JPS644996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for composting organic waste such as livestock manure, human waste treatment residue, sewage treatment sludge, and wastewater treatment sludge.

Conventionally, organic waste (hereinafter referred to as "processed material")
Composting is done by drying in the sun, sawdust and bark (water retaining material).
After adjusting the moisture content by adding compost and composting products, and mixing seeds as necessary, fermentation is carried out using horizontal rotary fermenters, vertical fermenters, open-air fermenters, etc. This is done by processing.

Each fermenter has been developed to be highly efficient and has its own characteristics. However, the drawbacks have not been completely eliminated, and many problems unique to each fermenter still remain to be solved.

The purpose of the present invention is to eliminate the disadvantages peculiar to each type of fermenter, and this purpose is achieved not by improving the fermenter of the relevant type, but by using different types of fermenters together. A major feature of this invention is that it has been found that by using a horizontal rotary fermenter and a vertical fermenter in combination, it is possible to take advantage of the advantages of both while compensating for their drawbacks.

Horizontal rotary fermentation tanks are: (1) The entire tank rotates, allowing for efficient aeration with a small amount of power; (2)
Advantages include: (1) uniform fermentation due to good ventilation, (3) easy collection of odor and easy installation of deodorizing equipment due to closed system, (4) granulation that is convenient for handling. There is a point. On the other hand, (1) it requires a larger installation area than a vertical fermenter when used for long-term fermentation, or when processing large amounts of water, (2)
There are drawbacks such as moisture vaporized by fermentation heat condensing in the latter half of fermentation, resulting in the treated product adhering to the tank wall surface and an increase in granulation size.

On the other hand, vertical fermenters (1) have a small installation area and are suitable for large-scale processing; (2) the processed material is input from above and the fermented product is taken out from below; as fermentation progresses, the processed material is removed from above. Continuous processing is possible by moving downward, (3)
By ventilating from the bottom to the top, there are advantages such as the fact that fermentation heat can be effectively used to promote fermentation of the processed material. On the other hand, (1) if it is simply loaded, it will be impossible to ventilate or take out due to compaction; (2) an internal stirring device is required to improve the ventilation or drying effect, and its power is large. (3) Space is required to increase stirring efficiency, and although the installation area is relatively small, equipment with a much larger capacity than the actual throughput is required.

The present invention first performs primary fermentation in which the fermentation of the processed material is activated and granulated in a horizontal rotary fermentation tank,
The processed product is then transferred to a vertical fermentation tank and further fermented until it reaches full ripeness.This allows the advantages of both to be maintained and the disadvantages to be compensated for.

In other words, since the horizontal rotary fermentation tank is used only for the first half of the fermentation, which involves activating the fermentation and completing proper granulation, the fermentation can be carried out uniformly without causing the processed materials to stick to the walls or increase the granulation diameter. The fermentation process can be started quickly and the residence time is short, so a small fermentation tank is required even for large-scale processing, and bad odors can be easily collected. In addition, since the granulated processed material is supplied to the vertical fermentation tank, there is no possibility of inability to ventilate or take out the material due to compaction.Therefore, there is no need for a stirring device, and the filling rate of the processed material can be increased to approximately 100%. Therefore, the installation area can be made even smaller than the conventional vertical fermentation tank, and as mentioned above, the horizontal rotary fermentation tank can also be small, so even if both are combined, the installation area is relatively small. Since it is small and the fermentation heat is effectively used, the fermentation is not affected by the temperature drop during transfer from the horizontal rotary fermenter to the vertical fermenter.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

1 is the treated product, which usually has a moisture content of 60% to 90%,
It has a pH of about 4 to 13. Generally, the optimum moisture content in composting fermentation is 40% to 60%, and if the moisture content is too high or the pH is too high, steps such as drying and neutralization are required. Normally, composted products are mixed to adjust the moisture content, but in this case a large amount of composted product is required, and if the pH is high, the rate of fermentation may be slow, so aerated sun drying, hot air drying, etc. It is advisable to include a process in which the moisture content is adjusted to a certain extent by drying, etc., and at the same time, air is supplied to adjust the pH to below 10 using carbon dioxide gas in the air.

2 is a dryer for controlling the moisture content and pH as described above, especially the horizontal rotary fermentation tank 4 which will be described later.
Air that has been heated by fermentation heat and has an increased amount of carbon dioxide gas is supplied through the vertical fermentation tank 6.

