OP-II-3

PP-I-60TWO CFD-BASED STEPS TO SOLUTION OF PROBLEMOF OPTIMAL TWO-STAGE CATALYTIC AMMONIA OXIDATIONSYSTEM DESIGNZakharov V.P., Isupova L.A.Boreskov Institute of Catalysis SB RAS, 5, Akad. Lavrentiev Ave.,Novosibirsk, 630090, Russia, xap@catalysis.ruTwo-stage catalytic system, consisting of a platinum gauze pad and an oxidehoneycomb bed, allows to decrease platinum loads and losses and is widely used inammonia oxidation process in a weak nitric acid large-scale production.Unfortunately, the system is applied without proper theoretical foundation of itscomposition, although attempts of consideration of some aspects of such foundationwere made [1-5]. Therefore the development of complete CFD-based model of twostagecatalytic system for ammonia oxidation process is still actual.Two steps in development of such model were made in the paper that allows toget the valid answer to the question: «How many platinum gauzes can be replacedwith honeycomb catalyst depending on its geometry and selectivity?». Each step wasdevoted to consideration of individual aspect of simulation of mass transfer processin the each stage.The first step allows to clarify whether knowledge of the ammonia conversiondegree over a single weaven gauze is sufficient to calculate correctly the ammoniaconversion degree over whole gauze pad. To reveal the influence of interstitial flowconditions on the mass transfer, the total ammonia conversion degrees overneighbour gauzes of a different gauze pads thickness were analyzed. The padsconsist of model geometry gauzes, because of otherwise it is impossible to providetheir spatial periodicity, that is an essential difficulty in the calculations conducting.Model gauze consists of two contacting rows of equidistant wires. Rows wiredirections are orthogonal. To understand the difference between single weavengauzes of the real or model geometries the mass transfer characters were obtainedand compared with each other. They were also compared with characters calculatedaccording to the simplest gauze model based on gauze notion by assembled parallelcylinders [6]. Mathematical model was based on assumptions that mass transferlimitation approach is just, gauzes surface is smooth and gas flow is isothermal. Twolast assumptions are not too strong, so far as the last gauzes (that are substituted326