WO2019165839A1 - Procédé de régulation de température de chaudière à vapeur surchauffée, dispositif et système - Google Patents

Procédé de régulation de température de chaudière à vapeur surchauffée, dispositif et système Download PDF

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WO2019165839A1
WO2019165839A1 PCT/CN2018/124152 CN2018124152W WO2019165839A1 WO 2019165839 A1 WO2019165839 A1 WO 2019165839A1 CN 2018124152 W CN2018124152 W CN 2018124152W WO 2019165839 A1 WO2019165839 A1 WO 2019165839A1
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temperature
desuperheater
value
outlet
stage
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PCT/CN2018/124152
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English (en)
Chinese (zh)
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张喜
耿国
潘再生
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德普新源（香港）有限公司
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22G—SUPERHEATING OF STEAM
    • F22G5/00—Controlling superheat temperature
    • F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays
    • F22G5/123—Water injection apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22G—SUPERHEATING OF STEAM
    • F22G5/00—Controlling superheat temperature
    • F22G5/20—Controlling superheat temperature by combined controlling procedures

Definitions

  • the invention relates to boiler intelligent control technology, and more particularly to a temperature control method, device and system for boiler superheated steam.
  • the superheated steam temperature of the boiler is an important parameter that affects the safety and economy of the unit's production process.
  • the superheater of modern boilers works under high temperature and high pressure conditions.
  • the superheated steam temperature at the outlet of the superheater is the highest point of the working temperature in the whole steam stroke of the unit, and it is also the highest point of the metal wall temperature.
  • the superheater is made of high temperature and high pressure resistant alloy material.
  • the normal operating temperature of the superheater is close to the maximum temperature allowed by the material. If the temperature of the superheated steam is too high, it will easily damage the superheater, and it will cause excessive thermal expansion of some components in the steam pipeline and the steam turbine, which will damage the safe operation of the unit.
  • the thermal efficiency of the unit will be reduced.
  • the steam temperature is reduced by 5-10 °C, and the thermal efficiency is reduced by about 1%, which not only increases the fuel consumption, wastes energy, but also makes the steam humidity of the last stage of the steam turbine. Increase, accelerate water erosion of turbine blades.
  • the decrease of the superheated steam temperature will also cause the enthalpy of the steam in the high-pressure stage of the steam turbine to decrease, causing the reaction to increase and the axial thrust to increase, which also adversely affects the safe operation of the turbine. Therefore, the temperature of the superheated steam is too high or too low, which is not allowed in the production process.
  • the flat steam temperature characteristics can be obtained.
  • the superheater outlet steam temperature is within a certain load range, and the boiler load is still increased. Raised.
  • the control of the superheated steam temperature is to maintain the temperature of the superheated outlet steam within the allowable range and protect the superheater so that the wall temperature does not exceed the allowable operating temperature.
  • the temperature of superheated steam can generally be regarded as a controlled object of multi-capacity distribution parameters, and its dynamic characteristic description can be expressed by multi-capacity inertia link, and the object has obvious hysteresis characteristics.
  • the superheated steam temperature object In addition to the characteristics of multi-capacity, large inertia and large delay, the superheated steam temperature object also exhibits certain nonlinear and time-varying characteristics.
  • the desuperheater control system of superheated steam is usually a cascade two-loop control system.
  • the schematic block diagram is shown in Figure 1. It has two internal and external loops.
  • the inner loop is composed of a desuperheater outlet steam temperature transmitter, a sub-regulator, an actuator, a desuperheating water regulating valve and a desuperheater;
  • the outer loop is composed of a main steam temperature transmitter, a main regulator and an entire inner loop. Connected to form.
  • the main steam temperature at the superheater outlet is the adjusted variable of the main loop regulation loop, and the actual temperature feedback value is sent to the main loop to be compared with its set value to form the temperature deviation value of the steam temperature at the superheater outlet.
  • the desuperheater outlet temperature is the adjusted variable of the secondary loop regulating loop, and the measured value of the temperature is sent to the secondary loop to be compared with its given value to form a temperature deviation value of the steam temperature at the outlet of the desuperheater.
  • the set value of the secondary loop is formed by superimposing the output of the primary loop controller and the temperature feedforward value.
