportion renewable energy penetration, the role of traditional combined heat and power units in the power grid is gradually changing from "basic power source" to "flexible regulation power source". This change requires the unit to maintain stable supply to the industrial steam system under complex conditions such as deep peak shaving and low load operation. However, the existing combined heat and power system generally has strong heat and power coupling characteristics, i.e., the variation of electric load directly affects the steam extraction parameters, causing the pressure and temperature of industrial steam to fluctuate with the electric load, which seriously restricts the stability and reliability of the steam supply system.

[0003] Currently, industrial users have high requirements for the stability of steam parameters, usually requiring steam supply pressure not less than 1.6MPa-2.0MPa and temperature maintained within the range of 280℃-300℃. The traditional steam supply method usually relies on steam extraction from the intermediate pressure cylinder or reheated section of the steam turbine for adjustment. When the unit is in low load condition, the extraction pressure is reduced, which cannot meet the pressure requirement of industrial steam, causing the system to be unable to continue running or forced to maintain high load, resulting in a significant decline in operation economy. In addition, although some systems are equipped with electric heaters, heat pumps or standby small boilers for steam supplement, they have problems such as slow response, low energy efficiency or high operation cost, which are difficult to promote in large-scale industrial steam supply.

[0004] In order to alleviate the restriction of heat and power coupling and improve the stability of the steam supply system, existing research attempts to introduce heat storage technology to realize heat and power decoupling. Steam accumulator is a kind of energy storage device that releases heat by condensing high-pressure steam, which has the advantages of simple structure, fast response, low construction cost, etc., and is suitable for short-term heat storage and adjustment. On the other hand, steam ejector is a device that can realize pressure increase only by relying on the kinetic energy of high-pressure steam without mechanical drive, which can inject low-pressure steam to generate high-pressure steam that meets the use requirements, thereby reconstructing the steam parameters. Both types of equipment have good flexibility in adjusting industrial thermal systems.

[0005] However, in existing engineering, steam accumulators and steam ejectors are usually used separately, and there is a lack of cooperative optimization mechanism between them. Although the steam accumulator can store energy at high load and release high-pressure steam at low load, its output is saturated steam, which is difficult to meet the requirement of steam temperature; the ejector can reconfigure the steam pressure, but it depends on the continuous and stable high-pressure injection steam, especially in the deep adjustment state of the unit, the insufficient supply of high-pressure steam can easily lead to injection failure. In addition, in the traditional system, the steam supply path is single, and the storage and release control strategy is imperfect, which cannot effectively cope with the operation challenges of frequent variable load or large fluctuations of industrial steam. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the present application provides a combined heat and power system based on coupling of steam accumulator and ejector and a steam supply method, which aims to solve the problem that the existing combined heat and power system cannot effectively cope with variable load conditions.

[0007] To achieve the above-mentioned purpose, according to one aspect of the present application, a combined heat and power system based on coupling of steam accumulator and ejector is provided, which comprises a coal-fired boiler, a first molten salt steam heat exchanger, a steam accumulator, a first control valve, a steam ejector, a second molten salt steam heat exchanger, a first molten salt pump, a cold molten salt storage tank, a second control valve, a second molten salt pump, a hot molten salt storage tank and a third control valve, the main steam outlet of the coal-fired boiler is connected to the hot end inlet of the first molten salt steam heat exchanger, the hot end outlet of the first molten salt steam heat exchanger is connected to the inlet of the steam accumulator, the outlet of the steam accumulator is connected to the inlet of the steam ejector through the first control valve, the outlet of the steam ejector is connected to the cold end inlet of the second molten salt steam heat exchanger, and the cold end outlet of the second molten salt steam heat exchanger is used for steam supply; the inlet of the second molten salt pump is connected to the cold end outlet of the first molten salt steam heat exchanger, the outlet thereof is connected to the inlet of the hot molten salt storage tank, the outlet of the hot molten salt storage tank is connected to the hot end inlet of the second molten salt steam heat exchanger through the third control valve; the hot end outlet of the second molten salt heat exchanger is connected to the inlet of the first molten salt pump, the outlet of the first molten salt pump is connected to the inlet of the cold molten salt storage tank, and the outlet of the cold molten salt storage tank is connected to the cold end inlet of the first molten salt steam heat exchanger through the second control valve.

