JP2020124679A - Processing method of incineration ash and processor - Google Patents

Abstract

To provide a processing method and processor, capable of preventing sticking of incineration ash and at the same time, reducing an amount of NOx emission from a cement plant.SOLUTION: In the method, sticking prevention material P is blended with an incineration ash A, ammonia is recovered from an ammonia-containing gas G1 formed on blending, and the recovered ammonia (gas) G3 is introduced to a cement firing process.The incineration ash can be a main ash or fly ash formed on incineration of municipal wastes or sewage sludge, the sticking prevention material can be an inorganic system powder containing oxides of alkali metals or alkaline earth metals, and quick lime, a cement firing intermediate raw material, or a coarse powder recovered from a chlorine bypass dust can be used.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for treating incinerated ash, and to a method and an apparatus for reducing NOx emission from a cement plant while preventing sticking which is a problem when recycling the incinerated ash as a cement raw material.

Cement factories use incinerated ash generated as a result of incineration of waste as a raw material for cement, and are promoting resource recycling.However, in order to remove foreign substances such as metal lumps before they are put into the raw material process. Pretreatment such as coarse crushing, sieving, and magnetic selection is carried out.

However, the incinerated ash may contain a large amount of water due to water sprinkling for cooling or outdoor storage after incineration. Aggregation of ash and ash occurs and the inside of the facility is blocked, and the production efficiency is reduced due to a reduction in the amount of processing, stoppage of the facility, work to remove adhered substances, and the like. Therefore, it is necessary to reduce the water content of the incinerated ash in advance to prevent sticking, but when using equipment such as a dryer, an increase in manufacturing cost due to the introduction of equipment and an increase in fuel consumption is an issue. Becomes

Further, Patent Document 1 describes a method for preventing sticking of municipal waste incineration ash contaminated with radioactive cesium by adding modifiers such as quick lime, slaked lime, calcium carbonate and cement. The treatment of the ammonia gas generated when the modifier is mixed poses a problem.

On the other hand, in the cement burning process, it is known that NOx is generated in the exhaust gas mainly due to the use of fossil fuel, and the emission standard is set because it causes air pollution. In addition, in recent years, the amount of waste that is recycled as raw fuel in cement plants has been increasing, and the burning of these wastes at high temperatures oxidizes the nitrogen components contained in the wastes, generating NOx. As a source of NOx, when incinerated ash remains, the nitrogen contained in the original waste to be incinerated and in the fuel used for incineration remains, which causes NOx generation when used as a cement raw material. Is a problem.

Therefore, in cement plants, a method of adding ammonia gas, urea or the like as a denitration agent is generally used as a measure for reducing various NOx. However, the use of chemicals such as ammonia gas and urea increases the manufacturing cost.

As a measure for improving it, for example, in Patent Document 2, a method of introducing an organic sludge containing ammonia between the lower part of the preheater and the kiln bottom of the dry cement kiln at the time of firing the cement to reduce NOx Is disclosed.

Further, in Patent Document 3, quick dehydration lime is added to dewatered sludge having a water content of 40 to 85% obtained by treating and dehydrating organic wastewater in an amount of 300 to 1000% by weight of the solid content of the dehydrated sludge, and the mixture is stirred to be aged. Then, the sludge dry powder having a water content of 10% or less is supplied to the cement burning furnace and burned, and the gas generated in the burning process is passed through a high temperature part of 500°C or higher in the burning furnace. A sludge treatment method for reducing nitrogen oxides in exhaust gas is shown.

However, in these cases, a method for preventing sticking of dehydrated sludge is not particularly described, and a method using incinerated ash has not been proposed.

Japanese Patent No. 6313205 JP, 10-194800, A JP-A-7-239118

The present invention has been made in view of the problems in the above-mentioned conventional techniques, preventing sticking of incinerated ash that becomes a problem when recycling incinerated ash as a cement raw material, and at the same time, from a cement factory The purpose is to reduce NOx emissions.

In order to achieve the above-mentioned object, the inventors of the present invention have diligently studied, and prevent sticking by reducing the water content in the incinerated ash to a predetermined value by mixing an incinerator ash with an anti-sticking material, and incinerating ash. By releasing ammoniacal nitrogen contained in the incineration ash to generate ammonia gas when the anti-sticking material is mixed, the nitrogen component that can be a NOx generation source during firing is reduced, and the further released ammonia-containing gas It was found that by selectively recovering ammonia using a distillation column or an adsorption column and introducing it as a concentrated ammonia gas or a concentrated ammonia aqueous solution into the cement firing section, NOx generated during cement firing can be reduced at the same time. The present invention has been completed.

That is, the method for treating incinerated ash according to the present invention comprises mixing the incineration ash with an anti-sticking material, recovering ammonia from the ammonia-containing gas generated during mixing, and introducing the recovered ammonia into the cement firing step. Characterize.

