WO2010098343A1

WO2010098343A1 - Methane fermentation system and apparatus for producing fertilizer using same

Info

Publication number: WO2010098343A1
Application number: PCT/JP2010/052844
Authority: WO
Inventors: 潤一高橋; 一孝梅津; 修濱本; 卓也三崎; 良則久芳
Original assignee: 三井造船株式会社; 国立大学法人帯広畜産大学
Priority date: 2009-02-27
Filing date: 2010-02-24
Publication date: 2010-09-02
Also published as: JP2010201297A; JP5491046B2

Abstract

To obtain a fermentation liquor by which the problem of the pollution of underground water with nitrogen can be reduced when the fermentation liquor is applied back to a farm land as a fertilizer, disclosed is a methane fermentation system characterized by being provided with a methane fermentation tank, a heating tank for heating a fermentation liquor released from the methane fermentation tank to a temperature higher than the fermentation temperature in the methane fermentation tank, and an ammonia-removing device for removing ammonia from the fermentation liquor released from the heating tank. According to this methane fermentation system, organic nitrogen in the fermentation liquor released from the methane fermentation tank is degraded into ammonia nitrogen so that the ratio of ammonia nitrogen is increased, and ammonia is then removed by the ammonia-removing device in the following step. Thus, nitrogen in the methane fermentation liquor can be reduced.

Description

Methane fermentation system and fertilizer production equipment using the same

The present invention relates to a methane fermentation system for reducing the amount of nitrogen contained in a fermented liquid (methane fermented liquid) obtained by subjecting a material to be fermented to methane fermentation, and a fertilizer manufacturing apparatus using the same.

Conventionally, organic waste such as food waste, livestock manure and sewage treatment sludge is used as raw material (fermented material) to perform anaerobic methane fermentation treatment, and biogas generated at that time is collected and recycled energy The technique utilized as is known (Patent Document 1). On the other hand, methane fermentation liquor (digested liquor) is reduced to farmland because it contains a large amount of plant nutrients, and its use as a fertilizer is being studied.

However, when the methane fermentation liquor is used as fertilizer for agricultural land reduction, there are the following problems.
The fermented liquid contains a considerable amount of organic nitrogen and ammonia nitrogen, and the value of Kjeldahl nitrogen (total of organic nitrogen and ammonia nitrogen) in the fermented liquid is considerably high. When reduced to farmland as fertilizer, the organic nitrogen and ammonia nitrogen are converted into nitrate ions and nitrite ions by microorganisms in the soil, and excess nitrogen content that is not absorbed by the plants out of these nitrate nitrogen enters the groundwater. There was a problem of polluting (nitrogen contamination).

The present invention has been made in view of the above circumstances, and its problem is that a methane fermentation system capable of obtaining a fermented liquid in which the nitrogen contamination problem of groundwater is reduced when reduced to farmland as a fertilizer and fertilizer production using the same To provide an apparatus.

In order to achieve the above object, the first aspect of the present invention includes a methane fermentation tank, a heating tank that raises the fermentation liquid from the methane fermentation tank to a temperature higher than the fermentation temperature of the methane fermentation tank, An methane fermentation system comprising: an ammonia removal device that removes ammonia from a fermentation liquor coming out of a temperature raising tank.

According to this aspect, in the temperature raising tank, the temperature of the fermentation liquid (methane fermentation liquid) coming out of the methane fermentation tank is increased to a temperature higher than the fermentation temperature of the methane fermentation tank, so that the organic nitrogen in the fermentation liquid is increased. Reaction which decomposes | disassembles into ammonia nitrogen advances, and the ratio of ammonia nitrogen which exists in fermentation liquid can be increased. In order to increase the proportion of ammonia nitrogen, it is more effective to raise the temperature of the heating tank to 55 ° C. or higher, 60 ° C., 62 ° C., 65 ° C., or even 70 ° C.
And, since the ammonia removal by the ammonia removing device is performed on the fermentation liquid in a state where the existence ratio of the ammonia nitrogen is increased, the ammonia nitrogen can be effectively reduced and contained in the fermentation liquid. The total amount of organic nitrogen and ammonia nitrogen can be effectively reduced.
That is, the total amount of nitrogen in the fermentation broth can be reduced to remove in advance the excess nitrogen that becomes the source of nitrogen contamination, thus reducing the problem of nitrogen contamination of groundwater when the fermentation broth is reduced to farmland as a fertilizer can do.

Further, when the temperature of the heating tank is increased to 60 ° C., 62 ° C., 65 ° C., or 70 ° C. as described above, the sterilization effect of the fermentation broth itself can be obtained at the same time in addition to the reduction of the excess nitrogen. it can. That is, bacteria and viruses can be sterilized at the same time, and the problem of soil contamination with bacteria and viruses when the fermented liquor is reduced to farmland can be prevented. Above 70 ° C, porcine prabovirus can be killed in a short time.

According to a second aspect of the present invention, in the methane fermentation system according to the first aspect, the ammonia removing device diffuses and removes ammonia from the liquid by gas-liquid contact between the supplied gas and the fermentation broth. It is a tower and is configured to utilize part or all of the biogas produced in the methane fermentation tank as the gas supplied to the ammonia diffusion tower.

