JP4827093B2 - Boiler equipment - Google Patents

Description

  The present invention relates to a boiler ash removal device and a boiler device equipped with a control device for the boiler. Particularly, in coal with high ash adhesion such as PRB coal (Powder River Basin coal), ΔFEGT (furnace outlet gas temperature before and after ash removal). The present invention relates to an ash removal device that suppresses ΔROT (difference in steam temperature at the reheater outlet before and after ash removal) within the limit value and a boiler device that includes the control device.

  In coal-fired boilers, the degree of adhesion of ash and soot to the heat transfer surface of the boiler differs depending on the melting point and components of the ash contained in the coal used. Changes, especially the heat absorption rate of the furnace. For this reason, in a coal fired boiler, a plurality of soot blowers are installed, and air and steam are ejected by the soot blowers to remove the attached ash and soot.

  Regarding the control method for coal-fired boilers that burn bituminous coal, an intelligent soot blower control method (Japanese Patent Laid-Open No. 11-148633) has already been put into practical use, taking into account the gas temperature distribution and heat load distribution of the furnace. Ash removal.

  This intelligent soot blower control method calculates the current effective furnace area from the relationship between the estimated furnace outlet gas temperature and the effective heat quantity of the furnace, and the ratio of the effective furnace area to the designed furnace effective area In this method, the degree of contamination is estimated, the activation request degree of the soot blower is calculated, and when this exceeds a predetermined value, the soot blower is activated according to the activation order and the number of activations set in advance.

  Coal-fired boilers have limit values for ΔFEGT and ΔROT before and after ash removal, but in bituminous coal-fired furnaces, these limit values can be cleared by the intelligent soot blower control system.

  Now, considering not only the domestic market but also the global market, it is also necessary to consider the ash removal control in the case of burning foreign coal with poor ash adhesion compared to bituminous coal. Especially for PRB coal (coal with severe ash adhesion distributed in North America) etc., before the problems such as △ FEGT and △ ROT before and after ash removal mentioned above, ash adhesion is based on the energy balance of the boiler. Since the estimated furnace outlet gas temperature (hereinafter sometimes referred to as FEGT) exceeds the design value and there is a possibility that the rear heat transfer section may be blocked, the ash removal control affects the availability of boiler operation. It becomes the most important matter.

  In the case of a domestic bituminous coal-fired furnace, a steam soot blower having an effective removal range of about 2 m in radius is installed in a place where ash easily adheres, that is, in the furnace from the burner installation part to the nose part of the furnace wall.

  The soot blower is controlled based on the intelligent control method described above, but outside the effective ash removal range, there is an area where ash remains without being removed, but it is relatively difficult to use bituminous coal as fuel. Since ash having low caking property and low strength adheres to the region, it can be sufficiently removed by load change.

  On the other hand, when using foreign charcoal that easily adheres to ash, the amount of ash adhering is larger than that of bituminous coal in Japan, and if the timing of ash removal is delayed, it is difficult to remove glass. There is a problem of changing to ash. For this reason, the conventional ash removal apparatus and control method cannot sufficiently cope.

First, ash removal requires that the ash be removed with a water stream because the ash does not fall with a steam-based device. In addition, the ash is not easily left in the entire area where the ash is likely to adhere (the ash in the remaining part is highly caustic, so it is difficult to fall off due to load changes), and the ash changes to a glassy ash that is difficult to remove. It is necessary to use an ash removal control device incorporating logic that can remove ash at an appropriate timing.
JP-A-11-148633 JP-A-8-75137

  The intelligent control method that takes into account the energy balance of the boilers described in Patent Documents 1 and 2 applied to steam soot blowers in domestic bituminous coal-fired furnaces keeps △ FEGT and △ ROT before and after ash removal within the limits. It is effective as an ash removal control method. This method is a method of calculating the degree of contamination in the furnace by dividing the furnace only in the gas flow direction in the furnace and calculating the ash distribution in the ash adhesion height direction (ash adhesion thickness direction). I have not taken into account. However, the heat load in the furnace varies significantly depending on the amount of ash deposited, that is, the height of ash deposited. For this reason, the methods described in Patent Documents 1 and 2 cannot be applied to foreign coal with high ash adhesion to the furnace. The reason is that in the entire area where the ash in the furnace is likely to adhere, there is a need for logic to remove the ash at an appropriate timing before changing to glassy ash that is not left behind and difficult to remove. Because.

  An object of the present invention is to provide an ash removal control in which the difference between the furnace outlet fluid gas temperature and the reheater outlet steam temperature before and after the removal of ash in the furnace is within the limit value even in overseas coal with high ash adhesion. It is to propose a boiler device equipped with the device.

