Processing method for separation of ammonia included in waste, ammonia recycling method, cement raw material conversion method, and cement production system

Abstract

To provide a cement production system that can effectively recycle a wet sludge including ammonia and also suppress dissipation of ammonia to the environment.SOLUTION: In a cement production system that includes a kiln for introducing a clinker raw material and firing cement clinker, the cement production system further includes a drying system for drying a wet sludge including ammonia to obtain a dry sludge, and an ammonia separation system for processing an exhaust gas including the ammonia discharged from the drying system to separate the ammonia, wherein the dry sludge is introduced into the kiln as the clinker raw material and is recycled as a fuel and / or a cement raw material, and the ammonia separated by the ammonia separation system is introduced into the kiln and recycled as a fuel.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a treatment method for separating ammonia contained in waste, a method for converting ammonia into a resource, a method for converting ammonia into a cement raw material, and a cement production system. [Background technology]

[0002] In recent years, ammonia has attracted attention as a storage and transportation medium for hydrogen energy (energy carrier), and the development of a supply network has begun to be considered, with its use expected to expand in the future. As ammonia does not emit CO2 when burned, it is expected to be used as an alternative fuel to coal in kiln burners in addition to its use as a conventional denitrification agent in the cement manufacturing process.

[0003] Generally, waste materials containing ammonia nitrogen, such as sewage sludge, are treated at cement plants for use as cement raw material. Specifically, in the cement production process, direct charging is used to feed the kiln end or calciner, while flash drying is used. This involves crushing the sludge together with the extracted gas from the upper stage of the preheater, drying it with a flash, and then feeding the resulting dried sludge into the calciner, with the resulting dried gas returned to the bottom cyclone outlet. However, in both methods, ammonia, along with water vapor and other odorous components, is considered a waste gas, reducing production efficiency and contributing to odors. Furthermore, if ammonia remains in the flue gas without being decomposed, it reacts with SO3 in the flue gas to produce ammonium sulfate, which can contribute to white smoke and ash deposition on flue equipment.

[0004] As a technique for separating ammonia contained in waste, for example, Patent Document 1 discloses a treatment method in which ammonia nitrogen contained in wastewater or treated wastewater is released as ammonia gas by ammonia stripping, and this is captured with sulfuric acid to form an ammonium sulfate aqueous solution, which is then transported to an ammonia utilization facility, and ammonia gas is released from the ammonium sulfate aqueous solution by ammonia stripping, and the ammonia gas is used for denitrification of exhaust gas containing nitrogen oxides.

[0005] For example, Patent Document 2 discloses a method for producing ammonia by absorbing and fixing ammonia from exhaust gas containing ammonia in a fixing agent, heating the fixing agent, and introducing the separated ammonia into a combustion furnace or a cement burning furnace. X A treatment method is disclosed in which the gas components are burned while reducing the carbon dioxide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-275540 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-63430 Summary of the Invention [Problem to be solved by the invention]

[0007] However, Patent Document 1 does not describe a method for separating ammonia from exhaust gas. Furthermore, Patent Document 2 describes a method for separating ammonia by absorbing and immobilizing ammonia from exhaust gas in an immobilizing agent, and then heating the immobilizing agent after absorption and immobilization. However, there is a problem that general adsorbents such as zeolite and activated carbon do not easily exhibit their adsorption performance in a high humidity environment, and are not suitable for environments filled with water vapor or other gases.

[0008] An object of the present invention is to provide a treatment method capable of effectively and efficiently separating ammonia from an ammonia-containing exhaust gas. Another object of the present invention is to provide a cement production system that can effectively utilize the resource of ammonia-containing wet sludge and suppress the dissipation of ammonia into the environment. [Means for solving the problem]

[0009] In order to achieve the above object, in a first aspect, the present invention provides a treatment method for separating ammonia contained in waste, the treatment method comprising the following steps: (1) an ammonia condensation step in which an ammonia-containing exhaust gas is supplied as the waste to an absorption tower and the ammonia contained in the exhaust gas is condensed together with absorption water; (2) a pH adjustment step of adjusting the pH of the ammonia liquid containing the ammonia condensed in the ammonia condensation step to alkaline. (3) an ammonia separation step in which the ammonia contained in the ammonia liquid whose pH has been adjusted in the pH adjustment step is vaporized and separated; (4) a water circulation process in which the wastewater remaining after the ammonia has been separated in the ammonia separation process is neutralized and recycled as absorption water in the absorption tower.

