WO2017065703A1 - Production of building materials from high free lime content fly ash - Google Patents
Production of building materials from high free lime content fly ash Download PDFInfo
- Publication number
- WO2017065703A1 WO2017065703A1 PCT/TH2016/000083 TH2016000083W WO2017065703A1 WO 2017065703 A1 WO2017065703 A1 WO 2017065703A1 TH 2016000083 W TH2016000083 W TH 2016000083W WO 2017065703 A1 WO2017065703 A1 WO 2017065703A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- fly ash
- proportion
- range
- dry weight
- cement
- Prior art date
Links
Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
- C04B18/08—Flue dust, i.e. fly ash
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/021—Ash cements, e.g. fly ash cements ; Cements based on incineration residues, e.g. alkali-activated slags from waste incineration ; Kiln dust cements
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Definitions
- the present disclosure relates to building materials. More particularly, the present disclosure relates to the production of building materials from high free lime content fly ash.
- Fly ash particles are formed by the combustion of coal and biomass or other solid fuels such as wood waste, rice husks, bagasse, palm residue, corn, cassava and palm leaf. Fly ash particle size is about 0.5 to 300 microns. Fly ash is not acutely toxic or harmful but it can in the long term affect the respiratory system. Landfill disposal is one way to manage fly ash, however: 1) the space for landfill is limited; 2) fly ash dust is formed during the landfill disposal; and 3) groundwater can be contaminated by fly ash leachate. Fly ash can be used in concrete mix, in cement or building materials. However, the most suitable fly ash for those applications is fly ash with small size and spherical physical shape.
- Fly ash can be created by commercial combustion processes such as Pulverized Coal Combustion (PCC) at high temperature (see 1-1 of FIG. 1) and Circulating Fluidized Bed combustion (CFBC) at lower temperatures (see 2-1 of FIG. 2).
- PCC Pulverized Coal Combustion
- CFBC Circulating Fluidized Bed combustion
- S0 2 sulfur dioxide
- NO x nitrogen oxides
- the low amount of S0 2 in flue gas can be scrubbed by adding limestone into the combustion process.
- fly ash is sensitive to pozzolanic reaction, can react with water on its own (self-cementitious), and may reduce the strength of products. If fly ash is used as a building material, the high sulfur trioxide (S0 3 ) in fly ash can cause the expansion of the building materials over time. Thus, the fly ash containing high free lime and sulfur trioxide is not typically suitable for the production of building materials.
- the more suitable free lime and S0 3 quantity of fly ash for cement industry, concrete ready mix, and building materials should be less than 4% and 5%, respectively.
- a primary embodiment of the invention is a process for the production of building materials using at least a proportion of high free lime fly ash in the fly ash composition.
- the high free lime fly ash is mixed with low free lime fly ash to maintain a specific range of free lime and sulfur trioxide in the fly ash composition.
- low pressing pressure is used to conserve energy consumption in the production process, extend machine lifetime and reduce maintenance costs.
- cement is also included in the building material, in the range of 0-20% by dry weight of the mixture.
- FIG. 1 pictures PCC fly ash under a microscope.
- FIG. 2 pictures CFCB fly ash under a microscope.
- FIG. 3 is a flowchart representing an embodiment of invention. Detailed Description
- a primary embodiment of the invention is a process for the production of building materials using at least a proportion of high free lime fly ash in the fly ash composition.
- the high free lime fly ash is mixed with low free lime fly ash to maintain a specific range of free lime and sulfur trioxide in the fly ash composition.
- low pressure pressing is used to conserve energy consumption in the production process, extend machine lifetime and reduce maintenance costs.
- FIG. 3 represents a flowchart of an embodiment of the invention's process 3-1.
- the first step 3A is to create a mixture containing an aggregate, a cement, water and a fly ash composition.
- the second step 3B is to incubate the mixture in the temperature range of 25-45 ° C.
- the third step 3C is to press the mixture at pressing pressure in the range of 5-15 MPa to create green brick.
- the fourth step 3D is to cure the green brick in autoclave with temperature range of 150- 250 ° C.
- fly ash for the fly ash using in the process of slurry mixing (fly ash + water), fly ash can be prepared by mixing two types of fly ash including 1) high-free lime fly ash, 2) low-free lime fly ash.
- the fly ash come from Circulating fluidized bed combustion (CFBC) or Pulverized Coal Combustion (PCC) processes which coal and/or biomass is used as fuel.
- CFBC Circulating fluidized bed combustion
- PCC Pulverized Coal Combustion
- the amount of free lime and sulfur trioxide of "high-free lime fly ash” are 6-20% and 7- 12%, respectively, while that of "low-free lime fly ash” are 0-6% and 0-7%, respectively.
- Both types of fly ash is blended together, controlling the amount of free lime and sulfur trioxide of the blended fly ash between 0-12% and 0-1 1%, respectively.
- the high free lime fly ash can be in the range of 25-75% by dry weight of the total fly ash composition.
- the blended fly ash is mixed with water to make a slurry, where appropriate ratio between fly ash and water is 1 to 10 or 10% by dry weight of dry fly ash.
