CN113374539A - Steam inlet control system of double-cylinder double-pressure waste heat generating set and steam supplementing control method thereof - Google Patents
Steam inlet control system of double-cylinder double-pressure waste heat generating set and steam supplementing control method thereof Download PDFInfo
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- CN113374539A CN113374539A CN202110642432.2A CN202110642432A CN113374539A CN 113374539 A CN113374539 A CN 113374539A CN 202110642432 A CN202110642432 A CN 202110642432A CN 113374539 A CN113374539 A CN 113374539A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D17/00—Regulating or controlling by varying flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D13/00—Combinations of two or more machines or engines
- F01D13/02—Working-fluid interconnection of machines or engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01D15/10—Adaptations for driving, or combinations with, electric generators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
Abstract
The invention relates to the field of steam admission control of a generator set, in particular to a steam admission control system of a double-cylinder double-pressure waste heat generator set and a steam compensation control method thereof, and the scheme is summarized as follows: the steam turbine comprises a main steam adjusting unit, a steam supplementing adjusting unit and a DEH (steam extraction) unit, wherein the main steam adjusting unit comprises a medium pressure collecting box, a first quick-switching valve and a first adjusting valve; the steam supplementing adjusting unit comprises a steam-water separator, a heater, a second quick-switching valve and a second adjusting valve, wherein a gas inlet of the heater is respectively connected with a gas outlet of the steam-water separator and a gas outlet of the medium-pressure header, a gas outlet of the heater is connected with the second quick-switching valve, and the second adjusting valve is respectively connected with a low-pressure cylinder of the generator set and the second quick-switching valve; the first fast cut valve, the second fast cut valve, the first regulating valve and the second regulating valve are all connected with the DEH control module. The invention is suitable for steam inlet control of the generator set.
Description
Technical Field
The invention relates to the field of steam admission control of a generator set, in particular to a steam admission control system of a double-cylinder double-pressure waste heat generator set and a steam compensation control method thereof.
Background
The steam turbine generator is a rotary power machine which converts the energy of steam into mechanical power, and the working principle is that the superheated steam generated by boiler enters into steam turbine to do work by expansion, so that the blades rotate to drive the generator to generate electricity.
Saturated steam cannot be directly used as steam for generating electricity by a steam turbine basically because the saturated steam contains water, has low pressure and no power, and steam has hardness and is easy to scale blades of the steam turbine and the like, and a steam turbine generator applies work to superheated steam with higher heat and specific volume. Compared with the heat efficiency of steam work, the generator set consumes high-pressure high-temperature or medium-pressure medium-temperature steam, the utilization of industrial low-pressure steam can only be recycled from the energy-saving perspective for a long time, and the application experience of how to scientifically use steam, especially the reuse of 70t/h large-steam-quantity and impact steam sources is short.
The existing low-pressure steam power generation has the following technical difficulties:
defects of low-pressure steam power generation
The low-pressure steam source of steam compensation, one is saturated steam from a steel converter, the steam is generated in stages under the influence of the process, the pressure and the flow both fluctuate greatly, and the impact steam source can cause the load of a unit to fluctuate greatly in the operation of a double-pressure unit and influence the safe operation of the unit. The other is the residual steam which is mainly used for auxiliary links such as canteens and bathrooms for heating and providing cold sources for refrigerating systems at present by steel enterprises, and the existing low-pressure steam is about 70T/H.
When saturated steam, particularly a staged steam source, is directly used for steam supplementing power generation of a unit, in order to ensure the power output stability of the unit, the steam supplementing flow of the saturated steam cannot exceed one third of the total flow, and meanwhile, the low-pressure saturated steam can seriously erode the last-stage blade of the steam turbine, thereby seriously limiting the power generation efficiency and the service life of the unit.
Do not have two DEH function control model of meneing vapour formula generating set of pressing
The DEH function of the turbonator is a digital electro-hydraulic control system of the unit, which consists of a computer control part and an EH hydraulic actuating mechanism part and is automatic control equipment for controlling the starting, stopping, rotating speed control and power control of the steam turbine.
The control modes of main steam regulation and steam supplement regulation of most units adopt manual modes, namely, the main steam and gas supplement regulating valves are manually kept at certain opening degrees, and the power of the generator fluctuates within a certain range along with the change of steam pressure. When the steam source is greatly changed, the opening intervention is manually carried out by a human. This control scheme does not achieve the goal of stable, safe, efficient use of low pressure steam and high automation levels. Therefore, the automatic control method for high-flow and impact low-pressure steam compensation is still a blank area at present.
