Zone refining zone refining is a technique used to purify materials, mainly semiconductors by melting a short region i. A diagram of the vertical zone refining process used to grow singlecrystal ice from an initially polycrystalline material. Single crystal growing could be performed by zone refining together with zone leveling homogenous distribution of impurities, which are the. In the zone refining process, optimum processing parameters were determined through a series of experiments on the traveling rate of heating zone and number of the passages. Zone refining refers to the method of purifying a crystal wherein a thin region of the crystal undergoes melting. Energy bandwidth for petroleum refining processes 4 the total crude distillation capacity of all the refineries in the u. This process is also known as the float zone process, particularly in semiconductor materials processing. Zone refining principle and process of purifying metals via. Other processes for obtaining alumina from metal ores are also in use in some refineries, particularly in china and russia, although these make up a relatively small percentage of global production. Process flow schemes, emission characteristics, and emission control technology are discussed for each process. Ime process metallurgy and metal recycling, rwth aachen.
Values of k are indicated on each line, zone size though, of course, if the technique has optimum zone size for 1st pass not shown is 100% for all k. Preparation of high purity tellurium by zone refining. Simulation for purification process of high pure germanium by. Zone refining definition is a technique for the purification of a crystalline material and especially a metal in which a molten region travels through the material to be refined, picks up impurities at its advancing edge, and then allows the purified part to recrystallize at its opposite edge called also zone melting.
Silica reacts with iron oxide and forms iron silicate, which is removed as slag. The process flow sheet for cadmium purification is given. Zone refining definition, a process of purifying any of various metals and other materials, as germanium or silicon, by passing it in bar form through an induction coil. The virtues of zone melting emerge, however, when a molten zone is passed through an ingot many times see iliristrrctions on next page. For example, you wouldnt put crude oil in the gas tank of your car. If two of e elements, germanium and silicon, not been available in the desired in zone refining, which is probably the most important zone melting technique, a number of molten zones are passed through the charge in one direction. Scheme of zone refining process a and part of binary phase diagram b. For example, the refinery process is used to produce gasoline, kerosene, light oils, lubricating oils, and gases. It is based on the principle that the impurities are more soluble in the melt of the metal than they are in the solid state of the metal. Zone refining this technique is based on the standard. Process automation by newly designed stepper motor drive and allied process control instruments circumvent the complexity of electrical motors. The crude distillation capacity of individual refineries varies widelyfrom 4,000 to 843,000 bpsd doe 2004. This method is based on the principle that impurities are more soluble in the molten state of metal the melt than in the solid state. Pdf zone refining of cadmium and related characterization.
Zone refining is an industrial process which makes use of the fact that a material often solidifies with a higher purity than the surrounding liquid, in order to produce materials of very high purity. Pdf preparation of high purity tellurium by zone refining. Each zone carries a fraction of the impurities to the end of the solid charge, thereby. In the process of zone refining, a circular mobile heater is fixed at one end of a rod of impure metal. In order to understand zone refining, and zone melting in general, one must understand what is meant by the distri. Zone refining definition of zone refining by merriamwebster. Development of zone refining william pfann and henry theurer develop zone refining techniques for production of ultrapure semiconductor materials. Therefore, numerical simulations can provide effective and inexpensive measures of many parameters during zr process which can be used to predict system design. Realization of the zone length measurement during zone. Us2743199a process of zone refining an elongated body of.
Basic equations in zone refining to analyze the impurities distribution in zone melting in a simple way, following. The liquid zones are formed by heating and by cooling the adjacent solids. Refining process flow diagram introduction to refining the modern crude oil refinery is designed to convert basic raw crude oil into various useful products through a series of separation and chemical processes. The convection in the melt is a result of waters density maximum at 4 c. The bayer process is the most economic means of obtaining alumina from bauxite. When the temperature of such a solution is lowered to the freezing point, the first ip crystals to form do not contain the same concentration of salt as the original solution does. Zone refining technique purification of silicon youtube. The principle of zone refining is that the impurities in an ingot or ore of metal are more soluble in the melt state when compared to the corresponding solid state of the impurities.
In zone refining, a solid is refined by passing a number of molten zones through it in one direction. Zone refining has been utilized as the ultimate purification technique for hundreds of substances, but it has the disadvantage of being a relatively slow process. Four tantalum boats were loaded with plutonium impurity alloy, placed in a vacuum furnace, heated to 700degreesc, and held at temperature for one hour. In the zone refining process, the impurities are concentrated at one end of the block of metal so that the rest of the block is purified. Step 1 in the refining process is to remove these contaminants so as to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning catalysts in processing units. Process of zone refining an elongated body of metal download pdf info publication number us2743199a. Principle impurities are more soluble in the molten state of metal the melt than in the solid state. Develop an understanding of zone refining with respect to the. Jun 29, 2017 for the love of physics walter lewin may 16, 2011 duration.
