JPH0875137A - Method and device for controlling soot blower by divided furnace model - Google Patents

Abstract

PURPOSE: To provide a soot blower control device for a boiler furnace which is constituted to start a soot blower in a place where the interior of a furnace is really fouled, and effectively remove the fouling and to provide a method therefor. CONSTITUTION: In a boiler having a plurality of soot blowers corresponding to a furnace and the heat transfer surfaces of a bank part, the heat transfer surface of the interior of the furnace is divided into a plurality of spots, and the degree of fouling of each division heat transfer surface is evaluated by an integral type degree of fouling computing part 2 to effect computation of the degree of fouling by a furnace integral model based on process data inputted to an input part 1 and a division type degree of fouling computing part 3 to effect computation of the degree of fouling by a furnace division model. When fouling of a heat transfer surface exceeds an allowable limit, a corresponding soot blower is operated. The degree of fouling is not calculated integrally with the furnace but the furnace is vertically divided to effect heat transfer calculation. The degree of fouling of each division is calculated, and a portion (a section) to which coal ash is adhered is reliably detected. Only a soot blower corresponding to the portion is started to remove fouling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soot-blower control device for removing dirt on a heat transfer surface of a boiler, which effectively removes dirt in a furnace and enables highly efficient operation regardless of fuel properties. The present invention relates to a soot blower control device.

[0002]

2. Description of the Related Art Conventional soot blowers are used to improve combustion efficiency and recover boiler characteristics by removing the ash adhering to the heat transfer surface of the furnace wall of a boiler or superheater by steam injection by burning coal. To be Soot blowers are installed on furnace walls, superheaters, reheaters, and economizers, and there are short-drag, long-drag, and half-drag types. The short slip type sootblower cleans the furnace wall with the medium jetted from the nozzle while rotating 360 degrees. Further, the long pull-out type soot blower is a soot blower used for a high temperature gas part, and sprays an injection medium from a tip end nozzle to a boiler pipe group while rotating it for 360 degrees for cleaning. The half-drag soot blower is a soot blower used for the low temperature gas part (coal saving part) and has the same function as the long-drag difference type.

In a boiler using many kinds of coal, the degree of the amount of coal ash adhering to the heat transfer surface varies depending on the type of coal. Therefore, the sequence control for starting the soot blower in a predetermined cycle requires a true start. If there is a deviation from the time, and if this is an excessive number of start-ups, the soot blower injection medium consumption amount is increased, or the soot blower injection medium consumption amount becomes insufficient, and in each case a situation such as a decrease in boiler efficiency occurs. To do. Therefore, regarding the AI soot blower control system that comprehensively judges changes in the operating conditions of the boiler such as the fouling state of the heat transfer surface and the gas temperature at the outlet of the economizer, and determines the optimum soot blower starting point and automatically controls it. , We invented earlier (Japanese Patent Publication No. 62-467)
68, Japanese Patent Publication No. 62-46769, etc.). In addition to the manual mode and the sequencer mode (the operator starts the kick for uniform automatic start by the sequencer), these inventions determine the optimum start point of the soot blower from the degree of fouling on the heat transfer surface and the boiler state, and operate completely automatically. The present invention relates to a soot blower automatic control device having (intelligent mode). In the above invention, the unit for calculating the degree of contamination of the heat transfer surface is generally the furnace and each bank surface. That is, the fouling degree is calculated as one unit in the entire furnace, and the activation of the sootblower in the furnace is cyclically selected in order.

[0004]

Explaining with an example of a coal-fired boiler in which soot blower is most important, dirt on the heat transfer surface in the furnace is the temperature at which coal ash is in the plastic region (not solid or liquid). It often occurs in places of obi. The initial change temperature of ash and the pour point (temperature) are a measure of contamination on the heat transfer surface in the furnace, but they vary greatly depending on the type of coal.
Also, the soiled parts in the furnace differ depending on the type of coal. The reason is that the temperature in the plastic region varies depending on the type of coal, and the temperature distribution in the furnace is not uniform, so the location of fouling in the furnace varies depending on the type of coal. Furthermore, the temperature distribution in the furnace is distributed in the temperature range of about 1000 to 1500 ° C. from the fuel zone to the end of the furnace.