In order to achieve the above object, the invention claimed in the present application is as follows.
The invention according to claim 1 is a heat exchanger including a reheater that reheats after the steam generated in the furnace is used in the utilization equipment, and a heat exchanger tube of the heat exchanger suspended in the furnace wall or the furnace. A plurality of metal thermometers or a plurality of heat flux sensors for measuring the heat flux in the furnace, a high temperature thermometer provided at or near the furnace outlet, and a plurality of in order to remove ash in the boiler furnace In a boiler apparatus provided with an ash removal device for each section of (a), when the measured value of any one of the metal thermometers or the measured value of the heat flux sensor is less than or equal to a threshold value serving as an index for starting the ash removal device, or (B) Even if the measured value of the metal thermometer or heat flux sensor is higher than a preset threshold value, the furnace outlet gas temperature estimated based on the measured value of the high temperature thermometer or the energy balance of the boiler activates the ash removal device And the indicator to That is a boiler apparatus provided with a control device incorporating a logic that transmits ash removal start signal when the threshold value or more to become.

  In the invention according to claim 2, when the measured value of one of the metal thermometers or the heat flux sensor is equal to or less than a threshold value that serves as an index for starting the ash removal device, the control device is equal to or less than the threshold value. The location where the metal thermometer or heat flux sensor is installed is recognized as the start point of ash removal, and the measured value of one of the metal thermometers or the measured value of the heat flux sensor is higher than the threshold value. Since the furnace outlet gas temperature estimated based on the value or the energy balance of the boiler is equal to or higher than a threshold value that is an index for starting the ash removal device, when the ash removal device is started, the metal thermometer or the heat flux sensor Control that recognizes the installation location of the metal thermometer or heat flux sensor that displays the value closest to the threshold value that is the index for starting the ash removal device among the measured values, as the ash removal start point A boiler apparatus according to claim 1, wherein a control unit for.

  Invention of Claim 3 is a control apparatus which performs the control which the said control apparatus changes the ash removal area including an ash removal start point by the ash removal start point in consideration of the difference in heat load and ash thickness. It is a boiler apparatus of Claim 1 or 2.

  According to a fourth aspect of the present invention, the control device sets the ash removal area so that the reheater outlet steam temperature is within a limit value based on the relationship between the ash removal area, the furnace outlet gas temperature, and the reheater outlet steam temperature. It is a boiler apparatus in any one of Claims 1-3 which performs control to set.

  According to a fifth aspect of the present invention, after the control device transmits the ash removal start signal, the ash removal of the designated one section is finished once, and the transmission of the next ash removal signal includes ash removal. The boiler apparatus according to any one of claims 1 to 4, which is performed after waiting for the changed reheater outlet steam temperature to recover within a pre-specified fluctuation width with a change in the furnace atmosphere.

  According to a sixth aspect of the present invention, the control device arranges the metal thermometer or the heat flux sensor only in a partial region of each wall surface of the furnace including the front of the can, the rear of the can, the right side of the can, and the left side of the can. If the metal thermometer or heat flux sensor is not installed in another area on the same wall adjacent to the ash, the metal thermometer or heat flux sensor is not arranged after removing the ash in the area where the metal thermometer or heat flux sensor is installed. The boiler apparatus according to any one of claims 1 to 5, wherein the ash removal in the adjacent area is performed after a predetermined time interval has elapsed.

  According to a seventh aspect of the present invention, the control device performs control for designating a minimum time interval of ash removal between each portion when there is an ash removal start command at a plurality of portions at a time. It is a boiler apparatus in any one of.

  In the invention according to claim 8, when the control device continuously performs ash removal on the same spiral tube among a large number of spiral tubes constituting the furnace wall, the minimum time interval of ash removal start It is a boiler apparatus in any one of Claims 1-7 which perform control which designates.

  According to the first aspect of the present invention, (a) when the measured value of the metal thermometer or heat flux sensor provided in the furnace is equal to or less than a threshold value that serves as an index for starting the ash removal device, and (b) the metal temperature Even if the value of the meter or heat flux sensor is higher than the threshold value, the furnace outlet estimated based on the furnace outlet gas temperature (FEGT) measured by a high-temperature thermometer provided at or near the furnace outlet or the energy balance of the boiler When the gas temperature (FEGT) is equal to or higher than a threshold value that is an index for starting the ash removal device, by incorporating a logic for starting the ash removal device, the attached ash becomes a glassy ash that is difficult to remove. The ash removal device can be activated at an appropriate timing.

