Ministry of Higher and Secondary Special Education of the Republic of Uzbekistan
Download 289.73 Kb.
|
ВКР. Ашурова О.Э.
- Bu sahifa navigatsiya:
- » kafedrasi
- Bitiruv ishi buyicha maslaxatchilar
- Bitiruv ishini bajarish rejasi
Ministry of Higher and Secondary Special Education of the Republic of Uzbekistan Almalyk branch of Tashkent State Technical University named after Islam Karimov Faculty of Energy and Mechanical Engineering Department of Chemical Technology Graduate qualifying work Theme: Selection and calculating of zinc sulfate production technology. Leader Niyazmetov B. Student of 40-16 ChT Ashurova O.E. Almalyk 2020. o’zbekiston Respublikasi oliy va o’rta maxsus ta’lim vazirligi islom karimov nomidagi toshkent davlat texnika uniVersiteti olmaliq filiali “Energetika va mashinasozlik” Fakulteti «kimyoviy texnologiya» kafedrasi «tasdiqlayman» Kafedra mudiri dots. Mamatqulov N ___________________ Malakaviy bitiruv ishi bO’yicha topshiriq Talaba ___Ashurova Odalat Erbutayevna Bitiruv ishining mavzusi:__ Selection and calculating of zinc sulfate production technology. ____________ __2020 yilda kafedraning ____ – sonli majlisida ma’qullangan. Bitiruv ishini topshirish muddati______________________________ Bitiruv ishini bajarishga doir boshlang’ich ma’lumotlar________________ ____________________________________________________________________________________________________________________________________ __________________________________________________________________ __________________________________________________________________ Xisoblash – tushuntirish yozuvlarining tarkibi (ishlab chiqiladigan masalalar ro’yxati) 1. Kirish. 2. Loyixani texnik – iqtisodiy asoslash. 3. Ishlab chiqarilayotgan maxsulotga qo’yiladigan texnik talablar. 4. Ishlab chiqarishdagi fizik-kimyoviy jarayonlarnining nazariy asoslari. 5. Xom ashyo materiallar ta’rifi va ularga qo’yiladigan talablar. 6. Moddiy balans xisobi. 7. Ishlab chiqarish usulini tanlash. 8. Ishlab chiqarishning texnologik tizimini tanlash va uning bayoni. 9. Texnologik jixozlarni tanlash, ularning texnik ta’rifi va xisobi. 10. Issiqlik qurilmasining issiqlik texnik xisobi. 11. Ishlab chiqarishning nazorati. 12. Ekologik qism. 13. Mehnat muxofazasi. 14. Fuqarolar muxofazasi. 15. Avtomatlashtirish qismi. 16. Iqtisodiy qism. 17. Foydalanilgan adabiyotlar ro’yxati.
Bitiruv ishini bajarish rejasi
Bitiruv ishi rahbari ______Niyozmetv B. ______ (familiyasi, ismi, sharifi) (sana) Topshiriqni bajarishga oldim_Ashurova A.E _______ familiyasi, ismi, sharifi) (sana) Topshiriq berilgan sana ____________yil. Plan of Graduate qualifying work Introduction Main part Technologic part. Technological computation. Ecology and labor protection. Conclusions Bibliography. Introduction "Evaluating the years we spent in the past," who was yesterday, who are we today? " Based on the question, we have a deeper understanding of their nature and meaning. At the same time, we need to think about the question “who will we be tomorrow and what new goals we will achieve”, and not only think about it, but also answer it with our practical work” Islam Karimov. Currently, the products of the ferrous and non-ferrous metallurgy of the chemical industry plays an important role in the development of engineering, electronics, automotive, aircraft, oil and gas, light industry and others. Today it plays an important role in the development of ferrous and nonferrous metallurgy, chemical products, machinery, electronics, automotive, aircraft, oil and gas, light industry, etc. In the development of non-ferrous metallurgy and chemical industry in Uzbekistan there are Navoi Hydrometallurgical Combine, Navoi Nitrogen Combined Chemical Plant, Samarkand Superphyrate Plant, Almalyk “Amafos Maxam” Chemical Plant and other manufacturing enterprises. During the competitions, the diversity of industrial products and the production of rare metals took their place in the world market. Non-ferrous metals: copper, gold, silver, osmium, indium, molybdenum, zinc, lead, etc. are mined and processed. Zinc metal is formed from sulfides into sulfates, mineral fertilizers for industrial and agricultural plants, pesticides. Zinc sulphate is used in the metallurgical industry to enrich ores. Zinc sulphate is obtained by heating the zinc sulfide in an oven and selectively dissolving the sulphate compound in the boiling layer. In the metallurgical industry, the method of enrichment based on the property of which the properties of the minerals to be separated from each other differs greatly from each other. However, in order to obtain pure zinc by pyrometallurgical method, the amount of zinc in the raw material should not be less than 16%. Graduation thesis on “Methods and calculation of zinc sulfate”. Zinc and its compounds are introduced in several ways in the production of zinc sulfate. Sulfide zinc concentrate is fed to the firing, often after enrichment