The requirement on the dual-pressure control function is complex, and the control requirement is high
Aiming at the goal of stably, safely and efficiently utilizing low-pressure steam and realizing power generation at a high automation level, the control of the double-compressor set needs to meet the functional requirements of main directivity: firstly, the unit can safely use low-pressure steam parameters; the operation mode of low-pressure steam compensation in the unit operation; cutting off low-pressure steam supplement under the condition of abnormal operation of the unit; the effective utilization rate of low-pressure steam; the coordination operation of medium-pressure steam and low-pressure steam, and the like.
Disclosure of Invention
The invention aims to provide a steam admission control system of a double-cylinder double-pressure waste heat generating set and a steam compensation control method thereof, which realize automatic control of steam admission of the generating set and greatly improve the running stability of the generating set; the generator set is prevented from being drained, so that the generating efficiency of the generator set is improved, and the service life of the generator set is prolonged; meanwhile, the steam supplementing control flow is optimized.
The invention adopts the following technical scheme to realize the purpose, and the steam inlet control system of the double-cylinder double-pressure waste heat generating set comprises a main steam adjusting unit, a steam supplementing adjusting unit and a DEH (steam injection valve), wherein the main steam adjusting unit comprises a medium-pressure collecting box, a first quick-switching valve and a first adjusting valve; the steam supplementing adjusting unit comprises a steam-water separator, a heater, a second quick-switching valve and a second adjusting valve, wherein a gas inlet of the heater is respectively connected with a gas outlet of the steam-water separator and a gas outlet of the medium-pressure collecting tank, a gas outlet of the heater is connected with the second quick-switching valve, and the second adjusting valve is respectively connected with a low-pressure cylinder of the generator set and the second quick-switching valve; the first fast cut valve, the second fast cut valve, the first regulating valve and the second regulating valve are all connected with the control module of the DEH.
Further, the main steam adjusting unit further comprises a pressure equalizing box, and the pressure equalizing box is connected with an air outlet of the medium-pressure collecting box.
Further, the steam supplementing regulating unit further comprises a low-pressure energy accumulator, and the low-pressure energy accumulator is connected with an air inlet of the steam-water separator.
Further, the steam inlet control system of the double-cylinder double-pressure waste heat generating set further comprises a pressure detection device, and the pressure detection device is used for detecting the pressure of the main steam adjusting unit and the steam supplementing adjusting unit pipe network in real time.
The steam supplementing control method of the double-cylinder double-pressure waste heat generating set is applied to the steam inlet control system of the double-cylinder double-pressure waste heat generating set, and comprises the following steps:
step 1, starting and operating a second regulating valve;
step 2, detecting the pressure of a pipe network of the steam supplementing adjusting unit in real time, and entering step 3 when the pressure of the pipe network is greater than a first threshold pressure; when the pipe network pressure is smaller than the second threshold pressure, entering a step 4;
step 3, automatically increasing the opening of the second regulating valve according to the setting conditions;
and 4, automatically reducing the opening degree of the second regulating valve according to the set conditions.
Further, in step 1, the conditions for starting the operation of the second regulator valve include: the control method comprises the steps that a generator set is connected to the power grid, the power of the generator set is larger than a set first threshold rated power, the opening of a first regulating valve is larger than a set first threshold opening, a main steam regulating unit is under the control of the first regulating valve, a second quick-switching valve is fully opened, the steam temperature of a heater air outlet is larger than a first threshold temperature, the steam temperature difference between the heater air outlet and a generator set steam supply opening is smaller than a second threshold temperature, and the pressure ratio of a generator set regulating level to the steam supply opening is larger than a set value.
Further, in step 1, in the operation process of the second regulating valve, when any one of the following conditions is met, the second regulating valve is automatically closed and the function is locked: (1) tripping the generator set; (2) splitting the generator; (3) the power of the generator set is less than the set second threshold rated power; (4) the opening degree of the first regulating valve is smaller than a set second threshold opening degree; (5) the pressure difference between the air inlet and the air outlet of the second regulating valve is less than the set threshold pressure; (6) the steam temperature at the air outlet of the heater is less than a first threshold temperature; (7) the steam temperature difference between the air outlet of the heater and the steam supplementing port of the generator set is larger than a second threshold temperature; (8) the pressure ratio of the regulating stage of the generator set to the steam supplementing port is less than a set value; the first threshold value rated power is larger than the second threshold value rated power, the first threshold value opening degree is larger than the second threshold value opening degree, and the first threshold value temperature is larger than the second threshold value temperature.
