Ammonia recovery device and recovery method

Abstract

To provide an ammonia recovery device and recovery method which can reduce a labor burden of a worker and can obtain recovery liquid whose concentration is stably adjusted, in recovery of an ammonia component by acid treatment.SOLUTION: An ammonia recovery device 1 which brings an acidic solution into circulation contact with treated gas containing ammonia, and finally discharges storage liquid 10 containing an ammonia component accumulated in a treatment container as recovery liquid includes: a pH sensor 7 for measuring a pH of the storage liquid 10; a liquid amount sensor 8 for measuring a liquid amount of the storage liquid 10; a discharge valve V3 for discharging the storage liquid 10 from a treatment container 2; and a control device 11, wherein the control device 11 controls opening / closing of the discharge valve V3, on the basis of the pH and the liquid amount of the storage liquid 10 in the treatment container 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ammonia recovery apparatus and recovery method, and more particularly to an ammonia recovery apparatus and recovery method for recovering ammonia from odor-causing gases generated during composting. [Background technology]

[0002] In the livestock industry, composting livestock waste is widely practiced. For example, a composting device that utilizes the fermentation action of microorganisms is known as a device for composting livestock waste. The composting device is a sealed, vertical, cylindrical tank-shaped device that dries and ferments organic waste while forcibly aerating it.

[0003] During the composting process of livestock manure, odor-causing gases, including ammonia and lower fatty acids such as propionic acid and normal butyric acid, are generated, making odor control an important measure. To address this issue, a deodorizing system, such as a soil deodorizer or sawdust deodorizer, is often installed alongside the composting system. However, for example, sealed vertical composting systems can emit high concentrations of odor-causing gases, which may not be fully treated depending on the capacity of the deodorizing system.

[0004] On the other hand, ammonia, the main odor-causing gas, is a nitrogen-containing substance, so from the perspective of being a fertilizer component in soil, the release of ammonia into the environment can be considered a loss of fertilizer components. For this reason, there are currently known technologies for recovering ammonia components from odor-causing gases generated during the composting process.

[0005] For example, it is known to use inexpensive sulfuric acid and bubble the odor-causing gas through a sulfuric acid solution to capture the ammonia in the gas and recover it as an ammonium sulfate solution.

[0006] Patent Document 1 also describes an exhaust gas treatment device that is installed in a suction aeration type compost production facility, which uses suction from the compost fermentation tank to vent the inside of the compost raw materials accumulated in the compost fermentation tank. This exhaust gas treatment device describes how ammonia in odor-causing gas is brought into contact with an acidic solution such as sulfuric acid or phosphoric acid, and the ammonia component is recovered in a chemical tank. In this device, the chemical solution that flows down into the chemical tank is circulated again by a circulation pump and continues to be used in circulation until the chemical solution (acidic solution) loses its ability to react with ammonia.

[0007] Furthermore, Patent Document 2 describes a system that cools the high-temperature odor-causing gas generated from compost and dissolves ammonia in the resulting condensed water to recover it. However, it is believed that the amount of ammonia that can be removed by this method and the concentration of the ammonia component in the recovered liquid are limited. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4418886 [Patent Document 2] Patent No. 7241275 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, ammonia in odor-causing gases reacts chemically with sulfuric acid, phosphoric acid, etc., and the liquid stored in a treatment vessel is ultimately recovered as a versatile liquid fertilizer (containing ammonium sulfate, ammonium phosphate, etc.). However, in such ammonia recovery systems using acidic solutions, the treatment vessel is large, and workers must add large amounts of water and chemical solutions and recover the stored liquid. This addition and recovery work is relatively frequent, and may take two to three days depending on the amount of gas generated by the composting system. Furthermore, the work time cannot be determined depending on the state of the composting system, which places a heavy burden on workers.

