JPS6161008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for incinerating sludge containing organic matter.

In recent years, progress has been made in the development of urban sewage systems and wastewater treatment.
As a result of this treatment, a huge amount of organic water-containing sludge is generated. In particular, recently constructed basin sewerage treatment plants are large in scale and generate a large amount of sludge.

In order to process such huge amounts of sludge in conventional incinerators such as multi-stage furnaces, fluidized bed furnaces, and rotary kilns, it is necessary to increase the scale of the equipment or to arrange many equipment in parallel. This not only makes operations such as operation and management complicated, but also
Huge capital investment is required.

Furthermore, when sludge is incinerated, the proportion of ash generated in the dried sludge is 20 to 50% (by weight).
Even if it is incinerated, the weight and volume are only about 1/5 to 1/2, and this incinerated ash becomes fly ash at the dumping site, causing problems. For this reason, recent efforts have been made to prevent the generation of fly ash by adding coagulants such as cement to the sludge incineration ash to solidify it, or by turning the incineration ash into lumps and melting them together with fuel such as coke in a shaft kiln. However, the running costs are quite high. Another method has been considered in which the ash is melted and solidified at the same time as incineration, but the temperature inside the furnace becomes high and the insulated chamber is formed using high-grade refractories, heat insulating materials, and heat insulating materials, making the furnace expensive.
Sludge incinerators are often started and stopped repeatedly, and there are many thermal fluctuations, and great care is required when managing high-grade refractories that are sensitive to these thermal shocks.

Furthermore, polymer flocculants have recently been increasingly used for dewatering water-containing sludge, but the ash content of this sludge has a high melting point. Some refractories can reach temperatures as high as 1,400°C, and currently there are few refractories that can withstand this high temperature and thermal fluctuations, and they are also expensive.

Furthermore, conventional incineration methods, such as fluidized fluidized furnaces, multi-stage furnaces, and rotary kilns, have been used to dry and incinerate water-containing materials such as sewage sludge in the same furnace. The calorific value is low, making high-temperature combustion impossible, and it has generally been thought that high-temperature, high-load combustion is impossible for sludge combustion.

The object of the present invention is to provide an effective sludge incineration treatment method that eliminates the various drawbacks of such conventional methods.

That is, in the present invention, after drying and pulverizing organic water-containing sludge into powder, this is injected into a combustion chamber space surrounded by a water-cooled pipe wall, and is combusted in a floating state in the combustion chamber space. The temperature of the combustion chamber space is set to be higher than the melting point of the ash of the sludge, and the ash is allowed to flow out of the combustion chamber while adhering to the wall surface of the water-cooled pipe in a molten state, and is cooled and solidified. This is a unique sludge incineration treatment method.

Generally, when the combustion chamber space is constructed of water-cooled pipe walls, the amount of heat released from the combustion chamber is large and the combustion temperature or ash melting temperature is not reached, resulting in misfires, an increase in unburned materials,
The ash may not melt and may slick.

However, the amount of heat released to the water-cooled tube at a certain combustion chamber temperature is affected by the gas composition, bright flame, amount of soot particles, gas flow rate, etc. Even if these conditions change, the amount of heat released will be infinitely large. Even if the amount of heat radiation increases within a certain range, if the load on the combustion chamber is large enough to accommodate this amount, the proportion of heat radiation from the water-cooled pipes will decrease, and the amount of heat radiation in the combustion chamber will decrease. reaches the combustion temperature or ash melting temperature. On the other hand, looking at the surface condition of the water-cooled pipe wall, since the pipe wall is initially water-cooled, the ash that melts in the combustion chamber space cools and solidifies on the pipe wall surface.
It gradually thickens. However, when the thickness increases to a certain level, the amount of heat transferred to the water-cooled pipe decreases, the surface temperature of the adhered solidified ash gradually rises, and the adhered solidified ash on the wall surface dissolves and the layer thickness reaches a certain equilibrium value. As mentioned above, the combustion chamber composed of water-cooled pipe walls also forms a kind of heat insulation chamber due to the adhesion of a certain amount of solidified ash, so there is no need to use expensive refractories and there is no need to worry about thermal spalling. This makes it possible to incinerate at high temperatures.

In the present invention, since the sludge that has gone through the drying and pulverizing steps is burned, the contact with the combustion air is extremely good.Furthermore, the heat transfer areas of radiation, convection, and conduction are significantly increased, so even a small amount of excess air can be used. Since safe combustion is possible, the amount of heat taken out of the exhaust gas can be limited to a small amount.

The present invention uses a high-temperature combustion method, which not only has the advantage of a sufficiently high heat transfer rate for the combustibles to reach the combustion temperature, but also injects the dried and pulverized combustibles into the combustion chamber. Since oxygen is supplied, collision between oxygen and the combustible material is good, and a strong turbulent state is created in the combustion chamber, resulting in extremely efficient combustion.

