JPS5924113A - Vertical multistage incinerator - Google Patents

Abstract

PURPOSE:To reduce the generation of bad smell and unburnt gas in case dehydrated sludge, having a high calorific value, is incinerated by a method wherein gas, discharged from a drying stage above a furnace, is cooled and dehumidified, thereafter, is re-circulated to a cooling stage below the furnace, while exhaust gas of a combustion stage effects heat exchange between combustion air, thereafter, is passed through a scrubber. CONSTITUTION:The exhaust gas, containing smelly constituents discharged from the multistage furnace 1, is introduced into a cooling and cleaning tower 32 through a duct 8, is cooled, dehumidified and cleaned here by contacting with original or treated water or the like sprayed from a spraying nozzle 30, thereafter, is returned to the cooling stage 17 of the multistage furnace through a pipeline 34 and the unburnt gas, containing the smelly constituents, is burnt perfectly in the combustion stage 16 above the cooling stage. The heat of the exhaust gas, extracted from the combustion stage 16, effects the heat exchange between the combustion air in a heater 42, thereafter, alkali washing of the gas is effected in the scrubber (or a mist cottrel) 44 and, then, the washed gas 48 is dissipated into atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vertical multistage incinerator, and more particularly to an incinerator for odorous sludge with a high calorific value using a polymer flocculant or the like.

BACKGROUND ART As one method for treating odoriferous sludge discharged from wastewater treatment equipment, sewage treatment equipment, etc., a method of incinerating the sludge in a vertical multi-stage furnace is known. Before incineration, sludge is usually added with a suitable flocculant and dehydrated in a dehydrator, reducing the water content to approximately 8.
After turning into 0% dehydrated sludge, it is fed to a vertical multi-stage furnace. As the above-mentioned flocculant, an inorganic flocculant such as ferric chloride or lime is used. sludge) is obtained. Vertical multi-stage incinerators can be said to be the most suitable incinerators for sludge.

In contrast, recently, for reasons such as reducing the volume of sludge and reducing processing costs, polymer compounds have come to be used as flocculants in place of lime and the like. The dehydrated sludge thus obtained (hereinafter referred to as polymer sludge) has a high solid content calorific value of 4,000 to 5,000 -/solid content) and a low water content of about 75%. When such sludge is incinerated in a multi-stage furnace, it is natural, and the auxiliary fuel that has been required in the past becomes unnecessary or requires only a small amount, which is very effective in terms of energy saving. However, compared to polymer sludge, conventional multistage furnaces (hereinafter referred to as conventional furnaces) incinerate lime sludge. However, it has been found that various inconveniences arise when applied.

FIG. 1 and FIG. 2 are diagrams showing combustion conditions in a conventional furnace when lime sludge and polymer sludge are incinerated, respectively. In the figure, dehydrated sludge 5 is introduced from the top of a furnace 1 through a supply hole 4, passes through a hearth 2 and two people installed on the furnace wall, and sequentially falls through the processes of drying, combustion, and cooling. The incinerated ash is discharged from the chute 6 at the bottom of the furnace. A rotating shaft 10 at the center of the furnace is rotationally driven by a motor 11. On the other hand, air 12 passes through the rotating shaft 10 and is preheated, then is introduced from the lower stage of the furnace as air 13 for sludge combustion, comes into countercurrent contact with the falling sludge, is used for cooling and combustion, and then is combusted. It is discharged from the furnace top exhaust gas duct 8 in the form of exhaust gas. In addition, in the figure, 3 is a stirring blade provided on the rotating shaft 10, and 14 is a hot air generating furnace.

In the case of lime sludge shown in Figure 1, the dehydrated sludge and sludge combustion exhaust gas come into contact with each other in the drying stage at the upper part of the furnace (this is the stage where the drying section 15 is located), and efficient drying is carried out, resulting in moderate drying. The sludge falls into a combustion stage (a stage in the combustion section 16), and combustible volatiles in the sludge are combusted with flame 19. In this case, the combustible volatiles are almost completely combusted in the combustion section 16, mix with the sludge combustion exhaust gas without remaining soot, and rise through the drying section, and after drying the dehydrated sludge, become the furnace top exhaust gas 9. It is discharged from the furnace top exhaust gas duct 8 at the top. In this manner, when incinerating lime sludge, the boundary between the drying section 15 where water in the sludge is evaporated and the combustion section 16 where combustible volatile matter is burned is clear, and the exhaust gas is also clean. In addition, from the viewpoint of operability of the furnace, the position of the combustion stage, which is a key point of operability, can be easily fixed by adjusting the amount of auxiliary fuel used in the hot air generating furnace 14. The technology of incinerating lime sludge can be said to be a perfected technology in terms of exhaust gas properties and furnace operability.

On the other hand, in the case of the polymer sludge shown in FIG. 2, since the polymer sludge has a low water content and a large calorific value, it can be self-combusted without requiring auxiliary combustion oil or the like.

Also, compared to the situation when incinerating lime sludge, the number of drying stages is higher! Since the amount of combustible volatile matter in the sludge is large, the flame generated from the combustion section 16 becomes longer and reaches the drying section 15. In such a situation, the flame 19 is cooled by the sludge in the middle of drying, and a large amount of combustible volatile matter remains in the exhaust gas along with unburned matter. Furthermore, the sludge in the drying stage is also heated by the sludge combustion flame, and if localized excessive drying occurs, not only moisture evaporates, but flammable volatile matter is generated, which can ignite instantaneously. Even. The combustible volatile matter generated in the drying stage is sufficiently burnt -1, -1, passes through the drying stage as unburned matter, and is included in the furnace top exhaust gas 8. Further, such combustible volatile matter also contains the right-most component, and there is a problem in that this waste furnace top exhaust gas 8 generates a bad odor. Therefore, when treating organic sludge treated with a polymer flocculant, there is a disadvantage that a deodorizing device or the like must be installed in addition to an incinerator.

