JPH09273730A - Restraining method of unburnt constituent in exhaust gas of incinerating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain unburned constituents in exhaust gas by burning and reducing to ashes completely on a rear combustion grating. SOLUTION: The condition of wastes on a rear combustion grating 3C is judged based on the measuring values of a main flue thermometer 14, a concentration meter 16 of O2 in exhaust gas, a CO concentration meter 17, an air pressure meter 18a under rear combustion grating and the like to judge a tendency of falling into shortage of temperature, shortage of air or shortage of fuel quickly and control the amount of air to the rear combustion grating, the amount of air after combustion and grating speed after combustion. According to this method, incomplete combustion condition is improved in the stage of primary combustion and the generation of unburned constituents, such as PCDDS (polychlorinated-dibenzo-p-dioxins), carbon monoxide and the like, can be restrained and, at the same time, blowing of unnecessary secondary air can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing unburned components in exhaust gas by controlling combustion in a grate-type waste incinerator, and in particular, the amount of post-combustion air for complete combustion of unburned components in the furnace. And a post-combustion grate velocity control method.

[0002]

2. Description of the Related Art Municipal solid waste incinerators play an important role in treating various wastes discharged in social life. In addition to this, the heat generated by the combustion of waste is used to generate steam, and the waste neergi is effectively used.

[0003] In a refuse incinerator, refuse is intermittently put into a hopper at intervals of several tens of minutes by a crane and temporarily stored. Under the hopper, there is a dry grate that also serves as a feeder, and the refuse is sent into the furnace at a constant supply rate. The sent-in waste is burned on several levels of grate by primary air blown from under each grate, and is discharged as ash behind the furnace. The final stage of these grate is the post-combustion grate.

On the other hand, secondary air is blown above the combustion zone to oxidize unburned components and prevent overheating of the furnace.
A partition is provided above the blow-in port so that the secondary air does not go directly to the furnace outlet and mixes well with the combustion gas. The combustion gas bypasses this partition wall and goes to the upper part of the furnace. The bypass path on the furnace front side of the partition wall is called the secondary flue and the bypass path on the rear side is called the main flue. Combustion gases passing through both flues combine in the mixing chamber above the partition. The purpose of the mixing chamber is to further remove unburned components in the combustion gas in the front, and it is also called a secondary combustion chamber. Most of the combustion gases generated in the rear of the furnace or in the post combustion grate enter the mixing chamber through the main flue. The gas exiting the mixing chamber passes through a heat exchanger at the exit of the furnace to recover the energy it has and then exhaust it.

In such a refuse incinerator, in general, the feed rate of the refuse into the furnace, the amount of air, the exhaust gas temperature, the exhaust gas component, etc. are set to these reference values each time the garbage is put into the hopper, and according to this, It has been controlled.

In particular, with the increase in the amount of incineration in recent years, it has become more and more important to suppress the generation of exhaust gas components, particularly harmful components such as dioxins and CO, and strict control of these has become necessary. .

Therefore, the combustion gas is allowed to stay in a high temperature state (800 ° C. or higher) for a long time, and the gas generated by the combustion is sufficiently mixed with the air in the flue and the mixing chamber to be completely burned. It is expected.

In order to satisfy these conditions, in addition to the setting of the standard value at the time of throwing in the waste, the CO concentration representing the unburned components in the exhaust gas is used as a standard, and the concentration is controlled so as to be suppressed. .

Conventionally, as a control method thereof, the CO concentration or the O ₂ concentration in the exhaust gas in the furnace is measured, and the amount of secondary air blown mainly into the secondary combustion chamber is controlled on the basis of the measured value to control the unburned components. It has been proposed that the primary air amount be supplementarily adjusted to achieve complete combustion of. For example, JP-A-5
In JP-A-248618, the amount of secondary air is controlled so as to maintain the combustion gas temperature on the post-combustion zone side at a reference temperature, and when the temperature is still below the reference temperature, O _{2 in} the combustion gas on the post-combustion zone side is controlled. A method of measuring the concentration and reducing the primary air when O ₂ is in excess to control the CO concentration is described.

[0010]

However, the properties and components of the waste are not constant, and the waste that has reached the post-combustion grate may already be ash. It may contain a lot. Moreover, such a state of dust does not always change gradually, and it is not unusual for it to change rapidly.

For example, when incombustible refuse is sent into the furnace subsequent to inflammable refuse, the deposits on the post-combustion grate change from ash-based deposits to unburned-rich deposits. If the amount of unburned waste is large, the temperature of the combustion gas on the side of the post-combustion zone becomes high, but the air required for combustion is insufficient and unburned components such as CO are generated. In such a case, if the amount of primary air supplied to the post-combustion grate, that is, the amount of post-combustion air, is not increased and the combustion of unburned waste is not promoted, the unburned waste on the post-combustion grate should be completely ashed. I can't. In this case, just relying on secondary air for complete combustion of unburned components is not a fundamental solution.

