FACTORS AFFECTING THE STABILITY OF COAL CAKE AND ITS IMPACT ON STAMP CHARGING OPERATION

Stamp charging is ideally suitable under Indian condition for production of high strength blast furnace coke. At present this technology is working satisfactorily in battery No.7 of Tata Steel. The battery No.5 and 6 of Top charging operation are also being converted to stamp charging operation. The success of stamp charging hinges around the production of a stable coal cake. The most important characteristics of coal cake are its density, compressive strength and shear strength. For adequate stability of coal cake the minimum compressive and shear strength required are 1600 and 150 g/cm2 respectively in order to prevent breakage during transport from stamping machine to.the coke overchamber. The present work was undertaken to assess the influence of crushing fineness (- 3.2 mm fraction), proportion of undersize fraction (-0.5 mm), moisture content and stamping energy on density, compressive strength and shear strength of coal cakes for the coal blend used presently at battery No.7 of Tata Steel. The test coal cakes (50 mm dia x 50 mm height) were formed by compacting the coal charge with hammer in a cylindrical mould. It has been established that for production of stamped coal cake with required density and strength, it is necessary to maintain the crushing fineness (-3.2 mm fraction), undersize fraction (0-5 mm), moisture content and stamping energy at 90%, 40-60%, 8-9% and 450-500 Nm/Kg respectively.