Superheated steam drying of Brewer’s spent grain in a rotary drum

Relative to conventional air drying, superheated steam (SHS) drying provides a number of benefits such as increased efficiency, reduced risk of fire and explosion, sterilization, deodorization and faster drying rates. Brewer’s spent grain (BSG) is the by-product from beer brewing. It is a sticky material with a tendency to foul drying equipment. This paper evaluates the drying behaviour of BSG in a pilot-scale rotary SHS dryer. The evaluation is based on product moisture content, measurements of sticking and energy consumption. The results of an experimental design for three system parameters (steam temperature, steam velocity and feed rate) are presented for two processing levels. The critical parameters with the most significant effect on the moisture content are the feed rate and the inlet steam temperature. The sticking profile was found to vary exponentially along the drum length. A correlation between sticking and product moisture content was obtained and the operating conditions which minimize sticking were determined. An evaluation of the energy consumption showed that around 70% of the heater energy was used in drying. The remaining energy is lost due to surface losses and cold air ingress. This study has demonstrated that BSG can be dried successfully and efficiently with the proposed technology.