(100d) Glycol Loss Minimization for a Natural Gas Dehydration Plant Under Upset Conditions

Low-temperature separation with Mono Ethylene Glycol (MEG) injection process is a common dehydration technique for natural gas processing, which needs to maintain a hydrocarbon dew point. However, dehydration systems based on glycol frequently result in a significant loss of glycol during plant upset conditions such as rapid flow fluctuation, refrigeration system failure and inadequate control of stripper column [1]. These losses occur due to carryover with gas, hydrocarbon and vaporization from stripper column overhead. For this reason, it is important to develop process operation methodologies for reducing glycol losses and thereby reducing emissions.

In this research, steady-state and dynamic models are developed using the Aspen Plus simulation framework. A parametric analysis of inlet flow fluctuation, temperature fluctuation of the low-temperature separator (LTS), stripper column overhead temperature fluctuation and reboiler temperature fluctuation were conducted under steady-state conditions. Simulation results indicated that that most of the glycol is lost via vaporization through the stripper column overhead and some glycols are carried over with gas and hydrocarbon from LTS. Dynamic simulations were utilized to develop a new control strategy for optimum column operation along with an improved stripper model. It is shown that the simulation results can be used to study plant upset conditions, minimize glycol loss, improve product gas specifications and reduce plant operating costs. In particular, it is shown that the improved design has the potential to reduce glycol losses by over 70%, lower emissions and provide plant stability.

References

1. Haque, M. E.; Ethylene Glycol Regeneration Plan: A Systematic Approach to Troubleshoot the Common Problems. Journal of Chemical Engineering, IEB, 27, No. 1, 21-26, 2012.