[0008] Further, the inlet of the steam accumulator is also connected to a makeup water pipe.

[0009] Further, the inlet of the steam ejector is also connected to a steam supply pipe, and the reheated steam from the unit enters the steam ejector through the steam supply pipe.

[0010] Further, the combined heat and power system further comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, the main steam outlet of the coal-fired boiler is connected to the inlet of the high-pressure cylinder, the outlet of the high-pressure cylinder is connected to the inlet of the medium-pressure cylinder, the outlet of the medium-pressure cylinder is connected to the inlet of the low-pressure cylinder, and the outlet of the low-pressure cylinder is connected to the coal-fired boiler through a cooling tower.

[0011] Further, the molten salt used by the combined heat and power system is sodium nitrate-sodium nitrite mixed salt, and the temperature range is 250-550 DEG C.

[0012] Further, the volume of the hot molten salt storage tank is 1200 m 3 .

[0013] Further, the ejector is an axisymmetric single-stage structure, which comprises three parts of a nozzle, a mixing section and a diffuser section connected in sequence.

[0014] Further, the steam ejector is dynamically matched through a flow regulating valve.

[0015] Further, the combined heat and power system further comprises an electric auxiliary steam heater for low-load starting and standby heating, and the electric auxiliary steam heater is connected in parallel between the second molten salt steam heat exchanger and an industrial steam supply main network.

[0016] The application further provides a steam supply method, which uses the combined heat and power system based on steam accumulators and ejectors as described above to supply steam.

[0017] Overall, compared with the prior art, the combined heat and power system based on steam accumulators and ejectors and the steam supply method provided by the application mainly have the following beneficial effects:

[0018] 1. The combined heat and power system cooperatively couples steam accumulators and steam ejectors, so that the system can stably output industrial steam meeting parameter requirements under different operating load conditions, realizes flexible operation of the combined heat and power system without interrupting industrial steam supply, and further provides an efficient and stable industrial steam supply method.

[0019] 2.The present application makes the heat load in the traditional combined heat and power system no longer strictly dependent on the electricity load by constructing a combined heat and power system with steam accumulators and steam ejectors cooperating, so that high-parameter steam meeting industrial demand can still be stably output in a low-load or even deep peak-regulation state. The steam accumulator can store excess high-pressure steam when the load is high, and release it at the appropriate time through the control system to be used as the steam induced by the ejector, thereby avoiding the problem of steam supply interruption caused by insufficient steam extraction pressure. Compared with the traditional system that can only "follow the heat with the electricity", the present application significantly improves the autonomy of operation regulation and the load response range, and truly realizes the "thermal-electric decoupling" between heat supply and power generation.

[0020] 3.The present application realizes dynamic control of steam parameters, can adjust the steam pressure and temperature according to industrial demand, and overcomes the defects of rigidity and regulation lag of the traditional steam supply system; the present application introduces a molten salt heat exchanger, a molten salt storage tank and the like to form a molten salt heat storage subsystem, which has a significant temperature stability control capability. During the low-load operation stage of the system, when the steam parameters deviate from the temperature range required by the industrial user, the mixed steam can be heated or temperature-adjusted by the molten salt heat exchanger, so that the final steam temperature can be effectively improved, and the continuity and safety of the industrial process can be ensured. The molten salt has the characteristics of high specific heat, good stability and long heat storage time, can realize cross-period heat buffering, and make the heat stored during the non-working condition valley period be efficiently released during the heat demand period.

