S Srikanth

Combustion and deposit formation behavior on the fireside surfaces of a pulverized fuel boiler fired with a blend of coal and petroleum coke

The thermochemistry of the combustion of a blend of coal and 5% petroleum coke was analyzed. Thermodynamic modeling and microscopic techniques were used to study the behavior of the inorganic constituents upon combustion of the blend of coal and petroleum coke. The chemical composition and phase constitution of the combustion products, as well as the deposits at several temperatures corresponding to those at the various parts of the boiler, were deduced by free-energy minimization. These results were compared with actual results obtained from a commercial pulverized fuel boiler fired with coal and petroleum coke blend. The deposits on the fireside surfaces of the boiler tubes in the various parts (water walls, platen superheater, final superheater, economizer, and electrostatic precipitator) of the commercial pulverized fuel boiler fired with coal and 5% petroleum coke were characterized by particle size analysis, chemical analysis, x-ray diffraction, optical microscopy, and scanning electron microscopy. The combustion gas composition was measured using a portable on-line gas analyzer for N 2 , O 2 , CO 2 , H 2 O, CO, NO, and SO 2 . The thermodynamically predicted compositions and phase constitutions for the gas phase as well as the condensed phases are in good agreement with the experimental results.

Measurement of non-isothermal oxygen potentials in a Cu–Fe–Ca–S–O liquid during reduction of chalcopyrite in lime and carbon mixtures

Abstract The reduction of Indian chalcopyrite concentrates from the Ghatshila mines with carbon was studied in the presence of lime in the temperature range of 1123–1573 K. An attempt was made to determine the oxygen potential corresponding to the selective separation of two metals, copper and iron, during the reduction of chalcopyrite by carrying out electro-motive force (emf) measurements under isochronal heating rate conditions using an yttria-stabilised zirconia solid electrolyte cell with Cu/Cu2O as the reference electrode. The isochronal rate data for oxygen potential measurements were analysed by comparing them with the data from isothermal kinetics studies on the reduction of natural and synthetic chalcopyrite minerals in the above temperature range. The analyses of phases formed were carried out using the X-ray powder diffraction and scanning electron microscopic techniques, which showed the presence of a new quinary solid solution CIII phase. The solid solution phase CIII [Cu2S-CII(FeS⋅CaO)] forms as a result of mixing between the two rhombohedral lattices: high-temperature form of Cu2S and CII (FeO⋅CaS) compounds. The mechanism of reduction of chalcopyrite with carbon in the presence of lime is illustrated by the explanation of the role of the intermediate phases, CII, CIII and matte phases.