Abstract:
A method is provided to produce a clean resid from a heavy hydrocarbon, the method including the steps of: feeding a heavy hydrocarbon to a conversion unit to convert at least a portion of the heavy hydrocarbon to lighter products and producing a resid, the resid comprising at least ten percent by weight components having true boiling points greater than 380° C. and further comprising at least some asphaltenes; contacting the resid with a naphtha to produce a mixed naphtha and resid, the naphtha comprising paraffin having from four to twelve carbons, the ratio of naphtha to resid high enough to result in precipitation of at least a portion of the asphaltenes in the resid; and separating a reject stream comprising asphaltenes and at least some solids from the resid to form a clean resid.

Description:
RELATED CASES 
       [0001]    This application claims benefit of U.S. Provisional Application No. 61/831,815, filed on Jun. 6, 2013, which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Heavy oils produced from, for example, the Athabasca region in northern Alberta, may be upgraded by, for example, a resid hydrocracking process such as “LCFining” so that the product may be sold to refiners on a basis similar to crude oils. The produced oils are refered to as “Syn Crude”. Thus, rather than the market for the heavy oils being restricted to purchasers with facilities specifically built to upgrade such heavy oils, the product may be sold in the broader market for crude oils. This results in better utilization of existing capital investments and improves profitability for both the upstream heavy oil producers and the refiners. The goal of this upgrading is therefore to provide a product that is similar to crude oils and at a minimum, meet specifications to be accepted by pipelines. So typically, the amount of upgrading, or the severity of the upgrader is dictated by the asphaltene content of the upgraded heavy oil. Other characteristics of the upgraded heavy oil will determine the value of the upgraded product. One of these characteristic is the amount of solids in the upgraded heavy oil. Solids in the upgraded oil decrease the value of the upgraded oil because of a tendency for the solids to foul heat exchangers and furnaces or become deposits on catalysts beds. 
         [0003]    Syn Crudes are often not solely the products of an upgrader, but a combination of the heavier portion of the upgrader product, along with a portion of naphtha diluted bitumen that has not been upgraded, and other steams such as depropanizer bottoms (mixtures of hydrocarbons containing four or five carbon atoms), to result in a product that meets pipeline specifications and can be marketed on a basis similar to crude oil. Depropanizer bottoms may be a naphtha boiling range material produced as a product of the upgrader such as a hydrocracker. U.S. Pat. No. 7,799,206 discloses a method to produce stable pipelineable blend from heavy residue for a catalytic hydroconversion process operating at a relatively high conversion rate by blending the heavy residue with virgin bitumen. The product from an upgrader being operated at high conversion rates would not meet pipeline specifications because the remaining asphaltenes in the product tend to precipitate. Blending the upgrader product with untreated bitumen is more economical that upgrading the whole volume to a lower conversion, and can result in a pipeline transportable product. 
         [0004]    U.S. Pat. No. 8,075,763 suggests a method to improve stability of aged crude oil to permit blending with lighter components without precipitation of asphaltenes by blending the aged crude with a phenol resin. It is also suggested that solids may be removed from the treated aged crude oil, and that the solid removal could be by filtration. The treated aged crude could be used, for example, as a bunker fuel, a fuel oil, or blending component therefore. 
         [0005]    U.S. Pat. No. 7,223,331 suggests a method for settling suspended finely divided inorganic solid particles from a hydrocarbon slurry using a hydroxy-terminated polyoxyalkylate additive and a polymer. The additive and polymer are added to the slurry in the range of 300-10,000 ppm and achieve solid removal over 50%. 
         [0006]    U.S. Pat. No. 4,572,777 discloses a method to produce a bitumen product having a low solids content by combining a tar sand with a solvent such that up to 25 percent of the bitumen remains undissolved, and separating the solids from the solution of solvent and dissolved bitumen is recovered. 
         [0007]    U.S. Pat. No. 6,059,957 suggests a process to convert heavy hydrocarbon into lighter product by using soluble transition metal salt and synthesis gas including soot particles and other impurities, e.g., silica fines, iron oxides. Such a process is reported to reduce sediment formation in the oil. 
       SUMMARY OF THE INVENTION 
