WO2023158010A1 - 매립-석탄재의 활용을 위한 전처리 방법 - Google Patents
매립-석탄재의 활용을 위한 전처리 방법 Download PDFInfo
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- WO2023158010A1 WO2023158010A1 PCT/KR2022/003144 KR2022003144W WO2023158010A1 WO 2023158010 A1 WO2023158010 A1 WO 2023158010A1 KR 2022003144 W KR2022003144 W KR 2022003144W WO 2023158010 A1 WO2023158010 A1 WO 2023158010A1
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- Prior art keywords
- landfill
- coal ash
- cpa
- screening
- recovery
- Prior art date
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- 238000002203 pretreatment Methods 0.000 title claims abstract description 36
- 239000003245 coal Substances 0.000 title abstract description 19
- 239000010883 coal ash Substances 0.000 claims abstract description 170
- 238000012216 screening Methods 0.000 claims abstract description 73
- 238000007885 magnetic separation Methods 0.000 claims abstract description 60
- 238000000227 grinding Methods 0.000 claims abstract description 41
- 238000000926 separation method Methods 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims description 70
- 239000002245 particle Substances 0.000 claims description 69
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- 239000000463 material Substances 0.000 claims description 35
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- 229910052799 carbon Inorganic materials 0.000 claims description 20
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- 238000002156 mixing Methods 0.000 claims description 10
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- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 229910052770 Uranium Inorganic materials 0.000 description 3
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 3
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- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
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- HNSDLXPSAYFUHK-UHFFFAOYSA-N 1,4-bis(2-ethylhexyl) sulfosuccinate Chemical compound CCCCC(CC)COC(=O)CC(S(O)(=O)=O)C(=O)OCC(CC)CCCC HNSDLXPSAYFUHK-UHFFFAOYSA-N 0.000 description 1
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- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B5/00—Washing granular, powdered or lumpy materials; Wet separating
- B03B5/28—Washing granular, powdered or lumpy materials; Wet separating by sink-float separation
- B03B5/30—Washing granular, powdered or lumpy materials; Wet separating by sink-float separation using heavy liquids or suspensions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B9/00—General arrangement of separating plant, e.g. flow sheets
- B03B9/06—General arrangement of separating plant, e.g. flow sheets specially adapted for refuse
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C1/00—Magnetic separation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
- B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
- B07B1/46—Constructional details of screens in general; Cleaning or heating of screens
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/30—Destroying solid waste or transforming solid waste into something useful or harmless involving mechanical treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/30—Destroying solid waste or transforming solid waste into something useful or harmless involving mechanical treatment
- B09B3/35—Shredding, crushing or cutting
Definitions
- the present invention relates to a pretreatment method for utilization of landfill-coal ash, and more particularly, to screening, float-sink, floatation, grinding, and magnetic separation. It relates to a pretreatment method for landfill-coal ash that can utilize landfill-coal ash with high utilization through a simple separation process of.
- Coal ash is an inorganic waste that remains unburned in the blast furnaces of coal-fired power plants (CPPs). It is largely divided into fly ash (collected from electrostatic precipitators) and bottom ash (collected from the bottom of a boiler). The particle size ranges from less than 0.1 ⁇ m to more than 5 cm in diameter, and the main components are silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), iron oxide (Fe 2 O 3 ), calcium oxide (CaO), and magnesium oxide. (MgO) (Lee, S. et al., Renew. Sust. Energy Rev. 50, 186-193, 2015; Liang, W. et al., J. Energy Inst.
- the list includes concrete admixtures such as ready-mixed concrete, cement raw materials, lightweight aggregates, raw materials for secondary cement products, aggregates for embankment, aggregates for covering soil, aggregates for roads, raw materials for wood adhesives, substitutes for cement clinker manufacturing raw materials, drainage layer aggregates, materials for ceramics, rubber ⁇ Plastic fillers, raw materials for paints/abrasives/insulation materials, raw materials for iron and steel making, and raw materials for bed soil fertilizers are included in 16 items.
- laws and regulations regarding coal ash vary from state to state.
- the Pennsylvania Department of Environmental Protection has developed “Beneficial Uses of Coal Ash” under the Solid Waste Control Act (Department of Environmental Protection, 2021).
- coal ash types depend on landfill disposal types.
- MT 9.4 million tons
- recycling was the largest at 8.0MT (85.1%).
- landfill was 1.4MT (14.9%), followed by incineration ( ⁇ 0.1MT, ⁇ 1%) (Um, N. et al., 2018. Study on the Performance Improvement of Domestic ManagementSystem for Effective Control of Transboundary Movements of Waste. National Institute of Environmental Research, Incheon (South Korea)).
- coal ash as an alternative raw material for cement and auxiliary fuel for cement was the highest at 7.1 MT (88.8%), followed by filling materials and covering materials (0.4 MT, 5%). Recycling of coal ash from bricks (0.2 MT, 2.5%) and other sectors (0.3 MT, 3.8%) indicates a strong dependence on the cement industry.
- several studies on the use of coal ash in the cement industry include cement resources and concrete aggregates (Mangi, S.A. et al., 2019. Resources 8(2), 99; Navdeep, S. et al,, 2019. Resour. conserve Recycl. 144, 240-251; Qin, Q. et al., 2020, Bioresour. Technol.
- recyclers preferentially consider direct recycling without pretreatment in order to reduce additional costs such as transportation, treatment, and facility installation.
- the physical and chemical composition (properties) of coal ash may fall short of the quality standards required for recycled products. These concerns are not limited to South Korea.
