On the basis of analysis of experimental data on the temperature in a reactor for Fischer–Tropsch synthesis, a method for prediction of loss in thermal stability of such a reactor by extrapolating the reactor temperature in time with the use of the first-order and second-order time derivatives of experimental data on this temperature has been developed. Since, in this case, the calculation of derivatives is an incorrect procedure because of the rapid changes in the reactor temperature and the accidental errors in its measurement, this problem was solved using the Tikhonov stabilizing-functional method. An integro-differential equation of calculating the first-order and second-order time derivatives of experimental temperatures of the reactor, providing a minimum of the stabilizing functional, has been derived. The possibility of predicting the behavior of the temperature in a reactor under the conditions of loss in its thermal stability was demonstrated through the comparison of calculation and experimental data on the reactor temperature. The method proposed can be used for development of an automated system for control over the working conditions of a reactor for Fischer–Tropsch synthesis for prevention of its thermal explosion.

A scaled up process of the longer carbon nanotube synthesis is reported. The developed suspended-bed synthesis rig is capable of producing carbon nanotube cotton in spools or piles in kilogram amounts. A possibility to produce free-standing non-woven nanotube thin films is demonstrated. The embryonation and initial growth periods are recorded. The carbon nanotube cotton was investigated by electron microscopy (SEM/TEM), Raman spectroscopy and thermal analysis. It was shown that the material is dominated by double-walled nanotubes. Opportunities of combing, roving and spinning the carbon nanotube cotton are discussed. In conclusion this successful scale-up development paves the way for intensification of the development in macroscopic carbon nanotube-based fibers and composite materials.

The productivity of Fischer-Tropsch reactors is determined by the efficiency of heat and mass transfer processes inside the catalyst granules. To reduce the diffusion resistance the granules base is made from ceramic highly porous material. The porous structure of the granules causes a discrete arrangement of cobalt metallic microparticles whose size can reach tens of microns. Cobalt particles are the active centres on which the synthesis reactions are realized. The distance between these active centres significantly exceeds their characteristic size and the homogeneous model for heat and mass transfer is incorrect. In our paper a mathematical model of heat and mass transfer processes in a porous spherical granule with localised active centres is proposed. The heat of the exothermic synthesis reaction is removed from the surface of the granule by heat transfer into the synthesis gas stream washing the granule. The components of the synthesis gas enter to the granule surface as a result of mass transfer. On the basis of the mean-field approach the values of the temperature and concentration of the synthesis gas components at the active centres inside the granule were determined. In the reactor tube, where the catalyst granules are placed, there is a critical temperature. The excess of the critical temperature leads to a thermal explosion, i.e. a substantial overheating of the active centres. In this case, the surface of the catalyst granule is superheated slightly. The principal difference between the homogeneous and heterogeneous models in catalytic reactions is discussed. We analysed influence of the temperature inside the reactor tube, size of the granule, and coefficient of thermal conductivity on the thermal stability of the granule. (C) 2018 Elsevier Ltd. All rights reserved.

Composite pelletized catalysts for higher one-pass conversion and productivity in the Fischer–Tropsch process are reported. The introduction of aluminum metal powder as a thermal conductor leads to the formation of a new family of composite pelletized catalysts, very different from reference systems. In particular, these catalysts retain high activity and C5+ selectivity at increasing gas-hour space velocities of up to 5,000 h−1. The productivity of these composite catalysts increases almost fourfold for fivefold GHSV increase. Composite catalysts with different types of active cobalt (conventional, introduced by impregnation, or skeletal) show similar values of one-pass conversion and productivity but give different fractional and group composition of liquid hydrocarbon products. Testing of these highly productive catalysts in reactors with different aspect ratios showed that high productivity and one-pass conversion can be achieved in industrial-size units, where feasible liquid yield of up to 140 barrels per million standard cubic feet (MMSCF) of natural gas can be reached.

