JPH09126436A - Combustion controller of dust coal combustion boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion controller capable of optimum vapor temperature control even when an in-furnce water wall pipe heat transfer surface of a coal combustion boiler is contaminated and a fuel ratio of stock coal is changed. SOLUTION: A dust coal combustion boiler is adapted such that it includes grinders 58, 59 to which stock coals 56, 57 having different fuel ratios are supplied respectively, and a corresponding burner is connected with each grinder, and that, it receives supply of dust coal from the corresponding grinder, and the coal is burned in the furnace to form a flame 15. When a detection value 64 of furnace outlet combustion gas temperature or an estimation value of the same temperature estimated by a heat transfer dynamic characteristic model 40 is higher than an output value (outlet temperature set value) 63 of a furnace outlet gas temperature setting unit 45, the amount of supply of X stock coal 56 having a lower fuel ration is increased through a grinder coal delivery amount controller 39, and the amount of supply of Y stock coal 57 having a higher fuel ration is reduced. In contrast, when a detection value or an estimation value of the outlet gas temperature is lower than a set value, the amount of the X stock coal 56 is reversely reduced, and the amount of supply of the Y stock coal 57 having a higher fuel ration is correspondingly increased. A mechanism to achieve the above operation is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for a pulverized coal combustion boiler, and more particularly to a pulverized coal combustion boiler suitable for always ensuring good control response even for a wide variety of coals. The present invention relates to a combustion control device.

[0002]

2. Description of the Related Art FIG. 2 shows a pulverized coal production facility, a boiler device for burning pulverized coal calculated by the facility, and a control device according to a conventional technique. The coal feeder 2 supplying the coking coal 1 adjusts the coking coal transportation speed according to the speed signal 3 and supplies the hopper 4 of the pulverized coal manufacturing facility (crusher) 10 with the coking coal proportional to the signal 3. The raw coal 1 is rotated by an electric motor 5 and drops onto a turntable 6 which is a mixing unit, and is mixed with a collecting coal 11 and 13 by a classifying unit to be described later to form a holding coal 7. The retained charcoal 7 is supplied by centrifugal force between the outer circumference of the above-mentioned turntable 6 which constitutes the grinding means and the roller 8 placed thereon, and is ground by the rolling force and rotation of the roller and blows on the outer circumference of the turntable. It is conveyed upward in the crusher 10 by the conveying air 9 to be raised, the coarse particles 11 are separated in the middle thereof, and the remaining coarse particles 13 are separated when passing through the vane 12 of the classifier, and then the turntable 6 is separated. Will be returned. The pulverized coal from which the coarse powder has been separated is conveyed to the burner portion of the boiler through the pulverized coal transportation pipe 14 together with the carrier air 9 and forms a flame 15 by combustion.

In such a boiler device, the water supply 16
Is supplied from the water supply pump 37 to the drum 17, and the downcomer pipe 1
8, the water passes through the water cooling wall 19 and the riser 20, becomes steam, and is accumulated in the upper portion of the drum 17, and then the superheater connecting pipe 21.
And is overheated by the superheater 29. The proportional / integral element (PID controller) 35 is set by the deviation between the signal from the steam temperature detector 31 and the steam temperature target value (setting) signal 33 from the steam temperature setter 32 with respect to the superheated steam exiting the superheater. The opening degree of the water injection valve 36 is adjusted by using the steam temperature controller 30 to control the steam temperature by the water injection in the steam desuperheater 30. On the other hand, most of the steam flow of the steam supply line is supplied by evaporation by the furnace water cooling wall 19 except for the small amount of water injected by the water injection valve 36, so the steam pressure controls the amount of pulverized coal that controls the heat absorption amount of the furnace water cooling wall 19. The vapor pressure can be controlled by adjusting the amount of fuel supplied by the transportation pipe 14. Therefore, the deviation 26 between the signal from the steam pressure detector 22 and the steam pressure setting signal 24 is given to the PID controller 27 to obtain the coal feeder speed signal 3.

