Patent Publication Number: US-2013228497-A1

Title: Systems and methods for filtering metals from fluids

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     1. Field of the Disclosure 
     This disclosure is directed to the filtering fluids having metals. More specifically, the present disclosure relates to the removal of metals from crude oils. 
     2. Background of the Disclosure 
     It is common to use relatively heavy crudes and petroleum residues as the feedstock for various operations. This feedstock may contain relatively high contents of contaminating metals and sulfur. The high metal content of heavy crude oils and petroleum residues may be undesirable for a variety of reasons, such as the detrimental effects of these metals on various catalysts used in various petroleum treatment processes. 
     The present disclosure addresses the need to remove metals from crude oils or other fluids. 
     SUMMARY OF THE DISCLOSURE 
     In aspects, the present disclosure provides a method of processing crude oil. The method may include increasing an iron content in the crude oil to a specified value using a desalter; drawing an effluent from the desalter, the effluent being crude oil having an increased iron content; and reducing the iron content of the effluent using a magnetic field in the filter. 
     In aspects, the present disclosure also provides a system for processing crude oil. The system may include a desalter; a line drawing a fluid effluent from the desalter; and a magnetic filter configured to apply a magnetic field to the fluid effluent. 
     In aspects, the present disclosure further provides a method of processing a liquid having magnetic particles. The method may include increasing a magnetic particle content in at least a portion of the liquid; forming an effluent using the portion of the liquid that has the increased magnetic particle content; and filtering the effluent using a magnetic field. 
     Examples of certain features of the disclosure have been summarized (albeit rather broadly) in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       For detailed understanding of the present disclosure, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing: 
         FIG. 1  schematically illustrates a magnetic filtering system for treating crude oil or other metal-containing fluids according to one embodiment of the present disclosure; 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The present disclosure relates to methods and devices for removing magnetic particles from liquids. While the present disclosure may be applied to a variety of applications, for brevity, the present disclosure will be discussed in the context of removing metals from crude oil. 
     Referring now to  FIG. 1 , there is shown one embodiment of a filtration system  10  for reducing the amount of magnetic material in a liquid. For convenience, crude oil will be used as an illustrative liquid. The system  10  may include a desalter  20  and a filter  30 . The desalter  20  may be a conventional device adapted to remove contaminants such as salts (e.g., calcium, sodium and magnesium chlorides), suspended solids, and water-soluble trace metals in the crude oil. The desalter  20  may use chemical, electrostatic separation, or any other separation technique to remove the contaminants from the crude oil. A pump  22  or other suitable fluid mover may be used to flow crude oil into the desalter  20 . 
     The filter  30  applies a magnetic field to a fluid effluent from the desalter  20  to remove magnetic particles such as ferrites (e.g., iron). In one embodiment, the filter  30  includes a plurality of parallel flow lines  32  fed via a manifold  34 . The manifold  34  can hydraulically isolate one or more of the flow lines  32 . The flow lines  32  may be tubulars, channels, plates, or other known fluid conduits and may incorporate drums. Each of the parallel flow lines  32  are positioned such that the effluent passes through a magnetic field generated by an electrically charged media  36 . The media  36  may include electromagnetic elements that generate the magnetic field when energized with electrical energy. For example, the media  36  may include wire coils and use direct current to generate a magnetic field. The magnetic particles in the crude oil will be attracted to the energized media and held in place until the media is de-energized. Illustrative magnetic filters include, but are not limited to, T-Trap magnetic filters and rotating wet drum magnetic filters. In other embodiments, permanent magnetic separators that use permanent magnet material may be used. 
     As the magnetic particles accumulate on the electrically charged media  36 , the effectiveness of the filtering process may diminish. Thus, periodically, one or more of the flow lines  32  may be sealed off using the manifold  34  and back-flushed using a suitable cleaning fluid to remove the accumulated particles. During the back-flush process, the unsealed flow lines  32  continue to operate and filter the crude oil without interruption. A suitable back-flushing system  38  may be used to circulate and/or purge the cleaning fluid In some embodiments, the back-flush fluid may be subjected to further processing and used; e.g., the back-flush fluid may be processed to a slurry that may be burned in cement kilns or discharged to a waste plant for processing and disposal. 
     In one embodiment, a line  40  directs the fluid effluent from the desalter  20  to the filter  30 . An oil and brine typically mix to form a “rag” layer  42  at an interface between two phases, here water and oil. In one arrangement, a port  44  of the line  40  may be positioned at the rag layer  42  in the desalter  20 . Because the rag layer  42  may be dynamic, the port  44  may be configured to float or otherwise orient itself to remain in fluid communication with the rag layer  42 . That is, as the rag layer  42  rises or falls in the desalter  20 , the port  44 , or a component of the port  44 , may also move to draw in the rag layer  42 . 