However, the above-mentioned invention of the AI sootblower control device of the present applicant does not consider the above points, and only one fouling degree is calculated for the entire furnace. There was a problem that the sootblower could only be activated cyclically in sequence, and the sootblower could not be activated at a location where the heat transfer surface of the furnace had the highest degree of contamination. Further, in the invention of the present applicant, the degree of fouling of the heat transfer surface of the furnace is 1.0 if the effective area of the furnace is the same as the calculated value (that is, not dirty), and the smaller the effective area is if it becomes dirty. Therefore, the values are large, 1.1 and 1.2. Therefore, when the degree of contamination of the heat transfer surface in the furnace exceeds a certain threshold value (for example, 1.2), the soot blower in the furnace is activated (injected). If the dirt on the heat transfer surface is removed by this start-up, the dirt level will be reduced, so all of the soot blowers in the furnace will be stopped. For this reason, no consideration was given to the fact that the location of contamination in the furnace differs depending on the type of coal. SUMMARY OF THE INVENTION It is an object of the present invention to provide a soot blower control device and method for a boiler furnace that activates the soot blower in a truly dirty place in the furnace and effectively removes the dirt.

[0006]

The above object of the present invention can be achieved by the following constitutions. That is, in a boiler equipped with a plurality of soot blowers corresponding to the heat transfer surfaces of the furnace and bank, the heat transfer surface inside the furnace is divided into multiple parts, and the degree of contamination of each divided heat transfer surface is evaluated. ,
When dirt on the heat transfer surface exceeds the allowable limit, the soot blower control method by the split furnace model that operates the soot blower corresponding to each split furnace heat transfer surface, or the input section for inputting process data and the input section Based on the process data, the integrated fouling degree calculation unit that calculates the fouling degree by the furnace integrated model, the division type fouling degree calculation unit that calculates the fouling degree by the furnace division model, and the fouling degree for each furnace division section individually A soot blower control device according to a split furnace model including a start determination unit that determines a soot blower corresponding to each divided furnace heat transfer surface to be started, and an output unit that performs a soot blower start kick to an external device.

[0007]

The fouling degree of each divided furnace according to the present invention is calculated as follows. 1. Calculation of furnace heat absorption Qwi (n) for each section The furnace is modeled as a distribution, that is, the inside of the furnace is divided into burner sections, port sections, etc., and radiant heat transfer is calculated for each section, and the outlet gas temperature is calculated. Tgi (n) and furnace heat absorption Qw
Calculate wi (n). (N is a section suffix) The basic arithmetic expression of the split furnace model is shown in Expression (1). In this model, the sum of the fuel calorific value Q ₁ and the heat input Q ₂ that air, recirculation gas, etc. bring into the furnace for each divided section is the heat transfer amount Q ₃ to the heat transfer surface (water wall) and By solving the heat balance equation that is equal to the sum of the heat output amount Q ₄ , the section outlet gas temperature TG and the section heat transfer amount Q ₄
And calculate. Q ₁ (heat generation amount) + Q ₂ (heat input amount) = Q ₃ (heat transfer amount) + Q ₄ (heat output amount) (1)

Further out heat Q ₄ in each heat of the arithmetic expression (2) to (5) shown in the expression of the heat input Q ₂ formula (n-
1) shows the amount of heat carried in from the lower section. Q ₁ = GFUEL * HU * F1 * SRBNR (2) Q ₂ = GAIR * CP ₁ * TAIR + GFUEL * CP ₂ * TFUEL + GGR * CP ₃ * TGR + Q ₄ (n-1) (3) Q ₃ = A * F * FCG * σ * ((TG / 100) ⁴ − (TM / 100) ⁴ ) + A * α * (TG-TM) (4) Q ₄ = (GGAS + GRAIR + GRFUEL + GGR) * CP ₄ * TG (5) (GFUEL: Fuel flow rate GAIR : Air flow rate GG
R: Recirculation gas flow rate GGAS: Combustion gas flow rate GRAIR: Excess air flow rate GRFUEL: Excess fuel flow rate TFUEL: Fuel temperature TAIR: Air temperature TGR: Recirculation gas temperature TG:
Section gas temperature TM: Metal temperature HU: Calorific value SRBNR: Burner air ratio CP: Specific heat A: Heat transfer area σ: Stefan-Poltsman definition α: Contact heat transfer coefficient F1: Burning coefficient F: Radiation coefficient
FCG: emissivity) Here, the heat transfer amount Q ₃ corresponds to the heat absorption amount Qw i (n) to the furnace in the section n.