According to this aspect, by configuring the ammonia removal device as an ammonia diffusion tower capable of gas-liquid contact, a large amount of ammonia can be effectively diffused and removed from the fermentation broth in a state in which the proportion of ammonia nitrogen is increased. Is possible.
Furthermore, since part or all of the biogas produced in the methane fermentation tank is used as gas-liquid contact gas supplied to the ammonia diffusion tower, the gas-liquid contact gas supply device is separately installed. This eliminates the need to reduce the manufacturing cost of the entire system.
Furthermore, if the ammonia removed from the fermentation liquor in the ammonia diffusion tower is returned to the original biogas line and sent to the desulfurizer, it is possible to prevent pH reduction (acidification) accompanying the desulfurization process of the desulfurizer. it can.

A third aspect of the present invention is characterized by comprising a methane fermentation tank in which a fermentation process is performed at a temperature of 60 ° C. or higher, and an ammonia removal device that removes ammonia from the fermentation liquor discharged from the methane fermentation tank. It is a methane fermentation system.

According to this aspect, compared with so-called medium temperature methane fermentation (about 37 ° C.) and high temperature methane fermentation (about 55 ° C.), a normal high temperature fermentation of 60 ° C. or higher, for example, 62 ° C. or 65 ° C., or even 70 ° C. By performing high-temperature methane fermentation exceeding 1, the reaction in which organic nitrogen in the fermentation broth decomposes into ammonia nitrogen proceeds, and the proportion of ammonia nitrogen present in the fermentation broth can be increased. In order to increase the proportion of ammonia nitrogen, it is more effective to raise the fermentation temperature in the methane fermenter to 62 ° C., 65 ° C., or even 70 ° C.
And, since the ammonia removal by the ammonia removing device is performed on the fermentation liquid in a state where the existence ratio of the ammonia nitrogen is increased, the ammonia nitrogen can be effectively reduced and contained in the fermentation liquid. The total amount of organic nitrogen and ammonia nitrogen can be effectively reduced.
That is, the total amount of nitrogen in the fermentation broth can be reduced to remove in advance the excess nitrogen that becomes the source of nitrogen contamination, thus reducing the problem of nitrogen contamination of groundwater when the fermentation broth is reduced to farmland as a fertilizer can do.

Further, when the temperature of the methane fermenter is increased to 60 ° C., 62 ° C., 65 ° C., or 70 ° C. as described above, the sterilizing effect of the fermentation broth itself can be obtained at the same time in addition to the reduction of excess nitrogen. it can. That is, bacteria and viruses can be sterilized at the same time, and the problem of soil contamination with bacteria and viruses when the fermented liquor is reduced to farmland can be prevented. Above 70 ° C, porcine prabovirus can be killed in a short time.

According to a fourth aspect of the present invention, in the methane fermentation system according to the third aspect, a part of the fermentation broth that has exited the ammonia removing device is returned to the methane fermentation tank. .

When ultra-high temperature methane fermentation was performed as described above, a large amount of ammonia was generated in the methane fermenter compared to medium temperature methane fermentation (about 37 ° C.) and high temperature methane fermentation (about 55 ° C.). A phenomenon in which fermentation is difficult to proceed due to ammonia, that is, a phenomenon of ammonia inhibition appears.

According to this aspect, since the fermentation liquor that has come out of the ammonia removal device has undergone ammonia removal treatment, the ammonia concentration in the fermentation liquor in the methane fermentation tank can be reduced by returning this fermentation liquor to the methane fermentation tank. Thus, ammonia inhibition can be prevented.

A fifth aspect of the present invention is characterized in that in the methane fermentation system according to the first aspect or the second aspect, the methane fermentation tank is subjected to a fermentation treatment in a temperature range of 35 to 40 ° C.

Medium temperature methane fermentation (35 ℃ ~ 40 ℃) with low temperature has the merit that methane fermentation can be performed without worrying about the problem of ammonia inhibition, but the resulting fermentation broth has a high proportion of organic nitrogen and ammonia. The state of nitrogen is low. Therefore, even if ammonia is removed from the fermentation liquid as it is, the efficiency of ammonia removal is low.
According to this aspect, since the temperature raising tank is provided in the latter stage of the medium temperature methane fermentation tank, in addition to the above-described effects of the first aspect or the second aspect, the fermentation liquid discharged from the medium temperature methane fermentation tank Even if a large amount of organic nitrogen is contained therein, the organic nitrogen in the fermentation broth can be decomposed into ammonia nitrogen by raising the temperature of the fermentation broth to 60 ° C. or higher in the heating tank.

A sixth aspect of the present invention is characterized in that, in the methane fermentation system described in the first aspect or the second aspect, the temperature in the heating tank is 65 to 80 ° C.

According to this aspect, since the temperature in the heating tank is high, the operational effects of the first aspect or the second aspect can be obtained more effectively. That is, the amount of nitrogen in the fermentation broth that has passed through the ammonia removing device can be greatly reduced.

The seventh aspect of the present invention is characterized in that, in the methane fermentation system described in the third aspect or the fourth aspect, the temperature in the methane fermentation tank is 65 to 80 ° C.

According to this aspect, since the temperature in the methane fermenter is high, the operational effect of the third aspect or the fourth aspect can be obtained more effectively. That is, the amount of nitrogen in the fermentation broth that has passed through the ammonia removing device can be greatly reduced.

The eighth aspect of the present invention utilizes a methane fermentation system characterized in that the fermentation liquid after removal of ammonia obtained from the methane fermentation system described in the first aspect or the third aspect is used as a fertilizer. It is a fertilizer manufacturing device.