Further, in step 3 or step 4, a specific method of automatically controlling the opening of the second regulating valve according to the setting condition includes: calculating the deviation delta X between the set value SP of the process parameter and the measured value PV, wherein the delta X is the regulation deviation; then, using PID automatic operation, the size of the opening of the second regulating valve is controlled so that Δ X ≈ SP-PV ≈ 0.
Further, in the PID automatic operation process, setting a negative deviation regulation dead zone for the PID, setting the negative deviation regulation dead zone as (M,0), wherein M is a negative number, and when the delta X is a positive deviation, namely SP is greater than PV, the PID automatically increases the opening of the second regulating valve; when the delta X is less than M, namely SP is less than PV + M, the PID automatically reduces the opening degree of the second regulating valve; when M is larger than delta X and smaller than 0, PID does not operate, and the opening degree of the second regulating valve is kept.
Furthermore, in the PID automatic adjustment process, a set value smoothness processing function is introduced to enable the set value SP to change smoothly.
According to the invention, the steam regulating unit and the steam supplementing regulating unit are respectively provided with the quick-cutting valve and the regulating valve, and the valves are automatically controlled by the control module of the DEH, so that the automatic control and regulation of the whole steam inlet system are realized, and the running stability of the generator set is greatly improved; the steam-water separator is arranged in the steam supply adjusting unit, so that the hydrophobic water is prevented from entering the generator set, the generating efficiency of the generator set is improved, and the service life of the generator set is prolonged; in the steam supplementing control process, the automatic control and regulation of the second regulating valve are carried out according to the pressure of a steam supplementing regulating unit pipe network, and a steam supplementing input condition, namely the starting condition of the second regulating valve, and a steam supplementing removing condition, namely the automatic closing condition of the second regulating valve are also set, so that the safety of steam supplementing control is greatly improved; meanwhile, a negative deviation regulation dead zone is introduced, the function ensures that the regulation valve keeps the regulation characteristic of approaching opening, the steam supplement flow is increased when the low-pressure steam is surplus, and the steam admission amount is kept when the low-pressure steam is slightly insufficient, so that the aim of generating power by utilizing the low-pressure steam is fulfilled, the regulation frequency can be reduced, and the regulation stability of the steam supplement is improved.
Drawings
FIG. 1 is a structural block diagram of a steam inlet control system of the double-cylinder double-pressure waste heat generating set.
In the drawing, 101 is a main steam regulating unit, 102 is a steam supplementing regulating unit, 201 is a first quick-cut valve, 202 is a first regulating valve, 203 is a second quick-cut valve, 204 is a second regulating valve, and 301 is a steam turbine.
Detailed Description
The steam inlet control system of the double-cylinder double-pressure waste heat generating set comprises a main steam adjusting unit, a steam supplementing adjusting unit and a DEH (steam exhaust heat) unit, wherein the main steam adjusting unit comprises a medium-pressure collecting box, a first quick-switching valve and a first adjusting valve; the steam supplementing adjusting unit comprises a steam-water separator, a heater, a second quick-switching valve and a second adjusting valve, wherein a gas inlet of the heater is respectively connected with a gas outlet of the steam-water separator and a gas outlet of the medium-pressure collecting tank, a gas outlet of the heater is connected with the second quick-switching valve, and the second adjusting valve is respectively connected with a low-pressure cylinder of the generator set and the second quick-switching valve; the first fast cut valve, the second fast cut valve, the first regulating valve and the second regulating valve are all connected with the control module of the DEH.
The main steam adjusting unit further comprises a pressure equalizing box, and the pressure equalizing box is connected with an air outlet of the medium-pressure collecting box.
The steam supplementing adjusting unit further comprises a low-pressure energy accumulator, and the low-pressure energy accumulator is connected with an air inlet of the steam-water separator.
The steam inlet control system of the double-cylinder double-pressure waste heat generating set further comprises a pressure detection device, and the pressure detection device is used for detecting the pressure of the main steam adjusting unit and the steam supplementing adjusting unit pipe network in real time.
The steam supplementing control method of the double-cylinder double-pressure waste heat generating set is applied to the steam inlet control system of the double-cylinder double-pressure waste heat generating set, and comprises the following steps:
step 1, starting and operating a second regulating valve;
step 2, detecting the pressure of a pipe network of the steam supplementing adjusting unit in real time, and entering step 3 when the pressure of the pipe network is greater than a first threshold pressure; when the pipe network pressure is smaller than the second threshold pressure, entering a step 4;
step 3, automatically increasing the opening of the second regulating valve according to the setting conditions;
and 4, automatically reducing the opening degree of the second regulating valve according to the set conditions.
