A kinetic simulation on BTEX destruction in Claus furnace by oxidizing agents

  • Ramees K. Rahman

Student thesis: Master's Thesis

Abstract

The demand for low sulfur content in hydrocarbon fuels and the stringent environmental regulations has led to an increased production of acid gas (H2S and CO2) as byproducts in oil and gas industry. Consequently, the need for efficient treatment of acid gas has surfaced. Sulfur recovery units (SRU), consisting mainly of a furnace and catalytic reactors, are widely used to recover sulfur and thermal energy from acid gas. The contaminants in acid gas such as benzene, toluene, ethylbenzene, and xylenes (BTEX) and frequent variation in its composition causes flame instability and the production of unwanted byproducts such as polycyclic aromatic hydrocarbons (PAHs), CO, COS and CS2, which reduce process efficiency and increase operational cost through frequent catalyst deactivation. In this work, a detailed reaction mechanism is presented for SRU that includes reactions for the combustion of acid gas and its contaminants, and the formation and oxidation of large PAHs by several oxidants (O, O2 and OH). In order to improve xylene profile, reactions were added for xylene from the literature. Oxidation reactions for BTX by SO2 were also added into the base mechanism. In addition, rate constants for oxidation reactions for PAHs by SO2 were estimated from the reactions for smaller aromatics and these were also added. The resulting mechanism is validated with different sets of experimental data, and is used to investigate the process conditions that triggers the oxidation of aromatics (BTX and PAHs) in the furnace. The roles of feed flow rate, oxygen concentration, feed preheating and fuel gas flow rate in aromatics destruction are examined. A decrease in aromatics is observed with low acid gas flow rate due to enhanced residence time in the furnace. The increase in acid gas preheating temperatures, oxygen concentration in air and fuel gas flow rate resulted in reduced aromatics production due to their oxidation by SO2 and O2. The reaction mechanism alongside simulation results, presented herein, provide viable means of optimizing SRU to achieve efficient aromatics destruction.
Date of Award2016
Original languageAmerican English
SupervisorAbhijeet Raj Gupta (Supervisor)

Keywords

  • Applied sciences
  • BTEX
  • Claus
  • PAH
  • Simulation
  • Chemical engineering
  • 0542:Chemical engineering

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