JPH0127986B2 - - 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. 1988-
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, thoroughly predried in a sintering furnace, and then ignited and sintered, making it extremely practical in terms of effective utilization of coal ash. However, the process of adjusting the amount of unburned carbon before granulation is complicated, requires a large amount of fuel for preliminary drying, and the combustion rate is slow due to the small amount of unburned carbon, making it difficult to sinter. The sintering furnace required a large sintering furnace because it took a long time to dry and required space for preliminary drying.

(Objective of the Invention) The present invention solves the problems of the prior art, enables quick sintering with a simple process, downsizes equipment, and is economical with low fuel consumption. It was completed with the aim of producing a lightweight aggregate using coal ash, which has high properties, as a raw material.

(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 750 to 1150Kcal/Kg, and if pulverized coal is used, the calorific value to 450 to 600Kcal/Kg.
The raw material powder is granulated to a predetermined size, stacked in a sintering furnace, and only the surface layer is dried, while the inside remains moist, using the deflagration ignition method that uses volatile components. It is characterized in that it is ignited, sucked in from below and ventilated, and then self-combusted and sintered downward.

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, with a particle size of 44 to 149μ.
After the particle size is adjusted to 10 to 40%, preferably 20 to 30%, the powder is supplied to a humidifying kneader 4 such as a pug mixer together with the combustible powder in the combustible hopper 2. In this case, the mixture ratio of combustible powder to coal ash is 7 to 8% 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. 525～
The calorific value of the mixture is adjusted to 600 Kcal/Kg, and 18 to 23% when dry sludge is used as the combustible powder to 900 to 1150 Kcal/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 6 to 7% and the calorific value of the mixture is 450 to 450.
525 Kcal/Kg, and when dry sludge is used as the combustible powder, the mixing rate is 15-20% and the calorific value is adjusted to 750-1000 Kcal/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. In the method of the present invention, the calorific value is
If it is less than 450 Kcal/Kg, sintering will be insufficient, and if it is more than 1150 Kcal/Kg, the granules will melt and clinker will easily form. 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 further heated by the pan-shaped granulator 6 to achieve the desired lightweight. Granules are granulated to the required size depending on the particle size of the aggregate. 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 granules are stacked in the sintering cart 9 of this type of sintering furnace using a filling machine 11 to a thickness of 200 to 400 mm, and this granulated material is
Pre-drying is performed for a very short time of about 5 minutes to dry only about 5 mm of the surface layer. In this way, the amount of heat required to dry only the surface layer is about 1/10 of the conventional amount of heat required for complete drying, which was 400,000 Kcal per ton of coal ash, and is sufficient.
Conventionally, a large space was required on the sintering furnace for pre-drying for 40 to 50 minutes, but there is an advantage in that this can be omitted. The sintering cart 9 stacked with granules whose surface layer portions have been dried is transported by the drive device 12 to reach the lower part of the ignition lid 13, where the surface thereof is ignited. The ignition method is to close the damper 14 of the wind box 10 and stop the downward suction, and then move the ignition lid 13 to the sintering cart 9.
Put a lid on the top surface and use the ignition lid 13 to heat the granulated material for 30 to 30 minutes.
It is heated for 90 seconds to generate volatile components from the granules, and when the volatile gas fills the upper space of the sintering cart 9, the damper 14 is opened to introduce outside air and cause explosive combustion. It is carried out using the deflagration ignition method. This deflagration ignition method has the advantage that the entire surface of the granules stacked on the sintering cart 9 is ignited evenly. The ignited granules are transported from the wind box 10 to the exhaust gas fan 15 while the sintering cart 9 moves backward intermittently.
If the unburned carbon and combustible powder in the stacked granules are self-combusted by aeration while sucking downward at 150 mmAq, the granules with a calorific value adjusted to 450 to 1150 Kcal/Kg will be internally heated. The granules, which are in a wet state, gradually move downward while drying and quickly burn, burning away the combustible powder and sintering the coal ash in the granules to form porous granules. The heavy granules are 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 25 to 30 minutes. The resulting lightweight aggregate has a crushing strength of 30-40
Kg/cm ² and water absorption rate of 16-18%.

(Effects of the Invention) As is clear from the above description, the present invention applies combustible powder to coal ash containing unburned carbon containing volatile components selected from dry sludge powder or pulverized coal at a combustion rate etc. The corresponding calorific value is 450~
The raw material powder is mixed and adjusted to 1150Kcal/Kg, and then this raw material powder is granulated and piled up in a sintering furnace to dry only the surface layer, leaving the inside moist to produce deflagration using volatile components. The ignition method is used to ignite, and the unburnt carbon in the coal ash and combustible powder are self-combusted and sintered to obtain lightweight aggregate, and the calorific value of pulverized coal and dried sludge is accurate. The calorific value can be easily and accurately adjusted simply by mixing a predetermined amount of combustible powder, which is known in the art, and the process before granulation can be simplified compared to the prior art. In addition, since a large amount of fuel is not required for pre-drying, the total amount of heat required in the method of the present invention is 60 to 70% of the conventional method, even when adding up the amount of heat added to the raw material as combustible powder. The amount of expensive oil used for preheating can be reduced, and cheap pulverized coal and dry sludge, which cost almost nothing, can be used, so fuel costs can be reduced to about 1/3 of conventional methods. Moreover, the present invention has the advantage of being able to eliminate the part used for pre-drying in the sintering furnace, making it possible to downsize the equipment, and the lightweight aggregate obtained by the present invention has a high strength. Since it is an excellent product, it has the advantage of having a wide range of uses such as building materials, sound-absorbing materials, and heat-insulating materials, and it is an extremely important 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 combustible powder containing volatile components selected from dry sludge powder or pulverized coal, and when using dry sludge powder, increase the calorific value to 750 to 1150 Kcal/Kg. In addition, when using pulverized coal, the calorific value is adjusted to 450 to 600 Kcal/Kg, and this raw material powder is granulated to a predetermined size and then stacked in a sintering furnace to dry only the surface layer. Coal ash is used as a raw material, and is ignited by a deflagration ignition method using volatile components while the inside is still wet, and is suctioned from below while ventilating, and then self-combust and sinter downward. A method for producing lightweight aggregate.