Classification of processes and apparatus

Classification of the basic processes and apparatus Classification of processes according to the method of propulsion forces: - mass transfer - hydromechanical - mechanical – heat transfer - chemical

1) Mass transfer is the transition of a substance from one phase to another is carried out due to diffusion. Depending on the transition from phase to phase the process is called: TV → W (melting) g → W (condensation, absorption) W → TV (crystallization) TV → g (sublimation) W → f (extraction) g → TV (adsorption) W → g (evaporation, desorption) W ↔ p (rectification) The driving force in mass transfer processes is the concentration difference of the speed of the process is determined by laws of mass transfer.

2) Hydromechanical associated with the processing of suspensions (heterogeneous system consisting of liquids or gases and suspended therein particles W/TV. body. - the movement of liquid or gas; - mixing in a liquid medium; - separation of liquid heterogeneous systems (sedimentation, filtration, centrifugation); - cleaning of gases from dust;

The driving force of these processes is the pressure difference due to density difference of the material being processed and the speed determined by the laws of hydromechanics of heterogeneous systems.

3) Mechanical – associated with processing and rigid body motion. Include: grinding, dosing, mixing, screening, transportation. The driving force is the difference between the forces, pressures, or the gradient of stress (compression, shear, tension). The speed of the process is determined by the laws of mechanics of a rigid body.

4) Thermal processes connected with the transfer of heat from one body to another. Heating, cooling, evaporation, condensation, melting, solidification, evaporation, crystallization. Speed is determined by the laws of heat transfer. The driving force is temperature difference.

5) Chemical – involves chemical transformations involved in the process substances and the production of new compounds. Include catalytic cracking, Hydrotreating, reforming, pyrolysis, coking, polymerization, alkylation. The driving force is the difference of concentrations of the reacting substances. The speed of the process is determined by laws of chemical kinetics.

By way of the organization of chemical-technological processes are divided into intermittent, continuous and Combined.

1. Periodic. Have unity the locations of the various stages of the process and therefore transient state in time (temperature, pressure, concentration, and other parameters During the change process). Periodic processes can occur in Closed systems that do not exchange matter with the environment, and in open systems.

2. Continuous. Characterized by unity of time carrying out all process steps, each of which is carried out in a special apparatus, characterized by established in time mode. This ensures continuous supply of raw materials and output products. The devices have the same classification as the processes: 1) Mass-transfer - absorbers, adsorbers, desorbers, distillation columns, extractors, dryers, crystallizers. 2) Hydro – filters, cyclones, dehydrators, strainers, centrifuges, mixers 3) Machine – crushers, sieves, mixers, batchers. 4) Heat – exchangers, coolers, evaporators, condensers, furnaces. 5) Chemical reactors of different types (with fixed catalyst bed, fluidized bed, spouted bed).

The combined process is either a continuous process, individual stages of which are conducted intermittently or batch process, one or more steps which are carried out continuously. Periodical processes are useful in the production of small scale, often changing range of products. Conducting processes on a continuous basis allows to significantly improve the performance of the equipment and the quality of products to fully automate and mechanize production. So in industry, especially in large-tonnage production, intermittent processes are replaced by continuous everywhere. The use of periodic processes is justified in small-scale industries with frequently changing product range.

The majority of chemical processes multi-stage and usually includes several successive stages. Often one of the stages is by far the slowest, limiting the speed of the entire process. In this case, in order to increase the overall speed of the process, it is advisable to act primarily at the limiting stage. Knowing what stage of this process is limiting, often allows to simplify the analysis, description, and the intensification of the process. In recent years significant impact on the intensity of the typical processes of chemical technology the effect of different factors (electric and magnetic fields, laser radiation, pulsations involved in the process fluid flows, etc.).