JPH05280703A - Boiller scale estimating device - Google Patents

Abstract

PURPOSE:To indicate the present scale of the heat transfer surfaces of a boiler and predict and indicate the scale at an optional succeeding step. CONSTITUTION:From information of sensors 21, a state judging device 23 judges how a boiler is operated on what loading level at present. A fuel property decision device 24 decides the fuel property from fuel information 22. A gas temperature cumulative arithmetic device 25 performs cumulative arithmetic according to information from the state judging device 23 and the fuel property decision device 24, and estimates the gas temperatures on the heat transfer surfaces to obtain the heat transmission coefficient. A static scale state arithmetic device 27 compares the heat transmission coefficient with that obtained from actual observations to obtain a static scale state factor. A dynamic characteristic scale arithmetic device 28 obtains a dynamic characteristic scale factor from the static scale state factor, and the estimation device 29 obtains the scale state at an optional succeeding step and indicate it on the scale indicator 30.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] The present invention relates to a boiler contamination estimating device for estimating the contamination state of each heat transfer surface in a commercial or industrial boiler.

[0002]

2. Description of the Related Art In a conventional thermal power plant, the electric power supplied is a low load, but recently, DSS has been used.
(Daily start / stop) is progressing, and it is compensating for the insufficient load. If the electric power supplied as in the conventional case is a low load, there is no load fluctuation, and the contamination of the heat transfer surface is proportional to the elapsed time. Moreover, since the types of coal used in the coal-fired boiler plant were 1 to 2 types, the manner of fouling by the coal type was uniform, and it was not necessary to estimate the fouling of the heat transfer surface of the boiler, and it was not necessary to estimate the fouling of the boiler heat transfer surface at regular intervals. I was activating the sootblower device. When a start command is given, the soot blower device blows steam inside or outside the boiler onto the heat transfer surface for cleaning.

[0003]

However, recently, D
Due to rapid load fluctuations due to SS and multi-carbon type fuel, stains on each heat transfer surface of the boiler are much more diverse than in the past. In addition, since the boiler is a plant with a large time constant, when the load fluctuations increase, it is not possible to immediately observe the fluctuations, which results in the handling of data during plant transients, resulting in a decrease in reliability. There was a problem. Further, it is up to the plant operator's subjectivity to judge the state of dirt, and automation of the apparatus has not yet been made.

The present invention has been made in view of the above-mentioned circumstances, and can monitor the fouling state of the boiler heat transfer surface regardless of the transient state of the boiler due to load fluctuations and the difference in fuel type during normal operation. It is an object of the present invention to provide a boiler fouling estimation device that can predict fouling of a boiler heat transfer surface several steps away.

[0005]

A boiler fouling estimation apparatus according to the present invention is a state determination apparatus for grasping the operating status of a boiler from observation values obtained from various sensors, and a fuel property used by the boiler from fuel information. A fuel property determination device that determines the gas temperature, a gas temperature stacking calculation device that determines the gas temperature of each boiler heat transfer surface by a stacking method, and a heat transfer coefficient calculation that calculates the boiler heat transfer coefficient from the gas temperature obtained by this calculation device. The device, a static state fouling computing device for obtaining a fouling index in the boiler from the ratio of the fouling factor obtained by this heat fusing factor calculation device and the actual observation value,
A dynamic characteristic dirt calculator for calculating a dynamic dirt index by performing a metal temperature correction process and a time averaging process for pipes based on a static state dirt index and a dynamic characteristic correspondence model obtained by this calculator, and this dynamic characteristic dirt calculator A stain prediction device for predicting stain at an arbitrary step destination from the obtained stain index and data of the past several points is provided.

[0006]

[Operation] Observe each state of the plant by various sensors,
The state determination device determines which load level the boiler is currently operating, and when it is determined that the boiler is in a state of, for example, 30% or more in the low load zone, a calculation start instruction and detection information are added to the gas temperature accumulation calculation. Input to the device.

