JPH0226129B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention forms a high-temperature hearth in the lower part of the furnace by burning carbon-based combustible materials, supplies industrial waste or its intermediate processed material to the high-temperature hearth, and melts it. The molten material is taken out of the furnace from the lower part of the floor, and a part of the combustion exhaust gas discharged from the upper part of the furnace is cooled and then supplied to the upper part of the high-temperature hearth. A temperature control mechanism adjusts the detected furnace temperature so that it is maintained within a set range, and a feedback type automatic pressure adjustment mechanism adjusts the amount of combustion exhaust gas discharged from the furnace so that the detected furnace pressure is maintained within a set range. Concerning automatic control methods for industrial waste melting furnaces.

The above control method was previously proposed in Japanese Patent Application No. 147089 of 1982, and it is possible to control the temperature of the flue gas above the high-temperature hearth by supplying cooled flue gas into the furnace to ensure sufficient combustion of unburned gas. By adjusting the furnace internal pressure,
By supplying an appropriate amount of high-temperature gas to the molten material removal path, the molten material can be discharged without being hindered by cooling and solidification.
It has the advantage that it can be carried out smoothly.

However, there was room for improvement in the following points.
In other words, when the amount of cooled flue gas supplied into the furnace is changed, especially when the change is rapid and wide, the furnace pressure fluctuates greatly, and the furnace pressure changes due to the action of the feedback type automatic pressure regulating mechanism. The pressure chattering occurs, and it takes a long time to return the furnace pressure to within the set range.To do this, excessive supply of high-temperature gas to the melt discharge passage, cold air intake from the melt discharge passage into the furnace, etc. There was a drawback that it was difficult to fully achieve smooth and reliable discharge of the molten material.

In view of the above-mentioned circumstances, an object of the present invention is to effectively suppress fluctuations in furnace pressure due to changes in the amount of cooled combustion exhaust gas.

The characteristic structure of the automatic control method for an industrial waste melting furnace according to the present invention is that a feed-back system is used to control the amount of cooled combustion exhaust gas based on information from a feedback-type automatic temperature control mechanism that adjusts the supply amount of the cooled combustion exhaust gas so that the detected furnace temperature is set. Ward-type automatic pressure regulation mechanism changes combustion exhaust gas emissions in a preset direct proportional relationship according to changes in cooling combustion exhaust gas supply, and detects combustion exhaust gas emissions The furnace pressure is maintained within the set range. The purpose of the present invention is to automatically adjust the furnace pressure by both a feedback type automatic pressure regulating mechanism that adjusts the pressure as described above and the feed forward type automatic pressure regulating mechanism.

The effects of the characteristic means of the present invention are as follows. In other words, when the furnace temperature rises and the amount of cooled flue gas supplied is increased, the amount of flue gas discharged is increased at the same time as the amount of supply is increased.
In addition, when the furnace temperature falls and the amount of cooled combustion exhaust gas supplied is reduced, the amount of combustion exhaust gas discharged is reduced simultaneously with the operation of reducing the amount of supply;
According to a preset program according to the characteristics of the melting furnace, the larger the variation in the amount of cooling flue gas supplied, the greater the change in the amount of flue gas emissions.
Furnace pressure is adjusted using a feed-forward automatic pressure regulating mechanism. As a result, fluctuations in furnace pressure caused by automatic furnace temperature adjustment can be reduced or almost eliminated, and chittering in furnace pressure caused by the action of the feedback automatic pressure adjustment mechanism can be eliminated or fluctuations in furnace pressure can be absorbed in a short time. Overall, the predetermined furnace pressure is maintained accurately and reliably to prevent coke, etc. from flying out due to excessive supply of high-temperature gas to the molten material discharge path, and melting due to insufficient supply of high-temperature gas to the molten material discharge path. Trouble such as clogging, etc.
It has now become possible to more effectively prevent the problem and ensure good melting treatment of industrial waste.

Next, examples will be shown with reference to drawings.

