JPH0510160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a methane fermentor forming part of a methane fermentation system.

Recently, methane fermentation using agricultural and livestock waste has been attracting attention as part of efforts to create local energy and prevent environmental pollution, and efforts are being made to develop methane fermentation systems of various sizes for practical use. It is being With the current state of technology, a large-scale methane fermentation system for over 10,000 pigs would be similar to a sludge digestion system at a sewage treatment plant, which would increase system equipment costs. Therefore, there are very few customers who can install such a methane fermentation system. On the other hand, in the case of small and medium-sized enterprises with 500 to 5,000 pigs, there are many customers who can install medium-scale or small-scale methane fermentation systems. However, for these consumers,
The amount of funds that can be invested in system equipment costs is relatively small, and the price and construction costs of the methane fermentation tank itself generally account for a large proportion of the total cost of the methane fermentation system, so the cost performance of the methane fermentation tank is low. This holds the key to whether or not a methane fermentation system can be introduced.

FIG. 1 shows an entire example of the above-mentioned medium-sized and small-scale methane fermentation system, and a cylindrical vertical methane fermentation tank is used in this methane fermentation system.

First, an overview of the methane fermentation system will be explained.
The manure 3 discharged from the pigpen 1 into the waste reservoir 2 is
The waste is pumped into a cylindrical vertical methane fermentation tank 5 by a pump 4 . This methane fermentation tank 5 is provided with a stirring pump 6 that sucks in at the bottom and discharges at the top. 7 is provided. The stirring pump 6 is driven by an electric motor, and an electric wiring 8 runs through the methane fermentation tank 5.

Digested methane gas generated in the methane fermentation tank 5 is supplied to a water seal gas holder 11 via a dehydrator 9 and a desulfurizer 10. A part of the methane gas held in the gas holder 11 is used as fuel for the boiler 12, and hot water produced by the boiler 12 is sent to the internal hot water coil 7 for heating.

The above-mentioned cylindrical vertical methane fermentation tank 5 has the following drawbacks.

1. Due to cost considerations, cylindrical tanks made of double fiber-reinforced plastic plates with intermediate insulation are used; however, as the internal volume of these cylindrical tanks increases, the fermentation efficiency decreases due to transportation and heating. In order to prevent this, the height is increased, which makes it more likely to collapse during an earthquake or typhoon. For example, in a methane fermentation system that can accommodate 500 pigs, the internal volume of the methane fermentation tank is limited to ^20m3 (tank outside dimensions: φ2280mm x 5921mmH), and if the height is lowered and the outer diameter is increased, transportation is possible. becomes difficult.

2. As the height increases, the water pressure of the fermented liquid in the methane fermentation tank 5 increases, making it difficult to withstand water pressure at the bottom of the methane fermentation tank 5.

3. As the height increases, the lift height of the waste pump 4 and stirring pump 6 increases, and the energy consumption of these pumps 4 and 6 increases considering their scale.

4. Higher heights require lightning rods and other lightning protection measures.

5. Maintenance of the internal heating coil 7 and stirring pump 6 is difficult.

6. In order to prevent a decrease in the fermentation efficiency of the internal hot water coil for heating, that is, to prevent a decrease in fermentation efficiency, the hot water coil has a concentric multilayer structure in order to uniformly heat the tank in the horizontal direction.

FIG. 2 shows a typical example of a cylindrical horizontal methane fermentor. This methane fermentation tank 15 has three stirring pumps 16 of the same type as the stirring pump 6, spaced apart from each other in the lateral direction. These stirring pumps 16 are connected to the tank 1 of the methane fermentation tank 15.
It is inseparable from 5a. In addition, the tank 15a
An internal hot water coil 17 for heating extends in the lateral direction of the tank 15a from the side of the tank 15a to the lower part of the tank 15a. This heating internal hot water coil 1
7 is also inseparable from the tank 15a.

The above-mentioned cylindrical horizontal methane fermentation tank 15 includes:
There are the following drawbacks.

7 Stirring pump 16 and internal heating coil 1
7 is inseparable from the tank 15a, making maintenance and inspection difficult.If maintenance and inspection are to be performed, the tank 15a must be emptied.

8 The methane fermentation tank 15 can be transported by ordinary truck, and in order to increase the internal volume, the outer diameter must be
Although the length is 2.8 m or less and the length is 10 m or less, uniform heating and stirring over the entire length of the fermenter 15 is difficult.