with particle size <0.076 mm and therefore cannot be milled. It is necessary to average the charge before firing. At zinc plants, averaging is carried out by layer-by-layer blending of various concentrates and circulating materials on concrete sites and their subsequent mixing using clamshell cranes. In some cases, magnetic separation is included in the zinc concentrate preparation scheme to remove metal objects from them. The concentrate is fed into the furnace in the form of pulps or in dry form. The mixture is fed in the form of pulp in the case when the plant is located next to the concentration plant, when concentrates, which vary greatly in composition, go to the mixture, since such a mixture is easier to mix. However, such a charge is more difficult to distribute over the fluidized bed of the furnace. The mixture moisturizes the exhaust gases, which makes it more difficult to process, and the wear of equipment and exhaust systems increases. At high humidity, the concentrates are dried in rotary kilns with nozzle or furnace heating to a residual moisture content of 6-8%. For the destruction of lumps using disk crushers. The oxygen content in the blast should not exceed 29-30%, since the solubility of zinc and specific productivity with a further increase in its concentration does not increase significantly. In addition, when the content in the blast exceeds 30% O2, it is difficult to eliminate the increasing excess of heat in the layer, for example, using tubular caissons used on furnaces. Enriching the blast with oxygen up to 30% allows to increase the firing performance up to 9 t / m3, and the SO2 content in gases reaches 14-16%; however, the lining of the furnace wears out faster and intensive heat removal is required due to the possibility of melting the cinder, all this limits the addition of oxygen. Dust removal during firing is 30-50% and depends on the dispersion of the charge and the hydrodynamic mode of firing. Up to 90-95% of the dust carried by the gas stream is captured in cyclones and 3-6% in the fine dust collection system. When processing in a fluidized bed of granular material, dust removal is reduced to 5-25%. In most cases, the composition of dust and cinder is the same. In foreign practice, at a high speed of air blasting, the cinder exhaust through the drain threshold is low (18-40%), most of the material is carried to dust. A decrease in dust removal is facilitated by an increase in the superlayer volume, as well as the return of cyclone dust to the COP (recovery cyclone), which leads to coarsening of dust and increases the proportion of material discharged from the furnace through the drain threshold. Blowing speed also affects the process. With increasing speed of the blast (up to 600-675m3 / m2h), dust removal from the BL furnace is enhanced. In foreign practice, with forced air blast, the release of cinder through the threshold is low. This increases the proportion of burnt the mixture in suspension and reduces the performance of the calcined material suitable for leaching, and also has other undesirable consequences. In production, the normal state of the fluidized bed is created at a pressure of 15-16 kPa, of which 4-6 kPa falls on overcoming the hydraulic resistance of the hearth of the furnace. Main part The source of zinc is the ore raw material, which is usually in a sulfide state, and zinc is mainly represented by sphalerite (ZnS). Ores are always complex, contain, in addition to zinc, lead, copper, iron, silver, etc. Recently, secondary raw materials have been used in countries with high consumption. Approximately 50% of world zinc production is spent on coating iron products to protect them from rust. More than 30% of all zinc production in the world is used for alloy production. An alloy of zinc with copper and tin is called bronze. Various types of bronzes are widely used in mechanical engineering. Zinc alloys with copper and nickel are called nickel silver and nickel silver. Due to its ability to produce alloys with silver and gold, zinc is used in metallurgy to extract precious metals. Zinc dust is used to precipitate gold and silver from solutions upon their receipt by the hydrometallurgical method, to purify solutions of copper and cadmium before electrolysis of zinc solutions. Zinc oxide is widely used in rubber production and processing. It improves the quality of rubber tires and a number of other rubber products. Pure zinc sulfate is widely used in the manufacture of cord-axle tires. Zinc compounds, in particular its antimonide, are used as intermetallic semiconductors in devices for converting electrical energy into heat. Zinc antimonide is also used for point cooling of detector devices in space exploration. In industry, oxidized ZnS is processed to obtain ZnO by the hydrometallurgical method, consisting in the fact that an aqueous ZnSO4 * aq solution obtained by acidic dissolution of