  In the first aspect of the invention, the reason for incorporating the logic in the case (b) other than the case (a) is as follows. In other words, when the respective regions of the metal thermometers and heat flux sensors installed on the furnace wall are compared, there is a difference in the amount of attached ash. Therefore, if a thermometer or heat flux sensor is installed in a place where ash is difficult to adhere, the indicated value of the thermometer or heat flux sensor will never fall below the threshold, but the FEGT will rise, The rear heat transfer surface may be blocked, making it difficult to operate the boiler. Therefore, in the present invention, in order to avoid these situations, FEGT is measured, or the distribution of the amount of ash adhesion to the furnace wall or the heat exchanger suspended in the furnace is estimated from the energy balance of the furnace, Even when the indicated value of the measured thermometer or heat flux sensor does not correspond to the threshold value, the ash removal start signal is output when the measured value of the FEGT or the FEGT obtained based on the energy balance is equal to or greater than the threshold value serving as an index for starting the ash removal device Is the logic to send

  According to the invention described in claim 2, in addition to the action of the invention described in claim 1, (a) the value of the metal thermometer or the heat flux sensor is equal to or less than a threshold value serving as an index for starting the ash removal device. When starting the ash removal device, the location where the metal thermometer or heat flux sensor below the threshold is set as the ash removal start point, giving priority to the place where the attached ash tends to become glassy. Ash can be removed, and (b) the FEGT estimated based on the measured temperature of the high-temperature thermometer or the energy balance of the boiler, although the value of the metal thermometer or heat flux sensor is higher than the threshold, When the ash removal device is activated, the metal temperature indicating the value closest to the threshold value of the metal thermometer or the heat flux sensor is displayed. Alternatively the installation location of the heat flux sensor by the ash removal starting point, adhering ash can be removed preferentially ash from the point prone to glassy.

  Further, the larger the ash thickness (the larger the ash adhesion amount), the higher the heat load in the furnace, and the larger the ash removal area, the larger the ΔFEGT and ΔROT. Therefore, according to the invention described in claim 3, in addition to the operation of the invention described in claim 1 or 2, it is different for each region by incorporating the logic for changing the ash removal area depending on the location of the ash removal start point. In consideration of the effect at the time of ash removal, the ash removal control can be performed so that ΔROT is within the set limit value. For example, the thicker the ash, the greater the amount of heat collected at the furnace wall when removing the ash, even if ash with the same removal area is removed. By setting the area to be relatively small, the ash removal control can be performed so that ΔROT is within the set limit value.

  Furthermore, as shown in FIG. 7, the relationship between the ash removal area and ΔFEGT differs depending on the region in the furnace. Therefore, according to the invention described in claim 4, in addition to the operation of the invention described in claims 1-3, each set according to the region in the furnace so that the set ΔROT falls within the range of the limit value. The ash removal area is set in consideration of the relationship between the different ash removal areas and ΔFEGT. That is, in a region where ash easily adheres, ΔROT can be kept within a set limit value by setting the ash removal area relatively small so that ΔFEGT does not fluctuate greatly.

  The opening of the two gas flow paths obtained by dividing the furnace outlet duct in half in the gas flow direction so that the steam temperature at the reheater outlet (hereinafter sometimes referred to as ROT) is always a constant value. Since the flow rate distribution in each gas flow path is adjusted by changing with a parallel damper, the ROT changes with a certain fluctuation width by adjusting the opening of the gas flow path regardless of the presence or absence of ash removal. Yes. If the next ash removal is performed during the adjustment of the gas flow rate distribution, the adjustment of the ROT becomes difficult. Then, according to invention of Claim 5, in addition to the effect | action of Claim 1-4, after an ash removal start signal is transmitted once and ash removal is performed with an ash removal apparatus, an ash removal apparatus is The ash removal device is not restarted until the ROT is recovered within a predetermined limit value after the operation is stopped.

  According to invention of Claim 6, in addition to the effect | action of invention of Claims 1-5, each wall surface of the front of the can where the metal thermometer or the heat flux sensor is arranged, the rear of the can, and the left of the can After removing the ash in the area in one furnace wall, continuously removing the ash in the area where the metal thermometer or heat flux sensor is not placed on the same furnace wall adjacent to the area where the ash was removed. If this is done, the influence of the metal temperature of the ash removal portion becomes too great, and the influence on ΔROT and ΔFEGT becomes excessive, so that it can be performed only after a predetermined time interval has elapsed.

  According to the invention described in claim 7, in addition to the effects of the inventions described in claims 1-6, the effect on ΔROT and ΔFEGT is excessive when it is necessary to remove ash at a plurality of locations at once. Therefore, the ash removal is performed at each position with a predetermined time interval.

  According to the invention described in claim 8, in addition to the effects of the inventions described in claims 1 to 7, in order to prevent a large influence on ΔROT and ΔFEGT, ash removal on the same spiral tube is performed. In order not to carry out continuously, it carried out at predetermined time intervals.