[0010] The treatment method provided by the present invention takes advantage of the high solubility of ammonia in water to condense ammonia from exhaust gas together with absorption water in an absorption tower, adjust the pH of the ammonia solution to an alkaline value, and then vaporize and separate the ammonia, thereby effectively and efficiently separating ammonia from other components contained in the waste, such as water vapor and odorous components. Furthermore, the wastewater remaining after vaporization of ammonia is recycled and reused as water for the absorption tower, thereby reducing the amount of water used. This also contributes to reducing the amount of exhaust gas (water vapor) discharged outside the system.

[0011] In the above treatment method, an ammonia-containing waste liquid may be added as another waste material to at least one of the ammonia liquid containing ammonia condensed in the ammonia condensing step and the ammonia liquid alkali-adjusted in the pH adjusting step, and then the alkali-adjustment in the pH adjusting step is performed to separate the ammonia contained in the ammonia-containing exhaust gas and the ammonia contained in the ammonia-containing waste liquid. This makes it possible to treat and separate ammonia derived from the ammonia-containing exhaust gas treated as waste and ammonia derived from the ammonia-containing waste liquid, such as methane fermentation digestate, as other waste material.

[0012] In the above-described treatment method, an ammonia stripping unit may be used in the ammonia separation step, which allows the use of an existing equipment system for vaporizing and separating ammonia.

[0013] In the above treatment method, in the ammonia condensation step, the absorber exhaust gas discharged from the absorber may be used as a gas blown into the ammonia stripping unit. This allows the exhaust gas discharged from the absorber to be used as a substitute for steam and heated air required in the ammonia stripping unit, thereby contributing to a reduction in energy consumption.

[0014] In the above treatment method, the neutralization of the wastewater in the water circulation process may be performed using kiln exhaust gas or chlorine bypass exhaust gas from a cement manufacturing facility. These exhaust gases contain CO2, which generates carbonate ions when dissolved in water. By using this for neutralization, the cost of using a neutralizing agent can be reduced. Furthermore, if a pH adjuster containing calcium, such as lime, is used to adjust the pH to alkaline in the pH adjustment process, the CO2 contained in the exhaust gas can be immobilized as calcium carbonate. Additionally, the sulfur contained in the exhaust gas reacts with the precipitated calcium carbonate, resulting in a desulfurization effect.

[0015] In the above-described treatment method, a recycled resource containing a water-soluble alkaline component may be used as a pH adjuster for adjusting the pH in the pH adjustment step. This reduces the cost of using the pH adjuster. Furthermore, when using recycled resources containing water-soluble alkaline components such as woody biomass combustion ash or chlorine bypass dust (high in alkalis, particularly potassium, such as KO, NaO, and CaO), this method also has the effect of washing away repulsive components (potassium, chlorine, etc.) that may be harmful when converting the recycled resource into cement raw material.

[0016] In the above-described treatment method, the pH adjustment step may use a pH adjuster containing quicklime. This promotes the volatilization of ammonia due to the heat of reaction, facilitating vaporization and separation from the ammonia liquid. Furthermore, when using recycled resources containing quicklime, such as woody biomass combustion ash or chlorine bypass dust (high in alkalis, particularly potassium, such as KO, NaO, and CaO), this method also has the effect of washing away repulsive components (potassium, chlorine, etc.) from the recycled resources when they are used as cement raw materials.

[0017] In the above treatment method, the ammonia contained in the ammonia liquid may be volatilized by the heat of reaction with the pH adjuster in the pH adjustment step, thereby vaporizing and separating the ammonia in the ammonia separation step. This allows both the pH adjustment of the ammonia liquid to an alkaline state and the step of vaporizing and separating the ammonia from the alkaline-adjusted ammonia liquid to be performed in the pH adjustment tank, thereby simplifying the system configuration for achieving the treatment.

