JP2002029791A - Firing process of cement clinker raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement clinker raw material firing process by which cement clinker having stable quality can be produced even when a combustible synthetic resin is employed as a fuel for a rotary kiln used. SOLUTION: This firing process involves injecting a combustible synthetic resin employed as an auxiliary fuel at an injection velocity lower than that of a main fuel and also at a <=20 deg. angle of the whirling motion, together with the main fuel, into a rotary kiln to fire a cement clinker raw material, wherein the maximum ratio of the calorific value supplied from the auxiliary fuel to the total calorific value supplied from all the fuels used is 70%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for firing a raw material of cement clinker using a combustible synthetic resin as an auxiliary fuel.

[0002]

2. Description of the Related Art Flammable synthetic resins such as plastics have an extremely high calorific value of about 10,000 Kcal / Kg and can be used as fuel. Among these resins, chlorine-containing resins such as vinyl chloride, which are produced in large quantities, are heated to about 800 ° C
Since harmful dioxins are generated by the following calcination, it is necessary to burn in a high temperature region where dioxins are decomposed.
For this reason, utilization of fuel in a cement clinker manufacturing apparatus (rotary kiln) in which firing is performed at 1400 to 1500 ° C. is being studied. In this case, it is generally known that the fuel is introduced from before the rotary kiln kiln in a use form that replaces a part of a normal fuel such as heavy oil and / or pulverized coal. As disclosed in JP-A-7-277788, JP-A-8-283051, JP-A-8-283052 and JP-A-8-283053, the combustion of plastic in a rotary kiln is performed by landing and burning at an appropriate landing or falling range in the rotary kiln. The fired product obtained is generally fired in an oxidizing atmosphere in the same manner as fired with a normal fuel, so that a fired product of stable quality is obtained.

[0003] However, strict adjustment of the landing and falling range of the input fuel due to landing combustion is not only visually difficult to grasp the behavior during combustion, but also considerably affected by the form of the input. Therefore, it is not very easy. For example, when a part of the combustible material having a large particle size (approximately several mm to 20 mm) is included, some of the combustible material falls near the kiln cooler entrance without burning to reach a desired drop position and burns. If something that lands and deviates from a desired position is seen, regardless of the degree, a part of the cement clinker is fired in a reducing atmosphere, and the quality of the clinker, particularly the color tone, is liable to change significantly. To prevent this phenomenon, for example, the input fuel should be pulverized as a whole to a size comparable to pulverized coal fuel,
Pulverization of plastics is not easy because the pulverized material also functions as a buffer, and requires extremely high processing costs. Furthermore, flammable synthetic resins have a higher ignition temperature and a longer time to complete combustion than ordinary fuels, so combustion efficiency is generally inferior, and a large amount of such synthetic resins is used as fuel for clinker firing. Has practical limitations.

[0004]

When a combustible synthetic resin is used as a burning fuel, the main cause of deterioration of the cement clinker is landing combustion of the fuel, that is, when burning on the burning material, the burning material becomes a reducing atmosphere combustion. And the increase in the proportion of flammable synthetic resin in the fuel, the radiant heat transfer from the main fuel flame decreases, the ignition delay of the resin becomes remarkable, and the burning temperature decreases easily. Can be The present invention
It is an object of the present invention to provide a method of firing a raw material of a cement clinker which eliminates such a cause of deterioration of a cement clinker and can obtain a stable clinker even when a flammable synthetic resin is used as a part of a fuel. .

[0005]

As a result of various studies, the inventors of the present invention have found that a combustible synthetic resin can be space-burned without landing combustion, and a main fuel of an auxiliary fuel that does not lead to a decrease in the burning temperature. The present invention was completed because a cement clinker of stable quality was obtained by sintering the clinker raw material while determining an alternative use rate for the clinker.

That is, the present invention relates to a method of injecting a combustible synthetic resin into a rotary kiln as an auxiliary fuel at a main fuel ejection speed or less and a turning angle of 20 ° or less, and firing a cement clinker raw material together with the main fuel. The amount of heat supplied from the fuel accounts for at most 70% of the amount of heat supplied from the whole fuel.

