JPH01312314A - Soot blower control device - Google Patents

Abstract

PURPOSE:To reduce the generation of NOx, which is an object for environmental regulation, by allowing a furnace outlet gas temperature priority in terms of a furnace/water wall section in a boiler state priority setting instrument to comprise a furnace outlet gas temperature as a function of nitrogen portion contained in fuel. CONSTITUTION:A soot blower control main body 100 is provided with a recirculation gas flow rate control valve 24, a gas thermometer 30, an oxygen densitometer 31, and an air flow meter 33 and the like. These detection signals and the signals transmitted from a coal property setting instrument 46 are input respectively. A fouling state priority computing element 104 is provided with a function to compute a soot blower starting priority based on the judgment of a fouling state of a heating surface. The fouling state priority stands for a soot blower starting priority of its related heat exchanger in terms of said other heat exchanger. Especially, to inhibit the generation of NOx when the nitrogen portion contained in the coal is plenty, the furnace outlet gas temperature priority must be increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a soot blower control device installed in a boiler, and in particular, the present invention relates to a soot blower control device provided in a boiler, and in particular, the present invention is provided with a computing unit that determines the starting point of the soot blower in order to reduce NOx in boiler exhaust gas. The present invention relates to a soot blower control device.

[Conventional technology]

In a typical boiler system, heat exchangers such as a heater, reheater, and flame contactor are arranged in the furnace ice wall and the gas passage connected to it, and the water and steam supplied to these heat exchangers are The fluid to be heated is heated by the high temperature combustion gas generated in the furnace. When this boiler equipment is operated, ash and soot adhere to the heat transfer surface of the heat exchanger.

It accumulates and reduces the heat exchange performance on the heat transfer surface.

Furthermore, the temperature inside the furnace rises, the spray injection flow rate decreases as the temperature and pressure of the steam in the superheater decreases, and the amount of heat absorbed in the reheater becomes insufficient.
An excessive amount of recirculation gas must be input, or the boiler outlet gas temperature may rise excessively, resulting in an unhealthy boiler condition. Therefore, in order to start the stove blower at the appropriate location, by organically combining the boiler condition and the dirty state of the heat transfer surface, the unhealthy state of the boiler becomes large and the dirt on the corresponding heat transfer surface becomes large. A control method has been proposed for starting the stove blower in case of a fire (Japanese Unexamined Patent Publication No. 61-3916).

[Problem to be solved by the invention]

The above-mentioned conventional technology does not consider a soot blower starting method for reducing NOX in exhaust gas.

The purpose of the present invention is to increase the activation priority of the soot blower in the furnace/ice wall section in order to control the temperature inside the furnace based on the information G when fuel with high nitrogen content is injected, thereby making it a target of environmental regulations. The objective is to reduce the generation of NOx.

The amount of NOx generated in the boiler varies depending on the type of coal used as fuel, and is approximately 100 to 300 PPM. At normal furnace combustion temperatures and with a normal amount of nitrogen bones in the fuel, about 80% of the amount of NOx generated is due to nitrogen bones in the fuel (FuelNOX), and about 20% is due to nitrogen bones in the air. Combustion oxidation valve (Thermal NOx)
This is due to

The higher the temperature inside the furnace, the more ThcrmalN Ox is generated.

When there are many nitrogen bones in the fuel, the amount of Fuel Nox generated increases, so when suppressing the total amount of NOx generated, it is necessary to suppress Thermal NOx as much as possible. Therefore, it is necessary to lower the furnace temperature (furnace outlet temperature as an index).

When the soot blower in the furnace/ice wall section is started, the heat transfer surface of the furnace/ice wall section becomes clean, so the amount of heat absorbed increases, and as a result, the temperature inside the furnace decreases. However, unless the soot blower is activated in balance with the activation of other heat transfer surfaces, the boiler efficiency will be reduced.

