JPS6217013A - Production of gamma-type dicalcium silicate powder - Google Patents

Abstract

PURPOSE:To produce efficiently the excellent gamma-type dicalcium silicate powder which is extremely dusted by calcining a blend of a calcareous raw material having specific composition and a siliceous raw material, cooling it slowly and thereafter quenching it. CONSTITUTION:After blending a calcareous raw material (e.g. limestone) and a siliceous raw material (e.g. silica rock) so that 1.5-12.5wt% total of Al2O3 and Fe2O3, <=1.25wt% total of Na2O and K2O and 1.90-2.10 molar ratio of CaO/SiO2 are obtained in a mixture after the calcination at 1,000 deg.C, a mixed raw material is obtained by regulating it so that the residual of 88mu sieve is made to <=20wt%. Next after molding this mixed raw material in a pellet-shape, it is calcined at 1,300-1,500 deg.C with a rotary kiln and slowly cooled up to 600-1,250 deg.C and thereafter quenched up to 350 deg.C and crushed in accordance with the necessity so that the specific surface area of the grain is made to 4,000-9,000cm<2>/g.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a powder whose main component is γ-type dicalcium silicate powder, which is a type of dicalcium silicate.

(Prior art) Dicalcium silicate is 20aO・S k 02 (hereinafter referred to as C2
It has the chemical formula S) and is one of the main minerals that make up Portland cement. There are four types of metamorphosis of C2S: α, α', β and r. Among these, r-type C25 (referred to as γ-C2S) has no hydraulic property and γ
-C2S is considered to be a very undesirable mineral in the production of cement clinker because it exhibits a phenomenon in which it becomes powder (hereinafter referred to as dusting) when it is generated, that is, during its transition. For this reason, many studies have been conducted to prevent the formation of r-02S in the production of cement clinker.

On the other hand, γ-C2S powder itself has traditionally attracted attention as a filler material for synthetic resins and other materials because it is a stable fine particle of calcium silicate, and recently there has been research into using it as an air-hardening cement by curing it with carbon dioxide gas. This is becoming the case in some areas. However, r-
C2S is expensive, partly because mass production technology has not been established so far, and when it comes to product quality, there are problems such as the production technology for good γ-C2S powder has not yet been established. are doing.

Traditionally, r-C2S is contaminated with impurities (e.g. Al2O., F
It was synthesized only from high-purity lime and silicic raw materials with low e2O3°Na2O, K2O). Dusting of γ-C2S is a phenomenon that occurs when C2S changes from a substance with high specific gravity to a substance with low specific gravity and expands in volume when it transitions from β type to γ type. However, if there are impurities in the raw materials used, the transition of β-C2S to γ-C2S is suppressed, and β-C2S is cooled to room temperature and becomes stable, and in this case, the clinker does not dust. Or dusting only locally, resulting in good r-
Unable to obtain C2S.

For these reasons, to date, there have been no reports of industrially producing γ-C2S and using it as an industrial material. Furthermore, at present, there are almost no research publications on technology for industrially producing high-quality γ-C2S.

(Problems to be Solved by the Invention) In view of the expected expansion of the range of use of r-C2B powder, the present invention aims to improve
The aim is to find a method for industrial production that is inexpensive and efficient. That is, the inventor found that γ-C2S powder easily reacts with carbon dioxide gas and solidifies, and can be effectively used as a binder when manufacturing concrete.
It has been confirmed that when concrete is manufactured using S as a binder, it develops high strength in a very short time, within one hour, even when cured at room temperature. From this point on,
This invention aims to industrially produce γ-C2S that is well dusted and has good quality.

