Configuration system for coal power unit to adapt to deep peak regulation

Abstract

The utility model provides a configuration system for a coal power unit to adapt to deep peak regulation, the configuration system is additionally provided with an external steam cooler and a temperature reduction module, steam with a higher pressure grade than regenerative steam extraction of a high-pressure cylinder is subjected to temperature reduction through the temperature reduction module and then heats feed water in the external steam cooler; steam at a steam outlet of the external steam cooler is conveyed into the existing final-stage high-pressure heater to heat the feed water at the front end of the external steam cooler, so that the temperature of the feed water in the boiler of the unit under the deep peak regulation working condition is increased, and the utilization rate of heat is also increased; a certain feed water pressure is maintained while the feed water temperature is increased, feed water at an outlet of a coal economizer is kept at a certain supercooling degree, dry-state operation of a boiler is maintained under the deep peak regulation working condition, hydrodynamic stability is maintained, and a denitration system is continuously and stably put into operation.

Description

Technical Field

[0001] The utility model relates to the technical field of power generation, in particular to a configuration system for coal-fired power generation units adapted to deep peak regulation. Background Art

[0002] Currently, ultra-supercritical (USC) units, featuring high performance, large capacity, high efficiency, and low carbon emissions, have become the mainstream choice for new thermal power plant construction. These units primarily feature capacities of 350MW, 660MW, and 1000MW, with a smaller number of 1200MW and 1350MW units also available.

[0003] The installed capacity and power generation of new energy have reached new highs. Due to the uncertainty of power generation in new energy power generation, traditional thermal power units, especially coal-fired power units, must assume the role of basic power supply and flexible peak-shaving power supply to cooperate with new energy power generation.

[0004] Taking a 1000MW ultra-supercritical unit as an example, the regional power grid dispatches loads between 40% and 100% THA. The boiler feedwater flow rate corresponding to this unit's load is higher than the minimum flow rate required for the boiler to maintain dry operation. Therefore, within the current normal load dispatch range, the boiler always maintains dry operation without any dry-wet state transition. However, with the rapid development of renewable energy, the regional power grid has now notified the unit that it needs to operate in a deep peak-shaving cloud mode, with the load dispatch lower limit required to be as low as 20%. The boiler feedwater flow rate corresponding to this 20% load is already lower than the minimum flow rate required for the boiler to maintain dry operation, forcing the boiler to switch to wet operation.

[0005] For ultra-supercritical (supercritical) units that need to participate in deep peak load regulation operation, such as those with a load variation range of 20%-100% THA, and deep peak load range of 20%-30% THA or even lower, they will face the following problems:

[0006] (1) Under deep peak load regulation conditions, the boiler switches frequently between dry and wet states, and the control of coal, water, and air is very difficult, resulting in a sharp increase in the risk of boiler shutdown.

[0007] (2) Under deep peak load regulation conditions, the risk of water wall overheating and tube burst increases sharply due to the increase in the water wall inlet feed water enthalpy and poor hydrodynamic stability.

[0008] (3) Under deep peak load conditions, the flue gas temperature at the economizer outlet will be lower than the lower limit of the normal operation temperature of the denitrification catalyst (such as 300°C), and the denitrification system will not be able to operate normally. It is foreseeable that NO X Emissions will increase dramatically and far exceed the standard requirements, such as the emission index from 25mg / Nm 3 Exploded to 200mg / Nm 3 Above, far exceeding the standard value of 50mg / Nm3 .

[0009] (4) Under the wet operation condition of the boiler, if the water separated from the steam-water separator at the outlet of the boiler water-cooled wall is directly discharged into the atmospheric expansion tank, it will cause a large amount of working fluid and its energy loss, the energy consumption of the unit will increase significantly, and the operating economy will decrease significantly.

[0010] Therefore, how to maintain dry operation of the boiler under deep peak-shaving conditions, and maintain hydrodynamic stability and continuous and stable operation of the denitrification system has become an urgent problem that needs to be solved. Utility Model Content

[0011] The technical problem to be solved by the present invention is how to maintain the dry operation of the boiler under deep peak regulation conditions, and keep the hydrodynamic stability and the denitrification system in continuous and stable operation, and provide a configuration system for coal-fired power units that is suitable for deep peak regulation.

