JPH11173760A - Lining structure of rotary kiln for manufacturing cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lining structure of a rotary kiln for manufacturing a cement for preventing a corrosion of a shell of the kiln by reducing 'an attack by a corrosive gas' for the shell. SOLUTION: An 'attack of corrosive gas (corrosive gas such as chlorine, sulfur or the like) to a shell 11 for a rotary kiln 10 is reduced by the lining structure of the kiln for manufacturing a cement via a mineral sheet (MgO- material sheet 12) between the shell 11 and lining bricks (magnesia spinel- material bricks 13), thereby preventing a corrosion of the shell 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lining structure of a rotary kiln for cement production, and more particularly, to reducing "attack by corrosive gas" on a shell (steel shell) of the kiln, thereby reducing the shell corrosion. The present invention relates to a lining structure of a rotary kiln for cement production for preventing the occurrence of cracks.

[0002]

2. Description of the Related Art A rotary kiln for cement production is a kiln having a structure in which a cylindrical steel shell having a diameter of 4 to 6 m and a length of 50 to 110 m is lined with a refractory brick inside. Used in the production of cement clinkers.

Here, a typical method for producing a conventional cement clinker is described as follows: "lime, clay, silica,
The main raw material is iron and some other raw materials are mixed.
Fuel is supplied to the tarry kiln, while fuel (coal, heavy oil, etc.) is blown from the opposite direction of the raw material supply port, and
Cement clinker is manufactured by a method of "baking at about 1450 [deg.] C. until it becomes semi-molten while rotating at a speed of two to three times a minute."

[0004] In the production of cement clinker, "corrosive gas such as chlorine and sulfur" contained in the raw material and fuel used evaporates and circulates in the rotary kiln.

[0005] Then, a part of the corrosive gas penetrates the lining brick layer to reach the iron shell, and reacts with iron to corrode the shell. In addition, when the lining brick is constructed, ball paper having a thickness of 2 to 4 mm is usually used as the joint material in the axial direction, but the ball paper disappears (burns) as the temperature in the kiln increases. Therefore, part of the corrosive gas penetrates through the joint between the bricks, reaches the shell similarly, and reacts with iron to corrode the shell. As described above, in a rotary kiln for cement production, "shell corrosion" caused by corrosive gas such as chlorine and sulfur is caused.
Has been a problem.

[0006] In recent years, recycling resources have been actively utilized, and in the field of cement production technology, various kinds of waste have been recycled and turned into resources. Of the recycled resources, those that become cement components are used as “cement raw materials” and those that become thermal energy are used as “fuel for producing cement”.

For example, waste tires, municipal waste, sewage sludge, and the like are used. These are sources of "corrosive gas such as chlorine and sulfur", and therefore, the amount of corrosive gas is increased more than before. Increasingly, the problem of "shell corrosiveness" due to this has become even more important.
(Note that chlorine sources include municipal waste and sewage sludge, and sulfur sources include waste tires.)

As means for solving the above problems, namely,
For the purpose of preventing corrosive gases such as chlorine and sulfur from coming into contact with the shell surface, a "method of applying phosphoric acid or an inorganic paint to the inner surface of the shell" has been proposed.

In the above-mentioned conventional phosphoric acid coating method, phosphoric acid is applied to the lower half peripheral surface of the shell, made to be a little dry, then inverted, and the remaining upper half peripheral surface is applied. Then, as shown in the following equation (1), phosphoric acid reacts with iron to form an FePO ₄ film, thereby preventing contact between corrosive gas and iron. Formula (1): 2H ₃ PO ₄ + 2Fe → 2FePO ₄ + 3H ₂

On the other hand, in the method of applying an inorganic paint, after removing dust and oil film on the surface to be applied, an inorganic material is applied to the lower half peripheral surface of the shell by using a brush or a roller in the same manner as in the phosphoric acid application method. Apply a system paint, make it slightly dry, turn it over, and apply the remaining upper half circumference. In this manner, the inorganic coating film is formed over the entire periphery of the shell to prevent the corrosive gas from coming into contact with iron.

