Influence of Injecting Some Chemicals on MEG Inhibition Performance for Less Recycled MEG

Abstract

Monoethylene glycol (MEG) is often injected into submarine transportation pipelines, from offshore oil and gas platforms, to suppress hydrate formation. MEG can be recovered, for recycling, through a MEG regeneration plant, onshore. The costs related to hydrate inhibition operations are significant; thus, introducing new methods of reducing the volumes of MEG required by the system potentially will provide significant economic benefits for the operation. The objectives of this study were to evaluate the influence of ammonium hydroxide (NH4OH), sodium hydroxide (NaOH), potassium hydroxide (KOH), and methyl diethanolamine (MDEA) on inhibition performance when separately combined with a MEG 20 wt % solution in a methane gas system. The pH levels applied were 10.96, 10.84, 10.62, and 10.07 for NaOH, KOH, NH4OH, and MDEA, respectively. The results indicated that these compounds suppressed the hydrate dissociation temperatures, to different degrees, when compared with a normal MEG 20 wt % solution. The temperatures were reduced by an average, across the range of pressures, of 0.72, 0.78, and 0.94 °C in the case of MDEA, KOH, and NaOH, respectively. However, when combined with NH4OH, the reduction in dissociation temperature was even more significant, averaging 1.68 °C. An economical assessment of the benefits of reducing the inhibition temperature by this amount, through the combination with NH4OH, indicated an operational cost saving of about 17% within the MEG regeneration process. This level of cost reduction will be of significant interest to the offshore gas-producing industry.