Introduction About Carbon Plant - Online Article

The Carbon Plant is the part of the Hindalco. In Carbon plant to make Aluminium. In the manufacturing parts are:

  1. Paste plant
  2. Baking furnace
  3. Rodding room
  4. Potroom

In carbon plant the main function are to produce Aluminium. In this plant to producing to making anode by Carbon. In this moping Al for to cathode & anode Catalyst. In Potroom to making the anode to catalyst electrolyte in two produce large temp. 18000C approx. In this paste plant making anode (Carbon) & in the baking furnace in again making & in the rodding room to reuses of the anode. In pot room to making the Al. & produce Al.

Aluminium Production

The most abundant structural element in the earth's crust is aluminium. It composes eight per cent of the earth's mineable layer and is most abundant as aluminium oxide or combined oxides in a wide variety of minherals. The most important aluminous are for the manufacture of aluminium is bauxite. Which lies relatively close to the surface and is strip mined. It consists of several hydrous aluminium oxide phases [ gibbsite (Al (OH)3] , boehmite (AIOOH) and diaspore (AL2O3.H2O)]. Bauxite contains 40-60 per cent alumina (Al2O3) combined with small amounts of silicon, iron and titanium compounds as well as other trace impurities. Nearly all of which appear in commercial aluminium. High-quality deposits are found in Australia, Brazil, Guinea. Jamaica and other tropical and semitropical areas where selective leaching has produced high alumina concentrations.

Alum has been known since ancient time, but not until the middle of the eighteenth century did chemists learn that it contains two bases and not simply terra calcaria, a lime-like substance with which alum had been identified since 1702. Pure alumina was first prepared form alum in 1746 by J.H. Pott and was first distinguished from lime by Marggraff in 1754 when he prepared alumina from clay. Marggraff also showed that silica (SiO2) and the 'earthy' base of alum are nearly the sole components of pure white clay. In 1761, in France. D. Morveau proposed the name alumina for this base in alum, and this name was accepted in Britain until about 1820 when it was anglicized to alumina [1,2].

Karl Joseph Bayer patented an improved process for making pure alumina from bauxite in 1888, and from that time bauxite-type materials have been the preferred ores for aluminium production [2,3]. Although this material has been used for virtually all commercial aluminium production, by 1983 proven reserves containing 40-60 per cent alumina exceeded 24 billion short tons, which represent greater than a projected 300-year supply at estimated future aluminium production rates [4,5]. At a bauxite quality of 35-40 per cent alumina. Which would require some what higher capital and operating costs for processing, known reserves exceed 1000 years. And if one were to use tha abundant clay deposits found all over the world, this proven reservoir of alumina could be extended almost indefinitely.

Alumina Production

Introduction

The literature on alumina production has been rather sparse. Prior to 1960, information was largely confined to publications on the physical chemistry of the solutions [1] and short descriptions of the operations in the process [2,3]. This situation may have been due to production being confined to a very few intensely competitive. Firms. In 1962 the American Institute of Mining and Metallurgical Engineers (AIME) organized a symposium on aluminum that resulted in the publication of the first [4] of a series that has now become annual [5]. More recently, the International Congress for study of Bauxite and Alumina (ICSOBA) in Europe and the International Bauxite Association (IBA) have convened other meetings to discuss the process. These groups together with the formation of joint ventures of aluminum-producing companies have broadened the exchange of technical information. As yet no one has combined all of the available information into a published book. Virtually all alumina (Al2O3) comes from bauxite via the Bayer process developed by Karl J. Bayer in 1887. Current world capacity is approaching 1.9x107 short tons per year. This process takes advantage of the fact that gibbsite [Al(OH)3] and boehmite [AlOOH] are soluble in sodium hydroxide (NaOH). The solubility being temperature dependent. Further most of the impurities in bauxite are not soluble in NaOH. And the one that is reactive silica (SiO2) forms a quite insoluble compound during processing. The process can be, and is operated under a wide variety of conditions. The equipment used varies almost as widely. It is the purpose of this review to illustrate the choices that must be made in designing a plant and to show how chemistry and economics affect these choices.