[0010] Meanwhile, the liquid stored in the treatment vessel contains not only ammonia but also condensed water derived from the water vapor in the odor-causing gas. The amount of condensed water generated varies greatly depending on the outside temperature, and as a result, the amount of condensed water contained in the stored liquid varies. Fluctuations in the amount of condensed water result in fluctuations in the concentration of ammonia and other components in the final recovered liquid, making it difficult to obtain recovered liquid with a stable concentration.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ammonia recovery apparatus and recovery method that can reduce the workload of operators and obtain a recovered solution with a stable concentration in the recovery of ammonia by acid treatment. [Means for solving the problem]

[0012] The ammonia recovery apparatus of the present invention is an ammonia recovery apparatus that circulates an acidic solution in contact with a gas to be treated that contains ammonia, and ultimately discharges a stored liquid containing an ammonia component that has accumulated in a treatment vessel as a recovered liquid, and the ammonia recovery apparatus has a pH measurement means that measures the pH of the stored liquid, a liquid volume measurement means that measures the liquid volume of the stored liquid, a discharge valve that discharges the stored liquid from the treatment vessel, and a control device, and the control device is characterized in that it controls the opening and closing of the discharge valve based on the pH and liquid volume of the stored liquid in the treatment vessel.

[0013] The control device is characterized in that when the pH of the stored liquid reaches a predetermined value and the amount of the stored liquid is a predetermined amount, the control device opens the discharge valve to discharge the stored liquid.

[0014] The ammonia recovery device has a water valve that supplies water to the treatment vessel, and when the pH of the stored liquid reaches a predetermined value and the amount of the stored liquid is less than a predetermined amount, the control device opens the water valve to supply water until the stored liquid reaches a predetermined amount, and then opens the discharge valve to discharge the stored liquid.

[0015] The control device is characterized in that it notifies of an abnormal state when the amount of the stored liquid reaches a predetermined amount before the pH of the stored liquid reaches a predetermined value.

[0016] The ammonia recovery device has a water valve that supplies water to the treatment vessel and a flow rate measuring means that measures the circulating flow rate of the stored liquid, and the control device is characterized in that, when the circulating flow rate of the stored liquid falls below a predetermined amount before the pH of the stored liquid reaches a predetermined value, the control device opens the water valve to supply water to the treatment vessel and dilute the stored liquid.

[0017] The storage liquid is characterized by containing a phosphoric acid solution.

[0018] The ammonia recovery method of the present invention is an ammonia recovery method in which an acidic solution is circulated and brought into contact with a gas to be treated that contains ammonia, and a stored liquid containing an ammonia component that has accumulated in a treatment vessel is finally discharged as a recovered liquid, and the ammonia recovery method is characterized by having a pH measurement step of measuring the pH of the stored liquid and a liquid volume measurement step of measuring the liquid volume of the stored liquid, and automatically controlling the discharge of the stored liquid from the treatment vessel based on the pH and liquid volume of the stored liquid in the treatment vessel measured in these steps. [Effects of the Invention]

[0019] The ammonia recovery apparatus of the present invention circulates an acidic solution through contact with ammonia-containing gas to be treated, ultimately discharging the ammonia-containing liquid stored in a treatment vessel as a recovered liquid. The apparatus includes a pH measuring means for measuring the pH of the stored liquid, a liquid volume measuring means for measuring the volume of the stored liquid, a discharge valve for discharging the stored liquid from the treatment vessel, and a control device. The control device controls the opening and closing of the discharge valve based on the pH and volume of the stored liquid in the treatment vessel, allowing the recovery of the stored liquid to be performed mechanically or automatically, reducing the workload of the operator. Furthermore, since the discharge of the stored liquid is controlled based on the volume as well as the pH of the stored liquid, the concentration of the ammonia component can be adjusted, resulting in a recovered liquid with a stable concentration, making the apparatus particularly suitable for use as liquid fertilizer. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of an example of an ammonia recovery apparatus of the present invention. [Figure 2] 1 is a graph showing the ammonia removal effect by the ammonia recovery device. [Figure 3] 1 is a graph showing the change in pH of a phosphoric acid solution during ammonia recovery treatment. [Figure 4] FIG. 1 is a diagram showing measurement results of various items regarding the recovered liquid after the ammonia recovery treatment. [Figure 5] 3 is a flowchart showing an example of a processing procedure performed by a control device in the ammonia recovery apparatus of the present invention. [Figure 6] This is a photograph of the circulation path in a state where it has solidified due to the precipitation of salt contained in the stored liquid. [Figure 7] 1 is a graph showing an example of monitoring in the ammonia recovery apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The ammonia recovery system of the present invention treats ammonia-containing gas to recover it as liquid fertilizer containing ammonia components, for example. Examples of ammonia-containing gas to be treated include odor-causing gases generated during composting in livestock facilities. These gases are emitted, for example, from suction-aeration composting facilities and sealed vertical composting systems.