The fertilizer manufactured by the fertilizer manufacturing apparatus using the methane fermentation system according to the present embodiment can reduce the problem of nitrogen contamination of groundwater when it is returned to farmland.
Moreover, when the fertilizer is returned to farmland, the problem of soil contamination with bacteria and viruses can also be prevented.

According to the present invention, the amount of nitrogen in the methane fermentation broth can be reduced, the amount of nitrogen contained in the fermentation broth obtained by this system is small, and nitrogen pollution of groundwater when reduced to farmland as fertilizer Problems can be reduced.

The schematic block diagram of the methane fermentation system which concerns on the 1st Embodiment of this invention. The schematic block diagram of the methane fermentation system which concerns on the 2nd Embodiment of this invention. The schematic block diagram of the methane fermentation system which concerns on the 3rd Embodiment of this invention. The figure showing the relationship between the process conditions in the heating tank in Example 1- Example 6 which concerns on this invention, and the total nitrogen amount in the ammonia removal fermentation liquid corresponding to it. The figure showing the relationship between the temperature in the stripping tower in the ammonia stripping tower which concerns on this invention, and the density | concentration of the exiting ammonia diffused.

Hereinafter, embodiments of the methane fermentation system according to the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a methane fermentation system according to the present invention.
In the methane fermentation system of the first embodiment, a methane fermentation solution 1 ′ obtained by subjecting the material to be fermented M to methane fermentation is finally sprayed onto farmland, and the material M to be fermented is subjected to methane fermentation. The obtained biogas G is collected by the gas holder 10 and is finally provided with a line L2 that is used as energy for the gas engine 11 or the like.

The line L1 for spraying the methane fermentation broth 1 ′ onto the farmland (agricultural land reduction) is a methane fermentation broth (digestion liquid) obtained by fermentation treatment of the material M to be fermented in the methane fermentation tank 1 and the methane fermentation tank 1. ) When 1 ′ is derived from the methane fermentation tank 1, the temperature of the methane fermentation liquid 1 ′ is increased and the temperature of the methane fermentation liquid 1 ′ is increased by the heat exchanger 5 for sending it to the temperature raising tank 2. The temperature of the methane fermentation broth 1 'is decomposed into ammonia nitrogen, and the temperature of the methane fermentation broth 1' is heated in the temperature riser 2 so that the fermentation broth 2 is heated. After being subjected to an ammonia emission treatment in the ammonia diffusion tower 3 and the ammonia diffusion tower 3 for causing the fermentation liquid 2 'derived from the heating tank 2 to come into gas-liquid contact and to diffuse and remove the ammonia in the fermentation liquid 2'. Disperse the obtained fermented liquid 3 'to farmland It is composed of a 'heat exchanger 5 for recovering the temperature of' the fermentation liquor 3.

On the other hand, the line L2 that uses the biogas G obtained by subjecting the material to be fermented M to methane fermentation as the energy of the gas engine 11 or the like is a discharge pipe 6 for deriving the biogas G generated in the methane fermentation tank 1. In order to send the desulfurization device 4 for removing sulfur content in sulfur compounds (for example, hydrogen sulfide, mercaptan, etc.) generated together with biogas by methane fermentation, and to send biogas after desulfurization to the gas engine 11 and the like, It is comprised from the gas holder 10 for storing biogas temporarily.

The lead-out pipe 6 includes a biogas introduction pipe 6 'branched in the middle. This biogas introduction pipe 6 ′ is used to feed biogas generated in the methane fermentation tank 1 as a gas to be brought into gas-liquid contact with the fermentation liquid 2 ′ treated in the temperature raising tank 2 and the ammonia diffusion tower 3. is there. In addition, the ammonia diffused by the gas-liquid contact in the ammonia diffusion tower 3 is returned through the ammonia lead-out pipe 7 connected to the lead-out pipe 6 and sent to the desulfurizer 4 together with the biogas in the lead-out pipe 6. It has become.

Examples of the material to be fermented M to be subjected to methane fermentation in this system include livestock waste, organic sludge, green farm waste, and the like. Examples of livestock waste include manure of livestock (eg, pigs, cows, chickens, etc.), carcasses and / or processed products thereof. Green farm waste includes agricultural waste, food processing waste, and the like as household waste, as well as household waste.

The methane fermenter 1 is composed of a tank in which air is shut off in order to maintain the activity by the absolute anaerobic methane fermentation bacteria. Fermenter 1 has a solids concentration (usually in the range of 3 to 40% by weight) and fermentation temperature (usually about 32 to 37 ° C for medium temperature fermentation, about 52 to 55 ° C for high temperature fermentation, and about 60 to 70 ° C for ultra high temperature fermentation. ), The shape and operating conditions vary. For example, in the case of a raw material (up to a solid concentration of 10% by weight) having a high water content by mixing washing wastewater, a wet type complete mixing type fermenter is used.
In addition, it is preferable to provide the heating means for heat retention in a fermenter as needed.

In the case of raw materials with a high water content (solids concentration up to about 10% by weight), a complete mixing type fermenter is used. About 15 days, high temperature methane fermentation bacteria (optimum temperature 55 ° C) may have a retention time (Retention Time) of about 15 days, and medium temperature methane fermentation bacteria (optimum temperature 37 ° C) may have a residence time of about 25-30 days. Is possible.