[0011]

However, in the above-mentioned conventional phosphoric acid coating method, (1) the phosphoric acid used is strongly acidic. (2) The reaction between phosphoric acid and the shell produces an unpleasant odor, which worsens the working environment. (3) It takes at least one day to dry after applying phosphoric acid. (4) There is a problem that the working efficiency is low because the rotary kiln must be applied in a unit of a half turn.

In the above-mentioned conventional method of applying an inorganic paint, there is a problem that the work efficiency is low because the paint has to be dried after the application and must be applied in a unit of a half circumference.

Further, in the above-described phosphoric acid coating method and inorganic coating method, the thickness of the formed coating film is extremely small, and the "difference in thermal expansion between the lining brick and the shell" which occurs during the operation of the rotary kiln. ”Causes the lining brick to slip,
The formed thin film (coating film) is worn out or scraped off, exposing the inner surface of the shell, and causing a situation in which it comes into contact with corrosive gas. Therefore, it has a common disadvantage that the corrosion prevention effect is small. Also, the temperature of the shell may be 300 during operation.
Since the temperature rises to 400 ° C., there is also a disadvantage that the coating film is peeled off due to a difference in thermal expansion between the shell and the coating film.

The present invention solves the above-mentioned problems and disadvantages, reduces the "attack by corrosive gas" on the shell, and prevents the shell from corroding.
It is intended to provide a kiln lining structure.

Although it does not relate to the lining structure of a rotary kiln for cement production, Japanese Patent No. 2,634,356 discloses a method for producing activated carbon by the zinc chloride method.
It describes a lining structure of a rotary kiln used in producing titanium oxide by a sulfuric acid method.

That is, the rotary kiln lining structure described in the above publication has an organic impermeable membrane (tetrafluoroethylene) on the inner surface of a shell (iron can) in order to prevent the penetration of corrosive gas. (Film or tetrafluoroethylene resin). However, this is a rotary kiln for producing activated carbon and titanium oxide, which is durable because the furnace temperature of the rotary kiln during operation is as low as "1000 ° C. or less". In the case of a rotary kiln for industrial use, the firing zone and the transition zone of the kiln during operation are at a higher temperature (about 1450 ° C.) than the temperature at the time of production of activated carbon and titanium oxide. It is impossible to apply an organic-based impermeable membrane.

Also, in the above-mentioned Patent No. 2,634,356,
In order to prevent "permeation of corrosive gas" from the joint of the lining brick, it is also described that a brick layer bonded by a water glass-based acid-resistant mortar is formed between the lining bricks. In the case of a tarry kiln, when such acid-resistant mortar is used as a jointing material, the mortar portion and the cement component react with each other and are eroded. As a result, the lining brick (magnesia-chromium brick, magnesia-
It is not applicable because it greatly reduces the service life of spinel bricks.

In addition to the "rotary kiln lining structure" described in the above-mentioned Japanese Patent No. 2,634,356, as another conventional example, a raw material for producing lime, alumina, and magnesia is used as a raw material.
It is also known that a tally kiln is provided in which a felt such as a heat-resistant fiber is interposed between the shell and the lining brick in order to reduce the temperature of the shell. However, since such a felt has many pores, penetration of corrosive gas or alkali cannot be prevented, and therefore, cement production for the purpose of “prevention of shell corrosion” due to intrusion of corrosive gas is performed. Its use is meaningless in a rotary kiln.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a shell.
"Attacks with corrosive gas" for (steel shell)
It is an object of the present invention to provide a rotary kiln lining for cement production, which reduces the corrosion of the shell and prevents shell corrosion.

[0020]

SUMMARY OF THE INVENTION The present invention is characterized in that an inorganic sheet is interposed between a lining brick and a shell, thereby reducing the attack of corrosive gas on the shell. To provide a lining structure for a cement rotary kiln.

