JP6515627B2 - Method and apparatus for removing methane fermentation unsuitable - Google Patents

Description

  The present invention relates to a method and apparatus for removing methane fermentation unsuitable substances such as eggshells contained in food waste and the like discharged from household food waste and business food waste such as a restaurant.

  There is a methane fermentation method as one of the methods to process the garbage discharged from homes, restaurants, confectionery stores and the like, and the food manufacturing factory and the fishery factory. In that case, since inorganic substances such as eggshells contained in these raw wastes are not subject to methane fermentation treatment, in general, water is added to raw wastes to form a slurry, which is left for a long time to keep eggshells etc. It is separated by settling.

  For example, according to Patent Document 1, the organic waste is put into the separation tank, solubilization of the organic matter is advanced by utilizing the difference between the solubilization time of the organic matter and the calcium-containing contaminants, and the unsolubilized state is In the method, the calcium-containing contaminants remaining in the above are separated by a specific gravity difference, and the precipitated calcium-containing contaminants are discharged from the bottom of the separation tank.

JP, 2011-167604, A

  However, in the method of solubilizing organic matter in food waste and then settling and separating eggshells and the like, the residence time in the separation tank is long and the apparatus becomes very large. In addition, there is a problem that separation becomes impossible when the viscosity of the slurry becomes high. In particular, soluble calcium, such as eggshell, which has been dissolved once precipitates due to changes in the environment, etc. Transfer piping from the receiving separation device to the adjustment tank, piping after the fermentation tank, fermentation residue storage tank, sludge treatment facility piping, etc. It causes troubles such as blockage of piping in various places.

  An object of the present invention is to provide a method and apparatus for efficiently removing methane fermentation unsuitable substances such as eggshells causing piping troubles and the like from organic wastes containing methane fermentation unsuitable substances such as eggshells at low cost. .

  As a result of intensive studies to solve the above problems, the inventors of the present invention have generated swirl flow in the longitudinal direction in the apparatus from the conventional sedimentation separation method to flow the garbage slurry, thereby achieving a large specific gravity eggshell. Etc. It has been found that it is possible to efficiently separate out the fermentation unsuitable substances in a short time, and furthermore, this method has a very wide range of applicable slurry viscosity. More specifically, a stirring vessel is provided in two stages in the separation tank to form a swirling flow, and by adjusting the position and diameter of the stirring fan, and further adjusting the number of rotations, the range in which eggshells etc. can be efficiently separated and separated is It has been found that it is possible to efficiently collect and separate eggshells and the like in the center of the bottom by making the bottom of the separation tank used as the stirring tank inverted.

That is, the present invention
An organic waste containing calcium-containing methane fermentation impurities and having a viscosity of 8 Pa · s or less is fed into a stirring vessel equipped with a bottom having a downward cone shape and a two-stage stirring blade, and at a predetermined rotation speed A method of removing a methane-containing unsuitable substance containing calcium, characterized in that the methane-fermented unsuitable material contained in the organic waste is accumulated and separated at the bottom of the stirring tank by stirring;
An apparatus for removing methane fermentation impurities which is used in the method for removing methane fermentation impurities comprising calcium described above, which is an organic waste containing calcium fermentation methane unsuitable substances having a bottom in the shape of a downward cone. A stirring vessel, a stirrer provided with a two-stage stirring blade for stirring the contents of the stirring vessel, a discharge means for the methane fermentation non-suitable substance accumulated at the bottom of the stirring vessel, and the methane fermentation non-suitable substance An apparatus for removing calcium-containing methane fermentation impurities having organic waste discharge means,
Among the two-stage stirring blades, the distance between the upper end and the lower blade of the bottom of the stirring tank and the distance between the lower blade and the upper blade are substantially equal, and the upper blade diameter is larger than the lower blade diameter. It is an object of the present invention to provide an apparatus for removing the above-mentioned calcium-containing methane fermentation material which is characterized by being large.

  According to the present invention, the methane fermentation non-suitable substance can be efficiently separated from the organic waste containing the methane fermentation non-suitable substance such as eggshell in a short time. Since the method and apparatus of the present invention have a very wide range of applicable slurry viscosity, it is possible to cope with fluctuations in the input slurry concentration and viscosity.