  • the control system usually introduces a temperature feedforward value, such as the differential value of the steam flow, the differential value of the fuel command, the main steam pressure value, and the combustion air volume value.
  • the temperature setting of the desuperheater controller is the load function curve in the normal operation mode of the boiler, or the operator manually inputs the temperature setting value according to the operating state of the boiler.
  • Superheated steam temperature regulation usually uses water spray and temperature reduction as the main adjustment means. Due to the high quality of the boiler feed water, the desuperheater usually uses feed water as the cooling medium.
  • the method of water spray desuperheating is to spray water directly into the superheated steam to be mixed with it, and the heat absorbed by the superheated steam heats itself, evaporates, overheats, and finally becomes part of the superheated steam.
  • the superheated steam that has been tempered is cooled due to heat release, and the temperature adjustment is achieved.
  • the water spray desuperheating adjustment operation is simple. As long as the corresponding desuperheating water is adjusted according to the change of the steam temperature to adjust the valve opening degree, the desuperheating water entering the desuperheater can be changed to achieve the purpose of adjusting the superheated steam temperature.
  • the large desuperheater regulating valve increases the amount of desuperheating water; when the steam temperature is low, the small regulating valve reduces the amount of desuperheating water, or the desuperheater is taken out of operation as needed.
  • the conventional desuperheater control method is cascade control of two PID controllers (proportional-integral-derivative controller). Since the primary and secondary loops in the cascade system are two independent and closely related loops. If, under certain disturbances, the change of the main parameter enters the secondary loop, the amplitude of the parameter in the secondary loop is increased, and the change of the secondary parameter is transmitted to the primary loop, and the amplitude of the primary parameter is forced to increase, so that the cycle is repeated. It will cause the main and auxiliary parameters to fluctuate greatly for a long time. This is the so-called "resonance phenomenon" of the cascade system. Once resonance occurs, the system loses control.
  • PID controllers proportional-integral-derivative controller
  • the two PID controllers are in a series structure and work in one system, they have more or less influences on each other, so the tuning of the parameters in the cascade control system is better than the single PID.
  • the controller (proportional-integral-derivative controller) system is complex and debugging is more difficult. Especially for biomass boilers, the type of fuel, moisture, and calorific value will change at any time and cannot be predicted. This conventional desuperheater control method cannot meet the control requirements in biomass boiler control.
  • the thermal power boiler superheating system adopts two-stage desuperheater design, and the control process and control target of the two-stage desuperheater are completely independent.
  • a multi-stage desuperheating system may be used, such as a three-stage desuperheating system, if three conventional cascade two-loop control methods are used to separately control three
  • the desuperheater system there will be inconsistencies in the adjustment direction of the desuperheaters in the system when the temperature of the superheated steam changes between different desuperheaters, and the contradiction between the front and the back will cause the superheated steam temperature to fluctuate greatly.
  • the temperature of the primary superheater outlet after the primary desuperheater rises, and the amount of water sprayed by the secondary and tertiary desuperheaters does not change.
  • the corresponding superheater outlet temperature will rise, therefore, in order to maintain the set superheater outlet temperature remains unchanged, the first, second, and third stage desuperheaters will increase the amount of water spray, after several control cycles, one
  • the superheater outlet temperature after the stage desuperheater returns to the set value. At this time, the superheater outlet temperature after the second stage and third stage desuperheater will cause the temperature to fall below the setting due to the injection of excessive desuperheating water.
  • the secondary and tertiary desuperheaters will simultaneously reduce the amount of desuperheated water injected at the same time.
  • the superheater outlet temperature after the secondary desuperheater returns to the set value
  • the superheater temperature after the tertiary desuperheater When it exceeds the set value, the third stage desuperheater will increase the amount of water spray and eventually restore the superheater temperature to the set value.
  • the three desuperheaters are independent of each other, the actual action in the adjustment process is inconsistent with the expected target.
  • the PID controller (proportional-integral-derivative controller) is composed of a proportional unit P, an integral unit I and a differential unit D. Through the setting of three parameters of Kp, Ki and Kd.
  • the PID controller (proportional-integral-derivative controller) is mainly suitable for systems where the basic linearity and dynamic characteristics do not change with time.
  • the PID controller is a common feedback loop component for industrial control applications.
  • the controller compares the collected data with a setpoint and then uses this difference to calculate a new input value.
