CN116357951A - Control method for preventing overcurrent protection of primary air fan from triggering MFT of boiler - Google Patents

Abstract

The invention discloses a control method for preventing an overcurrent protection trigger boiler MFT of a primary fan, which comprises the following steps: 1. performing primary fan tripping judgment; 2. the protection action after the primary fan trips: after the trip of the single-side primary fan is monitored, the trip fan is automatically released, the trip fan outlet baffle door is closed, the unit control mode is switched from the coordination mode to the machine following mode, and meanwhile, corresponding response is made according to the load of the unit, so that the triggering of the boiler MFT is avoided. The invention discloses a control method for preventing an overcurrent protection trigger boiler MFT of a primary fan, and aims to prevent the overcurrent protection trigger boiler MFT of a fan caused by improper adjustment of the primary fan at the other side after the primary fan at one side trips, thereby effectively ensuring the stable and safe operation of a unit.

Description

Control method for preventing overcurrent protection of primary air fan from triggering MFT of boiler

Technical Field

The invention belongs to the technical field of automatic control and protection of thermal engineering, and particularly relates to a control method for preventing an overcurrent protection trigger boiler MFT of a primary fan.

Background

In actual operation, the fact that the primary air fan of the thermal generator set B is fully closed due to hydraulic cylinder faults and the like, the set RB (RUNBACK) protects the movable blades, the movable blades of the primary air fan A are automatically opened, the current of the primary air fan A exceeds rated current in the adjustment process, the primary air fan A trips due to 6kV switch inverse time limit protection action, and all coal mills trip due to low primary air flow and lose total fuel, so that the boiler MFT is caused.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention aims to provide a control method for preventing an overcurrent protection of a primary fan from triggering a boiler MFT.

In order to achieve the above purpose and achieve the above technical effects, the invention adopts the following technical scheme:

the control method for preventing the overcurrent protection of the primary air fan from triggering the boiler MFT is used for preventing the overcurrent protection of the fan from triggering the boiler MFT caused by improper adjustment of the primary air fan at the other side after the primary air fan at one side trips, and comprises the following steps:

1. performing primary fan tripping judgment;

2. the protection action after the primary fan trips:

when the trip of the single-side primary fan is monitored, the trip fan is automatically released, the trip fan outlet baffle door is closed, the unit control mode is switched from the coordination mode to the machine following mode, and meanwhile, corresponding response is made according to the load of the unit, so that the triggering of the boiler MFT is avoided.

Further, the primary fan tripping judgment basis comprises:

the fan is considered to trip if the primary fan meets all of the following conditions:

(1) The primary fan is started to run for more than 10 minutes;

(2) The primary fan current is less than 5A;

(3) The differential pressure between the inlet and the outlet of the primary fan is less than 1kPa.

Further, the calculation formula of the primary fan inlet and outlet differential pressure is as follows:

primary fan inlet-outlet differential pressure = primary fan outlet total pressure-primary fan inlet total pressure.

Further, the step of responding correspondingly according to the load of the unit and avoiding triggering the boiler MFT comprises the following steps:

when the actual unit load is more than Y, automatically reducing the unit load to Y, automatically adjusting the tracking load of a blower and a draught fan, automatically increasing the output to the opening X of the blower by operating a primary blower, then automatically removing the blower, automatically jump-grinding a coal mill from top to bottom, maintaining the operation of a bottom Z coal mill, and automatically putting two oil guns into stable combustion;

when the actual unit load is less than or equal to Y, the unit load is kept unchanged, the blower and the induced draft fan are kept automatically controlled, the number of running coal mills is kept unchanged, the primary air pressure set value of the primary air pressure under the current load is automatically increased by running the primary air blower, and the primary air pressure set value is automatically thrown into two oil guns for stable combustion.

The opening degree X of the primary fan when the primary fan reaches rated current, the unit load Y and the running number Z of the coal mill are determined through tests.

