JP6617868B2 - Membrane separation methane fermentation equipment - Google Patents

Description

  The present invention relates to a membrane-separated methane equipped with a device for removing calcium-containing unsuitable methane fermentation materials such as eggshells contained in food waste, etc. discharged from household food waste and business food waste such as food manufacturing factories. The present invention relates to a fermentation apparatus.

  There is a methane fermentation method as one of methods for treating garbage discharged from homes, restaurants, confectionery stores, etc., and food waste from food manufacturing factories, livestock farms and the like. In the methane fermentation method, the membrane separation methane fermentation method that separates sludge containing methane-fermenting bacteria and removes treated water can increase the concentration of sludge. is there. However, in the case of membrane separation methane fermentation from raw garbage, clogging due to calcium clogging derived from eggshells and shells and clogging due to scale generation in pipes, etc. are known. A method has been developed.

  The method of Patent Document 1 is a method in which a membrane separation tank is partitioned by a partition, and the inflow side from the methane fermentation tank is separated as a sedimentation tank such as eggshell or shell, and the liquid overflowing the partition is separated by membrane.

  Moreover, the method of patent document 2 adds sodium carbonate to a membrane permeation | transmission liquid, precipitates and removes calcium as calcium carbonate, returns the liquid which removed this calcium to a methane fermenter as a concentration adjustment liquid, and dilutes it. It is.

JP 2006-272105 A JP 2004-148269 A

  The method of Patent Document 1 requires a large sedimentation tank because it takes time to settle eggshells, shells, and the like. There is a problem of clogging and clogging due to scale generation in piping.

  In the method of Patent Document 2, it is necessary to return a considerable amount of the concentration adjusting solution to the methane fermenter in order to reduce the calcium concentration in the methane fermenter, and the methane fermenter becomes large and removes calcium. Therefore, there is a problem that the use of sodium carbonate is expensive.

  The object of the present invention is to perform membrane separation that can efficiently and efficiently remove methane fermentation inadequate materials containing calcium such as eggshells that cause piping troubles, etc., from organic waste containing methane fermentation inadequate materials such as eggshells. It is to provide a methane fermentation apparatus.

  As a result of intensive studies to solve the above problems, the present inventors have generated a swirl flow in the vertical direction in the apparatus from the conventional sedimentation separation method to flow organic waste slurry such as garbage. Thus, it has been found that methane fermentation unsuitable substances containing calcium such as eggshell having a large specific gravity can be efficiently separated in a short time, and that this method has a wide viscosity range of adaptable organic waste slurry. More specifically, a stirring blade is provided in two stages in the stirring separation tank to form a swirling flow, and by adjusting the position and diameter of the stirring blade and the rotation speed, the methane fermentation inappropriate material is efficiently settled and separated. It has been found that there is a possible range, and it has been found that by making the bottom of this stirred separation tank into an inverted cone shape, it is possible to efficiently collect and separate methane fermentation unsuitables at the center of the bottom. And it discovered that this stirring separation tank was especially suitable for the membrane separation methane fermentation method which makes sludge highly concentrated and performs methane fermentation efficiently, and came to complete this invention.

That is, the present invention
A stirrer having a bottom-conical bottom portion into which an organic waste containing calcium-inappropriate methane fermentation containing organic waste is charged, and a stirrer equipped with two stirrer blades for stirring the contents of the stir separation tank And a removing device for discharging the inappropriate methane fermentation material accumulated at the bottom of the stirred separation tank, and a membrane separation tank at the rear stage of the methane fermentation tank. A membrane separation methane fermentation apparatus characterized by comprising:
A stirring / separating tank into which a fermentation broth containing a methane fermentation inappropriate material containing calcium and having a bottom-conical bottom portion is charged; and a stirrer equipped with two-stage stirring blades for stirring the contents of the stirring / separating tank; Membrane-separated methane, comprising a removal device provided with a discharging means for discharging the inappropriate methane fermentation material accumulated at the bottom of the stirred separation tank, at a stage subsequent to the methane fermentation tank and before the membrane separation tank A fermentation apparatus;
Among the two-stage stirring blades, the distance between the upper end of the bottom of the stirring separation tank and the lower blade is substantially equal to the distance between the lower blade and the upper blade, and the upper blade diameter is smaller than the lower blade diameter. The membrane-separated methane fermentation apparatus is characterized by being large.

