JPH07323299A - Sludge recycling method - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a method for neutralizing highly alkaline sludge to render it harmless and to recycle it. [Structure] A sludge recycling method includes a step 1 of converting the sludge into a slurry, and a step 2 of blowing a carbon dioxide-containing gas into the sludge slurry and reacting the carbon dioxide with lime in the sludge to convert to calcium carbonate. Step 3 of dehydrating the sludge slurry in which the contained lime is calcium carbonate and 200 times of the dehydrated sludge
It comprises a step 4 of obtaining a resource-recycling product by drying or baking at a temperature of ℃ or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detoxifying construction sludge and sewage sludge resulting from civil engineering works such as pile driving work and sewage shield excavation method, and reusing them as soil and roadbed materials.

[0002]

2. Description of the Related Art Construction sludge and sewage sludge resulting from civil engineering work are charged with slaked lime, cement, etc. for the purpose of improving dewatering property and handling property. Since it contains lime with a high concentration of about 30%, it is highly alkaline, and when rainwater invades, alkaline water flows out, which causes groundwater pollution. Therefore, the sludge as it is is harmful to the natural environment, especially to the growth of plants, and is not suitable as a backfilling soil or a construction material such as a roadbed material. Therefore, conventionally, such sludge has been dehydrated to some extent and then landfilled as industrial waste.

[0003]

However, the above sludge is generated in Japan more than 17 million tons per year,
Moreover, since the amount of waste generated is increasing year by year, securing landfill is a major issue. Also, pollution problems sometimes occur due to illegal dumping.

An object of the present invention is to solve the above problems and to provide a method for neutralizing highly alkaline sludge to render it harmless and to recycle it.

[0005]

A first method for recycling sludge as a resource according to the present invention is a step of slurrying lime-containing sludge, and blowing carbon dioxide gas or carbon dioxide-containing gas into the sludge slurry to convert carbon dioxide gas to sludge. A step of reacting with the lime in it to convert it into calcium carbonate, a step of dehydrating the sludge slurry in which the contained lime is calcium carbonate, and a step of dehydrating sludge
It is characterized by comprising a step of obtaining a recyclable product by drying or baking at a temperature of 00 ° C or higher.

In the first method for recycling sludge, the concentration of solids in the sludge slurry is preferably 20% or less. The reason is that the concentration of solids in the sludge slurry is 2
When it exceeds 0%, the reaction between carbon dioxide gas and carbon dioxide contained in the carbon dioxide gas or carbon dioxide gas-containing gas in the subsequent step cannot be kept good, and at the same time, carbon dioxide gas or carbon dioxide gas-containing gas is not mixed in the slurry. This is because the dispersion may not be uniform. Further, in the first method, the drying or firing temperature of the dehydrated sludge is limited to 200 ° C. or higher in order to increase the thermal efficiency and to secure the strength as a resource product, for example, a sand sand substitute.

A second sludge recycling method according to the present invention comprises a step of slurrying lime-containing sludge, and blowing carbon dioxide gas or carbon dioxide-containing gas into the sludge slurry to cause the carbon dioxide gas to react with lime in the sludge. To convert calcium carbonate to calcium carbonate, a step of dehydrating the sludge slurry in which the contained lime is calcium carbonate, and a water content ratio of the dehydrated sludge of 15 to 4
It is characterized by comprising a step of drying to 5%, a step of granulating the dried sludge to an appropriate particle size, and a step of drying or firing the granular sludge at a temperature of 200 ° C. or higher to obtain a recycled product. To do.

In the second method for recycling sludge, it is preferable that the concentration of solids in the sludge slurry is 20% or less. The reason is the same as in the case of the first method. In the second method, the water content of the dried sludge is limited to 15 to 45% because it is less than 15% or 4%.
This is because if it exceeds 5%, the granulation in the next step will not be successful. Here, the water content ratio is (water content / solid content) × 100.
(%) Value, which varies depending on the particle size distribution of sludge, the content of organic substances, the crystalline state of the composition compounds, and the like. Also, sludge has a water content ratio peculiar to sludge that can be treated as a solid, but this is called a plastic water content ratio, which is generally in the range of 15 to 45%. In the second method, the grain size of the granular sludge obtained by granulation varies depending on the purpose of recycling, but in the case of a sand sand substitute, for example, 1 to 10 m.
It is preferably about m. Further, in the second method, the drying or firing temperature of the granular sludge is set to 200 ° C.
The reason for limiting the above is the same as in the case of the first method.