Based on a complex mathematical model of the Fischer–Tropsch process the high-perfimance cobalt catalyst for synthetic oil production is developed and tested. The catalyst is granular thermally conductive composite material with a well-developed system of transport pores, which provides an effective mass and heat transfer in the granules. The influence of nature of the heat-conducting aluminum- containing additives on the physical properties of the support and catalytic properties of Fischer–Tropsch catalyst is shows. Found that increasing of catalysts granules thermal conductivity is one of the factors that increase the performance of the catalyst. In the presence of developed catalyst the performance for hydrocarbons С5+ achieved 600 g/(kg·h) or 480 g/(l·h) at 0,8 g/cm3 packing density. A pilot plant to obtain up to 20 liters of synthetic oil per day from natural gas using the catalyst is established and put into operation. Catalyst testing in this plant has confirmed receipt in the laboratory performance of granular bed.

Рассмотрены технологические схемы производства жидких углеводородов из природного газа. На основе предлагаемых схем построена математическая модель процесса. Рассчитаны материальные балансы и энергетические показатели процесса в целом. Показано, что применение циркуляционных схем позволяет получить высокие выходы целевого продукта с единицы сырьевого газа.

A new method is suggested for calculating the thermodynamic equilibrium in a multicomponent multiphase system without chemical reactions. This method is based on ideas of statistical physics and non-equilibrium thermodynamics and includes numerical minimization of the Gibbs energy of the complex system. Component concentrations and the physically realizable roots of the equation of state are calculated as the steady state solutions of the set of ordinary differential equations that is implied by the procedure of seeking the probability maximum for the realization of the equilibrium distribution. The approach developed here is used to calculate the equilibrium distribution of the concentrations of vaporous, liquid, and solid substances in the Fischer-Tropsch synthesis products. A thermodynamic model of the formation of solid paraffins from the synthesis products is presented. The calculation of the properties of pure substances and liquid and gaseous products is based on the Lee-Kesler equation of state. The wax formation thermodynamics is considered in the regular solid solution approximation (Hildebrand-Scott model) and in the solid solution approximation taking into account the nonideality of the system (NRTL model). The calculated mass fractions of vaporous, liquid, and solid synthesis products are presented as a function of temperature for different values of the chain propagation constant.

Process flow schemes of the production of liquid hydrocarbons from natural gas were considered. Based on the proposed flow schemes, a mathematical model of the process was constructed. The overall material balances and energetic characteristics of the process were calculated. The application of recirculation circuits was shown to have high target product yields per unit feedstock gas.

Fluid dynamics in a microchannel of a new-generation Fischer-Tropsch reactor for artificial petroleum synthesis is reported. Liquid and gaseous product downflows are modeled in the annular flow approximation. The conjugate flow of gaseous and liquid products is investigated in terms of integral momentum balance equations with capillary effects and microchannel wall roughness taken into consideration. A simulation procedure appropriate for the method of deposition of catalyst particles onto the inner wall is suggested for modeling a random inner surface of the microchannel. The simulation procedure takes into account the variation of the synthesis product composition and the variation of the thermal properties of the liquid and gas phases along the microchannel length. A stable computational procedure has been devised for calculating fluid dynamic parameters of the two-phase flow. The effects of the synthesis gas flow rate and conversion, microchannel diameter, chain propagation constant, temperature, and pressure on the two-phase flow parameters and on the aerodynamic resistance of the gas have been investigated.

Hydrodynamics of liquid and gaseous products in microchannel reactor for Fischer–Tropsch synthesis is considered. It is supposed, that liquid and gaseous products of the synthesis move downward in annular flow regime. A microchannel with irregular internal walls is investigated in cylindrical symmetry. In proposed numerical technique the peculiarities of coating the microchannel walls by cobalt-based catalytic particles are taken into account. System of equations of two-phase hydrodynamics is based on the generalized equations for mass flowrate and momentum of liquid film and gaseous phase. Stable numerical algorithm for calculation the thermodynamic equilibrium in gas–liquid mixtures of synthesis products is proposed. Calculation results illustrate thermophysical properties of liquid and gaseous products. In the hydrodynamics model variations along a microchannel mass fractions and thermophysical properties of liquid and gaseous products were taking into account. Principal hydrodynamical difference between a smooth microchannel and a microchannel with random roughness is explained. Hydrodynamical parameters and gradient of pressure are investigated as functions of pressure, temperature, averaged diameter of a microchannel and chain growth probability.