  • the purpose of this new input value is to allow the system's data to be reached or maintained at the setpoint.
  • the PID controller can adjust the input value based on the historical data and the occurrence rate of the difference, which makes the system more accurate and more stable. It can be proved mathematically that a PID (proportional-integral-derivative) feedback loop can keep the system stable while other control methods cause the system to have stable errors or process iterations.
  • Biomass boilers transfer energy from the flue gas produced by the fuel to the superheated steam by burning the biomass solid fuel.
  • Superheated steam is delivered to the steam turbine power generation system to convert thermal energy into electrical energy.
  • the superheater system of the biomass boiler contains a four-stage superheater, as shown in Figure 2.
  • the saturated steam is introduced into the saturated steam collecting tank by the saturated steam connecting pipe on the drum, and enters the primary superheater along the connecting pipe.
  • the superheater is arranged in the reverse flow direction, and after exiting the primary superheater, it is desuperheated by the primary desuperheater and then enters the first stage.
  • the superheater is then passed through the secondary desuperheater, the secondary superheater, the tertiary desuperheater, the tertiary superheater, and then into the main steam pipe, and finally the main steam pipe enters the steam turbine.
  • the present invention provides a temperature control method, apparatus and system for boiler superheated steam.
  • a temperature control method for superheated steam of a boiler comprising: step 1: obtaining an outlet temperature of the desuperheater of the stage, and obtaining an outlet temperature of the superheater of the stage; and step 2: calculating a temperature feedforward of the desuperheater of the stage Value; Step 3: Calculate the temperature deviation value of the superheater of this stage; Step 4: Send the result of adding the temperature feedforward value and the temperature deviation value to the PID controller, and control the water spray of the desuperheater by the PID controller the amount.
  • step 2 includes: step 21: setting a first-order function Pt(x) and an integral function I(x), the time coefficient of the first-order function and the time coefficient of the integral function are linearly related to the boiler load value; step 22: calculating The temperature feedforward value of this stage, the formula is:
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • X t is the outlet temperature of the current stage desuperheater at time t
  • K is a proportional coefficient
  • the initial value of Z is the outlet temperature of the desuperheater of the present stage.
  • the temperature feedforward value of the desuperheater outlet can be used to predict the temperature change trend of the desuperheater of the stage, and the pre-judgment is given. After superimposing on the PID controller, the desuperheating water can be controlled more accurately, so that the desuperheater The temperature of the outlet changes smoothly.
  • step 2 further includes: step 23: outputting a temperature feedback value Z t+1 of the outlet of the stage desuperheater for calculating a temperature deviation value of the upper superheater outlet.
  • step 3 includes: step 31: setting a set value or calculating a set value; and step 32: calculating a difference between the superheater outlet temperature of the stage and the set value as a temperature deviation value.
  • the set value can be set manually or calculated. There are two calculation methods:
  • min is a small function
  • f(x) is a function
  • x is the main steam flow of the boiler load
  • ⁇ t is a manually set correction value
  • a temperature control device for superheated steam of a boiler including a desuperheater, a superheater connected to the desuperheater, a feedforward module connected to the outlet of the desuperheater, and a connection to the outlet of the superheater.
  • a deviation calculation module an adder, a PID controller, a desuperheater regulating valve connected to the PID controller and the desuperheater, wherein
  • a feedforward module is connected between the desuperheater outlet and the adder module for obtaining the temperature of the desuperheater outlet, calculating a temperature feedforward value and outputting to the adder;
  • the feedforward module includes a first order function Pt(x) and The integral function I(x), the time coefficient of the first-order function and the time coefficient of the integral function are linear with the boiler load value; the temperature feedforward value is calculated as:
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • X t is the outlet temperature of the current stage desuperheater at time t
  • K is a proportional coefficient
  • the initial value of Z is the outlet temperature of the desuperheater of the present stage.
  • the feedforward module further outputs a temperature feedback value Z t+1 of the desuperheater outlet to the deviation calculation module of the upper desuperheater.
  • the deviation calculation module is connected between the outlet of the superheater and the adder for obtaining the temperature of the superheater outlet and comparing with the set value, taking the difference between the superheater outlet temperature and the set value as the temperature deviation value, and then The temperature deviation value is sent to the adder.
