JPS62102899A - Drying method for organic sludge - Google Patents

Abstract

PURPOSE:To eliminate the need for expenses for deodorization by dividing the drying of dehydrated cake of org. sludge to two stages; predrying and finish drying to make efficient and rational drying and utilizing the dry waste gas having offensive odors for a biological treatment of sanitary sewage. CONSTITUTION:The dehydrated cake of the org. sludge generated in the org. sanitary sewage treatment of waste water, etc., is subjected to drying by hot air 3 by using a continuous pelletizing and drying machine 2 using a stirred and fluidized layer. The dry waste gas 5 from a hot air drying stage thereof is mixed with the suction air of an aeration blower 7 for the bilogical treatment of the sewage 15. The discharge air from the blower 7 is directly contacted with the drying material 12 of a dryer 11 discharged from the above-mentioned hot air drying stage and is further dried; thereafter, such air is used for the biological treatment of the sewage 15. As a result, the drying of the dehydrated cake of the org. sludge is effectively and rationally executed and further the need for the expenses for deodorization of the dry waste gas is thoroughly eliminated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the dewatering of organic sludge (including sludge and sedimentation) generated in the treatment of organic sewage such as sewage, human waste, and various industrial wastewater. The present invention relates to a method of drying a cake in an extremely rational and energy-saving manner.

(Prior Art) A typical and common method is to dispose of organic sludge through a serial process of dehydration, drying, and incineration.

However, organic sludge has poor dehydration properties, and the moisture content of the dehydrated cake is as high as 75-85%, so in addition to requiring a large amount of fuel when drying and incinerating it, it also requires deodorizing treatment of the dried exhaust gas. The drawback is that it requires deodorizing equipment and high deodorizing costs, and the key point is how effectively and rationally drying can be carried out, especially since the subsequent incineration process depends on the quality of drying. It has become.

[Problem that the invention attempts to solve]

As described above, the prior art has serious problems in that it requires a large amount of fuel to obtain a dry product with low moisture content, and also requires deodorizing equipment to deal with the foul odor of the dried exhaust gas.

The present invention divides the drying of a dehydrated cake of organic sludge into two stages, pre-drying and final drying, to perform effective and rational drying, and further reduce the cost of removing drying exhaust gas. The idea is to make it completely unnecessary.

[Means for solving problems]

The present invention involves drying a dehydrated cake of organic sludge with hot air, mixing the dry exhaust gas from the cough hot air bottle drying process with the suction air of an aeration blower for biological treatment of sewage, and using the discharge air of the blower with the hot air. There are ten methods for drying organic sludge, which are characterized in that they are brought into direct contact with the dried material discharged from the drying process, further dried, and then used for biological treatment of sewage.

[For production]

To explain the operation of the present invention with reference to a drawing showing one embodiment thereof, a dehydrated cake 1 of organic sludge dehydrated to about 75 to 85% moisture is dried in a closed first hot air dryer 2.
The sludge is dried by hot air 3 at a temperature of 200 to 800°C, and is discharged as dried sludge 4 with a water content of about 40 to 50%. In addition, the dry exhaust gas 5 (which has a bad odor) discharged from the first hot air dryer 2 is passed through a dust remover 6 such as a cyclone to an aeration blower that supplies aeration air for biological treatment of wastewater. The aeration blower 7 mixes the dry exhaust gas 5 into the suction air 9, sucks it together and compresses it, and uses adiabatic compression to lower the temperature by about 50 degrees Celsius than the temperature of the gas to be sucked. The discharged air 10 becomes heated.

On the other hand, the dried sludge 4 discharged from the first hot air dryer 2 is
It is supplied from the upper part of the second stage closed type aerated dryer 11 to form a packed layer 12 in the aerated dryer 11.
The discharge air 1 of the aeration blower 7 mentioned above from the lower part of 1112
0 is aerated in an upward flow, water in the sludge forming the packed bed 12 is evaporated and removed by the heat possessed by the discharged air 10, and final drying is performed. This final dried lη mud 13 is highly dried by the discharge air 10 of the aeration blower 7, is taken out from the aeration dryer 11 in batches or continuously, and is effectively used as solid fuel or fertilizer. Ru.

In this way, the moisture in the packed bed 12 of the dried sludge 4 is evaporated, the heat is consumed, the discharged air 14 is cooled and discharged from the ventilation dryer 11, and has almost no pressure loss.
The wastewater 15 is supplied to an aerator 17 in a biological treatment tank 16 that receives the wastewater 15, and is blown out within the tank 16 as air lane air.

In addition, it is preferable to insulate the part where the piping for the discharged air 10 of the aeration blower 7 connects to the ventilation dryer 11, and especially if the piping is exposed outdoors, it will not cool down significantly due to rain, snow, etc. It is a good idea to install a cover to prevent rain and snow from coming into direct contact with the pipes. Further, it is preferable to use a non-clog type diffuser such as a diffuser for the diffuser 17 in the biological treatment tank 16 in order to prevent clogging due to dust.

Although various types of first hot air dryer 2 can be used for drying the first stage, it is preferable to use a continuous granulation dryer using an agitated fluidized bed. is a spherical Pele.

