Date of Award

6-2019

Degree Name

MS in Civil and Environmental Engineering

Department

Civil and Environmental Engineering

Advisor

Yarrow Nelson

Abstract

A model was developed for predicting the performance of direct contact membrane distillation (DCMD) to evaluate the feasibility of using sensible heat to drive DCMD treatment of oilfield produced water. Algorithms for performance prediction of instantaneous and counter-current DCMD flow were developed. These algorithms used equation-based models of heat transfer, mass transfer, concentration polarization, and counter-current flow to predict performance of DCMD systems. The performance prediction model was validated against experimental data from the literature, and limitations to the accuracy of predictions were identified. The model was applied to evaluate performance sensitivity to nine operational parameters. The model was applied to evaluate the feasibility of sensible heat driven DCMD treatment of produced water using DCMD alone and using a reverse osmosis-DCMD hybrid system. The largest water recoveries that were energetically favorable (lower energy demand than reverse osmosis) for sensible heat driven DCMD produced water treatment were 0.5% and 0.75% for 1% and 3.5% NaCl feeds, respectively. As feed NaCl concentration increased, higher recoveries were energetically favorable over RO. A bulk NaCl concentration of 6% was evaluated to simulate the feasibility of further treatment of reverse osmosis retentate using sensible heat driven DCMD. Compared to treatment alternatives of multiple-stage flash distillation (MSF) and multiple-effect distillation (MED), recoveries up to 2.5% were favorable and up to 4.0% were competitive. Due to model limitations, the performance of optimal conditions for sensible heat driven DCMD produced water treatment could not be predicted, so the recoveries presented in this work are likely lower than the expected recoveries for optimal field conditions. Water recovery of produced water using sensible heat driven DCMD is limited thermodynamically to low recoveries, but any treatment using sensible heat that is energetically favorable reflects the utilization of two waste streams (produced water and waste heat) to produce high quality water. Using sensible heat to drive produced water treatment could be useful for providing small quantities of usable water, but would only result in a very small reduction of the volume of produced water needing to be disposed.

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