[0018] In addition, in a second aspect, the present invention provides a method for recovering ammonia as a resource, in which the ammonia separated by the above-mentioned treatment method is used as a fuel resource for a kiln in a cement manufacturing facility.

[0019] According to the above-described method for recovering ammonia as a resource, the separated ammonia can be effectively utilized.

[0020] Furthermore, in a third aspect, the present invention provides a method for producing a Ca-containing precipitate produced by the pH adjustment step in the above-described treatment method as a cement raw material, which comprises charging the Ca-containing precipitate into the kiln bottom or a calciner of a cement production facility and firing it together with other clinker raw materials.

[0021] According to the above-mentioned cement raw material production method, when the pH adjustment step uses recycled resources containing calcium, such as lime, to adjust the alkalinity, a calcium-containing precipitate is generated during the pH adjustment step, but this precipitate can be effectively utilized as a cement raw material. Furthermore, the recycled resources can be effectively washed to remove repellent components such as potassium and chlorine, promoting their use as cement raw materials.

[0022] On the other hand, in a fourth aspect, the present invention provides a cement production system including a kiln for introducing clinker raw materials and burning cement clinker, the system further including a drying system for drying wet sludge containing ammonia to form dried sludge, and an ammonia separation system for treating exhaust gas containing the ammonia discharged from the drying system to separate the ammonia, wherein the dried sludge is introduced into the kiln as the clinker raw material and recycled as a fuel and / or cement raw material, and the ammonia separated by the ammonia separation system is introduced into the kiln and recycled as a fuel.

[0023] In this case, in the cement production system according to the fourth aspect, the ammonia separation system is preferably configured to use the treatment method for separating ammonia contained in the waste, and to treat the ammonia-containing exhaust gas discharged from the drying system as the ammonia-containing exhaust gas in the treatment method.

[0024] On the other hand, in a fifth aspect, the present invention provides a cement production system including a kiln for introducing clinker raw material and burning cement clinker, the cement production system further including a drying system for drying wet sludge containing ammonia to produce dried sludge, an ammonia separation system for treating exhaust gas containing ammonia discharged from the drying system and separating the ammonia, and a methane fermentation system for producing a digested liquid containing ammonia, wherein 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 derived from the wet sludge and the ammonia derived from the methane fermentation system, which have been separated by the ammonia separation system, are introduced into the kiln and recycled as fuel.

[0025] In this case, in the cement production system according to the fifth aspect, the ammonia separation system is the above-mentioned treatment method for separating ammonia contained in waste, which is configured to treat an ammonium-containing waste liquid in addition to an ammonia-containing exhaust gas, and is preferably configured to treat an ammonia-containing exhaust gas discharged from the drying system as the ammonia-containing exhaust gas of the treatment method, and to treat a digested liquid generated in the methane fermentation system as the ammonia-containing waste liquid of the treatment method. [Effects of the Invention]

[0026] According to the treatment method provided by the present invention, ammonia can be effectively and efficiently separated from an ammonia-containing exhaust gas.

[0027] According to the cement production system provided by the present invention, wet sludge containing ammonia can be effectively utilized as a resource, and the dissipation of ammonia into the environment can be suppressed. [Brief explanation of the drawings]

[0028] [Figure 1]FIG. 1 is a flow chart illustrating one embodiment of a treatment method for separating ammonia contained in waste provided by the present invention. [Figure 2] FIG. 1 is a flow chart illustrating another embodiment of a treatment method for separating ammonia contained in waste, provided by the present invention. [Figure 3] 1 is a schematic diagram illustrating an embodiment of a processing method for separating ammonia contained in waste, provided by the present invention, for use in cement production. [Figure 4] FIG. 1 is a schematic diagram illustrating another embodiment of the method for separating ammonia contained in waste, according to the present invention, for use in cement production. [Figure 5] FIG. 1 is a schematic diagram illustrating a configuration of yet another embodiment of the method for separating ammonia contained in waste, provided by the present invention, for use in cement production. [Figure 6] FIG. 1 is a schematic diagram illustrating a configuration of yet another embodiment of the method for separating ammonia contained in waste, provided by the present invention, for use in cement production. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the embodiments of the present invention will be described in more detail with reference to the drawings.

