Report on continuous operation of the TORWASH® pilot plant for the treatment of fruit & vegetable waste
The F-CUBED pilot plant operated for a total of 472 hours, producing 10,652 kg of TORWASH® effluent, corresponding to 22.8 kg per hour. Dewatering of the effluent resulted in 117 kg of dry press cake which was converted into 104 kg of pellets by CPM EUROPE. For every 1000 kg of effluent, 11 kg of dry press cake was produced. In the early days of the long-duration testing, it was shown that the process was highly sensitive to the operation temperature, with small fluctuations resulting in a drop in product yield and a reduced dewaterability of the effluent slurry. Therefore, some modifications were implemented to make the process less sensitive to temperature fluctuations, resulting in a more consistent dewaterability and quality of the produced solid cake.
Salts such as chlorine, potassium and sodium are commonly found in biomass and can cause corrosion, ash slagging and agglomeration when burned. Therefore, the quantities of salts in biomass must be reduced by 10 to 20 times to be within acceptable levels of thermal conversion standards. The TORWASH® reactor operates at relatively mild temperatures (150 – 250 °C) and results in fibres in the wet residues becoming brittle, allowing for more efficient dewatering and removal of salts that have dissolved in the process, resulting in a higher quality bioenergy pellet and less disruption and complications during the thermal conversion process. With the F-CUBED process the bulk of the sodium and potassium is effectively removed from the solid material and a large part of the total ash content and chlorine is removed from the solids.
Overall, The F-CUBED process was able to reduce the volume of the orange peel waste stream by 85% and achieve almost 90% moisture removal from the orange peel feedstock without applying additional chemicals or flocculation agents. Once obstacles surrounding operating temperature and solid capture were overcome, the F-CUBED pilot plant showed that continuous operation and significant reduction to the volume and moisture content of orange peel waste residue can be achieved, and the remaining solids could be successfully converted into intermediate bioenergy carriers (pellets).