JP2007076966A - Method for producing hauyne - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing hauyne efficiently with stable quality and production volume while suppressing reduction and variation in production volume caused by decomposition of CaSO<SB>4</SB>which takes place when a firing temperature around the decomposition temperature of CaSO<SB>4</SB>is adopted for avoiding the difficulty in forming hauyne due to dominant formation of calcium aluminate, and without using an excessive amount of CaSO<SB>4</SB>. <P>SOLUTION: The method for producing hauyne comprises firing an object to be fired at 1,250-1,400°C, the object to be fired comprising 100 pts.mass of CaSO<SB>4</SB>, 150-260 pts.mass of Al<SB>2</SB>O<SB>3</SB>, and 80-130 pts.mass of CaO, wherein at least 30 mass% of CaO is a powder of unslaked lime. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a compound Erwin (3CaO.3Al ₂ O ₃ .CaSO ₄ ) known as a quick hardening component of a hydraulic substance or a hydraulic composition.

Erwin (3CaO · 3Al ₂ O ₃ · CaSO ₄ ) is a compound with a fast hydration rate, and is used as a fast-hardening component of fast- and ultra-hard-hardening cements. It is utilized for such as. (For example, refer to Patent Documents 1 and 2.) Industrially, Irwin's production method is, for example, a calcareous raw material such as limestone or calcium carbonate as a CaO source, and a clay mineral, bauxite, or CaSO ₄ source as an Al ₂ O ₃ source. As a raw material, for example, waste gypsum or the like is used as a raw material, and a mixture of a predetermined amount thereof is used as a material to be fired, and a clinker containing an Irwin phase is obtained by firing at about 1200 ° C. to 1300 ° C. with a firing device such as a rotary kiln. (For example, refer to Patent Document 3.) Irwin generation reaction and crystal growth become easier as the firing temperature is higher, but CaSO ₄ in the raw material starts to decompose at a temperature around 1300 ° C., and gaseous sulfur oxides are formed. Therefore, when the volatilization amount of the sulfur oxide increases, the generation amount of Irwin inevitably decreases. On the other hand, in order to avoid decomposition of CaSO _{4, when} a fired product made of the raw material as described above is baked at a temperature lower than the decomposition temperature, for example, 1000 to 1200 ° C., 12CaO · 7Al ₂ O ₃ etc. The formation of calcium aluminate becomes dominant, and only clinker in which calcium aluminate and CaSO ₄ coexist and erwin is hardly seen can be obtained. In addition, when calcined at a slightly higher temperature, for example, 1250 to 1400 ° C., calcium aluminate is once formed during the temperature rising process, but erwin is subsequently formed from this calcium aluminate and CaSO ₄ . Irwin may be obtained. (For example, see Patent Documents 4 to 5.)

However, since this temperature corresponds to the decomposition temperature of CaSO ₄ as described above, the loss of the CaSO ₄ component in the material to be fired occurs due to the decomposition. The raw material composition of CaO, Al ₂ O ₃ , and CaSO _{4 to} be baked is an excess amount of CaSO ₄ than the stoichiometric ratio (CaO: Al ₂ O ₃ : CaSO ₄ = 3: 3: 1) of the Erwin component. With this formulation, as the excess amount of CaSO ₄ is increased, the shortage of erwin production due to decomposition of CaSO ₄ can be compensated and the erwin production can be increased. Since this method has low erwin generation efficiency, it involves the uneconomical use of excess CaSO ₄ , and in addition, exhaust gas treatment of sulfur oxides that decompose and volatilize is also required. Furthermore, the degradation rate of CaSO _4, it is highly dependent trend slight differences, such as the firing temperature in the vicinity of particular decomposition temperature, residual CaSO ₄ weight this slight difference can contribute to Irwin formation, i.e. formation of Erwin Will affect the amount. In particular, in an industrial-scale baking apparatus, it is generally not easy to control delicate temperature conditions, and it is difficult to obtain a stable reproducibility with respect to the amount of erwin formation and its crystallinity.
JP-A-57-175762 JP 2002-316860 A Japanese Unexamined Patent Publication No. 57-200252 Japanese Patent Publication No. 51-222013 Japanese Patent Application Laid-Open No. 11-12009

The present invention is based on the loss of CaSO ₄ components accompanying the thermal decomposition of CaSO ₄ that occurs when the temperature at which erwin can be stably generated without the presence of calcium aluminate is set as the firing temperature for erwin production. Irwin production method capable of suppressing the reduction and fluctuation of the amount of erwin generation, easily obtaining erwin with stable quality and generation amount, and obtaining a large amount of erwin without using excessive amount of CaSO ₄ It is an issue to provide.