[0030] FIG. 1 shows a flow diagram illustrating an embodiment of a processing method according to the present invention.

[0031] As shown in FIG. 1 , in the treatment method according to the present invention, first, 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 absorption water W1, thereby obtaining an ammonia liquid containing ammonia. This ammonia condensation step can be performed by means of, but is not limited to, a device generally called an absorption tower. In a typical absorption tower configuration, an injection gas is introduced through an inlet at the bottom of the absorption tower and flows upward or sideways inside the tower. Meanwhile, absorption water is introduced through a spray nozzle having multiple nozzles installed at the top or wall of the tower or in multiple stages, and is sprayed into the tower. The ammonia that comes into contact with the absorption water dissolves and migrates into the absorption water at the gas-liquid interface, becoming an ammonia liquid. This ammonia liquid is then collected at the bottom of the absorption tower or discharged from a separate outlet.

[0032] Next, the pH of the ammonia solution formed in the ammonia condensation step is adjusted to alkaline (step "S2" in the figure). This facilitates evaporation of the ammonia in the solution. The alkaline agent (pH adjuster) used is not limited, but examples include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and calcium hydroxide (slaked lime). These alkaline agents may be used in the form of an aqueous solution or a slurry. Alternatively, recycled resources containing water-soluble alkaline components may be used, such as woody biomass combustion ash, chlorine bypass dust (high in alkaline content, particularly potassium, such as KO, NaO, and CaO), waste alkali, and waste glass (soda-lime glass). The pH after alkaline adjustment is preferably adjusted to pH 10 or higher, particularly pH 10.5 to 12.

[0033] Next, the ammonia contained in the ammonia liquid is vaporized and separated from the ammonia liquid whose pH has been adjusted to alkaline in the pH adjustment step (step "S3" in the figure). As described above, adjusting the pH of the solution to alkaline makes the ammonia more easily vaporizable. Therefore, the ammonia, which has been transferred to the liquid phase together with other components such as water vapor and odorous components, is transferred to the gas phase in this step, allowing for separation of ammonia with increased purity. This ammonia separation step can be performed by, but is not limited to, a conventional gas-liquid contact method using a bubble column, a packed column, a plate column, or the like. Alternatively, it can be performed by a means generally known as an ammonia stripping apparatus. In a typical ammonia stripping apparatus, an injection gas is introduced from an inlet at the bottom of the absorption column and is allowed to flow upward or sideways inside the column. Meanwhile, ammonia liquid is introduced through a spray nozzle with multiple nozzles installed at the top, wall, or multiple stages of the column, and is sprayed into the column. The ammonia that comes into contact vaporizes and migrates to the injected gas side at the gas-liquid interface, becoming a gas containing ammonia, which is then discharged from an exhaust port separately provided at the top.

[0034] Generally, the vaporization efficiency of materials in gas-liquid contact methods is said to be affected by the temperature and pH of the raw water, among which the gas-liquid ratio is one of the factors related to gas. In other words, since mass transfer occurs at the gas-liquid interface, the index is how large this gas-liquid interface can be made, and for example, the guideline is to operate under conditions where the gas-liquid ratio is in the range of 300-5000. Here, the gas-liquid ratio is the amount of gas (G [m 3 / h) and wastewater volume (L [m 3 The ratio (G / L) of the amount of ammonia discharged to the amount of ammonia discharged (G / L) is 1 / 1000. In order to facilitate the evaporation of ammonia, it is effective to increase the temperature of the wastewater and adjust the pH to alkaline. Therefore, if the temperature of the supplied gas is low, the water temperature will drop and the efficiency of ammonia evaporation will decrease, so it is preferable that the gas to be blown in is heated. The temperature of the gas should be equal to or higher than the raw water temperature, and particularly preferably 25°C or higher.

