Abstract:
A filtration apparatus is disclosed for the removal of metals from jet fuel at high flow rates and limited pressure drops. The filter comprises a monolayer of immobilized chelating agent on packed silica gel. The filtration apparatus is particularly useful for the removal of copper from jet fuel.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    The U.S. Government has rights in the invention pursuant to contract N68335-06-C-0241 awarded by the United States Navy. 
     
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0002]    Not Applicable 
       INCORPORATED-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates to the rapid removal of dissolved contaminants from large volumes of liquid. In particular, the invention is an apparatus and associated method for high flow rate, low pressure drop removal of metals from fuels. 
         [0006]    2. Description of Related Art 
         [0007]    Trace amounts of metals such as copper, zinc, iron, and lead in hydrocarbon fuels can cause undesirable oxidative degradation and reduced thermal stability of the fuels and, in some cases, can damage aircraft engines, reducing their working life. Consequently apparatus and methods for removing metals from fuels are needed. 
         [0008]    Materials useful for the removal of dissolved metals from liquids such as water and hydrocarbon fuels are known in the art. U.S. Pat. No. 6,077,421 discloses metal chelating molecules linked to a solid substrate for the removal of a metal ion from a liquid. U.S. Pat. No. 6,297,191 discloses a composition for removing metals from jet fuel comprising a solid substrate linked to an organic macrocycle or polyol metal chelant. U.S. Pat. No. 6,248,842 discloses synthetic polymer matrices having selective chelation sites. 
         [0009]    The use of chelating agents to remove metals such as copper from hydrocarbon fuels is known in the art. Puranik et al. (1998) Energy and Fuels 12:792-797 discloses the removal of copper from fuel by chelating agents linked to a solid support. Specifically, this reference discloses the use of 70-230 mesh silica modified with DETA 1,4,8-11-tetraazacyclotetradecane (cyclam) or N 1 -[3-(trimethoxysilyl)propyl]diethylenetriamine (DETA) for the removal of copper from jet fuel. 
         [0010]    While agents capable of removing copper and other metal contaminants from petroleum fuels are known, the removal of contaminants from fuels has not thus far been possible in practice. For the known agents to be of practical utility, methods and apparatus are needed that will allow the efficient removal of metal contaminants from fuels at flow rates of tens and hundreds of gallons per minute. Thus far, attempts to increase the scale of fuel decontamination from small volumes (&lt;1 liter) at low flow rates (&lt;100 ml per minute) to practical flow rates and pressure drops has not been achieved (Puranik 1998). The present invention overcomes the existing limitations of scale to fill the need for an apparatus and method capable of removing metal contaminants from hydrocarbon fuels at useful flow rates and pressure drops. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The present invention provides for the removal of copper and other contaminating metals from hydrocarbon fuels at useful flow rates and with relatively low pressure drops. The apparatus and method of the present invention balance pressure drops, residence times, flow rates, flow distribution, reactor bed particle sizes, and chelating efficiency to decontaminate fuels at useful flow rates and pressure drops. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]      FIGS. 1  A and B is a graph showing the calculated dependency of copper concentration and pressure drop on solid support bead size for different flow rates for an apparatus according to the present invention. 
           [0013]      FIG. 2  is a graph showing the calculated dependency of copper concentration and pressure drop on solid support bead size for different flow rates for an apparatus according to the present invention. 
           [0014]      FIG. 3  is a table showing representative design parameters for a pancake bed apparatus according to the present invention. 
           [0015]      FIGS. 4  A and B are side and cross-sectional views of a fuel purification decontamination apparatus having a convex disc-shaped separation chamber. 
           [0016]      FIGS. 5  A and B are side and cross-section views of a fuel purification decontamination apparatus having a cylindrical-shaped separation chamber. 
           [0017]      FIG. 6  is a table showing representative design parameters for an annular reactor bed apparatus according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The example of removing of copper from jet fuel is described in detail to provide written description of the invention but is not in any way intended to limit the scope of the invention to any contaminant, fuel, or chelant. 
         [0019]    Scaling up laboratory scale processes for removing metal contaminants from fuels to commercial aid industrial scales is a technical challenge and requires simultaneous balancing of flow patterns, pressure drops, binding kinetics and transport, and depth and size distribution of solid supports for chelants. 
         [0020]    Theoretical analysis and multiphysics CFD simulations (CFD)-ACE+®. ESI Group) of fluid flow and chemical reactions were performed as functions of multiple variables including reactor volume, aspect ratio, flow rates, solid support particle sizes, and chemical chelant. Configurations were identified that maximize contaminant removal and minimize pressure drop at desired flow rates. Small and intermediate scale laboratory tests confirmed results of the simulations. Scaling (sizing) analysis calculations based on the simulations and experiments are shown in  FIGS. 1  A and B and  FIGS. 2  A and B. The information in these graphs corresponds to an initial copper concentration of 350 ppb and a disc-shaped reactor bed 120 mm thick. 
         [0021]      FIG. 3  presents representative design parameters for intermediate scale (240 mL/min), through full-scale (600 gpm) pancake filter reactors. The 1 gpm reactor is ˜5″ long and ˜8″ in diameter, while the 500 gpm reactor is 9.2″ long and 137.8″ in diameter. These designs are based on diffusion-limited adsorption reaction and a residence time of ˜60 seconds. 
         [0022]      FIG. 4A  is an exterior side view of an apparatus comprising a convex, disc-shaped separation chamber  1 , fuel inlet  2 , and fuel outlet  3  shown.  FIG. 4B  is a cross-sectional side view of the apparatus showing reactor bed  4  bounded by porous barriers such as perforated steel sheeting upstream  5  and downstream  6  of the solid support upon which chelant is immobilized. The distance between upstream  5  and downstream  6  barriers defines the depth of the reactor bed. In this case reactor bed  4  is planar in shape with constant depth. It is also envisioned that the reactor bed can be non planar to increase surface area within the volume of the separation chamber while maintaining a constant normal distance between  5  and  6  throughout. The performance of reactor beds can deteriorate as the diameter of the reactor bed increases to large industrial-scale systems. Effective fluid distribution in the reactor bed is most preferably achieved using flow diverters known in the art. 
         [0023]    One alternative to the pancake reactor bed configuration is an annular filter. In the annular design, the inner cylindrical gap acts as a flow distribution gap.  FIG. 5  A is an exterior side view of an apparatus with an annular design comprising a cylindrical-shaped separation chamber  1 , fuel inlet  2 , and fuel outlet  3  shown.  FIG. 5B  is a cross-sectional side view of the apparatus showing reactor bed  4  bounded by porous barriers upstream  5  and downstream  6  of the solid support upon which chelant is immobilized. The distance between upstream  5  and downstream  6  barriers defines the depth of the reactor bed. In this case reactor bed  4  is cylindrical in shape with constant depth. It is also envisioned that the shape of the reactor bed can be changed to increase surface area within the volume of the separation chamber while maintaining a constant normal distance between  5  and  6  throughout. The dome on top of the chamber is optimally removable for filter service,  FIG. 6  provides parameters for one embodiment of an apparatus having an annular design. 
         [0024]    In addition to the elements shown, the fuel decontamination apparatus may include chemical sensors for dissolved metal concentration at the outlet and additional inlets and outlets upstream and downstream of the rector bed. In the event that sensors detect an unacceptable level of contaminant in the fuel at fuel outlet  4 , filter regeneration may be performed, for example by passing a fluid through the reactor bed that displaces reversibly bound metal. 
         [0025]    In addition to DETA-silane, chelants useful for removing dissolved copper from fuel may include acyclic and macrocyclic polyamines such as cyclam, TETA, HDDETA, HDTETA, and aminopropyl silica. 
         [0026]    Chelants useful for the removal of other metal contaminants are provided in Table 1. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Chelants functionalized to capture metal ions. 
               
