JPH06329453A - Production of cement - Google Patents

Abstract

PURPOSE:To provide a method for producing a cement having the same quality as that of a conventional cement clinker, capable of easily burning non-burnt carbon contained in a carbon ash, by directly blowing the coal ash into a cement kiln from its front part and burning the non-burnt carbon in the coal ash in the cement kiln. CONSTITUTION:This method for producing a cement by mixing a cement raw material with a coal ash and calcining the mixture, when the cement raw material is calcined in a cement kiln, is to directly blow the coal ash into the cement kiln from its front part, burn non-burnt carbon contained in the coal ash, add the residual ash to a cement clinker, and to subsequently calcine the mixture. The method enables to easily burn the non-burnt carbon in the coal ash, utilize the generated heat as the combustion energy for the cement clinker, and produce a cement having the same quality as that of a conventional cement clinker, because the produced carbon-free coal ash is solid-dissolved in the cement clinker.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cement in which coal ash is mixed, and more particularly to a technique applicable even when unburned carbon is mixed in the coal ash.

[0002]

2. Description of the Related Art The amount of coal ash discharged from a coal-fired power plant is increasing year by year, and it is feared that the disposal site will be insufficient. On the other hand, as one of the methods for effectively utilizing coal ash, a method is known in which coal ash is mixed in cement and used as a cement material for producing mortar or concrete. FIG. 2 is for explaining an outline of a conventional method for producing a coal ash mixed cement, in which reference numeral 1 is a raw material mixing silo, 2 is a preheater, 3 is a rotary kiln, 4 is a burner, 5 is a cooler. Is. In the production of coal ash mixed cement by the conventional method, coal ash is added to a cement raw material in which limestone or clay is finely pulverized, and the raw material mixing silo 1 mixes the mixture uniformly, and the mixed raw material is introduced into the preheater 2. While moving sequentially in the furnace arranged in multiple stages, the mixed raw material is preheated by the high temperature exhaust gas from the rotary kiln 3, the preheated mixed raw material is calcined in the rotary kiln 3, and further cooled through the cooler 5 to produce a clinker. . Gypsum and the like are added to the obtained clinker, and the mixture is ground and mixed in a cement mill to obtain a product cement.

[0003]

However, the use of coal ash as a cement admixture has the following problems. In the case of thermal power generation using coal as a fuel, strict regulations are applied to its combustion conditions in order to reduce emissions of air pollutants, and unburned carbon in coal ash tends to increase accordingly. Increasing coal ash is unsuitable for use as a cement admixture. Further, since coal ash has a lower melting temperature than that of the cement raw material, if a large amount of this is added to the cement raw material, the coating may adhere to the preheater portion that preheats the cement raw material, which may cause a problem in operation.

The present invention has been made in view of the above circumstances, and can be applied to coal ash mixed with unburned carbon, and even if a large amount of coal ash is used, it does not hinder the operation. It is an object of the present invention to provide a manufacturing method capable of manufacturing cement mixed with coal ash.

[0005]

In order to solve such problems, the present invention is to blow coal ash directly into the cement kiln from the kiln front part of the cement kiln, and burn unburned carbon contained in the coal ash. At the same time, the remaining ash was mixed in cement clinker and fired.

[0006]

[Operation] By blowing coal ash directly into the cement kiln, burning the unburned carbon contained in the coal ash, and mixing the remaining ash with the cement clinker and firing it, the unburned carbon in the coal ash is removed. It can be easily burned, and its heat can be used as the burning energy of the cement clinker, and since coal ash that does not contain carbon dissolves in the cement clinker,
The quality of cement is the same as that of ordinary cement clinker.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 illustrates an example of a method for producing cement according to the present invention. In this method, a cement raw material obtained by finely crushing limestone or clay is uniformly mixed in a raw material mixing silo 1 and the cement raw material is preliminarily mixed. While introducing into the heater 2 and sequentially moving through the furnaces arranged in multiple stages, the high temperature exhaust gas from the rotary kiln 3 preheats the mixed raw material, and then the preheated cement raw material is carried into the rotary kiln 3 for high temperature firing. A blowing tube 6 for coal ash is installed in the kiln front part of the rotary kiln 3, and the coal ash is blown directly into the rotary kiln 3 and mixed with the cement raw material and fired.

