JPH0465290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to facilities where flue gas from a waste incinerator is cooled with a waste heat boiler, or to cooling flue gas by spraying cooling water onto the flue gas in a gas cooling room. This article relates to an automatic combustion control method in waste incinerators used in cooling facilities.

BACKGROUND OF THE INVENTION Various automatic combustion control methods for stabilizing combustion have been provided and implemented, for example in grate-type garbage incinerators. In these controls, as a method of detecting the actual combustion amount at each time in the waste incinerator, the waste heat boiler type uses the amount of steam generated in the boiler as an index, and the water injection method uses the amount of injected water as an index. It has been implemented. There is also an example in which the outlet temperature of a waste incinerator is controlled as an index of the actual amount of combustion at each time in the waste incinerator. However, these indicators are affected not only by the actual amount of combustion in the waste incinerator but also by the amount of air sent in as waste combustion air, so it is difficult to say that they accurately detect the actual amount of combustion. There were flaws. In addition, in response to changes in the combustion conditions in the waste incinerator, changes in the amount of steam generated in the boiler, changes in the amount of water injected in the gas cooling room, and changes in the outlet temperature of the waste incinerator are accompanied by a time delay. The drawback was that the instantaneous combustion amount could not be detected accurately. For this reason, the control that detects the amount of steam generated in the boiler, the amount of water injected in the gas cooling room, and the outlet temperature of the waste incinerator and keeps these detected values constant lacks accuracy and speed, and completely automatic combustion is not possible. In some ways, it is difficult to say that this is a control method.

From the above, if we find an index that can more accurately and quickly detect the actual amount of combustion at each time in a garbage incinerator and implement control to keep this index constant, it will be easier than conventional automatic combustion control. , it becomes possible to perform more reliable automatic combustion control.

Therefore, recently, a method shown in FIG. 5 has been used as a combustion control method for garbage incinerators. In this Fig. 5, 21 is a waste incinerator into which waste 22 is thrown, an incinerator cooling blower 23 and a forced air blower 2.
4 are in communication via pipes 25 and 26, respectively. The combustion exhaust gas 27 from the garbage incinerator 21 is
It flows from a heat treatment device 28 such as a waste heat boiler or a gas cooling room to a dust collector 29, and then to an induced blower 3.
0 to the chimney 31. Combustion control using this method involves controlling the opening degree of the inlet damper 32 of the induced blower 30 so that the gas pressure inside the garbage incinerator 21 is constant, and also controlling the opening degree of the inlet damper 32 of the induction blower 30 so that the temperature at the outlet of the garbage incinerator 21 is constant. In addition, the opening degree of the outlet damper 33 of the furnace cooling blower 23 is controlled to control the amount of furnace cooling air.

In this case, when the combustion amount in the waste incinerator 21 changes, the furnace pressure changes correspondingly, and as a result, the furnace pressure is kept constant based on the detection signal E from the furnace pressure detector 34. Induced blower 30
Since the opening degree of the inlet damper 32 is controlled, the amount of combustion exhaust gas sucked and exhausted by the induced blower 30 changes. Therefore, if the temperature composition of the flue gas 27 sucked and exhausted by the induced fan 30 does not change significantly, the driving power (KW) of the induced fan 30 will be equal to the amount of flue gas at the exit of the waste incinerator 21 (Nm ³ /h). will change accordingly. Therefore, when the above-mentioned control to keep the furnace internal pressure constant is performed, the change in the driving power of the induced fan 30 can be used as an index representing the change in the actual combustion amount in the waste incinerator 21. If the change in drive power is taken as the change in drive current, if this drive current is used, the garbage incinerator 21 will be activated without time delay.
This makes it possible to accurately detect the combustion situation inside. FIG. 6 shows an example of the relationship between the amount of air blown (the amount of exhaust gas), the required current, and the static pressure in the induced fan 30.