However, in the suppression method described in Japanese Patent Laid-Open No. 5-248618, only the amount of secondary air is controlled, and rather the primary air is reduced when the O ₂ concentration on the post combustion zone side is high. .

As described above, conventionally, the combustion condition is controlled according to the state of the deposit on the post-combustion grate, and C in the exhaust gas is controlled.
Unburned components such as O could not be suppressed.

The present invention has been made for the purpose of fundamentally solving this problem. By adapting the combustion conditions to the state of deposits on the post-combustion grate, complete combustion in primary combustion is achieved, and exhaust gas is exhausted. The purpose is to suppress unburned components such as CO.

[0015]

Means for achieving this object are the means described in the following (1) to (8).

The means (1) measures one or more of the main flue temperature of the incinerator or the main flue temperature and the O ₂ concentration in the exhaust gas, the CO concentration in the exhaust gas, or the pressure difference above and below the post-combustion grate, Waste incinerator exhaust gas characterized by periodically comparing each measured value with each reference value and controlling the amount of after-combustion air or the amount of after-combustion air and the after-combustion grate velocity based on this comparison result. This is a method for suppressing medium unburned components.

Combustion gas generated by burning dust on the post-combustion grate mixes with a part of the secondary air and is guided to the mixing chamber through the main flue. Therefore, the main flue temperature reflects the combustion conditions on the afterburning grate.

Therefore, by measuring the main flue temperature and comparing the measured value with the reference value, the combustion state of dust on the post-combustion grate can be grasped. Then, by controlling the amount of post-combustion air based on the grasped combustion state, it is possible to completely incinerate the dust on the post-combustion grate and suppress the generation of unburned components.

In addition to the main flue temperature,
There are O ₂ concentration and CO concentration in the exhaust gas as well as a pressure difference between the upper and lower sides of the post combustion grate. The O ₂ concentration and CO concentration in the exhaust gas reflect the combustion state of dust on the post-combustion grate, and the pressure difference above and below the post-combustion grate reflects the amount of dust on the post-combustion grate.

Therefore, in addition to the measurement of the main flue temperature,
When the O ₂ concentration or CO concentration in the exhaust gas is measured, in addition to the measurement information of the main flue temperature, direct information about the excess or deficiency of the air amount or unburned components can be obtained. The combustion state of can be grasped with higher accuracy, and the amount of post-combustion air can be controlled more appropriately. That is, in addition to the excess and deficiency values of the main flue temperature, the amount of deviation of the components in the exhaust gas from the proper value can be used for control.

In addition to the amount of post-combustion air, another control is the post-combustion grate velocity. The state of combustion of waste depends on the amount of waste sent in addition to the amount of air. Therefore, when the amount of post-combustion air is controlled and the amount of dust is adjusted by controlling the post-combustion grate velocity, the combustion state of dust is adjusted more quickly and appropriately.

By carrying out the measurement periodically, the combustion state of the refuse on the post-combustion grate is always monitored,
The post-combustion grate velocity can be adjusted in advance to catch small changes that can lead to abnormal conditions. In particular, it is possible to cope with a sudden change when very easily burnable refuse or, on the contrary, difficultly burnable refuse comes on the grate. And
The shorter the measurement cycle, the higher the control frequency, and the finer control becomes possible.

The means (2) measures the main flue temperature, reduces the amount of post combustion air when the main flue temperature does not reach the reference temperature, and reduces the post combustion air amount when the main flue temperature exceeds the reference temperature. This is a method of suppressing unburned components in exhaust gas from a refuse incinerator that increases the amount of combustion air.

The deposits on the post-combustion grate generally have a large amount of ash, but especially when the state rapidly shifts to a state where there is little unburned waste and a large amount of ash, the amount of post-combustion air becomes excessive with respect to the amount of waste.
If the degree is large, the deposits will cool on the post-combustion grate and the temperature will be insufficient, and the ignition of unburned waste will not proceed smoothly, resulting in an incomplete combustion state. In this condition, the main flue temperature will be lower than normal.

Thus, by lowering the main flue temperature,
An insufficient temperature condition on the afterburning grate is detected. And
On the post-combustion grate, it is estimated that unburned waste is incompletely burned and unburned components are generated.

FIG. 2 shows the result of examining the relationship between the main flue temperature and the CO concentration in the exhaust gas. The (a) figure shows the change of the main flue temperature, and the (b) figure shows the CO concentration in the exhaust gas. It is a result of simultaneously measuring the main flue temperature and the CO concentration in the exhaust gas in a state where the post-combustion air amount is operating at the reference amount.

The main flue temperature is temporarily lowered less than two hours after the start of measurement and immediately before and after the fourth hour, and in response to this, the CO concentration in the exhaust gas is also temporarily high. Has become. That is, when the main flue temperature is lower than normal, unburned components are generated. This is because there is unburned dust on the post-combustion grate and the standard amount of post-combustion air is blown in, but the temperature is insufficient among the three elements required for combustion, resulting in an incomplete combustion state. It means that

On the post-combustion grate, the deposits in front of it are mostly ash and the temperature has dropped, and unburned waste has arrived there suddenly but is not ignited. Since the post-combustion air blown at a low temperature further promotes the temperature decrease, in this state, the post-combustion air becomes an excessive amount in terms of the cooling effect even if it is the reference amount.