2. Calculation of the degree of furnace fouling df (n) for each section in the furnace The degree of furnace fouling df (n) of each section is defined as follows. Current effective furnace area of section n (n) = Current effective furnace area x (Qwwi (n) / ΣQwi (n)) (6) Here, the current effective furnace area is the total effective furnace area used in the above-mentioned conventional technique. It is the area of the furnace and is calculated by the method described below. Furnace fouling degree in section n df (n) = design effective furnace area in section n (n) / current effective furnace area in section n (n) (7) Here, the design effective furnace area in section n (n) is determined in advance. It is the designed numerical value. In this way, instead of performing the fouling degree calculation with the furnace integrated, the furnace is divided in the vertical direction to perform the heat transfer calculation, the fouling degree calculation is performed for each divided surface, and the adhesion site (section ) Is surely detected, only the sootblower corresponding to the part is activated, and the dirt is removed.

[0010]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a block diagram of a soot blower control device of this embodiment, and FIG. 2 shows an example of division of a section of a furnace of a boiler. In FIG. 2, the burner section in the furnace is divided into a plurality of sections along the flow direction of the combustion gas.
Provide multiple sections from the port to the superheater. In the sootblower controller of FIG. 1, the process amount is input to the input unit 1, and the fouling degree calculation is performed by the integrated fouling degree computing unit 2 that performs the fouling degree computation by the furnace integrated model and the furnace split model shown in FIG. It is provided with a division type dirtiness degree calculation section 3, an activation determination section 4 for individually determining a sootblower to be activated from the dirtiness degree for each section, and an output section 5 for performing a sootblower activation kick to an external device. Further, the activation of the individual sootblower is configured to be electrically activated by the sootblower conductor panel 7 via the sootblower drive control device 6 having an interlock condition on the activation of the sootblower.

In the input unit 1, interface of process data, averaging, abnormality determination, etc. are carried out, and the result is sent to the integrated stain degree calculation unit 2 and the split stain degree calculation unit 3. The integrated fouling degree calculation unit 2 calculates the current effective furnace area of the entire furnace by the conventional method and sends it to the divided fouling degree calculation unit 3. The fouling degree calculation in the fouling degree fouling calculation unit 2 which performs fouling degree calculation by the furnace integrated model is performed according to the following equation according to the flow shown in FIG. Furnace fouling degree df = Design effective furnace area / Current effective furnace area (8)

Since the design effective furnace area is a set value, if the current effective furnace area is obtained, the degree of furnace contamination d
f is required. The current effective furnace area for the entire furnace is determined as follows. The furnace outlet gas temperature (FEGT) shown in FIG. 2 is obtained from the flow shown in FIG. 3, and as shown in FIG. 4 from this value, the furnace outlet gas temperature (FEGT) and the effective heat quantity / currently effective state for the furnace are obtained. From the graph showing the relationship between furnace area (HA / SC), HA / SC
Ask for. Since the effective heat quantity for the furnace is calculated by the type of fuel, etc., the current effective furnace area of the entire furnace is determined.

The furnace outlet gas temperature (FEGT) is determined as follows according to the flow shown in FIG. The amount of heat absorbed by each bank (coil) portion is determined by the water system energy balance equation (9) shown in FIG. _{Q = F × (H o -H} i) (9) where, Q is heat absorption amount of the aqueous (kcal / s), H _o enthalpy (kcal / kg) of aqueous outlet, H _i the aqueous inlet enthalpy ( kcal / kg), F is the flow rate (kg /
s). The temperature of each part on the gas side is calculated by the energy balance shown in FIG. _{tg i = tg o + Q /} Cpg · Wg (10) where Q is the amount of heat absorbed water obtained from equation (9), tg
_i is the economizer inlet gas temperature, tg _o the economizer outlet gas temperature,
Cpg is gas specific heat (calculated from gas temperature) (kcal / k
g ° C), Wg is the gas amount (kg / s) obtained by calculation
Is. Therefore, if found to economizer outlet gas temperature tg _o, (10) economizer from the equation inlet gas temperature tg _i
Can be obtained. In this way, by performing the same calculation for the heat transfer surface on the gas upstream side, the furnace outlet gas temperature (FEGT) can be finally obtained.

