Fuel saving control method during supercritical boiler startup

Abstract

The present invention relates to the technical field of thermal power plants, and discloses a method for controlling fuel saving during the startup of a supercritical boiler, the method comprising: putting all the oil guns of the C layer into the C layer of the boiler and putting all the large oil guns of the D layer of the boiler into the D layer and igniting them; putting auxiliary steam into the deaerator for heating to increase the water temperature in the deaerator; starting the C layer coal mill; after the coal fire detection intensity of the C layer burner is higher than a specific value, withdrawing the D layer oil gun; waiting for the C layer plasma burner to release normal plasma arc to open the exhaust electric valve and the exhaust check valve connected to the turbine intermediate pressure cylinder, and putting the steam in the intermediate pressure cylinder into the steam side of the No. 2 high pressure heater to increase the feed water temperature; after the C layer coal mill increases to more than a specific amount of coal, except for the oil guns of the burners with coal fire detection intensity lower than the specific value, withdrawing the oil guns of the burners with coal fire detection intensity higher than the specific value. The above technical scheme can be set to stabilize combustion, improve the efficiency of fuel combustion in the oil gun, achieve the effect of fuel saving, and save fuel saving costs.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power plants, and in particular to an oil-saving control method during the startup of a supercritical boiler. Background Art

[0002] Deep peak load regulation of thermal power units has become the norm, and the start-up and shutdown of units for peak load regulation has become more and more frequent. Among them, the number of unit starts in our plant was 12 times in 2018, 16 times in 2019, and 15 times as of October 30, 2020, and the start-up oil consumption has increased. During the low-load operation and start-up and shutdown process of the boiler, oil needs to be added to assist combustion. The C-layer coal mill of our plant's boiler is equipped with a plasma burner, which has a certain combustion-supporting ability, and there is room for reducing the use of combustion-supporting oil. Summary of the invention

[0003] The purpose of the present invention is to provide an oil-saving control method during the startup of a supercritical boiler, which can solve the problem of large oil consumption during low-load operation and start-up and shutdown of the boiler in the prior art.

[0004] In order to achieve the above-mentioned object, the present invention provides a method for controlling oil saving during the startup of a supercritical boiler, comprising a boiler, wherein the boiler has multiple layers, each layer is equipped with a coal mill and a burner, and each layer of the burner has 6 oil guns; the C layer and the D layer are arranged horizontally and are located at the bottom layer of the boiler, wherein the C layer burner includes a plasma burner, and the oil gun of the D layer burner is a large oil gun; the method comprises: S1, putting all the oil guns of the C layer into the C layer of the boiler and putting all the large oil guns into the D layer of the boiler and igniting them; S2, putting auxiliary steam into the deaerator for heating to increase the water temperature in the deaerator; S3, starting the C layer Coal mill; after the coal fire intensity of the C-layer burner is higher than a specific value, withdraw the oil gun of the D-layer; S4, put the C-layer plasma burner into operation to release plasma arc; S5, open the exhaust electric valve and exhaust check valve connected to the turbine intermediate pressure cylinder, and put the steam in the intermediate pressure cylinder into the steam side of the No. 2 high-pressure heater to increase the feed water temperature; S6, after the C-layer coal mill increases to above a specific amount of coal, retain the oil gun of the burner with a coal fire intensity lower than a specific value, and withdraw the oil gun of the burner with a coal fire intensity higher than a specific value.

[0005] Through the setting of the above technical scheme, the auxiliary steam can increase the feed water temperature, thereby increasing the water-cooled wall temperature, and the large oil guns in the adjacent layer can assist in ignition, avoid the flameout of small oil guns in this layer, and withdraw the oil guns according to the flame intensity in the furnace. The subsequent combustion in the furnace is maintained by the plasma arc; through the above measures, the combustion can be stabilized, the efficiency of fuel combustion in the oil gun can be improved, the fuel saving effect can be achieved, and the fuel saving cost can be saved.

[0006] Furthermore, the auxiliary steam comes from the auxiliary steam main pipe of the whole plant.

[0007] Furthermore, the boiler is provided with 6 layers.

[0008] Furthermore, the interval between S2 and S3 is 10 minutes to give S2 sufficient time to gradually increase the water-cooled wall temperature.

[0009] Furthermore, the specific value of the coal fire detection intensity described in S6 is greater than 70%.

[0010] Furthermore, the specific coal amount in S6 is 25 t / h.

[0011] Furthermore, after the generator of the unit is connected to the grid, the oil gun in the D-layer burner is put into operation in the D-layer, the D-layer coal mill is started, and the coal grinding amount of the C-layer coal mill and the D-layer coal mill is adjusted.

