Experimental characterization of a novel, multistage, countercurrent, cavitational solid-liquid extractor and its applicability to agro-food industrial waste valorization

The purpose of the thesis is to study a novel, multistage, countercurrent, cavitational solid-liquid extractor and its applicability to agro-food industrial waste valorization. The machine taked into consideration, named TURBEX, consist of a hydrodynamic cavitational extractor. During the period of development of the thesis, by participating in an internship with Andritz, it was possible to take part in various functional tests carried out on the prototype in its development phase. It was possible to collect two samples of the extract, one for each matrix tested, and some matrix samples before and after the extraction. The analyses on solid matrices are carried out at the DISAT laboratories of the Polytechnic of Turin and have the aim of calculating the variation of some parameters of the matrix following extraction. In particular, the variation in the bulk density, the moisture content, the static angle of repose and the particle size distribution are calculated. The analyses on the two extracts are instead conducted at the chemistry laboratories of the University of Turin, with the aim of determining the extraction efficiency of TURBEX by comparing it with a single-stage reference extraction. The analyses carried out show that the theoretically expected results are respected during the TURBEX extraction process. The experimental yields and number of countercurrent stages results, obtained from the analysis of the extracts and the functional parameters of the extractor, have been used for the design of two plants for the valorisation of two agro-industrial residues produced in large quantities at European and global level: olive leaves and brewer's spent grain. The first plant is, located in Turkey where the cultivation of olive trees to produce oil is widespread. The plant can process 25,000 tons of leaves a year, working over a period of twenty weeks a year close to the months of olive harvesting and tree pruning. The plant leads to the production of an extract in powder form with a capacity of about 2.5 tons per year and a concentration of oleuropein equal to 33%. The product thus obtained has a commercial value of about 20/25 euros per kilo. The second plant is designed a plant based in Siberia, in the province of Novosibirsk. The plant treats 20,000 tons per year of BSG and aims at the production of four distinct products: a lipid fraction obtained with a capacity of 45 tons per year, having a commercial value of 1 euro per kilogram; a polyphenol rich powder with a capacity of 93,6 ton/y and a value of 50 euro per kilogram; a Protein powder with a capacity of 1161 tons/y and a value of 2,5 euro/kilogram; a dietary fibers powder with a capacity of 1161 tons/y and a value of 0,10 euro/kg. In conclusion, the development of the thesis project led to a first test phase of the industrial prototype of the TURBEX cavitational extractor. This study made it possible to have a first idea of the potential of the machinery, confirming the expected results and paving the way for future evaluations. It has also been shown that the machine is able to be effectively inserted into industrial processes, achieving excellent performances.