JPS6056965B2 - Incineration method and equipment for sludge, etc. - Google Patents

Description

[Detailed description of the invention] The present invention provides organic sludge such as sewage sludge and industrial wastewater sludge,
The present invention relates to a method and apparatus for incinerating or similar materials thereof.

Conventionally, methods using multi-stage furnaces, rotary kilns, fluidized bed furnaces, etc. have been widely used to incinerate sewage sludge, etc.
In any of these methods, in order to completely incinerate the organic matter contained so that no unburned matter is included in the residue,
It is necessary to raise the combustion temperature, to increase the excess air ratio to introduce a considerably larger amount of air than the theoretical amount of air, or to use both in combination.

However, if such a method of increasing the combustion temperature and/or excess air ratio is adopted, the NOx concentration in the combustion exhaust gas will increase, and the chromium metal 6 contained in the incinerated material will increase.
The conversion rate of valent chromium is increased and soluble 6 is added to the combustion residue.
Problems arise such as chromium being mixed in and causing secondary pollution.

Therefore, as a method to improve these drawbacks of conventional incinerators, combustion is performed in a reducing atmosphere by reducing the excess air ratio in a multi-stage incinerator, thereby suppressing the production of hexavalent chromium, and Gas can be post-combusted for the purpose of deodorization, or solid supplements such as pulverized coal can be added as a reducing agent in a fluidized combustion furnace to suppress the generation of hexavalent chromium and NOx (Japanese Unexamined Patent Application Publication No. 1983-1982). -8
0674, Japanese Unexamined Patent Publication No. 50-120175) has been developed. In particular, if the conventional method described in JP-A-50-80674 is reproduced as far as it relates to the method of the present invention, a normal fluidized bed furnace has a particle bed height of 500 to 1000 m at the time of discharge! t
1. A fluidized bed with a temperature of 750 to 850°C is formed by supplying a small amount of excess air (1.1 to 1.3) (column 5, line 8 to column 7, 1 digit). 1), and the secondary air is supplied to the so-called Nj part N (shown in the specification) between the supply port and the upper surface of the fluidized bed at λ>1 (i.e., excess air ratio 1.0 or more). (Column 10, lines 3 to 8) shows a method for incinerating dehydrated cakes with high moisture content and poor combustibility. When sludge is incinerated using a normal method, most of the chromium metal contained in the sludge is oxidized and converted to soluble hexavalent chromium. The present inventors have carried out research and experiments on the incineration treatment of organic sludge and its analogues, with the aim of preventing the conversion to hexavalent chromium, and have obtained several new findings. Table 1 is one of the results of the experiment. Knowledge No. 1 is that it is possible to prevent the conversion of chromium metal in materials to be incinerated to hexavalent chromium by keeping the excess air ratio during combustion at a low level of 1.0 or less in the fluidized bed. The second method is to keep the fluidized bed in a reducing atmosphere by lowering the excess air ratio, and to reduce the amount of unburned organic matter that is burned in the upper part of the fluidized bed by keeping the amount of unburned organic matter as low as possible. By reducing the amount of incineration, good incineration treatment conditions can be maintained, and as a result, unburned matter in the residue can be almost completely treated in the fluidized bed. During the combustion process, a fluidized bed with sufficient overflow is required to ensure that the temperature is maintained at .
It was found that directly supplying the auxiliary fuel to an appropriate position at the bottom of the fluidized bed where the auxiliary fuel can diffuse properly avoids local heating and increases the effective efficiency of the fuel used.

(Table 1 shows the relationship between the excess air ratio and the amount of hexavalent monochromium produced when sludge is burned in a fluidized fluidized furnace. From this, there is a clear correlation between the two, and the excess air ratio (It is known that hexavalent chromium is hardly produced when the When a reducing substance such as carbon is present in the fuel, NOx is reduced and its generation and emission are suppressed.

Therefore, the method of suppressing the excess air ratio or adding a reducing substance in this way is effective in suppressing the production of hexavalent chromium and NOx. However, in both of the above-mentioned improved methods, the former method, which uses a multi-stage furnace to suppress the excess air ratio, has difficulty in reducing the amount of unburned matter in the combustion residue;
It is necessary to carry out after-combustion (of combustion gas generation exhaust gas),
At this time, there are problems such as the generation of NOx due to the high temperature atmosphere, and the latter method, in which solid reducing auxiliary fuel in a fluidized bed is added, requires complete combustion of this reducing auxiliary fuel. requires a high temperature reaction,
For this reason, there are problems such as an increase in the size of the heat recovery device from the exhaust gas and a need for a mixing device for the above-mentioned auxiliary fuel such as pulverized coal, which causes an increase in equipment costs.

