JPH0359026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing lightweight aggregate using sludge such as sewage sludge as a raw material.

(Prior art) Conventionally, in order to manufacture lightweight aggregates using sludge such as sewage sludge as a raw material, auxiliary materials such as bentonite, clay, and shale have been added to increase granulation strength, expandability, and foamability. After adding it to the raw material sludge, binders such as lignin, CMC, PVA, and water glass are added to granulate it, and the granules are sintered using external heat in a rotary kiln, airflow sintering furnace, etc. Since the method is hot, large amounts of auxiliary raw materials, binders and fuels are required, which has the drawback of increasing equipment costs, running costs and manufacturing costs. In addition, the purpose of producing lightweight aggregate using sludge as a raw material is to reduce the volume and weight of the generated sludge, stabilize it so that heavy metals do not elute, and facilitate the reduction and securing of disposal sites, as well as the effective use of sludge. However, the conventional manufacturing method has the disadvantage that the amount of lightweight aggregate generated is extremely large compared to the amount of sludge generated.

(Objective of the Invention) The present invention solves the above-mentioned drawbacks and reduces the amount of auxiliary raw materials, binders, fuel, etc. used, thereby reducing equipment costs, running costs, and manufacturing costs, as well as reducing the amount of materials generated in various industries. This was completed with the aim of producing a lightweight aggregate using sludge as a raw material, which would enable the disposal and effective use of sludge, which is difficult to treat and dispose of.

(Structure of the invention) The present invention mixes sludge incineration ash with combustible powder mainly composed of dried sludge powder to increase the calorific value from 150 to 150.
After the raw material powder adjusted to 500Kcal/Kg is granulated to the required size, the granules are stacked in a downward suction type sintering furnace, ignited from above, and air is supplied from above. It is characterized by sintering by self-combustion without moving the granules by suctioning from below and without heating from the outside.

(Example) Next, an example of the present invention will be described in detail with reference to a flow sheet illustrating a sintering furnace 1 for incinerating dehydrated sludge generated from a sludge treatment plant.
The sludge incineration ash obtained by sintering and crushing or crushing is stored in the main raw material silo 3 as a main raw material containing a large amount of inorganic powder. 2 is a dryer for drying dehydrated sludge, which is installed separately from the sintering furnace 1 and dries a part of the dehydrated sludge without sintering;
The dried sludge is crushed and classified into dry sludge, and the dried sludge is stored in the auxiliary raw material silo 4 as the main material for combustible powder as an auxiliary raw material, and is added to the dried sludge as needed to form combustible powder as an auxiliary raw material. Other combustible materials such as pulverized coal, which become part of the pulverized coal, are stored in another auxiliary raw material silo 5. 6 is a classifier for classifying the sludge incineration ash supplied from the main raw material silo 3, and the sludge incineration ash stored in the main raw material silo 3 is divided into predetermined particle sizes, e.g. coarse incinerated ash powder of 44μ or more, and incineration ash coarse powder of 44μ or less. The incinerated ash is classified into fine incinerated ash powder and stored in the incinerated ash coarse powder silo 7 and the incinerated ash fine powder silo 8 which are arranged in parallel with the auxiliary raw material silos 4 and 5. Then, the amount of combustibles contained in the coarse incinerated ash powder, fine incinerated ash powder, dried sludge, and other combustibles added as necessary is measured, and the optimal amount is determined from both granulation and combustion perspectives. The ratio is set using the mixing ratio setting device 9 so that the desired mixing ratio can be obtained, and according to the ratio, the coarse incinerated ash powder, the fine incinerated ash powder, the dried sludge, and other combustible materials are quantitatively mixed from the weighing machine 10 into the mixer. 11, sludge incineration ash, which serves as the main raw material, is mixed with combustible powder, which serves as an auxiliary raw material, to obtain a raw material powder with a calorific value adjusted to 150 to 500 Kcal/Kg. Incidentally, the amount of combustible powder in the raw material powder is generally about 5 to 15% by weight in many cases. Next, this mixed and adjusted raw material powder is supplied with water by a water supply machine 12 and humidified and kneaded by a humidifying kneader 13 such as a pug mixer so that the water content becomes 5 to 20% by weight, and primary aggregation for granulation is performed. After that, in order to further increase the granulation strength, a predetermined proportion, for example 2 to 5, is added to the raw material powder.
% binder is supplied from a binder silo 14, and then humidified and granulated in a granulator 15 such as a pan-type pelletizer to form granules with a moisture content of 10 to 25% by weight and a desired size, for example, a particle size of 0.3 to 20 mm. Granulate into Next, the granules classified into a predetermined particle size by the classifier 16 are transferred to a downward suction type sintering machine in which a box-shaped sintering cart 21 having a grate 17 at the bottom moves over a large number of wind boxes 22. 200~ in the sintering cart 21 of the sintering furnace
The filling machine 18 stacks the materials to a thickness of 400 mm, and the sintering cart 21 loaded with the stacked materials is transferred to the drive device 2.
3 to the ignition chamber 19, the surface of the stack is initially ignited by the ignition burner 20, and further, while it is being transferred from the ignition chamber 19, it is ventilated while being suctioned downward at 5 to 150 mmAq from the wind box 22 by the exhaust gas fan 24. If the combustible powder in the piled up granules is self-combusted, the combustible powder will be burned out and the sludge incineration ash in the granules will be sintered and become porous granules. The heavy granules are discharged by reversing the sintering cart 21 and stored in the aggregate silo 25 as lightweight aggregate. The conditions necessary for the sintering are, for example, maintaining the temperature at 1000 to 1100°C for several minutes, blowing high-temperature hot air downward to dry the granules in the lower layer, and applying heat to the surface layer of this stack. A certain granule is combusted, and then it is ignited to move the combustion position downward one by one, and when the combustion position reaches the grate 17 surface, the sintering cart 2
Sintering of all layers of the stack in 1 is completed. In addition, the calorific value of the raw material powder was limited because the type and amount of combustible powder contained in sludge varies considerably depending on the season and date and time, and the relationship between the amount of combustible material in dried sludge and the calorific value is not constant. Therefore, it is not appropriate to limit the amount of combustibles to the sludge weight by expressing it as a weight percentage. Therefore, for sludge where the type and amount of combustibles are almost fixed, the amount of combustibles should be managed as a weight percentage to the sludge weight. By doing so, it is also possible to manage the amount of heat generated.

