24 November 2009

Fermentation plant upgrades QZ

Municipal waste disposal works invests in Querstromzerspaner

The fermentation plant in the county of Böblingen is configured for an annual through-put of biological waste of 30,000 metric tonnes. However, the technology that was originally deployed quickly reached its limits due to the different composition of the supplied material in biological waste bins. The municipal waste disposal works has now invested in the Querstromzerspaner made by MeWa. In doing so, they have optimised the entire process of disposal.

With the annual throughput volume of 30,000 metric tonnes and a maximum power output of around 1.5 Megawatts (electrical), the fermentation plant in Leonberg is one of the largest in Germany.

However, the reality used to be different. The target value appeared to be unattainably high for the two block-type thermal power stations because the actual gas yield was significantly lower than the plant design seemed to promise. To increase the economic efficiency and to reduce the vulnerabilities for extraneous material, the plant operators began looking for a technology that could replace the shredders that has been used to date.

The local council found what they were looking for at MeWa: the patented Querstromzerspaner. With its chains, the machine processes the initial materials significantly more efficiently, exposing packaging materials, plastics, textiles, pieces of wood or bones. Even pieces of metal are no obstacle for the QZ (which in fact has its origins in recycling technology).

After separation, around 30 metric tonnes of iron parts and 300 metric tonnes of other non-organic wastes, for the most part plastics, accumulate in the Leonberg fermentation plant every year. Until now, the material was inadequately broken down by a first shredder, which meant it had to run through a second granulation stage and was then fed back into the grading screen. Even then, the plant operators identified an inorganic proportion in the separated material that was much too high. The multiple runs in the granulation stages also meant that extraneous materials were granulated further, thus enabling them to enter the fermenter. The two shredders and the return circuit have since been removed from the process.

A scrapping belt conveyor is now transporting the input material directly into the QZ. The material is perfectly processed in only one work step. Metal and other packaging is removed from the screened organic material, which can now be transported directly into the storage bin and pumped into the fermenter.