Drying systems are energy-hungry pieces of equipment, using as much as 10-15% of all energy expended in industry in developed countries. The main reason is the heat supply required to evaporate moisture in the product. The drying technique and associated options that are chosen thus influence the profits of the operator significantly. The need to comply with environmental regulations further complicates matters.

By analysing energy use, starting from the amount of heat inherently required by the process, various cost-saving opportunities can be identified. These may include reducing overdrying, reducing the initial moisture content of the product, changing dryer operating parameters or improving the energy supply system.

The heat source can be changed or augmented by using heat pumps, incorporating a combined heat and power (CHP) system or adopting alternative fuel sources. The feasibility of some of these process changes can be determined by means of pinch analysis.

Among the factors influencing the choice of energy source are:

• Fuel price and availability.
• The application and whether it allows for direct drying. This is seldom the case when product contamination is unacceptable.
• The energy recovery possibilities and additional costs (handling, waste management etc.) associated with the fuel.

Each feedstock type and set of operating conditions should be assessed independently to determine the merits of the available options.