JP4010339B2 - Cement clinker manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a cement clinker, and more particularly, to a method for producing a cement clinker that can reduce the calorific value in the firing step.

  In recent years, remarkable progress in cement manufacturing technology is said to be the development of technology that reduces the calorific value of cement clinker (hereinafter referred to as clinker). In other words, from the wet firing method that required a large calorific value by adding water to the original blended raw material and then calcining it, the cement raw material is crushed after drying with hot air and then calcined to reduce the calorific value. New suspension that has shifted to the dry firing method, and calcined the pre-heated raw material in advance with a pre-heater, and putting the obtained calcined raw material into a rotary kiln (hereinafter referred to as a kiln) to further reduce the calorific value. There is a series of changes in firing technology, such as the development of a method of firing.

Then, as a technique for further reducing the calorific value, (1) a method of changing the main chemical composition of the blended raw material (Non-Patent Document 1), and (2) a method of using flux (Non-Patent Document 1) Each was developed.
The method (1) is a method in which the content of alumina, iron, sulfur, etc. is changed to increase the amount of liquid phase during firing so that clinker is easily generated even at a relatively low temperature.
The method (2) is a method in which a flux such as meteorite (calcium fluoride) that accelerates the firing reaction is added to the cement raw material.
Author; F. W. Taylor, publication name; Cement Chemistry, issuing country; UK, issuing office; ACADEMIC PRESS LIMITED, date of issue; 1990, number of pages; (1) page 80 for a method of changing the main chemical composition of the raw material; (2) Page 93 on how to use flux.

However, these (1) methods of greatly changing the main chemical composition of the blended raw materials and (2) methods of using flux have the following problems.
That is, (1) In the method of greatly changing the main chemical composition of the blended raw material, a clinker having a mineral composition different from that of general-purpose Portland cement is generated. Therefore, when the manufactured cement is used to produce concrete or mortar, these will exhibit unique fluidity and strength development. As a result, the use of cement was limited, and this could not be used in a wide range.
In addition, (2) in the method using flux, the component element of the flux (for example, fluorine) volatilizes in the kiln, which adheres to the inner wall of the kiln or preheater and causes a coating trouble, or is unique due to the influence of the flux component. Cement with various physical properties was sometimes produced. These became more noticeable as the amount of flux added increased.

Thus, as a result of intensive research, the inventor has focused on alite, which is a kind of clinker's main constituent mineral. In other words, it was discovered that if the growth mechanism of alite that grows by heterogeneous nucleation is used and the generation of alite is promoted from a lower temperature than before, the calorific value can be further reduced. Completed the invention.
This invention does not significantly change the main chemical composition and mineral composition of cement, and does not deteriorate the quality, and is effective in reducing the preheater coating amount and extending the life of the refractory brick, while reducing the calorific value. It aims at providing the manufacturing method of the cement clinker which can aim at.

The invention according to claim 1 is a method for producing a cement clinker in which a blended raw material composed of a plurality of cement raw materials mixed in a raw material step is fired in a firing step to produce a cement clinker containing alite. A cement clinker, cement, or refractory brick that has a melting point higher than the phase temperature and that has a particle size of 0.01 mm or less is charged from the front of the rotary kiln to form a rotary kiln. Manufacture of cement clinker that reduces the amount of calcining heat of cement clinker by reducing the amount of calcining of cement clinker compared to before charging by landing between the place where the liquid phase of cement clinker starts to form in the kiln and the place where alite begins to form. Is the method.
This blended raw material includes cement clinker in the firing process.

According to the invention described in claim 1, it is difficult for alite, which is a main constituent mineral of cement clinker, to spontaneously generate alite nuclei under normal cement clinker production conditions. It has the property of forming a nucleus (heterogeneous nucleus) and starting crystal growth.
Therefore, the substance is added from outside the growing environmental phase and coexists in the liquid phase cement clinker. By doing so, the generation of alite is promoted from a lower temperature than in the prior art using the added substance as a nucleus. As a result, the time until generation of alite is completed is shortened, and the maximum heating temperature is also lowered. As a result, the calorific value can be reduced without changing the main mineral composition of the cement or using a flux.
Crystal growth consists of two elementary processes: nucleation in which crystal buds are produced from an empty environmental phase and steady crystal growth after nucleation. Nucleation is classified into two types: natural nucleation in which the growing substance itself nucleates and heterogeneous nucleation in which a different substance nucleates. Even if it is the same crystal as the growing crystal, it is included in the category of heterogeneous nucleation when it is added from outside the growing environmental phase and grown as a nucleus as in the case of the present invention. is there.

