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    • 专利摘要:
    Procedure for obtaining calcium aluminates from non-saline aluminum slags. The present invention relates to a process for obtaining calcium aluminates for metallurgical use from non-saline aluminum slags by means of reactive grinding and thermal treatment. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2603605A1
    申请号:ES201531116
    申请日:2015-07-28
    公开日:2017-02-28
    发明作者:Félix Antonio López Gómez；Francisco José Alguacil Priego
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；Varmoxz；
    IPC主号:
    专利说明:

    5The present invention relates to a process for obtaining aluminates ofCalcium for metallurgical use from non-salt aluminum slags byreactive grinding and heat treatment. 10 STATE OF THE TECHNIQUE
    Calcium aluminates are described in the binary phase diagram CaO-Al2O3 [R.W. Nurse, J.H. Welch and A.J. Majumdar, The CaO-Al2O3 System in a Moisture-free Atmosphere, Trans. Br. Ceram. Soc., 64, 409-418 (1965)]. In this system, five binary compounds can be distinguished generically called calcium aluminates: CaAl2O4 (CA), CaAl4O7 (CA2), Ca12All4O33 (C12A7), Ca3AlO6 (C3A)
    and CaAl12O19 (CA6) where C = CaO and A = Al2O3.
    The CaO-Al2O3 system has been studied by numerous researchers. One of the
    20 first works was that of De Keyser [W.L. From Keizer, Contribution à l´étude des réactions à l’état solide between la chaux et lálumine, Bull. Soc. Chim. Belg., 60, 516-541 (1951).], In which he established the principle that in the CaO-SiO2-Al2O3 system, the direction and sequence of the reactions do not depend on the concentrations of the constituents of the mixture . Macias and Welizek [J. Macias and Z. Weliszek, Cement
    25 Wapno-Gibs, 19, 170-177 (1964)] calculated that, whatever the initial molar ratio in a reaction between CaO and Al2O3, the first product obtained is CA. Audouze
    [B. Audouze, Solid-State Reactions Between CaO and Al2O3, Silicates Industries, 26, 179-190 (1961).], Babushkin and Mchedlow-Petrosyan [V. Babushkin and O. Mchedlov-Petrosyan, Silicattenchn, 9, 109-120 (1958).] Established different sequences of 30 reactions. Willianson and Glasser [J. Williamson, F.J. Glasser, Reactions in Heated Lime-Alumina Mixtures, J. Appl. Chem. 12 535-538 (1962).] Studied different CaO: Al2O3 molar relationships, not finding that any preferred phase was formed as the first reaction product. These studies, sometimes with conflicting results, have led to consider the following
    35 sequence of reactions as the most likely:


    A + C ĺ AC + C ĺ C12A7 + C ĺ C3A (1)A + C ĺ AC + A ĺ CA2 + A ĺ CA6 (2)
    These reactions are mainly produced by the diffusion of Ca2 + within the5 Al2O3, resulting in the sintering of CaO and Al2O3 mixtures at temperatures oforder of 1300ºC, a sequence of phase contents that responds to the relationship:
    C3A> C12A7> CA6> CA2 § CA.
    10 Calcium aluminates have applications as refractory cement due to their high temperature stability among other characteristics and are also used within the metallurgical process of steelmaking, where the contribution of a synthetic slag based on calcium aluminate favors the process of desulfurization of steel and obtaining clean steels from inclusions, especially Al2O3. Besides, the
    The presence of a molten calcium aluminate slag on the steel facilitates work in secondary metallurgy, due to its adequate fluidity, and protects the steel against re-oxidation processes and temperature losses [Harold E. McGannon, The Making, Shaping and Treating of Steel (Steel Making and Refining), 11th Edition, American Society for Metals, United States Steel Corporation, Pittsburgh, Pennsylvania
    20 (1998)].
    Most of the calcium aluminate consumed by the steel sector is sintered from mixtures of bauxite and lime. The use of slags from the fusion of aluminum, and therefore, with a high content of Al2O3, is
    25 shows as an alternative to the use of bauxites for the production of calcium aluminates.
    Industrially, the obtaining of calcium aluminate base materials is carried out by cold sintering or by hot sintering. In the processes of
    30 Cold sintering is based on bauxite, aluminum slags, mainly salt slags, or products resulting from the recovery of salts by hydrolysis and crystallization from salt slags. Normally, commercial, ground CaO is used, which is mixed with the slag in varying proportions, ranging from 0.2-1.8 CaO: Al2O3. The mixtures are ground and the milled product is added
    35 classic binders to carry out a pelletizing process (diameter pellets


