阅读说明：本技术 一种炉循泵水位控制方法 (Furnace circulating pump water level control method ) 是由 曹维 吴春晓 江颖 于 2021-09-26 设计创作，主要内容包括：本发明公开了一种炉循泵水位控制方法,主要涉及火电厂等工业直流锅炉(带炉循泵)启动、停运过程中,水位调整、干、湿态转换的自动控制技术,本发明基于火电厂等工业自动控制特点,从智能、自动、安全的角度出发,实现直流锅炉(带炉循泵)水位调整、干、湿态转换等自动完成,减少人员操作量,减少安全风险,为实现日后的机组一键启、停奠定基础。(The invention discloses a water level control method of a boiler circulating pump, which mainly relates to an automatic control technology of water level adjustment and dry-wet state conversion in the starting and stopping processes of industrial direct-flow boilers (with boiler circulating pumps) of a thermal power plant and the like.)

1. A water level control method of a boiler circulating pump is applied to a once-through boiler with a boiler water circulating pump;

the method is characterized in that the allowable conditions of the water level control of the once-through boiler are judged;

when the current operation parameters of the once-through boiler reach the allowable conditions for controlling the water level of the once-through boiler, automatically adjusting the water level of the boiler water circulating pump;

in the automatic adjustment process of the water level of the boiler water circulating pump, judging the finishing condition of the water level control of the once-through boiler;

and according to the current water level parameter of the boiler water circulating pump, when the current operation parameter of the once-through boiler is judged to reach the completion condition, the automatic water level adjustment of the boiler water circulating pump at the current stage is completed.

2. The control method according to claim 1, wherein judging the permission condition for the once-through boiler water level control includes:

presetting a first operation state of the once-through boiler, and comparing whether the current operation state of the once-through boiler meets the first operation state;

and when the current running state of the once-through boiler meets the condition of the first running state, judging that the once-through boiler reaches the allowable condition of the once-through boiler water level control.

3. The control method according to claim 2, wherein the completion condition of the once-through boiler water level control includes:

presetting a second running state of the once-through boiler, and comparing whether the current running state of the once-through boiler after the automatic water level adjustment process of the boiler water circulating pump meets the second running state;

and when the current running state of the once-through boiler meets the condition of a second running state, judging that the once-through boiler reaches the completion condition of the water level control of the once-through boiler.

4. The control method according to claim 3, wherein the first operation state is capable of setting a plurality of different allowable conditions for the once-through boiler water level control according to preset different combinations of the once-through boiler operation parameters;

the automatic adjustment process of the water levels of the furnace water circulating pumps corresponding to different first running states;

the second operation state can set various different conditions for finishing the water level control of the once-through boiler according to preset different running parameter values of the once-through boiler;

and different second running states corresponding to different automatic water level adjusting processes of the furnace water circulating pump.

5. The control method according to claim 4, characterized in that, when it is judged that the current operating state of the once-through boiler satisfies the first operating state, the automatic adjustment process corresponding to the current first operating state is executed;

presetting different running parameter thresholds of the once-through boiler correspondingly according to a plurality of different first running states, and comparing the current running parameter value of the once-through boiler with the running parameter threshold;

and adjusting the current operation parameter value according to the operation parameter threshold value so as to adjust the current operation state of the once-through boiler until the current operation state of the once-through boiler meets the condition of a second operation state corresponding to the current automatic adjustment process, and finishing the automatic water level adjustment process of the boiler water circulating pump.

6. The control method of claim 5, wherein the automatic water level adjustment process of the boiler water circulation pump comprises:

the water level of the water storage tank of the separator is automatically adjusted, and the separator is automatically operated from a wet state to a dry state and from the dry state to the wet state.

