JPH0224599B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a method for drying sludge and other granular and lumpy water-containing solids generated in the treatment of sewage, human waste, various industrial wastewater, etc. using hot air. It's about how to do it.

[Prior art]

Conventionally, the aeration drying method for hydrated solids involves drying granular or lumpy hydrated solids in a thick layer on a porous support bed.
They were laminated to a thickness of about 100 to 200 mm and dried by blowing hot air through the bottom of the porous support bed.

[Problem that the invention seeks to solve]

However, the problems with the conventional ventilation drying method are:
It is difficult to completely equalize the air flow within the water-containing solid layer, and uneven drying tends to occur in some areas. This drying unevenness was particularly likely to occur when the water-containing solid was in the form of flakes.

To prevent uneven drying, if a fluidized bed drying method can be applied, this problem can be solved without any problem, but if the particle size of the water-containing solid is large (for example, about 10 to 20 mm), The flow rate becomes extremely large, leading to wasted energy, or fluidization itself becomes impossible, so the fluidized drying method is not a fundamental solution.

The present invention provides a method that makes it possible to prevent uneven drying and improve drying efficiency in the aerated drying method, and is particularly suitable for large-sized hydrated solids and flaky hydrated solids. The purpose is to provide an effective aeration drying method.

[Means for solving problems]

The present invention involves filling a container with water-containing solids to form a packed bed, blowing hot air through the packed bed to perform ventilation drying, and intermittently jetting compressed air into the packed bed to absorb water. This is a method for aeration drying a water-containing material, which is characterized by changing the filling position of the solid material.

〔Example〕

An embodiment of the present invention will be described by taking a dehydrated cake of sewage sludge as an example and referring to the drawings.
A dehydrated cake A having a moisture content of about 65 to 80% and a particle size of about 10 to 30 mm is fed from a supply port 1 through a valve 2 into a dryer 3 to form a packed bed 4.

The bottom of the dryer 3 is preferably provided with an inverted cone-shaped member 5 that forms a space above the bottom, and communicates with the inside of the dryer 3 at the center. Hot air 6 is sent by a blower 7 and flows upward through the packed bed 4 from the center, and exhaust gas 8 is discharged to the outside from an upper exhaust pipe 9.

The appropriate thickness of the packed layer 4 is 300 to 1500 mm, and when the water content of dehydrated cake A is about 65%, the packed layer 4 of about 1500 mm is formed, and the water content of dehydrated cake A is about 80%. In this case, a filling layer 4 of about 300 mm is appropriate. Further, the temperature of the hot air 6 is not particularly limited, but a temperature range of about 60 to 200° C. is suitable for reducing the bad odor of the exhaust gas 8.

In this way, the moisture content of the dehydrated cake gradually decreases as it undergoes ventilation drying, but since it is difficult to obtain a completely uniform ventilation flow, there are some areas where drying has not progressed sufficiently. Therefore, the compressed air 10 is instantaneously jetted into the packed bed 4 to instantaneously fluidize the packed bed 4. As a result, the position and arrangement of the particles of the dehydrated cake A constituting the packed bed 4 change, so the hot air 6
Particles that have not been in contact with the hot air 6 are given a sufficient chance to come into contact with the hot air 6. In the figure, 11 is a storage tank for compressed air 10, and by opening a valve 12, compressed air 10 is instantaneously blown out into packed bed 4.

As a device for blowing out the compressed air 10, a device that stores the compressed air 10 intermittently and blows it out instantaneously may be used, for example, once every several tens of minutes. Further, the compressed air 10 may be ejected anywhere within the packed bed 4;
It is most effective to squirt upwards from the bottom.

In this way, the dehydrated cake A is dried to become a dried cake B with a moisture content of 10 to 30%, and the hopper 1 is dried by opening the valve 13 at the bottom of the dryer 3.
4, and is discharged outside the system by an arbitrary discharge mechanism 15 such as a rotary valve, double damper, screw conveyor, etc., and used as fertilizer or solid fuel.

Note that when this aerated drying is used for drying water-containing solids generated during the treatment of organic wastewater such as sewage, human waste, and various industrial wastewaters, it is extremely energy-saving and advantageous.

In other words, a large amount of aeration air is supplied from a blower to an aeration tank for biological treatment, such as activated sludge treatment of organic wastewater. Conventionally, this blower simply supplies the air necessary for biological treatment. Only a single function was used. but,
As shown in the adiabatic compression theory of gases in thermodynamics, the temperature of the hot air discharged from the aeration blower is significantly higher than that of the blower suction air, reaching 60 to 80°C.

Therefore, the air discharged from the aeration blower that supplies aeration air is supplied into the dryer 3 as the hot air 6 for drying, and after the retained heat is used as a heat source for drying, the air is cooled and discharged from the exhaust pipe 9. If the exhaust gas (air) is supplied to the diffuser in the aeration tank, the heat source for drying can be obtained at no cost, resulting in extremely energy saving, and the bad odor in the exhaust gas (air) discharged from the exhaust pipe 9 can be reduced. Since it is biologically deodorized in the aeration tank, there is no need for special deodorization equipment or deodorization costs.

〔Effect of the invention〕

As described above, according to the present invention, the following beneficial effects are produced.

It is possible to prevent the uneven drying which conventionally tends to occur when drying water-containing solids through air, and in particular, it is possible to effectively air-dry water-containing solids in the form of flakes and large particles.

During ventilation drying, high moisture content and hot air are always in effective contact, resulting in excellent heat utilization efficiency.

[Brief explanation of drawings]

The drawing is a system explanatory diagram showing an embodiment of the present invention. 1... Supply port, 2... Valve, 3... Dryer, 4...
...Filled bed, 5...Inverted conical member, 6...Hot air, 7...
...Blower, 8...Exhaust gas, 9...Exhaust pipe, 10
...Compressed air, 11...Storage tank, 12...
Valve, 13... Valve, 14... Hopper, 15... Discharge mechanism, A... Dehydrated cake, B... Dry cake.

Claims (1)

[Claims] 1. Filling a container with hydrated solids to form a packed bed, blowing hot air through the packed bed to perform ventilation drying, and intermittently blowing compressed air into the packed bed. A method for aeration-drying a water-containing material, characterized by changing the filling position of the water-containing solid material. 2. The method for aeration-drying a water-containing solid material according to claim 1, wherein the compressed air is blown upward from the bottom of the packed bed. 3. The method for aeration drying water-containing solids according to claim 1 or 2, wherein the hot air is air discharged from an aeration blower that aerates organic sewage or sludge.