JPH0260928B2 - - 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, a waste heat boiler is heated by the combustion exhaust gas discharged from the upper part of the furnace, and the industrial waste or intermediate treated material to be supplied to the high temperature hearth is converted into the waste heat. This paper relates to an automatic control method for an industrial waste melting furnace that is pre-dried using steam from a boiler.

The above-mentioned industrial waste melting uses the thermal energy of high-temperature combustion exhaust gas for pre-drying, so it has good overall thermal efficiency. Stability is necessary to ensure good furnace operation, and for this purpose it is necessary to control the pre-drying capacity.

Conventionally, in order to control the preheating drying capacity, as shown in FIG. The flow control valve 45 of the steam discharge path 44 is automatically operated to maintain the detected value of the pressure gauge 39 within the set range, and the width of the industrial waste and its intermediate processed material 6 to be supplied to the high-temperature hearth 5 is controlled. In order to maintain sufficient pre-drying capacity regardless of fluctuations in calorific value, carbon-based The amount of combustible material supplied by the quantitative feeder 36 was set and kept constant.

The disadvantage of the conventional control method described above is that the amount of carbon-based combustible material supplied becomes excessive on average, and a large amount of thermal energy is wasted as surplus steam. The point is that the initial purpose has been lost.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to maintain the amount of steam generated by a waste heat boiler at the minimum necessary level, thereby effectively saving energy.

The characteristic means of the automatic control method for an industrial waste melting furnace according to the present invention is based on information from a sensor that detects changes in the amount of steam generated in a waste heat boiler for pre-drying industrial waste heated by combustion exhaust gas from the upper part of the furnace. Based on this, the controller controls the supply amount of the feeder for supplying carbon-based combustible material to the high-temperature hearth for melting industrial waste formed at the lower part of the furnace, and the controller controls the supply amount of the feeder containing oxygen for combustion to the high-temperature hearth. The purpose is to change the gas supply amount so that the detected value of the sensor is maintained within a set range.

The effects of the characteristic means of the present invention are as follows. In other words, when the amount of steam generated increases more than necessary, the amount of carbon-based combustible material supplied is reduced, and the amount of oxygen-containing gas supplied for combustion is reduced by an amount commensurate with the reduction in carbon-based combustible material. Wasteful consumption of carbon-based combustible materials is suppressed, and when the amount of steam generated is reduced to less than necessary, the supply amount of carbon-based combustible materials is increased and only the amount commensurate with the increased amount of carbon-based combustible materials is burned. By increasing the amount of oxygen-containing gas supplied to the furnace, pre-drying of the industrial waste or its intermediate products to be supplied to the furnace can be carried out as specified.

As a result, even if the calorific value of industrial waste or its intermediate products supplied to the high-temperature hearth fluctuates widely, it is possible to pre-dry industrial waste or its intermediate products with good furnace operation. This makes it possible to reliably reduce the consumption of useful carbon-based combustible substances, such as coke, to the necessary minimum while ensuring that the process can be carried out easily and reliably, which is extremely advantageous in terms of energy saving and running costs. Ta.

Furthermore, for example, it is possible to keep the amount of carbon-based combustible material supplied to the furnace constant and control the amount of heat generated by an auxiliary burner attached to the waste heat boiler in accordance with changes in the amount of steam generated by the waste heat boiler. However, this is accompanied by a rise in equipment costs due to the auxiliary burner and its fuel supply equipment, etc., and requires two types of fuel: fuel for the auxiliary burner and carbon-based combustible material for melting industrial waste, so fuel management is difficult. However, according to the present invention, since the supply amount of the carbon-based combustible material that is originally used is controlled, there is no problem in terms of equipment costs and fuel management as described above. As a whole, it is possible to perform industrial waste melting treatment with extremely excellent economic efficiency.

Next, an example will be shown with reference to FIG.

The water treatment sludge from the hopper 31 is supplied to the dryer 33 by the quantitative feeder 32 while maintaining the weight per unit time within the set range.
The pre-dried water treatment sludge is continuously supplied to the input conveyor 34, the coke from the hopper 35 is supplied to the input conveyor 34 by a quantitative feeder 36 whose supply amount can be freely set, and the water treatment sludge from the input conveyor 34 is supplied to the input conveyor 34. A mixture of coke and coke is supplied from the hopper 2 into the vertical furnace 3 by automatically and selectively opening the double dampers 1a and 1b in short cycles, and the coke layer filled in the lower part of the furnace is passed through the primary tuyere. The sludge 6 is combusted by air supplied from 4 to form a high-temperature hearth 5, and the sludge 6 is heated and melted in the upper part of the high-temperature hearth 5.
The melt 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.

Preheating the combustion air supplied from the blower 15 to the primary tuyere 4 by the air preheater 11 to maintain the temperature of the high-temperature hearth 5 at a high enough temperature for sludge melting;
Then, based on the information from the furnace pressure detector 26 at the top of the furnace 3, the controller 30 automatically operates the damper 16 to adjust the furnace interior and adjust the proportion of combustion exhaust gas supplied to the exhaust gas path 8 and the exhaust path 7 as appropriate. Set.

