At the beginning of 2018, the consortium of plant manufacturers WELLE (China) and E-Square Environment and Engineering Co., Ltd. (Thailand) received an order from A2 Technologies Co. Ltd. for the construction of a mechanical biological waste treatment plant for mixed household waste at the On Nut Solid Waste Disposal Center in Bangkok. The "Maximum Yield Technology" (MYT) process developed in Germany at the On Nut Solid Waste Disposal Center in Bangkok separates the high-calorific fraction from the mixed household waste and treats and dewaters the organic fraction biologically. The substitute fuel (RDF) produced with the MYT plant will then be mixed in future with the waste to be incinerated in the thermal waste management systems to increase the calorific value.
Photo 1: E-Square, A2 and WELLE, signing the contract
Construction work on the MYT plant began in September 2018. At the same time, the mechanical engineering components were manufactured in China.
Photo 2: Aerial view of the MYT construction site On Nut February 2019
After separation of the larger waste contents in two sieve drums, the sieve overflow is energetically utilized in various thermal plants. The screen undersize grain is fed into a percolation system.
Photo 3: At the factory acceptance test of the screen drum
The percolation consists of four vertically arranged plug flow reactors (multi-zone reactor MZR). The acidification of the organic components of the waste takes place in the reactors. Each reactor has a volume of 450 m³. The waste is mixed and homogenized in the reactor with a slow-running agitator. The hydrolysis of the organic components of the waste and the spatially separated methane production enables the treatment of large quantities of waste with short residence times. The low pH value in hydrolysis also prevents waste precipitation, a common problem with existing fermentation technologies.
After a residence time of only 2.5 days, the waste is then dewatered using screw press separators. Part of the process water is returned to the hydrolysis reactor for further leaching of the organic acids onto the waste surface. The percolate collected at the reactor bottom is then fed to the anaerobic stage together with the liquid phase of the press screw separators. The anaerobic stage consists of 4 reactors with a volume of 3,800 m³ each. There, the washed-out organic acids are converted to 43,000 m³ of biogas per day. The biogas is converted into electricity and heat in a combined heat and power plant. In this way approx. 32,500 MWh/a of electrical energy are generated.
The solid phase from the dewatering is mixed with the screen oversize of the screen drum. The substitute fuel produced in this way then reaches a calorific value greater than 10,000 kJ/kg and is used in several thermal recycling plants to increase the calorific value.
Mr. Suriyon Udcharchon, Managing Director of A2 Technologies Company Ltd. said: "After intensive discussions with various technology providers, WELLE/ESQUARE was selected as our partner for the supply of the technology. The plant will go into operation at the end of 2019 and process approx. 280,000 t/a of mixed waste into approx. 190,000 t/a of substitute fuel and biogas. The mixed waste delivered in Asia is much wetter and contains more organic matter than the waste in Europe. The MYT technology is ideally suited for such waste. The experienced consortium partners from Thailand and China as well as the technical conception and support from Germany have convinced us both technically and economically".
Photo 4: 3D animation of the future plant On Nut
After completion of the first constructional measures, the equipment was delivered to the plant at the beginning of March. The conveying technology, the screening drums, the reactors and the anaerobic biogas plant will be supplied by WELLE, Changzhou.The treatment of the waste water will be supplied by Esquare in cooperation with the German plant manufacturer WEHRLE Umwelt GmbH.
With the start of assembly of the components in March 2019, the Kahlenberg Waste Disposal Association (ZAK) Supervisory Board visited the plant location and was informed on site about the construction progress and the technical implementation of the plant.
Over the next six months, the delivered individual components will be assembled at the site to form a MYT plant. Commissioning is expected to start in October. This will make the MYT On Nut plant the world's largest and first plant in Southeast Asia.
Mr Gibis, head of the ZAK, was very impressed by the system components that have been implemented to date: "The components manufactured in China meet German quality standards. The cooperation with the Chinese MYT licensee WELLE has worked very well so far. We hope that following the successful commissioning of the plant in Bangkok, other Municipalities, cities and waste disposal companies will also be interested in the technology we have developed“.
Photo 5: Members of the ZAK Supervisory Board visiting the MYT construction site on site
Dr. Yuezhong Li, Chairman of the WELLE Group, says: "The Kahlenberg plant built in Germany sets global standards for modern, environmentally friendly waste disposal and recycling. In recent years, many potential interested parties from Asia have visited the plant in Germany, and the response from visitors has been very positive throughout. We hope that the On Nut plant will also be a showcase for MYT technology in Asia in the future".
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