German dryers help increase returns

Feb. 22, 2012, Duren, Germany – Renewable energies are becoming increasingly important as substitute for fossil and nuclear energy sources. According to estimates by experts of the International Economic Forum of Renewable Energies (IWR), they provided almost 20 percent of Germany's power requirement in 2011. The German Government is promoting power generation from water, sun, wind and biomass through legal provisions and state subsidies. During the recycling of biomass, digestate dryers make a valuable contribution to increase the returns of biogas plants. As one of Germany's leading manufacturers of dryers for pumpable or spreadable digestates, NEWeco-tec Verfahrenstechnik GmbH has established itself in the market within three years. For the container-based construction of the patent-pending, compact low-temperature belt dryers, the company located in Mühldorf am Inn relies on process belt technology from GKD – Gebr. Kufferath AG.

Instant success

In 2008, NEWeco-tec Verfahrenstechnik GmbH was founded by Christian Wenner. Prior to this – after completing his studies in mechanical and process engineering at Munich Technical University – he held management positions with various machinery and system manufacturers in the areas of drying, biogas plants and digestate treatment. His business idea of drying digestates in standardized sea containers on belt dryers addressed a real gap in the market. Together with marketing expert and co-partner Martin Bickel, the first two plants were sold straight from the drawing board.

In 2008, Christian Wenner founded the NEWeco-tec Verfahrenstechnik GmbH. Image courtesy of GKD. Advertisement

Just shortly after start-up of the plant, the neighbors realized its' potential and also had their harvested products, like rapeseed, linseed, grass seed, grains and maize kernels dried for increased storage life. At the same time, the first two-belt dryer started operation in Lower Saxony.

Since 2008, Christian Wenner has installed about 100 belt dryer units with more than 525.600 kW heat output per year through NEWeco-tec. In addition to engineering, the complete set-up of each compact dryer, including functional test and customized painting, takes place at the in-house facility. German-based production and turn-key shipping ensure high quality and performance of the plants. Three to five days after delivery, the NEWtainer compact belt dryers are ready for operation. There is an enormous demand: Each week at least one compact belt dryer leaves the factory.

Versatile plant

The concept of the compact belt dryer, marketed by NEWeco-tec under the name NEWtainer, is as convincing as it is efficient: In contrast to conventional dryers, process optimization is based on heating the product as well as allowing free flow through the product, not the space. Prerequisite for this process is a reliable airtight space in which negative pressure is used to draw warm air through the substrate via a suction fan located below the dryer belt. Christian Wenner recognized the required potential in ship containers, same as used for combined heat and power units. Applying the container construction to his concept allowed him to offer cost-effective standardized, space-efficient, portable and expandable plants with certified statics from a standing start. The containers are weatherproof, highly versatile, robust and quickly available. Complete interior wall cladding made of stainless steel ensures permanent corrosion resistance and durability. Since the construction is made entirely of industrial components, the plants withstand continuous 24/7 operation. Due to their standard dimensions, the containers – even with superstructures – allow regular transport on trucks and modular expansion if necessary.

Construction as needed

The construction of the compact belt dryers is based on a platform principle: Four different models are available. Depending on desired heat absorption and size, the NEWeco-tec compact belt dryers are equipped with one or two belt dryers, fans and heat exchangers.

Containers by NEWeco-tec are clad with stainless steel from the inside. Image courtesy of GKD.

For large-scale plants, a corresponding number of containers with a length of 6 meters are lined up crosswise to achieve the required dryer length. According to the required belt length, the control and exhaust air units are located either inside the container or in an additional container superstructure. Feeders that can be filled directly from the outside or equipped with upstream separators are used to apply the substrate to be dried in an even 100 – 200 mm thick layer on an endless, air-permeable synthetic mesh belt type Conducto 5065. A high-performance heat exchanger positioned above the belt supplies the required process temperature via the heat from a connected biogas plant or an adjacent CHP. Industrial fans positioned below the belt draw the warm air through the substrate layer and the belt by means of negative pressure.