7. The control method according to claim 6, characterized in that the first operating state is set to: the first running state is that the water circulating pump is started, the outlet regulating door of the furnace circulating pump reaches a first opening range, and the main water supply electric door is closed;

when the current running state of the once-through boiler meets the first running state, automatically adjusting the water level of a water storage tank of the separator;

the operating parameter threshold comprises:

the first change rate of the separator water level, the first change rate of the separator water storage tank water level, the first change rate of the main steam pressure, the first separator water level, the first water storage tank water level and the second water storage tank water level;

judging and comparing the current separator water level change rate of the once-through boiler with the first separator water level change rate, the first separator water storage tank water level change rate and the first separator water storage tank water level change rate;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both smaller than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, opening a bypass adjusting valve of the main water supply electric door;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both greater than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, continuously judging the magnitude relation between the main pressure change rate and the first change rate of the main steam pressure of the once-through boiler;

if the main gas pressure change rate of the once-through boiler is greater than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the first water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the first water level of the water storage tank, opening a bypass regulating valve of a main water supply electric door, and continuously executing comparison and judgment of the current water level change rate of the separator and the water level change rate of the water storage tank of the separator of the once-through boiler relative to the first water level change rate of the separator and the first water level change rate of the water storage tank of the separator;

if the main gas pressure change rate of the once-through boiler is smaller than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

and closing the bypass adjusting door of the main water supply electric door if the water level of the separator and the water level of the water storage tank are both greater than the first water level of the separator and the first water level of the water storage tank.

8. The control method according to claim 6, characterized in that the first operating state is set to: the running of the unit of the once-through boiler reaches a first load interval, the coal burning amount in unit time reaches a first coal amount interval and is kept stable, the once-through boiler runs in a wet state, a main water supply electric door is closed, and the rotating speed of a steam pump reaches a first rotating speed value;

when the current running state of the once-through boiler meets the first running state, executing automatic operation from a wet state to a dry state;

the operating parameter threshold comprises:

the first water level of the separator, the third water level of the water storage tank, a first difference value between the main steam flow and the water flow on the boiler, a second difference value between the main steam flow and the water flow on the boiler and a first opening degree of an outlet of a boiler circulating pump are adjusted;

judging and comparing the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the third water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the third water level of the water storage tank, continuously judging the size relation between the opening of the furnace circulating pump outlet regulating door and the first opening of the furnace circulating pump outlet regulating door;

if the opening degree of the furnace circulating pump outlet regulating door is larger than the first opening degree of the furnace circulating pump outlet regulating door, closing the furnace circulating pump outlet regulating door, and continuing to judge and compare the size relationship between the separator water level and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank after the preset duration;

if the opening degree of the furnace circulating pump outlet regulating door is smaller than the first opening degree of the furnace circulating pump outlet regulating door, the furnace circulating pump outlet electric door is completely closed, the furnace circulating pump is stopped and water supply is automatically carried out, and the automatic operation from the wet state to the dry state is completed;

judging and comparing the size relationship between the water level of the separator and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank, and simultaneously judging and comparing the size relationship between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the size relationship between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, the main water feeding bypass valve is closed, and the relationship between the main steam flow and the boiler water feeding flow difference, the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow is continuously judged and compared.

9. The control method according to claim 6, characterized in that the first operating state is set to: the running of the unit of the once-through boiler reaches a first load interval and is kept stable, the boiler runs in a dry state, the superheat degree of the once-through boiler is smaller than a first superheat degree, a main water supply electric door is closed, and a steam pump exits parallel running;

when the current running state of the once-through boiler meets the first running state, automatically operating from a dry state to a wet state;

the operating parameter threshold comprises:

a second water level of the water storage tank, a first opening degree of an outlet of the boiler circulating pump, a first difference value between the main steam flow and the water flow on the boiler, and a second difference value between the main steam flow and the water flow on the boiler;

relieving the water supply automation, starting a boiler water circulating pump, and judging and comparing the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

if the water level of the water storage tank is higher than the second water level of the water storage tank, opening a circulating pump outlet regulating door of the large furnace, and judging and comparing the size relation between the opening of the circulating pump outlet regulating door of the large furnace and the first opening of the circulating pump outlet regulating door of the large furnace;

if the opening degree of the furnace circulating pump outlet regulating valve is smaller than the first opening degree of the furnace circulating pump outlet regulating valve, after the preset time is continued, continuously judging and comparing the size relation between the water level of the water storage tank and the second water level of the water storage tank;

if the opening degree of the outlet regulating valve of the boiler circulating pump is larger than the first opening degree of the outlet regulating valve of the boiler circulating pump, judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler, the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, closing the main water feeding bypass regulating valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the boiler water feeding flow and the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow;

and if the difference between the main steam flow and the water flow on the boiler is between the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler, the automatic operation from the dry state to the wet state is completed, and the automatic adjustment of the water level of the water storage tank of the separator is executed.

