JPH0233659B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing cement, and more particularly, to a method for manufacturing cement that can solve the problem of false setting of cement and the difficulty in supplying gypsum. To adjust the setting time of cement,
It is necessary to adjust the SO ₃ content to approximately 2% by weight.
Conventional cement clinker contains about 0.5% _SO3 by weight
When it is crushed to make cement, it is necessary to add gypsum during the clinker crushing process. The gypsum used in this case is dihydrate gypsum (CaSO ₄ .2H ₂ O), but there is no problem as long as the temperature of the pulverized material in the cement mill during pulverization is about 110°C. However, since its temperature usually reaches about 130°C and sometimes about 180°C, the majority of dihydrate gypsum is either hemihydrate gypsum (CaSO ₄ 1/2H ₂ O) or soluble anhydrous gypsum (CaSO ₄ ). It's getting old. These hemihydrate gypsum and soluble anhydrous gypsum have the disadvantage that when the cement containing them is mixed with water, they become dihydrate gypsum again, and the cement tends to cause false setting. Additionally, approximately 5.5 million tons of gypsum is currently produced annually as a by-product of industries such as the chemical industry and thermal power plants. However, in recent years in Japan, the development of using gypsum as a noncombustible building material has made it difficult to provide a stable supply to the cement industry, and there is a desire for another source of gypsum to be supplied. The present inventors conducted experiments to solve the problem of false setting and the difficulty in supplying gypsum. As a result, in the cement firing process, the cement raw material was supplied to the cement clinker manufacturing equipment, and sulfur or sulfur-containing compounds ( The present invention was completed based on the knowledge that the problem could be solved by feeding the clinker (hereinafter referred to as sulfur raw material) from a specific location, adding a specific amount of gypsum to the resulting clinker, and pulverizing the resulting clinker. That is, the gist of the present invention is, in a cement manufacturing method using a rotary kiln with a suspension preheater, supplying cement raw materials to the rotary kiln via the suspension preheater,
Furthermore, a sulfur-containing compound or a sulfur-containing compound is fed alone into the part of the suspension preheater where the gas temperature is 850°C or higher to the kiln outlet end and fired, and the obtained clinker is used as it is or added per clinker ton. There is a method for manufacturing cement characterized by adding and crushing 16 kg or less of gypsum. In the rotary kiln with a suspension preheater used in the present invention, for example, 4 to 5
A conventional type is used in which multiple cyclones are provided in each stage, and each cyclone is connected to the adjacent one through a ventilation duct, so that the exhaust gas of the rotary kiln and the raw material for cement clinker exchange heat. . An example is shown in the figure. The inlet for the sulfur raw material must be located at a point in the exhaust gas passage of the rotary kiln or suspension preheater where the internal temperature is 850°C or higher.
In the figure, the kiln bottom 14 and the rotary kiln outlet end 15 are examples of raw material input ports, but from the viewpoint of combustion efficiency, it is preferable that the feeding point is the rotary kiln exit end. The above points are in order.
If the temperature of the sulfur input point is below 850℃, the combustion heat of the sulfur cannot be used effectively, and SO ₂ is emitted in the exhaust gas.
This is undesirable because it pollutes the air. In addition, the amount of gypsum added to the sulfur raw material when clinker is crushed is 16 per ton of clinker.
It is necessary to adjust the supply amount so that it is less than Kg. The reason for this is that when the amount of gypsum added when crushing clinker increases, it causes false coagulation. According to the present invention, instead of gypsum, which is in short supply in the industry, a sulfur source, which is in surplus, can be used and contained as SO ₃ in cement clinker. Further, since the amount of gypsum added to the resulting cement clinker is zero or small, false setting of the cement is extremely reduced. Furthermore, there is no air pollution caused by sulfur combustion.
The combustion heat can be used effectively. Examples Next, the present invention will be described with reference to examples. Examples 1 to 3, Comparative Example 1.2 The rotary kiln with suspension preheater shown in the figure was used. Commercially available liquid simple sulfur was used, and its inlet was placed in parallel with the fuel combustion burner at the outlet end 15 of the rotary kiln, and the mixture was blown into the rotary kiln at the blending ratio with cement clinker shown in Table 1. Each obtained cement clinker was analyzed and each cement clinker was
Add gypsum so that SO ₃ is approximately 2.0% by weight,
The obtained mixed composition was pulverized at the temperature shown in Table 1 to give a specific surface area of approximately 3200 cm ² /g to obtain cement. Regarding the obtained cement, JISR5201−1977
False coagulation was measured according to the coagulation test. That is, a standard softness paste was prepared using the cement to be measured, poured into a mold with a depth of 35 mm, and a descending rod was inserted over time to determine the penetration depth. The smaller the numerical value of this penetration depth, the stronger the degree of false coagulation. The results are shown in Table 2. Furthermore, data on setting, bending strength, and compressive strength are also listed in the same table.

【table】

[Table] As is clear from Table 2, the cement obtained according to the present invention had extremely reduced false setting, and was able to eliminate practical quality problems.

[Brief explanation of drawings]

1 is a schematic diagram of a cement clinker manufacturing apparatus used for manufacturing cement clinker according to an embodiment of the present invention. 1: rotary kiln, 2, 3, 4, 5: cyclone, 6, 7, 8: ventilation duct, 9: exhaust passage,
10: kiln bottom, 11: kiln outlet end, 12: raw material inlet, 13: combustion burner, 14, 15: sulfur raw material inlet, 16: exhaust windmill.

Claims (1)

[Claims] 1. In a cement manufacturing method using a rotary kiln with a suspension preheater, cement raw materials are supplied to the rotary kiln via the suspension preheater, and sulfur or sulfur-containing compounds are added alone to a location where the gas temperature of the suspension preheater is 850°C or higher. The clinker is fed into the area from
A method of manufacturing cement characterized by adding and crushing gypsum of less than 1 kg.