JPS6225620B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing artificial lightweight aggregate using fly ash as the main raw material, and in particular, by devising the particle size structure and blending ratio of materials mixed with fly ash, it is possible to produce lightweight aggregate with excellent water absorption. This is what I did. As a technology for utilizing fly ash generated from coal-fired boilers, etc., there is a technology to sinter granules made from fly ash as the main raw material to produce lightweight aggregate, and the present inventors have previously filed a patent application for an improved method. Showa 55
-112806, patent application No. 175020, etc. In other words, fly ash originally contains some unburned carbon, but if necessary, combustible carbon material (pulverized coal or coke) is added, water is used as a binder, and the mixture is kneaded and granulated to form raw pellets. This is then charged onto a moving grate and transported while drying, preheating, igniting, sintering, retaining heat, and cooling in order to produce an artificial lightweight aggregate. The lightweight aggregate thus obtained (lightweight aggregate A) has an apparent specific gravity of 1.3 to 1.5.
Since it is relatively small at g/ ^cm3 , it is expected to be used effectively as a lightweight aggregate for construction. However, general-purpose lightweight aggregate obtained by firing expanded rock in a rotary kiln (lightweight aggregate B: apparent specific gravity 1.2 to 1.3
g/cm ³ ), and in order to expand its use as a lightweight aggregate for construction, it is necessary to achieve a weight reduction comparable to that of lightweight aggregate B. On the other hand, the water absorption rate of lightweight aggregate A (water absorption rate after 24-hour immersion) is 10 to 18%, and the water absorption rate of lightweight aggregate B is 3.
It shows a much larger value compared to ~6%, and is more suitable than lightweight aggregate B for applications such as a humidity control material for concentrated horticulture, a watering material, and a fertilizing material in greenhouses and the like. However, in order to improve the adaptability to such uses, it is desirable to further increase the water absorption rate. As mentioned above, lightweight aggregate A satisfies the required quality for normal use, but there is a strong demand for further weight reduction and improved water absorption.If these points can be satisfied, fly aggregate use will be possible. It is expected that it will further expand. In particular, as the oil situation worsens, it is clear that coal-fired combustion will increase even more in the future, and it is extremely important to expand the fields in which fly ash can be effectively used, as this is expected to increase dramatically. Under these circumstances, the present invention was completed as a result of intensive research with the aim of establishing a manufacturing method that can reduce the weight of lightweight aggregate A and further improve its water absorption rate. Its composition is made by kneading fly assemblage as the main raw material and water as a binder.
In a method for producing porous aggregate, in which raw pellets obtained by rolling granulation are placed on a moving nuclear grate and sintered while being transferred, the raw pellet raw material has a particle size of 1.
Each of the following additive groups whose particle size content is 60 to 90% by weight: Coal ash: 5 to 30% by weight Coarse pulverized coal: 3 to 10% by weight Ground solids containing organic matter: 1 to 30% by weight The gist is that raw pellets are granulated by rolling by blending one or more selected from the following on the basis of the dry weight of all raw materials. The fly ash used in the present invention may vary slightly depending on the quality of the raw material pulverized coal burned in the boiler, etc., but the particle size of the fly ash used in the present invention is approximately 325 mesh or less.
The combustible carbon material is a fine powder that accounts for 70% by weight (hereinafter simply referred to as %), and may be added as necessary to improve the self-combustibility of raw pellets, with a particle size of 74 μm or less. About 70 things
% of pulverized coal is preferred. In the present invention, the above ingredients are basically the main ingredients, but one or more additives selected from the group consisting of relatively large-grained coal ash, coarse pulverized coal, and organic matter-containing solids are added to these ingredients. By sintering the granules with a composition added in a predetermined range, it was possible to obtain lightweight aggregate with good water absorption. All of the above three types of additives must have a particle size content of 60 to 90% of 1 mm or less, and by using particles with such a particle size composition, the porosity of the sintered pellets can be reduced. It is possible to achieve both the objectives of heightening, weight reduction, and high water absorption. i.e. particle size 1mm
If the amount exceeds too much, the bonding force will be poor and it will be difficult to granulate, and even if granules can be granulated, they will easily collapse during sintering and the yield will decrease. If the content is less than 60%, fine fly ash will be trapped between these particles, making it impossible to increase the porosity. Next, the reasons for setting the blending ratios for each of the above three types of additives will be explained. First, when adding coal ash, the blending ratio is based on the dry weight of all raw materials (based on anhydrous raw pellets, the same applies hereinafter).
If the blending ratio exceeds 30%, the coal ash will be coarse particles and will have poor binding strength, making it difficult to granulate. On the other hand, if it is less than 5%, the effect of improving porosity is insufficient and the effect of reducing weight and improving water absorption rate does not appear.
Examples of coal ash include bottom ash discharged from a coal-fired boiler etc. which is pulverized into the particle size range described above, and cinder ash discharged from the vicinity of the air heater or economizer of the boiler.
