JP3671001B2 - Ammonia treatment method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ammonia treatment method and apparatus that removes ammonia nitrogen in waste water and sludge by treating waste water and sludge containing ammonia nitrogen by an ammonia stripping method, etc., in particular ammonia nitrogen and SS content, hardness Treatment method and apparatus for wastewater and sludge containing components (Ca, Mg) or metal ions that generate hydroxide when pH is raised, and treatment method for ammonia-containing wastewater or sludge that easily causes scaling and clogging And related to the device.
[0002]
[Prior art]
Examples of waste water in which ammonia nitrogen and hardness components coexist include gypsum by injecting Ca salt in a flue gas desulfurization device installed for the purpose of removing soot and SO ₂ gas in boiler exhaust gas at a thermal power plant. However, there is a gypsum-saturated desulfurization effluent containing ammonia discharged from the apparatus and containing ammonia resulting from ammonia injection in the preceding electric dust collector.
The wastewater and sludge in which ammonia nitrogen and SS are coexisted include livestock sewage, human waste or domestic wastewater.
[0003]
Biological nitrification and denitrification treatment is generally used as a method for removing ammonia nitrogen from wastewater. However, this biological treatment method is difficult to manage and requires a large installation space. It is necessary to treat the generated sludge, and it is not suitable for the treatment of wastewater containing high concentration of ammonia nitrogen (the limit is to remove ammonia nitrogen with a concentration of several hundred mg / L). A physicochemical ammonia nitrogen removal method as an alternative to the chemical treatment method is being proposed.
[0004]
With regard to such a physical ammonia nitrogen removal method, for example, an ammonia stripping method or the like has been proposed, and this ammonia stripping method converts ammonium ions into free ammonia by raising the pH of the water to be treated, The ammonia is removed by moving the ammonia from the water to be treated into steam or air by steam or air stripping. Conventionally, a stripping tower that performs steam or air stripping has been filled with a plastic filler or the like in order to ensure sufficient contact between steam or air and the water to be treated. Water is sprayed more and falls between the fillers, repeating the formation and destruction of water droplets. During this time, the water droplets come into contact with steam or air, and ammonia is diffused from the water into the steam or air as a gas.
[0005]
The pH of the water to be treated is adjusted with an alkali source such as sodium hydroxide, calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, and calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, etc. are inexpensive. However, when these alkali sources are used, they react with carbonates and sulfates contained in the water to be treated to produce calcium or magnesium carbonates or sulfates or hydroxides. As a result of these adhering as a scale between the packing materials inside the diffusion tower, it is necessary to block the inside of the diffusion tower, hinder long-term continuous operation, and to frequently clean the inside. In addition, when the wastewater to be treated contains substances that cause precipitation due to alkali, for example, magnesium sulfate, aluminum sulfate, etc., the scale adheres to the packed bed regardless of which alkali source is used, and the above problem May occur.
[0006]
[Problems to be solved by the invention]
In order to eliminate such drawbacks, Japanese Patent Application Laid-Open No. 55-42239 discloses that a plurality of reaction vessels divided by partition plates are formed in a horizontal reaction vessel, and each reaction vessel is provided with a gas-liquid contact device and the device. A gas blowing pipe and a liquid warming device provided at the lower part of the reactor are disposed, and a safety water injection pipe, a calcium hydroxide injection pipe for ammonia solution decomposition, and a safety water discharge pipe are attached to the reaction tank. Ammonia containing wastewater (hereinafter referred to as raw water) is sequentially passed through to strip the ammonia in the raw water.
However, since the conventional technology is such that gas is blown into a plurality of locations along the flow direction in the tank while continuously flowing the raw water in a meandering shape by the partition plate, it is horizontal and has a large installation area and continuously. Since there is a hardness component such as Ca or Mg in the waste water, since these components circulate slowly in the equation, these components will precipitate as scales in the processing equipment (heat exchanger, heater, processing tank, piping, etc.) The problem cannot always be solved.
[0007]
Further, in order to solve the above-mentioned drawbacks, in Japanese Patent Application Laid-Open No. 2000-301137, an alkali is added to ammonia-containing wastewater, and this is brought into contact with the air circulating between the ammonia recovery tower and the ammonia in the water to be treated. In the air, the inside of the stripping tower is hollow, the stripping tower is formed to extend in the horizontal direction, and is divided into two or more regions in which the water to be treated is sprayed in the horizontal direction, A technique is proposed in which treated water brought into contact with circulating air in the region is extracted and the ammonia conversion reaction is promoted in the reaction tank, and then returned to the downstream region of the stripping tower.