FIG. 3 shows how the amount of post combustion air becomes excessive and the state of incomplete combustion occurs. In FIG. 3, (a) shows the change with time of the post-combustion air amount, and (b) shows the CO concentration in the exhaust gas measured at the same time. Although the amount of post-combustion air increased at the start of measurement, and about 1 hour and 2.7 hours after the start of measurement, the CO concentration in the exhaust gas was correspondingly high. That is, when the amount of after combustion air is excessively increased, the CO concentration in the exhaust gas becomes high, and this state disappears when the amount of after combustion air goes out of excess.

As described above, the main flue temperature decreases when the amount of post-combustion air is excessive with respect to the amount of unburned waste on the post-combustion grate, and at this time, the temperature on the post-combustion grate is insufficient due to insufficient temperature. Generates combustion components. That is, when the main flue temperature is lower than the reference temperature, the amount of post-combustion air is excessive with respect to the amount of unburned waste on the post-combustion grate. Occurs.

Therefore, if the amount of post-combustion air is reduced when the main flue temperature is lower than the reference temperature, the temperature decrease is prevented and normal combustion is restored, so that the generation of unburned components can be reduced.

As described above, in the post-combustion grate, since the complete combustion of the waste is aimed at, a little more than the theoretical amount of air is usually supplied. However, when the amount of non-combustible dust is particularly large, unburned dust may remain in excess on the post-combustion grate above the reference amount. In this state, unburned refuse corresponding to the amount of supplied air burns, so the main flue temperature becomes higher than usual. However, most of the excess unburned waste is in an oxygen-deficient state, and unburned components are generated from this. That is, when the main flue temperature exceeds the reference temperature, the amount of post-combustion air is insufficient with respect to the amount of dust on the post-combustion grate, and therefore oxygen is one of the three elements required for combustion on the post-combustion grate. There is a shortage and unburned components are generated.

Therefore, if the amount of post-combustion air is increased when the main flue temperature exceeds the reference temperature, the air shortage state can be eliminated and the generation of unburned components can be reduced.

[0034] (3) means of the O ₂ concentration of the main flue temperature and the exhaust gas was measured, O ₂ does not reach the main flue temperature to a reference temperature
When the concentration exceeds the reference value, the amount of post-combustion air is reduced, and when the main flue temperature exceeds the reference temperature and the O ₂ concentration does not reach the reference value, the amount of post-combustion air is increased. It is a suppression method.

When the main flue temperature is lower than the reference temperature, the amount of post-combustion air is excessive with respect to the amount of unburned waste on the post-combustion grate, and therefore the temperature is insufficient on the post-combustion grate and unburned. Ingredients are generated.

It is confirmed that the amount of post combustion air is excessive with respect to the amount of unburned waste on the post combustion grate due to the high concentration of O ₂ in the exhaust gas. This is because if the amount of after combustion air is excessive, unreacted O ₂ is contained in the combustion gas in a large amount, and the O ₂ concentration in the exhaust gas becomes high.

Therefore, if the amount of after-combustion air is reduced when the main flue temperature does not reach the reference temperature and the O ₂ concentration exceeds the reference value, the temperature drop on the after-combustion grate is prevented, and normal combustion is achieved. Return, the generation of unburned components is reduced.

On the other hand, when the main flue temperature exceeds the reference value, the amount of post-combustion air is insufficient with respect to the amount of waste on the post-combustion grate. Combustion components are generated.

It is confirmed that the amount of post combustion air is insufficient with respect to the amount of unburned waste on the post combustion grate due to the low O ₂ concentration in the exhaust gas. This is because if the amount of post-combustion air is insufficient, unreacted O ₂ will disappear and the O ₂ concentration in the exhaust gas will decrease.

Accordingly, when the main flue temperature exceeds the reference temperature and the O ₂ concentration does not reach the reference value, increasing the amount of post-combustion air eliminates the insufficient amount of air and reduces the generation of unburned components. You can

The means (4) measures the main flue temperature and the CO concentration in the exhaust gas, and when the main flue temperature is below the reference temperature and the CO concentration exceeds the reference value, the amount of post-combustion air is reduced to When the flue temperature exceeds the reference temperature and the CO concentration exceeds the reference value, it is a method of suppressing unburned components in the exhaust gas of the refuse incinerator that increases the amount of post-combustion air.

When the main flue temperature is lower than the reference temperature, the amount of post-combustion air is excessive with respect to the amount of unburned waste on the post-combustion grate, and therefore the temperature is insufficient on the post-combustion grate and unburned. Ingredients are generated.

