JPH1094799A - Granulation drying method of sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a granular dry sludge having a uniform particle diameter and no fine power by mixing a powder sludge primarily dried by a rotary drum dryer with a fresh feed dehydrated sludge and finish-drying while covering the surroundings of the granulated material as a nucleus with the sludge. SOLUTION: The dehydrated sludge dehydrated by a dehydrator is charged into the rotary drum dryer 1 and dried while crushing the sludge with a hot air of 600-800 deg.C. The dried sludge is in a granular and powder state, has ununiform particle diameter and contains an appreciable quantity of fine powder recovered in a dust collector 3. The granular and powder sludge and the dehydrated sludge are charged into a vertical stirring and mixing dryer 2 having a spiral ribbon rotary blade and finish-dried. In such a case, the charged granular and powder sludge may be either of the whole of powder primarily dried in the rotary drum dryer 1 or powder remaining after taken out as a product. At this time, the fine powder recovered by the dust collector 3 is also easily treated by charging the fine powder in the vertical stirring and mixing dryer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying various sludges such as human waste sludge, sewage sludge, and food wastewater treatment sludge, and more particularly to a method for granulating and drying sludge.

[0002]

2. Description of the Related Art Various types of sludge discharged from night soil treatment plants, sewage treatment plants or food factories are dehydrated by a belt press or centrifugal dehydrator and then dried. A dryer is used. A specific drying method using this rotary drum type dryer is, for example, a dewatered water content of 85% W. B. Dewatered sludge is introduced into the apparatus and dried with hot air of about 600 to 800 ° C. to a target moisture value while stirring.

[0003] The above-mentioned drying method using a rotary drum type dryer has the following problems. That is, the sludge dried by the rotary drum dryer has a wide particle size distribution and an irregular particle size, and contains a large amount of fine particles having a particle size of 100 μm or less. The mixture of fine powders generates dust when handling the dried sludge, which causes deterioration of the working environment and environmental pollution. Further, the irregular particle size is inconvenient when used as a dry sludge fertilizer when it is mechanically scattered or mixed with a chemical fertilizer.

[0004]

The problem to be solved by the present invention is to provide a method for granulating and drying sludge having a small particle size and a uniform particle size. Can be reduced by finishing and drying while coating and granulating with dewatered sludge in a vertical stirring and mixing dryer,
Furthermore, the sludge was sized and focused on its potential.

[0005]

Means for solving the above-mentioned problems are as follows. A dewatered sludge is put into a rotary drum type drier and primary dried with hot air. The sludge is introduced into a vertical stirring and mixing dryer, and the granulated sludge is finished and dried while being covered with newly introduced dewatered sludge. According to the present invention, the granular sludge primary-dried by the rotary drum type dryer is mixed with the newly introduced dewatered sludge, and is further dried while covering the sludge around the granular material as a core. As a result, granular sludge is almost eliminated and the granular sludge is adjusted in particle size.

Means for solving the problems described in claim 2 include, in addition to the requirements described in claim 1, a method in which primary drying is performed to substantially achieve a target moisture content, and final drying is performed for newly introduced dewatered sludge. It is characterized in that the moisture is removed only. According to the present invention, the product is dried to almost the product target moisture by primary drying in which drying is performed by hot air at a relatively high temperature of about 600 to 800 ° C., and a minimum required amount of evaporating moisture for finish drying is newly added. Since the water removal of the dewatered sludge is limited, the size of the vertical stirring and mixing dryer can be minimized, and the drying efficiency of the entire system can be increased.

Further, a method for granulating and drying sludge according to claim 3 is characterized in that, in addition to the requirements described in claim 1 or 2, the final drying is performed under vacuum. According to the present invention, since vacuum drying is used, a large temperature difference can be obtained compared to normal pressure drying, the evaporation rate per unit area increases, the dryer can be reduced in size, and the amount of exhaust gas is small, so that it is necessary for exhaust gas treatment. Costs can be reduced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the method for granulating and drying sludge of the present invention will be described with reference to the flow sheet of FIG. Reference numeral 1 denotes a rotary drum type dryer having crushing and stirring blades in the longitudinal direction of the rotary cylinder, which is used to dry sludge while crushing it with hot air of about 600 to 800 ° C. Reference numeral 2 denotes a vertical stirring and mixing dryer. Here, a conduction heat transfer dryer having a spiral ribbon rotating blade in an inverted conical container and heating a jacket with steam is used. Without
One having a spiral stirring blade in a cylindrical container or one having a stirring blade at the bottom of the cylindrical container may be used. Symbol 3 is
It is a dust collector for removing fine powder from exhaust gas of a rotary drum type dryer. The present invention is carried out using these devices.