The raw material process is an initial step of the cement manufacturing process, and cement raw materials such as limestone, clay, silica stone, and iron raw materials are charged into a raw material mill and pulverized to a predetermined particle size while mixing these raw materials. Moreover, the clays before pulverization are dried with a clay dryer, if necessary.
In the firing step, the blended raw material is put into a kiln which is a main device of the clinker firing equipment, and then heated to about 1450 ° C. in the firing zone while gradually moving downstream in the kiln. In the middle of the process, the raw materials are dried, dehydrated, and decomposed, and lime (calcium oxide), silica, alumina, etc. in the raw materials are recombined with each other in the vicinity of the calcining zone to produce a clinker composition compound. . In the process, a liquid phase is generated. The generation temperature of the liquid phase (hereinafter, liquid phase temperature) is around 1200 to 1300 ° C.

  The main constituent mineral of cement clinker consists of alite, belite, and interstitial phase filling between them. Alite is a mineral occupying about half of the clinker composition, and its average particle size is about 20 μm. This alite is a substance that generates heterogeneous nuclei.

The substance that forms the core of alite (hereinafter referred to as the substance that forms the core) must not decompose or melt even when it comes into contact with the liquid phase. For that purpose, the melting point of the substance needs to be higher than the liquid phase formation temperature of cement clinker (around 1200 to 1300 ° C.). In this case, refractory bricks, magnesium oxide, platinum, rhodium, and the like can also be used as the substance that forms the nucleus. However, among the cement clinker baked out from the rotary kiln, a substance that stably exists as a solid phase is preferable. For example, a cement clinker that can be easily obtained in a cement factory, and a cement manufactured therefrom. In addition, when limestone fine powder is thrown into the high-temperature rotary kiln during operation from before the kiln, the limestone fine powder is decarboxylated under high heat and changed to quick lime fine powder before coming into contact with the blended raw material or cement clinker. Thereby, the substantially same effect as the case where quick lime fine powder is thrown in is acquired. Thus, if a substance having a melting point exceeding 1300 ° C. is added from the outside as a core, the generation of alite is promoted, and the calorific value of cement clinker is reduced.
The material that forms the nucleus may be cement clinker, cement, or refractory brick. Further, a mixture of both cement clinker and cement may be used. The mixing ratio in that case is 5: 95-50: 50, for example.
The type of cement is not limited. Examples thereof include various Portland cements such as ordinary Portland cement, early-strength Portland cement, and moderately hot Portland cement. As the cement clinker, a cement clinker used as a raw material for these various Portland cements can be employed. In particular, early-strength Portland cement with a large amount of alite or a cement clinker therefor is preferable.
The smaller the particle size of cement, cement clinker, and refractory bricks, which are the substances that form the core, is preferable. For example, it is 5 μm or less.

  The cement clinker, cement, or refractory brick, which is a substance that forms the core of this generation, is charged in the firing step. Alternatively, the material serving as the nucleus of the generation or the material containing the nucleus may be input into both the firing process and the raw material process.

The cement clinker, cement, or refractory brick, which is a substance that forms the core of the generation, may be mixed in at least one of the cement raw material and the blended raw material in advance in the raw material process. Specifically, this substance may be charged together with the cement raw material into a raw material mill or into a clay dryer.
There is no limitation on the amount of substances that become the core of the production. For example, it is 5 parts by weight or less with respect to 100 parts by weight of the prepared raw material. Moreover, the mixing amount of the core-containing material is not limited. For example, it is 5 parts by weight or less with respect to 100 parts by weight of the prepared raw material in terms of a substance that is a nucleus of generation.
Cement clinker, cement, refractory brick fine powder, or the like can be used as the material that forms the nucleus.

  The place where the input material lands in the rotary kiln is between the place where the liquid phase of the cement clinker in the firing process begins to form and the place where alite begins to form. Before the core material or core-containing material reaches the area where alite can be generated in the rotary kiln, it changes to another compound, whose melting point is lower than the liquidus temperature and does not promote the generation of alite. In order to prevent this, it is necessary to devise the place and method of the input while evaluating the operation status of the rotary kiln and the quality of the cement clinker.

In order to put the substance that is the core of the generation of alite into the clinker firing facility, an existing one in the clinker firing facility may be used, or a dedicated one may be used. For example, the substance may be mixed into a fuel such as pulverized coal using an existing fuel burner and put into a rotary kiln. Or you may throw in in a preheater or a rotary kiln by a dedicated blowing pipe or chute. When the material that becomes the core of alite generation is introduced from the kiln bottom, either the combustible material or the cement raw material is mixed with the core material, and this is spherical, cylindrical, donut-shaped, etc. It is preferable to increase the moving speed of the material in the rotary kiln in the forward direction of the kiln. Thereby, before the substance used as this nucleus reaches the liquid phase production | generation area | region in a rotary kiln, it is hard to react with a preparation raw material and to become another compound.
Further, the location where the substance is introduced into the rotary kiln is preferably in the liquid phase generation region of the rotary kiln during firing or at a lower temperature side. The specific inlet is in front of the kiln of the rotary kiln.