Bauxite

The process begins with the formations of bauxite. This aluminous ore is always derived from a parent rock, which may be as diverse as granite and limestone. The conditions required are plentiful rainfall and good drainage through the deposit. The presence of decaying vegetation is also helpful. So bauxites are found where the climate was tropical or semitropical at the time of formation. Bauxite formation depends on the fact that alumina is virtually insoluble in neutral solutions but is quite soluble in both acids and alkalies. In experiments with feldspar [6], a potential parent of bauxite, 0.004 mmol/I of alumina (Al2O3) was dissolved in pH 7 while 1.35 mmoI/I were dissolved in pH 4. Silica showed solubilities of 0.55 and 1.46 mmoI/I at the same pH values. This permits two formation processes. If the ground water is acidic (tropical teams can be at pH 4) both Al2O3 and SiO2 and SiO2 are dissolve. When the solution meets a neutral or alkaline body of water say at a marshy shore, the Al2O3 is precipitated and most of the SiO2 remains in solution. Alternatively, if the ground water is neutral, SiO2 would be preferentially dissolved and the Al2O3 left behind. There is Evidence that both processes have formed bauxite. Geological elevated many deposits and erosion divided them so that bauxite is often found on plateaus.

Most bauxites are not beneficiated before entering the process, but some are washed on screens to separate and discard a fine fraction. Which is high in reactive silica [kaolinite (Al2O3 .2 SiO2 . 2H2O)]y.

Carbon

Carbon is another reactant that could present a cost-reduction opportunity in Hall-Heroult smelting if an after native method was able to combine separate reduction and purification steps. Coal or metallurgical coke is usually less costly than the petroleum coke and coal tar pitch now used in formulating carbon anodes for the Hall-Heroult process. The ash in coal and metallurgical coke contains substantial quantities of aluminous materials that could supplement the alumina-bearing ores. The non-aluminous ash components or their reduction products could be removed in the purification step.

Energy Sources

Three sources of energy are commonly employed to meet the theoretical energy needs for the reduction of alumina. They are electrovtic sources, chemical reductants and thermal sources. Thermal energy is required in all processes.

Statistical thinking in Operations such as Carbon Plants

Abstract

Statistical thinking is based on the principles that all work occurs in interconnected processes, variation exists in all processes, and reducing this variation is the key to process improvement. The effective use of statistical methods such as Statistical Process Control requires that an implementation framework be established through statistical thinking. Several examples relevant to Carbon Plant operations are provided where the failure to apply statistical thinking to process monitoring and improvement has resulted in waste and lost opportunities. Some appropriate actions for Managers in applying statistical thinking are then outlined.

Introduction

Since the early 1980's, statistical methods and tools such as Statistical Process Control (SPC) have been widely applied in the process industries. Many practitioners found a powerful rationale for the use of these methods in an interpretation of Dr. W. Edwards Deming's contribution to the success of several Japanese companies. However, it was often overlooked that Deming's message had objectives that went well beyond the application of statistical methods.

There was on overwhelming emphasis on training and then changing the work of Plant Operators, Supervisors, and Technicians.

"All work occurs in a system of interconnected processes. Variation exists in all processes, and Understanding and reducing variation are keys to success."

COIN2_Temp.jpg

Applying statistical methods without context from statistical thinking is analogous to "putting the cart before the horse". Managers need to take a different approach-they need to define how their process adds value to their customers and to the business. To do this they must understand the lateral relationships (Supplier-Customer) as well as the hierarchical ("Causal") relationships in their areas of the business.

Process Thinking

Statistical thinking begins with a process orientation, including recognition that all work occurs in a system of interdependent processes. The performance of a business is strongly affected by complex interactions between these processes. Supplier-Customer interfaces are the most critical of these interactions.

In Carbon Plants, internal Supplier-Customer relationships (Green Carbon-Carbon Baking Furnace - Rodding Room) result in strong interdependencies along the anode production process (We seek to moderate the impact of these dependencies by placing inventory at the interfaces.) Other interdependencies in the Carbon Plant, such as the recycling of anode butts from the Rodding Room to Green Carbon, and the reprocessing of scrap products, further complicate Supplier-Customer relationships.

The process map is an essential tool for improving process thinking. These maps may be "lateral" showing a sequence of process steps, or "causal" showing the successive layers of sub-processes that make up the higher level processes.

Lateral Process Maps

A SIPOC (Supplier Input Process Output Customer) diagram is the starting point of a lateral process map.

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In process operations such as Carbon Plants, the inherent interdependencies often mean that a reduction in variation at one point in the process (e.g. Reduced baking temperature variation) creates value elsewhere in the business (e.g. Lower anode dusting from the well-baked anodes increases current efficiency in the Pot rooms).

  • Customer or Business Value Measures (CVM)-the level where value is created or destroyed.
  • End of Line (EOL) measures-a process capability or product characteristic that defines how the process creates value.
  • End of Process (EOP) measures product and process measures at the interfaces of steps in the production process.
  • Critical Process variables (CPV) - the key measures and activities that need to be "right" to ensure the output meet Customer requirements.
  • Assigning accountability for resolving a problem to people who don't have control of the problem.
  • Spending money for new capital equipment that is not needed.
  • Wasting time creating explanations for data points when questions should be asked about process design. Taking action when it would better to do nothing.

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