The treated product whose moisture content and pH have been adjusted in this manner is sent to the crushing mixer 3, where it is crushed and mixed with seeds. It is preferable to use a fermented material that has been subjected to primary fermentation and is heated at a high temperature as described below as a seed because a good start of fermentation can be obtained. At this time, if the processed material has a pH of about 4 to 10, it will be neutralized to about pH 7 to 8 by the respiration of the seeds and by the buffering action. The amount of seeds used ranges from treated product 3:seed 1 to treated product 1:seed 2.
A portion of the composted product may be added for moisture control during mixing and crushing. Alternatively, the treated material may be separately pulverized and then mixed with the seeds, and it is preferable that the moisture content of the mixture of the treated material and the seeds (raw material for preparation) is about 40 to 60%.

It is also suitable for the crushing mixer 3 to be of the hammer type, flash type, or cutting blade type.

The crushed and mixed raw materials are fed into a horizontal rotary fermentation tank 4 and subjected to primary fermentation. By rotating the cylindrical body of the horizontal rotary fermentation tank 4,
The raw materials are stirred and mixed, but at this time, air (oxygen) necessary for fermentation is constantly released from the bottom of the cylindrical body.
It is preferable to carry out aeration to promote aerobic fermentation.

The conditions for primary fermentation are horizontal rotary fermentation tank 4.
The filling rate is preferably about 60 to 80% of the internal volume, and should be adjusted depending on the moisture content of the raw materials and their physical properties. When ventilating, the temperature is 20
The temperature may be ˜30° C., and the amount may be 5 to 10% per minute based on the volume of the raw material to be charged. If the filling rate is too low, the processing efficiency will be poor, and if the filling rate is too high, the turning effect due to rotation will not be sufficiently obtained. If the aeration temperature is too low, the rise in fermentation temperature will be slow, resulting in poor start-up, while if it is too high, too much water will evaporate, hindering fermentation.
In addition, if the amount of aeration is too small, it will be difficult to obtain an aeration effect, and if it is too much, the temperature will be lowered or drying will be too rapid, which will hinder fermentation.

The rotation speed of the cylindrical body is set depending on the scale of the fermentation tank 4, the physical properties of the raw material, fermentation time, desired particle size, etc., but for example, the inner diameter is 1 m, the moisture content of the raw material is 50%, and the fermentation time is 50 hours. , when the granulation diameter is 5 mm or less, the circumferential velocity of the cylindrical body is approximately 0.16 cm/
It is preferable that it is about seconds (one rotation/every 30 minutes) or less. If the rotation is too fast or too slow, it will be difficult to achieve proper granulation.

Suitable granulation is to use granules with a particle size of about 20 mm or less, especially if the particle size is mainly in the range of 1 mm to 10 mm, the height of the vertical fermenter can be reduced by several degrees. There is no risk of uneven fermentation or anaerobic fermentation due to lack of ventilation even when stacked as m.
Good aerobic fermentation conditions are obtained.

In the primary fermentation, in order to reduce the installation area and improve processing efficiency, it is preferable to activate the fermentation as quickly and uniformly as possible, and to perform evaporation of water at high temperatures and appropriate granulation in a short time.

Regarding the fermentation speed, by using the fermented product that has undergone primary fermentation and reached a high temperature as a seed,
Rapid fermentation is possible, reaching the maximum temperature (70-80°C) in 8-20 hours. This rapid fermentation not only shortens the overall processing time, but also shortens the residence time in the horizontal rotary fermenter 4, allowing the fermenter 4 to be more compact.

Moisture evaporation and granulation are important items in terms of the characteristics of the secondary fermentation process, and the main focus is to prevent fillers from adhering to the inner wall of the primary fermentation tank and to reduce the moisture content of the primary fermentation product as low as possible. It is preferable to operate as follows. In other words, in order to cause a large amount of water vapor generated as the temperature rises to flow out of the tank, the ventilation rate is increased from 5 to 10% per minute of the charged amount of raw materials from the period when the temperature rises or when the maximum temperature is reached. min 15-25% and/or
Alternatively, by blowing air from the upper side of the fermentation tank to the upper surface of the filling material, etc., steam flows out of the tank without filling the tank.

By evaporating water in this way,
Even when the water content of the raw material is relatively high, it is possible to reduce the water content in a vertical fermentation tank in a short time to a level that prevents the inability to aerate or take out the material due to compaction. Therefore, in addition to the above-mentioned effect of preventing wall adhesion and increase in granule size, composting products for controlling moisture content,
seeds, heating energy can be minimized.

It is desirable that the temperature of the filling during this period has risen to at least 50° C. due to fermentation. This is because unless the fermentation period is active, the temperature may drop due to a large amount of aeration, which may hinder fermentation.

