JP2023056673A - Processing method for separating ammonia included in waste, method for recycling ammonia, method for producing cement raw material, and system for manufacturing cement - Google Patents

Abstract

To provide a processing method that effectively and efficiently can separate ammonia from ammonia-containing exhaust gas.SOLUTION: A processing method for separating ammonia included in waste comprises: an ammonia condensing step in which ammonia-containing exhaust gas is supplied to an absorption tower and the ammonia contained in the exhaust gas is condensed together with service water for absorption; a pH adjusting step in which pH of ammonia liquid including the ammonia condensed in the ammonia condensing step is adjusted to pH of alkali; an ammonia separating step in which ammonia included in the ammonia liquid is gasified and separated from the ammonia liquid having pH adjusted in the pH adjusting step; and a service water circulating step in which drainage water remaining after separating the ammonia in the ammonia separating step is neutralized and cyclically used as service water for absorption in the absorption tower.SELECTED DRAWING: None

Description

The present invention relates to a treatment method for separating ammonia contained in waste, an ammonia resource recycling method, a cement raw material recycling method, and a cement manufacturing system.

In recent years, ammonia has attracted attention as a medium for storing and transporting hydrogen energy (energy carrier), and preparation of a supply network has begun to be considered, and its use is expected to expand in the future. Since ammonia does not generate CO ₂ when burned, it is expected to be used as an alternative fuel for coal in kiln burners, in addition to being used as a conventional denitration agent in the cement manufacturing process.

In general, waste such as sewage sludge containing ammoniacal nitrogen is treated, for example, by receiving it in a cement factory and using it as a raw material for cement. Specifically, in the cement manufacturing process, there is a direct injection method that puts it into the kiln bottom or the calciner, or crushes the sludge with the extraction gas at the upper stage of the preheater, and the sludge that is dried by air current heating is put into the calciner. A flash drying method is known, in which the dry gas is fed back into the bottom cyclone and the dry gas is returned to the outlet of the bottom cyclone. However, in any of these methods, ammonia is regarded as a waste gas together with water vapor and other odorous components, and is regarded as a cause of reduced production efficiency and odor due to an increase in exhaust gas, and is not effectively utilized. In addition, if ammonia remains in the flue gas without being decomposed, it reacts with SO ₃ in the flue gas to form ammonium sulfate, which can become a factor that promotes the generation of white smoke and adhesion of ash to flue equipment.

As a technique for separating ammonia contained in waste, for example, Patent Document 1 discloses that ammonia nitrogen contained in waste water or treated waste water is released as ammonia gas by ammonia stripping, and this is treated with sulfuric acid. Disclosed is a treatment method in which, after collecting and forming an aqueous ammonium sulfate solution, this is transferred to an ammonia utilization facility, ammonia gas is released from the aqueous ammonium sulfate solution by ammonia stripping, and used for denitrification of exhaust gas containing nitrogen oxides. ing.

Further, for example, in Patent Document 2, ammonia is absorbed and fixed in a fixing agent from exhaust gas containing ammonia, the fixing agent that has been absorbed and fixed is heated, the separated ammonia is introduced into a combustion furnace or a cement burning furnace, and NO _X is released. A treatment method is disclosed that reduces and burns gaseous components.

Japanese Patent Application Laid-Open No. 2003-275540 JP 2015-63430 A

However, Patent Document 1 is not a method for separating ammonia from exhaust gas. Moreover, in Patent Document 2, ammonia is separated from exhaust gas by absorbing and fixing ammonia in a fixing agent, and then heating the fixing agent after absorption and fixing. The agent has a problem that it is difficult to exhibit adsorption performance in an environment with high humidity, and it is not suitable for an environment full of water vapor and other gases.

An object of the present invention is to provide a treatment method capable of effectively and efficiently separating ammonia from ammonia-containing exhaust gas. From another point of view, it is an object of the present invention to provide a cement manufacturing system that can effectively utilize ammonia-containing wet sludge as a resource and can suppress the diffusion of ammonia into the environment.