(Another means to solve the problem) This invention solves the problem of Al2O in the mixture after firing at 1000°C.
The total amount of 3 and Fe2O3 is 1.5 to 12.5%, and N
Calcareous raw materials and silicic raw materials are blended so that the total amount of a20 and K2O is 1.25 weight or less, and the molar ratio of Cao/SiO2 is 1.90 to 2.10, and this is
Prepared so that the 8μ sieve residue is 20% by weight or less,
After that, this blended raw material is heated in a rotary kiln to 1,300 to 1
Calcined at 500℃, then slowly cooled to 600-1250℃, then clinker temperature is 350℃
This is a method for producing a γ-type dicalcium silicate powder, characterized by rapidly cooling the powder until the γ-type dicalcium silicate powder has a plain specific surface area of 4000 to 9000 c.
This is a method for producing γ-type dicalcium silicate powder, which is characterized in that it is pulverized to a particle size of 747 mm.The present invention will be further explained below.

The raw materials used in this invention are calcareous raw materials and silicic raw materials. As the former calcareous raw material, limestone, slaked lime, quicklime, or a mixture thereof can be used. Of these, limestone, which is used for cement production, is cheap and economical. In addition, silica raw materials include silica stone, silica sand, clay, amorphous silica, □
or a mixture thereof. Among these, it is economical to use silica stone and clay. Calcareous raw material 2 Silicic material■0 distribution company1゛0°■"0pa" company 11.90~2.10
shall be. If it is outside this range, the amount of γ-C2S produced will decrease and good γ-C2S will not be obtained. Furthermore, Al2O is added to the mixture of calcareous raw material and silicic raw material after firing.
The total amount of 3 and Fe2O is 1.5 to 12.5% by weight and N
a The total amount of 20 and K2O should be 1.25 parts ff11 or less. Therefore, it is necessary to select and mix calcareous raw materials and silicic raw materials so as to satisfy this condition. The total amount of At2o3 and Fe2O in the blended raw materials is 1.5% by weight
If it is less than γ-C2, when firing in a rotary kiln to generate C2S, the liquid phase component will be insufficient and the reaction will be insufficient.
The amount of S produced decreases. In addition, the blended raw materials Al2O3 and F
e2O.

If the total amount exceeds 12.5 cm, β-C2 in the clinker
S is stabilized, the amount of γ-C2S produced decreases, and the clinker may not be dusted or the dusting may be localized, which is undesirable. Furthermore, Na 20 in the raw materials for preparation
and K2O shall be 1.25% by weight or less. When such alkalis exceed 1.25% by weight, β
-C2S is stabilized and good γ-C2S powder cannot be obtained. The blended raw materials are pulverized and the residue through an 88 μ sieve is 20 weight fA.
% or less. 88μ sieve residue is 20
If it exceeds 1, the reaction for producing r-C2S becomes insufficient, and good γ-C2S cannot be obtained. Note that the finer the powderiness of the raw materials, the better.

The calcareous raw material and the silicic raw material may be mixed and pulverized, or they may be pulverized separately and then mixed. This mixed raw material may be inserted into the rotary kiln as it is in powder form or after being formed into pellet form, but from the point of view of making the cooling rate of the clinker uniform after firing, it is preferable to form it into pellet form. Among rotary kilns, it is particularly convenient to use a repo kiln for firing. Firing temperature is 1300~15
00℃ range. If the firing temperature is less than 1,300°C, the firing reaction will be insufficient, which is not preferable. Also, the firing temperature is 15
If it exceeds 001:, the amount of γ-C2S produced decreases, resulting in insufficient dusting.

This is considered to be because a large amount of impurities in the raw materials are dissolved in the C2S crystal. Furthermore, even if it is fired at a temperature exceeding 1500°C, the properties of the γ-C2S powder are not particularly improved, and instead only cause heat loss during firing. The clinker fired at the above temperature has a clinker temperature of 60
It is slowly cooled to a temperature of 0-1250°C. Good γ-C2S can be obtained by such firing. This is because Al2O3 and Fe2O3 in the raw materials are mainly melilite (
2CaO+ Al2O3(F'5203) -Sin□
), which suppresses the production of β-02S. If this temperature exceeds 1250° C., the clinker transition from β-C2S to γ-C2S will be insufficient, and the amount of r-C2S produced will decrease, resulting in insufficient dusting. Also, cooling to a temperature below 600°C is undesirable because the clinker immediately starts dusting when it is next quenched in the cooler and becomes powdered in the cooler. The clinker is then rapidly cooled in a cooler until its temperature reaches 350°C. Clinker dusting is 300-3
Since the clinker starts at 50℃, if the clinker temperature is cooled to 350C or less, it will turn into powder during quenching in the cooler, so the quenching in the cooler should be stopped at 350℃, and then the clinker should be transferred to an external device such as on a belt conveyor. and then cooled to room temperature.