However, since the prior art has a horizontally long structure in which the diffusion tower is formed by extending in the horizontal direction and divided into two or more regions in which the water to be treated is sprayed in the horizontal direction, the installation area becomes large, and the receiving tank Many ancillary facilities such as pumps and pumps are required.
[0008]
Furthermore, in JP 2000-288538 A, a waste water in which ammonia nitrogen and a hardness component coexist is brought into contact with a cation exchange resin tower to remove a hardness component in the waste water. Thereafter, a technique for removing ammonia nitrogen by treating the waste water with an ammonia nitrogen removing apparatus by an ammonia stripping method or a catalytic oxidation method has been proposed.
[0009]
However, since this technology removes hardness components (Ca, Mg) in wastewater in advance using ion exchange resin, it is suitable for cases where there are many SS (floating matter, suspended matter) such as livestock wastewater and human waste. Even if this is not possible, the ion exchange resin must be changed frequently.
[0010]
In view of the problems of the prior art, the present invention is a method for treating wastewater and sludge containing ammonia ions and SS, hardness components (Ca, Mg) or metal ions that generate hydroxide when the pH is raised. It is an object of the present invention to provide an ammonia treatment method and apparatus that are particularly effective for ammonia-containing wastewater or sludge that tends to cause scaling and blockage.
More specifically, ammonia can be efficiently stripped and removed without clogging the distillation column even for ammonia-containing wastewater mixed with substances that cause precipitation due to SS and alkali. A method and apparatus for treating ammonia in wastewater or sludge capable of long-term operation is provided.
Another object of the present invention is to provide an ammonia treatment method and apparatus capable of obtaining high removal performance with a small amount of steam blowing.
Still another object of the present invention is to provide an ammonia treatment method and apparatus capable of greatly reducing the installation area compared to the prior art.
[0011]
[Means for Solving the Problems]
In order to solve such a problem, the present invention connects a group of evaporators having substantially hollow interiors in a series in a vertical direction from the upper stage evaporator into which the raw water containing ammonia is introduced toward the downstream stage evaporator group. ammonia processing apparatus formed by arranging the vertical using Te, the raw water containing ammonia, was placed in the upper side of the evaporation in the can, after distillation of the ammonia vapor by stirring with steam, to stop the steam introduction, the upper The inside of the evaporator on the side is discharged into the lower evaporator by releasing the atmosphere, and then the process water is discharged to the next stage by introducing and stopping the steam and opening the atmosphere to the evaporator until reaching the final stage for each evaporator. The ammonia distillation is carried out by repeating the batch processing operation by sequentially switching to the above.
[0012]
According to this invention, scale removal is possible while operating for batch processing.
As in the prior art shown in FIG. 2 (a), the packed tower 101 and the plate tower have a large number of reduced portions 102 in the flow path. It becomes smaller and there are many scale troubles.
On the other hand, as shown in FIG. 2B, the present invention uses hollow cylindrical cans 11 to 13 so that the overall flow path area is reduced even if the scale 9 adheres to the inner wall surface of the cylindrical can. The scale trouble can be greatly reduced, and the maintenance interval for removing the scale can be greatly reduced.
As a method for reducing the amount of steam used in the present invention, as shown in the examples described later, a method of flowing the evaporator group in series may be adopted, and a combination with steam recovery using a steam compressor and an ejector is possible. May be used.
[0013]
In the present invention, since the internal structure is simple due to the batch type cylindrical can, chemical cleaning is easy. For example, scale components such as Mg and Ca are known to dissolve by acidifying the pH, and in the case of hard Ca scale, ethylenediaminetetraacetic acid (EDTA) is effective for dissolution. It has been known.
[0014]
According to a second aspect of the invention, a concatenation of evaporators group series (series), the actual qualitative uppermost side evaporator downstream stage evaporation the evaporator group cavity raw water containing ammonia is introduced It is an ammonia treatment device that is connected to a series in a vertical type for a group of cans and arranged in a vertical type,
Steam introduction means for sequentially introducing the steam introduced into the downstream-stage evaporator into the upstream-stage evaporator;
Treated water discharge means for connecting an atmosphere opening passage to each of the evaporators, sequentially opening the evaporators to the atmosphere through the passages, and sequentially dropping the treated water treated on the upstream stage side to the evaporator on the downstream stage side,
Switching means for selectively introducing the steam and releasing the atmosphere;
The ammonia processing apparatus is characterized in that ammonia distillation is performed by repeating the batch processing operation by switching the steam supplied and stopped by the switching means and discharging the treated water to the next stage by opening to the atmosphere for each evaporator .
