BEHAVIOR OF ALKALI METAL CYANIDES IN THE BLAST FURNACE STACK (VAPORIZATION, REACTION, CATALYSIS, BOUDOUARD REACTION, COKE)

Experimental measurements are reported on the: kinetics of vaporization of molten alkali metal cyanides, thermodynamics of the reaction of molten potassium cyanide with carbon monoxide-nitrogen gas mixtures in presence of graphite, and effects of alkali metal cyanides on the coke-carbon dioxide reaction, with emphasis on the role of structural parameters.; The kinetics of vaporization of molten potassium and sodium cyanides was studied as a function of temperature, gas flow rate and type of inert gas. The mechanism of vaporization was examined and the relevance of kinetic data to the blast furnace operation is discussed. The reaction of molten potassium cyanide contained in graphite crucible with carbon monoxide-nitrogen gas mixtures was studied as a function of gas composition and temperature. The reaction products were identified by X-ray diffraction and wet chemical analysis. Composition of the melt was determined by nitrogen, carbon, potassium and potassium cyanide analysis. The activities of potassium compounds in the melts were predicted from models. The standard free energy changes of the reaction between KCN and CO/N(,2) gas mixtures and the cyanide and the oxide capacities of the K-O-C-N melts were determined.; The rate of reaction between carbon dioxide and coke with or without the addition of alkali metal cyanides was studied using thermogravimetry. The chemical stability of KCN or NaCN during reaction, the changes in the concentration of potassium or sodium in coke, specific surface area and pore size distribution of coke were studied as a function of time. The influences of the above mentioned variables on the rate of coke-CO(,2) reaction were determined. Since the catalysis depends on the catalyst-carbon contact, the distribution of potassium in the coke structure was examined. A porous solid reaction model was used to examine the contributions of chemical reaction and pore diffusion in the overall rate of coke-CO(,2) reaction.