- 13 MT of a total of 30 MT of coal ash were recycled in 2016, of which >70% was used as a substitute raw material for cement (raw, mixed cement and concrete additives) (European Coal Combustion Products Association, 2021).
- European Coal Combustion Products Association 2021
- only 41 MT of a total of 110 MT of coal ash were recycled in 2018 as cement feedstock for the manufacture of concrete, concrete products and grout (EPA, 2021).
- Landfill treatment of coal ash generated from 11 domestic nuclear power plants (Hadong, Taean, Yeosu, Yeongdong, Yeongheung, Samcheonpo, Donghae, Honam, Dangjin, Seocheon, Boryeong) is being carried out at landfills near the coast near each coal-fired power plant.
- coal ash landfills are composed of a mixture of fly ash and bottom ash.
- fly ash the particles are spherical or sharp, and the particle size is less than 0.1 ⁇ m, so the particle size distribution is uniform, so the characteristics may be different from those of the bottom ash.
- fly ash is landfilled, it is mixed with bottom ash and the two types are treated separately and are not landfilled.
- the construction of new landfill sites is essential as most landfill sites are actually full.
- landfill-coal ash is a mixture of fly ash and bottom ash, its characteristics should be examined.
- the characteristics of each coal-fired power plant can affect landfill-coal ash.
- landfill-coal ash can be affected by seawater, a brine solution containing a large amount of chloride anion (19.344g/kg Cl) (Ito, K. et al. , 2009, Comprehensive Handbook of Iodine, pp.83-91).
- the present inventors have made diligent efforts to solve the above problems and increase the recycling rate of landfill-coal ash produced in large quantities in coal-fired power plants, and as a result, screening, float-sink, floatation, and grinding ( It was confirmed that the recycling rate of landfill-coal ash increases to a considerable level when the simple separation process of grinding and magnetic separation is performed under optimal conditions, and the present invention was completed.
- An object of the present invention is to provide a pre-treatment method for landfill-coal ash that can increase the recycling rate as a preliminary step before utilizing the landfill-coal ash.
- the present invention provides (a) landfill-screening coal ash using a sieve to classify into coarse particles, medium particles and fine particles; (b) floatating the microparticles obtained in step (a); (c) float-sinking the intermediate particles obtained in step (a); and (d) mixing the residue obtained in step (c) with the residue obtained in step (b), and then subjecting the mixture to magnetic separation to obtain iron oxide-containing fine materials and Si and Al-containing fine materials. It provides a pretreatment method of coal ash comprising the step of obtaining.
- the present invention also includes (a1) screening and recovering landfill-coal ash; (a2) screening, flotation and recovery of landfill-coal ash; (a3) screening, gravity screening, grinding, flotation and recovery of landfill-coal ash; (a4) screening, gravity screening, magnetic separation and recovery of landfill-coal ash; (a5) mixing the by-products obtained from screening, gravity separation, first magnetic separation and grinding of landfill-coal ash with the residue obtained in step (a2), followed by second magnetic separation and recovery; or (a6) purity of unburned carbon (UC) and amorphous components (AC) from landfill-coal ash (CPA) comprising the step of magnetically sorting and recovering the residue obtained in step (a5) It provides a method for obtaining a by-product with increased
- the present invention also includes (b1) landfill-screening and recovering coal ash; (b2) screening, flotation and recovery of landfill-coal ash; (b3) screening, gravity screening and recovery of landfill-coal ash; and (b4) mixing the by-products obtained from screening, gravity screening, and pulverization of the landfill-coal ash with the residue obtained in step (b2), followed by magnetic separation and recovery; or (b5) magnetically sorting and recovering the residue obtained in step (b4).
- the present invention also includes (c1) grinding, magnetic separation and recovery of landfill-coal ash; or (c2) a method for obtaining only Fe oxide from landfill-coal ash (CPA) comprising the steps of pulverizing, primary magnetic separation, secondary magnetic separation, and recovering the landfill-coal ash.
- the present invention also provides a method for obtaining only Fe oxide from landfill-coal ash (CPA) for reducing the energy cost of the grinding process, which additionally includes a magnetic separation step before the grinding of (c1) and (c2). do.
- CPA landfill-coal ash
- the present invention also includes (d1) pulverizing, flotation and recovery of landfill-coal ash; (d2) crushing, flotation, magnetic separation and recovery of landfill-coal ash; or (d3) a method for obtaining only unburned carbon and Fe oxide from landfill-coal ash (CPA) comprising the steps of pulverizing, flotation, primary magnetic separation, secondary magnetic separation, and recovering the landfill-coal ash.
- CPA a method for obtaining only unburned carbon and Fe oxide from landfill-coal ash
- the present invention also includes (e1) screening and recovering landfill-coal ash; (e2) screening, flotation and recovery of landfill-coal ash; or (e3) providing a method for obtaining a by-product with increased strength from landfill-coal ash (CPA) comprising the steps of screening, gravity screening, and recovering landfill-coal ash.
- CCA landfill-coal ash
- CPPs coal-fired power plants
- APs landfills
- FIG. 2 is a view showing an XRD pattern of landfill-coal ash (CPA) according to an embodiment of the present invention.
- CPA landfill-coal ash
- AC amorphous components
- UC unburned carbon
- mullite mullite
- quartz e
- Figure 4 is a landfill separated using a specific gravity screening process having various specific gravities (SGs) according to an embodiment of the present invention - the weight of coal ash (CPA), unburned carbon (UC) and amorphous compounds (ACs) It is a diagram showing the distribution (a) and XRD pattern (b) of (including Al species and glass phase).
- Experimental conditions solid/liquid 200 (g/L), reaction temperature 20 °C, reaction time 4 hours, stirring speed 100 rpm, CCl 4 and CH 2 Br 2 reagents for SG.