[0015]
In this case, an air release passage is connected to each of the evaporators, the evaporators are sequentially opened to the atmosphere through the passages, and the treated water processed on the upstream stage side is sequentially dropped into the evaporator on the downstream stage side to perform the multi-stage treatment. Further, it is preferable that a switching means for selectively introducing the steam and releasing the atmosphere is provided so that the ammonia treatment in each evaporator can be processed batchwise.
[0016]
Furthermore, the present invention relates to a steam introduction means, the ammonia vapor that has been distilled in evaporator downstream stage side, by a means that is introduced into the evaporator of the entrained sequentially upstream the steam towards the evaporator upstream stage side It is preferable that the ammonia vapor sequentially introduced into the upstream evaporator by the introduction means is sequentially concentrated and distilled.
This makes it possible to obtain high-concentration ammonia distilled water with a reduced ammonia concentration in the treated water and a small amount of steam.
[0017]
Further, in the present invention, the diameter of the treated water discharge pipe for connecting the group of substantially hollow evaporators in series may be 1/20 or more, preferably 1/4 or more and 1 or less of the diameter of the evaporator. Thereby, even when a scale adheres to the treated water discharge pipe, blockage can be prevented. Further, in the present invention, it is preferable that a treatment water discharge pipe for connecting the evaporator group in series is provided with a means for absorbing expansion or vibration such as expansion.
Furthermore, in the present invention, for batch processing, a heat absorbing means for absorbing the vibration even when vibration is generated is provided at the connecting portion of each stage of the evaporator. For this reason, the connecting portion is not damaged even by repeated introduction of steam and release to the atmosphere.
[0018]
Furthermore, a mist removing device is interposed in the pipe line for introducing the steam into each of the evaporators, thereby preventing the scale from adhering to the steam pipe.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, unless otherwise specified, the dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention.
FIG. 1 shows a three-stage batch type ammonia stripping apparatus according to an embodiment of the present invention, in which an evaporator group in which evaporators 11 to 13 are connected in series in three stages is vertically arranged.
As shown in FIG. 2 (b), the evaporators 11 to 13 are don-shell cylindrical cans with no filling inside, and a discharge pipe 21 for discharging treated water into the next stage evaporator or treatment tank is provided at the bottom. It has been. In addition, as shown in FIG. 1, the connection part of the discharge pipe 21 of each step | paragraph is made to function as a heat | fever extension or vibration absorption part through the expansion 18 for vibration absorption as shown in FIG. Further, the evaporators 11 to 13 may be not only cylindrical cans but also rectangular tubes and truncated cone cans having a conical bottom. By setting the diameter of the discharge pipe to 1/20 or more, preferably 1/4 to 1 with respect to the diameter of the evaporator, it is possible to discharge at once, and clogging does not cause clogging.
[0020]
A pipe 20 for supplying raw water whose pH is adjusted is connected to the first-stage evaporator 11 via a raw water supply valve 23. Reference numeral 29 denotes a concentrated ammonia vapor extraction pipe, and the concentrated ammonia vapor extracted from the pipe 29 is cooled and condensed by the cooling water in the condenser 14 and led to the recovered ammonia water tank 50.
30B is a pipe for introducing the steam from the second stage evaporator into the first stage evaporator through the mist removing device 17, and the pipe 30B is an air release valve from the air vent pipes 10 and 10A after the completion of the steam introduction heating. The atmosphere is introduced by opening 15 and the opening of the discharge valve 24 (open to the atmosphere), so that the treated water can be discharged to the second stage evaporator 12 at once.
[0021]
The second-stage evaporator 12 is also connected to a pipe 21 for supplying treated water from the first-stage evaporator 11 via an expansion 18 and a discharge valve 24. 30A is a pipe for introducing the vapor from the third stage evaporator into the second stage evaporator through the mist removing device 17, and the pipe 30A is air-conditioned from the air vent pipes 10 and 10B after completion of the steam introduction heating. The atmosphere is introduced by opening the release valve 16 and the discharge valve 25 (open to the atmosphere), and the treated water can be discharged to the third stage evaporator 13 at a stretch.
[0022]
The third-stage evaporator 13 is also connected to a pipe 21 for supplying treated water from the second-stage evaporator 12 via an expansion 18 and a discharge valve 25. Reference numeral 30 denotes a pipe through which steam is blown into the third-stage evaporator 13 by the steam supply valve 31.