[0012] Further, the adjusting the coal grinding amount of the C-layer coal mill and the D-layer coal mill includes reducing the coal grinding amount of the C-layer coal mill and gradually reducing the coal grinding amount of the D-layer coal mill.

[0013] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0014] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0015] In the present invention, unless otherwise stated, the directional words such as "upper" and "lower" usually refer to the orientation in the assembled state. "Inside" and "outside" refer to the inside and outside relative to the outline of each component itself.

[0016] The present invention provides a method for controlling fuel saving during the startup of a supercritical boiler. The present invention provides a method for controlling fuel saving during the startup of a supercritical boiler, including a boiler, wherein the boiler has multiple layers, each layer is equipped with a coal mill and a burner, and each layer of the burner has 6 oil guns; the C layer and the D layer are arranged horizontally, and are located at the bottom layer of the boiler, wherein the burner of the C layer includes a plasma burner, and the oil gun of the burner of the D layer is a large oil gun; preferably, the boiler has 6 layers, which are EF, AB, and CD from top to bottom, wherein the EF, AB, and CD layers are the same and are arranged horizontally. It should be noted that the oil output of the large oil gun is greater than that of other oil guns, such as the oil guns in the A, B, C, E, and F layers; the large oil gun is dedicated to the startup of the boiler.

[0017] The method comprises:

[0018] S1, put all the oil guns on the C layer of the boiler and all the large oil guns on the D layer of the boiler into operation and ignite them to avoid the main fuel trip (MFT) caused by the failure of small oil guns when the boiler is ignited;

[0019] S2, add auxiliary steam to the deaerator for heating, increase the water temperature in the deaerator, and then increase the water wall temperature to stabilize combustion. The auxiliary steam comes from the auxiliary steam main pipe of the whole plant, that is, the auxiliary steam manifold, and its steam source is the steam of adjacent units and / or the steam supply of the reheat cold section and / or the steam supply of the steam turbine extraction;

[0020] S3, start the C-layer coal mill; after the coal fire detection intensity of the C-layer burner is higher than a specific value, withdraw the D-layer oil gun; preferably, the specific value of the coal fire detection intensity described in S6 is above 70%. Preferably, the interval between S2 and S3 is 10 minutes, so as to give S2 sufficient time to gradually increase the water-cooled wall temperature;

[0021] S4 is put into the plasma burner of the C layer to release plasma arc; the plasma arc can ignite the coal powder and can replace part of the oil gun ignition, thus achieving the effect of saving oil;

[0022] S5, open the exhaust electric valve and exhaust check valve connected to the intermediate pressure cylinder of the steam turbine, and release the steam in the intermediate pressure cylinder to the steam side of the No. 2 high-pressure heater to increase the feed water temperature; it should be noted that there are three high-pressure heaters, namely No. 3, No. 2, and No. 1, and each high-pressure heater has only one steam side and one water side; among them, the steam side of the No. 1 high-pressure heater is connected to the high-pressure cylinder of the steam turbine, the steam side of the No. 2 high-pressure heater is connected to the high-pressure side of the intermediate pressure cylinder of the steam turbine, and the steam side of the No. 3 high-pressure heater is connected to the low-pressure side of the intermediate pressure cylinder of the steam turbine; the unit is started using the intermediate pressure cylinder start-up method, and only the high-pressure side of the intermediate pressure cylinder has steam, which can increase the temperature of the feed water in the No. 2 high-pressure heater.

[0023] S6, after the C-layer coal mill increases to a specific coal quantity, the oil guns of the burners with coal fire detection intensity lower than the specific value are retained, and the oil guns of the burners with coal fire detection intensity higher than the specific value are withdrawn. Preferably, the specific coal quantity in S6 is 25t / h. The oil guns are withdrawn according to the flame intensity in the furnace, and the subsequent combustion in the furnace is maintained by the plasma arc, which can reduce the fuel consumption during operation.

[0024] Through the above measures, the method can ensure stable combustion in the furnace, improve the fuel combustion efficiency in the oil gun, achieve the effect of saving fuel, and save fuel costs.

[0025] The fuel consumption comparison data of the cold start of the unit without using the fuel saving measures of using the above auxiliary steam to increase the feed water temperature, timely withdrawing the oil gun, and plasma combustion without using the oil gun is as follows:

[0026] Unit #1 started a total of 16 times from 2018 to May 16, 2020, two of which were started after holiday adjustments, with short downtime and less oil consumption in hot start, and the rest were cold starts. The average oil consumption of each cold start of unit #1 from 2018 to 2020 was 29.47t.