- UC 5 is a pH effect on the adsorption kinetics of unburnt carbon (UC) according to an embodiment of the present invention (a), Brunauer-Emmett-Teller (BET) adsorption isotherm (b), (C o -C) / It is a diagram showing C versus C o /(C o -C)U sec (c).
- Experimental conditions 13 (g/L) solid/liquid (a) and 6.5, 13, 19.5, 26, 39 and 52 (g/L) solid/liquid (b); 20° C. reaction temperature; 60 second response time (a) and 10 second response time (b); 10L/min flow rate of air gas; and 0.5 g/L kerosene and 0.08 g/LMIBC.
- Figure 6 is a scanning electron microscope photograph (untreated landfill- Coal ash (CPA) particles (left b) and landfill-coal ash (CPA) particles pulverized by milling for 20 minutes (right b)).
- FIG. 7 is a graph showing changes in recovery (Y Fe ) and purity (P Fe ) of Fe oxides of iron material separated by various magnetic forces of 0.1, 0.5, 1, and 2 T.
- AC amorphous compound
- UC unburned carbon
- Fe oxide Fe oxide
- Al species Al 2 O 3 xH 2 O
- CPA landfill-coal ash
- a pretreatment method was considered as a preliminary step before utilizing landfill-coal ash (CPA).
- CPA landfill-coal ash
- This method does not mean that landfill-coal ash (CPA) can be directly recycled after removing or stabilizing specific hazardous substances, but corresponds to an intermediate process including a simple separation method to increase the recycling efficiency of the final recycling process.
- CPA landfill-coal ash
- several investigations were conducted using landfill-coal ash (CPA) samples collected from a landfill (AP) located near the Boryeong Coal-fired Power Plant (CPP) in Korea.
- Coal ash is referred to as CA
- coal-fired power plants as CPP
- ash ponds as AP
- landfill-coal pond ash as CPA
- the present invention is concerned about the possibility of environmental contamination of the landfill (AP) where coal ash (CA) generated from a coal-fired power plant (CPP) is buried, and proposes a method of increasing the utilization of landfill-coal ash (CPA).
- the CA embedded in the AP is regarded as the CPA.
- the CPA properties were investigated.
- the present invention includes (a) screening the landfill-coal ash using a sieve and classifying it into coarse particles, medium particles, and fine particles; (b) floatating the microparticles obtained in step (a); (c) float-sinking the intermediate particles obtained in step (a); and (d) mixing the residue obtained in step (c) with the residue obtained in step (b), and then subjecting the mixture to magnetic separation to obtain iron oxide-containing fine materials and Si and Al-containing fine materials. It relates to a pretreatment method of coal ash comprising the step of obtaining.
- step (a) using a standard sieve having a grid of 0.15 mm and 2.36 mm in diameter, coarse particles with a diameter of more than 2.36 mm, medium particles with a diameter of 0.15 to 2.36 mm and less than 0.15 mm It can be classified as microparticles with a diameter of .
- Step (b) a pH adjuster is added and stabilized to adjust to the most suitable pH, and the desired by-product is sequentially floated on the surface of the water to obtain it, and then dehydrated and dried.
- Step (b) may be performed at pH 7.
- specific gravity separation may be performed using a solution having a specific gravity of 2.2 in step (c).
- step (c) magnetic separation of the obtained residue at a magnetic field strength of 1.0 T, and grinding the separated Fe oxide-containing material may be further included. there is.
- step (d) the mixture of the residue obtained in step (c) and the residue obtained in step (b) was subjected to high purity Fe using a 0.1 T wet magnetic separator.
- the low-purity Fe oxide-containing fine material may be separated using a 1.0 T wet magnetic separator.
- the pretreatment method according to the present invention can be changed through various combinations of each separation process, and a desired final by-product can be selectively obtained.
- another aspect of the present invention is (a1) landfill-screening and recovering coal ash; (a2) screening, flotation and recovery of landfill-coal ash; (a3) screening, gravity screening, grinding, flotation and recovery of landfill-coal ash; (a4) screening, gravity screening, magnetic separation and recovery of landfill-coal ash; (a5) mixing the by-products obtained from screening, gravity separation, first magnetic separation and grinding of landfill-coal ash with the residue obtained in step (a2), followed by second magnetic separation and recovery; or (a6) purity of unburned carbon (UC) and amorphous components (ACs) from landfill-coal ash (CPA) comprising the step of magnetically sorting and recovering the residue obtained in step (a5)
- UC unburned carbon
- ACs amorphous components
- Another aspect of the present invention is (b1) landfill-screening and recovering coal ash; (b2) screening, flotation and recovery of landfill-coal ash; (b3) screening, gravity screening and recovery of landfill-coal ash; and (b4) mixing the by-products obtained from screening, gravity screening, and pulverization of the landfill-coal ash with the residue obtained in step (b2), followed by magnetic separation and recovery; Or (b5) a method for obtaining a by-product with an increased recovery rate of Fe oxide from landfill-coal ash (CPA), comprising the step of magnetically sorting and recovering the residue obtained in step (b4), wherein the method is shown in FIG. As shown in (b) of 9.
- CCA a method for obtaining a by-product with an increased recovery rate of Fe oxide from landfill-coal ash
- Another aspect of the present invention is (c1) pulverizing, magnetically separating and recovering landfill-coal ash; Or (c2) a method for obtaining only Fe oxide from landfill-coal ash (CPA) comprising the steps of pulverizing, first magnetic separation, second magnetic separation and recovering the landfill-coal ash, the method shown in FIG. 9 ( As shown in c-1).