Further, after the completion of the steam blowing, the three-stage evaporator 13 is introduced with the atmosphere by opening the air release valve 16 and opening the discharge valve 26 from the steam pipe 30A and the air vent pipes 10 and 10B (open to the atmosphere), and the treated water tank. 60 is configured such that treated water can be discharged at once.
[0023]
The pH adjusting tank 41 is configured to supply a pH adjusting agent in accordance with a pH meter 46 attached to the treated water tank 60 after supplying raw water from the raw water supply pipe 20A. Caustic soda is the most common pH adjuster, but relatively inexpensive calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, and the like can also be used.
The pH adjustment can be performed by supplying a pH adjusting agent according to a pH meter 45 attached to the pH adjusting tank 41. The pH at this time is preferably 9 to 10.5 in the treated water tank and 9 to 12 in the pH adjusting tank.
[0024]
The raw water whose pH has been adjusted as described above is supplied from the raw water supply pipe 20 through the raw water supply valve 23 until the level reaches a predetermined level by a level meter 51 attached to the first stage evaporator. 11 is sent.
On the other hand, a level meter 52 is connected to the recovered ammonia water tank 50 on the outlet side of the condenser 14, and the amount of steam is adjusted via the steam supply valve 31 so that the amount of recovered ammonia water evaporated becomes a predetermined amount.
[0025]
Next, the operation procedure of this embodiment will be described.
The first discharge valve 24 is closed, the pH-adjusted raw water is introduced into the first evaporator 11, and the valve 23 is closed. Then, the steam is supplied to the third stage evaporator 13 through the steam blowing pipe 30. It introduce | transduces and the treated water of this evaporator 13 is heated. When the temperature in the evaporator 13 is heated, the ammonia vapor, along with water vapor, passes through the steam pipe 30A and enters the second stage evaporator 12, and similarly, the treated water is heated by steam and the ammonia in the treated water is heated to the steam side. Taken out. Subsequently, ammonia vapor from the second stage evaporator 12 together with water vapor passes through the steam pipe 30B and enters the first stage evaporator 11, and is heated in the same manner, and ammonia in the treated water is further taken out to the steam side. As a result, the concentration of recovered ammonia increases. The ammonia vapor generated in the uppermost evaporator 11 is extracted from the extraction pipe 29, cooled and condensed by the cooling water in the condenser 14, and led to the recovered ammonia water tank 50.
In the recovered ammonia water tank 50, after a predetermined amount of concentrated ammonia is recovered by the level meter 52, the steam supply valve 31 is closed and the introduction of steam is stopped.
[0026]
After the stop of the blowing of steam, the third stage evaporator 13 is treated with the atmosphere introduced from the steam pipe 30A and the air vent pipes 10 and 10B by opening the atmosphere release valve 16 and opening the discharge valve 26 (atmosphere release). The treated water is discharged into the water tank 60 at once.
After that, when the discharge valve 26 is closed and the discharge valve 25 is opened, the atmosphere is introduced from the steam pipe 30 </ b> A and the air vent pipes 10, 10 </ b> B by opening the atmosphere release valve 16 (atmosphere release). The treated water is discharged into the can 13.
Further, when the discharge valve 25 is closed and the discharge valve 24 is opened, the first-stage evaporator 11 is also introduced into the first-stage evaporator 11 by opening the atmosphere release valve 15 from the air vent pipes 10 and 10A (open to the atmosphere). The treated water is discharged to the second stage evaporator 12.
[0027]
Then, the first discharge valve 24 is closed, the raw water supply valve 23 is opened, and the raw water whose pH is adjusted is dropped into the first evaporator 11.
Thereafter, steam is introduced into the third-stage evaporator 13 through the steam blow-in pipe 30 to heat the treated water in the evaporator 13 and perform ammonia distillation. When the temperature in the evaporator 13 is heated, ammonia vapor, along with water vapor, passes through the steam pipe 30A and enters the second stage evaporator 12, and similarly, the treated water is steam-heated to perform ammonia distillation. Subsequently, when the inside of the second stage evaporator 12 is heated, the ammonia vapor and water vapor pass through the steam pipe 30B and enter the first stage evaporator 11, and similarly heated to perform ammonia distillation. The ammonia vapor generated in the uppermost evaporator 11 is extracted from the extraction pipe 29, cooled and condensed by the cooling water in the condenser 14, and led to the recovered ammonia water tank 50.
