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Double sized

Pulsator with two bellows heads assures continuous operation of an extraction column
Double sized

Extraction is commonly used when rectification is unsuitable for technical or commercial reasons. Two typical applications are extracting plant materials such as active or flavour ingredients from an aqueous solution and isolating hormones from a complex reaction mixture. Pulsators clearly improve the separation efficiency of an extraction column by moving the liquid up and down.

Jens Voigt

The pulsator itself is similar to a plunger pump with a variable stroke length and frequency. Just like the columns, there are many different sizes and types of pulsator depending on the process and the desired result. In practice, the pulsator typically forces a multi-component mixture through the perforated plates in the extraction column. The volume of liquid moved with each stroke can be adjusted by varying the stroke length setting on the pulsator. During the positive pressure stroke, the lighter (dispersed) phase is forced through the holes and dispersed into droplets. During the suction stroke, the denser (continuous) phase is subject to speed and pressure changes as it is drawn through the perforations. Repeated many times, this results in complete mixing and a uniform distribution of the two phases. Depending on the pulsation frequency, the dispersed phase is now present in the form of countless tiny droplets with an enormous surface area.
Reliable operation
Lanxess use a pulsator in their waste water treatment plant in Antwerp. The Bran+Luebbe H5-32 dual pulsator is based on an H5 Novados gear with a 60 mm stroke. Two drives and two bellows pulsator heads with a diameter of DN 400 work in boxer fashion to ensure a uniform distribution of waste products within the 18 m tall liquid/liquid extraction column and provide a total stroke volume of 12 l. The two pulsators are combined in a pipe connection with a DN 500 outlet.
The Novados H type gears were developed to meet the increasingly demanding requirements of European regulations. They comply with Machinery Directive 98/37/EC and Atex 94/9/EC up to category 2. A large-volume oil sump with immersion lubrication minimises the thermal load on the lubricant and reduces noise. The rugged housing helps guarantee a long, reliable life under the toughest conditions and cut lifecycle costs. Interfaces are provided for the modern sensor technology employed in Bran+Luebbe’s automatic diagnostic system.
Each pulsator head has a volume of 6 l. A liquid detector senses any damage to the bellows and transmits a signal to a control unit, which can sound an alarm or stop the pump. A pressure stabiliser protects the bellows and prevents an inadmissibly high difference between the pressure in the liquid and the atmospheric pressure inside. The type normally used is an external pressure vessel, which ensures that the pressurisation of the bellows interior is always comparable to that of the liquid being pumped. The pressure stabiliser allows the bellows to maintain a stable form and not collapse under the pressure of the liquid in the column. The dual pulsator in place at Lanxess contains an integrated pressure vessel, which has the advantage of simplifying installation by eliminating external pipes. Atex regulations are met by using an inert gas whose pressure can be checked with the built-in pressure gauge.
Reduced maintenance costs
Routine maintenance costs are reduced by an isolation valve built into each pulsator head. When closed, these valves allow tasks such as degassing the pulsator heads, replacing the bellows or servicing the drive to be carried out without having to empty the column. If necessary, the pulsator can continue to run on one head while the other is being serviced, greatly reducing the time and cost of repairs.
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