- magnetic separation may be additionally performed before the crushing of (c1) and (c2), and the method is as shown in (c-2) of FIG. .
- Another aspect of the present invention is (d1) landfill-crushing, flotation and recovery of coal ash; (d2) crushing, flotation, magnetic separation and recovery of landfill-coal ash; Or (d3) a method for obtaining only unburned carbon and Fe oxide from landfill-coal ash (CPA) comprising the steps of crushing, flotation, first magnetic separation, second magnetic separation and recovery of the landfill-coal ash, The method is as shown in FIG. 9(d).
- Another aspect of the present invention is (e1) landfill-screening and recovering coal ash; (e2) screening, flotation and recovery of landfill-coal ash; Or (e3) a method for obtaining a by-product with increased strength from landfill-coal ash (CPA) comprising the steps of screening, gravity screening and recovery of the landfill-coal ash, which method is shown in FIG. 9 (e ) as shown in
- CPPs located in the Boryeong region, where bituminous coal is mainly used were selected, and CPA samples for all experiments were collected from APs located near the selected CPPs.
- a total of 9 CPA samples were collected from the 3 sites of the AP as shown in Figure 1.
- the weight of each sample was 200 kg. Samples with various moisture contents were dried at 100 °C for 24 hours. Then, it was passed through 5 standard sieves (Test Sieves, 200 ⁇ 50 mm) with grids of 0.15, 0.3, 0.6, 1.18, and 2.36 mm diameters to obtain less than 1.15, 0.15-0.3, 0.3-0.6, 0.6-1.18, 1.18- Samples with the required particle sizes such as 2.36 and greater than 2.36 mm were obtained.
- the chemical composition of CPA and the contents of Si, Al, Fe, Ca, Mg, K, Na, Ti and Mn were measured using an X-ray fluorescence spectrometer (XRF 3726AI, Rigaku).
- the unburnt carbon (UC) content was obtained using the Korean standard LOI method (ES 06303.1) (Ministry of Environment, 2011). 20 g of the sample from which moisture was removed was taken and heated in an electric furnace at 815° C. for 3 hours. After drying in a desiccator, the UC content (w/w.%) was evaluated from the weight difference before and after the LOI. In the case of Cl, an initial amount was obtained after dissolving in an acidic solution.
- the concentration of dissolved Cl after acid decomposition was measured using ion chromatography (ICS-3000, Dionex). CPA samples untreated or treated with specific separation methods were measured by XRD (PW3040/00, Philips) to confirm the mineralogical stage. In addition, the surface of the target particle was analyzed using a scanning electron microscope (JEOL).
- Table 1 shows the UC content of each particle size, which was evenly distributed over the entire particle size, while the UC content of particle sizes larger than 2.36 mm and 1.18-2.36 mm was the highest at 28.4% and the lowest at 9.3%, respectively.
- the content (mg/kg) of CPA samples with a particle size of 2.36 or more, 1.18 to 2.36, 0.6 to 1.18, 0.3 to 0.6, 0.15 to 0.3, or 0.15 mm or less was 42, 74, 112, 184, 273, and 392 respectively.
- CPA AP around the Boryeong Thermal Power Plant is located near the coast, so CPA can be affected by seawater, because seawater contains a lot of chloride anion (19.344g/kg Cl) as a brine solution (Ito, K. et al., 2009. Chapter 9 - Iodine and Iodine Species in Seawater: Speciation, Distribution, and Dynamics. Comprehensive Handbook of Iodine, pp.83-91). Most of the Cl in CA was removed by washing with water, and through this, it was determined as soluble chloride.
- Mullite (3Al 2 O3 2SiO 2 ), quartz (SiO 2 ), calcite (CaCO 3 ), magnetite (Fe 3 O 4 ) and corundum (Al 2 O 3 ) can be observed in the XRD pattern of CPA in FIG. 2 .
- These peaks, as shown in Table 1, provide evidence that CPA contains Si, Al, Fe, and Ca as main elements.
- the angle of the x-axis moves from 15 ⁇ to 35 ⁇ , it can be seen that the background peak changes in the form of ⁇ . This is UC (Bartonova, L., 2015. FuelProcess. Technol. 134, 136-158; Tai, FC et al., 2009, J. Raman Spectrosc.
- FIG. 3 shows a SEM image of CPA particles. Among them, FIG. 3(a) shows the AC of the CPA particle surface. In addition, FIG. 3(b) shows the shape of CPA including spherical Fe oxide.
- FIG. 3(c), FIG. 3(d), and FIG. 3(e) show the components of UC, mullite, and quartz, respectively.
- Table 1 shows the chemical composition and weight distribution of landfill-coal ash (CPA) for each particle size fraction (the experiment was determined for each data in 3 repetitions, and the standard deviation of each data was estimated).
- the pH value was adjusted to 2, 7, and 12 using hydrochloric acid (HCl) and sodium hydroxide (NaOH), respectively, to confirm the pH effect on flotation.
- HCl hydrochloric acid
- NaOH sodium hydroxide
- the experiment was conducted for 60 seconds using 26 g of sample at each pH condition to confirm the pH effect on the UC adsorption kinetics.
- BET Brunauer-Emmett-Teller
- an experiment was performed for 10 seconds using six samples of 6.5, 13, 19.5, 26, 39, and 52 g.
- All grinding experiments were performed using a batch mill (SH-BALL700B, Weus) with a diameter of 200 mm, an inner diameter of 160 mm, and a length of 180 m.
- the ball was packed into the mill with a ratio of 0.4 between the volume of the ball with a diameter of ⁇ 1.6 mm and the volume of the internal space of the mill.