Furthermore, a worrying problem when using a conventional fluidized fluidized furnace is that even if it is operated with a low excess air ratio, the production of hexavalent chromium and NOx is suppressed, as in the case of the multistage furnace described above. However, the combustion of organic matter in the materials to be incinerated becomes extremely incomplete. The present invention was made in order to improve the drawbacks of the conventional sludge incineration method and incineration equipment as described above, and its purpose is to eliminate hexavalent chromium, NOx, etc. by a low-cost and relatively simple method. In addition to suppressing the generation of such substances and reliably preventing the occurrence of secondary pollution,
It can almost completely decompose and burn the organic matter in the incinerated material,
The present invention provides a method for incinerating organic sludge, etc., and an apparatus for incinerating organic sludge, etc., which can almost eliminate unburned content in the generated residue, and the structure of the apparatus is relatively simple and can be manufactured at low cost.

That is, in the present invention, in order to achieve the above object, inorganic particles such as silica sand having a normal average particle size of 0.4 to 0.5 Tn are filled into the body of a fluidized fluidized incinerator as a heat medium, and these particles are used for combustion. Materials to be incinerated, such as organic sludge, are supplied to a fluidized bed formed by fluidization with air, and the materials to be incinerated and a heat medium are rapidly mixed and stirred in the fluidized bed to heat, dry, and burn. In a fluidized bed incinerator, the bed height during operation of the fluidized bed (normally 1 when stationary)
．． 5 times) for 1.5m, or more than 2.5m. A fluidized bed deeper than that of conventional furnaces is formed as described below, and an amount of air corresponding to 85 to 100% of the theoretical air amount required for actual combustion is supplied from the bottom of the fluidized bed, A method for incinerating sludge, etc., in which air corresponding to the remaining 20 to 35% is supplied as secondary air to the vicinity of the upper end of the fluidized bed. It is characterized in that the auxiliary fuel is directly supplied to the lower part up to approximately 113.

The device of the present invention has a bed height of 1.5 mm inside the fluidized bed during operation.
A fluidized incinerator body in which a fluidized bed is formed by inorganic heat transfer medium particles of TrL or more and 2.5TrL or less, a dispersion plate having an air blowing nozzle is disposed in the lower part, and an exhaust gas outlet is provided in the upper part. and the theoretical air amount of 85~1
00% of the air is supplied to the lower part of the fluidized bed through the distribution plate, and the theoretical air amount is 25 to 30%.
% of secondary air near the upper end of the fluidized bed, an incineration material supply mechanism that supplies incineration material such as organic sludge into the fluidized bed, and One embodiment of the invention is characterized in that it is equipped with a combustion residue overflow mechanism, and as one embodiment thereof, an auxiliary fuel is provided to the lower part of the fluidized bed up to approximately 113. It is characterized by being equipped with an auxiliary fuel supply mechanism. Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows an example of a fluidized incinerator. Reference numeral 1 denotes a substantially cylindrical fluidized incinerator body made of a heat insulating material and an exterior steel plate. At the bottom of the body 1, a dispersion plate 3 equipped with a number of air blowing nozzles 2 connects the opening at the lower end of the body 1. It is arranged so that it is closed.

