JP3660191B2 - Fermentation drying method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fermentation drying method, and more particularly to a fermentation drying method for performing fermentation drying of sludge.
[0002]
[Prior art]
As a treatment method of surplus sludge (consisting of activated sludge and coagulated sediment sludge) that is generated when sewage is treated with activated sludge, composting treatment is known in which these sludge is composted and reused as resources. Yes.
[0003]
FIG. 7 is a schematic configuration diagram of a conventional composting processing system. Part of the sludge in the sludge storage tank 1 is sent to the sludge dryer 14 and dried, and then sent to the mixer 15 to mix with the sludge that has not been dried or the return compost, so that the water content is about 55%. Adjusted. This sludge is fermented at least at 65 ° C. or more for at least 2 days in the primary fermentation apparatus 5a, and sent to the secondary fermentation apparatus 5b in about 10 days. The compost fermented for two months in the secondary fermentation apparatus 5b is formed by the granulator 16 and then divided and shipped as a product by the bagging apparatus 9.
[0004]
[Problems to be solved by the invention]
As described above, the conventional composting processing system includes the mixer 15, the primary fermentation apparatus 5a, the secondary fermentation apparatus 5b, and the granulator 16, and the apparatus configuration is large and complicated. For this reason, although it is suitable for a large-scale treatment system, it is not suitable for application to the composting treatment of surplus activated sludge such as small-scale sewage treatment plants and agricultural settlement wastewater treatment facilities.
[0005]
Then, this invention makes it a subject to provide the fermentation drying method with a simple apparatus structure and easy application to a small-scale composting process.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the fermentation drying method according to the present invention includes (1) (a) a rotatable drum-shaped main body in which a rotation shaft is arranged in a substantially horizontal direction, and (b) an outer periphery inside the main body. In the main body of the fermentation dryer comprising: an outer blade arranged in a spiral on the side; and (c) an inner blade arranged in a spiral intersecting with the outer blade on the inner peripheral side of the outer blade. The dehydrated sludge is charged into the mixture, mixed with the remaining dry compost, and the moisture content is at least 45% , and (2) while stirring the sludge after mixing by rotating this body, Injecting air to maintain aerobic conditions and fermenting sludge; (3) Discharging a portion of the sludge after fermentation to the outside of the fermentation dryer; (4) In the fermentation dryer And a step of heating and drying the remaining sludge.
[0007]
In a state where the dry compost remains in the drum-shaped main body of the fermentation dryer having the above-described configuration, the dehydrated sludge is further introduced, and the main body is rotated about its rotation axis. Then, the introduced sludge and the remaining dry compost are moved in a predetermined direction (hereinafter referred to as a first direction) along the rotation axis by the outer blades arranged spirally on the outer peripheral side in the main body. It is done. And the sludge and dry compost that have reached one end in the main body are moved in the direction opposite to the first direction along the same rotation axis by the inner blade arranged in a spiral shape opposite to the outer blade. . As a result, the internal sludge and dry compost are agitated and mixed.
[0008]
At this time, the water content of the sludge at the end of the mixing step is at least 45%. According to the inventor's knowledge, when dewatered sludge and dry compost are mixed, rolling granulation phenomenon occurs in which the sludge of several centimeters to several tens of centimeters is formed as the water content of the sludge after mixing increases. It's easy to do. And when this water content was made into 45% or less, it discovered that this rolling granulation phenomenon could be suppressed to a required level.
[0009]
Thereafter, the organic matter in the sludge is decomposed by the aerobic fermentation bacteria (fermentation), and the water in the sludge is evaporated by the heat generated during the decomposition. In order to maintain the aerobic state, air is injected into the sludge, and the fermentation dryer body is rotated to cut back the sludge / dried compost mixture.
[0010]
After completion of the fermentation, a part of the generated compost is left and discharged, and the remaining compost is heated to further evaporate water and dried. By mixing the compost and sludge thus dried, the water content of the sludge can be adjusted to a water content suitable for fermentation.
[0011]
The fermentation drying method according to the present invention measures the humidity of exhaust gas discharged from this fermentation dryer, calculates the moisture content of sludge in the fermentation dryer, and controls the fermentation and drying state based on this. preferable.
[0012]
By observing the humidity in the exhaust gas, it is possible to calculate the amount of water evaporation from the sludge and to estimate the moisture content of the sludge. As the fermentation progresses, the evaporation of water proceeds due to the amount of heat generated during the fermentation as described above, so that the fermentation state can be estimated from the moisture content, and the fermentation state can be controlled. Further, it is possible to similarly estimate the moisture content of the compost when the compost is dried, and the dry state can be controlled similarly.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0016]
FIG. 1 is a schematic configuration diagram of a fermentation drying system for performing a fermentation drying method according to the present invention. This system is a system centering on the fermentation dryer 5. The fermentation dryer 5 has a drum-shaped rotatable main body 51, and its central axis (rotating axis) is horizontally arranged. A motor 6 for rotating the drum body is attached.