- the sample was packed inside the mill with a sample volume of 1.2 per volume of the empty space inside the ball-filled mill.
- the grinder is rotated at 70% of the critical rotational speed. The grinding was performed by rotating for each grinding time (5, 10, 20 and 40 minutes).
- CPA consists of four major by-product groups of inorganic materials including AC, Si and Al including UC, Fe oxides, Al species (Al 2 O 3 .xH 2 O) and glass phases.
- Point 2 The particle size of 2.36 mm or more has a high UC content and almost no Fe content. Therefore, it is possible to secure coarse particles having a high UC content by separating particles of 2.36 mm or more through screening.
- Point 3 UC and AC, which have relatively smaller SG values than other substances in CPA, can be separated using the SG characteristics. Therefore, a gravity screening process with a separation principle using the SG difference can be considered (Wills, B.A. et al., 2016. Wills’ Mineral Processing Technology, pp. 245-264). However, for small particles such as 0.15 mm or less, the separation efficiency is not good.
- Point 4 For particles smaller than 0.15 mm, the UC content ratio is 10.5%, which is not high compared to other CPA particle sizes. However, 41.2% of the total UC content is present in particles of 0.15 mm or less, which is the highest among the weight distributions of UC. Therefore, for CPA particles smaller than 0.15 mm, UC separation can be the main process. Flotation can be considered for the separation process here (Eisele, T.C. et al., 2010. Miner. Process. Extr. Metall. Rev. 23, 1-10; Zhang, R. et al., 2019. Waste Manag 98, 29-36; Zhou, F. et al., 2017. Fuel 190, 182-188),
- Point 5 Fe oxide can be easily separated using magnetic separation.
- spherical Fe oxide having a particle size of 0.15 mm or less when spherical Fe oxide having a particle size of 0.15 mm or less is liberated from CPA, the separation effect can be enhanced. Therefore, a grinding process for liberation (0.15 mm or less) can be considered before the magnetic separation process.
- Point 6 According to Points 1, 2, 3, 4 and 5, CPA particle size classification should be considered to increase the separation efficiency of the four major groups of by-products. Thus, three ranges of particle size can be classified: greater than 2.36 mm, 0.15-2.36 mm and less than 0.15 mm.
- Point 7 Coastal seawater influences the Cl content of CPA during cooling in AP. However, since most of the contents are soluble chlorides, they can be easily removed by simple operation of the wet separation process.
- Figure 4 (b) shows the XRD peak changes of UC and AC of CPA separated by gravity line in various SG ranges. This supports the UC distribution results in Fig. 4(a) by showing UC and AC peaks only in the two XRD patterns in the 1.8-2.2 SG and less than 1.8 SG ranges. According to the results, Figure 4 shows that the most efficient SG value for separating UC and AC using gravity screening is 2.2SG.
- Flotation was performed under various solution conditions of pH 2, 7, and 12, and the effect of pH on adsorption kinetics between UC and bubbles was investigated to confirm effective separation of UC.
- CPA with a particle size of 0.15 mm or less was selected in this experiment.
- Figure 5(a) shows the kinetic curve of UC adsorbed by air bubbles according to the floating time.
- CR represents the UC adsorption (%) after the required flotation time and can be calculated as:
- C 0 and C denote the initial UC weight (mg) of untreated CPA and the weight (g) of the remaining UC (unseparated) of CPA after flotation, respectively. All curves increased rapidly initially and remained constant after 10 seconds.
- the CR of pH 7 was the highest with 78.8%, followed by pH 2 with 70.4% and pH 12 with 59.2%.
- UC was adsorbed on the surface of bubbles generated at the bottom of the column equipment and floated to the top of the solution.
- the adsorption between the UC and the bubble can be expressed using the BET adsorption isotherm transformed through the axes x(C) and y(U, the weight of the UC separated by the flotation in g).
- U can be derived based on k and U monolayer-max as follows (Anderson, RB, 1946. J. Am. Chem. Soc. 68, 686-691).
- Equation (3) Equation (3) was rearranged to obtain Equation (3) as follows:
- this equation consists of C o / ( C o - C ) U on the x-axis, ( Co - C ) / C on the y-axis, kU monolayer-max on the slope, and - k on the y-intercept. Therefore, the C o / ( C o - C ) U value calculated from C o , C , and U is displayed for (( C o - C ) / C as shown in FIG. 5(c). As a result, the pH 7 condition , the BET model effectively described an adsorption isotherm with an R value of 0.9427.
- FIG. 6 shows the change in the particle size distribution of CPA according to the grinding time. After 20 minutes, most of the particles were milled to ⁇ 0.15 mm.
- FIG. 6(b) shows images of CPA containing Fe oxide before grinding and Fe oxide freed from CPA after grinding, respectively. Because Fe oxide in CPA has a relatively high strength compared to other materials, it did not break during grinding under the conditions suggested in ‘2-3: grinding’. According to the results, Fig. 6 shows well that grinding affects the Fe oxide liberation effect.
- Magnetic separation was performed with four magnetic forces of 0.1, 0.5, 1, and 2 T, and the recovery rate and purity of separated Fe oxide were confirmed according to the strength of each magnetic force.
- three samples were selected in this experiment considering points 1, 2, 5 and 6.
- Two are CPA with a particle size of 0.15-2.36 mm and less than 0.15 mm.
- the other is CPA with a particle size of less than 0.15 mm, obtained by grinding the particles to less than 0.15 mm from CPA with a particle size of 0.15-2.36 mm.