In order to achieve the above object, the present invention, in its first aspect, provides a treatment method for separating ammonia contained in waste, the treatment method having the following steps. .
(1) Ammonia condensation step of supplying ammonia-containing exhaust gas as the waste to the absorption tower and condensing the ammonia contained in the exhaust gas together with absorption water (2) Ammonia liquid containing the ammonia condensed in the ammonia condensation step (3) Ammonia separation step of vaporizing and separating ammonia contained in the ammonia solution from the ammonia solution pH-adjusted in the pH adjustment step (4) The ammonia separation step A water circulation step of neutralizing the waste water remaining after the ammonia is separated in and circulating it as absorption water in the absorption tower

According to the treatment method provided by the present invention, taking advantage of the fact that ammonia has a high solubility in water, ammonia is condensed from exhaust gas together with water for absorption in the absorption tower, and the ammonia solution is converted to an alkaline pH. Since ammonia is vaporized and separated after adjustment, ammonia can be effectively and efficiently separated from other components such as water vapor and odorous components contained in the waste. In addition, since the waste water remaining after vaporization of ammonia is recycled as service water used in the absorption tower, it is possible to reduce the amount of water used. Therefore, it also contributes to the reduction of the exhaust gas amount (water vapor amount) to the outside of the system.

In the above treatment method, an ammonia-containing waste liquid is added as another waste to at least one of the ammonia-containing ammonia condensed in the ammonia condensation step and the ammonia liquid alkali-adjusted in the pH adjustment step. In addition, the ammonia contained in the ammonia-containing waste liquid may be separated together with the ammonia contained in the ammonia-containing exhaust gas by performing alkali adjustment in the pH adjustment step. According to this, ammonia from ammonia-containing exhaust gas to be treated as waste, ammonia from ammonia-containing waste liquid such as methane fermentation digestive liquid as other waste, and ammonia derived from each are treated together, can be separated.

In the above treatment method, an ammonia stripping device may be used in the ammonia separation step. According to this, an existing apparatus system can be used for vaporization and separation of ammonia.

In the above treatment method, in the ammonia condensation step, the absorption tower exhaust gas discharged from the absorption tower may be used as the gas to be blown into the ammonia stripping device. According to this, the exhaust gas discharged from the absorption tower can be used to replace the steam and heated air required for the ammonia stripping device. Therefore, it contributes to the reduction of the energy used.

In the above treatment method, the neutralization of the wastewater in the water circulation step may be performed using kiln exhaust gas or chlorine bypass exhaust gas from a cement manufacturing facility. According to this, these exhaust gases contain CO ₂ and generate carbonate ions when dissolved in water. By using this for neutralization, the cost of using the neutralizing agent can be reduced. . Further, when adjusting to alkalinity in the pH adjusting step using a pH adjusting agent containing Ca such as lime, CO ₂ contained in the exhaust gas can be fixed as calcium carbonate. In addition, since the sulfur contained in the exhaust gas reacts with the precipitated calcium carbonate, a desulfurization effect can also be obtained.

In the above treatment method, in the pH adjustment step, a recycled resource containing a water-soluble alkaline component may be used as a pH adjuster for adjusting the pH. According to this, the cost of using the pH adjuster can be reduced. In addition, when using woody biomass combustion ash, chlorine bypass dust (high in alkali content such as K ₂ O, Na ₂ O, CaO, especially potassium), etc. as recycled resources containing water-soluble alkaline components, It also has the effect of washing repellent components (potassium, chlorine, etc.) with water when using recycled resources as raw materials for cement.

In the above treatment method, in the pH adjusting step, a pH adjusting agent containing quicklime may be used for adjusting the pH. According to this, the volatilization of ammonia is accelerated by the heat of reaction, and vaporization and separation from the ammonia liquid are likely to occur. In addition, when using recycled resources containing quicklime such as woody biomass combustion ash and chlorine bypass dust (high in alkali content such as K ₂ O, Na ₂ O and CaO, especially potassium), the recycled resources can be used as cement. It also has the effect of washing away repellent ingredients (potassium, chlorine, etc.) in raw materials.

In the above treatment method, the ammonia contained in the ammonia solution volatilizes due to the heat of reaction with the pH adjuster in the pH adjustment step, so that the ammonia is vaporized and separated in the ammonia separation step. good. According to this, the pH adjustment of the ammonia solution to alkalinity and the step of vaporizing and separating ammonia from the ammonia solution after the alkali adjustment can both be performed in the pH adjustment tank, and the system for realizing the treatment. The configuration can be simplified.

In addition, in its second aspect, the present invention provides a method for recycling ammonia, which utilizes the ammonia separated by the above treatment method as a fuel resource for a kiln of a cement manufacturing facility.

According to the ammonia resource recycling method, the separated ammonia can be effectively utilized.