ZnO is subjected to electrolysis at an electrolyte temperature of not more than 40 °C. In the hydrometallurgical method of producing zinc, firing is carried out to obtain a cinder of the powder at a temperature of 800-1000 °C. High dispersion of the cinder contributes to its rapid and complete leaching in a solution of sulfuric acid. Firing is a heterogeneous process of heat treatment of zinc raw materials. This process has been and remains the main method of oxidation of sulfide raw materials. However, extensive studies have shown the possibility of oxidation of concentrates with dissolved oxygen in acidified aqueous pulps at T> 100C and Р tot> 105 Pa (autoclave conditions). With regard to hydrometallurgical technology, this has its advantages: combining the oxidation and leaching of raw materials, obtaining sulfur in an elementary form, etc. But this method has significant drawbacks that inhibit its distribution. Thus, firing is the most common and used process. The objectives of this course project is to consider the process of roasting zinc concentrates, which provides high technical and economic indicators, the calculation of the necessary indicators, the choice of the firing scheme and the selection of the main equipment for the production program, as well as the calculation of material and heat balances. The main task of roasting is to turn sulfide zinc into oxide faster, more complete and at the lowest cost, from which it is more rational to restore zinc. At the same time, the cinder must be obtained in such a state that it is most favorable for the implementation of subsequent stages of technology and ultimately ensures high technical and economic indicators of production as a whole. Firing of zinc concentrates in BL furnaces
Many domestic plants process concentrates of not one, but several concentration plants. Such concentrates often differ in both chemical and particle size distribution. Therefore, the concentrates of different deposits are averaged before firing. Sometimes concentrates are dehydrated to a pulp state (> 30% moisture). A pulp mixture is preferable when the zinc plant is located next to the concentrating plant, or when concentrates of very different composition go into the mixture. However, the loading of pulp moistens the exhaust gases, and this complicates their processing, increases the corrosion of equipment and exhaust systems. The pulp is more difficult than a dry charge to evenly distribute in a fluidized bed. Currently, industry is firing in highly productive, economical and automated fluidized bed furnaces. With it, as a rule, there is a device for dust collection, called a cyclone. They are intended for rough cleaning of gases from dust, capable of reducing the dust content of exhaust gases from 140-160 to 3-6 g / m2 in one step. After cyclones with various types of exhaust fans, the exhaust gases are sent through a dirty gas collector for fine cleaning of dust, which allows reducing dust content to 0.1-0.2 g / m2. Apply electrostatic precipitators. The purified gas goes to the production of sulfuric acid. The advantage of oxidative roasting is a consequence of the burning of a concentrate brought into a special state of fluidization. The concentrate is continuously loaded into the working zone of the furnace, and the firing product is gravity-removed from the furnace. The fluidized bed is characterized by a constant temperature at all points and intense heat transfer (t = 940-980 ° C). It should also be noted that the fluidized bed is characterized by high values of thermal conductivity of the layer itself, which reaches 2500 W / m2 0С and more. Consequently, temperature leveling across the layer occurs at high speeds. When blowing from below through a layer of granular gas material, this layer, under certain blowing parameters (the air flow in front of the furnace is divided into two, one enters the prechamber. The advantage of oxidative roasting is a consequence of the burning of a concentrate brought into a special state of fluidization. The concentrate is continuously loaded into the working zone of the furnace, and the firing product is gravity-removed from the furnace. The fluidized bed is characterized by a constant temperature at all points and intense heat transfer (t = 940-980 ° C). It should also be noted that the fluidized bed is characterized by high values of thermal conductivity of the layer itself, which reaches 2500 W / m2 0С and more. Consequently, temperature leveling across the layer occurs at high speeds. When blowing from below through a layer of granular gas material, this layer, under certain blowing parameters (the air flow in front of the furnace is divided into two, one enters the prechamber, the other into the main part of the furnace) to such a state that it acquires the properties of a liquid. The fluidized state occurs at the speed of the gas stream, when its lifting force