Further, the present invention is the above method for firing a raw material of cement clinker, wherein the auxiliary fuel is a powder having a particle size of 1 mm or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material of cement clinker used in the production of cement clinker in the present invention may be any known cement raw material preparation. The present invention is to obtain a cement clinker of stable quality by firing a raw material of a cement clinker together with a conventionally used main fuel such as heavy oil or pulverized coal in a rotary kiln using a combustible synthetic resin as an auxiliary fuel.

The combustible synthetic resin used for the auxiliary fuel is not limited in terms of chemical components as long as it is a synthetic resin in a solid state at room temperature, such as a molded product, a lump, a sheet, and a powder. More preferably, the use of waste materials such as waste plastics among the synthetic resins is particularly desirable in terms of cost reduction as an inexpensive fuel source and from the viewpoint of reducing the social burden of disposal. The resin used in the present invention is made into particles having a size of about 1 mm or less, preferably 600 μm or less, by any method such as pulverization, crushing, cutting, and classification.
Adjustment of the particle size distribution width does not need to be particularly performed. 1m particles
If the size exceeds m, the combustion efficiency decreases. That is,
It is not preferable because fuel particles that do not completely burn out appear in the sintering zone in the rotary kiln, and the calorie supply for sintering the cement clinker becomes insufficient. Although the use of fine powder particles having a size of about 100 μm or less is generally desirable, the pulverization treatment that causes a remarkable increase in the pulverization cost can be used as fuel without any intention in the present invention.

A rotary kiln (internally heated rotary kiln) used for firing cement clinker raw materials is provided with a main fuel burner in front of the kiln, and continuously supplies materials to be fired, such as cement-mixed raw materials, from the kiln tail to fire. However, in the present invention, a burner dedicated to auxiliary fuel independent of the main fuel burner is installed before the kiln. The auxiliary fuel burner has an auxiliary fuel injection pipe, and the injection pipe is provided with a cooling treatment such as, for example, a double pipe structure in which an outer pipe portion is made to flow a cooling medium such as water or gas. The material of the burner dedicated to auxiliary fuel is not limited as long as it is a heat-resistant material like the main fuel burner, but the outermost surface is desirably formed of a refractory. In addition, the auxiliary fuel burner is independently installed in parallel with the main fuel burner, and is preferably installed as close as possible to the main fuel burner.

In the main fuel burner, fuel such as heavy oil or pulverized coal is supplied and combusted by diffusion with combustion air. When the temperature inside the rotary kiln reaches a temperature suitable for calcination of the cement-mixed raw material, the auxiliary fuel dedicated burner is used. The combustible synthetic resin particles air-conveyed from the burner are blown and burned. Since the combustible synthetic resin particles are spatially burned in the firing zone in the rotary kiln, in the present invention, the injection speed of the auxiliary fuel into the kiln is set to be equal to or lower than the injection speed of the main fuel. Preferably, it is 25 m / sec or less. At a speed higher than this, particles that ignite or complete combustion appear outside the sintering zone, flames due to the auxiliary fuel are likely to be formed at positions off the sintering zone, and the amount of heat from the auxiliary fuel does not sufficiently contribute as the clinker firing amount, which is preferable. Absent. Furthermore, the auxiliary fuel is injected into the kiln at a turning angle of 20 ° or less. Exceeding the turning angle of 20 ° is not preferable because particles that collide with the kiln wall before the completion of combustion and land and burn increase. Desirably, it is good to throw into a kiln as a straight flow. The main fuel injection speed in the present invention may be generally the same as the fuel injection speed to the rotary kiln when only the main fuel used in cement production is used. In addition, the calorific value in the kiln during sintering may be kept constant. For this reason, the amount of heat from the main fuel corresponding to the amount of heat from the auxiliary fuel is reduced from the time of auxiliary fuel injection (the amount of main fuel used is reduced). (Reduce). In the present invention, since the combustible synthetic resin particles are spatially burned, the possibility that unburned particles often mixed in the material to be fired, which is often seen in landing combustion, can be significantly reduced, and therefore, the use ratio of the auxiliary fuel composed of the resin can be increased. Can be. That is, the usage rate of the auxiliary fuel in all the fuels provided for combustion can be up to 70% of the total calorie in terms of calorific value. If the auxiliary fuel usage ratio is increased to a value exceeding this, the radiant heat of the flame formed by the main fuel is reduced, and the possibility that the combustion of the combustible synthetic resin particles is delayed increases, which is not preferable.

