JP2510580B2 - Soot blower control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler soot blower control device, and more particularly to a soot blower control device capable of performing soot blow while always maintaining a normal operating state of the boiler.

[Conventional technology]

Dust (soot) generated by combustion of fuel adheres to the heat transfer surface of a heat exchanger such as a boiler. This dust becomes a factor to hinder the heat transfer on the heat transfer surface, and the heat transfer of the heat transfer tube is reduced due to the adhesion and growth of dust, and the heat absorption amount of the fluid such as water and steam flowing in the tube is reduced. The thermal efficiency of is reduced. For this reason, a large number of soot blowers are installed in large-scale boilers for offices including large-scale boilers for thermal power plants, and the heat transfer surfaces are regularly cleaned. In particular, when dust adheres to a specific part of the boiler in a concentrated manner, the heat absorption rate at that part decreases, and the heat absorption balance of the entire boiler is lost. Especially when coal, bark, or other ash-rich substances are used as fuel, dust removal measures are important.

As the operation of the sootblower, a regular or interval start method which is usually started by using a timer, or a manual operation method which is appropriately started by the operator's judgment is adopted.
In this way, the reason why the operation method that is not directly related to the actual dust adhesion state is adopted is that the dust adhesion surface is 30
Since the temperature is as high as 0 to 700 ° C, there is a problem that there is no means for directly measuring the adhesion state of dust to each heat transfer surface. For this reason, conventionally, there have been proposed some methods of determining the dust adhesion state based on indirect information and operating the sootblower based on this determination.
For example, a method of starting the soot blower in response to the temperature of each part of the boiler and the draft (Japanese Patent Application No. 40-71966), a method of calculating the degree of contamination of the boiler, and a method of increasing or decreasing the activation interval of the soot blower according to this degree of contamination ( Japanese Patent Application No. 61-51355) has been proposed.

[Problems to be solved by the invention]

After all, the method of starting the sootblower with a periodic trigger such as an interval or a regular start is an operation method that does not necessarily correspond to the dirty state of the heat transfer surface, and the part where dust is attached is left for a long time, or conversely By performing a cleaning operation on a portion that does not yet need to be cleaned, wasteful use of a medium such as steam or compressed air may occur.

The above-mentioned method for avoiding the above problems has been proposed, but in these conventional proposals, emphasis is placed on the removal of dust itself, and whether or not the state of the boiler as the heat exchange device is normal, that is, Changes in the heat absorption of the boiler have not been taken into consideration. That is, if the heat transfer surface is cleaned, the heat absorption rate of that part will rise in a short time, and the heat absorption balance of the entire boiler will be lost, and the soot blow will cause the boiler state to deviate from the normal state. However, the conventional method has not taken this point into consideration.

[Means for solving problems]

The present invention is configured in view of the above-mentioned problems, and a measured value indicating the operating condition of the boiler, for example, the temperature of the gas passing through the heat transfer surface or the gas differential pressure, the temperature of the fluid flowing in the heat transfer surface, A heat transfer coefficient calculation means for calculating the heat transfer coefficient of each heat transfer surface based on the flow rate, etc., and information for determining the necessity of operating the soot blower on each heat transfer surface, for example, for each heat transfer surface. A measurement database in which the heat transfer coefficient immediately after the soot blow is registered, and the heat transfer coefficient obtained by the heat transfer coefficient calculating means,
Based on the information registered in the measurement database, first determining means for determining the necessity of operating the sootblower, and information for determining whether the operating state of the boiler is a normal state or an abnormal state, for example, Information on the relationship between the increase in the superheater spray amount, the decrease in the amount of recirculated gas, and the dust adherence on the water wall, the information on the relationship between the decrease in the superheater spray amount and the amount of dust in the superheater, the increase and decrease in the amount of recirculation gas. Whether the current operating state of the boiler is normal based on the knowledge base in which information related to dust adhesion of the heater is registered, and the current operating state of the boiler and the information registered in the knowledge base. A second determining means for determining whether the boiler is in an abnormal state, the first determining means determines that the soot blower needs to be operated, and the second determining means determines that the boiler is in an abnormal operating state. Judged That the, is characterized in that it is configured to perform the operation of soot blowers in the heat transfer surface.

[Action]

The present invention, as described above, only when the first determining means determines that the soot blower needs to be operated, and the second determining means determines that the current operating state of the boiler is abnormal. It is configured to execute the operation of the soot blower on the heat transfer surface.

Therefore, by soot-blowing, it is possible to eliminate the conventional drawback that the normal boiler state deviates from this state, that is, the boiler operating state does not affect the operating state of the boiler as a disturbance. Soot blow can be performed while always maintaining a normal state.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 4 concretely shows an arrangement state of soot blowers in a boiler and an object to be measured.