Since CO represents an unburned component, it is confirmed that the deposits on the post-combustion grate are in an unburned state due to the high CO concentration in the exhaust gas. This CO is unburned CO in which the amount of post-combustion air is excessive with respect to the amount of unburned waste on the post-combustion grate, resulting in a temperature shortage state, and is not oxidized to CO ₂ .

Therefore, when the main flue temperature does not reach the reference temperature and the CO concentration exceeds the reference value, if the amount of after-combustion air is reduced, the temperature drop on the after-combustion grate is prevented, so that normal combustion is achieved. The generation of returned unburned components can be reduced.

On the contrary, when the main flue temperature exceeds the reference temperature, the amount of post-combustion air is insufficient with respect to the amount of unburned waste on the post-combustion grate, so that oxygen is insufficient on the post-combustion grate. Then, unburned components are generated.

The CO concentration in the exhaust gas is high because the amount of post-combustion air is insufficient with respect to the amount of unburned waste on the post-combustion grate, and the unburned state occurs in the deposits on the post-combustion grate. Is.

Therefore, when the main flue temperature exceeds the reference temperature and the CO concentration exceeds the reference value, if the post-combustion air amount is increased, the insufficient state of the air amount is eliminated, so that the generation of unburned components should be reduced. You can

The means (5) controls the amount of after combustion air, measures the difference between the pressure under the after combustion grate and the pressure in the furnace, compares these measured values, and based on the comparison result. This is a method of controlling unburned components in exhaust gas from a refuse incinerator by controlling the post combustion grate velocity.

While the main flue temperature, the O ₂ concentration and the CO concentration in the exhaust gas reflect the combustion state of the post-combustion grate, the difference between the pressure under the post-combustion grate and the pressure in the furnace is the after-combustion. The pressure difference above and below the grate and reflects the amount of deposits on the post-combustion grate.

The pressure inside the furnace is measured by a pressure gauge installed above the grate and is constantly controlled to a negative pressure so that the gas during combustion does not leak from the furnace. Comparing this in-furnace pressure with the pressure under the post-combustion grate, the post-combustion air is blown under the after-combustion grate, the pressure under the after-combustion grate is higher than the pressure in the furnace, and The larger the resistance, the larger the difference between the pressure under the post-combustion grate and the pressure in the furnace (hereinafter simply referred to as the pressure difference). That is, when the pressure difference is small, most of the deposit on the post-combustion grate is ash and has a small volume, and when the pressure difference is large, most of the deposit is unburned waste and has a large volume.

By periodically grasping the combustion state of the dust on the post-combustion grate as well as the amount of unburned dust in the deposit, the post-combustion grate velocity is appropriately controlled in addition to the control of the post-combustion air amount. can do. For example, if the post-combustion air amount is increased and the post-combustion grate velocity is reduced when the amount of waste is excessive, the amount of unburned waste gradually decreases and burns out over time.

The means (6) measures the difference between the main flue temperature, the pressure under the post-combustion grate and the pressure in the furnace, and the main flue temperature does not reach the reference temperature and the pressure under the post-combustion grate. If the difference between the pressure in the furnace and the pressure in the furnace does not reach the standard difference, the amount of post-combustion air is reduced and the speed of post-combustion grate is increased, the main flue temperature exceeds the reference temperature, and the pressure under the post-combustion grate and the furnace When the difference in internal pressure exceeds the reference difference, it is a method of suppressing unburned components in the exhaust gas of a refuse incinerator, in which the amount of post combustion air is increased and the velocity of the post combustion grate is reduced.

When the main flue temperature is low, the amount of post combustion air is excessive with respect to the amount of unburned waste on the post combustion grate, and the temperature is insufficient on the post combustion grate, and unburned components are generated. It can be seen that, because the pressure difference is small, most of the deposits in the post-combustion grate are ash and the amount of unburned waste is small.

Therefore, when the main flue temperature does not reach the reference temperature and the pressure difference does not reach the reference difference, by reducing the amount of post-combustion air and increasing the post-combustion grate velocity, it is possible to prevent the temperature from decreasing. Since the dust that is the fuel is replenished and the normal combustion is restored, the generation of unburned components can be reduced.

On the other hand, when the main flue temperature is high, the amount of post-combustion air is insufficient with respect to the amount of unburned waste on the post-combustion grate, and oxygen is insufficient on the post-combustion grate to generate unburned components. To do. When the pressure difference is large, the amount of unburned waste is large in the deposit on the post-combustion grate.

Therefore, when the main flue temperature exceeds the reference temperature and the pressure difference exceeds the reference difference, if the post combustion air amount is increased and the post combustion grate speed is decelerated, an oxygen shortage state and an excess fuel state occur. It is possible to eliminate this and reduce the generation of unburned components.

