JP2013224810A5 - - Google Patents

Description

Sewage sludge treatment equipment

  The present invention relates to a treatment apparatus for drying and incinerating sewage sludge.

Sewage sludge produced in large quantities in treating sewage is generally incinerated after dewatered sludge. The water content of the dehydrated sludge not only is expensive and large amounts require fossil fuels such as heavy oil is about 80-85%, preferably in terms of global warming wards.

Under such circumstances, the inventors used a dryer to dry the dehydrated sludge to a self-combustible water content and then incinerated it with biomass fuel, which is an auxiliary fuel. Has been developed, and a compact and economical processing apparatus has been developed that supplies the generated steam to a dryer and uses it to dry dewatered sludge (Patent Document 3).
This processing apparatus uses a dryer that attaches sludge to two heating drums heated with steam and dries. For the biomass boiler, it includes a screw conveyor that sequentially transfers the dried sludge to the combustion section. Yes. The boiler is provided with a concentric cylindrical inner wall at the upper part of the vertical cylindrical furnace body, and also serves as air cooling of the outer wall that spirally swirls from the upper part of the furnace body to the space between the furnace body and the inner wall. Combustion air is sent in, the dried sludge at the upper end of the screw conveyor is burned, and the combustion gas is introduced into a heat exchanger provided immediately above the furnace body.

JP-B 61-061009 Shoko 61-057964 W02010 / 150523

As in the present case, in order to continuously operate the steam using a method for drying dehydrated sludge, it is necessary to dry the sludge to a low water content. At that time, the energy necessary for drying cannot be obtained even using only the self-combustion heat of the sludge. In addition to the self-combustion heat of sludge, it is necessary to obtain steam using auxiliary fuel.
The processing methods in Patent Document 1 and Patent Document 2 require fossil fuels, and the same auxiliary fuel is used as the incinerated ash by drying and incinerating dehydrated sludge directly in the furnace in a large oil-fired or gas-fired incinerator. It is a fossil fuel. Since the energy of the auxiliary fuel is used for steam generation and drying the dewatered sludge with the energy of the steam, a larger amount of fuel is required than the general method of drying and incineration directly in the furnace. A large amount of fossil fuel is required compared to a burning incinerator.

It can be said that the system of patent document 3 is a compact processing apparatus and an economical processing method which can incinerate sewage sludge continuously using only biomass fuel as an auxiliary fuel.
However, the system of Patent Document 3 employs a method of pelletizing fuel as a continuous supply method for maintaining a good combustion state when supplying dried sludge to a combustion section with a screw conveyor. Therefore, a pelletizer called pelletizer must be installed. Moreover, since the amount of steam required in the dryer is insufficient with the energy obtained from only sludge, it is necessary to mix biomass-based fuel with dry sludge as auxiliary fuel when pelletizing. Therefore, a mixing apparatus for mixing them is also necessary. In addition, there are quite a few things that fall into the ash reservoir in an unburned state, and because the surface of the heat exchanger is easily contaminated by combustion gas, the combustion efficiency is reduced and the heat generation steam generation amount is lower than expected. There is also the problem of tending.

Therefore, the present invention provides a sewage sludge treatment apparatus that has good thermal efficiency, is compact, and is economical, in which complete combustion is performed so that a sufficient amount of steam is obtained, and a pellet production machine and auxiliary fuel mixing device are not required The purpose is to do.

The sewage sludge treatment apparatus of the present invention employs the following means in order to achieve the above object. That is, dehydrated sludge is dried in a dryer and self-combusted as a moisture content of dried sludge, incinerated with a biomass boiler, and in the sewage sludge treatment apparatus using the obtained steam as the heat source of the dryer, the biomass boiler is The furnace body having a vertical cylindrical outer wall is provided with a cylindrical inner wall concentric with the outer wall, and a combustion air supply port is swirled around the outer periphery of the inner wall spirally from above. And a supply means for feeding the dried sludge into the furnace at the upper part of the outer wall, and a screw conveyor for sequentially transferring the biomass fuel to the position directly above the inner wall. A screw-shaped grate that is gradually lowered and inclined toward the outer wall, and is also supplied from the inside of the biomass fuel in the combustion section. The rotating shaft is hollow, and a hollow stirring blade is fixed to the upper end of the rotating shaft. A large number of injection holes are provided in the upper end of the rotating shaft and the stirring blade, and the biomass fuel is burned at the upper end of the screw conveyor. In addition, the dried sludge is sent to the upper part of the furnace and burned in a floating state, and the combustion gas is introduced into the heat exchanger provided directly above the furnace body by raising the central part of the inner wall. It is said.

The dewatered sludge is a water content of 80 to 85% with a dewatering machine at a sewage treatment facility.
  The dryer uses two heating drums that rotate inward to each other in parallel, and that sewage sludge adheres to the heating drum in a sheet form and is dried, and scraped off with a scraper. Steam obtained from a biomass boiler is used as the heat source of the heating drum.