The powdered γ-C2S obtained as described above contains 60% or more of particles of 40μ or less, and has a plain specific surface area of 250%.
It is about 0 to 3000 cm279. Although it can be used as a binder for carbonation curing as it is, it is preferable to use it after pulverizing it to a plain specific surface area of 4,000 to 9,000 crn"7g. If it is less than 4,000.279, the strength after carbon dioxide curing is small, so Also 900 a
When rm2/9 is exceeded, even if the material is ground very finely, the increase in strength after carbon dioxide curing is small, resulting in a loss of grinding energy, which is not preferable. This invention will be further explained below by giving experimental examples.

Experimental Example 1 Limestone and silica stone, which had been dried at 110° C. and crushed through 11 sieves, were mixed and crushed in a sol mill to prepare a blended raw material having the following properties. In addition, the chemical composition of the blended raw materials is 100%
The analytical values after firing at 0°C are shown. Further, the fineness of the blended raw material was set to 10.5% as a residue after passing through an 88μ sieve.

Table 1 R2O3; Al2O3 + Fe203 R20; 2° to Na2O+ The raw materials were then granulated using a gun pellet, dried and sieved to form pellets with a diameter of 9.52 to 12.7+ m. This infarct was then placed in a platinum dish, placed in an electric furnace at 800°C, heated, and fired at 1400°C for a predetermined period of time. This was then slowly cooled in a furnace to various temperatures.

Immediately thereafter, the platinum plate was taken out from the furnace, and the clinker was discharged into an iron container and rapidly cooled. This was left to cool to room temperature, and after dusting, the amount of clinker powder passing through a 40μ sieve and the amount of free lime in ft' were measured.

The results are shown in Table 2.

It can be seen from Table 2 that the clinker after firing needs to be slowly cooled to 1250° C. or lower.

In addition, A14 was insufficiently baked with a baking time of 2.5 minutes.
Some of the products obtained were not dusted.

Experimental Example 2 Limestone and silica stone, which had been dried at 110° C. and crushed through a 1-inch sieve, were mixed and crushed in a ball mill to obtain a mixed raw material having the following properties. The chemical components of the raw materials shown in Table 3 are the analytical values after firing at 1000°C. In addition, the fineness of the blended raw material was set to 6.5 cm as a residue after passing through an 88μ sieve.

Table 3 R20; Al2O. +Fe2O.

R20; Na2O+K2O This blended raw material was then granulated using a pan pelletizer, dried and sieved to form pellets with a diameter of 9.52 to 12.7. This beret was then placed in a platinum plate and experiment example 1
The amount of free lime and the amount passing through a 40μ sieve were measured, and the results shown in Table 4 were obtained. The firing and cooling conditions were as follows.

Firing temperature: 1250-1550°C.

Temperature increase rate: Temperature increase rate from 800°C to each firing temperature + 301? :/min.

Annealing rate; rate of temperature drop from firing temperature to annealing temperature, 25
°C/min.

Cooling after taking out from the furnace: Rapid cooling in the same manner as in Experimental Example 1.

Table 4 From Table 4, it can be seen that when fired at a temperature of 1300 to 1500°C, r-C2S becomes the main component, but l5
The temperature exceeds 00 and reaches 1550℃.
(b) does not increase, so it can be seen that exceeding 1500'Ct- is undesirable as it will result in a loss of thermal energy.

