(49d) Novel TSA Process for Enhanced Hydrocarbon Recovery From Produced Water

“Produced Water" is the largest byproduct stream by volume associated with oil and gas (O&G) production (75 billion barrels (bbls) of produced water worldwide annually). The O&G industry in USA produces about 18 billion bbls of produced water (≈7 bbl of water per bbl of oil). Management of produced water is a challenge due to its complex composition which includes compounds ranging from simple hydrocarbons to complex polynuclear aromatics and a variety of salts. The cost of managing large volumes of produced water can be as high as 60% of cost of oil per bbl making it an important component in the overall cost of producing oil.

Produced water, often considered as waste is now being viewed as a potential profit stream.  A process for high recovery and low cost desalination of the produced water is required. Such a process will reduce the water consumption in O&G extraction (75-225 billion bbls worldwide annually) by improving recyclability. In addition, a recovery of the hydrocarbons present in produced water is desired as it can be used as a feedstock for downstream operations.

Membrane technologies such as reverse osmosis (RO) are used to desalinate produced water. Hydrocarbon fouling and/or precipitation of salts on the membrane surface limits the water recovery. Thus, we propose an adsorption/ion exchange (IEX)/RO desalination process with an adsorption pretreatment to remove the hydrocarbons and other dissolved organic substances, an ion exchange system to remove divalent salts, and an optimized multi-stage RO system to produce both pure water and concentrated brine that is used to regenerate the ion exchanger. Since the IEX/RO system has been studied previously^1,2, the current focus of the research is on the adsorption system.

Since the feed is liquid, the energy requirements are minimized by regeneration with liquid.  In order to remove heavy components, regeneration is done by water at high temperature with pressure high enough to prevent boiling³. Feasibility of this process for binary aqueous solutions containing benzene or pyrene has been established by simulation using Aspen Chromatography(Regeneration water: Feed Water ratio 0.3). Since high temperature adsorption data is scarce, the isotherms and mass transfer coefficients were extrapolated from lower temperature data.  Simulation results for multicomponent interacting solutes will also be presented.

1. A. Venkatesan and P. C. Wankat, Desalination 271 (2011) 122-131
2. A. Venkatesan and P. C. Wankat, Desalination 286 (2012) 176-186
3. J. K. Kim,  G. Natarajan, and P. C. Wankat, Adsorption 9 (2003), 117-123