Conversely, if the current of the drive machine of the induced fan 30 is controlled to be constant, if the temperature and composition of the combustion exhaust gas 27 are approximately the same, the amount of combustion exhaust gas sucked and exhausted by the induced fan 30 will be constant; As a result, the actual amount of combustion in the waste incinerator 21 and the air ratio during combustion (actual amount of air supplied ÷
The theoretical amount of air required for combustion is controlled to be almost constant.

As a result, if the drive current of the induced fan 30 is detected and the air volume control end 36 of the forced air fan 24 is controlled so that this value becomes constant, the equilibrium air flow rate will be constant due to the forced air fan 24 and the induced air fan 30.
Since the amount of combustion air sent into the waste incinerator 21 becomes constant, it becomes possible to control the actual amount of combustion to be constant.

When implementing the above control, the garbage incinerator 2
When the actual amount of combustion in the waste incinerator 21 fluctuates in the short term, the fluctuation appears as a change in the outlet temperature of the waste incinerator 21, and as a result, the outlet damper changes based on the detection signal F from the temperature sensor 35. 33, and the outlet temperature is controlled to be constant, so the amount of furnace cooling air changes. However, since the amount of combustion air sent into the waste incinerator 21 (=the amount of air blown by the forced air blower + the amount of air blown by the furnace cooling fan) is constant, the actual amount of combustion inside the waste incinerator 21 increases. In this case, the amount of air blown by the in-furnace cooling blower 23 increases to completely burn the unburned components in the combustion exhaust gas 27, and the amount of air blown by the forced air blower 24 decreases, so that The actual combustion amount is controlled to decrease.

Conversely, when the actual combustion amount in the waste incinerator 23 decreases, the outlet temperature control of the waste incinerator 21 is activated, so the amount of air blown by the in-furnace cooling blower 23 decreases, but the forced air blower Since the amount of air blown into the waste incinerator 21 by the waste incinerator 24 increases, the actual combustion amount in the waste incinerator 21 is controlled to increase.

Therefore, the forced air blower 24 and the furnace cooling air blower 2
3. In the balanced ventilation system consisting of the induced fan 30, the air volume control end 36 of the forced fan 24 is controlled so that the current of the driver of the induced fan 30 is constant, and the outlet temperature of the waste incinerator 21 is kept constant. Outlet damper 3 of the blower 23 for cooling inside the furnace
By performing the opening degree control in step 3, it becomes possible to stabilize the actual combustion amount in the waste incinerator 21 and to achieve complete combustion of unburned gas such as carbon monoxide and hydrocarbons. .

Problems to be Solved by the Invention Fig. 4 shows the current value A of the induced fan 30 and the opening degree (%) of the outlet damper 36 of the forced fan 24 during normal operation without combustion air amount control in a water injection system, for example. ), NOx concentration (ppm) [O ₂ 12
% conversion]. During this normal operation
Since the NOx concentration is 140 to 200 ppm [O ₂ 12% conversion], it has not been sufficiently reduced, and the outlet damper 36 is manually operated, so it is troublesome to operate (control) it frequently. Since the opening degree remains constant after operation, the change in combustion
NOx concentration will further increase.

Means for Solving the Problems In order to solve the above problems, the automatic combustion control method for a garbage incinerator according to the first invention is such that the current value of the drive machine of the induced blower communicating with the inside of the garbage incinerator is constant. In addition, while detecting the current value during operation, the air volume control end of the forced fan is controlled based on this detected value, and the air volume for cooling the waste incinerator is also controlled based on the detected value of the exhaust gas temperature at the waste incinerator outlet. In addition to the first aspect of the present invention, the secondary aspect of the present invention detects the thickness of the dust layer on the combustion grate, and controls the speed of the drying grate and the combustion grate based on this detected value. This is what we do.

