JPH02187200A - Granulation and dehydration of sludge - Google Patents

Abstract

PURPOSE:To obtain a sludge cake low in water content by mixing aluminum oxide and aluminum hydroxide with a water permeable dry powder and adding the resulting mixture to a primary dehydrated cake to perform secondary dehydration. CONSTITUTION:A sludge charge port 19 is arranged on the upstream side of a rotary drum 14 and a dry powder charge port 20 is arranged on the downstream side thereof. A primarily dehydrated sludge cake is supplied into the rotary drum 14 from the sludge charge port 19 and a prepared dry powder whose component is prepared by an aluminum compound is supplied to a dry powder conveyor 18 from the dry powder charge port 20 to be supplied into the rotary drum 14. The sludge cake in the rotary drum 14 is broken by a screw 16 and a paddle 17 and tumbled in the rotary drum to be granulated. By this method, the heat value of a secondary dehydrated cake is enhanced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for granulating and dewatering sludge generated in sewerage systems, etc., and in particular, it involves refining a sludge cake that has undergone primary dewatering using a water-permeable dry powder. Forms sludge particles, which are further dehydrated for a second time,
This invention relates to a sludge granulation and dewatering method for obtaining a sludge cake with a low water content.

[Conventional technology]

BACKGROUND ART Conventionally, in order to dehydrate sludge generated in sewers and the like to obtain a sludge cake with a low water content, a sludge cake that has been subjected to primary dewatering has been subjected to secondary dewatering. For example, the magazine [Reproduction and Utilization J1981. As disclosed in νo1-4. 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 a method for improving this, as disclosed in Japanese Patent Publication No. 59-48160, water-permeable dry powders such as diatoms, slaked lime, calcium carbonate, incinerated ash, and pulverized coal are added to the primary dewatered sludge as a dehydration aid. is added in an amount of 10 to 100% of the dry weight of the sludge cake, and the surface of the sludge grains is covered with the above-mentioned dewatering aid while preventing fluctuation changes to form tempered sludge grains, which are then pressure-pressed. The idea was to reduce the water content of the sludge cake to 50% or less.

[Problem that the invention seeks to solve]

However, in the sludge dewatering method described above, diatomaceous earth,
Conditioned sludge granules are prepared using components of water-permeable dry powder (hereinafter referred to as dry powder) such as incinerated ash, pulverized coal, slaked lime, and calcium carbonate in an unprepared state, which is then subjected to secondary dewatering. As a result of subsequent experiments by the inventors, the following problems were found.

Dry powders generally have excellent water permeability, but some do not have the desired effect of improving water permeability and dewatering properties, and their apparent specific gravity is large, making it difficult to achieve high dewatering performance at a given addition rate. This means that the addition rate of dry powder to the primary dehydrated cake must be increased. Furthermore, since dry powder mainly composed of inorganic substances is used, when the secondary dehydrated cake is incinerated, heat loss due to the dry powder increases, resulting in a decrease in energy efficiency, which is an important problem.

[Means for solving problems]

The present invention provides a method for granulating a sludge cake that has been subjected to primary dewatering and performing secondary dehydration.
Water-permeable dry powder consisting of one lining of calcium carbonate, etc.
A prepared dry powder prepared by mixing aluminum oxide or aluminum hydroxide in an amount of 1 to 20% by dry weight is added to the primary dewatering cake, and tempered sludge particles are produced by rolling granulation. This is a sludge granulation and dewatering method characterized by secondary dewatering using a high-pressure dehydrator.

〔Example〕

Embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a flow sheet of the present invention, Fig. 2 is a conceptual diagram of a granulator in the rolling granulation process in Fig. 1, and Fig. 3 is a view taken along arrow A-A in Fig. 2. 4 is a diagram showing the dehydration results, and FIG. 5 is a diagram showing the dehydration limits of dried powder and prepared dry powder.

First, the system flow will be explained with reference to FIG. This system consists of a primary dehydration cake supply process, a dry powder supply process, a rolling granulation process, and a high-pressure dehydration process. In the dry powder supply step, dry powder and aluminum compound are stored in a dry powder storage hopper 1 and an aluminum compound storage hopper 2, respectively. A dry powder quantitative feeder 3 and an aluminum compound quantitative feeder 4 are installed at the bottom of the dry powder storage hopper 1 and the aluminum compound storage hopper 2, respectively, and the dry powder and aluminum compound are dried through the quantitative feeder. A fixed quantity is supplied to the powder preparation tank 5. A mixing device 6 such as a stirrer is installed in the dry powder preparation tank 5, and mixes the dry powder and aluminum compound so that they are homogeneous.

In this way, the prepared dry powder with homogeneous components is supplied to the rolling granulation process via the tempering material quantitative feeder 7 installed below the dry powder preparation tank 5.