The temperature of the air blowing depends on the air flow rate, but fermentation will be hindered unless the temperature of the filling is lowered, so it is preferable to use hot air at a temperature of 30 to 70°C, which is higher than the initial temperature. . Furthermore, the air blowing time is sufficient to reach the set moisture content in secondary fermentation, which is usually 10 to 20 minutes.
The time is sufficient, and the filling at this time is completely granulated into spherical particles and has no bad odor. In particular, since aerobic fermentation is carried out uniformly, almost no odor is generated due to anaerobic fermentation. Furthermore, the moisture content of the primary fermentation product when subjected to secondary fermentation is approximately 40% to 50%. Too high a temperature will cause compaction; too low a temperature will inhibit fermentation.

In this way, the primary fermentation is completed in 20 to 45 hours, and a primary fermented product is obtained.

The primary fermentation product can be taken out of the tank while still at a high temperature (60 to 70°C), and a portion of it can be used as seeds as described above. At this time, it is a good idea to sieve and return the larger particles as seeds.

The primary fermentation product is transferred to a vertical fermentation tank 6 by a belt conveyor 5 and subjected to secondary fermentation treatment. conveyor 5
During transportation, the temperature of the primary fermented product is high and steam is generated, so in order to prevent steam condensation and to aid water evaporation, belt conveyor 5 is used.
It is preferable to set the belt at a low speed and to use a porous or net-like belt to spread the primary fermentation product thinly to a thickness of about 5 cm or less, and to blow air from the bottom of the belt. In this case, the amount of air blown should be approximately 5 to 10% of the total amount of primary fermentation product on the belt. If it is too large, the temperature of the primary fermentation product will drop drastically, so it is best to keep the temperature at a level that does not drop below 40℃. preferable.

Furthermore, the moisture content of the primary fermented product to be transferred should be around 40% or less, as mentioned above, and if the temperature is low and the moisture content is low, secondary fermentation will be hindered.

As a method of blowing the air, it is also possible to install the conveyor 5 inside the duct and blow the air from one end or the center of the duct by pressure feeding or suction.

In this way, the primary fermented product transferred has physical properties with dry powder attached to the surface of the particles,
The top layer of the vertical fermentation tank 6 is filled.

The vertical fermentation tank 6 is preferably piped to allow ventilation from the bottom or at a stacking height of 2 m or more to a temperature of several stages (more preferably, the tank wall has a double structure, so that the internal surface temperature The second fermentation is carried out under aeration until the fermentation is fully ripe.

When performing ventilation, the temperature should be between 30 and 70℃, and the ventilation rate should be 10 to 70 degrees per minute based on the volume of the packed material.
It is appropriate to set it to about 25%. Due to the primary fermentation process, the surface area is reduced by granulation, dry powder is attached to the surface of the particles, and the moisture content is reduced, resulting in very good air permeability and compaction of the filling. The adhesion caused by this will be reduced. By removing the fermented product from the bottom by gravity, the residue from the top smoothly moves to the bottom, eliminating the need for a mechanical stirring device.

The aerated air contributes to drying at the bottom due to the final stage of fermentation, and the contained oxygen is hardly used, but is gradually used as you move up to the top. Contributes to high temperature fermentation. The residence time in the vertical fermentation tank 6 is 4 to 10 days, which is determined by the physical properties of the raw materials and the final product settings, but the goal is to complete the decomposition and fermentation of easily decomposable organic substances (lower fermentation temperature). However, the temperature of the product is
It may be taken out at 20 to 40°C and with a moisture content of around 30%, and used as a product as is, but a portion may be used to adjust the moisture content in the raw materials for primary fermentation.

The effects of the present invention as described above are summarized and listed as follows.

That is, since the fermentation is divided into primary fermentation and secondary fermentation, and these are carried out in a horizontal rotary fermentation tank and a vertical fermentation tank, the following benefits can be obtained.

(1) Benefits of horizontal rotary fermentation (a) Appropriate granulation of processed materials without causing wall adhesion.

(b) A homogeneous fermented product can be obtained by fermentation with a good start-up.

(c) Since the residence time is not long, there is no need for a large installation area like in the past.

(d) Since it is taken out at high temperatures, moisture evaporates rapidly, and the surface area is large, allowing a large amount of moisture to be dissipated by ventilation, and the surface of the fermented product is covered with dry powder, which prevents adhesion between particles.

(2) Benefits of vertical fermentation tanks (a) Since the process is filled with granulated and somewhat reduced water content, there is no close contact due to compaction of the filling, and a gravity flow method can be used.