According to the present invention, the sticking of the incineration ash is prevented by mixing the sticking preventive material with the incineration ash, the pretreatment process when the incineration ash is added to the cement manufacturing process is made efficient, and the incineration ash is generated. By introducing ammonia into the cement burning process, it is possible to reduce the amount of NOx in the exhaust gas of the cement plant at low cost.

The incinerated ash may be main ash or fly ash generated when incinerating municipal waste or sewage sludge, and as the anti-sticking material, an inorganic powder containing an oxide of an alkali metal or an alkaline earth metal. The body can be used. Further, as the inorganic powder containing the oxide of the alkali metal or alkaline earth metal, coarse powder recovered from quicklime, cement firing intermediate raw material or chlorine bypass dust can be used.

Further, the apparatus for treating incinerated ash according to the present invention, a mixing device for mixing the incineration ash and the anti-sticking material, an ammonia recovery device for recovering ammonia from the ammonia-containing gas generated during mixing by the mixing device, An ammonia introduction device for introducing the ammonia recovered by the ammonia recovery device to the cement burning step.

According to the present invention, it is possible to prevent the incineration ash from sticking by mixing the incineration ash and the anti-sticking material in the mixing device, and to improve the efficiency of the pretreatment process when the incineration ash is put into the cement manufacturing process. .. At the same time, the amount of NOx in the exhaust gas of the cement plant can be reduced at a low cost by recovering the ammonia generated from the incineration ash by the ammonia recovery device and introducing the ammonia recovered by the ammonia introduction device into the cement firing process. Is possible.

As the ammonia recovery device, a distillation column or an adsorption column that removes water vapor from the ammonia-containing gas can be used. In addition, a dust collector that collects dust from the ammonia-containing gas is provided, and ammonia is recovered by the ammonia recovery device from the ammonia-containing gas that has been collected by the dust collector, thereby recovering ammonia in the ammonia recovery device. The efficiency can be improved and the collected dust can be used as a cement raw material.

As described above, according to the present invention, it is possible to prevent the incineration ash from sticking and reduce the NOx emission amount from the cement factory.

1 is an overall configuration diagram showing an embodiment of an incineration ash treatment apparatus according to the present invention.

Next, an embodiment of a method for treating incinerated ash and a treatment apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment method of an apparatus for treating incinerated ash according to the present invention. This treating apparatus 1 includes an incinerator ash storage tank 2 for storing incinerated ash A and an anti-sticking agent for storing anti-sticking material P. Material storage tank 3, mixing device 4 for mixing incineration ash A and anti-sticking material P, bag filter 5 for removing dust from ammonia-containing gas G1 generated when incineration ash A and anti-sticking material P are mixed, and bag filter A distillation column 6 for removing water vapor from the ammonia-containing gas G2 discharged from the column 5, a neutralization tank 7 for neutralizing the water W recovered in the distillation column 6, and a concentrated ammonia gas G3 obtained in the distillation column 6. An ammonia introduction device 8 for introducing into the cement firing process is provided.

The type of the mixing device 4 is not particularly limited as long as it has an intake port for transporting the generated ammonia-containing gas G1 to the bag filter 5. For example, a ribbon mixer, a screw mixer, a planetary mixer or the like can be used as the fixed container type mixing device, and a horizontal cylindrical type mixer, a V type mixer or the like can be used as the container rotating type mixing device. If the work site is a closed system where the walls and top surface are not open, you may use a self-propelled cultivator, wheel loader, backhoe, bulldozer, or other heavy machinery to mix on the floor, and use a scoop or the like. It may be mixed by manually turning it back. In these cases, the generated ammonia gas can be sent to the recovery facility by installing a local exhaust device, a blower, an exhaust fan, etc. around the work place.

The bag filter 5 is provided to remove dust from the ammonia-containing gas G1 generated when the incineration ash A and the sticking prevention material P are mixed in the mixing device 4, and a dust collecting device other than the bag filter can be used.

The distillation column 6 is provided to remove water vapor generated at the same time as ammonia by mixing the incineration ash A and the sticking prevention material P. An adsorption tower using an adsorbent such as zeolite may be provided in place of the distillation tower 6, and a larger adsorbent Al/Si ratio is preferable because the adsorption efficiency becomes higher.

The neutralization tank 7 is provided to neutralize the water W recovered in the distillation column 6 because it is a dilute aqueous ammonia solution containing a small amount of ammonia.

Next, the operation of the processing apparatus 1 having the above configuration will be described.

The incinerated ash A and the sticking prevention material P are received and stored in the incineration ash storage tank 2 and the sticking prevention material storage tank 3, respectively.