Experimental Example 3 The limestone and silica stone used in Experimental Example 2 were mixed and pulverized, and raw materials were prepared by changing the CaO/SiO□ molar ratio of the blended raw materials. 7
A pellet of m diameter was prepared. Thereafter, this was fired in an electric furnace, and the results shown in Table 5 were obtained. In addition.

The firing conditions were as follows.

Firing temperature: 1450°C, firing time: 10 min
.

Heating rate: 30°C/min, slow cooling temperature: 1200°C.

Slow cooling rate: 25°C/min.

Mayu, 88μ sieve residue of blended raw materials 13~'1
The range was set at 5%.

From the results shown in Table 5, it can be seen that in order to produce a good r-C2B powder, the blending ratio of CaO and SiO is in the range of 1.90 to 2.10 in terms of CaO/SiO2 molar ratio. Outside this range, large amounts of β-C2S, C3S2, etc. are generated, and the amount of r-C2S generated decreases.

Experimental Example 4 Al2O3 of limestone, silica sand, silica stone, and pongee. Fe2O3
゜MgO, Na2Co3. 6th using K2CO2
The raw materials having the chemical components shown in the table were mixed and ground in a ball mill. The fineness of each blended raw material was 11 to 13 inches when passed through an 88μ sieve. Thereafter, the blended raw materials were made into pellets having a diameter of 9.52 to 12.711I11 in the same manner as in Experimental Example 1.

This pellet was then fired in an electric furnace to obtain the results shown in Table 7. The firing conditions were as follows.

Firing temperature: 1400°C, firing time: 15 minutes heating rate;
30℃/min (heating rate from 800℃ to 1400℃ slow cooling temperature; 1200℃, slow cooling rate; 25℃/min
The results are shown in Table 7.

Table 7 R2O3: Al2O s + Fe 203R20
;Na2O+K2O From the results in Table 7, in order to produce good γ-C2S, the total amount of Al2O3 and Fe2O3 in the blended raw materials must be 1.
It can be seen that the content needs to be 5 to 12.5% by weight. A
When the total amount of 12O3 and Fe2O3 is less than this lower limit, the amount of liquid phase components produced during firing is small, resulting in insufficient firing reaction, and unreacted substances remain in the clinker. For this reason, γ
-The amount of C2S produced decreases, which is not preferable. Also, AL2
0. When the total amount of Fe205 and Fe205 exceeds the above upper limit, 2C&0.Al2O3 (Fe203).5iO2 (melilite) is not produced and a large amount of β-C2S is stabilized, which is not preferable.

Makoto, the total amount of Na20 and K2O in the blended raw materials is 1.2
5 weight - or less. If this total amount exceeds this, melilite will not be generated and β-C2S will be stabilized.

Experimental Example 5 Limestone, silica stone, and clay were mixed and pulverized in a sol mill, and pellets with a diameter of 9.52 to 12.7 m were prepared in the same manner as in Experimental Example 1. Chemical components of this mixed raw material (however, 10
The analytical values after firing at 00°C are as follows.

Table 8 This pellet was then fired in an electric furnace to obtain the results shown in Table 9. The firing conditions were as follows.

Firing temperature: 1450°C, firing time: 1 o minute.

Temperature increase rate: 30℃/min, (from 800℃ to 1450℃
(Temperature increase rate up to) Annealing temperature: 1200℃, annealing rate: 25℃/ml n
.

Table 9 It can be seen from Table 9 that the blended raw material is preferably ground so that the residue on the 88μ sieve is 20 inches or less.

Experimental Example 6 The limestone and silica stone f used in Experimental Example 1 were mixed and ground in a ball mill to prepare 1000 kg of blended raw materials having the following properties. The chemical composition of the ζ0 blended raw material (analyzed value after firing at 1000°C) was as follows. Further, the fineness of the blended raw material was 10.5%, which remained after passing through an 88μ sieve.

The raw materials prepared in Table 10 were then granulated using a pan pelletizer, dried and sieved to form pellets with a diameter of 7.9 to 15.9. Next, this pellet has an inner diameter of 270mm and a length of 4500wn.
The mixture was fed into a small rotary kiln (No. 5) at a rate of 9/hr (No. 15) for firing.