       [0008]    A method is provided to produce a clean resid from a heavy hydrocarbon, the method comprising the steps of: feeding a heavy hydrocarbon to a conversion unit to convert at least a portion of the heavy hydrocarbon to lighter products and producing a resid, the resid comprising at least ten percent by volume of components having true boiling points greater than 380° C. produced by the conversion unit, and further comprising at least some asphaltenes ; contacting the resid with a naphtha to produce a mixed naphtha and resid, the naphtha comprising paraffin having from four to twelve carbons, the ratio of naphtha to resid high enough to result in precipitation of at least a portion of the asphaltenes in the resid; and separating a reject stream comprising asphaltenes and at least some solids from the resid to form a clean resid. 
         [0009]    The naphtha is preferably a light naphtha having greater than eighty percent by weight of the naphtha having true boiling point less than the boiling point of benzene. The weight ratio of naphtha combined with the resid may be between about 0.5 and 3. This amount of light naphtha may result in precipitation of less than about twenty percent by weight of the asphaltenes present in the resid, but removal of more than fifty percent weight of solids as indicated by the ash content of the resid. Reduction of the solids content of the resid significantly improves the fouling characteristics of the resid, and therefore renders the resid a much more desirable feedstock for refining. 
         [0010]    Blending of the clean resid of the present invention with untreated heavy hydrocarbon and naphtha may result in an advantageous marketable product. The product could contain a more severely hydrocracked residual, and less naphtha then a similar blend using residual not treated by the present process. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0011]    The FIGURE is a process flow diagram for one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to  FIG. 1 , a system according to the present invention is shown. A heavy hydrocarbon feed steam,  110 , which could be a bitumen or diluted bitumen, is feed to an upgrader  101 . The heavy hydrocarbon may have a specific gravity of 0.90 to, for example, 1.07 and could contain above 10% by weight components having a true boiling point above 380° C., or in other embodiments, more than 50 percent by weight components having a true boiling point above 380° C. The heavy hydrocarbon stream could be a vacuum flasher resid stream, or bitumen. The bitumen may have been produced from oil sands by a froth treatment process such as the process disclosed in U.S. Pat. No. 5,236,577, or a paraffinic solvent froth process such as the process disclosed in Canadian patent 2,232,929, the disclosure of which is incorporated herein by reference. The bitumen could also be produced from an insitu process such as cyclic steam injection or SAGD, or other improvements thereof such as solvent assisted SAGD. Diluted bitumen may be the bitumen, further comprising from one to thirty five percent by volume of naphtha, natural gas condensate or other hydrocarbon stream used, for example, to render the bitumen transportable by pipelines. 
         [0013]    The upgrader  101  may be a hydrocracker, fluid catalytic cracker, or a thermal cracker. When the upgrader is a hydrocracker, it may be a LCFining or H-Oil. A hydrocracker such as a LCFining or H-Oil process may operate at 40 to 85 percent conversion with conversion defined as the percent by weight conversion of 380° C. and heavier true boiling point components to products with true boiling points less than 380° C. These processes produce fine solid particles as a result of, for example, attrition of catalyst particles and production of coke. These solid fines remain in the residual liquid streams after distillation of the upgraded bitumen, and are concentrated in the resid. Thermal crackers may operate at conversions as low as ten to fifteen percent, and fluid catalytic crackers may operate at conversions as high as ninety eight percent. The upgrader preferably operates at a conversion in excess of 80 percent, with conversion, or within a range of 60 to 98 percent. 
         [0014]    Reactor products from the upgrader reactor pass through a series of separators and heat exchangers to provide recycle hydrogen, and an unstablized liquid product  111  that is then fractionated by conventional distillation into products having desired boiling ranges in fractionators  102 . Although the fractionator  102  is shown as one unit, it is to be understood that economical separation of the reactor products into maketable or further upgradable products may be accomplished in different known ways by one or more fractionators, fractionators with side draws and side draw strippers, vacuum fractionators, and/or separators. Fractionator  102  produces a resid  112  and at least one stream containing light products  113 . The stream containing light products  113  may then be, for example, fractionated into produced naphtha  115  and a light ends  114  in a depropanizer  103 . The depropanizer could remove most of the propane and lighter components from the stream containing light products, or it could be designed to remove butanes and lighter, or pentanes and lighter, depending on the desired products. The naphtha  115  could contain products having, for example, four to twelve carbon atoms each, four to eight carbon atoms each, or five to nine carbon atoms each. 