The gas temperature accumulation computing device operates according to an instruction to start computation, and estimates the gas temperature of each heat transfer surface on the upstream side of the boiler from the observed value of the gas temperature at the inlet of the economizer. That is, although the gas temperature of each heat transfer surface cannot be directly measured, the gas temperature of the outlet of the economizer at the most downstream side of the boiler can be observed. Therefore, the gas temperature of each heat transfer surface on the upstream side is estimated from that temperature. The estimated gas temperature is input to the boiler heat transmission coefficient calculation device to obtain the heat transmission coefficient, and is input to the dynamic characteristic contamination calculation device.

This static-state fouling calculator calculates the ratio between the theoretical heat transfer coefficient input from the boiler heat transfer coefficient calculator and the water and steam side heat transfer coefficient obtained from the actual observed values. Calculate the static dirt index of the boiler with. Further, in the dynamic characteristic dirt calculator, a dynamic dirt index is obtained by performing a metal temperature correction process and a time averaging process of the pipe by the static state dirt index and the dynamic characteristics correspondence model, and further, the dynamic dirt index and the past number. Predict the stain at any step ahead from the point data. Depending on how the dirt changes, the operator can know the start timing of the soot blower, and the boiler state can be easily understood.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a system diagram of a boiler to which the present invention is applied. In FIG. 1, 1 is a coal feeder, 2 is a pulverized coal machine, 3 is a furnace, 4 is a gas recirculation aerator, 5 is an air preheater, 6 is a forced draft fan, 7 is a suspension superheater, and 8 is horizontal. Superheater, 9 main steam pipe, 10 high temperature reheat steam pipe, 11 low temperature reheater, 12 reheater pipe, 13 primary superheater pipe, 14
Is a secondary superheater tube, and 15 is a economizer.

The boiler is a device for combusting fuel to generate steam. First, the air fan sucks the outside air, and the fuel blown from the burner in the furnace 3 is mixed well with the air and burned. Heat is absorbed from the high temperature combustion gas generated there, and the gas is cooled to a certain temperature. A thin tube is stretched around the furnace wall, and the water drawn up by the water supply pump circulates in it.
Heat exchange between water and gas. This is called an evaporation tube. In the furnace 3, the cooling effect is enhanced and radiant heat is absorbed.

The superheaters 7 and 8 superheat the steam generated in the evaporation pipes, and depending on the difference in the heat transfer system, the radiation type, the contact type,
Radial contact type. The radiant superheater is arranged in the high temperature region of the combustion gas, that is, in the upper part of the furnace 3 or in the furnace wall, and performs heat exchange by radiant heat. The contact type superheater is arranged in the cold gas passage of the boiler body and absorbs radiant heat. The radiant contact superheater is located near the furnace outlet and absorbs heat by both radiation and contact.

The reheater 11 is of a radial type, a contact type, or a radial contact type, like the superheaters 7 and 8. The reheater 11 takes out steam from the high pressure part of the turbine and reheats it in the boiler.
Return to low pressure turbine. Also, the outlet of the reheater 11 is placed in a relatively hot part of the gas. The reheater 11 exchanges heat with the combustion gas and recirculation gas in the boiler. The economizer 15 makes effective use of the retained heat of the gas discharged from the chimney, and improves the thermal efficiency.

The air preheater 5 recovers the heat of the combustion gas emitted from the economizer 15 and preheats the air supplied to the boiler to improve the efficiency of the boiler. In other words, the exhaust gas temperature should be lowered as much as possible, but care must be taken as oxides are generated by the anhydrous sulfuric acid in the gas if it is lowered too much.

FIG. 2 is a block diagram of a dirt estimating device for estimating the dirt of the boiler. In the figure, 21 is various sensors attached to each part of the boiler, for example, the main feed water flow rate, reheat steam flow rate, feed water pressure / temperature, main steam / reheat steam inlet / outlet pressure and temperature, etc. are detected to determine the state. Input to the device 23. In addition, fuel information 22 regarding the fuel used by the boiler, for example, when coal is used, is input to the state determination device 23. The state determination device 23 determines how and at what load level the boiler is currently operating from the above input information. For example, when it is determined that the boiler is in a state of 30% or more of the low load zone, the calculation is started. The instruction and various detection information are input to the gas temperature accumulation computing device 25.