Further, in the primary dehydrated cake supply step, the primary dehydrated cake is primarily stored in the primary dehydrated cake hopper 9 and discharged via the dispensing device 10 provided at the lower part of the primary dehydrated cake hopper 9. The discharged primary dewatered cake is weighed via the weighing conveyor 11, and the amount of cut-out by the dispensing device 10 is controlled so that the sludge cake can be supplied in a constant quantity to the rolling granulation process. In this way, from the primary dehydrated cake and the prepared dry powder supplied to the rolling granulation process so that the ratio is constant, tempered sludge particles are produced in the granulator 8, and then transferred to the granulated sludge supply conveyor 12.
It is sent to a high-pressure dewatering process via a hydraulic press type or diaphragm type high-pressure dehydrator 13 and is compressed and dehydrated.

Next, the action in the rolling granulation process will be explained with reference to FIGS. 2 and 3. 14 in the figure is a rotating drum, tilted to the left side of the figure.
C, and is supported by rollers 15 and rotated by a drive device (not shown). A screw 16 and a paddle 17 are coaxially attached to the rotating drum 14 and rotated, and a dry powder conveyor 18 is disposed above it. and rotating drum 14
A sludge inlet 19 is provided on the upstream side, and a dry powder inlet 20 is provided on the downstream side. The primary dehydrated sludge cake is fed into the rotating drum 14 from the lη mud inlet 19, and the prepared dried powder whose components are prepared with an aluminum compound is dried powder inlet 2.
0 to the dry powder conveyor 18 and into the rotating drum 14. The sludge cake in the rotating drum 14 is crushed by the screw 16 and the paddle 17, and granulated while rolling in the rotating drum 14, the surface of which is covered with prepared dry powder.

Next, FIG. 4 shows an example of the dewatering results of the sludge granulation and dewatering system shown in FIG. 1. The figure shows the addition rate and water reduction rate (amount of water discharged by secondary dehydration/moisture amount of the primary dehydrated cake)
This shows the relationship, with the ratio of aluminum compound added to the dry powder taken as a parameter. As a result of the same figure, in the range of the addition rate of 10 to 40%, the water reduction rate increases as the addition rate increases, but once a certain value is exceeded, the increase in the water reduction rate shows a tendency to saturate and becomes flat. It can also be seen that the addition rate at which the increase in water reduction rate remains unchanged depends on the addition ratio of the aluminum compound to the dry powder. That is, when comparing the addition rate at which the water reduction rate reaches the saturation point in each dry powder and the water reduction rate at that time, when no aluminum compound is added, the addition rate is 40% and the water reduction rate is 60%. On the other hand, aluminum compounds with IO and 2
In the prepared dry powder whose ingredients were prepared by adding 0% (relative to dry powder), the saturation point of the water reduction rate was 3025% addition rate and 64.67% water reduction rate, respectively, and by preparing the ingredients with an aluminum compound, The addition rate could be reduced by 10 to 15%, and the achieved water reduction rate could be improved by 4 to 7%. FIG. 5 is a diagram showing the dehydration limits of dry powder and prepared dry powder.

Dry powder slurry with a concentration of 30% at a pressure of 50 kgf/cri
As shown in the figure, adding an aluminum compound lowers the water content at the dehydration limit of the prepared dry powder, and adding an aluminum compound to the dry powder as described above improves the performance. Significant improvement.

〔Effect of the invention〕

According to the present invention, it is possible to achieve a high water reduction rate that could not be achieved even with conventional sludge dewatering methods, especially those that add secondary dehydration.Furthermore, it is possible to reduce the addition rate of dry powder, and as a result, the secondary dewatering cake In addition to improving the calorific value of the process, it also made it possible to reduce the size of equipment in the post-processing process.

[Brief explanation of the drawing]

Figure 1 is the flow sheet of the present invention, Figure 2 is a conceptual diagram of the granulator used in the rolling granulation process in Figure 1, and Figure 3 is the flow sheet of the present invention.
A-A arrow view in the figure, Figure 4 is a diagram showing the relationship between the dry powder addition rate and water reduction rate in the present invention, and Figure 5 is a diagram showing the dehydration limit of the dry powder and prepared dry powder used in the present invention. FIG. Fig. 3 Fig. Unadded rate (%) (Dry lamp powder + aluminum compound) Fig. 2゜ Aluminum compound unadded (%)

Claims (1)

[Claims] In a method of granulating a sludge cake that has been subjected to primary dewatering and performing secondary dehydration, a water-permeable dry powder consisting of one or more of diatomaceous earth, incinerated ash, pulverized coal, slaked lime, calcium carbonate, etc. is added in a dry weight ratio. A prepared dry powder prepared by mixing 1 to 20% of aluminum oxide or aluminum hydroxide is added to the primary dewatering cake, and tempered sludge particles are produced by rolling granulation. A sludge granulation and dewatering method characterized by secondary dewatering.