         [0015]    The resid stream  112  contains the unconverted bitumen having a true boiling point of 380° C. and greater, and also could contain lighter components such as gas oil or kerosene distillation range products depending on the distillation process utilized, and depending on the sharpness of the separations achieved in the fractionators  102 . 
         [0016]    The resid  112  is feed to a mixer  104  where it is combined with naphtha  117 . The naphtha  117  could be, for example, depropanizer bottoms, or it could be imported naphtha  116  from a source other than the upgrader products. For example, the imported naphtha could comprise stabilized or unstabilized natural gas condensate. The naphtha may contain at least thirty percent by weight paraffinic hydrocarbons. The paraffinic hydrocarbons may contain between four and twelve carbon atoms, or between five and eight carbon atoms. The naphtha could be a mixture containing at least ninety percent by weight of five and six carbon atom paraffins. For example, the naphtha could contain at least twenty percent by weight pentane. The naphtha preferably contains less than about fifty percent by weight aromatics and more preferably less than about five percent by weight aromatics. The amount of naphtha needed to be effective may depend on the composition of the naphtha, but general, a volume ratio of naphtha to bitumen may be between about 0.1 and 6 or between about 0.5 and 3. When the naphtha is a mixture of mostly pentanes and hexanes with greater than about 85 percent by weight paraffins, a weight ratio of between about 0.5 to 3 of naphtha to resid may be used. The ratio of naphtha to resid should be sufficient, considering the composition of the naphtha, to result in precipitation of at least some asphaltenes. Preferably at least five but not more than about fifty percent by weight of the ashphaltenes in the resid stream are caused to precipitate as a result of the combination of the resid stream with the naphtha. 
         [0017]    The tendency of asphaltenes to precipitate is indicated by the P-value of the mixture. The P-Value is the measured ratio between the peptizing power, or available aromaticity, and the flocculation ratio, which is the aromaticity required to keep the asphaltenes in solution. The P-value test is described in the paper “Developments in Fuel Oil Blending” presented by F. G. A. van den Berg at the 7th International Conference on Stability and Handling of Liquid Fuels in Graz, Austria, 24-29 Sep., 2000 (IASH-2000), the disclosure of which is incorporated herein by reference. A P-value less than 1 indicates that asphaltenes are subject to precipitation. Sufficient naphtha is added combined with the resid to result in the P-value of the resulting mixture to be one or less. This results in precipitation of asphaltenes. 
         [0018]    Mixer  104  may be a static mixer, a pump, or any know means to create contact between two fluids. The mixed naphtha and resid  119  is then separated by separator  105  to a clean resid  121  and a reject stream  120 . The reject stream may contain mineral solids, coke particles and asphaltenes along with along with some resid. The reject stream may contain at least fifty percent of the ash in the resid, or greater than eighty percent of the mineral solids from the original resid, as indicated by the ash content of the two streams. The clean resid may contain less than about 0.2 percent by weight ash. The reject stream may contain more than five percent of the asphaltenes from the resid, but sufficient removal of solids may be accomplished with removal of less than twenty percent of the ashpaltenes present in the resid. In one embodiment, between one and ten percent of the ashpaltenes are removed by the present invention. This level of asphaltene removal may be effective to result in a twenty percent, or a fifty percent reduction of the ash content of the resid. Although decreasing the asphaltenes content of the resid increases the value of the resid, a significant benefit of the present process is reduction of the solids content of the stream. It has been found that precipitation of ashphaltenes from this stream according to the present invention enhances agglomeration of the solids with ashphaltenes and enables removal of solids. Clean resid may be produced that contain having, for example, ash content of less than 0.05 percent as measured by ASTM D-473. 
         [0019]    The mixer  104  and separator  105  may be combined in one unit operation where the naphtha and resid are contacted and then separated, or a system similar to know solvent deasphalting processes such as the processes disclosed in WO/2007/001706, which disclosure is incorporated herein by reference, may be utilized. 
