Shale gas flowback water desalination: Single vs multiple-effect evaporation with vapor recompression cycle and thermal integration

This paper introduces a new optimization model for the single and multiple-effect evaporation (SEE/MEE) systems design, including vapor recompression cycle and thermal integration. The SEE/MEE model is specially developed for shale gas flowback water desalination. A superstructure is proposed to solve the problem, comprising several evaporation effects coupled with intermediate flashing tanks that are used to enhance thermal integration by recovering condensate vapor. Multistage equipment with intercooling is used to compress the vapor formed by flashing and evaporation. The compression cycle is driven by electricity to operate on the vapor originating from the SEE/MEE system, providing all the energy needed in the process. The mathematical model is formulated as a nonlinear programming (NLP) problem optimized under GAMS software by minimizing the total annualized cost. The SEE/MEE system application for zero liquid discharge (ZLD) is investigated by allowing brine salinity discharge near to salt saturation conditions. Additionally, sensitivity analysis is carried out to evaluate the optimal process configuration and performance under distinct feed water salinity conditions. The results highlight the potential of the proposed model to cost-effectively optimize SEE/MEE systems by producing fresh water and reducing brine discharges and associated environmental impacts.