Optimizing the catalyst circulation ratio in a reformer with a moving bed via a combination of real and computational experiments

During the operation of continuous catalyst regeneration reformers, the problem of optimizing the catalyst circulation ratio in the reactor-regenerator system arises. This problem is solved by a combination of real and computational experiments to investigate the regularities of coking on a catalyst’s surface. Based on TGA results for industrial Pt-Sn/γ-Al₂O₃ catalyst, it is concluded that amorphous coke is formed on the catalyst’s surface during reforming, its quantity at the reactor block outlet being 4–6%, depending on the feed composition and technological parameters of the process. The specific surface of samples is 152 m²/g for the fresh catalyst, 140 m²/g after regeneration, and 118 m²/g at the reactor outlet, which correlates with the quantity of coke on the surface of samples. Mathematical analysis of the coking processes in a reformer with a moving bed show that the catalyst circulation ratio must be maintained in the range of 0.008–0.010 m³/m³ to increase the operating efficiency of an industrial unit. Maintaining optimal conditions enables us to control the coking process, keeping coke concentration as low as possible and the catalyst specific surface as high as possible.     

Influence of Feedstock Group Composition on the Octane Number and Composition of the Gasoline Fraction of Catalytically Cracked Vacuum Distillate

Thermodynamic parameters for the reactions of vacuum distillate catalytic cracking in a riser reactor have been calculated using the density functional theory. The list of the reactions has been compiled on the basis of laboratory studies on determining the group and structural-group composition of the vacuum distillate and the results of thermodynamic analysis. A kinetic model of the catalytic cracking process has been developed on the basis of a formalized scheme of the hydrocarbon conversion mechanism. By using the kinetic model derived, the effect of the group composition of four vacuum distillate samples on the octane number and the composition of the gasoline fraction of the catalytic cracking process has been assessed.     

Development of an intelligent system for controlling paraffin dehydrogenation catalyst operation in production of linear alkyl benzenes

In this article, we present the main results on the modeling of the industrial process of catalytic C₉–C₁₄ n-paraffin dehydrogenation, which is one of the technological stages in the production of linear alkyl benzenes used for the synthesis of synthetic detergents. The application of the developed mathematical model for evaluating the influence of the raw material composition on the target product yield is considered. The calculation results on the optimal technological modes for different dehydrogenation Pt catalysts and also on the prediction their lifetime are given.     

Monitoring of the commercial operation of reforming catalysts using a computer simulation system

A methodology of constructing nonstationary kinetic models of multicomponent catalytic processes of hydrocarbon conversion on platinum-containing catalysts was developed. Their kinetic and technological parameters in industrial catalytic reforming were estimated. The simulation system in gasoline production allows for the testing and choosing of an optimum catalyst depending on the composition of the processed hydrocarbon raw materials. The developed testing technique is based on the processing of the results of the commercial operation of platinum-containing reforming catalysts using the computer simulation system. It allows the estimation of kinetic parameters, the prediction of selectivity, and raw cycle duration after catalyst regeneration under conditions of commercial operation, taking into account the reactivity of hydrocarbons.     

Intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by redistribution of hydrogen between the units

