JPH0285605A - Control device of soot blower - Google Patents

Abstract

PURPOSE:To control generation of NOx, by providing an arithmetic instrument for soot blower starting position decision which selects the highest value among degrees of synthetic priority put out through a degree of priority in a synthetic state arithmetic instrument. CONSTITUTION:A degree of priority in a dirty state and a degree of priority in a boiler state are compared with each other every heat exchanger by signals through a degree of priority in a dirty state arithmetic instrument 104 and a degree of priority in a boiler state arithmetic instrument 106 and a lower side of them is selected, in a degree of priority in a synthetic state arithmetic instrument 107. A soot blower starting position decision instrument 108 decides a soot blower starting position with signals through a gas thermometer of a boiler outlet from a boiler state arithmetic instrument 102 and the degree of priority in the synthetic state arithmetic instrument 107. In other words, when a generating quantity of NOx is larger than an allowable value, it becomes a function of a furnace outlet gas temperature and a signal through an Nox meter 30 and when the signal through the NOx meter 30 becomes large, the title device actuates so that a degree of priority in soot blower starting becomes high. Consequently, the generating quantity of thermal NOx is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a soot blower attached to a combustion device such as a boiler or a cracking/reforming furnace, and particularly to a control device for maintaining the function of the combustion device in a healthy manner. The present invention relates to a soot blower control device including a computing unit that determines the starting point of the soot blower.

[Prior art] In a normal boiler, heat exchangers such as a superheater, a reheater, two economizers, etc. are arranged in the ice wall of the furnace and the gas passage connected thereto. A fluid to be heated, such as water or steam, is heated by high-temperature combustion gas generated in the furnace.

When this boiler is operated, ash and soot in the combustion gas adhere to and accumulate on the heat transfer surface of the heat exchanger, reducing the heat exchange performance of the heat transfer surface. Furthermore, as the heat exchange performance deteriorates, the temperature of the combustion gas at the furnace outlet increases, and as the steam temperature and pressure increase in the superheater decreases, the spray water injection flow rate decreases, and the reheating This can lead to various problems such as having to input an excessive amount of recirculated gas due to insufficient heat absorption in the boiler, or causing the boiler to become unhealthy due to excessive rise in the boiler outlet gas temperature. arise.

Therefore, it is necessary to start a soot blower that uses steam as an injection medium at an appropriate time to remove and clean the ash, soot, etc. adhering to the heat transfer surface of the heat exchanger.

[Problems to be Solved by the Invention] Conventionally, the location and timing of starting a soot blower was determined by estimating the dirt status on the heat transfer surface of each heat exchanger.
The size of the dirt was displayed on a CRT screen, and the operator issued a command to start the soot blower for areas with a large degree of dirt.

However, such a soot blower control device has the following problems.

(1) Since the operator must constantly monitor the CRT screen, the operator's work efficiency is poor.

(2) Soot blowers are originally activated to clean the heat transfer surface to prevent the steam temperature from becoming unstable, and should not be activated solely due to the degree of dirt on the heat transfer surface. In other words, the soot blower should be activated only when the steam temperature becomes unstable and the heat transfer surface is heavily contaminated.

Conventional soot blower control devices do not have a function in this regard, and the activation is determined based solely on the level of dirt.

As described above, the conventional soot blower control device does not take into consideration the activation of the soot blower to reduce NOx in the exhaust gas.

The present invention aims to eliminate such conventional drawbacks,
The purpose of this is that when exhaust gas with a high NOx value is discharged, the signal activates the soot blower in the furnace ice wall preferentially in order to suppress the gas temperature inside the furnace, thereby suppressing the generation of NOx. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a contamination state calculator that calculates the contamination state of the heat transfer surface of a heat exchanger, and a contamination state priority calculator that calculates the priority of the contamination state. With degree setting device.