The present invention is to produce a clinker by firing a cement clinker raw material by the above-described fuel combustion method. The firing temperature, the clinker input kiln input amount,
Conditions and operations that are not particularly mentioned, such as the residence time in the kiln, may be the same as the conditions and operations during the production of a cement clinker that have been conventionally performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary kiln with a total length of 27 m and an inner diameter of 1.5 m has a main fuel injection nozzle (main burner) for heavy oil at the kiln front, and an auxiliary fuel above the main fuel injection nozzle so as to be parallel to it. A jet nozzle (auxiliary fuel burner) was installed. This auxiliary fuel jet nozzle has a triple pipe structure with a total length of 4 m, a heat-resistant alloy inner tube with an inner diameter of about 30 mm at the tip opening for injecting auxiliary fuel, and a stainless steel pipe through which cooling air at the tip closed flows around the outer pipe. The inner tube is made up of a heat-resistant alloy outer tube on the outer periphery for carrying out air after cooling.The inner tube and the outer tube have a structure that communicates with each other at the tip, and the outer tube wall is made of castable refractory material. Covered. A movable ejector turning plate (made of heat-resistant ceramics) was attached to the tip of the auxiliary fuel ejection nozzle.

On the other hand, waste plastic products mainly composed of polyethylene were pulverized and cut by a Bima pulverizer and a CS cutter, and then classified by a vibrating sieve to obtain particles of 1 mm or less, which were used as auxiliary fuel. The auxiliary fuel was supplied to the rotary kiln by a blower after being adjusted by a fixed-quantity supply device.

Using this rotary kiln, first, the main fuel using heavy oil is burned only by the main burner, and the main fuel is injected into the kiln shown in Table 1 at the main fuel injection speed.
80 liter / hour was blown in, and the temperature in the kiln near the flame was set to about 1600 ° C. Then, the auxiliary fuel composed of the waste plastic ground particles was blown in with the auxiliary fuel burner under the conditions shown in Table 1, and the main fuel blowing amount was set to the conditions shown in Table 1, and the mixed raw material for ordinary Portland cement (clinker raw material) was used. ) Was supplied from a rotary kiln kiln, and calcination was performed by combined use of main fuel and auxiliary fuel.

[0016]

[Table 1]

The color tone of the calcined cement clinker is J
It was measured by the b value according to a method according to IS Z8722. Table 1 shows the results. A cement equivalent to ordinary Portland cement was prepared from the cement clinker, and a mortar was prepared by mixing and kneading 50 parts by weight of water with 100 parts by weight of the cement. The compressive strength of this mortar at a material age of 28 days was measured by a method according to JIS R5201. The results are also shown in Table 1.

[0018]

According to the method of the present invention, a cement clinker calcined only with the main fuel according to the conventional cement clinker manufacturing method can be used to perform a complicated adjustment operation of a cement clinker which is comparable in terms of quality, properties and color tone. It can be manufactured stably without performing.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoichi Ono 6276 Onoda, Onoda-shi, Yamaguchi Pref. Taiheiyo Cement Co., Ltd. Central Research Laboratory (72) Inventor Umiki Tamashige 3-1-1 Nishikanda, Chiyoda-ku, Tokyo No. Taiheiyo Cement Co., Ltd. F-term (reference) 4G012 KA02 4K061 AA08 BA01 DA01

Claims (2)

[Claims] 1. A method of blowing a combustible synthetic resin as a supplementary fuel into a rotary kiln at a speed of not more than a main fuel ejection speed and a turning angle of not more than 20 °, and firing a cement clinker raw material together with the main fuel. A calcining method for a raw material of cement clinker, wherein a calorific value accounts for at most 70% of a caloric value supplied from all fuels. 2. The method according to claim 1, wherein the auxiliary fuel is a powder having a particle size of 1 mm or less.