An object of the present invention is to provide a vertical multistage furnace that generates less bad odor and unburned matter when incinerating dehydrated sludge containing a polymer flocculant and the like and having a high calorific value.

The vertical multistage furnace of the present invention is divided into a drying stage section, a combustion stage section, and a cooling stage section from the top, and combustion air is distributed from the bottom to the top, while the materials to be combusted are passed from the top drying stage to the bottom stage. In a device equipped with an incinerator for sludge containing polymeric substances, which is supplied to , a gas processing system that cools and dehumidifies the gas discharged from the drying stage in the upper part of the furnace in an external cooling cleaning tower, and then recirculates it to the cooling stage in the lower part of the furnace; It is characterized by being equipped with a gas exhaust system that exchanges heat with combustion air and then discharges it to the atmosphere through a scrubber.

In the present invention, it is preferable that the combustion space has a volume such that the load rate is 250,000/hr/combustion unit or less, and the space has a volume for extracting part of the combustion exhaust gas. Preferably, a duct is provided.

Further, a baffle plate for promoting combustion may be provided in the space, and a communication hole may be provided in the center of the baffle plate to guide the sludge to the tapered portion so that the sludge falls smoothly.

Furthermore, in the present invention, a means for blowing oxygen-containing gas can be provided in the fore-fertilization combustion space. a plurality of gas blowing tubes inserted radially along the circumference of the furnace wall, and a gas blowing tube protruding radially along the circumference of the rotating shaft inside the furnace. An example is one in which a plurality of stages are arranged in the vertical direction and gas is ejected from a small hole in the gas blowing pipe into the space between the combustion chambers.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. Fourth
The figure is a system diagram showing an embodiment of the incinerator of the present invention. This device includes a vertical multistage incinerator 1 having a drying stage section 15, a combustion stage section 16, and a cooling stage section 1'1, an exhaust gas duct 8 provided in the drying stage section 15 of the incinerator 1, and an exhaust gas duct 8 provided in the drying stage section 15 of the incinerator 1. A cooling cleaning tower 32 in which gas is introduced and comes into gas-liquid contact with the cleaning water sprayed from the water spray nozzle 3o, and a tank for recirculating the gas cleaned in the cooling cleaning tower 32 to the cooling stage section 17 of the multistage furnace 1. A pipe 34 equipped with a proar 36', a pipe 38 for extracting exhaust gas from the combustion stage section 16 of the multistage furnace 1, and an air heater 42 for exchanging heat between the exhaust gas in the pipe 38 and the combustion air 40; It is comprised of a scrubber 44- for cleaning the exhaust gas exiting the heater 4.2, and a blower 46 for the exhaust gas.

In the apparatus configured as described above, the exhaust gas containing odorous components leaving the multi-stage furnace 1 is introduced into the cooling cleaning tower 32 from the duct 8,
Here, the raw water sprayed from the water nozzle 30 comes into contact with treated water, etc., is cooled and dehumidified, and is then returned to the cooling stage section 1'7 of the multi-stage furnace through the pipe 34, where it is returned to the cooling stage section 1'7 of the multi-stage furnace. The fuel is completely combusted in the combustion stage section 16 of the soil section. The exhaust gas extracted from the combustion stage unit 6 undergoes heat exchange with the combustion air in the heater 42, and is then cleaned with alkali in the scrubber (or mist cotterel) 44. After 4 days, the cleaning gas is released into the atmosphere. Dissipated.

As shown in the above embodiment, according to the present invention, by dehumidifying the furnace top exhaust gas in the drying stage and returning it to the furnace, unburned gas containing odor components is completely combusted in the combustion stage. , it is possible to eliminate the bad odor in the combustion gas discharged from here.

This eliminates the need for deodorizing equipment, which was conventionally installed separately outside the incinerator, and also provides benefits such as dehumidifying the exhaust gas at the top of the incinerator and reducing the heat load on the multi-stage incinerator.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing lime sludge rising and polymer sludge being combusted using a conventional vertical multi-stage furnace, respectively, and Figure 3 is a cross-sectional view of the vertical multi-stage furnace used in the present invention. The sectional view, FIG. 4, is a system diagram of a vertical multistage incinerator showing one embodiment of the present invention. The explanation of the symbols is as follows. 1...Furnace, 8...Furnace top exhaust gas duct,
15... Drying stage section, 16... Combustion stage section, 17... Cooling stage section, 32... Cooling washing tower, 42...・Gas heater, 4.4...
・Scrubber, 48...Clean gas. Agent Patent Attorney Takenaga Kawakita

Claims (1)

[Claims] (1) In a device that is divided from above into a drying stage section, a combustion stage section, and a cooling stage section, and in which combustion air can be circulated from below to above, flammable substances generated from sludge are found on the hearth of the combustion stage section in the furnace. The gas discharged from the drying stage in the upper part of the furnace is cooled and dehumidified in a cooling washing tower installed outside, and then recirculated to the cooling stage in the lower part of the furnace. A vertical multi-stage incinerator characterized by comprising: a gas processing system for exchanging heat with combustion air for the exhaust gas of the combustion stage section, and a gas exhaust system for discharging the exhaust gas to the atmosphere through a scrubber.