JPS6071100A - Sludge treating method - Google Patents

Abstract

PURPOSE:To perform economical and effective sludge treatment, by a method wherein alkali silicate is added to a dehydrated cake of sludge and, thereafter, an acid is added thereto to adjust the pH thereof and, subsequently, the pH adjusted cake is brought into direct contact with combustion exhaust gas to dry the same. CONSTITUTION:Sludge (a) is introduced into dehydrating equipment 1 and a flocculant (b) is added thereto to dehydrate the same. This dehydrated sludge is introduced into a kneading tank 2 and sodium silicate (c) is added to said sludge to be kneaded therewith and, subsequently, the resulting mixture is introduced into a kneading tank 3 where an acid is added to and kneaded with the sludge to adjust the pH thereof to 6.5-8. In the next step, the mixture is introduced into a solidifying dryer 4 and brought into direct contact with high temp. exhaust gas (e) containing a large amount of carbon dioxide from a sludge incinerator 5. A hard solidified dehydrated cake is formed within a short time by hydrothermal reaction and syneresis action and a part thereof is crushed in a crusher 6 and recirculated to the dehydrating equipment 1 to be reused as the dehydrating aid (f) of dehydrating process. The remainder of the solidified cake is burnt in the incinerator 5 and combustion ash is subjected to melt solidifying treatment in a melting furnace 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently treating various sludges such as sewage sludge, human waste sludge, and purified 4'fJfF5 mud using alkali silicate.

Conventionally, as a sludge treatment method, Japanese Patent Application Laid-Open No. 52-51746
As shown in the publication, a technique is disclosed in which a thorium silicate coagulant is added to sludge, and heat is applied thereto to generate hard aggregates similar to gravel through a hydrothermal reaction. In this prior art, the necessary thermal energy is transferred from another field, which is extremely uneconomical and inefficient, and the condensation reaction also has a problem in that the reaction rate is slow if thermal energy alone is used.

The inventors of the present invention have conducted extensive research in order to solve the problems mentioned in 2.
By using alkali silicates such as potassium silicate for sewage sludge, human waste sludge, septic tank sludge, etc., it is possible to improve economical and
It was discovered that efficient sludge treatment can be performed.

The present invention has been made based on the above knowledge, and is a method for treating various types of sludge such as sewage sludge, human waste sludge, and septic tank sludge. is added and kneaded to adjust the pH, and then the mixture is brought into direct contact with combustion exhaust gas from various industrial furnaces, including sludge incinerators, to dry and solidify the dehydrated cake. We developed a sludge treatment method that can obtain a hard coagulated dehydrated cake in a short period of time through the synergistic effect of this action and the acceleration of hardening due to the chemical reaction between carbon dioxide, which is always contained in large amounts in exhaust gas, and alkali silicate. This is what we intend to provide.

In the method of the present invention, further efficiency can be achieved by recycling and using the sludge incinerator exhaust gas containing carbon dioxide gas. This reaction is based on Na2O・nSiO2+
mH2O+CO2→Na2C○3+nS i O2-m
Indicated by H2O, silica gel strengthens the mud, and the water floated away due to the syneresis phenomenon dries quickly. ! f. The hard substance obtained by this reaction is composed of an irreversible gel that does not dissolve again in water, and more efficient and economical effects can be obtained in the post-process incineration disposal.

Hereinafter, the configuration of the present invention will be explained based on the drawings.

FIG. 1 shows an example of the invention. Sludge dewatering equipment 1
After dehydration by adding a flocculant (organic polymer flocculant, inorganic flocculant), the mixture is introduced into the kneading tank 2 and silicic acid is added.
IJum is added and kneaded, then introduced into the kneading tank 3, and acid is added and kneaded to adjust the pH to 6.5-8. The mixture is then coagulated and dried iv! The sludge is introduced into the vessel 4 and brought into direct contact with the exhaust gas from the sludge incinerator 5 which is at high temperature and contains a large amount of carbon dioxide gas. Mizuyu) A hard dehydrated cake coagulate is produced in a short time by reaction and syneresis, and a part of the coagulate is crushed by a crusher 6 and circulated to the dehydration equipment 1 as a dehydration aid in the dehydration process. Reuse. The remainder of the solidified material is incinerated in an incinerator 5, and the incinerated ash is melted and assimilated in a melting furnace 7 such as a microwave melting furnace to be fluidized. The coagulated material coming out of the coagulation dryer 4 is a hard insoluble material that can be used as a dehydration aid as described above, and has a low moisture content and high organic matter content, and has high fuel value even when mixed with the dehydrated cake before coagulation. , it is possible to save energy during incineration. Furthermore, the incineration ash from the incinerator 5 contains a large amount of silica, which promotes fluidization of the molten material and facilitates treatment.

In the present invention, the addition rate of the flocculant is 0.00% per sludge solids.
5-1.5 wt%, the addition rate of sodium silicate is 5-15 wt% based on sludge solids.