Furthermore, in the third aspect of the present invention, the precipitate containing Ca generated by the pH adjustment step in the above treatment method is put into a kiln kiln bottom or a calciner of a cement manufacturing facility to produce another clinker raw material. To provide a method for making cement raw material by sintering together.

According to the cement raw material conversion method, when adjusting the alkalinity in the pH adjustment step using a recycled resource containing Ca such as lime, a precipitate containing Ca is generated in the pH adjustment step. This can be effectively utilized as a raw material for cement. In addition, an effect of washing away repellent components such as potassium and chlorine from the recycled resource can be obtained, and the utilization of the recycled resource as a raw material for cement can be promoted.

On the other hand, in its fourth aspect, the present invention provides a cement manufacturing system comprising a kiln for introducing a clinker raw material and firing cement clinker, further comprising drying wet sludge containing ammonia to obtain dry sludge. and an ammonia separation system for treating the ammonia-containing exhaust gas discharged from the drying system to separate the ammonia, and introducing the dried sludge into the kiln as the clinker raw material for fuel. and/or recycling ammonia as a raw material for cement, and introducing the ammonia separated by the ammonia separation system into the kiln and recycling it as fuel.

In this case, in the cement manufacturing system according to the fourth aspect, the ammonia separation system is based on the above-described treatment method for separating ammonia contained in the waste, and the ammonia-containing exhaust gas in the treatment method is Preferably, it is arranged to treat the ammonia-containing exhaust gas discharged from the drying system.

On the other hand, in its fifth aspect, the present invention provides a cement manufacturing system comprising a kiln for introducing a clinker raw material and firing cement clinker, further comprising drying wet sludge containing ammonia to obtain dry sludge. a system, an ammonia separation system for treating the ammonia-containing exhaust gas discharged from the drying system to separate the ammonia, and a methane fermentation system for producing an ammonia-containing digestive juice, wherein the dried sludge is is introduced into the kiln as the clinker raw material and recycled as fuel and / or cement raw material, and the ammonia derived from the wet sludge and the ammonia derived from the methane fermentation system separated by the ammonia separation system are used as the To provide a cement manufacturing system introduced into a kiln and recycled as fuel.

In this case, in the cement manufacturing system according to the fifth aspect, the ammonia separation system, in the treatment method for separating the ammonia contained in the waste, separates the ammonium-containing waste liquid in addition to the ammonia-containing exhaust gas. The ammonia-containing exhaust gas in the treatment method is the ammonia-containing exhaust gas discharged from the drying system, and the ammonia-containing waste liquid in the treatment method is the methane fermentation. Preferably, the system is configured to process digestive juices produced.

According to the treatment method provided by the present invention, ammonia can be effectively and efficiently separated from ammonia-containing exhaust gas.

According to the cement production system provided by the present invention, the ammonia-containing wet sludge can be effectively used as a resource, and the diffusion of ammonia into the environment can be suppressed.

1 is a flow diagram illustrating one embodiment of a treatment method for separating ammonia contained in waste provided by the present invention; FIG. FIG. 2 is a flow diagram illustrating another embodiment of a treatment method for separating ammonia contained in waste provided by the present invention; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram showing one embodiment for utilizing a treatment method for separating ammonia contained in waste provided by the present invention for manufacturing cement. FIG. 2 is a schematic configuration explanatory diagram showing another embodiment for utilizing the treatment method for separating ammonia contained in waste provided by the present invention for manufacturing cement. FIG. 10 is a schematic configuration explanatory diagram showing still another embodiment for utilizing the treatment method for separating ammonia contained in waste provided by the present invention for manufacturing cement. FIG. 3 is a schematic configuration explanatory diagram showing still another embodiment for utilizing the treatment method for separating ammonia contained in waste provided by the present invention for manufacturing cement.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings.

FIG. 1 shows a flow diagram for explaining one embodiment of a processing method according to the present invention.

As shown in FIG. 1, in the treatment method according to the present invention, first, an ammonia-containing exhaust gas G1 and absorption water W1 are combined to condense the ammonia contained in the exhaust gas G1 (step "S1" in the figure). . That is, by utilizing the high solubility of ammonia in water, the ammonia contained in the exhaust gas G1 is transferred to the liquid phase of the absorption water W1 to obtain an ammonia liquid containing ammonia. This ammonia condensing step can be done by, but not limited to, means commonly referred to as an absorber tower. In a typical absorber tower configuration, the blow gas is introduced through an inlet at the bottom of the absorber tower, and the blow gas flows upward or sideways inside the tower. On the other hand, absorption water is introduced through spray nozzles having a plurality of liquid spray nozzles installed in the tower top, tower wall, or in multiple stages so that the inside of the tower is sprayed. Since the contacted ammonia dissolves and migrates to the absorption water side at the gas-liquid interface to become an ammonia liquid, it is stored in the lower part of the absorption tower or is discharged from a separately provided discharge port.