         [0020]    Separator  105  may be a centrifuge, cyclone or hydroclone, or may be a settler such as a parallel plate separator or a gravity settler. A filter could also be utilized. Any means known to be effective for removal of solids from fluids may be utilized. If a centrifuge is used, it may be a centrifuge which is capable of applying at least 100 times the acceleration of gavity (100 g forces). The settler could be accomplished in a gravity settling vessel. The separation of the reject stream from the mixed naphtha and hydrocracked resid could beaccomplished at a temperature of between 20° C. and 300° C., or between 50° C. and 150° C. 
         [0021]    Optionally, naphtha could be removed from the clean hydrocracked resid by vacuum distillation or by flashing off naphtha in naphtha removal vessel  106  to provide a removed naphtha  122  and a clean solvent-free resid  123 . Removed naphtha  122  could be recycled to naphtha  117 , or could be produced as a naphtha product. This could be desirable if it is desired to use a higher ratio of naphtha  117  to hydrocracked resid  112  than what would be necessary to obtain an on-specification marketable product. Removal of some naphtha may also result in a more stable mixture with respect to asphaltene precipitation, than the clean hydrocracked resid. 
         [0022]    The clean resid  121 , or clean solvent-free resid  123  could be combined with raw bitumen, diluted bitumen, natural gas condensate, and/or middle distillates  124  and/or additional naphtha,  126  to form a marketable product  125 . The marketable product may meet relevant pipeline specifications and has low fowling characteristics. The ratio of clean resid to bitumen that has not been hydrocracked may be between 0.1 and 10, or in another embodiment, between about 0.5 and 5. 
         [0023]    Use of a light naphtha stream as naphtha  117 , comprising more than eighty percent by weight components lighter than benzene could reduce the amount of naphtha necessary to cause precipitation of ashpaltenes. After removal of the naphtha from the clean hydrocracked resid, a heavier naphtha, comprising less than twenty percent by weight of components lighter than benzene, could be used as diluent to produce marketable product. 
         [0024]    Because benzene toluene and other aromatics may be included in this heavy naphtha, it could enable production of a marketable product having a higher P-value, or reduce the amount of other components needed to result in an acceptable marketable product. 
       EXAMPLES 
     Example 1 
       [0025]    A hydrocracked heavy resid (sample 1) and a light hydrocracked stream, produced from the same hydrocracking process, were mixed in a capped container at ambient condition for around 2 hours until a homogenous blend was reached. The light hydrocracked stream contained about 6.7 weight percent normal butane, 20.1 weight percent by weight isopentane, 2.6 percent by weight normal pentane, 2.4 percent by weight cyclopentane, 1.5 percen tby weight nomal hexane, 3 percent by weight methylcyclopentane, 0.8 percen tby weight benzene, 2.4 percent by weight cyclohexane, and 9.2 percent by weight six carbon number isoparaffins. The light hydrocarbon mixture contined about 42 percent by weight components having true boiling points less than about 65° C., and about 1.3 percent by weight components having a true boiling point abouve 200° C. The light hydrocracked stream had an API gravity of 72. The light hydrocracked stream was mixed with the heavy resid at ratios of, 0.25:1 and 0.45:1 (vol/vol). The two resultant light/heavy blends (samples 2 and 3 respectively) were separated to two phases by gravity by letting the samples sit at ambient temperature for 48 hours. The lighter phase was decanted and then centrifuged at 20000 rpm for fifteen minutes (samples 4 and 5). The bottom phase (samples 6 and 7) contained more heavy materials, e.g., asphaltene. The top phases contain less heavy materials. 
         [0026]    Characterization of the two separated product samples from each blend were carried out in order to determine the product properties as specified in the results Table. It is quite clear that there is only a small reduction of asphaltene, e.g., from 8.39wt % and 7.78wt %, in samples 2 and 3, to 6.86wt % and 5.68wt %, in samples 5 and 6, respectively. Similarly, densities of the corresponding samples were also slightly decreased. The solid content in the samples are found to drop significantly. For example, toluene insolubles dropped from 0.24wt % to 0.05wt % for sample 4 and from 0.29wt % to 0.02wt % for sample 5. As a result, there was a significant increase of toluene insolubles in the bottom samples, samples 6 and 7. Furthermore, ash content in the samples dropped significantly. Properties of the streams are shown in Table 1. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 ASTM 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Test 
               