10. The control method according to any one of claims 7 to 9, wherein in performing automatic adjustment of the water level of the boiler water circulating pump, when there is a judgment condition that the operating parameter threshold value is not satisfied, then the current operating state of the once-through boiler satisfies a condition of a second operating state, and it is judged that the current operating parameter of the once-through boiler reaches the completion condition.

Technical Field

The invention mainly relates to an automatic control technology of water level adjustment and dry-wet state conversion in the starting and stopping processes of industrial once-through boilers (with boiler circulating pumps) in thermal power plants and the like, in particular to a boiler circulating pump water level control method.

Background

In the starting and stopping processes of the existing once-through boiler (with a boiler circulating pump), water level adjustment, dry-state and wet-state conversion are very critical operations. For a long time, limited by automatic control technology, a manual operation mode is always adopted, and an operator comprehensively considers key points such as water flow, feed water flow, main steam pressure, separator water level, separator water storage tank water level and the like on a boiler according to operation order steps, continuously adjusts adjusting adjustment quantities such as the opening of a water feeding adjusting valve of the boiler, the rotating speed of a feed water pump and the like, and finally finishes water level adjustment, dry-state and wet-state conversion. During the operation, there is a great safety risk to the operation due to the difference in the technical strength of the personnel.

Disclosure of Invention

According to the problems, the invention discloses a boiler circulating pump water level control method, which is based on the industrial automatic control characteristics of a thermal power plant and the like, and from the aspects of intelligence, automation and safety, realizes the automatic completion of water level adjustment, dry-state and wet-state conversion and the like of a direct-flow boiler (with a boiler circulating pump), reduces the operation amount of personnel, reduces the safety risk, lays a foundation for realizing one-key start and stop of a unit in the future, and is used for solving the risk problem of manually completing the water level adjustment, the dry-state and the wet-state conversion of the direct-flow boiler (with the boiler circulating pump) in the prior art.

In some embodiments of the invention, a method for controlling water level of a boiler circulating pump is disclosed, which is applied to a once-through boiler with a boiler water circulating pump.

The control method comprises the following steps:

judging the allowable conditions of the water level control of the once-through boiler;

when the current operation parameters of the once-through boiler reach the allowable conditions for controlling the water level of the once-through boiler, automatically adjusting the water level of the boiler water circulating pump;

in the automatic adjustment process of the water level of the boiler water circulating pump, judging the completion condition of the water level control of the once-through boiler;

and according to the current water level parameter of the current boiler water circulating pump, when the current operation parameter of the once-through boiler is judged to reach the completion condition, the automatic water level adjustment of the boiler water circulating pump at the current stage is completed.

Based on the basic concept, the technical scheme mainly comprises three parts, namely, automatic adjustment of the water level of the water storage tank of the separator, automatic operation from a wet state to a dry state, and automatic operation from the dry state to the wet state, and finally automatic completion of water level adjustment, dry and wet state conversion and the like of the direct-flow boiler (with a boiler circulating pump).

In practical technical applications:

1. automatic water level adjustment for water storage tank of separator

The allowable conditions of the once-through boiler water level control are as follows: the first running state is that the water circulating pump is started, the outlet regulating door of the furnace circulating pump reaches a first opening range, and the main water supply electric door is closed.