Next, the pH of the ammonia solution formed in the ammonia condensation step is adjusted to alkaline (step "S2" in the figure). This facilitates vaporization of ammonia in the liquid. Examples of the alkali agent (pH adjuster) to be used include, but are not limited to, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide (slaked lime), and the like. Moreover, the form of use of these alkaline agents may be any of an aqueous solution, a slurry, and the like. Alternatively, water-soluble alkaline components such as woody biomass combustion ash, chlorine bypass dust (high in alkali content such as K ₂ O, Na ₂ O, CaO, especially potassium), waste alkali, waste glass (soda lime glass), etc. Recycled resources may be used. The pH after alkali adjustment is preferably adjusted to pH 10 or higher, particularly pH 10.5 to 12.

Next, the ammonia contained in the ammonia solution is vaporized and separated from the ammonia solution whose pH has been adjusted to alkaline in the pH adjustment step (step “S3” in the figure). As described above, when the pH of the solution is adjusted to alkaline, ammonia is easily vaporized. Ammonia with increased purity can be separated. This ammonia separation step is not limited, but can be carried out, for example, by a normal gas-liquid contact method using a bubble column, a packed column, a plate column or the like. Alternatively, it can be done by means commonly referred to as an ammonia stripper. In a typical ammonia stripping unit, the blow gas is introduced through the lower inlet of the absorber tower and the blow gas is caused to flow upward or sideways inside the tower. On the other hand, the ammonia liquid is introduced through a spray nozzle having a plurality of liquid spray nozzles installed in the top part, the wall of the tower, or in multiple stages so that the ammonia liquid is sprayed inside the tower. The contacting ammonia evaporates and migrates to the blown gas side at the gas-liquid interface and becomes a gas containing ammonia, which is discharged from an exhaust port separately provided at the top.

Generally, the vaporization efficiency of materials in the gas-liquid contact method is said to be affected by the temperature, pH, etc. of the raw water. That is, since the mass transfer occurs at the gas-liquid interface, the index is how large the gas-liquid interface can be, and for example, the condition that the gas-liquid ratio is in the range of 300 to 5000 is a guideline. Here, the gas-liquid ratio is the ratio (G/L) between the amount of gas supplied to the apparatus (G [m ³ /h]) and the amount of waste water (L [m ³ /h]). Also, in order to facilitate the vaporization of ammonia, it is effective to increase the water temperature of the waste water and adjust the pH to alkaline. Therefore, if the temperature of the gas to be supplied is low, the temperature of the water will decrease and the vaporization efficiency of ammonia will decrease. The temperature is desirably equal to or higher than the raw water temperature, and particularly preferably equal to or higher than 25°C.

As shown in FIG. 1, in the treatment method according to the present invention, waste water W2 remaining after ammonia is separated in the ammonia separation step is neutralized and circulated as absorption water W1 to be supplied to the ammonia condensation step. I am trying to use it (step "S4" in the figure). As a result, although the absorption water W1 is required for the condensation of ammonia from the exhaust gas G1, the total amount of water used can be suppressed by recycling it. It also contributes to the reduction of the exhaust gas amount (water vapor amount) to the outside of the system. Examples of neutralizing agents to be used include, but are not limited to, sulfuric acid, hydrochloric acid, and the like. Moreover, the form of use of these neutralizers may be either an aqueous solution, a slurry, or the like. Alternatively, kiln off-gas and chlorine bypass off-gas in cement production facilities contain CO ₂ which, when dissolved in water, produces carbonate ions, which can be used for neutralization. The pH after neutralization is preferably adjusted to pH 8 or less, particularly pH 7 or less.

It should be noted that the absorption water W1 to be circulated may be appropriately discharged to the outside of the system as blow water, or part or all of it may be replaced with fresh absorption water in order to maintain freshness. Fresh absorption water may be added. As the absorption water, water may be used, and water to which sulfuric acid, hydrochloric acid, boric acid, phosphoric acid or the like may be optionally added may be used as necessary. The inorganic salt lowers the pH of the absorption water, thereby increasing the absorption efficiency of ammonia.

