KR100846821B1 - An improved process for the production of geopolymeric material from fly ash - Google Patents

Abstract

A method for producing a geopolymeric material from fly ash is provided to reduce a production cost largely, to emit little or no carbon dioxide by using low-temperature treatment, and to produce the geopolymeric material having improved strength. A method for producing a geopolymeric material from fly ash includes the steps of: (a) activating dry fly ash and reducing the fly ash to the size ranging from 1 to 30 micron by high energy milling for 10-60 minutes; (b) mixing 5-50wt% of an alkaline activator with 50-95wt% of water for 10-60 minutes; (c) mixing 60-95wt% of the vacuum-milled fly ash of the step (a) with 10-40wt% of the alkaline activator solution for 15-30 minutes; (d) vacuum-compressing the mixed powders for 2-10 minutes or compressing the mixed powders with a pressure of 50-250 kg/cm^2; and (e) drying the formed material at ambient temperature for 2-24 hours, and hardening the dried material at 50-200 °C for 1-24 hours. Further, the high energy milling is selected from vibration milling, abrasion milling, jet milling and oiliness milling.

Description

AN IMPROVED PROCESS FOR THE PRODUCTION OF GEOPOLYMERIC MATERIAL FROM FLY ASH}

The present invention relates to a process for producing geopolymer material from fly ash, and more particularly to a process for producing geopolymer material from fly ash, which is a waste generated from a thermal power plant. In particular, the present invention relates to a process for preparing geopolymer material from mechanically activated fly ash.

The products produced by the manufacturing process according to the invention will utilize fly ash, which is abundantly available in India and around the world, as its main component. This manufacturing process does not require large energy consumption and does not emit CO ₂ . The product produced by the manufacturing process according to the invention may have very good volume stability, moderate strength gain in a short time, good durability and high fire resistance. The geopolymer material according to the present invention is useful as a main component of geopolymer cement and concrete for fireproof and insulation panels, decorative stone products, building materials, ceramic tiles, heat resistant materials, aluminum castings, buildings, etc., and fixing of toxic wastes. something to do.

The processes for producing geopolymer materials known to date use pure materials such as alumina and silica as the main raw materials and sodium or potassium as the alkaline activator. Conventional manufacturing processes use from 10 to 50% by weight of alumina and from 50 to 90% by weight of silica. Conventional manufacturing processes for producing geopolymer materials include grinding and milling raw materials in a ball mill or vertical roller mill, blending raw materials in a mechanical mixer, and alkaline activators such as silicates or hydroxides of potassium or sodium. Mixing with, and curing in a temperature range of 60 to 250 ℃ after molding to the desired shape.

Other known manufacturing processes for producing geopolymer materials use naturally occurring silica containing minerals such as quartz and quartz rock, and alumino-silicate containing minerals such as kaolinite and illite. The conventional manufacturing process is a step of grinding and milling quartz or quartz arm in a ball mill or vertical roller mill, kaolinite or illite, etc. in a gaseous furnace or electrically heated furnace in the temperature range of 950 to 1050 ℃. After calcination, cooling to ambient temperature, mixing raw materials in a mechanical mixer, mixing with alkaline activators such as silicates or hydroxides of potassium or sodium, and shaping to the desired form after 60 to 250 It consists of curing in the temperature range of ℃.

Another known manufacturing process for producing geopolymer materials uses fly ash, sand and granite aggregates as raw materials. This manufacturing process comprises the steps of blending raw fly ash, clay and aggregate in unison, mixing with sodium / potassium added alkaline activator, and curing in the temperature range of 60-200 ° C. after shaping into the desired form. It consists of.

A conventional manufacturing process (J. Davidovits, Geopolymer 2002 Conference, 28-29 October 2002, Melbourne, Australia) consists of mixing fine powders of silica and alumina in a mixer for 10 to 60 minutes. The geopolymerization reaction is carried out in an alkaline environment using sodium or potassium addition activator and curing at a temperature range of 60 to 200 ° C.

Another well-known manufacturing process (D. Hardjito et al., Invented Paper, Concrete World: Engineering and Materials, American Concrete Institute, India Chapter, Mumbai, India, 9-12 December 2004), Mixing of ash, sand and granite aggregates, addition of sodium-added alkaline activators, vibratory casting in molds is used. The vibrated cast material is cured at elevated temperature to produce a geopolymer material to be used as concrete.

The known manufacturing process has the following limitations.

1. The manufacturing cost of geopolymer materials is relatively high when using expensive raw materials such as pure silica and alumina.