An air supply main pipe (wind box) 4 is attached to the lower end surface of the main body 1, and high temperature air supplied from the air inlet 5 passes through the nozzle 2 and enters the main body 1 from below to above. The particles filled in the main body 1 usually have an average diameter of 0.4 to 0.5 wft.
Inorganic particles 6 such as silica sand are fluidized by the inflow of air, and the layer height is 1.5 to 1.5 with the inorganic particles 6 as heat transfer particles.
A fluidized bed 7 of 2.5 m is formed above the distribution plate 3. The lower limit of fluidized bed depth is 1.5m.
This is determined as a requirement to maintain a good diffusion area for the necessary auxiliary fuel to reduce unburned organic matter to an acceptable level, and its upper limit of 2.5 TrL is the lower limit for NOx generation, and this upper limit Settings greater than the value are unnecessary/necessary. Further, inside the main body 1, there is a solid separation section 8 above the fluidized bed 7 that reduces the flow velocity of the fluidized gas to separate inorganic solids, which are fluidized heat carriers, and combustion residues with large particle sizes. Here, solid particles with a relatively large particle size accompanying the generated combustion exhaust gas are separated, and the combustion exhaust gas from which the solid particles have been separated is discharged from the exhaust gas outlet 9 at the upper end opening of the main body 1. ing. Main body 1 above
On the lower side of the fluidized bed 7, there is a position (approximately 113) below the fluidized bed 7.
Auxiliary fuel supply pipe 1 that supplies auxiliary fuel F such as heavy oil to a position approximately 0.5 to 0.8 m above the distribution plate 3
As shown in FIG. The tip of a screw feeder (combustible material supply device) 11 that supplies the incineration material S is disposed, and the fluidized bed is located near the boundary between the fluidized bed 7 and the solid separation section 8 on the side of the main body 1. 7 Secondary air supply pipe 1 that supplies secondary air near the upper end
2 are arranged along the circumferential direction for a predetermined number of times. In the figure, 13 is a supply pipe for heat medium particles (inorganic particles) 6, 14 is a heat medium particle discharge pipe, and 15 is an overflow pipe for combustion residues communicating with the vicinity of the upper end of the fluidized bed. FIG. 2 shows a flow sheet of the entire combustion apparatus incorporating the incinerator configured as described above, in which one end is connected to the combustion air blower 16, and a heat exchanger 17 and a flow meter 18 are interposed. Conduit 19
The other end is connected to the wind box 4, and one end is connected to the conduit 19.
The branch pipe 22 is connected to a predetermined location between the heat exchanger 17 and the flow meter 18, and the other end of the branch pipe 22 is connected to the air supply pipe 12, and the control valve 20 and the flow meter 21 are interposed therein. By appropriately adjusting the control valve 20, an amount of primary air corresponding to 85 to 100% of the theoretical air amount is supplied to the lower part of the fluidized bed 7 through the blower 16, the conduit 19, and the inside of the wind box 4. At the same time, air is supplied from the conduit 19 through the branch pipe 22 and the air supply pipe 12 to the vicinity of the upper end of the fluidized bed 7 at a concentration of 35 to 25% of the theoretical air amount (as indicated in the above-mentioned primary air percentage display). A corresponding amount of secondary air is provided.

Further, the extraction port 9 at the upper end opening of the main body 1 communicates with the inside of the cyclone 24 via a conduit 23, and this cyclone 24 is connected to a multi-cyclone 26 via a conduit 25, and this multi-cyclone 26 is connected to a conduit. It is connected to the heat exchanger 17 via 27. And the above-mentioned extraction port 9
The combustion exhaust gas discharged from the cyclones 24,
After passing through the heat exchanger 17 and the conduit 28, the air is further purified by an electrostatic precipitator (not shown) if necessary, and then released into the atmosphere. At the same time, the fly ash separated by the cyclone 24 is returned to the main body 1 through the conduit 29, and the fly ash from the multi-cyclone 26 is discharged outside the system through the conduit 30. It's summery. Next, organic sludge such as sewage sludge, industrial wastewater sludge, etc.
A method for incinerating other items to be incinerated will be explained.

First, at the start of operation, inorganic heat-resistant heat transfer medium particles 6 such as silica sand having an average particle diameter of about 0.4 to 0.5 Tn are supplied from the heat transfer medium particle supply pipe 13 to the fluidized fluidized incinerator main body 1, and the blower 16 is turned on. When activated, heated air is blown through the air box 4 and the blowing nozzle 2 sequentially from the air blowing port 5 upward from the lower end of the main body 1, fluidizing the particles 6 and increasing the bed height to 1. A fluidized bed 7 of .5 to 2.5 m is formed.

Then, when the temperature of the particles 6 reaches the ignition temperature of the auxiliary fuel F such as heavy oil, the auxiliary fuel F is supplied from the auxiliary fuel supply pipe 10 and combusted, and the temperature of the fluidized bed 7 is set to a predetermined temperature, usually 600°C. The temperature is raised to ~850'C1, and then the material to be incinerated S is supplied from the material to be incinerated supply device 11. Then, the material to be incinerated S supplied into the fluidized bed 7 is immediately dried, and the organic matter contained therein is combusted. In this case, since the amount of oxygen consumed increases, secondary air is also supplied to the vicinity of the upper end of the fluidized bed 7 from the secondary air supply pipe 12. Next, the combustion exhaust gas generated by the incineration process of the materials to be incinerated is discharged outside the system through the gas outlet 9 as will be described later. The oxygen concentration in this exhaust gas is measured, and the By adjusting the amount of air to be fed so that the overall excess air ratio is 1.1 to 1.2, and further adjusting the control valve 20 as appropriate, the combustion air is pressurized by the combustion air blower 16, and heat exchange is performed. Of the inlet air heated in the container 17, the theoretical air amount is 85
Adjustment is made so that an amount of air corresponding to ~100% of the primary air passes through the flow meter 18 and further passes through the wind box male nozzle 2 to the lower part of the fluidized bed 7, and the remaining theoretical air After an amount of air corresponding to 25 to 35% of the amount passes through the control valve 20 as secondary air and is measured by the flow meter 21,
The secondary air is adjusted so that it is supplied to the vicinity of the upper end of the fluidized bed 7 through the interior of the secondary air supply pipe 12, and thereafter the operation is continued while maintaining the above state, and the material to be incinerated S is continuously processed.

