Н . В . Б е л о у с о в а Изложен курс теории металлургических про- , Н.В. Белоусова, А.С. Ясинский А цессов, включающий три основных раздела, . С ТЕОРИЯ МЕТАЛЛУРГИЧЕСКИХ . посвященных теоретическим вопросам пиро-, Я гидро- и электрометаллургии. си ПРОЦЕССОВ н с THEORY OF NON-FERROUS EXTRACTIVE к и й METALLURGY У ЧЕБНОЕ ПОСОБИЕ Т е о р и я м е т а л л у р г и ч е с к и х п р о ц е с с о в // T h e o r y o f N o n - F e r r o u s E x t r a c t ISBN 978-5-7638-3979-1 ive M e t a llu ИНСТИТУТ ЦВЕТНЫХ МЕТАЛЛОВ И МАТЕРИАЛОВЕДЕНИЯ r g y Министерство науки и высшего образования Российской Федерации Сибирский федеральный университет Н.В. Белоусова А.С. Ясинский ТЕОРИЯ МЕТАЛЛУРГИЧЕСКИХ ПРОЦЕССОВ THEORY OF NON-FERROUS EXTRACTIVE METALLURGY Учебное пособие Красноярск СФУ 2019 1 | Theory of Non-Ferrous Extractive Metallurgy УДК 669.2/8=111(07) ББК 34.33я73+81.432.1я73 Б438 Рецензенты: М.Я. Шестаков, доктор технических наук, профессор кафедры электронной техники и телекоммуникаций Института информатики и телекоммуникаций Сибирского государственного университета науки и технологий имени академика М.Ф. Решетнёва; А.М. Жижаев, кандидат технических наук, заведующий лаборатори- ей рентгеновских и спектральных методов анализа Института химии и химической технологии Сибирского отделения Российской академии наук Белоусова, Н.В. Б438 Теория металлургических процессов = Theory of Non-Ferrous Extractive Metallurgy : учеб. пособие / Н.В. Белоусова, А.С. Ясин- ский. – Красноярск : Сиб. федер. ун-т, 2019. – 216 с. ISBN 978-5-7638-3979-1 Изложен курс теории металлургических процессов, включающий три основных раздела, посвященных теоретическим вопросам пиро-, гидро- и электрометаллургии. Предназначено студентам магистратуры направления подготовки 22.04.02 «Металлургия», программа 22.04.02.02 «Металлургия цветных ме- таллов». УДК 669.2/8=111(07) ББК 34.33я73+81.432.1я73 Электронный вариант издания см.: http:/catalog.sfu-kras.ru © Сибирский федеральный ISBN 978-5-7638-3979-1 университет, 2019 2 | Theory of Non-Ferrous Extractive Metallurgy CONTENT INTRODUCTION .................................................................................................................. 6 1. PYROMETALLURGICAL PROCESSES ..................................................................... 7 1.1. THERMODYNAMICS OF THERMAL DISSOCIATION ............................................ 8 1.1.1. General Notions ........................................................................................................... 8 1.1.2. Effect of Phase Transitions on Dissociation Process ................................................ 11 1.1.3. Dissociation of Compounds with Different Oxidation Numbers ............................. 14 1.1.4. Dissociation of Oxides at Solution Formation .......................................................... 15 1.2. THERMODYNAMICS AND KINETICS OF SOME COMBUSTION REACTIONS.......................................................................................................................... 17 1.2.1. General Characteristic of Gaseous Atmospheres ...................................................... 17 1.2.2. Interaction of Carbon with Oxidant Gases ............................................................... 18 1.2.3. Kinetics of Carbon Combustion and the Boudouard-Bell Reaction ......................... 20 1.3. REDUCTION PROCESSES ........................................................................................... 22 1.3.1. Thermodynamics of Metal Oxide Reduction by Hydrogen and Carbon Monoxide ............................................................................................................................. 22 1.3.2. Reduction of Oxides of Volatile Metals ................................................................... 25 1.3.3. Reduction of Oxides in Systems with Solutions ....................................................... 25 1.3.4. Carbon Reduction of Oxide ....................................................................................... 26 1.3.5. Metallothermy ............................................................................................................ 30 1.4. OXIDATION OF METALS AND SULFIDES. OXIDIZING REFINING................... 32 1.4.1. Theory of Oxidation of Metals .................................................................................. 32 1.4.2. Thermodynamics of Oxidation of Sulfides and Interaction of Sulfides and Oxides ........................................................................................................................... 36 1.4.3. Kinetics of Oxidation of Sulfides .............................................................................. 39 1.4.4. Thermodynamics of Oxidizing Refining ................................................................... 40 1.4.5. Oxidizing Refining of Metals with Introduction of Chemically Active Additions . 