Vol 51, No 2 (2017)

A simulation procedure and results of simulation are reported for the operation of a cascade of packed distillation columns for heavy water deprotiation. The mathematical model is based on the results of laboratory-scale tests of a rolled ribbon–screw structured packing developed at the Mendeleev University of Chemical Technology of Russia an a random spiral prismatic packing made from stainless steel. Use of the rolled ribbon–screw packing in the columns provides means to diminish the volume of the separation equipment without changing the cascade throughput capacity and separation factor.

A fundamentally new low-temperature method of synthesizing ammonia has been suggested, which is carried out directly in a hydrogen-producing matrix with a material made of cellulose fabric with porous layers of ethanol–cyclam PVC derivatives with activated carbon with aquacomplexes of sodium hydroxide grafted onto its fibers. Complexes of zero-valent nickel and iron within the cyclam structure are formed in the matrix. Hydrogen is formed on the cathode in the course of electrolysis of water from sodium hydroxide aqua complexes on particles of activated carbon as microelectrodes. Hydrogen forms bonds with complexes of zero-valent nickel. Nitrogen from adsorbed air is bound in complexes of zero-valent iron and interacts with active atomic hydrogen. Water is transported to carbon particles through the fabric onto which the layer is grafted. The process is carried out at the room temperature. It has been found that the forming hydrogen is almost completely used. As opposed to the existing methods of synthesis of ammonia, the suggested process is carried out at room temperature and normal pressure.

Using theory of turbulence, particularly using turbulence spectrum analysis, the relations ε^* = ε/(u⁴/ν) = const., v_K/u = const. and Λ/η_K = const. were derived. Assuming that u ∝ (Nd) from this it follows that the widely used dimensionless local turbulent energy dissipation rate defined as ε/((N³d²) is directly proportional to impeller Reynolds number, i.e. ε/((N³d²) ∝ Re, and length scale ratio Λ/d is indirectly proportional to impeller Reynolds number, i.e. Λ/d ∝ Re^–1, in an agitated vessel at high Reynolds number. The relations obtained by turbulence spectrum analysis were used for estimation of local turbulent energy dissipation rates experimentally measured by Ståhl Wernersson and Trägårdh (1998, 1999) covering the range of Re = 87600–910200 and own experimental data covering the range of Re = 50000–189000. The experiments have been performed in tanks of 300 mm and 400 mm in the inner diameter for three different viscosities and for various impeller rotational speeds.

The thermal rectification method, which comprises the condensing of vapors on steps and subsequent exposure of the heat flow on condensate before it is introduced into the falling reflux, has been studied. The results of the study of strengthening ethanol–water mixture upon the condensation of vapors on the heat-transfer surface have been presented. The basic parameters of the process have been revealed, which ensure the strengthening of the mixture on the stage upon condensate evaporation, and the empirical relationship for determining the effectiveness has been obtained. The studies of the thermal rectification of the ethanol–water mixture have been performed in a column with 24 contact stages made of horizontal plates, and conditions have been established that provide the greatest efficiency. The evaluation of thermal rectification contribution to the overall efficiency of the stage is performed that allows one to intensify the process by up to four times.

The kinetics of the isomerization of cyclohexane to methylcyclopentane on Pd-mordenite catalyst in a flow reactor has been studied. In the experiments, parameters such as the volumetric flow rate of the feedstock, the component composition of the feed gas (cyclohexane, methylcyclopentane, hydrogen), and the temperature and pressure in the reactor have been varied. The concentrations of hydrogen, cyclohexane, and methylcyclopentane in the feed gas have been determined. A stepwise reaction mechanism of cyclohexane isomerization has been suggested. A kinetic model that contains the direct constant of the limiting stage rate and the combination of equilibrium constants of the fast stages in a set for estimating the constants has been built. An additional precision (improving) experiment has shown that the model constants are estimated with a high accuracy. A predictive ability of the model under experimental conditions has been proved to be high.

The results of an investigation of the modification kinetics of chlorine-containing epoxy resins by 1,4-butanediol in the presence of alkali catalyst have been considered. Experimental investigations have been carried out using a Setaram C80 calorimeter of heat flow in combination with analytical methods for determining initial and final functional groups. The link between conversion and the heat effect was set. A two-phase kinetic model of the modification process was proposed. The parameters of the proposed model have been determined from the condition of minimum disagreement between the experimental and calculated data using nonlinear programming methods in order to find the minimum. The task of finding the optimal temperature profile has been set and solved. A scheme of process control for maintaining the optimal temperature has been proposed.

A method was suggested for modeling the chemical process systems using the business process models based on SADT, which takes into account the fixed technological structure of chemical process objects.