In the first or second sludge recycling method, the combustion exhaust gas used in the firing step may be used as the carbon dioxide gas-containing gas. By doing this, there is no need to separately prepare carbon dioxide gas or carbon dioxide-containing gas,
The cost will be lower. When the combustion exhaust gas used in the firing step is used as the carbon dioxide gas, a part of the combustion exhaust gas used in the firing step may be reduced to the fuel combustion section of the fuel combustion type calciner. With this, the concentration of CO ₂ in the combustion exhaust gas blown into the sludge slurry can be increased, and lime can be converted to calcium carbonate more efficiently.

In the above first or second method for recycling sludge, sludge slurry is sequentially sent to a plurality of reaction tanks, and carbon dioxide gas or carbon dioxide-containing gas is blown into the sludge slurry in each reaction tank. There is. In this way, calcification of lime can be carried out completely.

In the first or second sludge recycling method, the sludge slurry is charged into the reaction tank, and carbon dioxide gas or carbon dioxide-containing gas is blown into the sludge slurry in the reaction tank. The sludge slurry may be stirred in the reaction tank. In this way, the sludge slurry and carbon dioxide gas are efficiently mixed, the reaction between lime and carbon dioxide gas is promoted, and lime is converted into calcium carbonate.

Further, in the first or second sludge recycling method, the firing temperature may be 600 ° C. or lower. The reason for this is that when firing at a higher temperature,
This is because the produced calcium carbonate (CaCO ₃ ) is decomposed into quick lime (CaO), and when the quick lime reacts with water, it returns to slaked lime (Ca (OH) ₂ ).

A third sludge recycling method according to the present invention comprises a step of drying the lime-containing sludge, a step of granulating the dried sludge to an appropriate particle size, and a step of firing the granular sludge at a temperature of 600 ° C. or lower. During the firing of the granular sludge, carbon dioxide gas in the combustion exhaust gas used in the firing is reacted with lime in the sludge to be converted into calcium carbonate.

In the above, the reason for limiting the firing temperature to 600 ° C. or lower is that when firing is performed at a temperature higher than this, the produced calcium carbonate (CaCO ₃ ) is decomposed into quick lime (CaO), and quick lime is converted to water. When reacted, slaked lime (C
This is because it returns to a (OH) ₂ ).

In the third sludge recycling method, a part of the combustion exhaust gas used in the firing step may be reduced to the fuel combustion section of the fuel combustion type calciner. With this, the CO ₂ concentration in the combustion exhaust gas used in the firing step can be increased, and lime can be converted to calcium carbonate more efficiently.

[0016]

【Example】

 Example 1 This example is shown in FIG.

In FIG. 1, the sludge recycling method comprises a lime-containing sludge slurrying step (1), a carbon dioxide-containing gas blowing step (2) of blowing a gas containing carbon dioxide into the sludge slurry, and a dehydration step. (3) and a high temperature firing step (4) of firing the dehydrated sludge at a high temperature or a drying step.

Sludge generated from civil engineering works such as the sewage shield construction method and pile driving work and sewage sludge have a large amount of water content and are generated in the form of slurry. These slurries are dehydrated at the generation site and transported to a treatment plant for storage, or they are transported to the treatment plant and dehydrated and then mostly disposed of in landfill.
In order to implement such sludge as a resource, first, in the slurry formation step (1), the sludge concentration of these sludges should be reduced to 20%.
% So that the slurry becomes less than or equal to%. The sludge slurry is put into the neutralization reaction tank.