2. Formation of geopolymer materials is an energy intensive process when using naturally occurring raw materials such as quartz, quartz rock, kaolinite and illite. The grinding and milling of quartz or quartz rock and the high temperature calcination of kaolinite and illite consume large energy.

3. The compressive strength characteristics of geopolymers are low when using fly ash as one of the raw materials. Because of the low reactivity of the fly ash, low compressive strength is obtained. Therefore, only a small amount of fly ash is used in the geopolymer.

Traditionally, geopolymer materials have been prepared by mixing silica or silica containing minerals and fine powders of alumina or alumina, alumino-silicate containing minerals with sodium and potassium added alkaline activators and curing at elevated temperatures (J. Davidovits, Geopolymer 2002 Conference, 28-29 October 2002, Melbourne, Australia). Conventional methods for preparing geopolymer materials using sodium, silica and alumina have been patented by Davidovits in the United States (US Patent 4,509,985, Davidovits et al., Early high-strength mineral polymers). See also US Pat. No. 4,472,199 for synthetic mineral polymer compounds of the silico-aluminate family of Davidovits et al. And manufacturing processes wherein cast or molded geopolymers were prepared by conventional processes for zeolite applications. D. Hardjito et al., "Concrete World: Engineering and Materials, American Concrete Institute, India Chapter, Mumbai, India, December 9-12, 2004", where a large amount of fly ash in geopolymer concrete The use attracted intensive research. Fine milling and mechanical activation of fly ash is proposed to enhance its reactivity (A.Z. Juhasz, L. Opoczky, Mechanical Activation of Minerals by Grinding: Powdered and Structured Particles, Ellis Horwood Limited, NY, 1994). Various types of milling devices have been tested for fine milling and mechanical activation of fly ash. You can also refer to Sanjay Kumar et al. 'Using large amounts of blast furnace slag and fly ash in high-energy milling,' published in the International Conference Bulletin on Advanced Concrete Structures (Chennai, January 2005). The fly ash reactivity was increased by mechanical activation in the vibration mill.

According to literature and patent research and available information, it can be said that there is currently no process for preparing geopolymer materials using mechanically activated fly ash. The goal of this development is to produce value-added products such as geopolymer materials for a variety of applications, using abundantly available waste materials such as 'fly ash' that cause environmental pollution.

It is an object of the present invention to provide a process for preparing geopolymer materials using mechanically activated fly ash.

Another object of the present invention is to provide a process for producing a geopolymer material that can significantly reduce energy consumption.

It is another object of the present invention to provide a process for producing geopolymer materials with significantly reduced manufacturing costs and improved product properties.

It is yet another object of the present invention to provide a process for preparing geopolymer materials in which the reactivity of the fly ash is increased by mechanical activity and the strength development of this product is improved.

The fly ash used in the present invention includes silica (SiO ₂ ), alumina (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), CaO, MgO, and MnO, some of which are crystal structures and some of which are amorphous structures. .

In geopolymer materials prepared by conventional manufacturing processes, fly ash does not actively participate in geopolymer reactions because of poor reactivity. The outer surface of the fly ash particles in contact with the alkaline activator reacts but not the inner center of the particles. As a result, the resulting geopolymer material is inconsistent in strength development and poor. In addition, because of this poor reactivity, only limited amounts of fly ash are used in geopolymer materials. In the manufacturing process of the present invention, the fly ash is ground in a high energy mill and mechanically activated. The milling medium of the high energy mill provides a wider contact surface between the medium and the fly ash, and faster stirrer speeds or vibrations generate higher kinetic energy of the medium. High energy milling processes mechanically activate the fly ash, increasing its reactivity. When an alkaline activator such as sodium or potassium is added, decomposition of the fly ash particles begins. Increased fly ash reactivity improves its degradation activity. The mixing of the mechanically activated fly ash and alkaline activator is formed into the desired form by vibratory casting or uniaxial compression. For the geopolymerization reaction, this formed material is cured in the temperature range of 50 to 200 ° C. Because of the elevated curing temperature, this decomposition reaction proceeds simultaneously with the gel formation and polycondensation reactions, resulting in the condensation of the geopolymer material and the development of strength. In addition, due to the increased reactivity, higher proportions of fly ash are used in geopolymer materials.

Accordingly, the present invention provides a process for preparing a geopolymer material from a fly ash, comprising a) mechanically activating the fly ash by high energy milling for 10 to 60 minutes in a dry state and ranging in size from 1 to 30 microns. Reducing to; b) mixing 5-50 wt% of alkaline active agent with 50-95 wt% of water while stirring for 10-60 minutes; c) intimately mixing 60 to 90 wt% of the vibration milled fly ash obtained in step a) and 10 to 40 wt% of the alkaline activator solution obtained in step b) for 15 to 30 minutes; d) forming the mixed powder by vibrating compaction for 2 to 10 minutes or by compressing to a pressure in the range of 50 to 250 kg / cm 2; And e) drying the formed material for 2 to 24 hours at ambient temperature and curing for 1 to 24 hours at a temperature in the range of 50 to 200 ° C. .