[0022] The ammonia recovery apparatus of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of an ammonia recovery apparatus. First, the basic configuration of a general ammonia recovery apparatus will be described below.

[0023] As shown in FIG. 1, the ammonia recovery device 1 includes a storage container 2, a reaction chamber 3 provided in communication with the upper part of the storage container 2, a gas supply pipe 4 connected to the side of the reaction chamber 3, a gas exhaust pipe 5 provided in the upper part of the storage container 2, and a circulation path L connecting an outlet 2a of the storage container 2 and the upper surface of the reaction chamber 3. a and,

[0024] The internal volume of the storage container 2 is not particularly limited, but is, for example, 300 L or more. The storage container 2 is made of a resin such as polyvinyl chloride, and stores the storage liquid 10 inside. Note that the storage container 2 is often installed in an environment exposed to the outside air, and the outer surface of the storage container 2 may be covered with a heat insulating material such as a foam material to prevent the temperature of the gas to be treated from dropping excessively.

[0025] The stored liquid 10 is an acidic solution containing an acidic chemical solution, and is circulated through a circulation path L by a circulation pump 6. a The stored liquid 10 is supplied to the reaction chamber 3 via a nozzle. In the reaction chamber 3, the stored liquid 10 is sprayed as fine droplets from above. A gas to be treated containing ammonia is also supplied to the reaction chamber 3 from a gas supply pipe 4, and the gas to be treated and the sprayed liquid undergo a chemical reaction in the reaction chamber 3. The cylindrical interior of the reaction chamber 3 is filled with a carrier 3a to increase the gas-liquid contact efficiency. For example, a drip-removal net made of overlapping stainless steel mesh or a drip-removal net made of rolled stainless steel mesh can be used as the carrier 3a.

[0026] Ammonia is removed from the gas to be treated and the spray liquid contains ammonia components through the chemical reaction in the reaction chamber 3. The gas to be treated from which the ammonia components have been removed is discharged to the outside through the gas exhaust pipe 5 and is led to, for example, a biological deodorization device.

[0027] On the other hand, the spray liquid that has captured the ammonia component from the gas to be treated flows down into the storage container 2 and is stored as the stored liquid 10. Then, the spray liquid is again pumped through the circulation path L a The stored liquid 10 is sprayed in the reaction chamber 3 through the fertilizer. In this way, the stored liquid 10 is used until it loses the ability to react with ammonia, and is finally discharged and recovered as a recovered liquid (liquid fertilizer).

[0028] After the stored liquid 10 is discharged, the treatment vessel 2 is refilled with an acidic solution, and an ammonia recovery treatment is carried out.

[0029] The effectiveness of acid treatment in removing ammonia and the change in the pH of the stored liquid will be explained using a test example conducted at a pig farm. In this test, the exhaust gas from a sealed vertical composting system was supplied to an ammonia recovery system with the basic configuration described above.

[0030] The test was conducted over four periods: November 17th to 26th (autumn), January 16th to 25th (winter), April 10th to 19th (spring), and July 6th to 15th (summer). Approximately 90 L of industrial-grade phosphoric acid (63% phosphoric acid concentration) and approximately 200 to 250 L of water were mixed and filled into the treatment vessel, and the circulation pump was operated. In this test, the phosphoric acid solution was replaced every three days, resulting in three recovery solutions during each test period. Approximately 300 mL of phosphoric acid solution was collected once a day. When the phosphoric acid solution was replaced, the entire recovery solution was withdrawn using the circulation pump at the bottom of the device and collected in a container. A recovery solution sample was then taken.

[0031] The NH3 concentration in the gas was measured once a day between 7:00 and 10:00 a.m., when the NH3 concentration reaches its highest point during the day, before new raw materials are added to the sealed vertical composting equipment. The NH3 concentration was measured by pumping the gas to be measured into a collection bottle for approximately one minute, and the concentration in the collection bottle was measured using the detector tube method. Measurements were taken once a day for each test period, a total of nine times, and the average values ​​are shown in Figure 2. The NH3 removal rate [%] calculated using the following formula (1) is also shown. Removal rate=[(C1-C0) / C1]×100...(1) C1: NH3 concentration before ammonia recovery unit [ppm] C0: NH3 concentration after ammonia recovery unit [ppm]

[0032] As shown in Figure 2, the NH3 concentration in the gas emitted from the sealed vertical composting system was approximately 1800-3200 ppm (average 2666 ppm), but this was reduced to an average of 135 ppm by the ammonia recovery system. This concentration can be adequately treated by the biological deodorization system normally installed next to the system. The average NH3 removal rate was 94.7%.