[0012] The utility model solves the above technical problems through the following technical solutions:

[0013] The utility model provides a configuration system for coal-fired power units adapted to deep peak regulation, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the boiler comprises an economizer, a water-cooled wall and a superheater connected in sequence through pipelines; the feed water inlet of the existing final-stage high-pressure heater is connected to the feed water outlet of the deaeration system, the feed water outlet of the existing final-stage high-pressure heater is connected to the feed water inlet of the boiler, the steam outlet of the boiler is connected to the high-pressure cylinder through a main steam pipeline, the steam inlet of the existing final-stage high-pressure heater is connected to the steam extraction port of the high-pressure cylinder through a steam inlet pipeline; a main steam throttling component is provided on the main steam pipeline ; A steam extraction isolation valve is arranged on the steam inlet pipe; in addition, the configuration system is also provided with an additional temperature reduction module and an external steam cooler. The external steam cooler is arranged on the water supply pipe between the water supply inlet of the boiler and the water supply outlet of the existing final high-pressure heater. The steam side inlet of the external steam cooler is connected to the temperature reduction module, and the inlet of the temperature reduction module is connected to steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder; the steam side outlet of the external steam cooler is connected to the steam inlet pipe and is located downstream of the steam extraction isolation valve, so as to improve the inlet water temperature of the unit under deep peak regulation conditions.

[0014] In this solution, on the basis of the existing boiler feed water heating, an external steam cooler is added to the feed water pipeline between the boiler feed water inlet and the feed water outlet of the existing final stage high-pressure heater, and the steam side inlet of the external steam cooler is connected to the temperature reduction module, the inlet of the temperature reduction module is connected to the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder, the steam side outlet of the external steam cooler is connected to the steam inlet pipeline and is located downstream of the steam extraction isolation valve, the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is cooled by the temperature reduction module and first goes to the external steam cooler to heat the feed water, and then the steam at the steam outlet of the external steam cooler is sent to the existing final stage high-pressure heater to heat the feed water at the front end of the external steam cooler. When the external steam cooler is connected to the steam inlet pipeline, the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is cooled and then sent to the external steam cooler to heat the feed water. When the steam at the steam side outlet of the reactor enters the existing final high-pressure heater to heat the feed water, the extraction isolation valve is in a closed state upstream, that is, the steam at the outlet of the newly added external steam cooler replaces the existing final high-pressure heater heat recovery extraction steam; during the whole process, the steam coming out of the temperature reduction module first heats the rear end feed water in the external steam cooler, and then the steam at the steam side outlet of the external steam cooler is sent to the existing final high-pressure heater to heat the front end feed water, which not only improves the unit's inlet feed water temperature under deep peak regulation conditions, but also improves the heat utilization rate; as the unit's inlet feed water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement.

[0015] Preferably, the cooling module comprises an isolation valve, a pressure reducing valve and a cooler which are sequentially connected through pipelines, and cooling water is connected to the cooler.

[0016] In this solution, steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder enters the cooling module, is reduced in pressure through the pressure reducing valve, and enters the desuperheater to be mixed with the cooling water to achieve cooling and pressure reduction. The cooling and pressure reduction of steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is achieved through the action of the cooling module, thereby ensuring the safe operation of the system.

[0017] Preferably, the steam pressure at the steam side outlet of the external steam cooler is higher than the heat recovery extraction pressure of the high-pressure cylinder.

[0018] In this solution, the steam pressure at the steam side outlet of the external steam cooler is higher than the heat recovery extraction pressure of the high-pressure cylinder, so that the steam pressure entering the existing last-stage high-pressure heater is higher than the heat recovery extraction pressure of the high-pressure cylinder, thereby further increasing the feed water temperature after heating by the existing last-stage high-pressure heater.

[0019] Preferably, a heat exchanger is provided between the outlet of the desuperheater and the steam side inlet of the external steam cooler.

[0020] In this solution, a heat exchanger is provided between the outlet of the desuperheater and the steam side inlet of the external steam cooler, so that the steam after the desuperheater first enters the heat exchanger to heat other working fluids, such as air, water, coal, etc., and then enters the external steam cooler to heat the feed water. In this way, the steam temperature entering the external steam cooler can be guaranteed and the steam inlet flow rate of the external steam cooler can be relatively increased.

[0021] Preferably, the source of steam with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder is main steam, and the inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam.

