JPH10146576A - Method for treating combustion ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix a sulfate group contained in combustion ash as sulfate at the same time when ammonia is highly efficiently recovered and attempted to be utilized by a method wherein alkali and a small amount of water are added to the combustion ash containing ammonium sulfate and treated by kneading under a semi-dry state. SOLUTION: At least any alkali of quicklime, slaked lime and limestone of 1-1.5 equivalent to sulfate group in ammonium sulfate contained in combustion ash, preferably 1.1-1.3 equivalent is added to the combustion ash containing ammonium sulfate, mixed with a stirring mixer 10. Further, a small amount of water of 10-40wt.% of total amount of the alkali and the combustion ash, preferably 20-35wt.%, further preferably 25wt.%,. and more further preferably about 25wt.% is added thereto, which is treated by kneading for 1-10min under a semi-dry state with a kneader 12. Thereby, the ammonium sulfate is decomposed to remove and recover ammonia, and the sulfate group in ammonium sulfate is fixed as gypsum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ammonium sulfate such as ammonium sulfate (ammonium sulfate) or ammonium hydrogen sulfate among combustion ash discharged from a boiler or a heating furnace using heavy oil, heavy oil, orimulsion or the like as a fuel. The present invention relates to a method for treating combustion ash containing a large amount of ash.

[0002]

2. Description of the Related Art Conventionally, as fuel for boilers and heating furnaces, heavy oil and heavy oil containing a large amount of sulfur, which are low-cost fuels, have been widely used. In addition, emulsions) are attracting attention as fuel substitutes for heavy oil. These fuels containing a large amount of sulfur are included in the exhaust gas as SO
_{Since 2} (sulfurous acid gas) is generated in a large amount, ammonia is injected in front of the electrostatic precipitator for dust removal, and is captured as ammonium sulfate together with the dust by the electric precipitator. Therefore, a large amount of ammonium sulfate is contained in the dust collected from the combustion exhaust gas using these sulfur-rich fuels, and ammonia is separated and recovered by a wet method when treating the recovered combustion ash. Alternatively, thermal decomposition removal by heat treatment is performed as a dry method.

In Japanese Patent Publication No. 47-32504, lime or carbide slag and the like are added to those containing ammonium sulfate, etc., of the combustion dust of petroleum fuels such as heavy oil and crude oil, and uniformly mixed in the presence of water. While heating to about 120 ° C. to separate and recover ammonia, the ammonia recovery residue is used as it is as a hydraulic material, or the ammonia recovery residue is incinerated at about 700 ° C. to remove unburned carbon in the residue. A method is described in which the waste is incinerated and used as a raw material for recovering valuable raw materials such as vanadium and nickel.

[0004]

However, the conventional wet method and dry method have problems that the process is complicated and the processing cost is high. Further, wastewater treatment is required, a large amount of auxiliary fuel is required for incineration, and there is a problem that NOx and SOx are generated by heating and firing. Further, in the conventional method, a large amount of heat is required when recovering ammonia.

In the method disclosed in Japanese Patent Publication No. 47-32504, lime or carbide slag is added to combustion dust containing ammonium sulfate and the like, and the dust is reduced by 7%.
This is a wet method in which about 0 wt% of water is added and mixed and heated, and has the same problems as described above. Further, it is necessary to heat to recover ammonia.

The present invention has been made in view of the above points, and an object of the present invention is to add an alkali and a small amount of water to a combustion ash containing ammonium sulfate such as ammonium sulfate or ammonium hydrogen sulfate, and to prepare a semi-dry type. It is an object of the present invention to provide a method capable of recovering ammonia with high efficiency and effectively utilizing the same by performing a kneading treatment, and at the same time, fixing a sulfate group contained in combustion ash as sulfate. Further, an object of the present invention is to add an alkali and a small amount of water to combustion ash containing ammonium sulfate and perform a kneading treatment in a semi-dry state, so that the process is simpler than a conventional wet method or dry method. It is another object of the present invention to provide a method which can be processed at low cost, does not generate waste water, and does not generate NOx and SOx by heating and firing.

[0007]

In order to achieve the above object, a method for treating combustion ash according to the present invention comprises adding an alkali and a small amount of water to combustion ash containing ammonium sulfate and kneading the mixture in a semi-dry state. In this way, ammonium sulfate is decomposed to remove and recover ammonia (NH ₃ ), and sulfate (SO ₄ ^2- ) contained in combustion ash is fixed as sulfate. In the above method of the present invention, the combustion ash containing ammonium sulfate is added to the sulfate (SO) in the ammonium sulfate contained in the combustion ash.
₄ ^2- ) 1 to 1.5 equivalents of quick lime (CaO), slaked lime (Ca (OH) ₂ ) and / or limestone (CaCO ₃ ) It is desirable to add 10 to 40% by weight of water and knead using a high-speed kneader.