In the process, the air is charged with moisture. A radial fan is used to transport the moist air to the outside, while the belt serves as a dust filter for the air conduction from the top downward. Fine particles are retained in the substrate layer. Depending on the quantity of heat available and process parameters, like ingoing dryness and desired residual moisture, the dryer adjusts belt speed and temperature via a PLC. Matching functional modules, such as separation unit, mixing, conveying, pelleting or briquetting equipment as well as exhaust washer complete the concept.

Mixing equipment that blends dried product and raw digestates allows direct application of digestates starting at 6 percent dry solids. Upstream solid/liquid separators increase the input dry matter content to 20 to 30 percent. Following the drying process in NEWtainer, the products have a residual moisture of 15 percent only, equaling 85 percent dry solids. The efficiency of the plant is impressive: In addition to extremely low power consumption – a 40-foot container consumes only 10 kWh – the savings in volume and weight of the dried product speak for themselves. A biogas plant with an annual output of 500 kW produces 10.000 – 12.000 t of digestates per year. The 40-foot compact belt dryer for a 500 kW plant withdraws two thirds of the water content from digestates and lowers the weight per hour from 600 kg to 190 kg.

Special mesh construction

The endless, patented process belt of type Conducto 5065 made by GKD – Gebr. Kufferath AG plays a decisive role in this high efficiency. Thanks to the special mesh construction, the synthetic mesh dryer belt has a high level of air permeability in spite of small mesh opening. Nevertheless, it reliably retains dust and fine particles. This is of particular importance for biomass substrates like fermentation substrate, sawdust or wood chips, since the efficient retention rate not only prevents interruptions in production due to clogged mesh pores, but also eliminates additional external air purification measures to comply with limit values. Bronze wires woven in running direction prevent electrostatic charging. The robust construction is easy to clean, temperature-resistant up to 120 °C, tensile, abrasion-resistant, with cross-stability and high running accuracy. Each dryer in the 40-foot NEWeco-tec container is equipped with one or two 2.30 m wide and 24 m long belts made of Conducto mesh.

Fruitful cooperation

When selecting the process belt technology, Christian Wenner was influenced, along with his own many years of experience regarding belt dryers, by the consistently positive reputation of the GKD belts. Three years later, in summary of his earlier decision, he states: "Conducto belts are actually as good as their reputation in the industry“. He also has very positive memories of the initial consultation by GKD technicians, who provided him with advice and intensive support concerning the optimal mesh configuration for his new compact belt dryer. In view of the fast growth of NEWeco-tec, the reliable as well as flexible delivery of the various belt types became increasingly important to the owner. The robust, consistently high quality of the belts strengthens the high-performance image of his plants. He states that "the cooperation with GKD has been absolutely excellent from the start“. Marketing Manager Martin Bickel adds: "We would not like to miss the personal, trustful cooperation with GKD. It is the best basis for continuing growth."

About GKD – Gebr. Kufferath AG

With two divisions – WORLD WIDE WEAVE for technical meshes and CAPITAL EQUIPMENT for capital equipment and engineering – the owner-managed technical weaver GKD – Gebr. Kufferath AG is the world market leader for metal and plastic woven solutions. The division WORLD WIDE WEAVE comprises the business units SOLID WEAVE for filtration and separation media, WEAVE IN MOTION for process belt technology and CREATIVE WEAVE for metallic fabrics for the architecture and design sector. The division CAPITAL EQUIPMENT, with its unit GKD-CompactFiltration, sets international standards in capital engineering for clearly defined markets in the solid/liquid filtration sector. With seven production facilities – the headquarters in Germany, the others in the USA, Great Britain, France, Spain, South Africa and China – as well as branches in Dubai and Qatar and agents around the world, GKD is always close to the market and its customers.