Configuration system for coal power unit to adapt to flexible operation
By adding a new final-stage high-pressure heater and an external steam cooler to the boiler feed water pipe and using the high-pressure cylinder heat recovery extraction steam for double heating, the problem of frequent switching between dry and wet states of the boiler under deep peak-shaving conditions is solved, the dry operation of the boiler and the stability of the denitrification system are achieved, and the operating economy of the unit is improved.
Patent Information
- Application Number
- CN202422800442.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2034-11-18
AI Technical Summary
Under deep peak-shaving conditions, the boilers of ultra-supercritical units frequently switch between dry and wet states, resulting in an increased risk of boiler shutdown, poor hydrodynamic stability of the water-cooled wall, and inability to operate the denitrification system normally. This increases unit energy consumption and reduces operating economy.
A new final-stage high-pressure heater and an external steam cooler are added to the feed water pipeline of the existing final-stage high-pressure heater. By introducing high-pressure cylinder heat recovery extraction steam with a higher pressure level for double heating, the feed water temperature into the boiler is increased, the dry operation of the boiler is maintained, the hydrodynamic stability is enhanced, and the flue gas temperature requirements of the denitrification system are met.
The unit's inlet water temperature under deep peak-shaving conditions is increased, the water-wall inlet enthalpy is reduced, the hydrodynamic stability is enhanced, the normal operation of the denitrification system is ensured, energy consumption is reduced and the operating economy is improved.
Smart Images
Figure CN223399749U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of power generation, in particular to a configuration system for coal-fired power generation units adapting to flexible operation. 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 can adapt to flexible operation.
[0012] The utility model solves the above technical problems through the following technical solutions:
[0013] The utility model provides a configuration system of a coal-fired power unit adapted to flexible operation, comprising a boiler, a deaerator 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 deaerator system comprises a deaerator, a pre-pump and a feed water pump 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 deaerator 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, and the steam inlet of the existing final-stage high-pressure heater is connected to the steam inlet of the boiler. It is connected to the steam extraction port of the high-pressure cylinder through a steam inlet pipe; a main steam throttling assembly is provided on the main steam pipe; an extraction isolation valve is arranged on the steam inlet pipe; from the outside, a newly added final-stage high-pressure heater and an external steam cooler are sequentially provided on the water feed pipe between the water feed outlet of the existing final-stage high-pressure heater and the water feed inlet of the boiler, and the steam side inlet of the external steam cooler is connected to a cooling module, the inlet of the cooling module is connected to steam of a higher pressure grade than the heat recovery extraction steam of the high-pressure cylinder, and the steam side outlet of the external steam cooler is connected to the steam inlet of the newly added final-stage high-pressure heater.
[0014] In this solution, on the basis of the high-pressure cylinder heat recovery extraction steam of the unit entering the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater and an external steam cooler are sequentially arranged on the feed water pipeline between the feed water outlet of the existing final-stage high-pressure heater and the feed water inlet of the boiler, and the steam side inlet of the external steam cooler is connected to a 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. After the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is cooled and reduced in the temperature reduction module, it is first sent 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 newly added final-stage high-pressure heater. The feed water heated by the existing final stage high-pressure heater is supplementarily heated to increase the feed water temperature of the unit under deep peak-shaving conditions. That is, on the basis of the normal operation of the existing final stage high-pressure heater to heat the feed water, steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is introduced to perform supplementary heating twice in the external steam cooler and the newly added final stage high-pressure heater respectively. This not only improves the feed water temperature of the unit under deep peak-shaving conditions, but also improves the heat utilization rate; as the feed water temperature of the unit 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 main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.
[0018] 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.
[0019] 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.
[0020] 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 newly added final-stage high-pressure heater is higher than the heat recovery extraction pressure of the high-pressure cylinder, thereby realizing supplementary heating of the feed water heated by the existing final-stage high-pressure heater at the newly added final-stage high-pressure heater.
[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 scheme, the inlet of the temperature reduction module is connected to the main steam pipeline. By introducing part of the main steam into the temperature reduction module, it is 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 reheat steam of this unit or the main steam or reheat 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 configuration system is configured to: utilize the main steam throttling component to throttle the main steam to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling.
[0026] 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 after being cooled and reduced in the temperature reduction module, and enters the newly added final-stage high-pressure heater from the external steam cooler for supplementary heating of 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 main steam is throttled using the original high-pressure cylinder steam inlet valve group. 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.
[0027] 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.
[0028] 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.
[0029] The positive progressive effect of the present invention is that: on the basis of the normal use of the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater and an external steam cooler are sequentially arranged on the feed water pipeline between the feed water outlet of the existing final-stage high-pressure heater and the feed water inlet of the boiler, the steam side inlet of the external steam cooler is connected to a temperature reduction module, and steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is introduced at the inlet of the temperature reduction module, and by introducing steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder, two supplementary heatings are performed in the external steam cooler and the new final-stage high-pressure heater respectively, which not only improves the feed water temperature of the unit under deep peak-shaving conditions, but also improves the utilization rate of heat; while increasing the feed water temperature, a certain feed water pressure is maintained, and the feed water at the economizer outlet is kept at a certain degree of subcooling, so as to achieve dry operation of the boiler under deep peak-shaving conditions, and maintain hydrodynamic stability and continuous and stable operation of the denitrification system. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 This is a schematic diagram of a boiler feed water heating system in the prior art.
[0031] Figure 2 This is a configuration system for a coal-fired power unit adapted to flexible operation according to an embodiment of the present utility model. DETAILED DESCRIPTION
[0032] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.