  According to the present invention, it is possible to efficiently perform membrane-separated methane fermentation by efficiently separating methane fermentation unsuitable materials in a short time from organic waste containing methane fermentation unsuitable materials containing calcium such as eggshell. . Furthermore, since it can be applied to organic waste slurries with a wide viscosity range by a device for removing inappropriate methane fermentation containing calcium, it can be used when the properties of organic waste to be treated fluctuate. In addition, it is possible to carry out membrane separation methane fermentation stably and efficiently.

It is a block diagram which shows one embodiment of this invention. It is a block diagram which shows another embodiment of this invention. It is sectional drawing of the removal apparatus of the methane fermentation unsuitable thing used in Example 1 of this invention.

The organic waste which is the treatment target of the present invention includes a methane fermentation inappropriate material containing calcium. Inappropriate methane fermentation containing calcium is eggshell, seashell, vertebrate bone, crustacean outer bone, etc. Specific gravity is about 2.40 to 3.00 g / mL, usually about 2.60 to 2.84 g / mL. . The organic waste containing these includes, for example, household waste discharged from homes, garbage discharged from restaurants or other restaurants, food waste discharged from supermarkets and convenience stores, and the like. An organic waste slurry (hereinafter simply referred to as “slurry”) obtained by adding water to this organic waste to form a slurry is used as a raw material. The method of the present invention has a wide range of slurry viscosities, and can be applied to those of 8 Pa · s or less. If it exceeds 8 Pa · s, the removal rate of methane fermentation unsuitables decreases. The preferred viscosity is in the range of 0.1 to 8.0 Pa · s, and the particularly preferred viscosity is in the range of 0.4 to 5.0 Pa · s. The specific gravity in the slurry state is about 1 g / mL, and is usually about 1.00 to 1.05 g / mL.

  Fermented sludge is sludge generated by methane fermentation of the organic waste, and is discharged from the methane fermentation tank. The fermented sludge has a TS of 1.5 to 3.0% by mass, usually about 2.0 to 2.5% by mass.

  Methane fermentation may be performed according to a known method. The methane fermentation tank has a sealed structure in order to effectively use methane produced by fermentation, in which methane fermentation is anaerobic fermentation. The shape may be a box shape or a cylindrical shape. A stirrer may not be provided inside, but a draft tube or the like may be provided.

  The fermentation broth that is run out of methane fermentation in the methane fermentation tank contains a large amount of methane bacteria, so in order to maintain the methane bacteria at a high concentration and perform fermentation efficiently, Separate the treated water and collect the remaining fermentation sludge and return it to the methane fermentation tank. The membrane separation tank attached to this methane fermentation tank can utilize what is disclosed by Unexamined-Japanese-Patent No. 2001-170631. As the membrane to be used, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane) or the like can be used, and the shape of the membrane includes a flat membrane, a hollow fiber membrane and the like. An air diffuser is provided under the membrane to increase the flow velocity of the membrane surface and prevent adhesion of fermented sludge and the like to the membrane surface. Nitrogen gas, carbon dioxide gas, or the like may be used as the gas used in the air diffuser, but biogas mainly composed of methane generated by methane fermentation is preferably used.

  In the apparatus of the present invention, not only the object of methane fermentation, but also deposits on the membrane surface to inhibit membrane separation, or remove unsuitable fermentation materials such as calcium that deposit on pipes and inhibit flow and the like. .