Further, the test steps for determining the opening degree X of the primary fan, the unit load Y and the running number Z of the coal mills when the primary fan reaches rated current comprise the following steps:

starting a single-side primary fan, putting in blowers and induced fans at two sides, gradually increasing the unit load, gradually increasing the running number of coal mills according to the unit load, keeping the unit load unchanged when the current of the primary fan reaches rated current, and recording the opening degree X of the fan, the unit load Y and the running number Z of the coal mills at the moment.

Compared with the prior art, the invention has the beneficial effects that:

the invention discloses a control method for preventing an overcurrent protection trigger boiler MFT of a primary fan, and aims to prevent the overcurrent protection trigger boiler MFT of a fan caused by improper adjustment of the primary fan at the other side after the primary fan at one side trips, thereby effectively ensuring the stable and safe operation of a unit.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Detailed Description

The present invention is described in detail below so that advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making clear and unambiguous the scope of the present invention.

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

As shown in fig. 1, a control method for preventing overcurrent protection of a primary fan from triggering a boiler MFT includes the following steps:

1. primary air fan tripping judgment:

the single-side primary air fan is considered to trip when all the following conditions are met:

(1) The primary fan is started to run for more than 10 minutes;

(2) The primary fan current is less than 5A. The fan current signal can be obtained through the DCS control system;

(3) The differential pressure between the inlet and the outlet of the primary fan is less than 1kPa. And the inlet and the outlet of the primary fan are respectively provided with a pressure measuring point, and the differential pressure between the inlet and the outlet of the primary fan is equal to the total pressure of the outlet of the fan and the total pressure of the inlet of the fan.

2. The protection action after the primary fan trips:

after the single-side primary fan is monitored to trip, the trip fan is automatically released, the trip fan outlet baffle door is closed, and the unit control mode is switched from a coordination mode to a machine following mode. Judging the current unit load:

when the actual unit load is more than Y, automatically reducing the unit load to Y, automatically adjusting the tracking load of a blower and a draught fan, automatically increasing the output to the opening X of the blower by operating a primary blower, then automatically removing the blower, automatically jump-grinding a coal mill from top to bottom, maintaining the operation of a bottom Z coal mill, and automatically putting two oil guns into stable combustion;

when the actual unit load is less than or equal to Y, the unit load is kept unchanged, the blower and the induced draft fan are kept automatically controlled, the number of running coal mills is kept unchanged, the primary air pressure set value of the primary air pressure under the current load is automatically increased by running the primary air blower, and the primary air pressure set value is automatically thrown into two oil guns for stable combustion.

The opening degree X of the primary fan, the unit load Y and the running number Z of the coal mill when the primary fan reaches rated current can be determined through experiments. The test steps are as follows:

starting a single-side primary fan, putting in blowers and induced fans at two sides, gradually increasing the unit load, gradually increasing the running number of coal mills according to the unit load, keeping the unit load unchanged when the current of the primary fan reaches rated current, and recording the opening degree X of the fan, the unit load Y and the running number Z of the coal mills at the moment.

Example 1

As shown in FIG. 1, a No. 4 unit of a certain power plant is a 660MW ultra-supercritical unit, and is provided with 2 double-stage movable blade adjustable axial-flow primary fans, namely primary fans A/B, and the No. 4 unit of 2018 is loaded with 640MW in a coordinated mode and is operated by AGC. The coal mill A, B, C, D, E, F runs, the coal quantity is 237t/h, the primary air blower A/B runs, the movable blade is thrown automatically, the current is 126/133A, the feedback of the movable blade actuating mechanism is 50/44%, and the primary air blower pipe pressure is 8kPa. The primary fan B of the No. 4 unit is tripped due to the fact that a hydraulic cylinder breaks down, the movable vanes are fully closed, the RB of the unit protects the movable vanes, the movable vanes of the primary fan A are automatically opened, the current of the primary fan A exceeds rated current in the adjustment process, the primary fan A trips due to the 6kV switch inverse time limit protection action, all coal mills trip due to low primary air flow, and the boiler MFT is caused by total fuel loss.