[0035] As shown in FIG. 1, in the treatment method according to the present invention, wastewater W2 remaining after ammonia separation in the ammonia separation process is neutralized and recycled as absorption water W1 to be supplied to the ammonia condensation process (step "S4" in the figure). Although absorption water W1 is required for condensing ammonia from exhaust gas G1, recycling the water reduces the overall amount of water used. This also contributes to reducing the amount of exhaust gas (water vapor) emitted outside the system. Examples of neutralizing agents used include, but are not limited to, sulfuric acid and hydrochloric acid. These neutralizing agents may be used in the form of an aqueous solution, a slurry, or the like. Alternatively, kiln exhaust gas and chlorine bypass exhaust gas in cement manufacturing facilities contain CO2, which generates carbonate ions when dissolved in water, and this CO2 can be used for neutralization. The pH after neutralization is preferably adjusted to 8 or less, particularly 7 or less.

[0036] The surplus of the recycled absorption water W1 may be appropriately discharged outside the system as blow water, or part or all of it may be replaced with fresh absorption water or fresh absorption water may be added to maintain freshness. The absorption water may be water, or may contain sulfuric acid, hydrochloric acid, boric acid, phosphoric acid, or the like, as needed. The inorganic salts mentioned above lower the pH of the absorption water, thereby increasing the ammonia absorption efficiency.

[0037] The separated ammonia can be recovered and reused as appropriate. For example, ammonia-containing gas discharged from an ammonia stripping unit or the like can be dehumidified through a collection tower or piping and, if necessary, a partial condenser, and used as a gaseous fuel resource for a kiln or the like in a cement manufacturing facility. Alternatively, the ammonia can be absorbed and fixed in an ammonia fixative such as activated carbon, zeolite, silica gel, magnesium chloride, or calcium chloride, or recovered in an ammonia recovery liquid such as a sulfuric acid solution or a phosphoric acid solution.

[0038] The ammonia-containing exhaust gas G1 to be introduced into and treated by the treatment method according to the present invention is not particularly limited as long as it contains ammoniacal nitrogen, and examples thereof include dried gas of organic sludge generated in facilities that treat wastewater mainly polluted with organic matter, such as sewage treatment plants, food factories, and paper and pulp factories.

[0039] FIG. 2 shows a flow chart illustrating another embodiment of the processing method according to the present invention.

[0040] As shown in Fig. 2, in this embodiment, the embodiment described in Fig. 1 is further subjected to treatment of an ammonia-containing waste liquid W3. Specifically, the ammonia-containing waste liquid W3 is added to the ammonia liquid obtained in the ammonia condensation step and / or the ammonia liquid whose alkalinity has been adjusted in the pH adjustment step, and the pH is then adjusted to alkalinity in the pH adjustment step. In this way, the ammonia-containing exhaust gas G1 is treated and the ammonia-containing waste liquid W3 is treated, and ammonia is separated from both the exhaust gas G1 and the waste liquid W3.

[0041] The ammonia-containing waste liquid W3 to be introduced into and treated by the treatment method of the present invention is not particularly limited as long as it contains ammoniacal nitrogen, and examples thereof include industrial wastewater discharged from thermal power plants, chemical plants, amine production plants, food manufacturing plants, cement factories, etc., human waste, domestic wastewater such as urban sewage, and treated wastewater such as activated sludge treated water and digested sludge treated water.

[0042] Figure 3 shows one embodiment for utilizing the treatment method of the present invention in cement production. In the embodiment shown in Figure 3, the cement production system includes a kiln for receiving clinker raw materials and calcining cement clinker, and further includes a drying system for drying wet sludge containing ammonia to produce dried sludge, and an ammonia separation system for treating the ammonia-containing flue gas discharged from the drying system to separate the ammonia, and the dried sludge obtained by the drying system and the ammonia separated by the ammonia separation system are introduced into the kiln for receiving clinker raw materials and calcining cement clinker. This will be described in further detail below.

