JPH035611A - Waste melting furnace - Google Patents

Abstract

PURPOSE:To prevent deflection in the flow of the charge in a furnace and an insufficient quantity of generated heat by forming a filling zone for massive carbonaceous combustible matters of on a shaft section which is provided with a tuyere and tap hole, connecting to the shaft a charging port for combustionble waste matters and connecting a hollow conical body to which an exhaust gas pipe is connected, and burying in the center of the hollow conical body a charging cylinder for waste matters and fuel. CONSTITUTION:In a melting furnace 1 a high temperature furnace bed 12 into which massive carbonaceous combustible matters B (cokes) of are filled and a hollow conical body 15 which has an expanded upper section are connected to the shaft section 11 to form a filling zone 13 to fill wastes, cokes B, and limestone C and a filling zone 14 to fill cokes B. The diameter of this coke filling zone 14 is expanded about 3 times as large as the diameter of the cross section through the tuyeres so as to reduce the speed of the combustion exhaust gases and exhaust gas pipes 17 are provided above the coke filling zone 14 with an equal distance among them. And, a charging cylinder 19 for charging wastes A, cokes B, and limestone C is provided with its lower end buried in the coke filling zone 14. With this constitution it is possible to prevent deflection in the flow of the charge in the furnace and an insufficient quantity of generated heat.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention. In a high-temperature hearth formed of lumpy carbon-based combustible materials, municipal waste, sewage sludge, various industrial wastes, or intermediate products obtained by dehydrating, drying, incinerating, or crushing them are melted and processed to produce non-combustible materials. This invention relates to a waste melting furnace that recovers waste as slag.

[Conventional technology]

In a typical waste melting furnace, waste such as municipal waste to which coke has been added as a lumpy carbon-based combustible material is charged from the top of a vertical shaft furnace, and the waste is charged into the drying zone, carbonization gasification zone, and It descends sequentially through the combustion melting zone. On the other hand, oxygen-containing gas or oxygen-enriched gas is blown into the furnace through the furnace, and coke and carbonaceous matter produced by thermal decomposition are burned at high temperature in the high-temperature hearth. generated.

At this time, in order to reduce the viscosity of the slag, limestone or silica stone is charged from the top of the furnace together with the waste as a basicity regulator. The high-temperature combustion exhaust gas rises as a countercurrent through the waste-filled bed in the shaft, thermally decomposing the waste, and organic matter in the waste is discharged as flammable gas and recovered as combustion heat.

In addition, the following was announced in Japanese Patent Publication No. 63-49128. In this method, a waste material charging tube is installed in the center of the top of the shaft furnace, the lower end is buried in the coke filling area, a coke charging port is arranged around the waste material charging tube, and an exhaust pipe is installed around the waste material charging tube. It is arranged. Waste is placed in the center and coke is charged separately to cover the periphery, in order to prevent dust blowing up from the waste filling area due to exhaust gas by the suppressing action of the coke.

[Problem to be solved by the invention]

However, since the bulk carbon-based combustible material to be filled is distributed within the furnace at an angle of repose, the ventilation pressure loss at the peripheral wall portion where the filling height is low is small, and drifting occurs in the radial direction within the furnace. The charged lumpy carbon-based combustible material tends to have coarse grains distributed in the peripheral wall and fine grains in the center, and the coarse grained part has a smaller ventilation pressure drop than the fine grained part. be done.

This is because the lumpy carbon-based combustible material charged into the furnace flows in while rolling over the lumpy carbon-based combustible material that was previously charged and resting, and the coarse particles roll quickly into the lower part of the peripheral wall. reach. This is a phenomenon caused by the presence of space within the furnace.

As a result of the uneven flow, the peripheral flow becomes an uneven flow with more gas flow in the periphery and less gas flow in the center, which reduces heat exchange between waste and carbon-based combustible materials in the center of the furnace, reducing the thermal efficiency of the furnace. However, there are disadvantages in that the exhaust gas temperature rises in the peripheral area, the superficial velocity increases, and the amount of entrained dust in the exhaust gas increases.