The incineration ash A is main ash or fly ash generated by incineration of general waste such as municipal waste or industrial waste, and sewage sludge, or ash to be landfilled. This incinerated ash A contains the solid content in the incinerated ash A as 100 parts by weight and contains 5 to 300 parts by weight of water, preferably the solid content in the incinerated ash A as 100 parts by weight and the water content as 10 parts by weight. Up to 150 parts by weight. Further, considering the effect obtained by the sticking prevention material P and the cost required for the sticking prevention material P, it is preferable that the solid content in the incineration ash A is 100 parts by weight and the water content is 20 to 100 parts by weight. When the solid content in the incineration ash A is 100 parts by weight and the water content is less than 5 parts by weight, it is difficult for the original incineration ash A to adhere to the equipment. Therefore, it is necessary to add the anti-sticking material P. However, if the water content is 300 parts by weight or more, the amount of the sticking preventive material P to be used becomes large, which is not economically preferable.

The anti-sticking material P is an inorganic powder that causes an exothermic reaction with water and behaves as a strong base. Among the inorganic powders having these characteristics, inorganic powders containing an oxide of an alkali metal or an alkaline earth metal are preferable. Furthermore, since the calorific value is large, it is preferable to use one containing at least one of Na ₂ O, MgO, and CaO as a component. Furthermore, from the viewpoint that the residue after modification is suitable as a cement raw material, it is most preferable to use an inorganic powder containing CaO as a component. As the inorganic powder containing CaO, not only quicklime, but also coarse powder recovered from cement calcination intermediate raw material or chlorine bypass dust can be used.

Next, the incineration ash A and the sticking prevention material P are mixed by the mixing device 4. In the present invention, the sticking prevention material P is mixed with the incinerated ash A to prevent sticking of the incinerated ash. The amount of the sticking preventive material P used is appropriately determined according to the CaO content in the sticking preventive material P and the water content in the incineration ash A. When the ratio of the amounts is CaO/water ratio, it is preferable to mix so that the CaO/water ratio is 0.2-2. Further, from the viewpoint of the effect of the anti-sticking material and the cost, it is preferable to mix them so that the CaO/water ratio is 0.5 to 1.5. When the CaO/water ratio is less than 0.2, the water content in the incineration ash A is not sufficiently reduced, the effect as the sticking preventive material P is not sufficient, and the amount of the ammonia-containing gas G1 generated at the time of mixing is insufficient. Is also not preferable because it becomes a very small amount. In addition, when the CaO/water ratio is larger than 2, the cost of the sticking preventive material P increases, and a large amount of unreacted CaO component remains when mixed with the incinerated ash A, and when used as a raw material. It is not preferable because it may affect the quality of cement.

The incineration ash A and the sticking prevention material P, which are put into the mixing device 4, are continuously or sequentially mixed. When continuously mixing, the mixing time is about 20 to 360 minutes, preferably about 30 to 180 minutes. When sequentially mixing, at least every 1 hour, mixing is performed for 1 minute or more, and the aging time is also treated for 1 to 6 hours, preferably 1 to 3 hours.

Since the anti-sticking material P has a strong basicity, when mixed with the incinerated ash A, ammonia nitrogen dissolved in water in the incinerated ash A is liberated and an ammonia-containing gas G1 is generated. Further, the reaction between the anti-sticking material P and water generates heat, which promotes volatilization of liberated ammonia.

The modified ash R1 obtained by mixing in the mixing device 4 is discharged from the lower part of the mixing device 4, sent to the cement raw material pretreatment step 9, and introduced into a magnetic separator, a pulverizer or a specific gravity separator. The modified ash R2 that has undergone the cement raw material pretreatment step 9 is recycled as a cement raw material. On the other hand, the ammonia-containing gas G1 generated when the incineration ash A and the sticking prevention material P are mixed is introduced into the bag filter 5.

Dust is removed from the ammonia-containing gas G1 in the bag filter 5. The dust collecting dust D removed by the bag filter 5 can be recycled as a cement raw material as it is because large lumps such as metal lumps are removed. The ammonia-containing gas G2 from which dust has been removed by the bag filter 5 is transported to the distillation column 6 by a transportation pipe.

In the distillation column 6, by mixing the incinerated ash A and the anti-sticking material P, water vapor generated at the same time as ammonia is removed, and concentrated ammonia gas G3 is obtained from the upper part of the distillation column. At this time, the water W recovered in the distillation tower 6 is drained after being neutralized by the neutralization tank 7.

The concentrated ammonia gas G3 obtained in the distillation column 6 is transported again by the transportation pipe and introduced into the cement burning equipment by the ammonia introduction device 8 provided between the cement preheater and the cement kiln kiln bottom. The introduced ammonia gas G3 causes a NOx removal reaction with NOx generated at the time of burning the cement, thereby reducing NOx in the exhaust gas.