When only coal ash is used as an additive, it is desirable to mix pulverized coal as necessary to adjust the amount of internal carbon material contained in the raw pellets to 4 to 6%. Next, when adding coarse powder coal, the blending ratio must be selected from the range of 3 to 10% based on the raw pellets, and if the blending ratio exceeds 10%, the raw pellets will be added as is the case with coal ash. It becomes difficult to granulate the sintered product and the strength of the sintered product becomes weaker. On the other hand, if the content is less than 3%, it is impossible to reduce the weight of the sintered product or improve its water absorption rate. Examples of coarse pulverized coal include coarsely pulverized coal. Coarse pulverized coal contains a large amount of combustible carbon and has the effect of giving self-combustibility to the raw pellets, so it is not necessary to use pulverized coal together, but in any case, the inner carbon material contained in the raw pellets It is best to adjust the blending ratio so that the amount is 3 to 10%. In addition, when adding organic matter-containing solids, the blending ratio must be selected from the range of 1 to 30% based on the raw pellets, and if the blending ratio exceeds 30%, similarly,
It becomes difficult to granulate raw pellets, while 1
If it is less than %, it is not possible to reduce the weight of the sintered product or improve its water absorption rate. Examples of the ground material containing organic matter include pulp waste, sawdust, wood chips, plastic pieces, etc., ground to the above-mentioned particle size. When using solids containing organic matter, depending on the combustible carbon content, it is necessary to use an appropriate amount of pulverized coal in order to give the raw pellets self-combustibility, but in any case, the interior content of the raw pellets The amount of carbon material is 2
It is desirable to adjust it to ~6%. The three types of additives mentioned above can be incorporated into the fly ash basic composition individually, or they can be incorporated in an appropriate combination.In fact, the effects of the present invention can be further enhanced by the combination. The present invention is configured as described above, and it has become possible to provide a lightweight aggregate that is lightweight and has excellent water absorbency while maintaining sufficient strength for use in construction, etc. It is of great significance to make it widely available for other uses (such as lightweight aggregate for horticultural culture as mentioned above). Examples of the present invention will be described below. Example 1 Fly ash containing 3% unburned carbon (particle size 44μ)
Mix 10% of pulverized bottom ash (containing 60% of particles with a particle size of 1 mm or less) with 70% of particles with a particle size of 1 mm or less, and add pulverized coal of normal particle size to the mixture so that the carbon content is 5%. Add 16% water and granulate into pellets of approximately 12 mmφ. A tilted dish granulator was used for granulation (the same applies hereinafter). The pellets were charged into a Dwight Lloyd sintering machine to a thickness of approximately 300 mm, ignited by applying heat of 16,000 Kcal/m ² ·min for 2 minutes, and then sintered by self-combustion while suctioning from below. A pellet was obtained. Example 2 In the same fly ash as used in Example 1, 20% cinder ash (containing 30% particles with a particle size of 74μ or less and 80% particles with a particle size of 1 mm or less) was added.
After mixing, pulverized coal was added and mixed so that the internal carbon content was 5%, and about 17% of water was added to form pellets of about 12 mmφ, and then sintered pellets were made in the same manner as in Example 1. Obtained. Example 3 Coarsely crushed coal (70% of which had a particle size of 1 mm or less) was placed in a fly ash similar to that used in Example 1.
Mix 10% of (containing) and add about 16% of water to make approx.
It was granulated into pellets with a diameter of 12 mm. The pellets were charged into a Dwight Lloyd type sintering machine to a thickness of about 250 mm, preheated by applying a heat amount of 5.000 Kcal/ ^m2・min for 2 minutes, and then heated to a heat value of 16.000 Kcal/ ^m2・min. After being ignited for a few minutes, the pellets were sintered by self-combustion while suctioning from below to obtain sintered pellets. Example 4 Pulverized coal was added to the same fly ash as used in Example 1 so that the carbon content was 4%, and dried and ground sawdust (70% of which had a particle size of 1 mm or less) was added.
Add 10% of (containing) and add about 20% of water to make about 12mm.
After granulation into pellets of φ, sintered pellets were obtained in the same manner as in Example 3. Comparative example Pulverized coal (containing 67% particles with a particle size of 74 μm or less) was added to the same fly ash as used in Example 1.
was added to make the carbon content 5%, and 17% water was added to make raw pellets of approximately 12mmφ, which were prepared in Example 1.
Sintered pellets were obtained in the same manner as above. Table 1 shows the apparent specific gravity, water absorption rate, and crushing strength of each sintered pellet obtained in the above examples and comparative examples.

[Table] is fine.

Claims (1)

[Claims] 1. Kneading fly ash generated from a coal-fired boiler etc. as the main raw material and water as a binder,
In a method for producing porous aggregate in which raw pellets obtained by rolling granulation are sintered while being transferred on a moving grate, the raw pellet raw material contains a particle size fraction of 1 mm or less. A method for producing porous aggregates, which comprises blending 60 to 90% by weight of one or more selected from the following additive groups based on the dry weight of the total raw materials and rolling granulation. Coal ash: 5 to 30% by weight Coarse pulverized coal: 3 to 10% by weight Ground material of organic matter-containing solids: 1 to 30% by weight 2. In claim 1, raw pellets granulated by blending coal ash. The combustible carbon content is 4~
A method for producing porous aggregate containing 6% by weight. 3 In claim 1, raw pellets granulated with coarse powdered coal have a combustible carbon content of 3 to 3.
A method for producing porous aggregate containing 10% by weight. 4. The method for producing porous aggregate according to claim 1, wherein the raw pellets granulated by blending the ground material containing organic matter contain 2 to 6% by weight of combustible carbon.