An extended graphical targeting technique for direct reuse/recycle in concentration and property-based resource conservation networks

Minimum flowrate targeting methods for resource conservation networks (RCNs) have been developed over the last decades. The existing methodologies still have certain drawbacks. Their design insights could be deepened and some steps should be more convenient for the users. A targeting tool called the material surplus composite curve (MSCC), which is an improvement of the surplus diagram for water and hydrogen networks is introduced. The approach is illustrated on several cases selected from the literature. Using this technique, it is possible to determine rigorous flowrate targets for different variants of the RCN problem.     

An optimization approach for the synthesis of recycle and reuse water integration networks

This paper presents a convex mathematical programming model for the global optimization of recycle/reuse water networks. The model is based on a general superstructure that includes the major configurations of interest such as segregation, mixing, recycle, bypass, and treatment of streams needed to satisfy the process and environmental constraints. The basic idea of the model formulation is to consider component balances, treating as optimization variables the individual flowrates. This formulation avoids the bilinear terms that appear when the compositions and total flowrates are considered as optimization variables. The objective function consists in the minimization of the total annual cost including the fresh sources costs, the treatment units costs (which are reformulated as convex functions) and the piping costs. Four examples problems are solved to show the applicability of the proposed model.     

An algebraic targeting approach for effective utilization of biomass in combined heat and power systems through process integration

Green house gases (GHGs) pose some of the most profound impact on the environment. One viable alternative for reducing GHGs is the utilization of biomass to generate heat and power for processing facilities. The purpose of this paper is to address the utilization of biowaste or biomass source in a processing facility for combined heat and power (CHP). In particular, the paper addresses the following questions: How to incorporate biomass utilization in cofiring and energy production within an existing process? How to reconcile thermal demands with opportunities for power cogeneration through a process-integration framework? What are the economic factors that will insure the feasibility of biomass utilization and power cogeneration? What is the impact on GHG emissions and what are the necessary GHG emission pricing options? A systematic algebraic procedure for targeting cogeneration potential ahead of detailed power generation network design is presented. The approach presented here effectively utilizes biomass and biowaste sources as external fuel, and matches them with the use and dispatch of fuel sources within the process, heating and non-heating steam demands, and power generation. The concept of extractable power introduced by Harell and El-Halwagi AIChE Spring Meeting, New Orleans, March (2003) has been used as a basis of constructing this algebraic cogeneration targeting approach. Steam surpluses and deficits are identified by header balance. Flow balance is performed by cascade diagram techniques and extractable power is computed from net flows to target the cogeneration potential. Next, the paper discusses important economic factors (e.g., GHG pricing options) required for the cost-effective utilization of sole biomass feed or a co-fed mixture of biomass and fossil fuels for CHP. Two case studies are discussed to illustrate the presented approach. The first case study illustrates the developed targeting approach when no external fuel is required and all the higher pressure surplus streams are able to satisfy the lower pressure deficit headers. The second case shows the application of algebraic targeting to obtain the external fuel requirement when surplus headers are not able to meet the deficit demands. Further, this case shows the use of biomass for meeting the demands and the subsequent effects on economics and GHG emissions for the process.     

An integrated approach to the facilities and material handling system design

The facility layout problem involves the optimal location of manufacturing facilities into a workshop. The classical approach to the layout design is carried out in two separate steps: the first step is the construction of the block layout, i.e. the location of the departments into the workshop, and the second step is the design of the material handling system. The separate optimization of these two aspects of the problem leads to solutions that can be far from the total optimum. In this paper, an integrated approach to the facilities and material handling system design is proposed. Referring to a physical model, named the bay structure , and to a unidirectional AGV system, a genetic approach is proposed to individuate the locations of the departments, the positions of the pickup/delivery stations and the direction of the flow-path. The minimization of material handling cost is adopted as optimality criterion.     

An isogeometric approach to topology optimization of multi‐material and functionally graded structures

A new isogeometric density‐based approach for the topology optimization of multi‐material structures is presented. In this method, the density fields of multiple material phases are represented using the isogeometric non‐uniform rational B‐spline‐based parameterization leading to exact modeling of the geometry, removing numerical artifacts and full analytical computation of sensitivities in a cost‐effective manner. An extension of the perimeter control technique is introduced where restrictions are imposed on the perimeters of density fields of all phases. Consequently, not only can one control the complexity of the optimal design but also the minimal lengths scales of all material phases. This leads to optimal designs with significantly enhanced manufacturability and comparable performance. Unlike the common element‐wise or nodal‐based density representations, owing to higher order continuity of density fields in this method, their gradients required for perimeter control restrictions are calculated exactly without additional computational cost. The problem is formulated with constraints on either (1) volume fractions of different material phases or (2) the total mass of the structure. The proposed method is applied for the minimal compliance design of two‐dimensional structures consisting of multiple distinct materials as well as functionally graded ones. Copyright © 2016 John Wiley & Sons, Ltd.     

