Theoretical Foundations of Chemical Engineering最新文献

Thermal energy is the most common and important type of energy used. At present, the efficient use and management of thermal energy is very important and provides an effective way to combat the energy crisis. With stricter emission regulations and rising fossil fuel prices, energy conservation and emission reduction have become especially important for any heat-based distillation process. Currently, energy-saving methods include the use of columns with a partition wall or other configurations. Using thermal rectification technology can play a positive role in promoting the development and use of clean energy and reducing carbon dioxide emissions. Energy-saving methods mainly used to improve rectification include heat-pump technology, the Rankine cycle, Stirling engine, and others. The purpose of the work is to investigate the operation of an engine due to cyclic compression and expansion of air or another gas at various temperatures. The engine is used to drive a fan in industrial steam condensation processes from a distillation column. The fan can promote vapor condensation, improving heat transfer and process efficiency. The other part of the engine must be cooled to create a temperature gradient. This can be achieved by using a coolant. The water first passes through the cold part of the engine, and then is injected into the air stream, which the fan pumps through an air condenser. The results show that water injection makes it possible to reduce the air temperature more effectively, which contributes to better condensation of liquid vapors from the distillation column.

The paper presents the results of obtaining diesel fuel with improved characteristics using a developed method. The essence of the developed method is that the Hydro Plus diesel fuel is produced in a diesel fuel hydrotreating unit by combining diesel fractions from atmospheric–tubular units and light gas oils from vacuum units, a catalytic cracking unit, and a delayed coking unit and hydrotreating the resulting mixture with hydrogen-containing gas formed in a catalytic reforming unit. After hydrotreating, technical kerosene (up to 15%) produced in atmospheric-tubular units is added to its composition. In the proposed method for increasing the volume and improving the performance properties of hydrotreated diesel fuel (ecologically clean fuel), the following additives are proposed to be used to level and improve some technical indicators of this fuel: Keroflux 6100—this additive prevents the formation of crystals of interconnected hydrocarbons of the limiting series, resulting in a decrease in the maximum filtration temperature and the freezing temperature of the resulting diesel fuel; Keroflux 3614—this additive acts as a paraffin dispersant by reducing the size of the resulting crystals of paraffin alkanes, as well as due to electrostatic forces; and Kerokorr LA99C—this additive increases the lubricating properties of the diesel fuel, resulting in increased wear resistance and service life of the engine. In addition, adding a certain amount of technical kerosene to the resulting environmentally clean diesel fuel leads to an overall increase in the volume of the product produced, as well as an improvement in some performance characteristics of the final product (flash point and freezing point).

In order for extracted natural gas to meet regulatory requirements, it must be cleaned of the liquid phase before being fed into the transport pipeline. There are numerous technical methods to achieve the separation of gas and liquid, i.e., gravitational, inertial, filtration, and centrifugal separation. Using vortex effects ensures the most efficient separation of dispersed particles. The study aims to identify the primary factors influencing the dispersed composition of droplets within a rotating layer of droplets in a separator with a tangential swirl. The dispersion of the liquid phase is analyzed using a photographic method over a wide range of loads. It is found that the liquid is crushed almost instantly and secondary crushing of the droplets does not occur. The composition of the dispersed droplets is determined by measuring their diameters. A method for determining the composition of dispersed droplets in a layer is proposed. The average particle size in a rotating droplet layer in a vortex device with tangential-blade swirl gas flow is found to depend on surface tension. The characteristic frequency curves of the droplet size distribution in vortex devices with a tangential-blade swirl obtained for the air–water system are presented. The frequency distribution of the dispersed phase in a rotating droplet layer within a vortex-type device is weakly dependent on operating conditions, primarily due to the impact of liquid droplets on swirling blades. When the liquid is crushed, sufficiently large droplets are produced, which are fully separated by a tangential-blade swirl in a vortex separator. The average diameter of the droplets depends slightly on the amount of liquid loaded onto the device.

A method for predicting the condition of lubricants is presented, based on the use of graphical tools to display analytical indicators of the destruction of lubricants. This method makes it possible to calculate with high accuracy the optical density, evaporation, and coefficient of thermal oxidative degradation of lubricating oil based on two experimental data points.

The paper reveals the thermodynamic and kinetic patterns of phase-forming vitrification. The conversion of a low-molecular-weight substance into a glassy state enables to increase the chemical activity of this substance with respect to its standard crystalline state without changing the reaction consuming this substance. An expression has been obtained to quantify this increase. To distinguish the reactivity of polymorphic modifications of a crystalline reagent, the following rule of fining activation has been substantiated: a reaction consuming a crystalline reagent should be carried out in region of its polymorphic transformation using exactly the modification that is more susceptible to domainization. The multiplicity of reaction acceleration due to the domainization of the reagent has been determined.

