Olefins from conventional and heavy feedstocks: Energy use in steam cracking and alternative processes

Steam cracking for the production of light olefins, such as ethylene and propylene, is the single most energy-consuming process in the chemical industry. This paper reviews conventional steam cracking and innovative olefin technologies in terms of energy efficiency. It is found that the pyrolysis section of a naphtha steam cracker alone consumes approximately 65% of the total process energy and approximately 75% of the total exergy loss. A family portrait of olefin technologies by feedstocks is drawn to search for alternatives. An overview of state-of-the-art naphtha cracking technologies shows that approximately 20% savings on the current average process energy use are possible. Advanced naphtha cracking technologies in the pyrolysis section, such as advanced coil and furnace materials, could together lead to up to approximately 20% savings on the process energy use by state-of-the-art technologies. Improvements in the compression and separation sections could together lead to up to approximately 15% savings. Alternative processes, i.e. catalytic olefin technologies, can save up to approximately 20%.     

Using non-food information to identify food-choice segment membership

Food companies, governments, and societal organizations use an increasing number of food-choice motives to persuade consumers to buy food products, and the question which combinations of motives matter for which type of consumer has become of central relevance. In this study, we use a concomitant mixture-modeling approach to uncover consumer segments in terms of food-choice motives, using a nationwide sample in the Netherlands. The results reveal seven segments with distinct profiles and demonstrate that age and membership of environmental organizations play an essential role in segment membership probabilities. Our findings support the idea that information about non-food-related consumer behavior improves the identification of segments. In an additional analysis, we demonstrate how organizational membership also provides an effective way to access consumer segments as compared to diverse media outlets. We discuss the implications of our findings for segmentation practice.     

Assessment of bottom-up sectoral and regional mitigation potentials

The greenhouse gas mitigation potential of different economic sectors in three world regions are estimated using a bottom-up approach. These estimates provide updates of the numbers reported in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). This study is part of a larger project aimed at comparing greenhouse gas mitigation potentials from bottom-up and top-down approaches. The sectors included in the analysis are energy supply, transport, industry and the residential and service sector. The mitigation potentials range from 11 to 15 GtCO₂eq. This is 26–38% of the baseline in 2030 and 47–68% relative to the year 2000. Potential savings are estimated for different cost levels. The total potential at negative costs is estimated at 5–8% relative to the baseline, with the largest share in the residential and service sector and the highest reduction percentage for the transport and industry sectors. These (negative) costs include investment, operation and maintenance and fuel costs and revenues at moderate discount rates of 3–10%. At costs below 100 US$/tCO₂, the largest potential reductions in absolute terms are estimated in the energy supply sector, while the transport sector has the lowest reduction potential.     

A simplified modeling approach using microbial growth kinetics for predicting exposure concentrations of organic chemicals in treated wastewater effluents

Various mathematical relationships have been used to assess exposure concentrations of organic chemicals when emissions occur via wastewater treatment. These relationships range from a simple removal factor calculation to more sophisticated approaches using kinetic based mathematical models. While these existing approaches have been used by decision makers to screen new chemicals for exposure assessments, they all have limitations in the predictive capabilities. Thus, a simplified modeling approach grounded in sound scientific fundamentals that utilizes relatively easy to obtain input parameters is needed. In this paper a simplified modeling approach that utilizes microbial growth kinetics was developed for predicting effluent concentrations in secondary biological wastewater treatment systems. Receiving water predicted exposure concentrations (PEC) are assessed by using a dilution factor. One advantage of this approach is that it allows for wastewater treatment plant effluent concentrations, and therefore receiving water exposure levels, to be predicted with a minimum amount of experimental data. It also provides quantitative data that can be used to assess the relative biodegradability of different chemicals for use in regulatory and risk assessment activities.     

Domain-integral analysis of channel waveguides in anisotropicmultilayered media

A domain-integral equation method is presented to determine both propagation constants and the electromagnetic field distributions of guided surface wave modes in integrated optical waveguides. Both the waveguide and its multilayered embedding are anisotropic. The permittivity tensor of the embedding is assumed to be piecewise homogeneous. The kernels of the domain-integral equations consist of Green's tensors. The integral equations form an eigenvalue problem where the electric field strength represents the eigenvector. This problem is solved numerically by applying the method of moments. Numerical results are presented for an anisotropic ridge waveguide, embedded in an anisotropic multilayered medium     

A normalized approach to the design of low-loss optical waveguidebends

A normalized approach for optimal design of abrupt junctions between straight and curved waveguides operating in the whispering gallery mode regime is presented. The optimization includes the widths of both the straight and the curved waveguides, the lateral offset between them, and the bending radius of the curved waveguide. With this approach, optimum bend design is possible from a simple set of formulas or normalized graphs. Predicted transmission losses for optimally designed junctions are well below 0.1 dB     

Chirping of an MMI-PHASAR demultiplexer for application in multiwavelength lasers

We report the first chirped multimode interference-based phased-array (MMI-PHASAR) for application in multi-wavelength lasers (MWLs). To avoid wavelength ambiguity in MWLs, undesired orders are suppressed by chirping the array of arms in the demultiplexer. Simulations show that a suppression of adjacent orders of more than 2 dB can be achieved. A 1/spl times/5 MMI-PHASAR has been realized in which the effect of the chirping is clearly visible according to the simulations.