The automatic water level adjusting process of the water storage tank of the separator comprises the following steps: judging and comparing the current separator water level change rate of the once-through boiler with the first separator water level change rate, the first separator water storage tank water level change rate and the first separator water storage tank water level change rate;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both smaller than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, opening a bypass adjusting valve of the main water supply electric door;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both greater than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, continuously judging the magnitude relation between the main pressure change rate and the first change rate of the main steam pressure of the once-through boiler;

if the main gas pressure change rate of the once-through boiler is greater than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the first water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the first water level of the water storage tank, opening a bypass regulating valve of a main water supply electric door, and continuously executing comparison and judgment of the current water level change rate of the separator and the water level change rate of the water storage tank of the separator of the once-through boiler relative to the first water level change rate of the separator and the first water level change rate of the water storage tank of the separator;

if the main gas pressure change rate of the once-through boiler is smaller than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

and closing the bypass adjusting door of the main water supply electric door if the water level of the separator and the water level of the water storage tank are both greater than the first water level of the separator and the first water level of the water storage tank.

2. Automatic operation from wet state to dry state

The allowable conditions of the once-through boiler water level control are as follows: the running of a unit of the once-through boiler reaches a first load interval, the coal burning amount in unit time reaches a first coal amount interval and is kept stable, the once-through boiler runs in a wet state, a main water supply electric door is closed, and the rotating speed of a steam pump reaches a first rotating speed value;

the automatic operation process from the wet state to the dry state comprises the following steps:

judging and comparing the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the third water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the third water level of the water storage tank, continuously judging the size relation between the opening of the furnace circulating pump outlet regulating door and the first opening of the furnace circulating pump outlet regulating door;

if the opening degree of the furnace circulating pump outlet regulating door is larger than the first opening degree of the furnace circulating pump outlet regulating door, closing the furnace circulating pump outlet regulating door, and continuing to judge and compare the size relationship between the separator water level and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank after the preset duration;

if the opening degree of the furnace circulating pump outlet regulating door is smaller than the first opening degree of the furnace circulating pump outlet regulating door, the furnace circulating pump outlet electric door is completely closed, the furnace circulating pump is stopped and water supply is automatically carried out, and the automatic operation from the wet state to the dry state is completed;

judging and comparing the size relationship between the water level of the separator and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank, and simultaneously judging and comparing the size relationship between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the size relationship between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, the main water feeding bypass valve is closed, and the relationship between the main steam flow and the boiler water feeding flow difference, the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow is continuously judged and compared.

3. Automatic operation from dry state to wet state

The allowable conditions of the once-through boiler water level control are as follows: the running of the unit of the once-through boiler reaches a first load interval and is kept stable, the boiler runs in a dry state, the superheat degree of the once-through boiler is smaller than a first superheat degree, a main water supply electric door is closed, and a steam pump exits parallel running;

the automatic operation process from the dry state to the wet state comprises the following steps:

relieving the water supply automation, starting a boiler water circulating pump, and judging and comparing the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

if the water level of the water storage tank is higher than the second water level of the water storage tank, opening a circulating pump outlet regulating door of the large furnace, and judging and comparing the size relation between the opening of the circulating pump outlet regulating door of the large furnace and the first opening of the circulating pump outlet regulating door of the large furnace;

if the opening degree of the furnace circulating pump outlet regulating valve is smaller than the first opening degree of the furnace circulating pump outlet regulating valve, after the preset time is continued, continuously judging and comparing the size relation between the water level of the water storage tank and the second water level of the water storage tank;

if the opening degree of the outlet regulating valve of the boiler circulating pump is larger than the first opening degree of the outlet regulating valve of the boiler circulating pump, judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler, the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, closing the main water feeding bypass regulating valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the boiler water feeding flow and the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow;

and if the difference between the main steam flow and the water flow on the boiler is between the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler, the automatic operation from the dry state to the wet state is completed, and the automatic adjustment of the water level of the water storage tank of the separator is executed.

The three processes are written into the DCS in a modular mode, man-machine interaction is achieved in the mode of an operation window, the operation amount of personnel is reduced, the operation risk is reduced, and the automation rate is improved.

The invention has the beneficial effects that:

1) effectively solve the safety risk that personnel misoperation brought.

2) The operation efficiency is improved, and the working time is saved.

