Boiler and its starting method

Abstract

The present invention relates to the technical field of boilers, and in particular to a boiler and a method for starting the boiler. The boiler includes a first furnace, a second furnace and a coal mill for providing fuel for the boiler. The first furnace is connected to a first furnace primary air duct, and the second furnace is connected to a second furnace primary air duct. The first furnace primary air duct includes a first furnace side primary air main pipe and a first heater side primary air duct connected to the first furnace side primary air main pipe. The second furnace primary air duct includes a second furnace side primary air main pipe and a second heater side primary air duct connected to the second furnace side primary air main pipe. The first furnace side primary air main pipe is connected to the second furnace side primary air main pipe. A first valve is provided at the connection point between the first furnace side primary air main pipe and the second furnace side primary air main pipe. The first heater side primary air duct is provided with a second valve, and the second heater side primary air duct is provided with a third valve. That is, the boiler shortens the warm-up time, reduces energy consumption, reduces the workload of operators, and increases the reliability of the equipment.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of boilers, and in particular to a boiler and a starting method thereof. Background Art

[0002] Take a 2X330MW coal-fired generator set operated by a certain unit as an example. The boiler is equipped with two (inverter regulated) centrifugal primary fans, and the pulverizing system uses a medium-speed coal mill cold primary air positive pressure direct blowing pulverizing system equipped with five medium-speed coal mills. In normal operation, two primary fans are used, four coal mills are in operation, and one is on standby. The heater is installed at the hot primary air duct on the A and B sides, and is used to heat the primary air to supply the coal mill when the boiler is cold started. The plasma ignition device is arranged in the two layers of burners at the bottom of the boiler, A and B, one layer is in operation and the other layer is on standby. Plasma technology is used in boiler ignition and stable combustion cleaner. The plasma ignition device replaces oil with electricity and coal with oil during the cold start and low-load stable combustion of the boiler, achieving the purpose of no oil, and it can be put into electrostatic precipitator operation before the boiler is ignited, reducing the emission of atmospheric pollutants, which is both economical and environmentally friendly.

[0003] In view of the problem of low air and powder temperature at the outlet of the positive pressure direct-blowing medium-speed coal mill at the initial start-up of the boiler, a hot primary air communication pipe is designed to connect the #1 boiler and the #2 boiler. When the boiler is started in a cold state, the hot primary air of the running boiler is sent to the hot primary air mother pipe in front of the coal mill, so that the start-up of the pulverizing system is no longer restricted by the primary air temperature of the boiler. The pulverizing system can be put into use in advance, thus shortening the start-up time and providing more options for boiler shutdown maintenance and winter antifreeze.

[0004] Take the start-up of unit #2 in actual working conditions as an example. At 04:21, the furnace purge of #2 furnace was completed, the primary fan was started, and the A and B side heaters were put into use to heat the primary air for warm grinding. At 05:27, the outlet temperature of the coal mill reached 73°C, and the coal mill boiler was started to ignite. After the coal mill was started, the coal volume was 11t / h, and the outlet temperature of the coal mill dropped to 43°C. At 06:32, the boiler began to pressurize; at 07:33, the outlet temperature of the coal mill began to rise from 43°C; at 08:29, the hot primary air temperature at the outlet of the air preheater reached 172°C, and the A and B side heaters began to exit operation. At 10:00, the #2 machine began to run. During the run-up, the coal mill inlet air volume was 44.6kNm3 / h, and the outlet temperature was 69.7°C.

[0005] It can be seen from the above process that it takes more than 1 hour to warm up the mill when started in the existing way, and the mill outlet temperature decreases after starting the mill. At the same time, due to the low temperature of the hot primary air, a large air volume is required to maintain the mill outlet temperature; secondly, the heater runs for more than 4 hours; the boiler temperature and pressure rise time is relatively long, at 4 hours and 33 minutes. According to the boiler cold start curve, the time from ignition to start-up is about 3 hours and 15 minutes.

