Packed columns in the technology of obtaining natural refrigerant — propane (R290)

The article is devoted to the current scientific and technical problem — the search and implementation of energy-efficient and environmentally safe working fluids for refrigeration systems. The natural refrigerant — propane (R290), which is characterized by zero ozone depletion potential (ODP = 0) and extremely low global warming potential (GWP ≤ 3), is considered. The use of hydrocarbons is a strategic alternative to synthetic freons (HFC), which have fallen under the strict restrictions of international protocols and F-Gas regulation. The paper proposes a technology for extracting propane and other hydrocarbons (ethane (R170), isobutane (R600a) from a wide fraction of light hydrocarbons (С₂₊) formed during the preparation of natural gas for transportation and LNG production. Analysis of phase equilibria of binary mixtures of natural gas components confirmed their non-azeotropic nature, which allows the use of multi-stage rectification methods for deep purification. For low-tonnage production conditions, the use of packed columns with irregular elements is justified. A comparative analysis of three types of packings is carried out: mesh saddle-shaped, spiral and spiral-prismatic. A constructive calculation algorithm is implemented in the Mathcad environment, which made it possible to determine the optimal parameters for the separation of propane-isobutane and propane-propylene mixtures. It was established that to achieve a purity of 99.9% when separating a mixture with propylene, significantly more transfer units are required (more than 200 HETP) than for a mixture with isobutane (~40 HETP). The study showed that purification from high-boiling and low-boiling impurities is technically impossible in one apparatus due to differences in hydraulic modes and temperature conditions. The results of the work can be used in the design of compact installations for obtaining ultrapure refrigerants by triple distillation.