JPS6357690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a waste incinerator equipped with a waste heat boiler as an accessory equipment so as to constantly stabilize the amount of steam generated by the boiler.

Traditionally, the thickness of the dust layer on the combustion grate was measured and
The technology for controlling the dust feeding speed of the drying grate and the combustion grate so that the thickness of the dust layer on the combustion grate is within an appropriate range is disclosed in Japanese Patent Publication No. 42-45425 and Japanese Patent Publication No. 53
It is known from Publication No.-11154.

However, this method only maintains the thickness of the garbage layer within an appropriate range, meaning that it is not too thick or too thin, so although it is possible to maintain the combustion state with some fluctuation, it does not stabilize the amount of heat generated. There is a problem with that purpose. In other words, miscellaneous municipal waste may contain more or less water, or may contain more or less paper even if the water content is the same, so the lower calorific value Hu ( kcal/Kg) varies widely. Therefore, if waste with different Hu values is fed into the furnace, even if the thickness of the waste layer on the combustion grate is controlled to be constant, the amount of heat generated cannot be stabilized, especially if a waste heat boiler is installed. In this case, a problem arises in that the amount of steam generated by the boiler constantly fluctuates.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to control the amount of steam generated by the waste heat boiler basically based on the lower heating value Hu of waste, and to further It is an object of the present invention to provide a control method for a waste incinerator in which the combustion state in the furnace is controlled by the combustion pattern of waste in order to perform highly accurate control.

An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is an explanatory diagram showing the general configuration of a waste incinerator incorporating a waste heat boiler as an accessory equipment, and Fig. 2 is an explanatory diagram showing the control system of this waste incinerator. The incinerator has a hopper 1 into which the waste stored in the waste storage pit is thrown in by operating a crane 2, and a first stage and a second stage where the waste thrown into the hopper is dried while being moved at an appropriate speed. Dry grate 3, 3, combustion grate 4 which burns dry waste supplied from this second stage dry grate 3 while moving it, rotary kiln 5 which burns unburned material after combustion, and combustion chamber 6. a waste heat boiler 7 that is heated using the exhaust gas combusted in the hopper 1, a weight scale 8 that measures the amount of garbage input into the hopper 1, and a flow meter that measures the combustion air flow rate F to the combustion grate 4. 9a, 9b, a temperature detector 10 that detects the temperature TA of combustion air LF, and a furnace temperature control air LC.
a flow meter 11 that measures the air amount BC, a pressure gauge 12, 13 that measures the pressures P1 and P2 at the upper and lower parts of the combustion grate 4, a temperature detector 14 that measures the boiler feed water temperature TB, and a temperature sensor 14 that measures the boiler feed water temperature TB. A flow meter 15 that measures the amount GS, a temperature detector 16 that detects the temperature TG of the outlet gas that has passed through the boiler 7, a detector 23 that measures the amount of combustion air BD, and the amount of garbage input G,
Calculate the heat balance from the combustion air amount BD, the air amount for furnace temperature control BC, the boiler feed water temperature TB, the boiler steam amount GS, the boiler outlet gas temperature TG, and the combustion air temperature TA, and calculate the lower heating value Hu (kcal) of the waste. /Kg)
The Hu calculation device 17 determines the amount of garbage to be supplied into the furnace from this lower calorific value Hu and the target steam generation amount of the boiler 7, and determines the basic garbage feeding speed V of the drying grate 3 corresponding to this amount. , a computing device 20 that provides the signal 18 to the drying grate drive 19;
The combustion pattern of the garbage on the combustion grate 4 is estimated from the indirect measurement value of the combustion area area A, and if the estimated value of the combustion pattern exceeds the upper limit of the appropriate range that maintains the optimal garbage combustion pattern, the dry grate is Drying grate drive device 1 sends a correction signal 21 to increase the speed of No. 3 by a certain ratio from the above-mentioned basic garbage feeding speed V, and to lower it by a certain ratio when the speed falls below the lower limit of the above-mentioned appropriate range.
9, and a calculation device 22 for estimating the combustion pattern.

