JP5682440B2 - Cement production method using rice husk ash - Google Patents

Description

  The present invention relates to a method for producing cement using rice husk ash, and more particularly, to a method for producing cement, which is used in the field of civil engineering and construction, and uses rice husk ash to enhance strength as desired over a long period of time. .

  Conventionally, rice husk ash has been used not as a raw material for cement but as a material used in preparing concrete ("Use of rice husk ash as an admixture for concrete" Ishiguro, Agricultural Civil Society, 65, 145- 150, 1997 (Non-Patent Document 1), “Effect of mixing of rice husk ash on the durability of mortar and concrete”, Wada et al., Cement concrete papers, 53, 340-345, 1999 (Non-patent document 2)).

  In order to obtain such rice husk ash, Japanese Patent No. 3580896 (Patent Document 1) discloses a technique for burning rice husks using the hot gas of a clinker cooler in a cement baking apparatus and recovering the ash with dust. Has been.

  In addition, in Japanese Patent Application Laid-Open No. 2010-230196 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2005-272297 (Patent Document 3), rice husk is simply regarded as one of biomass fuels and used as an auxiliary fuel instead of coal. In addition, in Japanese Patent Application Laid-Open No. 2010-120778 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2005-111374 (Patent Document 5), a fermentation process for converting sewage sludge or the like into fuel is disclosed. Technology has been developed to produce fuel after mixing.

  Therefore, when rice husk is used as fuel, the burned ash is unintentionally used as a raw material for cement, but the calorific value of rice husk is 2000 to 3000 kcal, which is lower than that of coal. Replacement is impossible, and as a result, the amount of ash used as a raw material is extremely small.

  For example, in the above Japanese Patent Application Laid-Open No. 2005-272297 (Patent Document 3), an example in which 10% of rice husk is used as auxiliary fuel is described. However, if all the auxiliary fuel is rice husk, it is used as a raw material. The ash content is about 0.1 to 0.2 parts by weight per 100 parts by weight of the clinker.

  Moreover, in the said Unexamined-Japanese-Patent No. 2005-111374 (patent document 5), 15 weight part of wood chips is mixed as a ventilation improvement material with respect to 100 weight part of sewage sludge, and the fermented deposit is 2 per 100 weight part of clinker. Although an example of charging at a ratio of parts by weight has been described, even if wood chips are all made into rice husks, the ratio at which rice husks are charged is about 0.3 parts by weight, and when the ash content is 0.1% Less than parts by weight.

Moreover, rice husk ash is amorphous silica, and a technique for improving the easy calcination property by using amorphous silica as a firing raw material is described in JP-A-2009-29679 (Patent Document 6). In such a document, attention is paid only to the amount of free lime, and no modification of C ₂ S is described.

Japanese Patent No. 3580896 JP 2010-230196 A JP 2005-272297 A JP 2010-120778 A JP 2005-111374 A JP 2009-29679 A

“Use of rice husk ash as an admixture for concrete” Ishiguro, Agricultural Society of Civil Engineers, 65, 145-150, 1997 “Effect of rice husk ash mixing on durability of mortar and concrete” Wada et al., Cement concrete papers, 53, 340-345, 1999

Therefore, an object of the present invention is to provide a simple and economical method for producing cement that can obtain desired long-term strength by using rice husk ash as waste as a raw material for cement clinker feeding kiln. .
Furthermore, it aims at the effective utilization of the rice husk ash which is a waste material.

The present invention, long-term strength to focus on the most significant influence C _{2 S} mineral, using rice husk ash as a cement clinker raw material, beta-C ₂ with increasing alpha 'phase of C _{2 S} cement obtained It has been found and achieved that the lattice volume of S is increased to increase the hydration reactivity and the long-term strength of the cement is increased.

  That is, according to the method for producing a cement using rice husk ash according to the present invention, when producing 1 ton of cement clinker, 25 to 350 kg of rice husk ash (Ig.loss = 0% conversion) is blended and fired. It is the manufacturing method of the cement using rice husk ash characterized by preparing.

Preferably, in the method for producing cement, rice husk ash is used as a SiO ₂ raw material in a cement clinker feed kiln raw material at a ratio of 10 to 100% by mass to produce a cement clinker.
More preferably, the cement is a low heat Portland cement or a medium heat Portland cement.

