The dew point control unit of PENGBO has a problem of increasing ethylene glycol loss of hydrate inhibitor, due to equipment aging, process changes and other reasons. On the basis of analyzing the process flow and parameters of dew point control system, utilizing the HYSYS software to establish the simulation model, and combining the experimental analysis, the eight aspects of ethylene glycol injection concentration and injection volume, reboiler temperature, light hydrocarbon entering ethylene glycol regeneration system, ethylene glycol entering dry gas or light hydrocarbon recovery process, false emission, glycol decomposition have been analyzed. It is found that the ethylene glycol entering the liquid hydrocarbon recovery process and the liquid hydrocarbon entering ethylene glycol regeneration system as a result of ethylene glycol foaming and low operating temperature turns out to be the primary cause of high loss of ethylene glycol. In addition, the large injection volume is discovered to be the subordinate reason for the high loss of ethylene glycol. According to the analysis results, three measures of regular hydrocarbon expulsion, adding defoamer and reducing injection volume have been proposed. Field implementation has proved that the average consumption of ethylene glycol has been reduced from 450L/d to 130L/d under the premise of ensuring reliable operation of dew point control unit. It effectively solves the problem of ethylene glycol loss and achieves considerable economic benefits.
The dew point control system of PENGBO FPSO is assembled into a skid by American TOROMENT company, the designed processing capacity is 141.6×104m3/d. The system is divided into two trains. Train 1 is mainly used by the platform itself, while Train 2 is mainly used for external transmission. The treatment capacity of both trains is about 34 × 104m3/d, and the designed dew point of natural gas is −6.7°C. As the service time of the FPSO goes on, the ethylene glycol loss of the dew point control system increases gradually, because of equipment aging and process changing, etc. At present, about 450L of 80% ethylene glycol needs to be added, which influences the economic benefits of the platform.