Further, the method for treating combustion ash of the present invention comprises adding at least one alkali of quick lime, slaked lime and limestone to combustion ash containing ammonium sulfate, and at least one of coal combustion ash and cement. After adding a solidifying agent, adding 10 to 40% by weight of water based on the total amount of combustion ash, alkali and solidifying agent containing ammonium sulfate, and kneading using a high-speed kneading machine,
It is characterized by performing steam heating at a temperature of 80 ° C.

In another method of the present invention, at least one of alkali such as quicklime, slaked lime and limestone and a small amount of water are added to a combustion ash containing ammonium sulfate and unburned carbon, followed by kneading in a semi-dry state. In this way, ammonium sulfate is decomposed, ammonia is removed and recovered, and the sulfate groups contained in the combustion ash are fixed as sulfates. After incineration of carbon, at least one of coal-burning ash and cement solidifying agent and a small amount of water are added to the incineration residue,
The mixture is kneaded in a semi-dry state, and the obtained mixture is
It is characterized by performing steam heating at a temperature of 0 to 180 ° C. In these methods described above, when a forming step is provided immediately before the steam heating step, the processed product is obtained as a solidified product, which can be used effectively.

The ammonia recovered in the method of the present invention is blown into an upstream portion of a flue gas denitration device installed in a boiler flue and used as a NOx reducing agent, or blown into an upstream portion of an electrostatic precipitator to be discharged into exhaust gas. SO ₂ included
Can be used for neutralization.

As described above, the upper limit of the amount of water added for performing the kneading treatment in a semi-dry state is 40 wt% with respect to the total amount of combustion ash and the like, from the viewpoint of maintaining a funicular state. Is 35% by weight. On the other hand, from the viewpoint of securing the amount of water necessary for the metathesis reaction of ammonium sulfate, the lower limit is 10% by weight, preferably 20% by weight, based on the total amount of combustion ash and the like.
The upper limit of the amount of alkali added to the combustion ash containing ammonium sulfate is 1.5 equivalents, preferably 1.3 equivalents, relative to the sulfate group, from the viewpoint of preventing an increase in waste. On the other hand, in order to fix all the sulfate groups contained, the lower limit is 1 equivalent to the sulfate group, preferably 1.1 equivalent. In addition, in the case of performing the steam heating treatment after the kneading treatment, the lower limit is 50 ° C., preferably 65 ° C., from the viewpoint of promoting the solidification reaction. On the other hand, considering the decomposition of the reaction product, the upper limit is 180 ° C., preferably 10 ° C.
0 ° C.

[0012]

Embodiments of the present invention will be described below in detail. FIG. 1 is a flow sheet showing a first embodiment of the method for treating combustion ash of the present invention. FIG.
Shows a flow in the case of performing a semi-dry alkali addition stabilization treatment on combustion ash containing ammonium sulfate (ammonium sulfate). In FIG. 1, the combustion ash containing ammonium sulphate ((NH ₄ ) ₂ SO ₄ ) contains the sulfate groups (S
O ₄ ^2-) against 1.5 equivalents, preferably 1.1 to
1.3 equivalent quicklime (CaO), slaked lime (Ca (OH)
₂ ) and at least one alkali of limestone (CaCO ₃ ) is added and mixed with the stirring mixer 10;
A small amount of water (for example, industrial water, seawater, etc.) of about 10 to 40% by weight, preferably about 20 to 35% by weight, more preferably about 25% by weight based on the total amount of alkali and combustion ash is added,
Ammonium sulfate is decomposed by removing and recovering ammonia (NH ₃ ) by performing a kneading treatment in a semi-dry state for 1 to 10 minutes using the kneading treatment machine 12, and a sulfate group in the ammonium sulfate is removed by gypsum ( CaSO ₄ ).

