JP2887439B2 - Method and apparatus for drying organic excess sludge with gas deodorization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for simultaneously drying organic surplus sludge generated in large quantities in a sewage treatment plant and the like and economical biological deodorization of odor gas.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application No. 4-184598 (publication number is unknown at present) discloses a method of adding a polyvalent metal salt and / or a polyvalent metal oxide to excess activated sludge, drying and fixing the sludge, and deodorizing the deodorant. Are described. JP-A-58-367
No. 00 describes a method of utilizing sludge dry odor gas for incineration of sludge and simultaneously performing sludge combustion and deodorization by thermal decomposition. In Japanese Patent Publication No. 3-74159,
A method for drying organic sludge in which odor gas generated when drying sludge is passed through an activated sludge aeration tank to deodorize the sludge is described. Japanese Patent Publication No. Sho 59-14708 discloses a sludge drying apparatus in which a combustion deodorization apparatus is incorporated in a sludge dryer to reuse heat and suppress odor generation. Japanese Patent Publication No. 56-9394 discloses a sludge drying treatment apparatus in which drying and exhausting of sludge is dehumidified and then circulated to reduce odor leakage. Japanese Patent Application Laid-Open No. 53-58172 discloses that when waste such as sludge is incinerated, incineration exhaust gas is used for preliminary drying of the sludge, and the drying exhaust gas containing odor is dried by incinerators. And incineration methods.

[0003]

However, the above-mentioned prior art has the following problems. (1) When the odor component in the odor gas is high, the odor component removal capability is low. (2) With the deodorant manufactured in the prior art, a period of acclimation of one week or more is required until the deodorizing ability is developed. (3) In the prior art, in order to dry sludge at high temperature,
The useful microorganisms in the sludge cannot be used effectively. (4) In the prior art, odor is generated when sludge is dried, and odor is generated from dried sludge. (5) The combustion deodorization method requires a large amount of energy. (6) In the aeration type deodorization, the odor removal efficiency is low, and it is impossible to completely reduce the odor. In recent years, in various sludge treatment plants, in order to facilitate handling and disposal, the tendency to solidify and reduce the volume of hydrous sludge into dry sludge has been increasing.

The present invention has been made in view of the above points, and an object of the present invention is to introduce an odor gas at a temperature of 100 ° C. or lower to remove a part of the odor component while removing excess sludge from a biological treatment plant. An object of the present invention is to provide a method and an apparatus for drying sludge accompanied by gas deodorization, in which the primary deodorization is performed in a drying zone by drying, so that the capacity of a deodorizing apparatus at the subsequent stage can be reduced. Another object of the present invention is to secondarily deodorize the first-treated odor gas at the outlet of the dryer in a biological deodorization tower previously filled with a part of the dried sludge, thereby removing the sludge while treating the odor gas. An object of the present invention is to provide a method and an apparatus for drying sludge with gas deodorization, which can be dried and can also produce a deodorant.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the method for drying organic excess sludge accompanied by gas deodorization according to the present invention provides a method for dehydrating wastewater containing organic matter generated by biological treatment. has been the odorous gas from excess sludge and organic sludge, the microorganism is killed with a deodorizing capability in the sludge
Or deactivate to reduce the deodorizing efficiency, and
In order to sufficiently dry the sludge, the sludge is contacted at a temperature of 90 to 40 [deg.] C. , and the excess sludge is dried while removing at least a part of the odor component. Dehydration treatment
As described above, the temperature of the drying zone where the waste sludge is brought into contact with the odor gas derived from the organic sludge is in the range of 90 to 40 ° C.
It is an enclosure . If it is higher than this range, microorganisms having a deodorizing ability in sludge will be killed or inactivated, and the efficiency of primary deodorization tends to decrease. On the other hand, if it is lower than this range, sludge will be insufficiently dried. There is.

[0006] The method of the present invention is also capable of removing excess sludge that has been subjected to dehydration treatment and that is generated when biologically treating wastewater containing organic matter.
It has the ability to deodorize odor gas derived from organic sludge in sludge.
Microorganisms are killed or inactivated and deodorization efficiency decreases
So that sludge can be dried sufficiently without
To, by contacting at a temperature of 90 to 40 ° C., the excess sludge is dried while primary deodorization to remove a portion of odorous, de
It is characterized in that a secondary deodorization for removing residual odor components is performed by bringing a packed layer, which has been previously filled with a part of dry sludge as an odorant, into contact with a primary deodorized odor gas.

