CALCULATION OF SPECIFIC SURFACE AREA AND POROSITY OF PACKING OF MASS-EXCHANGE COLUMN WITH MODIFIED RASHIG RINGS

Abstract

New modified Rashig rings are proposed for mass transfer packing columns. Inside these rings, plate elements are attached to rods or springs in the form of rolled spirals with spiral gaps to increase the contact surface area of the phases. A formula linking the porosity and specific surface area of the packing through its geometric dimensions is obtained, allowing for the theoretical determination of one of these parameters based on the known value of the other. An example calculation of specific surface area using the derived formula for a standard Rashig ring is provided. It is demonstrated that the calculation results coincide with reference tabular values. The use of the derived formula in technological calculations of mass transfer columns allows for the theoretical determination of initial parameters (porosity or specific surface area of the packing) without the need for reference or experimental data. An analytical formula for determining the specific surface area of the proposed modified packing is derived. The ordered arrangement of this packing on the support grids of the mass transfer column apparatus is considered, with the spiral element of the modified packing having three turns with uniform spiral gap and made of thin plates. An example calculation of the specific surface area of the proposed modified Rashig ring is given for the considered packing arrangement in the column apparatus. The porosity of the modified packing is calculated using the proposed formula. A comparative analysis of the porosity and specific surface area of the proposed modified Rashig ring with a plate rolled in a spiral inside it and the standard Rashig ring is performed. The results show an increase in specific surface area of the packing in the modified ring by 1.5 times or more, from 65 to 102.7 m2/m3, with a slight decrease in porosity from 0.6 to 0.55 m3/m3. This reduces the calculated height of the packing layer in the mass transfer column apparatus and, consequently, the height and volume of the apparatus itself. The use of the new modified Rashig rings allows for a significant reduction in the total volume of packing in packing columns during extraction, absorption, desorption, and rectification processes.