The boiler apparatus shown in FIG. 2 operates in principle on the assumption that an arbitrary amount of steam at a steam demand destination is extracted, and the control loops having the proportional / integral adjusting element 35 and the element 27 as cores respectively have a steam temperature. , Controls to keep the pressure at a constant value regardless of the amount of steam. The boiler control device works well if the boiler and the coal crusher are less contaminated and the coal properties are almost constant.

[0005]

The above-mentioned prior art has a problem that when the boiler becomes dirty or the coal property changes, it may not be possible to cope with transient fluctuations in steam temperature, as will be described later. FIG. 3 shows the relationship between the heat absorption amount of the reactor water cooling wall, which is said to control the control characteristics of the boiler, the fuel ratio indicating the ratio of the fixed carbon content to the volatile content of coal, and the contamination of the reactor water cooling wall. Even if combustion is performed at the same fuel flow rate, the heat absorption amount of the water wall of the furnace water decreases with an increase in the fuel ratio and the contamination of the furnace, and the heat absorption of the superheater on the downstream side of the combustion gas increases. At this time, the furnace outlet gas temperature increases, and in a steady state with the same fuel amount, the furnace water cooling wall heat absorption amount and the furnace outlet gas temperature can be uniquely obtained by knowing one another, so the furnace water cooling wall heat absorption amount The characteristics are handled as furnace outlet gas temperature characteristics that are easy to understand.

Based on the above, the boiler device of FIG. 2 has the following problems. That is, the heat absorption distribution of the furnace water cooling wall 19 and the superheater 29 changes due to the change of the fuel ratio of coal and the progress of fouling of the furnace. Regarding the change of the heat absorption balance, when the heat absorption in the furnace water cooling wall 19 decreases and the heat absorption in the superheater 29 increases due to the increase in the fuel ratio, for example, the superheater outlet steam temperature rise prevention and the evaporation in the water cooling wall It is necessary to increase the opening degree of the water injection valve 36 in order to supplement the insufficient amount. Since the balance correction is constantly required including the reverse case, it is likely that the water injection valve 36 is always operated near the fully opened or fully closed position. In the vicinity of the fully open and fully closed positions, there is little room for control of the opening degree of the water injection valve 36 on one side, and it may not be possible to cope with the transient fluctuation of the steam temperature.

An object of the present invention is to provide a boiler combustion control device capable of optimal control even with respect to changes in the fuel ratio and fouling of the furnace.

[0008]

The invention claimed in the present application to achieve the above object is as follows. (1) Pulverized coal burners are arranged at a plurality of positions in the boiler furnace, and the pulverized coal burners are provided with means for supplying pulverized coal with different fuel ratios individually or in groups, In a combustion control device of a pulverized coal combustion boiler provided with an adjusting means and provided with a superheater that superheats steam generated in the water wall of the furnace, the measured value of the furnace outlet combustion gas temperature measuring instrument and / or the furnace outlet gas temperature A means for adjusting the proportion of pulverized coal with different fuel ratios to the boiler supplied through the pulverized coal burner according to the deviation between the calculated value by the calculation model and the target value of the furnace outlet gas temperature is provided. Combustion control device for pulverized coal combustion boilers.

(2) A plurality of pulverizers for respectively supplying raw coals having different fuel ratios and pulverizing the coals, and pulverized coals connected to each pulverizer and having different fuel ratios are supplied to the boiler furnace. In the combustion control device of the pulverized coal combustion boiler, which is provided with a plurality of pulverized coal burners that burn inside, and a superheater provided in the downstream region of the furnace that superheats the steam generated in the water wall of the furnace, A temperature measuring device and / or the temperature calculation model is provided, and the measured value of the measuring device and / or
Alternatively, when the value calculated by the calculation model is higher than the target temperature value, the amount of coal supplied to the crusher for crushing the raw coal with a low fuel ratio is increased, and the crusher for crushing the raw coal with a high fuel ratio is added. Mechanism for reducing the amount of coal supply, and the amount of coal supplied to the pulverizer for pulverizing the raw coal having a low fuel ratio when the value measured by the measuring instrument and / or the value calculated by the calculation model is lower than the temperature target value. And a mechanism for increasing the amount of coal fed to a pulverizer for pulverizing a raw coal having a high fuel ratio, and a combustion control device for a pulverized coal combustion boiler.