Next, a carbon dioxide-containing gas blowing step (2)
In, the carbon dioxide-containing gas is blown into the sludge slurry in the neutralization reaction tank by a gas blowing pipe. Then, carbon dioxide reacts with lime in the sludge and is converted into calcium carbonate. The gas in which the carbon dioxide gas is fixed by being blown into the sludge slurry is released into the atmosphere. When combustion exhaust gas containing carbon dioxide from factories such as cement plants and power plants is used as carbon dioxide-containing gas, it becomes possible to fix carbon dioxide in exhaust gas, which is said to be one of the causes of global warming. , Contribute to the suppression of global warming by carbon dioxide.

Next, in the dehydration step (3), the sludge slurry in which the contained lime is calcium carbonate is dehydrated by a dehydrator.

Next, in the high temperature calcination step (4) or the drying step, the dehydrated sludge is introduced into a high temperature calcination furnace (calciner) such as a rotary kiln and calcined or dried at a high temperature of 200 ° C. or higher to obtain soil or soil. Obtain resources such as roadbed materials. If the firing temperature is 600 to 700 ° C. or higher, the calcium carbonate in the sludge is converted back into lime and alkalized, so the firing should be performed at a temperature lower than this temperature. However, in the case of obtaining a recycled product that may contain a small amount of lime, that is, in the case of obtaining a construction material such as a roadbed material in which a little alkalinization is allowed, 700 ° C or higher for the purpose of ensuring strength. You may bake in.

Example 2 This example is shown in FIG.

In FIG. 2, the sludge resource recycling method comprises a lime-containing sludge slurrying step (10), a carbon dioxide-containing gas blowing step (11) of blowing a gas containing carbon dioxide into the sludge slurry, and a dehydration step. (12), drying step (13), granulation step (14), high temperature firing step (15) for firing the granular sludge at high temperature
Alternatively, it comprises a drying step.

From the slurry forming step (10) to the dehydrating step (12), the slurry forming step (1) to the dehydrating step (3) of Example 1 above are performed.
Same as above.

After the dehydration step (12), in the drying step (13), the dehydrated sludge is dried until the water content ratio becomes 15 to 45%.

Next, in the granulation step (14), for example, when obtaining a sand-sand substitute, the dried sludge is granulated to have a particle size of 1 to 10 mm.

Next, in the high temperature calcination step (15) or the drying step, the granular sludge is introduced into a high temperature calcination furnace such as a rotary kiln, and calcined or dried at a high temperature of 200 ° C. or higher to obtain resources such as soil and roadbed materials. Get the chemical products. In the case of this example as well, as in the case of Example 1 above, when the firing temperature is 600 to 700 ° C. or higher, the calcium carbonate in the sludge is converted to lime again and alkalized, so a temperature lower than this temperature is used. It is good to do it in. However, in the case of obtaining a recycled product that may contain a small amount of lime, that is, in the case of obtaining a construction material such as a roadbed material in which a little alkalinization is allowed, 700 ° C or higher for the purpose of ensuring strength. You may bake in.

In the above two embodiments, the carbon dioxide gas-containing gas is blown into the sludge slurry, but the present invention is not limited to this, and carbon dioxide gas may be blown alone.

Example 3 This example is shown in FIGS.

In FIG. 3, the sludge resource recycling method comprises a lime-containing sludge slurrying step (20) and a wet sieving step (21).
And a concentration / sedimentation step (22) and a carbon dioxide-containing gas injection step (2 in which a gas containing carbon dioxide is injected into the sludge slurry.
3), dehydration step (24), granulation step (25), and drying step (26)
And a high temperature firing step (27) for firing the granular sludge at a high temperature, and a cooling step (28).

The slurry forming step (20) is the same as the slurry forming step of the first embodiment.

After the slurrying step (20), the wet sieving step (2
In 1), for example, a sieve having a mesh size of 0.5 mm is used to collect sand, and the collected sand is reused as washing sand at, for example, a construction civil engineering site.

Next, in the concentration / sedimentation step (22), the fine particle slurry under the sieve is condensed / settled and sent to the neutralization reaction tank.