The means (7) measures the main flue temperature, the O ₂ concentration in the exhaust gas, the pressure difference under the post-combustion grate and the furnace pressure, and the main flue temperature does not reach the reference temperature. _{2 When the} concentration exceeds the reference value and the difference between the pressure under the post-combustion grate and the pressure in the furnace does not reach the reference difference, the amount of post-combustion air is decreased and the post-combustion grate velocity is increased to When the temperature exceeds the reference temperature, the O ₂ concentration does not reach the reference value, and the difference between the pressure under the post-combustion grate and the pressure in the furnace exceeds the upper limit of the reference difference range, the post-combustion air amount is increased and the post-combustion grate is increased. This is a method of suppressing unburned components in the exhaust gas of a refuse incinerator that reduces the speed.

When the main flue temperature is low and the O ₂ concentration in the exhaust gas is high, the temperature is insufficient on the post-combustion grate due to an excessive amount of post-combustion air, and unburned components are generated. It can be seen that, since the pressure difference does not reach the standard difference, most of the deposit on the post-combustion grate becomes ash, and no unburned dust remains.

Therefore, when the main flue temperature does not reach the reference temperature, the O ₂ concentration in the exhaust gas exceeds the reference value, and the pressure difference does not reach the reference difference, the amount of post combustion air is reduced and the post combustion grate velocity is reduced. When the speed is increased, the temperature drop is prevented and the fuel is replenished, so that the normal combustion is restored and the generation of unburned components can be reduced.

On the contrary, the main flue temperature is high and the O _{2 in the} exhaust gas is
When the concentration is low, the amount of post-combustion air is insufficient with respect to the amount of unburned waste on the post-combustion grate, and the post-combustion grate is in an oxygen-deficient state and unburned components are generated. It can be seen that the large pressure difference causes a large amount of unburned waste to be contained in the deposit on the post-combustion grate.

Therefore, when the main flue temperature exceeds the reference temperature, the O ₂ concentration in the exhaust gas does not reach the reference value, and the pressure difference exceeds the reference difference, the post combustion air amount is increased and the post combustion grate velocity is increased. By decelerating, the excess fuel state and the oxygen deficient state are eliminated, and the generation of unburned components can be reduced.

The means (8) measures the main flue temperature, the CO concentration in the exhaust gas, the pressure under the post-combustion grate and the pressure in the furnace, and the main flue temperature does not reach the reference temperature and the CO concentration Exceeds the reference value and the difference between the pressure under the post-combustion grate and the pressure in the furnace does not reach the reference difference, the amount of post-combustion air is reduced and the post-combustion grate velocity is increased, and the main flue temperature is set to the standard. Over temperature C
When the O concentration exceeds the reference value and the difference between the pressure under the post-combustion grate and the pressure in the furnace exceeds the reference difference, the amount of post-combustion air is increased and the post-combustion grate velocity is reduced. It is a method of suppressing components.

When the main flue temperature is low and the CO concentration in the exhaust gas is high, the temperature of the post-combustion grate becomes insufficient due to an excessive amount of post-combustion air, and unburned components are generated. And
It can be seen that most of the deposits on the post-combustion grate are not ash due to the large pressure difference.

Therefore, when the main flue temperature does not reach the reference temperature, the CO concentration in the exhaust gas exceeds the reference value, and the pressure difference does not reach the reference difference, the amount of after combustion air is reduced and the after combustion grate velocity is reduced. When the speed is increased, the temperature drop on the post-combustion grate is prevented and the fuel is replenished, so that the normal combustion is restored and the generation of unburned components can be reduced.

On the contrary, when the main flue temperature is high and the CO concentration in the exhaust gas is high, the amount of post-combustion air is insufficient with respect to the amount of unburned waste on the post-combustion grate, and unburned components are generated. . It can be seen that the large pressure difference causes a large amount of unburned waste to be contained in the deposit on the post-combustion grate.

Therefore, when the main flue temperature exceeds the reference temperature, the CO concentration in the exhaust gas exceeds the reference value, and the pressure difference exceeds the reference difference, the amount of post combustion air is increased and the post combustion grate speed is reduced. Then, the oxygen deficiency state and the unburned waste excess state are resolved, and the generation of unburned components can be reduced.

The control of the post-combustion grate velocity is carried out by obtaining the main flue temperature or the main flue temperature and O _{2 in the} exhaust gas without obtaining the pressure difference.
It is also possible to control the post-combustion air amount and the post-combustion grate velocity by measuring the concentration or CO concentration.

[0068]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the concept of a refuse incinerator and a control system. Reference numeral 1 denotes an incinerator, and the waste introduced from the waste inlet 2 is sequentially sent to the dry grate 3a, the combustion grate 3b, and the post-combustion grate 3c to become ash, and the ash is taken out from the falling port 4. Each grate is driven by the grate driving device 3d and sends the garbage at a predetermined speed. However,
Only the afterburning grate 3c is shown.

Under each grate, the primary air for drying or combustion supplied by the primary air fan 5 is sent.
Dust is mainly dried in the dry grate 3a, burned in the combustion grate 3b, and completely burned in the post-combustion grate 3c to become ash. This ash falls from the ash fall port 4 and is discharged outside the furnace. The primary air is a dry grate lower air damper 13a for adjusting the dry grate air amount, and a combustion grate front lower air damper 13 for adjusting the combustion grate front air amount.
b, a combustion grate rear lower air damper 13c that adjusts the combustion grate rear air amount, and a rear fuel grate lower air damper 13d that adjusts the after combustion grate air amount.

