For its new crushing and refining process for siliceous earth, Hoffman Mineral relies on ZS screw blower offering clean, efficient oil-free air for pneumatic conveying and air separation.
Hoffmann Mineral requires 5,000 standard cubic meters of oil-free compressed air per hour, with a pressure of 0.8 bar and at a defined temperature.
The manufacturer found that Atlas Copco offered the most efficient solution for this. The Atlas Copco ZS 132 screw blower provides the precise regulation required for the process, and needs one third less energy than the next best available solution in order to supply the volume flow required.
“Our industry involves a very high level of automation,“ explains Dr. Karlheinz Schmidt, Managing Director of production and technology at the siliceous earth processing company Hoffmann Mineral GmbH, based in Neuburg an der Donau in Germany.
“We invest a lot, including countercyclical investments, and are constantly growing. Our most recent investment is an air separation mill, including a separator, which we use to crush the siliceous earth agglomerates that result from heat treatment in a new preceding process step.”
“The key element is that, unlike almost all other mills, this mill doesn’t work mechanically, but instead works using compressed air. The process is much more gentle — both for our product and for the machines.”
After all, mechanical mills, or “impact mills”, work in a very abrasive way: the plants are worn after only a few thousand operating hours and the abrasion causes the manufactured products to be impure.
“The products become gray and conductive,” says the engineer, continuing his explanation. For our customers’ diverse range of applications, neither of these properties is desirable.”
The company’s products are used industrially as additives for rubber (around 70%), paints and varnishes. At Atlas Copco, the company found what they were looking for — in the form of an oil-free compressing screw blower, model ZS 132, the rotation speed of which is controlled via a separate frequency converter.
“The advantage is that the machine is designed to deliver pressures of 0.3 –1.2 bar and can generate precisely the pressure that we need. With another screw compressor, we would have had to compress to 3 bar and then decompress again, which was out of the question.”
They also ruled out the alternative approach of using a lobe blower: It was only capable of delivering a pressure of 0.9 bar and would have been pushed to its limits.
“The installed power is 132 kW. This is a lot lower than the 200 kW of the next-best solution which was offered by another supplier.This meant that at full capacity, the machine uses at least a third less energy.