Next, a carbon dioxide gas-containing gas blowing step (23)
In the high temperature firing step (27), the combustion exhaust gas generated in the fuel combustion section of the fuel combustion type firing machine and used for firing is blown into the sludge slurry in the neutralization reaction tank. The temperature of the combustion exhaust gas blown in is set to 100 ° C or lower. Then, carbon dioxide reacts with lime in the sludge and is converted into calcium carbonate. The gas in which the carbon dioxide gas is fixed by being blown into the sludge slurry is released into the atmosphere.

Next, in the dehydration step (24), the sludge slurry in which the contained lime is calcium carbonate is dehydrated by a dehydrator. The water content of the dehydrated cake is 20 to 50%. The water obtained in this step (24) is used in the wet sieving step (21).

Next, in the granulation step (25), the particle size is about 1 to 10 mm in the agitation granulator and about 5 mm in the extrusion granulator.

Next, in the drying step (26), the granulation step (2
The granular sludge granulated in 5) is dried so that the water content becomes about 5 to 10%. This drying is performed using the combustion exhaust gas used for firing in the high temperature firing step (27).

Next, in the high temperature calcination step (27), the granular sludge is introduced into a fuel combustion type high temperature calcination machine such as a rotary kiln, and the flue gas generated in the fuel combustion section is used at 600 ° C. or lower. And preferably, it is fired at a temperature of 200 ° C. or higher. The combustion exhaust gas used for firing is used in the drying step (26) and the carbon dioxide gas-containing gas blowing step (23) as described above.

Next, in the cooling step (28), the calcined sludge is cooled to obtain a resource-recycling product as a construction material such as soil or roadbed material.

FIG. 4 partially shows an example of the apparatus used for carrying out the method of Example 3.

In FIG. 4, a plurality of neutralization reaction tanks (30) for blowing a carbon dioxide-containing gas into the sludge slurry (31) are provided, and the sludge slurry (31) has a plurality of neutralization reaction tanks (30).
It is supposed to be sent sequentially to. Each neutralization reaction tank (30) is equipped with a stirrer (32). In addition, each neutralization reaction tank (3
At the bottom of (0), a combustion exhaust gas supply pipe (33) for supplying combustion exhaust gas from a high temperature firing machine (not shown) through a dryer is connected, and a sludge slurry is provided by a blower (34) provided in the middle of the pipe. Combustion exhaust gas is blown into (31). Then, in each neutralization reaction tank (30), a stirrer
Combustion exhaust gas is blown into the sludge slurry (31) while stirring the sludge slurry (31) by (32).

FIG. 5 partially shows another example of the apparatus used to carry out the method of Example 3.

In FIG. 5, the sludge slurry circulation path (42) is provided in the neutralization reaction tank (40) for blowing the carbon dioxide-containing gas into the sludge slurry (41), and this circulation path (42)
A sludge slurry circulation pump (43) is provided midway. Further, the neutralization reaction tank (40) is provided with a stirrer (44). At the bottom of the neutralization reaction tank (40), a combustion exhaust gas supply pipe (45) for supplying combustion exhaust gas from a fuel combustion type high temperature baking machine (not shown) through a dryer is connected, and is provided in the middle of the pipe. The flue gas is blown into the sludge slurry (41) by an existing blower (46). Further, a combustion exhaust gas discharge pipe (47) for discharging combustion exhaust gas in which carbon dioxide gas is fixed by being blown into the sludge slurry (41) is connected to the top of the neutralization reaction tank (40). An ejector (48) is provided in the middle of the sludge slurry circulation path (42), and a combustion exhaust gas circulation pipe (49) is provided between the combustion exhaust gas discharge pipe (47) and the ejector (48). .

In such a structure, each neutralization reaction tank (4
In (0), the sludge slurry (41) is stirred by the stirrer (44), and the sludge slurry circulation pump (43) moves the sludge slurry (41) between the circulation path (42) and the neutralization reaction tank (40). Combustion exhaust gas is blown into the sludge slurry (41) while circulating. A part of the combustion exhaust gas blown into the sludge slurry (41) and discharged from the combustion exhaust gas discharge pipe (47) is part of the ejector (4
8) Suctioned by the sludge slurry (41) flowing at high speed,
It flows into the circulation path (42) through the exhaust gas circulation pipe (49) and is returned to the neutralization reaction tank (40) together with the sludge slurry (41).