The separated ammonia can be appropriately recovered and used. For example, the ammonia-containing gas discharged from an ammonia stripping device or the like is dehumidified through a collection tower or piping, and if necessary, through a partial condenser, and the gas is used as fuel for a kiln of a cement manufacturing facility. It can be used as a resource. Alternatively, it may be absorbed and immobilized by an ammonia-fixing agent such as activated carbon, zeolite, silica gel, magnesium chloride or calcium chloride, or may be recovered in an ammonia recovery liquid such as a sulfuric acid solution or a phosphoric acid solution.

The ammonia-containing exhaust gas G1 to be introduced and treated in the treatment method according to the present invention is not particularly limited as long as it contains ammonia nitrogen. Examples include dry gas of organic sludge generated in equipment for treating organically polluted wastewater.

FIG. 2 shows a flow diagram illustrating another embodiment of the processing method according to the present invention.

As shown in FIG. 2, in this embodiment, the ammonia-containing waste liquid W3 is further treated in the embodiment described in FIG. Specifically, the ammonia-containing waste liquid W3 is added to the ammonia solution obtained in the ammonia condensation step and/or the ammonia solution alkali-adjusted in the pH adjustment step, and the pH to the alkali in the pH adjustment step making adjustments. As a result, the ammonia-containing waste liquid W3 is treated together with the ammonia-containing exhaust gas G1, so that ammonia is separated from both the exhaust gas G1 and the waste liquid W3.

The ammonia-containing waste liquid W3 to be introduced and treated in the treatment method according to the present invention is not particularly limited as long as it contains ammonia nitrogen. Examples include thermal power plants, chemical plants, amine production plants, and food production plants. , industrial wastewater discharged from cement plants and the like, night soil, domestic wastewater such as urban sewage, treated wastewater such as activated sludge treated water, digested sludge treated water, and the like.

FIG. 3 shows an embodiment for applying the treatment method according to the invention to cement production. In the embodiment shown in FIG. 3, a cement manufacturing system comprising a kiln for introducing a clinker raw material and firing a cement clinker further comprises a drying system for drying wet sludge containing ammonia into dry sludge, and the drying system. and an ammonia separation system for treating the ammonia-containing exhaust gas discharged from the system and separating the ammonia, and the dry sludge obtained in the drying system and the ammonia separated by the ammonia separation system. is introduced into a kiln for introducing a clinker raw material and firing cement clinker. Further details will be described below.

(drying system)
Ammonia nitrogen-containing sludge such as sewage sludge that is usually brought in to be treated at a cement plant is in a wet state with a moisture content of about 70 to 80%. For this purpose, the clinker is dried to a moisture content of 20% or less, put into the bottom of the kiln, and fired together with other clinker raw materials. In the embodiment shown in FIG. 3, steam, gas, or hot air is introduced into the drying device 1 as a heat source for drying to evaporate the water content of the wet sludge to obtain dry sludge. As the drying device 1, a plate heat exchanger, a shell and tube heat exchanger, a shell and plate heat exchanger, or the like can be used. According to these indirect drying, steam or gas is not blown directly onto the sludge to dry it (direct drying), but only the heat of the steam is used to dry the sludge using a heat exchanger, etc. It does not increase the amount of exhaust gas (water vapor amount).

(Ammonia separation system)
Normally, when ammoniacal nitrogen-containing sludge such as sewage sludge brought in to be treated at a cement plant is made into dried sludge, the exhaust gas from the drying equipment contains ammonia, odorous components, water vapor, and the like. Therefore, in the embodiment shown in FIG. 3, the structure of the absorption tower 2, the pH adjustment tank 3, and the ammonia separation device 4 separates ammonia from this.

First, the exhaust gas from the drying apparatus 1 is introduced from the inlet provided at the bottom of the absorption tower 2, and an ascending current is generated inside the cylinder by the blown gas. On the other hand, the absorption water W1 is introduced from above the tubular interior through an injection nozzle having a plurality of nozzles, and is sprayed from above. As described above, the contacted ammonia dissolves and migrates to the absorption water side at the gas-liquid interface to become an ammonia-containing ammonia liquid, which is taken out from the outlet separately provided at the bottom of the absorption tower, It is made to accumulate in the pH adjustment tank 3.