Since dry sludge 4 having a moisture content of 40 to 50% can be obtained in the form of a sheet, not only can a packed bed 12 with extremely good air permeability be formed in the aerated dryer 11 by the second stage aeration blower 7, but also Since it is in the form of spherical pellets, it has good fluidity, and there is no problem of not being able to discharge the dried material due to bridging in the ventilation dryer.

The gist of the technical idea of the present invention described above is as follows.

That is, when a granulation dryer using an agitated fluidized bed is used as the first hot air dryer 2, the temperature of the dry exhaust gas 5 is the wet bulb temperature (5
0 to 75°C), therefore, by mixing it with the suction air 9 of the aeration blower 7, it becomes possible to increase the temperature of the suction air 9.

Therefore, it is possible to obtain discharge air 10 with a higher temperature than when only suction air 9 (outside air) is sucked in and adiabatically compressed using an aeration blower, and as a result, the amount of heat used for drying in the ventilation dryer 11 is increases, and a final dried sludge 13 with lower moisture content can be obtained.

Furthermore, a major problem when drying a dehydrated cake of organic sludge with hot air is that the dried exhaust gas 5 has a strong odor.
Deodorizing equipment such as combustion deodorizing equipment must be installed, and the equipment and operating costs are high. However, in the present invention, the dry exhaust gas 5 during hot air drying is mixed with the suction air 9 of the aeration blower 7 and supplied to the biological treatment tank 16 for wastewater.
Since deodorization is carried out biologically by microorganisms (activated sludge) along with aeration, deodorization equipment and deodorization operating costs (running costs) are completely unnecessary.

[Example] A mixed sludge of 1200 kg/7 days of dry solids, which is a mixture of excess activated sludge generated from a low dilution two-stage activated sludge process and coagulated sedimentation sludge discharged from the tertiary treatment process, with a processing amount of 10 kg/day of human waste, The cake (82.0% moisture) dehydrated with a belt press type dehydrator was first fed to a stirred fluidized bed continuous granulation dryer with a diameter of 50ONφ, and hot air at a temperature of 800°C was supplied, resulting in a moisture content of 45%. Dried sludge in the form of spherical pellets with a particle size of 3 to 5 grains was obtained. The temperature of the dry exhaust gas discharged from the continuous granulation dryer at this time was 75°C (wet bulb temperature)
The flow rate was 7.1 Nm/min, and it had a bad odor.

This dry exhaust gas is transferred to an aeration blower with suction air (temperature 25°C).
) was compressed using an aeration blower (required compression power: 90 kW), resulting in a temperature of 110°C and a flow rate of ft 80 r.
Blower discharge air was obtained at a pressure of 0.53 kgf/c+d and a gauge pressure of 0.53 kgf/c+d. Next, the air discharged from the blower was passed through a packed bed in which dried sludge in the form of spherical pellets obtained in the continuous granulation dryer was filled in an aeration dryer to a diameter of 1 mφ and a layer thickness of 1 m. A highly dried final dried sludge of 5-7% was obtained.

On the other hand, the air discharged from the ventilation dryer (odor concentration 150
0 to 20 QO) was supplied as air for air lane to the nitrification tank of the low dilution two-stage activated sludge process. When we sampled the aeration air discharged from the water surface of the nitrification tank and measured the odor concentration, it was found to be 400 to 50.
0, there was no bad odor, and the odor was like earth.

〔Effect of the invention〕

As described above, according to the present invention, the following remarkable effects can be obtained.

■ As a result of adopting a new configuration in which the dehydrated cake of organic sludge is dried in two stages, and the latter drying process is performed in an energy-saving manner with zero fuel consumption, the overall drying cost is significantly reduced.

■ The structure is such that the dry exhaust gas from the hot air drying process (which has a higher temperature than the outside air) is mixed with the outside air sucked into the aeration blower, which supplies energy for the air drying process and the wastewater air lane. The waste heat from the previous drying process can be utilized to increase the drying thermal energy for the latter drying process, and as a result, in combination with the effect (2) above, an extremely energy-saving sludge drying process can be established.

■ Dry exhaust gas with a bad odor is guided to the biological treatment of wastewater and used, and at the same time it is biologically deodorized, eliminating the need for deodorizing equipment and deodorizing costs.

[Brief explanation of drawings]

The drawing is a system explanatory diagram showing one embodiment of the present invention. 1... Dehydrated cake, 2... First hot air dryer, 3...
・Hot air, 4... Dried sludge, 5... Dry exhaust gas, 6.
... Dust remover, 7... Aeration blower 18... Installation room, 9... Suction air, 10... Discharge air, 11...
Ventilation dryer, 12... Filled bed, 13... Final dried sludge, 14... Discharged air, 15... Sewage, 16...
Biological treatment tank, 17... air diffuser.

Claims (1)

[Claims] 1. A dehydrated cake of organic sludge is dried with hot air, and the dried exhaust gas from the hot air drying process is mixed with suction air of an aeration blower for biological treatment of sewage, and the discharge air of the blower is mixed with the air discharged from the blower. A method for drying organic sludge, which is characterized in that it is brought into direct contact with dried material discharged from a hot air drying process, further dried, and then used for biological treatment of sewage. 2. The method for drying organic sludge according to claim 1, wherein the hot air drying employs granulation drying using an agitated fluidized bed.