In one embodiment of the invention, the fly ash used, SiO ₂ - 40 to 70 wt%, Al ₂ O ₃ - 20 to 40 weight%, Fe ₂ O ₃ - 0 greater than 5% by weight, CaO - 0 exceeds Composition ranges within 5% by weight, greater than MgO-0 and less than 1% by weight, and greater than MnO-0 and 2% by weight.

In another embodiment, the alkaline active agent used is selected from the group consisting of sodium oxide, sodium hydroxide, sodium silicate, sodium nitrate, potassium oxide, potassium hydroxide, potassium silicate and potassium nitrate.

In another embodiment, the high energy milling used is selected from vibratory milling, wear milling, jet milling and planetary milling.

In another embodiment, the resulting geopolymer material has a compressive strength in the range of 30 to 160 MPa depending on the production time of 4 to 24 hours.

In another embodiment, the resulting geopolymer material has an autoclave expansion in the range of 0.01 to 0.02% and a hardness of 5 or more.

In yet another embodiment, the resulting geopolymer material has a fire resistance of about 900 ° C.

The novelty of the present invention is the use of inexpensive raw materials, such as fly ash obtained from industrial waste, mechanically activating the fly ash, resulting in an excellent compressive strength of 30 to 150 MPa obtained in a very short time of 4 to 24 hours, about 900 Geopolymer materials having a hardness of at least 5 are prepared with a refractory value of < RTI ID = 0.0 > C < / RTI >

The following examples are provided for illustrative purposes and should not be construed as limiting the scope of the invention.

Example 1

600 grams of fly ash were mechanically activated by wear milling for 10 minutes. Average particle size (X ₅₀₎ obtained after the abrasion milling was 8㎛. 400 grams of alkaline activator was prepared by mixing water and sodium hydroxide in a ratio of 1: 1 for 15 minutes. Mechanically activated fly ash and alkaline activator were mixed closely for 15 minutes. Mechanically activated fly ash and alkaline activator were mixed to form a 50 mm thick 50 mm dia cylinder using uniaxial compression at 100 kg / cm 2 pressure. This sample was dried for 6 hours at ambient temperature. The dried sample was cured at 60 ° C. for 2 hours in an electric oven and then cooled to ambient temperature for various tests. Physical tests such as compressive strength, fire resistance, autoclave expansion, and hardness were conducted according to standard test methods. The properties obtained are shown in Table 1.

Table 1: Properties of the Geopolymer Material

Property value Compressive strength (MPa) 4 hours 24 hours     100 130 Autoclave expansion (%) 0.02 Fireproof Withstand 900 ℃ Hardness (Moss Hardness Tester) > 5

Example 2

700 grams of fly ash were mechanically activated for 30 minutes by vibratory milling. Average particle size (X ₅₀₎ obtained after the vibration mill was 12㎛. 300 grams of alkaline activator was prepared by mixing water and potassium hydroxide in a 2: 1 ratio for 20 minutes. Mechanically activated fly ash and alkaline activator were mixed closely for 15 minutes. Mechanically activated fly ash and alkaline activator were mixed to form a 50 mm thick 50 mm diamond cylinder using uniaxial compression at 120 kg / cm 2 pressure. This sample was dried at ambient temperature for 8 hours. This dried sample was cured at 80 ° C. for 2 hours in an electric oven and then cooled to ambient temperature for various tests. Physical tests such as compressive strength, fire resistance, autoclave expansion, and hardness were conducted according to standard test methods. The properties obtained are shown in Table 2.

Table 2: Properties of the Geopolymer Material

Property value Compressive strength (MPa) 4 hours 24 hours     80 95 Autoclave expansion (%) 0.02 Fireproof Withstand 900 ℃ Hardness (Moss Hardness Tester) > 5

Example 3

800 grams of fly ash were mechanically activated for 30 minutes by jet milling. The average particle diameter (X ₅₀ ) obtained after jet milling was 10.2 μm. 200 grams of alkaline activator was prepared by mixing water and sodium silicate at a ratio of 8: 2 for 30 minutes. Mechanically activated fly ash and alkaline activator were mixed closely for 20 minutes. Mechanically activated fly ash and alkaline activator were mixed to form a 50 mm thick 50 mm diamond cylinder using uniaxial compression at 150 kg / cm 2 pressure. This sample was dried at ambient temperature for 8 hours. This dried sample was cured at 100 ° C. for 16 hours in an electric oven and then cooled to ambient temperature for various tests. Physical tests such as compressive strength, fire resistance, autoclave expansion, and hardness were performed according to standard test methods. The properties obtained are shown in Table 3.