Further, the fuel information 22 is input to the fuel property determination device 24. This fuel property determination device 24 is
The current fuel properties such as whether the coal in the mill is a mixed coal or a single coal type is determined from the fuel information 22, and the information is input to the gas temperature accumulation calculation device 25.

The gas temperature stacking computing device 25 carries out a stacking computation based on the instruction and input information from the state determining device 23. From the observed value of the gas temperature at the economizer inlet, each heat transfer surface (primary overheating) of the boiler is detected. The gas temperature is estimated up to the equipment inlet) and is input to the boiler heat transmission coefficient calculation device 26. The heat transmission coefficient calculation device 26 obtains the heat transmission coefficient based on the gas temperature estimated by the gas temperature accumulation calculation device 25, and inputs it to the static state contamination calculation device 27.

The static-state fouling calculator 27 compares the heat-penetration factor input from the boiler heat-penetration factor calculator 26 with the heat-penetration factors on the water and steam sides obtained from actual observation values, and compares them with each other. The dirt index is obtained and input to the dynamic characteristic dirt calculator 28. The dynamic characteristic stain computing device 28 obtains a dynamic characteristic stain index from the static stain index and outputs it to the stain predicting device 29 and the stain display device 30. The stain display device 30 displays both the current stain obtained by the dynamic characteristic stain computing device 28 and the stain at an arbitrary step destination obtained by the stain prediction device 29.

Next, the operation of the above embodiment will be described with reference to the flow chart shown in FIG. Plant observation values and fuel information 22 from various sensors 21 are input to the state determination device 23. The state determination device 23 determines whether the boiler is at the beginning of a static state or a transient state or the end of the transient state, for example, from the fuel amount, the steam amount, the steam temperature, and the pressure at the current load level, based on each observed value of the plant. To determine if That is, the state determination device 23 determines how and at what load level the boiler is currently operating from the above input information, and when it determines that the boiler is in a state of 30% or more of the low load zone, the calculation start And the detection information are input to the gas temperature accumulation arithmetic unit 25.

The critical pressure boiler targeted here is
In the low load region (less than 30%), the state becomes a subcritical pressure state, and the state of steam becomes a state where there is no moisture, and the state where the moisture-laden water and the steam begin to separate. In this state, the temperature does not rise above the saturation temperature even if the steam pressure changes, so the outlet temperature of the furnace does not rise above a certain level. Also, the enthalpy becomes saturated. Since the heat exchange is performed by the steam and the gas, when the steam temperature does not rise in a saturated state, the gas temperature accumulation calculation device 25 does not perform the calculation because the actual operation is not performed.

Further, the fuel property determination device 24 uses the data of the fuel properties of coal, such as the carbon content and hardness, among the plant observation values, and the fuel information 22 for determining the fuel properties currently used by the boiler. Determine the current fuel properties such as whether the coal in the mill is mixed coal or single coal type,
The information is input to the gas temperature accumulation computing device 25.

The gas temperature stacking calculation device 25 operates according to an instruction from the state determination device 23, and the gas from the observed value of the gas temperature at the inlet of the economizer to each heat transfer surface on the upstream side of the boiler (primary superheater inlet) Estimate the temperature. That is, although the gas temperature of each heat transfer surface cannot be directly measured, the temperature of the outlet gas of the economizer at the most downstream side of the boiler can be observed. Therefore, the temperature of the gas of the economizer inlet immediately upstream of the temperature can be obtained. As for how to obtain it, how much heat is exchanged at the heat transfer surface is designed in advance, so the heat exchange will be accumulated from the current temperature. The order to be obtained is the economizer, the flue vaporizer, the horizontal reheater, the horizontal superheater, the suspension reheater, the tertiary superheater, the secondary superheater, and the primary superheater.

Further, the boiler heat transfer coefficient calculating device 26 calculates the heat transfer coefficient from the gas temperature sent from the gas temperature accumulation calculating device 25, and outputs it to the static state contamination calculating device 27.

The static-state fouling calculator 27 calculates the ratio between the theoretical coefficient of heat transfer inputted from the coefficient of heat transfer coefficient calculation device 26 and the coefficient of heat transfer on the water and steam sides obtained from the actual observation value. By taking the static dirt index of the boiler, it is input to the dynamic characteristics dirt calculator 28.