Next, in the pH adjustment tank 3, as described above, the pH of the ammonia solution is adjusted to alkalinity under arbitrary conditions. In addition, the pH adjusting tank 3 may be provided with a device for stirring or heating the stored liquid as required. Then, the ammonia liquid that has been treated in the pH adjusting tank 3 is introduced into the ammonia separator 4 .

Finally, the ammonia separator 4 separates ammonia. In this embodiment, the blowing gas is introduced from the introduction port provided below the ammonia separation device 4, and an upward current is generated by the blowing gas inside the cylinder. On the other hand, the ammonia solution that has been treated in the pH adjustment tank 3 is introduced from above the tubular interior through an injection nozzle having a plurality of nozzles, and is sprayed from above. As described above, the contacting ammonia vaporizes and migrates to the blown gas side at the gas-liquid interface and becomes a gas containing ammonia, which is taken out from an outlet separately arranged in the upper part of the absorption tower. ing.

In the embodiment shown in FIG. 3, the ammonia-containing gas discharged from the ammonia separator 4 is fed into the front of the kiln as it is. Dried sludge dried by the drying device 1 is introduced into the kiln 5 from the bottom of the kiln kiln and fired together with other clinker raw materials. Air warmed by heat exchange is introduced, and together with the ammonia-containing gas introduced in front of the kiln 5, assists the clinker firing. Main fuel sources for the kiln 5 include coal, heavy oil, recycled oil, and waste plastics.

(Absorptive water circulation system)
As shown in FIG. 3, in this embodiment, waste water remaining after ammonia is separated is taken out to the treatment tank 7 and neutralized. The processing bath 7 may be provided with a device for stirring or heating the stored liquid as required. After the treatment in the treatment tank 7, the waste water is returned to the absorption tower 2 and recycled as absorption water W1 to be supplied to the absorption tower 2. In addition, by discharging the surplus to the outside of the system as blow water, the amount of the absorption water W1 to be recycled can be adjusted.

As noted above, neutralizing agents that may be used include, but are not limited to, sulfuric acid, hydrochloric acid, and the like. Moreover, the form of use of these neutralizers may be either an aqueous solution, a slurry, or the like. Alternatively, kiln off-gas and chlorine bypass off-gas in cement production facilities contain CO ₂ which, when dissolved in water, produces carbonate ions, which can be used for neutralization. The pH after neutralization is preferably adjusted to pH 8 or less, particularly pH 7 or less.

In the embodiment shown in FIG. 3, the neutralization treatment is performed by a tank method using the treatment tank 7, but it may be performed by a method other than the tank method _. An in-line method by injecting the exhaust gas may be used. In addition, the wastewater remaining after the ammonia is separated may be subjected to other treatment besides neutralization if necessary. For example, it may be stored in a coagulating sedimentation tank for a predetermined time. to remove suspended matter (SS content). Further, a treatment for removing phosphorus may be applied. A common phosphorus treatment method includes a coagulation sedimentation method in which an aluminum salt or an iron salt is added as a coagulant.

FIG. 4 shows another embodiment for applying the treatment method according to the invention to cement production. In the embodiment shown in FIG. 4, a cement manufacturing system comprising a kiln for introducing a clinker raw material and firing cement clinker further comprises a drying system for drying wet sludge containing ammonia into dry sludge; An ammonia separation system for treating the exhaust gas containing ammonia discharged from the system to separate the ammonia, and a methane fermentation system for producing a digestive juice containing ammonia, and the The dried sludge and the ammonia derived from the wet sludge and the ammonia derived from the methane fermentation system separated by the ammonia separation system are introduced into a kiln for introducing a clinker raw material and firing cement clinker. Further details will be described below.

(Methane fermentation system)
As shown in FIG. 4, this embodiment further includes a methane fermentation tank 8 and a solid-liquid separator 9 in addition to the embodiment described in FIG. Since the fermented digestive juice produced by methane fermentation contains a high concentration of ammonia, the digestive juice from the methane fermentation tank 8 is solid-liquid separated by the solid-liquid separator 9, and the liquid portion is stored in the pH control tank 3. I'm trying to be

In the embodiment shown in FIG. 4, in the pH adjustment tank 3, the ammonia liquid from the absorption tower 2 and the liquid portion derived from the digestive juice from the methane fermentation system are mixed to adjust the pH to alkaline. I have to. In subsequent steps, ammonia is separated in the same manner, and the ammonia-containing gas discharged from the ammonia separator 4 is introduced into the front of the kiln 5 .