  The bottom of the stirring separation tank of the apparatus for removing inappropriate methane fermentation according to the present invention has a downward cone shape. The bottom part is shaped like a downward cone in order to accumulate methane fermentation inappropriate substances there, and the angle of the cone face is suitably about 30 to 60 degrees with respect to the horizontal plane (the plane perpendicular to the axis) of the stirring separation tank. It is. The cone shape is usually a cone, but may be a pyramid or the like.

  The agitation / separation tank is provided with an agitator inside to form a vertical swirling flow of the slurry to fluidize the slurry. The swirling flow may be either an upward flow or a downward flow on the peripheral surface side of the stirring separation tank, and a downward flow or an upward flow on the central portion of the stirring separation tank. Is preferably an upward flow. By this swirl flow, unsuitable methane fermentation having a large specific gravity is settled and accumulated at the center of the bottom of the tank. For this purpose, the present inventors have found that the stirring blades of the stirrer need to have two stages. As the stirring blade, a propeller blade, a paddle blade having an inclined blade surface, or the like is used to form a vertical swirling flow. In any case, the conditions for sedimentation and accumulation of methane fermentation unsuitable substances are very delicate. Basically, it is better to test and set for each stirring separation tank, but the position and diameter of the stirring blades are important. is there. Specifically, the distance between the upper end of the bottom of the stirring separation tank (upper edge of the downward cone) and the lower blade and the distance between the lower blade and the upper blade are substantially equal, and the ratio of the two intervals is 1 : About 0.5 to 2, preferably about 1: 0.75 to 1.5, more preferably about 1: 0.8 to 1.3, and the diameter of the upper blade is smaller than the diameter of the lower blade. The diameter of the upper blade / the lower blade should be about 1.1 to 2, preferably about 1.2 to 1.5.

  The agitation / separation tank further has an inlet for organic waste or fermentation liquid, an outlet for inappropriate methane fermentation accumulated at the bottom, and an outlet for organic waste or fermentation liquid from which inappropriate methane fermentation has been removed. Provided.

  The number of rotations of the stirrer is also important as a condition for accumulating unsuitable methane fermentation substances at the bottom of the stirring separation tank, and it is necessary to control according to the concentration and viscosity of the slurry. On the other hand, the stirring time may be short, depending on the scale of the stirring and separation tank, but may be about 1 minute to 1 hour, usually about 2 minutes to 15 minutes. Moreover, it is not necessary to remove 100% of methane fermentation unsuitable substances, and practically, the removal rate may be about 70 to 95%.

  The apparatus for removing unsuitable methane fermentation may be provided in front of the membrane separation tank, may be provided in front of the methane fermentation tank, or may be provided between the methane fermentation tank and the membrane separation tank. By providing it in front of the methane fermentation tank, scale generation in the piping to the methane fermentation tank, the methane fermentation tank, or the like is suppressed. By providing it between the methane fermentation tank and the membrane separation tank, the solid residence time of the fermented sludge is as long as about 25 to 35 days. The frequency of changing separation conditions can be reduced.

One embodiment of the present invention is shown in FIG. In this apparatus, a device for removing inappropriate methane fermentation is provided in the previous stage of the methane fermentation tank. Organic waste such as kitchen waste is put into a stirring and separation tank. In the agitation / separation tank, inadequate methane fermentation materials such as eggshell in the garbage are settled and discharged continuously or intermittently from the lower outlet. Organic waste from which methane fermentation unsuitables have been removed is supplied to the methane fermenter and subjected to methane fermentation, and the fermentation liquor is continuously or intermittently extracted from the methane fermenter and sent to the membrane separation tank. . Since the concentration of organic substances such as SS and COD _Mn is low in the treated water in which the fermentation liquid is separated into the treated water and the fermented sludge in the membrane separation tank, post-treatment such as sewage discharge is simplified. The biogas consisting mainly of methane and carbon dioxide generated in the methane fermentation tank can be used as power generation fuel. Part of the biogas is sent to the membrane separation tank via a blower or the like and used for aeration. Garbage etc. can be directly put into the methane fermentation tank together with water if necessary, or can be put into the methane fermentation tank after adjusting the viscosity and specific gravity by adding water in the adjustment tank.