- Figure 7 shows the change in the recovery rate ( Y Fe ) and purity ( P Fe ) of Fe oxide according to various magnetic forces for three samples.
- equations (4) and (5) are applied to estimate Y Fe and P Fe using the experimental data of F 0 , F r , and W t .
- F o and F s represent the initial weight (g) of Fe oxide in the untreated sample and the weight (g) of Fe oxide in the material separated by magnetic separation, respectively.
- W t represents the total weight (g) of material separated by magnetic separation.
- the overall flow chart (pretreatment process) as shown in FIG. 8 was derived and the experimental results were obtained.
- CPA was screened at 2.36 mm and 0.15 mm. At this time, wet screening may be applied to remove soluble chlorides.
- CPAs with sizes between 0.15 and 2.38 mm and less than 0.15 mm were treated by gravity screening and flotation, respectively.
- step 4 the material containing Fe oxide was separated from the residue after the specific gravity separation process through the first magnetic separation at 1T (magnetic strength). Then, the material containing Fe oxide was pulverized using a grinder (Step 5).
- Fe oxide was separated from the residue from step 2 and the pulverized material from step 5 through secondary (0.1T) and tertiary (1T) magnetic separation processes. Therefore, seven final by-products (recoveries 1-7) can be obtained through this pretreatment process.
- a laboratory-scale experiment was performed on a 200 kg Boryeong CPA according to the designed pretreatment method outlined in FIG. 8 .
- Table 2 shows the isolated amounts and chemical compositions of the final by-products (recoveries 1-7) for each process in the lab-scale experiment.
- the molecular weights for coarse particles with UC purity of 28.4% in recovery 1 and fine particles with UC purity of 62.1% in recovery 2 were 4.2 kg (2.1%) and 11.0 kg (5.5%), respectively.
- Amorphous compound with Al species Al 2 O 3 .xH 2 O
- a glass phase Al 2 O 3 .xH 2 O
- Figure 9 shows various designs of pretreatment methods for desired final by-products and provides several examples.
- Figure 9 (a) shows that the mixture of UC and AC recovered after the gravity separation process can be separated by increasing the purity through additional grinding and flotation. However, the additional process increases energy costs.
- the process shown in FIG. 9 (b) can increase the recovery rate of Fe oxide compared to FIG. Excluding the first magnetic separation after the specific gravity separation process allows the recovery of Fe oxide from CPA to be increased through the second and third magnetic separation processes. However, this increases the energy cost of grinding. Two pretreatment methods can be considered to maximize Fe oxide recovery.
- FIG. 9(c-1) is a method of recovering Fe oxide as much as possible while bearing a high pulverization energy cost burden, while FIG. 9(c-2) reduces dependence on pulverization compared to FIG. 9(c-1) It is a method for recovering Fe oxide.
- the method shown in FIG. 9(d) can be designed.
- the weak strength of CA is one of the major problems that hinders its use in construction sites (Mangi, S.A. et al., 2019. Resources 8(2), 99; Luna, Y.L. et al., 2014. Int. J. Energy Environ Eng. 5, 387-397).
- UC and AC are substances that reduce the strength of CPA, it is possible to secure an inorganic material capable of producing higher strength through the separation process of UC and AC as shown in FIG. 9 (e).
- UC can be a suitable carbon source for some applications. It can be used as an auxiliary fuel in power plants or incineration facilities or as an adsorbent with high porosity (Evans, M.J.S. et al., 1999. Carbon 37, 269-274; Lee, S. et al., 2014. Journal of Korean inst. of Resources Recycling 23, 40-47).
- natural graphite is considered a scarce commodity, it may be a desirable alternative resource for synthetic graphite production applications (Cabielles, M. et al., 2008. Energy Fuels 22, 1239-1243; Camean, I.
- AC having an Al species and a glass phase
- it can be a raw material for zeolite, an inorganic polymer used as a cation exchanger and adsorbent (Jin, X. et al., 2015. Procedia Eng. 121, 961-966; Lee, Y.R. et al., 2017. Chem. Eng. J. 317, 821-843; Penilla, R.P. et al., 2006. Fuel 85, 823-832).
- Zeolitized (synthesized) AC can also be used as an immobilizing agent, a hazardous removal agent for polluted water, and a remediation factor for polluted soil (Fernandez-Pereira, C. et al., 2002. J. Chem. Technol. Biotechnol 77 (Issue 3); Sarkar, D.K., 2015. Thermal Power Plant.Elsevier, pp. 139-158; Sarkar, M. et al., 2006. Waste Manag. 26, 559-570; Sitarz-Palczak, E. et al., 2012. J. Environ. Prot. (Irvine, Calif) 3, 1373-1383).
- Table 3 shows the characteristics of 11 domestic coal-fired power plants. It shows that 10 of the 11 CPPs are currently in operation, and the remaining one is Seocheon CPP, which was discontinued in 2017.
- CPA volume (MT) coal pond capacity (m 3 ) X 1,420 kg/m 3 (1,420 kg/m 3 is calculated from references (National Coal Ash Board, 2006; Rhie et al., 2017; Thi et al. ., 2019; US Department of Transportation, 2016)).
- FIG. 1 shows a map where each CPP is located around the coast.
- AP related drawings located around the Boryeong Thermal Power Plant on the map are extracted from Lee's thesis (Lee, SJ et al., 2007, Geosystem Eng. 10, 47-52).
- the combustion method of each CPP is mostly operated by the pulverized coal combustion (PCC) method.
- Donghae Thermal Power Plant (400 MW) and Yeosu Thermal Power Plant (340 MW) have recently been constructed and are operated using a circulating fluidized bed combustion (CFBC) method.