[0017]
A belt press dehydrator 4 is disposed above the sludge inlet of the fermentation dryer 5 for dewatering the sludge into a sheet and discharging it. The sludge agglomeration tank 3 is connected to the sludge inlet of the belt press dehydrator 4, and the sludge agglomeration tank 3 is connected to the sludge agitation tank 1 and the polyiron sulfate storage tank 2.
[0018]
An air supply line via a blower 8 and an air heater 7 is connected to the fermentation dryer 5. A hygrometer 11 and a flow meter 12 are arranged on the exhaust line discharged from the fermentation dryer 5, and the exhaust line is led to the exhaust treatment facility 10. On the other hand, the compost discharged from the fermentation dryer 5 is guided to the bagging device 9.
[0019]
The outputs of the hygrometer 11 and the flow meter 12 are sent to the control device 13 that controls the motor 6, belt press dehydrator 4, air heater 7, and blower 8.
[0020]
Here, the internal structure of the fermentation dryer 5 will be described with reference to FIGS. As shown in FIGS. 2 to 5, four outer blades 52 are arranged spirally on the outer peripheral side inside the drum-shaped main body 51 of the fermentation dryer 5 (see FIGS. 3 and 4). On the inner peripheral side, two inner blades 53 are arranged in a reverse spiral shape intersecting with the outer blade 52 (see FIGS. 3 and 5). The inner blade 53 is fixed to the drum body 51 by a member 54. The outer blade 52 and the inner blade 53 are not integrated as shown in the figure, and may be configured by combining a plurality of blades. In that case, it is not necessary for each blade to be connected.
[0021]
Subsequently, the operation of the fermentation drying system, that is, the fermentation drying method according to the present invention will be described.
[0022]
The sludge storage tank 1 stores surplus activated sludge such as agricultural settlement drainage, industrial wastewater, and small-scale sewage treatment. This and the iron polysulfate solution in the iron polysulfate storage tank 2 are introduced into the sludge coagulation tank and mixed to coagulate and precipitate the sludge. The sludge after the coagulation sedimentation is guided to the belt press dehydrator 4 and dehydrated to a water content of about 80%, processed into a thin sheet having a thickness of about 1 to 3 mm, and discharged.
[0023]
By disposing the outlet of the belt press dehydrator 4 at a position 1 to 2 m directly above the sludge inlet of the fermentation dryer 5, the discharged sludge is subdivided, and the drum-shaped main body 51 of the fermentation dryer 5 is used as it is. Drops into and throws in. The belt press dehydrator 4 has the advantage that the apparatus is small and inexpensive compared to other filter press dehydrators and the like. The fermentation drier 5 is filled with compost adjusted to a moisture content of 25 to 35% and 30 to 40% of the volume in the fermentation drier 5, and the introduced sludge is mixed with this compost.
[0024]
At this time, the main body 51 of the fermentation dryer 5 is rotated once in 2 minutes by the motor 6, and the sludge and compost in the main body 51 are stirred and mixed by this rotation. Specifically, when the main body is rotated in the A direction in FIG. 3, the sludge / compost located on the outer peripheral side is moved in the arrow B direction by the outer blade 52. On the other hand, the sludge / compost located on the inner side is moved in the direction of arrow C opposite to the direction of arrow B by the inner blade 53. Thereby, sludge and compost are mixed well. The sludge is additionally added until the water content after mixing is about 45%, and the sludge and compost are mixed and the fermentation process is started. This water content is calculated from the amount of sludge input and the amount of remaining compost by estimating the moisture content of sludge and compost.
[0025]
When sludge and compost are mixed in a drum-like container such as the fermentation dryer 5 of the present embodiment, a so-called rolling granulation phenomenon occurs in which massive sludge of several centimeters to several tens of centimeters is formed by the rotation of the drum. Conventionally, in order to prevent such rolling granulation, a method of introducing a large amount of auxiliary materials such as rice husk and wood chips has been adopted, but this method increases the volume of sludge and increases the size of the device. There was a drawback of doing. Furthermore, in such massive sludge, fermentation does not proceed to the inside and cannot be used as compost. As a result of examining the relationship between the moisture content at the time of mixing and the granulation rate (residual rate on the 8 mm sieve), the present inventor found that the moisture content at the time of mixing was maintained at 45% or less as shown in FIG. It was found that the granulation rate acceptable as a product can be maintained at 10% or less.
[0026]
In the present invention, a moisture content that does not exceed the allowable limit of the granulation rate can be maintained by mixing sludge with dry compost. Further, the dry compost has a smaller volume than the auxiliary material, and the apparatus does not become large.