  Another embodiment of the present invention is shown in FIG. In this apparatus, a device for removing inappropriate methane fermentation is provided between the methane fermentation tank and the membrane separation tank. Organic waste such as garbage is put into the methane fermentation tank to perform methane fermentation, and the fermentation liquor is continuously or intermittently extracted from the methane fermentation tank and supplied to the stirring and separation tank. In the agitation / separation tank, inadequate methane fermentation materials such as eggshell in the garbage are settled and discharged continuously or intermittently from the lower outlet. The fermentation liquor from which methane fermentation inappropriate substances have been removed is sent to a membrane separation tank and separated into treated water and fermentation sludge. In addition, the removal apparatus of a methane fermentation unsuitable thing can also be provided in both the positions shown in FIG. 1 and FIG.

  Fermented sludge taken out from the system is returned to the methane fermentation tank, but may be incinerated, or dried and used as fertilizer or fuel. Egg shells, shells, etc. can be washed and used as chalk raw materials or cement raw materials.

Example 1
The apparatus shown in FIG. 1 was used.

The methane fermentation tank used was a box-shaped sealed tank with a capacity of 1,500 L, and the membrane separation tank was equipped with a microfiltration membrane having a filtration area of 0.1 m ² × 5. The apparatus shown in FIG. 3 was used as an apparatus for removing inappropriate methane fermentation. In this apparatus, the stirring / separation tank 1 has a cylindrical shape with an inner diameter of 200 mm and a height of 300 mm, and the bottom 2 has a downward conical shape with an angle of 30 degrees with respect to the horizontal plane. The leg 3 is extended by 100 mm. On the side wall of the main body 1, the slurry raw material inlet 4 is located 180 mm above the bottom 2, the separation liquid outlet 5 from which the eggshell (unsuitable for methane fermentation) has been removed is slightly above the bottom 2, and the bottom 2 Is provided with a concentrate discharge port 6 including eggshells, to which a pipe having a valve is connected. The volume of the stirring / separation tank is about 9 L, and the materials are all made of transparent polyvinyl chloride. In the center of the stirring / separation tank 1, a stirrer 7 is installed with the shaft vertical, and a stirring blade 8 is attached to the lower end of the shaft and slightly above. The stirring blade is composed of six paddle blades whose upper and lower angles are 45 degrees, and three blade diameters (Φ) of 80 mm, 100 mm, and 120 mm are prepared.

  Using this apparatus, water is added to household waste, viscosity is 0.85 to 1.35 Pa · s, specific gravity is about 1.0 g / mL, TS (evaporation residue) 3.6 to 5.1% by mass, An slurry having an eggshell concentration of 0.7 to 3.6 g · dry eggshell / kg · wet raw material was put into a stirring separation tank. The eggshell was settled and separated, and the separation liquid from which the eggshell had been removed was supplied to a methane fermentation tank to perform methane fermentation. The obtained fermentation broth was supplied to a membrane separation tank and separated into treated water and fermentation sludge. Here, in the apparatus for removing unsuitable materials for methane fermentation, the eggshell separation test was performed by changing the number of stirrer blades in the stirrer / separation tank, the blade diameter, the height from the bottom of the lower blade, and the blade interval. .

条件１〜３では、攪拌が不足したため、卵殻以外の有機物（人参、米粒等）が卵殻とともに堆積し、卵殻を選択分離できなかった。また、条件７〜９では、攪拌が過剰であったため、底部に一度沈降した卵殻が攪拌流により巻き上げられ、卵殻除去量が低下する現象が観察された。条件４〜６において、卵殻を効率的に底部に集積させることができた。目視での比較では、条件４での卵殻分離状況が条件５、６での分離状況より多くの卵殻を選択的に集積していた。 The results are shown in Table 1. Here, as an evaluation, the eggshell removal rate represented by the following formula was calculated, and the removal rate was 80% or more: ◎, 70-80%: ○, 50-70%: Δ, 50% or less: x.