    between 1 and 50 mm) or briquettes (sizes between 4 and 100 mm). Pellets or briquettes are screened, dried and packaged.
    In hot sintering processes, pellets or briquettes are sintered in
    5 rotary furnaces, reverbero or mobile grill ovens, at a temperature of about1100 ° C to obtain a product concentrated in C12A7 aluminate (Ca12Al14O33). HeFinal product is classified and packaged. DESCRIPTION OF THE INVENTION
    The present invention relates to a method of exploiting non-salt aluminum slags from obtaining aluminum from scrap or second fusion products. Through the process of the invention the non-salt aluminum slags are transformed into calcium aluminates CaO-Al2O3, which are
    15 synthetic slags for metallurgical use, in particular for the manufacture of steels.
    From a metallurgical point of view, the use of calcium aluminates in the manufacture of steels has the following advantages:
    20 a) Rapid slag formation: The low melting point of calcium aluminates, between <1325 ° to 1375 ° C, causes them to melt in contact with the steel, dissolving other components, such as lime, obtaining a fluid and homogeneous slag. b) The addition of calcium aluminates improves desulfurization kinetics due to
    25 the rapid slag formation, which allows the start of desulfurization reactions as soon as the pouring spoon is filled. The increase in desulfurization speed can achieve a lower sulfur content and therefore a higher quality of steel; increase productivity thanks to less treatment time; reduce costs due to the possibility of
    30 use cheaper raw materials with higher sulfur content. c) Steel cleaning: the use of calcium aluminates, with a composition close to that of the final slag composition, produces the capture of non-metallic inclusions as soon as the pouring spoon is filled. Therefore, it is possible to remove these impurities when they form and reduce the
    35 need for further treatment.


    d) Increased productivity: The use of calcium aluminate increases the predictability and reproducibility of laundry, accelerates the formation of fluid and homogeneous slags, reducing the refining time and reducing the total casting time.
    5 e) Cost reduction due to the decrease in corrosion of furnace refractory linings, thereby increasing the durability of refractory materials.
    In a first aspect, the present invention relates to a process for obtaining calcium aluminates (hereinafter "process of the invention") which
    It comprises the following steps: a) carry out a reactive grinding of the non-saline aluminum slag in the presence of calcium carbonate CaCO3; b) thermally treat the product obtained in step a) at a temperature
    15 between 700 ° C and 750 ° C; and c) heat treating the product obtained in step b) at a temperature between 1300 ° C and 1400 ° C.
    In the present invention, calcium aluminates are those CaO systems
    20 Al2O3 described in R.W. Nurse, J.H. Welch and A.J. Majumdar, The CaO-Al2O3 System in a Moisture-free Atmosphere, Trans. Br. Ceram. Soc., 64, 409-418 (1965), within the binary phase diagram. The term refers to the following five binary compounds: CaAl2O4 (CA), CaAl4O7 (CA2), Ca12All4O33 (C12A7), Ca3AlO6 (C3A) and CaAl12O19 (CA6) where C = CaO and A = Al2O3.
    The term "non-saline aluminum slag" is understood in the present invention as those non-salt aluminum slags with different contents in aluminum hydrates derived from obtaining aluminum from scrap or second fusion products.
    In a preferred embodiment, the non-saline aluminum slag from step a) has a percentage of hydrated aluminum oxides of between 5% and 65%.
    The aluminate content increases in sintering in inverse relation to the content of aluminum hydrates in the slag. It is likely that part of the mechanical energy supplied to the mixture during the reactive grinding is used, in the form of


    heat, in dehydrating aluminum oxides, but it is likely that the aluminum oxide resulting from this process is less reactive than the initial Į-Al2O3, existing in the slags. In stage a) of the process, non-saline aluminum slag is milled in the presence
    5 of calcium carbonate CaCO3 with the molar ratio Al2O3: CaO between
    1: 1 and 1: 3; preferably 1: 3.
    The increase in the content of C3A increases as the Al2O3 / CaO ratio increases from 1: 1 to 1: 3 and this growth is accompanied by a decrease in the contents of CA and C12A7. 10 This is a reactive grind where binders are not used.
    Grinding is done using ball mills or concentric rings as grinding bodies. Preferably, the grinding of step a) is carried out
    15 by ball mill. The mill rotates at high speed (> 500 rpm). The energy produced in the friction or energy of Coriolis, produces an increase in the temperature of the mixture of slag and carbonate, enough to initiate the dehydration reactions of aluminum hydrates, even, in initiating the carbonate decomposition reaction.
    Preferably, the product obtained in step a) has an average particle size of less than 40 μm.
    Step b) of the process of the invention consists in thermally treating the product obtained in stage a) at a temperature between 700 ° C and 750 ° C to complete the decomposition of calcium carbonate.
    Step c) of the process of the invention consists in thermally treating the product obtained in step b) at a temperature between 1300 ° C and 1400 ° C.
    The product obtained in step c) is packaged. Figure 1 represents the scheme of the process of the invention.
    Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the


    invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention. BRIEF DESCRIPTION OF THE FIGURES
    FIG. 1 Basic scheme for obtaining calcium aluminate.FIG. 2. X-ray diffraction diagrams of slags; (a) Al-1, (b) Al-2, (c) Al-3 and
    (d)  EM.FIG. 3. Rietveld method curves for slags; (a) Al-1, (b) Al-2, (c) Al-3 and
    (d)  EMFIG. 4. (a, b) Image of secondary electrons of the Al-1 slag.FIG. 5. (a, b) Image of secondary electrons of the Al-2 slag.FIG. 6. (a, b) Image of secondary electrons of the Al-3 slag.FIG. 7. RX diffraction diagrams of sintered products at 1300ºC
    obtained from the different slags studied (a) Al-1S; (b) Al-2S and (c) Al-3S
    (Reactive grinding: 1h. Al2O3 molar ratio: CaO: = 1: 1).FIG. 8. Variation of the contents in crystalline phases depending on the time ofreactive grinding, after sintering at 1300 ° C, for the slags used.a) Al-1S; b) Al-2S and c) Al-3S.
    FIG. 9. SEM images (secondary electrons) of the sintered ones obtained at 1300 ºC for a molar ratio Al2O3: CaO 1: 1. Symbols


    Slag Al-1 one
    Slag Al-2 2
    Slag Al-3 3
    Sintered slag Al-1 (Al2O3 ratio: CaO 1: 1) 1S
    Sintered slag Al-2 (Al2O3 ratio: CaO 2S
    1: 1) 3S
    Sintered slag Al-3 (Al2O3 ratio: CaO
    1: 1)
    Silico magnesium aluminate SA
    Calcium Monoaluminate (CA) AC
    Mayenite (C12A7) M
    Mg-Fe spinel Efe
    Melanite I
    Calcium Trialuminate C3A
    Mg spinel AND
    Grossite (CA2) G
    Gehlenite Ge
    5H hibonite H
    Bredigita B
    Wollastonite W
    Vesuvianite V
    FIG. 10. SEM (backscattered electrons) image of the sintered ones obtained at 1300 ºC and 1: 1 molar ratio. a) Al-1S; b) Al-2S and c) Al-3S (S = 5 mg silicate aluminate, CA = calcium aluminate, M = mayenite or C12A7 and E = spinel; Ge = gehlenite).
    FIG. 11. Phase diagrams of the Al2O3-SiO2-CaO system showing the initial slags and sintered products obtained with molar ratios 10 Al2O3: CaO of 1: 1; 1: 2 and 1: 3.
    Symbols
    Indication in the
    diagram
    Slag Al 1 one
    2


    Slag Al 2 Slag Al 3 Sintered obtained from slag Al 1 for a molar ratio Al2O3 1: 1 Sintered obtained from slag Al 2 for a molar ratio Al2O3: CaO 1: 1 Sintered obtained from slag Al 3 for a molar ratio Al2O3: Sintered CaO 1: 1 obtained from slag Al 1 for a molar ratio Al2O3: CaO 1: 2 Sintered obtained from slag Al 2 for a molar ratio Al2O3: CaO 1: 2 Sintered obtained from slag Al 3 for a molar ratio Al2O3: CaO 1: 2 Sintered obtained from slag Al 1 for a molar ratio Al2O3: CaO 1: 3 Sintered obtained from slag Al 2 for a molar ratio Al2O3: Sintered CaO 1: 3 obtained from slag Al 3 for a molar ratio Al2O3: CaO 1: 3 Slag Average Slag obtained from middle slag for a molar ratio Al2O3: CaO 1: 2 Sintered obtained from the average slag for a molar ratio Al2O3: Ca Or 1: 3 3 1S 2S 3S 1S2 2S2 3S2 1S3 2S3 3S3 EM S2 S3
    FIG. 12. SEM (backscattered electrons) image of the sintered ones obtained at 1300 ºC and 1: 3 molar ratio. (a) Al-1 3S; (b) Al-2 3S and (c) Al-3 3S (C3A = calcium trialuminate, M = mayenite or C12A7, Mg = MgO, P = Al1.95 Fe0.49Mg2.65O12Si2.91, Gr = Ca3Al2 (SiO4) 3, K = Ca6 (SiO4) (Si3O10), and He = FeAl2O4.