A dirt status priority calculator that calculates the starting priority of the soot blower based on the signals from the dirt status calculator and the dirt status priority setter; a boiler status calculator that calculates the operating status of the heat exchanger; and a dirt status calculator that calculates the operating status of the heat exchanger. A boiler state priority setting device that calculates a boiler state priority based on a signal, and a boiler state priority calculating device that calculates a starting priority of a soot blower based on signals from the boiler state computing device and the boiler state priority setting device.

a composite state priority computing unit that compares the fouling state priority output from the fouling state priority computing unit and the boiler status priority output from the boiler status priority computing unit and selects the lower value of both priorities; , and a soot blower activation point determining calculator that selects the highest value of the composite priorities output from the composite state priority calculator.

[Operation] When the NOx generation amount is lower than the NOx allowable value at the boiler outlet, the soot blower activation priority due to the furnace outlet gas temperature is a function only of the furnace outlet gas temperature.

On the other hand, when the amount of NOx generated is larger than the allowable value, it becomes a function of the furnace outlet gas temperature and the signal from the NOx meter, and NO
As the signal from the x-meter increases, the soot blower activation priority increases. Therefore, the frequency of activation of the soot blower against the furnace ice wall increases, and the cleanliness of the furnace ice wall heat transfer surface increases. As a result, the amount of heat transferred in the ice wall of the furnace increases, the gas temperature in the furnace decreases, and the N
J'J Thermal NO due to the major cause of Ox generation
The amount of x generated is reduced, and NOx generation is suppressed as a whole.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 8 is a schematic configuration diagram of a boiler equipped with a soot blower control device according to an embodiment.

1 in the figure is a boiler, and the high-temperature combustion gas generated in the furnace 2 is transferred to the heat exchanger group, namely the furnace ice wall section 12, the superheater 3, the reheater 4, and the carbon-saving The air passes through the air heater 5 sequentially, gives heat to the water and steam in the heat exchanger, and then passes through the air preheater 7 and is discharged to the outside of the system.

Coal, which is a fuel, is supplied from a coal feeder 21 to a pulverized coal machine 9, and then passes through a pulverized coal pipe 13 and a burner wind box 8, and is burned in a pulverized coal burner 15. On the other hand, combustion air passes through the main air passage 17 by the forced draft fan 1o, passes through the pulverized coal machine 9, and is supplied to the pulverized coal burner 15 along with pulverized coal.

The recirculated gas enters the furnace 2 from the hopper 25 through a recirculated gas flue 26 by means of a draft fan 14 . The amount of recirculated gas is
It is controlled by a recirculation gas flow control valve 24.

Water, which is the fluid to be heated, is sent to the economizer 5 by the water supply pump 6, and then passes through the furnace ice wall 12 and the superheater 3, where it absorbs heat and rises in temperature, becoming high-temperature, high-pressure steam and flowing into the main steam pipe 18. and is sent to a high-pressure turbine (not shown) outside the system.

The low temperature, low pressure steam used in the high pressure turbine is
It passes through the low-temperature reheat steam pipe 19 and enters the reheater 4 where it absorbs heat, becomes high temperature and high pressure again, and is sent to a low-pressure turbine (not shown) outside the system through the high-temperature reheat steam pipe 20. In addition, if it is necessary to control the steam temperature in the superheater 3, the spray 23
As a result, low temperature water is injected into the steam of the superheater 3.

When the temperature and pressure of the steam sent to the high-temperature reheat steam pipe 20 are below the specified values, the amount of recirculated gas is adjusted by the recirculated gas flow rate control valve 24 in order to improve the heat transfer efficiency in the reheater 4. increase.

Additionally, if the gas temperature at the furnace outlet 22 is too high,
Since this will adversely affect the material and lifespan of the superheater 3, the recirculation gas flow rate control valve 24 is closed to reduce the amount of recirculation gas.

Furthermore, if the gas temperature at the boiler outlet 16 is higher than the specified value, this indicates that the boiler efficiency is low.

The amount of spray injected into the superheater 3 by the above-mentioned spray 23 (for generalization, take the ratio of the amount of spray to the amount of main steam, that is, the spray ratio), the amount of recirculated gas (for generalization, the amount of recirculated gas) In this embodiment, the boiler operating state is defined as the ratio of the gas amount due to combustion and the recirculated gas amount ratio), the gas temperature at the furnace outlet 22, and the gas temperature at the boiler outlet 16.

