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AssigneeExxon Research & Engineering Co.
InventorsDouglas G. Ryan, Donald B. Trust, Rudolph R. Savory
Estimating the term…
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.
A method of removing haze from dewaxed hydrocarbon oil mixture boiling in the lubricating oil range which is hazy, comprising the steps of (a) passing undewaxed hydrocarbon oil mixture boiling in the lubricating oil range through a dewaxing plant including a filtration stage, (b) introducing the hazy oil mixture into the dewaxing plant directly at its filtration stage, so as to combine the hazy oil mixture and the undewaxed oil mixture and subject them to concurrent filtering in said filtration stage, and (c) introducing free charge which is net unipolar into the hazy dewaxed oil mixture before that oil mixture is combined with the undewaxed oil mixture, the introduction of free charge being effected at least predominantly by electron emission which causes the dewaxed hydrocarbon oil mixture to act as a medium through which volumetric distribution of the introduced charge takes place by charge motion relative to the dewaxed hydrocarbon oil mixture, there being a sufficient excess of free charge introduced such that the volumetric charge distribution causes, in the filtration stage of the dewaxing plant, both an electric field to be induced in the oil mixture in said filtration stage and the haze therein to become charged, and the induced electric field and the charge on the haze interact to produce an electrical driving force acting on the haze to promote removal of haze from the dewaxed oil mixture during the filtering.
A method as claimed in cIaim 1, wherein the undewaxed oil mixture is introduced into a filter vat of a rotary drum filter for performing the filtration and wherein the charged hazy dewaxed oil mixture is sprayed through a gas or vapor space onto the wax cake formed on the filter drum, whereby said dewaxed oil mixture is filtered in the filtering means concurrently with filtration of said undewaxed oil mixture.
Dependencies are inferred from the claim text.