Journal of the University of Chemical Technology and Metallurgy, XXXVII, 2001, Book 2
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METALLURGY
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BRIQUETTABILITY OF SLURRIES FROM DIFFERENT METALLURGICAL PRODUCTIONS
R. Paunova, Ks. AlipievaKINETIC INVESTIGATION OF THE OXIDATION OF DIFFERENT KINDS OF ZINC SULPHIDE IN NON-ISOTHERMAL CONDITIONS
N.Moldovanska a, R.Dimitrov bDYNAMIC MODELS OF METALLURGICAL CRANES
D. Karaivanov
BRIQUETTABILITY OF SLURRIES FROM DIFFERENT METALLURGICAL PRODUCTIONS
R. Paunova, Ks. Alipieva
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: rossi@uctm.eduReceived 21 August 2001
Accepted 05 September 2001
The briquettability of the slurries from different metallurgical productions was studied. Anthracite concentrate was used as carbonic addition and as connecting addition – water glass, flocculent AATFM, flocculent FA-10 and modified starch (15% solution) were employed. The combined briquetting of the slurries from Blast furnace, LD Converter and Electric steel-making productions briquettes were obtained with high mechanical strength - yield point of pressure 425 - 533 kg cm-3 and wearability 86 % - 96 %.
In spite of the high quality of carbonic addition used a high degree of zinc and lead separation (45 %-50 %) in the reduction roasting of the obtained slurry briquettes has not been achieved. The degree of metallization was relatively high (74 %). The same pelletizing and reduction roasting slurries had a degree quite high of separation of zinc (97 % - 98 %) and lead (95 % - 96 %) and a high degree of metallization. That is why, the slurry briquettes are not suitable for blast furnace production.
Keywords: slurry, briquette, yield point of pressure, wearability
KINETIC INVESTIGATION OF THE OXIDATION OF DIFFERENT KINDS OF ZINC SULPHIDE IN NON-ISOTHERMAL CONDITIONS
N.Moldovanska a, R.Dimitrov b
a University of Plovdiv,
24 Tsar Assen Str., 4000, Plovdiv, Bulgaria ;
E-mail: nedmol@pu.acad.bg
b University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, BulgariaReceived 29 October 2001
Accepted 09 November 2001
The object of this investigation is the oxidation of different kinds of zinc sulphide – synthetic, crystal ZnS, natural sphalerite containing less than 1% Fe, and sphalerite rich in Fe – 10.8% - marmatite, by means of differential-thermal analysis. The apparent activation energy of the oxidation process in non-isothermal conditions has been calculated using the method of Kissinger [1]. The limiting stage has been established. It has been demonstrated that depending on the origin, kind and content of impurities of the zinc sulphide, the mechanism of oxidation corresponds to one of the two theories developed so far – the oxide and the sulphate ones.
Keywords: ZnS, oxidation, kinetics, marmatite, DTA, TG.
THERMODYNAMIC STUDY OF THE HEATING OF TITANIUM MAGNETITE CONCENTRATE CONTAINING VANADIUM IN THE PRESENCE OF DIFFERENT ALKALI SALTS
R. Paunova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: rossi@uctm.eduReceived 18 October 2001
Accepted 29 October 2001
Thermodynamics of a process of heating of titanium magnetite concentrate in the presence of 6%Na2CO3, 6%Na2SO4 and 6%NaCl has been studied using the EMF method, DTA and X-rays analysis. The experiments were carried out in the temperature range 298K-1273 K. Functions such as lgP?O2=f(T) and EMF=f(T) for the probable processes that take place within the concentrate were described for a fixed temperature range (900K-1273K). DTA analysis shows that the processes in the mixtures in the presence of alkali salts are characterized mostly by two endothermic effects in the temperature ranges 383K-433K and 933K-963K and one exothermic effect in the temperature range 683K-793K. The X-ray analysis of the obtained products at the intermediate and end temperatures shows mostly a presence of a Fe3O4, Fe2O3 and FeO in different proportions. The free phases of vanadates can not be observed probably because they are formed in quantity less than 5%. So they can not be marked on the X-ray patterns. The oxygen partial pressure data of the mixture with 6%Na2CO3 are close to the data of the three-phase equilibrium (Fe-wustite-Na2Fe2O4). That is not valid for the other two mixtures. In the presence of NaCl the sample has the highest oxygen potential at 1173K.
Keywords: EMF method, DTA analysis, titanium magnetite concentrate, oxygen partial presssure, X-ray analysis
DYNAMIC MODELS OF METALLURGICAL CRANES
D. Karaivanov
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: dipekabg@yahoo.comReceived 08 October 2001
Accepted 26 October 2001
The study considers a metallurgical crane of bridge type whose load is rigidly suspended. The essential importance of the occurring dynamic loads for the crane proper operation is also discussed. As found, the crane and wheelbarrow driving mechanisms are the main disturbance sources. Four-, three- and two-mass crane models are proposed, accounting for the operation of the driving mechanisms. On one hand, those models may help to the calculation of the crane metal structure and on the other hand, they could facilitate the determination of the actuation parameters (start and brake torques) of existing crane structures. Thus, one can improve the crane exploitation characteristics. The dynamic model is mathemati-cally designed by using Lagrange’s method. Recommendations to the choice of the most appropriate dynamic model are made, considering the specific machine structure characteristics.
Keywords: metallurgical crane, dynamic model