               
                 Property 
                 method 
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Density 
                 D-4052 
                 Kg/m 3   
                 1030.7 
                 987.5 
                 954.7 
                 984.1 
                 947 
                   
                   
               
               
                 Viscosity 
                 D-445 
                 cSt 
                   
                   
                 1638 
                 8143 
                 1114 
               
               
                 at 40° C. 
               
               
                 P value 
                 D-7060 
                   
                 1.01 
                 .97 
                 .96 
                 1.04 
                 1.17 
               
               
                 nC7 
                 D-3279 
                 Wt % 
                 7.28 
                 8.39 
                 7.78 
                 6.86 
                 5.68 
                   
                 26.39 
               
               
                 insoluble 
               
               
                 Toluene 
                 D-473 
                 Wt % 
                 0.18 
                 0.24 
                 0.29 
                 0.05 
                 0.02 
                 1.5 
                 2.92 
               
               
                 insoluble 
               
               
                 Ash 
                 D482 
                 Wt % 
                 0.62 
                 0.058 
                 0.056 
                 0.029 
                 0.010 
                 0.244 
                 0.413 
               
               
                   
               
             
          
         
       
     
       Example 2   
       [0027]    A hydrocracked heavy resid, was blended with a commercial light paraffinic solvent of C4-C7 at weight ratios of 0.5, 1.0, 1.5 and 2.0 of solvent to resid. The resultant blends were allowed to gravity separate for about 48 hours under ambient conditions. A top phase was decanted and processed in a rotary evaporator at about 110° C. to remove the light paraffinic solvent. These samples were then tested for various properties as listed in Table 2. The total solids (determined by ASTM D7840) were reduced substantially from 0.21wt % in the feed sample to less than 0.01wt % in the products. The asphaltene content was significantly lower in the decanted material as opposed to the initial resid. The initial resid contained 9.2wt % asphaltenes and the decanted products contained about 1-2wt % asphaltenes. The asphaltene stability (P-value) increased from 1.05 for the feed to 1.18-2.24, depending on the solvent ratio. The higher the solvent/feed ratio, the more stability improvement was detected in the product, and the more reduction in asphaltene content as well as the total solid content. Furthermore, density and viscosity, albeit with only one data set for the 0.5 S/F sample, were also found to improve (decrease). Properties for the heavy hydrocracked resid and resid after having been combined with the solvent, decanted, and solvent removed, are shown in Table 2. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 ASTM 
                   
                 Solvent to heavy 
               
               
                   
                 Test 
                 Heavy 
                 resid weight ratio 
               
             
          
           
               
                 Property 
                 method 
                   
                 resid 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
               
               
                   
               
             
          
           
               
                 Total 
                 D-7840 
                 Wt % 
                 0.21 
                 &lt;0.01 
                 &lt;0.01 
                 &lt;0.01 
                 &lt;0.01 
               
               
                 solids 
               
               
                 nC7 
                 D-3279 
                 Wt % 
                 9.2 
                 7.04 
                 4.72 
                 1.17 
                 2.19 
               
               
                 Insoluble 
               
               
                 p-value 
                 D-7060 
                   
                 1.05 
                 1.18 
                 1.41 
                 2.24 
                 1.55 
               
               
                 Viscosity 
                 D-445 
                 cSt 
                 189.7 
                 133.7 
               
               
                 at 100° C.