JPH0523697A - Sludge treatment method - Google Patents

Abstract

(57) [Summary] [Purpose] Sludge treatment that can perform sludge treatment with the simplest possible process and can reduce the amount of required coagulant, and can solve problems such as sludge transportation and malodor. To get a way. [Structure] Concentration step of mechanically concentrating sludge generated from wastewater treatment, and subsequently to the concentration step, a plurality of rotating blades 12 are provided on the side wall of the heat transfer drum 18 by a plurality of rotating blades 12 to a water content that allows the sludge to be charged into the melting furnace 9. A drying step of drying by a centrifugal thin film dryer 10 for drying a material to be dried while forming a thin film, a sludge processing step of burning and melting the dried sludge in a melting furnace 9, and an exhaust gas generated from the melting furnace 9. g
A sludge treatment method including a drying steam generating step of generating a drying steam s supplied to the centrifugal thin film dryer 10 by the waste heat boiler 22 using the waste heat contained in 1.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the concentration, drying, incineration of sludge generated from sewage treatment facilities, industrial wastewater treatment facilities, etc.
The present invention relates to a sludge treatment method for melting treatment.

[0002]

2. Description of the Related Art As a sludge treatment method of this type that has been already proposed, for example, a sewage treatment system as shown in FIG. 3 is known. That is, the sludge generated in the sewage treatment facility and the like is sent to the aeration tank 2 by the first settled sludge that is first settled and separated from the sewage before being biologically treated and the sewage that has passed through the first settling basin 1. It consists of surplus sludge in the final settling sludge that has been subjected to biological treatment and then settled and separated by the final settling tank 3. Here, the water content of the first settled sludge separated in the first settling basin 1 is about 98%, and since it contains only a small amount of microorganisms and the like, it is sufficiently adapted to gravity concentration.
On the other hand, the excess sludge separated from the final settling tank 3 has a water content of about 99.3%, contains a large amount of microorganisms and the like, and requires mechanical concentration that is not compatible with gravity concentration. Under such circumstances, the aforementioned first settling sludge is concentrated in the gravity thickening tank 4 and the water content is reduced to about 96%. Further, the above-mentioned surplus sludge is treated by a mechanical concentrator such as the centrifugal concentrator 5, and the water content is reduced to about 96%. Here, in this mechanical concentration step, the coagulant is added in a solid content ratio of 0.2 to
About 0.5% is added. Furthermore, after performing each of the above-mentioned concentration, these are mixed in the mixing tank 6, and the coagulant is added to the mixed sludge in this mixed state in a solid content ratio of 1.0 to.
About 1.5% is added, and a mechanical dehydrator such as a belt press dehydrator 7 is used for dehydration treatment. By the dehydration operation by the dehydrator 7, the water content of the mixed sludge is reduced to about 78%, and the dehydrated cake can be put in a solid state and dried in the disk type dryer 8 in the subsequent step. It was done like this. After this treatment, the dehydrated dehydrated cake is reduced in water content to about 40% by the disk type dryer 8, and then the dried mixed sludge is put into the melting furnace 9 and burned. ,
It was melted and taken out as the molten slag produced.

[0003]

However, the above-mentioned sludge treatment method has the following drawbacks.
That is, this method requires a dehydrator because it employs a dryer such as a disk type dryer that needs to be charged with solid matter, and many problems are caused by this dehydrator. . The problems in using the dehydrator are listed below. (B) A large amount of coagulant is required in the dehydrator. (B) Since the performance of the dehydrator is affected by the properties of the sludge to be dehydrated, it is difficult to control the addition amount of the coagulant, and further maintenance and maintenance are not easy because the filter cloth needs to be washed and replaced. (C) The dehydrator has a complicated structure, requires a conveyor, etc., has a large transport space, and requires a solid transport process. Is likely to occur. (D) Due to the above-mentioned reasons, it is necessary to install a dehydrator inside the building to provide deodorizing equipment as a measure against odor. The present invention has been made in view of such a situation, an object of the present invention is to perform sludge treatment in a process as simple as possible, and it is possible to reduce the amount of the required coagulant, It is to obtain a sludge treatment method capable of solving problems such as sludge transportation and malodor.

[0004]

Therefore, the characteristic means of the sludge treatment method according to the present invention is a concentration step of mechanically concentrating sludge generated from wastewater treatment, and following the concentration step, the mixed sludge is put into a melting furnace. A drying step of drying with a centrifugal thin film dryer that forms a thin film on the side wall of the heat transfer drum by a plurality of rotating blades to a water content that can be input, and a drying step of drying the dried mixed sludge. Using a sludge treatment step of combustion and melting treatment in a furnace and waste heat contained in exhaust gas generated from the melting furnace, a drying steam for generating a drying steam to be supplied to the centrifugal thin film dryer by a waste heat boiler And a generation step.

