JPH06134496A - Dehydration of sludge in system to utilize sludge as resource - Google Patents

Abstract

PURPOSE:To carry out dehydration of sludge efficiently at a low cost by using a precoat filter type dehydrator in the case dehydrated sludge is granulated, dried, and fired after the dehydration and using collected dust or pulverized materials for the precoat material. CONSTITUTION:Sludge is supplied to a raw water tank 11 of a precoat type dehydrator 1. Meanwhile, collected dust of dust collecting apparatus 7 and a pulverized material of a pulverizer 8 are respectively supplied as a precoat material to a precoat tank 12 of the dehydrator 1. At first, the precoat liquid is supplied to a tank 14 of the precoat filter 13 and a thin layer of the precoat material is formed on the surface of a rotating filtration cylinder 15. Next, raw liquid consisting of sludge is supplied to the tank 14 and while the pressure of the inside of the rotating filtration cylinder 15 is decreased by a vacuum pump 16, dehydration and filtration of sludge is carried out. Then, dehydrated sludge adhering to the surface of the filtration cylinder 15 is removed and supplied to respective driers 2, 4, a granulating apparatus 3, an incinerator 5, and a screen 6 successively and then returned to the precoat tank 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge resource recycling system for dehydrating, drying, granulating and firing sludge generated from, for example, a water purification plant and sludge accumulated in rivers and lakes. The present invention relates to a sludge dewatering method in the sludge resource recycling system.

[0002]

2. Description of the Related Art Conventionally, sludge generated from water purification plants and sewage treatment plants and sludge dredged from rivers and lakes (sludge) are
After being dehydrated, most of it was landfilled. However, in view of the fact that the sludge treatment amount is increasing and it is becoming difficult to secure landfill, it is possible to granulate, dry, and calcine the above sludge as a raw material to obtain a granular product with high product value. A sludge resource recovery system for obtaining the above has been proposed.

By the way, even in the above sludge resource recycling system, it is necessary to first dehydrate sludge, such as sludge generated from a water purification plant, used as a raw material. As a method therefor, a gravity dehydration method such as a dehydration drum dehydrator is used. There were a machine, a pressure type dehydrator such as a belt press and a filter press, and a precoat filter type dehydrator using diatomaceous earth as a precoat material.

[0004]

However, the above-mentioned conventional sludge dewatering method has the following problems. That is, first, the method using a gravity type dehydrator such as a dehydration drum dehydrator has a low dehydration efficiency, and therefore, a heavy burden is required when drying the dehydrated sludge in a subsequent drying step, and it is uneconomical in terms of thermal efficiency. . Moreover, in the gravity type dehydrator, it was necessary to add a large amount of water glass or a polymer-based coagulant to concentrate and coagulate the sludge.

When a pressure type dehydrator such as a belt press and a filter press is used, the apparatus is expensive and it takes a long time to dehydrate, which is not economical, and the dehydrated sludge (filter cake) obtained is compared. Since it is a large plate, it is difficult to cut out the storage tank, a large opening and a wide cutting device are required, and the dehydrated sludge or its dried product is sized to be suitable for granulation before the granulation process. It was necessary to provide a crushing step.

The method using a precoat filter type dehydrator which uses diatomaceous earth or the like as a precoat material has an advantage that the apparatus is relatively inexpensive, but diatomaceous earth or the like used in large amounts as the precoat material is expensive. Depending on the purpose of recycling sludge, it may not be desirable to mix a precoat material such as diatomaceous earth into the sludge.

[0007] In view of the above situation, the present invention is a method for dehydrating sludge in a sludge resource recovery system which can efficiently perform sludge dehydration at low cost and does not mix other substances undesired for sludge resource recovery. The purpose is to provide.

[0008]

Means and Actions for Solving the Problems The sludge dewatering method in the sludge resource recycling system according to the present invention is devised to achieve the above-mentioned object. After sludge is dehydrated, it is granulated, dried and fired. In the sludge resource recycling system, a pre-coat filter type dehydrator is used as the dehydrator, and dust collected in the firing waste gas, fine-grain burned products and / or crushed coarse-grain burned products are used as the pre-coat material. It is characterized by doing.

The water content of the dehydrated sludge obtained by the above method is usually 60 to 75% by weight.
It is preferable to dry to 5 to 45% by weight. Therefore, the dehydrated sludge is primarily dried by a highly efficient primary dryer, and then granulated. As a primary dryer,
An indirect heat medium dryer with high heat efficiency is preferably used, but a hot air dryer may be used. Further, since the dehydrated sludge obtained by the above method is a relatively thin layer and has a small lump, it can be directly supplied to the granulator through the primary dryer and granulated to a required particle size.