The fermented liquid after methane fermentation of the above-mentioned high water content type is a liquid containing, for example, a moisture content of 95% by weight and a solid content of about 5% by weight, and is a variety of liquids derived from anaerobic microorganisms and their metabolites. It contains a large amount of amino acids (containing a lot of organic nitrogen) and organic acids.

A well-known thing can be used about the heat exchangers 5 and 5 '. For example, a multi-tube cylindrical heat exchanger, a double tube heat exchanger, a plate heat exchanger, a coil heat exchanger, a spiral heat exchanger, and the like can be given.
The heat exchanger 5 is provided to feed the methane fermentation liquid 1 ′ fermented in the methane fermentation tank 1 after raising the temperature to the temperature raising tank 2. Thereby, in the temperature rising tank 2, the time until the temperature in the tank is raised to a predetermined temperature can be shortened.
The heat exchanger 5 ′ is provided for recovering the temperature of the fermentation liquid 3 ′ from which ammonia is removed by the ammonia diffusion tower 3 and coming out of the diffusion tower 3. In addition, the recovered heat recovered by the heat exchanger 5 ′ can be used for heating and heat insulation of the methane fermentation tank 1.

The temperature raising tank 2 is not particularly limited, and the temperature of the fermentation broth 1 can be raised to about 55 ° C. to 80 ° C., preferably 60 ° C. to 75 ° C., more preferably 62 ° C. to 70 ° C. (heating) Etc.). It is still preferable if it can be heated by steam.

In the present invention, when the temperature of the methane fermentation broth 1 ′ obtained by fermentation in the methane fermentation tank 1 is increased in the temperature raising tank 2, the organic nitrogen in the methane fermentation broth 1 ′ is decomposed into ammonia nitrogen. Therefore, the temperature of the methane fermentation liquid 1 ′ is increased and heat-treated to increase ammonia nitrogen in the fermentation liquid 2 ′.

The ammonia is removed by passing the fermented liquid 2 'through an ammonia removing device by the ammonia diffusion tower 3 in the subsequent stage, and as a result, the amount of organic nitrogen in the methane fermented liquid 1 is reduced.

The temperature of the heating tank 2 and the heat treatment time for decomposing the organic nitrogen in the methane fermentation liquid 1 into ammonia nitrogen vary depending on the conditions of the methane fermentation treatment.

For example, the processing conditions of the methane fermentation broth 1 in the temperature raising tank 2 are as follows: when medium temperature fermentation (about 37 ° C.) is performed, 70 to 80 ° C. for about 1 hour, and when high temperature fermentation (about 55 ° C.) is performed. When the ultra-high temperature fermentation (about 60 ° C.) is performed at 60 ° C. to 70 ° C. for about 1 to 4 hours, basically the temperature raising tank as in another embodiment (third embodiment) described later No processing in 2 is necessary. The reason is that the organic nitrogen is already decomposed into ammonia nitrogen during the fermentation process because it is processed at an extremely high temperature, and is present in the methane fermentation liquid 1 as ammonia nitrogen. In addition, when carrying out ultra-high temperature fermentation, there is no problem in providing a temperature raising tank 2 and performing a process of decomposing organic nitrogen remaining in the methane fermentation liquid 1 into ammonia nitrogen in the temperature raising tank 2. .

As mentioned above, although the process conditions of the methane fermentation liquid 1 in the temperature rising tank 2 change with conditions of a methane fermentation process, it is not limited to the conditions mentioned above, Temperature and heat processing time are suitably set according to the kind of methane fermentation process. It is possible to set.
Moreover, sterilization of the methane fermentation liquid 1 can also be performed by processing the methane fermentation liquid 1 subjected to the methane fermentation treatment in the heating tank 2.

The fermented liquid 2 ′ treated in the temperature raising tank 2 is introduced from the temperature raising tank 2 to the ammonia removing device. In this embodiment, an ammonia diffusion tower 3 is provided as an ammonia removing device.
The ammonia stripping tower 3 used in this embodiment introduces a liquid (fermented liquid 2 ′) from the top of the ammonia stripping tower 3 and introduces a gas (biogas G supplied from the biogas introduction pipe 6 ′) from the bottom. Thus, the liquid and the gas are made to face each other and come into contact with each other. Of course, the ammonia diffusion tower 3 should just be comprised so that gas-liquid contact can be carried out, and is not restricted to an opposing type.

In this embodiment, the biogas introduced into the ammonia diffusion tower 3 is biogas G generated from the methane fermentation tank 1. The biogas G outputs the feed force of the biogas G by the pressure accompanying the production of the biogas G itself generated in the methane fermentation tank 1, and the biogas G passes through the biogas outlet pipe 6 by the feed force. It is introduced into the ammonia diffusion tower 3 from the biogas introduction pipe 6 '. However, since the amount of biogas G produced varies, the pressure changes accordingly, and the feed force of biogas G is not constant. Therefore, in order to introduce a certain amount of biogas G into the ammonia diffusion tower 3, a valve 8 is provided on the biogas outlet pipe 6 to adjust the amount of biogas G introduced into the ammonia diffusion tower 3 to be constant. It is preferable to do this.