  According to the invention described in claim 1, since the ash removal device can be started at an appropriate timing before the ash attached in the furnace becomes glassy ash which is difficult to remove, Even when used as fuel, the furnace outlet fluid gas temperature and ΔROT associated with ΔFEGT during ash removal can be within the limit values.

  According to invention of Claim 2, in addition to the effect of invention of Claim 1, when starting an ash removal apparatus, it removes ash preferentially from the location where adhering ash tends to become glassy. Thus, the attached ash can be easily removed.

  According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, in addition to changing the ash removal area according to the location of the ash removal start point, the limit value for which ΔROT is set Can be controlled within.

  According to the fourth aspect of the present invention, in addition to the effects of the first to third aspects of the invention, in the region where the ash is easily attached, the ash removal area is made relatively small so that the ΔFEGT does not fluctuate greatly. Thus, ΔROT can be set within the set limit value.

  According to the fifth aspect of the invention, in addition to the effects of the first to fourth aspects of the present invention, once the ash removal is performed by the ash removal device, the ash removal device is started at the same location next time. By not transmitting the next ash removal start signal until ΔROT recovers within a predetermined value, ΔROT can be kept within a set limit value.

  According to the sixth aspect of the invention, in addition to the effects of the first to fifth aspects of the invention, after removing the ash from the furnace wall in which the metal thermometer or the heat flux sensor is installed, the metal adjacent thereto The ash removal in the region where the thermometer or the heat flux sensor is not arranged is not continuously performed, so that ΔROT and ΔFEGT are not greatly affected.

  According to the invention described in claim 7, in addition to the effects of the inventions described in claims 1 to 6, when it is necessary to remove ash at a plurality of locations at once, a predetermined time interval is provided for each location. By performing the ash removal, it is possible to prevent ΔROT and ΔFEGT from being greatly affected.

  According to the invention described in claim 8, in addition to the effects of the inventions described in claims 1-7, the ash removal on the same spiral tube is not carried out continuously, which greatly affects ΔROT and ΔFEGT. You can avoid giving.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a flow of ash removal start determination of the ash removal device provided in the boiler device according to the present embodiment. In this example, a metal thermometer that measures the heat flux on the heat transfer tubes (superheater, evaporator, economizer, reheater heat transfer tubes) of the heat exchanger suspended in the boiler furnace wall and the furnace or A plurality of heat flux sensors are installed, and the degree of ash adhesion to the furnace wall is monitored by the value of a metal thermometer or heat flux sensor. The measured value of the metal thermometer or heat flux sensor decreases as ash adhesion to the furnace wall progresses. Further, the ash removal start instruction value (= threshold value) is a value that indicates how much the ash must be removed when the measured value decreases.

  When the measured value of any metal thermometer or heat flux sensor installed on the furnace wall is equal to or less than a threshold value that serves as an index for starting the ash removal device, an ash removal start signal is first transmitted. However, when comparing the areas handled by each metal thermometer and heat flux sensor installed on the furnace wall, there is always a difference in the amount of ash adhering, and there is a distribution in the amount of ash adhering throughout the furnace wall. The temperature information from the furnace wall (water wall) and the heat exchanger tubes of the heat exchanger suspended in the furnace is not sufficient.

  If a thermometer or heat flux sensor is installed in a place where ash is difficult to adhere, the ash removal start instruction value based on the measured value of the thermometer or heat flux sensor will never fall below the threshold value. It is possible that the outlet gas temperature (FEGT) rises and the rear heat transfer surface of the furnace is blocked, making it difficult to operate the boiler. The quantitative distribution of adhering ash on the furnace wall and the like varies depending on the boiler load and the burner pattern, so it cannot be solved directly by increasing the number of thermometers or heat flux sensors.

  Therefore, in this embodiment, in order to avoid these situations, the amount of ash attached to the heat exchanger suspended in the furnace wall or furnace from FEGT estimated from the energy balance of the furnace or measured from the energy balance of the furnace. Even if the ash removal start instruction value based on the measured values of the thermometer and the heat flux sensor does not correspond to the threshold value, if the FEGT exceeds the threshold value serving as an index for starting the ash removal device, the ash removal start value is estimated. Start removal.

  Once the ash removal start signal is sent, the ash removal device is started and the soot blower is executed, the interval between the completion of the soot blower and the next start of the soot blower is within the value specified in advance by ROT While monitoring whether it has recovered. Specifically, the logic is such that the start signal is not transmitted until the ROT that has changed due to the ash removal is recovered within a predetermined value.