Water or steam inside the boiler is heated through the heat transfer surfaces from the gas temperature obtained by the gas temperature accumulation calculator 25, and absorbs energy. That is,
If all the energy on the gas side is transferred to the water or steam side,
It is considered that the heat transfer surface is not contaminated, and if the heat transfer surface is contaminated, all energy will not be transferred. here,
In order to determine the fouling of the heat transfer surface, the ratio of the theoretical heat transfer coefficient obtained by stacking the gas temperatures and the heat transfer coefficient obtained on the actual observation value (on the water and steam sides) is taken as the fouling index. Specifically, the dirt index is obtained by the following procedure. If the amount of heat released from the gas, the amount of heat received from the steam supply, and the amount of heat transferred from the gas to the water supply are equal, the following relationship holds. Qg = Cpg (Tg1-Tg2) Wg Qs = Cps (Ts2-Ts1) Ws Qk = KHsΔTm where Qg is the amount of heat released from gas, Qs is the amount of heat received from steam supply,
Qk: Heat transfer amount from gas to water supply, each symbol is Cpg: Gas specific heat Cps: Water supply or steam specific heat Hs: Heat transfer area ΔTm: Logarithmic mean temperature K: Heat transfer coefficient Tg1: Inlet gas temperature Tg2: Outlet gas Temperature Ts1: Inlet water supply or steam temperature Ts2: Outlet water supply or steam temperature Wg: Gas flow rate Ws: Water supply or steam flow rate

The fouling index is the ratio of the theoretical heat transfer coefficient to the heat transfer coefficient calculated back from the observed data, and if the heat transfer amount Qk from the gas to the water supply and the gas release heat amount are equal, the fouling is " .alpha. = K.Hs.Tm / Qk ". At this time, the gas temperature estimated value obtained from the gas temperature accumulation arithmetic unit 25 is used.

FIG. 3 shows the calculation sequence of each heat transfer surface. In order to estimate the gas temperature, calculation is performed from the observed gas temperature at the outlet of the economizer, which is the downstream side of the boiler, toward the upstream side of the boiler. The boiler heat output A5 is calculated from the main feed water flow rate A1, the reheat steam flow rate A2, the feed water pressure / temperature A3, the main steam / reheat steam inlet / outlet pressure and the temperature 4. Also,
From the fuel property A6 and the exhaust gas temperature / oxygen amount A7 determined by the fuel property determination device 24, the boiler efficiency theoretical gas amount A
Ask for 8. Furthermore, gas recirculation fan (GRF), damper opening A9, etc. are used for gas recirculation (GR: GAS RECURCURATION).
) Obtain the quantity A10. And the boiler heat output A5,
The total gas amount A11 at the furnace outlet is calculated from the theoretical gas amount A8 and the GR amount A10 of the boiler efficiency. Furthermore, this furnace outlet total gas amount A11
Then, the pass gas amount (superheat / reheater) A13 is obtained from the reheater pass economizer outlet gas temperature and the flue evaporator inlet gas temperature A12.

On the other hand, the economizer bypass gas amount A15 is obtained from the economizer bypass temperature, the economizer outlet gas temperature, the denitration gas temperature, and the GR amount A14. Then, the amount A15 of bypass gas for the economizer and the amount A13 of pass gas (superheater / reheater) are sent to the boiler heat transmission coefficient calculation device 26, and the heat absorption amount of each part heat transfer surface, that is, the boiler heat transmission coefficient is obtained. Be done. The boiler heat transmission coefficient calculated by the boiler heat transmission coefficient calculation device 26 is sent to the static state contamination calculation device 27.

The static-state fouling calculator 27 compares the heat-penetration factor from the boiler heat-penetration factor calculator 26 with the heat-penetration factor B1 on the water and steam sides obtained from the actual observation value, as described above. Determine the static dirt index.

