JPH03288600A - Method for dehydrating and incinerating sludge - Google Patents

Abstract

PURPOSE:To reduce the treatment cost of sludge by coating the surfaces of sludge particles obtained by granulating a primary dehydrated cake with incineration ash obtained by incinerating a mixture of a secondary dehydrated cake and CaCO3 to form conditioned sludge particles. CONSTITUTION:A secondary dehydrated cake and CaCO3 are mixed and incinerated to form incineration ash. The primary dehydrated cake obtained from a primary dehydrator 1 is about 75-85% but this cake is supplied to a granulator 3 to be ground and granulated. Subsequently, the surfaces of the sludge particles are coated with the aforementioned incineration ash supplied from an incineration ash storage hopper 7 to form conditioned sludge particles which are, in turn, supplied to a secondary dehydrator 2 to be pressed and squeezed to form a secondary dehydrated cake reduced to about 50% or less in water content. This method is invented by utilizing that dehydration effect depends on the amount of CaCO 3 in incineration ash.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for treating sludge generated in sewerage systems, etc., and particularly relates to a method for dewatering sludge to form a sludge cake and incinerating it. .

[Prior Art] Conventionally, in order to dehydrate sludge generated in sewerage systems and the like to obtain a sludge cake with a low water content, the primary dewatered sludge cake is further dehydrated for a second time.For example, magazine[
Reproduction and Utilization J 1981. As disclosed in Vol-4. However, this method involves secondary dehydration of the sludge cake that has been subjected to primary dewatering, and it was not possible to obtain a sufficient dehydration effect with this method alone. Therefore, as an improvement method for this, as disclosed in Japanese Patent Publication No. 59-48160, the primary dewatered sludge cake is mixed with mainly incinerated ash as a dehydration aid, as well as diatomaceous earth, slaked lime, and calcium carbonate.

Dry powder with high water permeability such as pulverized coal is added in an amount of 10 to 100% of the dry weight of the sludge cake to form sludge grains while preventing fluctuation changes, and the surface of the sludge grains is covered with the dry powder. The method was to produce tempered sludge particles and pressurize them to reduce the moisture content of the sludge cake to 50% or less.

[Problems to be Solved by the Invention] However, in the above-mentioned sludge granulation and dewatering method, components such as incineration ash are used in an unadjusted state to produce tempered sludge particles, which are then subjected to secondary dewatering. As a result of subsequent experiments by the inventors, the following problems were found.

In general, incinerated ash has excellent water permeability, but some incineration ash does not have the required water permeability and dehydration effect, and a high dehydration effect cannot be obtained at a specified addition rate, so incineration ash that is added to the primary dewatered cake cannot be used. This means that the addition rate of ash must be increased. Furthermore, since the incinerated ash is composed of inorganic substances, when the secondary dehydration cake is incinerated, an important problem is that the energy efficiency decreases because the heat loss due to the incinerated ash increases.

[Means for Solving the Problems] The present invention provides a method for dewatering and incinerating sludge, which includes:
The secondary dehydrated cake and CaCO3 are mixed and supplied and incinerated to produce incineration ash, the primary dehydrated cake is crushed and granulated,
The surface of the sludge grains is coated with the incineration ash to form tempered sludge grains, the tempered sludge grains are compressed and subjected to secondary dehydration to form a secondary dehydrated cake, and the secondary dehydrated cake and CaCO3 are mixed. It is characterized by being incinerated.

Originally, when sludge is incinerated, Ca C03 is stored in the incinerator.
Supplying gas is commonly used as a flue gas desulfurization technology.

The outline of this method is to cause SO□ in the flue gas to react with CaCO3, and to fix SO3 as Ca5O.

However, when CaCO3 is supplied in excess, a reaction occurs in which it decomposes and generates CaO.

This CaO comes to exist in the incineration ash.

The inventors' research has revealed that the dehydration effect becomes greater in secondary dewatering when sludge particles are coated with CaO-containing incineration ash.

