A unit deep peak shaving operation control method

Abstract

The application discloses a kind of unit deep peak shaving operation control method, effectively guarantee the feed water flow under the condition of unit low load, realize the quick promotion feed water flow under special working condition.It includes the following steps: control opening two steam pumps in unit recirculation at 50% opening, and the speed control of two steam pumps is automatically invested;unit is equipped with two feed water pumps, when detecting that one of feed water pumps is tripped, and the feed water flow of unit boiler is less than the set protection value, another running feed water pump is automatically closed by thermal logic automatic control recirculation, and the speed of running feed water pump is automatically increased, to increase feed water flow until not less than the set protection value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal-fired unit peak regulation, in particular to a unit deep peak regulation operation control method. BACKGROUND

[0002] At present, the unit generally only has the ability of conventional peak regulation, but with the development of new energy such as wind power and solar energy, in order to adapt to the operation of renewable new energy in the unit, the unit is required to have the ability of deep peak regulation, which usually needs to run at an output lower than the minimum value of normal operation in conventional peak regulation. In order to ensure the stable operation of the unit, the requirement of deep peak regulation of the unit is also higher and higher, but with the further exploration of the depth of peak regulation, the automatic adjustment of important parameters of the unit under low load and the hidden danger of safe operation of important auxiliary equipment are increasingly prominent. At present, the unit deep peak regulation mainly has the following technical problems:

[0003] In order to ensure the safe, stable and economic operation of the unit under low load, the operation personnel use the simulator to carry out load reduction operation drill, and drill each item of equipment failure under deep peak regulation state, and summarize the processing method according to different failures. From the drill of each failure, the failure problem of the feed water pump related equipment is the most prominent. The feed water pump tripping, the feed water pump outlet door closing, the low pressure regulating valve of the small machine suddenly closing, the pre-pump tripping and other failures are easy to cause the boiler MFT caused by the condition that the boiler feed water quantity <537T / H delay 10S, and the feed water pump tripping under different operating conditions is simulated many times, for example, under the condition of 285MW of the unit, the feed water quantity is 746T / H, when a single small machine trips, the feed water quantity suddenly drops, and it is difficult for the personnel to manually operate to increase the feed water quantity to above the protection value within 10S, which is easy to cause equipment failure and even affect the safety of the whole unit. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a unit deep peak regulation operation control method, which effectively guarantees the feed water flow under the condition of low load of the unit, and realizes the rapid increase of the feed water flow under special working conditions.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme:

[0006] A unit deep peak regulation operation control method, comprising the following steps:

[0007] Control the two steam pumps in the unit to recycle at 50% opening, and the rotating speed control of the two steam pumps is automatically put into operation;

[0008] The unit is configured with two feed water pumps, when one of the feed water pumps is tripped and the boiler feed water flow of the unit is less than a set protection value, the other running feed water pump is automatically controlled to recirculate and automatically shut down through thermal logic, and the rotating speed of the running feed water pump is automatically increased to increase the feed water flow until it is not less than the set protection value.

[0009] Preferably, the flow of the pre-pump of the two steam pumps is not less than 500T / H.

[0010] Preferably, the implementation logic of the feed water pump recirculation automatic shutdown protection is as follows:

[0011] When one of the two feed water pumps is tripped and the unit load is greater than 180MW, the outlet electric door of the running steam pump is in the fully open position and the outlet pressure of the steam pump is greater than the feed water main pipe pressure, the running feed water pump is forced to recirculate and shut down, and the recirculation valve of the running steam pump is set to the automatic state, so that the feed water pump recirculation automatic shutdown protection is realized.

[0012] Preferably, the set protection value is that the feed water flow is 537T / H and the delay is 30S.

[0013] Further, the unit boiler is further provided with a fire detection intensity detection;

[0014] When the fire detection intensity is 70% to less than 80%, the plasma automatic input is controlled to be turned on to realize stable combustion of the boiler;

[0015] When the fire detection intensity is less than 70%, the corresponding oil gun is controlled to be automatically input to realize stable combustion of the boiler.

[0016] Further, the unit further comprises a deep peak shaving picture before deep peak shaving is performed, and when the unit load is less than 320MW, an audible and visual alarm is sent.

[0017] Further, when the unit is in dry state operation, a feed water flow switching module is further added, and when the unit load is less than 250MW, the lower limit set value of the feed water flow is modified to 600T / H.

