Heat transfer evaluation and economic characteristics of falling film brine concentrator in zero liquid discharge processes

Abstract

Zero Liquid Discharge processes have been believed as a sustainable solution for industrial wastewater reuse and brine management. However, the high cost of treatment is a challenge to the attractiveness of these processes. To overcome this, pre-concentration of wastewater feed, before being sent to the crystallizer, appears to be a practical solution to decrease the expenses of zero liquid discharge process. While using a falling film brine concentrator could be a helpful solution to achieve this point, the lack of applicable information on heat transfer performance and thermohydraulic characteristics of vertical tube falling film evaporators is an attentive constraint. The main objective of this work is to evaluate the effect of different evaporative heat transfer coefficients on energy consumption and expenses of wastewater treatment in a falling film brine concentrator. For this reason, seven remarkable evaporative heat transfer correlations were collected and comprehensively argued. A thermo-economic model along with a developed code is proposed to conduct the study. While the economic evaluation indicates that evaporator effects contribute to 16% of total investment cost, the sensitivity analysis demonstrated that applying various heat transfer correlations appears to have a more significant influence on capital cost (around 9%) rather than operating expenses (almost 1%). Among the correlations, the most consistent one to the experimental data was recommended for designing a reliable brine concentrator with the minimum level of uncertainties.