    FIG. 13. Images obtained in a heating microscope in which a sintered sample obtained from the middle slag (MS), at 1300 ° C and with an Al2O3: CaO ratio is heated at 10 ° C / min from room temperature to 1350 ° C EXAMPLES
    The invention will now be illustrated by tests carried out by the inventors, which demonstrates the effectiveness of the product of the invention.
    10 Four samples of non-salt aluminum slags, identified as Al-1, have been worked on; Al-2; Al-3 and EM. THE SAMPLES Al-1; AL-2 and Al-3 are slags produced in the fusion plant that differ from each other in the time they have been stored outdoors. The EM sample is a mixture of the
    15 three slags described above. The mixture consisted of 30% by weight of the Al-1 slag; 20% of the Al-2 slag and 50% of the Al-3 slag. The percentages by weight of each of the slags were chosen with effectiveness criteria.
    Sample Al-1: aluminum slag with an age of 3 to 7 years.
    20 Sample Al-2: aluminum slag with an age of 7 to 10 years, stored outdoors. Sample Al-3: recent aluminum slag, generated between 2013-2014. EM sample: aluminum slag, mixture of slags Al-1; Al-2 and Al-3 (30-20-50)
    25 Analysis of the chemical composition of aluminum slag samples
    The aluminum slags received were cracked and dried in an oven (80ºC / 24 h), determining the humidity of each sample. Subsequently, the samples were ground in a TEMA mill for 15 minutes to obtain materials with a
    30 particle size less than 40 μm.
    The samples were attacked with lithium metaborate at 1050 ° C and acidified with concentrated nitric (HNO3) to determine their chemical composition by Inductive Coupling Plasma Spectroscopy, using a
    35 ICP-OES optical emission spectrophotometer, model 725-ES from Varian.


    Likewise, calcination losses were determined according to ISO 1171: 2010. (815 ° C / 1 h).
    Table 1 shows the chemical composition of the slags.
    Table 1. Chemical composition of slags (% by weight expressed as oxides). (* PxC = Calcination losses)
     Al-1 Al-2Al-3EM
    Al2O3  75.6758.4281.9475.35
    CaO 4.544.594,7184.64
    Fe2O3  3.704.551.842.94
    MgO 3.171.963.353.02
    SiO2  2.995.244.584.24
    MnO2  0.100.250.200.27
    CuO 0.140.400.100.17
    ZnO 0.042.510.050.54
    NiO 0.030.030.010.02
    PxC 7.3817.393.257.32
    Humidity  2.4311.6700
    10 Al-1 and Al-3 slags have similar chemical compositions, while Al-2 slag has a lower Al content and a higher percentage of Zn. Losses from calcination, which include moisture, interstitially absorbed water, water of crystallization of mineralogical phases and decomposition of mineralogical phases, present very different values from each other.
    15 Analysis of the mineralogical composition of aluminum slag samples.
    The mineralogical composition of the aluminum slag samples was obtained by X-ray Diffraction using a Siemens model D5000 diffractometer, equipped with a Cu anode (Cu KĮ radiation) and LiF monochromator to eliminate the K radiación radiation from the samples containing iron. The generator voltage and current were 40 kV and 30 mA respectively. The measurement has been carried out continuously with a step of 0.03º and a time of 3 s for each step. The interpretation of