[0033] Next, Figure 3 shows the change in pH of the phosphoric acid solution during the ammonia recovery process during each test period. The pH change is shown as the time from when the phosphoric acid solution was added to the treatment vessel and operation began, and is the average value of three measurements for each test period. As shown in Figure 3, the pH started out below 1 and rose over time, eventually converging to around pH 6.6. It took about 2.5 days for the pH to rise to 6.6.

[0034] Next, the measurement results for each item regarding the properties of the recovered liquid are shown in Figure 4. For each item, the solids concentration (TS) was determined by leaving approximately 100 mL of the recovered liquid in a thermostatic chamber at 105°C until there was no more mass loss and drying, and then measuring the mass before and after drying. pH was measured using the glass electrode method, ammonium nitrogen concentration (TA-N) was measured using the indophenol blue method, and water-soluble phosphate concentration (WP) was measured using a colorimetric method.

[0035] As shown in Figure 4, the nitrogen concentration of the recovered liquid was 6.08-6.60%, and the phosphoric acid concentration (WP) was 18.6-20.5%. + Ions and PO4 3- The ion abundance ratio (N / P ratio) was calculated to be approximately 1.6, and the solid concentration (TS) was approximately 35%. + Ions and PO4 3- Of the compounds whose main components are ions, the solubility in water of (NH4H2PO3) with an N / P ratio of 1 is 27.2 g / 100 g, and the solubility in water of ((NH4)2HPO3) with an N / P ratio of 2 is 40.8 g / 100 g. The solid concentration in the recovered liquid is approximately 35%, which is intermediate between the solubilities of these compounds, so it is thought that the recovered liquid contains a mixture of (NH4H2PO3) and ((NH4)2HPO3).

[0036] On the other hand, as shown in Figure 4, the amount of recovered liquid increased relative to the amount of phosphoric acid solution used. Most of this increase is thought to be the moisture resulting from the condensation of the removed NH3 and water vapor in the treated gas. Furthermore, in the summer, when temperatures are high and water vapor in the treated gas is less likely to condense, the increase in the amount of recovered liquid was smaller than in cooler periods. In other words, the amount of recovered liquid varies with the seasons, which in turn causes changes in the concentrations of components in the recovered liquid (such as nitrogen and phosphoric acid concentrations). Furthermore, in the summer, when temperatures are high, the increase in the amount of recovered liquid is small, but under certain conditions the concentration can become high, which could lead to the solidification of ammonium salts.

[0037] Furthermore, in the above-described ammonia recovery apparatus, the intervals between replacement (discharge and introduction) of the stored liquid are relatively short, and the replacement work places a heavy burden on the workers.

[0038] Therefore, in the ammonia recovery system of the present invention, the properties of the liquid stored in the treatment vessel, particularly the pH and liquid volume, are monitored during the ammonia recovery process, and the opening and closing of the discharge valve (discharge means) and other operations are automatically controlled based on the monitoring results, thereby reducing the workload of the operator and taking into account seasonal fluctuations in the amount of condensed water to obtain a recovered liquid (liquid fertilizer) with a stable component concentration. The specific configuration of the ammonia recovery system that achieves this function will be described with reference to Figure 1.

[0039] In FIG. 1, the ammonia recovery device 1 includes a water valve V1 for supplying water to the treatment vessel 2, a chemical valve V2 for supplying an acidic chemical solution to the treatment vessel 2, a discharge valve V3 for discharging the stored liquid from the treatment vessel 2, and a circulation path L a Each of these valves V1 to V4 is, for example, an electromagnetic valve, and the opening and closing of the valves is controlled by electronic control of the control device 11.

[0040] The water valve V1 is provided on a water supply pipe L1 that supplies water to the treatment vessel 2. The water to be supplied is, for example, tap water, groundwater, river water, or the like.