Effect According to the configuration of the first invention described above, the air volume control end of the forced air blower can be automatically controlled at any time, and furthermore, according to the configuration of the second invention, the thickness of the dust layer can be automatically kept constant. can be done.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 denotes a waste incinerator into which waste 2 is thrown, and an in-furnace cooling blower 3 and a forced air blower 4 are connected through pipes 5 and 6, respectively. The combustion exhaust gas 7 from the garbage incinerator 1 is transferred from a heat treatment device 8 such as a waste heat boiler or a gas cooling room to a dust collection device 9.
through the induced blower 10 to the chimney 1
Flows to 1. 12 is an inlet damper of the induced blower 10; 13 is an outlet damper of the furnace cooling blower 3;
4 is a furnace pressure detector, 15 is a temperature sensor, 16 is an outlet damper of the forced air blower 4, and 17 is a current detector. Further, 18X indicates a drying grate, 18Y indicates a combustion grate, and 18Z indicates a post-combustion grate.

FIG. 3 shows the current value A of the induced blower 10 and the forced blower 4 when low air ratio operation is performed using the above-mentioned combustion air control in a water injection system, for example.
The relationship between the opening degree (%) of the outlet damper 16 and the NOx concentration (ppm) [O ₂ 12% conversion] is shown. Figure 1,
In FIG. 3, the drive current value of the induced fan 10 is detected by the current detector 17, and the output damper 16 of the forced fan 4 is detected by the detection signal G so that the drive current value of the induced fan 10 becomes constant. If the opening degree of is automatically controlled, the suction and exhaust amount of combustion exhaust gas 7 by the induced fan 10 and the amount of combustion air by the forced fan 4 will be stabilized, so that the NOx concentration will be reduced to 140 to 200 ppm during normal operation (Figure 4). 80~ compared to
It was significantly reduced to 140ppm [O ₂ 12% equivalent].

If the opening degree of the outlet damper 16 of the forced air blower 4 is automatically controlled so that the drive current value of the induced air blower 10 is kept constant in this way, the actual combustion amount in the waste incinerator 1 can be stabilized. Compared to conventional combustion control methods that use the amount of steam generated in the waste heat boiler, the amount of water injected in the gas cooling chamber, or the outlet temperature of the waste incinerator 1 as indicators, more accurate and faster control can be achieved. Furthermore, when using the above index, deterioration of the detector and work such as maintenance and inspection are required, but when the drive current of the induced fan 10 is used as the index as in the present invention, these problems are eliminated.

By implementing the above control, it is possible to stabilize the actual combustion amount on the combustion grate 18Y in the waste incinerator 1, but it is possible to stabilize the actual combustion amount on the combustion grate 18Y in the waste incinerator 1. When the properties related to combustibility change rapidly, it may become difficult to control the combustion amount of the waste 2 on the combustion grate 18Y and stabilize the combustion. In such a case, in addition to controlling the amount of combustion air described above, the thickness of the dust layer on the combustion grate is also detected, and the drying grate 18 is adjusted so that the thickness of the dust layer remains constant.
By simultaneously controlling the speed of X and the speed of combustion grate 18Y, the amount of combustion on the combustion grate can be stabilized more reliably.

The thickness of the garbage layer can be detected by directly detecting the thickness of the garbage layer on the grate, which has been conventionally used, using ultrasonic waves or light, or by measuring the amount of combustion air passing through the garbage layer and the amount before and after the garbage layer. A method such as calculation based on the air (gas) pressure difference can be used.
If the thickness of the dust layer on the combustion grate 18Y detected by these methods is thicker than the set dust layer thickness, the speed of the drying grate 18X is slowed down (if the drying grate operates intermittently, (extend the pause time). At this time, if you increase the speed of the combustion grate 18Y (if the combustion grate operates intermittently, shorten its pause time), the thickness of the dust layer on the combustion grate 18Y can be increased. It becomes possible to quickly thin the film. Conversely, if the detected dust layer thickness on the combustion grate 18Y is thinner than the set dust layer thickness, the drying grate 1
Increase the speed of 8X (if the drying grate operates intermittently, shorten its downtime). Also, at this time, if the speed of the combustion grate 18Y is slowed down (if the combustion grate operates intermittently, the pause time is lengthened), the thickness of the dust layer on the combustion grate 18Y can be further reduced. It becomes possible to quickly increase the thickness.