  During the operation of the furnace, the opening of the two gas flow paths obtained by dividing the duct at the furnace outlet in half in the gas flow direction is changed by a parallel damper so that the ROT always becomes a constant value. The gas flow distribution in the road is adjusted. The distribution of the gas flow rates of the two gas passages by changing the opening degree of the parallel damper does not depend on whether or not the ash is removed, but the ROT changes with a certain amplitude by adjusting the opening degree of the gas passage. If the next ash removal is performed during the adjustment of the opening degree of the parallel damper, it becomes difficult to adjust the ROT.

  Here, an example of ash removal operation and ROT behavior is shown in FIG. Moreover, the flowchart of the ash removal operation shown in FIG. 9 is shown in FIG. The elapsed time taken until the ROT changed by the ash removal is recovered within a predetermined value is defined as t2. If the elapsed time t from the end of the previous ash removal is smaller than the elapsed time t2, the ash removal is not performed even if the ash removal start signal is transmitted by the metal temperature of the boiler furnace wall or the FEGT. Actually, the elapsed time t2 required until the ROT is recovered is a minute unit (5 to 10 minutes), whereas the time t required until the FEGT is recovered after removing the ash once is 1-2 hours. Therefore, regarding FEGT, it is unlikely that the threshold will be exceeded before the elapsed time t2 is recovered.

  When elapsed time t> elapsed time t2, if necessary, a signal for starting the ash removal device is transmitted based on the metal temperature of the boiler furnace wall or the information of FEGT. Further, in this logic, every time the ash removal device is activated, the elapsed time t is set to t = 0.

In summary, the logic flow for determining the start of ash removal is to monitor the elapsed time t = t + Δt from the end of the previous ash removal, and when t> t2, the metal in the boiler furnace wall The presence / absence of activation is determined from the temperature and FEGT information.
In addition, the method of estimating the distribution of the ash adhesion amount (heat transfer surface contamination degree) to the heat transfer tubes of the heat exchanger suspended in the FEGT, the furnace wall, or the furnace from the energy balance in the furnace is as follows. is there.

  As shown in FIG. 4, in the case of a furnace, the heat transfer surface contamination degree is calculated by calculating the current effective furnace area with respect to the design furnace area, and setting the ratio as the contamination degree of the heat transfer surface of the furnace, In the case of the rear heat transfer surface of the furnace, the current heat flow rate is calculated with respect to the design heat transfer rate, and the ratio is calculated as the degree of contamination of the rear heat transfer surface.

  As shown in the algorithm of FIG. 4, the furnace outlet gas temperature is calculated from the coal properties 11 and the oxygen concentration at the economizer outlet (Eco) outlet oxygen concentration (economizer outlet oxygen concentration) 12 at the most downstream of the rear heat transfer section. 13 is calculated, and the total gas amount 15 is calculated from the gas amount 13 and the recirculated gas amount 14.

In addition, the inlet / outlet water in the pipe of each bank section (the heat transfer surface of the heat exchanger suspended in the furnace and referred to as the convection heat transfer section, whereas the furnace wall is referred to as the radiation heat transfer section) The endothermic amount 18 of each bank part is calculated from the steam temperature 16 and the inlet / outlet water / steam pressure 17 in the pipe of each bank part. The heat absorption amount of each heat transfer surface is obtained from the equation (1) by the water-based energy balance equation.
Q = F × (Ho−Hi) (1)
Q: Aqueous heat absorption (Kcal / s)
Ho: Water system exit enthalpy (Kcal / kg)
Hi: Water system enthalpy (Kcal / kg)
F: Flow rate (kg / s)

Further, with respect to the process amount in which the data has a temporal shift (phase difference) such as the gas system state quantity and the water system state quantity, the phase difference is corrected by taking into consideration the heat capacities of the metal and the fluid.
{Wm × (Cm / Cf) + (Vp / V)} × dHo / dt + F (Ho−Hi) = Q (1 ′)
Wm: Metal mass (Kg)
Cm: Metal specific heat (Kcal / Kg ° C)
Cf: Fluid specific heat (Kcal / Kg ° C)
Vp: Fluid volume (m ³ )
V: Fluid specific volume (m ³ / Kg)

The equation (1 ′) is relative to the heat transfer surface,
Since the relationship of outlet fluid heat amount + heat transfer surface heat storage amount = inlet fluid heat amount + heat amount lost in the gas system is established, it can be developed by the following expression representing this.
F × Ho + dqt / dt = F × Hi + Q (1 ″)
qt: Temporary heat storage (Kcal / s)

Moreover, in the evaporator installed boiler, since the heat absorption amount of the evaporator cannot be obtained from the water system, it is calculated by the following energy balance equation of the gas system.
Q = (tgi-tgo) × Cpg × Wg
tgi: Inlet gas temperature (° C)
tgo: outlet gas temperature (° C)
Cpg: Gas specific heat (Kcal / Kg ° C)
Wg: Gas amount (Kg / s)

Next, the gas temperature outside the pipe at each bank portion entrance / exit is calculated from the total gas amount 15 and each bank portion endothermic amount 18. The temperature of each part on the gas side outside the tube is calculated by the energy balance equation using the water endothermic amount obtained by the equation (1).
That is, if the economizer (Eco) outlet gas temperature is known (if the gas temperature is actually measured), the economizer inlet gas temperature can be obtained from equation (2).