On the other hand, above the combustion zone, the secondary air supplied from the secondary air fan 10 is blown from the blowing port 9 to oxidize unburned components and prevent overheating of the furnace. The secondary air does not escape directly to the furnace outlet, and the partition wall 1 is inclined above the blowing port 9 so as to mix well with the combustion gas.
1 is provided. The passage in front of the partition wall 11 is the secondary flue and the passage in the rear is the main flue. The combustion gas that has passed through both flues mixes again in the mixing chamber 6 above the partition wall 11.

The gas exiting the mixing chamber 6 passes through a heat exchanger 8a installed at the exit of the furnace and is exhausted after energy is recovered. Reference numeral 7 is a furnace outlet thermometer, 8b is a boiler, and 12 is a flow meter for measuring the amount of steam. Also, 14 is a main flue thermometer, 1
6 is an exhaust gas O ₂ concentration meter, 17 is an exhaust gas CO concentration meter, 18
Reference numeral a is a furnace pressure gauge, and 18b is a post-combustion grate under pressure gauge.

Reference numeral 15 is a control device, which is a main flue thermometer 1
4, the exhaust gas O ₂ concentration meter 16, the exhaust gas CO concentration meter 17, the in-furnace pressure gauge 18a, and the post-combustion grate lower pressure gauge 18b as inputs, and the post-combustion grate lower air damper 13d and the grate driving device 3d The control value signal is output to. Controller 15
For example, a computer is used for this.

The control device 15 calculates the control value based on the input signal periodically. The movement of garbage on the grate is slow,
Since it takes several tens of minutes to pass over the post-combustion grate,
It is suitable to carry out the calculation at a cycle of several tens of seconds to several minutes.

The control value is calculated as follows. First, the control of the amount of post combustion air will be described.

Control of post-combustion air amount based on main flue temperature
When you do, set the reference temperature of the main flue to T _set, This time measured value
Where T is the control value F of the post combustion air amount_nThe following equation (1)
Calculate with.

[0076]

[Equation 1]

However, F _n-1 is the previous control value, and k _T is a control parameter for the main flue temperature, which is positive.

When the amount of post-combustion air is controlled on the basis of the main flue temperature and the O ₂ concentration in the exhaust gas, the reference value of the O ₂ concentration in the exhaust gas is [O ₂ ] _set and the measured value this time is [O ₂ ], The control value F _n of the post combustion air amount is calculated by the following equation (2).

[0079]

[Equation 2]

However, k _O2 is a control parameter for the O ₂ concentration in the exhaust gas, but the measured value T of the main flue temperature is lower than the reference temperature T _set and the measured value of the O ₂ concentration in the exhaust gas [O
₂ ] is larger than the reference value [O ₂ ] _set , or the measured value T of the main flue temperature is larger than the reference temperature value T _set and the measured value [O ₂ ] of the O ₂ concentration in the exhaust gas is the reference value. It is negative when it is smaller than [O ₂ ] _set , and zero otherwise.

When the amount of post-combustion air is controlled on the basis of the main flue temperature and the CO concentration in the exhaust gas, the standard value of the CO concentration in the exhaust gas is [CO] _set , and the measured value this time is [CO]. The control value F _n of the combustion air amount is calculated by the following equation (3).

[0082]

(Equation 3)

However, k _CO is a control parameter for the CO concentration in the exhaust gas, but the measured value T of the main flue temperature is smaller than the reference value T _set and the measured value of the CO concentration in the exhaust gas [C
O] is negative when it is larger than the reference value [CO] _set, the measured value T of the main flue temperature is larger than the reference value T _set , and the measured value [CO] of the CO concentration in the exhaust gas is the reference value [CO]. CO]
It is positive when it is greater than _set , and zero otherwise.

Next, the case of controlling the post combustion grate velocity together with the amount of post combustion air will be described.

When the post combustion air amount is controlled based on the main flue temperature and the post combustion grate velocity is controlled based on the pressure difference, the control value F of the post combustion air amount is calculated using the equation (1). _{The n} is obtained, and the control value G _n of the post-combustion grate velocity is calculated by the following equation (4), where the pressure difference is ΔP and the reference difference is ΔP _set .

[0086]

(Equation 4)

However, G _n-1 is the previous control value, and h _P is a control parameter for the pressure difference and is negative.

When the post combustion air amount is controlled based on the main flue temperature and the O ₂ concentration in the exhaust gas, and the post combustion grate velocity is controlled based on the pressure difference, the post combustion is performed using the equation (2). obtains a control value F _n of the air quantity, obtains a control value G _n of the post-combustion grate velocity using equation (4).