That is, the lining structure of the rotary kiln for cement production according to the present invention is characterized in that an inorganic sheet is interposed between the shell and the lining brick (claim 1). And the material of the inorganic sheet is Al ₂ O ₃ or Al ₂ O ₃ —SiO ₂
(Al ₂ O ₃ is 45 wt% or more), SiO ₂ −Al ₂ O ₃ (Al ₂ O ₃
of less than wt%), MgO quality, MgO-Cr ₂ O ₃ quality is any one of MgO-C protein (claim 2), - the inorganic sheet - DOO is double-sided adhesive tape - flop or organic Being attached to the inner surface of the shell with an adhesive (claim 3); the thickness of the inorganic sheet being 1 to 10 mm
(Claim 4).

(Action) In the present invention, by interposing an inorganic sheet between the shell and the lining brick,
The corrosive gas that penetrates the lining brick layer reacts with the inorganic sheet to form secondary minerals. And, by this secondary mineral, reduce corrosive gas reaching the shell inner surface,
The effect of reducing the attack on the shell by this gas and protecting the shell is produced.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the present invention, a flexible inorganic sheet having a thickness of 1 to 10 mm made of an inorganic raw material is attached to the inner surface of a shell, and the conventional sheet is used thereon. The lining brick has been constructed.

Examples of the inorganic sheet include “Al ₂ O ₃ , SiO _{2
2, MgO, Cr 2 O 3} , C " , either alone or inorganic sheet obtained from them and the combined material - a preparative, Al ₂ O ₃ quality, Al ₂
O ₃ -SiO ₂ material (Al ₂ O ₃ is 45wt% or more), SiO ₂ -Al ₂ O ₃ material
(With less than 45 wt% Al ₂ O ₃ ), MgO, MgO-Cr ₂ O ₃ , Mg
OC-based sheets are preferred.

These inorganic sheets can be produced arbitrarily. For example, for example, a desired amount of the above raw material powder (Al ₂ O ₃ , SiO ₂ , Mg) is added to a vinyl acetate solution.
O, Cr ₂ O ₃ , and C) are added to form a sheet and then dried at 70 ° C. (Note that the raw material may be a natural product or an artificial product.) The inorganic sheet obtained as described above is a non-sintered sheet having flexibility. In addition, since it can be processed and deformed into an arbitrary shape, there is an advantage that the construction along the circumferential direction of the rotary kiln is easy.

The above-mentioned inorganic sheet used in the present invention will be described in more detail. The inorganic sheet is not limited to the following specific examples. The material is commercially available mainly for use, and for example, the following inorganic sheets can be used.

(1) As an Al ₂ O ₃ sheet or an Al ₂ O ₃ —SiO ₂ sheet (with an Al ₂ O ₃ content of 45 wt% or more), the trade name “CRX
-SA7L ”“ High alumina flexible sheet (Chemical composition → Al ₂ O
_{3: 70wt%, SiO 2:} 25wt%, Na 2 O: 4wt%, Ig.loss: 12w
(%), (2) SiO ₂ —Al ₂ O ₃ sheet (with a content of Al ₂ O ₃ of less than 45 wt%; including SiO ₂ sheet) includes the trade name “CRX-S
K9 ”“ Silica flexible sheet (chemical composition → SiO ₂ : 95wt)
%, Al ₂ O ₃ : 2 wt%, Na ₂ O: 1.5 wt%, Ig.loss: 12 wt%
%) ”, (3) As the MgO sheet, the product name is“ CRX-SM9 ”
"Magnesia flexible sheet (Chemical composition → MgO: 90wt)
%, SiO ₂ : 3 wt%, Na ₂ O: 2.0 wt%, CaO: 0.5 wt%, Ig.l
oss: 12 wt%), and (4) MgO-Cr ₂ O ₃ material sheet is a “magcro flexible sheet (Chemical composition → MgO: 50 wt%, Cr ₂ O ₃ : 15 wt%, Al ₂ O ₃ : 7.5 wt%,
_{Fe 2 O 3: 7wt%,} SiO 2: 4wt%, Ig.loss: 16wt%) ", (5)
As the MgO-C sheet, “Magnesia-carbon flexible sheet (Chemical composition → MgO: 85)” of the product name “CRX-SM8C”
wt%, CaO: 1.5wt%, Al 2 O 3: 0.5wt%, SiO 2: 3wt%,
C: 5.5 wt%, Ig.loss: 17.5 wt%) ".

