Competing Rates in Mixing Sensitive Processes: Test Cells and Models for Robust Design from the Bench Scale (1L) to the Mega-L and micro-L Scales

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There are two interesting global trends to watch in chemical process engineering. In Europe, land is scarce and there is a strong commitment to process intensification. This has led to the development of micro-reactors which are extremely small (volumes of the order of micro-litres). In the global commodity chemicals market, economies of scale drive process design and "record capacity" plants are regularly commissioned. These reactor volumes are typically 1 Mega-litre. Two important industries in Canada, oil sands extraction and mineral processing, require some of the largest vessels in the world. These two industries also face difficult problems in multi-phase and partially-miscible multi-component mixing.Nano-technology has taught us that dramatic changes of scale require a shift in thinking: the physics stays the same but the dominant variables change. On moving from the litre to the micro-litre scale, the particle mass becomes negligible and tiny surface charges become extremely important. On moving from the 1L to the 1 ML scale, the blend time becomes so long relative to the key process time-scales that it is essentially infinite. At the Mega-Scale, local mixing conditions become extremely important and often dominate process performance.To successfully design and operate 1ML process vessels, clear mixing specifications are needed. The relationship between the local mixing conditions and the important process rates (e.g. reaction rates) must be defined. Two innovative test vessels provide tightly controlled mixing which satisfies this need. The first has been applied to scale-down of nano-particle precipitation; the second has successfully predicted improved demulsifier performance at the Mega-Scale. In this research these test cells find two new applications, developing the fundamental theory and models which will allow robust mixing design from the micro-litre to the Mega-litre scale.