New Chemical Additive to Enhance Reduction of Oil Carryover in Gas
Authors: Khatib Z.I. 
Published: December 2007

Foaming and fouling in glycol contactors and/or in amine treating systems are frequent problems in gas treatment processes due to the entrainment of liquid and solid aerosols in the gas stream. Entrainment of these aerosols leads also to mechanical damage of turbines and/or unscheduled shutdown of compressor units. A new chemical additive was developed and applied in the gas stream. The additive was successful in preventing the dissemination of the oil and/or condensate carryover into aerosol sizes, thereby enhancing the performance of coalescer filters and scrubbers.

Introduction

A recurring problem in gas treatment processes is the entrainment of liquid and solid aerosols in the inlet gas. This entrainment, particularly oil and condensate aerosols, causes foaming, corrosion, and fouling within the equipment of these processes. Fouling and foaming in the glycol contactors and in amine treating systems are examples of this frequent problem. In addition, entrainment of these aerosols leads to potential mechanical damage of turbines and/or shutdown of compressor units.

Generally, aerosol-size droplets are created when a predominantly gaseous stream containing some liquid is passed at relatively high velocity through an orifice, valve, bend, tee, choke, etc., or is subjected to compression. Recent developments in demisters, scrubbers, and coalescer filters have improved their removal efficiency, but removing droplets of aerosol size remains difficult.

With the continuous increase in gas production and the need to process gas closer to design capabilities, foaming and fouling were major concerns for Shell. The need to suppress foaming and fouling and to investigate ways that would lead to an incremental increase in gas capacity became an important issue to address. Recent laboratory and field studies have led to the development of a novel chemical additive that was successful in preventing oil and condensate carryover from being degraded to aerosol sizes in gas streams and in enhancing the performance of the coalescer filters in removing the entrained hydrocarbon droplets upstream of the treating facilities. A Shell patent on the development, deliverability, and application of this chemical additive is pending.

This paper presents the development of the chemical application and summarizes the performance of the chemical additive in two field applications: the Yellowhammer Sulfinol Plant and the Denver Unit SulFerox* Plant. The development of the chemical application includes a description of the properties of the chemical additive, a demonstration of its effectiveness through experimental verification, and the development of the analytical method to detect its concentration in a hydrocarbon matrix.

Chemical Additive as a Demisting Agent

Background.

The addition of dilute solutions of high molecular weight polymers to liquids to reduce aerosol formation has been demonstrated in a variety of studies and operations. These include the anti-misting of jet fuels to produce a coarser spray and the anti-misting of machining fluids in metal-working operations to minimize worker exposure to aerosol-laden air. The success of these anti-misting applications was attributed to the elongational viscosity of the solutions that is contributed by the polymeric additive. Due to the similar properties of jet fuels and the oil/condensate from gas streams, the use of high molecular weight polymer as an anti-misting additive was investigated.

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