Dependence of operational properties on reboiler duty in the removal of CO2 from natural gas with aspen Hysys

Abstract

Obtaining CO2 specification for cooking-gas requires an equilibrium stage in the absorption column of an existing plant. The column temperature influences the stage efficiency, 25 %, which must be kept constant for all stages to optimize the absorption temperatures. Additionally, the procedure employed the consistent daily plant data which were simulated directly. In this method the recycled 29 % monoethanol amine (MEA) start-up was imposed, so that 10 stages within 20–60 °C at 1.1 × 102kPa were subjected to a circulation rates of 6000–16,000kg.mol/h. These parameter were used to evaluate the reboiler duty. The Kent−Eisenberg thermodynamic model renders circulation rate the most effective operational property. The reboiler duty at 1.19 × 109W yielded 81.08 % grade of natural gas with negligible amount of CO2 retained in the natural gas; which implies that a high stage efficiency was attained. Cleaner aqueous amine was obtained by raising the reboiler temperature to yield higher absorption efficiency, but the temperature was restricted to a maximum value of 120 °C due to amine degradation at higher temperatures. Thus, by adding the loss due to old circulation pump, the overall efficiency is significantly improved and the energy requirement is minimized.

Keywords

• Absorption
• Carbon dioxide
• Natural gas
• Circulation rate
• Reboiler duty
• CO2 specification