The biomass boiler is a hollow ring that is provided with a screw conveyor that sequentially transfers biomass fuel to the upper center of the furnace body having a vertical cylindrical outer wall, and that gradually descends and slopes outward at the upper end of the casing of the screw conveyor. The grate is fixed away from the outer wall. A cylindrical inner wall concentric with the outer wall is provided at the upper portion, and combustion air is swung around the outer periphery of the inner wall from above, and the rotating shaft of the screw conveyor is made hollow, and a hollow shape is formed at the upper end thereof. Stirring blades are fixed and combustion air is supplied.
  The dried sludge is supplied on swirling combustion air or supplied to the inside of the inner wall using a blower.
And the biomass fuel transferred with the screw conveyor is burned, and dry sludge is burned in a substantially floating state by this thermal power.

In the biomass fuel combustion section, a ring-shaped grate that gradually slopes downward toward the outside is fixed to the upper end of the casing of the screw conveyor, apart from the outer wall, and almost completely burned on the grate.
Combustion air is blown from the bottom of the dried sludge with the screw conveyor shaft hollow, and a large number of air holes through which combustion air blows out are provided at the upper end of the screw conveyor to supply as much combustion air as possible. Moreover, in order to prevent a clinker, the hollow stirring blade which blows off combustion air to the upper end part of the rotating shaft of a screw conveyor is fixed.

Combustion gas from incineration of dried sludge and biomass fuel flows from the center of the inner wall into the heat exchanger provided directly above, and generates steam that serves as a heat source for the dryer. In addition, as described in claim 3, the heat exchanger has a fence-like structure in which vertical cylindrical water tubes are arranged in two rows on a concentric circle and surrounded by two concentric circles, and the upper part is arranged on the outer periphery. The water pipe group on the inner circumference and the water pipe group on the inner circumference are each provided with a separate pipe, and the lower pipe is constructed so that the outer water pipe group and the inner water pipe group communicate with each other. It is desirable to allow a cleaning tool to be inserted between them.

Combustion gas that has passed through the heat exchanger is processed by the exhaust gas treatment device and discharged to the outside air. As described in claim 2, a part of the combustion gas sent to the exhaust gas treatment device is returned to the combustion section in the furnace. Is desirable.

As described above, the sewage sludge treatment apparatus of the present invention is a drying sludge with a dryer that attaches the dewatered sludge to the surface of the heating drum, and has a cylindrical inner wall at the top of the vertical cylindrical furnace body, A screw conveyor is provided below the inner wall, and the biomass fuel is sequentially transferred directly above and burned completely in the grate at the upper end. The dried sludge is supplied with combustion air and incinerated in a floating state, and the combustion gas is directly above the furnace body. Since the central part of the inner wall is raised and introduced into the heat exchanger installed in the plant, combustion efficiency is good, and a conventional pelletizing device and a device for mixing biomass fuel and dry sludge are required. Instead, a predetermined amount of sewage sludge can be treated continuously with a compact device. In addition, since the dried sludge is incinerated at a high temperature, generation of harmful substances such as dioxins can be prevented, and ash shells and incombustibles do not accumulate in the combustion section, and therefore clinker is not formed. Furthermore, since no fossil fuel is used, there is an effect that it is environmentally friendly.

Further, if a part of the combustion gas that has passed through the heat exchanger is circulated to the combustion section (claim 2), the emission amount of nitrogen oxides can be reduced and the thermal efficiency can be increased.

In addition, as described in claim 3, the heat exchanger has a fence-like structure in which vertical cylindrical water tubes are arranged in two rows on concentric circles and surrounded by two concentric circles, and the upper part is arranged on the outer periphery. The water pipe group and the water pipe group arranged on the inner circumference are each provided with a separate nozzle, and the lower pipe is attached to the surface of the water pipe if the outer water pipe group is connected to the inner water pipe group. Incineration ash removal and cleaning can be done easily. In addition, this technique is applicable also to the biomass boiler of the sewage sludge processing apparatus conventionally (for example, patent document 3).

It is a whole lineblock diagram showing an embodiment of a processing device of sewage sludge of the present invention. It is sectional drawing and sectional perspective view which show the Example of the combustion part of a biomass boiler. It is sectional drawing and AA view which show another Example similarly. It is sectional drawing which shows the Example of the supply apparatus of biomass fuel same as the above. It is sectional drawing which shows another Example of the supply apparatus of biomass fuel same as the above. It is sectional drawing which shows the combustion part of the biomass boiler which supplied dry sludge with combustion air. It is sectional drawing of the combustion part which shows another Example same as the above. It is sectional drawing and the top view which show the Example of the heat exchanger of a biomass boiler.