[Means to solve the problem]

The above purpose is to configure the furnace outlet gas temperature priority corresponding to the furnace/ice wall section in the boiler condition priority setting device as a function of the furnace outlet gas temperature and the nitrogen bone in the fuel, and use the furnace outlet gas temperature as an input signal. This is accomplished by making the nitrogen bones from the fuel conditioner.

[Effect]

The furnace exit gas temperature priority is a function of the furnace exit gas temperature and the nitrogen content in the fuel.

As a characteristic, the higher the furnace outlet gas temperature is, the more nitrogen bones there are in the fuel, the higher the furnace outlet gas temperature priority. As a result, if the nitrogen content in the fuel increases, the start-up demands on the furnace and ice walls will increase by calculating the balance of start-up demands on other heat transfer surfaces.

Therefore, the temperature inside the furnace decreases and Therma'IN
The amount of Ox generated is suppressed.

[Embodiments of the invention]

FIG. 1 is a schematic configuration diagram of a boiler device equipped with a soot blower control device according to an embodiment. 1 in the figure is a boiler device, and the high temperature combustion gas generated in the furnace 2 is transferred to the induced draft fan 11.
The pressure difference caused by the heat exchanger group, i.e. the furnace
Ice wall section 12. The air passes through a superheater 3, a reheater 42, and an economizer 5 in order to give heat to the water/steam in the heat exchanger, and then passes through an air preheater 7 and is discharged outside the system.

Coal, which is fuel, is supplied from the coal feeder 21 to the pulverizer 9, and then passed through the pulverized coal pipe 13. Burner 1 through burner wind box 8
It is burned in 5. On the other hand, the combustion air is supplied by a forced draft fan 10.
The pulverized coal passes through the main air passage 17 and is supplied to the burner 15 via the pulverizer 9 with pulverized coal.

The recycle gas is passed through the recirculation gas flue 2 by the ventilator 14.
6 and enters the furnace 2 from the hopper 25.

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

Steam that is used in a high-pressure turbine and has a low temperature and low pressure is
It passes through the low-temperature reheat steam pipe 19 and enters the reheater 4 where it absorbs heat, becomes high temperature again, and is sent to a low-pressure turbine (not shown) outside the system through the high-temperature reheat steam pipe 20.

Note that when it is necessary to control the steam temperature in the superheater 3, low-temperature water is injected into the steam in the superheater 3 by the spray 23.

If 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.

The exhaust gas temperature immediately before the superheater 3, that is, the furnace outlet gas temperature, the spray amount injected into the superheater 3 by the spray 23 (for generalization, take the ratio of the spray amount to the main steam amount, that is, the spray ratio), the recirculation gas quantity (to generalize,
In this embodiment, the boiler state is defined as the ratio of the recirculated gas amount to the combustion gas amount, that is, the recirculated gas amount ratio.

In such a boiler device 1, by burning the supplied pulverized coal in the burner 15, the furnace and
Ice wall section 12. Superheater 3. Ash, soot, etc. adhere to and accumulate on the heat transfer surface of the reheater 4° economizer 5, reducing heat transfer efficiency and making the boiler 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 shown in the figure.

Next, the soot blower control device will be explained.

A gas thermometer 30 and an oxygen concentration meter 31 are provided at the boiler outlet 16 to check the properties of the combustion gas.

An air flow meter 33 is installed in the main air duct 17 to measure the amount of combustion air supplied to the burner 15. Gas flow meter 34. to measure the amount of recirculated gas supplied to hopper 25. Air condition measuring boxes 28 each containing a dry bulb thermometer 44 and a wet bulb thermometer 45 are arranged.

A feed water flow meter 35 is installed on the outlet side of the feed water pump 6, a spray feed water thermometer 41 is installed on the inlet side of the spray 23, and a low temperature reheat steam pressure meter for flow rate estimation is installed on the outlet side of the low temperature reheat steam pipe 19. A total of 43 are arranged.