First, in FIG. 4, the soot blower S is provided with a plurality of heat transfer surfaces such as the superheater 32 of the boiler, the evaporator tube group 34, and the economizer 35. Soot blowers are grouped for each heat transfer surface, and evaluation of whether to activate soot blowers,
The judgment is also performed for each sootblower group corresponding to the heat transfer surface. The measurement targets shown in the figure are as follows.

T1 ・ ・ ・ Superheater inlet gas temperature T2 ・ ・ ・ Superheater outlet gas temperature T3 ・ ・ ・ Evaporation water pipe outlet gas temperature T4 ・ ・ ・ Carbon saver middle part gas temperature T5 ・ ・ ・ Carbon saver outlet gas temperature T6 ・..Carbon economizer inlet feed water temperature T7 ... Carbon economizer outlet feed water temperature T8 ... Carbon economizer outlet vapor temperature D1 ... Superheater inlet-coefficient economizer outlet gas differential pressure D2 ... Carbon economizer Inlet-coal saver outlet Gas differential pressure F1 ・ ・ ・ Supply water flow rate F2 ・ ・ ・ Steam flow rate F3 ・ ・ ・ Press water flow rate This method controls the operation of each soot blower by incorporating the above information of each part of the boiler.

FIG. 2 shows the outline of the system for carrying out the method of the present invention. In the figure, the measurement signal of each measuring device installed in the boiler 21 is input to the control device 26 via the signal converter 22, and the central processing unit (CPU) 23 refers to the memory 24 that stores various data. Set the start timing of the sootblower and operate each sootblower. Reference numeral 25 is an interface, 27 is a display device (CRT), and 28 is a keyboard.

Next, the method of the present invention will be specifically described mainly with reference to FIG.

First, the measured value of the measurement object shown in FIG. 2 is read and 1 is performed, and thereby the heat transfer coefficient of each heat transfer section is calculated.

 The heat transfer coefficient U can be calculated by the following formula.

Here, Q: heat exchange amount [kcal / h] Hs: heat transfer area [m ² ] ΔT: logarithmic average temperature difference [deg].

 The following formula is established for the above Q.

Q = Mw (Cpo × to−Cpi × ti) [kcal / h] where Mw: Mass flow rate of fluid (water, steam) to the heat transfer surface [kg / h] Cpi: Specific heat of inlet [kcal / kg ・deg] Cpo: Specific heat of outlet [kcal / kg · deg] ti: Inlet temperature [deg] to: Outlet temperature [deg].

 Further, the following equation holds for ΔT.

ΔT ₁ = (ti-to) ΔT ₂ = (to-ti) ΔT = (ΔT ₁ −ΔT ₂ ) / ln (ΔT ₁ / ΔT ₂ ) [deg] where ti: gas inlet temperature [deg] to: This is the gas outlet temperature [deg].

When the calculation 2 of the heat transfer coefficient of each part of the boiler is performed in this way, the measurement database 3 is referred to, and the determination 4 of whether or not the operation of the soot blower is necessary is performed based on the heat transfer coefficient and the measurement database of the part. Specifically, the heat transfer coefficient immediately after the soot blow registered in the measurement database 3, that is, the coefficient that can be regarded as a standard heat transfer coefficient without dust adhesion is calculated, and the degree of dirt on the heat transfer surface is calculated. To do. In this case, the dirt level (dust adhesion level) is defined as follows.

Dirt level = current heat transfer coefficient / heat transfer coefficient immediately after soot blowing Here, the fluid is water or steam, and the heat exchange amount and heat capacity can be easily obtained as follows.

Heat exchange amount = fluid flow rate × (outlet heat capacity−inlet heat capacity) Heat capacity = temperature × specific heat Next, referring to the knowledge base 5, the present operation 6 of the boiler is judged. That is, if the knowledge base 5 does not have a current driving state, the operator is inquired 8 by displaying it on a CRT or the like, and if it is in the knowledge base 5, the judgment 7 is made based on this knowledge base. Perform. In the knowledge base 5, the measured values and the evaluations corresponding thereto are separately stored in the normal state and abnormal state of the boiler.

Here, the normal state is a state in which it is determined that it is not necessary to activate the soot blower as a knowledge pace, and the abnormal state is a state in which it is determined that the soot blower should be activated. Since no data has been input to the knowledge base 5 in the initial state where the knowledge data pace is not yet stored,
When reaching the stage of the decision 6, the control device makes an inquiry 8 to the operator as to whether or not the current state is normal. On the other hand, the operator judges whether the operation state of the boiler is normal or abnormal from various measured values and inputs the result to the control device. By repeating this response, the knowledge base 5 is gradually formed in the control device, and the inquiry 8 to the operator is given.
Also decreases with the accumulation of this base. In addition, the judgment 7 based on the knowledge base is performed by statistically processing the set of measurement data of the normal state and abnormal state of the boiler stored in the knowledge base 5 to determine which set the measured data belongs to. To do. In this case, if it is unknown which set it belongs to, an inquiry 8 is made to the operator.