Next, a method of calculating the degree of contamination of the heat transfer surface of each bank (coil) portion in which the superheated tubes and the like are arranged will be described. The current heat transmission coefficient K is obtained from the following equation (11). Q = K · A · Δt (11) where Q is the amount of heat absorption of the water system obtained from equation (9), A is the heat transfer area that is the design value, and Δt is the logarithmic average obtained from equation (12) below. It is the temperature difference. _{△ t = {(tg i -ts} o) - (tg o -ts i)} / {ln (tg i -ts o) / (tg o -ts i)} (12) the reference heat transfer coefficient K ₀ is the following It is obtained from the equation (13). K ₀ = {(Ucg + Urg) × Ucs} / (Ucg + Urg + Ucs) (13) where Ucg is the gas-side convection heat transfer coefficient (calculated from the gas amount and gas temperature), and Urg is the gas-side radiant heat transfer coefficient (from the gas temperature). Ucs is a steam-side convection heat transfer coefficient (calculated from steam temperature and steam flow rate). Thus, the contamination degree df of each heat transfer surface of the bank (coil) portion is calculated by df = K ₀ / K (14).

Next, in the division type dirt calculator 3 of FIG. 1, the dirt degree calculation for each section is carried out by the above equations (6) and (7), and the result is sent to the start judging section 4. The activation determination unit 4 compares the dirt level of each section with a preset threshold value, selects which soot blower should be activated according to the order in the same section, and sends it to the output unit 5. The output unit 5 commands the sootblower drive control device 6 to start the sootblower to be started. In addition, the bank (coil) portion in which the superheated tubes and the like are arranged is performed by the contamination degree calculation method disclosed in the related art.

[0016] In this way, the area (section) where the coal ash or the like adheres to the heat transfer surface of the furnace can be reliably detected, and the dirt due to the adhesion of the coal ash or the like can be removed. Therefore, it is possible to prevent the occurrence of erosion due to the frequent activation of the sootblower and the damage to the equipment, and it is possible to significantly reduce the amount of steam used for the sootblower. Further, in the conventional technology, the static characteristics of the boiler are deviated depending on the ash adhesion location, which reduces the control margin of the control device (for example, the damper does not reach the control value even when the damper is fully opened). It was However, according to this embodiment, it is possible to deal with any fuel and coal. At the same time, by optimizing the static characteristics, the dynamic characteristics are also improved, which can greatly contribute to the improvement of the load change rate.

[0017]

EFFECTS OF THE INVENTION According to the present invention, it is possible to reliably detect the dirt part of the furnace and remove the dirt, so that it is possible to prevent not only the decrease in boiler efficiency but also the occurrence of erosion and the damage to the equipment due to the frequent activation of the sootblower. In addition, the amount of steam used in the soot blower can be significantly reduced. Further, according to the present invention, by optimizing the static characteristics, it becomes possible to deal with all kinds of fuel and coal, and at the same time, the dynamic characteristics are improved, which can greatly contribute to the improvement of the load change rate.

[Brief description of drawings]

FIG. 1 is a block diagram of a sootblower control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of division of sections of a furnace of a boiler according to an embodiment of the present invention.

FIG. 3 is a diagram showing a flow of calculating a degree of fouling in an integrated fouling degree calculation unit that performs a degree of fouling calculation by a furnace integrated model of a boiler according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a furnace outlet gas temperature (FEGT) and a effective heat quantity / current effective furnace area (HA / SC) for the furnace, which is obtained in advance for the boiler according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating an energy balance of a water system for calculating a heat absorption amount of a bank portion of a boiler according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating an energy balance for calculating the temperature of each part on the gas side of the boiler according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input part, 2 ... Integrated dirt degree calculation part, 3 ... Divided type dirt degree calculation part, 4 ... Activation determination part, 5 ... Output part, 6 ... Soot blower drive control device, 7 ... Soot blower conductor board

Claims (2)

[Claims] 1. A boiler having a plurality of soot blowers respectively corresponding to the heat transfer surfaces of the furnace and the bank part, wherein the heat transfer surface inside the furnace is divided into a plurality of parts, and the degree of contamination of each divided heat transfer surface. And a soot blower corresponding to each split furnace heat transfer surface is operated when the contamination of the heat transfer surface exceeds an allowable limit. 2. An input section for inputting process data, an integrated fouling degree calculation section for calculating a fouling degree by a furnace integrated model based on the process data input to the input section, and a fouling degree calculation by a furnace divided model. The division type fouling degree calculation part to perform, the start determination part to judge the soot blower corresponding to each divided furnace heat transfer surface to be started individually from the fouling degree of each furnace division section, and the output to perform the soot blower start kick to the external device A soot-blower control device based on a split-furnace model, characterized in that