In such a boiler 1, by burning the supplied pulverized coal in the pulverized coal burner 15, the furnace ice wall portion 12. Superheater 3. Ash, soot, etc. adhere and accumulate on the heat transfer surface of the reheater 4° economizer 5.

As the heat transfer efficiency decreases, the operating condition of the boiler becomes unhealthy. In order to blow away the adhering ash and soot mentioned above, a soot blower 27 is arranged corresponding to each heat exchanger, but in order to avoid complicating the drawing, in FIG.
Only the soot blower 27 corresponding to the above is shown in the figure.

Next, a soot blower control device will be explained. A gas thermometer 2 is installed at the boiler outlet 16 to understand the properties of the combustion gas.
8. Oxygen concentration meter 29. A NOx meter 30 is provided.

The NOx meter 30 measures the amount of NOx at the boiler outlet 16, and the amount of NOx generated in the boiler 1 varies depending on the type of coal supplied as fuel and ranges from 100 to 300 pp.
It is about m.

If the gas temperature in the furnace is normal and the nitrogen content in the fuel is the normal amount, approximately 80% of the NOx generated is fuel NOx due to the nitrogen content in the fuel, and 20%
The degree of oxidation thermal (T) due to combustion of nitrogen in the air
(hermal) NOx. The higher the gas temperature in the furnace, the more this thermal NOx is generated.

Therefore, when the amount of NOx in the exhaust gas is high, the gas temperature in the furnace is suppressed (the index is the furnace outlet gas temperature).
There is a need.

When the soot blower of the furnace ice wall section 12 is activated, the heat transfer surface of the furnace ice wall section 12 is cleaned, so the amount of heat absorbed by the furnace water wall section 12 increases, and as a result, the temperature dust in the furnace decreases.

An air flow meter 31 is installed in the main air passage 17 to measure the amount of combustion air supplied to the pulverized coal burner 15, and a gas flow meter 32 is installed in the main air passage 17 to measure the amount of recirculated gas supplied to the hopper 25.
are placed respectively.

A water supply flow meter 33 is installed on the outlet side of the water supply pump 6.
A spray feed water thermometer 34 is arranged on the inlet side of the spray pipe 230, and a low-temperature reheat steam pressure gauge 85 for estimating the flow rate is arranged on the outlet side of the low-temperature reheat steam pipe 19.

Additionally, thermometers and pressure gauges are installed on the inlet and outlet sides of each heat exchanger to ascertain the properties of water and steam. Only those related to vessel 5 are shown.

That is, an inlet thermometer 36 and an inlet pressure gauge 37 are installed on the inlet side of the economizer 5, and an outlet thermometer 38 and a pressure gauge 39 are installed on the outlet side.
is located.

A coal feed needle 40 is provided on the exit side of the coal feeder 21, and a coal property setting device 41 for inputting coal properties is also provided.

As shown in FIG. 2, the soot blower control unit main body 100 includes a recirculation gas flow rate control valve 24. Gas thermometer28. Oxygen concentration meter 29. NOx total 30. Air flow meter 31. Gas flow meter 32. Water supply flow meter 33° Spray water supply temperature meter 34.
Low temperature reheat steam pressure gauge 35, thermometer 36.38. Pressure gauge 3
7.39. A detection signal from a coal feeding needle 40 and a signal from a coal property setting device 41 are respectively input.

Next, a schematic configuration of the soot blower control section main body 100 will be explained with reference to FIG. 1.

As shown in FIG. 1, a heat transfer surface contamination condition calculator 101 and a contamination condition priority setting device 103 are paired and input to a contamination condition priority degree calculation device 104. Further, the boiler status calculator 102 and the boiler status priority setting unit 105 are paired together to form a boiler status priority calculator 106.
It is now entered into

This boiler status priority setting device 105 has N.

A signal from the X total 30 is input.

The contamination state priority calculating unit 104 has a function of calculating the activation priority of the soot blower based on judgment from the viewpoint of the contamination state of the heat transfer surface.

On the other hand, the boiler status priority calculator 106 has a function of calculating the activation priority of the soot blower based on judgment from the viewpoint of the boiler status.

