May 2025

Process Optimization

Emulsion breaker increases refinery profitability and treating performance

This article details a novel emulsion breaker that was used at Reliance Industries Ltd.'s Jamnagar refinery in India.

IP: 10.3.32.10

Throughout the development of the petrochemical industry, liquified petroleum gas (LPG), a C3 and C4 hydrocarbon, is drawing more attention as a basic raw material for refinery processes and the chemical industry. 

LPG can be turned into ethylene, propylene, butylene, butadiene and other gases through separation and conversion processes to produce different materials such as synthetic plastic, synthetic rubber and synthetic fiber, as well as raw material to produce pharmaceuticals and dyestuff. Butane, a C4 hydrocarbon within LPG, also serves as a feedstock for several processes that can convert it into high-octane compounds through various forms of alkylation, which is then used in gasoline blending. 

In a petroleum refinery, LPG is produced through both catalytic and non-catalytic processes. Catalytic processes like fluid catalytic cracking (FCC) and hydrocracking rely on conversion, while non-catalytic processes utilize various means of separation, such as a visbreaker, coker and crude distillation unit (CDU). Propylene, a C3 hydrocarbon present or derived from LPG, is a basic raw material for the chemical and petrochemical industries used to manufacture chemical and polymer-grade propylene. 

LPG contains sulfur contaminants, mainly hydrogen sulfide (H2S) and various mercaptan species. These sulfur compounds act as a poison to many of the conversion catalysts by causing deactivation and must be removed before the conversion catalysts can be used as a feed source for the downstream units. The co-authors’ caustic mercaptan oxidation (Merox) process unit^a removes sulfur compounds like mercaptans and carbonyl sulfide, commonly present in LPG material. 

Aside from sulfur compounds, LPG produced from catalytic cracking, thermal cracking and bio-feedstock processing contains contaminants that can cause hydrocarbon and aqueous phase emulsions. The contaminants can cause emulsions by themselves after they react with the caustic in the Merox unit or with the solvent in an amine unit. The formation of emulsions often results in reduced amine absorber and Merox extractor unit efficiency and a reduction of overall capacity, in addition to caustic or amine solvent phase carryover to the downstream units. This results in multiple potential problems: 

• Off-specification product 

• Loss of LPG treatment and a subsequent decrease in propylene production 

• Poisoning of downstream catalyst beds 

• Increased acid consumption in alkylation units when processing LPG 
• Stress corrosion cracking caused by caustic. 

Emulsions are stable dispersions of small immiscible liquid-contaminant droplets (micron size) contained in a liquid phase. Typical emulsions are generally comprised of hydrocarbons and water or water-based solution mixtures. The formation and stability of emulsions are caused primarily by the presence of surfactants. These components are usually molecules with polar and nonpolar groups that decrease the surface and interfacial tension of immiscible liquid phases. Surfactants stabilize the liquid-liquid interface by creating an elastic film that encapsulates the contaminant droplet. Certain submicron-sized solids can also stabilize emulsions. FIG. 1 shows an example of an emulsion of hydrocarbon droplets dispersed in amine solvent. The image was taken using a 10x magnification microscope equipped with polarized light. It is interesting to note that solids are also visible and predominately populating the emulsion droplet interface. 

FIG. 1. Image of an emulsion of hydrocarbon droplets dispersed in amine solvent.  

CASE STUDY 

The co-authors’ proprietary emulsion breaker^b solution is an effective and economical solution to mitigate the emulsion issues seen in the amine absorber and the Merox extraction unit. The technology effectively destabilizes emulsions by creating weak points in the emulsion elastic film, causing it to quickly collapse.  

Customer case study details. Reliance Industries Ltd. (RIL) owns the DTA refinery at Jamnagar, India, which has two Merox extraction units (i.e., Unit 415 and Unit 417) that take LPG feed from the FCC unit (FCCU) and coker units. FIG. 2 shows the details and configuration of Unit 415, including the amine unit absorber. 

FIG. 2. RIL’s caustic merox process unit (Unit 415).  

LPG Merox (Unit 415) has a methyldiethanolamine (MDEA) amine absorber to remove bulk H2S from the feed followed by a continuous amine water wash settler to remove entrained and dissolved amine solvent from the amine unit treated LPG product. The residual H2S is then removed via caustic in the caustic prewash. Mercaptans present in the LPG are then removed with caustic in the trayed extractor column, and product caustic specifications are met by the caustic knockout (KO) drum and the downstream sand filter. The rich caustic formed by the extraction of mercaptans is then sent to the regeneration section where it is sustainably regenerated for reuse instead of being disposed. The caustic regeneration section also contains a two-stage wash-oil system (not shown in FIG. 2) to reduce disulfide sulfur back-extracted from the caustic by the LPG and minimize sulfur in the caustic-treated LPG product. 

RIL’s refinery operation. RIL processes LPG from its FCCU and coker units through its Merox Unit 415 to extract mercaptans and reduce the total sulfur component in the treated product. The LPG is routed to downstream units to produce propylene and butylene. High-severity FCC generates increased unsaturated hydrocarbons like olefins and diolefins, along with oxygenates such as formic acid, acetic acid and others. Coker-derived LPG contains even higher levels of these contaminants, which increases the potential of forming emulsions and/or emulsion precursors with amine solvent and/or caustic solvent. RIL has experienced frequent emulsion issues in both the amine absorber and the extractor columns resulting in frequent solvent carryover, hindering the unit performance and the ability to achieve higher throughputs. 