Therefore, the method for controlling a waste incinerator according to the present invention includes (1) calculating the heat balance of the incinerator system that integrates the incinerator body and the waste heat boiler 7 as an auxiliary equipment, and Find the lower heating value Hu. This calculation of Hu is based on the signal of the garbage input amount G (Ton/h) measured by the weighing scale 8, the signal of the combustion air amount BD (Nm ³ /h) measured by the detector 23,
Air amount BC (N) for furnace temperature control measured by flowmeter 11
m ³ /h), the boiler feed water temperature TB (°C) measured by the temperature detector 14, and the flowmeter 1.
The signal of the boiler steam amount GS (Ton/h) measured in step 5, the boiler outlet gas temperature TG (°C) measured by the temperature detector 16, and the combustion air temperature TA (°C) measured by the temperature sensor 10 are combined. Arithmetic device 1
7 and calculate the heat balance,
Find the unknown Hu.

(2) Calculate the amount of waste to be supplied into the furnace from the lower heating value Hu of the waste and the target steam generation amount of the waste heat boiler 7 using the arithmetic unit 20, and dry grate 3 corresponding to this amount of waste to be supplied. determine the basic waste feed rate V and provide the signal 18 to the drying grate drive 19.

(3) On the other hand, the combustion pattern of the garbage on the combustion grate 4 is estimated by indirectly measuring the area A of the combustion area.

An incinerator is a thermal process with a large capacity, and it is a process that requires an order of magnitude of time to go through the two processes of drying and combustion, and finally turn into ash. Furthermore, since the waste is not uniform, the combustion conditions inside the incinerator vary considerably.

Therefore, as a result of experiments and analysis, we found that there is an optimal pattern for the combustion state of garbage on the combustion grate 4 for stabilizing the amount of steam generated, but that the combustion state deviates significantly from that optimal pattern. It was discovered that the amount of steam generated sometimes fluctuated easily.
As shown in FIG. 3a, the optimal state is when combustion is sufficiently occurring at the rear of the combustion grate 4 and there is sufficient unburned waste at the front. This is because if this condition is maintained, there will be a sufficient amount of dried waste among the unburned waste stored at the front of the combustion stage, and the combustion condition will deteriorate and the amount of steam generated will drop. Sometimes, by increasing the speed of the combustion grate 4, the dried waste can be immediately introduced into the combustion zone and the combustion can be accelerated. On the other hand, figure b
In this state, the combustion stage is completely burnt, so when the combustion condition becomes poor, there is almost no effect even if you speed up the combustion grate 4, and even if you speed up the drying grate 3, it will not dry out. Since the garbage on the step is not necessarily dried, this is not necessarily effective either. Furthermore, in the state shown in FIG. 4C, unburned waste remains on the combustion grate 4 over almost the entire area, and the combustion condition has deteriorated considerably, so there is no choice but to be patient until the combustion becomes active.

Therefore, in order to reduce and stabilize fluctuations in the amount of steam generated by the waste heat boiler 7, it is necessary to maintain an optimal combustion pattern as shown in FIG. 3a.

Therefore, the method for estimating this combustion pattern is as follows.
Think of it as follows. When the combustion air of the garbage is in the state shown in FIG. 3a, most of the combustion air sent from below the combustion grate 4 passes through the thin part of the garbage. This corresponds well to the position of the burning flames, and can be seen by the way the flames emerge from the surface of the garbage. This is because the surface of the unburned part of the garbage is dried by the high-temperature gas inside the furnace, and is almost ready to burn at any time.If air (oxygen) is sent here, the flame will spread quickly. The fact that no flame is generated despite the transition to a combustion state indicates that almost no air passes through the thicker parts of the garbage, and only through the thinner parts.

Therefore, if we calculate the area of the area on the combustion stage where the flame is well exposed, that is, the area through which the combustion air passes, we get:
Distinction (estimate) between combustion patterns in Figure 3 a, b, and c
will be possible.

Therefore, in the area where combustion is actively occurring, the amount of garbage has decreased greatly and it has become very close to ash, so the thickness h _p (m) of that area is a value determined based on the garbage incineration base. Almost close to. Garbage incineration base is WKg/h, ash ratio is a, combustion grate 4
If the speed at which the waste moves on the combustion stage is V'm/h, then if there is a part on the combustion stage that is completely turned into ash, the height h _A (m) of that ash part is calculated by the following formula: It can be found by

h _A = aW/γA×V′×l γA: Density of ash (Kg/m ³ ) l: Furnace width (m) Since h _p is the height where the garbage has not completely turned into ash, It can be considered that the value is slightly larger than h _A above.