  The mixing amount of the substance serving as the nucleus of generation is 5 parts by weight or less with respect to 100 parts by weight of the prepared raw material. If the amount exceeds 5 parts by weight, the quality of the cement clinker is lowered depending on the type of the substance. A preferable mixing amount of a substance serving as a nucleus of generation is 0.05 to 1.0 part by weight. If it is this range, the more suitable effect of the quality improvement by the further reduction of the calorie | heat amount of baking of a cement clinker, the reduction | decrease of a free lime, etc. will be acquired.

When the particle size of the cement clinker, cement, or refractory brick, which is a material that forms the core, exceeds 5 mm, the quality of the cement clinker decreases depending on the type of the material. The particle size of the substance is 0.01 mm or less. If it is this range, the more suitable effect of the further reduction of the calorie | heat amount of a cement clinker and the quality improvement will be acquired.

  The invention according to claim 2 is the method for producing a cement clinker according to claim 1, wherein the firing in the firing step is performed by a clinker firing facility having a calciner.

According to the method for producing a cement clinker according to the present invention, cement, cement clinker, or refractory brick, which is a core material for generating alite, is put in front of the kiln of the rotary kiln. For this reason, the production | generation of alite can be accelerated | stimulated from low temperature compared with the past. Thereby, a high quality cement clinker can be baked with a calorific value basic unit smaller than before.

  Examples of the present invention will be specifically described below.

First, materials used in test examples, reference examples, and comparative examples, test items, and test methods are shown below.
1. Materials used 1) Refractory bricks; Spinel bricks 2) Cement mixed raw materials; Limestone, clay, silica stone, iron raw materials (weight ratio, 78: 15: 5: 2)
3) Fine powder of normal and early strength Portland cement clinker; made by Mitsubishi Materials Corporation 4) Normal and early strength Portland cement; made by Mitsubishi Materials Corporation

2. Test items and test methods
(1) Free Lime Cement Association standard test method “Quantitative method of free calcium”. That is, the sample is boiled with a mixed solvent of glycerin and alcohol to elute calcium, and titrated with an alcohol solution of ammonium acetate.
(2) Clinker calorific value basic unit This is the value obtained by dividing the calorific value of fuel per hour (unit kcal / h) required for calcining cement clinker by the amount of clinker produced per hour (unit t / h). . The calorific value of the fuel is obtained by multiplying the amount of fuel used per hour by the low calorific value.

(Reference Example 1, Comparative Example 1)
When refractory brick fine powder having a melting point of about 1800 ° C. (particle size of 149 μm or less) is used as a normal Portland cement mixed material (particle size of 210 μm or less) in the raw material process, 2 parts by weight were mixed. This was put into a rotary kiln and baked at about 1450 ° C. The maximum heating temperature during firing is 1500 ° C. (maximum heating temperature 1500 ° C. when refractory brick fine powder is not added). The composition of the refractory bricks is SiO ₂ : 0.3%, Al ₂ O ₃ : 17.1%, Fe ₂ O ₃ : 3.0%, CaO: 0.5%, MgO: 79.1%. Table 1 shows the mineral composition of the obtained cement clinker. Here, a sample in which fine powder of refractory bricks was added was referred to as Reference Example 1, and a sample in which the fine powder was not input was referred to as Comparative Example 1.

  The obtained ordinary Portland cement clinker has substantially the same main chemical composition as when no refractory brick fine powder is added. However, the average content of free lime in ordinary Portland cement clinker when the rotary kiln was operated for one week decreased from 0.9% when the refractory brick fine powder was not added to 0.6%. Moreover, the calcining calorific value of cement clinker decreased by about 1% from 650 kcal / t when refractory brick fine powder was not added to 644 kcal / t.

(Test Example 2, Comparative Example 2)
Cement clinker cooler's electric dust collector collects ordinary Portland cement clinker particles (particle size of 5mm or less), and in front of the kiln, it is put into a rotary kiln with a dedicated blowing facility, and the cement clinker 1t 8 kg was charged per unit. In a rotary kiln, normal Portland cement clinker is being fired at about 1450 ° C. The maximum heating temperature during firing is about 1500 ° C. (the maximum heating temperature when normal Portland cement clinker particles are not charged is about 1550 ° C.). The melting point of ordinary Portland cement fine powder is about 1700 ° C. The mineral composition of the obtained cement clinker is also shown in Table 1. Here, Test Example 2 was used when particles of ordinary Portland cement clinker were added, and Comparative Example 2 was used when the particles were not input.