During firing, the clinker's highest temperature, the baking point temperature, was held constant at 1430 to 1450°C, and the clinker temperature at the kiln outlet was changed by moving the burner in and out of the kiln.

The clinker that fell from the kiln was forced to air cooled by a fan from the bottom on a perforated steel conveyor. The clinker on the conveyor was then dusted into a steel container. After the dusted clinker was cooled to room temperature, the number of minutes it passed through a 40μ sieve was measured, and the results are shown in Table 11.

,'1 In Table 11, set the clinker drop temperature to 500℃ by operating the burner.
Because it was impossible to lower the temperature to
The sample was held for a period of time, and the sample was immediately taken out of the electric furnace and dropped onto a steel conveyor.

The residence time of the nozzle in the kiln was approximately 60 minutes, and the residence time of the clinker at the baking point was 7 to 10 minutes.

As is clear from Table 11, in the rotary kiln, γ-
When producing C2S, the clinker is placed in the kiln at 125
It can be seen that it is necessary to gradually cool down to below 0°C and then rapidly cool it. Furthermore, if clinker is slowly cooled to 500℃ in a kiln, the small-diameter clinker will dust and become powder as soon as it falls into the cooler from the kiln, so the generated r-C2S particles will flow back into the kiln, which is undesirable. . Measure the dusting start temperature of clinker, 9 results, 3
It was found that dusting occurs at temperatures between 00 and 350 degrees Celsius, so
The lower limit of clinker cooling with a cooler is 350°C. Experimental Example 7 Limestone and silica stone were pulverized in a Ga-Lumill with different blending ratios, and the chemical composition shown in Table 12 (however, analysis after firing at 1000°C) value) was used as the raw material for the preparation.

The fineness of the powder was set to 14 to 16 inches after passing through an 88μ sieve. Thereafter, this was carried out in the same manner as in Experimental Example 6, and 7.9 to 15.
A pellet with a diameter of 9 m was prepared, and 100 yu of each pellet was prepared.

Table 12 This pellet was then put into the rotary kiln used in Experimental Example 7 and fired, and the results shown in Table 13 were obtained. The firing conditions were as follows.

Baking point temperature: 1430-1460°C, clinker kiln outlet temperature: 1180-1230°C.

Table 13 As is clear from Table 13, Ca07810 of the blended raw material
Good r-C2 when the molar ratio of 2 is between 1.90 and 2.10.
S powder can be produced in a rotary kiln.

Experimental Example 8 Limestone, silica stone, and clay were crushed in a galvanic mill and 500kl of mixed raw materials having the particle size and components shown below were prepared. Prepared. The fineness of this blended raw material is 88 μ sieve residue 17.9
%, and its chemical components (however, the analytical values after firing at 1000°C) were as shown in Table 14.

Table 14 CaO/5102 molar ratio: 1.97 9.52 to 15.
The pellets were granulated into 9-diameter pellets, which were then dried at 110°C. The pellets were then fed into the small rotary kiln used in Experimental Example 6, fired, and cooled in the same manner as in Experimental Example 6. The firing conditions were as follows: Baking point temperature: 1250-1550℃ Kiln drop temperature: 1200-1230℃
Regarding the clinker powder cooled to room temperature in this manner, the amount passing through a 40μ sieve and the amount of free lime were measured, and the results shown in Table 15 were obtained.

Table 15 Umbrella clinker easily forms large lumps at the burning point.

It was difficult to drive safely continuously.

As is clear from Table 15, when r-C2S powder is fired in a rotary kiln, the firing temperature is between 1300 and 1
It is necessary to set the temperature to 500°C.

Experimental Example 9 The blended raw materials prepared in Experimental Example 8 were fed into a kiln in the same manner as in Experimental Example 8 and fired in the form of powder without being made into pellets. The burning point temperature was 1400 to 1430°C. The particle size of the r-C2B powder obtained here was 81 inches that passed through a 40μ sieve.