[0041] The chemical valve V2 is provided on a chemical supply pipe L2 that supplies an acidic chemical to the processing vessel 2. The supplied chemical is, for example, a phosphoric acid solution or a sulfuric acid solution, which is stored in a chemical tank (not shown). The concentrations of the phosphoric acid solution or sulfuric acid solution supplied to the processing vessel 2 are not particularly limited, and may be the concentrations of commercially available industrial products.

[0042] The discharge valve V3 is connected to the circulation path L a The discharge pipe L3 is provided in the discharge pipe L3 branched from the circulation path L a When the circulation pump 6 is operated, the stored liquid is discharged from the discharge pipe L3.

[0043] The circulation valve V4 allows the stored liquid 10 to flow through the circulation path L a The discharge valve V3 and the circulation valve L4 are opened when the stored liquid 10 is circulated through the circulation path L1, and closed when the stored liquid 10 is discharged through the discharge pipe L3.a Alternatively, a three-way valve may be provided at the connection point between the drain pipe L1 and the drain pipe L3. In this case, the control device 11 switches the flow path via the three-way valve to control the discharge or circulation of the stored liquid.

[0044] The ammonia recovery device 1 has a pH sensor 7 that measures the pH of the stored liquid 10. The pH sensor 7 is provided in a lower part of the storage container 2, at a location that is normally filled with the stored liquid 10. A sensor with well-known specifications can be used as the pH sensor 7, and for example, one based on the glass electrode method can be used.

[0045] The ammonia recovery device 1 has a liquid quantity sensor 8 that measures the liquid quantity of the stored liquid 10 in the container. For example, a water level sensor can be used as the liquid quantity sensor 8. Types of water level sensors include float-type, capacitance-type, and optical-type level switches. The liquid quantity sensor 8 is not limited to a water level sensor, and a weight sensor or the like may also be used. For example, the storage container 2 may be placed on a weight sensor, and the liquid quantity of the stored liquid 10 in the container may be determined by the weight sensor.

[0046] In addition, in FIG. 1, the ammonia recovery device 1 includes a circulation path L a The water supply pipe L1, the chemical solution supply pipe L2, and the discharge pipe L3 may each be provided with a flow sensor that measures the flow rate of the liquid passing through each of the pipes.

[0047] In FIG. 1, the ammonia recovery apparatus 1 does not have a heating means such as a heater for heating the stored liquid 10 in the treatment vessel 2.

[0048] The control device 11 is mainly composed of a microcomputer including a well-known CPU, ROM, RAM, etc. The control device 11 acquires signals output from the various sensors 7, 8, 9 and other sensors, and controls the opening and closing of the discharge valve V3 based on the detection results. The control device 11 may be configured to continuously acquire and store various detection results, and may also have various calculation functions.

[0049] In the present invention, for example, in order to automate the operation of the ammonia recovery apparatus 1, sensors that are kept out of contact with the gas to be treated as much as possible are used, and stable control is performed by the control device 11. An example of the control by the control device 11 is as follows. - Non-contact sensor for constant supply of water and acidic chemicals - Stable operation through multi-stage monitoring of pH, water level, and pump flow rate -Adjusting the concentration of stored liquid by controlling the water level - Ammonia concentration of the treated gas and the treated gas, and air volume are not monitored.

[0050] Specifically, in the ammonia recovery device 1, the condition inside the treatment vessel 2 is grasped from the values ​​of the pH, liquid volume, and circulation flow rate of the stored liquid 10, and the exchange (recovery / introduction) of the stored liquid 10 is automated and the concentration of the recovered liquid is automatically adjusted simply by operating the circulation pump 6 and each valve V1 to V4.

[0051] The processing procedure performed by the control device 11 during the ammonia recovery process will be described below.

[0052] First, the processing procedure up to the operation of the circulation pump 6 will be described. In the initial state, the processing vessel 2 is empty, and the valves V1 to V4 are closed. The control device 11 opens the water valve V1 to supply water into the storage vessel 2. At this time, the amount of water supplied is measured by a flow sensor or the like, and once a predetermined amount has been supplied, the water valve V1 is closed. Next, the control device 11 opens the chemical valve V2 to supply the chemical into the storage vessel 2. At this time, the amount of chemical supplied is measured by a flow sensor or the like, and once a predetermined amount has been supplied, the chemical valve V2 is closed. As a result, the water and the chemical are mixed in the processing vessel 2, and an acidic solution to be used in the reaction with ammonia is prepared. This acidic solution is also the stored liquid 10.