In this way, the material to be incinerated S is incinerated, and the combustion exhaust gas generated at this time is extracted after separating the accompanying fluid heat medium 6 and the combustion residue, which have relatively large particle sizes, in the solid separation section 8. It flows from the outlet 9 through the conduit 23 into the cyclone 24, where it collects and separates ash with large particle size, and then enters the multi-cyclone 2 through the conduit 24, where it collects and separates finer ash. Then, the heat is recovered by a heat exchanger 17, and if necessary, after being purified by an electrostatic precipitator or the like, it is released into the atmosphere. On the other hand, combustion residue generated by incineration of the material to be incinerated S is discharged from the overflow pipe 15, and ash etc. collected by the cyclone 24 is discharged from the conduit 2.
9 and return to the inside of the main body 1, and the multi-cyclone 26
The collected ash is discharged outside the system. Next, the operation of the present invention will be explained.

In the incineration treatment of materials to be incinerated, such as sewage sludge handled in the present invention, which have a high moisture content, poor combustibility, and contain chromium metal with a high conversion rate to hexavalent chromium, 1.5
A deep fluidized bed 7 of ~2.5 TrL is formed, and an amount of primary air corresponding to 85 to 100% of the theoretical air amount is supplied to the lower part of this fluidized bed 7, and theoretical air is supplied near the upper end of the fluidized bed 7. 35-25% of the amount (L primary air%)
By supplying secondary air in an amount equivalent to Conversion to hexavalent chromium is suppressed, the minimum depth of the fluidized bed is sufficient, and an upward diffusion area for auxiliary fuel is secured, so incineration materials such as organic activated sludge can be reliably treated. Ru. Combustible exhaust gas generated by reducing the stoichiometric air ratio in the fluidized bed to 1.0 or less, unburned matter in the combustion residue in the fluidized bed, that is, unburned combustible organic matter contained in the solid-liquid at the top of the fluidized bed. In the separation section, secondary air is supplied to achieve almost complete combustion. In addition, the amount of NOx generated can be reduced, and even if chromium metal is contained in the incinerated material, it will not be converted to hexavalent chromium due to oxidation, and the generation of secondary pollution can be reliably prevented. . That is, if the fluidized bed 7 is formed shallowly as in the conventional method, there is a risk that the amount of NOx and hexavalent chromium produced increases as described above. The incineration process was not carried out properly, resulting in problems such as a considerable amount of unburned matter being included in the residue, and the fluidized bed was
w1. If the bed is formed considerably deeper than 2.5 TrL, the required air pressure will increase as the depth of the fluidized bed increases, resulting in a loss of effectiveness.
There is no need to raise the temperature any higher than this, and if almost all of the air is supplied from the bottom of the fluidized bed, problems such as an increase in the amount of hexavalent chromium produced may occur. On the other hand, if the amount of air supplied to the lower part of the fluidized bed is too small, a good fluidized bed will not be formed and the materials to be incinerated will not be properly processed. However, in the present invention, the layer height is 1
．． Since a moderately deep fluidized bed 7 of 5 to 2.5 m is formed, and 85 to 100% of the theoretical air amount is supplied from the bottom, the inside of the fluidized bed 7 is maintained in a reducing atmosphere, and hexavalent chromium is The generation of NOx can be reliably suppressed and the amount of NOx generated can be reduced, and the air pressure required to form the fluidized bed 7 is not unnecessarily high, so a stable fluidized bed can be formed with little loss of effectiveness. Therefore, the waste to be incinerated can be processed without any trouble, and the theoretical air amount of 25
Since ~35% of secondary air is supplied, the organic matter in the material to be incinerated and the generated exhaust gas are reliably combusted, and the inconvenience that a considerable amount of non-combustible matter remains in the combustion residue does not occur. Furthermore,
By directly supplying auxiliary fuel such as heavy oil to approximately 1'3 of the lower portion of the fluidized bed 7, the fluidized bed 7 can be reliably maintained at a predetermined temperature, and the materials to be incinerated can be treated satisfactorily.
Therefore, in the present invention, without adopting a method of reducing the excess air ratio as a whole, hexavalent chromium,
It is possible to suppress the generation of Mn, and there is no need to add reducing solid auxiliary fuel such as pulverized coal, and the incineration material can be treated by fluidizing only inorganic particles such as silica sand as heat carrier particles, and it is easy to operate. The incineration process can be carried out efficiently and easily, and the equipment does not need to be large or complicated, and it is also economical.