will be balanced by the mass of bulk material. With minimal critical velocity, the layer of bulk material goes into a pseudo-liquid state, and at maximum into a suspended state with free flow of particles. In the working space of the furnace above the level of the fluidized bed, some of the smaller grains are suspended in suspension. To activate the firing of this component of the charge in the zone of suspended state serves a secondary blast. Let us consider the firing process in a fluidized bed furnace in more detail using chemistry, thermodynamics, and kinetics. The effect of firing conditions on the process performance In the firing process, temperature plays a significant role. Temperature can vary from 850 to 980 0C. At low temperatures, the firing process is slow and incomplete; at high temperatures, the material is melted and firing is not of high quality. To control the temperature, water coolers are used (cooling), receiving steam, and a certain temperature is maintained by the loading speed. So that the concentrate does not grow larger during firing, it is necessary to maintain a temperature of not more than 970 0C. A moderate content of soluble sulfate sulfur is achieved at a temperature of 950-970 0C. With increasing temperature, at the same time, there is a need to resolve the issue of removal and utilization of excess heat from the BL zone. At low temperatures, firing of sulphide materials promotes the formation of sulphates both because the dissociation pressure at these temperatures is lower and because the pressure of PSO3 in the furnace gases is higher. Technological Part Selective dissolution of zinc concentrate depends on the regime. The composition of the concentrate of a single-stage selective dissolution solution is 97% Zn, 98% Cd, 68% Cu,12% Fe, 75-80% as sulfur element, 5-10% sulfate. 98,5% Zn of the solution in two stage selective melting. Horizontal autoclave with 2-4 chambers in selective melting: diameter 3,2 m, length 15.2 m, geometric volume 130 m3 , working volume 100m3 , consisting of anti-acid brick, steal … and asbestos layer. In each selection is used a trubine torch mixer. Chemical cleaning of zinc sulfate. The chemical cleaning process is carried out by cementation of zinc solution 1.Enhanced the purification of alloys (copper, nickel and cobalt) in the solution. 2.Cementation of the above metal ions that is precipitation in the form of salt. 3. The specific consumption during cementation is reduced. 4. Ensures efficient operation in the production of equipment. The temperature pH environment plays an important role in making a zinc powder mixture. The method of cementation is based on the scientific point of view that when particles of a reacting substance collide with each other, an internal energy, that is the enthalpy process, is activated as a result of the separation of election pairs between the particles. Particle collisions occur at the right times. The formation of chemical processes in the process leads to the formation of heat . The process of electrochemistry differs from chemical changes in that the particles move in opposite directions. Heat is also generated in this movement. Cementation of solutions is an electrochemical process. When one of the electrodes comes into contact with the electron-carrying phase ion-carrying electrolyte, sulfate ions are distributed in the zinc metal aqueous electrolyte in the zinc solution. In the purification of zinc dust solution is the formation of a metal galvanic element together with a zinc precipitate. In this case , it acts as a cathode. With the activation of the galvanic cell , the cementation process takes place at the cathode, where zinc is dissolved. 3 xxxx 2
In terms of physical properties, the meta ion lattice is cation positively charged, and the lattice nodes are distributed in equivalent amounts. Conditionally, if the ion in the metal is Me0 , a chemical potential change occurs with the difference in the amount of hydrated cation 1 grammol of ion. ∆WM=MMe0-M0Me++=(∆G0Meo-∆GMe++) TRTln│aMeo(aMe). As a result a change in the electropotential between the metal ion and the solution is observed y>o
Thus, the metal ion from the solution turns into a metal and the structure of the metal atoms ensures the formation of internal active potential energies. In this case, the hydrated ions are equal to the ionic radius of the electric charge layer. ….. In a zinc powder solution, silicic acid is in the form of a gel, which is removed from the pulp by filtration. Heavy particles make filtration difficult and contaminate the sediment. 1.Copper and cadmium are released during the first stage of cementation. 2. Medium voltage metals: Cu, Ag, Fe, Ni, Co, Pd. 3. Low voltage metals: Pt, Ru, Rh. The current strength is determined by the Tafel equation based on the magnitude of the stresses of the metal, the hydrogen potential and the zinc electrode potential.
