•System reliability is incorporated as an objective function into the design of cost-effective HEN.•NSGA-II is applied in multi-objective optimization of HEN.•The results of three cases shows the tradeoff between economic and system reliability.Optimization of heat exchanger network (HEN) has traditionally been driven by economic objectives. Notwithstanding the importance of minimizing the total annual cost (TAC) of HEN, it is also important to ensure reliability. In order to obtain economical HEN considering system reliability simultaneously, a multi-objective optimization formulation of economic and system reliability is proposed in the design of HEN. A stage-wise superstructure is used to obtain feasible HEN, and the system reliability based on the number of heat exchangers in maximum irrelevant sub-network of HEN and the TAC are calculated as two objective functions. Then the non-dominated sorting genetic algorithm (NSGA-II) is applied to solve the multi-objective optimization mixed integer nonlinear programming model. Three case studies from literatures are used to assess the applicability and performance of the optimization formulation and solution algorithm. The system reliability is enhanced with TAC closes to the reported minimum, which is more meaningful than those obtained using single-objective optimization. The optimal solution set can aid in the selection of a safe and cost-effective network configuration for industrial plants and the proposed approach can easily be applied to include other objectives (e.g., sustainability and safety).Download high-res image (107KB)Download full-size image

Dioctylsulfosuccinate sodium surfactant (AOT) was selected as a structure-directing agent to prepare mesoporous MgO adsorbent by a hydrothermal method. The anionic AOT surfactant combines with Mg(OH)2 crystallites to form AOT·Mg(OH)2 micelle colloids by hydrogen bonding and electrostatic attraction to template the mesopores with diameter of 10–20 nm in MgO nanoplates The whole process is composed of three stages: nucleation, orientation growth, and porecreating. The results demonstrated that the presence of AOT surfactant was essential to produce the mesopores and to adjust the structural parameters of the nanoplates. Because of their higher specific surface area and porous structure, the MgO materials exhibit a satisfactory adsorptive property to three typical azo dye pollutants, Congo red (471–588 mg/g), Methyl orange (∼370 mg/g) and Sudan III (∼180 mg/g), and good performance for decolorization of low-concentration dyes. The highly adsorption capacities of the adsorbents are ascribed to their mesoporous structures which can provide more interaction sites, facilitate the mass diffusion in pores and help the dye molecules to contact the adsorptive sites more easily. The present work provided an alternative approach for preparation of inorganic adsorbent with controlled porous structures and high adsorption ability for hazardous dyes.Graphical abstractNovel mesoporous MgO nanostructures: higher adsorption capacity and good decolorization performance to azo dye pollutants.Highlights► A novel mesoporous MgO adsorbent with higher surface area was prepared. ► The mechanism for designing the porous structures in MgO was proposed. ► The MgO materials exhibit high adsorption capability to azo dyes. ► The MgO show good performance for decolorization of low concentration dyes. ► The ability to obtain such MgO structure is useful in other adsorbent preparation.