[0053] As described above, bumping can be prevented by supplying water before the chemical solution to the treatment vessel 2. Alternatively, an acidic solution in which the chemical solution is diluted to a predetermined concentration may be supplied from the chemical solution supply pipe L2 via the valve V2.

[0054] After a predetermined amount of the stored liquid 10 is filled in the treatment vessel 2, the control device 11 opens the valve V4 and operates the circulation pump 6 to start the ammonia recovery treatment. a The ammonia is supplied to the reaction chamber 3 via the valve V4, and ammonia recovery is initiated. During the ammonia recovery process, the control device 11 performs multistage and continuous monitoring of the pH and liquid volume of the stored liquid 10 in the treatment vessel 2, as well as the circulation flow rate. Note that although the opening and closing of the valve V4 will be omitted hereafter, the opening and closing of the valve V4 is controlled in the opposite direction to that of the valve V3.

[0055] The processing procedure of the control device after the ammonia recovery process has started will be described using the flowchart in Fig. 5. The processing from start to end in Fig. 5 is repeated at predetermined time intervals (for example, every few minutes). Of the steps shown in Fig. 5, steps S12 to S19 indicate processing procedures during normal operation, and the other steps indicate processing procedures during abnormality.

[0056] First, the flow during normal operation will be described. When the stored liquid in the processing vessel is circulated while the circulation pump is running, the acid in the stored liquid is neutralized by reaction with ammonia in the gas to be processed, and the pH increases over time (see, for example, FIG. 3). During normal operation, the stored liquid is circulated until the pH of the stored liquid in the processing vessel reaches a predetermined value Th1 (if steps S12, S21, and S31 are No). The predetermined value Th1 is a value that is set in advance, for example, approximately 6.5 to 6.8.

[0057] When the pH of the stored liquid reaches a predetermined value Th1 (if S12 is Yes), the water valve V1 is opened (step S13) to supply water into the treatment vessel. When the amount of stored liquid measured by a water level sensor or the like reaches a predetermined value Th2 (if step S14 is Yes), the water valve V1 is closed (step S15). Note that the predetermined value Th2 is a preset value, and is set based on the amount of liquid in winter, for example, when there is a large amount of condensed water.

[0058] Then, the drain valve V3 is opened (step S16) to drain the stored liquid. A circulation pump is used to drain the stored liquid, and this circulation pump continues to operate. Then, for example, a flow rate sensor provided in the drain pipe measures the drainage rate of the stored liquid. When the drainage rate falls below a predetermined value Th3 (if S17 returns Yes), the drainage is considered complete, the circulation pump is stopped (step S18), and the drain valve V3 is closed (step S19).

[0059] As in step S12, a predetermined amount of ammonia components is recovered by adjusting the pH of the stored liquid in the treatment vessel to a predetermined value. Furthermore, as in step S14, the concentration of the ultimately discharged recovered liquid can be adjusted by adjusting the volume (e.g., water level) of the stored liquid. As shown in FIG. 4, for example, in summer, the amount of condensed water is small, and the stored liquid tends to be highly concentrated, while in winter, the amount of condensed water is large, and the stored liquid tends to be low. To eliminate such concentration differences, adjusting the liquid volume in addition to the pH allows for the production of a recovered liquid (liquid fertilizer) with a stable concentration. For example, when a phosphate solution is used as the chemical solution, an N / P ratio of approximately 1:1.6 can be stably obtained.

[0060] Finally, when the discharge of the stored liquid is completed, the process returns to the above-described process procedure up to the operation of the circulation pump, and the acidic solution is refilled into the processing vessel to resume the ammonia recovery process.

[0061] Next, as a processing procedure for an abnormality, a case where an excessive amount of condensed water occurs in winter when the outside air temperature is low will be described in steps S21 to S26. If the amount of stored liquid in the processing container reaches a predetermined value Th2 due to an excessive increase in condensed water (if S21 is Yes) before the pH of the stored liquid reaches a predetermined value Th1 (if S12 is No), it is determined that an abnormality has occurred and an abnormal state is notified (step S22). Specifically, an alarm is sounded and an alarm is issued on the monitor or with a lamp display. In this case, it is determined that the nitrogen concentration in the stored liquid has fallen below the standard value due to the excessive generation of condensed water.