[0027] The #2 unit had a total of 12 cold starts from 2018 to 2020. Due to a fuel base data failure before November 5, 2019, the fuel consumption of 3 starts could not be counted. The average fuel consumption of 7 cold starts from November 28, 2019 to July 2020 was 26.6t. After the above fuel-saving measures were adopted in the two cold starts on August 10 and September 18, 2020, fuel consumption was 8.69t and 8.14t respectively, and the average fuel consumption for the two times was 8.41t.

[0028]

[0029] In summary, the average fuel consumption of the 21 cold starts of #1 and #2 units from 2018 to August 1, 2020 was 28.51 tons. After adopting fuel-saving measures, each cold start saves about 20 tons of fuel. According to the calculation of 15 unit starts in our plant in 2020, about 300 tons of fuel were saved, with a unit price of 6,000 yuan / ton, saving 1.8 million yuan in costs.

[0030] Furthermore, after the boiler C layer is able to supply power to the generator and is connected to the grid, the D layer starts to burn. The oil gun in the D layer burner is put into the D layer, the D layer coal mill is started, and the coal grinding amount of the C layer coal mill and the D layer coal mill is adjusted. Preferably, the adjustment of the coal grinding amount of the C layer coal mill and the D layer coal mill includes reducing the coal grinding amount of the C layer coal mill, and gradually reducing the coal grinding amount of the D layer coal mill while ensuring that the C layer coal mill can operate under high coal volume conditions. Through the setting of the above technical solution, reducing the coal grinding amount of the C layer coal mill after starting the D layer coal mill can prevent too much coal powder from being added to the furnace, thereby preventing excessive combustion and causing overheating of the water-cooled wall to affect the operation of the equipment, thereby improving the safety of the equipment and saving coal powder costs.

[0031] The D layer is located at the lowest layer of the boiler. After the C and D layers are fully burned, the temperature inside the boiler, including the water-cooled wall, gradually increases. The start-up of the EF and AB layer pulverizers and the combustion of coal powder have sufficient conditions, and combustion can be easily carried out in the D layer manner, thereby gradually increasing the boiler's power generation capacity.

[0032] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0033] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0034] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A fuel saving control method for a supercritical boiler during startup, characterized in that: The boiler comprises multiple layers, each layer is equipped with a coal mill and a burner, and each layer has six oil guns in the burner; the C layer and the D layer are arranged horizontally and are located at the bottom layer of the boiler, wherein the burner of the C layer comprises a plasma burner, and the oil gun of the burner of the D layer is a large oil gun; the method comprises: S1, put all the oil guns on the C layer of the boiler into the C layer and put all the large oil guns on the D layer of the boiler into the D layer and ignite them; S2, input auxiliary steam to the deaerator for heating and increase the water temperature in the deaerator; S3, start the C-layer coal mill; after the coal fire detection intensity of the C-layer burner is higher than a specific value, withdraw the D-layer oil gun; S4, putting the C-layer plasma burner into operation to release plasma and draw an arc; S5, open the exhaust electric valve and exhaust check valve connected to the intermediate pressure cylinder of the steam turbine, and release the steam in the intermediate pressure cylinder to the steam side of the No. 2 high-pressure heater to increase the feed water temperature; S6, after the C-layer coal mill increases to above a specific coal amount, the oil guns of the burners whose coal fire detection intensity is lower than a specific value are retained, and the oil guns of the burners whose coal fire detection intensity is higher than a specific value are withdrawn.

2. The fuel saving control method during supercritical boiler startup according to claim 1, characterized in that: The auxiliary steam comes from the auxiliary steam main pipe of the whole plant.

3. The fuel saving control method during supercritical boiler startup according to claim 1, characterized in that: The boiler is provided with 6 layers.

4. The fuel saving control method during supercritical boiler startup according to claim 1, characterized in that: The interval between S2 and S3 is 10 minutes to give S2 sufficient time to gradually increase the water-cooled wall temperature.

5. The fuel saving control method during supercritical boiler startup according to claim 1, characterized in that: The specific value of the coal fire detection intensity described in S6 is 70% or more.

6. The fuel saving control method during supercritical boiler startup according to claim 1, characterized in that: In S6, the specific coal amount is 25 t / h.

7. The method for controlling fuel saving during startup of a supercritical boiler according to any one of claims 1 to 6, characterized in that: After the unit generator is connected to the grid, the oil gun in the D-layer burner is put into operation, the D-layer coal mill is started, and the coal grinding amount of the C-layer coal mill and the D-layer coal mill is adjusted.

8. The method for controlling fuel saving during startup of a supercritical boiler according to claim 7, characterized in that: The adjusting the coal grinding amount of the C-layer coal mill and the D-layer coal mill includes reducing the coal grinding amount of the C-layer coal mill and gradually reducing the coal grinding amount of the D-layer coal mill.

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