Table 3: Properties of the Geopolymer Material

Property value Compressive strength (MPa) 4 hours 24 hours     40 60 Autoclave expansion (%) 0.01 Fireproof Withstand 900 ℃ Hardness (Moss Hardness Tester) > 5

Example 4

900 grams of fly ash were mechanically activated for 60 minutes by planetary milling. Average particle size (X ₅₀₎ obtained after the planetary mill was 8.5㎛. 100 grams of alkaline activator was prepared by mixing water and sodium nitrate in a ratio of 1: 1 for 30 minutes. Mechanically activated fly ash and alkaline activator were mixed closely for 15 minutes. This mechanically activated fly ash and alkaline activator were mixed to form a 50 mm thick 50 mm diamond cylinder using uniaxial compression at 200 kg / cm 2 pressure. This sample was dried at ambient temperature for 12 hours. This dried sample was cured at 60 ° C. for 24 hours in an electric oven and then cooled to ambient temperature for various tests. Physical tests such as compressive strength, fire resistance, autoclave expansion, and hardness were conducted according to standard test methods. The properties obtained are shown in Table 4.

Table 4: Properties of the Geopolymer Material

Property value Compressive strength (MPa) 4 hours 24 hours     40 65 Autoclave expansion (%) 0.01 Fireproof Withstand 900 ℃ Hardness (Moss Hardness Tester) > 5

1. The manufacturing process according to the present invention can produce a geopolymer material using a larger amount of abundantly available industrial waste (fly ash) as the main raw material, thereby significantly lowering the manufacturing cost compared to the conventional manufacturing process.

2. The manufacturing process according to the present invention helps to conserve resources by replacing expensive raw materials, such as alumina, silica, quartz, quartz rock, kaolinite, illite, etc., with industrial waste.

3. The manufacturing process according to the present invention replaces alumina, silica, quartz and quartz rock powders produced by the energy intensive milling process and replaces kaolinite and illite, which are calcined at high temperatures by industrial waste (fly ash). As a result, the energy consumption is significantly reduced compared to the conventional manufacturing process.

4. The production process according to the invention comprises low temperature treatment (50 to 200 ° C.), thereby releasing little or no CO ₂ .

5. The product developed by the manufacturing process according to the present invention is superior in terms of short-term strength development compared to the product produced by the conventional manufacturing process. This is achieved by mechanically activating the fly ash, thereby increasing its reactivity and improving its strength.

Claims (7)

a) mechanically activating the fly ash by high energy milling for 10 to 60 minutes in a dry state and reducing its size to a range between 1 and 30 microns; b) mixing 5-50 wt% of alkaline active agent with 50-95 wt% of water while stirring for 10-60 minutes; c) intimately mixing 60 to 90 wt% of the vibration milled fly ash obtained in step a) and 10 to 40 wt% of the alkaline activator solution obtained in step b) for 15 to 30 minutes; d) forming the mixed powder by vibrating compaction for 2 to 10 minutes or by compressing to a pressure in the range of 50 to 250 kg / cm 2; And e) drying the formed material for 2 to 24 hours at ambient temperature, and curing for 1 to 24 hours at a temperature range of 50 to 200 ℃ Process for producing a geopolymer material from a fly ash comprising a. The method of claim 1, The fly ash is a SiO ₂ - 40 to 70 wt%, Al ₂ O ₃ - 20 to 40 weight%, Fe ₂ O ₃ - 0 greater than 5% by weight, CaO - 0 greater than 5% by weight, MgO - 0 exceeds 1 And a composition range of less than 2% by weight and less than 2% by weight of MnO. The method of claim 1, Said alkaline activator is selected from the group consisting of sodium oxide, sodium hydroxide, sodium silicate, sodium nitrate, potassium oxide, potassium hydroxide, potassium silicate and potassium nitrate. The method of claim 1, Wherein said high energy milling is selected from vibration milling, wear milling, jet milling and planetary milling. The method of claim 1, The geopolymer material is characterized in that it has a compressive strength in the range of 30 to 160 MPa according to the production time of 4 to 24 hours. The method of claim 1, Wherein the geopolymer material has an autoclave expansion of less than 0.5% and a hardness of 5 or more with a Mohs hardness tester. The method of claim 1, Wherein said geopolymer material has a refractory value of 900 ° C.