Furthermore, since no carbon-based combustible material is supplied to the waste charging tube located in the center of the furnace body,
It is difficult to supply carbon-based combustible materials to the center of the high-temperature hearth, making it impossible to maintain the bed height of carbon-based combustible materials, resulting in insufficient heat generation necessary for melting, and making stable continuous operation difficult. .

In order to compensate for this drawback, the fuel ratio must be increased, the oxygen enrichment rate must be increased, and uneconomical operations must be performed.

It is an object of the present invention to provide a waste melting furnace that suppresses the occurrence of undesirable drift in the furnace and eliminates the disadvantage of insufficient heat generation in the high-temperature hearth.

[Means for Solving the Problem] In order to solve the problem, the waste melting furnace of the present invention connects a hollow cone with an enlarged upper part on a shaft portion provided with a tuyere and an outlet. Next, a filling area of the lumpy carbon-based combustible material is formed in the hollow cone, and a charging tube for charging the waste and the lumpy carbon-based combustible material from above the high-temperature hearth formed in the center of the shaft is inserted into the filling area. It will be buried in the Then, a plurality of bulk carbon-based combustible material charging ports and a plurality of exhaust gas pipes are connected to the upper part of the hollow vertebral body. The inner surface of the upper part of the hollow cone was formed at an angle equal to or greater than the angle of repose of the bulk carbon-based combustible material.

[For production]

A lump of carbon-based combustible material (hereinafter referred to as carbon-based combustible material) is filled into a carbon-based combustible material charging port and charged into a carbon-based combustible material filling area without emptying. When the carbon-based combustible material flows into the filling area, it gradually descends to the upper part of the hollow cone below the charging port. At this time, since the inner surface of the upper part of the hollow vertebral body is formed at an angle equal to or greater than the angle of repose of the carbon-based combustible material, no space is created in the furnace. Therefore, the carbon-based combustible material is inflowed and filled without rolling. Therefore, it is uniformly distributed in the furnace, no particle size segregation occurs, the ventilation pressure loss is uniform, and no uneven flow of combustion exhaust gas occurs.

Since the lower end of the exhaust gas pipe comes into contact with the slope of the carbon-based combustible material, the filling height is kept constant. Therefore, the pressure loss of the exhaust gas is also kept constant.

From the central waste charging tube, waste and part of the carbon-based combustible material are charged alternately or mixed to form a waste filling area. Therefore, the necessary carbon-based combustibles are supplied to the high-temperature hearth, and there is no shortage of calorific value.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained using examples with reference to the drawings.

FIG. 1 shows a sectional view of a waste melting furnace 1 and a waste melting treatment system according to a first embodiment of the present invention.

For example, this is an example of a case where there is a large amount of ash and non-combustible content, such as incineration ash of municipal waste or sewage sludge.

This waste melting furnace 1 has a high-temperature hearth 12 in which a shaft portion 11 is filled with a lumpy carbon fiber combustible material B (hereinafter an example using coke), and an upper part with an inclination angle of 60 degrees is enlarged above the hearth 12. The hollow cones 15 are connected to form a filling area 13 for waste A, coke B and limestone C, and a filling area 1 for coke.
4. Inside the melting furnace, these filling areas13.14
It is filled with air and has no space.

The diameter of the coke filling area 14 is expanded to three times the diameter of the tuyere cross section to reduce the superficial velocity of the combustion exhaust gas, and a 50 degree slope is formed around the upper peripheral wall 16 of the coke filling area 14. Four exhaust gas pipes 17 are installed at equal intervals. The combustion exhaust gas E is transferred from the exhaust gas pipe 17 to the secondary combustion chamber 2,
Air preheater 3, gas cooler 4, dust collector 5, smoke cleaning device 6,
It is discharged through an induced blower 7 and a chimney 8.

The above-mentioned inclination angle and dimensional ratio are for the case where a medium lump of blast furnace coke is used, and are preferably changed depending on the lumpy carbon-based combustible material used, such as petroleum coke, pitch coke, electrode scrap, etc.