    diffractograms were carried out with the help of the reference database Powder Diffraction File (PDF-2) of the ICDD (International Center for Difraction Data) and the DIFFRACplus EVA software package from Bruker AXS.
    5 Figure 2 shows the diffraction diagrams of the slags studied. Benote that the oldest slags (Al-1 and Al-2) have a greater characteramorphous than the most recent slag (Al-3), which clearly presents a higher degreeof crystallinity
    10 It is observed that samples Al-1 and Al-3 have a similar mineralogical composition. In Al-2 slag, boehmite and gibbsite appear, which do not appear in the other two slags and at the same time, phases such as norstrandite, enstatite and magnesite and Mg spinel are not present in this slag. The Al-2 sample is more hydrated than the other two, possibly due to having been stored outdoors during
    15 years.
    The quantitative study of the crystalline phases present in the slag samples was carried out using the Rietveld method, from the X-ray diffraction diagrams (DRX) (Figure 3).
    20 The quantification of the phases was performed using the Rietveld Topas analysis program (Bruker AXS) for the refinement of DRX data. Once the adjustment, its quality and reliability, the% of each phase was calculated from the residual values, R (Figures of Merit, FOM), considering that residual values below 10%
    25 guarantee the goodness of fit and the reliability of the determination. Table 2 includes the quantitative mineralogical composition of the slags studied.
    Al-2 slag, the oldest, presents greater differences in its mineralogical composition, observing that it has a lower content of
    30 metallic aluminum (Al) and aluminum nitride (AlN) and instead, has a high content of hydrated aluminum oxides, gibbsite (Ȗ-Al (OH) 3) and boehmite (AlO (OH)), which represents 50 , 41% of the total.
    The hydrated phases of aluminum may have formed as a result of
    35 hydration of metallic aluminum and aluminum nitride, according to reactions (3) to (5):


    2 Al + 6 H2O ĺ 2 Al (OH) 3 + 3H2 (3) 2 Al + 4 H2O ĺ 2 AlO (OH) + 3H2 (4) AlN + 3 H2O ĺ NH3 + Al (OH) 3 (5)
    Table 2. Quantitative mineralogical composition of the slags studied, expressed in%.
    Crystalline phase Al-1Al-2Al-3EM
    Al1.99Fe0.11Mg0.9O4 AlN Į-Al2O3 Al Al2.4Mg0.4O4 Į-Al (OH) 3 Al (OH) 3 Ca (OH) 2 CaCO3 SiO2 MgSiO3 MgCO3 Ȗ-AlO (OH) Ȗ-Al (OH) 3 Ca14Mg2 (SiO4) 8 23.30 13.91 8.34 11.36 23.30 5.91 1.82 1.40 8.66 0.78 0.75 0.56 ---13.57 3.07 6.21 3.82 -3.44 -2.24 10.28 1.04 --50.41 5.91 -24.16 12.89 12.00 14.40 15.82 2.13 0.89 2.91 6.37 0.41 4.46 --- 3.576.71 11.38 13.16 18.57 37.2 --1.72 6.35 0.97 0.05 0.33 --3.44
    10 The total carbohydrate content of Al and Ca varies in the order:
    Al-2 (62%)> Al-1 (9.13%)> Al-3 (5.95%),
    which is the same order in which calcination losses vary. fifteen
    Microstructural analysis of aluminum slag samples.
    The microstructural analysis was performed by Scanning Electron Microscopy (FESEM)
    in a HITACHI model S-4800, using a voltage of 15 kV. Samples 20 for microscopy were embedded in a polymeric resin and polished with sandpaper.


    600, 1200 and 2000 (adding carnauba to these to protect the sample). Subsequently, they were polished with 3 and 1 μm diamond paste and metallized with carbon in a JEOL JEE 4B model.
    5 The morphological study is summarized in Figures 4 to 6. Figure 4 (a, b)corresponding to slag Al-1, shows a heterogeneous morphology in size andappearance. The presence of released grains in which aluminum is observed is observed.It combines with oxygen (alumina) and with Mg-Fe (spinels). Also appearparticles in which the majority element is aluminum, without association with oxygen
    10 (metallic aluminum).
    Figure 5 (a, b) shows the morphology of the Al-2 slag that has a heterogeneous surface in grain size and appearance. Aluminum appears associated with iron and magnesium (spinel), calcium (in mixed grains alumina-calcite and / or
    15 portlandite) and silicon (in alumina-silica mixed grains) (a, c). The presence of metallic aluminum is not observed.
    Figure 6 (a, b) corresponding to slag Al-3. It has a heterogeneous appearance surface in grain size and aspect. Morphologically, the scum is
    20 similar to slag Al-1.
    The procedure outlined in Figure 1 was then carried out.
    Influence of reactive grinding time
    25 First, the influence of reactive grinding time on aluminate formation was studied. For this, the slags Al-1; Al-2 and Al-3 were mixed with CaCO3 in a molar ratio Al2O3: CaO equal to 1: 1, to subsequently prepare, by mechanical compaction, mini-briquettes to undergo different treatments
    30 thermal. A "quality reagent for analysis" PA CaCO3 from PANREAC was used.
    Reactive grinding was carried out during different times (4, 8, 12, 16 and 24 h), in a Pulverisette 6 mill in Fritsch, at 450 rpm, with 5 stainless steel balls, the weight ratio being balls / mix of 6.5 .


