The Fear of Fouling and Solid Streams – Overcoming this Barrier to Improve Energy Efficiency in Intensified Processes

In streams and unit operations where solid particles may be present or anticipated most process engineers recognise that they can lead to fouling, ultimately blocking heat transfer channels and plant failure. Other difficulties may be associated with abrasion, separation challenges and particle size classifcation. Introducing the adjective 'smaller' into the definition immediately – for a process engineer – flashes a 'caution' warning. The implied size reduction in plant is the principal feature of 'process intensification' – a familiar example of which is a compact heat exchanger with, for example, 2 mm diameter tubular flow passages. Process intensification (PI) grew in importance in the chemical processing industry and may be concisely defined as: Any chemical engineering development that leads to a substantially smaller, cleaner, safer and more energy efficient technology. Its application is not limited to the chemicals sector, however. If one rephrases the definition in terms of heat and mass transfer enhancement – the main methods by which plants handling fluids can have their performances improved, the scope becomes much wider. A major part of the Euro10 million project involves demonstrating, in pilot plant or at full scale, the energy, environmental and economic benefits of PI in sectors including metal ore processing (using flash flotation), ceramic powder drying and granulation, including the use of toroidal fluidised bed technology, and microwave-assisted drying of pharmaceuticals. The Coflore chemical reactor forms the basis of a Case Study specifically dealing with solid particles, and the technique may have wider applications. Another Case Study in Italy involves intensifying high density ceramic powder production using highly efficient classification methods. The paper presents information on some of the intensified technologies that might be applied to the sectors targeted in the IbD study – which include pharmaceuticals, mineral and metal processing, ceramics and chemical reactions in the presence of solids – and the likely energy and environmental benefits.