Four lumpy carbon-based combustible material charging ports 18 (hereinafter referred to as coke charging ports) are provided in the upper part of the hollow cone 15. The upper inner surface of the hollow cone 15 is formed at an angle of 45 degrees, which is greater than the angle of repose of coke, and is connected to the charging port 18.

A charging tube 19 for charging waste A, coke B, and limestone C is arranged in the center of the furnace, and the lower end of the charging tube 19 is buried in the coke filling area 14.

From the charging tube 19, 30 to 70 percent of waste A and coke B are charged in a layered or mixed form.

At this time, limestone C is charged from the charging tube together with the waste. A plurality of optimal combinations of the number of exhaust gas pipes 17 and coke charging ports 18 are selected depending on the scale of the waste melting furnace and the equipment layout conditions around the furnace.

Further, a forced air blower 9 is installed in the shaft portion 11 so as to burn the coke in the furnace and form a grate with a high temperature atmosphere.
Eight lower air blowing windows 20 blow preheated oxygen-containing gas (hereinafter referred to as blast air D) through the empty air preheater 3, and eight upper air blowing windows 20 for the purpose of preheating the surrounding coke and expanding the high-temperature atmosphere. The blast air blowing tuyere 21 is symmetrically arranged in the middle of the lower blast air blowing tuyere 20. There is no problem if the tuyere 20, 21 is configured in one stage rather than in two stages, upper and lower.

Further, at the bottom of the furnace below the shaft part 11, there is provided an outlet 22 for discharging molten slag in which waste ash, non-combustible matter, coke, and limestone ash are melted and mixed at high temperature and the basicity has been adjusted. .

The waste A descends into the charging tube 19 and comes to form a filling zone 13 . During this process, the waste is placed in the charging tube 19 for 50 m
Deposit 0 to 800mm and reduce combustion exhaust gas temperature to approximately 250°
In this state, the waste reaches a temperature of 700 to 1000°C at the center of the lower level of the charging tube. High temperature hearth 1
By the time the temperature reaches 2, the ash and non-combustibles rapidly soften, melt, melt, and melt in the voids in the coke grate due to the radiant heat from the red-hot coke and the high-temperature combustion exhaust gas from coke combustion.
Start dripping.

The coke charged from the coke charging port 18 forms a coke filling area 14, where it exchanges heat with the combustion exhaust gas discharged into the exhaust gas pipe 17 while descending, and the coke gradually increases its temperature and is blown into the upper stage. When reaching the air blowing tuyere, a part of the CO gas in the flue gas rising from below is preferentially combusted, and the resulting heat is used to further heat the CO gas to a higher temperature. In this region, as mentioned above, the ash and non-combustible components have started to soften and melt, making it relatively difficult for the rising gas to pass through. A ring-shaped coke layer is formed on the peripheral wall side, and rising gas passes through this portion with good air permeability. At this time, the flow rate of the rising gas is
Since a uniform flow is maintained in the circumferential direction and the flow velocity is increased, heat transfer is enhanced at the boundaries of the filled areas 13,14.

Furthermore, in the high-temperature hearth 12, the coke bed is maintained by the coke supplied into the central charging cylinder, and the high-temperature coke grate is stably maintained by the preheated air blown from the lower air blowing tuyere 20. be done.

The filling height in the furnace in this example is approximately 1.8 m, the ventilation pressure loss of the packed bed is 200-300 mm water column, and the gas ejected from the tap has a flame length of 150-200 mm when released to the atmosphere. It is burned with

In addition, the upper air blowing tuyere 21 has 10~
Injection of 20% of the amount was effective in lowering the coke-fuel ratio, raised the temperature of the molten slag, and produced stable tapped slag.

FIG. 2 shows a second embodiment. In the waste melting furnace 1 of this embodiment, exhaust gas may also be discharged from the charging tube 19. Further, each exhaust gas pipe 17 may be provided with an exhaust gas flow rate control valve 26, respectively. Furthermore, a charging cylinder exhaust gas flow rate control valve 25 may also be installed in the charging cylinder 19.