[0018] Further, when one of the primary air fans of the unit fails, the upper layer coal mill is automatically tripped, the remaining three coal mills continue to operate, and the primary air pressure is maintained.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The application provides a unit deep peak regulation operation control method, which further improves the reliability of existing unit deep peak regulation operation, and specifically, according to the fault simulation result, the fault problem of the feedwater pump related equipment is the most prominent, therefore, aiming at the problem that the feedwater flow of the feedwater system suddenly drops below the protection value, in order to ensure that the feedwater flow quickly returns to above the set protection value under abnormal working conditions, the deep peak regulation operation measures are formulated, two steam pumps are manually controlled to start recycling at 50% opening degree in advance, both pumps are automatically put into operation, the steam pump pre-pump flow cannot be lower than the set value, and meanwhile, the new thermal protection logic is added, when one feedwater pump trips during the operation of the two feedwater pumps, the feedwater pump recycling automatic shutdown protection is started, the boiler feedwater flow is timely increased, and the boiler water wall heating surface temperature is protected from over-limit. The two feedwater pumps are kept operating at low load, and the recycling opening degree is kept above 50% opening degree, which is beneficial to the adjustment when the feedwater pump has a problem. The deep peak regulation operation control for the feedwater flow regulation in the application effectively guarantees the feedwater flow under low load, and the logic has been verified to be effective in actual production, and can quickly improve the feedwater flow under special working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The thermal protection logic diagram for the feedwater flow regulation in the application. DETAILED DESCRIPTION

[0022] In order to enable the personnel in the art to better understand the application scheme, the technical solutions in the embodiments of the application will be clearly and completely described below in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the personnel in the art without creative labor should belong to the protection scope of the application.

[0023] It should be noted that the terms "first", "second" and the like in the specification and claims of the application and the above-described drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0024] The application will be further described in detail below in combination with the drawings:

[0025] Based on the existing anomalies in thermal power plant units, a deep peak-shaving team was established to oversee all aspects of deep peak-shaving operations. Through the implementation of measures, thermal optimization, and gradual experimentation and improvement, the deep peak-shaving capabilities of the units were further enhanced. Operating personnel used simulators to analyze existing problems and, through experiments and other methods, summarized effective solutions.

[0026] Based on the above, the present invention provides a deep peak-shaving operation control method for generating units, comprising the following steps:

[0027] Control the recirculation of the two steam pumps in the unit to 50% opening, and put both steam pump sets into automatic operation;

[0028] The unit is normally equipped with two feedwater pumps. When one of the feedwater pumps is detected to have tripped and the boiler feedwater flow rate is less than the set protection value, the thermal logic automatically controls the other running feedwater pump to automatically shut down for recirculation. At the same time, it automatically increases the speed of the running feedwater pump and increases the feedwater flow rate until it is not less than the set protection value.

[0029] This invention designs a deep peak-shaving operation control method for generating units, further improving the reliability of existing deep peak-shaving operations. Specifically, based on the results of fault drills, the most prominent problem is the failure of feedwater pump-related equipment. Therefore, to address the issue of a sudden drop in feedwater flow rate below the protection value, and to ensure that the feedwater flow rate quickly returns to the set protection value (feedwater flow rate ≥ 537 T / H, delay 30 seconds) under abnormal operating conditions, deep peak-shaving operation measures are implemented. This involves manually controlling the recirculation of two steam pumps to 50% opening in advance, with both pumps in automatic mode. The flow rate of the booster pumps for both steam pumps must not be lower than 500 T / H. During low load conditions, both feedwater pumps are kept running, with the recirculation opening maintained above 50%, which facilitates adjustments when feedwater pump problems occur. The deep peak-shaving operation control method for feedwater flow regulation described in this invention effectively ensures feedwater flow rate under low load conditions. The effectiveness of this logic has been verified in actual production, and it can quickly increase feedwater flow rate under special operating conditions.

[0030] The specific implementation logic of the deep peak-shaving operation control method for water supply flow regulation described in this invention is as follows: Figure 1 When both feedwater pumps are running, if feedwater pump B trips, feedwater pump A will be forcibly shut down for recirculation when the following conditions are met, and the recirculation valve of the running steam pump will be set to automatic mode.

[0031] The conditions include:

[0032] A) Unit load > 180MW

[0033] B) The electric valve at the outlet of pump A is in the fully open position.

[0034] C) Pump outlet pressure > feedwater mains pressure

[0035] D)B pump tripped.

[0036] In addition to the aforementioned deep peak-shaving operation control method for feedwater flow regulation, this invention, when simulating the existing problems using a simulator, also discovered other problems with deep peak-shaving in other units, specifically including:

[0037] Primary air fan failure problem

[0038] When the unit load is below 340MW and all four mills are operating, the coal mills will not automatically trip when the primary air fan trips. This can easily lead to problems such as low primary air pressure, overcurrent in the primary air fan motor, and mill blockage. Currently, our plant's RB protection is set to trigger when the unit load is above 360MW and a major auxiliary machine fails, reserving the remaining three mills and automatically engaging plasma combustion stabilization. However, when the load is low, the combustion stabilization measures after a major auxiliary machine trip cannot be automatically executed.