For example, when the amount of generated biogas G is small, the gas pressure is small, so the valve 8 is closed and the biogas G is introduced into the ammonia diffusion tower 3 through the biogas introduction pipe 6 '. On the other hand, when the amount of biogas G generated is large, the gas pressure is large, so that the valve 8 is opened by a predetermined amount, a part of the biogas G is introduced into the ammonia diffusion tower 3, and a part is introduced into the desulfurization tower 4. What should I do?

Examples of the ammonia diffusion tower described above include a spray type and a shelf type.
The temperature in the ammonia diffusion tower may be a temperature at which ammonia in the fermentation broth 2 ′ treated in the heating tank 2 can be appropriately diffused and removed, and is preferably about 55 to 80 ° C.

Furthermore, the ammonia removal device is not limited to the ammonia diffusion tower 3, and examples thereof include a membrane separation device.

Ammonia diffused in the ammonia stripping tower 3 is returned to the biogas lead-out pipe 6 through the ammonia lead-out pipe 7 connected to the biogas lead-out pipe 6, and introduced into the desulfurization tower 4 together with the biogas G to be desulfurized. The For example, when hydrogen sulfide or the like is biodesulfurized into sulfuric acid as in biodesulfurization treatment, the acidity in the desulfurization tower 4 is increased by the production of the sulfuric acid. As the acidity increases, the desulfurization capacity decreases. However, in this embodiment, since the biogas G contains ammonia diffused from the ammonia diffusion tower 3, the sulfuric acid is neutralized by the ammonia, so that the alkalinity can be ensured during desulfurization and the desulfurization conditions are maintained. It becomes easy. For example, it is effective when the desulfurization conditions must be maintained at pH 6 or higher.

The biogas G desulfurized by the desulfurization apparatus 4 is temporarily stored in a gas holder and used as energy for the gas engine 11 or the like as necessary.

On the other hand, the fermented liquid 3 ′ from which ammonia has been removed by gas-liquid contact in the ammonia diffusion tower 3 has reduced nitrogen that causes soil contamination, and is derived from the ammonia diffusion tower 3 and heated by the heat exchanger 5 ′. It is exchanged and sprayed on farmland as fertilizer (returned to farmland).

Thus, in the methane fermentation system of the present invention, it is possible to produce a fertilizer with reduced nitrogen content that can prevent groundwater contamination by nitrogen.

FIG. 2 is a schematic diagram showing a second embodiment of the methane fermentation system according to the present invention. The parts different from the first embodiment will be described, and the description of the common parts will be omitted.
In this embodiment, a blower 9 and a heat exchanger 5 ″ are provided, and warm air is introduced into the ammonia diffusion tower 3. With such a configuration, a certain amount of gas (air) can be introduced into the ammonia diffusion tower 3 regardless of the amount of biogas G that fluctuates.

The introduced air and the fermented liquid 2 ′ treated in the heating tank 2 are in gas-liquid contact in the ammonia diffusion tower 3, and the diffused ammonia is introduced into the deodorizing device 12 through the ammonia outlet pipe 7 ′ and deodorized. . The deodorization tower 12 removes ammonia and malodorous components (mercaptan, skatole, etc.) diffused together with ammonia.
In addition, it is also possible to make it the structure which can utilize the gas deodorized with the deodorizing apparatus 12 as a gas introduce | transduced into the ammonia diffusion tower 3 through the blower 9 again.

FIG. 3 is a schematic view showing a third embodiment of the methane fermentation system according to the present invention. The parts different from the first embodiment will be described, and the description of the common parts will be omitted.
This aspect is one aspect of the methane fermentation system according to the present invention when the ultra-high temperature methane fermentation treatment is performed.
In this embodiment, since the ultra-high temperature methane fermentation (about 60 to 70 ° C.) treatment is performed, the temperature of the methane fermentation liquid 1 ′ obtained by fermentation in the methane fermentation tank 1 is as high as about 60 to 70 ° C. Therefore, organic nitrogen in the methane fermentation broth 1 ′ is decomposed into ammonia nitrogen, and the proportion of ammonia nitrogen in the methane fermentation broth increases. Therefore, even if the temperature raising tank 2 is not provided as in Embodiment 1 or Embodiment 2, most of the organic nitrogen has already been decomposed into ammonia nitrogen in the methane fermentation liquid 1 ′. The methane fermentation liquor 1 ′ emitted from the gas can be directly introduced into the ammonia stripping tower 3 and brought into gas-liquid contact to dissipate ammonia, thereby reducing the amount of nitrogen in the methane fermentation broth 1 ′.

Here, as a characteristic of ultrahigh temperature methane fermentation, as described above, ammonia nitrogen in the methane fermentation broth 1 'increases, that is, the concentration of ammonia increases to cause fermentation inhibition. Therefore, in this embodiment, in order to reduce the ammonia concentration in the methane fermentation solution 1 ′, the fermentation solution 3 ′ from which ammonia has been removed by gas-liquid contact in the ammonia diffusion tower 3 is removed through the ammonia removal fermentation solution outlet pipe 7 ″. By returning to the fermenter 1, the ammonia concentration in the methane fermentation liquid is reduced to suppress ammonia inhibition.