As described above, the same calculation is sequentially performed on the heat transfer surface on the upstream side of the gas, so that the furnace outlet gas temperature (FEGT) 20 can be finally obtained.
tgi = tgo + {Q / (Cpg · Wg)} (2)
tg: Gas temperature (Each part inlet gas temperature is calculated sequentially from Equation (2) from the economizer outlet gas temperature)
Q: endothermic amount (calculated from equation (1)) (Kcal / s)
Cpg: Gas specific heat (calculated from gas temperature) (Kcal / kg ° C.)
Wg: Gas amount (calculation) (kg / s)

  The current effective furnace area 22 can be known from the relationship between the effective heat quantity (effective area as a radiation source) 21 and the furnace outlet gas temperature (FEGT) 20 that is the design condition of the furnace of the coal fired boiler. In short, if the furnace outlet gas temperature (FEGT) 20 is higher than the design condition, it indicates that the contamination is progressing.

Then, as shown in the equation (3), the furnace heat transfer surface contamination degree 24 can be estimated from the ratio of the current effective furnace area and the structure area (design furnace effective area).
Furnace contamination degree df = Design effective furnace area / Current effective furnace area (3)

Further, the degree of contamination of the heat transfer surface of the bank is determined based on the heat flow rate of the heat transfer surface.
Here, the current heat transmissibility 25 is Q = K · A · Δt (4)
Q: Calculated from endothermic equation (1) A: Heat transfer area (design value)
Calculate according to
Δt: Logarithmic average temperature difference standard heat permeability 26
Ko = (Ucg + Urg) × Ucs / (Ucg + Urg + Ucs (5)
Ucg: Gas side convection heat transfer coefficient (calculated from gas volume and gas temperature)
Urg: Gas-side radiant heat transfer coefficient (calculated from gas temperature)
Ucs: Steam side convective heat transfer coefficient (calculated from steam flow rate and steam temperature)
Calculate according to

And as shown in (6) Formula, each bank part heat-transfer surface dirt | cleaning degree 27 can be estimated from the ratio of the present heat-transfer rate and a reference | standard heat-transfer rate.
Degree of fouling on heat transfer surface of each bank part df = reference heat transmissivity / current heat transmissivity

Next, FIG. 2 shows a block diagram of an ash removal control apparatus according to the present invention.
This control device includes a device having a function of determining the start of ash removal, a function of determining an ash removal start point, and a function of calculating an ash removal area. In this configuration, after the start of ash removal is determined, the ash removal start point is determined. When the metal temperature and heat flux sensor are below the threshold, the starting point is also determined when the ash removal start is determined, but when the FEGT exceeds the threshold, the ash removal starts and the metal temperature and The location where the thermometer showing the value of the heat flux sensor closest to the threshold value provided for them is the ash removal start point.

Next, the setting of the ash removal area including the ash removal start point will be described.
When ash removal is performed, heat absorption of the furnace wall (water wall) and the heat exchanger suspended in the furnace is improved, and accordingly, FEGT is lowered and ROT is also lowered. FIG. 3 shows the relationship between ΔROT and ΔFEGT of a 1000 MW class boiler. The relationship between ΔFEGT and ΔROT is proportional, and the upper limit ΔFEGT before and after ash removal is determined by the limit value of ΔROT. If the limit value of ΔROT is assumed to be within ± 1 ° C., ΔFEGT at this time needs to be within ± 5 ° C.

  ΔFEGT at the time of ash removal is determined by the heat load, ash thickness, and removal area of the ash removal location. FIG. 5 is a result of numerical analysis of ΔFEGT when a part of the ash on the furnace front wall is removed. ΔFEGT increases as the ash removal area increases. FIG. 6 shows three types of ΔFEGT at the time of ash removal by numerical analysis. In both cases, the attached ash is removed with the same removal area on the right wall of the furnace, but even if the ash removal area is the same, ΔFEGT is different, so in addition to the ash removal area, the heat load and the ash thickness are △ FEGT. You can see that it affects.