According to the judging basis of the invention, as the movable blades of the primary air fan B are fully closed, the current is less than 5A, and the differential pressure between the inlet and the outlet of the primary air fan B is less than 1kPa, the primary air fan B is judged to trip, so that the primary air fan B is released automatically by a controller, the outlet baffle door of the primary air fan B is closed, the unit load is higher at the moment, the output of the single-side primary air fan cannot meet the current load requirement, the unit load is automatically reduced to the highest load 350MW which can be reached by the rated current of the primary air fan B by the controller, the tracking load of the air fan and the induced draught fan is automatically turned down by the controller, the opening degree of the movable blades A is automatically opened to 93% of the rated current maximum opening degree by the controller, the automatic opening degree of the movable blades A of the primary air fan A is released, the opening degree of the movable blades A is kept unchanged, the upper layer D, E, F coal mills are automatically jumped off by the controller, the bottom layer A, B, C coal mills are maintained to operate, the No. 1 and No. 3 oil guns are controlled by the controller to stably burn, and the boiler MFT is prevented from being caused by the reverse time protection action caused by the excessive rated current of the running current.

Parts or structures of the present invention, which are not specifically described, may be existing technologies or existing products, and are not described herein.

The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related arts are included in the scope of the present invention.

Claims (5)

1. The control method for preventing the overcurrent protection of the primary air fan from triggering the boiler MFT is characterized by comprising the following steps of:

1. performing primary fan tripping judgment;

2. the protection action after the primary fan trips:

when the trip of the single-side primary fan is monitored, the trip fan is automatically released, the trip fan outlet baffle door is closed, the unit control mode is switched from the coordination mode to the machine following mode, and meanwhile, corresponding response is made according to the load of the unit, so that the triggering of the boiler MFT is avoided.

2. The control method for preventing an overcurrent protection trigger boiler MFT of a primary air fan according to claim 1, wherein the primary air fan trip judgment basis comprises:

the fan is considered to trip if the primary fan meets all of the following conditions:

(1) The primary fan is started to run for more than 10 minutes;

(2) The primary fan current is less than 5A;

(3) The differential pressure between the inlet and the outlet of the primary fan is less than 1kPa.

3. The control method for preventing an overcurrent protection triggering boiler MFT of a primary fan according to claim 2, wherein the calculation formula of the primary fan inlet-outlet differential pressure is:

primary fan inlet-outlet differential pressure = primary fan outlet total pressure-primary fan inlet total pressure.

4. The control method for preventing an overcurrent protection trigger boiler MFT of a primary air blower according to claim 1, wherein the step of avoiding triggering the boiler MFT in response to the unit load level comprises:

when the actual unit load is more than Y, automatically reducing the unit load to Y, automatically adjusting the tracking load of a blower and a draught fan, automatically increasing the output to the opening X of the blower by operating a primary blower, then automatically removing the blower, automatically jump-grinding a coal mill from top to bottom, maintaining the operation of a bottom Z coal mill, and automatically putting two oil guns into stable combustion;

when the actual unit load is less than or equal to Y, the unit load is kept unchanged, the blower and the induced draft fan are kept automatically controlled, the number of running coal mills is kept unchanged, the primary air pressure set value of the primary air pressure under the current load is automatically increased by running the primary air blower, and the primary air pressure set value is automatically thrown into two oil guns for stable combustion.

The opening degree X of the primary fan when the primary fan reaches rated current, the unit load Y and the running number Z of the coal mill are determined through tests.

5. The control method for preventing an overcurrent protection trigger boiler MFT of a primary fan according to claim 4, wherein the test step of determining a fan opening X, a unit load Y, and a number Z of coal mill operations when the primary fan reaches a rated current comprises:

starting a single-side primary fan, putting in blowers and induced fans at two sides, gradually increasing the unit load, gradually increasing the running number of coal mills according to the unit load, keeping the unit load unchanged when the current of the primary fan reaches rated current, and recording the opening degree X of the fan, the unit load Y and the running number Z of the coal mills at the moment.

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