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, but for the sake of simplicity, Figure 1 shows the energy saving device. Only those related to 5 are shown. That is, an inlet thermometer 36 and a pressure gauge 37 are disposed on the inlet side of the economizer 5, and an outlet thermometer 38 and a pressure gauge 39 are disposed on the outlet side, respectively.

A coal feed amount needle 42 is provided on the exit side of the coal feeder 21, and a coal property setting device 46 for inputting coal properties is also provided.

As shown in FIG. 2, the soot blower control unit body 100 includes a recirculation gas flow rate control valve 24. Gas thermometer 30. Oxygen concentration meter 31. Air flow meter 33. Gas flow meter 34. Water supply flow meter 35. Inlet thermometer 36° Pressure gauge 37. Outlet thermometer 3
8. Pressure gauge 39. Spray water supply thermometer 41. Coal feed amount needle 42. Low temperature reheat steam pressure gauge 43. Dry bulb thermometer 44. Detection signals from wet bulb thermometer 45 etc. and coal property setting device 46
The signals from each are input.

Next, a schematic configuration of the soot blower control section main body 100 will be explained with reference to FIG. 3.

As shown in the figure, a heat transfer surface contamination status calculator 101 and a contamination status g(f priority setting unit 103) are paired together to input a signal to a contamination status priority computing unit 104.

In addition, the boiler status calculator 102 and the boiler status priority setter 105 are paired together to form a boiler status G (I' priority calculator 10
The signal is input to 6.

A signal from the coal property setting device 46 is input to the boiler condition priority setting device 105 .

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 the boiler status.

Further, a combined state priority computing unit 107 performs a minimum type multi-value logical operation based on the signals from the dirt status computing unit 104 and the boiler status priority computing unit 106, and signals from the computing unit 107 and the boiler status computing unit 102. A soot blower activation point determination calculator 108 is provided to determine the activation point of the soot blower.

A drive signal from the soot blower control unit main body 100 (the soot blower activation point determination calculator 108) is input to the soot blower driving device 29, and the selected soot blower 27 is thereby activated.

The contamination condition calculating unit 101 calculates the contamination condition of the furnace ice wall section 12 based on the 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 K f
= Uc /Us (11 where, Kf: Contamination condition index Uc: Current heat transmission coefficient Us: Standard state heat transmission coefficient. Uc is obtained from the following formula.

A・Δt [J (= f2) where A: Heat transfer area of heat exchanger Q: Endothermic amount ΔL dilogarithmic average temperature difference It is.

The heat transfer area A is determined from design data.

The endothermic iQ is FXtl(Tsi, Psi) +Q = H(Tso, P
so) XF (3).

Here, F: Water/steam flow rate H: Enthalpy calculation formula Ts, Ps: Water/steam temperature and pressure, and suffixes i and o are the inlet side.

Shows the exit side.

The logarithmic average temperature difference Δt is in the case of counterflow, Tg is the gas temperature, and i and o indicate the inlet side and the outlet side.

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 economizer 5, an exit thermometer 38 and an inlet thermometer 36 are used.

The gas temperatures Tgi and Tgo are determined by the following formula.

Here, Cpg: Gas specific heat Wg: Gas flow rate The measured value at the gas thermometer 30 is the outlet gas temperature T of the economizer 5.
go, and the inlet gas temperature T g i of the economizer 5 determined by the above equation (3) is calculated.

Similarly, the inlet gas temperature of the reheater 4 is calculated by using the inlet gas temperature Tgi of the economizer 5 as the outlet gas temperature of the reheater 4, and finally the inlet gas temperature of the superheater 3, that is, the furnace outlet 22 It is possible to estimate the gas temperature of

The gas flow rate Wg is the recirculation gas amount measured by the gas flow meter 34,
Combustion air amount by air flow meter 33, air quality data by dry bulb thermometer 44 and wet bulb thermometer 45, coal feeder 4
2 and the signal from the coal property setting device 46.