[0033] Figure 1 This is a schematic diagram of a conventional boiler feedwater heating system. The system includes a boiler, a deaerator system, a high-pressure cylinder, and an existing 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 existing 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 existing 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.
[0034] like Figure 2As shown, the utility model is based on the normal use of the existing final-stage high-pressure thermal heater to heat the feed water, that is, the extraction steam isolation valve is in the open state, and a new final-stage high-pressure heater and an external steam cooler are sequentially arranged on the feed water pipeline between the feed water outlet of the existing final-stage high-pressure heater and the feed water inlet of the boiler, and the steam side inlet of the external steam cooler is connected to a temperature reduction module, 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, and the steam side outlet of the external steam cooler is connected to the steam inlet of the new final-stage high-pressure heater, and the steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is cooled and reduced in the temperature reduction module before it is sent to the external steam cooler to replenish the feed water. Heat is obtained, and the steam from the steam outlet of the external steam cooler is sent to the newly added final-stage high-pressure heater to supplement the heating of the feed water heated by the existing final-stage high-pressure heater. That is, on the basis of the normal operation of the existing final-stage high-pressure heater to heat the feed water, steam with a higher pressure level than the heat recovery extraction steam of the high-pressure cylinder is introduced to perform two supplementary heatings in the external steam cooler and the newly added final-stage high-pressure heater respectively, which not only improves the feed water temperature of the unit under deep peak regulation conditions, but also improves the utilization rate of heat; as the feed water temperature of the unit increases, the water temperature at the economizer inlet is increased, and then the water temperature at the economizer outlet is increased, and the flue gas temperature at the economizer outlet is increased and meets the flue gas temperature requirement of the denitrification inlet.
[0035] like Figure 2 As 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 operation of the system.
[0036] 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 newly added 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 heating by the existing final-stage high-pressure heater.
[0037] The main steam pipe is equipped with a main steam throttling assembly. Figure 2The main steam throttling component is a high-pressure cylinder steam inlet valve group. Of course, a regulating valve can also be selected. The high-pressure cylinder steam inlet valve group adjusts the pressure and flow of the main steam. It should be emphasized here that the steam with a higher pressure level than the heat recovery steam of the high-pressure cylinder enters the external steam cooler to supplement the heating of the feed water after cooling and reducing pressure in the cooling module, and enters the newly added final high-pressure heater after the external steam cooler to supplement the heating of 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, so as to ensure the normal operation of the unit. As the feed water temperature of the unit into the furnace increases, the water temperature of the economizer inlet is increased, and then the water temperature of the economizer outlet is increased, and the flue gas temperature of the economizer outlet is increased and meets the flue gas temperature requirement of the denitrification inlet; while the water temperature of the economizer outlet is increased, a certain feed water pressure is maintained so that the feed water of the economizer outlet maintains a certain degree of subcooling; as the water temperature of the economizer outlet increases, the water temperature of the water-cooled wall inlet is increased, thereby reducing the water-cooled wall inlet enthalpy and enhancing the hydrodynamic stability; as the water temperature of the water-cooled wall inlet increases, the steam at the water-cooled wall outlet can maintain a certain degree of superheat, that is, the dry operation of the boiler is achieved.
[0038] Of course, in other embodiments, a throttling component, such as a regulating valve, may be 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 and keep the feed water at the economizer outlet at a certain degree of subcooling.
[0039] like Figure 2 As 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 in sequence, is mixed with the desuperheating water, and is then sent to the external steam cooler to supplement the heating of the feed water. The steam at the steam outlet of the external steam cooler is then sent to the newly added final-stage high-pressure heater to supplement the heating of the feed water heated by the existing final-stage high-pressure heater, so as to improve the feed water temperature entering the boiler 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, on the premise that the steam entering the external steam cooler is higher than the existing heat recovery extraction steam.
[0040] 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.
[0041] Specifically, take the data of a 1000MW unit under 20% THA condition as an example.
[0042] Existing plan: The main generator load is 220MW, the existing last-stage high-pressure steam inlet parameters are 1.75MPa, 436℃ and the outlet feed water parameters are 6MPa, 192℃, the economizer outlet water temperature is 240℃ (subcooling 36℃, under-enthalpy 176kJ / kg), the economizer outlet flue gas temperature is 245℃, the water-cooled wall outlet is wet saturated steam, the unit is in wet operation state, and the denitrification system cannot be put into use.
[0043] In this embodiment, the main generator load is 220MW, the new final high-pressure heater inlet steam pressure and temperature parameters are: 6.2MPa, 350℃, and the outlet feed water pressure and temperature parameters are: 12MPa, 274℃, the water side temperature rise of the newly added external steam cooler is 7℃, the economizer outlet water temperature is 306℃, the subcooling degree is 18.7℃, the underenthalpy is 116.3 kJ / kg, the economizer outlet flue gas temperature is 311℃, the water wall outlet superheat is 12℃, the unit is in dry operation, the underenthalpy of the water at the water wall inlet is relatively reduced by 59.7 kJ / 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.
[0044] 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 a coal-fired power unit adapted to flexible operation, 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 new final-stage high-pressure heater and an external steam cooler are sequentially arranged on the water feed pipe between the water feed outlet of the existing final-stage high-pressure heater and the water feed inlet of the boiler, and the steam side inlet of the external steam cooler is connected to a 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, and the steam side outlet of the external steam cooler is connected to the steam inlet of the new final-stage high-pressure heater.
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 main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.
4. The configuration system according to claim 3, 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.
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 system according to any one of claims 1 to 6, 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 economizer outlet feed water at a certain subcooling degree.
8. The configuration system according to any one of claims 1 to 6, 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.