[0022] In this solution, the inlet of the temperature reduction module is connected to the main steam pipeline. Part of the main steam is introduced into the temperature reduction module, and then sent to the external steam cooler for heating the feed water after temperature reduction and pressure reduction, so as to increase the feed water temperature of the unit under deep peak regulation conditions.

[0023] Preferably, the source of steam with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder is the reheated steam of this unit or the main steam of other units or the reheated steam of other units.

[0024] In this solution, the source of steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is the reheat steam of this unit or the main steam of other units or the reheat steam of other units. On the premise that the steam entering the external steam cooler is higher than the existing heat recovery extraction steam, the operating flexibility of the unit is improved.

[0025] Preferably, the main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

[0026] In this solution, the main steam throttling assembly adopts a high-pressure cylinder steam inlet regulating valve group or a regulating valve to facilitate the adjustment of the pressure and flow of the main steam.

[0027] Preferably, the system is configured to: throttle the main steam using a main steam throttling assembly to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling.

[0028] In this scheme, steam with a higher pressure grade than the heat recovery steam of the high-pressure cylinder enters the external steam cooler for supplementary heating of the feed water after being cooled and reduced in the temperature reduction module, and enters the existing final-stage high-pressure heater from the external steam cooler to heat the feed water to increase the feed water temperature of the unit under deep peak regulation conditions. By operating the high-pressure cylinder steam inlet valve group, the original high-pressure cylinder steam inlet valve group is used to throttle the main steam. The purpose is to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling to prevent vaporization from occurring while increasing the feed water temperature, thereby ensuring the normal operation of the unit.

[0029] Preferably, a throttling component is provided in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0030] In this solution, a throttling component, such as a regulating valve, can also be installed in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0031] The positive progressive effect of the present invention is that an external steam cooler and a temperature reduction module are added, and steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is first heated in the external steam cooler after being cooled by the temperature reduction module, and then the steam at the steam outlet of the external steam cooler is sent to the existing last-stage high-pressure heater to heat the feed water located at the front end of the external steam cooler, which not only improves the unit's inlet feed water temperature under deep peak-shaving conditions, but also improves the heat utilization rate; while increasing the feed water temperature, a certain feed water pressure is maintained, and the economizer outlet feed water is kept at a certain degree of subcooling, so as to maintain the dry operation of the boiler under deep peak-shaving conditions, and maintain the hydrodynamic stability and continuous and stable operation of the denitrification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of a boiler feed water heating system in the prior art.

[0033] Figure 2 This is a configuration system for a coal-fired power unit adapted to deep peak regulation in one embodiment of the utility model. DETAILED DESCRIPTION

[0034] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.

[0035] Figure 1This is a schematic diagram of a conventional boiler feedwater heating system. The system includes a boiler, a deaerator system, a high-pressure cylinder, and a conventional final-stage high-pressure heater. The boiler includes an economizer, water-cooled walls, and a superheater, all connected in sequence by pipes. The deaerator system includes a deaerator, a pre-pump, and a feedwater pump, all connected in sequence by pipes. The feedwater inlet of the conventional final-stage high-pressure heater is connected to the feedwater outlet of the deaerator system, which in turn is connected to the feedwater inlet of the boiler. The boiler's steam outlet is connected to the high-pressure cylinder via a main steam pipeline, and the steam inlet of the conventional final-stage high-pressure heater is connected to the steam extraction port of the high-pressure cylinder via a steam inlet pipeline. A high-pressure cylinder steam inlet valve group is provided on the main steam pipeline, and an extraction isolation valve is arranged on the steam inlet pipeline. Low-pressure condensate from the deaerator outlet is pressurized by the pre-pump and feedwater pump, then enters the high-pressure heater for heating. The heated feedwater enters the boiler, where it is heated by heating surfaces such as the economizer, water-cooled walls, and superheater, ultimately generating main steam that enters the high-pressure cylinder to perform work. The high-pressure cylinder steam inlet valve group regulates the pressure and flow of the main steam.