Although the ammonia-containing gas G2 discharged from the bag filter 5 may be directly blown into the cement manufacturing process, the distillation tower 6 or the adsorption tower effectively separates the ammonia gas and water vapor to concentrate the ammonia for use. Is more preferable. Concentrated ammonia can be used by adjusting the concentration according to the generation state of NOx, and can also be introduced as a gas or an aqueous solution.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[Confirmation of incineration ash sticking status]
500 g of municipal waste incineration ash (including 28 parts by weight of water relative to 100 parts by weight of solid content) discharged from the cleaning plant and accepted by the cement plant after transportation was collected, and CaO powder was exposed. A CaO/water ratio of 1 was added, and the mixture was rapidly mixed for 1 minute with an experimental mixing device (high power blender, manufactured by Waring Co.), and then aged for 3 hours. The modified ash thus obtained was dried in a dryer set at 105° C. until the loss on drying per hour was 0.1% or less, and the water content was calculated from the mass before and after drying. In addition, 100 g of the obtained modified ash was put into an experimental crusher (Wonder Blender, manufactured by Waring Co., Ltd.) assuming a pretreatment process for cement raw material, crushed at a rotation speed of 25000 rpm for 10 seconds, and then put into the crusher. Was visually evaluated. The results are shown in Table 1. In addition, the evaluation of the adhesion state is as follows.
×: A large amount of adhesion occurs in the crusher and sticks and cannot be peeled off Δ: A large amount of adhesion occurs in the crusher, but easily peels off when force or vibration is applied ○: Small amount of adhesion in the crusher Occurs, but does not affect crushing ◎: Almost no adhesion in the crusher

From Table 1, it was found that the condition of CaO/water ratio of 0.1 or less was not preferable for preventing sticking of incinerated ash, because adhesion to the crusher was observed frequently. When the CaO/water ratio was 0.2 or more, the amount adhering to the pulverizer tended to decrease, and the adhering condition improved as the CaO/water ratio increased. From these results, it was found that the CaO powder was added so that the CaO/water ratio was 0.2 or more to prevent the incineration ash from sticking and to efficiently pulverize the incineration ash.

[Measurement of ammonia generation from incineration ash mixed with anti-sticking material]
500 g of municipal waste incineration ash (containing 28 parts by weight of water relative to 100 parts by weight of solid content) discharged from the cleaning plant and received at the cement plant after transportation was collected, and CaO powder was added thereto. The CaO/water ratio shown in Table 2 below was added, and the mixture was rapidly mixed for 1 minute with an experimental mixing device (high power blender, manufactured by Waring Co.), and then aged in a closed container for 30 minutes. An ammonia detector tube (manufactured by Gastec Co., Ltd.) was inserted into the airtight container after aging, and the ammonia concentration in the gas generated by mixing was measured. In addition, a thermometer was inserted into the closed container during the aging period to measure the temperature inside the sample during the aging period. The results are shown in Table 2.

From Table 2, when the CaO/water ratio was 0.2 or more, the sample temperature increased and the ammonia concentration tended to increase. Further, it can be confirmed that the ammonia concentration sharply increases when the CaO/water ratio is 0.5 or more. From this, it was found that when the CaO/water ratio is 0.2 or more, the generated ammonia can be used as a denitration agent, and NOx can be reduced.

1 Incinerator ash treatment device 2 Incineration ash storage tank 3 Anti-sticking material storage tank 4 Mixing device 5 Bag filter 6 Distillation tower 7 Neutralization tank 8 Ammonia introduction device 9 Cement raw material pretreatment process

Claims (7)

Mix incineration ash with anti-sticking material,
Ammonia is recovered from the ammonia-containing gas generated during mixing,
A method for treating incinerated ash, which comprises introducing the recovered ammonia into a cement burning step. The method for treating incinerated ash according to claim 1, wherein the incinerated ash is main ash or fly ash generated when incinerating municipal solid waste or sewage sludge. The method for treating incinerated ash according to claim 1 or 2, wherein the anti-sticking material is an inorganic powder containing an oxide of an alkali metal or an alkaline earth metal. The incineration according to claim 3, wherein the inorganic powder containing an oxide of an alkali metal or an alkaline earth metal is a coarse powder recovered from quicklime, cement firing intermediate raw material or chlorine bypass dust. Ash treatment method. A mixing device for mixing the incineration ash and the anti-sticking material,
An ammonia recovery device for recovering ammonia from the ammonia-containing gas generated during mixing by the mixing device;
An incinerator ash treatment apparatus comprising: an ammonia introduction device that introduces the ammonia recovered by the ammonia recovery device into a cement calcination process. The incineration ash treatment device according to claim 5, wherein the ammonia recovery device is a distillation column or an adsorption column that removes water vapor from the ammonia-containing gas. 7. A dust collector that collects dust from the ammonia-containing gas is provided, and ammonia is recovered by the ammonia recovery device from the ammonia-containing gas that has been collected by the dust collector. Incinerator ash processing equipment.

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