During cementation, the solution is hydrolyzed in the presence of cobalt, nickel, copper, zinc dust and hydrogen, forming a precipitate of zinc sulfate. Simultaneously in the form of zinc oxide sulfate ZnSO4·3Zn(OH)2+4H2O zinc hydroxide and sulfate are insoluble during cementation. In the regeneration process, the return of the anode and cathode fields occurs in the presence of zinc metal. Zn+2H2O=Zn(OH)2+H2 3Zn(OH)+ZnSO4+4H2O=ZnSO4·3Zn(OH)2·H2O The concentration of zinc sulfate is directly proportional to the amount of weak zinc hydroxide sulfuric acid. Cementitious sediment is identified. A 3 gram-mol zinc sulfate compound is detected. ZnSO4·3Zn(OH)2+4H2O The solution undergoes the following chemical reaction during the cementation process. Me SO4+2Zno+H2O=MeO+H2+ZnSO4+Zn(OH)2 View of potential energies between electrodes: Zn+2H2O=Zn(OH)2+2H+2e Eo=-0,439v 2Sb+3H2O=Sb2O3+6H++6e E0=+0,152v Cu+H2O=CuO+2H+2e E0=+0,57v Scheme of hydroxyl and sulfate compounds by cobalt and hydrogen regeneration during cementation: CO+2 ↓
↓ Zn(OH)2 ZnSO4·3Zn(OH)2+4H2O In this case, cobalt and hydrogen are differentiated in the cathode field. When we return the cation, copper-lead cementation begins, the temperature decreases in the galvanic process between the cathode and the anode, and the consumption of copper sulfate increases. At a temperature of 85-90oC the cementation section and the oxidation of zinc are accelerated in solution. The method of Yarozit-process is widely used in foreign metallurgical plants. This method is based on the reduction of ferrous sulfate in zinc concentrate of alkaline earth metals (sodium, potassium) to a trivalent invariant precipitate. The formula of compounds: RFe3(SO4)2·(OH)8 R=K, Na, NH4+ ZnSO4,H2O (monohydrate); ZnSO4,7H2O (heptahydrate) Relative molecular mass. 179.5 (monohydrate); 287.5 (heptahydrate). Chemical name. Zinc sulfate monohydrate; CAS Reg. No. 7446-19-7 (monohydrate). Zinc sulfate heptahydrate; CAS Reg. No. 7446-20-0 (heptahydrate). Description. A white or almost white, crystalline powder, or colourless, transparent crystals. Solubility. Very soluble in water, practically insoluble in ethanol (~750 g/l) TS. Category. Adjunct to oral rehydration salts in ( prevention and) treatment of dehydration due to diarrhoea; astringent. Storage. Zinc sulfate should be kept in a well-closed, non-metallic container. Labelling. The designation on the container should state whether the substance is in the monohydrate or heptahydrate form and, where appropriate, that it is suitable for use in the manufacture of parenteral dosage forms. Requirements Definition. Zinc sulfate monohydrate contains not less than 99.0% and not more than 101.0% of ZnSO4,H2O. Zinc sulfate heptahydrate contains not less than 99.0% and not more than 104.0% of ZnSO4,7H2O. Zinc sulfide concentrates and optimization of their roasting in fluidezed bed Reactor
Abstract—The production of glass, ceramic materials and many non-ferrous metals (Zn, Cu, Pb, etc.), ferrous metals (pig iron) and others is connected with the use of a considerable number of initial solid raw materials. Before carrying out the basic technological processes (oxidized roasting, melting, agglomeration, baking) it is necessary to mix and homogenize the raw materials that have different chemical and phase content, granulometry and humidity. For this purpose zinc sulfide concentrates differing in origin are studied for their more complete characteristics using chemical, X-ray diffraction analyses, DTA and TGA as well as Mössbauer spectroscopy. The phases established in most concentrates are: β-ZnS, mZnS.nFeS, FeS2, CuFeS2, PbS, SiO2 (α-quartz). With the help of the developed by us a Web-based information system for a continued period of time different mix proportions from zinc concentrates are calculated and used in practice (roasting in fluidized bed reactor), which have to conform to the technological requirements of the zinc hydrometallurgical technological scheme. ERY often in zinc production by the hydrometallurgical