[Example 1]
Hereinafter, the present invention will be described based on examples.
Using a 10 L methane fermentation tank, a medium temperature methane co-fermentation treatment (37 ° C.) between the separated garbage and the excreta of the milking cow was performed.
Next, the methane fermentation liquid (digested liquid) obtained by the methane fermentation treatment was introduced into the temperature raising tank through a heat exchanger.
Then, the temperature rising tank was heated up to 70 degreeC in the airtight state, and the methane fermentation liquid was heat-processed at 70 degreeC for 1 hour. Next, the fermented liquid heat-treated in the temperature raising tank is sprayed from the upper part of the ammonia diffusion tower whose interior is maintained at 65 ° C., and the biogas and gas produced by the intermediate temperature methane fermentation process introduced from the lower part of the ammonia diffusion tower. The fermented liquor which made the liquid contact and performed the ammonia removal process was obtained.
And total nitrogen and Kjeldahl in each fermented liquid of the methane fermented liquid which performed the intermediate temperature methane fermentation process, the fermented liquid after the temperature rising process in the temperature rising tank, and the fermented liquid (ammonia removed fermented liquid) which performed the ammonia removal process Nitrogen, ammonia-nitrogen sewerage test method ("Sewerage test method (1974 version), publisher: Takehide Ito, publisher: Japan Sewerage Association, first edition published on November 20, 1974, 3rd edition (1977) Quantification was carried out according to the method described in (May 20).

Here, the amount of total nitrogen, Kjeldahl nitrogen, and ammonia nitrogen will be described.
Nitrogen contained in fermentation broth obtained by fermenting organic fermented materials (eg, livestock manure) is classified as organic nitrogen, ammonia nitrogen, nitrate nitrogen and / or nitrite nitrogen. .
The total nitrogen amount refers to the total amount of nitrogen contained in the fermentation broth, that is, the total amount of organic nitrogen, ammonia nitrogen, nitrate nitrogen and / or nitrite nitrogen.
In the determination of Kjeldahl nitrogen, in addition to the amount of organic nitrogen, the amount of ammonia nitrogen existing in advance is also added.
In the methane fermentation (anaerobic fermentation) according to this embodiment, since nitrogen is anaerobic, most of the nitrogen is present in the form of organic nitrogen and ammonia nitrogen, not nitrate nitrogen and / or nitrite nitrogen. To do.

Expressing the above relationship in an example to be described later in an equation,

Total nitrogen amount = organic nitrogen amount + ammonia nitrogen amount + nitrate nitrogen and / or nitrite nitrogen amount
Kjeldahl nitrogen quantitative value = organic nitrogen + ammonia nitrogen
It becomes. Therefore,

Total nitrogen = Kjeldahl quantitative nitrogen + nitrate and / or nitrite nitrogen
However, in methane fermentation (anaerobic fermentation), since there is no generation of nitrate nitrogen and / or nitrite nitrogen, the amount of nitrate nitrogen and / or nitrite nitrogen is zero.
Therefore, the total nitrogen amount = Kjeldahl nitrogen amount.

[Example 2]

The heat treatment conditions of the methane fermentation liquid in the temperature raising tank were set at 65 ° C. for 1 hour, and the fermentation liquid treated in the temperature raising tank in the ammonia diffusion tower maintained at 60 ° C. was used as the ammonia diffusion tower. Example 1 is the same as Example 1 except that gas-liquid contact is made with the biogas produced by the intermediate temperature methane fermentation process introduced from the lower part of the sample.

[Example 3]
The heat treatment condition of the methane fermentation liquid in the temperature raising tank was set to 4 hours at 60 ° C., and the fermentation liquid treated in the temperature raising tank in the ammonia diffusion tower whose interior was maintained at 55 ° C. Example 1 is the same as Example 1 except that the gas-liquid contact is made with the biogas produced by the intermediate temperature methane fermentation process introduced from the lower part.

[Example 4]
The heat treatment condition of the methane fermentation liquid in the temperature raising tank was set to 1 hour at 60 ° C., and the fermentation liquid treated in the temperature raising tank in the ammonia diffusion tower whose interior was maintained at 55 ° C. Example 1 is the same as Example 1 except that gas-liquid contact is made with the biogas produced by the intermediate temperature methane fermentation process introduced from the lower part of the sample.

[Example 5]
The heat treatment condition of the methane fermentation liquid in the temperature raising tank was set at 55 ° C. for 4 hours, and the fermentation liquid treated in the temperature raising tank in the ammonia diffusion tower maintained at 50 ° C. was used as the ammonia diffusion tower. Example 1 is the same as Example 1 except that gas-liquid contact is made with the biogas produced by the intermediate temperature methane fermentation process introduced from the lower part of the sample.

[Example 6]
The heat treatment condition of the methane fermentation liquid in the temperature raising tank was set at 55 ° C. for 1 hour, and the fermentation liquid treated in the temperature raising tank in the ammonia diffusion tower maintained at 50 ° C. was used as the ammonia diffusion tower. Example 1 is the same as Example 1 except that gas-liquid contact is made with the biogas produced by the intermediate temperature methane fermentation process introduced from the lower part of the sample.

[Comparative example]
A 10 L methane fermenter was subjected to a medium temperature methane co-fermentation process (37 ° C.) with 1: 1 garbage of separated garbage and milk of cow's manure.
Next, the methane fermentation broth obtained by the intermediate temperature methane fermentation treatment is sprayed from the upper part of the ammonia diffusion tower whose inside is maintained at 35 ° C., and is introduced by the intermediate temperature methane fermentation treatment introduced from the lower part of the ammonia diffusion tower. The produced biogas was brought into gas-liquid contact to obtain a fermentation broth that had been subjected to ammonia removal treatment.
Then, the total nitrogen in the fermented liquid of the fermented liquid which performed the ammonia removal process was measured.

