JPH0224600B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for dewatering organic sludge generated from an aerobic microbial treatment device, an anaerobic microbial treatment device, etc. using a screw press type dehydrator. A conventionally used screw press type dehydrator is, for example, as shown in Figure 1, and has a sludge inlet 1 equipped with a hopper at one end, and a dewatered cake outlet at the other end. A screw shaft 6 rotatably supported by bearings 4 and 5 is attached to an outer cylinder 3 made of punching metal or the like having a diameter of 1. A screw cylinder 7 with a smaller diameter on the first side is installed, and the screw cylinder 7
A screw blade 8 is wound around the screw blade 8 in a spiral shape. When dewatering sludge using such a screw press type dehydrator, flocculated sludge that has been flocculated with an organic polymer flocculant or the like is fed into the input port 1, and the screw shaft 6 is moved by a motor ( (not shown), etc. In this way, the water in the flocculated sludge that is relatively easy to separate is first released from the through hole 9 of the outer cylinder 3 due to overaction in the natural dewatering section A near the inlet 1. removed. Next, the flocculated sludge is pushed out in the direction of the discharge port 2 by the screw blades 8, but the flocculated sludge is pushed out in the direction of the discharge port 2 by the screw cylinder 7 and the outer cylinder 3.
Since the volume of the sludge gradually decreases as it approaches the discharge section 2, the flocculated sludge is also gradually squeezed, and the water remaining in the sludge is removed from the outer cylinder 3.
Water oozes out from the through hole 9, dewatering is performed, and a dehydrated cake is extruded from the discharge port 2. Furthermore, in the conventional screw press type dehydrator, as shown in FIG.
The heated gas is transferred to the screw shaft 6 and the screw barrel 7.
The waste gas is ejected from the spout 13 into the space 11 composed of It is said that when this is done, the viscosity of water is reduced, the rate of aggregation reaction between the organic polymer flocculant added to the sludge and the sludge is increased, and the dewatering performance is improved. For the reasons mentioned above, when organic sludge generated from an aerobic microbial treatment device or an anaerobic microbial treatment device is dehydrated using the dehydrator,
Traditionally, various organic polymer flocculants have been added to the sludge to cause it to flocculate, and then the entire flocculated sludge inside the dehydrator is heated and dehydrated. It was found that heating the flocculated sludge produced by the reaction with the sludge reduces the dewatering effect due to overaction, especially in the natural dewatering section A near the input port, which causes a decrease in the overall dewatering rate. . However, if you do not heat the sludge thoroughly, the dehydration effect in the press dewatering section B will decrease, so in the case of organic sludge, the best dehydration effect is achieved only when only the press dewatering section B is heated without heating the vicinity of the sludge inlet side. was found to increase. The present invention was constructed based on the above findings, and includes a rotatable screw barrel equipped with screw blades in an outer cylinder having a large number of perforations, and a screw cylinder equipped with screw blades that is rotatably disposed within an outer cylinder having a large number of perforations. When dewatering organic sludge using a screw press type dehydrator that has a natural dehydration section and a press dehydration section, it is possible to perform dehydration by heating only the press dehydration section without heating the natural dehydration section. The present invention relates to a method for dewatering organic sludge. The present invention will be explained in detail below with reference to the drawings. FIG. 2 is a sectional view showing an example of a screw press type dehydrator used in the dewatering method of the present invention, in which 1 is an inlet, 2 is an outlet, 3 is an outer cylinder made of punched metal, etc., and 4 and 5 are Bearing, 6 is screw shaft, 7 is screw body, 8 is screw blade, 9
is a through hole, and the structure of this part is exactly the same as that of a conventional screw press type dehydrator. However, as shown in FIG. 2, the dehydrator used in the present invention has a dewatering section between the natural dehydrating section A near the input port 1 and the compressing dehydrating section B formed from the outer cylinder 3 and the screw body 7.
By installing a heat shielding wall 14 in the space 11 consisting of the screw shaft 6 and the screw body 7, the space is divided into 11a and 11b, and the air pipe 10 attached to one end of the screw body 6 is extended. However, the spout 13 is provided inside the space 11b, and the natural dehydration section A is configured not to be heated.
Note that 12 is an exhaust pipe for waste gas, and one end is connected to the exhaust port 2.
It is opened into the side space 11b, and the other end is opened outside. If steam is used as the heating gas, a steam trap (not shown) is attached to the other end of the exhaust pipe 12. Next, to explain the dewatering method of the present invention, one or two types of organic polymer flocculants selected from cationic, anionic, or nonionic are added to organic sludge and stirred to cause flocculation, and the flocculated sludge is introduced. Insert from mouth 1. Further, the screw shaft 6 is slowly rotated, and heated gas such as steam is introduced from the air pipe 10. As mentioned above, in this dehydrator, the heated gas does not come into contact with the space 11a, so the flocculated sludge in the natural dewatering section A is not heated, and the water coexisting in the sludge that is relatively easy to separate is efficiently removed by overaction. Dehydrate well. Next, the flocculated sludge whose water content has been reduced in this way is pushed out one after another to the press dewatering section B, but the flocculated sludge is heated only after reaching the press dewatering section B, and due to this heating, the flocculated sludge remains in the flocculated sludge. Moisture easily oozes out, and residual moisture oozes out from through hole 9, and the dehydrated cake is discharged from outlet 2.
discharge from. Although the heating temperature varies somewhat depending on the type of organic sludge, it is preferable that the temperature of the aggregated sludge in the space 11b is 40 to 90°C. As explained above, since the dewatering method of the present invention does not heat the natural dewatering section A near the sludge input hopper, the decrease in dewatering efficiency in the natural dewatering section A that occurs in conventional screw press type dehydrators is eliminated. The moisture content of the dehydrated cake discharged from the discharge port 2 can be lowered compared to the conventional dehydration method under the same conditions in other parts. In addition, in the conventional dehydration method, the space 11a was also heated, so 1 of the amount of heat in the hot gas flowing from the air pipe 10
However, in the present invention, only the flocculated sludge that has been previously dehydrated in the natural dewatering section A is transferred to the compressed dewatering section. Since heating is performed only after reaching B, the moisture content is reduced accordingly. Therefore, when steam is used as the heating gas, the amount of steam used can be saved, and running costs can also be reduced. In the embodiment shown in FIG. 2, heating gas is used to heat the compression dehydration section B, but the present invention is not limited to this. For example, heating wires may be attached to the inner surface of the screw barrel 7 corresponding to the compression dehydration section B. It is okay to heat it. Further, in some cases, the heat shielding plate 14 may be attached slightly closer to the compressing and dehydrating section B so that the relatively low pressure compressing and dehydrating section B is not heated. Examples will be described below to make the effects of the present invention more clear. Example Surplus activated sludge from a human waste treatment plant (brown in appearance, PH
7.2, MLSS 1.8%, loss on ignition 76.1%), and a cationic organic polymer flocculant of 0.6% for solids.
% was added for flocculation treatment, and the flocculated sludge was dehydrated under the following conditions. (1) Inner diameter of the outer cylinder of the screw press type dehydrator used: 300 mm Total length of the screw cylinder: 3000 mm Small diameter of the screw cylinder: 180 mm Large diameter of the screw cylinder: 260 mm (2) Rotational speed of the screw cylinder: 0.36 rpm (3) Feed amount of aggregates 0.96m ³ /H Under the above conditions, the method of the present invention introduces steam from the middle of the screw barrel as shown in Figure 2, and removes the flocculated sludge present in the press dewatering section without heating the natural dewatering section. The sample was heated to 80°C for dehydration. In addition, as a conventional method, as shown in Figure 1, steam is introduced from near the small diameter part of the screw barrel to heat the natural dewatering section as well as the flocculated sludge present in the press dewatering section to a temperature of 80°C. , and one which was dehydrated at room temperature without introducing steam into the screw barrel. The dehydration results are shown in Table 1.