Us in (1) above is determined by the following.

Us = f (Tg,, Ts, Vg, Vs)
(61 Here, Vg: Gas flow rate vs: Steam flow rate The boiler condition calculator 102 calculates the gas temperature at the furnace outlet 22, which is calculated based on the equation (5), and the gas temperature meter 3.
0 spray water supply flowmeter 40 and water supply flowmeter 35
Spray amount and water supply flow rate ratio according to signals from coal feed needle 4
2. The ratio of the amount of combustion gas calculated based on the signals from the coal property setting device 46, air flow meter 33, dry bulb thermometer 44, and wet bulb thermometer 45 and the amount of recirculated gas measured by the gas flow meter 34. demand.

The dirty state priority setter 103 is set so that a numerical value between 0 and 1 can be calculated depending on the degree of dirt on 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 (g) and the contamination state index (Kf) in each heat exchanger will be explained with reference to FIG. 4. The same figure (al is a characteristic diagram of the furnace ice wall part 12, the same figure fb is a characteristic diagram of the superheater 3, the same figure (C1 is a characteristic diagram of the reheater 4, the same figure (d+ is the characteristic diagram of the economizer 5) It is.

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

In the dirt state priority calculator 104, the dirt state priority calculator 10
The dirt state priority level Yj is calculated from the signal Kfj from 1 and the characteristic diagram of the dirt state priority setter 103.

Figure 5 diagrammatically shows the calculation of this priority Y, where KfβKfu is the lower limit and upper limit of the dirt condition index,
Yβ and Yu are the lower limit value and upper limit value of the priority.

As is clear from this figure, becomes.

Note that j represents the type of heat exchanger.

The boiler condition is 1m (l The advance setting device 105 is capable of calculating a numerical value from 0 to 1 depending on the degree of unsoundness of the boiler condition.

The boiler condition priority means a function to check the soot blower activation priority from the boiler condition with respect to the dirt condition priority.

In this embodiment, the furnace outlet gas temperature is defined as the furnace/ice wall portion 12, the spray amount ratio is defined as the superheater 3, and the recirculation gas amount ratio is defined as the boiler state of the reheater 4.

Figure 6 shows the relationship between each boiler condition and the soot blower starting priority. (C) shows the relationship between the ratio and the recirculation gas amount ratio.These (a).

fb), (C1 is the furnace ice wall section 12. superheater 3.
This is related to the dirt in the reheater 4.

Then, the value on the horizontal axis in FIG. 6 fa) is changed based on the signal of the nitrogen content in the coal from the coal property setting device 46.

The horizontal axis in (a) is the furnace outlet gas temperature.

This temperature shall be scaled by the nitrogen content.

That is, here, Tf: Furnace outlet gas temperature , u: Suffix indicating lower limit value and upper limit value According to the above formula, when the nitrogen content is large, the soot blower activation priority becomes high even at the same furnace outlet temperature Tf. The α, β, and upper and lower limits in these figures are set based on simulations and operator experience, and the higher the priority, the more unhealthy the boiler condition is.

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

The composite state priority calculator 107 compares the dirty state priority and boiler state priority for each heat exchanger j based on the signals from the dirty state priority calculator 104 and the boiler state priority calculator 106, and calculates the result. Choose the smaller one.

FIG. 7 is a diagram showing an example of the calculation result by the composite state priority calculation unit 107, in which the dirty state priority calculation unit 104
The ○ mark indicates the priority regarding the contamination state respectively output from the boiler state priority calculation unit 106.
1 is the furnace fouling condition B priority, and the circle mark is the boiler condition priority at the furnace outlet gas temperature.Since both are related to the furnace and ice wall, they are shown on the same line of that item.・Mark 203
is the superheater dirty state priority, and 204 marked with a circle is the boiler state priority based on the spray amount ratio, and since both are related to the common heater, they are shown on the same line of the items.・The mark 205 is the reheater dirty state priority, and the circle 206 is the boiler state priority regarding the recirculation gas amount ratio.Since both are related to the reheater, they are shown on the same line for that item. .・Mark 20
7 is the dirt status priority of the economizer, and in this embodiment, the dirt status regarding the economizer is not specified.