An embodiment of a sewage sludge treatment apparatus of the present invention will be described with reference to the drawings.
  FIG. 1 is an overall system diagram showing an embodiment of a sewage sludge treatment apparatus of the present invention. This device is connected to the dewatering device of the sewage treatment facility, and dries the dewatered sludge into an almost powdery dry sludge, and incinerates the dry sludge with the incineration heat of the biomass fuel. A biomass boiler including a heat exchanger that generates steam with combustion gas is used as a core.

As shown in FIG. 1, the dryer supplies dehydrated sludge to the center of the two heated drums rotating from the top, adheres to the surface of the heated drum as a thin sheet, and dries it with a scraper. It is what you take. And the piping for supplying dehydrated sludge to the upper part, and the piping for taking out the vapor | steam with the odor which generate | occur | produced at the time of drying to a deodorizing apparatus are provided.
This heating drum is provided with piping for taking in steam from the heat exchanger of the biomass boiler.
The dried sludge dried by the dryer is transferred from below the dryer and sent to the biomass boiler via the meter.

As shown in FIG. 7, the biomass boiler has a vertical cylindrical outer wall fixed on a gantry, a screw conveyor is provided vertically in the center of the lower part, and a cylindrical shape concentric with the outer wall is provided above it. There is an inner wall.
As shown in FIG. 2 in an enlarged manner, the screw conveyor has a rotating shaft in which screw blades are fixed in a spiral shape in a casing, and the rotating shaft is connected to driving means installed outside the gantry. . And three stirring blades are horizontally installed near the upper end of the rotating shaft. This stirring blade is hollow and has a large number of air holes on its upper surface.

As shown in FIG. 3, the screw conveyor has a small diameter blade blade on the upper end side of the screw conveyor and has a cross section in its outer peripheral portion so as to form a conical shape in the combustion portion of the biomass fuel transferred immediately above. An eight-shaped hollow circumferential guide member is provided and connected to a hollow ring-shaped hollow member for supplying combustion air provided on an outer wall of a cylindrical casing that houses a screw conveyor. The internal combustion air can be supplied.

A hollow ring-shaped grate is fixed on the upper circumference of the casing cylinder of the screw conveyor. The grate has an upper surface that is inclined downward toward the outside, can supply combustion air therein, and is provided with a large number of air holes.
In addition, an inclined fuel supply hopper penetrating the outer wall is fixed to the lower part of the side of the casing of the screw conveyor to supply woody biomass fuel (wood chips), which is connected to the conveyor for transferring biomass fuel. Has been.

Here, as shown in FIG. 5, the fuel supply device is provided with two partition plates that are slid and opened and closed between a batch type quantitative hopper and a downwardly inclined shatter (fuel transfer unit) for transferring fuel. The quantified fuel is once stored in the space between the two partition plates and then dropped into the starter. As a result, fuel is supplied in a state where the space from the combustion section to the fuel storage section is always partitioned by any of the partition plates, so that backfire can be completely prevented. In addition, by installing one sensor on the stator and measuring the interval of the signal notifying that the fuel level has fallen below the height of the sensor installation part and a certain amount of fuel has been conveyed, The amount of fuel actually supplied per hour can be grasped. It can also be detected that a bridge is formed on the shuter.

In addition, as shown in FIG. 4, the biomass fuel supply apparatus may be provided with a screw conveyor for transferring in the lateral direction. Thereby, the instability of quantitative supply to the combustion section can be alleviated.

On the other hand, a dry sludge supply port is provided at the upper part of the outer wall, and a hopper for storing the dried sludge transferred from the dryer is provided in the vicinity thereof, and the dried sludge is placed in the furnace by the blower (inside the inner wall). (Refer to FIG. 7).

As shown in FIG. 5, the means for supplying the combustion air is provided with a supply port to the grate and a hollow ring-shaped supply port provided at the middle height position of the casing of the screw conveyor. .
The rotating shaft of the screw conveyor is hollow, and a stirring blade provided with a large number of air holes is fixed at the upper end thereof, and a supply port is provided at the lower part of the pedestal for sending combustion air to these. .
Moreover, the ash storage part with which the circumference | surroundings were closed is formed under the screw conveyor, and the taking-out port for taking out ash is provided.

A heat exchanger is disposed immediately above the combustion section.
As shown in FIG. 8, this heat exchanger has a fence-like structure in which two vertical cylindrical water tubes are arranged on concentric circles and surrounded by two concentric circles. And about the upper part, it has the structure where the water pipe group arranged in the outer periphery and the water pipe group arranged in the inner circumference each have a header separately, and each header performs the function of air-water separation separately. The lower header is a general header structure in which the outer water tube group and the inner water tube group communicate with each other. The water tube group arranged on the outer periphery and the water tube group arranged on the inner periphery are respectively a water tube and a water tube. Combustion gas flows into the space between the outer periphery and the inner periphery, and has an inlet on the inner periphery and an outlet on the outer periphery so that it is discharged through heat exchange. Yes.