[0005]

In other words, in this sludge treatment method, the sludge generated from the wastewater treatment is simply mechanically concentrated in the concentration step regardless of its properties. Then, after this concentration step, it is put into a centrifugal thin film dryer. This centrifugal thin film dryer dries the material to be dried while forming the material to be dried in a thin film on the side wall portion of the heat transfer drum by a plurality of rotating blades, and has a very high drying ability. Is put into a dryer in a fluidized state to dry the material to be dried, and the solid dried material is discharged.
In the sludge treatment process after the drying process, the dry solid mixed sludge is put into a melting furnace and burned, melted and slag-treated. In this way, the sludge treatment is completed. By the way, in the drying steam generation step, the heat quantity of the exhaust gas from the melting furnace is used to generate steam by the waste heat boiler, and this steam is used for drying the mixed sludge in the centrifugal thin film dryer described above. Of.

[0006]

As described above, according to the present invention, in the concentration step, the first settling sludge and the surplus sludge, which have conventionally been separated from the treatment step, are mechanically concentrated regardless of their properties. The gravity concentration process that was conventionally used to treat the first sludge is omitted. Furthermore, due to the adoption of a centrifugal thin film dryer in the drying process, it is possible to add the mixed sludge to this dryer in a fluid state, so the water content of the input sludge is greatly reduced as in the past. There is no need for a spin dryer and no need for a dehydrator. Therefore, the above-mentioned various problems caused by the dehydrator can be avoided, and the need for an expensive coagulant, which has been conventionally required in this step, can be reduced. Moreover, since the sludge can be put into the dryer in a fluid state, the sludge can be transported from the mechanical concentrator to the dryer through a pipeline or the like, and it is easy to prevent the bad odor from the sludge from being released to the outside. The transportation space is smaller than transportation. In the end, overall, it was possible to improve the workability while reducing the running cost with a small number of steps, and also to improve the sludge treatment environment.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A treatment system to which the sludge treatment method of the present application is applied will be described below with reference to the drawings. FIG. 1 shows a process system from the process of receiving waste water to the process of melting furnace of the waste water treatment system and the subsequent treatment of the exhaust gas g1. further,
FIGS. 2A and 2B show the structure of the centrifugal thin film dryer 10 used in this wastewater treatment system.

The entire processing system will be described step by step. First, the waste water a is separated into treated water and initial settled sludge by the settling separation by the settling tank 1. Then, the treated water is biologically treated in the aeration tank 2 and sent to the final settling basin 3, and the final settling sludge is settled and separated in the final settling basin 3. Here, the treated water is subjected to biological treatment while being circulated between the aeration tank 2 and the final settling tank 3 together with the activated sludge. The surplus sludge and the first settling sludge in the final settling sludge are respectively sent to the mixing tank 6 through the first settling and the final settling mixing paths 2a and 3a, and are mixed there. Explaining the water content of each sludge, the initial sludge is 98%, the final sludge is about 99.3%, and the mixed sludge after mixing is about 99%. Now, this mixed sludge has a water content of 86% by a centrifugal concentrator 50 which is a mechanical concentrator.
It is concentrated to a degree. At this time, the solid matter ratio is 0.1 to 0.5.
A degree of polymeric flocculant is added. This process is called a concentration process.

In the drying step which is the next step, the mixed sludge is dried by the centrifugal thin film dryer 10 to a water content of about 40 to 45%. First, the centrifugal thin film dryer 1 will be described below.
The configuration of 0 will be described. FIG. 2A shows a vertical sectional view of the dryer 10, and FIG. 2B shows details of the blade portion 11 mainly responsible for the drying operation of the dryer 10. The centrifugal thin film dryer 10 is arranged in a vertical position, and the blade 1 is arranged with a plurality of layers in the peripheral portion.
The rotating main shaft 13 provided with 2 is configured to be rotated by an electric motor 15 disposed on the head of the main body frame 14, and the mixed sludge b1 that is an object to be dried remains in a liquid state from the inlet nozzle 16 Be made to flow. The inflow mixed sludge is distributed in the circumferential direction by the distribution ring 17 and is made to flow down along the heat transfer cylinder 18 provided so as to face the blade 12 described above. On the outer peripheral portion 18a of the heat transfer cylinder 18, a steam flow-through portion 19 through which the drying steam s flows is formed between the heat transfer cylinder 18 and the heating cylinder 20. That is, heat is transferred from the drying steam s flowing through the steam flow-through part 19 to the mixed sludge b1 flowing down the inner wall part 18b of the heat-transfer cylinder 18 through the heat-transfer cylinder 18 and is dried. Is there. Mixed sludge b below
A mechanism for forming 1 into a thin film on the inner wall portion 18b of the heat transfer cylinder 18 will be described. This dryer 10
In Fig. 2, a plurality of blades 12 shown in Fig. 2B are rotating, and the gap t between the blade tip 12t and the heat transfer cylinder 18 is suppressed to several mm. Therefore, the mixed sludge b1 flowing down is pressed against the heat transfer cylinder 18 side by the centrifugal force and is formed into a thin film by the blade 12, so that the mixed sludge b1 is always kept under high drying conditions. ing. Further, in the centrifugal thin film dryer 10 of the present application, the exhaust gas supply path 21 is connected to the discharge side of the dryer 10, and the exhaust gas g1 generated from the melting furnace 9 described later is used as the waste heat boiler 22 and the air preheater 23. After the heat is recovered by, etc., a part of this is the exhaust gas supply path 2
It is configured to be forwarded to 1. Thus, in the centrifugal thin film dryer 10, the drying steam,
Therefore, both of the exhaust gas and the exhaust gas are configured to contribute to the drying of the mixed sludge b1. Thus, the fluid-like mixed sludge b1 having a water content of about 86% at its inlet
Is a solid mixed sludge b2 having a water content of 40 to 45%. This process is called a drying process.