Under conditions 1 to 3, since stirring was insufficient, organic substances other than eggshell (carrot, rice grain, etc.) were deposited together with eggshell, and eggshell could not be selectively separated. In addition, under conditions 7 to 9, since stirring was excessive, the eggshell that once settled at the bottom was rolled up by the stirring flow, and a phenomenon that the amount of eggshell removed was reduced was observed. Under conditions 4 to 6, the eggshell could be efficiently accumulated at the bottom. In the comparison by visual observation, the eggshell separation state under the condition 4 selectively accumulated more eggshells than the separation states under the conditions 5 and 6 .

上記評価は、回転数１００〜２５０ｒｐｍでの攪拌分離槽底部における卵殻の集積状況を目視観察で行なったものである。
実施例２
図２に示す装置を用いた。メタン発酵槽は容積１，５００Ｌの箱型の密閉槽を、そして、膜分離槽には濾過面積０．１ｍ²×５個の精密濾過膜を装着したものを用いた。メタン発酵不適物の除去装置には実施例１と同様に図３に示すものを用いた。攪拌分離槽１が内径が２００ｍｍ、高さが３００ｍｍ、の円筒形で、底部２が水平面に対する角度が３０度の下向き円錐状をしており、底部２からは、この円筒が下に脚部３として１００ｍｍ延設されている。本体１の側壁には、底部２から上１８０ｍｍのところにメタン発酵槽からの発酵液の原料投入口４が、底部２のやや上には卵殻（メタン発酵不適物）を除去した分離液排出口５が、そして底部２の中心には卵殻を含む濃縮液排出口６が設けられ、それぞれに弁を有する配管が接続されている。攪拌分離槽の容積は約９Ｌであり、材質はいずれも透明のポリ塩化ビニルでできている。攪拌分離槽１の中央には攪拌機７が軸を垂直にして設置され、軸の下端とそのやや上に攪拌羽根８が取着されている。この攪拌羽根は上下いずれも角度を４５度にした６枚のパドル翼よりなり、羽根径（Φ）は８０ｍｍ、１００ｍｍ、１２０ｍｍの３種類が準備されている。

The above evaluation was performed by visual observation of the accumulation state of eggshells at the bottom of the stirring / separation tank at a rotational speed of 100 to 250 rpm.
Example 2
The apparatus shown in FIG. 2 was used. The methane fermentation tank used was a box-shaped sealed tank having a capacity of 1,500 L, and the membrane separation tank was equipped with a microfiltration membrane having a filtration area of 0.1 m ² × 5. As in Example 1, the apparatus shown in FIG. The stirring / separation tank 1 has a cylindrical shape with an inner diameter of 200 mm and a height of 300 mm, and the bottom 2 has a downward conical shape with an angle of 30 degrees with respect to the horizontal plane. As 100 mm. On the side wall of the main body 1, the raw material input 4 of the fermentation liquid from the methane fermentation tank is 180 mm above the bottom 2, and the separation liquid discharge port from which the eggshell (improper methane fermentation) is removed slightly above the bottom 2 5 and at the center of the bottom 2 is provided with a concentrate discharge port 6 including eggshells, and a pipe having a valve is connected to each. The volume of the stirring / separation tank is about 9 L, and the materials are all made of transparent polyvinyl chloride. In the center of the stirring / separation tank 1, a stirrer 7 is installed with the shaft vertical, and a stirring blade 8 is attached to the lower end of the shaft and slightly above it. The stirring blade is composed of six paddle blades whose upper and lower angles are 45 degrees, and three blade diameters (Φ) of 80 mm, 100 mm, and 120 mm are prepared.

