Triboelectric separation of a starch-protein mixture – Impact of electric field strength and flow rate

Triboelectric separation is a method for separating dry particulate systems due to their different electrostatic chargeability. Previous applications are limited to the separation of coarse powders. The aim of the present study is to examine the influence of the flow conditions and the influence of the electric field strength on the separation efficiency of starch and protein particles. Very fine organic powders are separated in a simple bench scale electrostatic separator to extend this technique to powders below 50?µm. The influence of different gas flow rates in the turbulent flow regime on particle charging and subsequent separation is investigated.As an organic model substrate, a mixture of barley starch and whey protein was used. The tribocharger consists of a PTFE charging tube and a rectangular separation chamber where an electric field is applied between two electrodes. The particles are conveyed through the charging tube and charged by frictional contact with the tube wall. It is shown that different gas flow rates at a turbulent flow regime in the charging tube did not change the separation characteristics. In contrast, increasing electrical field strength increases separation efficiency of protein particles regardless of gas flow conditions. The proportion of starch at the anode is the same for all the investigated parameters.     

Energy-saving occupant behaviours in offices: change strategies

As regulated energy consumption in buildings is reduced, the proportional importance of unregulated energy consumption increases. Reducing unregulated energy use in the commercial office requires an understanding of the factors that influence workplace behaviour. To date these factors have been assumed to be similar to those that influence behaviour in the home. However, the social dynamics of the workplace are different to those in the home. This study examines the degree to which theories of behaviour change generated largely in a domestic building setting could be used as the basis for designing interventions to reduce unregulated energy consumption in the workplace. It studies the unregulated energy consumption of 39 workers engaged in office-type activities in two separate locations. Following a 100-day monitoring period, three behaviour change interventions were developed and their impact measured over a 100-day period. Results from the study found, on average, an 18.8% reduction in energy use was achieved. Furthermore, by comparing pre- and post-intervention responses to an environmental questionnaire, it was evident that savings were realized without significant changes to pro-environmental attitude or perceived social norms, which may have implications for energy-saving interventions in the commercial sector.