Non Cryogenic processes of Air Separation Jul25

Non Cryogenic processes of Air Separation...

Non Cryogenic processes of Air Separation   Dry air contains by volume 78.08 % of nitrogen, 20.95 % of oxygen, and 0.93 % of argon along with traces of a number of other gases (Fig 1). Atmospheric air can contain varying amount of water vapor (depending upon humidity) and other gases produced by natural processes and human activities. Fig 1 Composition of air Non cryogenic air separation processes are near ambient temperature separation processes and are used for the production of nitrogen or oxygen as gases. These processes are cost effective choices when demand of gases are relatively small and when very high purity of the gases is not required. Non cryogenic plants are compact and produce gaseous nitrogen which is typically 95.5 % to 99.5 % oxygen free or gaseous oxygen which is 90 % to 95.5 % pure. Non cryogenic plants are less energy efficient than cryogenic plants (for comparable product purity) but at the same time cost less to build. The physical size of the plant can be reduced as required purity is reduced, and the power required to operate the unit is reduced as well.  Non cryogenic plants are relatively quick and easy to start up and can be brought on line in less than half an hour. This is useful when product is not needed full time. Like cryogenic plants, non cryogenic air separation processes also start with compression of air. Unlike cryogenic plants which use the difference between the boiling points of nitrogen and oxygen to separate and purify these products, non cryogenic air separation plants use physical property differences such as molecular structure, size and mass to produce nitrogen and oxygen. Non cryogenic processes are based on either selective adsorption or permutation through membranes. The most common technologies...

Fuel gases used in steel industry...

Fuel gases used in steel industry Fuel gas is a fuel which under ordinary conditions is in the form of gas. Fuel gases are used in steel plants for different applications which include (i) a source of heat (ii) as a reductant and (iii) cutting and welding application. Fuel gases usually used in steel industry are natural gas (NG), liquefied petroleum gas (LPG), acetylene, by product gases (blast furnace gas, coke oven gas and converter gas). Natural gas Natural gas is a gaseous fossil fuel which is extracted from deposits in the earth. It is a mixture of hydro carbons consisting primarily of methane (generally greater than 80 %) but includes varying amounts of other higher alkanes such as ethane, propane and butane etc. It may even contain some small percentage of nitrogen, carbon dioxide and hydrogen sulphide. It is an odorless, colourless, tasteless and non toxic gas. Natural gas is lighter than air and it burns with a clean blue flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning it produces primarily heat, carbon dioxide and water. Quantities of natural gas are measured in normal cubic meters (corresponding to 0 deg C and I Kg/Sq cm pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 psia pressures). The higher heat value of one cubic meter of natural gas varies from around 9500 Kcal to 10,000 Kcal. Its density is around 0.85 Kg/Cum. The main usage of natural gas in the steel industry is in iron making. For production of direct reduced iron it is reformed to produce reducing gases which are then used for the reduction of iron ore. The main reforming reactions are as follows. 2CH4...

Steel industry and cost control...

  Steel industry and cost control  The cost control process in a steel plant is a multivariate system which is subjected to a large number of inter- influencing variables affecting the cost performance of the steel plant. It is necessary to isolate the inter influence of the variables to understand the role played by the each variable on the cost performance of the steel plant. Major variables affecting the cost performance of a steel plant are discussed below. Productivity – It is the specific rate of production. Higher is the productivity of the units of a steel plant, lower will be the cost of production. Higher productivity results in better utilization of plant and machinery. Production – Production is the physical output from a unit. For good cost control, it is necessary that each unit of the steel plant should run to its maximum capacity. When production from a unit is lower than its capacity then there is an increase in the specific consumption levels. Also when any unit is underutilized then it will result into higher fixed cost (over heads, depreciation, interest etc.) per unit output. Further It is needed that the capacity of each succeeding unit should match with the preceding unit so that there is no under utilization of any unit. Raw materials – In the present day scenario, raw materials contribute to major cost of production. Hence specific consumption of the raw material should not be more than what is required by the technology employed. Any wastage of raw materials and their deterioration during storage should be totally avoided. Further raw material quality plays very important role in cost control. Lower quality raw materials though cheaper per ton results into higher consumption of not only of its own but also of other raw...

Cryogenic process of Air Separation Jul20

Cryogenic process of Air Separation...

Cryogenic process of Air Separation   Dry air contains by volume 78.08 % of nitrogen, 20.95 % of oxygen, and 0.93 % of argon along with traces of a number of other gases. Ambient air may contain varying amount of water vapor (depending upon humidity) and other gases produced by natural processes and human activities. Air separation plants are used for the production of nitrogen or/and oxygen as gases and sometimes as liquid products. Some plants also produce argon.  All air separation plants employ either non cryogenic based technologies or cryogenic based technologies. Non cryogenic air separation plants produce gaseous nitrogen or oxygen products using near ambient temperature separation processes. These plant produce oxygen which is typically 90 % to 95.5 pure or nitrogen which is typically 95 5 to 99.5 % oxygen free. Cryogenic air separation plants are most commonly used to produce high purity products at medium to high production rates. They can produce products as gases or liquids. This technology is based on difference in boiling points of gases. All air separation processes start with compression of air. The cost of electric energy is the largest single operating cost incurred in air separation plants. It is usually in the range of one third or two thirds of the operating costs associated with producing gas and liquid products. Cryogenic plants Cryogenic plants are based on cryogenic air separation processes.  The basic process was commercialized early in the 20th century. Since then, a large number of process configuration variations have emerged, driven by the desire to produce particular gas products and product mixes as efficiently as possible at various required levels of purity and pressure. These air separation process cycles have evolved in parallel with advances in compression machinery, heat exchangers, distillation technology and gas expander technology....

Tinplate

Tinplate Tin plate is a thin steel sheet coated by tin. The thin steel sheet on which tin coating is done is known as black plate. Tin has several properties which make it suitable for use as a coating on steel. It has a good resistance to corrosion in a wide range of environments and in particular retains its appearance and surface properties extremely well in indoor atmosphere. It is easily soldered and the good corrosion resistance ensures effective retention of solderability. It is safe in contact with foods, neither producing risks to health nor impairing flavours. The softness of the metal, although disadvantageous for some uses of coatings, has merit for others, facilitating cold working, giving easy running threads on fasteners and helping to seal joints. Tin coatings are applied either by hot dipping or electrolytically coated. Both processes produce coatings which have characteristics of their own. Hot dip tin coating has advantages in being metallurgically bonded to base steel and of producing a smooth bright surface. Electrolytically coating is able to produce a uniform coating of controlled thickness. With electrolytically coating steel sheet can be differentially coated. In such coating heavy side coating is usually marked. The cross section of tin coating on steel sheet is given in Fig 1. Fig 1 Cross section of tin coating on steel sheet Features of tinplate The tinplate has the following features. Appearance – Tinplate is characterized by its beautiful metallic luster. Products with various kinds of surface roughness are produced by selecting the surface finish of the substrate steel sheet. Paintability and printability – Tinplates have excellent paintability and printability. Printing is beautifully finished using various lacquers and inks. Formability and strength – Tinplates have got very good formability and strength. By selecting a...