Furthermore, a composite state priority calculator 107 that performs a minimum type multi-value logical operation based on the activation priority signals of the dirty state priority calculator 104 and the boiler status priority calculator 106; 107 and a soot blower start point calculator 108 that determines the start point of the soot blower based on signals from the boiler state calculator 102.

A signal from the soot blower control unit main body 100 is input to the soot blower driving device 42, and the soot blower 27 is thereby activated.

Next, each arithmetic unit will be explained in detail.

The contamination condition calculator 101 calculates the contamination condition of the furnace ice wall section 12 based on signals from each detector that monitors the contamination condition of the heat transfer surface. Superheater 3. The contamination state of the heat transfer surfaces of the reheater 4 and the economizer 5 is calculated.

The calculation formula for calculating the contamination state of the heat transfer surface is Kf: contamination state index Uc: current heat transmission coefficient Us: standard state heat transmission coefficient. Furthermore, the current thermal conductivity Uc is determined by the following formula.

A: Heat transfer area of heat exchanger Q: Endothermic amount Δt: Logarithmic average temperature difference It is.

The heat transfer area A of the heat exchanger is determined from design data, and the amount of heat absorbed Q is determined from the heat balance between the gas side and the water vapor side of the heat exchanger.

The logarithmic average temperature difference Δt is It is.

here, Tg: gas temperature Ts: water/steam temperature Suffix i, 0 is inlet side, outlet side Mouth side shown.

The water/steam temperatures Tsi and Tso are measured by thermometers placed at the entrance and exit of each heat exchanger, and in the case of the energy saver 5, the outlet thermometer 38. Measured by inlet thermometer 36.

Gas temperature is not measured except in the low temperature section. Therefore, it is determined by calculation.

Cpg: Gas specific heat (constant) If the gas temperature Tg at the outlet of the low-temperature heat exchanger (eg, economizer) is measured, the inlet gas temperature Tgi can be found from the above equation.

If this inlet gas temperature Tgi is taken as the outlet gas temperature of the gas upstream heat exchanger, the inlet gas temperature of the heat exchanger can also be determined. In this way, the temperature of the superheater inlet gas, which is the most upstream side, can be determined.

The gas flow rate Wg is determined by the amount of recirculated gas determined by the gas flow meter 32, the total heat absorption amount of the boiler, and the coal property setting device 4.
It is determined by the sum of the combustion gas amounts determined by 1.

Furthermore, Us in the above formula (1) is as follows: Us=f(Tg* Ts, Vg, Vs) --(
5).

here, vs: water/steam flow rate vg: gas flow rate It is.

The boiler state calculator 102 determines the gas temperature at the furnace outlet 22, the spray amount ratio, and the recirculation gas amount ratio determined based on the above equation (4).

The contamination state priority setter 103 is capable of calculating a numerical value between 0 and 1 depending on the degree of contamination of the heat transfer surface of each heat exchanger.

The dirty state priority means the soot blower activation priority of the heat exchanger relative to other heat exchangers.

The relationship between the contamination state priority y and the contamination state index (Kf) in each heat exchanger will be explained using FIG. 3. Figure (a) is a characteristic diagram of the furnace ice wall section 12, figure (b) is a characteristic diagram of the superheater 3, figure (c) is a characteristic diagram of the reheater 4, and figure (d) is a characteristic diagram of the coal-saving 5 is a characteristic diagram of the device 5. FIG.

The inclination angle (gradient) and upper and lower limits of the characteristic line in this figure vary depending on each heat exchanger and operating condition, and are set based on simulations, operator experience, etc.

The dirt status priority calculator 104 is the dirt status calculator 101.
The signal Kf from the filter and the dirt state priority y from the dirt state priority setter 103 are calculated. Figure 4 diagrammatically shows how to calculate the dirt status priority level y.
u is the lower limit and upper limit of the soil condition index, and yu is the upper limit of the soil condition priority y.

As is clear from this figure, Here, j represents the type of heat exchanger.

The boiler condition priority setter 105 is capable of calculating a numerical value from 0 to 1 depending on the degree of unhealthiness of the boiler condition.

The boiler status priority means checking the soot blower activation priority from the boiler status with respect to the dirty status priority.