The results of Example 1 are shown in Table 1, and the results of Examples 2 to 6 and the comparative example are shown in Table 2.
In Examples 2 to 6 and the comparative example, the fermentation liquid finally sprayed onto the farmland (reduction in farmland) is a fermentation liquid (ammonia-removed fermentation liquid) that has been subjected to ammonia removal treatment. Since the effect of the present invention is obtained if the amount of nitrogen in the liquid is reduced, the measurement of the amount of nitrogen was made only to measure the total nitrogen in the fermentation broth subjected to the ammonia removal treatment. In addition, the total nitrogen amount in the methane fermentation broth obtained by performing the intermediate temperature methane fermentation treatment in Examples 2 to 6 and the comparative example is the same as the value in Example 1 because the same treatment as in Example 1 is performed. The same.

FIG. 4 is a graph showing the relationship between the treatment conditions in the heating tank in Examples 1 to 6 and the corresponding total nitrogen amount in the ammonia-removed fermentation broth.
FIG. 5 is a graph showing the relationship between the outlet concentration in the ammonia diffusion tower and the temperature in the ammonia diffusion tower.

The effects of the present invention will be described with reference to the results of other examples and comparative examples (Table 2), focusing on the results of Table 1 (Table 1).
In Example 1, in the methane fermentation liquid obtained by an intermediate temperature methane fermentation treatment (37 ° C.) that is anaerobic fermentation, as is apparent from Table 1, 1800 (mg / L) of nitrogen as the total nitrogen amount Is present.

As described above, since Kjeldahl nitrogen (amount) = organic nitrogen (amount) + ammonia nitrogen (amount), the amount of organic nitrogen in the methane fermentation liquid is 1800-800 = 1000 (mg / L). It becomes. Moreover, since a present Example is an anaerobic fermentation process, the total nitrogen amount and the Kjeldahl nitrogen amount are equal to 1800 (mg / L).

Next, when the amount of each nitrogen in the fermentation broth after heat-treating the methane fermentation broth at 70 ° C. for 1 hour in a heating tank, ammonia nitrogen is increased by 300 (mg / L). This is because organic nitrogen 300 (mg / L) is converted to ammonia by heating methane fermentation liquid in a heating tank at 70 ° C. for 1 hour in organic nitrogen 1000 (mg / L) in methane fermentation liquid. It means that it was decomposed into nitrogen. Therefore, the organic nitrogen is reduced from 1000 (mg / L) to 700 (mg / L) by the treatment in the heating tank.

Total nitrogen in the ammonia-removed fermentation broth obtained by bringing the fermented liquor after treatment in the heating tank into gas-liquid contact with the biogas produced by the medium-temperature methane fermentation treatment in an ammonia diffusion tower whose interior is maintained at 65 ° C When you see the amount of, you can see that it is drastically reduced to 600 (mg / L). This is due to the fact that a large amount of ammonia was diffused in the ammonia stripping tower. If the total amount of nitrogen in the ammonia-removed fermentation liquor is about 600 (mg / L), there will be no groundwater contamination. As the amount consumed.

In addition, ammonia nitrogen in the ammonia-removed fermentation broth has been drastically reduced. This is also due to the fact that a large amount of ammonia was diffused in the ammonia diffusion tower for the same reason that the total nitrogen amount was drastically reduced.
Organic nitrogen was not detected in the ammonia-removed fermentation broth (the amount of organic nitrogen was 0 because ammonia nitrogen and Kjeldahl nitrogen were the same amount). That is, the organic nitrogen that has been reduced to 700 (mg / L) by the treatment in the heating tank is decomposed from the organic nitrogen to the ammonia nitrogen by the ammonia removal treatment in the ammonia diffusion tower, and the ammonia nitrogen is converted into ammonia. It is thought that it was released from the diffusion tower.

In addition, since it is an anaerobic fermentation process in this example, the total nitrogen amount in the ammonia-removed fermentation liquid and the Kjeldahl nitrogen amount must be equal, but the total nitrogen amount is 600 (mg / L) in the results of Table 1. , Kjeldahl nitrogen is different from 500 (mg / L). This is due to the measurement method.
The quantitative measurement of nitrogen in the examples and comparative examples of the present invention is measured by absorptiometry. Therefore, in the ammonia-removed fermentation broth having a brown coloration of the humic substance, the quantitative value is affected by the coloration effect, and sometimes an error of several hundred mg / L may occur. Therefore, the difference between the total nitrogen amount 600 (mg / L) and the Kjeldahl nitrogen amount 500 (mg / L) is considered as an error range.

As described above, the present invention, for example, decomposes and removes organic nitrogen in a methane fermentation broth obtained by a medium temperature methane fermentation treatment (37 ° C.) into ammonia nitrogen, thereby removing all of the methane fermentation broth. The amount of nitrogen is reduced, and the fermented liquid has the effect of being able to be sprayed on farmland (agricultural land reduction) as a fertilizer that does not cause groundwater contamination by nitrogen.

In the comparative example of Table 2, the total nitrogen in the fermented liquid after the methane fermentation liquid obtained by carrying out the intermediate temperature methane fermentation process (37 degreeC) without performing the process by a temperature rising tank is ammonia removal process in an ammonia diffusion tower. Although the amount is shown, it is 1450 (mg / L), which is overwhelmingly higher than Example 1 of the present invention. From this, it can be seen that the present invention has the effect of reducing the total nitrogen amount.