The amine absorber is designed with an amine water wash to remove the dissolved amine (MDEA in this case) from the LPG. The amine water wash has continuous water circulation with a small continuous freshwater injection to maintain optimum amine removal, which is then collected in the settler vessel boot. RIL experienced extremely high amine content in the water boot, indicating abnormal amine carryover. 

Both the amine and extractor columns are liquid-liquid countercurrent contacting columns, where LPG is introduced to the bottom tray and lean solvent enters from the top tray. The caustic extractor columns are trayed with specific weir heights and are often at larger tray-to-tray distances than typical columns for efficient mixing and separation of the aqueous and hydrocarbon phases. The separation efficiency is reduced when emulsions form between the caustic and hydrocarbons, resulting in increased back-up of caustic in the trays. The backed-up  

caustic on the tray’s active areas can build in height until it fluidizes and exits all at once as slug along with the LPG and is collected in the caustic KO drum. This generally causes significant operational challenges. 

TABLE 1 indicates the LPG flowrate, wash water amine content and caustic carryover incident frequency as base values before the introduction of co-authors’ proprietary emulsion breaker^b to the process. 

Customer testing. Over the years, RIL and the co-authors’ company have investigated many different options to control these emulsions and reduce caustic carryover with limited success. After collaboration with the Reliance Technical Service team, it was agreed to run a laboratory-scale test to determine the effectiveness of the emulsion breaker. Rich caustic from the LPG extractor was mixed with hexane (a model solvent to simulate LPG) in different glass vials. The vials were treated with different versions of the co-authors’ emulsion breaker product line to evaluate their efficacy.  

All vials (with and without emulsion breaker) were vigorously shaken for 2 min to simulate dynamic contact on the active area of the tray. The vials were then set down to simulate the outlet weirs of the tray and to observe the duration for separation between the aqueous phase and the hydrocarbon phase to occur. It was observed that all but one vial containing emulsion breaker separated into two phases within 5 sec, while the vial without emulsion breaker took 75 sec to separate into the phases (FIG. 3). 

FIG. 3. Duration for separation for the test vials, with and without the co-authors’ emulsion breaker. 

Laboratory-scale testing. After the positive results from the laboratory-scale testing, it was agreed to use the co-authors’ proprietary emulsion breaker^b in one of RIL's operating Merox units during a 5-d trial that was conducted and observed by both RIL and the co-authors’ company. This additional trial with the Reliance Technical Services Team was a resounding success, and the use of proprietary emulsion breaker^b was continued after the trial for additional days.  

The dosing of the proprietary emulsion breaker^b was injected into the LPG stream at a low-point drain upstream of the amine absorber column. The initial dosing rate was started at 2.5 ppmv of the emulsion breaker into the hydrocarbon phase. The amine absorber and continuous amine unit water wash settler operation were monitored for amine content. After the emulsion breaker dosing, the level in the amine absorber water wash column stabilized, and the amine content in the spent water was reduced by 70%. Amine solvent carryover was calculated to be reduced by 2 MMkg/yr based on amine content. The proprietary emulsion breaker^b eliminated discrete amine carryover from the amine absorber column to match expected levels (FIG. 4). 

FIG. 4. Amine water wash operation graph, March 13, 2023–April 4, 2023. 

The proprietary emulsion breaker^b. Given the successful implementation of the proprietary emulsion breakerb in the initial trials, the teams increased the unit throughput to ascertain if these improvements were consistent and sustainable. The LPG flowrate was further increased stepwise with corresponding increases in the emulsion breaker dosing rate to 5 ppmv in the LPG. No caustic carryover from the caustic extractor to the downstream caustic KO drum was observed, despite a feed rate increase of 20% over base rates. At the same time, the amine content in the water wash settler decreased by 70% (FIG. 5). 

FIG. 5. Feed rate increase graph, March 13, 2023–April 4, 2023. 

Economic benefits. The proprietary emulsion breakerb was injected into the LPG upstream of the amine absorber in the LPG Merox unit (Unit 415). Substantial improvement was seen in the amine and caustic carryover after dosing of the chemical. This allowed an additional 20% throughput from the base case while maintaining the vast reduction in amine carryover and elimination of caustic carryover (TABLE 2). 

Takeaways. The successful implementation of the proprietary emulsion breakerb significantly improved the profitability of the refinery by allowing RIL to process additional LPG in the Merox unit with no carryover, minimizing downstream impacts. This, in turn, led to an increase in propylene and butylene production in the downstream units, providing another financial boost. This collaboration demonstrated the benefits of implementing simple innovative solutions to address complex operational challenges. The proprietary emulsion breakerb is a commercially proven, effective and economical solution to mitigate emulsion issues and improve plant performance 

NOTES  

^a Honeywell UOP’s Caustic Merox™ process unit 

^b Honeywell UOP’s EmulsEnd-318 Emulsion Breaker 

The Authors

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