Modelagem e simulação computacional de adsorção multicomponente para tratamento de gás natural proveniente de poços de petróleo maduros

Abstract

The research for efficient, cheap and clean methods becomes essential against exploitation in mature oil wells that produce only 3-100 barrels/day, where conventional treatment becomes economically unviable. The natural gas associated with the exploitation of petroleum produced has components such as methane and ethane with wide application in the industry, mainly in petrochemical. Thus, the competitive multicomponent adsorption on silica gel shows a promising method for the treatment of this gas in order to regulate the dew point of the hydrocarbons present. The numerical method of finite differences and discretization of implicit Euler delayed in time and centered in the space were used and to make the differential equations partial of the mass and energy balances in algebraic equations. By associating the Runge-Kutta method to these equations and implemented in MATLAB it was possible to solve in one dimension such EDP's together with the adsorption term by the Langmuir model. Among the gas components, isobutane, carbon dioxide, ethane and methane were monitored, the last two components being of interest for petrochemicals. Firstly, adsorption of methane is observed because it is a major component due to the existence of many free active sites, however, with the continuous entry of gas, there is adsorption of the other components that have greater affinity with adsorbent to the detriment of methane desorption. This phenomenon occurs by structural factors that derive from the affinity coefficients, the maximum surface concentration and the initial concentrations in the fluid phase. The energy balance that gives information of the temperature variation demonstrates a rapid dynamics and influence of the heat of adsorption. However, before 1 hour of process it is possible to notice that there is stabilization of this variable, since there are always adsorption and desorption processes combined in order to balance the temperature. It can be affirmed, then, that the adsorption will be an efficient method in the separation of the components and, consequently, in the regulation of the dew point, thus having the technical feasibility assured by the computational verification.