Conventional incineration methods have had the problem that the water in the sludge turns into water vapor and a large proportion of the amount of heat is taken out of the system.However, in the present invention, the drying process and incineration process are separated, so that the water vapor is The amount of heat taken out of the chamber is extremely small, making high-temperature combustion possible.

In the present invention, it is preferable that the drying step is performed such that the moisture content of the dried sludge is 5% or less (wet basis, the same applies hereinafter). In addition, in the grinding process, the dried sludge is made into a fine powder of 50 to 300 mesh, and the combustion chamber load is 50 to 500 Kcal/
It is desirable to adjust the amount of combustion air, etc. so that m ³ · h.

In addition, in the present invention, the exhaust gas of the combustion chamber is guided to the boiler, and this heat is recovered as steam, for example,
It is extremely rational because it can be used as a heat source necessary for drying and dehydrating water-containing sludge.

Next, an embodiment of the present invention will be explained with reference to the drawings. Sludge containing organic matter with a water content of 95% or more obtained in advance from a settling tank etc. is dehydrated using a vacuum filtration machine, a pressure dehydrator, a centrifugal separator, etc. It is made into a sludge cake with a moisture content of 60 to 80%. Next, the dehydrated cake is fed quantitatively to machine 1.
The water vapor 26 generated in the waste heat boiler 14 is used as a heat source to dry the sludge, but if the dehydrated cake has a high moisture content and the amount of heat generated from the sludge is insufficient, auxiliary fuel is supplied using the oil pump 29. to assist combustion. The dry solids obtained by drying the sludge to a moisture content of 5% or less are temporarily stored in a storage tank 3, cut out in a fixed amount by a quantitative feeder 4, pulverized by a pulverizer 5, and sent to a combustion burner 7 by an air conveyor 6. The fuel is supplied and injected into the combustion chamber 8 surrounded by a water-cooled pipe wall.

In the space within the combustion chamber 8, the finely powdered sludge is burned in a suspended state, and the ash in the sludge is melted.
The molten ash adheres to the surface of the water-cooled pipe wall of the combustion chamber 8, but the amount exceeding a certain thickness flows down and reaches the slag cooling tank 13 via the slag port 12, and the molten ash entrained in the combustion gas is Slag screen 9
The slag is collected, discharged from the slag port 12, and cooled and solidified in the slag cooling tank 13. On the other hand, the combustion gas from which the molten ash has been separated is cooled by dissipating heat in the radiation heat transfer section 10, then dissipates heat in the convection heat transfer section 11, and further in the air preheater 15, and is cooled to 200° C. to become waste gas.

The waste gas is induced by an induction fan 16 and sent to a desulfurization device 17, where the SOx content is removed, and then dust is removed by an electrostatic precipitator 19 and discharged into the atmosphere from a chimney 20.

On the other hand, the exhaust gas 31 from the dryer 2 is cooled by the gas cooler 21, and the dehumidified gas 27 is sent to the air preheater 15 by the induction fan 30, where it is heated and the combustion air 28- Used as 1. In addition, the steam 26 supplied from the waste heat boiler 14 supplies heat to the sludge in the dryer 2, and the condensed drain is discharged from the steam trap 23.
After being stored in the water supply tank 24, the water is circulated to the waste heat boiler 14 by the water supply pump 25.

A part of the preheated air 28 from the air preheater 15 is used as the sludge combustion air 28-1 as described above, but the remainder is used as the drying air 28-1.
2 is fed to the dryer. Moreover, the shortage of combustion air is replenished by suctioning air 32 from the atmosphere.

In the figure, both 18 and 22 are circulation pumps.

Next, an example carried out according to the above embodiment will be described. First, sludge containing organic matter with a solid content of 5% or less obtained from a sludge thickening tank was subjected to a dehydrator to form a sludge cake with a water content of 75%. This was supplied to the dryer 2 at a rate of 4,000 kg per hour using the quantitative feeder 1 to obtain 1,150 kg of dry solids with a water content of 5% or less, which was stored in the storage tank 3.

The dryer 2 is supplied with 7 kg/kg from the boiler 14.
It received 3900 kg of water vapor 26 cm ² G per hour and served as the heat source for the dryer.

The dried sludge passes through a quantitative feeder 4 attached to the lower part of the storage tank 3, is pulverized into 50 to 300 meshes by a pulverizer 5, and is transported from a combustion burner 7 to a combustion chamber 8 by an air conveyor 6 at a rate of 1000Nm ³ per hour. The air 28-1 heated to 400° C. by the air preheater 15 was blown at 3000 Nm ³ per hour as secondary air. The calorific value of the dry solid was 3000 Kcal/kg. The combustion chamber 8 is composed of a water-cooled pipe wall, and has a volume of 2.5 m ³ and a surface area of 11 m ²
It is. At the beginning of operation, the amount of heat dissipated from the water-cooled pipe wall was large and the temperature could not be raised to the melting point of the ash, so the oil pump 29 was operated to burn heavy oil to raise the temperature. The surface of the water-cooled pipe wall is gradually covered with molten ash, and its thickness is approximately 50 mm.
When the surface temperature of the molten ash layer reached 1400℃, the thickness of the molten ash layer reached equilibrium.