In order to avoid the fact that the formation of calcium aluminate is dominant and it is difficult to form erwin, the present inventors have fired the material to be baked near the decomposition temperature of CaSO _4. At that time, when a specific ratio of the CaO source material used for the object to be baked is used as quick lime powder, gaseous sulfur oxides such as sulfur dioxide generated by decomposition of CaSO ₄ due to calcination are generated in the CaO powder in the object to be baked. From the fact that it was captured in the process and again exhibited CaSO ₄ to be consumed for erwin formation, and an abundant amount of erwin could be stably generated without using an excessive amount of CaSO ₄ raw material. Was completed.

That is, the present invention is, CaSO ₄ 100 parts by weight of Al ₂ O ₃ 150 to 260 parts by weight, containing CaO80~130 parts by mass, and the target heating object at least 30 wt% is a quicklime powder CaO, 1250～ It is a manufacturing method of Irwin characterized by baking at 1400 ° C.

The present invention is also the above-mentioned Irwin production method, wherein the quicklime powder is a powder having a Blaine specific surface area of 2500 to 4000 cm ² / g.

According to the production method of the present invention, Irwin can be obtained with high production efficiency and little variation in production amount without continuing to use an excessive amount of CaSO ₄ raw material and delicate firing control. In addition, the amount of gaseous sulfur oxide (SOx) derived from the decomposition of CaSO ₄ components during firing is significantly reduced.

Examples of the CaSO ₄ used for the object to be fired in the Irwin production method of the present invention include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and may be not only natural gypsum but also so-called chemical gypsum. . Preferably anhydrous gypsum is used. In addition, Al ₂ O ₂ used for the object to be fired may be a waste recycling raw material such as aluminosilicate clay mineral or aluminum dross which is inexpensive in terms of cost. When it is desired to avoid the co-generation of compounds, the use of alumina or a hydrate thereof is preferable. It is desirable to use powdery materials for both the CaSO ₄ and Al ₂ O ₂ source materials. Moreover, CaO used for a to-be-baked material is not specifically limited, For example, although CaO source materials, such as limestone, a calcium carbonate, and calcium hydroxide, may be used, Preferably quick lime is used. In the present invention, in particular, it is essential that at least 30% by mass of the CaO equivalent value of the CaO source material to be used is quicklime powder. Preferably 70 mass% or more is quicklime powder. The quicklime powder to be used is preferably a powder having a Blaine specific surface area of 2500 to 4000 cm ² / g. When the specific surface area of the brane is less than 2500 cm ² / g, the reaction activity is low, and it may be difficult to react and trap the sulfur oxide generated by the thermal decomposition of CaSO ₄ , and when the specific surface area of the brane exceeds 4000 cm ² / g, a rotary kiln, etc. If it is fired, it will be scattered by the ventilation in the kiln, and the hygroscopicity will be high and the handling will be poor, so it is not suitable.

The mixing ratio of CaO, Al ₂ O ₂ and CaSO ₄ in producing the object to be fired is 150 to 260 parts by mass of Al ₂ O _{2 and} 80 to 130 parts by mass of CaO with respect to 100 parts by mass of CaSO ₄ . Preferably, it is set as _{200 to} 220 parts by mass of Al ₂ O ₂ and 100 to 130 parts by mass of CaO with respect to 100 parts by mass of CaSO ₄ . The value of the mixing ratio of the components shown here, value converted into CaO in CaO source material, value converted to CaSO ₄ in CaSO ₄ source material, a value in terms of Al ₂ O ₂ in Al ₂ O ₂ source material It is. Less than 150 parts by mass of Al ₂ O ₂ or less than 80 parts by mass of CaO is not preferable because excess CaSO ₄ that is not utilized for erwin formation increases, and the amount of erwin produced is at a low level relative to the amount of raw material used. On the other hand, if it exceeds 260 parts by mass of Al ₂ O ₂ or exceeds 130 parts by mass of CaO, excess CaO and Al ₂ O _{2 that} are not utilized for erwin formation increase, and the amount of erwin formation is low, which is not preferable. Further, in the present invention, quick lime powder is used for 30% by mass or more of CaO to be blended in the object to be fired. This captures sulfur oxides generated by thermal decomposition of CaSO ₄ occurring during firing. If the ratio of quicklime powder in the CaO raw material is less than 30% by mass, it is not preferable because the decrease in the amount of Irwin due to loss of volatilization of sulfur oxide due to thermal decomposition of CaSO ₄ cannot be suppressed. Preparation of the baked product in such proportion CaO, may be mixed Al ₂ O _2, and CaSO _4. The mixing method is not limited, and for example, dry mixing can be performed. The obtained mixture is not particularly required to have a shape such as a molded product, and can be subjected to firing in the form of a powder mixture. Moreover, as long as a desired amount of Irwin generation can be ensured, components other than CaO, Al ₂ O ₂ and CaSO ₄ may be contained in the object to be fired. Examples of such components include SiO ₂ , MgO, Fe ₂ O _3, etc., but depending on the coexistence of the product phase derived from the components, the properties as a fired product may change, so that the desired properties are obtained. In order to obtain a suitable fired product, it is desirable to adjust the types and amounts of the components.