(b) Since there is no close contact, the porosity is high and breathability is improved.

(c) Due to its high fluidity, it is possible to use a vertical type without an internal stirring device.

(b) Since a stirring device is not required, the installation area is smaller and equipment costs are lower.

(E) Since the filling rate can be approximately 100%,
The tank volume can be made equal to the actual processing amount.

(3) Overall benefits (a) Both the horizontal rotary fermenter and the vertical fermenter can be made relatively small, so the overall installation area can be small.

(b) Quick and uniform fermentation can be obtained.

(c) It is easy to use the primary fermentation product, which is heated at a high temperature during the process, as seeds.

(d) Fermentation status can be checked in the middle.

(e) A product with a uniform, fine particle shape that is easy to handle can be obtained.

(4) Benefits of using a high temperature fermented product immediately after the completion of primary fermentation as a seed (a) The temperature of the raw material to be prepared can be increased.

(b) The fermentation atmosphere of the new raw material is formed quickly due to the best condition of the seeds, and the initial fermentation is quick.

(c) This reduces residence time.

(5) Benefits of aerating the horizontal rotary fermentation tank during primary fermentation (a) By using the rotary tank and ventilation system, the filling amount in the tank can be increased. (No other accessories required to be installed in the tank).

(b) There is no moisture condensation on the side of the fermentation tank, and there is no adhesion of fillers.

(c) Therefore, the water content of the filling is also reduced and anaerobic fermentation is eliminated.

(d) The tank is no longer filled with foul odors.

(6) Benefits of supplying air to the primary fermentation product during transfer from the horizontal rotary fermentation tank to the vertical fermentation tank (a) The evaporation of water is promoted and the time for primary fermentation can be shortened accordingly.

(b) More securely prevents compaction in vertical fermenters.

(7) Benefits of supplying air from the bottom of a vertical fermentation tank (a) Fermentation is not hindered even if the fermentation temperature drops slightly during transfer.

(b) It is also effective in preventing fermentation from stopping due to drying.

The present invention has many advantages as described above, and takes advantage of the respective advantages of the conventional horizontal tank and vertical tank.
It can be said that this is a composting system that can cover each of the drawbacks.

Next, the present invention will be explained by examples, but these are merely illustrative and do not limit the present invention in any way.

Example 1 Sewage treatment sludge generated from a sewage treatment plant (water content
67%) was dried in the sun to obtain 280 kg of raw material with a moisture content of 53%.

To this, an equal volume (approximately 350) of seeds that have been fermented in advance and reached a high temperature period of 70℃ are crushed and mixed in a hammer mill at the same time, with a moisture content of 48% and a pH of 8.7.
560Kg (approximately 700) was obtained and sent to a ^1M3 horizontal rotary fermenter.

In the horizontal rotary fermentation tank, air at 20℃ is initially pumped every minute.
56, ventilate from the bottom and reduce the number of rotations of the cylindrical body to 1
When I started primary fermentation with rotation/every 30 minutes, 14
Temperatures ranged from an initial temperature of 29°C to a maximum of 74°C. When the maximum temperature is reached, hot air of 50℃ is blown from one side of the upper side of the cylindrical body at a rate of 100 degrees per minute, and then discharged from the outlet provided on the other side.
At 15 hours, 453 kg of the primary fermentation product was taken out.
At this time, the product temperature was 72°C, pH 8.6, and moisture content 42.6%. Of this amount, 225 kg (approximately 250 kg) was used as seeds for the next primary fermentation, and the remaining 228 kg was transferred to a vertical fermentation tank using a belt conveyor.

The belt conveyor has 16 mesh mesh belts and 5
The belt was moved at a rate of 1m per minute, the stacking height was set to 5cm, two ventilation pipes with holes equally spaced 10cm apart were arranged vertically on the lower side of the belt, and air was blown at a rate of 100cm per minute. It was filled into the tank using a bucket type conveyor.

The moisture content of the primary fermented product filled in the tank is 40.3%
It was becoming.

The vertical fermentation tank is filled with fermentation material that has undergone primary fermentation in advance, and at the top, the temperature reaches 68°C during secondary fermentation.
As the temperature rises to ℃, at the bottom, the secondary fermentation has finished and it is in the drying period. The above-mentioned primary fermentation product was sent onto it, and air at 30°C was aerated at a rate of 150 per minute.
After carrying out secondary fermentation and repeating the process of removing from the bottom and feeding to the top four times, I opened the damper at the bottom on the 5th day after filling the vertical fermenter, and the secondary fermented product was smooth and smooth. It leaked out and was easily acquired. The temperature of the obtained product at this time is
The moisture content at 28°C was 33%.