Next, Example 2 to Example 6 will be described.
Table 2 shows the treatment conditions (except for the comparative example) in the temperature raising tank, the temperature in the ammonia diffusion tower, the total nitrogen amount in the ammonia-removed fermentation liquid, and the methane fermentation tank liquid in each example and comparative example. Values for total nitrogen are shown.
In Example 2 to Example 6 and the comparative example, for the total nitrogen amount in the methane fermentation liquid, the methane fermentation treatment (medium temperature fermentation) is performed under the same conditions (37 ° C.) in each example and comparative example. The total amount of nitrogen in the obtained methane fermentation broth is the same.

However, depending on the processing conditions in the temperature raising tank, there is a difference in the total nitrogen amount in the ammonia-removed fermentation liquid that is finally reduced to farmland in each example.
In particular, when the treatment temperature in the heating tank is set to 60 ° C. or more (Examples 2, 3, and 4), the total nitrogen amount in the methane fermentation liquid is 1800 mg / L in the ammonia-removed fermentation liquid that is finally reduced to farmland. The total amount of nitrogen can be reduced to 800-870 mg / L.
That is, the present invention has the effect of reducing the total nitrogen amount in the methane fermentation broth by 930 to 1000 mg / L. Considering that the comparative example can only reduce the amount of total nitrogen in the methane fermentation broth by 350 mg / L, the present invention has a very significant effect on reducing the amount of nitrogen in the methane fermentation broth. It can be said.

FIG. 4 shows the relationship between the treatment conditions in the heating tank and the total nitrogen amount in the ammonia-removed fermentation broth in each example.
According to this, in this invention, it turns out that the amount of total nitrogen in an ammonia removal fermentation liquid is so small that the processing temperature in a temperature rising tank is high, and heating time is long. In other words, the higher the treatment temperature in the temperature raising tank, the longer the heating time, the more the organic nitrogen in the methane fermentation liquid is decomposed into ammonia nitrogen, and the ammonia nitrogen in the methane fermentation liquid increases, Since a large amount of ammonia is diffused and removed in the ammonia diffusion tower at the latter stage, the total amount of nitrogen in the ammonia-removed fermentation liquor is reduced.

FIG. 5 shows the relationship between the temperature in the diffusion tower in the ammonia diffusion tower and the outlet ammonia concentration to be diffused (concentration at the outlet of the ammonia diffusion tower). This shows that the higher the temperature, the more ammonia is released.

The present invention provides a methane for reducing nitrogen in a methane fermentation solution so that groundwater is not contaminated by nitrogen contained in the methane fermentation solution when the methane fermentation solution obtained by the methane fermentation treatment is reduced to farmland as a fertilizer. This is a fermentation system, and the methane fermentation broth can be effectively used according to the present invention.

Japanese Patent Laid-Open No. 10-235317

Claims

A methane fermenter,
A temperature raising tank that raises the temperature of the fermentation liquid coming out of the methane fermentation tank to a temperature higher than the fermentation temperature of the methane fermentation tank,
An ammonia removal device for removing ammonia from the fermentation liquor coming out of the heating tank;
A methane fermentation system characterized by comprising:
In the methane fermentation system according to claim 1,
The ammonia removal apparatus is an ammonia diffusion tower that diffuses and removes ammonia from the liquid by gas-liquid contact between the supplied gas and the fermentation liquid, and a part or all of the biogas generated in the methane fermentation tank is removed. It is comprised so that it may utilize as said gas supplied to the said ammonia diffusion tower, The methane fermentation system characterized by the above-mentioned.
A methane fermentation tank in which the fermentation process is performed at a temperature of 60 ° C. or higher;
An methane fermentation system comprising: an ammonia removal device that removes ammonia from a fermentation broth discharged from the methane fermentation tank.
4. The methane fermentation system according to claim 3, wherein a part of the fermentation liquor that has exited the ammonia removal device is returned to the methane fermentation tank.
3. The methane fermentation system according to claim 1 or 2, wherein the methane fermentation tank is subjected to a fermentation treatment in a temperature range of 35 to 40 ° C.
In the methane fermentation system according to claim 1 or 2,
A methane fermentation system, wherein the temperature in the temperature raising tank is 65 to 80 ° C.
In the methane fermentation system according to claim 3 or 4,
A methane fermentation system, wherein the temperature in the methane fermentation tank is 65 to 80 ° C.
A fertilizer production apparatus using a methane fermentation system, characterized in that the fermented liquid after removal of ammonia obtained from the methane fermentation system according to claim 1 or 3 is used as a fertilizer.
3. The methane fermentation system according to claim 2, wherein the gas exiting the ammonia diffusion tower is sent to a desulfurization apparatus for desulfurizing the biogas.
In the methane fermentation system according to claim 1 or 3,
The ammonia removal device is an ammonia diffusion tower that diffuses and removes ammonia from the liquid by gas-liquid contact between the supplied gas and the fermentation broth,
A blower for sending air to the ammonia diffusion tower;
A deodorizing device to which the gas exiting the ammonia diffusion tower is sent,
The methane fermentation system, wherein the gas exiting the deodorizing device is configured to be circulated to the ammonia diffusion tower through the blower.