Further, the charging cylinder 19 may be configured to be moved up and down using the drive device 23 while performing gas sealing with the expansion joint 24.

By providing flow rate control valves 25 and 26 in the middle of each exhaust gas flow path, it is possible to vary the flow rate of exhaust gas in the charging tube 19 depending on the type, property, bulk specific gravity, moisture, etc. of the waste, and The filling height is such that drying, preheating, carbonization gasification, etc. of It is adjustable, and furthermore, it is possible to control the sky tower speed with less dust scattering.

Maintaining the lower end level of the charging tube 19 at a temperature of approximately 700 to 1000°C above the high-temperature hearth 12 stabilizes the descent of the waste and reduces the charging pressure of the surrounding lumpy carbon-based combustible material. can suppress aggressive descent.

Therefore, by varying the charging tube up and down to achieve the above-mentioned temperature conditions in accordance with the operating conditions, it is possible to form an optimal heat pattern in the furnace with a reduced fuel ratio.

Furthermore, by moving the charging tube 19 up and down, the amount of descending peripheral coke can be controlled, which has the effect of accelerating the descent of central waste, and is effective in increasing the throughput and reducing the fuel ratio. Occasionally, when there are signs that the furnace condition is deteriorating, it has the advantage of being able to be moved up and down at a higher level and used as a means of forcibly supplying surrounding coke to the lower part of the furnace.

FIG. 3 shows a third embodiment of yet another aspect. This has four coke charging ports 18 and four exhaust gas pipes 1.
This is an embodiment in which the arrangement of 7 is reversed. This increases the degree of freedom in device layout.

〔Effect of the invention〕

As explained above, according to the present invention, the lumpy carbon-based combustible material is uniformly distributed within the furnace without creating any space, and no drift occurs. In addition, the combustion exhaust gas flows uniformly, ensuring a uniform high-temperature hearth of the lumpy carbon-based combustible material, and improving thermal efficiency.

Furthermore, since the pressure loss of the exhaust gas can be maintained constant, there is little variation in the amount of gas ejected from the tap, the oxygen-containing gas blowing pressure can be reduced to less than 1000 mm of water column, and the pressure fluctuation in the furnace is small, so the molten slag can be continuously You can get hot water stably. Therefore, since a lack of calorific value is not caused, a high temperature hearth can be uniformly maintained without increasing the fuel ratio, and effects such as stable operation can be achieved.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention, and FIG.
FIG. 2 is a drawing showing the second embodiment, and FIG. 3 is a drawing showing the third embodiment. A...waste, B...coke, C...limestone,
D... Blow air, E... Combustion exhaust gas, 1... Waste melting furnace, 2... Secondary combustion chamber, 3... Air preheater,
4... Gas cooler, 5... Dust collector, 6... Smoke cleaning device, 7... Induced blower, 8... Chimney, 9... Forced blower, 11... Shaft part, 12 ...High-temperature hearth, 13...Waste, coke, limestone filling area, 1
4... Coke filling area, 15... Hollow cone, 16
...Upper peripheral wall, 17...Exhaust gas pipe, 18...Coke charging port, 19...Charging tube, 20.21...Blow air blowing tuyere, 22...Tue outlet, 23... ...Drive device, 24...Expansion joint, 25.26...Exhaust gas flow rate control valve

Claims (1)

[Claims] A shaft section provided with a tuyere and a spout is connected to a hollow cone whose upper part is enlarged, and a region filled with a lumpy carbon-based combustible material is formed in the hollow cone, which is formed at the center of the shaft section. A charging tube for charging waste and lumpy carbon-based combustible material from above the high-temperature hearth is buried in the filling area, and a plurality of lumpy carbon-based combustible material charging ports are provided in the upper part of the hollow cone. 1. A waste melting furnace, characterized in that an exhaust gas pipe is connected thereto, and the inner surface of the upper part of the hollow cone is formed at an angle of repose at or greater than the angle of repose of a lumpy carbon-based combustible material.