III International Conference

FEATURES OF DRAG FACTOR FOR COMPLEX SHAPE CATALYSTSPP-III-69Hartmann V.L., Obysov A.V., Dulnev A.V., Savushkin S.Ju.JSC Novomoskovsk Institute of Nitrogen Industr, Novomoskovsk, Tula region, RussiaE-mail: vhart@narod.ruThe gas-dynamic drag of granular bed in the narrow tube filled with various complexshape catalysts for hydrocarbons reforming now widely used commercially was measured forseveral values of Reynolds number within the range of 2000÷9000. Data thus obtained areready for use in tube furnaces design. It is shown that they do not fit conventional correlationspresumably due to much more profound effects of granule shape and bed structure than iscommonly accepted.The common present-day tendency when revamping ammonia or methanol plants is to usethe existing equipment to the utmost extent. Nowadays the bottleneck stage of such a plant is thetube furnace. Of course, replacement of tubes by those with greater inner diameter can solve thisproblem partially. Nevertheless, renovating a plant from 1360 mtons per day to, say, 1700 mtonsper day may rise pressure drop across a tube furnace to the unallowable level.According to common approach [1], pressure drop across a granular bed can becalculated using the following expression:Δ = ⋅L 2 εP2ρw afe3где ΔP/L – pressure drop per unit length, Pa/m; w – superficial linear gas flow velocity (perfull bed cross-section), m/c; ρ – gas density, kg/m 3 ; a – specific geometrical surface of thebed, m 2 /m 3 ; ε – bed porosity; f e – drag factor.It is usually accepted that f e is a universalfunction of the Re number, the discrepancy forvarious granule shapes being limited to 30% [1].Taking into account that the performance of acatalyst bed in hydrocarbons reforming is mainlyproportional to a [2], the only way to raise itwithout simultaneous increase in pressure dropis to enlarge ε which is not the best way out. Onthe other hand, some commercially runningcatalysts show too low pressure drops.Fig. 1. Drag factor f e vs. effective Re number.597