[0006] In summary, the existing production method has the following defects:

[0007] 1. Long warm-up time. Since the heater has poor effect in heating the primary air, the temperature of the hot primary air can only reach about 120℃. It takes a long time to warm up the cold coal mill to above 70℃ and meet the conditions for starting the mill. It takes more than 1 hour to warm up the mill.

[0008] 2. The outlet temperature of the coal mill is low. After the coal mill is started, as the coal powder enters the coal mill for grinding and heating, the outlet temperature of the coal mill drops rapidly. In order to increase the outlet temperature of the coal mill and ensure the stable ignition of the coal powder, it is necessary to increase the hot primary air volume, but the outlet temperature of the coal mill can only be maintained at about 43°C.

[0009] 3. High energy consumption. It takes more than one hour to warm up the boiler from the completion of boiler purge to the start of coal mill. During this period, all boiler equipment consumes a lot of power. Furthermore, after the coal mill is started, a large amount of hot primary air is required, which increases the output of primary fan and induced draft fan, and also consumes a lot of power.

[0010] 4. Increase the workload of operators. As the outlet temperature of the coal mill decreases, the drying output and grinding output of the coal mill are reduced, and the amount of coal mill slag discharge increases, two people must be responsible for replacing the coal mill slag box to ensure smooth coal mill slag discharge.

[0011] 5. Low operational reliability. In the initial stage of boiler ignition, due to the low outlet temperature of the pulverizer, it is difficult for the pulverized coal to ignite, and the pulverized coal burns unsteadily. If the pulverized coal burns unsteadily, not only will the negative pressure in the furnace fluctuate greatly, but the furnace will also explode. In severe cases, the boiler fire extinguishing protection will be triggered, forcing the unit to be started and stopped, which will delay the unit's grid-connected load time. Summary of the invention

[0012] The purpose of the present invention is to provide a boiler which shortens the warm-up time, reduces the energy consumption, reduces the workload of operators and increases the reliability of the equipment.

[0013] A boiler is provided, comprising a first furnace, a second furnace and a coal mill for providing fuel for the boiler, wherein the first furnace is connected to a first furnace primary air duct, the second furnace is connected to a second furnace primary air duct, the first furnace primary air duct comprises a first furnace side primary air mother pipe and a first heater side primary air duct connected to the first furnace side primary air mother pipe, the second furnace primary air duct comprises a second furnace side primary air mother pipe and a second heater side primary air duct connected to the second furnace side primary air mother pipe, the first furnace side primary air mother pipe is connected to the second furnace side primary air mother pipe, a first valve is provided at the connection point between the first furnace side primary air mother pipe and the second furnace side primary air mother pipe, a second valve is provided at the first heater side primary air duct, and a third valve is provided at the second heater side primary air duct.

[0014] Optionally, a fourth valve is provided between the connecting point between the first furnace side primary air main pipe and the first heater side primary air duct and the first valve; a fifth valve is provided between the connecting point between the second furnace side primary air main pipe and the second heater side primary air duct and the first valve.

[0015] Optionally, the fourth valve and the fifth valve are electric gates.

[0016] The present invention further provides a method for starting the boiler as described above, comprising the following steps:

[0017] When using the first furnace hot air for ignition, within the preset time before the water supply is completed, close the second valve, open the coal mill outlet door and the hot and cold air shut-off doors, gradually open the first valve, and control the hot air pressure passing through the first valve at the preset pressure value until the coal mill outlet temperature reaches the preset temperature value;

[0018] When the boiler is ignited, the primary fan is started, and the speed and pressure of the primary fan are gradually increased until the outlet pressure of the primary fan reaches the preset pressure value, the first valve is adjusted to keep the outlet temperature of the coal mill within the preset temperature range, the inlet door of the coal mill is adjusted to make the inlet air volume of the coal mill greater than the preset air volume value, and the coal mill is started;

[0019] During the process of heating and pressurizing the boiler, the outlet temperature of the coal mill is controlled at a preset temperature value, the second valve and the third valve are gradually opened, and the first valve is gradually closed.