In step 1, the conditions for starting the operation of the second regulator valve include: the control method comprises the steps that a generator set is connected to the power grid, the power of the generator set is larger than a set first threshold rated power, the opening of a first regulating valve is larger than a set first threshold opening, a main steam regulating unit is under the control of the first regulating valve, a second quick-switching valve is fully opened, the steam temperature of a heater air outlet is larger than a first threshold temperature, the steam temperature difference between the heater air outlet and a generator set steam supply opening is smaller than a second threshold temperature, and the pressure ratio of a generator set regulating level to the steam supply opening is larger than a set value.
In the step 1, when the second regulating valve meets any one of the following conditions in the operation process, the second regulating valve is automatically closed and has the locked function: (1) tripping the generator set; (2) splitting the generator; (3) the power of the generator set is less than the set second threshold rated power; (4) the opening degree of the first regulating valve is smaller than a set second threshold opening degree; (5) the pressure difference between the air inlet and the air outlet of the second regulating valve is less than the set threshold pressure; (6) the steam temperature at the air outlet of the heater is less than a first threshold temperature; (7) the steam temperature difference between the air outlet of the heater and the steam supplementing port of the generator set is larger than a second threshold temperature; (8) the pressure ratio of the regulating stage of the generator set to the steam supplementing port is less than a set value; the first threshold value rated power is larger than the second threshold value rated power, the first threshold value opening degree is larger than the second threshold value opening degree, and the first threshold value temperature is larger than the second threshold value temperature.
In step 3 or step 4, the specific method for automatically controlling the opening of the second regulating valve according to the setting condition includes: calculating the deviation delta X between the set value SP of the process parameter and the measured value PV, wherein the delta X is the regulation deviation; then, automatic arithmetic control is performed using PID (proportional-integral-derivative control), and the size of the opening degree of the second regulating valve is controlled so that Δ X ≈ SP-PV ≈ 0.
In the PID automatic operation process, setting a negative deviation regulation dead zone for the PID, setting the negative deviation regulation dead zone as (M,0), wherein M is a negative number, and when delta X is a positive deviation, namely SP is greater than PV, the PID automatically increases the opening degree of the second regulating valve; when the delta X is less than M, namely SP is less than PV + M, the PID automatically reduces the opening degree of the second regulating valve; when M is larger than delta X and smaller than 0, PID does not operate, and the opening degree of the second regulating valve is kept.
In the PID automatic adjustment process, a set value smoothness processing function is introduced to enable the set value SP to change smoothly.
Fig. 1 is a structural block diagram of a steam admission control system of a double-cylinder double-pressure waste heat generator set, which comprises a main steam adjusting unit 101, a steam compensation adjusting unit 102 and a DEH, wherein the main steam adjusting unit comprises a medium pressure collecting box, a pressure equalizing box, a first quick-switching valve 201 and a first adjusting valve 202, an air outlet of the medium pressure collecting box is respectively connected with the first quick-switching valve 201 and an air inlet of the pressure equalizing box, and the first adjusting valve 202 is respectively connected with the first quick-switching valve 201 and a medium pressure cylinder of a steam turbine 301; the steam supplementing adjusting unit 102 comprises a steam-water separator, a steam supplementing heater, a second quick-switching valve 203 and a second adjusting valve 204, wherein a gas inlet of the steam supplementing heater is respectively connected with a gas outlet of the steam-water separator and a gas outlet of the medium-pressure header, a gas outlet of the steam supplementing heater is connected with the second quick-switching valve 203, and the second adjusting valve 204 is respectively connected with a low-pressure cylinder of the steam turbine and the second quick-switching valve 203; the first quick-cut valve 201, the second quick-cut valve 203, the first regulating valve 202 and the second regulating valve 204 are all connected with a control module (not shown) of the DEH. The medium pressure steam enters the medium pressure header, and the low pressure steam enters the steam-water separator.
The steam turbine generator is a medium-temperature, medium-pressure, double-cylinder, single-shaft, single-exhaust steam turbine and steam-supplementing and condensing impulse type steam turbine, and has rated parameters of N43SY. YX ZN30-4.0/[0.6]/450/[220], and uses medium-temperature and medium-pressure (pressure 4.0MPa, temperature 450 ℃) steam to enter (main steam regulation) and low-pressure (pressure 0.6MPa, temperature 240 ℃) steam to supplement (steam-supplementing regulation). The unit takes dry quenching boiler steam generated by recovering the sensible heat of the coking coke as main steam. The stage saturated steam from converter steelmaking and the waste heat boiler steam from sintering flue gas desulfurization are used as steam supplement to achieve the actual power generation of 30 MW.