When the amount of after-combustion air is controlled based on the main flue temperature and the CO concentration in the exhaust gas, and the after-combustion grate velocity is controlled based on the pressure difference, the after-combustion air is calculated using the equation (3). The control value F _{n of the} quantity is obtained, and the control value G _n of the post-combustion grate velocity is obtained using the equation (4).

It is also possible to measure the main flue temperature or the main flue temperature and the exhaust gas component concentration to control the amount of post combustion air and to control the post combustion grate velocity without obtaining the pressure difference. . As an example, main flue temperature and exhaust gas C
A case of controlling based on the O concentration will be described.

The control value F _n of the post-combustion air amount is obtained by using the equation (3), and the control value G _n of the after-combustion grate velocity is obtained by using the following equation (5).

[0092]

(Equation 5)

However, h _T is a control parameter for the main flue temperature and is negative. h _CO is a parameter for the CO concentration in the exhaust gas, and the measured value T of the main flue temperature is smaller than the reference value T _set and the measured value [CO] of the CO concentration in the exhaust gas is larger than the reference value [CO] _set. Is positive when the measured value T of the main flue temperature is greater than the reference value T _set and the measured value [CO] of the CO concentration in the exhaust gas is greater than the reference value [CO] _set , and otherwise Is zero when.

In the above calculation, if the reference values such as the main flue temperature, the O ₂ concentration in the exhaust gas, the CO concentration in the exhaust gas, the pressure difference, etc. are wide, the upper limit value or the lower limit value is used as the reference value and the measured value is used. If is within the limit range, the difference between the measured value and the reference value may be set to zero for calculation.

In addition to the above calculation, in addition to the measurement of the main flue temperature, the O ₂ concentration in the exhaust gas or the CO concentration, the CO concentration is measured at the same time as the measurement of the O ₂ concentration in the exhaust gas. In addition, calculation may be performed.

Regarding the measured values, the secondary air amount and the primary air amount under each grate may be measured, the fluctuations in these air amounts may be grasped, and the O ₂ concentration and CO concentration may be corrected before use. .

Further, it is also possible to use in combination with other control methods, for example, a method of measuring the furnace outlet temperature or the amount of generated steam and controlling the secondary air amount to keep these constant, and the present invention. It is also possible to use the above control method together.

[0098]

EXAMPLE The main flue temperature was measured by the control system shown in FIG. 1, the amount of post-combustion air was controlled, and the CO concentration in the exhaust gas was investigated.

The reference value T _set of the main flue temperature was 850 ° C., and the calculation cycle of the control value was 1 minute. The results of the examination are shown in Fig. 4 together with the measured values of the main flue temperature. In FIG. 4, (a) figure shows the change of the main flue temperature, and (b) figure shows the CO concentration in the exhaust gas measured at the same time.

The measurement was carried out for 5 hours, but since the combustion control was carried out on the after-combustion grate by controlling the amount of after-combustion air, the main flue temperature was controlled within the range of 820 ° C to 930 ° C. The CO concentration in the exhaust gas was suppressed to 20 ppm or less.

This result was compared with the conventional complete combustion control mainly for adjusting the secondary air amount. The conventional results are shown in FIG. In FIG. 5, (a) figure shows the change of main flue temperature,
The figure (b) shows the CO concentration in the exhaust gas measured at the same time. The main flue temperature fluctuated in the range of 750 ° C to 1050 ° C, and when the main flue temperature was high, the CO concentration in the exhaust gas was as high as 200 ppm or more.

When an air-deficient state appears in the post-combustion grate, unburned gas is often generated in the front-stage grate. This unburned gas is introduced into the mixing chamber through the auxiliary flue, but at the same time, after the combustion air that has been increased according to the present invention is introduced into the mixing chamber from the main flue in a high temperature state, the auxiliary smoke is introduced here. It contributes to the combustion of unburned components contained in the flue gas. Therefore, the increase amount of the secondary air due to the combustion of the unburned gas can be reduced by that amount, and the energy loss due to the unnecessary cooling effect of the secondary air blown at room temperature can be reduced.

[0103]

As described above, according to the present invention, the state of dust on the post-combustion grate is judged by measuring the temperature of the main flue, etc., and the temperature is insufficient, the air is insufficient, or the fuel is insufficient. The post-combustion air amount or the post-combustion air amount and the post-combustion grate velocity are controlled so as not to fall into. Therefore, the incomplete combustion state is immediately improved in the primary combustion stage, and the generation of unburned components such as dioxins and carbon monoxide is suppressed. At the same time, unnecessary blowing of secondary air is prevented. As described above, the effect of the present invention that achieves complete combustion and enables efficient use of waste energy is great.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a refuse incinerator and its control system used in an embodiment of the invention.

FIG. 2 is a graph showing changes in the main flue temperature and the CO concentration in exhaust gas for explaining the relationship between the two.

FIG. 3 is a graph showing changes in both of the post-combustion air amount and the CO concentration in exhaust gas in order to explain the relationship between them.

FIG. 4 is a graph showing changes in main flue temperature and CO concentration in exhaust gas according to an embodiment of the invention.

