Acetylene Gas- its Characteristics and Safety Requirements...

Acetylene Gas- its Characteristics and Safety Requirements Acetylene is  a gas used in steel plants for oxy-acetylene gas cutting and welding and also in flame cutting machines of continuous casting machines. It is sometimes used for carburization of steel, flame heating, flame gouging, flame hardening, flame cleaning, flame straightening, thermal spraying, spot-heating, brazing, texturing and profile-cutting, and carbon coating. Acetylene is the chemical compound with the formula C2H2. It is an unsaturated hydrocarbon and the simplest alkyne. An acetylene molecule is composed of two carbon atoms and two hydrogen atoms. The two carbon atoms are held together by what is known as a triple carbon bond having CH bond angle of 180 deg. This bond is useful in that it stores substantial energy that can be released as heat during combustion. However, the triple carbon bond is unstable, making acetylene gas very sensitive to conditions such as excess pressure, excess temperature, static electricity, or mechanical shock. Acetylene is a flammable and colourless gas. Its molar mass is 26.04 g/mol. It is unstable in pure form and thus is usually handled as a solution. Pure acetylene is odourless, but commercial grades usually have a marked garlic like odour due to impurities. It has a density of 1.11 kg/cum at 1 atmosphere pressure and 15 deg C. The specific gravity is 0.91 (air=1).  It is lighter than air so does not accumulate at low levels, where it could cause a potential hazard. The boiling point of gas is – 84.7 deg C and melting point is -80.75 deg C. The adiabatic flame temperature (AFT) in air at atmospheric pressure is 2534 deg C. The auto ignition temperature of acetylene gas is 305 deg C.  Its lower and upper explosive limits in air under STP conditions (0 deg C and 1.02 kg/sq cm) are 2.4 volume...

Desulphurization of Hot Metal Oct16

Desulphurization of Hot Metal...

Desulphurization of Hot Metal Removal of sulphur from hot metal is called desulphurization of hot metal. Sulphur is a desirable element in steel when good machinability is required from the steel product. However it is an unwanted element in most of the applications of steel due to the following reasons. Sulphur affects both internal and surface quality of steel Sulphur contributes to the steel brittleness and when it exists in sulphide phase it acts as a stress raiser in steel products. It forms undesirable sulphides which promotes granular weakness and cracks in steel during solidification. It has adverse effect on the mechanical properties. It lowers the melting point and intergranular strength and cohesion of steel. Unlike other impurities which are removed from the hot metal by oxidation in the oxygen converter, the most economic method of removing sulphur from the hot metal is by reduction either in the transfer ladle or in the charging ladle, before it is charged in the converter. A number of technologies have been developed for the external desulphurization of hot metal but all of them have the basic requirement of a reagent and a method of mixing. The difference between the technologies used is the properties of the reagents, the effectiveness of the reagent to remove sulphur and the effectiveness of the mixing method to get the reagent into solution. . Also the effectiveness of hot metal desulphurization is inversely proportional to the desulphurization reagent injection rate. The most popular desulphurizing process today is deep injection of desulphurizing agent in the hot metal. Desulphurization process Dip lance process is the most economical, effective and reliable method of desulphurization hot metal. It consists of pneumatic injection of fine grained desulphurization reagent into the hot metal with high dosing precision via...