    After the grinding time, cylindrical mini briquettes (13.5 mm (diameter) x 5.5 mm (height)) were prepared, without the addition of binders, by forming with a Specac Atlas 15 T hydraulic hand press. The pressure applied was 10543 kg / cm2 with a pressure of 1034 MPa. The quantification of the mixture components is shown in Table 3.
    Table 3. Amounts of calcium carbonate (C100) added to 100 g. slag for a 1: 1 molar ratio Al2O3: CaO
    Human waste  C100 (g)
    Al-1 105.63
    Al-2 85.00
    Al-3 107.64
    10 Subsequently, the mini-briquettes were sintered in a Termiber de Ingeniería Térmica, S.A. oven, at 1300 ° C for 1 h, with an isothermal pre-step at 750 ° C for 1 h. to achieve complete decomposition of calcium carbonate.
    15 Sintered products (Al-1S; Al-2S and Al-3S) were characterized by RX diffraction, Rietveld quantification, chemical analysis and morphological study by SEM, using the techniques and procedures described in a previous section. Figure 7 shows the diffraction diagrams of RX of the sintered products at 1300 ° C obtained for the different slags studied.
    20 From the study of the mineralogical composition of the sintered ones, it follows that there is no significant variation in the composition of the sintered ones as a function of the grinding time (Figure 8). Consequently, for the study of the rest of the process parameters, a reactive grinding time of 1 hour will be used.
    25 The influence of slag formation on aluminate formation is noteworthy. Thus, in the sintered Al-3S, a higher aluminate content (CA and C12A7) is observed than in the rest. In the sintered Al-3S, the total aluminate content is between 69% and 74%, compared to 49% - 56% in the sintered Al-1S and
    30 11% - 15% in the sintered Al-2S (Table 4).


    From the results obtained, the existence of an inverse relationship between the content of Ca and Al hydrates in the initial slag and the aluminate content in the sintered product is deduced.
    Hydrate content Al-2> Al-1> Al-3
    "Age" scum
    Aluminized content sintered product Al-2 <Al-1 <Al-3
    Table 4.- Mineralogical composition of sintered materials with each of the slags (CaO: Al2O3 1: 1 molar ratio. Reaction times between 1 h and 48 h)
    Crystal Phases Al-1S (%)Al-2S (%)Al-3S (%)
    Ca12Al14O33 (C12A7) 17.95 - 21.3910.96 - 15.5122.19 - 24.68
    Al2CaO4 (CA) 31.10 - 34.47í46.51 - 49.01
    Total aluminates 49 - 5611-1569-74
    Al 1.99 Fe 0.11Mg0.90O4 4.93 - 6.035.85 - 8.049.84 - 10.64
    Ca20Mg3Al26Si3O68 40.13 - 42.8676.45 - 82.82í
    Ca3Fe2 [SiO4] 3 (andradite) íí4.95 - 5.64
    Al2Ca2O7Si (gehlenite) íí13.03 - 15.13
    Total remaining Phases 45-4982-9128 - 33
    10 Finally, Table 5 shows the chemical composition of the sinters obtained for a reactive grinding time of 1h.
    Table 5. Chemical composition (% weight) of the sintered ones obtained for a grinding time of 1h and a molar ratio Al2O3: CaO equal to 1: 1


    Al2O3 51.7549.2556.63
    Fe2O3 2.682.271.54
    CaO 35.8739.6438.14
    MgO 2.031.401.84
    SiO2 5.447.827.51
    MnO2 0.210.140.18
    NiO 0.040.050.04
    CuO 0.120.350.09
    ZnO 0.292.800.16
    Morphologically, Figure 9 shows different aspects of sintering obtained from each of the slags studied for a reactive grinding time of 1h.
    5 In Figure 9, different mineralogical phases existing in the sintered ones can be identified by backscattered electrons.
    The ternary phase diagrams of the Al2O310 SiO2-CaO and Al2O3-MgO-CaO systems are shown in Figure 10, placing the three initial slags and sinters obtained with each of them (molar ratio Al2O3: CaO equal to 1: one).
    The sintered ones fall within the zone of chemical compositions of synthetic slags indicated by Richarson (1974) [Richarson, F.D. Physical chemistry of metal 15 are metallurgy. Vol. 2. Academic Press, 1974. Synthetic slags for steelmaking. AMG Vanadium, Inc. 2010.] (see Figure 10) as suitable for use in the manufacture of steels, especially for their desulfurizing effect. At the same time, the sintered ones have MgO contents around 2%, which represents an added value, since this compound has a favorable effect on the protection of
    20 refractories
    Influence of the CaO: Al2O3 molar ratio on calcium aluminate formation
    Slag mixtures were prepared with the amounts of CaCO3 listed in Table 6 for molar ratios Al2O3: CaO of 1: 1; 1: 2 and 1: 3. Reactive grinding time was 1 h. and the mini briquettes were sintered at 1300 ° C.


    Table 6. Amounts of calcium carbonate (C100) added to 100 g. slag for different molar ratios Al2O3 / CaO
    Human waste C100 (g)
    RatioRatioRatio
    1: 1 1: 21: 3
    Al-1 105.63211.26316.89
    Al-2 85.00170.00255.00
    Al-3 107.64215.28322.92
    EM -205.02338.28
    5 The chemical composition of the sinters obtained for the different molar and slag ratios used is shown in Table 7.
    Table 7. Average chemical composition of sintered materials obtained based on the molar ratio Al2O3: CaO. 10




    The mineralogical composition, after the quantification of phases carried out by the Rielved method, appears in Table 8.
    Table 8. Composition (%) in the crystalline phase of the sintered ones obtained for the molar ratio Al2O3: CaO equal to 1: 3 from the initial slags.


    Table 8 shows that the sintered ones obtained for molar ratios Al2O3: CaO greater than 1: 1 are mainly constituted by aluminates. On the other hand, for a 1: 1 molar ratio the content of silicates and other mineralogical phases is higher than the aluminate content, except for the case of
    5 slag Al3 in which the opposite occurs.
    Table 9 compares the contents of aluminates and silicates in the sintered products obtained for different molar and slag ratios.
    10 Table 9. Composition (%) in crystalline phases of the sintered ones obtained for the molar ratios Al2O3: CaO equal to 1: 1, 1: 2 and 1: 3.
    Sample (molar ratio Silicate aluminates and other Al2O3 phases: CaO) (%) (%)
    Al-1 (1: 1 ratio) 49.1 45.0 Al-1 (1: 1 ratio) 11.0 82.3 Al-1 (1: 1 ratio) 68.7 28.7 MS (1 ratio: one) --
    Al-2 (ratio 1 :) 81.9 16.0 Al-2 (ratio 1: 2) 80.5 19.9 Al-2 (ratio 1: 2) 80.7 17.6 MS (ratio 1: 2 ) 81.2 17.1
    Al-3 (1: 3 ratio) 90.2 4.4Al-3 (1: 3 ratio) 75.4 21.6Al-3 (1: 3 ratio) 92.2 3.1MS (1: 3 ratio) 88.6 2.9
    In general, an increase in the molar ratio Al2O3: CaO produces a decrease
    Significant silicate content since an increase in the calcium content in the system favors the reaction of this element with aluminum, to the detriment of the reaction of calcium with silicon.
    With a 1: 3 molar ratio, there is a significant change in the nature of the
    20 calcium aluminates in the sintered ones with respect to the composition of the sintered ones obtained at molar ratios Al2O3: CaO of 1: 1 and 1: 2. It is observed, for all slags, considered, the decrease in C12A7, the disappearance of


    CA monocalcium aluminate and the majority formation of tricalcium aluminate (C3A), by increasing the content of CaO in the sintered ones. This is due to the greater diffusion of Ca2 + within Al2O3 according to the reaction (6) that summarizes the mechanism of the formation process:
    5A + C or AC + C or C12A7 + C or C3A (6)
    It can be seen how the increase in CaO (C) in the system transforms the Al2O3
    (A) in monocalcium aluminate which is subsequently transformed into C12A7 and perhaps 10 other intermediate aluminates, and finally in tricalcium aluminate.
    Figure 11 places, on the CaO-Al2O3-SiO2 diagram, the sintered ones obtained for different molar ratios.
    15 In Figure 12, the mineralogical phases existing in the sintered ones obtained from each of the slags studied for a reactive grinding time of 1 h and a molar ratio Al2O3: CaO equal to 1: 3 can be identified by backscattered electrons .
    In the sintered Al1 2S, Al2 2S and Al3 2S, the major phases are calcium aluminates (calcium trialuminate -C3A and mayenite - C12A7), the majority being, in general, the C3A phase.
    Finally, in Figure 13 the study is collected by heating microscopy
    25 of a sintered sample obtained from the middle slag (MS) with an addition of CaO necessary to achieve an Al2O3: CaO ratio equal to 1: 3. The sintered sample was heated at 10 ° C / min to reach a final temperature of 1350 ° C. It is observed that at 1280 ° C there is a decrease in the area of the sample, indicative of the onset of deformation. However, at the final temperature of the test,
    30 the sample does not reach the temperature of the sphere or the hemisphere, thereby fulfilling one of the fundamental properties of aluminates for use in the metallurgical industry: thermal stability at temperatures of the order of 1300 ° C.