[0039] blower tripping problem

[0040] At 257MW, a single forced draft fan tripped, reducing the total airflow to 200kg / s, close to the unit's total airflow protection setting (≤163.7kg / s). When a forced draft fan trips, it is necessary to strengthen airflow monitoring and, if necessary, manually increase the operating forced draft fan airflow. Given that excessive adjustment of the forced draft fan's moving blades can easily lead to insufficient secondary airflow, an automatic limit of 15% on the forced draft fan inlet moving blades has been added to the unit.

[0041] Regarding the issue of sudden drop in flame detection under low load

[0042] The problem of sudden drop in flame detector is unpredictable. When the flame detector drops, the combustion can deteriorate rapidly. Relying on operators to monitor and detect the sudden drop before adding oil can easily lead to missing the optimal oil injection time. Therefore, it is necessary to add protection for automatic plasma injection and automatic oil injection based on flame detector difference.

[0043] Problem with automatic feedwater regulation after unit load drops to 220MW

[0044] Currently, the lower limit of automatic feedwater control for the unit is 660T / H. After the unit load drops to 220MW, the automatic feedwater control can no longer adjust automatically, and the corresponding automatic control loop needs to be modified. It is also necessary to study and improve the automatic feedwater control strategy after the dry-wet state transition.

[0045] To address the problems existing in deep peak shaving of the above-mentioned units, the improvements made by this invention include:

[0046] 1. Review the previous deep peak-shaving data, conduct hidden danger investigations, identify and formulate solutions to eliminate safety hazards affecting the deep peak-shaving of the units.

[0047] 2. Based on the data collected, propose optimization schemes for relevant thermal logic such as sliding pressure curves, feedwater regulation, condensate regulation, and high-pressure heater level regulation. These optimization schemes will be implemented after approval by relevant professionals and functional departments.

[0048] 3. Determine the minimum output of auxiliary equipment such as fans and water pumps, and determine the control and operation modes of small machines under deep peak shaving.

[0049] 4. Further optimize the deep peak-shaving test measures, improve risk control, further explore the peak-shaving load, and finally find the minimum load for stable combustion of the boiler without oil injection.

[0050] 5. Summarize and review the standard operating and control methods during peak shaving periods, strive to achieve automatic control, improve the automation level of the units, and ensure unit safety through technological improvements.

[0051] The main innovative improvements to the existing deep peak-shaving operation control methods for generating units include:

[0052] 1. Flame detector oil gun and automatic plasma dispensing.

[0053] When the flame intensity is less than 80%, the plasma system automatically activates to stabilize the boiler combustion. This is achieved automatically through thermal logic, avoiding the problem of delayed human intervention during critical moments.

[0054] When the flame detection intensity is less than 70%, the corresponding oil gun will be automatically engaged.

[0055] 2. To ensure that the feedwater flow rate quickly returns to the set protection value (≥537T / H) under abnormal operating conditions, deep peak-shaving operation measures are implemented. Two steam pumps are manually controlled in advance to operate at 50% recirculation level, with both pumps in automatic mode. The flow rate of the steam pump booster must not be lower than 500t / h. Additionally, new thermal protection logic has been added. If one feedwater pump trips while both are running, the recirculation protection of the running pump will automatically shut off, promptly increasing the boiler feedwater flow and protecting the boiler water-cooled wall heating surface temperature from exceeding limits. The specific implementation logic is attached. Figure 1 When both feedwater pumps are running, if feedwater pump B trips, feedwater pump A will be forcibly shut down for recirculation when certain conditions are met, and the steam pump recirculation valve will be set to automatic mode.

[0056] 3. During operation, each shift should ensure automatic tripping of the upper mill in case of primary air fan failure under low load conditions, maintaining the operational contingency plan for all three mills, and preserving primary air pressure. During operation, try to keep the two forced draft fan motors running automatically. Currently, a lower limit is set for the forced draft fan motors to prevent low secondary air volume from causing boiler MFT (Minimum Default Time) issues. When increasing load, pay attention to whether the fan commands and opening are consistent to avoid problems with air volume adjustment during load increases.

[0057] 4. Added deep peak shaving mode, automatically switch to plasma and oil gun stable combustion logic when the exhaust fan, primary air fan and primary air fan trip, to ensure stable combustion.

[0058] 5. Add a deep peak shaving screen for the unit. When the unit load is less than 320MW, issue an audible and visual alarm to prompt the operators to enter the deep peak shaving mode and check the corresponding deep peak shaving protection activation.

[0059] 6. A feedwater flow switching module has been added. When the unit load is lower than 250MW, the lower limit of feedwater flow is changed from 660T / H to 600T / H to ensure that the unit is not restricted when operating in dry state.