  • the set value in the deviation calculation module can be set manually or as one of the following formulas:
  • min is a small function
  • f(x) is a function
  • x is the main steam flow of the boiler load
  • ⁇ t is a manually set correction value
  • min(x, y) is the value of the small of x and y.
  • the expected front and rear temperature difference of the lower stage desuperheater is generated by the function of the main steam flow value representing the boiler load, and the operator can set a correction value for the front and rear temperature difference.
  • An adder is configured to receive the values sent by the feedforward module and the deviation calculation module, sum the values, and send the results to the PID controller.
  • the PID controller is configured to receive the summation result of the temperature values sent by the adder, and control the desuperheater regulating valve to adjust the water spray amount of the desuperheater by calculating the output valve position opening value.
  • a temperature control system for a superheated steam of a boiler comprising a first-stage desuperheater, a first-stage superheater, a second-stage desuperheater, a second-stage superheater, and a third-stage desuperheating.
  • the three-stage superheater, the first-stage desuperheater outlet is also connected to the first feedforward module, the first adder, the first PID controller, the first-stage desuperheater regulating valve, and the secondary desuperheater outlet is also compliant.
  • the second feedforward module, the second adder, the second PID controller, the second desuperheater regulating valve are connected, and the third stage desuperheater outlet is also connected to the third feedforward module, the third adder, and the third The PID controller and the third desuperheater regulating valve;
  • the first-stage superheater sequentially connects the first deviation calculating module, the first adder, and the second-stage superheater sequentially connects the second deviation calculating module, the second adder, and the third-stage The superheater sequentially connects the third deviation calculation module and the third adder;
  • a first feedforward module configured to acquire a connected first-stage desuperheater outlet temperature, and send a first temperature feedforward value to the first adder
  • a second feedforward module is configured to obtain a secondary desuperheater outlet temperature, send a second temperature feedforward value to the second adder, and further send a temperature feedback value of the secondary desuperheater outlet to the first deviation calculation module;
  • a third feedforward module is configured to obtain a third-stage desuperheater outlet temperature, send a third temperature feedforward value to the third adder, and further send a temperature feedback value of the third-stage desuperheater outlet to the second deviation calculation module;
  • the first deviation calculating module takes the difference between the first-stage superheater outlet temperature and the first set value as a temperature deviation value, and then sends the temperature deviation value to the first adder;
  • the second deviation calculation module takes the difference between the secondary superheater outlet temperature and the second set value as a temperature deviation value, and then sends the temperature deviation value to the second adder;
  • a third deviation calculating module the difference between the tertiary superheater outlet temperature and the third set value is taken as a temperature deviation value, and then the temperature deviation value is sent to the third adder;
  • An adder for outputting the result of adding the input values
  • a PID controller for converting temperature information into a control value
  • the desuperheater regulating valve receives the control value of the PID control and adjusts the water spray amount of the desuperheater.
  • the feedforward module includes a first-order function Pt(x) and an integral function I(x), and the time coefficient of the first-order function and the time coefficient of the integral function are linearly related to the boiler load value;
  • the formula for the value of the feed and temperature feedback is:
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • each level module can set each level function and proportional coefficient according to the demand
  • X t is the outlet temperature of the desuperheater connected to the feedforward module at time t
  • the initial value of Z is the outlet of the desuperheater temperature
  • the first set value min ((the expected temperature difference before and after the secondary desuperheater + the desuperheater temperature feedback value of the secondary desuperheater feedforward module output), the upper temperature limit of the first superheater outlet) ;
  • the second set value min ((the expected front and rear temperature difference of the three-stage desuperheater + the desuperheater temperature feedback value of the three-stage desuperheater feedforward module output), the upper temperature limit of the secondary superheater outlet);
  • the third set value min ((f (x) + ⁇ t), the upper limit of the tertiary superheater outlet temperature)
  • min is a small function
  • f(x) is a function
  • x is the main steam flow of the boiler load
  • ⁇ t is a manually set correction value
  • the expected front and rear temperature difference of the desuperheater is generated by the function of the main steam flow value representing the boiler load, and the operator can set a correction value for the front and rear temperature difference.
  • biomass boilers are composed of four-stage superheaters, that is, a superheater is connected in front of the primary desuperheater, so that the temperature of the superheated steam having the structure of the four-stage superheater plus the three-stage desuperheater can be connected in series.