In the above combustion air amount control, the opening degree of the outlet damper 16 of the forced air blower 4 is controlled.
The combustion area on the grate 18 in the waste incinerator 1 changes depending on the quality of the waste. When the calorific value of the waste 2 is low, there is a flame combustion area centered around the combustion grate 18Y and a part of which is applied to the post-combustion grate 18Z. Therefore, in order to keep the flame combustion area on the grate 18 in the garbage incinerator 1 at an appropriate position in accordance with the calorific value of the garbage 2, the damper 19X under the drying grate shown in FIG. By manually operating the damper under the grate 19Y and the damper under the post-combustion grate 19Z, the damper opening degree is adjusted to suit the type of garbage at the time.
Even if the quality of waste changes, the waste incinerator 1
Since the forced air blower 4 can pressurize combustion air in accordance with the combustion area on the grate inside the waste incinerator 1, the amount of combustion inside the waste incinerator 1 can be stabilized.

By supplying the furnace cooling air by controlling the outlet temperature of the waste incinerator 1, it is possible to stabilize the outlet temperature of the waste incinerator 1 and completely burn out the unburned matter in the combustion exhaust gas. If the unburned gas is introduced from a certain point, the unburned gas will cause intense local combustion at the furnace cooling air supply point, causing problems such as an increase in the NOx concentration in the combustion exhaust gas and clinker adhesion to the furnace wall. On the other hand, if the amount of air for cooling the furnace is reduced too much, the combustion of unburned components in the flue gas 7 will be insufficient, resulting in an increase in unburned components such as carbon monoxide and hydrocarbons in the flue gas 7. comes out. Therefore, the feeding position and feeding amount of the furnace cooling air are
As shown in the figure, depending on the amount of furnace cooling air required by constant control of the outlet temperature of the waste incinerator 1, the inlet position is changed as the amount increases, the furnace cooling air shown in FIG. At the air injection positions X, Y, and Z, only X, 2 locations at X and Y, and 3 locations at X, Y, and Z
The method will be to introduce furnace cooling air from a certain point. By controlling the feeding position and amount of the furnace cooling air using this method, it is possible to achieve complete combustion of the unburned components in the combustion exhaust gas 7, as well as complete combustion of the unburned components in the combustion exhaust gas 7. At the same time, local combustion of unburned gas in the combustion exhaust gas 7 can be prevented, and as a result, an increase in NOx concentration can be prevented, and
It is possible to prevent clinker from adhering to the furnace wall.

Next, if the quality of waste changes over the long term, if the same amount is incinerated and the theoretical air ratio for combustion is the same, the amount of combustion exhaust gas will increase or decrease in response to the increase or decrease in the calorific value of the garbage. Become. For this reason, the drive current of the induced blower 10 will vary depending on the amount of heat generated by the waste. Therefore, in response to long-term fluctuations in the calorific value of garbage, by changing the current setting value of the induced blower 10, even when the calorific value of the garbage changes, the combustion amount can be stabilized at a constant air ratio. Control becomes possible.

In the above embodiment, the type of garbage incinerator 1 is a grate type incinerator, but in the automatic combustion control method of the first invention, the garbage incinerator 1 is summarized as shown in FIG. 3 except for the details. Type 1 can be applied not only to grate-type incinerators but also to all types of incinerators such as fluidized bed incinerators, multi-stage incinerators, rotary kiln incinerators, fixed bed incinerators, and spray incinerators. It is something.

In Fig. 1, a flow sheet is shown in the case where the blower 3 for cooling the furnace is installed separately, but in this case, the blower 3 for cooling the furnace is not installed, and the branch duct from the outlet of the forced fan 4 is used for cooling the furnace. It may also be used as air for use. In this case, the automatic combustion control method described above can be applied by replacing the dampers at the branched portions with the outlet dampers 20A, 20B, and 20C of the in-furnace cooling blower 3 shown in FIG.

In addition, in this example, the furnace pressure control (exhaust gas amount control)
Although this is the case where this is performed using the inlet damper 12 of the induced fan 10, the present method can also be applied to cases where this method is performed by a combination of the inlet damper 12 and the rotation speed control of the induced fan 10.