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

That is, in the case of FIG. 7, the one marked with a lower priority is selected.

The soot blower starting point determiner 108 uses the boiler outlet gas temperature signal from the boiler state calculator 102 and the resultant state f
'J (l Determine the soot blower activation point based on the signal from the advance calculator 107.

That is, when the boiler outlet gas temperature becomes higher than a preset temperature, the location where the synthetic state priority shows the largest value is determined as the soot blower activation location. This situation is shown in Fig. 8. As shown in Fig. 7, the results of comparing the composite state priorities, the boiler state priority 202 regarding the furnace outlet gas temperature, and the superheater fouling state priority 203 for each heat exchanger. , reheater dirty state priority 205 and economizer dirty state priority 2
07 are selected, and among these, the furnace outlet gas temperature priority 202, which has the highest priority, is selected in this case. Based on this selection result, the soot blower 27 corresponding to the furnace/ice wall section is driven to clean the heat transfer surface.

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 soot blower activation point using the same process.

〔Effect of the invention〕

The present invention has the above-mentioned configuration as a whole, and ultimately, if the boiler efficiency is reduced at a location where the boiler condition is highly unhealthy and the heat transfer surface is heavily contaminated (the boiler outlet gas temperature is If the price increases), the price will be selected.

Since such areas are heavily contaminated, it can be said that the effect of starting the soot blower to eliminate the unsoundness level is large.

Special Q: In order to suppress the amount of NOx generated, when the nitrogen content in the coal is high, the furnace outlet gas temperature priority is increased in order to reduce the hermcβNOx.

As a result, the soot blower is activated more often for the furnace/ice wall, and the furnace/water wall is cleaned more frequently. As a result, the amount of heat absorbed in the furnace and ice wall increases, and the temperature inside the furnace (ultimately the temperature of the gas at the furnace outlet) decreases.
The amount of NOx generated can be suppressed.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a boiler device equipped with a soot blower control device according to an embodiment, Fig. 2 is a diagram showing the input/output relationship of the soot blower control device, and Fig. 3 is a soot blower control '4'.
A block diagram of the l'd main body, FIG. 4(a). (b), (cl, (d) are characteristic diagrams showing the contamination state priority and contamination state index in each heat exchanger, Fig. 5 is an explanatory diagram illustrating the calculation of the contamination state priority, and Fig. 6 ( at,
fb). (C) is a characteristic diagram showing the relationship between each detected value, calculated value, and boiler status priority; Figure 7 is an explanatory diagram showing an example of the calculation result by the composite status priority calculator; Figure 8 is the soot blower activation point FIG. 3 is an explanatory diagram showing an example of a calculation result by a decision calculation unit. 46...Coal property setting device, 104...Contamination condition priority computing device, 106...Boiler condition priority computing device. Figure 1 Figure 2 Figure 4 Figure 5/J k ~ Figure 6 (a)
(b) (C) Figure 7 part Figure 8

Claims (1)

[Scope of Claims] A dirt status calculator that calculates the dirt status of the electric heating surface of the heat exchanger, and a dirt status priority calculator that calculates the activation priority of the soot blower based on the signal from the dirt status priority setting device. , comprising a boiler status calculator that calculates the operating status of the heat exchanger, and a boiler status priority calculator that calculates the activation priority of the soot blower based on the signal from the boiler status priority setter, A soot blower control device that starts a soot blower based on signals from a degree computing unit and a contamination state priority computing unit, further comprising a fuel property setting device that outputs a signal to the boiler state priority setting device. Control device.