Thereafter, the above operation is repeated.
[0028]
According to such an example, when the evaporation rate was 20%, the ammonia concentration of the treated water decreased from 2500 ppm to about 500 ppm in one distillation process, but dropped into the evaporator for three stages and repeated three times. In the case of performing distillation, the ammonia concentration of the treated water could be greatly reduced from 2500 ppm to 15 ppm. In addition, as a result of continuous operation, the processing performance was not lowered due to scaling and the operation was not disabled.
【The invention's effect】
As described above, according to the present invention, the present invention uses an internal cavity type evaporator and is used for batch processing when ammonia nitrogen and SS content, hardness components (Ca, Mg) or pH is increased. Scaling and clogging do not occur even in the treatment of wastewater and sludge containing metal ions that generate hydroxide. More specifically, ammonia can be efficiently stripped and removed without clogging the evaporator even for ammonia-containing wastewater mixed with substances that cause precipitation due to SS or alkali. Ammonia treatment in waste water or sludge that can be operated for a long time can be performed.
Further, according to the present invention, since the evaporator group is connected in series, a high removal performance can be obtained with a small amount of steam blown.
Further, according to the present invention, by arranging the evaporators connected to the series in a vertical type, a large installation area can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a main part of a three-stage batch type ammonia stripping apparatus according to an embodiment of the present invention.
2A is a schematic diagram of a conventional packed tower, FIG. 2B is a schematic diagram of an evaporator according to the present invention, the left is a perspective view, the center is a plan view, and the right is a scale attached. FIG.
[Explanation of symbols]
11 to 13 Evaporator 10, 10A, 10B Air vent pipe 15, 16 Atmospheric release valve 23 Raw water supply valve 24, 25, 26 Discharge valve 14 Condenser 17 Mist removal device 18 Expansion 30, 30A, 30B Steam pipe 31 Steam supply valve 20A , 20 Raw water supply pipe 21 Drain pipe 29 of each stage 29 Ammonia vapor extraction pipe 41 pH adjustment tank 50 Recovery ammonia water tank 60 Treatment water tank 42 pH adjustment agent supply pipe 43 pH adjustment agent supply valve 44 Raw water supply pump 45 pH adjustment tank pH meter 46 Treatment water tank pH meter 51 Evaporator level meter 52 Recovered ammonia water tank level meter

Claims (5)

Using an ammonia treatment device that is arranged vertically in a series connected to a downstream stage evaporator group from an upper stage evaporator into which raw water containing ammonia is injected into a group of substantially empty evaporators, Raw water containing ammonia is put into the upper evaporator, and after the ammonia vapor is distilled by stirring with steam, the introduction of the steam is stopped, and the treated water is released into the lower stage by opening the upper evaporator to the atmosphere. discharged to the evaporator, to evaporate cans to the final stage following, the ammonia by distillation repeated batch processing operations sequentially switches the treated water discharged to the next stage by steam introduction and stop the air opening in each evaporator A method for treating ammonia. Real qualitatively cavity evaporator group vertical ammonia treatment device formed by arranging the vertical linked to series toward the downstream stage evaporator group than the uppermost side evaporation cans raw water is turned containing ammonia Because
Steam introduction means for sequentially introducing the steam introduced into the downstream-stage evaporator into the upstream-stage evaporator;
Treated water discharge means for connecting an atmosphere opening passage to each of the evaporators, sequentially opening the evaporators to the atmosphere through the passages, and sequentially dropping the treated water treated on the upstream stage side to the evaporator on the downstream stage side,
Switching means for selectively introducing the steam and releasing the atmosphere;
An ammonia treatment apparatus characterized in that ammonia distillation is carried out by repeating batch processing operation by switching the steam introduction and stop by the switching means and discharging the treated water to the next stage by opening to the atmosphere for each evaporator . The steam introduction means is a means for introducing ammonia vapor distilled in the downstream-stage evaporator into the upstream-side evaporator along with the steam directed to the upstream-stage evaporator , 3. The ammonia processing apparatus according to claim 2, wherein ammonia vapor sequentially introduced into the upstream evaporator by the means is configured to be successively concentrated and distilled.   3. An ammonia treatment apparatus according to claim 2, wherein means for extending or vibrating due to thermal expansion is interposed in the treated water discharge pipe connecting the evaporator groups in series.   The ammonia processing apparatus according to claim 2, wherein a mist removing device is interposed in a conduit for introducing steam into each of the evaporators.

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