Steam turbine structure optimization
The steam turbine cylinder is composed of a front cylinder, a middle cylinder and a rear cylinder, a steam supplementing port is positioned in a lower cylinder of the steam turbine, medium-temperature and medium-pressure steam is adopted in a main steam control mode to enter a main steam valve of a steam turbine unit, low-pressure saturated steam is conveyed to a steam-steam surface type heat exchanger in a steam supplementing control mode, the low-pressure saturated steam is heated to 220 ℃ by a heater to become superheated steam, and then the superheated steam enters the steam supplementing port of the steam turbine unit, so that the superheat degree of the low-pressure saturated steam is improved, the using amount of the low-pressure steam is increased, the input flow of the main steam and the input flow of the supplementing steam are both about 70T/H, and the flow ratio is more than or equal to 1: 1.
(1) optimizing a unit mechanism:
the structure adopted by combining the process requirements for steam supply control is optimized
Firstly, a cyclone steam-water separator is additionally arranged in front of a steam supplementing port to prevent drained water from entering a unit;
secondly, steam compensation is performed by adopting a variable cross-section annular volute; drainage grooves are arranged in front of each pressure stage of the through-flow part, and dehumidification drainage annular grooves are arranged on the partition plates at the last stages;
and thirdly, laser hardening treatment is carried out on the steam inlet edges of the last stage of blades and the like, so that the water erosion of low-pressure saturated steam to the last stage of blades is overcome.
(2) Staged steam source stability treatment:
in order to overcome the great influence of the operation of an impact steam source on the load of the unit, the low-pressure steam produced by the sintering waste heat boiler in steam supplement is kept at 20T/H and is used as the low-pressure steam base steam source of the unit. The staged saturated steam from converter steelmaking is subjected to pressure stabilization by the low-pressure accumulator, mixed with a basic steam source in the steam-water separator to complete water-steam separation, then enters the steam supplementing heater to be heated into superheated steam, and finally enters the steam supplementing port of the steam turbine, so that the influence degree of impact steam source sudden change on the steam supplementing throttle and the load of a unit is reduced.
Automatic control of main steam and supplementary steam
(1) The control of the medium pressure steam is the control mode of DEH. The machine set adopts medium-pressure steam to realize the impulse transfer, the grid connection and the initial load of the machine set. The combination of the main steam quick-switching valve (the first quick-switching valve) and the regulating valve (the first regulating valve) realizes the functions of starting-up and turning, rotating speed control, friction check, tightness test, activity test, overspeed oil injection test, synchronous grid connection, valve position control, power control, load shedding, high and low load limitation, primary frequency modulation, unit protection and shutdown and the like of the unit.
(2) A control model is established from equipment configuration of a steam compensation system to operation of a steam compensation function, process adjustment, efficient power generation, a protection function, quick recovery and the like.
Setting of a steam supplementing quick-cutting valve:
the double-compressor set is respectively provided with a hydraulic quick-cut valve and a regulating valve for medium-pressure steam and low-pressure steam, wherein the quick-cut valve is used for quickly cutting off the steam in an accident state, and the regulating valve is used for normally regulating the load of the generator set.
The steam supplementing quick-switching valve (second quick-switching valve) is arranged mainly for protecting the whole unit to quickly switch off steam together with the main steam quick-switching valve under the accident condition, so that the control method ensures that the unit can be safely shut down or maintain the idle running of 3000r/m when the unit is in protective shutdown or the generator is disconnected.
If the steam supplementing system is abnormal and needs to be split, the steam supplementing system can be put into operation quickly after being cut off abnormally, the production recovery time is shortened, and only the regulating valve is closed instead of the quick air supplementing switching valve. In addition, when the unit is not put into operation for a long time for steam compensation, the quick-cut valve heating pipe can be opened first, and the time for steam compensation is shortened.
And (3) setting of steam supplement input/removal:
the function of steam supply is input: the function of inputting and cutting the steam supply is a mode aiming at the whole steam supply regulating valve (second regulating valve). When the steam supplementing condition is met, an operator can manually put into operation the steam supplementing function, the steam supplementing adjusting valve is allowed to be opened, and the unit can perform steam supplementing adjustment. When the steam supply adjustment does not meet the conditions, the steam supply function is automatically cut off, or the steam supply function can be manually cut off, and the steam supply adjustment valve is automatically closed and locked.
