Likvefakcija mekog mrkog uglja Kosovskog Basena

The behaviour of Kosovo Basin (Yugoslavia) soft brown coal was studied during a direct liquefaction process by catalytic hydrogenation. A stream of hydrogen was passed through a tetralin dispersion of the pulverized coal in the presence of commercial extruded hydrogenating-desulphurizing cobalt-molybdenum/alumina catalyst. The experiments were carried out in the temperature range between 365 and 440°C at 13.5 and 15.0 MPa, the reactants being kept at selected stationary working conditions for 1-8 hrs. The yields of liquid products soluble in n-heptane (light oils), asphaltenes (n-heptane insoluble liquid products) and the solid coal residue served as a basis for the estimation of coal reactivity and for the calculation of total coal conversion. The liquid product yields varied substantially depending on the reaction temperature and the residence time. The total conversion under most of the applied reaction conditions was found to be around 80%, the highest (-86%) being observed with the longest, 8 h residence time. Various types of grains of modified coal and newly formed types of coal grains, as well as mineral matter were identified by micropetrographic analysis, indicating the release of gases in the initial stages of hydrogenation and the formation of semi-coke and coke by the polymerization of liquid products in the later reaction stages

Radix-8 Division with Over-Redundant Digit Set

We present a radix-8 divider that uses an over-redundant digit set for the quotient in order to obtain simple digit selection rules. We show that the proposed enlarged set of values for the quotient digit does not lead to increases both in the complexity and the delay of the adder required to update the remainder, with respect to similar solutions, since the values allowed for the quotient digit have been selected carefully. The digit selection process is subdivided into two concurrent steps, each one making reference to a secondary digit set and the resulting implementation can be cheaper and faster than other units which do not use over-redundant digit sets. A performance analysis estimates a speed improvement from 25% to 35% with respect to a radix-8 architecture by Fandrianto, and from 21% to 30% with respect to a radix-4 architecture with prescaling, presented by Ercegovac and Lang. As required from the IEEE 754 floating point standard, the proposed algorithm features the correct remainder of the division