[0020] Optionally, the preset time is 1 hour.

[0021] Optionally, the preset pressure value is 5 kPa.

[0022] Optionally, the preset temperature value is 80°C.

[0023] Optionally, the preset temperature range is 70-80°C.

[0024] Optionally, the preset air volume value is 30kNm3 / h.

[0025] Compared with the prior art, the boiler of the embodiment of the present invention has the following beneficial effects:

[0026] 1. Before the boiler is ignited, the two adjacent boilers can maintain a higher outlet temperature through warm grinding, so that the pulverized coal can be ignited and burned stably, and a good boiler water circulation can be established as soon as possible to enhance heat exchange and reduce the amount of boiler water change;

[0027] 2. In the initial stage of ignition, the coal mill can be put into operation about 1 hour earlier than when there is no hot air from the adjacent boiler. At the same time, due to the high temperature of the coal mill outlet air powder, the coal powder ignition and combustion are more stable, and the boiler operation is safer; at the same time, the time from boiler ignition to drum pressure rise will also be shortened;

[0028] 3. By using the hot primary air from the adjacent furnace for ignition, the coal mill can be put into operation about 1 hour earlier than when there is no hot air from the adjacent furnace, thus saving power consumption in the plant;

[0029] 4. Due to the increase in the inlet temperature of the coal mill, the drying output of the coal mill is enhanced, the grinding force is increased, the discharge of pebble coal is reduced, and the workload of operators handling pebble coal is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a partial schematic diagram of a boiler according to an embodiment of the present invention.

[0031] In the figure, 10, the primary air duct of the first furnace; 11, the primary air main pipe on the first furnace side; 12, the primary air duct on the first heater side;

[0032] 20. Primary air duct of the second furnace; 21. Primary air main pipe on the second furnace side; 22. Primary air duct on the second heater side;

[0033] 30. First valve;

[0034] 40. Second valve;

[0035] 50. The third valve;

[0036] 60. Fourth valve;

[0037] 70. The fifth valve. DETAILED DESCRIPTION

[0038] For ease of understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on another element, or there can be one or more centered elements therebetween. When an element is described as "connected to" another element, it can be directly connected to another element, or there can be one or more centered elements therebetween. The terms "vertical", "horizontal", "left", "right", "inside", "outside" and similar expressions used in this specification are for illustrative purposes only.

[0039] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0040] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] like Figure 1 As shown, it is a partial schematic diagram of a boiler in an embodiment of the present invention, the boiler includes a first furnace (not shown), a second furnace (not shown) and a coal mill (not shown) for providing fuel for the boiler, the first furnace is connected to the first furnace primary air duct 10, the second furnace is connected to the second furnace primary air duct 20, the first furnace primary air duct 10 includes a first furnace side primary air mother pipe 11 and a first heater side primary air duct 12 connected to the first furnace side primary air mother pipe 11, the second furnace primary air duct 20 includes a second furnace side primary air mother pipe 21 and a second heater side primary air duct 22 connected to the second furnace side primary air mother pipe 21, the first furnace side primary air mother pipe 11 is connected to the second furnace side primary air mother pipe 21, a first valve 30 is provided at the connecting point of the first furnace side primary air mother pipe 11 and the second furnace side primary air mother pipe 21, the first heater side primary air duct 12 is provided with a second valve 40, and the second heater side primary air duct 22 is provided with a third valve 50. The main innovation of the present invention is to connect the primary air main pipe 11 on the first furnace side and the primary air main pipe 21 on the second furnace side, so that the furnace heat of the first furnace can be transferred to the second furnace, which is equivalent to heating the second furnace and reducing the startup time of the second furnace.

