OP-II-3

PP-II-19decrease. So, the potential of the cylinder based shapes was exhausted at the verybeginning of the new millennium. The only way out was to change the basic shape tothe other one with greater external porosity.The idea is as follows. The minimal porosity ofcylinders dense packing is 9%. The same figure forspheres is 26%. One can expect that the externalporosity of real (disordered) bed of spheres isFig. 1. New spherical support.greater than that of cylinders.It should be mentioned that the attachment to cylindrical shape is due, mainly, tothe fact that the raw support granules are tabletted, and nobody succeeded to tableteven the cylinder with strongly convex faces (Cylinder2 in the Tables).Cylinders with such faces or spheres can be made by a ceramics technology.The appearance of perforated porous corundum spheres (Sphere1 and Sphere2in the Tables) hereby produced are shown on fig.1.Table 1. Characteristics of some NG reforming catalysts.Basic characteristics Cylinder Ring Cylinder2 Sphere1 Sphere2Diameter (mm) 15 15 16 16 10Height (mm) 15 12 14 - -Holes, number×diameter (mm) - 1×6 7×3 7×3 7×2a (m 2 /m 3 ) 180 330 430 450 730ε, (m 3 /m 3 ) 0.35 0.51 0.52 0.62 0.68The tube (inner diameter 89 mm) furnace of a Kellogg ammonia plant wasrecently loaded with the nickel-alumina spherical catalyst (Sphere1 type). Table 2shows catalyst performance data compared with those of the predecessor (Cylinder2type) in the same furnace at the start of its run 7 years ago.Table 2. Performance data of the catalysts in the tube furnace.Catalyst typeNG input flow Inlet pressure ΔP Т out Steam to [CH 4 ] out(kmol/hr) (bar gauge) (bar) (°С) NG ratio (vol %)Sphere1 1.8×10 3 30 1.4 796 3.6 9.5Cylinder2 1.8×10 3 28 2.6 790 3.7 10.4References:[1]. Temkin M.I. Advances in Catalysis, 1979, v.28, p.173.[2]. Aerov M.E., Narinskiy D.A., Todes O.M. Apparatuses with static granular bed // Khimiya –Leningrad, 1979.367