  • Control System Generally, biomass boilers are composed of four-stage superheaters, that is, a superheater is connected in front of the primary desuperheater, so that the temperature of the superheated steam having the structure of the four-stage superheater plus the three-stage desuperheater can be connected in series.
  • a set of desuperheaters, superheaters and corresponding feedforward modules and deviation calculation modules can be added/reduced in front of the above-mentioned three-stage desuperheater to meet actual needs.
  • one or more computer readable storage media storing computer readable instructions which, when executed by a device, cause the device to perform a temperature control method of the aforementioned boiler superheated steam.
  • the one or more computer readable storage media of this aspect of the invention may be, for example, one or more non-transitory computer readable media.
  • the technical solution of the invention adopts a PID controller instead of two PID controllers in the cascade double loop control system, which simplifies the controller structure and makes the control loop more simple in application.
  • the control circuit of the three-stage desuperheater of the present invention is related to each other and the control target is consistent, and the set value of the primary and secondary desuperheaters is changed from controlling the temperature of the superheater outlet to the temperature of the latter stage. The sum of the temperature difference before and after the device and the inlet temperature of the superheater will prevent the other superheaters from being opposite to each other due to fluctuations in the temperature of the superheated steam occurring during the adjustment of a certain stage desuperheater.
  • control system of the present invention also introduces a feedforward module to reflect the hysteresis and inertia characteristics of the superheated steam temperature change after the desuperheater is sprayed, so that the superheated steam temperature can be quickly and accurately adjusted to the set value.
  • Figure 1 is a schematic block diagram of a boiler double-loop control system for superheated steam temperature
  • FIG. 2 is a schematic diagram of a four-stage structure of a boiler superheated steam temperature control system
  • FIG. 3 is a flow chart of a method for controlling temperature of superheated steam of a boiler according to an embodiment of the present invention
  • FIG. 4 is a schematic structural view of a feedforward module of a temperature control device or system for superheated steam of a boiler according to an embodiment of the present invention
  • FIG. 5 is a schematic diagram showing the time coefficient of a function in a feedforward module of a boiler superheated steam temperature control device or system according to an embodiment of the present invention
  • FIG. 6 is a dynamic graph of superheated steam temperature in a feedforward module of a boiler superheated steam temperature control device or system according to an embodiment of the present invention
  • FIG. 7 is a schematic diagram of calculating an expected temperature difference in a deviation calculation module of a temperature control device or system for a superheated steam of a boiler according to an embodiment of the present invention
  • FIG. 8 is a schematic structural view of a temperature control device for superheated steam of a boiler according to an embodiment of the present invention.
  • FIG. 9 is a schematic structural view of a temperature control device for superheated steam of a boiler according to another embodiment of the present invention.
  • Figure 10 is a schematic view showing the structure of a temperature control system for superheated steam of a boiler according to an embodiment of the present invention.
  • a method for controlling the temperature of the superheated steam of the boiler includes the following steps: Step 1: Acquire the outlet temperature of the desuperheater of the stage, and obtain the outlet temperature of the superheater of the stage; Step 2: Calculate the reduction of the stage Temperature feedforward value of the heater outlet; Step 3: Calculate the temperature deviation value of the superheater outlet of the stage; Step 4: Send the result of adding the temperature feedforward value and the temperature deviation value to the PID controller, and control by the PID controller The water volume of the desuperheater of this class.
  • step 2 the temperature feedforward value is used to simulate the change in the temperature of the superheated steam in the superheater after the water spray is desuperheated. Its calculation method is as follows:
  • the first-order function Pt(x) and the integral function I(x) are set.
  • the time coefficient Tu of the first-order function is linear with the boiler load value.
  • Tu is a piecewise function.
  • Tu 300s
  • Tu 300s
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • X t is the outlet temperature of the desuperheater connected to the feedforward module D T at time t
  • the initial value of Z is the outlet temperature of the desuperheater
  • a multi-stage superheater is connected to the desuperheater, such as the 4-stage superheater and the 3-stage desuperheater structure shown in Fig. 2, the temperature feedback of the outlet of the desuperheater of the stage is also calculated and output.
  • the value Z t+1 is also calculated and output.
  • step 3 the temperature deviation value represents the expected deviation of the outlet temperature of the superheater.
