Pumps with extended service life for generating biogas from organic waste


Courtesy of ALLWEILER GmbH

When regular commercial pumps are used to process organic waste, they typically wear out after only a short period of time. Liquids pumped under these conditions attack pumps from two different angles: first with highly abrasive additives and second with liquids that have highly fluctuating pH values and therefore a high level of chemical aggressiveness. These conditions are very tough on seals and elastomer stators. As a result, these parts must be changed often, increasing downtime.

BioEnergie GmbH, located in Austria’s wine-growing region, has found a solution. This company collaborated with plant builders Komptech Anlagenbau GmbH and Allweiler AG to optimize the materials used in these pumps. The results are significantly longer service lives, even for pumps located at the beginning of the process where they are attacked the most.

Organic waste with packaging materials
The plant receives all conceivable types of organic waste. Household waste, leftover food, restaurant waste, and plant material are a few examples of the materials that find their way to the plant. Total volume is approximately 15,000 metric tons every year, 5000 metric tons of which are sent to a dump or used as fertilizer.

All waste is received in its packaging and processed without being separated. Examples of this include glass, metal lids and seals, wooden pallets, plastic packaging, and even metal drums. The first step in the process reduces the material to a grain size of no larger than 60 mm. Once reduced in size, a conveyor belt carries the material to a separation container. Process water is added, causing heavy extraneous materials to sink to the bottom where they can be removed. The remaining liquid contains 10% to 15% dry substance and a minimum pH of 4. A sieve retains solids with a diameter of greater than 12 mm before the first progressing cavity pump carries the mass to the grit separator. This is a AEB1E-series pump capable of moving up to 60 m3 per hour. Due to the highly variable chemical properties of the liquid and the presence of sand and other abrasive solids, this pump must be able to handle a high level of stress. Organic waste in particular has a highly variable composition, but it almost always contains sand, gravel, and glass.

ALLWEILER pumps for every process step.
The same or similar Allweiler progressing cavity pumps are used in the subsequent process steps. In total, the plant utilizes eleven progressing cavity pumps. They move the biomass from disinfection to the biogas reactor and then to the separator in addition to pumping process water within the plant.

Important characteristics for achieving a long pump service life are slow speeds and high quality materials. BioEnergie GmbH has chosen to run the pumps at about 200 rpm. In order to achieve the required pump capacity of up to 100 m3 /hour at such low speeds, the plant utilizes large pumps equipped with frequency-converter control.

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