[0043] (Drying System) Typically, ammonia-nitrogen-containing sludge, such as sewage sludge, delivered to a cement plant for processing is in a wet state with a moisture content of approximately 70-80%. To avoid a decrease in calorific value and an increase in exhaust gas volume due to moisture, the sludge is dried to a moisture content of approximately 20% or less and then loaded into the kiln's bottom section for burning together with other clinker raw materials. In the embodiment shown in FIG. 3, steam, gas, or hot air is introduced into the dryer 1 as a drying heat source to vaporize the moisture in the wet sludge and obtain dried sludge. The dryer 1 can be a plate-type heat exchanger, a shell-and-tube heat exchanger, a shell-and-plate heat exchanger, or the like. These indirect drying methods do not involve directly spraying steam or gas onto the sludge (direct drying), but instead utilize only the heat of the steam to dry the sludge, thereby preventing an increase in the amount of exhaust gas (water vapor) within the system.

[0044] (Ammonia separation system) Normally, when ammoniacal nitrogen-containing sludge such as sewage sludge that is brought to a cement factory for treatment is dried, the exhaust gas from the drying device contains ammonia, odorous components, water vapor, etc., so in the embodiment shown in FIG. 3, ammonia is separated from the exhaust gas by a configuration including an absorption tower 2, a pH adjustment tank 3, and an ammonia separation device 4.

[0045] First, exhaust gas from the drying device 1 is introduced through an inlet provided at the bottom of the absorption tower 2, and an ascending air current is generated inside the cylindrical interior by the injected gas. Meanwhile, absorption water W1 is introduced from above inside the cylindrical interior through a spray nozzle having multiple nozzles and is sprayed from above. As described above, ammonia that comes into contact with the absorption water dissolves and migrates to the absorption water side at the gas-liquid interface, becoming an ammonia-containing ammonia liquid, which is extracted from an outlet separately provided at the bottom of the absorption tower and accumulates in the pH adjustment tank 3.

[0046] Next, in the pH adjustment tank 3, as described above, the pH of the ammonia liquid is adjusted to alkaline under any appropriate conditions. The pH adjustment tank 3 may be equipped with a device for stirring or heating the stored liquid, as needed. The ammonia liquid that has been treated in the pH adjustment tank 3 is then introduced into the ammonia separation device 4.

[0047] Finally, ammonia is separated by the ammonia separator 4. In this embodiment, an injection gas is introduced from an inlet provided at the bottom of the ammonia separator 4, and an ascending air current is generated by the injection gas inside the cylindrical interior. Meanwhile, ammonia liquid that has been treated in the pH adjustment tank 3 is introduced from above the cylindrical interior via a spray nozzle having multiple nozzles and is sprayed from above. As described above, the ammonia that comes into contact with the gas vaporizes and migrates to the injection gas side at the gas-liquid interface, becoming a gas containing ammonia, which is then extracted from an outlet separately provided at the top of the absorption tower.

[0048] In the embodiment shown in Fig. 3, the ammonia-containing gas discharged from the ammonia separator 4 is fed directly to the front of the kiln. Dried sludge dried in the dryer 1 is introduced into this kiln 5 from the kiln bottom and burned together with other clinker raw materials, and air warmed by heat exchange with the clinker is introduced from a cooler 6 that cools the clinker produced through the burning process, and this air, together with the ammonia-containing gas fed to the front of the kiln 5, helps burn the clinker. Note that the main fuel sources for the kiln 5 include coal, heavy oil, recycled oil, and waste plastics.

[0049] (Absorption water circulation system) As shown in Fig. 3, in this embodiment, the wastewater remaining after ammonia has been separated is taken out into a treatment tank 7 and neutralized. The treatment tank 7 may be equipped with a device for stirring or heating the stored liquid as needed. The wastewater that has been treated in the treatment tank 7 is then returned to the absorption tower 2 and recycled as absorption water W1 to be supplied to the absorption tower 2. The amount of recycled absorption water W1 can be adjusted by discharging the surplus water outside the system as blown water.

