Exxon Research and Engineering Company

Donald B Trust

Douglas G Ryan

Rudolph R Savory

In a lube oil dewaxing plant in which waxy lube oil is firstly conditioned to promote wax crystallization, such as by adding an oil solvent and chilling the resulting admixture, and then filtered in at least one rotary drum filter (213), the filter includes at least one spray header (92') including a plurality of charge injectors (300) which inject charge by field emission into a field which is sprayed from orifices (246) in the underside of the header onto the filter drum (20). The injected charge has the effect of enhancing separation of haze from the lube oil in the rotary drum filter (213). The charge carrier fluid may for example be solvent-diluted waxy oil or oil solvent liquid alone.

Removing haze from dewaxed hydrocarbon oil mixture boiling in the

For removing haze from dewaxed hydrocarbon oil mixture boiling in the lubricating oil range which is hazy, the hazy oil mixture is filtered in the filtration stage (201) of a dewaxing plant which is concurrently filtering undewaxed hydrocarbon oil mixture boiling in the lubricating oil range. Prior to filtering, the hazy dewaxed oil mixture is subjected to pretreatment (in pretreatment stage 204) such as to promote removal of haze from the dewaxed oil mixture during filtering. This pretreatment is carried out independently of the undewaxed oil mixture and can involve dilution/chilling with an oil solvent (e.g. liquid propane) and/or introduction of free excess electric charge, for example by charge injection. As an alternative to the pretreatment, the temperature conditions under which filtration takes place may be low enough to promote wax crystallization. The filtration stage may comprise a rotary drum filter (213) in which the undewaxed oil mixture is introduced into the filter vat (10), whereas the pretreated dewaxed oil mixture is sprayed onto the wax cake formed on the rotary filter drum.

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Donald B Trust