There is a correlation between the fuel ratio of coal properties and the furnace outlet gas temperature. The lower the fuel ratio, the higher the proportion of volatile components, and therefore the higher the brightness of the burner flame, mainly in the burner zone. The radiant heat transfer amount increases, the furnace water cooling wall heat absorption amount increases, and the heat absorption of the superheater on the downstream side of the combustion gas decreases. Therefore, as a result, the steam temperature at the boiler outlet (superheater outlet) becomes low or the steam pressure becomes high, and the furnace outlet gas temperature becomes low.

Therefore, according to the deviation between the present furnace outlet gas temperature and the furnace outlet gas temperature target value obtained by the measuring device for the furnace outlet gas temperature and / or the heat transfer dynamic characteristic model for calculating the furnace outlet gas temperature. Since the furnace outlet gas temperature can be set to the target value at all times by adjusting the distribution ratio of the charging to the pulverized coal burner of a plurality of coal types having different fuel ratios to the boiler, it is possible to always ensure good control response.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention and shows a situation in which the present invention is applied to the boiler apparatus shown in FIG. 2 according to the prior art. Therefore, the description of the components common to FIG. 2 is omitted. In this embodiment, A
In the two crushers, crusher 58 and B crusher 59,
The X-coal coal 56 having a fuel ratio of about 1.5 is fed to the crusher 58, and the Y-coal coal 57 having a fuel ratio of about 2.0 is fed to the B crusher 59, and is incorporated in the furnace outlet gas temperature control device 38. According to the deviation between the present furnace outlet gas temperature obtained by the heat transfer dynamic characteristic model 40 and the furnace outlet gas temperature target value 63 obtained from the furnace outlet gas temperature setting device 45, Through 39, the amount of coal supplied to the A crusher 58 and the amount of coal supplied to the B crusher 59 are controlled to optimal values.

When the furnace outlet gas temperature at the present time is higher than the target value, the feed amount of the X coking coal 56 having a low fuel ratio is increased and the fuel ratio is high via the crusher coal output control device 39. The supply amount of the Y coking coal 57 is reduced, and as a result, the furnace outlet gas temperature is optimally controlled so as to reach the target value.
If the furnace outlet gas temperature is lower than the target value,
Decrease the amount of X coking coal and increase the amount of Y coking coal. Therefore, even if the coal properties change over time or the boiler fouls, the furnace outlet gas temperature can be controlled to the set value, so the deviation of the heat collection characteristics and steam temperature characteristics can be reduced, and even at high load change rates. Can handle.

The furnace outlet gas temperature is directly obtained by the furnace outlet gas temperature detector 60 as shown in FIG. 1 instead of being obtained by the heat transfer dynamic characteristic model 40.
It is also possible to perform the same control as described above in accordance with the deviation between the target value 63 of the furnace outlet gas temperature.

[0015]

【The invention's effect】

(1) It is possible to reduce fluctuations in the boiler outlet steam temperature and fluctuations in the steam pressure caused by a transient imbalance in the heat absorption amount between the superheater and the water cooling wall of the furnace, which occurs when the amount of steam withdrawn from the boiler changes. (2) Due to the change of the fuel ratio and the progress of fouling of the furnace, the heat absorption distribution between the water cooling wall of the furnace and the superheater is changed, and it is possible to prevent the deterioration of the controllability to the steam temperature fluctuation.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional technique.

FIG. 3 is a diagram showing a relationship between a heat absorption amount of a boiler furnace, a fuel ratio of fuel, and contamination of a heat transfer tube in the furnace.