43 1.4.6. Oxidizing Refining of Metals with Obtaining Gas Products (by the Example of Removal of Carbon from Iron) ....................................................................................... 44 1.4.7. Deoxidizing of Metals ................................................................................................ 45 1.5. PHYSICOCHEMICAL PROPERTIES OF METAL AND SLAG MELTS ................. 46 1.5.1. Metallurgical Slags and Their Functions in Metallurgy ........................................... 46 1.5.2. Composition and Structure of Molten Slags .............................................................. 46 1.5.3. Structure-Sensitive Properties of Metal and Slag Melts ........................................... 50 1.5.4. Viscosity .................................................................................................................... 50 1.5.5. Diffusion .................................................................................................................... 52 1.5.6. Electrical Conductivity .............................................................................................. 52 1.5.7. Surface Tension ......................................................................................................... 53 1.6. CRYSTALLIZATION METHODS REFINING ............................................................ 55 1.6.1. Liquation Refining ..................................................................................................... 55 1.6.2. Fractional Recrystallization ....................................................................................... 57 1.7. PROCESSES OF EVAPORATION, SUBLIMATION AND CONDENSATION ....... 60 Control Questions and Tasks .................................................................................................. 67 Conte nt | 3 2.HYDROMETALLURGICAL PROCESSES ................................................................ 67 2.1. HYDROMETALLUGY .................................................................................................. 68 2.2. LEACHING..................................................................................................................... 69 2.2.1. Gas – Liquid Solution Equilibrium in Binary Systems............................................. 69 2.2.2. Solubility of Solids .................................................................................................... 71 2.2.3. Thermodynamics of Simple Dissolution ................................................................... 72 2.2.4. Thermodynamics of Leaching Processes Followed by Chemical Reactions. Dissolution of Metals, Oxides and Sparingly Soluble Salts ............................................... 73 2.2.5. Reagent Consumption and Equilibrium Constant ..................................................... 76 2.2.6. Dilution of the Solution ............................................................................................. 78 2.2.7. Pourbaix Diagrams (-рН Diagrams) ........................................................................ 79 2.2.8. Kinetics of Leaching. Multi-Stage Nature of Leaching. Influence of Temperature .... 82 2.2.9. General Equation of Leaching Kinetics ..................................................................... 85 2.2.10. Features of Leaching Involving Gaseous Reagent .................................................. 89 2.2.11. Regularities of External and Internal Diffusion ....................................................... 90 2.2.12. The Regularities of the Process in the Kinetic Region ........................................... 92 2.2.13. Influence of Surface Modification of Solid Phase .................................................. 93 2.3. EXTRACTION AND ION EXCHANGE PROCESSES ................................................ 96 2.3.1. Fundamentals of Extraction Processes. General Information ................................... 96 2.3.2. Extractional Equilibrium ............................................................................................ 99 2.3.3. Synergic Effect with the Use of Two Extragents .................................................... 100 2.3.4. Kinetics of Extraction Processes .............................................................................. 100 2.3.5. Fundamentals of Ion Exchange Processes. General Information ........................... 102 2.3.6. Equilibrium of Ion Exchange ................................................................................... 104 2.3.7. Kinetics of Ion Exchange ......................................................................................... 105 2.3.8. Influence of Various Factors on the Process of Sorption ....................................... 106 2.4. FUNDAMENTALS OF METAL OR THEIR COMPOUNDS ALLOCATION FROM WATER SOLUTIONS ............................................................................................ 