method 6-10 initial zinc concentrates (of different origin) are used [1-3], as well as some semi-finished products. In most plants the content of 18 components and the humidity of the concentrates and the mix obtained from them are monitored. Some of them (Zn, S) are controlled by setting their minimum value necessary for the stable operation of the fluid bed reactor and maintaining the necessary temperature (900-950 оС). For the other components contained in the zinc concentrates (Fe, SiO2, Ga, In, Tl, Ge, As, Sb, etc.) a maximum content is determined, which depends on the used technological scheme . A large part of the technological processes are directed toward obtaining a ZnSO4 solution with a strictly determined content of impurities, which would allow for high purity cathode zinc (SHG) to be obtained by electrolysis at the best technical-economic indexes. In this regard the selection of a suitable proportion for the sulfide zinc concentrates and their homogenization before and during roasting are decisive. calculate the optimal mixing proportions for roasting in fluidized bed furnaces from the studied concentrates. RESULTS AND DISCUSSION The work of the fluidized bed furnace (FBF) (Fig 1) as a basic energy and technological link in the process of hydrometallurgical zinc production significantly influences the indexes of the process of production. The indexes of roasting depend on the technological regime, the FBF construction and to a great degree on the characteristics of the processed raw materials In order to be able to control roasting in FBF a more complete information is necessary about the influence of the concentrates and the products from their oxidation roasting on the indexes of the roasting process. The place of the oxidation roasting process in FBF in the technological scheme for zinc production is presented in Fig 2. It shows where the developed Web-based information system for zinc mix calculation is used. It is crucial for the optimal implementation of the oxidation process in FBF, the obtaining of a suitable in its content zinc calcine and all following processes – leaching, purification, electrolysis. The chemical composition of the studied concentrates is shown in table I. The origin of the studied concentrates is from: 1- Bulgaria; 2 – Peru; 3, 4- Serbia; 5, 6 – Macedonia; 7 – Bosnia&Herzegovina; 8 – Greece; 9 – Turkey. The process of zinc calcine leaching depends heavily on its phase composition. To a great degree it is determined by the initial phase and chemical composition of the concentrates, the roasting regime and the work of FBF. In this connection, a study of zinc concentrates in relation to their phase composition was performed by X-ray diffraction analysis. The obtained general results are presented in table II. The place of the developed software in the discussed scheme is in the process selection of raw materials and their suitable mixing. The goals in this specific case are: • Obtaining of a zinc calcine with a suitable chemical content
• To have the processes of ferrite formation and silicate formation take place at the lowest possible degree • Content of Zn and S in the calcine not less than 50 % for Zn and 31 % for S • Limiting the content of Pb, Fe, SiO2, Ge, Sb, As, Cl, CaO, F below the maximum admissible values. These values can be adjusted when necessary or when the technological scheme for calcine processing is changed. In all concentrates a basic phase is β-ZnS. The possible inclusion of a part of ZnS as marmatite (ZnxFe1-xS) was determined on the basis of the obtained Mössbauer spectra according to the distribution of iron between the phases ZnS, FeS2 and CuFeS2. Fig. 1 Technological scheme of roasting in fluid bed: 1 - hopper for Zn concentrate; 2 - hopper for start calcine; 3 - protective filter; 4 - air– cushion; 5 - air-compressor; 6 - disk feeder; 7 - slinger conveyor; 8 - motor valve; 9 - cooling elements Download 289.73 Kb. Do'stlaringiz bilan baham: 
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||