An overview of construction and demolition waste management in Canada: a lifecycle analysis approach to sustainability

The construction and demolition (C&D) waste generated by the Canadian construction industry accounts for 27 % of the total municipal solid waste disposed in landfills. However, it is evident that over 75 % of what the construction industry generates as waste has a residual value, and therefore could be recycled, salvaged and/or reused. The need for comprehensive and integrated waste management mechanisms, technologies, rating systems and policies is widely recognized. Owing to increasing C&D waste volumes, shortage of landfills and long-term adverse environmental, economic and social impacts of the disposed C&D waste, sustainable C&D waste management is becoming increasingly essential to protect public health and natural ecosystems. This paper proposes a conceptual C&D waste management framework to maximise the 3R (reduce, reuse and recycle) and minimise the disposal of construction waste by implementing sustainable and comprehensive strategy throughout the lifecycle of construction projects. In addition, a life cycle based C&D waste sustainability index is developed. This approach can be used to make decisions related to selection of material, sorting, recycle/reuse and treatment or disposal options for C&D waste.     

Prediction of mechanical properties of polypropylene/waste ground rubber tire powder treated by bitumen composites via uniform design and artificial neural networks

Polypropylene (PP)/waste ground rubber tire powder (WGRT) composites were studied with respect to the effect of bitumen and maleic anhydride-grafted styrene–ethylene–butylene–styrene (SEBS-g-MA) content by using the design of experiments (DOE) approach, whereby the effect of the four polymers content on the final mechanical properties were predicted. Uniform design method was especially adopted for its advantages. Optimization was done using hybrid artificial neural network–genetic algorithm (ANN–GA) technique. The results indicated that the composites showed fairly good ductibility provided that it had a relatively higher concentration of bitumen and SEBS-g-MA under the studied condition. A quantitative relationship was presented between the material concentration and the mechanical properties as a set of contour plots, which were confirmed experimentally by testing the optimum ratio.     

An approach to the mechanical behaviour of SiC/SiC and C/SiC ceramic matrix composites

The mechanical behaviour of two woven composites C/SiC and SiC/SiC was investigated at room temperature. The non-linear load-displacement curves and the damaging process were closely related to the specific structure of the composites, consisting of a network of impregnated bundles of fibres. The damage in the bundles proceeded by multiple cracking in the matrix before fibre failure, and dictated the response to the applied load. Other mechanisms, consisting mainly of distortions in bundles and their framework, induced a residual deformation and an energy dissipation. The behaviour was characterized according to the damaging process. Stress-electric strain curves revealed a mechanical response similar to those observed in unidirectional composites, although some effect of the specimen geometry on the curves was observed. Residual strains were similar in tensile and bending conditions. The work of fracture was consistently described by a volumetric rate of energy absorption, related to the applied strain, but the respective contributions of different damage mechanisms could not be determined.     

An XFEM/level set approach to modelling surface/interface effects and to computing the size-dependent effective properties of nanocomposites

In a nanostructured material, the interface-to- volume ratio is so high that the interface energy, which is usually negligible with respect to the bulk energy in solid mechanics, can no longer be neglected. The interfaces in a number of nanomaterials can be appropriately characterized by the coherent interface model. According to the latter, the displacement vector field is continuous across an interface in a medium while the traction vector field across the same interface is discontinuous and must satisfy the Laplace–Young equation. The present work aims to elaborate an efficient numerical approach to dealing with the interface effects described by the coherent interface model and to determining the size-dependent effective elastic moduli of nanocomposites. To achieve this twofold objective, a computational technique combining the level set method and the extended finite element method is developed and implemented. The numerical results obtained by the developed computational technique in the two-dimensional (2D) context are compared and discussed with respect to the relevant exact analytical solutions used as benchmarks. The computational technique elaborated in the present work is expected to be an efficient tool for evaluating the overall size-dependent elastic behaviour of nanomaterials and nano-sized structures.     

An integrated approach to determine the block layout,AGV flow path and the location of pick-up/delivery points in single-loop systems

Layout design and material handling system design are two of the major aspects of facility planning. Although both aspects directly influence each other, the classical approach to the layout design is carried out in two separate steps: in the first step the block layout, i.e. the location of the departments in the workshop, is constructed, and in the second step, the material handling system is designed. The separate optimisation of these two aspects of the problem leads to solutions that can be far from the global optimum. In this paper, we develop an integrated algorithm to design the facilities and material handling systems. We focus on single-loop AGV systems. The proposed algorithm determines the block layout, AGV single-loop flow path and pick-up delivery stations, simultaneously. The associated from–to chart and the area of departments are the principal inputs of the algorithm. The objective is minimising total material flow distance among all departments. The results of our computational experiments show the algorithm was coded using MATLAB 7.0, and that our integrated algorithm is more efficient in terms of both the objective function value and the runtime.