Study of Chemical Processes by Isotope Tracer Techniques

The flow of material was studied on a large scale in the laboratory, in a film reactor of novel type and in a gas-liquid contactor with perforated plates, and also in industrial equipment; namely, in the mixer of a continuous superphosphate plant and in an oven for the manufacture of calcium carbide. The novel type of film reactor is characterized by a rotor carrying four cylinders rolling on the inner surface of the cylindrical body of the film reactor. When the rotor revolves, the cylinders are pressed against the internal surface of the body and are compelled to rotate so that the liquid, introduced at the top of the apparatus, forms a film between the inner surface of the body and the outer surface of the rolling cylinders. in the investigation of the film reactor, the isotope tracer solution was injected momentarily into the continuous liquid feed (slug method), and samples were taken each 0.2 s from the liquid continuously leaving the film reactor at the bottom. On the basis of the specific activity of the samples, the residence-time distribution frequency function ('E'-function), and from this the residence-time distribution function ('F'-function were plotted. The analysis of the residence time distribution was carried out on the basis of the time at which the maximum of the 'E'-function occurs, the width of the curve corresponding to the half-height of the activity curve, and the mean residence time. Knowing the latter, conclusions were drawn on the thickness of the film layer formed under various operational conditions (variation of feed, speed of rotation, and viscosity-of the flowing liquid). In the reactor with perforated plates, developed for the continuous contacting of liquid-phase para- phenetidine and acetone vapour, the flow of the liquid was studied with 32P tracer and that of the iodine (used as catalyst) with 131I. In the Moritz-Standaert continuous superphosphate plant, flow and mixing conditions (established by varying the feed rate and the operation of the mixing apparatus) were studied by an isotope tracer technique. On the basis of experimental results, the residence time of the pulp flowing through the apparatus could be increased, resulting in an improvement in the quality of the product, and consequently in the economics. Similarly, the flow of raw material through an electric carbide oven was studied with the aid of the isotope 32P. Experimental results prompted on the one hand the modification of the oven, and on the other hand that of the operational conditions, and are expected to result in increased productivity. (author)