However, a transient state often occurs due to load fluctuations or different types of coal as fuel. In such a case, since the boiler is a process with a large time constant, it is difficult to obtain data that accurately indicates an arbitrary state due to a time delay or the like, and the data cannot be compensated. Therefore, in the dynamic characteristic dirt calculator 28, a dynamic characteristic model is used, a metal temperature correction term is provided therein, and time averaging processing is performed to find the dirt.

That is, in order to correspond to the calculation of the transient state caused by the fluctuation of the boiler load or the switching of the multi-coal species, the metal temperature correction term of the pipe is provided and the time averaging process is performed by the following dynamic characteristic model. The dirt is obtained by outputting the dirt to the dirt prediction device 29 and the dirt display device 30 for display. The dynamic characteristic model will be described below. The dynamic characteristic model is as follows: Z = a1 X2 + a2 X1

The relational expression (1) is created, and Z, X2, and X1 in the expression are calculated from the observed values of the plant. Next, Z, X2, X obtained from the present several past sampling data
Using the value of 1, the coefficients a1 and a2 are obtained by the method of least squares. The reciprocal of the obtained coefficient a1 is taken as the stain value. Here, a concrete form of the dynamic characteristic model is shown. Z = ifa-ife X2 = ^ Rg / θf ... In the case of a heat exchanger using radiant heat transfer,
Or X2 = Fg αg / Qf * (^ θg-θm) ... In the case of an exchanger using convective heat transfer. In addition, (^ (theta) g- (theta) m) was set as follows. X1 = (W / [theta] f) * (1 / [Delta] t) * {[theta] m (-1)-
θm} where: a2: correction coefficient ifa: heat exchanger tube outlet enthalpy ife: heat exchanger tube inlet enthalpy However, since the enthalpy cannot be directly observed, it is calculated from the temperature and pressure using a physical property table. Other symbols other than the above are shown below. ^ Rg: Estimated heat input from outside the tube when there is no contamination Qf: Heat exchanger tube flow rate Fg: Heat exchanger tube heat transfer area αg: Heat exchanger tube heat transfer coefficient ^ θg: Heat exchanger tube fluid Estimated average temperature θm: Average temperature between heat exchangers W = Cf Wf + Cm Wm Cf: Specific heat capacity of fluid in heat exchanger tube Cm: Specific heat capacity of heat exchanger tube Wf: Weight of fluid in heat exchanger tube Wm: Heat Exchanger tube weight Δt: Sampling period θm (-1): Average temperature of the tube before Δt time

This is because the variation of the transient state is absorbed by the metal temperature correction term, which is effective for a process having a time delay. Specifically, sampling is performed at intervals of about 2 to 5 minutes, and data for 10 points is used to
The parameters a1 and a2 of the dynamic characteristic model are estimated by using the least square method.

An example result is shown in FIG. In FIG. 4, 4
1 (Z) is the dynamic characteristic model coefficient entrance / exit enthalpy difference, 4
2 (x2) is dynamic characteristic model coefficient metal temperature correction term, 43
(X1) is the number of static states of the dynamic model, 44 (a1 ^* ) Is the dirt index according to the dynamic characteristic model, 45 (a1) is the static dirt index, and 46 is the power generation amount. For changes in the amount of power generation 46,
Compared to the value 44 calculated by the static state dirt calculator 27, the fluctuation of the dirt index 45 calculated by the dynamic characteristic dirt calculator 28 is small, and the current dirt is accurately indicated as "1".

The dirt estimating device 29 finds the dirt of the next step from the data of several points in the past, for example, the data of the past 10 points, using the dirt index 1 / a1 obtained by the dynamic characteristic model. For the stain prediction, the stain index of the past several points is used from an arbitrary past time to the present, and the stain of the next step is obtained using the format of y = ax + b. Here, y: stain index x: time data a: slope b: tip The above equation uses the past value of the tip, and since there is a value with a bias element, this value is used as tip b. There is.

Further, the stain prediction device 29 obtains the stain at an arbitrary step destination from the above calculation and displays it on the stain display device 30. In this case, since the sampling time is variable in one step, the sampling time is multiplied by n times. Therefore, when the sampling time is set to 2 to 5 minutes, it is possible to display the stain "(2 to 5 minutes) * n times" ahead.