Next, the dry solid state mixed sludge b2 discharged from the centrifugal thin film dryer 10 is melted together with a basicity adjusting agent for securing the fluidity of coke and slag, which are fuels required for incineration and melting, in the melting furnace 9. Be thrown into. When combustion and melting are performed in the melting furnace 9, the ash content in the sludge flows out as slag from the lower part of the melting furnace, and the slag is cooled and effectively used as a construction material. This process is called a sludge treatment process.

A processing system for the exhaust gas g1 discharged from the melting furnace 9 is shown on the lower right side of FIG. Exhaust gas g1 generated by combustion is discharged from the upper part of the melting furnace, and the air preheater 23 preheats combustion air g2 supplied to the melting furnace 9 from the outside. Further, a waste heat boiler 22 is provided in the exhaust gas treatment system, and a boiler boiler (not shown) provided for controlling the combustion temperature of the melting furnace 9 by generating high-pressure steam by the boiler 22. The steam generated together with the steam generated in 1 is used as the drying steam s of the centrifugal thin film dryer 10. Here, the process of forming the drying steam s by the waste heat boiler 22 by utilizing the heat amount of the exhaust gas g1 is called a drying steam generation process.

Further, the dust mixed in the exhaust gas g1 is dry EP (or cyclone) 24 and wet EP2.
Other chemical substances which are collected in 5 and may be further polluted into the atmosphere are removed by the smoke exhaust treatment tower 26 and released from the chimney 27 into the atmosphere. Further, the exhaust gas fan 28 is installed to keep a negative pressure inside the exhaust gas system during combustion, melting, and exhaust. Here, the flow of waste heat contained in the exhaust gas g1 will be described. Of the thermal energy generated in the melting furnace 9, 40% or more of this energy is recovered by the air preheater 23 and the waste heat boiler 22, About 20% remains in the exhaust gas g1 even after undergoing these treatments. In the sludge treatment system of the present application, a part of the exhaust gas g1 is branched from the downstream side of the device 23 and is supplied to the centrifugal thin film dryer 10 through the exhaust gas return path (29). -ing Therefore, this exhaust gas g1
As mentioned above, the amount of heat possessed by is also used for drying the sludge. In this way, the processing capacity of the centrifugal thin film dryer 10 can be improved as compared with the case of drying only with steam.

In the sludge treatment method according to the present invention, the first settling sludge and the surplus sludge are mechanically concentrated in a mixed state, and dried by the centrifugal thin film dryer 10 utilizing the waste heat of the melting furnace 9. Sludge can be treated with a simple system. And in this method,
Since the sludge can be sent to the centrifugal thin film dryer 10 in a fluid state, problems such as solid transport, bad odor, and space required for equipment, which have been conventionally problems, have been completely solved. Also, waste heat generated from the sludge melting furnace is effectively used.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a system diagram of a treatment system to which the sludge treatment method of the present invention is applied.

FIG. 2 is a diagram showing the structure of a centrifugal thin film dryer.

[Fig. 3] System diagram of conventional sludge treatment process

[Explanation of symbols]

9 melting furnace 10 Centrifugal thin film dryer 12 blades 18 heat transfer cylinder 22 Waste heat boiler g1 exhaust gas

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Tamura             Suka, Minamiogikubo 4-35-21, Suginami-ku, Tokyo             Icoat Ogikubo No. 107 (72) Inventor, Yanohei             2-4-28-5 Motohonokubo, Narashino City, Chiba Prefecture

Claims (2)

[Claims] 1. A concentrating step of mechanically concentrating sludge generated from wastewater treatment, and, following the concentrating step, by a plurality of rotating blades (12) up to a water content that allows the sludge to be charged into a melting furnace (9). A drying step of drying with a centrifugal thin film dryer (10) for drying while forming a material to be dried in a thin film on the side wall of the heat transfer cylinder (18), and burning the dried sludge in the melting furnace (9). Using the sludge treatment step of melting treatment and the waste heat contained in the exhaust gas (g1) generated from the melting furnace (9), the waste heat boiler (22) supplies the centrifugal thin film dryer (10). A method for producing sludge, which comprises producing a drying steam (s). 2. A part of the exhaust gas (g1) that has undergone heat exchange by the waste heat boiler (22) is delivered to the centrifugal thin film dryer (10) and used for drying the mixed sludge. The sludge treatment method according to claim 1.