The raw material powder that can be used in the present invention contains almost no combustible materials, and may also contain unburned carbon and organic matter, such as incineration ash of various sludges such as municipal waste and sewage sludge. The calorific value of the raw material powder is adjusted to 150 to 500 Kcal/Kg by adding and mixing dry waste, dry sludge, sawdust, pulverized coal, plastic powder, and other combustible powder. The reason for limiting the above range is that if the calorific value is less than 15 Kcal/Kg, the energy required for self-combustion and sintering of the granules will be insufficient, and the unburned portion will increase, resulting in a decrease in compressive strength. To prevent this, it is necessary to supply external energy such as high-temperature hot air, which requires equipment and fuel consumption, leading to an increase in product cost. If the temperature exceeds this value, the granules will melt and clinker will form and fuse, making it unsuitable as a porous body, and also making it difficult to transport from the sintering cart, which is undesirable. Furthermore, in the Examples, the reason why incinerated ash coarse powder and incinerated ash fine powder are mixed as sludge incinerated ash is that there is a difference between the particle size of sludge incinerated ash and the amount of combustible matter, since the amount of combustible matter in the coarse powder is generally large, and the fine powder is This is because there is a relationship between the amount of combustible materials in the sludge incineration ash and the fact that it is easier to mold it when a moderate amount of fine powder and coarse powder are mixed. It may be sufficient to simply cut particles smaller than or larger than the particle size, or in extreme cases, it may be left as is. In addition, in order to have granulation strength to the extent that the granules do not easily break during granulation and drying, binders such as CMC, PVA, and water glass are added to the raw material powder as shown in the examples. It is preferable to add about 5% by weight and coat the surface of the granules or mix them. The combustible powder is made from sludge incineration ash obtained by incinerating dehydrated sludge as the main raw material, and dried sludge obtained by drying a part of the dehydrated sludge as an auxiliary raw material, which is mixed and granulated and sintered to make it lightweight. If aggregate is manufactured, surplus heat generated in the incineration process can be recycled and used in the drying process and incineration process, so the system has extremely high thermal efficiency and is preferable in terms of energy conservation. The main raw material is dried sludge and pulverized coal as secondary raw materials, and several types of main raw materials and several types of composite materials are combined depending on the amount of sludge generated, the properties of the sludge, and the properties of the final product. Materials may also be manufactured.

(Effects of the Invention) As is clear from the above description, the present invention is made by mixing and adjusting combustible powder mainly composed of dried sludge powder with sludge incineration ash so that the calorific value is 150 to 500 Kcal/Kg. This method aims to obtain lightweight aggregate by pulverizing the raw material powder, stacking it in a sintering furnace after granulating it, and sintering it by self-combustion.In addition to the raw material sludge, a large amount of auxiliary raw materials and binders are used. without needing,
Since lightweight aggregates can be produced using almost only raw material sludge, such as a combination of sludge incineration ash obtained by incinerating raw material sludge and dried sludge obtained by drying raw material sludge, there is little increase in the amount of sludge to be disposed of, and moreover, there is no need to increase the amount of sludge in the raw material sludge. This makes it possible to effectively utilize combustible materials such as municipal waste, sewage sludge, etc., which are generated in large quantities from various industries and are difficult to dispose of. It has the great advantage that inorganic waste such as incineration ash and silica sand, and dried sludge such as sewage sludge and clean water sludge can be used to dispose and effectively utilize organic waste such as sawdust and pulverized coal at the same time. Since the lightweight aggregate obtained by the present invention has excellent strength, it has the advantage of being used in a wide range of applications such as building materials, sound absorbing materials, and heat insulating materials, and together with this, it will greatly contribute to the development of the industry. .

[Brief explanation of drawings]

The drawing is a flow sheet showing an embodiment of the invention.

Claims (1)

[Claims] 1 Mix sludge incineration ash with combustible powder mainly composed of dried sludge powder to adjust the calorific value to 150 to 500 Kcal/Kg, granulate the raw material powder to the required size, and then pour the granulated material downward. They are stacked in a suction type sintering furnace and ignited from above, and by supplying air from above and suctioning from below, self-combustion occurs without moving the granules or heating them from the outside. A method for producing lightweight aggregate using sludge as a raw material, which is characterized by sintering.