Effects of the Invention By implementing the automatic combustion control method of the first invention with the above configuration, the amount of steam generated in the conventional waste heat boiler, the amount of water injected in the gas cooling chamber, and the outlet temperature of the waste incinerator can be detected. The actual combustion amount in the waste incinerator can be detected more accurately and more quickly than when implementing a control method that controls the outlet damper opening of the forced air blower, each grate speed, etc. to stabilize the value. In addition, since the air volume control end of the forced air blower is used as the operating end, the response of combustibility in the waste incinerator is extremely fast, and it is possible to keep the actual amount of combustion in the waste incinerator constant. . Furthermore, even if the amount of combustion in the waste incinerator fluctuates due to changes in waste quality, implementing the above control will not only stabilize the amount of combustion in the incinerator, but also increase the amount of combustion in the combustion exhaust gas. It also becomes possible to completely burn the unburned matter. Furthermore, since the automatic combustion control method of the first invention is a method of controlling the amount of combustion air corresponding to the amount of incineration (the amount of air blown by the forced fan + the amount of air blown by the furnace cooling fan) to a constant amount, the current of the induced fan It has the advantage that the amount of combustion air sent to the waste incinerator can be controlled by increasing or decreasing the set value. Therefore, when the actual combustion amount in the garbage incinerator is the same, by manipulating this current setting value, it is possible to adjust the air ratio regarding combustion in the garbage incinerator. Therefore, if the automatic combustion control method of the first invention is used,
Stable low air ratio operation can be carried out, and if in-furnace water spraying is used to reduce NOx, it is possible to carry out operation that can further significantly reduce nitrogen oxides (NOx).

In addition to the combustion air amount control described above, if the stabilization control of the thickness of the waste layer on the combustion grate of the second invention is also carried out, even if the quality of waste changes rapidly, the It is possible to carry out stabilization control of the amount of actual garbage combustion.

Long-term fluctuations in the calorific value of waste can be dealt with by changing the current settings of the induced exhaust fan. By automatically inputting the set current value calculated from the planned incineration amount into this automatic combustion control device and creating a system that can automatically update the set current value, it is possible to respond to fluctuations in the calorific value of waste. There is no need to manually change the current setting value of the induced blower.

[Brief explanation of the drawing]

1 to 3 show one implementation of the present invention, and the first
The figure is a flow sheet diagram, Figure 2 is an explanatory diagram showing the relationship between the amount of furnace cooling air and the feeding position, Figure 3 is an explanatory diagram showing an example of an operation record during automatic operation, and Figures 4-
Fig. 6 shows a conventional example, Fig. 4 is an explanatory diagram showing an example of an operation record during manual operation, Fig. 5 is a flow sheet diagram, and Fig. 6 shows the relationship between air flow rate, required current, and static pressure in the blower. FIG. 1... Garbage incinerator, 3... Furnace cooling blower,
4... Forced blower, 8... Heat treatment device, 9... Dust collector, 10... Induced fan, 12... Inlet damper, 13... Outlet damper, 14... Furnace pressure detector, 15... Temperature detection vessel, 16...exit damper,
17... Current detector, 18X... Dry grate, 1
8Y... Combustion grate.

Claims (1)

[Scope of Claims] 1. While detecting the current value during driving so that the current value of the drive machine of the induced fan connected to the waste incinerator is constant, the air volume of the forced fan is controlled based on this detected value. 1. An automatic combustion control method in a waste incinerator, characterized by controlling the temperature of the exhaust gas at the waste incinerator outlet, and controlling the amount of blowing air for cooling the waste incinerator based on a detected value of the exhaust gas temperature at the outlet of the waste incinerator. 2. While detecting the current value during driving so that the current value of the drive machine of the induced fan connected to the garbage incinerator remains constant, the air volume control end of the forced fan is controlled based on this detected value, and The air flow rate for cooling the furnace is controlled based on the detected value of the exhaust gas temperature at the waste incinerator outlet, and the thickness of the waste layer on the combustion grate is also detected, and based on this detected value, the drying grate and combustion grate are An automatic combustion control method in a garbage incinerator characterized by controlling the speed of.