FIG. 5 shows yet another embodiment for applying the treatment method according to the invention to cement production. In the embodiment shown in FIG. 5, in addition to the embodiment described in FIG. 3 or FIG. 4, there is provided an equipment configuration that can be arbitrarily added according to need.

For example, a dehydrator 10 for dehydrating the contents taken out from the layer to obtain a solid portion is provided in the subsequent stage of the pH adjusting tank 3 . For example, but not limited to, recycled resources containing a water-soluble alkaline component as a pH adjuster include woody biomass combustion ash, chlorine bypass dust (alkali content such as K ₂ O, Na ₂ O, CaO, particularly high in potassium), etc. is used, a precipitate derived from the recycled resource is generated in the pH adjustment tank 3, so this is taken out and a cake is obtained by the dehydrator 10, introduced into the kiln bottom of the kiln 5, and used as a cement raw material. Can be recycled. It also has the effect of washing away potassium, chlorine, etc., which are repellent components when used as raw materials for cement. Note that the liquid portion generated by dehydration may be returned to the pH adjustment tank 3 .

Further, the kiln exhaust gas (containing CO ₂ ) discharged from the kiln 5 into the treatment tank 7 is introduced into the liquid in the tank through an air diffuser 11 by bubbling. This exhaust gas contains CO ₂ and produces carbonate ions when it dissolves in water, so it can be used to neutralize waste water discharged from the ammonia separator and remaining after ammonia is separated. and the cost of using the neutralizer can be reduced. Further, although not limited, when adjustment to alkalinity in the pH adjustment step is performed using a pH adjuster containing Ca such as lime, CO ₂ contained in the exhaust gas can be fixed as calcium carbonate. In addition, since the sulfur contained in the exhaust gas reacts with the precipitated calcium carbonate, a desulfurization effect can also be obtained.

Further, the absorption tower exhaust gas discharged from the absorption tower 2 is heated by the heating device 12 and then used as the blown gas to be introduced into the ammonia separation device 4 . As a result, it is possible to replace the steam and heated air required for the equipment, which contributes to the reduction of energy consumption.

Further, the ammonia-containing gas discharged from the ammonia separator 4 is dehumidified by the partial condensation device 13 before being introduced into the kiln 5 . It should be noted that moisture due to dehumidification may be discharged to the treatment tank 7 .

FIG. 6 shows yet another embodiment for applying the treatment method according to the invention to cement production. In the embodiment shown in FIG. 6, the ammonia separation device 4 provided in the system is not provided in the embodiments described in FIGS. 3 to 5, and ammonia is separated in the pH adjustment tank 3. Specifically, when limestone or the like is used as a pH adjuster, high heat of reaction is generated, and the heat of reaction volatilizes the ammonia contained in the ammonia solution whose pH has been adjusted to alkalinity in the pH adjustment tank 3. Since vaporization separation is performed, this is recovered and introduced into the kiln 5. In this case, the pH is 11 to 12 when the temperature of the ammonia solution is 20 to 30°C, 10.5 to 11.5 when it is 30 to 40°C, and 10 to 11 when it is 40 to 50°C. If the temperature is 50° C. or higher, it is preferable to adjust the pH to 9.5 to 10.5. Alternatively, a gas such as air may be heated as necessary and then introduced into the pH adjustment tank 3 through the air diffuser 14 to bubble through the ammonia liquid stored in the bed. This promotes vaporization of ammonia. In the embodiment shown in FIG. 6, the absorption tower exhaust gas discharged from the absorption tower 2 is heated by the heating device 12 and introduced into the liquid in the pH adjustment tank 3 through the air diffusion device 14 by bubbling. 5, the kiln exhaust gas (containing CO ₂ ) discharged from the kiln 5 into the processing tank 7 is introduced into the liquid in the tank through the air diffuser 11 by bubbling. Further, the ammonia-containing gas discharged from the ammonia separator 4 is dehumidified by the partial condensation device 13 before being introduced into the kiln 5 . It should be noted that moisture due to dehumidification may be discharged to the treatment tank 7 .

The present invention is not limited to the above-described embodiments, and various combinations and modifications within the scope disclosed herein are possible, and such embodiments are also within the technical scope of the present invention. It is included.