In the plurality of neutralization reaction tanks (30) shown in FIG. 4, the sludge slurry circulation path (42), the sludge slurry circulation pump (43), the combustion exhaust gas discharge pipe (47) and the ejector (48), respectively. And a combustion exhaust gas circulation pipe (49) may be provided.

FIG. 6 shows a part of the apparatus used for carrying out the method of Example 3 which differs from that of FIGS. 4 and 5.

In FIG. 6, a granulator (50), a dryer (51),
The fuel combustion type calciner (52) and the cooler (53) are provided in this order. The dehydrated cake obtained in the dehydration step (24) is sent to the granulator (50). The granular sludge obtained in the granulator (50) is sent to the calciner (51), and the calcined product obtained in the calciner (51) is sent to the cooler (53), where a recyclable product is obtained. To be

Between the calciner (52) and the dryer (51), the combustion exhaust gas generated in the fuel combustion section (52a) of the calciner (52) and used for calcining is dried (51 ) Is provided with a combustion exhaust gas delivery pipe (54). The dryer (51) is connected with a combustion exhaust gas supply pipe (55) for supplying the combustion exhaust gas used for drying to a neutralization reaction tank containing a sludge slurry (not shown). A blower (56) is provided in the middle of the combustion exhaust gas supply pipe (55), and the combustion exhaust gas used in the firing machine (52) by the blower (56) passes through the combustion exhaust gas delivery pipe (54) to the dryer (51 ), And then to the neutralization reaction tank through the combustion exhaust gas supply pipe (55). A damper (57) is provided in a portion of the combustion exhaust gas supply pipe (55) closer to the dryer (51) than the blower (56). In addition, a part of the combustion exhaust gas used in the dryer (51) is branched from a portion of the combustion exhaust gas supply pipe (55) closer to the dryer (51) than the damper (57), and a cooler (53). A flue gas circulation pipe (58) for sending to A damper (59) and a blower (60) are provided from the dryer (51) side in the middle of the combustion exhaust gas circulation pipe (58). Chiller
Between the (53) and the calciner (52), the combustion exhaust gas preheated by being used for cooling the calcined material in the cooler (53) (5
A combustion exhaust gas reduction pipe (61) for returning to the fuel combustion section (52a) of 2) is provided.

In such a structure, the combustion exhaust gas used in the firing of the dry granular sludge in the firing machine (52) is sent to the dryer (51) through the combustion exhaust gas delivery pipe (54), where it is granular. Used for drying sludge. Then, the combustion exhaust gas used for drying the granular sludge in the dryer (51) is the combustion exhaust gas supply pipe.
It is sent to the neutralization reaction tank through (55) and blown into the sludge slurry. Further, a part of the combustion exhaust gas used for drying the granular sludge in the dryer (51) is sent to the cooler (53) through the combustion exhaust gas circulation pipe (58), where it is used for cooling the fired product. Be preheated. The preheated combustion exhaust gas is returned to the fuel combustion section (52a) of the firing machine (52) through the combustion exhaust gas reduction pipe (61) and is used for combustion of fuel together with the primary air. Therefore, the CO ₂ in the combustion exhaust gas used in the calciner (52) is
The concentration is increased, and as a result, the CO ₂ concentration in the combustion exhaust gas blown into the sludge slurry in the neutralization reaction tank can be increased, and the calcium carbonate conversion of lime can be performed more efficiently.

Example 4 This example is shown in FIGS.

In FIG. 7, the sludge recycling method comprises a lime-containing sludge drying step (70), a granulating step (71), and a high-temperature firing step (72) for firing the granular sludge at a high temperature using combustion exhaust gas. )
And a cooling step (73).

