JPH11323359A - Preparation of solid fuel using sewage sludge as raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing an odor-free solid fuel from only a raw material derived from sewage sludge at a low cost. SOLUTION: Sewage sludge is dried in a drier 1 to a water content of pref. not more than 10%, and a part of the dried sewage sludge is carbonized and activated in a carbonization furnace 2 to prepare a sludge activated carbon. This sludge activated carbon in an amt. of 5 to 100% based on the dried sludge is added and mixed in a mixer 3, and the mixture is granulated by means of a granulator 4 to obtain a solid fuel. 1 to 10% quick lime or slaked lime may be added depending upon service conditions of the solid fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a solid fuel using sewage sludge as a raw material.

[0002]

2. Description of the Related Art Sewage sludge generated from a sewage treatment plant has conventionally been exclusively incinerated.
Higher heating value per S (Dry Solid) is 450
Since it is about 0 kcal / kg, which is almost the same as municipal solid waste, if it is dried until the water content becomes 10% or less, it is considered that it has utility value as fuel like municipal solid waste. For municipal solid waste, solid fuel has already been put into practical use as RDF.

[0003] However, unlike municipal solid waste, sewage sludge contains an odorous component. Therefore, even if solid fuel is manufactured by the same method as municipal solid waste, the odor during transportation and storage is strong, and the commercial value of the fuel is impaired. May be Further, if a deodorant is separately added to suppress odor, the cost of raw materials is increased by that amount, which deviates from the original purpose of effective use of wastes, and has a problem that the commercial value is impaired in terms of cost. For this reason, the production of solid fuel using sewage sludge as a raw material has not been put to practical use at present.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, suppresses the odor peculiar to sewage sludge without increasing the raw material cost, and can obtain a solid fuel having a high commercial value. The present invention has been made to provide a method for producing a solid fuel using sewage sludge as a raw material.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention provides sludge activated carbon obtained by carbonizing and activating a part of the dried sludge in a carbonization furnace to dry sewage sludge. It is characterized by being added, mixed and granulated. In addition, the mixing ratio of sludge activated carbon to dry sludge is 5 to 5.
It is preferably set to 100%. Depending on the conditions of use of the solid fuel, 1-10% of quicklime or slaked lime may be added to dry sludge in addition to sludge activated carbon.

According to the present invention, since activated sludge obtained by carbonizing and activating a part of dried sludge in a carbonization furnace is used as a deodorant, a solid fuel having no odor is obtained only from raw materials derived from sewage sludge. be able to. Therefore, a solid fuel with a low raw material cost and a high commercial value can be obtained using sewage sludge as a raw material. Further, since other raw materials are not required, a great effect can be obtained from the viewpoint of effective use of waste.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. As shown in FIG. 1, first, a dewatered cake of sewage sludge is passed through a dryer 1 to be dried sludge. Any type of dryer can be used as the dryer 1, and a hot-air dryer can be typically used. The moisture of the dried sludge is 1
It is preferably 0% or less. The reason is that the moisture is 1
If it exceeds 0%, it will rot and mold easily grow during storage. Also, if the water content is too large, the handling properties deteriorate.

[0008] A part of the dried sludge is led to the carbonization furnace 2,
It is brought into contact with water vapor in a high temperature non-oxidizing atmosphere to be carbonized and activated. As a result, sludge activated carbon having a porous inside is obtained. 50 to 55% of the combustible content of the dried sludge is carbon, and it is possible to obtain sludge activated carbon having a weight of about 1/5 of the introduced dry sludge. This sludge activated carbon has a slightly lower ability to adsorb substances than commercial products, but can be produced at extremely low cost because it uses dry sludge as a raw material.

The sludge activated carbon obtained in this way is sent to the mixer 3, where it is uniformly mixed with the dried sludge. It is preferable that the mixing ratio of sludge activated carbon to dry sludge is 5 to 100%. If the mixing ratio of sludge activated carbon is less than 5%, the deodorizing effect is insufficient. On the other hand, if it exceeds 100%, the flammability of the solid fuel is reduced, and the production cost is undesirably increased.

Next, the mixture is sent to a molding machine 4 where it is granulated into a solid fuel. An extrusion granulator or a briquette machine can be used as the molding machine 4 for this purpose.
Similar to RDF, the particle size is set at 10
It is preferable to use a spherical body or a cylindrical body having a size of about 50 mm. The solid fuel thus obtained is a conventional RDF
It can be used as a fuel, and activated sludge does not emit odor during storage or transportation because it absorbs and fixes odor components.

Since sewage sludge often has a higher sulfur content than general municipal solid waste, depending on the use conditions of solid fuel, not only activated sludge but also quicklime or slaked lime may be added to dry sludge. It is preferable to add 10% to 10%. Lime reacts with sulfur during combustion to form a stable compound and suppresses sulfur oxides in exhaust gas. Further, since this lime has a deodorizing effect, it can also contribute to suppression of odor. However, since lime is an inorganic component and does not contribute to combustion, it is not preferable to add more than 10%.

[0012]

EXAMPLE A dewatered cake of sewage sludge using a high-molecular flocculant generated from a sewage treatment plant in Aichi Prefecture (higher heating value 45)
(00 kcal / kg.ds, water content: 80%) was passed through a hot air dryer to dry the water to about 10% to obtain dried sludge. 100 kg of the dried sludge was brought into contact with water in a carbonization furnace to carbonize and activate the sludge to produce sludge activated carbon. The operating conditions of this carbonization furnace are an air ratio of 0.15 and a temperature of 800 ° C. The obtained sludge activated carbon weighed 1/5 and became 20 kg. 20 kg of this sludge activated carbon is uniformly mixed with 100 dry sludges, granulated by a briquette machine, and has a diameter of 15 kg.
mm solid fuel was obtained.

The obtained solid fuel did not have any odor peculiar to sewage sludge, and was left at room temperature for 6 months, but did not rot or generate mold. This solid fuel could be burned in the same manner as RDF using municipal waste as a raw material. Knox in the exhaust gas is 50 ppm or less, which is lower than that in the case of burning RDF made from municipal waste, and the dioxin content is 0.1% as in the case of burning RDF.
ng / Nm ³ or less. However, the amount of socks is larger than that in the case where RDF is burned, and it is necessary to remove the socks by an exhaust gas treatment facility.

[0014]

As described above, according to the present invention, a solid fuel having no odor can be produced at low cost from only a raw material derived from sewage sludge. Therefore, the present invention is highly effective in achieving effective utilization of waste.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a manufacturing process of the present invention.

[Explanation of symbols]

 1 dryer, 2 carbonization furnace, 3 mixer, 4 molding machine

Claims (3)

[Claims] 1. A sewage sludge raw material characterized by adding sludge activated carbon obtained by carbonizing and activating a part of the dried sludge in a carbonization furnace to dry sludge of sewage sludge, mixing and granulating. A method for producing a solid fuel. 2. The method for producing a solid fuel using sewage sludge as a raw material according to claim 1, wherein the mixing ratio of sludge activated carbon to dry sludge is 5 to 100%. 3. The method for producing a solid fuel using sewage sludge as a raw material according to claim 1, wherein 1 to 10% of quicklime or slaked lime is added to the dried sludge in addition to the sludge activated carbon.