DESCRIPTION OF SYMBOLS 1... Drying apparatus, 2... Absorption tower, 3... pH adjustment tank, 4... Ammonia separation apparatus, 5... Kiln, 6... Cooler, 7... Treatment tank, 8... Methane fermentation tank, 9... Solid-liquid separation apparatus, 10... Dehydrator 11, 14 Air diffuser 12 Heating device 13 Partial condensation device

Claims (14)

A treatment method for separating ammonia contained in waste, said treatment method comprising the following steps.
(1) Ammonia condensation step of supplying ammonia-containing exhaust gas as the waste to the absorption tower and condensing the ammonia contained in the exhaust gas together with absorption water (2) Ammonia liquid containing the ammonia condensed in the ammonia condensation step (3) Ammonia separation step of vaporizing and separating ammonia contained in the ammonia solution from the ammonia solution pH-adjusted in the pH adjustment step (4) The ammonia separation step A water circulation step of neutralizing the waste water remaining after the ammonia is separated in and circulating it as absorption water in the absorption tower Ammonia-containing waste liquid is added as another waste to at least one of the ammonia liquid containing ammonia condensed in the ammonia condensation step and the ammonia liquid alkali-adjusted in the pH adjustment step, and the pH adjustment is performed. 2. The treatment method according to claim 1, wherein alkali adjustment is performed in the process to separate the ammonia contained in the ammonia-containing waste liquid together with the ammonia contained in the ammonia-containing exhaust gas. 3. The treatment method according to claim 1, wherein an ammonia stripping device is used in said ammonia separation step. 4. The treatment method according to claim 3, wherein in said ammonia condensation step, an absorption tower exhaust gas discharged from said absorption tower is used as a blowing gas in said ammonia stripping device. The treatment method according to any one of claims 1 to 4, wherein the neutralization of the wastewater in the water circulation step is performed using kiln exhaust gas or chlorine bypass exhaust gas from a cement manufacturing facility. The treatment method according to any one of claims 1 to 5, wherein in the pH adjustment step, a recycled resource containing a water-soluble alkaline component is used as a pH adjuster for adjusting the pH. The treatment method according to any one of claims 1 to 6, wherein in the pH adjustment step, one containing quicklime is used as a pH adjuster for adjusting the pH. 8. The treatment method according to claim 7, wherein said ammonia is vaporized and separated in said ammonia separation step by volatilizing ammonia contained in said ammonia solution due to reaction heat with said pH adjuster in said pH adjustment step. A method for recycling ammonia, wherein the ammonia separated by the treatment method according to any one of claims 1 to 8 is used as a fuel resource for a kiln of a cement manufacturing facility. Cement raw material, wherein the Ca-containing precipitate generated by the pH adjustment step in the treatment method according to any one of claims 6 to 8 is put into a kiln kiln bottom or a calciner of a cement manufacturing facility and fired together with other clinker raw materials. conversion method. In a cement manufacturing system equipped with a kiln for introducing a clinker raw material and firing cement clinker,
Furthermore, a drying system that dries wet sludge containing ammonia to obtain dry sludge, and an ammonia separation system for treating the exhaust gas containing ammonia discharged from the drying system and separating the ammonia, The dried sludge is introduced into the kiln as the clinker raw material and recycled as fuel and/or cement raw material, and the ammonia separated by the ammonia separation system is introduced into the kiln and recycled as fuel. and cement production system. In a cement manufacturing system equipped with a kiln for introducing a clinker raw material and firing cement clinker,
Furthermore, a drying system for drying wet sludge containing ammonia to obtain dry sludge, an ammonia separation system for treating the exhaust gas containing ammonia discharged from the drying system to separate the ammonia, and ammonia a methane fermentation system that produces a digestive juice containing the dried sludge, introduced into the kiln as the clinker raw material to be recycled as fuel and/or cement raw material, and separated by the ammonia separation system, A cement manufacturing system in which ammonia derived from wet sludge and ammonia derived from the methane fermentation system are introduced into the kiln and recycled as fuel. The ammonia separation system is according to the treatment method of claims 1 to 8, and the ammonia-containing exhaust gas discharged from the drying system is treated as the ammonia-containing exhaust gas in the treatment method. Item 12. The cement production system according to item 11. The ammonia separation system is according to the treatment method of claim 2, and treats an ammonia-containing exhaust gas discharged from the drying system as the ammonia-containing exhaust gas of the treatment method. 13. The cement manufacturing system according to claim 12, wherein the digestive juice generated in the methane fermentation system is treated as the ammonia-containing waste liquid.

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