JPH07204683A - Methane fermentation apparatus - Google Patents

Abstract

PURPOSE:To reduce undigested material in fermentation liquid and to increase remarkably the methane fermentation capacity of raw liquid the volume of a fermentation apparatus by installing a fermentation liquid circulating pump which sucks fermentation liquid in a reactor, led to an overflow trough, to send the liquid to a liquid-liquid mixer to mix it with the fermentation liquid in the bottom part of the reactor. CONSTITUTION:Liquid containing scum rich in fat, floating in the upper part of fermentation liquid, flows, to be separated, into an overflow trough positioned below a fermentation liquid extraction pipe 7 which is installed on the upper side of a vertical cylindrical reactor 1 having a gas extraction pipe 3 at the top. The liquid is recovered by a circulating pump 6 to return to the bottom of the reactor and then mixed with sludge containing a lot of methane bacteria precipitated in the fermentation liquid by a liquid-liquid mixer 6. The mixture is circulated in the reactor 1 so that undigested material such as fat is sufficiently contacted with methane bacteria to promote fermentation-digestion efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methane fermentation apparatus used for treating rich organic wastes, especially livestock waste liquor such as livestock waste.

[0002]

2. Description of the Related Art Conventionally, livestock waste liquor such as livestock excrement has a very high biological oxygen demand, that is, BOD. It is considered to be appropriate to use the methane fermentation method because it is not economical.

As a fermentation apparatus used in such a methane fermentation method, since the temperature suitable for the activity of methane bacteria is relatively high, it is necessary to improve the heat retaining property. For example, a cylindrical shape having a diameter larger than the height or It was common to cover a large fermenter with an egg shape and a small surface area compared to the volume with a heat insulating material, and to operate in a pressurized state in order to keep the inside in an anaerobic atmosphere.

[0004] In such an apparatus, since the concentration of the contents is high, separation phenomena such as floating and sedimentation easily occur, and such mechanical separation alone suppresses the separation phenomena to homogenize the contents, thus facilitating a smooth fermentation. It was difficult to proceed the reaction. Therefore, in order to homogenize the contents, it is also used to blow the generated methane gas again from the bottom of the fermenter to promote vertical convection, but to prevent the contents from floating or settling. I couldn't.

Further, in such a conventional methane fermentation device, the fermentation liquor of a constant rate is obtained by continuously charging the large-scale fermentation tanks with animal liquor, etc., which are generated almost constantly, while maintaining a high concentration, thereby increasing the residence time. Since the idea of compensating for the delay was adopted, for example, the volume of the fermenter was designed to be 30 days or more of the amount of waste liquid produced from livestock, and the fermentation liquid was extracted each time according to the daily charging amount. It was usual to adopt such a driving method. However, the fermentation liquor extracted from such a methane fermenter still has a high BOD concentration, which is usually 3300 ppm.

[0006] In such a conventional fermentation apparatus, it is difficult to achieve complete homogenization of the contents, and scum with a large amount of fat comes up to hinder the efficient digestion of the fermentation, or the operation of the fermentation tank is prevented. There is a problem that various problems such as obstacles are likely to occur, and there is also a problem that the fermentation does not proceed efficiently even if the fermentation liquid containing a large amount of scum is further processed in the methane fermentation device in the next stage. Moreover, although the fermentation liquor having a high BOD concentration requires further wastewater treatment, an economical wastewater treatment method suitable for performing wastewater treatment conforming to the water quality standard of wastewater has not been established.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention provides an improved methane fermentation apparatus which has a high fermentation efficiency and is capable of advancing the fermentation of livestock waste liquor to the extent that secondary purification treatment is extremely easy. This is the purpose.

[0008]

The object of the present invention is as follows.
A stock solution distributor and a liquid-liquid mixer connected to the stock solution supply tube at the top, the fermentation solution removal tube on the upper side surface, and the overflow gutter on the upper inner wall surface at a position lower than the fermentation solution removal tube. In the lower bottom part, a vertical tubular reaction container provided respectively, and the fermentation liquid in the reaction container upper part that has flowed into the overflow gutter is sucked and fed into the liquid-liquid mixer to lower the reaction container. And a fermentation liquid circulation pump for mixing with the fermentation liquid in the bottom portion.