3) And the automatic input rate is improved.

Drawings

FIG. 1 is a flow chart illustrating an automatic adjustment process of the water level of the water storage tank of the separator according to the method for controlling the water level of the boiler circulating pump of the present invention;

FIG. 2 is a flow chart of an automatic operation process from a wet state to a dry state in a method for controlling a water level of a circulating pump of a furnace according to an embodiment of the present invention;

FIG. 3 is a flow chart of an automatic operation process from a dry state to a wet state in a method for controlling a water level of a circulating pump of a furnace according to an embodiment of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The invention discloses a boiler circulating pump water level control method which is applied to a once-through boiler with a boiler water circulating pump, and is used for automatically completing water level adjustment, dry-state and wet-state conversion and the like of the once-through boiler (with the boiler circulating pump) from the aspects of intelligence, automation and safety based on the industrial automatic control characteristics of a thermal power plant and the like.

The furnace circulating pump water level control method comprises the following steps:

judging the allowable conditions of the water level control of the once-through boiler;

when the current operation parameters of the once-through boiler reach the allowable conditions for controlling the water level of the once-through boiler, automatically adjusting the water level of the boiler water circulating pump;

in the automatic adjustment process of the water level of the boiler water circulating pump, judging the completion condition of the water level control of the once-through boiler;

and according to the current water level parameter of the current boiler water circulating pump, when the current operation parameter of the once-through boiler is judged to reach the completion condition, the automatic water level adjustment of the boiler water circulating pump at the current stage is completed.

Based on the above concept, it should be noted that the determining the allowable conditions for the once-through boiler water level control includes:

presetting a first running state of the once-through boiler, and comparing whether the current running state of the once-through boiler meets the first running state;

and when the current running state of the once-through boiler meets the condition of the first running state, judging that the once-through boiler reaches the allowable condition of the water level control of the once-through boiler.

The conditions for completing the water level control of the once-through boiler include:

presetting a second running state of the once-through boiler, and comparing whether the current running state of the once-through boiler after the automatic water level adjustment process of the boiler water circulating pump meets the second running state;

and when the current running state of the once-through boiler meets the condition of the second running state, judging that the once-through boiler reaches the completion condition of the water level control of the once-through boiler.

Based on the above description, wherein the first operating state may set the allowable conditions for controlling the water level of the once-through boilers according to the preset different combinations of the operating parameters of the once-through boilers, and the automatic adjustment process of the water level of the different boiler water circulating pumps corresponding to the different first operating states.

The second running state can be set according to preset different running parameter values of the once-through boiler, different water level control completion conditions of the once-through boiler and different second running states corresponding to different automatic water level adjustment processes of the boiler water circulating pump.

In some embodiments of the present invention, the method for controlling the water level of the furnace circulating pump may specifically be:

when the current running state of the once-through boiler meets the first running state, executing an automatic adjustment process corresponding to the current first running state;

presetting different running parameter thresholds of the once-through boiler according to a plurality of different first running states, and comparing the current running parameter value of the once-through boiler with the running parameter threshold;

and adjusting the current operation parameter value according to the operation parameter threshold value to adjust the current operation state of the once-through boiler until the current operation state of the once-through boiler meets the condition of a second operation state corresponding to the current automatic adjustment process, and finishing the automatic water level adjustment process of the boiler water circulating pump.

In practical production application, the automatic water level adjusting process of the boiler water circulating pump in the technical scheme of the invention can be mainly divided into three parts, namely automatic water level adjustment of a water storage tank of a separator, automatic operation from a wet state to a dry state, and automatic operation from the dry state to the wet state, so that automatic completion of water level adjustment, dry and wet state conversion and the like of the direct-flow boiler (with a boiler circulating pump) is finally realized.

1. Automatic water level adjustment of separator water tank (as figure 1)

The allowable conditions of the once-through boiler water level control are as follows: the first running state is that the water circulating pump is started, the outlet regulating door of the furnace circulating pump reaches a first opening range, and the main water supply electric door is closed.