In addition, in the same way as when preparing for the primary fermentation, the horizontal rotary fermentation tank and the vertical fermentation tank were each filled with 700 raw materials, and 20℃ air was aerated at a rate of 56 per minute, and the horizontal tank was rotated once per minute. When the vertical tank was rotated every 30 minutes and fermentation was carried out twice, the temperature reached 30℃.
It takes 5 days in the horizontal rotary fermenter and 7 days in the vertical fermenter to reduce the moisture content to 51% in the horizontal rotary fermenter.
The rate was 47% in the vertical fermentation tank, and 49% in the horizontal rotary fermentation tank, and approximately 150 kg of anaerobic sludge adhered to the inner wall of the cylindrical body. In addition, in the vertical fermentation tank,
Even if you open the damper at the bottom, the fermented product will not come out.
The product could only be obtained by applying impact with a stick from above, below or from the side. The horizontal rotary and vertical fermenters used were as follows.

Horizontal rotary fermentation tank: The cylindrical body rotates, with an inner diameter of 1m and a length of 1.5m.The cylindrical body is kept warm and has air ports with a diameter of 10cm on both sides of the top, from which air is blown and exhausted. I can do it. In addition, ventilation pipes are fixed to both ends of the inner wall at equal intervals parallel to the axis, one end of which is sealed, the other end of which gathers in the center of the side of the cylindrical body and leads to the outside. I made it possible to vent from the coming ventilation pipe. The ventilation pipe was made to allow air to escape by drilling holes with a diameter of 3 mm at 10 cm intervals toward the inner wall surface.

Vertical fermentation tank: Square type (width 80cm square x height 2.5m),
It is installed vertically with legs at the bottom, the bottom is square-shaped, a lid that can be opened and closed by a rotary damper is installed in the center, all sides are covered with heat insulating material, and the opposing inner wall is connected from the center of the tank and one side of the bottom. Several ventilation pipes were perforated at equal intervals until they were full, and the perforations were arranged so that the perforations faced downward, so that ventilation could be carried out from one or both of the upper and lower sides. Furthermore, the top of the tank was left open, and a roof was installed above the opening to prevent rain.

Example 2 Food wastewater treatment sludge (moisture content: 78
%) with a moisture content of 65% using a kiln type dryer, 250 kg (approx. The resulting product was 175Kg (moisture content
31%, 250) was crushed and mixed using a flash method to obtain 650 kg of a mixture with a moisture content of 50.1%. This mixture was filled into a horizontal rotary fermentation tank similar to that in Example 1, and fermentation was started by aerating 30°C air at a rate of 130 per minute. Next, 6 hours after the start of fermentation, warm air at 30°C was blown at a rate of 50 per minute from the upper side of the fermentation tank, and the maximum temperature reached 78°C 8 hours after the start of fermentation. The primary fermentation was stopped 22 hours after the start of fermentation (product temperature 76℃), and the primary fermentation product was 518Kg (moisture content 43.8%).
I got it. Of this, 200 kg was subjected to belt conveyor and secondary fermentation treatment according to Example 1, and after staying in the secondary fermentation tank for 5 days, the water content decreased.
We were able to obtain 29.3% of the product.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of the composting method according to the present invention. 1: organic waste, 2: dryer, 3: crushing mixer, 4: horizontal rotary fermentation tank, 5: belt conveyor, 6: vertical fermentation tank.

Claims (1)

[Scope of Claims] 1. In a method of aerobically fermenting and composting organic waste, as the primary fermentation process, a horizontal rotary fermentation tank is used to perform the fermentation process and after granulation. A method for composting organic waste, characterized in that a secondary fermentation process is performed using a vertical fermentation tank. 2. In the method described in claim 1,
A method for composting organic waste, which is characterized by drying by blowing warm air into a horizontal rotary fermentation tank from the temperature rise period of primary fermentation or the period when the maximum temperature is reached. 3 In the method described in claim 1,
A method for composting organic waste, which is characterized in that when transferring the primary fermented product to a vertical fermentation tank for secondary fermentation, the primary fermented product is spread thinly and loaded on a conveyor belt, and transferred while being blown dry. . 4 In the method described in claim 1,
A method for composting organic waste, characterized in that fermentation is carried out by aerating warm air from at least the lower part of a vertical fermentation tank for secondary aerobic fermentation. 5 In the method described in claim 1,
A method for composting organic waste, characterized in that a high-temperature fermented product immediately after completion of primary fermentation is used as seeds.