[0036] The utility model adds an external steam cooler and a temperature reduction module on the basis of the existing boiler feed water heating system. Figure 2 As shown, an external steam cooler is added to the water supply pipe between the water supply inlet of the boiler and the water supply outlet of the existing final-stage high-pressure heater, and the steam-side inlet of the external steam cooler is connected to the temperature reduction module. The inlet of the temperature reduction module is connected to the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder. The steam-side outlet of the external steam cooler is connected to the steam inlet pipe and is located downstream of the steam extraction isolation valve. The steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is first sent to the external steam cooler to heat the feed water after being cooled and reduced in pressure by the temperature reduction module. The steam at the steam outlet of the external steam cooler is then sent to the existing final-stage high-pressure heater to heat the feed water at the front end of the external steam cooler. When the steam-side outlet of the external steam cooler is When the steam enters the existing final-stage high-pressure heater to heat the feed water, the extraction isolation valve is closed upstream, that is, the steam at the outlet of the newly added external steam cooler replaces the existing final-stage high-pressure heat recovery extraction steam; during the whole process, the steam coming out of the temperature reduction module is first used to heat the rear-end feed water in the external steam cooler, and then the steam at the steam side outlet of the external steam cooler is sent to the existing final-stage high-pressure heater to heat the front-end feed water, which not only improves the unit's inlet water temperature under deep peak regulation conditions, but also improves the heat utilization rate; as the unit's inlet water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement.

[0037] like Figure 2As shown, the desuperheating module includes an isolation valve, a pressure reducing valve, and a desuperheater connected in sequence via pipes. The desuperheater is fed with desuperheating water. Steam at a higher pressure than the heat recovery steam from the high-pressure cylinder enters the desuperheating module, where it is reduced in pressure by the pressure reducing valve and then enters the desuperheater, where it mixes with the desuperheating water to achieve temperature and pressure reduction. The desuperheating module reduces the temperature and pressure of steam at a higher pressure than the heat recovery steam from the high-pressure cylinder, ensuring safe system operation.

[0038] The steam pressure at the steam side outlet of the external steam cooler is higher than the heat recovery extraction pressure of the high-pressure cylinder, so that the steam pressure entering the existing final-stage high-pressure heater is higher than the heat recovery extraction pressure of the high-pressure cylinder, thereby further increasing the feed water temperature after being heated by the existing final-stage high-pressure heater.

[0039] The main steam pipe is equipped with a main steam throttling assembly. Figure 2 The main steam throttling component is a high-pressure cylinder steam inlet valve group. Of course, a regulating valve can also be used. The high-pressure cylinder steam inlet valve group regulates the pressure and flow of the main steam. It should be emphasized here that steam with a higher pressure level than the reheated extraction steam of the high-pressure cylinder enters the external steam cooler for supplementary heating of the feed water after being cooled and reduced in the desuperheating module, and enters the existing final-stage high-pressure heater from the external steam cooler to heat the feed water to increase the feed water temperature of the unit under deep peak regulation conditions. By operating the high-pressure cylinder steam inlet valve group, the original high-pressure cylinder steam inlet valve group is used to throttle the main steam. The purpose is to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling, prevent vaporization from occurring while increasing the feed water temperature, and ensure the normal operation of the unit. Of course, in other embodiments, a throttling component, such as a regulating valve, can also be installed in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0040] In this embodiment, the steam at the outlet of the desuperheater directly enters the external steam cooler through a pipeline. Of course, in other embodiments, a heat exchanger can be provided between the outlet of the desuperheater and the steam side inlet of the external steam cooler, so that the steam after the desuperheater first enters the heat exchanger to heat other working media, such as air, water, coal, etc., and then enters the external steam cooler to heat the feed water. In this way, the steam temperature entering the external steam cooler can be guaranteed and the steam inlet flow rate of the external steam cooler can be relatively increased.

[0041] like Figure 2As shown, in this embodiment, the source of steam with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder is main steam. The inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam. The introduced part of the main steam enters the desuperheater through the isolation valve and the pressure reducing valve in the desuperheating module, is mixed with the desuperheating water, and is then sent to the external steam cooler to heat the feed water, so as to improve the feed water temperature entering the furnace of the unit under deep peak regulation conditions. Of course, in other embodiments, the source of steam with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder can be the reheat steam of this unit or the main steam of other units or the reheat steam of other units, so as to improve the operating flexibility of this unit, under the premise that the steam entering the external steam cooler is higher than the existing heat recovery extraction steam.