In this embodiment, the furnace outlet gas temperature is determined by
The spray amount ratio is for superheater 3, and the recirculation gas amount ratio is for reheater 4.
It is defined as the boiler condition.

Figure 5 shows the relationship between each boiler state and the soot blower startup priority. Figure 5 (a) is a characteristic diagram showing the relationship between the boiler state and the soot blower startup priority X depending on the furnace outlet gas temperature, and (b) (c) shows the relationship between the spray amount ratio and the recirculated gas amount ratio. These (a), (b), (c
) are the furnace ice wall portions 12. Superheater 3. This is related to dirt on the heat transfer surface of the reheater 4.

It is assumed that the value on the horizontal axis in FIG. 5(a) is changed by the signal from the NOx meter 30.

The horizontal axis in (a) is the furnace outlet gas temperature. It is assumed that this temperature is changed depending on the magnitude of the signal from the NOx meter 30.

Case (1) When N<Ns, T'f x TfΩ, then X=XQ T f Q < T f <, T f u,
X=aXTf+β If Tf>Tfu, then X=Xu where: Value from N5Ox meter NS: Allowable NOx value at boiler outlet shows.

According to the above formula, when N≦Ns, the value of the soot blower activation priority X increases as the furnace outlet gas temperature Tf increases. Further, in the case of N)Ns, the value of the furnace outlet gas temperature Tf virtually increases in accordance with the value of NOx.

Further, α, β, and upper and lower limit values are set based on simulation and operator experience.

The boiler state priority calculator 106 calculates the boiler state priority X based on the inputs from the boiler state calculator 102 and the boiler state priority setter 105. The substantial content of the calculation is almost the same as that of the dirty state priority calculation unit 104 described above.

The composite state priority computing unit 107 compares the fouling state priority and boiler state priority for each heat exchanger j based on the signals from the fouling state priority computing unit 104 and the boiler state priority computing unit 106. Choose the smaller one.

FIG. 6 is a diagram showing an example of the calculation result by the composite state priority calculation unit 107.
The 0 mark in the figure indicates the boiler state priority output from the boiler state priority calculator 106, and the symbol 201 indicates the dirt state priority of the furnace ice wall 12. , 202 with a 0 mark indicates the boiler condition priority at the furnace outlet gas temperature, and both of them are the boiler condition priority at the furnace outlet gas temperature.
These priorities are shown on the same line on the vertical axis.・The mark 203 is the superheater 3 dirty state priority, and the ○ mark 204 is the boiler state priority based on the spray amount ratio.Since both are priorities related to the common heating equipment, their priorities are vertically arranged. shown collinear with the axes.・The mark 205 is the dirty state priority of the reheater 4, and the circle mark 206 is the boiler state priority regarding the recirculation gas amount ratio.Since both are priorities related to the reheater, their The priorities are shown on the same line on the vertical axis.

The symbol 207 indicates the dirt status priority of the economizer 5, and in this embodiment, the boiler status of the economizer 5 is not specified.

The heat transfer surface contamination status priority and the boiler status priority are compared for one heat exchanger, and as a result, the lower priority is selected.

That is, in the case of FIG. 6, the priority with the wooden mark is selected.

The soot blower activation point determiner 108 determines the soot blower activation point based on the signal from the gas thermometer 28 at the boiler outlet 16 from the boiler state calculator 102 and the signal from the composite state priority calculator 107 .

That is, when the boiler outlet gas temperature becomes higher than a preset temperature, the location where the composite state priority shows the largest value is determined as the soot blower activation location. This situation is shown in FIG. 7. As shown in FIG. 6, as a result of comparing the composite state priorities, the boiler state priority 2o2 regarding the furnace outlet gas temperature is determined for each heat exchanger. The dirty state priority 203 of the superheater 3, the dirty state priority 205 of the reheater 4, and the dirty state priority 207 of the economizer 5 are selected, respectively.
In FIG. 7, the furnace outlet gas temperature 202 is selected. Then, based on the selection result, the furnace ice wall section 12 is
The corresponding soot blower is activated and the heat transfer surface is cleaned.

