Austrian-German waste processing technology firm, REDWAVE, has designed the process for a Mechanical Biological Treatment (MBT) plant which will pretreat destined for a waste to energy plant in the City of Lianyungang, Shandong Province north of Shanghai, China.
Presenting its design at the 7th International Symposium MBT, MRF & Recycling 2017 in Hannover, Redwave’s Tim van Heeswijk said that with more than 200 waste to energy plants already operating in China, MBT pretreatment is an ideal pretreatment to reduce the high moisture content of China’s waste.
Compared to Europe China’s household waste has a relatively high content of organics and moisture, so when incinerated a lower energy efficiency is achieved. Depending on regional conditions the calorific value of MSW in China is in the range of 3 – 6.7 MJ/kg, which is far less than the 9 - 11 MJ/kg in Europe.
The client, China Jinjiang Environment, placed the order with REDWAVE for the supply, installation and commissioning of the Lianyungang MBT plant.
The MBT is designed for an annual throughput capacity of 273,750 tonnes based on a daily input of 750 tonnes. The client ́s request was to increase the calorific value by drying the waste from an incoming moisture of 50% to a maximum moisture content of 30%.
REDWAVE explained that starting from a deep bunker a fully automated delivery crane conveys the waste into the hopper of the pre-shedder.
Via an overbelt magnet for ferrous separation the pre-shredded material is fed to an intermediate bunker. From there a fully automated overhead gantry crane conveys the waste to one of the 18 biodrying units. When ambient or re-circulated air ventilates the material in the box it heats up by an aerobic microbiological process.
The water is discharged of the drying box in the form of water vapour and the dry material remains in the box. Due to the individual control of each box it is possible to guarantee even and efficient drying.
The company added that relevant data such as the flow rate of circulated and fresh air, heat output capacity and the temperature curves are analysed in the process control.
Each biodrying unit has a removable lid on top designed as self-supporting insulated steel structure. The drying process inside the unit proceeds independently from the outside climatic conditions.
After the biodrying, the dried waste is processed in various steps including screening, airstream sorting, shredding, overbelt magnets, eddy current separators (ECS) and REDWAVE sensor based sorting systems and is turned into a high quality homogenous solid recovered fuel (SRF).
The biological drying and subsequent mechanical treatment increases the calorific value from 3 – 6.7 MJ/kg to approximately 12 – 14 MJ/kg.
The plant is currently under construction and is scheduled for compeltion at the end of 2017.
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