     In some embodiments, a cooler  46  may be used to cool the effluent fluid in the line  40 . Many conventional desalters  20  add significant thermal energy into the crude oil during the desalting process. Typically, a magnetic flux decreases with temperature. Therefore, the cooler  46  may be employed to reduce the temperature of the effluent fluid to a desired value. In some embodiment, the desired value may be approximately an ambient temperature. This may be desirable since the magnetic flux generated by the electromagnetic media  36  may not have to be intensified to adequately filter the rag layer or the residuum stream. The cooler  46  may be of a known type that actively reduces the thermal energy in a liquid stream; e.g., heat exchangers, chiller water pipes, etc. 
     In one arrangement, the filter  30  returns the filtered crude oil to a suction side  24  of the pump  22  via a line  48 . Thus, the pump  22  may be used to generate the pressure differential to flow the filtered crude oil from the filter  20 . This may reduce or eliminate the need to use a separate pump for pumping fluid from the filter  30 . In other embodiments, the filter  30  returns the filtered crude oil to desalter  20  via a line (not shown) that includes a dedicated pump or other fluid mover. 
     In one mode of use, a crude oil is supplied to the desalter  20 . As the crude oil is treated in the desalter  20 , the port  44  draws the rag layer  42  out of the desalter  20  to form a fluid effluent that mostly consists of the rag layer  42 . The effluent is cooled by the cooler  46  and sent to the manifold  34 . The manifold  34  directs the effluent to one or more of the lines  32 . As the effluent passes through the magnetic field generated by the electromagnetic media  36 , magnetic particles (e.g., iron) are attracted out of the effluent in the line(s)  32  and settle or otherwise layer the interior surfaces of the line(s)  32 . Thereafter, the filtered effluent is returned to the desalter  20  via line  48 . 
     It should be appreciated that cycling magnetically filtered effluent into the desalter  20  gradually reduces the overall iron content of the crude oil in the desalter  20 . After a desired iron content has been reached in the desalter  20 , a residuum stream from the desalter  20  may be drawn for further processing (e.g., phase separation). 
     In another mode of use, the crude oil in the desalter  20  is processed to achieve a desired iron concentration. Thereafter, the residuum stream from the desalter  20  is sent to the filter  30  for filtering. The residuum stream is not returned to the desalter  20 . 
     For back-flush operations, some of the lines  32  are sealed off and placed into fluid communication with the back-flush system  38 . The unsealed lines  32  continue to flow effluent through the filter  30 . A suitable cleaning liquid is circulated through the sealed lines  32  to dislodge and entrain the settled magnetic particles. In some embodiments, a portion or section of the electromagnetic media  36  that applied a magnetic field to the lines  32  being back-flushed may be de-activated to release the accumulated particles. The cleaning liquid and entrained magnetic particles are then disposed of or processed further. It should be appreciated that the selectively back-flush capability allows the effluent from the desalter  20  to be continually magnetically filtered. 
     It should be appreciated that the present disclosure may be susceptible to numerous variants. Illustrative variants are described below. 
     In some variants, a surface active reducing agent (surfactant) may be used to increase the efficiency of the filter  30 . For example, a surfactant supply  52  may be used to introduce one or more surfactants in the desalter effluent in line  40 . A suitable surfactant may reduce the surface tension on the solids (e.g., metals) bound in oil/water emulsions making up the rag layer  42 . Suitable surfactants include, but are not limited to, anionic, nonionic, cationic, amphoteric, zwitterionic, extended surfactants and blends thereof. Still other suitable nonionic surfactants include, but are not necessarily limited to, alkyl polyglycosides, sorbitan esters, methyl glucoside esters, amine ethoxylates, diamine ethoxylates, polyglycerol esters, alkyl ethoxylates, alcohols that have been polypropoxylated and/or polyethoxylated or both. 
     In some variants, some or all of the filtered crude oil may be conveyed via the line  50  to a separate location for further processing. For example, the line  50  may convey the filtered effluent to a separator (not shown) for phase separation or an oil recovery unit (ORU). For example, a centrifuge may be used to separate oil, water, and solids. The separated phases may be disposed of or processed further in devices such as an oil recover. Thus, the filtered crude oil does not necessarily have to be returned to the desalter  20 . 
     In some variants, the filter  30  may receive the residuum stream from the desalter  20 . That is, the desalter  20  processes the crude oil to a specified condition or parameter. Once the crude oil is processed to a specified condition, this processed crude oil is passed to the filter  30  at a flow rate low enough that the magnetic filtering can effectively remove the entrained magnetic particles. Thus, the filtered crude oil is not cycled back into the desalter  20 . 
     Some variants may also use additives or processing techniques to decrease a viscosity of the effluent entering the filter  30 . Maintaining a relatively low effluent viscosity may allow a more efficient migration of the magnetic particles through the effluent. 
     While the foregoing disclosure is directed to the preferred embodiments of the disclosure, various modifications will be apparent to those skilled in the art. It is intended that all variations within the scope of the appended claims be embraced by the foregoing disclosure.