A NEW APPROACH TO KINETIC-STUDY OF WET ATMOSPHERE ACTIVATION OF FUSEDIRON CATALYST

A new experimental method has been proposed enabling the determination of the effect of reduction degree (R) and concentration of water vapo ur (CH2O) on the activation rate (r=dR/dt) of the iron catalyst for am monia synthesis. A wetless mixture of H-2 and N-2 (3:1) was introduced into the reaction chamber of an automated flow thermobalance. The app lied reactor can be considered as a reactor with ideal mixing. A monol ayer of catalyst grains was reduced in wet atmosphere produced by redu ction itself. The reduction degree was calculated from the loss of mas s recorded during the reduction. The measured reduction rate and a kno wn fixed value of the flow rate of the gas mixture enabled us to calcu late the concentration of water vapour. The experiments differ from ea ch other by the initial mass of the catalyst and by the flow rate. The variability of these factors resulted in the variation of CH2O within the industrially important range of 1000-10 000 ppm. The final reduct ion degree varied from 78% to 95%. The results of the series of experi ments performed at ca. 550 degrees C were presented in the form of a 3 -D diagram: r=r(R, CH2O) The diagram cut by planes at cH(2)O=const yie lds curves r=r(R). These curves were described by a Gauss-like functio n. The diagram cut by plane R=10% yields the initial rate curve r=r(cH (2)O). The curve was described by an exponential function. The model f unction was proposed in order to describe the 3-D diagram, too. The ac quisition of data by the proposed method is relatively easy, especiall y because there is no need, similarly as in the industrial installatio ns, to saturate gases with water vapour. (C) 1997 Elsevier Science B.V .