[0050] As mentioned above, the neutralizing agent used is not limited, but examples thereof include sulfuric acid and hydrochloric acid. Furthermore, these neutralizing agents may be used in the form of an aqueous solution, a slurry, or the like. Alternatively, kiln exhaust gas and chlorine bypass exhaust gas from cement manufacturing facilities contain CO2, which generates carbonate ions when dissolved in water, and this can also be used for neutralization. The pH after neutralization is preferably adjusted to pH 8 or less, and particularly pH 7 or less.

[0051] In the embodiment shown in FIG. 3, the neutralization treatment is performed by a tank system using a treatment tank 7, but it may also be performed by a system other than a tank system. For example, it may be performed by an in-line system in which a neutralizing agent or CO2-containing exhaust gas is directly injected into a pipe. Furthermore, the wastewater remaining after the separation of ammonia from the ammonia may be subjected to other treatments as necessary in addition to the neutralization treatment. For example, the wastewater may be stored in a coagulation and sedimentation tank for a predetermined time to remove suspended solids (SS). Furthermore, treatment to remove phosphorus may be performed. A common phosphorus treatment method is a coagulation and sedimentation method in which aluminum salts or iron salts are added as a coagulant.

[0052] Figure 4 shows another embodiment for utilizing the treatment method of the present invention in cement production. In the embodiment shown in Figure 4, the cement production system includes a kiln for receiving clinker raw materials and calcining cement clinker, and further includes a drying system for drying ammonia-containing wet sludge to produce dried sludge, an ammonia separation system for treating the ammonia-containing flue gas discharged from the drying system to separate the ammonia, and a methane fermentation system for producing an ammonia-containing digested liquid, and the dried sludge obtained by the drying system and the ammonia derived from the wet sludge and the ammonia derived from the methane fermentation system, which are separated by the ammonia separation system, are introduced into the kiln for receiving clinker raw materials and calcining cement clinker. This will be described in further detail below.

[0053] (Methane fermentation system) 4, in this embodiment, a methane fermentation tank 8 and a solid-liquid separator 9 are further provided in addition to the embodiment described in FIG. 3. Since the fermented digested liquid produced by methane fermentation contains a high concentration of ammonia, the digested liquid from the methane fermentation tank 8 is separated into solid and liquid by the solid-liquid separator 9, and the liquid portion is stored in the pH adjustment tank 3.

[0054] 4, in the pH adjustment tank 3, the liquid portion derived from the digested liquid from the methane fermentation system is mixed with the ammonia liquid from the absorption tower 2, and the pH is adjusted to alkaline. In the subsequent process, ammonia is separated in the same manner, and the ammonia-containing gas discharged from the ammonia separator 4 is fed to the front of the kiln 5.

[0055] Fig. 5 shows yet another embodiment for utilizing the treatment method of the present invention in cement production. The embodiment shown in Fig. 5 includes an optional equipment configuration that can be added to the embodiment described in Fig. 3 or 4 as needed.

[0056] For example, a dehydrator 10 is provided downstream of the pH adjustment tank 3 to dehydrate the contents removed from the tank and obtain a solid fraction. For example, if woody biomass combustion ash or chlorine bypass dust (high in alkalis, particularly potassium, such as KO, NaO, and CaO) is used as a recycled resource containing a water-soluble alkaline component as a pH adjuster, a precipitate derived from the recycled resource will form in the pH adjustment tank 3. This precipitate can be removed and treated with the dehydrator 10 to obtain a cake, which can be introduced into the kiln end of the kiln 5 and recycled as a cement raw material. This also has the effect of washing away potassium, chlorine, and other components that are repulsive to cement production. The liquid fraction resulting from dehydration may be returned to the pH adjustment tank 3.

[0057] In addition, the kiln exhaust gas (containing CO2) discharged from the kiln 5 is introduced into the treatment tank 7 by bubbling it through the liquid in the tank via an aeration device 11. This exhaust gas contains CO2, which generates carbonate ions when dissolved in water. This can be used to neutralize the wastewater discharged from the ammonia separation unit, remaining after ammonia separation, thereby reducing the cost of using neutralizing agents. Furthermore, although not limited to this, when the pH adjustment process is performed using a pH adjuster containing calcium, such as lime, to adjust the alkalinity, the CO2 contained in the exhaust gas can be fixed as calcium carbonate. In addition, the sulfur contained in the exhaust gas reacts with the precipitated calcium carbonate, resulting in a desulfurization effect.

