Water Network Synthesis Using Mutation-Enhanced Particle Swarm Optimization

Different techniques for the synthesis of industrial water reuse/recycle networks have been developed in recent process integration research. These tools range from graphical pinch analysis approaches to mathematical programming models. The latter have the advantage of being flexible enough to incorporate various water network constraints, but in many cases these are often non-linear, thus making the identification of global optima difficult. Recent work has demonstrated the effectiveness of metaheuristic algorithms such as particle swarm optimization (PSO), for finding good solutions these problems. This work describes the use of a modified PSO for solving mixed integer non-linear programming (MINLP) models for water network synthesis. By incorporating a mutation operator for the binary variables in the model, the algorithm is able to escape sub-optimal network topologies and proceed towards better solutions than can be found with ordinary PSO. Two case studies involving water recycle/reuse are used to demonstrate the new design methodology.     

A graphical representation of carbon footprint reduction for chemical processes

Climate change has recently become a major focus for industry and government agencies. Some recent works have been reported on the use of pinch analysis techniques for carbon-constrained energy planning problems. This paper discusses a new application of graphical technique based on pinch analysis for company-level visualization and analysis of carbon footprint improvement. The technique is based on the decomposition of total carbon footprint into material- and energy-based components, or alternatively, into internal and external components. The decomposition facilitates the evaluation and screening of process improvement alternatives. Two industrial case studies on the production of phytochemical extracts and bulk chemicals are used to illustrate the new extension.     

Experiences from a Community Nature Project in a Housing Estate in Singapore

A city farm concept called the Nature Corner project, which involves both animals and plants, was initiated in Ghim Moh housing estate, Singapore, in 1997. The objectives of the community project were to introduce nature to residents and to encourage social interaction. The paper analyses the project's set-up, assesses the funding, maintenance and other issues involved and discusses the findings of a 1998 sample survey of users and non-users of the project. It was found from the survey that the project has been quite successful in introducing nature to users but less successful in encouraging social interaction among them.     

Game theory approach to the analysis of inter-plant water integration in an eco-industrial park

Industrial water conservation is an important adaptation to the effects of climate change. In addition to water conservation within individual plants, wastewater can be reused/recycled among different companies through inter-plant water integration (IPWI) schemes. Such schemes are based on the concept of industrial ecology and industrial symbiosis, and can be used to achieve greater water savings than when water conservation is implemented in individual companies separately. However, in IPWI, each participating company seeks to maximise its own benefits. In the absence of centralised authority dictating the terms of water integration schemes, conventional modelling techniques are not appropriate. This paper shows how a game theory-based approach can be used to analyse the interaction of participating companies in an eco-industrial park seeking to develop an IPWI scheme.     

Flowrate targeting for threshold problems and plant-wide integration for water network synthesis

Water reuse/recycle has gained much attention in recent years for environmental sustainability reasons, as well as the rising costs of fresh water and effluent treatment. Process integration techniques for the synthesis of water network have been widely accepted as a promising tool to reduce fresh water and wastewater flowrates via in-plant water reuse/recycle. To date, the focus in this area has been on water network synthesis problems, with little attention dedicated to the rare but realistic cases of so-called threshold problems. In this work, targeting for threshold problems in a water network is addressed using the recently developed numerical tool of water cascade analysis (WCA). Targeting for plant-wide integration is then addressed. By sending water sources across different geographical zones in plant-wide integration, the overall fresh water and wastewater flowrates are reduced simultaneously.     

Effects of H2O2 on growth,metabolic activity and membrane integrity in three strains of Microcystis aeruginosa

Environmental Science and Pollution Research - The application of hydrogen peroxide (H2O2) as a management tool to control Microcystis blooms has become increasingly popular due to its short...     

Ionic liquids for the inhibition of gas hydrates. A review

The formation of gas hydrates is a major issue during the operation of oil and gas pipelines, because gas hydrates cause plugging, thereby disrupting the normal oil and gas flows. A solution is to inject gas hydrate inhibitors such as ionic liquids. Contrary to classical inhibitors, ionic liquids act both as thermodynamic inhibitors and hydrate inhibitors, and as anti-agglomerates. Imidazolium-based ionic liquids have been found efficient for the inhibition of CO₂ and CH₄ hydrates. For CO₂ gas hydrates, N-ethyl-N-methylmorpholinium bromide showed an average depression temperature of 1.72 K at 10 wt% concentration. The induction time of 1-ethyl-3-methyl imidazolium bromide is 36.3 h for CO₂ hydrates at 1 wt% concentration. For CH₄ hydrates, 1-ethyl-3-methyl-imidazolium chloride showed average depression temperature of 4.80 K at 40 wt%. For mixed gas hydrates of CO₂ and CH₄, only quaternary ammonium salts have been studied. Tetramethyl ammonium hydroxide shifted the hydrate liquid vapour equilibrium to 1.56 K at 10 wt%, while tetrabutylammonium hydroxide showed an induction time of 0.74 h at 1 wt% concentration.

     

Situational and dispositional predictors of displays of positive emotions

The study examined the effects of situational (store busyness and customer demand) and dispositional (extraversion, neuroticism, and psychoticism) factors on the display of positive emotions. We found that for situational factors, customer demand was positively related to displayed positive emotions. For personality factors, extraversion was positively related to displayed positive emotions and neuroticism was negatively related to displayed positive emotions. Usefulness analysis showed that both situational and personality factors contributed significantly to explain the level of positive displayed emotion. Copyright © 2003 John Wiley & Sons, Ltd.