[0042] Preferably, a fourth valve 60 is provided between the first furnace side primary air main pipe 11 and the first heater side primary air duct 12 and the first valve 30; a fifth valve 70 is provided between the second furnace side primary air main pipe 21 and the second heater side primary air duct 22 and the first valve 30. More preferably, the fourth valve 60 and the fifth valve 70 are electric plug-in doors. In addition, in order to achieve precise adjustment, the first valve 30, the second valve 40 and the third valve 50 are all electric regulating valves.

[0043] In addition, the present invention also provides a method for starting a boiler, comprising the following steps:

[0044] When using the first furnace hot air for ignition, within the preset time before the water supply is completed, close the second valve 40, open the coal mill outlet door and the hot and cold air shut-off doors, gradually open the first valve 30, notify the furnace personnel to pay attention to the change of hot primary air pressure, and control the hot air pressure passing through the first valve 30 at the preset pressure value until the coal mill outlet temperature reaches the preset temperature value;

[0045] When the boiler is ignited, the primary fan is started, and the speed and pressure of the primary fan are gradually increased until the outlet pressure of the primary fan reaches a preset pressure value, the first valve 30 is adjusted to keep the outlet temperature of the coal mill within a preset temperature range, the coal mill inlet door is adjusted to make the primary air volume at the coal mill inlet greater than the preset air volume value, and the coal mill is started;

[0046] During the process of increasing the temperature and pressure of the boiler, the outlet temperature of the coal mill is controlled at a preset temperature value, the second valve 40 and the third valve 50 are gradually opened, and the first valve 30 is gradually closed. During the operation, the communication with the adjacent boiler is strengthened.

[0047] In actual production, when the first furnace is ignited with hot air, within 1 hour before the water supply is completed, close the second valve 40, open the coal mill outlet door and the cold and hot air shut-off doors, gradually open the first valve 30, notify the furnace personnel to pay attention to the change of hot primary air pressure, and control the hot air pressure passing through the first valve 30 at a preset pressure value of 5kPa until the coal mill outlet temperature reaches the preset temperature value of 80°C;

[0048] When the boiler is ignited, the primary fan is started, and the speed and pressure of the primary fan are gradually increased until the outlet pressure of the primary fan reaches the preset pressure value of 5kPa, the first valve 30 is adjusted to keep the outlet temperature of the coal mill in the preset temperature range of 70-80°C, the inlet door of the coal mill is adjusted to make the inlet air volume of the coal mill greater than the preset air volume value of 30kNm3 / h, and the coal mill is started;

[0049] During the process of increasing the temperature and pressure of the boiler, the outlet temperature of the coal mill is controlled at a preset temperature value of 80° C., the second valve 40 and the third valve 50 are gradually opened, and the first valve 30 is gradually closed.

[0050] In actual production operation, it is found that the present invention has the following advantages:

[0051] 1. Before the boiler is ignited, a higher outlet temperature can be maintained through warm grinding, so that the pulverized coal can be ignited and burned stably, a good boiler water circulation can be established as soon as possible, heat exchange can be enhanced, and the amount of boiler water change can be reduced. The water volume of the water-cooled wall is 130t, the water volume of the economizer is 28t, and the water volume of the normal water level of the drum is about 25t. Under the existing conditions, in order to increase the temperature of the lower wall of the drum, the boiler feed water needs to be heated to above 100°C, and the maximum feed water temperature is 121°C. The boiler is replenished and replaced with water 4 times (taking the start-up of the #2 unit on March 8, 2021 as an example), and the amount of desalted water wasted is about 700t, and there is also an incalculable amount of steam required to heat the desalted water. When the #1 unit was started after a minor overhaul on March 10, 2021, the boiler was replenished and replaced with water 7 times, and the feed water temperature was heated to a maximum of 162°C.