The purpose of the present invention is to eliminate the drawbacks of conventional cylindrical vertical and horizontal methane fermenters, enhance the heating and stirring effects, improve methane fermentation performance, and facilitate maintenance and inspection of the heating and stirring equipment. An object of the present invention is to provide a methane fermentation tank. In order to achieve this object, the present invention has a plurality of insertion ports opened at regular intervals along the longitudinal direction of the tank at the top of a tank constituting a cylindrical horizontal methane fermentation tank. The provided attachment/detachment flange has a spacer placed on the attachment/detachment flange at its upper end,
A support frame consisting of a plurality of rods extending below the spacer and a bottom plate fixed to the lower end of the rods, a submersible stirring pump installed in the support frame, and a liquid level from the stirring pump to the support frame. A heating/stirring unit consisting of a discharge pipe extending upward, and an internal hot water coil for heating spirally surrounding the submersible stirring pump and the discharge pipe is detachably installed. do.

Hereinafter, preferred embodiments of the present invention will be described in detail based on FIGS. 3 to 5. A substantially horizontal cylindrical methane fermentation tank 20 is fixed to a base surface 22 by a plurality of legs 21. The entire wall of the tank 20 has an inner wall and an outer wall made of fiber-reinforced plastic, and has a structure in which a heat insulating material made of polyurethane is filled between these walls. The outer diameter and overall length of the tank 20 are appropriately selected depending on the scale of the methane fermentation system.

However, considering transportation by large low-floor trucks rather than special transport vehicles such as large trailers, an outer diameter of 2.8 m or less is preferable.

It is easy to make units with a maximum internal volume of ^50m3 and expand them as the scale expands.

A plurality of insertion ports 23 are provided at the top of the tank 20 at regular intervals in the longitudinal direction of the tank 20.
is provided so as to protrude slightly upward. Each insertion port 23 has a square cross section and has a rectangular attachment/detachment flange 24 at its upper end.

A heating/stirring unit 25 is inserted into the tank 20 from each insertion port 23. This heating/stirring unit 25 mainly consists of a support frame 28 consisting of a plurality of vertically extending rods 26 and a bottom plate 27 fixed to the lower ends of these rods 26, and this support frame. A submersible stirring pump 29 as an agitator installed at the axial center of the stirring pump 28 , and this stirring pump 29
a discharge pipe 30 extending upwardly within the support frame 28;
An internal hot water coil 31 for heating spirally surrounds the stirring pump 29 and the discharge pipe 30 and extends upward while being inscribed in the bar 26; and a square spacer 32 placed on the attachment/detachment flange 24 of the insertion port 23. Consists of.

A stirring pump 2 is provided on the bottom plate 27 of the support frame 28.
9 is provided, and a suction port 33 for fermentation liquid circulation is provided at the lower end of the stirring pump 29 and communicated with the discharge pipe 30 via the stirring pump 29.

At the upper end of the discharge pipe 30, as shown in FIGS. 4 and 5, discharge pipe ports 34 are provided which cross in a cross shape and are open at each of four ends. Further, this discharge pipe 34 opens above the liquid level of the fermentation liquid 35, and furthermore, in order to improve circulation efficiency, an internal hot water coil 31 for heating is used as a heater.
Three are open on the inside and one is open on the outside.

The spacer 32 has a wall with the same structure as the wall of the tank 20, is hollow, and has a terminal box 36 for cable connection, a hot water inlet pipe 37, and a hot water inlet port 37 on two opposing sides, respectively, as shown in FIG. It has an outlet pipe port 38, and has gas discharge pipe ports 39 on the other two opposing sides. These gas discharge ports 39 are connected to a gas purification and storage device that constitutes the other part of the methane fermentation system. An electric cable 40 extends from the cable connection terminal box 36 to a motor (not shown) in the stirring pump 29. The hot water inlet port 37 and the hot water outlet port 38 are connected to the internal hot water coil 31 for heating.

A square top lid 4 is provided on the top surface of the spacer 32.
1 is placed. A fermentation gas inspection tube 41b equipped with a valve 41a is disposed approximately in the center of the upper lid 41 so as to communicate between the inside of the tank 20 and the atmosphere side. This fermentation gas test tube 41b is for sampling the gas in the tank 20 until methane fermentation is normally performed in the tank 20.

The number of heating/stirring units 25 may vary depending on the internal volume of the tank 20 and the required heating/stirring capacity.
One or more can be provided.

One side (left side in FIG. 4) of the tank 20 is provided with a fermentation stock solution input pipe port 42 at the top and a drain 43 at the bottom.

On the other side of the tank 20 (the right side in FIG. 4), a fermentation waste liquid discharge pipe port 44 and a liquid level gauge 45 are provided at the top, and a drain 43 is provided at the bottom.

