Capture of carbon dioxide by an ion-exchange resin: Influence of gas humidity on capture mechanisms

This paper evaluates moisture content effects on CO₂ capture of an ion-exchange resin (IER) functionalised with a primary amine group. IER capacities were determined by breakthrough with an inlet gas containing 10 vol% CO₂, nitrogen and various moisture contents. Three types of behaviour were identified according to humidity level. In saturated air conditions, the stoichiometry could be justified by carbonates and bicarbonates fixation. In dry conditions, we suspect a joint physical adsorption and reaction mechanism. For intermediate humidity, the stoichiometry of 1 CO₂ for 1 amine group is consistent with a bicarbonate fixation or carbamic acid formation.     

Underground production scheduling with ventilation and refrigeration considerations

Underground mine production scheduling determines when, if ever, activities associated with the extraction of ore should be executed. The accumulation of heat in the mine where operators are working is a major concern. At the time of this writing, production scheduling and ventilation decisions are not made in concert. Correspondingly, heat limitations are largely ignored. Our mixed-integer program maximizes net present value subject to constraints on precedence, and mill and extraction capacities with the consideration of heat using thermodynamic principles, while affording the option of activating refrigeration to mitigate heat accumulation. In seconds to hours, depending on the problem size (up to thousands of activities and 900 daily time periods), a corresponding methodology that exploits the mathematical problem structure provides schedules that maintain a safe working environment for mine operators; optimality gaps are no more than 15% and average less than half that for otherwise-intractable instances.

     

From cassava to gari: mapping of quality characteristics and end-user preferences in Cameroon and Nigeria

User’s preferences of cassava and cassava products along the value chain are supported by specific root quality characteristics that can be linked to root traits. Therefore, providing an evidence base of user preferred characteristics along the value chain can help in the functional choice of cassava varieties. In this respect, the present paper presents the results from focus group discussions and individual interviews on user preferred quality characteristics of raw cassava roots and the derived product, gari, – one of the major cassava products in Sub-Saharan Africa – in major production and consumption areas of Cameroon and Nigeria. Choice of cassava varieties for farming is mainly determined by the multiple end uses of the roots, their agricultural yield and the processing determinants of roots that support their major high-quality characteristics: size, density, low water content, maturity, colour and safety. Processing of cassava roots into gari goes through different technological variants leading to a gari whose high-quality characteristics are dryness, colour, shiny/attractive appearance, uniform granules and taste. Eba, the major consumption form of gari in Cameroon and Nigeria, is mainly characterised by its textural properties: smoothness, firmness, stickiness, elasticity and mouldability. Recommendations are made, suggesting that breeding will have to start evaluating cassava clones for brightness/shininess, as well as textural properties such as mouldability and elasticity of cassava food products, for the purpose of supporting decision-making by breeders and the development of high-throughput selection methods of cassava varieties. Women are identified as important beneficiaries of such initiatives giving their disadvantaged position and their prominent role in cassava processing and marketing of gari.     

Compatibility Tests for Some Model SAE 30-50 Engine Oil Formulations and Correlation of Properties

A series of laboratory tests have been conducted on commercially available model engine oils of SAE 30-50 grades obtained from different oil companies operating in Nigeria. Experimental analysis showed that these model oil formulations conform to certain standards governing their constituents and performance. All the samples have high viscosity index of 100 and above. Their pour points indicate low temperature fluidity and suitability to be used in cold weather conditions. Data correlation shows that viscosity and viscosity gravity constant (VGC) can be adequately used to characterize the oil samples. The semi-logarithmic plot of VGC against viscosity at 40°C produced the best correlation. The study further proves that VGC should find a wider application as a correlating parameter for the physical property of model oils.     

Graphite-Filled Polyethylene/Epoxy Blend for High-Conductivity Applications: The Immiscibility Edge

ABSTRACT

Polyethylene (PE)/epoxy blends filled with graphite were prepared and studied in this work. The in-plane and through-plane conductivities of the composites increased from 11.68 Scm^?1 to 73.11 Scm^?1 and 0.20 Scm^?1 to 4.12 Scm^?1, respectively, as graphite content increased from 30 to 80 wt%. Phase bonding effect of the compatibilizer and reinforcing effect of the filler enhanced the flexural modulus and strength of the composites up to 70 wt% filler content. The electrical conductivities attained by these composites being significantly higher than comparable composite formulations in literature show the edge of immiscible PE/epoxy blend for achieving high-conductivity polymer composites.