Optimal Design of Zero-Water Discharge Rinsing Systems

Abstract

This paper is about zero liquid discharge in processes that use water for rinsing. Emphasis was given to those systems that contaminate process water with valuable process liquor and compounds. The approach involved the synthesis of optimal rinsing and recycling networks (RRN) that had a priori excluded water discharge. The total annualized costs of the RRN were minimized by the use of a mixed-integer nonlinear program (MINLP). This MINLP was based on a hyperstructure of the RRN and contained eight counterflow rinsing stages and three regenerator units: electrodialysis, reverse osmosis, and ion exchange columns. A "large-scale nickel plating process" case study showed that by means of zero-water discharge and optimized rinsing the total waste could be reduced by 90.4% at a revenue of $448,000/yr. Furthermore, with the optimized RRN, the rinsing performance can be improved significantly at a low-cost increase. In all the cases, the amount of valuable compounds reclaimed was above 99%.

ECO-design of reuse and recycling networks by multi-objective optimization

“…The large circles indicate the single solution for extreme beta values (limits). amount can be achieved instead of applying an extra regenerator which causes hidden wastes.The results of RRN that are produced under the openloop condition show a comparable tendency as the closed-loop results calculated by Tho¨ming[11]. The highest TAC values are reached by fewer rinsing stages and with either RO or RO, IX.…”

“…All the solutions have reverse osmosis (RO) as a regenerator and additionally an ion-exchange (IX) regenerator. The structural presentation of the openloop global optima shows a similar configuration to the closed-loop optima [11]. The IX is connected to the initial rinsing stages while the RO receives the rich stream from the last stages and provides regenerated stream to the third or forth rinsing stages in the middle.…”

“…This large scale nickel plating process was previously defined as a closedloop system for zero-water discharge [11] with the closed-loop conditions W Z D and D Z C (see in Extending the closed-loop model to this openloop model, the potential environmental impacts of a wastewater discharge can be seen. In this study the following environmental impacts were considered: the amount of nickel in the wastewater stream, the water consumption of the system and the energy consumption for pumping and regenerator units.…”

“…A hybrid methodology of both approaches [11], integrates impact assessments, such as environmental considerations and socioeconomic factors with process synthesis, by means of multi-objective optimization. Another application within the hybrid methodology for minimization of single objective optimization problems was done by Diwekar et al [7].…”

Environmental and economic analysis of a water network system using LCA and LCC

“…Most studies have minimized a single contributor, such as a total freshwater flowrate, the number of interconnections, or fixed costs 6, 8‐11. Other studies have used the sum of the operating cost for freshwater and capital costs for pipes and wastewater treatment, the sum of the limited capital and operating costs,7, 12 or the sum of the costs of freshwater supply, water and wastewater treatment, pipes and sewers 13. One multi‐objective optimization studied to simultaneously minimize the total annualized cost and environmental impacts did not include piping costs 14…”