The reaction formula when slaked lime is used as the alkali to be added is as follows. (NH ₄ ) ₂ SO ₄ + Ca (OH) ₂ → CaSO ₄ .2H ₂ O
+ 2NH ₃ ↑ In addition, a universal kneader or the like is used as the stirring mixer 10, and a high-speed kneader, particularly a reverse-flow high-speed vertical kneader or the like is used as the kneading processor 12. In the present embodiment, it is of course possible to add water to the combustion ash simultaneously with the alkali, or to add a mixture of alkali and water in advance to the combustion ash for kneading. Further, it is also possible to omit the agitating mixer and supply the combustion ash, alkali and water to the kneading processor 12. As described above, in the method according to the present embodiment, ammonia which is a problem at the time of disposal and effective use can be efficiently removed by on-site relatively simple semi-dry kneading. The decomposed and recovered ammonia can be reused for denitration and for neutralizing SO ₂ . On the other hand, the deaeration rate of the obtained processed product exceeds 95%, and the processed product is obtained as a granular solidified material that can be easily handled, and is valuable such as vanadium (V), nickel (Ni), and gypsum (CaSO ₄ ). It can be used as raw material. In addition, the treated material conforms to the soil environmental standard value, and landfill disposal is possible.

FIG. 2 is a flow sheet showing a second embodiment of the method for treating combustion ash of the present invention. FIG. 2 shows a flow in a case where a combustion ash containing ammonium sulfate is subjected to a semi-dry alkali addition stabilization treatment and a high-strength solidified body is produced by adding a solidifying agent. In FIG. 2, the combustion ash containing ammonium sulfate contains at least 1 to 1.5 equivalents, preferably 1.1 to 1.3 equivalents of quick lime, slaked lime and limestone with respect to the sulfate in ammonium sulfate contained in the combustion ash. Any alkali and a solidifying agent such as coal ash or cement are added and mixed with the stirring mixer 10, and 10 to 40% by weight, preferably 20 to 40% by weight based on the total amount of the combustion ash, alkali and solidifying agent.
A small amount of water of about 35% by weight, more preferably about 25% by weight, is added.
After kneading for 10 minutes, the steam curing device 14
At 50 to 180 ° C., preferably 65 to 100 ° C., for 5 to 25 hours to obtain a granular high-strength solid.

In the present embodiment, kneading may be performed by adding water to the combustion ash simultaneously with the alkali and the solidifying agent, or adding a mixture of alkali and water in advance to the combustion ash and the solidifying agent. Of course it is possible. Further, it is possible to supply the combustion ash, the alkali, the solidifying agent and the water to the kneading treatment machine 12 by omitting the stirring and mixing machine. Other configurations, operations, and the like are the same as those in the first embodiment of the present invention. As described above, in the method according to the present embodiment, ammonia which is a problem at the time of disposal and effective use can be removed with high efficiency by a relatively simple semi-dry kneading process. The decomposed and recovered ammonia can be reused for denitration and for neutralizing SO ₂ . On the other hand, the residual NH ₃ concentration of the obtained solidified body is less than 100 ppm, and the solidified body is obtained as a granular high-strength solidified body that is easy to handle, and can be effectively used as a civil engineering material such as a roadbed material. The strength of the solidified body exceeds 50 kg / cm ² . In addition, as shown in FIG. 3, in the second embodiment of the present invention, when a molding machine 16 is provided in a stage preceding the steam curing device 14, a processed product is obtained as a molded solid.

FIG. 4 is a flow sheet showing a third embodiment of the method for treating combustion ash according to the present invention. FIG. 4 shows a flow in a case where a combustion ash containing ammonium sulfate and unburned carbon is subjected to a semi-dry alkali addition stabilization treatment and is combined with an incineration method. In FIG. 4, in the combustion ash containing ammonium sulfate and unburned carbon, quick lime and slaked lime in an amount of 1 to 1.5 equivalents, preferably 1.1 to 1.3 equivalents relative to the sulfate in ammonium sulfate contained in the combustion ash. And at least one alkali of limestone is added and mixed with the stirring mixer 10, and a small amount of about 10 to 40 wt%, preferably 20 to 35 wt%, more preferably about 25 wt% based on the total amount of combustion ash and alkali. Is added, and the mixture is subjected to kneading for 1 to 10 minutes in a semi-dry state using a kneading processor 12 to decompose ammonium sulfate, remove and recover ammonia, and remove sulfates in ammonium sulfate. After fixation as gypsum, then, the treated product was heated and fired at 600 to 900 ° C. in a heating and firing furnace 18 to incinerate unburned carbon in the combustion ash, and then to the obtained incineration residue,
While adding a solidifying agent such as coal ash and cement, a small amount of water of 10 to 40% by weight, preferably 20 to 35% by weight based on the total amount of the incineration residue and the solidifying agent is added.
The kneading treatment is carried out for 1 to 10 minutes in a semi-dry state using 0, and then the obtained kneaded material is heated at 50 to 180 ° C., preferably 65 to 100 ° C. in a steam curing device 14 at 5 to 100 ° C.
By performing the steam heating treatment for up to 25 hours, a granular high-strength solid is obtained. The residue obtained by heating and firing in the heating and firing furnace 18 to incinerate the unburned carbon in the combustion ash can be used as a raw material for recovering valuable resources such as vanadium and nickel.