  • the calculation method is:
  • the expected front-to-back temperature difference of the lower stage desuperheater is generated by the main steam flow value representing the boiler load via the function f(x), and the correction value can also be manually given.
  • the function f(x) is as shown in FIG. 7, and can be specifically modified according to the actual operating conditions of the boiler.
  • the temperature difference obtained before and after the step is added and the correction value is added and compared with the upper limit temperature of the outlet of the superheater of the stage, and a smaller value is taken as the set value of the desuperheater of the stage.
  • min is a small function
  • f(x) is a function
  • x is the main steam flow of the boiler load
  • ⁇ t is a manually set correction value
  • step 4 the result of adding the temperature feedforward value and the temperature deviation value is sent to the PID controller, and the PID controller controls the desuperheater water spray amount. Specifically, if the PID input is greater than 0, the PID output continues to increase, the temperature of the desuperheating water valve is continuously increased, and the water spray volume is continuously increased; when the PID input is equal to 0, the PID output remains unchanged, and the desuperheating water valve opening degree is maintained. It also remains unchanged, and the amount of water spray remains unchanged. If the PID input is less than 0, the PID output will continue to decrease, the opening of the desuperheating water valve will continue to decrease, and the amount of water spray will continue to decrease. By such control, the amount of water sprayed by the desuperheater can be adjusted to adjust the temperature of the superheated steam.
  • the temperature control method of boiler superheated steam disclosed herein may be implemented in an apparatus configured to include circuitry to perform the method, or may also be implemented using software stored on one or more computer readable storage media.
  • the computer readable medium includes computer executable instructions that, when executed by a device, cause the device to perform a temperature control method of the boiler superheated steam described above.
  • Such computer readable storage medium can be, for example, a non-transitory computer readable medium.
  • a temperature control device for superheated steam of a boiler comprising a desuperheater, a superheater connected to the desuperheater, a deviation calculation module connected to the outlet of the superheater, connected before the outlet of the desuperheater
  • the adder module is connected to the PID control module, the deviation calculation module and the feedforward module D T for adding the output of the deviation calculation module and the output value of the pre-feedback module, and the result is sent to the PID control module.
  • the PID control module is configured to receive the result sent by the adder module, control the connected desuperheating water regulating valve, thereby controlling the amount of water spray to achieve the purpose of adjusting the desuperheater.
  • the water spray flow rate of the desuperheater can be calculated from the steam enthalpy before and after the desuperheater.
  • the feedforward module D T operates according to the compensation principle according to the disturbance or the change of the given value.
  • the characteristic is that after the disturbance is generated, before the controlled variable has not changed, the control is performed according to the magnitude of the disturbance action to compensate the disturbance action pair.
  • the feedforward module D T is used properly, so that the disturbance of the controlled variable can be eliminated in the bud, so that the controlled variable will not be biased due to the disturbance action or the given value change, and it can be controlled more timely than the feedback control. And is not affected by system lag.
  • the feedforward module D T is connected between the desuperheater outlet and the adder module for obtaining the temperature of the desuperheater outlet, calculating the temperature feedforward value and then outputting the temperature feedforward value to the adder, as shown in FIG.
  • the feedforward module D T can also output the temperature feedback value of the desuperheater outlet to the deviation calculation module of the upper desuperheater.
  • the feedforward module D T is mainly composed of a first-order function Pt(x) and an integral function I(x), and the feedforward module D T performs a loop operation in real time, that is, this is a cycle cycle calculation process, and the next cycle calculation is used. The result of the previous cycle.
  • the function of the first-order function Pt is reflected in the superheater after the superheated steam has been sprayed and desuperheated.
  • the function of the integral function I can reflect the inertia and balance process of the superheated steam in the superheater after being sprayed and desuperheated. Therefore, the two functions can be combined to simulate the superheated steam spray reduction.
  • the dynamic curve of the input value X in the feedforward module D T is as shown in FIG. 6 .
  • the input value passes through the exit of the integral function I, it is split into two values, one is the temperature feedback value Z of the desuperheater outlet, and is output to the deviation module of the upper desuperheater for the set value calculation of the upper desuperheater. .
  • the difference between the other output value Y and the input value X is multiplied by the proportional coefficient K to form a temperature feedforward value output to the adder.
