Experimental investigation and kinetic modeling of nanocrystal growth for scale reduction in mono-ethylene glycol regeneration unit
Scale formation is the major problem in mono-ethylene glycol regeneration units of gas refineries. In this study, the effect of adding different concentrations of silica nanoparticles on the growth rate of salt crystals in a rich mono-ethylene glycol solution is investigated, and the corresponding mathematical model is introduced. To obtain the crystallization kinetics, the particle size distribution was measured in continuous intervals of time and temperature using a dynamic light scattering. Measurements were taken at four temperature levels, in 20-min intervals, and 1, 3, 5, and 9 wt% of silica nanoparticles. Results showed that silica nanoparticles reduced the activation energy needed for nucleation and crystallization by more than 50%. However, increasing the concentration of nanoparticles did not result in a further reduction in the activation energy. Rather, it contributed to the formation of larger primary nuclei that form a larger crystal structure. An increase in temperature from 25 to 50 °C led to an increase of 8.8% in the initial crystal growth. On the other side, increasing the concentration of nanoparticles from 1 to 10 wt% at a constant temperature increased the crystallization growth rate by 3.4%. The proposed mathematical model predicts the kinetics of crystal growth with an acceptable accuracy with the mean relative error of 6.19% for the whole range of concentration and temperature.