in Vol. 12 - March Issue - Year 2011
A Highly Effective Waste Water Treatment Technology Offers Optimum Solutions For Many Applications
A proven centrifugal technology
Centrifugal process water recycling systems are not only utilized for mass finishing applications, but they also offer excellent solutions for cleaning waste water containing glue residues and for the separation of solid particles from process liquids produced in glass processing, photovoltaic and semi-conductor industries
The systems with automatic sludge discharge are designed for an hourly capacity of up to 6,000 liters/hour
Rösler Oberflächentechnik GmbH is the world’s leading supplier of a complete range of mass finishing and shot blast equipment, paint and preservation lines as well as consumables for the surface treatment and surface preparation (deburring, descaling, desanding, polishing...) of metallic and non-metallic parts. Besides the German plants in Untermerzbach/Memmelsdorf and Bad Staffelstein/Hausen the company has branches in Great Britain, France, Italy, the Netherlands, Belgium, Austria, Switzerland, Spain, Romania, Brazil, South-Africa, China, India and USA.
Rösler, the world’s leading supplier of mass finishing equipment and consumables, also has extensive knowledge in the challenging field of process water treatment. Rösler centrifuges offer a highly effective two-phase separation process to follow any wet mass finishing process. The centrifuge separates the liquids from solid particles collected during mass finishing, but can also offer solutions for numerous other applications. These applications include the treatment and automatic discharge of sludge from painting operations and liquids containing glue residue, as well as glass and SiC particles.
Metal and grinding media fines, along with dirt removed from the finished parts, make the mass finishing process water highly abrasive. To ensure maximum up time for the centrifugal systems, the centrifuge and its individual components require a robust and, above all, wear-resistant design. These components include pumps, valves, the rotary drum, drum drive, and peeling knife. With the powerful and proven centrifugal systems for two-phase separation, the Rösler Oberflächentechnik GmbH offers solutions that are in high-demand. Each year Rösler delivers around 250 semi-automatic units and 100 fully-automatic systems with automatic sludge discharge. These machines are no longer used exclusively for mass finishing applications, but also for cleaning and recycling process liquid like the separation of paint sludge from waste water. Another common application for the wood processing industry is the removal of glue contamination from the water. This versatile technology is also used in such diverse industries as glass processing, photovoltaic, and semi-conductor production. Of course, the technical details can be adapted to each application. For example, centrifuges for treating process water containing SiC particles from the production of wafers must be equipped with a special drain for hydrogen gas.
High performance with automatic sludge discharge
Depending on the cleanliness requirements of the treated liquid and the physical limitations of the particle size and weight, the centrifuge systems with automatic sludge discharge have a capacity of up to 6,000 liters per hour. The 2,000 g acceleration guarantees that up to 90% of particles larger than 2.0 u are separated from the liquid and deposited on the wall of the rotating drum as solid sludge. The addition of an environmentally friendly cleaning compound into the waste water helps to remove fine particles and further increase the separation performance of the centrifuge. The cleaned process liquid is collected by a wear-resistant collecting tube at the bottom of the rotating drum and then is returned into the recycling system or directly down the drain.
The rotating drum has a capacity of up to 30 kg of sludge which, depending on the particle size and weight, has residual moisture of 40 to 60%. Once the sludge volume has been reached, the sludge deposits on the drum wall are peeled off with a special peeling knife and discharged into a sludge bin with a capacity of 300 liters. To prevent a drum imbalance, which causes premature wear of the bearings, sludge residues in the drum are flushed out after each peeling cycle by intensive rinsing. In addition, the centrifuge is equipped with an imbalance monitor that switches off the system if an imbalance is detected.
Robust design paired with easy maintenance guarantee high up time
Another important feature of the Rösler centrifuges is their proven design and ease of maintenance. The drive motor on each centrifuge is linked to the rotating drum with an indirect belt drive. This concept not only allows the optimum sizing of the motor and drum bearings, but it also ensures the lowest possible bearing load. For standard mass finishing applications the drum is made of aluminium, but for systems with more corrosive process liquids containing SiC, glass particles, copper, etc, stainless steel drums are utilized to prevent corrosion on the drum walls.
The high volume of the drum body with its large sludge capacity guarantees long operating times between peeling cycles. Another significant feature of the Rösler centrifuge is the peeling system itself. In conventional "peeling" centrifuges the peeling knife – driven by a gear motor – is constantly rotating. When the sludge deposits on the drum wall relatively low water content is used, making the deposits relatively hard. These systems run the risk of the drive motor stalling and interrupting the peeling process. This problem cannot occur in Rösler centrifugal systems because they are equipped with a stationary peeling knife. This knife is moved to the slowly rotating drum speed with pneumatically driven high-precision, linear guide system, allowing the machine to reliably peel the sludge from the drum wall without any significant load on the bearings.
Since Rösler is certified as a qualified waste disposal operation, many of our customers can return their sludge to the company from Untermerzbach, who disposes of it in an environmentally friendly manner.