  • the temperature feedforward value and temperature feedback value of the desuperheater are calculated as:
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • X t is the outlet temperature of the desuperheater connected to the feedforward module D T at time t
  • the initial value of Z is the outlet temperature of the desuperheater
  • the feedforward module D T can be used to simulate the hysteresis and inertia characteristics of the superheated steam temperature change after the desuperheater sprays water.
  • each desuperheater includes a feedforward module.
  • the deviation calculation module is connected to the outlet of the superheater and the adder module for obtaining the temperature of the superheater outlet and comparing with the set value, and taking the difference between the outlet temperature and the set value as the temperature deviation value of the outlet temperature of the superheater Then, the temperature deviation value is sent to the adder module.
  • the set value can be set or calculated, and the calculation method has been described above.
  • the temperature control device consists of a primary desuperheater and a superheater and their associated modules. By expanding the cascade, a multi-stage temperature control system with temperature feedback can be connected in series.
  • a temperature control system for superheated steam of a boiler is provided, as shown in FIG. 10, which includes a first stage desuperheater, a first stage superheater, a second stage desuperheater, and a second stage.
  • the first-stage desuperheater outlet is also connected to the first feedforward module, the first adder, the first PID controller, the first-stage desuperheater regulating valve, and the second
  • the stage desuperheater outlet is also connected to the second feedforward module, the second adder, the second PID controller and the second desuperheater regulating valve in sequence
  • the third stage desuperheater outlet is also connected to the third feedforward module in sequence.
  • the first superheater is sequentially connected to the first deviation calculating module, the first adder, and the second superheater is sequentially connected to the second deviation calculating module, a second adder, the third-stage superheater is sequentially connected to the third deviation calculation module and the third adder;
  • a primary superheater is added in front of the primary desuperheater to conform to the temperature control system structure of the boiler superheated steam shown in FIG. 2, and the principle of the three-stage desuperheater control in the entire desuperheater system
  • the block diagrams are shown in Figures 8, 9, and 10.
  • the first feedforward module is configured to acquire the connected first-stage desuperheater outlet temperature, and send the first temperature feedforward value to the first adder; where the first feedforward module no longer generates the outlet temperature feedback value. However, if it is necessary to increase the level, the temperature feedback value can also be output to the pre-deviation calculation module;
  • a second feedforward module is configured to obtain a secondary desuperheater outlet temperature, send a second temperature feedforward value to the second adder, and further send a secondary desuperheater outlet temperature feedback value to the first deviation calculation module;
  • a third feedforward module is configured to obtain a third-stage desuperheater outlet temperature, send a third temperature feedforward value to the third adder, and further send a third-stage desuperheater outlet temperature feedback value to the second deviation calculation module;
  • the first deviation calculating module takes the difference between the first-stage superheater outlet temperature and the first set value as a temperature deviation value, and then sends the temperature deviation value to the first adder;
  • the second deviation calculation module takes the difference between the secondary superheater outlet temperature and the second set value as a temperature deviation value, and then sends the temperature deviation value to the second adder;
  • the third deviation calculation module takes the difference between the tertiary superheater outlet temperature and the third set value as a temperature deviation value, and then sends the temperature deviation value to the third adder;
  • Adder for each stage, for outputting the result of adding the input values
  • PID controllers at various levels for converting temperature information into control values
  • the desuperheater regulating valve of each stage receives the control value of the PID control and adjusts the water spray amount of the desuperheater.
  • the temperature feedforward value of the desuperheater is calculated as:
  • Temperature feedforward value K*(X t+1 -Z t+1 )
  • X t is the outlet temperature of the desuperheater to which the feedforward module is connected at time t
  • the initial value of Z is the outlet temperature of the desuperheater at the start time.
  • the first set value min ((the expected temperature difference before and after the secondary desuperheater + the desuperheater temperature feedback value of the secondary desuperheater feedforward module output), the upper temperature limit of the first superheater outlet) ;
  • the second set value min ((the expected front and rear temperature difference of the three-stage desuperheater + the desuperheater temperature feedback value of the three-stage desuperheater feedforward module output), the upper temperature limit of the secondary superheater outlet);
  • the third set value is the last level, so another calculation method is used:
  • the third set value min ((f (x) + ⁇ t), the upper limit of the outlet temperature of the superheater of this stage)
  • min is a small function
  • f(x) is a function
  • x is the main steam flow of the boiler load
  • ⁇ t is a manually set correction value
  • the expected front and rear temperature difference of the desuperheater is generated by the function of the main steam flow value representing the boiler load, and the operator can set a correction value for the front and rear temperature difference.