[0042] In this way, under deep peak regulation conditions, taking the 20% THA condition as an example: the unit's boiler feed water temperature can be increased to a feed water temperature level of 75% THA or even 100% THA; as the unit's boiler feed water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement; while the economizer outlet water temperature is increased, a certain feed water pressure is maintained, so that the economizer outlet feed water maintains a certain degree of subcooling; as the economizer outlet water temperature increases, the water wall inlet water temperature is increased, and then the water wall inlet under-enthalpy is reduced, and the hydrodynamic stability is enhanced; as the water wall inlet water temperature increases, the water wall outlet steam can maintain a certain degree of superheat, that is, the boiler dry operation is achieved.

[0043] Specifically, take the data of a 1000MW unit under 20% THA condition as an example.

[0044] Existing plan: main generator load is 220MW, existing last stage high-pressure heater inlet steam pressure and temperature parameters are: 1.75MPa, 436℃ and outlet feed water pressure and temperature parameters are: 6MPa, 192℃, economizer outlet water temperature is 240℃, subcooling degree is 36℃, under-enthalpy is 176kJ / kg, economizer outlet flue gas temperature is 245℃, water wall outlet is wet saturated steam, the unit is in wet operation state, and the denitrification system cannot be put into use.

[0045] In this embodiment, the main generator load is 220MW, the existing last-stage high-pressure heater inlet steam pressure and temperature parameters are 6.2MPa and 340°C, and the outlet feed water pressure and temperature parameters are 12MPa and 280°C. The water-side temperature rise of the newly added external steam cooler is 6°C, the economizer outlet water temperature is 304°C, the subcooling degree is 20.7°C, the underenthalpy is 127.8 kJ / kg, the economizer outlet flue gas temperature is 309°C, the water-wall outlet superheat is 11°C, the unit is in dry operation, the underenthalpy of the water at the water-wall inlet is relatively reduced by 48.2kJ / kg, the water-wall outlet steam temperature deviation is controlled, the hydrodynamic stability is enhanced, and the denitrification system is stably and continuously put into use.

[0046] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of protection of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of protection of the present invention.

Claims

1. A configuration system for coal-fired power units adapted to deep peak regulation, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the boiler comprises an economizer, a water-cooled wall and a superheater connected in sequence by pipelines; the feed water inlet of the existing final-stage high-pressure heater is connected to the feed water outlet of the deaeration system, the feed water outlet of the existing final-stage high-pressure heater is connected to the feed water inlet of the boiler, the steam outlet of the boiler is connected to the high-pressure cylinder via a main steam pipeline, the steam inlet of the existing final-stage high-pressure heater is connected to the steam extraction port of the high-pressure cylinder via a steam inlet pipeline; a main steam throttling assembly is provided on the main steam pipeline; an extraction steam isolation valve is arranged on the steam inlet pipeline; and the characteristics are as follows: A cooling module and an external steam cooler are added. The external steam cooler is arranged on the water feed pipe between the water feed inlet of the boiler and the water feed outlet of the existing final-stage high-pressure heater. The steam side inlet of the external steam cooler is connected to the cooling module. The inlet of the cooling module is connected to steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder; the steam side outlet of the external steam cooler is connected to the steam inlet pipe and is located downstream of the steam extraction isolation valve, so as to improve the inlet water temperature of the unit under deep peak regulation conditions.

2. The configuration system according to claim 1, wherein: The temperature reduction module includes an isolation valve, a pressure reducing valve and a temperature reducer which are sequentially connected through pipelines, and the temperature reducing water is connected to the temperature reducer.

3. The configuration system according to claim 2, wherein: The steam pressure at the steam side outlet of the external steam cooler is higher than the heat recovery extraction pressure of the high-pressure cylinder.

4. The configuration system according to claim 3, wherein: A heat exchanger is provided between the outlet of the desuperheater and the steam side inlet of the external steam cooler.

5. The configuration system according to claim 4, wherein: The steam source with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder is main steam, and the inlet of the temperature reduction module is connected to the main steam pipeline to introduce part of the main steam.

6. The configuration system according to claim 4, wherein: The source of steam with a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder is the reheat steam of this unit or the main steam or reheat steam of other units.

7. The configuration system according to claim 3, wherein: The main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

8. The configuration system according to any one of claims 1 to 7, wherein: The configuration system is configured to: throttle the main steam using the main steam throttling assembly to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling.

9. The configuration system according to any one of claims 1 to 7, wherein: A throttling component is set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

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