[0058] In addition, the absorber exhaust gas discharged from the absorber 2 is heated by a heater 12 and used as the blown gas introduced into the ammonia separator 4. This allows it to replace the steam and heated air required for the equipment, contributing to a reduction in energy consumption.

[0059] The ammonia-containing gas discharged from the ammonia separator 4 is dehumidified by a partial condenser 13 before being introduced into the kiln 5. The moisture resulting from the dehumidification may be discharged into the treatment tank 7.

[0060] FIG. 6 shows yet another embodiment for utilizing the treatment method of the present invention in cement production. In the embodiment shown in FIG. 6, the ammonia separation device 4 provided in the system of the embodiment described in FIGS. 3 to 5 is omitted, and ammonia separation is performed in the pH adjustment tank 3. Specifically, when limestone or the like is used as a pH adjuster, a high heat of reaction is generated. This reaction heat volatilizes the ammonia contained in the ammonia solution, whose pH has been adjusted to alkaline in the pH adjustment tank 3, resulting in vaporization and separation of the ammonia. The ammonia is then recovered and introduced into the kiln 5. In this case, the pH of the ammonia solution is preferably adjusted to 11-12 if the temperature is 20-30°C; 10.5-11.5 if the temperature is 30-40°C; 10-11 if the temperature is 40-50°C; and 9.5-10.5 if the temperature is 50°C or higher. Alternatively, a gas such as air may be heated as needed and introduced into the pH adjustment tank 3 via an air diffuser 14, where it is bubbled through the ammonia solution stored in the tank. This promotes ammonia vaporization. In the embodiment shown in Fig. 6, the absorber exhaust gas discharged from the absorption tower 2 is heated by a heater 12 and then introduced into the liquid in the pH adjustment tank 3 by bubbling through an air diffuser 14. As in the embodiment described in Fig. 5, the kiln exhaust gas (containing CO2) discharged from the kiln 5 to the treatment tank 7 is introduced into the liquid in the tank by bubbling through an air diffuser 11. The ammonia-containing gas discharged from the ammonia separation device 4 is dehumidified by a partial condensation device 13 before being introduced into the kiln 5. Note that the moisture resulting from the dehumidification may be discharged into the treatment tank 7.

[0061] The present invention is not limited to the above-described embodiments, and various combinations and modifications within the scope of the disclosure in this specification are possible, and such embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0062] 1...Drying device, 2...Absorption tower, 3...pH adjustment tank, 4...Ammonia separation device, 5...Kiln, 6...Cooler, 7...Treatment tank, 8...Methane fermentation tank, 9...Solid-liquid separation device, 10...Dehydrator, 11, 14...Aeration device, 12...Heating device, 13...Partial condensation device

Claims

1. 1. A cement manufacturing system including a kiln for introducing clinker raw materials and burning cement clinker, The cement production system further comprises a drying system that dries wet sludge containing ammonia to produce dried sludge, and an ammonia separation system that treats exhaust gas containing the ammonia discharged from the drying system to separate the ammonia, wherein the dried sludge is introduced into the kiln as the clinker raw material and recycled as a fuel and / or cement raw material, and the ammonia separated by the ammonia separation system is introduced into the kiln and recycled as a fuel.

2. 1. A cement manufacturing system including a kiln for introducing clinker raw materials and burning cement clinker, The cement production system further comprises a drying system that dries wet sludge containing ammonia to produce dried sludge, an ammonia separation system that processes exhaust gas containing the ammonia discharged from the drying system to separate the ammonia, and a methane fermentation system that produces a digested liquid containing ammonia, wherein the dried sludge is introduced into the kiln as the clinker raw material and recycled as a fuel and / or cement raw material, and the ammonia derived from the wet sludge and the ammonia derived from the methane fermentation system, which are separated by the ammonia separation system, are introduced into the kiln and recycled as a fuel.

Images