[0060] 7. Develop contingency plans for dry and wet operation in case of sudden changes in fuel quantity.

[0061] When a single coal feeder stops producing coal, a coal mill trips, or the coal mill outlet damper suddenly closes during low-load operation, and the fuel quantity change does not exceed 40T / H, and two mills are operating normally, the unit should be kept in dry operation as much as possible by increasing the number of oil guns, increasing the coal quantity, and increasing the primary air pressure, and reducing the number of operations required to switch between dry and wet operation.

[0062] When two coal mills trip or two coal feeders stop supplying coal, the oil guns should be activated in time to stabilize combustion. Preparations should be made for the unit to quickly switch to wet operation. After starting the boiler water pump, the steam flow rate should be quickly calculated based on the unit load (10,000 kW) * 27. The feedwater flow rate should be kept basically consistent with the steam flow rate to avoid the problem of excessively high separator water level.

[0063] 8. The unit has now added a new control mode, including a wet-state coordination mode, and sequential control for switching between dry and wet states, as well as between wet and dry states and between the main and auxiliary feedwater valves. Under the wet boiler operating condition, the unit can maintain coordinated operation.

[0064] Practice has shown that by adopting the deep peak-shaving operation control method for generating units described in this invention, the deep peak-shaving capability of the generating units is steadily improved, and the stability of the generating units under low load operation is enhanced. Specific experimental results are shown below:

[0065] 1. By adopting the deep peak-shaving operation control method of the unit described in this invention, the unit can currently maintain stable operation at 250MW under dry conditions for a long time, which improves the deep peak-shaving capability of the unit and enhances economic benefits.

[0066] 2. The deep peak-shaving operation control method for the unit described in this invention maintains two small units operating under low load conditions, with the recirculation opening maintained at over 50%, which facilitates adjustments when feedwater pumps malfunction. In practice, the solution effectively ensures feedwater flow under low load conditions. The effectiveness of this logic has been verified in actual production, and it can quickly increase feedwater flow under special operating conditions.

[0067] 3. By adopting the deep peak-shaving operation control method of the unit described in this invention, when the power output is below 340MW, the steam source of the small turbine is switched to the auxiliary steam operation earlier, which is conducive to the stable operation of the small turbine and the adjustment when the unit operating conditions fluctuate.

[0068] 4. The deep peak-shaving operation control method of the unit described in this invention adopts logic modifications such as automatic plasma start-up of the coal mill and automatic shutdown of the feedwater pump recirculation, which avoids problems caused by untimely operation by personnel and improves the safety and reliability of the unit.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for deep peak-shaving operation control of a generating unit, characterized in that, Includes the following steps: Control the recirculation of the two steam pumps in the unit to 50% opening, and put the speed control of the two steam pumps into automatic mode; The unit is equipped with two feedwater pumps. When one of the feedwater pumps is detected to have tripped and the boiler feedwater flow rate is less than the set protection value, the other running feedwater pump is automatically shut down for recirculation through thermal logic. At the same time, the speed of the running feedwater pump is automatically increased to increase the feedwater flow rate until it is not less than the set protection value. The implementation logic for the automatic shut-off protection of the water pump recirculation is as follows: When two feedwater pumps are running, if one of them trips, and the unit load is detected to be greater than 180MW, the electric valve at the outlet of the operating steam pump is in the fully open position, and the outlet pressure of the steam pump is greater than the feedwater header pressure, the operating feedwater pump recirculation will be forcibly shut down, and the operating steam pump recirculation valve will be set to automatic mode to achieve automatic shut-off protection of the feedwater pump recirculation.

2. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, The flow rate of the booster pumps for both steam pumps is not less than 500T / H.

3. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, The set protection value is: water supply flow rate of 537T / H, delay of 30S.

4. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, This also includes conducting flame strength tests on the unit's boilers; When 70% ≤ flame detection intensity < 80%, the automatic plasma activation is controlled to achieve stable combustion in the boiler; When the flame detection intensity is less than 70%, the corresponding oil gun is automatically activated to achieve stable combustion in the boiler.

5. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, It also includes adding a deep peak shaving screen for the unit before deep peak shaving, and issuing an audible and visual alarm when the unit load is detected to be less than 320MW.

6. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, It also includes adding a feedwater flow switching module when the unit is running in dry condition, which modifies the lower limit setting of feedwater flow to 600T / H when the unit load is detected to be <250MW.

7. The deep peak-shaving operation control method for a generating unit according to claim 1, characterized in that, This also includes automatically tripping the upper coal mill in the event of a primary air fan failure in the unit, while keeping the other three coal mills running to maintain the primary air pressure.

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