[Table] As shown in Table 1, the method of the present invention has a higher cake moisture content compared to conventional dehydration methods in which neither the natural dehydration section nor the press dehydration section is heated, or when both the natural dehydration section and the press dehydration section are heated. The system is small, and compared to the conventional dehydration method that heats both the natural dehydration section and the compressed dehydration section, the amount of steam used can be reduced by 6.50%, reducing the running cost of the dehydration process.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional screw press type dehydrator, and FIG. 2 is a sectional view of a screw press type dehydrator used in the present invention. 1... Input port, 2... Outlet port, 3... Outer cylinder,
4, 5... Bearing, 6... Screw shaft, 7... Screw body, 8... Screw blade, 9... Through hole, 10... Air supply pipe, 11... Space, 12...
Exhaust pipe, 13... spout, 14... shielding wall, A...
... Natural dehydration section, B... Pressure dehydration section.

Claims (1)

[Claims] 1. A screw press in which a screw barrel equipped with screw blades is rotatably installed in an outer cylinder having a large number of through holes, and a natural sludge dewatering section and a pressing dewatering section are formed from the sludge input port toward the discharge port. A method for dewatering organic sludge, which is characterized in that when organic sludge is dehydrated using a type dehydrator, the dewatering process is performed by heating only the press dehydration part without heating the natural dehydration part.