The unit is required to be put into operation for steam compensation after being connected to the grid and reaching a certain initial power, and the specific conditions are as follows: the power of the unit is more than 30 percent of rated power, the opening of a main steam regulating valve is more than 15 percent, the main steam regulation is in a valve control state, a steam supplementing quick switching valve is fully opened, the steam temperature before the steam supplementing valve is more than 170 ℃, the steam temperature difference between the steam before the steam supplementing valve and the steam supplementing port is less than 50 ℃, and the pressure ratio of a unit regulation level to the steam supplementing port is more than 2.3.
And (3) removing the steam supplementing function: in order to ensure the operation safety of the unit, when any one of the following conditions occurs, the steam supplementing function is automatically cut off, the regulating valve is automatically closed, and the function is locked: (1) tripping the unit; (2) splitting the generator; (3) the power of the unit is less than 25% of rated power; (4) the opening degree of the main steam regulating valve is less than 11 percent; (5) the pressure difference between the front and the back of the steam-supplementing regulating valve is less than-10 KPa; (6) the steam temperature before the steam supplementing valve is less than 170 ℃; (7) the steam temperature difference between the front of the steam supply valve and the steam supply port is more than 50 ℃; (8) the pressure ratio of the regulating stage of the unit to the steam supplementing port is less than 2.3.
Setting a steam supplementing adjusting control mode:
after the steam supplementing function is put into use, the steam supplementing quantity can be controlled by steam supplementing adjustment. The steam supply adjustment has two modes of manual operation and automatic operation, and the steam supply adjustment opening is manually controlled to adjust the steam inlet amount in the manual mode; in the automatic mode, the operator sets the adjusted parameters, and the steam supplementing adjustment is carried out for automatic adjustment.
Selecting an automatic steam compensation adjusting object:
for example, the pressure of the low-pressure steam pipe network (namely the steam supplementing regulating unit pipe network) can be automatically regulated. When the pressure of the low-pressure steam pipe network is increased, the low-pressure steam surplus is increased, the opening degree of the regulating valve is automatically increased, and the steam supplementing flow is increased; when the pressure of the low-pressure steam pipe network is reduced, the low-pressure steam surplus is reduced, the opening degree of the regulating valve is automatically reduced, and the steam supplementing flow is reduced. Therefore, the low-pressure steam can be utilized to generate electricity to the maximum extent, and the effect of stabilizing the pressure of the pipe network can be achieved. Therefore, the 'pressure difference between the front and the back of the steam compensation adjusting valve' is finally selected as a control object of steam compensation adjustment.
The application of the function of adjusting the dead zone by the negative offset of the steam compensation:
the conventional automatic regulating function is to calculate the deviation Δ X between the set value (SP) and the measured value (PV) of the process parameter for PID automatic calculation, control the opening of the regulating valve, and keep the set value and the measured value substantially the same, i.e., the regulating deviation Δ X is about equal to SP-PV 0. In order to increase the use of low-pressure steam as much as possible and improve the power generation capacity, a negative deviation adjusting dead zone function is introduced into the automatic steam compensation adjustment.
And setting a negative deviation regulation dead zone for the PID, wherein the PID does not operate in the regulation dead zone, and the valve keeps the current opening. Setting the deviation regulation dead zone to be 0-minus 10KPa, namely when the delta X is positive deviation (namely SP is more than PV), the PID automatically opens the opening degree of the steam-supplementing regulating valve to increase the steam-supplementing flow; when the delta X is less than-10 KPa (SP is less than PV-10KPa), the PID automatically closes the steam supply regulation to reduce the steam supply flow; when the pressure is within the range of 0< delta X < -10KPa, PID does not operate, and the steam-supplementing regulating valve keeps the opening degree.
The function ensures that the regulating valve keeps the regulating characteristic of approaching opening, the steam supplementing flow is increased when the low-pressure steam is surplus, and the steam inlet quantity is kept when the low-pressure steam is slightly insufficient, so that the aim of generating electricity by utilizing the low-pressure steam is fulfilled, the regulating frequency can be reduced, and the steam supplementing regulating stability is improved.
PID adjustment set value smoothness processing:
conventional automatic control uses a control deviation Δ X (Δ X — SP PV) to perform PID calculation, where SP is a set value that is manually changed by an operator according to the operation requirement of the plant. The adjustment object in the steam supplementing adjustment is the pressure difference between the front and the back of a steam supplementing valve, the operation personnel is allowed to set within the range of 50-600 KPa, and the adjustable range is large. When an operator changes the set value SP greatly, the adjustment deviation delta X at the time is very large, and the instruction of the adjusting valve after PID operation is correspondingly changed greatly, so that the adjustment is fluctuated and unstable, and the operation stability of the steam supplement of the unit is not facilitated.