[0021] 4.The present application has good engineering adaptability and popularization, is suitable for various medium and large combined heat and power units, can be flexibly expanded to urban heat networks, industrial steam co-generation, distributed energy systems and the like, has a fast response speed, can quickly switch the steam supply mode during variable load operation, ensures the safe operation of the system and the stability of the steam quality, and effectively alleviates the restriction of heat-electricity coupling on the stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a partial schematic view of a combined heat and power system based on steam accumulators and ejectors provided by the present application;

[0023] Figure 2 is a regulation range schematic view of a combined heat and power unit with steam accumulators and steam ejectors of the present application;

[0024] Figure 3 is a diagram of the changes of the inlet and outlet steam flow and the internal liquid volume fraction during the charging process and the discharging process of the steam accumulator in the embodiment of the present application;

[0025] Figure 4 is a schematic view of the coal saving rate of the combined heat and power unit in the embodiment of the present application.

[0026] In all the drawings, the same reference signs are used to indicate the same elements or structures, wherein: 1 - first molten salt steam heat exchanger, 2 - steam accumulator, 3 - first control valve, 4 - steam ejector, 5 - second molten salt steam heat exchanger, 6 - first molten salt pump, 7 - cold molten salt storage tank, 8 - second control valve, 9 - second molten salt pump, 10 - hot molten salt storage tank, 11 - third control valve. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] Please refer to Figure 1 and Figure 2 The present application provides a combined heat and power system based on coupling of steam accumulator and ejector. The combined heat and power system cooperatively couples a steam accumulator and a steam ejector, so that the system can stably output industrial steam meeting parameter requirements under different operating load conditions, realizes flexible operation of the combined heat and power system without interrupting industrial steam supply, and further provides an efficient and stable industrial steam supply method.

[0029] Specifically, the combined heat and power system takes a steam accumulator as a high-pressure steam energy storage unit and takes a steam ejector as a steam pressure reconstruction device, and through the cooperative action of the two, stably outputs industrial steam meeting requirements under different load conditions.

[0030] The combined heat and power system comprises a coal-fired boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a first molten salt steam heat exchanger 1, a steam accumulator 2, a first control valve 3, a steam ejector 4, a second molten salt steam heat exchanger 5, a first molten salt pump 6, a cold molten salt storage tank 7, a second control valve 8, a second molten salt pump 9, a hot molten salt storage tank 10, and a third control valve 11.

[0031] The main steam outlet of the coal-fired boiler is connected to the inlet of the high-pressure cylinder and the hot end inlet of the first molten salt steam heat exchanger 1, respectively, the outlet of the high-pressure cylinder is connected to the inlet of the medium-pressure cylinder, the outlet of the medium-pressure cylinder is connected to the inlet of the low-pressure cylinder, and the outlet of the low-pressure cylinder is connected to the coal-fired boiler through a cooling tower.

[0032] The hot end outlet of the first molten salt steam heat exchanger 1 is connected to the inlet of the steam accumulator 2, the outlet of the steam accumulator 2 is connected to the inlet of the steam ejector 4 through the first control valve 3, the outlet of the steam ejector 4 is connected to the cold end inlet of the second molten salt steam heat exchanger 5, and the cold end outlet of the second molten salt steam heat exchanger 5 is used for steam supply. The inlet of the second molten salt pump 9 is connected to the cold end outlet of the first molten salt steam heat exchanger 1, and the outlet thereof is connected to the inlet of the hot molten salt storage tank 10. The outlet of the hot molten salt storage tank 10 is connected to the hot end inlet of the second molten salt steam heat exchanger 5 through the third control valve 11. The hot end outlet of the second molten salt heat exchanger is connected to the inlet of the first molten salt pump 6, the outlet of the first molten salt pump 6 is connected to the inlet of the cold molten salt storage tank 7, and the outlet of the cold molten salt storage tank 7 is connected to the cold end inlet of the first molten salt steam heat exchanger 1 through the second control valve 8.

[0033] The inlet of the steam accumulator 2 is also connected to a water supply pipe. The inlet of the steam ejector 4 is also connected to a steam supply pipe, and the reheated steam from the unit enters the steam ejector 4 through the steam supply pipe.