As the heating and firing furnace 18, a muffle furnace or the like is used. Other configurations and operations are the same as those in the first and second embodiments of the present invention. in this way,
In the method according to the present embodiment, by a relatively simple semi-dry kneading treatment, highly efficient removal of ammonia as a NOx generation source and SO _{2 which is a} problem at the time of incineration of unburned matter (carbon).
Can be fixed. The decomposed and recovered ammonia can be effectively used for denitration. On the other hand, the residue obtained by the incineration treatment can be used as a raw material for recovering valuable resources such as vanadium and nickel, and when used as a raw material for manufacturing a solidified body, a granular high-strength solidified body is obtained. . This embodiment is particularly suitable for treating heavy oil combustion ash containing a large amount of ammonium sulfate (ammonium sulfate) and unburned carbon, orimulsion / heavy oil mixed ash, etc. in the combustion ash. Further, as shown in FIG. 5, in the third embodiment of the present invention, when a molding machine 16 is provided in a stage preceding the steam curing device 14, a processed product is obtained as a molded solid.

[0018]

Next, an embodiment of the present invention will be described. Example 1 Example 1 will be described with reference to the flow sheet shown in FIG. To the orimulsion combustion ash containing ammonium sulfate, add 1.2 equivalents of slaked lime to the sulfate radicals in the ammonium sulphate contained in the combustion ash, mix with a universal kneader, and add 25 wt% to the total amount of slaked lime and combustion ash. % Of water and kneading for 5 minutes in a semi-dry state using a backflow high-speed kneader to decompose ammonium sulfate, remove and recover ammonia, and remove sulfuric acid in ammonium sulfate. The roots were fixed as plaster. The deaeration rate of the obtained processed product is 95%, and the processed product is obtained as a granular solidified material that can be easily handled.
The elution amounts of b, Cd, and Se were 0.01 ppm and 0.00, respectively.
The values were 08 ppm and 0.009 ppm, which were in conformity with soil environmental standard values.

Embodiment 2 Embodiment 2 will be described with reference to a flow sheet shown in FIG. Orimulsion combustion ash containing ammonium sulphate, 1.2 equivalents of slaked lime with respect to sulfate in ammonium sulphate contained in the combustion ash,
And coal combustion ash are added and mixed with a universal kneader, and 25 wt% based on the total amount of combustion ash, slaked lime and coal ash
After adding a small amount of water and performing a kneading treatment for 5 minutes in a semi-dry state using a backflow high-speed kneader, a steam curing device is used to perform steam heating treatment at a temperature of 95 ° C. for 12 hours. Thus, a granular high-strength solid was obtained. The residual NH ₃ concentration of the obtained solid was 90 ppm, and the solid was obtained as a granular high-strength solid that was easy to handle.

Embodiment 3 Embodiment 3 will be described with reference to a flow sheet shown in FIG. 1.2 mol of slaked lime based on ammonium sulfate contained in the combustion ash is added to the mixed ash containing the ammonium sulfate and unburned carbon, and mixed with a universal kneader. A small amount of water (about 25 wt%) is added to the total amount, and the mixture is kneaded for 5 minutes in a semi-dry state using a backflow high-speed kneader to decompose ammonium sulfate and remove and recover ammonia. At the same time, the sulfate groups in ammonium sulfate were fixed as gypsum, and then the treated product was heated and fired at 800 ° C. in a heating and firing furnace to incinerate unburned carbon in the combustion ash. 20 coal ash
wt% and a small amount of water of 35 wt% based on the total amount of incineration residue and coal ash, and kneading treatment in a semi-dry state for 5 minutes using a backflow high-speed kneader. The obtained kneaded material was subjected to steam heating treatment at a temperature of 95 ° C. for 12 hours using a steam curing device to obtain a granular high-strength solid. In addition, the residue obtained by burning and burning the unburned carbon in the combustion ash can be used as a raw material for recovering valuable resources such as vanadium and nickel.
The sulfated fixing rate of the obtained incineration residue is 90% or more,
The residue is obtained as a granular solid that is easy to handle,
The soil environmental standards were also met. In addition, NH ₃ was completely removed from the solidified product obtained from the incineration residue, and the solidified product was obtained as a granular high-strength solid that was easy to handle.