As organic waste to be fermented with methane, water is added to household garbage, viscosity 1.2-1.5 Pa · s, specific gravity about 1.0 g / mL, TS about 6% by mass, eggshell concentration 2.7 ~ The slurry made into 3.3g * dry eggshell / kg * wet raw material was thrown into the methane fermentation tank at the rate of 100 kg / day, and methane fermentation was performed at 38 degreeC. From the methane fermenter, TS 2.0-2.5 mass% of the fermented liquid is extracted at a rate of 300 kg / day, put into a stirring separation tank, the eggshell is settled and separated, and the fermented liquid from which the eggshell has been removed is put into a membrane separation tank. The fermented sludge sent and separated was circulated to the methane fermentation tank. The eggshell separation test was performed by changing the number of stirring blades in the stirring / separation tank, the diameter of the blades, the height from the bottom of the lower blades, and the distance between the blades.
The results are shown in Table 2. Here, the evaluation is the same as in Example 1.

条件１〜２では攪拌が不足したため、卵殻以外の有機物(人参、米粒等)が卵殻とともに堆積し、卵殻を選択分離できなかった。また、条件５〜７では、攪拌が過剰であったため、底部に一度沈降した卵殻が攪拌流により巻き上げられ、卵殻除去量が低下する現象が観察された。条件３〜４において、卵殻が効率的に底部に集積させることができた。

Under conditions 1 and 2, since stirring was insufficient, organic matter other than eggshell (carrot, rice grain, etc.) was deposited with eggshell, and eggshell could not be selectively separated. Moreover, in conditions 5-7, since stirring was excessive, the eggshell once settled to the bottom part was rolled up by the stirring flow, and the phenomenon that the amount of eggshell removal fell was observed. Under conditions 3 to 4, the eggshell could be efficiently accumulated at the bottom.

  Since the present invention can efficiently separate methane fermentation inadequate containing calcium from organic waste such as garbage discharged from households and restaurants, etc., a method for methane fermentation of these organic waste Can be used widely.

DESCRIPTION OF SYMBOLS 1 Stirring separation tank 2 Bottom part 3 Leg part 4 Raw material inlet 5 Separation liquid outlet 6 Concentrated liquid outlet 7 Stirrer 8 Stirring blade

Claims (2)

A stirrer having a bottom-conical bottom portion into which an organic waste containing calcium-inappropriate methane fermentation containing organic waste is charged, and a stirrer equipped with two stirrer blades for stirring the contents of the stir separation tank And a discharge means for discharging the methane fermentation inappropriate material accumulated at the bottom of the stirring / separation tank, and of the two-stage stirring blades, the upper end of the bottom of the stirring / separation tank and the lower blades The removal rate of methane fermentation inadequate containing calcium in the stirring time of 1 minute to 1 hour, with the interval and the interval between the lower blade and the upper blade substantially equal, the upper blade diameter is larger than the lower blade diameter A membrane-separated methane fermentation apparatus comprising a removal device having a concentration of 70 to 95% in a preceding stage of a methane fermentation tank and a membrane separation tank in a subsequent stage of the methane fermentation tank. A stirring / separating tank into which a fermentation broth containing calcium-containing unsuitable methane fermentation material having a bottomed cone-shaped bottom is charged, and a stirrer equipped with two-stage stirring blades for stirring the contents of the stirring / separating tank; A discharge means for discharging the methane fermentation inappropriate material accumulated at the bottom of the stirring / separation tank, and of the two-stage stirring blades, an interval between an upper end of the bottom of the stirring / separation tank and a lower blade. The distance between the lower blade and the upper blade is substantially the same, the upper blade diameter is larger than the lower blade diameter , and the removal rate of calcium-containing unsuitable methane fermentation is 70 minutes with stirring time of 1 minute to 1 hour. A membrane-separated methane fermentation apparatus comprising a removal device that is ˜95% in a stage subsequent to a methane fermentation tank and in front of a membrane separation tank.

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