It is sectional drawing of the removal apparatus of the methane fermentation unsuitable material used in the Example of this invention. It is a graph which shows the relationship between the viscosity of raw garbage slurry and the rotation speed which was optimal for isolation | separation obtained by measuring using this apparatus.

  The organic wastes to be treated according to the present invention include calcium-containing methane fermentation unsuitable substances. The methane fermentation unsuitable substances containing calcium are eggshells, shells and the like, and the specific gravity is about 2.40 to 3.00 g / mL, usually about 2.60 to 2.84 g / mL. The organic wastes including these are, for example, household waste discharged from a home, raw garbage discharged from a restaurant or other restaurant, raw garbage discharged from a supermarket or a convenience store, and the like. Water is added to the organic waste to form a slurry. The method of the present invention is widely applicable to slurry viscosity of 8 Pa · s or less. When the pressure exceeds 8 Pa · s, the separation efficiency of methane fermentation unsuited substances 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. In addition, the specific gravity of the slurry state is about 1 g / mL, and usually about 1.00 to 1.05 g / mL.

  Such organic waste is charged into a stirred tank. The organic waste may be previously made into a slurry, or water may be added after being introduced into a stirring tank to make a slurry.

  The bottom of the stirring tank is in the shape of a downward cone. The reason for making the bottom part in the shape of a downward cone is to accumulate methane fermentation unsuitable substances there, and the angle of the cone surface is suitably about 30 to 60 degrees with respect to the horizontal plane (the plane perpendicular to the axis) of the stirring tank is there. The cone shape is usually a cone but may be a pyramid or the like.

  The stirring tank is provided with a stirrer inside to form a longitudinal swirling flow of the slurry to fluidize the slurry. The swirling flow may be upward or downward flow on the circumferential surface side of the tank, and thus may be either downward or upward flow at the central portion of the tank, but downward flow on the circumferential surface side and upward on the central portion It is preferable to make it countercurrent. By this swirling flow, methane fermentation unsuitables having a large specific gravity are deposited and accumulated at the center of the bottom of the tank. The inventors have found that it is necessary to provide two stages of stirring blades for the stirrer. As the stirring blade, a propeller blade, a paddle blade with an inclined blade surface, or the like is used to form a swirling flow in the longitudinal direction. In any case, the conditions for sedimentation and accumulation of methane fermentation unsuitable substances are very delicate, and basically it is preferable to set and test each stirring tank, but the position and diameter of the stirring blade are important . Specifically, the distance between the upper end of the bottom of the stirring vessel (the upper edge of the downward cone shape) and the blades of the lower stage and the distance between the lower blades and the upper blades are approximately equal, and the ratio of the above two intervals is 1 0.5 to 2, preferably 1: 1: 0.75 to 1.5, more preferably 1: 0.8 to 1.3, and the diameter of the upper blade is greater than the diameter of the lower blade The diameter of the upper blade / the diameter of the lower blade may be about 1.1 to 2, preferably about 1.2 to 1.5.

  The stirring tank is further provided with an inlet for organic waste, an outlet for methane fermentation nonconforming material accumulated at the bottom, and an outlet for organic waste from which the methane fermentation nonconforming material is separated.

The rotation speed of the stirrer is also important as a condition for accumulating the methane fermentation unsuitable substance on the bottom of the stirring tank, and it is necessary to control according to the concentration, viscosity, etc. of the slurry. On the other hand, the stirring time may be short, and may be about 1 minute to 1 hour, usually about 2 minutes to 15 minutes, depending on the size of the stirring tank. In addition, it is not necessary to remove 100% of methane fermentation unsuitable substances, and the removal rate is practically 70
It should be about 95%.

  The organic waste from which methane fermentation impurities are removed can be methane fermented to produce methane gas. On the other hand, methane fermentation unsuitable substances such as eggshells and shells can be washed and used effectively for chalk and other applications.