Next, Table 2 shows the results when sewage sludge was actually incinerated using the method described above.

The fluidized incinerator body used in this example had an inner diameter of 2 m and a height of approximately 87 TL. As shown in Table 2, the method of increasing the depth of the fluidized bed, supplying combustion air in two stages, and directly supplying auxiliary fuel to the bottom of the fluidized bed reduces NOx in the combustion exhaust gas. It is clear that it is extremely effective in reducing the amount of hexavalent chromium in the combustion residue to zero and further lowering the unburned content in the residue (ash).

In the above embodiment, the incineration material supply device 11 is connected to the fluidized bed 7, but it is not limited to this, and it can be arranged to communicate with the solid separation section 8.
In addition, when incinerating most sludge, auxiliary fuel is required for heat balance, but if there is no problem in heat balance due to the introduction of high-temperature air and the generation of thermal energy by combustion of the material to be incinerated, auxiliary fuel can be supplied. It is not necessary to do so.

However, when supplementary fuel is supplied, it is preferable to directly inject it into the fluidized bed 7 at a height of about 113 of the total lower bed height or lower than this as described above. Furthermore, in the above embodiment, the amount of air introduced into the lower and upper parts of the fluidized bed 7 was controlled by the control valve 20 installed through the branch pipe 22, but various conventionally known methods may be used in addition to this. Various modifications may be made to other configurations without departing from the gist of the present invention. As explained above, according to the present invention, it is possible to suppress the generation of hexavalent chromium, NOx, etc., and incinerate materials such as sewage sludge and industrial wastewater sludge in a low-pollution state. In addition to reliably preventing the occurrence of pollution, it is also possible to almost completely decompose and burn the organic matter in the incinerated materials, and almost eliminate unburned matter in the generated residue. In addition to being able to reliably, easily, and efficiently process incinerated materials, it is also economical, and has the advantage that the structure of the device is relatively simple and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an example of a fluidized incinerator according to the present invention, and FIG. 2 is a flow sheet diagram for processing materials to be incinerated using the same incinerator. 1... Fluidized incinerator body, 2... Air blowing nozzle, 3
... Dispersion plate, 4 ... Wind box, 6 ... Heat carrier particles, 7
...Fluidized bed, 9...Exhaust gas outlet, 10...Auxiliary fuel supply pipe, 11...Incineration material supply device, 12...
Secondary air supply pipe, 15... Combustion residue overflow pipe, 16...
・Blower, 20...control valve.

Claims (1)

[Scope of Claims] 1. Incineration of organic sludge, etc. using a fluidized bed method, in which incineration of organic sludge, etc. is incinerated in a fluidized bed formed by fluidizing inorganic heat transfer medium particles with gas. In the method, the height of the fluidized bed during operation is set to 1.5 m or more and 2.5 m or more.
m or less, and an amount of air equivalent to 85 to 100% of the theoretical air amount is supplied to the lower part of the fluidized bed to also serve as a fluidizing gas, and 25 to 100% of the theoretical air amount is supplied near the upper end of the fluidized bed. A method for incinerating organic sludge, etc., characterized in that the material to be incinerated, such as organic sludge, supplied into the fluidized bed is incinerated by supplying secondary air in an amount corresponding to ~35%. 2. The method for incinerating organic sludge, etc. according to claim 1, wherein auxiliary fuel is directly supplied to approximately the lower one-third of the fluidized bed. 3. During operation, a fluidized bed of inorganic media particles with a bed height of 1.5 m or more and 2.5 m or less is formed inside, and
A fluidized incinerator body is provided with a dispersion plate having an air blowing nozzle in the lower part and an exhaust gas outlet in the upper part, and an amount of air corresponding to 85 to 100% of the theoretical air amount is passed through the dispersion plate. and supplying the fluidized bed to the lower part of the fluidized bed through the
An air supply mechanism that supplies secondary air in an amount equivalent to 25 to 30% of the theoretical air amount near the upper end of the fluidized bed, and an incineration material that supplies incineration materials such as organic sludge into the fluidized bed. An incineration device for organic sludge, etc., characterized by comprising a material supply mechanism and a combustion residue overflow mechanism. 4. The incineration apparatus for organic sludge, etc. according to claim 3, comprising an auxiliary fuel supply mechanism that supplies auxiliary fuel to approximately the lower one-third of the fluidized bed.