In this way, after selecting the heat exchanger that requires the most activation of the soot blower from among the multiple heat exchangers and cleaning the heat transfer surface, data from each detector is collected again. Select the starting point of the soot blower using the same process.

As described above, the present invention has the above-mentioned configuration, and ultimately, a location where the boiler condition is highly unhealthy and where the heat transfer surface is heavily contaminated is selected and the boiler is When the outlet gas temperature is high, that is, when the boiler efficiency decreases, the soot blower at that location is activated. Since such areas are highly contaminated, activating the soot blower has a great cleaning effect in order to eliminate unhealthy boiler conditions caused by contamination. In particular, when the amount of NOx generated is large, the amount of heat transfer can be increased by automatically raising the soot blower activation priority for the furnace ice wall and increasing the soot blower activation frequency for that heat transfer surface.

Therefore, the gas temperature in the furnace decreases, and the Thermal NO.
The amount of x generated decreases.

[Effects of the Invention] According to the present invention, when exhaust gas with a high NOx value is discharged, the soot blower in the furnace ice wall can be started preferentially to clean the furnace ice wall, and the amount of thermal NOx generated can be reduced. decreases.

[Brief explanation of drawings]

All figures are for detailed explanation of the present invention.
The figure is a block diagram of the soot blower control device, Figure 2 is a block diagram of the soot blower control body, Figure 3 (a), (
b), (c), and (d) are characteristic diagrams showing the relationship between the contamination state priority and the contamination state index in each heat exchanger;
The figure is an explanatory diagram illustrating the calculation of contamination state priority, and Figures 5 (a), (b), and (c) show boiler state priority, furnace volume, gas temperature, spray volume ratio, and recirculated gas volume. , a characteristic curve diagram showing the relationship with the ratio, FIG. 6 is an explanatory diagram showing an example of the calculation result by the composite state priority calculation unit, and FIG. 7 is an explanatory diagram showing an example of the calculation result by the soot blower activation point determination calculation unit. , FIG. 8 is a schematic configuration diagram of a boiler equipped with a soot blower control device according to an embodiment. 3... Superheater, 4... Reheater, 5...
...Cost saving device. 12...Furnace water wall section, 27...Soot blower, 28...Gas thermometer, 29...
・Oxygen concentration meter, 30... NOx meter, 31...
...Air flow meter, 32...Gas flow meter, 33
... Water supply flow meter, 34 ... Water supply temperature meter for spray, 35 ... Pressure gauge, 36 ...
・Inlet thermometer, 37... Inlet pressure gauge, 38...
...Outlet thermometer, 39...Outlet pressure gauge, 4
0... Coal feeding needle, 41... Coal property setting device, 42... Soot blower drive device, 100...
...Soot blower control unit main body. 101... Dirt status calculator, 102...
・Boiler condition calculator, 103...Dirty condition priority setting device, 104...Dirty condition priority calculator,
105... Boiler status priority setting device, 106.
...Boiler status priority calculator, 107...
- Synthesis state priority calculator, 108... Soot blower activation point determining calculator. Figure 2 Figure 3 (a) (b
)(C)
(d-n No. 45A Dirt → Dirt Selection 1) Figure 5 (a) (b) (C) Figure 6 Straight to the child 117 Figure 8

Claims (1)

[Scope of Claims] A contamination state calculator that calculates the contamination state of the heat transfer surface of a heat exchanger, a contamination state priority setting device that calculates the priority of the contamination state, and a contamination state calculator and contamination state priority setting. A dirt status priority calculator calculates the starting priority of the soot blower based on the signal from the NOx meter, a boiler status calculator calculates the operating status of the heat exchanger, and a boiler status priority calculator calculates the starting priority of the soot blower based on the signal from the NOx meter. A boiler status priority calculator that calculates the starting priority of the soot blower based on the signals from the boiler status calculator and the boiler status priority setter, and a dirt status priority calculator. A composite state priority calculator that compares the dirt status priority output from the boiler status priority calculator with the boiler status priority output from the boiler status priority calculator and selects the lower value of both priorities; 1. A soot blower control device, comprising: a soot blower activation point determining calculator that selects the highest value of the combination priorities output from the soot blower.