[0052] 2. In the initial stage of ignition, the coal mill can be put into operation about 1 hour earlier than when there is no hot air from the adjacent boiler. At the same time, due to the high temperature of the air powder at the outlet of the coal mill, the coal powder ignition and stable combustion are more stable, and the boiler operation is safer; at the same time, the time from boiler ignition to drum pressure rise will also be shortened. Because the hot primary air is supplied to the adjacent boiler, the current of the primary fan of the adjacent boiler will increase. When the hot primary air increases by about 50kNm3 / h, the power of the primary fan increases by about 10A, which is much smaller than the auxiliary power consumption reduced after the boiler start-up time is shortened. At the same time, because the plasma heater is out of operation, the amount of steam consumed by the plasma heater is further reduced. Each time the boiler is started, the plasma heater needs to be put into operation for more than 4 hours and consumes about 50t of steam.

[0053] 3. By using the hot primary air from the adjacent furnace for ignition, the coal mill can be put into operation about 1 hour earlier than when there is no hot air from the adjacent furnace (when Phase #2 was started on September 21, the A mill was warmed up for 1.5 hours before the coal mill outlet temperature reached 60°C), saving about 10,900 kWh of factory electricity (the standby transformer power was 10.9MW when it was started on May 8).

[0054] 4. Due to the increase in the inlet temperature of the coal mill, the drying output of the coal mill is enhanced, the grinding force is increased, and the discharge of pebble coal is reduced. When our factory starts the machine in the current way, one or two people must be arranged to be responsible for the discharge of pebble coal. The use of hot air from the adjacent furnace can greatly reduce the workload of the operating personnel.

[0055] It should be noted that the preferred embodiments of the present invention are given in the specification and drawings of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the present invention specification; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the protection scope of the present invention.

Claims

1. A boiler comprising a first furnace, a second furnace and a coal mill for providing fuel for the boiler, characterized in that: The first furnace is connected with a first furnace primary air duct, the second furnace is connected with a second furnace primary air duct, the first furnace primary air duct includes a first furnace side primary air mother pipe and a first heater side primary air duct connected with the first furnace side primary air mother pipe, the second furnace primary air duct includes a second furnace side primary air mother pipe and a second heater side primary air duct connected with the second furnace side primary air mother pipe, the first furnace side primary air mother pipe is connected with the second furnace side primary air mother pipe, a first valve is provided at the connection between the first furnace side primary air mother pipe and the second furnace side primary air mother pipe, a second valve is provided at the first heater side primary air duct, and a third valve is provided at the second heater side primary air duct; A fourth valve is provided between the connecting point between the primary air main pipe on the first furnace side and the primary air pipe on the first heater side and the first valve; A fifth valve is provided between the connecting point between the primary air main pipe on the second furnace side and the primary air duct on the second air heater side and the first valve.

2. The boiler according to claim 1, characterized in that: The fourth valve and the fifth valve are electric gates.

3. A method for starting a boiler according to any one of claims 1 to 2, characterized in that: The steps include: When using the first furnace hot air for ignition, within the preset time before the water supply is completed, close the second valve, open the coal mill outlet door and the hot and cold air shut-off doors, gradually open the first valve, and control the hot air pressure passing through the first valve at the preset pressure value until the coal mill outlet temperature reaches the preset temperature value; When the boiler is ignited, the primary fan is started, and the speed and pressure of the primary fan are gradually increased until the outlet pressure of the primary fan reaches the preset pressure value, the first valve is adjusted to keep the outlet temperature of the coal mill within the preset temperature range, the inlet door of the coal mill is adjusted to make the inlet air volume of the coal mill greater than the preset air volume value, and the coal mill is started; During the process of heating and pressurizing the boiler, the outlet temperature of the coal mill is controlled at a preset temperature value, the second valve and the third valve are gradually opened, and the first valve is gradually closed.

4. The method for starting a boiler according to claim 3, characterized in that: The default time is 1 hour.

5. The boiler startup method according to claim 3, characterized in that: The preset pressure value is 5kPa.

6. The boiler startup method according to claim 3, characterized in that: The preset temperature value is 80℃.

7. The boiler startup method according to claim 6, characterized in that: The preset temperature range is 70-80℃.

8. The boiler startup method according to claim 3, characterized in that: The preset air volume value is 30kNm 3 / h.

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