The method for producing a cement according to the present invention mixes an expensive special additive or the like without greatly changing exothermic characteristics and fresh properties, such as changing a chemical component of a cement or a specific surface area of a brane. Without using such an expensive and complicated method, rice husk ash, which is a waste, is used as a raw material for kiln when producing cement clinker, and as a result, C ₂ S produced in clinker is modified. Furthermore, it is possible to increase the lattice volume of C ₂ S to enhance the hydration activity and to obtain the long-term strength development properties of the cement by a simple manufacturing method and economically.
In addition, according to the method for producing cement of the present invention, it is possible to promote effective utilization of rice husk ash, which has conventionally been waste.

It is a diagram which shows an example of the calcination temperature conditions for manufacturing a clinker. Upon for clinker 1t production, shows a mass of rice husk ash was blended as a raw material, α'C 2 _S content in the prepared cement clinker and (mass%), the .beta.c 2 cell volume of _S (Å ³⁾ the amount of related It is. It is a diagram which shows an example of the relationship between the mass of the rice husk ash contained in a clinker, and the mortar intensity | strength seven days after casting. It is a diagram which shows an example of the relationship between the mass of the chaff ash contained in a clinker, and the mortar intensity | strength 28 days after placement. It is a diagram which shows an example of the relationship between the mass of the rice husk ash contained in a clinker, and the mortar intensity | strength 91 days after placement. It is a figure of the bar graph which shows the mortar intensity | strength seven days after casting, 28 days after casting, and 91 days after casting of each mortar obtained by the Example and the comparative example.

The present invention is illustrated by the following preferred examples, but is not limited thereto.
Concrete dams and concrete structures with large member dimensions, so-called mass concrete, are prone to cracking due to temperature stress, and therefore require cement with low heat of hydration and high long-term strength. Portland cement is used.
On the other hand, there are mainly 4 types of cement, 3CaO.SiO ₂ (C ₃ S), 2CaO · SiO ₂ (C ₂ S), 3CaO · Al ₂ O ₃ (C ₃ A) and 4CaO · Al ₂ O ₃ · Fe _2. O ₃ (C ₄ AF) cement clinker minerals are included, and strength development and hydration exothermic characteristics differ depending on the content of these minerals.

C ₃ S, which is one of the cement minerals, is closely related to the short-term strength development, especially when the amount of C ₃ S contained in the cement is large, the strength development is fast, and conversely, the strength development is slow. , for example, ordinary Portland cement C _{3 S} is about 55 wt%, more strength development early was high-early-strength 65% by weight Portland cement, moderate heat Portland cement with reduced strength development and hydration heat value conversely 40 About 25% by mass of low heat Portland cement is contained.
In addition, C ₂ S, which is one of the cement minerals, has a slower hydration reaction than that of alite. Therefore, in order to increase the long-term strength, it is necessary to increase the hydration activity of C ₂ S.

Here, the method for producing cement according to the present invention is a method for producing cement using rice husk ash, in which cement clinker is prepared by blending and firing 25 to 350 kg of rice husk ash for producing 1 ton of cement clinker. .
That is, it is C ₂ S among the above-mentioned four main clinker minerals that has the greatest influence on long-term strength, and long-term strength is controlled by changing the hydration reactivity of C ₂ S with rice husk ash. This is a method for producing cement.

Specifically, in producing cement clinker for 1 ton, by adding 25 to 350 kg of rice husk ash as a raw material and baking it, the α ′ phase of C ₂ S in the obtained cement clinker can be increased. , The lattice volume of the β phase of C ₂ S can be increased, and the long-term strength can be enhanced.
This is because C ₂ S, which was α ′ phase in the baking kiln, is usually mostly transferred to β phase with cooling, but the use of rice husk ash according to the present invention suppresses such transition, and more Many α 'phases are obtained, and the long-term strength is considered to increase. Thereby, the hydration activity can be increased.