  The apparatus shown in FIG. 1 was used. In this apparatus, the stirring vessel 1 is cylindrical 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. It is extended by 100 mm as the leg 3. At the side wall of the main body 1, an organic waste inlet 4 at a position 180 mm above the bottom 2, an outlet 5 for eggshell separated liquid from which eggshells have been removed slightly above the bottom 2, and at the center of the bottom 2. Is provided with an outlet 6 for eggshell concentrate, each of which is connected with a pipe having a valve. The volume of the stirring tank is about 9 L, and all materials are made of transparent polyvinyl chloride. A stirrer 7 is installed at the center of the stirring tank 1 with its axis vertical, and a stirring blade 8 is attached to the lower end of the axis and slightly above. The stirring blade is composed of six paddle blades each having an angle of 45 degrees in the upper and lower direction, and three types of blade diameters (Φ) of 80 mm, 100 mm and 120 mm are prepared.

  Using this apparatus, first, a viscosity of 0.85 to 1.35 Pa · s, a density of about 1.0 g / mL, a TS (evaporation residue) of 3.6 to 5.1% by weight, and an eggshell concentration of 0.7 to 3. Eggshell separation tests were conducted on 6-g · dry eggshell / kg · wet raw household garbage by changing the number of stages of stirring blades, the diameter of the blades, the height from the bottom of the lower blade, and the distance between the blades.

結果を表１に示した。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）が卵殻と同時に堆積し、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ため、条件４での検討を進めることとした。 The analysis method of eggshell concentration was performed by the following method.
(1) Each sample of the stock solution, the concentrated solution, and the separated solution is thoroughly mixed, collected to about 200 mL, and transferred to a 500 mL beaker. (Record the amount collected.)
(2) Transfer the beaker into a metal vat and gently stir with a stirrer.
(3) Gently pour running water into the beaker, and discharge organic substances, polymers and the like with small specific gravity from the beaker with running water.
(4) Stop running water when the water discharged from the beaker becomes clear.
(5) Pour the residual liquid (solids with a large specific gravity and a part of the polymer) in the beaker through a sieve (1 mm, 2.8 mm, 4 mm). Pour water into the beaker 2-3 times and transfer the contents thoroughly to the sieve.
(6) Pour the water through the sieve and spread the solids trapped on the sieve (mesh) on the sieve.
(7) Collect eggshells from the sieve with tweezers and place in a pre-weighed aluminum cup.
(8) Dry at 110 ° C. overnight and measure the weight.
(9) Calculate the eggshell quantity from the following formula.

The results are shown in Table 1. Under conditions 1 to 3, since the stirring was insufficient, organic substances other than eggshell (such as ginseng and rice grains) were deposited simultaneously with the eggshell, and the eggshell could not be selectively separated. Further, under the conditions 7 to 9, since stirring was excessive, a phenomenon was observed in which the eggshell sedimented once at the bottom was rolled up by the stirring flow, and the eggshell removal amount decreased. Under conditions 4 to 6, eggshells could be efficiently accumulated at the bottom. In comparison with visual observation, since the eggshell separation condition under the condition 4 selectively accumulated more eggshells than the separation condition under the conditions 5 and 6, the examination under the condition 4 was advanced.

上記評価は、回転数１００〜２５０ｒｐｍでの攪拌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。

The above evaluation is carried out by visual observation of the accumulation of eggshells at the bottom of the stirring tank at a rotational speed of 100 to 250 rpm.

