JPH0127985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing lightweight aggregate using coal ash containing unburned carbon generated in coal-fired power plants and the like as a raw material.

(Prior art) A method for producing lightweight aggregate using coal ash as a raw material is disclosed in Japanese Patent Application Laid-Open No. 58-92489 and Japanese Patent Application Laid-Open No. 1983-1989 by the present applicant.
Although it is already known from Publication No. 42490, etc., these prior arts focus on the fact that the amount of unburned carbon varies depending on the particle size of coal ash, and reduce the amount of unburned carbon by adjusting the particle size of coal ash. The coal ash was adjusted to 5.5 to 8.0% by weight, granulated, and then sintered in a sintering furnace, making it extremely practical in terms of effective utilization of coal ash. The adjustment process for the amount of unburned carbon is complicated, and since the amount of unburned carbon is small, the combustion rate is slow and sintering takes a long time.
The problem remained that the sintering furnace was also large.

(Objective of the Invention) The present invention solves the problems of the prior art and enables quick sintering with a simple process.
This was completed with the aim of producing a lightweight aggregate using coal ash as a raw material, which would allow for downsizing of equipment.

(Structure of the Invention) The present invention involves mixing coal ash containing unburned carbon with combustible powder containing volatile components selected from dried sludge powder or pulverized coal, and when dry sludge powder is used, the calorific value is to 400 to 700 Kcal/Kg, and if pulverized coal is used, the calorific value to 300 to 400 Kcal/Kg.
After granulating these raw material powders to a predetermined size, they are piled up in a sintering furnace, the whole is dried by preheating, and the surface is ignited using a deflagration ignition method that uses volatile components. It is characterized by suctioning and venting from below, causing self-combustion and sintering in the downward direction.

Next, to explain the embodiment of the present invention in detail using a flow sheet illustrating it, (1) is to store coal ash containing about 2 to 10% unburned carbon generated at a coal-fired power plant, etc. The main raw material is hoppa, (2)
is a combustible material hopper that stores combustible material powder such as pulverized coal or dried sludge obtained by drying dehydrated sludge generated from a sludge treatment plant. The coal ash from the main raw material hopper (1) is passed through a classifier (3) such as an air classifier to a particle size of 44 to 149μ.
After the particle size is adjusted to 10 to 40%, preferably 20 to 30%, the powder is fed to a humidifying kneader (4) such as a pug mixer together with the combustible powder in the combustible hopper (2). At this time, the mixing ratio of combustible powder to coal ash is 5 when the target lightweight aggregate is coarse particles with a particle size of 5 to 12 mm and pulverized coal is used as the combustible powder.
Assuming ~6%, the calorific value of the mixture is 375~400Kcal/
Kg, and when dry sludge is used as the combustible powder, the calorific value of the mixture is 600 to 14%.
Adjust to 700Kcal/Kg. In addition, when the target lightweight aggregate is fine particles with a particle size of 1 to 4 mm, and pulverized coal is used as the combustible powder, the mixing rate is 4 to 5 mm.
%, the calorific value of the mixture is 300 to 375 Kcal/Kg, and when dry sludge is used as the combustible powder, the mixing rate is 8 to 10%, and the calorific value of the mixture is 400 to 375 Kcal/Kg.
Adjust to ~600Kcal/Kg. In this way, when the particle size of the target lightweight aggregate is large, the calorific value of the mixture is set higher because larger particle sizes require more heat to proceed with sintering to the inside. . Further, when dry sludge is used as the combustible powder, the calorific value is set higher because the combustion rate is faster than that of pulverized coal, and a larger amount of heat is required for sintering. As mentioned above, it is important to adjust the calorific value of the mixture according to the combustible powder in order to obtain the desired lightweight aggregate, and if it deviates from these numerical limits, bursting and clinker may occur. I end up.

