Engine-boiler coupling flexible heat regeneration method for deep peak regulation

Abstract

The invention discloses a turbine-boiler coupling flexible heat regeneration method for deep peak regulation, and relates to the technical field of thermal power plant unit steam deep peak regulation. Comprising the steps that boiler fuel supply and combustion intensity are reduced, and a unit enters a low-load operation state; extracting part of high-temperature and high-pressure steam from a main steam pipeline in front of a steam turbine as a heat source; the pressure of the extracted high-temperature and high-pressure steam is reduced through a temperature and pressure reducing device, and water is sprayed for cooling; steam is introduced into the heat exchanger to release heat, primary air and secondary air are heated, and air needed by combustion is preheated through steam waste heat; the steam subjected to air heating exchanges heat with feed water through a first high-pressure heater; the amount of high-temperature and high-pressure steam extracted from a main steam pipeline in front of a steam turbine is adjusted, the load and the system efficiency are balanced, the steam distribution proportion and parameter setting are optimized, and deep peak regulation is achieved. Steam waste heat is comprehensively utilized to increase the air temperature, energy waste during peak regulation is reduced, and the overall efficiency of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of steam deep peak shaving technology for thermal power plant units, and particularly relates to a boiler-turbine coupled flexible regenerative heating method for deep peak shaving. Background Art

[0002] In recent years, with the increase in energy demand and the depletion of non-renewable resources, the technologies related to renewable resources have developed rapidly. Coal-fired power plants play an important role in the power system. The large consumption of fossil energy brings considerable pressure to the environment. As the main equipment of a thermal power generating unit, the boiler is a thermal energy power equipment and also the main source of high energy consumption and high pollution.

[0003] The exhaust gas loss of the boiler is the largest among all the heat losses of the boiler, accounting for about 70-80% of the boiler heat loss. An excessively high exhaust gas temperature leads to more energy consumption, which is undoubtedly a huge loss.

[0004] The cold source loss of the steam turbine is another relatively large heat loss in a thermal power plant. Even for the currently most advanced 1000MW ultra-supercritical unit in the world, the cold end loss accounts for more than 50% of the heat in the entire steam-water cycle. The energy loss in the power plant itself is very serious, and a large amount of energy has not been fully utilized.

[0005] Therefore, it is an urgent problem for those skilled in the art to propose a boiler-turbine coupled flexible regenerative heating method for deep peak shaving to solve the difficulties existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a boiler-turbine coupled flexible regenerative heating method for deep peak shaving, which comprehensively utilizes the waste heat of steam to increase the air temperature, reduce the energy waste during peak shaving, and improve the overall efficiency of the system.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A boiler-turbine coupled flexible regenerative heating method for deep peak shaving, comprising:

[0009] S1. Reduce the boiler fuel supply and combustion intensity, reduce the main steam output, and make the unit enter a low-load operation state;

[0010] S2. Extract a part of the high-temperature and high-pressure steam from the main steam pipeline in front of the steam turbine as a heat source;

[0011] S3. Reduce the pressure of the extracted high-temperature and high-pressure steam through a desuperheating and pressure-reducing device, and at the same time spray water to cool it down;

[0012] S4. Introduce the decompressed steam into the heat exchangers arranged in the primary air and secondary air pipelines. The steam releases heat to heat the primary air and secondary air, raising the air temperature, and preheating the combustion air using the waste heat of the steam.

[0013] S5. After the air is heated, the steam is led through a pipeline to the No. 1 high-pressure heater in the steam turbine regenerative system for heat exchange with the feed water to recover the remaining heat energy.

[0014] S6. Adjust the amount of high-temperature and high-pressure steam extracted from the main steam pipeline in front of the steam turbine to balance the load and system efficiency, optimize the steam distribution ratio and parameter setting, and achieve deep peak shaving.

[0015] For the above method, optionally, in S3, to reduce the pressure of the extracted high-temperature and high-pressure steam, specifically: reduce the pressure of the extracted high-temperature and high-pressure steam to the pressure range suitable for heating the air system and the high-pressure heater.

[0016] For spray cooling, specifically: spray demineralized water or low-temperature condensate to reduce the temperature of the extracted high-temperature and high-pressure steam to 200°C - 300°C.

[0017] For the above method, optionally, in S4, the heated primary air is used for coal powder drying and transportation; the heated secondary air is used as combustion-supporting air.

[0018] Adjust the steam flow rate and heat exchange efficiency to ensure that the temperatures of the primary air and secondary air are stable within the range required for the low-load operation of the burner.

[0019] For the above method, optionally, in S5, to recover the remaining heat energy, specifically:

[0020] The steam after heat exchange is introduced into the steam side of the No. 1 high-pressure heater through a pipeline.

[0021] The steam continues to release heat in the high-pressure heater to heat the boiler feed water and raise the temperature of the boiler feed water.