  • This set value calculation method can not only establish the mutual connection between different desuperheaters, but also convert the absolute temperature value control of the lower stage and the lower stage desuperheater into relative temperature value control.
  • the set value will be Follow the dynamic change of the outlet temperature of the desuperheater, so that when the temperature of the superheated steam in the first stage desuperheater fluctuates during the adjustment process, the set values of the other desuperheaters will be automatically corrected, so that the other decrements will not be affected.
  • the temperature control of the temperature controller avoids large fluctuations in the adjustment of the entire desuperheater system, so that all desuperheaters are in a stable and controllable state.
  • the set value of the three-stage desuperheater (such as 540 °C) is generated according to the boiler load, and the deviation between the set value and the outlet temperature of the tertiary superheater (T 0 in the figure)
  • the sum of the temperature feedforward value of the feedforward module D T output (such as [1] in the figure) forms a total temperature deviation.
  • the PID output continues to increase, and the third stage desuperheater water valve opening is continuously
  • the PID output remains unchanged, and the third-stage desuperheater regulator valve opening remains unchanged; if the temperature deviation is less than 0, the PID output continues to decrease, and the tertiary desuperheater water level The valve opening is constantly getting smaller.
  • the minimum value is the set value of the secondary desuperheater, the deviation between the set value and the outlet temperature of the secondary superheater (T 2 in the figure) and the temperature feedforward value of the feedforward module D T (as shown in the figure [3] The sum of the ]) forms a total temperature deviation.
  • the opening degree of the water regulator valve of the secondary desuperheater becomes larger; when the total temperature deviation is equal to 0, the opening degree of the water regulator of the secondary desuperheater is also It remains unchanged; if the temperature deviation is less than 0, the opening degree of the water regulator valve of the secondary desuperheater becomes smaller.
  • the temperature feedback value of the feedforward module D T of the secondary desuperheater (as shown in [4] 420 ° C and the expected temperature drop before and after the secondary desuperheater (50 ° C in the figure) and the high limit S p
  • the minimum value is the set value of the primary desuperheater, the deviation between the set value and the outlet temperature of the primary superheater (T 4 in the figure) and the temperature feedforward value of the feedforward module D T (as shown in the figure [5] The sum of the ]) forms a total temperature deviation.
  • the opening degree of the first-stage desuperheater water regulating valve becomes larger; when the total temperature deviation is equal to 0, the first-stage desuperheater water regulating valve opening degree is also It remains unchanged; if the temperature deviation is less than 0, the opening degree of the water regulator valve of the first stage desuperheater becomes smaller.
  • the device and the system the corresponding desuperheater, superheater and related modules can be added and reduced to meet actual needs.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Feedback Control In General (AREA)

Abstract

L'invention concerne un procédé de régulation de température de chaudière à vapeur surchauffée, dispositif et système. Le procédé de régulation de température comprend les étapes suivantes : étape 1 : consistant à acquérir une température de sortie d'un désurchauffeur de niveau actuel et d'une température de sortie d'un surchauffeur de niveau actuel; étape 2 : consistant à calculer une valeur de température prédictive du désurchauffeur de niveau actuel; étape 3 : consistant à calculer une valeur de température d'écart de sortie du surchauffeur de niveau actuel; et étape 4 : consistant à envoyer un résultat d'ajout de la valeur de température prédictive et de la valeur de température d'écart à un régulateur PID, et réguler la quantité d'eau pulvérisée du désurchauffeur de niveau actuel à l'aide du régulateur PID. Le procédé fourni par la présente invention permet de prédire fidèlement et avec précision la tendance de changement de la température de vapeur surchauffée, après avoir traversé un désurchauffeur, dans un système surchauffeur, de telle sorte qu'un dispositif de régulation détermine et régule de manière précise la quantité d'eau pulvérisée du désurchauffeur, et enfin, une température de vapeur surchauffée est maintenue dans une plage requise pour le fonctionnement de la chaudière.
PCT/CN2018/124152 2018-03-01 2018-12-27 Procédé de régulation de température de chaudière à vapeur surchauffée, dispositif et système WO2019165839A1 (fr)

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