In the above method, it is preferable that the excess sludge and the odor gas are brought into contact with each other in countercurrent. However, it is also possible to contact in co-current or cross-flow. In addition, surplus
As a pretreatment of mud, microbes with deodorizing ability in excess sludge
Death or inactivation of the material reduces the deodorizing ability during drying
Oxidative decomposition of organic matter in excess sludge
As the rate is not reduced, by washing steps and / or excess sludge is warmed aeration in the range of the excess sludge 30 to 80 ° C.
It is preferable to add a step of washing away the decomposition products of organic substances . The heating temperature is 30 to 80 ° C. as described above ,
The temperature is desirably 60 to 65 ° C. If it is higher than this range, microorganisms having a deodorizing ability in excess sludge will be killed or inactivated, and the primary deodorizing ability at the time of drying tends to decrease. The efficiency of the oxidative decomposition of the organic solvent decreases, and the organic matter which tends to decay after dehydration remains, which tends to cause the generation of sludge odor and mold. One or both of the above-mentioned heating aeration and water washing may be performed. When both are performed, it is necessary to perform heating aeration prior to water washing.

It is preferable that the sludge in the drying step is formed into a lump. The excess sludge used in the present invention is at least one of excess sludge discharged from a sewage treatment plant, excess sludge discharged from an activated sludge device, and excess sludge discharged from an oxidation ditch (oxidation pond). Can be mentioned.

As shown in FIG. 2, the apparatus for drying organic excess sludge accompanied by gas deodorization according to the present invention has a sludge inlet 10 at its upper part.
And a gas discharge port 12, and a dry sludge discharge port 14
And a odor gas introduction pipe 18 connected to a lower portion inside the body 16 so as to introduce an odor gas.
And a main body 16 provided below the sludge inlet 10.
The upper sludge conveying means 22 for contacting with the odor gas and pre-drying while conveying the sludge 20 charged therein, and the pre-dried sludge 24 provided below the upper sludge conveying means 22 Lower sludge conveying means 26 for contacting with odorous gas while carrying the main sludge, and plate-like sludge forming nozzle 2 provided at the upper end of lower sludge conveying means 26
8 and a sludge cutting roller 30 provided adjacent to the downstream side of the plate-like sludge forming nozzle 28.

In the above apparatus, the sludge cutting roller 30
Is preferably constituted by a first cutting roller 30a for cutting the plate-like sludge 24 in the transport direction and a second cutting roller 30b for cutting in the direction orthogonal to the transport direction. The second cutting roller 30b may be provided upstream of the first cutting roller 30a. In addition, the upper sludge conveying means 22
It is preferable that the lower sludge conveying means 26 be constituted by a belt conveyor including a porous belt 32 and a roller 34. 36 is a blower, 38 is a pre-dried sludge falling conduit, 4
0 is a pre-dried sludge receiver, 42 is a sludge extrusion pump, 44
Is a heater for heating the odor gas, and 46 is a product hopper.

Further, as shown in FIG. 1, in addition to the low-temperature dryer 50 shown in FIG. 2, a biological deodorization tower 52 previously filled with a part of sludge which has been completely dried is provided.
2 and the gas outlet 12 of the dryer main body 16 are connected via a primary deodorizing gas supply pipe 54 so that the primary deodorized odor gas is introduced into the biological deodorization tower 52 for secondary deodorization. Is preferred. 56 is a filling layer.

The low-temperature dryer 50 is not limited to the one having the above-described structure, but may be any as long as it can contact odor gas with all sludges having a low moisture content to sludges having a high moisture content. The dryer exhaust gas, whose odor has been reduced by passing through the dryer 50, is introduced into the biological deodorization tower 52 in which a part of the dried sludge has been filled in advance, and the residual odor is removed. The details will be described below. First, returned sludge from a sewage treatment plant or concentrated sludge obtained by pressurized flotation or the like is dewatered to a water content of 85 to 88 wt% by a continuous dehydrator (not shown) such as a centrifugal separator to obtain a dewatered cake. When the organic matter content of the sludge to be used is high, the sludge is aerated at 80 ° C. or less, preferably 65 ° C. or less for 12 to 24 hours to decompose the organic matter. When the amount of the decomposed product is large, the decomposed product is washed away by adding 1/5 to twice the amount of water of the sludge and then dewatering. This is because the removal of a large amount of organic substances suppresses the generation of odor from the sludge itself. Although any type of dehydrator may be used for dehydration, the concentration of the polymer flocculant or the like must be 2 wt% or less in order to increase the strength of the dried sludge.

