High Alumina Slag and Blast Furnace Operation May27

High Alumina Slag and Blast Furnace Operation...

High Alumina Slag and Blast Furnace Operation Blast furnace (BF) process of iron making is a process where liquid iron (hot metal) and liquid slag are produced by the reduction of iron bearing materials (sinter and/or pellet and lump ore) with coke and by fluxing of the gangue material of the feed materials. The process is the result of a series of chemical reactions which takes place in the blast furnace. The separation of slag from the hot metal takes place in liquid state. Slag has a lower melting point and is lighter than hot metal. In the blast furnace it is at a higher temperature than the hot metal. Blast furnace slag contain predominantly silica (SiO2), alumina (Al2O3), lime (CaO) and magnesia (MgO) along with smaller amounts of FeO, MnO, TiO2, Na2O, K2O and S. Blast furnace (BF) slag composition has very important bearing on its physicochemical characteristics which influences to a great degree the smooth operation of the blast furnace, slag handling, coke consumption, blast furnace productivity and the quality of the hot metal. Low alumina slag normally has low viscosity, high sulphide capacity and low liquidus temperature as compared to high alumina slag. Blast furnace slag alumina (Al2O3) is mainly dependent on the alumina content of the input materials mainly iron ore. In those cases where iron ore alumina is less than 1 % the alumina content in the slag hardly goes above 10 %. But in some iron ores (normally found in India) alumina content is 2 % and higher. Such ores raise the alumina levels in blast furnace slag to 20 % and higher. To operate a blast furnace with such high alumina slag is quite difficult and need a different type of skill from the blast furnace operators...

Hydraulic fluids

Hydraulic fluids Hydraulic oils are also called hydraulic liquids or hydraulic fluids. They are the medium by which power is transferred in hydraulic equipment. Hydraulic fluids have the primary purpose of transferring potential or kinetic energy (pressure and movements), create volume flow between pump and hydrostatic motor, and reduce the wear of parts that rub against each other. In addition, they protect the system from corrosion and help carry away the heat produced during energy transformation. The operating practices of yesterday in industry have changed a lot. But steady and dependable, hydraulic fluid technology did not change much for decades. But today, the pressure is on hydraulic systems. Hydraulic systems are expected to deliver optimum performance while operating at higher pressures, temperatures, and tougher operating conditions. Common hydraulic fluids are based on mineral oil or water. These oils have generally low compressibility. Hydraulic oils are circulation quality oils since they are in continuous use in an enclosed system with practically very little residence time in a reservoir or a storage tank. Hydraulic fluid has to perform the following tasks: Energy transmission Lubrication Heat removal The primary function of a hydraulic fluid is to convey power. However there are other important functions of hydraulic oils such as protection of the hydraulic machine components. The main functions of hydraulic oil and the corresponding properties of the hydraulic oil which affects its ability to perform the required function are given below: Hydraulic oil as medium for power transfer and control needs low compressibility (high bulk modulus), fast air release, low foaming tendency and low volatility. Hydraulic oil as medium for heat transfer requires good thermal capacity and conductivity. Hydraulic oil as sealing medium must have adequate viscosity and viscosity index as well shear stability. For hydraulic oil to perform the function...

Five Pillars of Quality...

Five Pillars of Quality Today in an era of cut throat competition, an organization can survive only if it is a quality organization and respecting the basic concept of quality. In fact, quality is the single most important issue which an organization faces every day of its existence. A reputation for quality is essential for the future of the organization. An organization to become a business leader has to ensure that it does everything in the organization where quality work can flourish and where quality becomes a competitive advantage. Quality improvement can happen in the organization if all the employees (from top to bottom) have a shared dedication towards quality with all its functions. Organizations, which are not quality conscious, are normally product oriented. In these organizations the emphasis is on detecting errors. The responsibility of maintaining the product quality lies with the quality control department and the problem solving is normally done by a few people in the authority at the top of the pyramid. These types of organizations are successful when the environment conditions favour them. Quality conscious organizations are those which have faith in quality principles. These organizations are customer oriented and focus on preventing errors. They balance short term objectives with the long term objectives. These are the organizations which survive even in most adverse environment. Quality conscious organizations are generally supported on five pillars of quality. Three main ingredients for the five pillars in a quality conscious organization are as follows. There must be a clear understanding of what is already in place, what is working well and what can be enhanced as the pillars of quality become central to every employee’s daily work. There must be vivid sense of where the organization wants to go. Organization should have...

Nitrogen in Steels May23

Nitrogen in Steels

Nitrogen in Steels All steels contain some nitrogen which can enter the steel as an impurity or as an intentional alloying addition. The quantity of nitrogen in steels normally depends on the residual level arising from the steelmaking processes or the amount aimed in case of deliberate addition. There are significant differences in residual levels of nitrogen in steels produced from the two main steelmaking processes. Basic oxygen furnace (BOF) process generally results into lower residual nitrogen in steels, typically in the range of 30 to 70 ppm while electric arc furnace (EAF) process results into higher residual nitrogen, typically in the range of 70 to 110 ppm. Nitrogen is added to some steels (e.g. steels containing vanadium) to provide sufficient nitrogen for formation of nitride to achieve higher strength. In such steels nitrogen levels can increase to 200 ppm or higher. Nitrogen in the liquid steel is present in the form of solution. During the solidification of steel in continuous casting, three nitrogen related phenomena can happen. These are Formation of blow holes Precipitation of one or more nitride compounds Solidification of nitrogen in interstitial solid solution. The maximum solubility of nitrogen in liquid iron is around 450 ppm, and less than 10 ppm at ambient temperature (Fig 1). The presence of significant quantities of other elements in liquid iron affects the solubility of nitrogen. Mainly the presence of dissolved sulfur and oxygen limit the absorption of nitrogen because they are surface active elements. Fig 1 Solubility of nitrogen in iron Nitrogen is generally considered as undesirable impurity which causes embrittlement in steels and affects strain aging. However nitrogen produces a marked (intersititial solid solution) strengthening when diffused into the surface of the steel, similar to the strengthening observed during case hardening (Nitriding)....

Lubricants

Lubricants A lubricant (also sometimes called as “lube”) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction between them which in turn improves the efficiency and reduces the wear. It also has the function of transporting foreign particles. A good lubricant possesses the following characteristics: High boiling point Low freezing point High viscosity index Thermal stability Hydraulic Stability Demulsibility Corrosion prevention High resistance to oxidation Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each other, by interposing a substance called lubricant between the surfaces to carry or to help carry the load (pressure generated) between the opposing surfaces. The interposed lubricant film can be a solid, (e.g. graphite and MoS2 etc.) a solid/liquid dispersion, a liquid, a liquid-liquid dispersion (a grease) or, exceptionally, a gas. Types of lubrication are shown in Fig 1. Fig 1 Types of lubrication Besides doing the function of lubricating, lubricants also carries out some or all of the following functions: Act as a coolant to remove the frictional heat which may be sometimes considerable. Keeps moving parts apart. Reduces friction between moving parts It dissolves and transports contamitants and debris arising both from internal and external sources. Acts as a hydraulic medium in some applications It protects against wear of highly loaded machine parts It prevents corrosion and rusting of machine parts It helps in transmitting power It offers protection against the accumulation of deposits (sludges and varnish) in lubrication system. It acts as a seal for gases It resists aeration and foaming, which can cause mal-functioning It resists or aid emulsion formation in wet systems. It stops the risk of smoke and fire of objects It has ability...