The operating parameter thresholds include:

the first change rate of the separator water level, the first change rate of the separator water storage tank water level, the first change rate of the main steam pressure, the first separator water level, the first water storage tank water level and the second water storage tank water level.

The automatic water level adjusting process of the water storage tank of the separator comprises the following steps: judging and comparing the current separator water level change rate of the once-through boiler with the first separator water level change rate, the first separator water storage tank water level change rate and the first separator water storage tank water level change rate;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both smaller than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, opening a bypass adjusting valve of the main water supply electric door;

if the change rate of the water level of the separator and the change rate of the water level of the water storage tank of the separator are both greater than the first change rate of the water level of the separator and the first change rate of the water level of the water storage tank of the separator, continuously judging the magnitude relation between the main pressure change rate and the first change rate of the main steam pressure of the once-through boiler;

if the main gas pressure change rate of the once-through boiler is greater than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the first water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the first water level of the water storage tank, opening a bypass regulating valve of a main water supply electric door, and continuously executing comparison and judgment of the current water level change rate of the separator and the water level change rate of the water storage tank of the separator of the once-through boiler relative to the first water level change rate of the separator and the first water level change rate of the water storage tank of the separator;

if the main gas pressure change rate of the once-through boiler is smaller than the first main gas pressure change rate, continuously judging the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

and closing the bypass adjusting door of the main water supply electric door if the water level of the separator and the water level of the water storage tank are both greater than the first water level of the separator and the first water level of the water storage tank.

2. Automatic operation from wet state to dry state (as shown in figure 2)

The allowable conditions of the once-through boiler water level control are as follows: the running of a unit of the once-through boiler reaches a first load interval, the coal burning amount in unit time reaches a first coal amount interval and is kept stable, the once-through boiler runs in a wet state, a main water supply electric door is closed, and the rotating speed of a steam pump reaches a first rotating speed value;

the operating parameter thresholds include:

the first water level of the separator, the third water level of the water storage tank, a first difference value between the main steam flow and the water flow on the boiler, a second difference value between the main steam flow and the water flow on the boiler and a first opening degree of an outlet of a boiler circulating pump are adjusted.

The automatic operation process from the wet state to the dry state comprises the following steps:

judging and comparing the size relationship between the separator water level and the first separator water level, and the size relationship between the water level of the water storage tank and the third water level of the water storage tank;

if the water level of the separator and the water level of the water storage tank are both smaller than the first water level of the separator and the third water level of the water storage tank, continuously judging the size relation between the opening of the furnace circulating pump outlet regulating door and the first opening of the furnace circulating pump outlet regulating door;

if the opening degree of the furnace circulating pump outlet regulating door is larger than the first opening degree of the furnace circulating pump outlet regulating door, closing the furnace circulating pump outlet regulating door, and continuing to judge and compare the size relationship between the separator water level and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank after the preset duration;

if the opening degree of the furnace circulating pump outlet regulating door is smaller than the first opening degree of the furnace circulating pump outlet regulating door, the furnace circulating pump outlet electric door is completely closed, the furnace circulating pump is stopped and water supply is automatically carried out, and the automatic operation from the wet state to the dry state is completed;

judging and comparing the size relationship between the water level of the separator and the first water level of the separator, the water level of the water storage tank and the third water level of the water storage tank, and simultaneously judging and comparing the size relationship between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the size relationship between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, the main water feeding bypass valve is closed, and the relationship between the main steam flow and the boiler water feeding flow difference, the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow is continuously judged and compared.

It should be noted that after the sequence control is finished, the operator should monitor the change of the superheat degree at the outlet of the separator and adjust the superheat degree bias in time.

After the circulation pump of the boiler is stopped, an operator should focus on monitoring the change conditions of parameters such as the wall temperature of the heating surface of the boiler.

3. Automatic operation from dry state to wet state (see fig. 3)

The allowable conditions of the once-through boiler water level control are as follows: the running of the unit of the once-through boiler reaches a first load interval and is kept stable, the boiler runs in a dry state, the superheat degree of the once-through boiler is smaller than a first superheat degree, the main water supply electric door is closed, and the steam pump exits parallel running.