[0013] The dehydrated cake thus prepared is
Upper sludge conveying means 2 composed of a multi-stage belt conveyor, etc.
2 in the drying sludge outlet 14, the moisture at the dryer outlet is 10 to 15 wt%, and the temperature in the machine is in the range of 90 to 40 ° C.
In becomes such conditions as to introduce the odorous gas. Then 8
The sludge cake preliminarily dried to about 2 to 85 wt% is extruded in a plate shape on the lower sludge conveying means 26. The dewatered cake is divided into a first cutting roller 30a and a second cutting roller 30b.
Thus, for example, by simply making a square cut in a 10 mm square, it can shrink in itself and become a dried body (product) molded in a dice shape, and the drying speed can be increased. Further, when this dried product is used as a deodorant, the deodorization rate can be increased. In the case of a dewatered sludge cake having a high releasability, the cake can be directly extruded onto the lower sludge conveying means 26 without passing through a preliminary drying step. On the other hand, apart from the dryer 50, a biological deodorization tower 52 in which a part of dried sludge (dried product) is packed in a packed tower is provided.
Dryer exhaust gas with reduced odor is introduced to the hopper to completely remove odor components.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples, and can be implemented with appropriate modifications. Example 1 A test was performed according to the flow shown in FIG. As a raw material,
Approximately 4 SS (Suspended Solid, solid content) obtained by concentrating excess sludge from sewage treatment plant by pressure flotation
wt% of the sludge while fresh
A dehydrated cake of 100 G and a water content of 88 wt% was used. A dryer having the structure shown in FIG. 2 was used as the dryer, and the dewatered cake was charged from the sludge inlet 10 and 85 wt.
%, The pre-dried sludge was extruded into a plate shape from the plate-shaped sludge forming nozzle 28 via the extrusion pump 42. The extruded plate sludge 24 is cut by a cutting roller 30a,
A cut was made at 30b and dried while being transported to the lower portion by the belt 32. Dry sludge having a moisture content of 15 wt% was stored in the product hopper 46. A gas containing odor is used as air for drying, and the odor gas is introduced from the odor gas introduction pipe 18 by the blower 36 and flows between the belt conveyors heated to 70 ° C. by the heater 44. On the contrary, it passed (counter-current), absorbed the sludge and discharged.

The results of measuring the odor at the dryer inlet and the odor at the dryer outlet and obtaining the odor component removal rate are shown in FIGS. 3 and 4. FIG. 3 shows that when the odor gas containing 15 ppm of H ₂ S is introduced into the dryer 50 to continuously dry the sludge, the amount of gas passing through the sludge volume (space velocity, SV) is changed.
It shows the results of measuring SV and the removal rate of H ₂ S.
FIG. 4 shows H ₂ in the odor gas introduced into the dryer 50.
By changing the S concentration, the SV was 35 h ^-1 and 90 h ^-1 at 70 ° C.
3 shows the results of measuring the removal rate of H ₂ S for the cases of 3,000 h ⁻¹ and 3,000 h ⁻¹ .

With respect to the introduced odor gas containing 15 ppm of H ₂ S, the amount of gas passing through the sludge volume (space velocity) (SV)
Approx. 80% when SV = 100 hr ^-1 and approx. 5 when SV = 200 hr ^-1
0% H ₂ S was removed (FIG. 3). Further, SV = 35
At hr ^-1 , an 80% removal rate was possible even with 80 ppm of H ₂ S (FIG. 4). Dried sludge dried with odorous gas (cut and dried into a 10 mm square die)
Did not differ from those dried with odorless air, and showed a sufficient performance as a deodorant in a packed tower deodorizer.

Example 2 Since sludge having a high organic matter content does not provide good deodorizing performance as it is, it is heated and aerated at 60 ° C. for a residence time of 24 hours, and then 3 wt% of an inorganic condensing agent (sulfuric acid band) ) Was added to obtain a dehydrated cake in the same manner as in Example 1. Then, by performing the same drying treatment as in Example 1, the dried sludge (which was cut into a 10 mm square die and dried) could be used as a deodorizing agent for filling.

[0018]

As described above, the present invention has the following effects. (1) In the drying zone, the dewatered sludge is dried and the primary deodorization of the odor gas derived from the organic sludge is performed. Therefore, the load and capacity of the deodorization device at the subsequent stage can be reduced. (2) to the subsequent, when installing the biological deodorization device used by filling the dried sludge as a deodorant can own production of deodorizer. (3) Since the drying temperature is controlled as low as 90 to 40 ° C., a low-temperature heat source can be used as a heat source for drying. (4) Since the dried sludge is dried at a low temperature of 90 to 40 ° C., a large amount of microorganisms having remaining activity are present. Therefore, the dried sludge can be effectively used as a biodeodorant or a raw material for compost. The sludge has been reduced in volume, making sludge disposal easier. (5) When the sludge to be put into the dryer is heated and aerated at 30 to 80 ° C. , washed with water and / or formed into a lump, the deodorizing ability and the drying speed can be improved.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing one embodiment of a device for drying organic excess sludge with gas deodorization of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an example of a low-temperature dryer in FIG.

FIG. 3 shows space velocity (SV) and H ₂ S in a low-temperature dryer.
It is a graph which shows the relationship with a removal rate.