Coke and industrial waste are alternately or simultaneously opened and closed by double dampers 1a and 1b,
The coke layer supplied from the hopper 2 into the vertical furnace 3 and filled in the lower part of the furnace is combusted by the air supplied from the primary tuyere 4 to form a high-temperature hearth 5. The waste 6 is heated and melted, and the molten material flows down the gap in the high-temperature hearth 5 and is taken out of the furnace from the lower part of the high-temperature hearth 5 through a discharge passage 7.

Most of the combustion exhaust gas rising from the high-temperature hearth 5 is transferred from an exhaust gas path 8 connected to the upper part of the furnace to an exhaust heat boiler 9, a dust removal cyclone 10, an air preheater 11,
It is sent to the desulfurization device 12, the wet dust removal device 13, and the exhaust blower 14 in that order and released into the atmosphere, and
A part of the combustion exhaust gas is passed through the exhaust passage 7 to keep the molten material warm.
released into the atmosphere. In addition, the air preheater 11 preheats the combustion air supplied from the blower 15 to the primary tuyere 4 to maintain the temperature of the high-temperature hearth 5 at a high enough temperature for melting industrial waste. 3
Based on the information from the furnace internal pressure detector 29 at the top, the damper 16 is automatically operated by the controller 30 to adjust the furnace internal pressure and appropriately set the combustion exhaust gas supply ratio to the exhaust gas path 8 and the exhaust path 7.

Combustible gas combustion air is supplied to the blower 15 from the secondary tuyere 17 and the tertiary tuyere 18 connected in parallel with the primary tuyere 4 above the high-temperature hearth 5 to the upper and lower parts of the furnace 3, The unburned gas from the waste 6 is completely combusted and the combustion exhaust gas is sent to the exhaust gas passage 8, and the combustion of the unburned gas is dispersed throughout the space above the high-temperature hearth 5, and the flame temperature is lowered to increase the furnace temperature. Suppresses internal temperature rise and prevents NOx generation and dust adhesion to the furnace inner wall.

Based on the information from the flow meter 19a, the controller 20a
The flow control valve 21a is automatically operated to maintain the amount of combustion air supplied from the primary tuyere 4 to the high-temperature hearth 5 almost constant, and the flow meter 19 is also automatically operated.
b. By the action of the controller 20b and the flow control valve 21b, the amount of air supplied from the tertiary tuyere 18 for combustible gas combustion is maintained almost constant, and the amount of combustion exhaust gas downstream of the flow meter 19c and the wet dust remover 13 Based on the information from the meter 22 that detects the oxygen gas concentration, the controller 20c automatically operates the flow control valve 21c to adjust the amount of air supplied from the secondary tuyere 17 for combustible gas combustion to the oxygen gas in the combustion exhaust gas. Adjust so that the concentration is maintained within the set range, for example around 2%,
In addition, the overall amount of air supplied should be just the right amount, coke should not be consumed more than necessary, and combustion should be sufficiently carried out in the furnace. In addition, secondary and tertiary tuyere 17, 18
The ratio of air supply from the secondary tuyere 17 is 70 to 80% of the total supply from both tuyeres 17 and 18.
Preferably, 30 to 20% of the amount is supplied from the tertiary tuyeres 18.

The combustion exhaust gas, which has been sufficiently cooled by the wet dust removal device 13, is transferred to the secondary tuyere 17, the primary tuyere 23a for cold exhaust gas directly above it, and the secondary tuyere 23b for cold exhaust gas further above it through a regulating valve. 24a, 24b, 24
c, the flow control valve 28 is automatically operated by the controller 27 based on the information from the flowmeter 25 and the thermometer 26 that detects the combustion exhaust gas temperature near the entrance of the exhaust gas path 8. Then, the total amount of cooled combustion exhaust gas supplied is adjusted so as to maintain the temperature detected by the thermometer 26 within the set range, for example, about 900°C, thereby more reliably preventing NOx generation due to the rise in temperature inside the furnace and the inside walls of the furnace. Prevents dust from adhering to the surface.

Based on the information from the cooling combustion exhaust gas supply amount controller 27, the feedforward controller 31 sends an operation command to the furnace pressure adjustment controller 30, and the damper 16 is automatically operated to start cooling combustion. The amount of combustion exhaust gas discharged from the furnace 3 is changed in a direct proportional correlation set in advance in accordance with the change in the amount of exhaust gas supply, so that the change in the furnace pressure due to the change in the amount of cooling combustion exhaust gas is small, and the furnace pressure is to restore to the set range in a short time.