[0034] The combined heat and power system further comprises an electric auxiliary steam heater for low load start-up and standby heating, which is connected in parallel between the second molten salt steam heat exchanger 5 and the industrial steam supply main pipe network, and is used to maintain the basic steam load when the steam ejector 4 is disabled or the pressure of the steam accumulator 2 is insufficient.

[0035] In operation, part of the high-temperature steam from the coal-fired boiler enters the first molten salt steam heat exchanger 1, and the steam is cooled by absorbing heat from the molten salt from the cold molten salt storage tank 7. The molten salt after absorbing heat enters the hot molten salt storage tank 10 through the second molten salt pump 9, and the cooled steam enters the steam accumulator.

[0036] The steam in the steam accumulator 2 enters the steam ejector 4 together with the reheated steam from the unit through the first control valve 3, and after mixing, the two enter the second molten salt steam heat exchanger 5 from the steam ejector 4, and are heated by the molten salt from the hot molten salt storage tank 10 to increase the temperature. The high-temperature steam after the temperature is increased enters the industrial steam pipe network from the outlet of the second molten salt steam heat exchanger 5. The molten salt after heating the steam enters the cold molten salt storage tank 7 from the hot end outlet of the second molten salt steam heat exchanger 5 through the first molten salt pump 6.

[0037] The design process of the combined heat and power system is as follows:

[0038] S1, establish a typical cogeneration system model. The thermal model of the entire cogeneration system is constructed, including coal-fired boiler, steam accumulator 2, steam ejector 4, cold molten salt storage tank 7, hot molten salt storage tank 10, industrial steam supply circuit, etc. The system adopts the method of function module dragging and pipeline connection to establish the main process, and sets the boundary conditions based on the flow direction of the working medium.

[0039] S2: Set up a bypass in the main steam pipeline of the unit and arrange a high-pressure steam accumulator 2. The steam accumulator 2 is a horizontal pressure vessel structure, which maintains a liquid-vapor two-phase state inside, and the energy storage medium is saturated water. The steam accumulator 2 is modeled and simulated using a thermodynamic non-equilibrium model, which considers the mass and energy conservation equations of the water phase and the steam phase respectively, and can accurately describe the dynamic phase change behavior in the process of rapid charging and discharging.

[0040] (1) Mass conservation

[0041] Water phase mass conservation:

[0042]

[0043] Steam phase mass conservation:

[0044]

[0045] Where, m PT1 = m c -m e , the mass change of the water phase due to condensation and evaporation; m PT2 = m e -m c , the corresponding mass change of the steam phase; M is the mass, m is the mass flow rate, t is the time; subscripts 1 and 2 are water and steam, respectively.

[0046] (2) Energy conservation

[0047] Water phase mass conservation:

[0048]

[0049] Steam phase energy conservation:

[0050]

[0051] Where, Q 21 represents the interfacial heat transfer rate of steam to water, p is the pressure, V is the volume, and h'' is the saturated steam enthalpy.

[0052] (3) Phase change rate expression

[0053] Evaporation rate:

[0054] When h1> h'

[0055] Condensation rate:

[0056] When h1 < h'

[0057] Where τ e and τ c are the relaxation times of evaporation and condensation, respectively, reflecting the hysteresis effect of phase change rate.

[0058] (4) Calculation of relaxation time

[0059] Through the thermodynamic derivation of mass transfer rate, the relaxation time can be calculated by the following formula:

[0060]

[0061] Where, is the unit interfacial heat transfer mass flux, a i is the specific surface area of the steam-water interface, calculated by the bubble concentration and diameter, k 1i is the heat transfer coefficient of the steam bubble interface to water.

[0062] S3: Introduce steam ejector 4, the driving end of which is connected to the outlet of steam accumulator 2, and reheat steam is introduced at the same time, and the outlet is connected to the industrial steam supply main pipe. The steam ejector 4 is an axisymmetric structure, including a nozzle, a mixing chamber, and a diffuser section. The steam ejector 4 is provided with a nozzle opening adjusting mechanism to adapt to different pressure ratio working conditions.