Combustible gas combustion air is supplied to the blower 15 above the high temperature hearth 5 from the secondary tuyere 17 and the tertiary tuyere 18 connected in parallel with the primary tuyere 4 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 Combustible gas is combusted from the secondary tuyere 17 by a feedback type automatic control mechanism configured to automatically operate the flow control valve 21c by the controller 20c based on information from the meter 22 that detects the oxygen gas concentration. The amount of air supplied is adjusted so that the oxygen gas concentration of the combustion exhaust gas is maintained within a set range, for example around 2%, and the amount of air supplied as a whole is adjusted to be just the right amount and coke consumption is controlled. In addition, ensure that sufficient combustion occurs within the furnace. In addition, secondary and tertiary tuyere 1
The air supply amount ratio from both tuyeres 17 and 18 is
70 to 80% of the total supply from 8 to secondary tuyere 17
It is preferable that 30 to 20% of the total amount be supplied from the tertiary tuyeres 18.

The moisture content of the dried sludge on the input conveyor 34 is measured continuously or intermittently using an automatic moisture measuring device 37, such as an infrared moisture meter, and
Based on the measured moisture content, a controller 46 controls a controller 20 for the air supply from the secondary tuyere 17.
A feed-forward automatic control mechanism is configured to transmit an operation command to the flow control valve 21c and automatically operate the flow rate control valve 21c. Even with the correlation determined, the amount of combustion air supplied to the furnace 3 is changed,
The oxygen concentration of the combustion exhaust gas is kept in a state where there is little change due to changes in the water content of the sludge, and the oxygen concentration is restored to the set range in a short time by the action of the feedback type automatic control mechanism.

More specifically, if the moisture content of the dried sludge increases, if the combustion air supply rate is not changed, after the dried sludge with the increased moisture content is supplied to the high temperature hearth,
The oxygen concentration of the combustion exhaust gas increases rapidly and greatly, and in order to suppress this increase in oxygen concentration, at the same time as dry sludge is supplied to the high-temperature hearth 5, a feed-forward type automatic control mechanism is used to control combustion air. The supply amount is reduced by an appropriate amount commensurate with the increase in moisture content. Conversely, when the moisture content of dried sludge decreases, the feed-forward automatic control mechanism increases the amount of combustion air supplied to reduce the amount of moisture in the combustion air so as to suppress the decrease in oxygen concentration in the combustion exhaust gas caused by the supply of sludge. The rate should be increased by an appropriate amount commensurate with the decrease in rate.

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 that the temperature detected by the thermometer 26 is maintained within the set range, for example, about 900°C. Prevents dust from adhering to the surface.

Based on the information from the pressure gauge 38 that detects the steam pressure supplied from the waste heat boiler 9 to the dryer 33,
The pressure control valve 40 is automatically operated by the controller 39 to maintain the detected pressure of the pressure gauge 38 within a set range,
The drying capacity of the dryer 33 is made constant.

Based on the information from the pressure gauge 38, a feed forward type controller 41 automatically adjusts the supply amount of the coke supply quantitative feeder 36 to reduce the coke supply amount when the steam supply pressure increases; Moreover, when the steam supply pressure decreases, the amount of coke supplied is increased, thereby allowing pre-drying to be carried out as desired while suppressing wasteful consumption of coke.

Based on the information from the controller 41 for adjusting the amount of coke supplied, the feed forward controller 42 issues an operation command to the controller 20a for the amount of air supplied from the primary tuyere 4, thereby adjusting the flow rate. By automatic operation of the valve 21a, the amount of combustion air to the furnace 3 is changed in a preset direct proportional correlation in accordance with the variation in the amount of coke to the high temperature hearth 5, so that when increasing the amount of coke, the amount of combustion air is changed. The amount of coke consumed in the high-temperature hearth 5 is increased by the increased amount, and when the amount of coke is reduced, the amount of coke consumed is decreased by the amount of the amount reduced.

Next, another example will be shown.

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. In addition to air, various oxygen-containing gases such as air suitably enriched with oxygen can be used for combustion.

In addition to water treatment sludge, various industrial wastes such as city garbage combustion ash, tire scraps, and waste catalysts, or intermediate products thereof, can be melted.

To detect changes in the amount of steam generated by the waste heat boiler 9, instead of the pressure gauge 38, for example, a steam exhaust amount detection device may be provided in the excess steam discharge path from the waste heat boiler 9, or the amount of steam supplied to the dryer 33 may be controlled. Various detection configurations can be used, such as a device for detecting changes in the opening of a valve for controlling the amount of steam or excess steam discharged, and these are collectively referred to as sensors 38.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of an apparatus used in the method of the present invention, and FIG. 2 is a flow sheet showing a part of an example of apparatus used in the conventional method. 3...furnace, 5...high temperature hearth, 3...waste heat boiler, 32...feeder, 38...sensor, 4
1,42...Controller.

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.
The waste heat boiler 9 is heated by the combustion exhaust gas discharged from the upper part of the industrial waste, and the industrial waste or intermediate treatment material supplied to the high temperature hearth 5 is pre-dried with the steam from the waste heat boiler 9. An automatic control method for a melting furnace, in which a feeder supplies carbon-based combustible material to the high-temperature hearth 5 by a controller 41 based on information from a sensor 38 that detects changes in the amount of steam generated in the waste heat boiler 9. 32, and the high temperature hearth 5 is controlled by the controller 42.
An automatic control method for an industrial waste melting furnace, characterized in that the amount of oxygen-containing gas supplied for combustion to the furnace is changed so that the detected value of the sensor 38 is maintained within a set range.