107 2.4.1. Selection of Small-Solved Compounds ................................................................... 107 2.4.2. Factors Affecting Solubility of Salts ........................................................................ 107 2.4.3. Conditions of Deposition of Hydroxides and Basic Salts ....................................... 109 2.4.4. Deposition of Metal Sulfides ................................................................................... 111 2.5. CEMENTATION .......................................................................................................... 111 2.5.1. Thermodynamics of Cementation ............................................................................ 111 2.5.2. Mechanism and Kinetics of Cementation ................................................................ 112 2.6. DEPOSITION OF METALS AND OXIDES FROM SOLUTIONS BY MEANS OF REDUCTION WITH HYDROGEN AND OTHER GASES ................. 114 Control Questions and Tasks ................................................................................................ 115 3.ELECTROMETALLURGICAL PROCESSES ......................................................... 117 3.1. ELECTROCHEMICAL SYSTEMS AND THEIR BASIC ELEMENTS .................... 118 3.2. EQUILIBRIUM IN SOLUTIONS OF ELECTROLYTES........................................... 120 3.2.1. Equilibrium of Electrolytic Dissociation ................................................................. 120 3.2.2. Criticism of the Arrenius Theory ............................................................................. 125 3.2.3. Electrostatic Theory of Strong Electrolytes ............................................................ 126 4 | Theory of Non-Ferrous Extractive Metallurgy 3.3. NON-EQUILIBRIUM PHENOMENA IN ELECTROLYTE SOLUTIONS .............. 132 3.3.1. Basic Concepts and Regulations .............................................................................. 132 3.3.2. Number of Transfer .................................................................................................. 138 3.3.3. Faradey’s Laws ........................................................................................................ 141 3.4. ELECTROCHEMICAL THERMODYNAMICS ......................................................... 143 3.4.1. Electrode Potential and Electromotive Force .......................................................... 143 3.4.2. Electrode Reactions and Electrochemical Chains .................................................... 147 3.4.3. Thermodynamics of Reversible Electrochemical Systems ..................................... 151 3.4.4. Classification of Reversible Electrodes ................................................................... 153 3.4.5. Electrochemical Circuits .......................................................................................... 159 3.5. ELECTROCHEMICAL KINETICS ............................................................................. 164 3.5.1. Types of Transfer in Electrochemical Systems........................................................ 168 3.5.2. Diffusional Overvoltage ........................................................................................... 169 3.5.3. Electrochemical Overvoltage ................................................................................... 172 3.5.4. Chemical Reaction Overvoltage .............................................................................. 174 3.5.5. Phase Overvoltage ................................................................................................... 175 3.6. REGULARITIES AND MECHANISM OF SOME ELECTRODE PROCESSES ..... 176 3.6.1. Electrolytic Evolution of Hydrogen ......................................................................... 176 3.6.2. Electrodeposition of Metals ..................................................................................... 179 3.6.3. Joint Reduction of Metal and Hydrogen Cations .................................................... 185 3.6.4. Joint Reduction of Multiple Metals ......................................................................... 188 3.6.5. Anodic Dissolution of Metals .................................................................................. 191 3.7. MOLTEN SALTS ELECTROCHEMISTRY ............................................................... 196 3.7.1. General Characteristics of Molten Salts................................................................... 197 3.7.2. Electrochemical Thermodynamics of Molten Salt Systems ................................... 199 3.7.3. Reference Electrodes and Rows of Potentials.......................................................... 202 3.7.4. Kinetics of Electrode Processes in Molten Salts ...................................................... 