FIG. 7 shows the relationship between the ash removal area and ΔFEGT. The numbers in the figure indicate the case study numbers, and the ash is removed from any location.
The lower solid line in FIG. 7 shows the relationship between the ash removal area and ΔFEGT in the region from the burner provided on the furnace wall to the after-airport, and the upper dotted line is from the after-air port to the nose portion A (see FIG. 2). The relationship between the removal area of ash in the region and ΔFEGT is shown. In either case, △ FEGT increases as the ash removal area increases. However, removing the ash adhering to the area of the nose portion A from the after airport causes the ash in the area from the burner to the after airport to be removed. Greater than if removed. This is due to the difference in the thickness of the attached ash. Usually, when the attached ash is removed, the amount of heat collected in the furnace increases, so the FEGT falls. The larger the area where adhering ash is removed, the greater the amount of heat collected in the furnace, and the lower the FEGT.

  In the two lines, the difference in the influence of the adhesion ash removal area on ΔFEGT is due to the difference in the thickness of the adhesion ash. If the adhesion ash is thick, the ash of the same area was removed. Even in this case, the amount of heat collected during ash removal is large. If it demonstrates in the example shown in FIG. 7, the thickness of the adhesion ash in the upper part of an after airport will be thick, and (DELTA) FEGT will also become large correspondingly.

As described above, ΔFEGT at the time of ash removal is determined by the thermal load, ash thickness, and removal area of the ash removal location, so the removal area with a limit of ΔFEGT <± 5 ° C. is 30 to 90 m ^2. .
The relationship between the ash removal area and ΔFEGT is the heat transfer tube including the furnace wall (water wall) and the heat exchanger suspended in the furnace, that is, the furnace wall, superheater, evaporator, economizer, reheater By obtaining each heat transfer tube in consideration of each installation location, the ash removal range including the ash removal start point can be determined for each point.

  The relationship between the ash removal area and ΔFEGT may be calculated using numerical analysis for new boiler furnaces (cans), or for boiler furnaces already delivered (cans already delivered). The operational conditions may be reflected to correct the relationship between the ash removal area and ΔFEGT.

FIG. 8 shows an example of a screen when the control device according to this embodiment is used.
FIG. 10 shows an example of ash removal in the case where one sensor handles a plurality of areas of the furnace. Each number is a number of each area that divides the inside of the furnace, and alphabets after the numbers indicate positions before, after, right and left of the can. For example, “before the can” means the front wall surface of the furnace in a state where the boiler furnace is installed at the installation position, and “can right” means the right side wall surface of the furnace.

  In the above arrangement, for example, when the sensor (1) determines that the ash removal of the zone 2F is necessary, the ash removal of the zone 1F is also performed after the ash removal of the zone 2F is completed. However, at this time, the minimum interval (about 10 minutes) for the start of ash removal is set. This is because it takes less than 1 minute to remove ash per cycle, so removing ash continuously in two adjacent zones on the same wall will have an excessive effect on ΔROT and furnace wall steam temperature. It is.

  Similarly, regarding the ash removal on the same spiral pipe (spiral pipe constituting the furnace wall), if the ash removal at different locations of the same spiral pipe is continuously performed, the influence of the metal temperature increases. Set the minimum interval for starting ash removal in two identical spiral tubes. That is, after the fluid in the spiral tube in a certain zone is cooled by the ash removal operation, the target location and schedule of ash removal are adjusted so that the ash removal operation is not performed again while flowing in the same spiral tube. It is.

  Summarizing the above, the present embodiment is a function for determining the start of ash removal from both the temperature information of the furnace water wall and the FEGT, a function for determining the ash removal start point, and a function for determining the removal area including the ash removal start point. The boiler device includes an ash removal control device having a function of determining the activation interval of the soot blower.

  Since the boiler apparatus of this embodiment is equipped with the ash removal control device incorporating the above logic, even in overseas coal with high ash adhesion, the furnace outlet gas temperature and ΔROT associated with the FEGT change during ash removal are the limit values. The ash can be removed within the range.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses the boiler using foreign coal with severe ash adhesion, the control which enables the ash removal which makes (DELTA) ROT accompanying the FEGT change at the time of furnace exit fluid gas and FEGT removal within a limit value can be performed.