- PCC pulverized coal combustion
- CA produced from the PCC type is characterized by pozzolanic reactivity and contains glassy aluminosilicates formed at high combustion temperatures (1300°C-1700°C) (Cheriaf, M. et al., 1999. Cem. Concr. Res. 29 (9), 1387-1391). This is also consistent with the results of the CPA characteristics (Al-based AC and glass phase) of the PCC-type Boryeong thermal power plant mentioned above.
- CA of CFBC is rich in free lime (Free CaO) and anhydrite due to limestone input during the desulfurization process and has self-hardening properties (Sheng, G. et al., 2012. Fuel 98, 61-66).
- Dangjin (6,040 MW), Yeongheung (5,080 MW), and Taean (6,100 MW), which have recently been installed, produce high thermal energy, while Boryeong (4,000 MW), Hadong (4,000 MW), and Samcheonpo (3,240 MW) produce high power generation capacity. It follows. Most of the types of coal used as the main fuel in each CPP are bituminous coal, and only small-scale Yeongdong and Donghae use anthracite. Anthracite has a high calorific value due to its high fixed carbon content (85-90%) despite its low volatility (3-7%). However, because of its slow burning rate, it is not suitable as a fuel for power generation.
- bituminous coal contains high amounts of volatiles and emits flames.
- Each CPP operates an AP for CA reclamation, and only small CPPs in the Honam, Donghae, and Yeosu regions entrust reclamation to nearby CPPs that operate their own APs.
- Boryeong Based on AP capacity and landfill volume, Boryeong has the largest CPP with 23,160,000 m 3 and 32.9 MT, followed by Dangjin (17,560,000 m 3 and 24.9 MT) and Samcheonpo (13,380,000 m 3 and 14.6 MT).
- the proposed pretreatment method is based only on the CPA in the Boryeong area. Therefore, the separation method and actual separation material may vary depending on the CPA buried in each AP (a total of 7 APs in Korea).
- previous studies have shown that the overall characteristics of CPA are influenced by the mode of combustion and the type of coal used. Since most CPPs are operated in the PCC method and mainly use bituminous coal as their main fuel, most CPAs (more than 92% of all CPAs in Korea) are expected to have free aluminosilicate and pozzolanic reactivity as shown in Table 3. It also has a relatively low UC content.
- the CPA buried in the AP near the Boryeong CPP represents all CPAs in Korea.
- the CPA of each AP may differ only in terms of the percentage content of each item in its chemical composition. Therefore, it was predicted that this pretreatment method would not be a problem if applied to all CPAs in Korea.
- the mass flow analysis of CPA in the proposed pretreatment method can be estimated using the total amount of CPA landfilled in all APs in Korea ( ⁇ 1,517.5 MT, see Table 3). After pretreatment, by-products containing Fe oxide were 317.1 MT, followed by carbon (115.3 MT), amorphous material (376.4 MT), and inorganic material mainly composed of Si and Al (708.7 MT).
- the pretreatment method proposed in the present invention can be applied to domestic CPA.
- the method according to the present invention is only an intermediate treatment to increase the recycling efficiency in the final recycling process, potential directions of research on each detail can be further discussed.
- a pretreatment method similar to the present invention should be developed through a logical review of various CPA characteristics.
- the pulverized coal combustion (PCC) method which is a major method of burning coal, has led to the construction of large-scale power plants, so it can be said to be the most used method in CPP not only in Korea but also worldwide (Sarkar, M. et al., 2005). J. Chem. Technol. Biotechnol.
- bituminous coal accounts for 73.85% of global coal supply, while anthracite accounts for 1.38% (Xia, X.H. et al., 2017. J. Clean. Prod. 143, 125-144), so CPPs around the world use bituminous coal as their main fuel.
- CPAs in other countries are compared with the CPAs covered in this study, it can be predicted that only the content ratio of items in the chemical composition may differ. Therefore, there will be no problem even if the pretreatment method according to the present invention is applied to CPAs in other countries.
- the results obtained in the present invention are directly applied to the same industry in other countries, it can be used as a basis for designing a new CA pretreatment plant buried in AP or modifying an existing design.
- the pretreatment method according to the present invention it is possible to increase the utilization of landfill-coal ash generated in a coal-fired power plant and buried in a landfill, and an amorphous state including unburned carbon, Al species (Al 2 O 3 xH 2 O) and a glass phase. It can be obtained by classifying into a group of compounds, inorganic materials including Si and Al, and ferrous materials.
Abstract
Description
Claims (13)
- 다음 단계를 포함하는 매립-석탄재(CPA)의 전처리 방법:(a) 매립-석탄재를 체(sieve)를 이용하여 스크리닝하여 조대입자, 중간입자 및 미세입자로 분류하는 단계;(b) 상기 (a) 단계에서 수득한 미세입자를 부유선별(floatation)시키는 단계;(c) 상기 (a) 단계에서 수득한 중간입자를 비중선별(float-sink)시키는 단계; 및(d) 상기 (b) 단계에서 수득한 잔류물과 상기 (c) 단계에서 수득한 잔류물을 혼합한 다음, 자력선별(magnetic separation)시켜 Fe 산화물 함유 미세 물질과 Si 및 Al 함유 미세물질을 수득하는 단계.
- 제1항에 있어서, 상기 (a) 단계에서 0.15mm와 2.36mm 직경의 격자가 있는 표준 체를 이용하여 2.36mm 초과의 직경을 갖는 조대입자, 0.15~2.36mm의 직경을 갖는 중간입자 및 0.15mm 미만의 직경을 갖는 미세입자로 분류하는 것을 특징으로 하는 매립-석탄재(CPA)의 전처리 방법.