[0063] S4: Arrange the heat exchanger and molten salt heat storage system module. The heat exchanger is arranged between the main steam outlet of the coal-fired boiler and the molten salt storage tank, and the main steam outlet pipeline is connected to the diverter assembly. Part of the main steam flows into the high-pressure cylinder, and the other part of the main steam flows into the molten salt heat storage system, which is used to transfer part of the main steam heat to the molten salt to form a high-temperature heat storage pool. The molten salt system participates in temperature rise when the mixed steam temperature of the ejector is insufficient, ensuring the stability of the final steam temperature.

[0064] The combined heat and power system has two operating modes, namely energy storage mode and energy release mode. In the energy storage mode, during the stable operation stage of the load, the control system instructs part of the main steam to flow into the steam accumulator 2 and the heat exchanger, and at the same time, the molten salt system is heated.

[0065] In the energy release mode, when the extraction steam pressure is lower than the industrial steam pressure demand, the steam accumulator 2 releases high-pressure steam as the motive flow of the steam ejector 4, and the reheat section steam as the induced flow. After mixing, the mixed steam is supplied. If the mixed steam temperature is insufficient, it is heated by the molten salt heat exchanger and then sent out.

[0066] The system operating state is identified and adjusted by the control system in real time. Key control parameters include the pressure and liquid level of the steam accumulator 2, the ejector entrainment ratio, the industrial steam supply pressure and temperature, and the unit electric load, etc.

[0067] The steady-state model established in S1 controls the maximum deviation within ±5% by comparing the system parameters under typical operating conditions with the design values. The mixing calculation of the steam ejector 4 is based on the momentum conservation equation, and the outlet pressure adjustment meets the downstream steam supply demand. The control system sets the start-stop conditions of the steam ejector 4 as follows: the accumulator pressure is lower than the required pressure of the entrained steam, and the entrained flow pressure is higher than the steam supply demand.

[0068] The heat exchanger is selected by matching the heat exchange area with the required temperature rise. The molten salt is selected as sodium nitrate-sodium nitrite mixed salt (60:40), the temperature range is 250℃-550℃, and the molten salt tank volume is designed as 1200m 3 , which meets the 4-hour continuous operation heat supply.

[0069] The application also provides a steam supply method, which uses the combined heat and power system based on the coupling of the steam accumulator 2 and the ejector as described above for steam supply.

[0070] In the high load operation stage of the unit, part of the main steam flow is heated by the heat exchanger to heat the molten salt, realizing the first-stage high-temperature sensible heat storage. At the same time, the heated main steam is introduced into the steam accumulator 2 to store heat energy through condensation heat exchange, forming a high-pressure saturated water vapor coexistence system as the second-stage latent heat mixed heat storage. The steam accumulator 2 is provided with a liquid level and pressure regulating device for dynamically controlling its energy storage state.

[0071] The steam ejector 4 is provided, the entrained steam inlet of which is connected to the outlet of the steam accumulator 2, and the entrained steam inlet is connected to the reheating steam pipeline. The ejector entrains low-pressure steam through high-pressure entrained steam, and outputs mixed steam meeting the industrial steam pressure and temperature requirements through mixing and pressure expansion processes.

[0072] When the unit load decreases and the steam extraction pressure is insufficient to meet the industrial steam demand, the system automatically switches to the energy release mode, opens the steam accumulator 2, releases high-pressure steam as the ejector entrained flow, and extracts reheating steam as the entrained flow, adjusts the entrainment ratio and steam flow of the steam ejector 4, realizes the reconstruction and stable supply of steam parameters.

[0073] The molten salt heat storage system is provided. If the ejector output steam temperature is insufficient, the system opens the heat exchanger and molten salt circulating pump to make the mixed steam and high-temperature molten salt exchange heat, so as to improve the steam temperature and make the steam temperature meet the industrial steam temperature standard.