The reaction vessel in the methane fermentation apparatus of the present invention has a vertical cylindrical shape and has a structure capable of withstanding the pressure of the generated methane and also has corrosion resistance.
And an overflow gutter is provided on the inner wall surface of the upper part of the reaction vessel at a position lower than the fermentation liquid withdrawal pipe, and a liquid-liquid mixer is provided at the bottom part of the reaction vessel, so that the fermentation flowing into the overflow gutter The liquid can be sent to the bottom of the reaction vessel by a pipe connected to a pump. The side wall of such a reaction vessel may be provided with a heating means such as a jacket or a coil that allows a heat medium such as air or water to flow therethrough.

The liquid-liquid mixer provided at the bottom of the reaction vessel is equipped with, for example, a Venturi tube, and the fermentation liquor fed by the fermentation liquor circulation pump is stagnant at the bottom of the reaction vessel. By mixing with, it is possible to make the reaction uniform. The shape and size of the overflow gutter provided on the inner wall surface of the reaction vessel are not particularly limited, but it is desirable that the overflow gutter is provided in an annular shape along the inner wall surface. The upper edge of the overflow gutter is provided 1 to 3 cm below the lower edge of the reaction solution withdrawal pipe, but if the difference in height is less than this, recovery of the fermented solution portion containing a large amount of scum is not possible. If the difference in height is too large, the fermented liquid part containing a large amount of scum will not be sufficiently separated and will be immediately withdrawn from the reaction vessel. It will not proceed. Therefore, in order to efficiently mix undigested content by sufficiently mixing and contacting the fat content, which is the main component of scum, with the sludge content containing a large amount of methane bacteria, the upper edge of the overflow gutter should be the same as that of the reaction solution extraction pipe. It is preferably provided 1 to 3 cm below the lower edge.

The fermented liquid circulation pump in the methane fermentation apparatus of the present invention may be, for example, a centrifugal turbine type pump or an axial flow type pump, and a slurry pump that does not hinder the operation even if gas or solid matter is sucked. Is preferred, but
The structure is not particularly limited as long as the pump has such a function. Further, such a pump may be provided outside the reaction container, or may be provided inside the reaction container. When installed outside the reaction vessel, it has the advantage that maintenance and inspection of the pump is easy.When installed inside the reaction vessel, less heat is released due to the circulation of the fermentation liquid, and the temperature control of the methane fermentation reaction is easy. There is an advantage to be.

The methane fermentation apparatus of the present invention separates livestock waste such as human waste from cows and pigs into solids having a diameter of a predetermined size or more and liquids containing finer solids in advance. The component is suitable for treating, for example, a liquid component only by treating with a composting device or the like. The methane fermentation apparatus of the present invention may be provided integrally with the above composting apparatus so as to surround the surroundings, or these apparatuses may be provided separately. However, when it is installed so as to be surrounded by a composting device,
Not only can the fermentation heat generated in the composting device be effectively used for heating or heat retention of the methane fermentation device,
The equipment can be made compact and economical in terms of construction costs and operating costs.

[0013]

In such a methane fermentation apparatus of the present invention, a liquid portion containing a fat-rich scum component that floats above the fermentation liquid flows into an overflow gutter and is separated. It is re-introduced into the bottom of the vessel and mixed with a sludge portion containing a large amount of methane cells precipitated at the bottom of the fermentation liquid by a liquid-liquid mixer. And since it is further circulated in the reaction vessel, fermentation digestion is efficiently promoted by sufficiently contacting undigested components such as fat with methane bacteria, resulting in uniform fermentation without formation of a scum layer. By proceeding, the fermentation liquor with little undigested content can be extracted.