[0022] The condensed drain water returns to the feed water system for recycling.

[0023] For the above method, optionally, in S6, to balance the load and system efficiency, specifically:

[0024] Establish a thermodynamic model of the unit under different loads, analyze the influence of the extraction steam pressure and temperature on the regenerative efficiency, and dynamically adjust the extraction steam amount through fuzzy control or model predictive control, reducing the extraction steam at low loads and increasing the extraction steam at high loads to balance the load and system efficiency.

[0025] As can be seen from the above technical solutions, compared with the prior art, the present invention provides a machine-boiler coupled flexible regenerative method for deep peak shaving, which has the following beneficial effects: By heating the primary air and secondary air, the present invention can improve the pulverized coal combustion efficiency under low load and avoid the risk of combustion fluctuations or even flameout caused by insufficient air temperature; the heated air can enhance the mixing effect of pulverized coal and air, reduce the local temperature deviation in the burner, and reduce the risk of tube explosion of the heating surface; preheating the air can reduce the energy consumption of auxiliary equipment such as coal mills and indirectly improve the overall energy efficiency of the unit; comprehensively utilize the waste heat of steam to increase the air temperature, reduce the energy waste during peak shaving, and at the same time improve the overall efficiency of the system by recovering the surplus steam through the first high-pressure heater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0027] Figure 1 It is a flowchart of a machine-boiler coupled flexible regenerative method for deep peak shaving provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] In the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "including a..." does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0030] Referring to Figure 1 As shown, the present invention discloses a machine-boiler coupled flexible regenerative method for deep peak shaving, including:

[0031] S1. Reduce the boiler fuel supply and combustion intensity, lower the main steam output, and put the unit into a low-load operation state;

[0032] S2. Extract a part of the high-temperature and high-pressure steam from the main steam pipeline in front of the steam turbine as the heat source;

[0033] S3. Reduce the pressure of the extracted high-temperature and high-pressure steam through a desuperheating and pressure-reducing device, and at the same time spray water to reduce the temperature;

[0034] S4. Introduce the depressurized steam into the heat exchanger arranged in the primary air and secondary air pipelines. The steam releases heat, heats the primary air and secondary air, raises the air temperature, and preheats the combustion-required air by using the waste heat of the steam;

[0035] S5. After the air heating is completed, the steam is led to the No. 1 high-pressure heater of the steam turbine regenerative system through a pipeline to conduct heat exchange with the feed water and recover the remaining heat energy;

[0036] S6. Adjust the amount of high-temperature and high-pressure steam extracted from the main steam pipeline in front of the steam turbine, balance the load and system efficiency, optimize the steam distribution ratio and parameter setting, and achieve deep peak shaving.

[0037] Furthermore, the boiler side adopts a variable pressure operation mode to reduce the main steam pressure to improve the low-load combustion stability; the flow area of the regulating stage of the steam turbine is dynamically adjusted to match the variable pressure steam flow and maintain the balance of output and efficiency.

[0038] Furthermore, in S3, to reduce the pressure of the extracted high-temperature and high-pressure steam, specifically: reduce the pressure of the extracted high-temperature and high-pressure steam to the pressure range suitable for heating the air system and high-pressure heater (such as 0.5 - 1.5 MPa);

[0039] To spray water to reduce the temperature, specifically: spray demineralized water or low-temperature condensate water to reduce the temperature of the extracted high-temperature and high-pressure steam to 200°C - 300°C to avoid overheating of the heat exchanger.

[0040] Furthermore, in S4, the heated primary air is used for coal powder drying and conveying; the heated secondary air is used for combustion-supporting air;

[0041] Adjust the steam flow rate and heat exchange efficiency to ensure that the temperatures of the primary air and secondary air are stable within the range required for the low-load operation of the burner;

[0042] Even further, by heating the primary air and secondary air, the coal powder combustion efficiency under low load can be improved, avoiding the risk of combustion fluctuations or even flameout caused by insufficient air temperature; the heated air can enhance the mixing effect of coal powder and air, reduce the local temperature deviation in the burner, and reduce the risk of tube explosion of the heating surface; preheating the air can reduce the energy consumption of auxiliary equipment such as coal mills and indirectly improve the overall energy efficiency of the unit.

[0043] Further, in S5, the remaining heat energy is recovered, specifically as follows:

[0044] The steam after heat exchange is introduced into the steam side of the No. 1 high-pressure heater through a pipeline;

[0045] The steam continues to release heat in the high-pressure heater, heating the boiler feed water and raising the temperature of the boiler feed water;

[0046] The condensed drain water returns to the feed water system for recycling;

[0047] Furthermore, after the steam after desuperheating and pressure reduction enters the No. 1 high-pressure heater, it can replace part of the extraction steam demand, reduce the extraction steam volume of the steam turbine, and further reduce the power generation load; this process recovers the waste heat of the steam, maintains the stability of the feed water temperature, and avoids the problem of deterioration of the boiler water dynamics caused by low-load operation.

