Determination of elemental sulfur deposition rates for different natural gas compositions

Natural gas is increasing its share in the worldwide energy market. However, it poses several problems during transportation. The formation and deposition of elemental sulfur (S8) in pipelines is the issue that has the greatest impact on both operational safety and maintenance costs. The formation of S8 as a yellow powder may be influenced by changes in operational conditions, such as pressure and temperature drops, and by the composition of the natural gas stream. This study aims to examine the contribution of the nucleation phenomenon to the process of S8 formation and deposition. Simulations were performed using the HYSYS® V7 process simulator, with the Peng-Robinson equation of state, and a MATLAB routine was devised to calculate the variables affecting the nucleation rate. The influence of natural gas composition on the nucleation rate was evaluated using thermophysical data of average gas streams from fields of the Brazilian states of Ceará/Rio Grande do Norte (CE/RN), Espírito Santo (ES), Rio de Janeiro (RJ) and Bahia (Fazenda Mamoeiro Field, FSP). The results show that gas composition and operational conditions may influence the amount of sulfur deposited in the pipelines, and the nucleation rate increases by reducing the temperature.