[0062] Then, the discharge valve V3 is opened (step S23), and the stored liquid is discharged until the discharge rate reaches a predetermined value Th3 or less (step S24). The circulation pump is then stopped (step S25), and the discharge valve V3 is closed (step S26). It is preferable to separate the recovery tank for the discharged stored liquid from the recovery tank used during normal operation. This prevents the recovery liquid with a nitrogen concentration below the standard from being mixed with the recovery liquid with a nitrogen concentration within the standard. For example, a shunt pipe may be provided branching off from the discharge pipe, and the shunt valve, which is normally closed, may be opened at that time to recover the liquid in a separate recovery tank.

[0063] Next, as a processing procedure for an abnormality, the processing flow when solidification occurs in the processing vessel due to an increase in the concentration of the stored liquid in summer when the outside temperature is high will be described in steps S31 to S38.

[0064] If the circulation flow rate of the stored liquid falls below a predetermined amount Th4 and exceeds a predetermined amount Th5 (if steps S31 and S32 are Yes) before the pH of the stored liquid reaches a predetermined value Th1 (if step S12 is No), an abnormality is detected and an abnormal condition is reported (step S33). In this case, the circulation flow rate of the stored liquid is determined to be somewhat lower than normal, and partial solidification has occurred inside the device. Then, the water valve V1 is opened (step S34), and a predetermined amount of water Th6 is supplied (step S35) to dilute the stored liquid, after which the water valve V1 is closed (step S36). Then, the process returns to the normal processing procedure.

[0065] On the other hand, if the circulation flow rate of the stored liquid is equal to or less than the predetermined amount Th5 (if step S32 is No), it is also determined to be an abnormality and an abnormal state is notified (step S37). However, in this case, it is determined that the circulation flow rate of the stored liquid has become significantly lower than normal, and that solidification has occurred throughout the device. Therefore, the circulation pump is stopped (step S38), and operation itself is brought to an emergency stop. For example, FIG. 6 shows a state in which the ammonium phosphate contained in the stored liquid has solidified throughout the circulation path.

[0066] As shown in Figure 5, the ammonia recovery system of the present invention is an ammonia recovery system that automatically adjusts the concentration of the stored liquid, and not only does it recover ammonia, but also controls the stored liquid at a predetermined pH and volume so that it can be used as a fertilizer with a certain quality. Furthermore, as shown in Figure 5, it is possible to automatically replace the chemical solution while adjusting the concentration, and it also addresses problems that may occur during operation of the ammonia recovery system (such as excessive condensation and solidification of the stored liquid), which can further reduce the labor required for maintenance, etc.

[0067] The configuration of the ammonia recovery device of the present invention is not limited to the content explained in Fig. 1 etc. Furthermore, the processing of the control device is not limited to the content explained in Fig. 5 etc.

[0068] The results of monitoring the pH, water level, and circulating water volume using sensors 7, 8, and 9 in the ammonia recovery system 1 shown in Figure 1 are explained using Figure 7. In this test, the exhaust gas emitted from a sealed vertical composting system was used as the gas to be treated. An approximately 42% phosphoric acid solution was used as the chemical solution. 40 L of the chemical solution and 50 L of water were placed in the treatment vessel, and the ammonia recovery treatment was carried out. The test was conducted in October (autumn).

[0069] The various setting conditions for the ammonia recovery device were a pH setting of 6.8 (equivalent to, for example, the predetermined value Th1 in FIG. 5), a water level at the time of discharge of 480 L (equivalent to, for example, the predetermined value Th2 in FIG. 5), and a water circulating rate by the circulation pump of 40 L / min (equivalent to, for example, the predetermined amount Th4 in FIG. 5).

[0070] Figure 7(a) shows the changes in pH, water level, and circulating water volume over time. Figure 7(a) shows data for one day of a three-day test. As shown in Figure 7(a), it can be seen that the pH and water level (i.e., liquid volume) of the stored liquid increased over time. The circulating water volume remained roughly constant, maintaining above the set value of 40 L / min. Although subsequent data is omitted, in this test, the pH reached the set value of 6.8 while the water level remained below the set value and the circulating water volume remained above the set value. Water was then added until the stored liquid level reached 480 L, and the stored liquid was finally discharged.