             
          
           
               
                   
                 Chelants 
                 Metal ions 
               
               
                   
                   
               
               
                   
                 2-Amino-1-cyclopentene-1- 
                 Ag(I), Hg(II), Pd(II) 
               
               
                   
                 dithiocarboxylic 
               
               
                   
                 acid (ACDA) 
               
               
                   
                 Bis(2-pyridylalkyl)amine 
                 Cu +2   
               
               
                   
                 Amidinothiourea 
                 Ag + , Au +3 , Pd +2   
               
               
                   
                 3-(1-thioureido) propyl 
                 Ag + , Au +3 , Pd +2 , Pt +2   
               
               
                   
                 3-(1-imidazolyl) propyl 
                 Transition Metals 
               
               
                   
                 3-(mercapto) propyl 
                 Hg +2   
               
               
                   
                 2 amino-1,3,4-thiadiazole 
                 Cu complex 
               
               
                   
                 2-Mercaptobenzimidazole 
                 Fe +3   
               
               
                   
                 2-Mercapto-5-phenylamino-1,3,4- 
                 Pb +2 , Cd +2 , Cu +2 , Hg +2   
               
               
                   
                 thiadiazole 
               
               
                   
                 1,8-Dihydroxyanthraquinone 
                 Fe +2 , Co +2 , Ni +2  Cu +2   
               
               
                   
                   
               
             
          
         
       
     
       EXAMPLE 
       [0027]    Copper was removed from Jet-A fuel at a flow rate of more than 1 gallon per minute (GPM) using a disc-shaped reactor bed ad shown in  FIG. 4 . The apparatus comprised a reactor bed 203 mm in diameter and having a depth of 127 mm packed with DETA-modified 70-230 mesh silica beads. Copper-laden Jet-A fuel having a copper concentration of 712 ppb was passed through this column. Samples were drawn from the effluent and tested for copper concentration. Copper concentration of effluent was found to be 65.9 ppb at a flow rate of 4300 mL/min (1.14 GPM) with a pressure drop of 11 psi. 
         [0028]    The reactor system selected to illustrate the present invention comprises a packed-bed reactor with DETA-silane supported on silica gel. In addition to packed-bed reactors other types of reactor configurations such as monolith and polylith reactors are also envisioned. 
         [0029]    Although there have been described particular embodiments of the present invention, it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.