Next, optimization of operating conditions under condition 4 was examined. The properties of household garbage in the experiment were viscosity 1.0 to 1.35 Pa · s, specific gravity about 1.0 g / mL, TS 4.9 to 5.0 wt%, eggshell concentration about 3.5 g · rdy eggshell / It was kg · wet material.
1) Examination of separation time The accumulation situation of eggshells at a rotational speed of 160 rpm was investigated in relation to time. The eggshell separation increased slightly after 2 and 5 minutes, but was almost saturated. Moreover, even if the situation after 10 minutes was observed, it was considered that the separation time was as short as 5 minutes because the accumulation situation of eggshells was similar every 5 minutes.
2) Examination of rotational speed With the test device specification and separation time fixed, the separation situation by the operating conditions (rotational speed) was investigated. The separation efficiency was highest at 140 to 160 rpm. In addition, when the rotation speed is lower than 140 rpm, the organic matter (rice grains, ginseng etc.) precipitates together with the eggshell, and when the rotation speed is higher than 160 rpm, the stirring velocity at the bottom is high and the precipitated eggshell is wound It was confirmed to go up.
3) Eggshell separation experiment (method to cope with the characteristic change of garbage)
Household garbage (viscosity 0.35 to 8.0 Pa · s, density 1 g / mL, TS 3.6 to 5.1% by weight, egg shell concentration 0.7 to 3.4 g · dry egg shell / kg · wet raw material) Using the test device specifications and the separation time, eggshell separation was verified. It was found that the separation situation was different even at the same rotation speed depending on the viscosity of the garbage slurry. Therefore, Table 2 shows the viscosity of the garbage and the rotation speed and eggshell separation efficiency appropriate for settling and separation. Here, the separation efficiency was calculated by the following equation.

表２より、生ごみ性状について、粘性に応じて回転数を変更することで卵殻を効率的に分離できる可能性が示唆された。また，卵殻の分離効率は７０〜９０％であった。

Table 2 suggested that eggshells could be separated efficiently by changing the number of revolutions according to viscosity for food waste properties. And the separation efficiency of eggshell was 70-90%.

  The relationship between the viscosity of the raw garbage slurry and the rotational speed that was optimum for separation is shown in FIG. From FIG. 2, it was found that a positive correlation was obtained between viscosity and rotational speed.

  Since the present invention can efficiently separate calcium-containing methane fermentation unsuitable substances from organic wastes such as garbage discharged from homes and restaurants etc., the method for methane-fermenting these organic wastes It can be used widely.

DESCRIPTION OF SYMBOLS 1 stirring tank 2 bottom part 3 leg part 4 organic waste inlet 5 outlet of eggshell separated liquid 6 outlet of eggshell concentrate 7 outlet 8 stirrer 8 stirring blade

Claims (3)

An organic waste containing calcium-containing methane fermentation impurities and having a viscosity of 8 Pa · s or less, a stirring basin provided with a bottom portion having a downward conical shape, and a two-stage stirring blade forming a swirling flow in the longitudinal direction The ratio of the distance between the upper end and the lower blade of the bottom of the stirring tank and the distance between the lower blade and the upper blade is 1: 0.75 to 1.5. It is contained in the said organic waste by sending to a stirring tank whose ratio of the diameter of the diameter of the blade of the upper row / the diameter of the lower blade is 1.1-1.5 and stirring at a predetermined number of rotations. A method for removing a methane-containing unsuitable substance containing calcium, characterized in that the methane-fermented inappropriate substance is accumulated and separated at the bottom of the stirring tank. An apparatus for removing methane fermentation impurities suitable for use in the method for removing calcium-containing methane fermentation impurities according to claim 1, which is an organic organic material containing calcium-containing methane fermentation impurities having a bottom in the shape of a downward cone. And a two-stage stirring blade for stirring the contents of the stirring tank to form a swirling flow in the longitudinal direction, and the upper end of the bottom portion of the stirring tank among the two-stage stirring blades The ratio of the distance between the lower blade and the lower blade and the distance between the lower blade and the upper blade is 1: 0.75 to 1.5, and the ratio of the diameter of the upper blade / the diameter of the lower blade is 1.1 Containing calcium with a stirrer of ̃1.5, discharge means of the methane fermentation unsuitable material accumulated at the bottom of the stirring tank, and discharge means of the organic waste from which the methane fermentation unsuitable material is separated Equipment for removing methane fermentation impurities. Of stirring blade of the second stage, the ratio of distance between the blade and the upper blade spacing the lower stage between the upper and lower blades of the bottom of the agitating vessel is 1: 0.8-1.3, The apparatus for removing methane fermentation nonsuitable substances containing calcium according to claim 2, wherein a ratio of upper blade diameter / lower blade diameter is 1.2 to 1.5 .

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