[0074] The system control logic is constructed to dynamically control the start-stop of the ejector, steam flow distribution and accumulator charging-discharging process according to the unit operation load, extraction pressure, industrial steam demand, state of the steam accumulator 2 and other parameters, to ensure stable operation of the system and compliance of the industrial steam quality.

[0075] The ejector is an axisymmetric single-stage structure, including a nozzle, a mixing section and a diffuser section. The nozzle is used to accelerate the high-pressure steam to supersonic speed, forming a low-pressure area, and to inject the injected steam into the mixing section, where momentum and energy exchange are realized. Finally, stable industrial steam is formed by expansion in the diffuser section. The steam ejector 4 is dynamically matched through a flow regulating valve.

[0076] To prevent the steam ejector 4 from failing due to excessively low pressure of the steam accumulator 2, a minimum working pressure threshold of the steam ejector 4 is set. When the pressure is insufficient, the system switches to the traditional extraction steam supply mode or activates the standby electric heating system to ensure steam supply. The industrial steam outlet temperature regulation range is 280℃-295℃, and the pressure fluctuation is not more than ±0.05MPa.

[0077] The molten salt system uses a mixture of sodium nitrate and sodium nitrite salt, with a temperature control range of 250℃-550℃. It is arranged in the main steam bypass, and the heat exchanger heat exchange area and heat supply are matched. During operation, the steam temperature is adjusted by controlling the flow of the molten salt pump.

[0078] The control system monitors key variables such as unit operation state, steam pressure and flow, accumulator state, etc. in real time. The opening logic of the steam ejector 4 is "extraction pressure lower than the set value and steam accumulator 2 pressure higher than the set value", and the injection ratio of the steam ejector 4 is automatically adjusted to maintain constant outlet pressure during operation.

[0079] The following specific examples are used to further illustrate the present application.

[0080] The research object of this example is the typical winter heating condition of a 660 MW ultra-supercritical combined heat and power unit under 40% THA load condition. A physical model of the steam supply system is constructed for the unit, including the main steam system, the reheat steam system, the steam accumulator 2, the ejector, the industrial steam user end, the molten salt heat storage system, and the control system. The initial operating conditions are set as follows: main steam temperature 566℃, pressure 25MPa; reheat steam temperature 600℃, pressure 4.5MPa; industrial steam demand 1.9MPa, 290℃, steam flow rate 150t / h. During the stable operation period when the unit load is greater than 75% THA, 100t / h of main steam is introduced into the shell-and-tube heat exchanger to charge the molten salt system; the heated steam is introduced into the steam accumulator 2 for energy storage, and the energy storage time is about 4 hours. After energy storage is completed, the molten salt system temperature is stabilized at 500℃, the accumulator liquid level rises to 90%, and the pressure rises to 9.0MPa, in a release preparation state.

[0081] After the load is reduced to 40% THA, the extraction steam pressure is reduced to 1.4MPa, which cannot directly supply industrial steam, and the control system switches to the steam supply guarantee mode, and the following operation logic is executed:

[0082] S31: open the outlet valve of the steam accumulator 2 to release high-pressure saturated steam as the injection steam of the steam ejector 4, and control the flow rate at 73t / h;

[0083] S32: introduce low-pressure steam from the reheat extraction pipeline as the injected flow, and the flow rate is 77t / h, and the two streams are mixed and pressurized in the steam ejector 4;

[0084] S33: the outlet steam pressure of the steam ejector 4 is 1.91MPa, and the initial temperature is 278℃, which is sent to the molten salt heat exchanger through the pipeline for temperature rise;

[0085] S34: the temperature of the mixed steam rises to 292℃ after heat exchange with the high-temperature molten salt, which meets the industrial user steam supply demand;

[0086] S35: adjust the nozzle opening, valve position, etc. to ensure stable operation of the system.

[0087] During the simulation verification period, the industrial steam pressure and temperature feedback are updated in real time. The steam pressure fluctuation is controlled within ±0.03MPa, and the temperature fluctuation is not more than ±2℃.