The term refining efficiency refers here to the maximum impurity removal a zone refining process can achieve. This paper describes purification process of tellurium metal using zone refining technique under high purity hydrogen gas ambient in normal room environment. Zone melting is a group of similar methods of purifying crystals, in which a narrow region of a. The development of crucibleless zone melting is progressing toward an increase in the size of single crystals a diameter of 5565 mm, intensification of the refining process, and achievement of homogeneous distribution of impurities and structural flaws. Jun 29, 2017 the solar grade silicon obtained from the union carbide process is then purified to 99. It is also referred to as zone melting, floating zone process, and traveling melting zone. Doitpoms tlp library solidification of alloys zone refining.
Zone refining is a technique used to purify material with sharp melting points from 99. Zone refining principle and process of purifying metals. Zone refining is the most important of the zonemelting techniques. Step 2 most typical methods of crudeoil desalting are chemical and electrostatic separation, and both use hot water as the extraction agent.
The process of separating the gold or other metals from the impurities surrounding it is called refining. Moreover, the flat re gion between n and b in the zone melting curve ran be exploited to produce an ingot whose content of a desired impurity is extremely uniform. Characterization and interpretation of the aluminum zone refining. The largest oil refinery is the paraguana refining complex in venezuela, which can process 940,000 barrels of oil each day. The zonemelting process in which redistribution of solute in a solid bar is effected by the passage of a molten zone is considered mathematically. Zone refining of plutonium metal unt digital library. The zone refining process is the most common way to achieve high purity in the final step of metal purification. It also may be concluded that a more sensitive ana lytical procedure than spectroscopy is required to evaluate quantitatively the purity of zonerefined metals. This section presents descriptions of those refining processes that are significant air pollutant contributors. In this process, a circular heater is fixed at one end of a rod of impure metal.
A bar is passed through a furnace that melts a small section of the bar. Hunt optimizing zone refining 685 will already be considerably purer than one puri fied using another zone size regime. Pdf we present the zone refining results of cadmium using horizontal resistive. A crucial semiconductor technology developed at bell labs in the early 1950s is zone refining, which leads to ultrapure samples of germanium and silicon with impurities as low as one part in. Zone refining is a technique used to purify an element or a compound or control its composition by melting a short region i. The purpose of this study was to investigate zone refining techniques for the purification of plutonium metal. Zone melting is apllying for deep cleaning of p olycrystalline germanium. In addition, the zonerefining process was simulated, and the distribution of the solute atoms after approximately 10 passes of zone. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind. It is the method of the horizontal directional crystallization which is carried out by crucible way.
Realization of the zone length measurement during zone refining. In zone refining, solutes are segregated at one end of the ingot in order to purify. Zone refining is a process in which a rod of impure material is purified by heating it so as to cause a molten zone to. Plutonium rods containing known amounts of impurities were melted inside tantalum boats and passed horizontally through a threeturn, highfrequency coil so as to cause a narrow molten zone to pass through each rod 10 times. As the heater moves, the molten zone of the rod also moves with it. The redistribution of 10 impurity elements from zone melting was examined. The method has unique advantages of simplicity and of freedom from contamination by. It is being widely used in the semiconductor industry for refining of germanium and silicon to purity levels of 9n and above i.
Preparation of high purity tellurium by zone refining process. Zone refining is a very useful method to get metals with very high purity such as silicon and germanium. Expired lifetime application number us7a inventor noble e hamilton. Materials and manufacturing processes 2011, 26 3, 493500. This method is based on various solubility of impurities in firm and liquid phases.
Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed. There are several different methods that can be used for refining metals including. It is then further heated to about 399c in a furnace and charged to the flash zone of the atmospheric fractionators. Zone refining is one of the methods of the refining of the ores. The furnace discharge temperature is sufficiently high 343 to 399c to cause vaporization of all products withdrawn above the flash zone plus about 10 to 20% of the bottoms product. Application of a genetic algorithm to optimize purification in the zone refining process. As the heater moves, the molten zone of the rod also moves along with it. An experiment demonstrated the possibility of developing a zone refining process that would produce the first plutonium metal of extremely high purity. After going through this learning aid, learner will be able to interpret the concept of zone refining. Zone melting or zone refining or floating zone process or travelling melting zone is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The refined metals through zone refining are typically in the form of polycrystalline structures 10.
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