Alba Carrero-Parreño

Multistage Membrane Distillation for the Treatment of Shale Gas Flowback Water: Multi-Objective Optimization under Uncertainty

Abstract In this work, we analyze the effect of shale gas well data uncertainty on the multi-objective optimization of a multistage direct contact membrane distillation (DCMD) model. The uncertain parameters, flowrate and salt concentration of the flowback water, are modelled by a set of correlated scenarios. A bi-criterion stochastic MINLP was formulated to minimize the expected total annual cost (TAC) and its variability, controlled by the worst case (WC) risk management metric. The model was solved using a modified version of the sample average approximation (SAA) algorithm, which decomposes the original problem into two: a deterministic MINLP model and a stochastic NLP model. The solution is a set of Pareto curves, where the two global extreme solutions provide the DCMD designs that achieve the minimum expected TAC and the minimum WC, respectively. Furthermore, both designs are able to satisfy the zero liquid discharge (ZLD) requirement imposed in the outflow stream.

Combining Forward and Reverse Osmosis for Shale Gas Wastewater Treatment to Minimize Cost and Freshwater Consumption

Abstract One of the challenges for the future of the shale gas production industry is the water management due to the large demand of water for wells drilling and fracturing and the high volumes of liquid effluent produced. On-site treatment is a convenient option for the reuse of the shale wastewater as drilling water for subsequent wells, which simultaneously reduces the freshwater consumption and the waste volume. While conventional desalination technologies are suitable for the treatment of flowback water, they are not appropriate for the hypersaline produced water, which is typically disposed into underground injection wells. In this work, we propose a mathematical model to address the optimal design of an on-site treatment for both flowback and produced waters, combining reverse and forward osmosis, to simultaneously minimize the freshwater consumption and the specific cost of the fracturing water. The results obtained show a clear trade-off between both objectives and highlight the potential of the proposed technology combination to give an environmentally friendly solution to the shale gas produced water.

Optimal Shale Gas Flowback Water Desalination under Correlated Data Uncertainty

Presentation at the 27th European Symposium on Computer-Aided Process Engineering (ESCAPE-27), Barcelona, 2017, 1-5 October.

Multi-Objective Optimization of Renewable Energy-Driven Desalination Systems

Abstract Environmental impacts related to increasing greenhouse gas emissions and depletion of fossil-fuel reserves and water resources are major global concerns. In this work, we introduce a new multi-objective optimization model for simultaneous synthesis of zero-emission desalination plants driven by renewable energy. The system is particularly developed for zero-liquid discharge (ZLD) desalination of high-salinity shale gas wastewater, aiming to enhance economic and environmental system performance. The mathematical model is based on a multistage superstructure, which integrates a solar assisted Rankine cycle to a multiple-effect evaporation with mechanical vapor recompression (MEE-MVR) plant. For achieving the goal of more sustainable ZLD process, we specify the discharge brine salinity near to salt saturation conditions. The model is formulated as a multi-objective multiperiod non-linear programming (NLP) problem. The model is implemented in GAMS and solved via epsilon-constraint method, through the minimization of total annualized cost and environmental impacts. The economic objective function accounts for capital cost of investment and operational expenses, while environmental criteria are quantified by the life cycle assessment (LCA)-based ReCiPe methodology. A case study is performed to demonstrate the capabilities of the developed model. The obtained set of trade-off Pareto-optimal solutions reveals that integration of renewable energy generation to ZLD desalination plants can lead to significant cost and environmental savings for shale gas industry.