The rice husk ash that can be used is not particularly limited, and conventionally used rice husk ash can be used in the present invention.
The rice husk ash is used as a raw material for SiO ₂ feed kiln, which is blended as a feed kiln raw material when producing a cement clinker. This is because the rice husk ash is amorphous silica.
Usually, when producing cement clinker, for example, silica stone is used as the raw material for the SiO ₂ feeding kiln, but some or all of the silica stone usually used as the raw material for SiO ₂ feeding kiln is replaced with the rice husk ash. use.
Its proportion is 10 to 100% by weight of SiO ₂ Okukama material, preferably replaces the 25 to 100% by weight rice hull ash.

  The rice husk ash is amorphous silica, but even if silica fume or silica gel, which is other amorphous silica, is used, the effect of the present invention cannot be obtained.

  The cement manufacturing method of the present invention can be applied to various cement manufacturing methods such as ordinary Portland cement, moderately hot Portland cement, and low heat Portland cement. Preferably, since the present invention can modify belite, it can be effectively applied to a method for producing a low heat Portland cement which is a high belite-containing cement.

The clinker feeding kiln raw material blended with rice husk ash at the above blending ratio is fired, for example, with an actual machine, and the cement clinker is fired.
Such firing conditions are not particularly limited, and the cement clinker is usually fired under conditions for firing cement clinker or any known conditions.
By manufacturing cement clinker this way, it is possible to increase the hydration activity of C _{2 S} to produce in the resulting cement clinker.

Thus, according to the present invention, the C ₂ S lattice volume can be reduced by blending and preparing a certain amount of rice husk ash when producing a cement clinker without changing the mineral composition and the specific surface area of the brane. Since the long-term strength can be changed as a result, it becomes possible to produce a cement having a desired long-term strength development property using rice husk ash as waste.

The present invention will be described in detail by the following examples and comparative examples.
Each raw material used for the production of cement clinker is shown in Table 1 below together with the chemical composition.

(Comparative Example 1)
The chemical composition of the low heat Portland cement clinker obtained using limestone, iron raw material, clay (1), clay (2) and silica stone, which are raw material for low heat Portland cement having the composition shown in Table 1 above. 2 is adjusted and blended as shown in FIG. 2 and baked at a baking temperature of 1000 ° C. for 30 minutes, and then the temperature is increased from 1000 ° C. to 15 ° C./minute and then heated at 1450 ° C. for 30 minutes (see FIG. The low-temperature Portland cement clinker was prepared by firing in a Kanthal super furnace under the temperature conditions shown in FIG. However, silica was blended at a rate of 273 kg per 1 ton of low heat Portland cement clinker to be obtained.

Dihydrate gypsum was added to the obtained low heat Portland cement clinker and pulverized by an actual machine finishing mill to obtain a low heat Portland cement having an average brain specific surface area of 3700 cm ² / g.
The gypsum was added so that the amount of SO ₃ contained in the resulting low heat Portland cement was 2.4% by mass.
CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ contained in the obtained low heat Portland cement were analyzed by JIS R 5202 “Chemical analysis method of Portland cement”, and C ₃ S, C ₂ S, C ₃ A, and C ₄ AF were calculated.
The results are shown in Table 3 below, including the amount of SO ₃ (gypsum) analyzed in JIS R 5202 “Chemical analysis method for Portland cement”.

(Comparative Example 2)
Except that 4.6% by mass (corresponding to 12.5 kg per 1 ton of clinker obtained) of silica used in Comparative Example 1 in producing a low heat Portland cement clinker was replaced with rice husk ash as shown in Table 1. In the same manner as in Example 1, a low heat Portland cement clinker was produced, and a low heat Portland cement was further prepared.

(Example 1)
Comparative Example 1 except that 9.2% by mass (corresponding to 25 kg per 1 ton of clinker obtained) of the silica used in Comparative Example 1 in producing the low heat Portland cement clinker was replaced with rice husk ash shown in Table 1. In the same manner as above, a low heat Portland cement clinker was produced, and a low heat Portland cement was further prepared.

(Example 1)
Except that 22.9% by mass (corresponding to 62.5 kg per 1 ton of clinker obtained) of silica used in Comparative Example 1 in producing the low heat Portland cement clinker was replaced with rice husk ash as shown in Table 1. In the same manner as in Example 1, a low heat Portland cement clinker was produced, and a low heat Portland cement was further prepared.