However, assuming that the air permeability there is approximately constant, h _p = _KP1 −P2/ν ^2-n ρ ^n-1 u ⁿ (1) P1: Grate lower pressure P2: Grate upper pressure ν: Combustion air viscosity ρ: Combustion air density u: Determined by combustion air flow rate. The above ν, ρ, and u change depending on the temperature of the combustion air, so ν=ν(TA) ………(2) ρ=ρ _p ×273/273+TA ………(3) u=F/A×273+TA/ 273 ......(4) Calculated using the formula. Here, TA is the combustion air temperature, ρ _p is the air density in standard conditions, F is the combustion air flow rate in standard conditions, A is the area of the combustion region, and from equations (1), (3), and (4) above, A is When you ask for So, if we write the constants together as K′, we get becomes.

This n is determined by air permeability etc.
We determined this as follows. When the amount of combustion air is changed stepwise, combustion does not follow immediately, so the combustion area area A should not change much before and after. Therefore, n was experimentally determined on the condition that the area A should be as unaffected by step changes in the combustion air flow rate F as possible.
The value of n varies depending on the furnace, but is approximately close to 1.

(4) After the area A of the combustion area on the combustion grate 4 is indirectly measured by calculation using the above equation (5), the dry fire is Grating drive device 1
9, and if the estimated value of the combustion pattern exceeds the upper limit of the appropriate range that maintains the optimal waste combustion pattern (pattern in Figure 3 a), the drying grate speed is adjusted to the lower waste heating value Hu and the target steam generation amount. The garbage combustion pattern in the combustion stage is always kept in the optimal state as shown in Figure 3a by increasing the basic garbage feed rate V by a certain ratio, and decreasing it by a certain ratio if it falls below the lower limit. The amount of steam generated by the boiler 7 is controlled so as to be maintained and the amount of steam generated by the boiler 7 is always stabilized.

By controlling the waste and the incinerator in this way, it is possible to suppress the fluctuations inside the furnace which are the cause of fluctuations in the amount of steam generated, and it is possible to stably maintain the target amount of steam over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the general configuration of a waste incinerator incorporating a waste heat boiler, Fig. 2 is an explanatory diagram showing the control system of this waste incinerator, and Figs. 3 a to c are illustrations of the combustion It is an explanatory view showing a burning pattern of the garbage on the grid. 1... Garbage input hopper, 2... Crane, 3... Drying grate, 4... Combustion grate, 5... Rotating kiln, 6
... Combustion chamber, 7... Waste heat boiler, 8... Weight scale, 9a,
9b... Combustion air flow meter, 10... Combustion air temperature detector, 11... Furnace temperature control air flow meter, 12,
13...Pressure gauge that measures the upper and lower pressures of the combustion grate, 14...Boiler feed water temperature detector, 15...Flow meter that measures the amount of boiler steam, 16...Temperature detector that detects the boiler outlet gas temperature, Hu...Garbage lower calorific value, G...garbage input amount, F...combustion air flow rate, BC
…Amount of air for furnace temperature control, BD…Amount of combustion air, TB…
Boiler feed water temperature, TG...boiler outlet gas temperature,
TA... Combustion air temperature, P1, P2... Pressure, 17...
Hu calculation device, 18... Signal, 19... Dry grate drive device, 20... Computation device, 22... Computation device for combustion pattern estimation, 23... Combustion air amount detector.

Claims (1)

[Claims] 1. Calculate the heat balance of the incinerator system, which includes the furnace body and the waste heat boiler as an attached equipment, to determine the lower calorific value of the waste, and then calculate the amount of heat inside the incinerator from this lower calorific value and the target steam generation amount of the boiler. Determine the amount of waste to be fed into the combustion area, determine the corresponding basic waste feed rate of the drying grate, give that signal to the drying grate drive device, and adjust the waste combustion pattern on the combustion grate to the combustion area. If this combustion pattern estimate exceeds the upper limit of the appropriate range to maintain an optimal refuse combustion pattern, as estimated from indirect measurements of area, the drying grate speed should be increased by a fixed percentage above the basic refuse feed rate. In addition, if the temperature falls below the lower limit of the above appropriate range, a correction signal is given to the drying grate drive device to lower it by a certain ratio, thereby maintaining the waste combustion pattern in the combustion stage in an optimal state and stabilizing the amount of steam generated by the boiler. A method for controlling a waste incinerator, characterized in that the waste incinerator is controlled as follows.