Extraction of reusable substances from plant waste
New plant makes several process stages superfluous.
Sonthofen, Germany, June 14, 2016 BHS-Sonthofen has received the order from an American customer to supply an indexing belt filter for extracting reusable substances from plant waste. With a filter area of almost 90 m², the type BF 350-255 filter plant is not only the largest plant that BHS has ever built, but it is also one of the most efficient of its kind in the world.
The indexing belt filter of type BF 350-255 will process up to 5,000 kg of fibrous plant waste hourly, extracting recoverable liquid components generated in a previous production process. The filtrate is used for the manufacture of basic chemicals, while the remaining solids, which could not previously be used, are reprocessed.
During project planning, the customer had initially envisaged a multi-stage process with a sequence of consecutive screening and filtration steps and with the solids being resuspended several times. The proposal from BHS-Sonthofen to use an indexing belt filter of type BF with a single process step convinced the customer, however. Not only is the process much simpler, but it also concentrates the reusable substances to a greater extent. This means that less energy is required for extracting the substances at a later stage in the process.
As part of the treatment process, the plant waste is first suspended in water. To ensure that the reusable substances dissolved in this can be extracted as effectively from the solid as possible, BHS implements a multistage counter-current wash process in the filter plant. This allows the filter to achieve a very good washout quality, thereby significantly increasing the concentration of the dissolved reusable product in the liquid. The BHS indexing belt filter of type BF 350-255 extracts approximately 10 percent more recoverable materials than conventional procedures.
Moreover, the operating costs are lower because the indexing belt filter requires about 30 percent less water than the multistage process. This also results in considerably lower investment costs as no multiple cascades of stirring tanks and filters are required. As the entire filter plant is much simpler in design than conventional plants, it ensures a high operational reliability. At the same time, maintenance costs are significantly lower in comparison to conventional plants.
After receiving the order in December 2015, BHS supplied the filter plant in spring 2016. Commissioning is planned for autumn 2016.
The indexing belt filter is a continuously operating, horizontal vacuum filter that allows for reliable and gentle separation of sedimentation solids from suspensions. The filter medium is a circulating belt, which moves forward in cycles.
Each time the cloth stops, the filtrate is sucked downwards. Then the vacuum is switched off to release the filter cloth, which can now be moved forward. The filter cake forms on top of the belt and can undergo further treatment by washing (co-current or counter-current), reslurrying, steaming, extraction, vacuum drying or pressing. During this process, the filtrates can be recovered individually from each vacuum tray and further processed without any cross-contamination. The filter cake is discharged at the discharge roller. The cloth is cleaned as the belt returns.
The design of the BHS indexing belt filter allows continuous, even feeding of the suspension via distribution devices, which also spread the solids gently. The filter cake formed by gravity and vacuum is not subject to any mechanical forces during transportation or further treatment. This makes the indexing belt filter suitable for pressure-sensitive solids as these can be processed without grain particle breakage.
BHS-Sonthofen GmbH is an owner-operated group of companies in the field of mechanical and plant engineering, based in Sonthofen (Germany). The company offers technical solutions for mechanical process engineering, concentrating primarily on mixing, crushing, recycling, and filtration. With more than 350 employees and several subsidiaries, BHS-Sonthofen has a global presence.
The Filtration Technology division manufactures machines and plants for mechanical solid/liquid separation using pressure or vacuum filtration. Key applications are processes in the chemical and pharmaceutical industry, the plastics industry, as well as for energy and raw material extraction.