The melting temperature of the ash was 1380°C. Also,
The exhaust gas temperature in combustion chamber 8 was 1500°C. Combustion is completed in the combustion chamber 8, and the combustion gas accompanied by the molten ash collides with the slag screen 9 to separate the molten ash, and the collected molten ash falls from the slag port 12 into the slag cooling tank 13. It is rapidly cooled and crushed into a sand-like solid. On the other hand, the combustion gas is cooled to 1000° C. or less in the radiation heat transfer section 10, and the accompanying uncollected molten ash is solidified and flows into the convection heat transfer section 11 where it is further cooled.

After heat recovery is performed in this way, the combustion chamber exhaust gas reaches approximately 500°C at the outlet of the waste heat boiler 14, and then flows into the air preheater 15, where it exchanges heat with dehumidified gas 27 as secondary air for combustion. After the heat is further recovered and the combustion chamber exhaust gas is sufficiently cooled, it is sent to the desulfurization device 17 by an induction fan. The SOx content is absorbed and removed in the gas absorption tower of the desulfurization device 17, and the soot and dust is further removed in the electrostatic precipitator 19, and finally released to the atmosphere from the chimney.

On the other hand, exhaust gas 31 from the dryer 2 enters the gas cooler 21 at 100°C, is cooled by treated sewage water, is induced at 40°C by an induction fan 30, and enters the air preheater 15 as dehumidified gas 27. Further, the drain from the dryer 2 is separated from water vapor 26 by a steam trap 23, temporarily stored in a water supply tank 24, and then supplied to the waste heat boiler 14 by a water supply pump 25. Water tank 24
The temperature of the water supply inside was approximately 80℃. As described above, in the treatment of organic water-containing sludge, the present invention pulverizes the sludge into powder after drying the sludge,
By injecting this into the combustion chamber space and burning it in a suspended state in the space, it improves contact with oxygen in the combustion air, increases the heat transfer area of radiation and convection, and also reduces the amount of excess heat. Since complete combustion is possible in air, the amount of exhaust gas is reduced, the heat recovery efficiency of the waste heat recovery device is increased, and auxiliary fuel can be saved, and the required capacity of the combustion exhaust gas treatment device is reduced. can be small, and
Combustion is performed while maintaining the temperature of the space above the melting point of the sludge ash, and the combustion chamber is constructed with a water-cooled pipe wall, thereby making it possible to melt the sludge ash with a high melting point without using high-grade refractories. ,
This sludge incineration treatment method has many advantages, such as the ability to incinerate large quantities by operating the combustion chamber under high load.

[Brief explanation of the drawing]

The drawings are system explanatory diagrams showing embodiments of the present invention. 1...Quantitative feeder, 2...Dryer, 3...Storage tank, 4...Quantitative feeder, 5...Pulverizer, 6...
Air conveyor, 7... Combustion burner, 8... Combustion chamber, 9... Slag screen, 10... Radiation heat transfer section, 11... Convection heat transfer section, 12... Slacksport, 13... Slag cooling tank , 14... Waste heat boiler, 15... Air preheater, 16... Induction fan,
17... Desulfurization equipment, 18... Circulation pump, 19...
...Electric dust collector, 20...Chimney, 21...Gas cooler, 22...Circulation pump, 23...Steam trap, 24...Water tank, 25...Water pump, 2
6... water vapor, 27... dehumidified gas, 28... preheated air, 29... oil pump, 30... induction fan, 31... exhaust gas, 32... air.

Claims (1)

[Claims] 1. After drying and pulverizing organic water-containing sludge into powder, this is injected into a combustion chamber space surrounded by water-cooled pipe walls, and is suspended in the combustion chamber space. combust the sludge so that the temperature of the combustion chamber space is higher than the melting point of the ash of the sludge, cause the ash to flow out of the combustion chamber while adhering to the wall surface of the water-cooled pipe in a molten state, and cool and solidify the ash. A sludge incineration treatment method characterized by: 2. The sludge incineration treatment method according to claim 1, wherein the drying step is to dry the sludge to a moisture content of 5% or less (based on wet amount). 3. The sludge incineration treatment method according to claim 2, wherein the drying step is performed using steam from a waste heat boiler attached to the combustion chamber as a heat source. 4 The pulverizing process reduces the sludge after the drying process to 50%
The sludge incineration treatment method according to claim 1, 2 or 3, wherein the sludge is pulverized into a fine powder of ~300 mesh. 5 The combustion process reduces the combustion chamber load to 50~
Claims 1, 2, ³ , or 4, which are carried out at a temperature of 500 kcal/m 3 h
Sludge incineration treatment method described in section.