FIG. 5 is a graph showing changes in main flue temperature and CO concentration in exhaust gas according to a conventional control method.

[Explanation of symbols]

1 Incinerator 3c Post-combustion grate 3d Grate drive 4 Droplet 5 Primary air fan 10 Secondary air fan 11 Partition 13d Post-combustion grate below air damper 14 Main flue thermometer 15 Controller 16 Exhaust gas O ₂ concentration meter 17 Exhaust gas CO concentration meter 18a In-furnace pressure gauge 18b Post-combustion grate pressure gauge.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F23G 5/50 ZAB F23G 5/50 ZABP

Claims (8)

[Claims] 1. A main flue temperature of an incinerator or one or more of a main flue temperature and an O ₂ concentration in exhaust gas, a CO concentration in exhaust gas, or a pressure difference above and below a post-combustion grate is measured, and each measured value is measured. Periodically compare with each reference value, based on this comparison result,
A method for suppressing unburned components in exhaust gas of a refuse incinerator, which comprises controlling the amount of afterburning air or the amount of afterburning air and the velocity of afterburning grate. 2. The main flue temperature of the incinerator is measured, and when the main flue temperature does not reach the reference temperature, the amount of post combustion air is reduced, and when the main flue temperature exceeds the reference temperature, the post combustion air. A method for suppressing unburned components in exhaust gas from a refuse incinerator, which is characterized by increasing the amount. 3. The main flue temperature and O ₂ concentration in the exhaust gas of the incinerator is measured, the main smoke in the exhaust gases not reach the road temperature is the reference temperature O ₂
Waste incinerator exhaust gas characterized by decreasing the amount of after combustion air when the concentration exceeds the reference value, and increasing the amount of after combustion air when the main flue temperature exceeds the reference temperature and the O ₂ concentration does not reach the reference value Medium Unburned component control method. 4. The main flue temperature of the incinerator and the CO concentration in the exhaust gas are measured, and when the main flue temperature is below the reference temperature and the CO concentration exceeds the reference value, the amount of post-combustion air is reduced to reduce the main flue gas. A method for suppressing unburned components in exhaust gas of a refuse incinerator, which comprises increasing the amount of post-combustion air when the temperature exceeds the reference temperature and the CO concentration exceeds the reference value. 5. The main flue temperature of the incinerator or one or more of the main flue temperature and the O ₂ concentration in the exhaust gas, the CO concentration in the exhaust gas, or the pressure difference above and below the post-combustion grate is measured, and each measured value is measured. Periodically compared with each reference value, while controlling the amount of post-combustion air based on the result of this comparison, the difference between the pressure under the post-combustion grate and the pressure in the furnace is measured, these measured values A method for suppressing unburned components in exhaust gas of an incinerator, comprising: comparing and controlling a post-combustion grate velocity based on the comparison result. 6. The difference between the main flue temperature of the incinerator, the pressure below the post-combustion grate and the pressure inside the furnace is measured, and the main flue temperature does not reach the reference temperature and the pressure below the post-combustion grate and the furnace. When the difference in internal pressure does not reach the standard difference, the amount of post combustion air is reduced and the post combustion grate velocity is increased, the main flue temperature exceeds the reference temperature, and the pressure under the post combustion grate and the furnace pressure When the difference exceeds the standard difference, the method for suppressing unburned components in the exhaust gas of a refuse incinerator is characterized by increasing the amount of post-combustion air and decelerating the speed of post-combustion grate. 7. The difference between the main flue temperature of the incinerator, the O ₂ concentration in the exhaust gas, the pressure below the post-combustion grate and the pressure inside the furnace is measured,
When the main flue temperature does not reach the reference temperature, the O ₂ concentration exceeds the reference value, and the difference between the pressure under the post-combustion grate and the pressure in the furnace does not reach the reference difference, the post-combustion air amount is reduced and the post-combustion is performed. When the grate velocity is increased, the main flue temperature exceeds the reference temperature, the O ₂ concentration does not reach the reference value, and the difference between the pressure under the post-combustion grate and the pressure in the furnace exceeds the reference difference, the post-combustion is performed. A method for suppressing unburned components in exhaust gas from a refuse incinerator, which comprises increasing the amount of air and reducing the velocity of a post-combustion grate. 8. The difference between the main flue temperature of the incinerator, the CO concentration in the exhaust gas, the pressure below the post-combustion grate and the pressure inside the furnace is measured,
When the main flue temperature does not reach the reference temperature, the CO concentration exceeds the reference value, and the difference between the pressure under the post-combustion grate and the pressure in the furnace does not reach the reference difference, the amount of post-combustion air is reduced and the post-combustion grate is reduced. When the speed is increased, the main flue temperature exceeds the reference temperature, the CO concentration exceeds the reference value, and the difference between the pressure under the post-combustion grate and the pressure in the furnace exceeds the reference difference, the post-combustion air amount is increased. A method for suppressing unburned components in exhaust gas from a refuse incinerator, which comprises reducing the speed of a post-combustion grate.