[Explanation of symbols]

1 ... Coking coal, 2 ... Coal feeder, 3 ... Coal feeder speed signal, 4 ... Hopper, 5 ... Electric motor, 6 ... Turntable, 7 ... Owned coal,
8 ... Crushing means, 9 ... Carrier air, 10 ... Crusher, 12 ... Vane, 14 ... Pulverized coal transportation pipe, 15 ... Flame, 17 ... Drum, 18 ... Downcomer pipe, 19 ... Water cooling wall, 20 ... Riser, 21
... superheater connecting pipe, 22 ... steam pressure detector, 23 ... signal setting device, 24 ... steam pressure setting signal, 28 ... furnace outlet combustion gas, 29 ... superheater, 30 ... desuperheater, 31 ... steam temperature detector , 32 ... Steam temperature setting device, 33 ... Steam temperature setting signal,
34 ... Steam temperature deviation signal, 36 ... Water injection flow control valve, 38
... Furnace outlet gas temperature control device, 39 ... Grinder coal output control device, 40 ... Heat transfer dynamic characteristic model, 44 ... Total fuel amount command signal, 45 ... Furnace exit gas temperature setting device, 46 ... Burner for A grinder Pulverized coal amount command signal, 47 ... B crusher compatible burner pulverized coal amount command signal, 49 ... Crusher coal feeding amount command signal, 53
... Signal setting device, 56 ... X coking coal, 57 ... Y coking coal, 58
... A crusher, 59 ... B crusher, 60 ... Furnace exit gas temperature detector, 61 ... Signal subtractor, 62 ... Furnace exit gas temperature deviation signal, 63 ... Furnace exit gas temperature setting signal, 64 ... Furnace exit gas temperature Detection signal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Yamamoto, 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi, Ltd. Kure Factory (72) Koho Miyama, 36-36 Takaracho, Kure, Hiroshima Babcock Hitachi Ltd. Kure Institute

Claims (2)

[Claims] 1. A pulverized coal burner is arranged at each of a plurality of positions in a boiler furnace, and the pulverized coal burner is provided with means for supplying pulverized coal with different fuel ratios individually or in groups, and each pulverized coal burner is provided. In a combustion control device for a pulverized coal combustion boiler equipped with a flow rate adjusting means and a superheater for superheating steam generated in the water wall of the furnace, the measured value of the furnace outlet combustion gas temperature measuring instrument and / or the furnace outlet gas A means was provided to adjust the proportion of pulverized coal with different fuel ratios to the boiler supplied through the pulverized coal burner according to the deviation between the value calculated by the calculation model for calculating the temperature and the target value of the furnace outlet gas temperature. A combustion control device for a pulverized coal combustion boiler, which is characterized in that 2. A plurality of pulverizers for respectively supplying raw coals having different fuel ratios and pulverizing the coals, and pulverized coals connected to the pulverizers and having different fuel ratios are supplied to the pulverizers and then supplied to a boiler furnace. In the combustion control device of the pulverized coal combustion boiler, which is equipped with a plurality of pulverized coal burners that burn in the furnace, and a superheater provided in the downstream region of the furnace that superheats the steam generated in the water wall of the furnace, A measuring device and / or the temperature calculation model is provided, and when the measured value of the measuring device and / or the value calculated by the calculation model is higher than the temperature target value, it is supplied to a crusher for crushing the raw coal having a low fuel ratio. A mechanism that increases the amount of coal and reduces the amount of coal supplied to a crusher that crushes raw coal with a high fuel ratio, and the measured value of the measuring instrument and / or the value calculated by the calculation model is lower than the temperature target value. When the source of fuel is low A pulverized coal combustion boiler characterized by being provided with a mechanism for reducing the amount of coal supplied to a pulverizer for pulverizing raw coal and increasing the amount of coal supplied to a pulverizer for pulverizing raw coal having a high fuel ratio. Combustion control device.