The granulated sludge is supplied to a calciner through a secondary dryer and calcined there. The firing temperature is generally 800 to 1200 ° C. A dust collecting device such as a bag filter is provided in the discharge path of the burning waste gas, and the dust collecting dust collected here is supplied to the precoat filter type dehydrator as a precoat material.

The granular fired products obtained by firing are screened and selected according to the fired product having an appropriate particle size. Among them, the fine-granular baked product is kept as it is, and the coarse-granular baked product having a relatively large particle size is pulverized by a pulverizer and then supplied as a precoat material to a precoat filter type dehydrator.

Therefore, according to the above method, as the precoat material for the precoat filter type dehydrator, instead of expensive diatomaceous earth or the like, dust collected in the firing waste gas, fine-grain fired product and / or coarse-grain fired Since crushed products are used, sludge can be dehydrated efficiently at low cost, and other substances such as diatomaceous earth that may not be desirable for recycling sludge can be mixed into sludge. Since it does not exist, there is an advantage that application development is easy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

This embodiment is a sludge resource recycling system for producing granular fired products that can be used as horticultural soil, etc., using the sludge generated in the water purification plant as a raw material. At the water treatment plant, the raw water drawn from the river is guided to a settling basin, etc., and a coagulant is added to this to coagulate and sediment the sediment contained in the raw water, which is then guided to a concentrating tank. Obtain a concentration of sludge.

The obtained high-concentration sludge is supplied to the stock solution tank (11) of the precoat filter type dehydrator (1). On the other hand, the dust collected from the dust collector (7) provided in the burning waste gas discharge passage described later and the pulverized product of the coarse-grained calcinated product of the pulverized product obtained by calcination by the crusher (8) Are supplied as precoat materials to the precoat tank (12) of the precoat filter type dehydrator (1), and are mixed there with fresh water to obtain a precoat liquid.

Then, first, while supplying the precoat liquid into the tank (14) of the precoat filter (13), the filtration cylinder (15) having its lower end immersed in the tank (14) is rotated, On the surface of the filtration cylinder (15), a thin layer of the pre-coat material composed of dust collected dust and a crushed product of the coarse-grain fired product is formed.

Then, the stock solution consisting of sludge is supplied from the stock solution tank (11) to the tank (14), and the vacuum pump (16) is operated to reduce the pressure in the filter cylinder (15) while the filter cylinder (15) is opened. Rotate and dehydrate and filter sludge.

The dehydrated sludge having a water content of about 65% by weight attached to the surface of the filtration cylinder (15) by dehydration filtration is removed by a scraper or the like, and a primary dryer composed of an indirect heat medium dryer having high heat efficiency. It is fed to (2) and dried there.

The dried product having a water content of about 45% by weight is sent to the granulator (3).

The sludge granulation product having a water content of about 45% by weight is then fed to the secondary dryer (4), where it is further dried.

The dried product having a water content of about 10% by weight is sent to a calciner (5) where it is calcined. Firing machine
The burning waste gas from (5) is sent to the dust collector (7) consisting of a bag filter, and the dust collected here is sent to the precoat tank (12) of the precoat filter dehydrator (1). To be

The granular fired product obtained by firing is sent to a screen (6) after cooling and is sorted according to the particle size. Then, the coarse-grained fired product having a particle size of 15 mm or more is supplied to the pulverizer (8) and pulverized there, and the obtained pulverized product is the precoat tank (1
Sent to 2).

[0023]

According to the present invention, after dewatering sludge,
In a sludge resource recycling system for granulating, drying and firing, a precoat filter type dehydrator is used as the dehydrator, and as the precoat material, instead of using conventional expensive diatomaceous earth, etc., Dust collection dust,
Since finely pulverized and / or coarsely pulverized pulverized products are used, sludge can be dehydrated efficiently at low cost, and it may not be desirable for sludge to be recycled as diatomaceous earth. Since other substances are not mixed in the sludge, there is an advantage that the application can be easily developed.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

[Explanation of symbols]

 (1) …… Pre-coated filter dehydrator (2) …… Primary dryer (3) …… Granulator (4) …… Secondary dryer (5) …… Firing machine (6) …… Screen (7) ) …… Dust collector (8) …… Crusher

Claims (1)

[Claims] 1. A sludge resource recycling system in which sludge is dehydrated, then granulated, dried and fired, and a precoat filter type dehydrator is used as the dehydrator, and dust collected in the firing waste gas is used as the precoat material. A method for dewatering sludge in a sludge recycling system, characterized by using a pulverized product of a fine-grain baked product and / or a coarse-grain baked product.