Therefore, the steam supply regulation control of the unit introduces a set value smoothness processing function, so that the set value SP changes smoothly, the PID output is naturally smooth and stable, and the steam supply regulation performance becomes stable.
A function of automatic intervention in advance of dysregulation:
in the steam supplementing automatic regulation process, when the power of the unit exceeds a rated value or the steam supplementing flow exceeds the rated value due to the increase of the steam supplementing amount, the control model can automatically intervene in advance to prevent the overload of the unit. When the opening degree of the main steam is reduced to a certain degree due to artificial or automatic adjustment, the use amount of the lowest medium-pressure steam cannot be guaranteed, and the control model can also automatically intervene in advance.
And (3) adjusting abnormal secondary advanced automatic intervention function:
the pressure difference between the front and the back of the steam supplementing valve is normally adjusted within the range of 50-600 KPa, and if the low-pressure steam pipe network is abnormal, the pressure of the pipe network is rapidly reduced, and even the steam supplementing of a unit is changed into steam extraction. Before the automatic release of the steam supply, the control model is provided with a secondary automatic intervention function, so that the condition of frequently cutting off the steam supply is avoided, and the long-term stable on-line operation of the steam supply is ensured.
Setting a guidance function interface and carrying out initial query:
in order to guide operation of an operator to the steam compensation adjustment and guide maintenance personnel to carry out fault treatment and accident recall, a steam compensation control instruction interface is set and first judgment of steam compensation removal is carried out when a control model is compiled, so that the simplicity of operation of a steam compensation system is ensured, and the reason analysis after the fault is clear.
According to long-term operation experience, a series of operation specifications in the processes of investment, operation and removal in a steam compensation adjusting system are formulated, low-pressure steam is utilized to the maximum extent to generate electricity, and meanwhile, the function of stabilizing the pressure of a pipe network can be achieved.
The steam supply DEH controls the completion of an oil path:
the DEH (digital Electric Hydraulic Control System) digital Electric Hydraulic Control system consists of a computer Control part and an EH Hydraulic oil circuit execution mechanism. The control precision of the main steam and the steam supply regulating valve can be improved by adopting DEH control. According to the requirement of the integral operation stability of the unit, the control oil circuit of the main steam and the supplementary steam is improved,
and I, connecting an AST oil circuit of a DEH control system of the medium-temperature and medium-pressure main steam adjusting loop with a low-pressure steam quick-switching valve control oil circuit, and realizing the closing of a steam-supplementing quick-switching valve after the main steam loop trips to realize the synchronous cutting-off of low-pressure steam.
And II, an OPC oil way of a DEH control system of the medium-temperature and medium-pressure main steam regulating loop is connected with a low-pressure steam regulating valve control oil way, so that when the main steam regulating valve closes the steam flow and reduces, the low-pressure steam is also closed synchronously, the steam supplementing quantity is ensured not to exceed the main steam quantity all the time, and the safe operation of the steam supplementing system is ensured.
In conclusion, the invention realizes the automatic control of the steam admission of the generator set, and greatly improves the running stability of the generator set; moreover, the generator set for generating the power by draining the water is avoided, so that the generating efficiency of the generator set is improved, and the service life of the generator set is prolonged; meanwhile, the steam supplementing control flow is optimized, automatic control and regulation of the second regulating valve are carried out according to the pressure of a steam supplementing regulating unit pipe network in the steam supplementing control process, steam supplementing input conditions, namely starting conditions of the second regulating valve, and steam supplementing removing conditions, namely automatic closing conditions of the second regulating valve are set, so that the safety of steam supplementing control is greatly improved; meanwhile, a negative deviation regulation dead zone is introduced, the function ensures that the regulation valve keeps the regulation characteristic of approaching opening, the steam supplement flow is increased when the low-pressure steam is surplus, and the steam admission amount is kept when the low-pressure steam is slightly insufficient, so that the aim of generating power by utilizing the low-pressure steam is fulfilled, the regulation frequency can be reduced, and the regulation stability of the steam supplement is improved.
Claims (10)
1. The steam inlet control system of the double-cylinder double-pressure waste heat generating set is characterized by comprising a main steam adjusting unit, a steam supplementing adjusting unit and a DEH (steam injection valve), wherein the main steam adjusting unit comprises a medium-pressure collecting box, a first quick-switching valve and a first adjusting valve; the steam supplementing adjusting unit comprises a steam-water separator, a heater, a second quick-switching valve and a second adjusting valve, wherein a gas inlet of the heater is respectively connected with a gas outlet of the steam-water separator and a gas outlet of the medium-pressure collecting tank, a gas outlet of the heater is connected with the second quick-switching valve, and the second adjusting valve is respectively connected with a low-pressure cylinder of the generator set and the second quick-switching valve; the first fast cut valve, the second fast cut valve, the first regulating valve and the second regulating valve are all connected with the control module of the DEH.
