The conversion of a BMA diffuser to a Bosch Projects chainless diffuser - the first season's experience.

During 2005, the UCL sugar factory was faced with the prospect of major costs on their BMA diffuser, including a chain replacement, drive repairs and the possible prohibitive cost of future capacity expansion. Bosch Projects introduced UCL to the concept of the chainless diff user, and a study showed that their BMA diffuser could be converted to the chainless design at a lower cost than the alternative maintenance costs. The conversion would also allow for cost-effective future expansions. A pilot plant was designed and installed at the UCL factory to test the chainless diffuser concept and to gather data for the conversion of the BMA diffuser. After successful trials, the design for the conversion of the BMA diffuser was carried out by Bosch Projects and the conversion performed in January and February 2006, with the milling season starting late in February. Performance results since commissioning are reported and compared with the diffuser performance prior to the conversion. Maintenance experience and costs are reported. Because this was the first installation of a novel design, compromises were made to allow for re-instatement of the old diffuser had this been necessary. In particular, the old perforated floor was initially retained, with the new chainless deck installed above it. This created a chamber in which fibrous deposits accumulated, causing blockages and sucrose destruction. At the time of writing, the chainless diffuser has been in operation for 9 months, achieving comparable throughput performance despite the reduced bed height. The extraction performance is a little less than that of the BMA diffuser at this time. This is explained by the initial compromises. Teething problems and design shortcomings have been identified. Some of these have been corrected while the rest will be addressed during the 2006-07 off-crop. This paper reviews the patented chainless diffuser concept, describes the pilot plant and the conversion of the BMA diffuser to a Bosch Projects Chainless Diffuser, and the operational and maintenance performance since commissioning.