The operating parameter thresholds include:

the second water level of the water storage tank, the first opening degree of the furnace circulating pump outlet adjusting valve, the first difference value of the main steam flow and the water flow on the boiler, and the second difference value of the main steam flow and the water flow on the boiler.

The automatic operation process from the dry state to the wet state comprises the following steps:

relieving the water supply automation, starting a boiler water circulating pump, and judging and comparing the size relationship between the water level of the water storage tank and the second water level of the water storage tank;

if the water level of the water storage tank is higher than the second water level of the water storage tank, opening a circulating pump outlet regulating door of the large furnace, and judging and comparing the size relation between the opening of the circulating pump outlet regulating door of the large furnace and the first opening of the circulating pump outlet regulating door of the large furnace;

if the opening degree of the furnace circulating pump outlet regulating valve is smaller than the first opening degree of the furnace circulating pump outlet regulating valve, after the preset time is continued, continuously judging and comparing the size relation between the water level of the water storage tank and the second water level of the water storage tank;

if the opening degree of the outlet regulating valve of the boiler circulating pump is larger than the first opening degree of the outlet regulating valve of the boiler circulating pump, judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler, the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the water flow on the boiler is larger than the first difference between the main steam flow and the water flow on the boiler, opening a main water supply bypass adjusting valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the water flow on the boiler and the first difference between the main steam flow and the water flow on the boiler, and the magnitude relation between the main steam flow and the second difference between the main steam flow and the water flow on the boiler;

if the difference between the main steam flow and the boiler water feeding flow is smaller than the second difference between the main steam flow and the boiler water feeding flow, closing the main water feeding bypass regulating valve, and continuously judging and comparing the magnitude relation between the difference between the main steam flow and the boiler water feeding flow and the first difference between the main steam flow and the boiler water feeding flow, and the second difference between the main steam flow and the boiler water feeding flow;

and if the difference between the main steam flow and the water flow on the boiler is between the first difference between the main steam flow and the water flow on the boiler and the second difference between the main steam flow and the water flow on the boiler, the automatic operation from the dry state to the wet state is completed, and the automatic adjustment of the water level of the water storage tank of the separator is executed.

In practical production applications, the parameter threshold values in the three adjustment flows are set as follows:

the first opening interval of the furnace circulating pump outlet adjusting door is 50% +/-5%;

the first load interval is 200-240 MW;

the first coal amount interval is 120-130 t/h;

the first rotation speed value is 4200 rpm;

the first degree of superheat is 10 ℃;

the first rate of change of separator water level is 0%;

the first change rate of the water level of the water storage tank of the separator is 0 percent;

the first change rate of the main steam pressure is 0 percent;

the first water level of the separator is 3 m;

the first water level of the water storage tank is 6m, and the second water level of the water storage tank is 5.5 m; the third water level of the water storage tank is 6.5 m;

the first opening degree of the furnace circulating pump outlet is 50%;

the first difference value between the main steam flow and the water flow on the boiler is 100t/h, and the second difference value between the main steam flow and the water flow on the boiler is 50 t/h;

the preset time is 5 s.

The three processes are written into the DCS in a modular mode, man-machine interaction is achieved in the mode of an operation window, the operation amount of personnel is reduced, the operation risk is reduced, and the automation rate is improved.

The water level adjustment, dry-state and wet-state conversion are very key operations in the starting and stopping processes of the direct-flow boiler (with the boiler circulating pump), the boiler circulating pump water level control method is based on the industrial automatic control characteristics of a thermal power plant and the like, and the automatic completion of the water level adjustment, the dry-state and wet-state conversion of the direct-flow boiler (with the boiler circulating pump) is realized from the aspects of intelligence, automation and safety, so that the personnel operation amount is reduced, the safety risk is reduced, and a foundation is laid for realizing the one-key starting and stopping of a unit in the future.

The invention has the beneficial effects that:

1) effectively solve the safety risk that personnel misoperation brought.

2) The operation efficiency is improved, and the working time is saved.

3) And the automatic input rate is improved.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.