Application: Process to produce high-melting and low-oil containing hard wax products for a wide range of applications.
Feeds: Different types of slack waxes from lube dewaxing units, including macrocrystalline (paraffinic) and microcrystalline wax (from residual oil). Oil contents typically range from 5–25 wt%.
Products: Wax products with an oil content of less than 0.5 wt%, except for the microcrystalline paraffins, which may have a somewhat higher oil content. The deoiled wax can be processed further to produce highquality, food-grade wax.
Description: Warm slack wax is dissolved in a mixture of solvents and cooled by heat exchange with cold main filtrate. Cold wash filtrate is added to the mixture, which is chilled to filtration temperature in scraped-type coolers. Crystallized wax is separated from the solution in a rotary drum filter (stage 1). The main filtrate is pumped to the soft-wax solvent recovery section. Oil is removed from the wax cake in the filter by thorough washing with chilled solvent.
The wax cake of the first filter stage consists mainly of hard wax and solvent but still contains some oil and soft wax. Therefore, it is blown off the filter surface and is again mixed with solvent and repulped in an agitated vessel. From there the slurry is fed to the filter stage 2 and the wax cake is washed again with oil-free solvent. The solvent containing hard wax is pumped to a solvent recovery system. The filtrate streams of filter stage 2 are returned to the process, the main filtrate as initial dilution to the crystallization section, and the wash filtrate as repulp solvent.
The solvent recovery sections serve to separate solvent from the hard wax respectively from the soft wax. These sections yield oil-free hard wax and soft wax (or foots oil).
Utility requirements (slack wax feed containing 20 wt% oil, per metric
ton of feed):
Steam, LP, kg 1,500
Water, cooling, m3 120
Electricity, kWh 250
Licensor: Uhde GmbH.