- slurry is mixed with coarse sand, bottom ash or slag from steel.
- the compositions of mixture consist of 35-75% of fly ash and 20-60% of aggregate.
- the particle sizes of aggregate is between 0.16 to 5 mm.
- this embodiment of the invention can use bottom ash, steel slag to replace some or all of coarse sand.
- the ratio for steel slag or bottom ash or steel slag is 30-55% by dry weight.
- Cement can be selected from Portland cement, or mixed cement, or white cement, or white lime, or lime cement etc. Cement can reduce water absorption, increase strength, and reduce the shrinkage of the building materials.
- the ratio of cement can be 0 to 20% by dry weight, or preferably between 10-15% by dry weight.
- the mixing process can be performed using forge-type mixer or vertical cone mixer or twin shaft mixer. The water is added to the mixture with the ratio of 5-15% by weight, or the optimal ratio is 10-12% by weight.
- the mixture After mixing, the mixture is pre-cured at a temperature of 25-45 °C in a closed system to retard pozzolanic reaction, and prevent serious reactions from free calcium (free lime, CaO) during autoclave process, which lead to be cracked inside construction specimens and result in reduction of the strength later.
- the pre-curing period of 1 -5 hours is appropriate, or the optimum pre-curing period is 1.0-2.0 hours.
- the mixture is grinded again using a grinder roller (Wheel mill) with the moisture in the mixture around 8-10%. The grinding process can separate hard particle from the mixture. And the metal in the mixture can be eliminated through magnetic metal separation unit.
- the pre-cured mixture, after grinding and separation, is formed to become building material by the hydraulic press with pressing pressure of 5-15 MPa, or the optimum pressing pressure is 8- 10 MPa.
- pressing pressure less than 10 MPa would cause the building material to have low density which affect the strength of the product, while pressing pressure more than 40 MPa would make the material density too high, and such material would be difficult to use for conveying to a high level, cutting, and drilling.
- the process in this embodiment of the invention can use pressing pressure lower than 10 MPa, and the building material still has high strength, durable, and suitable for use. This is a result of a mixture of fly ash with cement addition for increasing strength and durability, and decreasing water absorption of the building material.
- the reduction of the pressing pressure for the hydraulic press can reduce the energy consumption and machine lifetime in the production of building materials from fly ash.
- the specimens After pressing, the specimens is incubated at a temperature of 25-45 °C to reduce undesired reactions from free calcium (free lime, CaO) during a steam curing step using autoclave process with the temperature of 150-250 °C, which lead to be cracked on construction specimens and result in reduction of the strength and durability.
- free calcium free lime, CaO
- fly ash is mixed with water to make a slurry (Slurry), where fly ash containing 0-1 1% free calcium oxide (free lime, CaO) and 0-12% sulfur trioxide (S03).
- Slurry a slurry
- the amount of fly ash is 40-65% by dry weight.
- cement and water is filled to the mixture with a ratio of 0 to 20% and 5-15% by dry weight, respectively.
- Pre-cured mixture is formed by the pressing unit with pressing pressure of 5-15 MPa, called green brick.
- the green brick is incubated at a temperature of 25-45 ° C.
- Green brick is steam-cured in the autoclave process with the temperature of 150-250 ° C to obtain building materials from fly ash.
- Table 1 lists example brick quality compressive strength and water adsorption for various embodiments of the invention with different raw material composition, pressing pressure, autoclave temperature.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
TH1501006349 | 2015-10-15 | ||
TH1501006349A TH160463A (en) | 2015-10-15 | Fly ash building material manufacturing process |
Publications (1)
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WO2017065703A1 true WO2017065703A1 (en) | 2017-04-20 |
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PCT/TH2016/000083 WO2017065703A1 (en) | 2015-10-15 | 2016-10-12 | Production of building materials from high free lime content fly ash |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113896510A (en) * | 2021-11-27 | 2022-01-07 | 周振宇 | Process for preparing light building material by using fly ash |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5584895A (en) * | 1994-04-18 | 1996-12-17 | Ngk Insulators, Ltd. | Process for preparing solidified material containing coal ash |
JP2000169204A (en) * | 1998-12-03 | 2000-06-20 | Chuden Kankyo Technos Kk | Production of high-strength artificial aggregate |
JP2003119068A (en) * | 2001-10-11 | 2003-04-23 | Chugoku Electric Power Co Inc:The | Hydration cured body |
-
2016
- 2016-10-12 WO PCT/TH2016/000083 patent/WO2017065703A1/en active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5584895A (en) * | 1994-04-18 | 1996-12-17 | Ngk Insulators, Ltd. | Process for preparing solidified material containing coal ash |
JP2000169204A (en) * | 1998-12-03 | 2000-06-20 | Chuden Kankyo Technos Kk | Production of high-strength artificial aggregate |
JP2003119068A (en) * | 2001-10-11 | 2003-04-23 | Chugoku Electric Power Co Inc:The | Hydration cured body |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113896510A (en) * | 2021-11-27 | 2022-01-07 | 周振宇 | Process for preparing light building material by using fly ash |
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