It is a figure which shows the control flow of the ash removal start determination of the Example of this invention. It is a figure which shows the block diagram of the ash removal control apparatus which implements the control flow shown in FIG. It is a figure which shows the relationship between (DELTA) FEGT and (DELTA) ROT for the ash removal start determination of the Example of this invention. It is a figure which shows the heat transfer surface dirt posting algorithm in the furnace of the Example of this invention. It is a figure which shows (DELTA) FEGT (numerical analysis) at the time of removing some ash before the furnace can of the Example of this invention. It is a figure which shows (DELTA) FEGT (numerical analysis) at the time of removing a part of adhesion ash of the furnace can right of the Example of this invention. It is a figure which shows the ash removal area of the furnace of the Example of this invention, and the relationship of (DELTA) FEGT. It is a figure which shows the example of a screen using the ash removal control apparatus of the furnace of the Example of this invention. It is a figure which shows the relationship of the ROT behavior at the time of the ash removal operation | movement of the furnace of the Example of this invention. It is a figure for demonstrating the example of cleaning in case one sensor takes charge of the some area | region in the furnace of the Example of this invention.

Explanation of symbols

11 Coal properties 12 Economizer outlet oxygen concentration 13 Combustion gas amount 14 Recirculation gas amount 15 Total gas amount 16 Each bank part inlet / outlet water / steam temperature 17 Each bank part inlet / outlet water / steam pressure 18 Each bank part heat absorption 19 Each bank part inlet / outlet Gas temperature 20 Furnace outlet gas temperature 21 Furnace effective heat 22 Current furnace effective area 23 Design furnace effective area 24 Furnace heat transfer surface contamination 25 Current heat flow rate 26 Standard heat transfer rate 27 Degree of heat transfer surface contamination of each bank

Claims (8)

Heat exchangers including a reheater that reheats after the steam generated in the furnace is used in the equipment, and a plurality of metal thermometers installed in the heat exchanger tubes of the furnace wall or in the furnace Alternatively, a plurality of heat flux sensors for measuring the heat flux in the furnace, a high-temperature thermometer provided at or near the furnace outlet, and an ash removal device for each of the plurality of sections for removing ash in the boiler furnace In the boiler device provided with
(A) When the measured value of one of the metal thermometers or the measured value of the heat flux sensor is equal to or less than a threshold value that serves as an index for starting the ash removal device, or (b) The measured value of the metal thermometer or heat flux sensor is previously An ash removal start signal is generated when the furnace outlet gas temperature estimated based on the measured value of the high temperature thermometer or the energy balance of the boiler is equal to or higher than a threshold value that serves as an index for starting the ash removal device, even if it is higher than the set threshold value. A boiler device, characterized in that a control device for transmitting is provided.   When the measured value of one of the metal thermometers or the heat flux sensor is equal to or less than a threshold value that serves as an index for starting the ash removal device, the control device may detect the metal thermometer or heat flux sensor that is equal to or less than the threshold value. The installed location is recognized as the start point of ash removal, and the measured value of one of the metal thermometers or the measured value of the heat flux sensor is higher than the threshold, but based on the measured value of the high temperature thermometer or the energy balance of the boiler Therefore, when the ash removal device is started up, the ash removal gas temperature is the highest among the measured values of the metal thermometer or heat flux sensor. Control that recognizes the installation location of the metal thermometer or heat flux sensor displaying a value close to the threshold value as an index for starting the apparatus as the ash removal start point Motomeko 1 boiler apparatus according.   The said control apparatus performs the control which changes the ash removal area containing an ash removal start point by the ash removal start point in consideration of the difference in heat load and ash thickness. Boiler equipment.   The control device performs control to set the ash removal area so that the reheater outlet steam temperature is within a limit value based on the relationship between the ash removal area, the furnace outlet gas temperature, and the reheater outlet steam temperature. The boiler device according to any one of claims 1 to 3.   The control device, after sending the ash removal start signal, once until the ash removal of the specified section is finished, the next ash removal signal is sent in accordance with the change in the furnace atmosphere including ash removal. The boiler apparatus according to any one of claims 1 to 4, which is performed after waiting for the changed reheater outlet steam temperature to recover within a pre-specified fluctuation range.   The control device arranges a metal thermometer or heat flux sensor only in a partial area of each wall surface of the furnace consisting of the front of the can, the rear of the can, the right side of the can, and the left side of the can. If the metal thermometer or heat flux sensor is not installed in the area and the ash removal is performed in the area where the metal thermometer or heat flux sensor is installed, the ash removal in the adjacent area where the metal thermometer or heat flux sensor is not arranged is predetermined. The boiler apparatus according to any one of claims 1 to 5, wherein the boiler apparatus is performed after elapse of the time interval.   The said control apparatus performs the control which designates the minimum time interval of the ash removal between each location, when there are ash removal start instructions of several locations at once. The boiler device described in 1.   In the case where the ash removal on the same spiral pipe is continuously performed among the many spiral pipes constituting the furnace wall, the control device performs control for designating a minimum time interval for starting the ash removal. The boiler device according to any one of claims 1 to 7, characterized in that

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