More specifically, at the same time as the change in the amount of cooled flue gas supplied, or at a timing slightly earlier or later than that, the amount of supplied cooled flue gas is predicted while predicting the fluctuation in furnace pressure due to the change in the amount of cooled flue gas supplied. If the supply amount increases, the opening degree of the damper 16 is increased, and conversely, if the supply amount decreases, the opening degree is decreased.
Moreover, the larger the change in the supply amount is, the larger the change in the opening degree is. Then,
This is to maintain the furnace pressure with high precision in a state that allows for good furnace operation.

In addition, the industrial waste input from Hopper 2 is
For example, sewage sludge, municipal waste incineration ash, tire waste,
They are various things such as waste catalysts, or intermediate processed products thereof.

Next, another example will be shown.

In order to supply the cooled combustion exhaust gas to the upper part of the high-temperature hearth 5, one or two places above and below the furnace 3, or even four
In order to effectively suppress the local temperature rise of the flame, it may be carried out at more than one location, and the entire amount may be supplied from the same tuyere to the flammable gas combustion air or from a separate tuyere. When the same tuyere is used to supply the same tuyeres, the tuyeres may be either upper or lower, and furthermore, the collection position of the cooled combustion exhaust gas can be changed as appropriate.

In addition to coke, appropriate carbon-based combustible materials such as briquettes such as anthracite and graphite electrode scraps can be used to form the high-temperature hearth.

The specific configuration for adjusting the cooling combustion exhaust gas supply amount so that the furnace temperature detected at an appropriate position is maintained within an appropriate setting range can be changed in design as appropriate.
Feedback type automatic temperature control mechanism 26, 2
Collectively referred to as 7 and 28. In addition, the specific configuration for adjusting the amount of combustion exhaust gas discharged from the furnace 3 so that the furnace pressure detected at an appropriate position is maintained within an appropriate setting range can be changed as appropriate, and these can be adjusted using feedback-type automatic adjustment. They are collectively referred to as pressure mechanisms 29, 30, and 16. Furthermore, the specific configuration for changing the combustion exhaust gas emission amount based on the information from the automatic temperature control mechanisms 26, 27, and 28 with an appropriately set correlation can also be changed in design as appropriate, and these can be changed in the feed format. They are collectively referred to as Ward type automatic pressure regulating mechanisms 31, 30, and 16.

[Brief explanation of drawings]

The drawing is a flow sheet of an example of an apparatus used in the method of the present invention. 3... Furnace, 5... High temperature hearth, 26, 27, 28
...Feedback type automatic temperature control mechanism, 29,3
0,16...Feedback type automatic pressure regulation mechanism, 3
1, 30, 16...Feed forward type automatic pressure regulating mechanism.

Claims (1)

[Claims] 1 A high-temperature hearth 5 is formed in the lower part of the furnace by combustion of carbon-based combustible materials, industrial waste or its intermediate treatment is supplied to the high-temperature hearth 5 and melted, and the molten material is discharged from the lower part of the high-temperature hearth 5. Take out the furnace 3 and remove it from the furnace 3.
A part of the combustion exhaust gas discharged from the upper part of the furnace is cooled and then supplied to the upper part of the high-temperature hearth 5, and the amount of cooled combustion exhaust gas supplied is controlled by feedback type automatic temperature control mechanisms 26, 27, and 28 to adjust the detected furnace temperature. The industrial waste is adjusted so that the detected furnace pressure is maintained within the set range, and the amount of combustion exhaust gas discharged from the furnace 3 is adjusted so that the detected furnace pressure is maintained within the set range by the feedback type automatic pressure regulating mechanisms 29, 30, and 16. A method for automatically controlling a material melting furnace, wherein the automatic temperature control mechanism 26, 2
Based on the information from 7 and 28, the feed forward type automatic pressure regulating mechanisms 31, 30, and 16 adjust the combustion exhaust gas emissions with a preset direct proportional correlation according to the change in the cooling combustion exhaust gas supply amount. An automatic control method for an industrial waste melting furnace characterized by changes.