The sludge is made into a dehydrated cake in advance. Then, in the drying step (70), the dehydrated cake is put into a rotary dryer or a vibration aeration dryer and dried until the water content becomes 10% or less.

Next, in the granulating step (71), the dried sludge is crushed by a crusher to reduce the particle size to 5 mm or less. Granulation is performed for the purpose of increasing the surface area of sludge. The obtained granular sludge is made up of clay particles (74) and slaked lime particles (75), as shown in FIG.

Next, in the high temperature calcination step (72), the granular sludge is introduced into a fuel combustion type high temperature calcination machine such as a rotary kiln, and the flue gas generated in the fuel combustion section is used at 600 ° C. or lower. The firing is preferably performed at a temperature of 200 ° C. or higher. During the firing, the slaked lime in the granular sludge is heated to cause a dehydration reaction of Ca (OH) ₂ → CaO + H ₂ O to produce quicklime. Due to this dehydration reaction, the produced quicklime particles become porous and the surface area thereof increases. Then, CO ₂ in the combustion exhaust gas used for calcination is adsorbed on the surface of the quicklime particles that have become porous, and a reaction of CaO + CO ₂ → CaCO ₃ is caused to become calcium carbonate. In this way, the sludge made into calcium carbonate becomes a strong granular material.

Next, in the cooling step (73), the calcined sludge is cooled to obtain a resource-recycling product as a construction material such as soil or roadbed material.

FIG. 9 shows the apparatus used to carry out the method of Example 4.

In FIG. 9, a dryer (76), a crusher (77),
A fuel combustion type calciner (78) and a cooler (79) are provided in this order. The dehydrated cake obtained by dehydrating the sludge in advance is sent to the dryer (76) to be dried,
The dried sludge obtained in the dryer (76) is sent to the crusher (78) and crushed into granular sludge. This granular sludge is sent to the calciner (78), and the calcined product obtained in the calciner (78) is sent to the cooler (79), where a recycled product is obtained.

Between the calciner (78) and the dryer (76), the combustion exhaust gas generated in the fuel combustion section (78a) of the calciner (78) and used for calcining is dried (76). ) Is provided with a combustion exhaust gas delivery pipe (80). Combustion exhaust gas delivery pipe (80)
There is provided a combustion exhaust gas circulation pipe (81) which branches off from the combustion exhaust gas and is used to send a part of the combustion exhaust gas used in the calciner (78) to the cooler (79). A blower (82) is provided in the middle of the combustion exhaust gas circulation pipe (81). Between the cooler (79) and the calciner (78), the combustion exhaust gas that was used for cooling the calcined material in the cooler (79) and was preheated to the fuel combustion section (78a) of the calciner (78). A combustion exhaust gas reduction pipe (83) for returning is provided.

In such a structure, the combustion exhaust gas used in the firing of the dry granular sludge in the firing machine (78) is sent to the dryer (76) through the combustion exhaust gas delivery pipe (80), and here the particulate Used for drying sludge. The combustion exhaust gas used for drying the granular sludge in the dryer (76) is released. Also, the dryer
Part of the combustion exhaust gas used for drying the granular sludge in (76) is sent to the cooler (79) through the combustion exhaust gas circulation pipe (81) by the blower (82), where it is used for cooling the fired product. Used and preheated. Preheated flue gas returns to flue gas reduction pipe
It is returned to the fuel combustion section (78a) of the calciner (78) through (83) and is used for combustion of fuel together with the primary air. Therefore, the CO ₂ concentration in the flue gas used in the calciner (78) is increased, and as a result, lime can be converted to calcium carbonate more efficiently.

[0060]

According to the three methods for recycling sludge of the present invention, highly alkaline sludge containing lime, which was almost unprocessable except for landfill as industrial waste, is rendered neutral and harmless. it can. Moreover, when the construction material such as roadbed material is recycled as a resource, it is economical in logistics. In addition, since the final step is performed by drying or baking at a high temperature, it is possible to make the obtained resource-use product harmless, odorless, porous and highly permeable, breathable and water retentive. In particular, it can be a soil useful for plant growth.