[0048] Further, in S6, the load and system efficiency are balanced, specifically as follows:

[0049] A thermodynamic model of the unit under different loads is established, the influence of the extraction steam pressure and temperature on the regenerative efficiency is analyzed, and through fuzzy control or model predictive control, the extraction steam volume is dynamically adjusted, reducing the extraction steam at low loads and increasing the extraction steam at high loads to balance the load and system efficiency;

[0050] Furthermore, the parameters of the steam after desuperheating and pressure reduction need to be precisely controlled to ensure that they match the design requirements of the hot air system and the heater, avoiding a decrease in heat exchange efficiency or equipment damage; when the load changes rapidly under deep peak shaving conditions, the control logic needs to be optimized to achieve rapid coordination of the steam flow rate, air temperature, and combustion state.

[0051] In a specific embodiment, a 600MW supercritical unit is retrofitted. The flexible regeneration method is adopted. The main steam parameters are reduced to 0.8 - 1.3 MPa / 200 - 250 °C through a desuperheating and pressure reduction device. The temperature of the hot primary air heated by diverting part of the steam to the air duct heater can be increased to 150 - 180 °C, and the hot secondary air reaches 120 - 150 °C, significantly improving the combustion stability at low loads; the steam finally flows into the No. 1 high-pressure heater to maintain the feed water temperature above 220 °C, avoiding key equipment configuration for low-temperature corrosion;

[0052] After adopting the flexible regeneration method, when deep peak shaving to 25% load, the regenerative system still maintains 85% of the designed temperature rise, and the boiler efficiency is increased by 2.3%. The technical route of the main steam desuperheating and pressure reduction.

[0053] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for a system or system embodiment, since it is basically similar to a method embodiment, the description is relatively simple. For related parts, reference can be made to the corresponding description in the method embodiment. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative work.

[0054] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to a person skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flexible regenerative method for boiler-turbine coupling in deep peak shaving, characterized in that, Including: S1. Reduce the boiler fuel supply and combustion intensity, decrease the main steam output, and make the unit enter the low-load operation state; S2. Extract part of the high-temperature and high-pressure steam from the main steam pipeline in front of the steam turbine as the heat source; S3. Reduce the pressure of the extracted high-temperature and high-pressure steam through a desuperheating and pressure-reducing device, and at the same time spray water to cool down the steam; S4. Introduce the pressure-reduced steam into the heat exchanger arranged in the primary air and secondary air pipelines. The steam releases heat, heats the primary air and secondary air, raises the air temperature, and preheats the combustion-required air by using the waste heat of the steam; S5. After the air is heated, the steam is led to the No. 1 high-pressure heater of the steam turbine regenerative system through a pipeline, and exchanges heat with the feed water to recover the remaining heat energy; S6. Adjust the amount of high-temperature and high-pressure steam extracted from the main steam pipeline in front of the steam turbine, balance the load and system efficiency, optimize the steam distribution ratio and parameter setting, and achieve deep peak shaving.

2. A boiler-turbine coupled flexible regenerative method for deep peak shaving according to claim 1, wherein in S3, reducing the pressure of the extracted high-temperature and high-pressure steam specifically means: reducing the pressure of the extracted high-temperature and high-pressure steam to the pressure range suitable for heating the air system and the high-pressure heater; spraying water to cool down specifically means: spraying desalted water or low-temperature condensate to reduce the temperature of the extracted high-temperature and high-pressure steam to 200°C - 300°C.

3. A boiler-turbine coupled flexible regenerative method for deep peak shaving according to claim 1, wherein in S4, heating the primary air is used for coal powder drying and conveying; heating the secondary air is used for combustion-supporting air; adjust the steam flow rate and heat transfer efficiency to ensure that the temperatures of the primary air and secondary air are stable within the range required for the low-load operation of the burner.

4. A boiler-turbine coupled flexible regenerative method for deep peak shaving according to claim 1, wherein in S5, recovering the remaining heat energy specifically means: the heat-exchanged steam is introduced into the steam side of the No. 1 high-pressure heater through a pipeline; the steam continues to release heat in the high-pressure heater, heats the boiler feed water, and raises the temperature of the boiler feed water; the condensed drain water returns to the feed water system for recycling.

5. A boiler-turbine coupled flexible regenerative method for deep peak shaving according to claim 1, wherein in S6, balancing the load and system efficiency specifically means: establish a thermodynamic model of the unit at different loads, analyze the influence of the extraction steam pressure and temperature on the regeneration efficiency, and dynamically adjust the extraction steam amount through fuzzy control or model predictive control, reducing the extraction steam at low load and increasing the extraction steam at high load to balance the load and system efficiency.

Images