Simulação do processo de desidratação de gás natural em peneiras moleculares do tipo 4A

Abstract

Natural gas produced underground from oil or natural gas wells contains impurities such as water, carbon dioxide, other hydrocarbons, hydrogen sulfide, nitrogen, helium, and even mercury. To ensure the commercialization specifications of natural gas required by the consumer market, this natural gas undergoes several physical processes to remove impurities. Initially, natural gas produced from oil and natural gas wells undergoes primary processing to separate condensates and water. The natural gas is then sent for acid gas removal, water removal, condensate recovery, etc. Natural gas dehydration is a crucial step in the natural gas conditioning process and consists of reducing the water content in the produced gas. This process aims to prevent the formation of hydrates, the condensation of water molecules, and corrosion of transmission lines. Natural gas dehydration by fixed-bed adsorption is recommended in cases where the water content is desired to be reduced to levels much lower than conventional treatment in absorption columns. This work aimed to study the simulation process of a natural gas dehydration unit by adsorption on type 4A molecular sieves, using the Aspen Adsorption simulator. For this purpose, nonlinear regression was used to determine the equilibrium model parameters that best fit the experimental data extracted from the literature regarding adsorption capacities and partial pressures. The Sips isotherm model presented the best fit to the experimental data evaluated, with emphasis on the H2O molecule. Therefore, dynamic simulations were developed to evaluate the performance of the adsorbent bed under different operating conditions. Simulations 1, 2, 3, and 4 were executed, respectively, (1) evaluation of the bed efficiency; the results show a solute adsorption efficiency of 95.1% and a yield of approximately 99.94%; (2) optimization of operational parameters such as temperature, pressure, and molar flow rate; The results show a reduction in temperature from 40°C to 25°C, maximizing adsorption capacity; (3) Dynamic simulation under optimal conditions, which resulted in a yield of 99.93%; and (4) evaluation of the influence of molar flow rate; the result showed that the use of high flow rates reduces bed yield.