The dehydrogenation and dewaxing of hydrocarbons of middle-distillate fractions, which proceed in the hydrogen medium, are of great importance in the petrochemical and oil refining industries. They increase oil refining depth and allow producing gasoline, kerosene, and diesel fractions used in the production of hydrocarbon fuels, polymer materials, synthetic detergents, rubbers, etc. Herewith, in the process of dehydrogenation of hydrocarbons of middle distillate fractions (C₉–C₁₄) hydrogen is formed in the reactions between hydrocarbons, and the excess of hydrogen slows the target reaction of olefin formation and causes the shift of thermodynamic equilibrium to the initial substances. Meanwhile, in the process of hydrodewaxing of hydrocarbons of middle distillate fractions (C₅–C₂₇), conversely, hydrogen is a required reagent in the target reaction of hydrocracking of long-chain paraffins, which ensures required feedstock conversion for production of low-freezing diesel fuels. Therefore, in this study we suggest the approach of intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by means of redistribution of hydrogen between the two units on the base of the influence of hydrogen on the hydrocarbon transformations using mathematical models. In this study we found that with increasing the temperature from 470 °C to 490 °C and decreasing the hydrogen/feedstock molar ratio in the range of 8.5/1.0 to 6.0/1.0 in the dehydrogenation reactor, the production of olefins increased by 1.45–1.55%wt, which makes it possible to reduce hydrogen consumption by 25,000 Nm³/h. Involvement of this additionally available hydrogen in the amount from 10,000 to 50,000 Nm³/h in the dewaxing reactor allows increasing the depth of hydrocracking of long-chain paraffins of middle distillate fractions, and, consequently improving low-temperature properties of produced diesel fraction. In such a way cloud temperature and freezing temperature of produced diesel fraction decrease by 1–4 °C and 10–25 °C (at the temperature of 300 °C and 340 °C respectively). However, when the molar ratio hydrogen/hydrocarbons decreases from 8.5/1.0 to 6.0/1.0 the yield of side products in the dehydrogenation reactor increases: the yield of diolefins increases by 0.1–0.15%wt, the yield of coke increases by 0.07–0.18%wt depending on the feedstock composition, which is due to decrease in the content of hydrogen, which hydrogenates intermediate products of condensation (the coke of amorphous structure). This effect can be compensated by additional water supply in the dehydrogenation reactor, which oxidizes the intermediate products of condensation, preventing catalyst deactivation by coke. The calculations with the use of the model showed that at the supply of water by increasing portions simultaneously with temperature rise, the content of coke on the catalyst by the end of the production cycle comprises 1.25–1.56%wt depending on the feedstock composition, which is by 0.3–0.6%wt lower that in the regime without water supply.     

Calculating Overvoltages in Windings of Synchronous Motors with Thyristor Frequency Converters

Analysis of overvoltages on the windings of synchronous motors caused by recharging of the insulation capacitances of motor stator windings connected with switching of valve currents has been carried out. The effect of a connecting cable line on the overvoltages of the motor is demonstrated. Formulas for determining the EMF phases of the network and the motor are presented. Expressions for determining bias EMF and zero-sequence EMF are examined. Oscillograms of variations in the current of the motor phases, the output voltage of the rectifier, and the insulation voltage of the motor are presented. Based on an analysis of the calculated quantities, conclusions are drawn and recommendations given for switching on the windings of a smoothing throttle.     

Computer Modeling System of the Industrial Diesel Fuel Catalytic Dewaxing Process

An unsteady mathematical model and a computer modeling system of the diesel fuel catalytic dewaxing process (mild hydrocracking) were developed. The modeling system allows for calculating the optimal technological mode to produce low‐freezing diesel fuel with the required cold filter plugging point taking into account the feedstock composition and catalyst activity. The modeling system consists of the main blocks: database, knowledge base, unsteady mathematical model of the diesel fuel catalytic dewaxing process, and application program package. Using the developed computer modeling system, the influence of the feedstock composition and flow rate as well as of the catalyst activity on the cold filter plugging point and the yield of diesel fuel is demonstrated.     

Linear Alkylbenzenes Sulfonation: Design of Film Reactor and its Influence on the Formation of Deactivating components

Linear alkylbenzene sulfonic acid (ABSA) is a valuable product of inorganic chemistry that is used to obtain linear alkylbenzene sulfonates. The current method for industrial production of ABSA includes sulfonation of linear alkylbenzene (LAB) with sulfur trioxide in tubular falling film reactors. In this work, we analyze the dependence of the dynamics of the deactivating components formation (tetralines and sulfones) on the structural parameters for a multi-tube film sulfonation reactor. To achieve this, we used an unsteady-state mathematical model that considers the feedstock composition and the change in the reaction medium activity. We determined that the film sulfonation reactor of optimal construction has 40 tubes of diameter of 43 mm. It was revealed that with an increase of the LAB supply to the reactor tube, the mass transfer coefficient also increases. For LAB flows of (95∙10⁻⁵) and (2.86∙10⁻⁵) m³ s⁻¹ per tube, the mass transfer coefficient is (1.73∙10⁻²) m s⁻¹ and (2.08∙10⁻²) m s⁻¹, respectively.