The inorganic sheet used in the present invention reacts with a corrosive gas (corrosive gas such as chlorine or sulfur) to form secondary minerals, and the secondary minerals reach the inner surface of the shell. The gas can be reduced or shut off, reducing the attack on the shell by the gas and protecting the shell. For example, when a MgO-C sheet is used, as shown in the following formulas (2) and (3), MgCl ₂ or Mg
By forming secondary minerals of SO ₄ , corrosive gas reaching the inner surface of the shell can be reduced or blocked.・ Formula (2): 2MgO + 2Cl + C → 2MgCl ₂ + CO ₂・ Formula (3): MgO + SO ₃ → MgSO ₄

As a means for attaching the inorganic sheet to the inner surface of the shell, it is preferable to use a double-sided adhesive tape or an adhesive, so that the conventional phosphoric acid coating method and the inorganic coating method can be used. The lining brick can be constructed immediately without any need for drying.

In the present invention, the thickness of the inorganic sheet is
It is preferable to use one having a thickness of 1 to 10 mm. If the thickness is less than 1 mm, the inorganic sheet is worn, and it may not be possible to prevent the attack of the corrosive gas. On the other hand, if it exceeds 10 mm, the flexibility becomes small and the construction becomes difficult, and when it is worn, the lining bricks are unfavorably loosened. A particularly preferred thickness is 2
８8 mm.

The causes of abrasion of the inorganic sheet include: movement of the lining brick due to "difference in thermal expansion between the lining brick and the shell" generated during operation of the rotary kiln; This is probably due to the movement of the lining brick due to the rotation of.

In the present invention, it is not always necessary to attach an inorganic sheet of the same thickness to the inner surface of the shell. The rotary kiln is divided according to the degree of attack of corrosive gas, and the attack is severe. A thick inorganic sheet can be attached to one part and a thin inorganic sheet can be attached to another part. Also, two or more inorganic sheets of the same material or different materials are laminated,
This can be affixed to the inner surface of the shell, which is also included in the present invention.

In the present invention, the lining brick used is a lining brick commonly used in a rotary kiln for producing cement.
Magnesia-spinel bricks, magnesia-chromium bricks, dolomite bricks and the like.

[0034]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a view for explaining one embodiment (Example 1) of the present invention, and FIG. 1 (A) is a schematic view of a cross section of a rotary kiln for cement production lined therein. (B) is a development view of the lining structure of the kiln.

(Example 1) 5.4 mφ of a rotary kiln 10 for cement production, 25
An MgO sheet 12 having a thickness of 2 mm is adhered to the inner surface of an iron shell 11 (thickness: 35 mm) over a length of m using a double-sided adhesive tape (not shown). Lined with brick 13. At this time, joint 13a of magnesia-spinel brick 13 and seam 12 of MgO sheet 12
a was constructed so as not to overlap. In addition, MgO material
Examples of the sheet 12 include the aforementioned “magnesia flexible sheet (trade name“ CRX-SM9 ”) (chemical composition → MgO: 90 wt%, SiO ₂ : 3w).
_{t%, Na 2 O: 2.0wt} %, CaO: 0.5wt%, Ig.loss: 12wt
%)"It was used.

After operating the rotary kiln 10 for 320 days, the magnesia-spinel brick 13 is removed,
The “state of the MgO-based sheet” and “the presence or absence of a product on the inner surface (surface) of the shell” were observed, and the “thickness of the shell” was measured. As a result, the MgO sheet 12 was hard and sintered and was in a brittle state, but almost no iron compound was generated on the surface of the iron shell 11. The thickness of the shell 11 was 34 to 35 mm, which was a decrease of 0 to 1 mm.