[0021]

As described above, the present invention has the following effects. (1) By the semi-dry treatment, the treatment process is simple, the treatment cost is low, ammonia can be efficiently recovered on-site, and effective use can be achieved. The recovered ammonia can be reused for denitration and SO ₂ neutralization. (2) No pollutants such as wastewater, NOx and SOx are generated,
No auxiliary fuel is required for semi-dry processing. (3) The treated product is obtained as a granular solid that is easy to handle and can be used as a raw material for valuable resources such as vanadium, nickel, and gypsum. (4) The treated material conforms to the soil environmental standard values and can be landfilled. (5) When a solidifying agent is added and the mixture is kneaded and heated with steam to form a solid, the elution of harmful metals can be prevented. (6) When a treatment is performed by adding a solidifying agent, the treated product is obtained as a granular high-strength solidified material that is easy to handle,
It can be effectively used as civil engineering materials such as roadbed materials. (7) when combined with the incineration process can be performed with fixed unburned (carbon) NOx source of ammonia removal and SO ₂ in question during incineration. In addition, the residue obtained by incineration can be used as a raw material for recovering valuable resources such as vanadium and nickel,
It can also be used as a raw material for solidified body production. (8) Combination with the incineration method is particularly suitable for treating heavy oil combustion ash containing a large amount of ammonium sulfate and unburned carbon in the combustion ash, orimulsion / heavy oil mixed ash, and the like.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a method for treating combustion ash of the present invention.
It is a flow sheet showing a form.

FIG. 2 shows a second embodiment of the method for treating combustion ash of the present invention.
It is a flow sheet showing a form.

FIG. 3 is a flow sheet showing a case where a molding machine is provided in a stage preceding the steam curing device in the second embodiment of the present invention.

FIG. 4 shows a third embodiment of the method for treating combustion ash of the present invention.
It is a flow sheet showing a form.

FIG. 5 is a flow sheet showing a case where a molding machine is provided in a stage preceding the steam curing device in the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stirring mixer 12, 20 Kneading processing machine 14 Steam curing device 16 Molding machine 18 Heating and firing furnace

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriyuki Taniyama 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Plant (72) Inventor Yasushi Takahashi 2-1-1, Minamisuna, Koto-ku, Tokyo Kawasaki Heavy Industries Tokyo Design Office

Claims (5)

[Claims] 1. An alkali sulfate and water are added to a combustion ash containing ammonium sulfate, and the mixture is kneaded in a semi-dry state to decompose ammonium sulfate to remove and recover ammonia and to contain ammonia in the combustion ash. A method for treating combustion ash, comprising fixing sulfate sulfates as sulfates. 2. The combustion ash containing ammonium sulfate is added with 1 to 1.5 equivalents of alkali of at least one of quick lime, slaked lime and limestone with respect to the sulfate group in the ammonium sulfate contained in the combustion ash. 2. The method for treating combustion ash according to claim 1, wherein 10 to 40% by weight of water is added to the alkali and combustion ash, and the mixture is kneaded using a high-speed kneader. 3. A combustion ash containing ammonium sulfate, to which at least one alkali of quick lime, slaked lime and limestone is added, and a solidifying agent of at least one of coal combustion ash and cement is added. 10 based on the total amount of combustion ash, alkali and solidifying agent
A method for treating combustion ash, comprising adding up to 40% by weight of water, kneading using a high-speed kneading machine, and performing steam heating at a temperature of 50 to 180 ° C. 4. Combustion ash containing ammonium sulfate and unburned carbon is added with alkali and water of at least one of quick lime, slaked lime and limestone and kneaded in a semi-dry state to decompose ammonium sulfate. In addition to removing and recovering ammonia, fixing the sulfate groups contained in the combustion ash as sulfates, then heating and burning the combustion ash to incinerate the unburned carbon in the combustion ash, Combustion characterized by adding a solidifying agent and / or water of at least one of combustion ash and cement and kneading in a semi-dry state, and then subjecting the kneaded material to steam heating at a temperature of 50 to 180 ° C. Ash treatment method. 5. The method for treating combustion ash according to claim 3, wherein a molding step is provided immediately before the steam heating step.