[Example] Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a flowchart of equipment for carrying out the invention. 1 is a primary dehydrator, 2 is a secondary dehydrator, 3 is a granulator, 4 is an incinerator, and 5 is a CaCO3 feeder.

6 is a coarse dust collector, 7 is an incineration ash storage hopper, and 8 is a fine dust collector.

The secondary dehydrated cake obtained by dewatering the sludge in the primary dehydrator 1 is 75~
The water content is 85%, but this is supplied to the granulator 3, where the primary dehydrated cake is crushed and granulated, and the incinerated ash supplied from the incinerated ash storage hopper 7 is turned into sludge particles. The surface of the sludge is coated to form tempered sludge particles. The tempered sludge particles are fed to the secondary dehydrator 2 and compressed to form a secondary dehydrated cake with a water content reduced to about 50% or less.

In this embodiment, the term "water reduction rate" will be used hereinafter to indicate the dehydration effect. This is the value obtained by dividing the amount of water discharged by secondary dehydration by the amount of water contained in the primary dehydration cake, and can directly represent the dehydration effect.

At the beginning of operation, the incinerated ash before supplying CaCO3 is used to form tempered sludge particles, which are supplied to the incinerator 4, and CaCO3 is also supplied and incinerated in the incinerator 4. In the incinerator 4, So and CaCO3 react and produce Ca5O, but the excessively supplied CaC01 is decomposed by heat and becomes C.
aO is generated.

This CaO is mixed in the incinerated ash and is carried along with the exhaust gas to the coarse dust collector 6, where it is separated from the exhaust gas and collected as incinerated ash. Furthermore, the exhaust gas is passed through a fine dust collector 8.
Only the incinerated ash collected by the coarse dust collector 6, which is discharged after the fine powder has been removed, is stored in the incinerated ash storage hopper 7, and is taken out as needed and sent to the granulator 3. The secondary dewatered cake is crushed and granulated therein, and the surfaces of the sludge particles are coated with incineration ash to form tempered sludge particles. The tempered sludge particles are compressed and dehydrated in a secondary dehydrator 2, and then incinerated in an incinerator 4.

Figure 2 shows the water reduction rate when CaCo3 is mixed with a secondary dehydrated cake and incinerated, the incinerated ash is used to generate tempered sludge particles, and this is subjected to secondary dehydration, and the incinerated ash is generated. It shows the ratio of the dry weight of CaCO3 mixed with the secondary dehydrated cake (2y).

As the addition rate of CaCO3 increases, the water reduction rate also increases,
The dehydration effect has improved 1 Normally, when only desulfurization is performed, Ca
Although the proportion of CO3 supplied is about 2% of the weight of the dehydrated cake, as seen from FIG. 2, the effect of supplying CaCO3, that is, the greater the proportion of CaO present in the incineration ash, the greater the dehydration effect.

[Effects of the Invention] The present invention utilizes the fact that the dehydration effect depends on the amount of CaO present in the incineration ash, and the present invention utilizes the fact that the dehydration effect depends on the amount of CaO present in the incineration ash.
This can be achieved by simply increasing the ratio of mixed supply of sludge, so the sludge treatment cost can be kept low.

[Brief explanation of the drawing]

FIG. 1 shows a flowchart for implementing the invention, and FIG.
The figure is a diagram showing the relationship between the addition rate of Ca 2 CO and the water reduction rate in secondary dehydration. 1; Primary dehydrator, 2; Granulator, 3; Secondary dehydrator 4; Incinerator, 5; Caco3 feeder, 6: Coarse dust collector, 7; Incineration ash storage hopper, 8; Fine dust collector

Claims (1)

[Claims] A) Mixing the secondary dehydrated cake and CaCO_3 and incinerating it to produce incinerated ash; b) Crushing and granulating the primary dehydrated cake, and applying the incinerated ash to the surface of the sludge particles. coating to form tempered sludge particles, c) compressing the tempered sludge particles to perform secondary dehydration to form a secondary dehydrated cake, and d) mixing the secondary dehydrated cake and CaCO_3 and incinerating the mixture. A sludge dehydration and incineration method characterized by