206 Control Questions and Tasks ................................................................................................ 211 CONСLUSION ................................................................................................................... 213 BIBLIOGRAPHY .............................................................................................................. 214 Conte nt | 5 INTRODUCTION Extractive metallurgy is concerned with processes and methods of ex- traction of metals from natural raw materials or products of their dressing as well as with purifying the extracted metals. Ores often contain more than one valuable metal. Tailings of a previous process may be used as a feed in another process to extract a secondary product. In addition, a concentrate containing several valuable metals would be processed to separate them into individual constituents. The field of non-ferrous extractive metallurgy is traditionally divided in- to pyrometallurgy, hydrometallurgy, and electrometallurgy. Pyrometallurgical processes go at high temperatures in a medium involv- ing often molten materials, solids and gases. Pyrometallurgical processes with gases and solids are typified by calcining and roasting operations. Processes with molten products are referred to as smelting operations. Hydrometallurgical processes involve chemical reactions in aqueous so- lutions, in specific cases with participation of organic solvents or sorbents, at normal or increased pressure and temperatures of 20–200 °С. Electrometallurgical processes take place in some form of electrolytic cell. They can proceed both in aqueous solutions and in salt melts at increased temperatures. 6 | Theory of Non-Ferrous Extractive Metallurgy 1 PYROMETALLURGICAL PROCESSES Conte nt | 7 1.1. THERMODYNAMICS OF THERMAL DISSOCIATION 1.1.1. General Notions At high temperatures of pyrometallurgical processes, compounds of met- als stable under normal conditions can dissociate into constituent elements. This process is determined by the external factors (P, T) and the nature of the matters. The reaction of dissociation may be written in a generalized form as АВ = А + В, (1) where АВ can be oxide, sulfide, carbonate or another compound. А can be met- al, oxide or sulfide of metal which are gaseous or condensed. В is most com- monly gas. If В is a gas, the equilibrium constant may be written as а Р К  А В . (2) а АВ The equilibrium pressure of the gas (Р ) is said to be its dissociation В pressure (dissociation tension). It is taken to be a measure of the thermal stabil- ity of the given compound. Let us suppose that a reaction of dissociation of an oxide of a bivalent metal takes place: 2МО = 2М + О . (3) (s) (s) 2 If the oxide and metal form the pure condensed phases, i.e. they are not part of solutions, the equilibrium constant is given by K  Р . (4) Р О (МО) 2 The greater the dissociation pressure, the lower is the stability of the oxide. Another criterion of the thermal stability is the Gibbs energy change in this reaction, G. The more positive (or less negative) is G, the higher is the stability of the oxide. In other words, the less negative is the standard energy of formation of the given oxide, the lower is its stability. During oxide dissociation, the first portions of the metal go to the gas state, and as soon as the vapor pressure of the metal reaches the equilibrium value (the saturation vapor pressure), condensation of this metal begins. If the vapor pressure of the metal formed in dissociation doesn’t reach the equilibri- um pressure, the metal remains gaseous. 8 | Theory of Non-Ferrous Extractive Metallurgy Depending on the coexisting phases and temperature, three cases can be observed at dissociation (using oxide as an example): 1. The metal and its oxide belong to condensed phases and the composi- tions of these phases don’t change in reaction. 2. The metal and its oxide form solutions with varying compositions. 3. Both components dissolve into a solvent inert to the oxygen. We consider the first case. For the equation (3), the equilibrium constant has the form of the equation (4). On the other hand, according to the Van’t Hoff equation, dlnK H P  , (5) dT RT2 where H is the reaction enthalpy and R is the gas constant. The temperature dependence of the enthalpy is described by the Kirch- hoff’s law: T H H   C dT . (6) T 298 P 298 Here, C is the change of the heat capacity at constant pressure in the P reaction. The heat capacity depends on the temperature also, and this goes to a subsequent complication of the equations. However for practical aims, we may sometimes neglect the dependence of H and C on temperature and in P this case H lnP  const. (7) O 2 RT A dependence of P  f (T) will plot as a logarithmic curve and a O 2 lnP  1/T plot yields a straight line whose slope is H/R (Fig. 1). O 2 Fig. 1. A temperature dependence of oxide dissociation pressure P yr o m etal lur g ic a l Pr oc es s es | 9