Experimental Example 10 The γ-C2S powder (plain specific surface area 2810 cm2/9) obtained in Experimental Example 6 was ground to various degrees of fineness, and then γ-C2S and Toyoura standard sand were mixed at a weight ratio of 1:2. Mix and then mix 100! Add and mix 8 polymerized parts of water to part ii, molding pressure 100 and 9/an'' to φ=25 tx
A cylindrical body with a height of 30 cm was molded.

Each molded body was then cured for 1 hour in a carbon dioxide atmosphere at 20°C, and the compressive strength was measured. The results are all shown in the attached figure.

As is clear from the attached diagram, high strength can be achieved in one hour when γ-C2S powder is cured with carbon dioxide in the presence of water. The fineness of γ-C2S used as a binder for carbonation hardening is 4000~4000 in terms of plain specific surface core.
It can be seen that the range of 9000 Ka2/S' is preferable. 40
When it is coarser than 00 cm2/9, the strength is small, so 9
000 cm'' 79 or more is not preferable because the increase in strength is small even if it is finely ground.

Experimental Example 11 The r-C2S powder prepared in Experimental Example 10 (plain specific surface area 8100 cIn''/,!i') and Toyoura standard sand were mixed in 1:1 ratio.
After that, 8 parts by weight of water was added to 100 parts by weight of the mixture, and the molding pressure was 200 kp/cm.
Then, a cylindrical body with a diameter of 25 gourd and a height of 30 cm was molded. This molded body was then cured at 20° C. in a carbon dioxide atmosphere and its compressive strength was measured. For comparison, ordinary Portland cement and Toyoura standard sand were molded in the same manner, and then cured at 20° C. and a relative humidity of 80° C. or higher, and the compressive strength was measured. The results are shown in Table 16.

Table 16 As is clear from Table 16, γ-C2S powder 'ft'
It can be seen that when carbon dioxide gas cures in the presence of water, high strength can be achieved in a significantly shorter time than conventional cement.

(Effects of the Invention) As explained above, according to the present invention, it is possible to continuously produce a large amount of γ-C2S powder containing many particles of 40 μm or less. And since γ-C2S can be obtained from inexpensive calcareous raw materials and silicic raw materials,
The product can be inexpensive. In addition, when the r-C2S powder obtained in this way is further crushed and cured with carbon dioxide gas, its strength develops much faster than that of hydraulic cement, and the strength becomes high. Cost reduction will be achieved.

[Brief explanation of drawings]

Claims (2)

[Claims] (1) Al_2O_3 in the mixture after firing at 1000°C
The total amount of Fe_2O_3 and Fe_2O_3 is 1.5 to 12.5% by weight, the total amount of Na_2O and K_2O is 1.25% by weight or less, and the molar ratio of CaO/SiO_2 is 1.90 to 12.5% by weight.
2.10, calcareous raw material and silicic raw material are blended, and this is adjusted so that the residue on the 88 μ sieve is 20% by weight or less, and then this mixed raw material is heated in a rotary kiln for 1 hour.
Calcinate at 300-1500℃, then heat at 600-12℃
A method for producing γ-type dicalcium silicate powder, which comprises slowly cooling the powder to 50°C and then rapidly cooling it until the clinker temperature reaches 350°C. (2) Al_2O_3 in the mixture after firing at 1000°C
The total amount of Fe_2O_3 and Fe_2O_3 is 1.5 to 12.5% by weight, the total amount of Na_2O and K_2O is 1.25% by weight or less, and the molar ratio of CaO/SiO_2 is 1.90 to 12.5% by weight.
Calcareous raw materials and silicic raw materials were blended so that the ratio of
Calcinate at 300-1500℃, then heat at 600-12℃
The γ-type dicalcium silicate powder obtained by slow cooling to 50°C and then rapid cooling until the clinker temperature reaches 350°C has a plain specific surface area of 4000 to 9000 cm^2/
1. A method for producing γ-type dicalcium silicate powder, which comprises pulverizing it into g.