Example 3
Comparative Example 1 except that 45.8% by mass (corresponding to 125 kg per 1 ton of clinker obtained) of silica used in Comparative Example 1 in producing the low heat Portland cement clinker was replaced with rice husk ash shown in Table 1. In the same manner as above, a low heat Portland cement clinker was produced, and a low heat Portland cement was further prepared.

Example 4
In the same manner as in Comparative Example 1 except that the total amount of silica used in Comparative Example 1 for producing the low heat Portland cement clinker (equivalent to 273 kg per 1 ton of clinker obtained) was replaced with rice husk ash shown in Table 1, A low heat Portland cement clinker was produced, and a low heat Portland cement was prepared.

(Comparative Example 3)
In producing the low heat Portland cement clinker, the total amount of silica used in Comparative Example 1 (corresponding to 273 kg per 1 ton of clinker obtained) was replaced with silica gel shown in Table 1 in the same manner as in Comparative Example 1. Portland cement clinker was produced, and further low heat Portland cement was prepared.

(Comparative Example 4)
In the same manner as in Comparative Example 1 except that the total amount of silica stone used in Comparative Example 1 for producing the low heat Portland cement clinker (corresponding to 273 kg per 1 ton of clinker obtained) was replaced with silica fume shown in Table 1, A low heat Portland cement clinker was produced, and a low heat Portland cement was prepared.

(Test example)
Each clinker and each cement obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by the following test, and the results obtained are shown in Table 4 below.
(Test Example 1)
Each clinker obtained was measured for f-CaO in the clinker according to JCAS I-01. It should be noted that f-CaO is generally used as an index for judging good / bad firing, and if it is 1% by mass or less, firing is judged as “good”.
(Test Example 2)
Each obtained clinker was ground using a planetary mill PM-400 (manufactured by Retsch) at 300 rpm for 20 minutes until the brain value was about 6000 cm ² / g to prepare a test sample. Each test sample was measured for a diffraction peak at a tube current of 40 mA and a tube voltage of 45 kV using a powder X-ray diffractometer X'Pert MPD (manufactured by Panalical), and then subjected to Rietveld analysis using analysis software High Score Plus manufactured by the same company. Then, the content (mass%) of α′C ₂ S in the C ₂ S crystal phase in the cement clinker and the lattice volume of βC ₂ S were measured, and the results are shown in Table 4 and FIG.

(Test Example 3)
About each obtained cement, according to JISR5201 "the physical test method of cement", water was added so that water / cement ratio might be 50 mass%, and each mortar was prepared.
The mortar strength of each obtained mortar was measured according to JIS R 5201 “Cement physical test method”, and the strength after 7 days, 28 days, and 91 days after each mortar placement was measured. Shown in FIGS.

From the results of Table 4 and FIGS. 2 to 6, Examples 1 to 4 contained in an amount of 25 to 350 kg per ton of clinker from which rice husk ash is obtained have a large amount of α′C ₂ S having a high hydration activity. As can be seen, the lattice volume of βC ₂ S increases. Along with this, the mortar strength of the mortar obtained has greatly increased after 28 days. On the other hand, in Comparative Examples 3 and 4 using silica gel or silica fume, which is the same amorphous silica as rice husk ash, it is found difficult to increase the strength of the mortar.
Thus, by incorporating a rice hull ash which is amorphous silica gel at a constant rate, by the production of cement clinker, high α'C 2 _S of hydrous activity often generates, also grating .beta.c 2 _S The volume also increases, and as a result, the desired long-term strength of the cement can be developed.

  The cement obtained by the present invention is excellent in long-term strength, and can be usefully applied to civil engineering and construction fields in which cement is used, particularly concrete dams and concrete structures having a large member size, so-called mass concrete.

Claims (3)

A method for producing cement using rice husk ash, comprising preparing 25 to 350 kg of rice husk ash and calcining it to produce 1 ton of cement clinker. 2. The method for producing cement according to claim 1, wherein rice husk ash is used at a rate of 10 to 100% by mass as a SiO ₂ raw material in a cement clinker feed kiln raw material. Method. 3. The method for producing cement according to claim 1, wherein the cement is low heat Portland cement.

Images