- 제1항에 있어서, 상기 (b) 단계는 pH 7에서 수행하는 것을 특징으로 하는 매립-석탄재(CPA)의 전처리 방법.
- 제1항에 있어서, 상기 (c) 단계에서 비중(specific gravity)이 2.2인 용액을 사용하여 비중선별을 수행하는 것을 특징으로 하는 매립-석탄재(CPA)의 전처리 방법.
- 제1항에 있어서, 상기 (c) 단계를 수행한 다음, 수득한 잔류물을 1.0T의 자력세기로 습식 자력선별 시키고, 분리된 Fe 산화물 함유 물질을 분쇄(grinding)시키는 단계를 추가로 포함하는 매립-석탄재(CPA)의 전처리 방법.
- 제1항에 있어서, 상기 (d) 단계에서 상기 (c) 단계에서 수득한 잔류물과 상기 (b) 단계에서 수득한 잔류물의 혼합물을 0.1T의 습식 자력선별기(wet magnetic separator)를 이용하여 고순도 Fe 산화물 함유 미세물질을 분리한 다음, 1.0T의 습식 자력선별기를 이용하여 저순도 Fe 산화물 함유 미세물질을 분리하는 것을 특징으로 하는 매립-석탄재(CPA)의 전처리 방법.
- 제1항에 있어서, 상기 매립-석탄재(CPA)는 석탄화력발전소(CPP)에서 발생하고 매립지(AP)에 매립된 것을 특징으로 하는 매립-석탄재(CPA)의 전처리 방법.
- 다음 단계를 포함하는 매립-석탄재(CPA)로부터 미연소 탄소(unburned carbon, UC)와 비정질 화합물(amorphous components, ACs)의 순도를 증가시킨 부산물을 수득하는 방법:(a1) 매립-석탄재를 스크리닝 및 회수하는 단계;(a2) 매립-석탄재를 스크리닝, 부유선별 및 회수하는 단계;(a3) 매립-석탄재를 스크리닝, 비중선별, 분쇄, 부유선별 및 회수하는 단계;(a4) 매립-석탄재를 스크리닝, 비중선별, 자력선별 및 회수하는 단계;(a5) 매립-석탄재를 스크리닝, 비중선별, 1차 자력선별 및 분쇄에서 수득한 부산물과 상기 (a2) 단계에서 수득한 잔유물을 혼합한 다음, 2차 자력선별 및 회수하는 단계; 또는(a6) 상기 (a5) 단계에서 수득한 잔유물을 자력선별 및 회수하는 단계.
- 다음 단계를 포함하는 매립-석탄재(CPA)로부터 Fe 산화물의 회수율을 증가시킨 부산물을 수득하는 방법:(b1) 매립-석탄재를 스크리닝 및 회수하는 단계;(b2) 매립-석탄재를 스크리닝, 부유선별 및 회수하는 단계;(b3) 매립-석탄재를 스크리닝, 비중선별 및 회수하는 단계; 및(b4) 매립-석탄재를 스크리닝, 비중선별 및 분쇄에서 수득한 부산물과 상기 (b2) 단계에서 수득한 잔유물을 혼합한 다음, 자력선별 및 회수하는 단계; 또는(b5) 상기 (b4) 단계에서 수득한 잔유물을 자력선별 및 회수하는 단계.
- 다음 단계를 포함하는 매립-석탄재(CPA)로부터 Fe 산화물만을 수득하는 방법:(c1) 매립-석탄재를 분쇄, 자력선별 및 회수하는 단계; 또는(c2) 매립-석탄재를 분쇄, 1차 자력선별, 2차 자력선별 및 회수하는 단계.
- 제10항에 있어서, 분쇄공정의 에너지비용(energy cost)을 줄이기 위해 상기 (c1) 및 (c2)의 분쇄 전에 자력선별을 추가로 수행하는 것을 특징으로 하는 매립-석탄재(CPA)로부터 Fe 산화물만을 수득하는 방법.
- 다음 단계를 포함하는 매립-석탄재(CPA)로부터 미연소 탄소와 Fe 산화물만을 수득하는 방법:(d1) 매립-석탄재를 분쇄, 부유선별 및 회수하는 단계;(d2) 매립-석탄재를 분쇄, 부유선별, 자력선별 및 회수하는 단계; 또는(d3) 매립-석탄재를 분쇄, 부유선별, 1차 자력선별, 2차 자력선별 및 회수하는 단계.
- 다음 단계를 포함하는 매립-석탄재(CPA)로부터 강도(strength)를 증가시킨 부산물을 수득하는 방법:(e1) 매립-석탄재를 스크리닝 및 회수하는 단계;(e2) 매립-석탄재를 스크리닝, 부유선별 및 회수하는 단계; 또는(e3) 매립-석탄재를 스크리닝, 비중선별 및 회수하는 단계.
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KR101565906B1 (ko) * | 2015-03-03 | 2015-11-05 | 동아대학교 산학협력단 | 자력선별과 폐식용유를 이용한 바텀애쉬에서 미연탄소를 회수하는 방법 |
WO2020186241A1 (en) * | 2019-03-13 | 2020-09-17 | Valerio Thomas A | System and method for recovering metal from ash |
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KR20140001269A (ko) * | 2012-06-22 | 2014-01-07 | 코카스엔텍 주식회사 | 바텀애쉬 부유선별방법 |
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KR101565906B1 (ko) * | 2015-03-03 | 2015-11-05 | 동아대학교 산학협력단 | 자력선별과 폐식용유를 이용한 바텀애쉬에서 미연탄소를 회수하는 방법 |
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