FIG. 2 shows another example of the invention. In Fig. 2, sewage is treated in an initial sedimentation tank 8, an aeration tank 9, and a final sedimentation tank 10, and the surplus activated mud from the final sedimentation tank 10 is forcibly concentrated by a mechanical thickening equipment 11, and then dehydrated with a flocculant. I do. After adding sodium silicate to the dehydrated cake and neutralizing it with acid, it is coagulated and dried by the temperature of the exhaust gas from the incinerator 5 and the action of charcoal 1.Il gas. The coagulated product obtained by this coagulation drying has an extremely high organic matter content and is hard. On the other hand, the raw sludge extracted from the initial settling tank 8 is reduced to a high concentration in the gravity thickening tank 12, and its properties enable efficient digestion. This thickened sludge is treated in an anaerobic digestion tank 13. The anaerobic digested sludge has been improved to be easily dewaterable, and by dewatering this sludge in the dewatering equipment 14 using sandy coagulum as a dewatering aid, a dehydrated cake with an extremely low water content can be obtained.
By combining this dehydrated cake and the sandy coagulum and incinerating it, efficient combustion can be achieved. However, in a melting furnace such as a microwave melting furnace, the inclusion of silica allows the melt to be fluidized and can be effectively processed. The other configurations are the same as in the case of FIG.

Further, FIG. 3 shows still another example of the present invention. Third
In the figure, the sludge is introduced into the dewatering equipment, dehydrated by adding a flocculant, and then introduced into the kneading tank 2, where thorium silicate is added and kneaded, and then kneaded (acid is added in the tank 3). pH
After adjustment, it is put into the multistage incinerator 15. The dehydrated cake is agitated by teeth in the first stage of the multistage incinerator while coming into contact with high-temperature exhaust gas containing carbon dioxide gas, so it is quickly dried and becomes a solidified product. Therefore, the area required for drying is small, and the furnace can be made smaller compared to a normal multi-stage furnace.

Next, embodiments of the present invention will be described.

Example 1. Adding a polymer sludge to sludge with a sludge concentration of 2.5%. □wt%(
After adding 1Qwt% of sodium silicate (based on sludge solids) and kneading, add 1Qwt% of sodium silicate (based on sludge solids) and knead to adjust the pH to 7.
After adjusting to 0, dry and coagulate by contacting with incinerator exhaust gas, 80wt% of which is sent to the incinerator, 20wt%
% was crushed, pulverized, and used as a dehydration aid in the dehydration process. The temperature of the incinerator exhaust gas was 300°C, the CO2 concentration was 7.5%, the coagulation drying time was 20 minutes, the moisture content of the coagulated dry material was 25%, and the incinerator burning temperature was 800°C.

As explained above, according to the method of the present invention, the following effects can be obtained.

(1) The coagulated product of dehydrated cake using alkali silicate is a material with low moisture content and high fuel value, which can be burned in an energy-saving manner.

(2) By reusing the incineration exhaust gas generated in the sludge incineration process, the coagulation reaction is promoted, self-combustion combustion in the incinerator, and a simple and inexpensive incinerator type can be selected, which not only saves energy but also improves equipment. Significant cost reductions can be achieved.

(3) If a hard, rigid dehydrated cake containing high organic matter is obtained and this dehydrated cake is reused as a dehydration aid in the dehydration process, a significant increase in the dehydration effect can be expected, and Since the coagulated material itself is reused as a dehydration aid, a decrease in the organic matter content of the dewatered cake can be prevented, and economical sludge incineration becomes possible.

(4) When incineration ash is melted and assimilated using a microwave melting furnace, vitrification of the molten material is promoted and the melting and assimilation process is simplified.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an example of the sludge treatment method of the present invention, FIG. 2 is a flow sheet showing another example of the present invention, and FIG. 3 is a flow sheet showing yet another example of the present invention. . ]...Dewatering equipment, 2.3...Kneading tank, 4...Coagulation dryer, 5...Sludge incinerator, 6...Crusher, 7...
・Melting furnace, 8... First settling tank, 9... Aeration tank, 10... Final settling tank, 11... Mechanical concentration equipment, 12... Gravity type thickening tank, 13... Anaerobic Digestion tank, 14...Dewatering equipment, 15...Multi-stage incinerator Applicant Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] ■ In a method for treating various sludges such as sewage sludge, human waste sludge, and septic tank sludge, an alkali silicate is added to a dehydrated cake obtained by dehydrating the sludge and kneaded, and then an acid is added and kneaded to adjust the pH. A method for treating sludge, which comprises adjusting the mixture, and then bringing the mixture into direct contact with combustion exhaust gas from various industrial furnaces, including sludge incinerators, to dry and solidify the dehydrated cake. 2. In a method for treating various sludges such as sewage sludge, human waste sludge, and septic tank sludge, an alkali silicate is added to a dehydrated cake obtained by dehydrating the sludge and kneaded, then an acid is added and kneaded to adjust the pH, and then the mixture is mixed. The dehydrated cake is brought into direct contact with combustion exhaust gas from various industrial furnaces, including sludge incinerators, to dry and solidify it, and the solidified sludge is then crushed, and this crushed product is recycled as a dehydration aid when dewatering raw sludge. A sludge treatment method characterized by using 3. In the method of treating various sludges such as sewage sludge, human waste sludge, and septic tank sludge, an alkali silicate is added and mixed into a dehydrated cake obtained by dehydrating the sludge, and then an acid is added and kneaded to adjust the pH. The mixture is brought into direct contact with combustion exhaust gas from various industrial furnaces including sludge incinerators to dry and solidify the dehydrated cake, the solidified sludge is incinerated in a sludge incinerator, and the incinerated ash is melted in a melting furnace. A sludge treatment method characterized by: