The article presents the research results on the interaction of tricalcium phosphate with the products of carbothermic reduction of silicon oxide (SiOg, SiC, iron silicides). The research was carried out by computer thermodynamic modeling using the HSC-6.0 software package. It was established that SiOg, Si, and SiC are highly reactive towards tricalcium phosphate at relatively low temperatures. It was found that, according to the formation degree of gaseous phosphorus from Ca3 (PO4)2, silicon-containing reducing agents form a decreasing series: (SiOg, Si)>SiC>FeSi2>FeSi

Badikova, A. D.

Shevko, V. M.

Uteeva, R. A.

English

Hrčak - Portal of scientific journals of Croatia

447METALURGIJA 62 (2023) 3-4, 447-450V.M. SHEVKO, A.D. BADIKOVA, R.A. UTEEVAINTERACTION OF TRICALCIUM PHOSPHATE WITH PRODUCTS OF CARBOTHERMIC REDUCTION OF SILICON OXIDEReceived – Primljeno: 2023-02-28 Accepted – Prihvaćeno: 2023-04-30Preliminary Note – Prethodno priopćenjeThe article presents the research results on the interaction of tricalcium phosphate with the products of carbother-mic reduction of silicon oxide (SiOg, SiC, iron silicides). The research was carried out by computer thermodynamic modeling using the HSC-6.0 software package. It was established that SiOg, Si, and SiC are highly reactive towards tricalcium phosphate at relatively low temperatures. It was found that, according to the formation degree of gase-ous phosphorus from Ca3(PO4)2, silicon-containing reducing agents form a decreasing series: (SiOg, Si)>SiC>FeSi2>FeSi.Keywords: tricalcium phosphate, carbothermic reduction, temperature, silicon oxide, thermodynamic modelingISSN 0543-5846METABK 62(3-4) 447-450 (2023)UDC – UDK 669.891-661.632:66.094.1:536.377:661.68-541.451:536.777=111INTRODUCTIONIn blast-furnace production of cast iron, phosphorus, supplied with the charge as calcium and iron phosphates, is reduced and almost completely passes into cast iron [1, 2]. However, under certain conditions, the phosphorus transition degree from the charge into cast iron can be less and amounts to 90–94 % [3,4]. The reducing agents of phosphorus from phosphates are considered to be car-bon, hydrogen, and CO [1, 5]. This statement is not en-tirely correct, since it was made without taking into ac-count the effect of SiO2 reduction products. The reduc-tion of SiO2 in a blast furnace can be 5-26 %, depending on the type of cast iron produced [1, 2].According to [6], the products of SiO2 reduction are Si, SiOg, SiC, and in the presence of iron also FeSi, FeSi2, Fe3Si, Fe5Si3. The joint reduction of Ca3(PO4)2 and SiO2 has specific features. So, the works of Ko-nevsky [7] found that in the Ca3(PO4)2 – SiO2 – C system at a temperature of 1 400–1 500 °C the reduction rate of Ca3(PO4)2 is ten times higher than the reduction rate of SiO2, and at a temperature of 1 700 °C these rates are almost leveling off. Moreover, the resulting silicon is able to reduce Ca3(PO4)2 with the formation of gaseous phosphorus. However, there is no information on the comparative reduction ability of SiO2 reduction prod-ucts with respect to tricalcium phosphate. This paper presents the results of studies of the equilibrium interac-tion of Ca3(PO4)2 with Si, SiOg, SiC, FeSi2, and Fe3Si.MATERIALS AND METHODSThe study of the tricalcium phosphate interaction with the products of carbothermal reduction of silica V.M. Shevko, A.D. Badikova (sunstroke_91@mail.ru), R.A. Uteeva, Higher School of Chemical Engineering and Biotechnology, M.Auezov South Kazakhstan University, Shymkent, Kazakhstanа)b)Line numbers correspond to the reaction numbersFigure 1  The effect of temperature on ∆G° (а)  and ∆H° (b) for the interaction of Ca3(PO4)2  with silicon-containing substanceswas carried out using the HSC-6.0 software package de-veloped by the Finnish metallurgical company Outo-kumpu [8].At the first stage, the effect of temperature on ∆G0 and ∆Н0 of phosphorus formation from tricalcium phos-phate according to the following reactions was deter-mined (Figure 1): Са3(РО4)2+2,5Si=0,5P4g+Ca3Si2O7+0,5SiO2; (1) Са3(РО4)2+5SiOg=0,5P4g+3CaSiO3+2SiO2; (2)448  METALURGIJA 62 (2023) 3-4, 447-450V.M. SHEVKO et al.: INTERACTION OF TRICALCIUM PHOSPHATE WITH PRODUCTS OF CARBOTHERMIC… 3Са3(РО4)2+5SiC= =1,5P4g+5CaSiO3+4CaO+5CO; (3) Са3(РО4)2 +FeSi2=0,5P4g+FeO+Ca3Si2O7; (4) 3Са3(РО4)2 +5FeSi = =1,5P4g+3Ca3SiO5+5FeO+2SiO2; (5) Са3(РО4)2 +Fe3Si =0,5P4g+Ca3SiO5+3FeO. (6)It can be seen that Si, SiO and FeSi2 reduce phospho-rus from Ca3(PO4)2 in the temperature range of 500-1 800 °C, silicon carbide at the temperature of more than 1 032,2 °C, and FeSi at the temperature above 1 752,4 °C. The equilibrium of reaction 6 (with the participation of Fe3Si) is shifted to the left at 500-1 800 °С. In the Ca3(PO4)2 – Fe3Si system, phosphorus is not formed.At 1 000 °С, the reduction ability of the reducing agents decreases in the series: SiOg>FeSi2>Si>SiC> FeSi>Fe3Si; at 1 600 °С this series has the following form: (SiOg and SiC)>FeSi2>Si>FeSi>Fe3Si. It should be noted that the reactivity of SiOg, Si, FeSi2, and SiC with respect to Ca3(PO4)2 is higher than the reduction ability of carbon, which reduces tricalcium phosphate at temperatures above 1 496 °C. The interaction of SiOg, Si and FeSi2 with Ca3(PO4)2 occurs with the liberation of energy, and with SiC, FeSi, and Fe3Si – with the absorp-tion of energy.The second stage of the research was to determine the effect of temperature on the equilibrium distribution of elements for the interaction of Ca3(PO4)2 with SiOg, Si, FeSi2, SiC, FeSi, and Fe3Si. The quantitative (kg) distribution of phosphorus and silicon is shown in Fig-ures 2, 3.Based on these data, according to the algorithm devel-oped by us [9], the equilibrium distribution degrees of Si, Figure 2  The effect of temperature on the quantitative (kg) distribution of phosphorus (I) and silicon (II) during the interaction  of Ca3(PO4)2 with SiOg (a), Si (b) and FeSi2 (c)449V.M. SHEVKO et al.: INTERACTION OF TRICALCIUM PHOSPHATE WITH PRODUCTS OF CARBOTHERMIC…METALURGIJA 62 (2023) 3-4, 447-450P, Fe, Ca, C, and O (%) in the systems under study were calculated and the chemical equations of Ca3(PO4)2 inter-action with Si, SiOg, SiC, and FeSi2 were determined.RESULTS AND DISCUSSIONIn the Ca3(PO4)2 – SiOg system, gaseous phosphorus begins to form already at 500 °C. As the temperature rises above 700 0С, the P4(g) molecules decompose into P2(g). At 1 300 °C, the interaction occurs according to the following chemical equation: Са3(РО4)2+5SiOg=0,56P2(g)+0,2176P4(g)+ +2,3SiO2+0,297Ca3Si2O7+2,09CaSiO3  (7)P (1 300)With an increase in the temperature (for example, up to 1 700 °С), the interaction between the products of reaction 7 occurs according to the equation: P(1 300)=0,965Р2(g)+0,068Р4(g)+ +0,295Ca3Si2O7+2,33SiO2+2,06CaSiO3 (8)In the Ca3(PO4)2 – Si system at the temperature of ≥500 °C, the interaction is accompanied by the formation of P4(g), P2(g), CaSiO3, Ca3Si2O7, Ca3SiO5 и SiO2. At 1 700 °C, the interaction occurs according to the equation: Са3(РО4)2+2,5Si=0,965P2(g)+0,017P4(g)+ +0,6Ca3Si2O7+0,0743Ca3SiO5+ +0,95CaSiO3+0,274SiO2 (9)In the Ca3(PO4)2 – SiC system, the noticeable reduc-tion of tricalcium phosphate begins at the temperature of more than 600 °C. At temperatures above 800 °C, the main silicon-containing product is Ca3Si2O7. The inter-action at 900 °C occurs according to the equation: 3Са3(РО4)2+5SiС=1,225P4(g)+0,195 P2(g)+ +0,3537 Са3(РО4)2+2,086Ca3Si2O7+ +0,5245CaSiO3+0,09SiC+0,208Ca3SiO5 (10)P(900)At 1 700 °С, the products of reaction 10 interact with each other according to the equation: P(900)=2,96P2(g)+0,019P4(g)+1,33Ca3Si2O7+ +1,268Ca3SiO5+1CaSiO3+0,07SiO2 (11)In the Ca3(PO4)2 – FeSi2 system, iron phosphides (FeP2, Fe3P, FeP and Fe2P) are formed at 500-1 000 °C. Then, as the temperature rises, gaseous phosphorus ap-pears in the system. However, even up to 1 800 °C, the reduction of Ca3(PO4)2 to P2(g) occurs only by 42,3 %. With an increase in the temperature, the phosphorus transition degree from Ca3(PO4)2 into FeP2 decreases, while in Fe3P and Fe2P – it increases. At 1 700 °C, the chemical interaction occurs according to the reaction: Са3(РО4)2+FeSi2=0,366P2(g)+0,006P4(g)+ +0,426FeP+0,106FeP2+ +0,064Fe3P+0,134Fe2P+0,1921Cа3(РО4)2+ +0,471Ca3Si2O7+0,778CaSiO3+0,2096SiO2+ +0,069Ca3SiO5. (12)In the system Ca3(PO4)2 – 5FeSi in the temperature range of 600-1 700 0С phosphorus-containing products Figure 3  The effect of temperature on the quantitative (kg) distribution of phosphorus (I) and silicon (II) during the interaction  of Ca3(PO4)2 with FeSi (a) and SiC (b)450  METALURGIJA 62 (2023) 3-4, 447-450V.M. SHEVKO et al.: INTERACTION OF TRICALCIUM PHOSPHATE WITH PRODUCTS OF CARBOTHERMIC…are Fe3P, FeP, FeP2 and Fe2P. Gaseous phosphorus is formed at temperatures above 1 700 °C. The reaction between Ca3(PO4)2 and FeSi at 1700 °C is described by the equation: 3Са3(РО4)2 +5FeSi=  Са3(РО4)2+2,01FeP+0,702Fe2P+0,37Fe3P+ +0,445FeP2+1,128 Ca3Si2O7+2,019 CaSiO3+ +0,5SiO2+0,181Ca3SiO5 (13)In the Ca3(PO4)2 – Fe3Si system, the formation of gaseous phosphorus does not occur. At 1 800 °C, up to 60 % of phosphorus passes into the following phospho-rus-containing products: Fe2P, FeP and Fe3P. The rest of the phosphorus remains in tricalcium phosphate.Table 1 shows the effect of temperature on the extrac-tion degree of phosphorus into gas as Σ P2(g) and P4(g).It can be seen that SiOg, Si, and SiC are highly reac-tive towards tricalcium phosphate. According to the for-mation degree of gaseous phosphorus from Ca3(PO4)2, the silicon-containing reducing agents form a decreas-ing series: (SiOg, Si)>SiC>FeSi2>FeSi.СONCLUSIONBased on the results obtained at the computer ther-modynamic modeling of the tricalcium phosphate inter-action with silicon-containing reducing agents, the fol-lowing conclusions can be drawn:• SiOg and Si in the temperature range of 500-1 800 °C and SiC at the temperature of ≥1 000 °C re-duce Ca3(PO4)2 with the formation of ≥ 99,9 % of gaseous phosphorus;• at the reduction of tricalcium phosphate with FeSi2, the formation of phosphorus starts at 1 000 °C; the maximum reduction (42,32 %) occurs at 1 800 °C; the complete Ca3(PO4)2 reduction does not occur due to the formation of FeP2, FeP, Fe2P and Fe3P;• in the Ca3(PO4)2 – FeSi system, the gaseous phos-phorus starts to form at the temperature of more than 1 700 °C, the maximum of this process (4,36 %) is observed at 1 800 °C; the interaction in the system is accompanied by the formation of iron phosphides FeP2, FeP, Fe2P and Fe3P already at 500 °C;• in the Ca3(PO4)2 – Fe3Si system, the phosphorus-containing products are FeP, Fe2P and Fe3P, into which up to 60 % of phosphorus passes; phospho-rus in this system is not formed;• in comparison with iron silicides, SiOg, Si and SiC have a higher reactivity towards tricalcium phosphate. According to the formation degree of gaseous phosphorus from Ca3(PO4)2, the silicon-containing reducing agents form decreasing se-ries: (SiOg, Si) >SiC> FeSi2>FeSi.AcknowledgmentsThis study is funded by the Ministry of Science and Higher Education of the Republic of Kazakhstan (grant no. AP14869066).REFERENCES[1] V.G. Voskoboynikov, V.A. Kudrin, A.M. Yakushev, Obshchaya metallurgiya [General metallurgy], Aka-demkniga, Moscow, 2002, 786 (in Russ.)[2] M. Shamsuddin, Steelmaking, Minerals, Metals and Mate-rials Series (2021), 237-292. DOI: 10.1007/978-3-030-58069-8_7[3] L.A. Polulyakh Issledovaniye povedeniya fosfora v do-mennoy pechi s tsel’yu polucheniya chugunov s ponizhen-nym soderzhaniyem primesnykh elementov [Study of the behavior of phosphorus in a blast furnace in order to obtain cast iron with a reduced content of impurity elements], MI-SiS, Moscow, 2009, 145 (in Russ.)[4] L.A. Polulyakh, V.Ya. Dashevskii, A.Ya. Travyanov, Yu.S. Yusfin, A.L. Petelin, Behavior of phosphorus in the blast furnace in smelting hot metal and ferromanganese, Steel in Translation 39 (2009) 3, 187-189. DOI: 10.3103/S096 7091209030012[5] Y. Mukhametkhan, M. Mukhametkhan, S. Tleugabulov, G. Zhabalova, V. Shevko, Complete thermodynamic analysis of the interaction of iron phosphate (FePO4) with hydrogen (Н2) and carbon monoxide (CO), Metalurgija 60 (2021) 3-4, 306-308.[6] F.P. Yedneral, Elektrometallurgiya stali i ferrosplavov [Electrometallurgy of steel and ferroalloys], Metallurgiya, Moscow, 2007, 488 (in Russ.)[7] M.R. Konevskiy Sovmestnoye vosstanov-leniye fosfata kal’tsiya i kremnezema uglerodom v sisteme Ca3P2O8-SiO2 [Joint reduction of calcium phosphate and silica by carbon in the Сa3P2O8-SiO2 system], Issledovaniya v oblasti khi-micheskoy elektrotermii. Trudy instituta Lenniigiprokhim [Research in the field of chemical electrothermy. Procee-dings of the Lenniigiprokhim Institute] (1970) 3, 3-17 (in Russ.)[8] A. Roine, HSC Chemistry, [software] Metso, Outotec, Pori, 2021. Available at: www.mogroup.com/hsc [Accessed: 16 January 2023][9] V. Shevko, G. Sergeants, G. Karataeva, D. Amanov. Calcu-lation of the equilibrium distribution of elements in rela-tion to the HSC5.1 computer program. Certificate for the object protected by copyright of the Republic of Ka-zakhstan No. 1501 dated January 29, 2019.Note:  The responsible for English language is M.M. Yeskendirova, M.Auezov South Kazakhstan University, Shymkent, KazakhstanTable 1 The effect of temperature on the extraction degree of phosphorus into gas / %System*Temperature / °С500 600 700 800 900 1 000 1 100 1 200 1 300 1 400 1 500 1 600 1 700 1 800Са3(РО4)2-SiC 0,754 2,18 14,7 70,8 81,72 98,36 99,9 99,9 99,9 99,9 99,9 99,9 99,9 99,9Са3(РО4)2-FeSi2 <0,01 <0,01 <0,01 <0,01 <0,01 0,03 0,17 1,54 7,83 16,38 24,9 32,21 37,89 42,32Са3(РО4)2-FeSi 0 0 0 0 0 0 0 0 0,01 0,02 0,04 0,013 0,056 4,69*) In Са3(РО4)2 – SiОg and Са3(РО4)2 – S systems at 500-1 800 °C, the phosphorus extraction degree into gas is ≥ 99,9 %

Interaction of tricalcium phosphate with products of carbothermic reduction of silicon oxide

Abstract

Similar works

Full text

Available Versions

Hrčak - Portal of scientific journals of Croatia