Ros Roca Anaerobic Digestion
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The digestion process of Ros Roca is a wet technology and applicable for different types of organic waste. According to the quality of the organic waste different types of bunkers for receiving the waste are applicable. For reception of humid organic waste a closed deep bunker is very suitable. The bunker is discharged automatically with screws and a pump and can be cleaned afterwards. Also flat bunkers or deep bunkers with cranes can be used. The first step in the process is a wet pre-treatment. First of all the organic waste is mixed with process water in a turbomixer and a suspension with a solid concentration of up to 15 % is produced. It is possible to separate out of the turbomixer impurities like glass, stones or bones by means of a grit system The turbomixer is then discharged by hydraulic flow to a screening unit which separates floating material like plastic, wood and other non biodegradable structural material. The suspension passes the screen flows through an aerated sand trap where small inert particles like sand, glass, stones are separated. The result of an efficient wet pre-treatment is a suspension strongly enriched with biodegradable material and almost free of impurities. The suspension then passes a crushing unit to ensure that only particles with a size of less than 12 mm are charged via a suspension buffer tank to the sanitation process. The sanitation process works under batch conditions in mixed tanks. Thereby short circuit flow is safely precluded. The retention time as well as the sanitation temperature are controlled and monitored continuously. The exhaust heat from the co-generation unit is usually used for the sanitation process. After successful sanitation the suspension is charged continuously to the digester for anaerobic treatment. A digester without any moving aggregates inside is used in the process to ensure a high availability. For mixing the digester compressed biogas is used. The produced biogas is normally used in co-generation units for electricity production. The digestion process itself is characterised by a low electricity consumption and a high surplus of electricity which is very important for the economy of the plant.
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