Judgment based on the knowledge base 5 is, for example, if the amount of spray of the superheater increases and the amount of recirculation gas decreases, the furnace,
It is determined that dust is attached to the water wall, and if the superheater spray amount is decreasing, it is determined that dust is adhering to the superheater, and if the recirculation gas amount is increasing, For example, it is determined that dust is attached to the reheater.

In this way, the boiler state is judged 9, and if it is not normal, a decision 11 on whether or not to operate the sootblower is made by referring to the items stored in the rule base 10. In this case, the rule (logic) such as the following is input to the rule base 10.

This rule base is a rule based on the operator's knowledge, and the effect of the soot blower on the boiler is evaluated as a disturbance.

Rule 1: Boiler load is changing → Soot blower can be operated (Reason) If the load is changing, the soot blower will not be a disturbance because the boiler is in an unsteady state, so the soot blower can be operated.

Rule 2: Load fluctuation after 1 hour of boiler → Operation of soot blower is possible (Reason) If the boiler goes into an unsteady state in the near future, it means that soot blow is carried out in that unsteady state.

Rule 3: The ash content of fuel is not adherent → Soot blower cannot operate (Reason) Generally, in a coal-fired boiler for business use, multiple types of coal are used alternately as fuel. The adhesion of ash differs depending on the type of coal.For coal species with weak adhesion, the adhesion of dust is originally small, and even if dust adheres, the adhered dust naturally expands due to expansion and contraction of the heat transfer tube during load changes. Based on the knowledge that there is no need for soot blower operation because it falls into Since the type of coal cannot be incorporated as a measured value, it will be determined by inquiring the operator.

The coal adhesion is registered in the fact table 30 as shown in FIG. 3, and the adhesion is determined. In the figure, reference numeral 29 is an inference engine (a control portion for executing a solution of a given problem by using a knowledge base) for searching the adhesion of ash of coal type X.

Rule 4: Boiler load stabilization is required → Soot blower cannot be operated (reason) In a boiler for a thermal power plant, generated steam is supplied to a steam turbine for power generation. Therefore, since the load of the boiler is determined by the power demand, there are cases in which the amount of power generation must not fluctuate due to changes in the amount of steam generated by sootblowing. In such a case, the load stabilization request is stored in the control device in advance, and the operation of the soot blower is prohibited.

Note that the judgment 11 refers to the fact table 14 in addition to the rule base 10. In this fact table, for example, the ash properties corresponding to the type of coal used as fuel or the following is entered.

Coal type A: Cohesive large Coal type B: Cohesive slightly small Coal type C: Small cohesiveness ... Coal type N: Adhesiveness is very large.

Whether or not the soot blower can be operated is judged based on the judgment 11 described above.
I do. If the sootblower is operated, the data after the operation is registered 13 in the measurement database.

〔effect〕

The present invention, as described above, only when the first determining means determines that the soot blower needs to be operated, and the second determining means determines that the current operating state of the boiler is abnormal. It is configured to execute the operation of the soot blower on the heat transfer surface.

Therefore, by soot-blowing, it is possible to eliminate the conventional defect that the normal boiler condition deviates from this condition, that is, without affecting the boiler as a disturbance, the boiler operating condition is always maintained. You can soot blow while maintaining normal condition.

[Brief description of drawings]

FIG. 1 is a sootblower control flow chart showing the first embodiment of the present invention, FIG. 2 is a control system diagram showing an example of an apparatus for carrying out the present method, and FIG. 3 is the presence or absence of ash adhesion to coal species. FIG. 4 is a flow chart showing an example of the determination method of FIG. 4, and FIG. 3 ... measurement database, 5 ... knowledge base, 10 ... rule base, 14 ... fact table, 21 ... boiler, 23 ...
… CPU, 24… memory, 26… control unit, 28… keyboard, S… sootblower

Claims (1)

(57) [Claims] 1. A heat transfer coefficient calculating means for calculating a heat transfer coefficient of each heat transfer surface and a necessity of operation of a soot blower on each heat transfer surface are determined based on a measured value indicating an operating condition of a boiler. Based on the information registered in the measurement database, the heat transfer coefficient obtained by the heat transfer coefficient calculation means, the measurement database in which information for registration is registered,
A first judging means for judging whether or not the soot blower needs to be operated, a knowledge base in which information for judging whether the boiler is operating normally or abnormally is registered, and the current operating state of the boiler. A second determining means for determining whether the current operating state of the boiler is a normal state or an abnormal state based on the information registered in the knowledge base, and the operation of the sootblower by the first determining means. When it is determined that it is necessary and when the operating state of the boiler is abnormal by the second determining means, the soot blower is operated on the heat transfer surface. A special soot blower control device.