The fired product can be fired at 1250 ° C. to 1400 ° C. to obtain a fired product in which an Irwin compound is generated. When calcining below 1250 ° C., formation of calcium aluminate is dominant and stable, and it is not preferable because erwin is hardly generated. When calcining above 1400 ° C., decomposition of CaSO ₄ proceeds excessively, and quicklime powder Further, it is difficult to capture the gaseous sulfur oxide due to the above, and amorphous calcium aluminate such as 3CaO.Al ₂ O ₃ is generated, which is not preferable. The temperature raising rate is not particularly limited, but cooling is preferably slow cooling or natural cooling. When quenched, CaSO ₄ formed by trapping sulfur oxides may not contribute to the formation of an Irwin compound, and an amorphous phase may be formed, which is not appropriate. Moreover, baking can be performed in air | atmosphere. A baking apparatus is not specifically limited, For example, an electric furnace, a gas furnace, etc. are mentioned. In addition, firing on a rotary kiln is recommended for production on an industrial scale.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples shown here.
<Preparation of the object to be fired>
Next, the raw materials described below were all put into an air blending mixer so as to have the blending amounts shown in Table 1, and dry-mixed for about 10 minutes, and this was used as a material to be fired.
Type II anhydrous gypsum (Blaine specific surface area 4500 cm ² / g)
・ Aluminum ash (α-Al ₂ O ₃ content 90.9%)
・ Quicklime A (Blaine specific surface area 3300cm ² / g)
・ Quicklime B (Brain specific surface area 1500cm ² / g)
・ Calcium carbonate (Brain specific surface area 3300cm ² / g)

<Firing of the object to be fired>
The material to be fired as described above was fired at a measured maximum temperature shown in Table 2 at a feed rate of 150 kg / H using a rotary kiln (diameter 1100 cm, length 800 cm). During firing, a sulfur oxide (SOx) concentration measurement sensor was installed at intervals of about 1 m between the kiln bottom of the rotary kiln and the flue, and the SOx concentration in the gas in the kiln was measured. The average value of the measured values is shown in Table 2 as the SOx concentration.

<Detection and amount of product phase in fired product>
The produced phase of the fired product was examined by powder X-ray diffraction, and the rate of Erwin formation in the fired product was examined by an internal standard method of powder X-ray diffraction. Moreover, what embedded the baked material piece in resin was cut | disconnected, then the cut surface was mirror-polished, and the crystal diameter of the Irwin compound which appeared on this surface was measured with the X-ray microanalyzer. The above results are also shown in Table 2.

  The high-quality Irwin obtained by the present invention can be used as a quick-hardening base material and an admixture of cement as an expansion component, and as a fast-hardening material and expansion material for cement paste, mortar and concrete. This method can also be used as a method to suppress the inclusion of sulfur oxide gas into the exhaust gas due to the decomposition of raw materials when the raw material containing alkaline earth sulfate is baked at a temperature higher than the decomposition temperature of the sulfate. it can.

Claims (2)

Firing an object to be fired at 1250 to 1400 ° C. containing 100 parts by weight of CaSO ₄ , 150 to 260 parts by weight of Al ₂ O _{3 and} 80 to 130 parts by weight of CaO, and at least 30% by weight of CaO being quicklime powder. Irwin manufacturing method characterized by this. The method for producing Irwin according to claim 1, wherein the quicklime powder is a powder having a Blaine specific surface area of 2500 to 4000 cm ² / g.