[0014]

EXAMPLE An example of the methane fermentation apparatus of the present invention is shown in FIG. In the figure, reference numeral 1 is a cylindrical reaction vessel made of a steel plate having a diameter of 80 cm and a height of 250 cm, the inner surface of which is subjected to anticorrosion treatment, and a jacket 2 is provided along the outer wall surface of the reaction vessel 1 for circulating air. Here, 2a and 2b are an inlet and an outlet of air, respectively. Further, 3 is a gas extraction pipe, and 4 is a stock solution supply pipe connected to an annular stock solution distributor 5. 6 is a liquid-liquid mixer composed of a Venturi tube having a diameter of 10 cm and a length of 50 cm, and 7 is a fermentation liquid withdrawing pipe.

An overflow gutter 8 is provided so that its upper end edge 8a is located about 1.5 cm below the lower end edge of the fermentation liquid withdrawing pipe 7. The overflow gutter 8 is formed so as to project inward from the inner wall surface of the reaction vessel 1 in an annular shape having a width of about 10 cm and a depth of about 10 cm. Further, conduits 9a are provided to connect to the collecting ring 9 from a plurality of places (for example, 4 places) on the bottom surface, and from the collecting ring 9 to, for example, a fermentation liquid circulating pump 10 installed outside the reaction vessel 1. A connecting conduit 9b is provided. Further, a conduit 10a connecting the fermentation liquid circulation pump 10 to the liquid-liquid mixer 7 is also provided. Here, the fermentation liquid circulation pump 10 is shown as an example provided outside the reaction container 1, but it may be provided inside the reaction container 1. Incidentally, 11 is a safety valve, and 12 is a blow valve for discharging liquid.

[0016]

EFFECT OF THE INVENTION The methane fermentation apparatus of the present invention directly separates and collects the scum portion which is floated on the liquid surface in the conventional methane fermentation apparatus and the fermentation is difficult to proceed, and directly mixed with the sludge portion where the methane bacteria are concentrated again. By bringing them into contact with each other, the amount of undigested substances in the fermentation liquid can be effectively reduced,
Compared with the capacity of the fermenter, the methane fermentation capacity of the stock solution increased significantly, and it became extremely easy to maintain the fermentation temperature even when the heat generated by fermentation increased and the environmental temperature decreased. Therefore, it is possible to economically carry out the methane fermentation treatment of the concentrated organic waste liquid even in a cold region.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of a methane fermentation apparatus of the present invention.

[Explanation of symbols]

 1 Reaction Container 2 Jacket 2a Inlet 2b Outlet 3 Gas Extraction Pipe 4 Undiluted Liquid Supply Pipe 5 Undiluted Liquid Distributor 6 Liquid-Liquid Mixer 7 Fermentation Liquid Extraction Pipe 8 Overflow Trough 8a Overflow Trough Top Edge 9 Liquid Collection Ring 9a Conduit 9b Conduit 10 Fermentation liquid circulation pump 10a Conduit 11 Safety valve 12 Blow valve

Claims (6)

[Claims] 1. A stock solution distributor connected to a top of the gas drawing tube, a fermentation solution drawing tube to an upper side surface, an overflow gutter on a lower inner wall surface of the fermentation solution drawing tube, and a stock solution supply pipe. And a vertical cylindrical reaction container provided with a liquid-liquid mixer in the lower bottom part, and the fermentation liquid in the upper part of the reaction container flowing into the overflow gutter is sucked and fed into the liquid-liquid mixer. And a fermentation liquid circulation pump for mixing with the fermentation liquid in the bottom of the reaction vessel. 2. The methane fermentation apparatus according to claim 1, wherein the overflow gutter is provided along the inner wall surface of the reaction vessel. 3. The methane fermentation apparatus according to claim 1, wherein the upper edge of the overflow gutter is formed 1 to 3 cm below the lower edge of the fermentation liquid withdrawal pipe. 4. The methane fermentation apparatus according to claim 1, wherein the liquid-liquid mixer comprises a Venturi tube. 5. The methane fermentation apparatus according to claim 1, wherein the fermentation liquid circulation pump is provided outside the reaction vessel. 6. The methane fermentation apparatus according to claim 1, wherein a fermentation liquid circulation pump is provided inside the reaction vessel.