Exxon Research and Engineering Company

Thomas E Broadhurst

Stephen F Perry

James D Eagan

An apparatus and method for removing particles from refinery fluid hydrocarbon and organic streams comprising an elongated housing containing multiple layers of non-woven fabric arranged in said housing as discrete stratified layer array of filter fabric of increasing particle retentive power thus arranged in the housing in the direction of fluid flow. The fabric layer comprise thermally stable materials of different permeability which are mineral coated to provide structural, fluid compression resistance, and to which flint or talc particles are added to impact surface roughness to the fibers. A final layer of uncoated needled felt fine fabrics end caps the array. In operation the refinery fluid is passed through the filter array such that the direction of fluid flow is in the direction of increasing retentive power of the filter fabric array. The use of fabrics rather than particle beds permits the use of separation units of vertical upflow configurations in which gravity assists in particle retention and removal.

Filter comprising multiple layers of non-woven filter fabric of

Solvent dewaxing of waxy hydrocarbon oils using scraped surface chillers is improved by injecting cold solvent into the scraped surface chillers at multiple points to augment the indirect chilling occurring in said scraped surface chillers. In utilizing this multi-point cold solvent injecting process it is important to control the .DELTA.T occurring at each injection point within each chiller bank across the entire chiller train. The .DELTA.T at each injection point attributable only to cold solvent injection must be equal if one is to secure the benefit of the present invention which is an improved liquids/solids ratio without deterioration of the feed filter rate. Preferably, to avoid any possible deterioration of filter rate and/or liquids solids, the cold solvent injection should be completed prior to the slurry in the scraped surface chiller train experiences any shock chilling.

Multi-point cold solvent injection in scraped surface dewaxing chillers

The filtration performance of a slurry containing crystallized wax, dewaxed oil and dewaxing solvent is improved by use of an agitator means which possesses a characteristic dimension which when divided by the average wax crystal diameter yields a dimensionless number of about 1,500 or less, preferably about 1,000 or less, more preferably about 500 or less, most preferably about 250 or less. Use of an agitator means which possesses a characteristic dimension yielding a dimensionless number in the range recited above causes a reduction in the size of the vortex generated as the agitator means passes through the slurry during chilling. As a consequence, more intimate contacting of the wax particles during chilling is promoted. The needed characteristic dimension of the agitator may be obtained in any number of equally acceptable ways. Single large agitator blades can be replaced by more numerous smaller blades; large blades can be perforated, notched, etc. Any alteration which causes the agitator characteristic dimension to be reduced so that when it is divided by the average cyrstal wax size the resulting dimensionless number is about 1,500 or less in an acceptable modification.

Agitated dewaxing employing modified agitator means

An improved process for dewaxing waxy hydrocarbon oils, wherein said waxy oil is introduced at a temperature above its cloud point into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing a cold dewaxing solvent into at least a portion of said stages, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing thereof while cooling said solvent-waxy oil mixture, preferably at a rate of from about 1.degree. to 8.degree. F./min., as it progresses through said direct chilling zone to a temperature greater than the wax separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a solvent-oil mixture containing precipitated wax (slurry I), withdrawing said slurry I from said direct chilling zone and cooling same to the wax separation temperature in an indirect chilling zone thereby precipitating a further portion of wax from said waxy oil and separating said precipitated wax from the wax-oil-solvent mixture in solid-liquid separation means, the improvement comprising using as the indirect chilling zone an indirect heat exchanger means operated at a high level of agitation. Expressed in terms of Impeller Reynolds Number the agitation is on the order of about 1,000 to 1,000,000. Alternatively, the staged, agitated, direct chilling zone is totally replaced by the high agitation indirect heat exchanger means.

Agitated heat exchanger to chill solvent-oil and wax slurry to wax

An improved process for dewaxing waxy hydrocarbon oils, wherein said waxy oil is cooled in an indirect chilling zone to a temperature greater than the wax separation temperature whereby wax is precipitated to form a wax-oil-solvent slurry, cooling the slurry to the wax separation temperature in an indirect chilling zone thereby precipitating a further portion of wax from said waxy oil and separating said precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising using as the indirect chilling zone an indirect heat exchanger means operated at a high level of agitation. Expressed in terms of Impeller Reynolds Number the agitation is on the order of about 1,000 to 1,000,000. Alternatively, the direct chilling zone is totally replaced by the high agitation indirect heat exchanger means.

Dewaxing process using agitated heat exchanger to chill solvent-oil and

In hydrocarbon oil dewaxing processes comprising passing the waxy oil through a staged vertical tower, injecting cold solvent at a plurality of stages along the vertical tower under conditions of high agitation to achieve substantially instantaneous mixing at each point, continuing the chilling, preferably at a rate of from 1.degree. to 8.degree. F. per minute, by means of cold solvent injection until a temperature at least 30.degree. F. above the filtering temperature but less than about 40.degree. to 45.degree. F. above the filtering temperature is reached and completing the cooling of the oil to the separation temperature in rotating element scraped surface chillers, the improvement comprising operating the scraped surface chillers at a chilling temperature range of at least 30.degree. F. while reducing the operating speed of the rotating elements in the scraped surface chiller to a speed of from 5 to 20% preferably 8 to 14% of the original design operation speed. Operation at this reduced speed improves wax separation rates by about 10 to 20% while not adversely effecting the heat transfer performance of the chillers.

Dewaxing and wax filterability by reducing scraper speed in scraped

Particles of solid wax are separated from a slurry comprising said wax particles and a hydrocarbon oil by filtering the slurry through a cloth filter medium. It has been found that using, as the filter medium, a needled-felt cloth fabricated from fibers fusible by means of an open flame and having a singed surface on which the wax is collected results in an unexpected reduction in filter cloth blinding thereby yielding up to 30% increased throughput through the filter cloth and greatly reducing the frequency of washing the filter cloth. The cloth is further characterized in that it has a permeability to air in excess of about 3 cubic feet per minute per square foot of cloth surface at a differential pressure of 0.5 inches of water, a root mean square surface roughness in excess of 500 rms microinches and a fouling factor in excess of about 75%. This improved process has been found to be particularly useful for separating wax particles from a dewaxed lube oil slurry.

Wax separation process

An improved DILCHILL* dewaxing process wherein waxy lubricating oil stocks are solvent dewaxed by contacting them with successive increments of cold dewaxing solvent at a plurality of points along the height of a vertical tower divided into a plurality of stages while agitating the oilsolvent mixture in each stage to provide substantially instantaneous mixing of the waxy oil and solvent thereby precipitating wax from the oil while avoiding the well known shock chilling effect. The improvement resides in adjusting the cold solvent addition to each stage in a manner so as to modify the temperature profile along the tower to ensure that the temperature drop per stage in the initial stages in which wax precipitation occurs is greater than the temperature drop per stage in the final or later stages in which wax precipitation occurs.

Growing community of inventors

Sarnia, Canada

Thomas E Broadhurst