First, the dewatered sludge dewatered by an appropriate dehydrator is put into the rotary drum type dryer 1 and dried while crushing the sludge with hot air of about 600 to 800 ° C. Sludge dried by this rotary drum type dryer is powdery and granular, and the particle size is not uniform.
Some fine powder is collected by the dust collector 3. The granular sludge and the dewatered sludge are put into a vertical stirring and mixing dryer 2 having spiral ribbon rotating blades to perform finish drying. In addition, even if the granular sludge thrown in here is the whole amount of what was primary-dried by the rotary drum type dryer 1, a part of it, for example, this is sieved and the remaining part is taken out as a product. There may be. At this time, if the fine powder collected by the dust collector 3 is also charged into the vertical stirring and mixing dryer 2, the processing of the fine powder becomes easy.

A vertical stirring and mixing dryer 2 together with granular sludge
The dewatered sludge supplied to the tank has a water content of 75% W.S. B. If this is the case, it may be charged as it is. B. If less than 75
% W. B. Add water after adding water as described above. Here, the water content of the sludge fed is 75% W. B. It is important that this is the case. The granular sludge primary-dried by the rotary drum type dryer 1 is mixed with dehydrated sludge in the vertical stirring and mixing dryer 2, and is further dried while covering the surroundings of the granular material with the sludge. Therefore, there is no fine powder and the particle size is uniform, but the water content is 75% W. B. If it is less than this, the coating effect will be reduced by half.
This tendency is particularly strong in the case of organic sludge.

Further, in the present invention, the primary drying by the rotary drum type dryer 1 is performed to substantially dry the product to the target moisture, and the finish drying by the vertical stirring and mixing dryer 2 is performed to the extent that the newly introduced dewatered sludge is removed. It is desirable to stay there. In the primary drying, drying is performed with hot air at a relatively high temperature of about 600 to 800 ° C., and the final drying is a vertical stirring and mixing dryer 2 of a conduction heat transfer type, and the heating temperature is about 200 ° C. or less. Vertical stirring and mixing dryer 2 with low temperature difference due to low temperature
In this way, the vertical evaporation mixer 2 is reduced in size and the drying efficiency of the entire system is increased by limiting the evaporation water load in the apparatus to the minimum required level of water removal of newly added dewatered sludge. .

Further, in the present invention, the vertical stirring and mixing dryer 2
It is desirable that a vacuum pump and a condenser (not shown) are attached to the apparatus and finish drying is performed under vacuum. According to this, since the drying is performed under vacuum, a large temperature difference can be obtained as compared with the drying under normal pressure, the evaporation rate per unit area increases, the size of the dryer can be reduced, and the amount of exhaust gas can be reduced.

[0013]

Next, an embodiment to which the present invention is applied will be described. 84% W. B. Rotating body type dryer 1
And dried first with hot air at 800 ° C and moisture 10%
W. B. Of granular sludge was obtained. When this granular sludge was sieved, 2.4 mesh% for 4 mesh on, 1.5 weight% for 80 mesh pass, and the fine powder collected by the dust collector 3 was used for the primary dried granular sludge. 5% by weight. Primary dried granular sludge and the same weight of water, 84% W.W. B. Of dewatered sewage sludge is put into a vertical stirring and mixing dryer 2 (heating temperature: 130 ° C., degree of vacuum: 90 Torr), and finish drying is performed while coating the granular sludge with the dehydrated sludge to obtain a water content of 10% W. B. Was obtained. When this granular sludge was sieved, 4 mesh on disappeared,
The 80-mesh pass was reduced to 0.2% by weight, and a granular material having a uniform particle size and almost no fine powder could be obtained.

[0014]

[Table 1]

[0015]

According to the present invention, the dewatered sludge is put into a rotary drum type dryer and primary dried with hot air, and the obtained granular sludge and dehydrated sludge are put into a vertical stirring and mixing dryer, The method is characterized in that the granular sludge is finished and dried while being covered with dehydrated sludge, and it is possible to obtain granular dry sludge having a uniform particle size and without fine powder. Further, if the product is dried to the target moisture by the primary drying, not only can the vertical stirring and mixing dryer be reduced in size, but also the drying efficiency of the entire system can be increased. If the finish drying is performed under vacuum, the drying can be performed more efficiently.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary drum type dryer 2 Vertical stirring and mixing dryer 3 Dust collector

Claims (3)

[Claims] 1. A dewatered sludge is put into a rotary drum type drier and primary dried with hot air. The obtained granular sludge and the dehydrated sludge are put into a vertical stirring and mixing dryer to renew the granular sludge. A granulation and drying method for sludge, wherein the sludge is subjected to finish drying while being coated with dewatered sludge. 2. Drying to a target product moisture by primary drying.
2. The method for granulating and drying sludge according to claim 1, wherein the finish drying is performed only to a degree of removing water from newly introduced dewatered sludge. 3. The method for granulating and drying sludge according to claim 1, wherein the finishing drying is performed under vacuum.