    权利要求:
    Claims (5)
    [1]
    1. Procedure for obtaining calcium aluminates CaAl2O4 (CA), CaAl4O7 (CA2), Ca12All4O33 (C12A7), Ca3AlO6 (C3A) and CaAl12O19 (CA6), where C = CaO and A =
    5 Al2O3, which comprises the following steps: a) carry out a reactive grinding of the non-saline aluminum slag from the recovery by melting of aluminum scrap or second melting products of this metal in the presence of calcium carbonate CaCO3;
    10 b) heat treating the product obtained in step a) at a temperature between 700 ° C and 750 ° C; c) heat treat the product obtained in step b) at a temperature between 1300 ° C and 1400 ° C.
    Method of obtaining according to the preceding claim, wherein the non-saline aluminum slag of step a) has a percentage of hydrated aluminum oxides of between 5% and 65%.
    [3]
    3. Method according to any one of claims 1 or 2, wherein the 20 molar ratio Al2O3: CaO of the non-salt aluminum slag from step a) is 1: 3.
    [4]
    4. Method according to any of claims 1 to 3, wherein the milling of step a) is carried out by ball mill.
    Method according to any one of claims 1 to 4, wherein the product obtained in step a) has an average particle size of less than 40 μm.
    [6]
    Method according to any one of claim 3, wherein the calcium aluminate content CaAl2O4 (CA), CaAl4O7 (CA2), Ca12All4O33 (C12A7), Ca3AlO6
    30 (C3A) and CaAl12O19 (CA6), where C = CaO and A = Al2O3, from stage c) is between 70% and 92%.
    [7]
    7. Method according to any of claims 3 or 6, wherein the content
    in tricalcium aluminates Ca3AlO6 (C3A) is between 71% and 85%. 35

    FIG. one

    FIG. 2.

    FIG. 3.

    FIG. Four.

    FIG. 5.

    FIG. 6.

    FIG. 7.
    to)
    b)

    FIG. 8.

    FIG. 9.
    to)
    b)
    C)

    FIG. 10.

    FIG. eleven.

    FIG. 12.

    FIG. 13.
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    同族专利:
    公开号 | 公开日
    WO2017017304A1|2017-02-02|
    US20180222764A1|2018-08-09|
    US10858261B2|2020-12-08|
    EP3330226A4|2019-04-03|
    CA2993909A1|2017-02-02|
    ES2603605B1|2017-12-13|
    EP3330226A1|2018-06-06|
    MX2018001177A|2018-11-12|
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    ES201531116A|ES2603605B1|2015-07-28|2015-07-28|PROCEDURE FOR OBTAINING CALCIUM ALUMINATES FROM NON-SALINE ALUMINUM ESCORIES|ES201531116A| ES2603605B1|2015-07-28|2015-07-28|PROCEDURE FOR OBTAINING CALCIUM ALUMINATES FROM NON-SALINE ALUMINUM ESCORIES|
    MX2018001177A| MX2018001177A|2015-07-28|2016-07-26|Method for obtaining calcium aluminates from non-saline aluminium slags.|
    EP16829904.8A| EP3330226A4|2015-07-28|2016-07-26|Method for obtaining calcium aluminates from non-saline aluminium slags|
    PCT/ES2016/070566| WO2017017304A1|2015-07-28|2016-07-26|Method for obtaining calcium aluminates from non-saline aluminium slags|
    CA2993909A| CA2993909A1|2015-07-28|2016-07-26|Method for obtaining calcium aluminates from non-saline aluminum slags|
    US15/748,323| US10858261B2|2015-07-28|2016-07-26|Method for obtaining calcium aluminates from non-saline aluminum slags|
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