Such a mixture is kneaded inside the humidifying kneader 4 while receiving water from the water supply machine 5 so that the moisture content becomes 17 to 20%, and then the pan-shaped granulator 6 is used to adjust the particle size of the desired lightweight aggregate. It is granulated to the required size. Next, the granules classified into a predetermined particle size by the classifier 7 are sucked downward by a box-shaped sintering cart 9 having a grate 8 at the bottom and moving intermittently over a large number of wind boxes 10. The materials are stacked in the sintering cart 9 of a type of sintering furnace using a filling machine 11 to a thickness of 200 to 400 mm, and are preheated using an oil burner 12 for 40 to 50 minutes to dry the entire product. The sintering cart 9 on which the dried granules are piled up is transported by the drive device 16 and reaches below the ignition lid 13, where its surface is ignited. The ignition method is Damper 1 of Windbox 10.
4 is closed to stop the downward suction, the ignition lid 13 is placed on the top surface of the sintering cart 9, and the granules are heated with the ignition lid 13 for 30 to 90 seconds to volatilize from the granules. This is carried out by a deflagration ignition method in which components are generated, and when the upper space of the sintering cart 9 is filled with volatile gases, the damper 14 is opened to introduce outside air to cause explosive combustion. This deflagration ignition method has the advantage that the entire surface of the granules stacked on the sintering cart 9 is ignited evenly. The granules ignited in this way are ventilated through the wind box 10 while being suctioned downward at 50 to 150 mmAq by the exhaust gas fan 15 while the sintering cart 9 moves backward intermittently, and the granules are piled up. If the unburned carbon and combustible powder inside are allowed to self-combust, the calorific value can be reduced to 300~
The granules adjusted to 700Kcal/Kg burn downward rapidly, and the combustible powder is burnt out, and the coal ash in the granules is sintered and becomes porous granules. The material is discharged by reversing the sintering cart 9 and stored as lightweight aggregate in an aggregate silo. The sintering temperature is 1200 to 1400°C, and the time required for sintering is about 20 to 25 minutes. The obtained lightweight aggregate has excellent properties such as a crushing strength of 30 to 40 Kg/cm ² and a water absorption rate of 16 to 18%.

(Effects of the Invention) As is clear from the above description, the present invention adds combustible powder containing a volatile component selected from dried sludge powder or pulverized coal to coal ash containing unburned carbon at a combustion rate etc. The corresponding calorific value is 300~
The raw material powder is mixed and adjusted to 700Kcal/Kg, and then the raw material powder is granulated, piled up in a sintering furnace, dried by preheating, and then ignited by deflagration using volatile components. ignites the surface,
The aim is to obtain lightweight aggregate by self-combusting and sintering the unburned carbon in coal ash and combustible powder, and it is a combustible material whose calorific value is accurately known, such as pulverized coal or dried sludge. The calorific value can be easily and accurately adjusted simply by mixing a predetermined amount of powder, and the process before granulation can be simplified compared to the prior art. In addition, the present invention adjusts the calorific value to 300 to 700 Kcal/Kg, which is considerably higher than that of the prior art, allowing for rapid combustion, which has the advantage of reducing the size of equipment. Using a certain type of dried sludge has the advantage of extremely low running costs. As described above, the present invention solves the problems of the prior art, and since the lightweight aggregate obtained by the present invention has excellent strength, it can be used in a wide range of applications such as building materials, sound absorbing materials, and heat insulating materials. Together with the advantages it has, it makes a huge contribution 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 coal ash containing unburned carbon with dry sludge powder or combustible powder containing volatile components selected from pulverized coal, and when using dry sludge powder, reduce the calorific value to 400 to 700 kcal/Kg. In addition, when using pulverized coal, the calorific value is adjusted to 300 to 400 kcal/Kg, and this raw material powder is granulated to a predetermined size and stacked in a sintering furnace, and the whole is preheated. A lightweight bone made from coal ash, which is dried and then ignited on the surface using a deflagration ignition method using volatile components, and is suctioned from below while aerated, and then self-combusted and sintered downward. How the material is manufactured.