[0071] The discharged stored liquid contained fertilizer components with a nitrogen concentration of approximately 6% and a phosphorus concentration of approximately 19%, which met the standards for ordinary fertilizer and showed that it could also be used as a raw material for mixed compost compound fertilizer.

[0072] For reference, Figure 7(b) shows the changes in the NH3 concentration in the gas (gas to be treated) input into the ammonia recovery system and the NH3 concentration in the gas (treated gas) exhausted from the ammonia recovery system. As shown in Figure 7(b), it can be seen that the ammonia in the treated gas is effectively recovered by the ammonia recovery process. In practice, the ammonia recovery system of the present invention does not necessarily have a means for measuring the ammonia concentration in the gas to be treated and the ammonia concentration in the treated gas.

[0073] The ammonia recovery device of the present invention is a technology that can recover ammonia, which is a product of odor control measures mainly in the livestock industry, as liquid fertilizer that can be used as fertilizer.The main fields of use include the livestock industry and the fertilizer industry, but it can also be used in other industrial fields that emit ammonia. [Industrial Applicability]

[0074] The ammonia recovery apparatus of the present invention can reduce the workload of workers when recovering ammonia components through acid treatment, and can also produce a recovered solution with a stably adjusted concentration that can be used as fertilizer. Therefore, it can be applied to a wide range of fields, including the livestock industry, and is also excellent from the perspective of resource reuse. [Explanation of symbols]

[0075] 1. Ammonia recovery unit 2. Processing vessel 2a Outlet 3. Reaction chamber 4 Gas supply pipe 5 Gas exhaust pipe 6 Circulation Pump 7 pH sensors 8 Liquid level sensor 9 Flow Sensor 10 Retention fluid 11 Control device L1 water supply pipe L2 chemical supply pipe L3 discharge pipe L a circulation path V1, V2, V3, V4 valves

Claims

1. An ammonia recovery apparatus that circulates an acidic solution in contact with a gas to be treated that contains ammonia, and finally discharges a liquid containing an ammonia component accumulated in a treatment vessel as a recovered liquid, the ammonia recovery apparatus includes a pH measuring means for measuring a pH of the stored liquid, a liquid volume measuring means for measuring a liquid volume of the stored liquid, a discharge valve for discharging the stored liquid from the treatment vessel, and a control device; The ammonia recovery apparatus, wherein the control device controls opening and closing of the discharge valve based on the pH and amount of the stored liquid in the treatment vessel.

2. 2. The ammonia recovery apparatus according to claim 1, wherein the control device opens the discharge valve to discharge the stored liquid when the pH of the stored liquid reaches a predetermined value and the amount of the stored liquid is a predetermined amount.

3. the ammonia recovery device has a water valve for supplying water to the treatment vessel, 3. The ammonia recovery apparatus according to claim 2, wherein, when the pH of the stored liquid reaches a predetermined value and the amount of the stored liquid is less than a predetermined amount, the control device opens the water valve to supply water until the stored liquid reaches the predetermined amount, and then opens the discharge valve to discharge the stored liquid.

4. 3. The ammonia recovery apparatus according to claim 1, wherein the control device issues an alarm of an abnormal state when the amount of the stored liquid reaches a predetermined amount before the pH of the stored liquid reaches a predetermined value.

5. the ammonia recovery device has a water valve for supplying water to the treatment vessel and a flow rate measuring means for measuring a circulating flow rate of the stored liquid, 3. The ammonia recovery apparatus according to claim 1, wherein the control device opens the water valve to supply water to the treatment vessel to dilute the stored liquid when a circulation flow rate of the stored liquid becomes less than a predetermined amount before the pH of the stored liquid reaches a predetermined value.

6. 3. The ammonia recovery apparatus according to claim 1, wherein the stored liquid contains a phosphoric acid solution.

7. An ammonia recovery method in which an acidic solution is circulated and brought into contact with a gas to be treated containing ammonia, and a liquid containing an ammonia component accumulated in a treatment vessel is finally discharged as a recovered liquid, The ammonia recovery method includes a pH measurement step of measuring the pH of the stored liquid and a liquid volume measurement step of measuring the liquid volume of the stored liquid, and is characterized in that discharge of the stored liquid from the treatment vessel is automatically controlled based on the pH and liquid volume of the stored liquid in the treatment vessel measured in these steps.

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