For comparison, a rotary kiln in which the MgO sheet 12 was not stuck (a part where the MgO sheet 12 according to Example 1 was not stuck at 35 m from the entrance of the cement clinker) was also used. In the same manner as in Example 1, for the rotary kiln lined with magnesia-spinel brick 13 as in Example 1, after operating for 320 days, the magnesia-spinel brick 13 was removed and the "shell inner surface ( The “surface presence” and “shell thickness” of the surface) were observed. As a result, “formation of an iron compound” was observed on the surface of the shell, and the thickness of the shell was 33 to 34 m.
m.

As described above, in the "Embodiment 1 in which the MgO sheet 12 is interposed between the iron shell 11 and the magnesia-spinel brick 13", the thickness of the iron shell 11 is "34 to 34".
35 mm "and a decrease of 0 to 1 mm.
In comparison with "33 to 34 mm" shown in "Example for comparison without intervening g12", "reduction of shell damage" was confirmed. In Example 1, the thermal conductivity of the MgO-based sheet 12 and that of the magnesia-spinel brick 13 were almost the same, which led to a reduction in the shell temperature.

(Example 2) A small-sized kiln (3.4 mφ) having a 7 mm-thick Al ₂ O ₃ —SiO ₂ sheet on the inner surface of an iron shell extending 40 m from the exit of the kiln. And an organic adhesive, and a magnesia-spinel brick was lined thereon. In addition, Al ₂ O ₃ -S
As the iO ₂ sheet, the above-mentioned “trade name“ CRX-SA7
L "high alumina flexible sheet (Chemical composition → Al ₂ O ₃ : 70w
_{t%, SiO 2: 25wt%} , Na 2 O: 4wt%, Ig.loss: 12wt%) . "
It was used.

After operating the kiln for one and a half years (547 days), the brick was removed, and the “state of Al ₂ O ₃ —SiO ₂ sheet and the state of shell” were observed. As a result, the Al ₂ O ₃ —SiO ₂ -based sheet was sintered and in a hard state, but almost no corrosion of the shell was observed, and the sheet was in a clean state. Further, since the thermal conductivity of the Al ₂ O ₃ —SiO ₂ material sheet is almost the same as that of the magnesia-spinel material brick lined thereon, the same as in the first embodiment,
It also led to "reduction of shell temperature".

[0041]

As described in detail above, the present invention is characterized in that an inorganic sheet is interposed between a shell of a rotary kiln for cement production and a lining brick. The secondary mineral generated by the reaction with the oxidizing gas has an effect of reducing the attack of the corrosive gas on the inner surface of the shell and preventing the shell from corroding.

According to the present invention, since the sheet used is inorganic, it is not burned out, can withstand long-term operation, and the inorganic sheet is flexible. In addition to this, the sticking operation is easy, and the brick lining can be performed immediately after the sticking, so that the effect that the work can be performed in a short time is generated and the effect that the shell temperature is lowered is also generated.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining one embodiment (Example 1) of the present invention, in which (A) is a rotary for cement production lined.
It is the schematic of the cross section of a kiln, (B) is a development view of the lining structure of the kiln.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotary kiln for cement production 11 Iron shell 12 MgO sheet 12a Seam 13 Magnesia-spinel brick 13a Joint

Claims (4)

[Claims] 1. A lining structure for a rotary kiln for cement production, wherein an inorganic sheet is interposed between a shell of the rotary kiln for cement production and a lining brick. 2. The inorganic sheet is made of Al ₂ O ₃ , A
l ₂ O ₃ -SiO ₂ , SiO ₂ -Al ₂ O ₃ , MgO, MgO-Cr ₂ O ₃ ,
The lining structure of a rotary kiln for cement production according to claim 1, wherein the lining is made of any of MgO-C. 3. The cement manufacturing rotary according to claim 1, wherein the inorganic sheet is attached to the inner surface of the shell by a double-sided adhesive tape or an organic adhesive. -Kiln lining structure. 4. The thickness of the inorganic sheet is 1 to 10 m.
The lining structure of a rotary kiln for cement production according to any one of claims 1 to 3, wherein m is m.