[0088] The system runs in the "ejection steam supply + heat storage and energy release" mode for 15 hours in a day, and the total steam supply is 1350 tons. Compared with the traditional scheme, the invention can realize uninterrupted industrial steam supply under low load operating condition of the unit, and reduce the coal consumption of the boiler, about 123 tons of coal per day.

[0089] In the application embodiment, the import and export steam flow and the internal liquid phase volume fraction change in the steam accumulator charging process and the discharging process are as shown in Figure 3 The coal saving rate schematic diagram of the thermoelectric unit is as shown in Figure 4 .

[0090] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A combined heat and power system based on coupling of steam accumulator and ejector, characterized in that: the combined heat and power system comprises a coal-fired boiler, a first molten salt steam heat exchanger, a steam accumulator, a first control valve, a steam ejector, a second molten salt steam heat exchanger, a first molten salt pump, a cold molten salt storage tank, a second control valve, a second molten salt pump, a hot molten salt storage tank and a third control valve, the main steam outlet of the coal-fired boiler is connected to the hot end inlet of the first molten salt steam heat exchanger, the hot end outlet of the first molten salt steam heat exchanger is connected to the inlet of the steam accumulator, the outlet of the steam accumulator is connected to the inlet of the steam ejector through the first control valve, the outlet of the steam ejector is connected to the cold end inlet of the second molten salt steam heat exchanger, and the cold end outlet of the second molten salt steam heat exchanger is used for steam supply; the inlet of the second molten salt pump is connected to the cold end outlet of the first molten salt steam heat exchanger, the outlet thereof is connected to the inlet of the hot molten salt storage tank, the outlet of the hot molten salt storage tank is connected to the hot end inlet of the second molten salt steam heat exchanger through the third control valve; the hot end outlet of the second molten salt heat exchanger is connected to the inlet of the first molten salt pump, the outlet of the first molten salt pump is connected to the inlet of the cold molten salt storage tank, and the outlet of the cold molten salt storage tank is connected to the cold end inlet of the first molten salt steam heat exchanger through the second control valve. The inlet of the steam accumulator is also connected to a make-up water pipe.

2. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 1, characterized in that: The inlet of the steam ejector is also connected to a steam supply pipe, and the reheated steam from a unit enters the steam ejector through the steam supply pipe.

3. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 1, characterized in that: The combined heat and power system further comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, and the main steam outlet of the coal-fired boiler is also connected to the inlet of the high-pressure cylinder, the outlet of the high-pressure cylinder is connected to the inlet of the medium-pressure cylinder, the outlet of the medium-pressure cylinder is connected to the inlet of the low-pressure cylinder, and the outlet of the low-pressure cylinder is connected to the coal-fired boiler through a cooling tower.

4. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 1, characterized in that: The molten salt used in the combined heat and power system is sodium nitrate-sodium nitrite mixed salt, and the temperature range is 250-550℃.

5. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 1, characterized in that: The ejector is an axisymmetric single-stage structure, which comprises a nozzle, a mixing section and a diffuser section connected in sequence.

6. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 5, characterized in that: The hot molten salt tank has a volume of 1200 m 3 .

7. The combined heat and power system based on a steam accumulator coupled with an ejector according to any of claims 1 to 6, characterized in that: The steam ejector is dynamically matched through a flow regulating valve.

8. The combined heat and power system based on a vapor accumulator coupled with an ejector according to claim 7, characterized in that: The combined heat and power system further comprises an electric auxiliary steam heater for low-load start-up and standby heating, and the electric auxiliary steam heater is connected in parallel between the second molten salt steam heat exchanger and an industrial steam supply main pipe network.

9. The combined heat and power system based on a steam accumulator coupled with an ejector according to any of claims 1 to 6, characterized in that: The steam supply method uses the combined heat and power system based on coupling of steam accumulator and ejector according to any one of claims 1-9 for steam supply.

10. A method of steam generation, characterized by: ​

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