The method of pseudocritical thermodynamic parameters and the Lee-Kesler equation of state are used for calculating the thermal and physical properties of a solution and a mixture of gaseous paraffins that are major constituents of Fischer-Tropsch synthesis products. The dynamic viscosities of a solution and a vapor are modeled using an original procedure proposed by the authors. A surface tension is calculated by the parachor method. The composition of liquid and gaseous products is found using a stable iteration scheme proposed by the authors. The model is tested by a comparison with experimental data from the literature for model mixtures of hydrocarbons. The results of calculating the composition and thermophysical properties of a mixture of paraffins that model the composition of synthesis products at different values of the chain propagation parameter, temperatures, and pressures are presented.

The velocities of a freely rising gas slug and a phase boundary (gas-liquid) under conditions of liquid discharge in tubes of various diameters are experimentally studied. It is shown that the nonmonotonic character of the dependence of measured velocities on the angle of inclination is determined only by the curvature in the vicinity of the critical point of the head of the slug or the phase boundary during liquid discharge. Experimental results are obtained by measuring the profiles of curvature of the bubble head in mutually perpendicular planes. For these purposes, an appropriate computer program was developed, and an immersion optical procedure was used that made it possible to eliminate optical “noises” associated with the thickness of a tube wall.

The possibility of synthesizing a new material—completely deuterated hydrocarbons—by the Fischer-Tropsch process has been demonstrated. This is the first step toward the formation of a research-and-production basis for the creation of a pilot plant. There was no isotope effect; consequently, the key characteristics of the synthesis and products were determined by the properties of the catalyst and reaction conditions, irrespective of whether hydrogen or deuterium was used in the starting mixture. Waxes were removed from the catalyst surface under mild conditions; this did not require any special equipment or the transfer of catalyst to another reactor. The chosen catalyst was highly stable and can be used in a pilot plant for the production of completely deuterated waxes. The first evaluation of the properties of the new materials showed that they were promising as solvents for NMR, radioactive labels, targets, neutron flux moderators, etc.

A mathematical model of heat and mass transfer processes in the grain of the Fischer-Tropsch synthesis catalyst is presented that takes into account the effect of the capillary condensation of the products of the synthesis in the pores of the catalyst. The influence of capillary condensation on the processes of the diffusion transfer of heat and mass in the catalyst grain is analyzed using the proposed model. Dependences of the efficiency factor of the grain on the pressure and temperature of the process and the partial pressure of various components of a mixture are presented. The possibility of determining the optimum pressure and temperature of carrying out the process for the catalyst of a certain structure is shown.

A model for calculating the viscosity of individual paraffins that constitute the major part of the products of the Fischer-Tropsch synthesis is developed on the basis of the fluctuation hypothesis of the formation of vacancies in the liquid phase. All of the thermodynamic parameters of a substance and the energy barrier of the formation of vacancies are calculated using the Lee-Kesler equation of state. The results of the calculations of the viscosity of heavy paraffins are compared with the experimental data from published works.

Investigation of oscillation of temperature and synthesis gas concentration inside spherical catalytic particle it is executed. Approximate distributions of temperature and concentrations in a particle with internal heat release and synthesis gas consumption are obtained. Stationary distributions of thermal and gaseous parameters are found. In the frame of small disturbances of temperature and concentrations thermal stability is investigated. It is revealed, that diffusion resistance synthesis gas inside a porous particle can lead to occurrence oscillation regime.

A modified Peng-Robinson equation of state is used to develop the methods for calculating the liquid-vapor thermodynamic equilibrium in Fischer-Tropsch synthesis products. The critical thermodynamic parameters of paraffin and olefin hydrocarbons with a number of carbon atoms higher than 20 are determined using the correlations proposed in the present paper. The calculated results are compared with literature data and the data obtained in the Integrated Research and Development Center.