Hereinafter, the operation of the methane fermentation tank of the present invention described above will be explained. Fermentation stock solution is introduced into the fermentation stock solution input pipe port 4 by a suction pump 4 as shown in FIG.
2, it is put into the tank 20, and fermented during the retention period depending on the characteristics of the fermentation liquid, and overflows from the fermentation waste liquid discharge pipe port 44 as fermentation waste liquid. In other words, if we look at the entire methane fermentation tank statically, each time the fermentation stock solution is added every day, the fermentation waste solution is discharged according to the amount of the fermentation stock solution, and the fermentation waste solution is discharged from the tank 20.
The liquid level inside is regulated to a constant level.

The fermentation stock solution is sufficiently stirred and heated by the heating/stirring unit 25 to promote methane fermentation by methane bacteria present in the fermentation solution 35 in the tank 20 in an anaerobic environment. While releasing methane gas into the upper space, the fermentation stock solution input pipe port 42
The fermentation waste liquid gradually flows from the side to the fermentation waste liquid discharge pipe port 44 side.

The methane gas released into the upper space of the fermentation liquid 35 is sent to the gas purification and storage device via the gas release pipe port 39.

In the methane fermentation tank, the fermentation liquid 35 is pumped up by the stirring pump 29 from the water intake port 33 for fermentation liquid circulation, and is sprayed inside and outside of the internal hot water coil 31 for heating from the discharge pipe port 34 . The sprayed fermentation liquid is heated while passing inside or outside the heating internal hot water coil 31, and descends again toward the fermentation liquid circulation suction port 33. In this way, stirring and heating are efficiently repeated.

Since the heating/stirring unit 25 is only detachably supported by the attaching/detachable flange 24 at the spacer 32, the tank 2
The upper cover 41 can be easily removed from the tank 20, and during removal, the upper cover 41 is attached to the attachment/detachment flange 24 in a sealed state, thereby not damaging the anaerobic environment inside the tank 20.

As mentioned above, the present invention provides a heating/discharging system in which an insertion port with a removable flange is provided at the top of a cylindrical horizontal tank, a warmer and an agitator are provided within a support frame, and a spacer is provided at the top of the support frame. The stirring unit is inserted into the tank from the insertion port, and the spacer is removably attached to the detachable flange, so the volume of the tank, the characteristics of the fermented liquid,
The number of heating/stirring units can be freely selected depending on various conditions such as weather conditions in cold regions or warm regions.

The methane fermentation tank according to the present invention adopts a horizontal cylindrical shape as its basic shape, and the total height is necessarily limited to a certain value or less. Along with this, there is no risk of it collapsing due to an earthquake or typhoon, and the water pressure of the fermentation liquid in the tank is prevented from increasing more than necessary.
This has the advantage that the materials constituting the methane fermentation tank do not require special pressure resistance. Furthermore, the waste lifting pump and stirring pump have a small lift, and the energy consumption required to drive these pumps can be reduced.

Furthermore, the fermentation liquid is pumped up by a stirring pump,
By being heated while passing through the inside and outside of the internal heating coil, the circulation speed of the fermentation liquid is increased, and the stirring conditions and heating conditions can be controlled in relation to each other, thereby reducing the methane fermentation effect. It has the effect of being promoted.

Furthermore, since the heating/stirring unit can be attached to and removed from the tank, maintenance and inspection of the methane fermentation tank is easy, and maintenance such as replacement of parts can also be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a methane fermentation system according to the prior art, FIG. 2 is a schematic vertical sectional view of a horizontal cylindrical methane fermentation tank according to the prior art, and FIG.
4 is a partially omitted plan view of the methane fermentation tank according to the present invention, FIG. 4 is a cross-sectional view taken along the line -- in FIG. 3, and FIG. 5 is a cross-sectional view taken along the line -- in FIG. 4. 20...Tank, 23...Insertion port, 24...Detachable flange, 25...Heating/stirring unit, 2
8... Support frame, 29... Stirrer, 31... Warmer, 32... Spacer.

Claims (1)

[Claims] 1 A plurality of insertion ports are opened at regular intervals along the longitudinal direction of the tank at the top of the tank constituting the cylindrical horizontal methane fermentation tank, and the upper end is inserted into the attachment/detachment flange provided in the insertion port. a support frame comprising a spacer placed on the attachment/detachment flange, a plurality of rods extending below the spacer, and a bottom plate fixed to the lower end of the rod; It consists of a submersible stirring pump installed in a frame, a discharge pipe extending from the stirring pump above the liquid level, and an internal hot water coil for heating that spirally surrounds the submersible stirring pump and the discharge pipe. A methane fermentation tank characterized by a removable heating/stirring unit.