The design of vortex devices for carrying out various heat- and mass-transfer and separation processes should ensure the achievement of maximum efficiency with minimum energy costs; therefore, the task of determining their hydraulic resistance is relevant both in the development of new devices and improving existing technological installations and when solving the problems of optimizing their operation. The paper presents a method for calculating the hydraulic resistance of vortex devices based on the scheme of a centrifugal nozzle, according to which the medium is considered ideal and the flow in the nozzle is potential, with a break in flow continuity along the surface of the vortex radius. The calculation area is divided into three characteristic zones: the forward flow at the entrance to the device, the torsional flow at the outlet of the device, and the outflow of the swirling flow. Dependences are provided for each zone to determine the total pressure. A calculated relationship is obtained to determine the coefficient of hydraulic resistance of devices with moderate flow twist, which is determined by the coefficient of flow twist, the relative radius of the flow rupture surface, and the geometry of the swirler. The results of calculation of the coefficients of hydraulic resistance of vortex-type devices in the critical (on the basis of the maximum flow rate principle) and subcritical modes of flow (according to the condition of minimum kinetic energy of swirled flow and the condition of potential of flow) are presented. Comparison of the calculation results with experimental data show that the obtained relationship is universal and suitable for calculating the coefficient of hydraulic resistance of devices with swirling gas flow, when the influence of the dispersed phase on the hydraulic resistance of devices can be neglected.

Gas–liquid systems under the effect of gravity are separated in gravity separators, which, with sufficiently high efficiency, are structurally simpler and also create a lower pressure drop compared to cyclone separators. There are various domestic and foreign methods for calculating horizontal hollow gas–liquid separators. They have such disadvantages as applicability only to certain deposition modes, excessive simplification of the applied models, difficulty in automating the calculations, etc. The identification of these shortcomings makes it possible, based on the theory of deposition and the description of the geometry of the circular section of a horizontal gas–liquid separator, to develop a methodology in which the process of droplet deposition is described by a universal criterion equation and the degree of filling of the apparatus with liquid, affecting the height of droplet deposition, is also taken into account. The obtained method makes it possible to determine the product of the length of the separation zone by the separator radius and, based on this, select a typical device. The development of a new universal technique increases the reliability of the design of devices and their subsequent operation.

The use of swirling fluid flows in the working area of equipment contributes to a significant intensification of various technological processes. Consequently, vortex-type devices represent promising and highly efficient equipment, necessitating their thorough investigation. The performance of a gas–liquid vortex device is influenced by the droplet size distribution, and since several distinct zones can be identified within the device, it is essential to determine the droplet size distribution for each of them. This study analyzes the droplet formation mechanism resulting from the secondary breakup of the separated liquid film on the surface of a vane-type swirler in the transverse separation zone. By evaluating the influence of individual factors on the breakup process of jets, droplets, and liquid films, it is demonstrated that the experimental approach to studying the secondary breakup of the separated liquid film is the only justified method. It is established that using the relationship between droplet diameter and jet diameter, along with an empirical correlation derived from generalized data on the mean droplet diameters of low-viscosity liquids formed during the breakup of a separated liquid film, it is possible to estimate, in the first approximation, the probability of secondary breakup. Based on experimental data examining the droplet size distribution at the outlet of a tangent swirler in a vortex device, it is found that the modal droplet size increased by a factor of 6.3 and the droplet size distribution follows a lognormal distribution. This indicates a strong influence of random factors governing the interaction and breakup processes in the transverse separation zone.

In many industries, during technological operations, gas streams are formed that contain solid particles. These particles must be removed in order to prepare a heterogeneous environment for subsequent production stages or to extract valuable substances from the dispersed phase, as well as before releasing the gas phase into the atmosphere. The operating principle of modern dust collectors is based on the settling of particles in a field of centrifugal force. Centrifugal methods for separating particles from a gas flow are much more effective than gravitational settling, since the resulting centrifugal force is many times greater than the force of gravity. The processes occurring in such devices are very complex and depend on many factors; therefore, during theoretical calculations, many assumptions and simplifications have to be made. Consequently, there is no absolutely accurate theory for calculating centrifugal dust collectors. In this work, an attempt is made to calculate the minimum size of captured particles in the centrifugal stage of cleaning a dust collector developed at Yaroslavl State Technical University. The calculation is carried out using classical criterion equations that describe the deposition of particles in a field of centrifugal force. Comparison of the experimental and calculated data show that this calculation technique can be used for a preliminary assessment of the minimum particle size captured in the centrifugal stage of an inertial centrifugal dust collector.