Next, the operation of the biomass boiler configured as described above will be described.
  First, while driving a screw conveyor, a fan is operated and combustion air is supplied to the supply port of dry sludge and the supply port of combustion air.

The biomass fuel stored in the fuel supply hopper is transferred to the top by the screw conveyor one after another, and burns with combustion air from the top and combustion air from the inside of the biomass fuel at the upper end, and most of it becomes combustion gas It rises inside the wall and flows into the heat exchanger from the gas inlet.
What is still burning is burned completely by the biomass fuel and the stirring blades that are sequentially transferred from the bottom while moving outward along the inclination of the grate and becomes combustion gas and rises to the inside of the inner wall.

When the temperature of the combustion section rises to a predetermined temperature (for example, 800 ° C.) or more due to the combustion of the biomass fuel, the dried sludge stored in the supply hopper is fed into the furnace. Dry sludge is powdery or thin-skinned and burns almost in a floating state.
  In addition, 20% or more of incombustibles are contained in dry sludge, and some of them fall as combustion gas without rising, but they are incinerated on the grate and moved to the outer edge along the slope, and the ash storage part Fall to.

Combustion gas that has risen inside the inner wall 24 flows into the heat exchanger from the upper gas inlet, flows around the water pipe, and is sent from the exhaust port to the exhaust gas treatment device via the cyclone. Is returned to the furnace. Thereby, the nitrogen oxides of the exhaust gas generated in the combustion part can be reduced.

The steam generated in the heat exchanger is sent to the heating drum of the dryer. The steam used in the dryer is sent to a water storage tank where it is stored, and the reduced amount is supplemented and supplied to the heat exchanger.

The combustion gas flowing into the heat exchanger contains a considerable amount of incineration ash, which adheres to the surface of the water pipe and lowers the thermal efficiency. For this reason, although it is necessary to clean occasionally, in this embodiment, the upper end of the water pipe is separated from the outer periphery and the inner peripheral header, and a cleaning tool can be inserted between them, so cleaning with liquid is easy it can.

That is, when cleaning the water pipe, a liquid leakage prevention fitting is attached to the combustion gas inlet / outlet, the liquid is stored in the space, and a cleaning tool is inserted. It is to be noted that an operation for removing the liquid stored in the space from the lower portion of the space by installing a lower header through the lower portion of the space formed so as to be inclined downward toward the discharge port is more work. Convenient.

Claims (3)

In the sewage sludge treatment apparatus, the dehydrated sludge is dried by a dryer and incinerated with a biomass boiler as a moisture sludge capable of self-combustion, and the obtained steam is used as a heat source for the dryer. A cylindrical inner wall concentric with the outer wall is provided at the top of the furnace body having a cylindrical outer wall, and a combustion air supply port is provided on the outer wall so as to swirl around the outer periphery of the inner wall from above. In addition, a supply means for feeding the dried sludge into the furnace is provided at the upper part of the outer wall, and a screw conveyor is provided below the inner wall for sequentially transferring the wood-based biomass fuel directly above. A ring-shaped grate that gradually descends toward the bottom is fixed and separated from the outer wall, and the rotation of the screw conveyor is used to supply combustion air also from the inside of the biomass fuel in the combustion section. The shaft is hollow and a hollow stirring blade is fixed to the upper end of the shaft. A large number of injection holes are provided in the upper end of the rotating shaft and the stirring blade, and the biomass fuel is burned at the upper end of the screw conveyor. The dried sludge is sent to the upper part of the furnace and burned in a floating state, and the combustion gas is introduced into the heat exchanger provided directly above the furnace body by raising the central part of the inner wall. Sewage sludge treatment equipment. 2. The combustion apparatus according to claim 1, wherein a part of the combustion gas sent to the exhaust gas treatment apparatus through the heat exchanger is raised to the combustion part in the furnace by raising the central part of the inner wall. The sewage sludge treatment apparatus according to 1. A cylindrical inner wall concentric with the outer wall is provided at the top of the furnace body having a vertical cylindrical outer wall, and a screw conveyor for sequentially transferring the biomass fuel to the directly above the inner wall is provided directly above the furnace body. In the biomass boiler of the sewage sludge treatment apparatus equipped with a heat exchanger, the heat exchanger has a fence-like structure in which two rows of vertical cylindrical water tubes are arranged concentrically and surrounded by two concentric circles, For the upper part, the water pipe group arranged on the outer circumference and the water pipe group arranged on the inner circumference are provided with separate nozzles, respectively, and the lower pipe holder is structured so that the outer water pipe group and the inner water pipe group communicate with each other. A biomass boiler characterized in that a cleaning tool can be inserted between the inner and outer water tube groups.

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