  As a result, the obtained ordinary Portland cement clinker has substantially the same main mineral composition as when the cement clinker particles were not charged. However, when the rotary kiln was operated for one week, the average content of free lime in ordinary Portland cement clinker was 0.4%, which was substantially the same as or slightly decreased when the ordinary Portland cement clinker particles were not charged. Moreover, the calcining calorific value of cement clinker was reduced by about 2% from 652 kcal / t when normal Portland cement clinker particles were not charged to 640 kcal / t.

( Reference Example 3 , Comparative Example 3)
In the rotary kiln, 10 kg of early strong Portland cement clinker fine powder (brane value 3500 cm ² / g) was charged per 1 ton of cement clinker in the direction of the kiln axis from the bottom of the kiln with a dedicated burner. In a rotary kiln, normal Portland cement clinker is being fired at about 1450 ° C. The melting point of the fine powder of early strong Portland cement clinker is about 1700 ° C. The maximum heating temperature at the time of firing is about 1500 ° C. (the maximum heating temperature when the fine powder of early strong Portland cement clinker is not charged is about 1550 ° C.). The mineral composition of the obtained cement clinker is also shown in Table 1. Here, a sample in which fine powder of early-strength Portland cement clinker was added was referred to as Reference Example 3, and a sample that had not been input was referred to as Comparative Example 3.
As a result, the main mineral composition of the obtained ordinary Portland cement clinker is substantially the same as that when the cement clinker fine powder is not charged. However, the average content of free lime in ordinary Portland cement clinker when the rotary kiln was operated for a week decreased by 0.2% to 0.4%. Moreover, the cement clinker calorific value per unit of production was reduced by about 3% from 658 kcal / t when the early strong Portland cement clinker fine powder was not added to 641 kcal / t.

(Test Example 4, Comparative Example 4)
In the rotary kiln, early strong Portland cement (Brain value 4300 cm ² / g) was mixed with pulverized coal with a pulverized coal burner from the front of the kiln, and 20 kg per 1 ton of cement clinker was charged in the direction of the kiln axis. In the rotary kiln, early-strength Portland cement clicker is being fired at about 1500 ° C. The melting point of early strong Portland cement fine powder is about 1700 ° C. The maximum heating temperature at the time of firing is about 1550 ° C. (the maximum heating temperature when the fine powder of early strong Portland cement is not charged is about 1600 ° C.). The mineral composition of the obtained cement clinker is also shown in Table 1. Here, Test Example 4 was used in which a fine powder of early-strength Portland cement clinker was added, and Comparative Example 4 was used in which no powder was added.
As a result, the main mineral composition of the obtained early-strength Portland cement clinker is substantially the same as when the early-strength Portland cement was not input. However, the average content of free lime in the early-strength Portland cement clinker when the rotary kiln was operated for one week was almost the same as 0.5% or slightly decreased. In addition, the cement clinker calorific value per unit of production decreased by about 4% from 655 kcal / t when the early strong Portland cement fine powder was not added to 631 kcal / t.

( Reference Example 5, Comparative Example 5)
In a rotary kiln calcining furnace in which ordinary Portland cement clinker is being fired, fine powder (brane value 4100 cm ² / g) of early strong Portland cement clinker having a melting point of about 1700 ° C. is used using a blowing pipe at 5 kg per ton of cement clinker. I put it in. The maximum heating temperature at the time of firing is about 1500 ° C. (the maximum heating temperature when the fine powder of early strong Portland cement is not charged is about 1550 ° C.). The mineral composition of the obtained cement clinker is also shown in Table 1. Here, a sample in which fine powder of early-strength Portland cement clinker was added was referred to as Reference Example 5, and a sample that had not been input was referred to as Comparative Example 5.

  As a result, the main mineral composition of ordinary Portland cement clinker is substantially the same as when the clinker fine powder has not been added. However, the average content of free lime in ordinary Portland cement clinker when the rotary kiln was operated for one week decreased by 0.2% to 0.5%. Moreover, the cement clinker calorific value per unit of production decreased by about 2% from 647 kcal / t when pulverized early strong Portland cement clinker was not charged to 634 kcal / t.

Claims (2)

In the method for producing a cement clinker, a compound clinker comprising a plurality of cement raw materials mixed in the raw material step is fired in a firing step to produce a cement clinker containing alite.
A cement clinker, cement, or refractory brick that has a melting point higher than the temperature of the liquid phase of the cement clinker and has a particle size of 0.01 mm or less is used before the rotary kiln. The amount of calcining calcining of cement clinker is reduced compared to before charging, by landing between the place where the liquid phase of cement clinker begins to form in the rotary kiln and the place where alite begins to form. A method for producing cement clinker.   The method for producing a cement clinker according to claim 1, wherein the firing in the firing step is performed by a clinker firing facility having a calcining furnace.