2. The steam inlet control system of the double-cylinder double-pressure waste heat generator set according to claim 1, wherein the main steam adjusting unit further comprises a pressure equalizing tank, and the pressure equalizing tank is connected with an air outlet of the medium-pressure header tank.
3. The steam inlet control system of the double-cylinder double-pressure waste heat generator set according to claim 2, wherein the steam supply adjusting unit further comprises a low-pressure accumulator, and the low-pressure accumulator is connected with an air inlet of the steam-water separator.
4. The steam inlet control system of the double-cylinder double-pressure waste heat generator set according to claim 3, further comprising a pressure detection device, wherein the pressure detection device is used for detecting the pressure of the main steam adjusting unit and the steam supplementing adjusting unit pipe network in real time.
5. The steam supplementing control method of the double-cylinder double-pressure waste heat generator set is applied to the steam inlet control system of the double-cylinder double-pressure waste heat generator set according to any one of claim 4, and is characterized by comprising the following steps of:
step 1, starting and operating a second regulating valve;
step 2, detecting the pressure of a pipe network of the steam supplementing adjusting unit in real time, and entering step 3 when the pressure of the pipe network is greater than a first threshold pressure; when the pipe network pressure is smaller than the second threshold pressure, entering a step 4;
step 3, automatically increasing the opening of the second regulating valve according to the setting conditions;
and 4, automatically reducing the opening degree of the second regulating valve according to the set conditions.
6. The steam supplementing control method of the double-cylinder double-pressure waste heat generating set according to claim 5, wherein in the step 1, the condition for starting to operate the second regulating valve comprises the following steps: the control method comprises the steps that a generator set is connected to the power grid, the power of the generator set is larger than a set first threshold rated power, the opening of a first regulating valve is larger than a set first threshold opening, a main steam regulating unit is under the control of the first regulating valve, a second quick-switching valve is fully opened, the steam temperature of a heater air outlet is larger than a first threshold temperature, the steam temperature difference between the heater air outlet and a generator set steam supply opening is smaller than a second threshold temperature, and the pressure ratio of a generator set regulating level to the steam supply opening is larger than a set value.
7. The steam supplementing control method of the double-cylinder double-pressure waste heat generator set according to claim 6, wherein in the step 1, when the second regulating valve is in the operation process and any one of the following conditions is met, the second regulating valve is automatically closed and is locked in function: (1) tripping the generator set; (2) splitting the generator; (3) the power of the generator set is less than the set second threshold rated power; (4) the opening degree of the first regulating valve is smaller than a set second threshold opening degree; (5) the pressure difference between the air inlet and the air outlet of the second regulating valve is less than the set threshold pressure; (6) the steam temperature at the air outlet of the heater is less than a first threshold temperature; (7) the steam temperature difference between the air outlet of the heater and the steam supplementing port of the generator set is larger than a second threshold temperature; (8) the pressure ratio of the regulating stage of the generator set to the steam supplementing port is less than a set value; the first threshold value rated power is larger than the second threshold value rated power, the first threshold value opening degree is larger than the second threshold value opening degree, and the first threshold value temperature is larger than the second threshold value temperature.
8. The steam supplementing control method of the double-cylinder double-pressure waste heat generator set according to claim 5, wherein in step 3 or step 4, the specific method for automatically controlling the opening of the second regulating valve according to the setting condition comprises the following steps: calculating the deviation delta X between the set value SP of the process parameter and the measured value PV, wherein the delta X is the regulation deviation; then, using PID automatic operation, the size of the opening of the second regulating valve is controlled so that Δ X ≈ SP-PV ≈ 0.
9. The steam supplementing control method of the double-cylinder double-pressure waste heat generator set according to claim 8, characterized in that in the PID automatic operation process, a negative deviation regulation dead zone is set for PID, and the negative deviation regulation dead zone is set to (M,0), M is a negative number, when Δ X is a positive deviation, that is, SP > PV, the PID automatically increases the opening degree of the second regulating valve; when the delta X is less than M, namely SP is less than PV + M, the PID automatically reduces the opening degree of the second regulating valve; when M is larger than delta X and smaller than 0, PID does not operate, and the opening degree of the second regulating valve is kept.
10. The steam supplementing control method of the double-cylinder double-pressure waste heat generator set according to claim 9, characterized in that a gentle set value processing function is introduced in the PID automatic adjustment process to make the change of the set value SP gentle.
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