As the coal ash used here, coal ash from a coal-fired power plant or the like is used, and the coal ash may contain unburned carbon. The coal ash to be used is dried, finely pulverized if necessary, and kept in a state in which it can be easily blown into the rotary kiln 3 through the blowing pipe 6.

Air is usually used as a carrier gas for carrying the coal ash by air flow. In general, the exhaust gas from the rotary kiln 3 contains little oxygen gas,
If oxygen gas is present in the carrier gas for blowing in the coal ash, the unburned carbon in the coal ash can be easily burned.

The unburned carbon in the coal ash is blown into the rotary kiln 3 and is instantly burned to form ash containing no unburned carbon, which is mixed with the cement raw material, and fired at a high temperature in the rotary kiln 3 to produce the cement raw material. And ash form a solid solution to form a cement clinker, which is cooled through a cooler 5 and taken out from the rotary kiln 3. The obtained clinker is added with gypsum and the like and crushed and mixed with a cement mill to obtain a product cement, as in the case of a normal cement clinker.

As described above, coal ash is directly blown into the cement kiln to burn unburned carbon contained in the coal ash, and the remaining ash is mixed in the cement clinker to be burned. Unburned carbon can be easily burned, and its heat can be used as the burning energy of cement clinker, and since coal ash containing no carbon forms a solid solution in cement clinker, it has the same quality as ordinary cement clinker. To obtain cement. Hereinafter, the effects of the present invention will be clarified by experimental examples.

(Experimental example) The following experiment was carried out in order to grasp beforehand the properties of cement when coal ash was directly blown into the cement kiln. After calcining the sized cement raw material in an electric furnace at 1000 ° C, adhering coal ash around this and heating to 1450 ° C and heating for 1 hour, 5% of gypsum was added to the clinker, and the mixture was crushed with a ball mill. Brain 3
Trial cement was prepared by grinding to 300 cm ² / g. The mortar strength of this cement was compared with the test results of the cement prepared from the clinker of ordinary cement.
It measured according to ISR5201. The results are shown in Table 1 below.

[0013]

[Table 1]

As is clear from Table 1, the mortar strength of the trial cement produced by adding coal ash is 3 when compared with the cement prepared from the clinker of ordinary cement.
Although the strengths on the 1st and 7th days were slightly lower, the strength on the 28th day was the same, and there was no problem in quality, and it was possible to put it into practical use.

[0015]

As described above, in the method for producing cement according to the present invention, the coal ash is directly blown into the cement kiln to burn the unburned carbon contained in the coal ash and the remaining ash in the cement clinker. The unburned carbon in the coal ash can be easily burned by mixing with and burned, and the heat can be utilized as the burning energy of the cement clinker, and the coal ash that does not contain carbon is mixed in the cement clinker. Since it forms a solid solution, it is possible to obtain cement of a quality equivalent to that of ordinary cement clinker.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram for explaining an example of a method for producing cement according to the present invention.

FIG. 2 is a schematic configuration diagram for explaining a conventional method for producing a coal ash mixed cement.

[Explanation of symbols]

1 ... Raw material mixing silo, 2 ... Preheater, 3 ... Rotary kiln, 4 ... Burner, 5 ... Cooler.

Claims (1)

[Claims] 1. A method for producing cement by firing coal ash in a cement raw material when firing the cement raw material in the cement kiln, in which coal ash is directly blown into the cement kiln from the kiln front part of the cement kiln. A method for producing cement, which comprises burning unburned carbon contained in the coal ash and mixing the remaining ash with a cement clinker and firing the mixture.