As described above, it is possible to indicate to the operator the progress of dirt on the heat transfer surface, and it is possible to know the start timing of the soot blower when the operator operates the soot blower in a state not in automatic operation. These are also effective as a state monitoring device.

Further, when the soot blower is started by detecting dirt on the heat transfer surface of the boiler, each process amount of the boiler and
Unit computer (computer used for central control of power plant)
Various information from, for example, superheater soot blower is operating,
The N-stage burner ignition or the like is taken into the upper device of the device of the present invention, the conditions of the preset operation element and constraint element are judged, and the soot blower start command is output. For example, if the tertiary superheater inlet fluid temperature or the secondary superheater outlet fluid temperature is high, and the tertiary superheater heat transfer surface is heavily contaminated, a soot blower start command is output. In addition, in order to avoid sudden operation of soot blower, the past boiler state value,
Select the operation group (each heat transfer surface) according to the change of the dirt index and the longest interval, and start the group activation. The sootblower device operates according to the sootblower activation command, and blows steam inside or outside the boiler to each heat transfer surface of the boiler to clean the heat transfer surface.

[0038]

As described in detail above, according to the present invention, the boiler heat transfer surface is maintained regardless of the normal operation (static state), the transient state of the boiler due to load fluctuation, and the difference in fuel type. A dirt calculation can be performed to monitor the dirt condition, and the soot blower can be automatically activated according to the dirt. Further, the fouling index is calculated using the dynamic characteristic model, the fouling of the boiler heat transfer surface is predicted by several steps with the value, and the boiler state can be predicted by displaying the fouling index. By this prediction, the timing for starting can be grasped and it helps the operator to understand the boiler state.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a boiler.

FIG. 2 is a block diagram showing the configuration of a boiler dirt estimation device according to the present invention.

FIG. 3 is a diagram showing a calculation sequence of each heat transfer surface in the embodiment.

FIG. 4 is a diagram showing an example result of a dynamic characteristic model in the example.

[Explanation of symbols]

1 ... Coal feeder, 2 ... Pulverized coal machine, 3 ... Furnace, 4 ... Gas recirculation ventilator, 5 ... Air preheater, 6 ... Pushing ventilator, 7 ... Suspended superheater, 8 ... Horizontal superheater, 9 ... Main steam pipe, 10 ... High temperature reheat steam pipe, 11 ... Low temperature reheater, 12 ... Reheater pipe, 13
… Primary superheater tube, 14… Secondary superheater tube, 15… Economizer,
21 ... Various sensors, 22 ... Fuel information, 23 ... State determination device, 24 ... Fuel property determination device, 25 ... Gas temperature stacking computing device, 26 ... Boiler heat transmission coefficient computing device, 27 ... Static state fouling computing device, 28 … Dynamic characteristic dirt calculator, 29…
Dirt prediction device, 30 ... Dirt display device, 41 ... Dynamic characteristic model coefficient entrance / exit enthalpy difference, 42 ... Dynamic characteristic model coefficient Metal temperature correction term, 43 ... Dynamic characteristic model static state number, 4
4 ... Fouling index by dynamic characteristic model, 45 ... Static fouling index, 46 ... Power generation amount.

Claims (1)

[Claims] 1. A state determination device for grasping an operating condition of a boiler from observation values obtained from various sensors, a fuel property determination device for determining a fuel property used by the boiler from fuel information, and a heat transfer surface of each boiler. Gas temperature stacking calculation device that obtains the gas temperature of the above by a stacking method, a heat transmission coefficient calculation device that calculates the boiler heat transmission coefficient from the gas temperature obtained by this calculation device, and the heat obtained by this heat transmission coefficient calculation device. A static state fouling calculator that finds the fouling index in the boiler from the ratio of the fusing rate and the thermal fusing factor obtained from the actual observation value, and a pipe with a static state fouling index and a dynamic characteristic correspondence model found by this computing device. The dynamic characteristic dirt calculator for determining the dynamic dirt index by performing the metal temperature correction processing and the time averaging processing of the above, the dirt index calculated by this dynamic dirt calculator and the data of the past several points. A soil contamination estimation device for estimating soil contamination at an arbitrary step destination from the data.