FIG. 4 is a graph showing a relationship between H ₂ S concentration and H ₂ S removal rate in a low-temperature dryer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sludge inlet 12 Gas outlet 14 Dry sludge outlet 16 Dryer main body 18 Odor gas introduction pipe 20 Sludge 22 Upper sludge conveying means 24 Sludge 26 Lower sludge conveying means 28 Plate sludge forming nozzle 30 Sludge cutting roller 30a First cutting Roller 30b Second cutting roller 32 Porous belt 34 Roller 50 Low temperature dryer 52 Biological deodorization tower 54 Primary deodorizing gas supply pipe

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masao Hayashiya 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Plant (72) Inventor Masakazu Sawai 1-3-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe-shi No. Kawasaki Heavy Industries, Ltd. Kobe Head Office (56) References JP-A-60-17681 (JP, A) JP-A-58-208576 (JP, A) JP-B-1-24970 (JP, B2) (58) Survey Field (Int.Cl. ⁶ , DB name) C02F 11/00-11/20 B01D 53/34 F26B 13/00-25/22

Claims (10)

(57) [Claims] 1. A and odorous gas from excess sludge and organic sludge which has been dehydrated to occur when biological treatment of waste water containing organic substances, microorganisms is killed with a deodorizing capability in the sludge
Or deactivate to reduce the deodorizing efficiency, and
In order to sufficiently dry the sludge, the organic sludge is contacted at a temperature of 90 to 40 ° C. , and the excess sludge is dried while removing at least a part of the odor component. Drying method. Wherein the odorous gas from excess sludge and organic sludge which has been dehydrated to occur when biological treatment of waste water containing organic substances, microorganisms is killed with a deodorizing capability in the sludge
Or deactivate and reduce the efficiency of primary deodorization,
And 90 to 40 ° C. so that the sludge can be sufficiently dried.
The excess sludge is dried while performing primary deodorization to remove a part of the odor component by contacting at a temperature of, and a packed layer preliminarily filled with a part of the dried sludge as a deodorant and a primary deodorized odor gas are used. And a secondary deodorization for removing residual odor components by contacting the sludge with an organic solvent. 3. The method for drying organic excess sludge with gas deodorization according to claim 1, wherein the excess sludge and the odorous gas are brought into contact with each other in countercurrent, cocurrent or crossflow. 4. The pretreatment of the excess sludge includes the step of
Microorganisms with deodorizing ability are killed or inactivated and dry
Deodorizing ability during drying does not decrease, and in excess sludge
In order to prevent the efficiency of oxidative decomposition of organic substances from decreasing, a step of heating and aerating the excess sludge in the range of 30 to 80 ° C. and / or a step of washing the excess sludge with water and washing away the decomposition products of organic substances are added. 4. The method for drying organic excess sludge with gas deodorization according to claim 1, 2 or 3. 5. The method for drying organic excess sludge with gas deodorization according to claim 1, wherein the sludge in the drying step is formed into a lump. 6. The method according to claim 1, wherein the excess sludge is at least one of excess sludge discharged from a sewage treatment plant, excess sludge discharged from an activated sludge device, and excess sludge discharged from an oxidation ditch. The method for drying organic excess sludge with gas deodorization according to any one of claims 1 to 5. 7. A dryer body having a sludge inlet and a gas outlet at an upper portion and a dry sludge outlet at a lower portion, and an odor gas inlet connected to introduce a odor gas into a lower portion of the body. A pipe, an upper sludge conveying means provided below the sludge inlet, for conveying the sludge introduced into the main body and contacting it with an odor gas for preliminary drying, and under the upper sludge conveying means. Provided on the side, a lower-stage sludge conveying means for bringing the pre-dried sludge into contact with an odor gas while performing main drying, and a plate-like sludge forming nozzle provided at an upper end of the lower-stage sludge conveying means, A sludge cutting roller provided adjacent to the downstream side of the plate-like sludge forming nozzle; and a device for drying organic excess sludge accompanied by gas deodorization. 8. The sludge cutting roller comprises a first cutting roller for cutting plate sludge in a conveying direction and a second cutting roller for cutting plate sludge in a direction perpendicular to the conveying direction. For drying excess organic sludge with gas deodorization. 9. The drying of organic excess sludge with gas deodorization according to claim 7, wherein the upper sludge conveying means and the lower sludge conveying means are a belt conveyor comprising a porous belt and a roller. apparatus. 10. A biological deodorization tower which is separately filled with a part of sludge which has been completely dried in advance, and the biological deodorization tower and a gas outlet of a dryer body are connected via a primary deodorizing gas supply pipe. The apparatus for drying organic excess sludge with gas deodorization according to claim 7, 8, or 9.