According to the second method for recycling sludge of the present invention, the dehydrated sludge is dried until the water content ratio becomes 15 to 45%, and then the dried sludge is granulated to an appropriate particle size, Since the granular sludge is dried or calcined at a temperature of 200 ° C. or higher, there is an advantage that a high-quality recyclable product having a more uniform particle size and hardness can be obtained.

[Brief description of drawings]

FIG. 1 is a process diagram showing a first embodiment of a resource recycling method of the present invention.

FIG. 2 is a process diagram showing a second embodiment of the resource recycling method of the present invention.

FIG. 3 is a process diagram showing a third embodiment of the resource recycling method of the present invention.

FIG. 4 is a schematic diagram showing a portion of an example of an apparatus used for carrying out the method of Example 3.

5 is a schematic diagram showing a portion of another example of an apparatus used for carrying out the method of Example 3. FIG.

FIG. 6 is a diagram of an apparatus used to carry out the method of Example 3;
6 is a configuration diagram showing a part different from FIG.

FIG. 7 is a process drawing showing Example 4 of the resource recycling method of the present invention.

FIG. 8 is an enlarged view showing the granular sludge obtained in the granulation step.

FIG. 9 is a block diagram showing an example of an apparatus used for carrying out the method of Example 4.

[Explanation of symbols]

 (1) Slurrying process (2) Carbon dioxide containing gas blowing process (3) Dehydration process (4) High temperature firing process (10) Slurrying process (11) Carbon dioxide containing gas blowing process (12) Dehydration process (13) Drying Process (14) Granulation process (15) High temperature firing process (70) Drying process (71) Granulation process (72) High temperature firing process (73) Cooling process

Claims (9)

[Claims] 1. A step of slurrying lime-containing sludge,
Blowing carbon dioxide or carbon dioxide-containing gas into sludge slurry, reacting carbon dioxide with lime in sludge to convert to calcium carbonate, dehydrating sludge slurry in which lime is calcium carbonated, dehydrated sludge To 200
A method for recycling sludge, comprising a step of obtaining a recycled product by drying or baking at a temperature of ℃ or higher. 2. A step of slurrying lime-containing sludge,
Blowing carbon dioxide or carbon dioxide-containing gas into sludge slurry, reacting carbon dioxide with lime in sludge to convert to calcium carbonate, dehydrating sludge slurry in which lime is calcium carbonated, dehydrated sludge A water content ratio of 15 to 45%, a step of granulating the dried sludge to an appropriate particle size, and a step of drying or firing the granular sludge at a temperature of 200 ° C. or higher to obtain a recyclable product. A method for recycling sludge as a resource. 3. The method for recycling sludge as a resource according to claim 1, wherein the carbon dioxide-containing gas is combustion exhaust gas used in the firing step. 4. A part of the combustion exhaust gas used in the firing step is reduced to the fuel combustion section of the fuel combustion type calciner.
Method for recycling sludge as described. 5. The sludge recycling method according to claim 1, wherein the sludge slurry is sequentially sent to a plurality of reaction tanks, and carbon dioxide gas or a carbon dioxide-containing gas is blown into the sludge slurry in each reaction tank. 6. The sludge slurry is put into a reaction tank, and carbon dioxide gas or a carbon dioxide gas-containing gas is blown into the sludge slurry in the reaction tank, and the sludge slurry is stirred in the reaction tank. 2. The method for recycling sludge as described in 2. 7. The firing temperature is 600 ° C. or lower.
Alternatively, the sludge recycling method described in 2. 8. A step of drying the lime-containing sludge, a step of granulating the dried sludge to an appropriate particle size, and a step of granulating the sludge at 600 ° C.
And a step of firing at the following temperature, during the firing of the granular sludge, the carbon dioxide in the combustion exhaust gas used in the firing reacts with the lime in the sludge to convert to calcium carbonate sludge resources Method. 9. The method according to claim 8, wherein a part of the combustion exhaust gas used in the firing step is reduced to the fuel combustion section of the fuel combustion type calciner.
Method for recycling sludge as described.