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Completely dry-running

Vacuum technology for phenolic resin production
Completely dry-running

Dynea Erkner produces phenolic resins for further processing in many areas of industry. The chemical reactions take place in facilities of different sizes and at different temperatures and pressures. In recent years, this tradition-rich company has made huge investments in its production equipment. The vacuum for 16 reactors is now supplied by the latest generation of a dry-running vacuum system from K. Busch.

The author: Uli Merkle Marketing Services Manager, Dr.-Ing. K. Busch

Phenolic resin production has been taking place in Erkner since as far back as 1909, when the products were sold under the name “Bakelite”. Following a long and varied history under a number of different owners, the production plant in Erkner was finally taken over by the Dynea Group in 2002 and now operates under the name Dynea Erkner GmbH. Today, phenolic resin, which is used as a binding agent for grinding discs, non-woven fabrics, filter papers and fire-resistant applications, is produced by 115 staff working in three shifts. Phenolic resins are also required to manufacture mineral and rock wool, decorative laminates and derived timber products.
Approximately 150 types of phenolic resin are manufactured in non-continuous operation in 16 reactors measuring 4 to 32 m3. The batch run time is between 8 and 60 h and the reaction takes place exothermically, with water as a by-product.
In order to achieve different reaction temperatures, the boiling point of the reaction mixture is lowered using vacuum. Thanks to the lower boiling point, the water can then be expelled from the reaction mixture at temperatures of between 40 and 60 °C during vacuum distillation.
Due to the large number of products with diverse parameters for processes and raw materials, in combination with the different reactor sizes, the demand for vacuum is highly variable. In order to handle peaks in consumption, four buffer tanks, each with a volume of 43.5 m3, are placed between the reactors and the vacuum system. The central vacuum system is in use around the clock six days a week. The operating pressure in the complete system is permanently between 50 and 60 mbar.
The vacuum supply was previously maintained by two rotary vane vacuum pumps lubricated with fresh oil, each with a pumping speed of 1000 m3/h. A Roots vacuum pump with a speed of 2000 m3/h was also installed upstream of each of these rotary vane pumps to provide an additional boost. This pump setup was not satisfactory for ensuring trouble-free production, as the rotary vane vacuum pumps often failed and the outlay for maintenance and repair was high. This meant that an identical, third vacuum unit had to be kept available and ready for operation at all times as a reserve pumping station. The failures were caused by phenolic and formaldehyde vapours also being sucked in, and then condensing and reacting with each other in the compression chamber. This resulted in particles and specks of phenolic resin forming in the vacuum pump. They could only partially be washed out via the fresh oil lubrication and stuck to the compression chamber of the rotary vane vacuum pump, ultimately resulting in a shut-down period. In principle the same reaction process ran inside the vacuum pump as in the reactor. Problems were also caused by the filters installed downstream of the rotary vane vacuum pumps, which served to extract the oil sprayed on as lubrication. The fluid created due to the oil bonding with the phenolic and formaldehyde vapours completely clogged the filter elements, which consequently had to be replaced at very short intervals of just one or two weeks.
Highly efficient
In January 2011, the old pumping unit at Dynea Erkner, with its rotary vane vacuum pump lubricated with fresh oil and Roots vac-uum pump, was replaced with a vacuum system from Busch. The new system consists of two Cobra screw vacuum pumps, each with a pumping speed of 400 m3/h, and a Panda Roots vacuum pump with a pumping speed of 2000 m3/h. The vacuum system is controlled in such a way that the same speed as before is achieved with vacuum pumps which are much larger but have smaller aggregates, leading to huge energy savings. The previous pumping station had a connected load of 41 kW. The new vacuum system from Busch runs with just 27.5 kW, which represents a reduction of over 30 %. This pumping station is completely dry-running, meaning that no oil is required in the compression chambers. As a result, a downstream oil separator can be dispensed with and the costs for the oil as well as for removing old oil and clogged filters have been eliminated.
The system conforms to Atex (Ex II 2G IIB T3). The inside is defined as Zone 1; no zone is specified for the outside around the vacuum pump. However, the process is only relevant to Atex during the start-up phase because solvent vapours could be present in the system. In any case, the system makes itself inert on starting, after which there is no longer any risk of explosion.
According to Dynea Erkner, the vacuum system has been operating without any problems and with very little maintenance ever since it was commissioned more than two years ago. In a statement the company claims: “So far we have been really satisfied.” The vacuum system is serviced and checked over by Busch once a year. Oil changes in the vacuum pump gear units are carried out in-house.
Hall 9, Booth E23
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