[0027]
In the fermentation process, organic substances in the sludge are decomposed by aerobic fermentation bacteria, and moisture is evaporated from the sludge / compost by the generated heat. In order to maintain aerobic properties, air is blown into the fermentation dryer 5 by the blower 8. In addition, sludge and compost are turned back by rotating the main body 51 once every 3 to 5 hours for about 10 minutes. Thus, the sludge is composted by fermentation.
[0028]
A fermentation temperature of 65 ° C. or higher is maintained for 2 days or more, and when the water content reaches 30 to 40% (corresponding to 4 to 5 days as a whole process), a predetermined amount of the generated compost is transferred from the fermentation dryer 5 The product is discharged and guided to the bagging device 9, and is divided into small product bags. The moisture content is calculated based on the detection results of the hygrometer 11 and the flow meter 12 installed on the exhaust line. First, the controller 13 calculates the amount of evaporated water, and based on the amount of evaporated water, The moisture content of sludge and compost. In addition, in the case of agricultural settlement drainage or the like, it is difficult to maintain a sufficient fermentation temperature with only excess sludge, so it is preferable to add additives such as oil cake, rice bran, and dried chicken manure.
[0029]
The bagged compost is used as a product after secondary fermentation for 1-2 months. On the other hand, compost remains in the main body 51. The compost is then dried for use in adjusting the moisture content of the sludge to be fermented. Specifically, the air supplied from the blower 8 is heated by the air heater 7 and fed into the main body 51, whereby the moisture of the compost is evaporated by heating to adjust the moisture content to 25 to 35%. This moisture adjustment is also performed by the controller 13 calculating the amount of evaporated water based on the detection results of the hygrometer 11 and the flow meter 12 installed in the exhaust line as described above.
[0030]
Here, an example in which the exhaust flow rate is directly measured by the flow meter 12 has been described, but the exhaust flow rate can also be estimated from the supply amount of the blower 8.
[0031]
In the present invention, as compared with the fermentation drying system shown in FIG. 7, the mixer 15 to the granulator 16 can be used only by the fermentation dryer 5, and downsizing is possible. Moreover, since the fermentation process and the drying process which occupy most of the processes are automated, labor saving is possible, and it is particularly suitable for small-scale processing facilities.
[0032]
【The invention's effect】
As described above, according to the present invention, sludge and dry compost can be mixed inside the fermentation dryer, and can be directly fermented and dried, so that the processing equipment can be downsized. Furthermore, by measuring the humidity of the exhaust gas and calculating the amount of evaporated water, the fermentation and drying processes of the fermentation dryer can be automated, saving labor and being suitable for small-scale processing facilities.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a fermentation drying system for performing a fermentation drying method according to the present invention.
FIG. 2 is a diagram illustrating the internal structure of the fermentation dryer in FIG.
FIG. 3 is a diagram showing a relationship between inner blades and outer blades of the fermentation dryer in FIG. 2;
4 is a view showing outer blades of the fermentation dryer in FIG. 2. FIG.
FIG. 5 is a diagram showing inner blades of the fermentation dryer in FIG. 2;
FIG. 6 is a graph showing the relationship between the moisture content before mixing and the residual rate on the sieve.
FIG. 7 is a block diagram of a conventional fermentation drying system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sludge storage tank, 2 ... Polysulfate iron storage tank, 3 ... Sludge aggregation tank, 4 ... Belt press dehydrator, 5 ... Fermentation dryer, 6 ... Motor, 7 ... Air heater, 8 ... Blower, 9 ... Packing DESCRIPTION OF SYMBOLS 10 ... Exhaust treatment equipment, 11 ... Hygrometer, 12 ... Flow meter, 13 ... Control apparatus, 51 ... Main body, 52 ... Outer blade, 53 ... Inner blade, 54 ... Support member.

Claims (2)

A fermentative drying method in which sludge is fermented and dried to produce compost,
A rotatable drum-shaped main body having a rotation axis disposed in a substantially horizontal direction, an outer blade disposed in a spiral shape on the outer peripheral side of the main body, and the outer blade on the inner peripheral side of the outer blade. Sludge that has been dehydrated is put into the main body of a fermentation drier having inner blades arranged in a crossing spiral shape, and mixed with the remaining dry compost so that its moisture content is at least 45% or less . Process,
Stirring the sludge after mixing by rotating the main body, injecting air and maintaining the aerobic state, and performing the sludge fermentation;
Discharging part of the sludge after fermentation to the outside of the fermentation dryer;
Heating and drying the sludge remaining in the fermentation dryer; and
A fermentation drying method comprising: The measures the humidity of the exhaust gas discharged from the fermentation dryer fermentation water content in the dryer of the sludge was calculated, fermentation of claim 1, wherein the controlling the fermentation dryness this basis Drying method.

Images