SORDS PURIFICATION by LBPSE A System And Method For Processing Backwashed Catalyst Ret

Abstract

A method for separating catalyst particles from the FCC slurry oil present in the retentate of a filtered FCC slurry oil run-down stream is disclosed. The method comprises backwashing the run-down stream filter with a low boiling point solvent to extract slurry oil from the catalyst in the retentate. The backwash solution is sent to a digester where the catalyst fines are separated from the hydrocarbon component (solvent and slurry oil). The catalyst fines are collected and dried. The dried catalyst fines can be transported via pneumatic systems, and can be regenerated for further use as FCC catalysts. The solvent vapor from the drying process is collected for potential reuse. The hydrocarbon component is sent from the digester to an evaporator to evaporate the solvent from the slurry oil. The FCC slurry oil and the solvent exiting the evaporator can be independently collected. The solvent from the evaporator can be reused in the process.

Claims

1. A method for processing a backwash feed resulting from the backwashing of catalyst retentate filtered from a FCC slurry oil run-down stream (SORDS) generated by a fluid catalytic cracker to separate catalyst fines from FCC slurry oil and to purify the catalyst fines; the backwashed feed comprising catalyst fines backwashed from the filtration, residual FCC slurry oil that has been retained in the pores or on the surface of the catalyst, and low boiling point solvent used as a backwash medium; the method comprising: a. feeding the backwashed feed to a digester; b. separating the catalyst fines of the backwash feed from the low boiling point solvent and slurry oil of the backwash feed; c. decanting the solvent/slurry oil layer from the digester; d. separating the solvent from the slurry oil; e. delivering solvent-moist catalyst fines from the digester to a dryer; and f. drying the catalyst fines.

2. The method of claim 1, further comprising agitating the backwash feed in the digester.

3. The method of claim 1, further comprising adding additional low boiling point solvent to the backwashed catalyst retentate.

4. The method of claim 3 wherein the additional low boiling point solvent is introduced into the digester independently of the backwashed catalyst retentate.

5. The method of claim 1 wherein the step of separating the catalyst fines from the low boiling point solvent and slurry oil comprising allowing the catalyst fines to settle out of the solvent/slurry oil portion by gravity.

6. The method of claim 1 wherein the step (d) of separating the slurry oil from the solvent is accomplished by evaporation.

7. The method of claim 1 including a step of filtering the solvent/slurry oil solution prior to the separating step (d) to remove any remaining catalyst fines from the solution.

8. The method of claim 1 wherein the step of separating the solvent from the slurry oil comprises evaporating the solvent out of the solvent/slurry oil solution.

9. The method of claim 1 including the steps of: g. isolating the solvent from the solvent/slurry oil portion; and h. isolating the slurry oil from the solvent/slurry oil portion.

10. The method of claim 9 wherein the isolated solvent is used as at least part of the backwash medium.

11. The method of claim 9 wherein the isolated slurry oil is transferred to a slurry oil storage tank.

12. The method of claim 1 wherein solvent vapor evaporated from the solvent-moist catalyst fines during the drying step is reclaimed.

13. The method of claim 1 including a step (i) of collecting the dried catalyst fines.

14. The method of claim 1 wherein the dryer comprises a conveyor dryer or an auger dryer.

15. The method of claim 14 wherein the conveyor dryer is sloped, such that an entrance end of the conveyor is below an exit end of the conveyor.

16. The method of claim 1 wherein the drying step comprises drying the catalyst such that the catalyst is less than about 2% solvent.

17. The method of claim 1 wherein the drying step comprises drying the catalyst such that the catalyst is less than about 1% solvent.

18. The method of claim 1 wherein, the catalyst delivered to the dryer contains up to about 4% solvent by volume.

19. The method of claim 1 wherein, the catalyst delivered to the dryer contains about 20% to about 40% solvent by volume.

20. (canceled)

21. (canceled)

22. (canceled)

23. A method for processing and purifying a slurry oil run-down stream (SORDS) generated by a fluid catalytic cracker in order to reduce deleterious effects of using FCC Slurry Oil as backwash to an FCCU riser; the method comprising: a. filtering the FCC slurry oil run-down stream in a filter on a continuous basis to separate catalyst fines in the slurry oil run-down stream from slurry oil of the stream; b. periodically backwashing the filter with a solvent to remove catalyst fines trapped by the filter from the filtering step to generate a backwashed catalyst retentate, said retentate comprising catalyst fines backwashed from the filtration, residual slurry oil that has been retained in the pores or on the catalyst surface, and low boiling point solvent used as a backwash medium; and c. processing the backwashed catalyst retentate (i) to substantially remove the slurry oil from the catalyst fines and (ii) to separate the solvent from the catalyst fines and slurry oil.

24. The method of claim 23, wherein said step of processing the backwashed catalyst comprises: d. feeding the backwashed catalyst retentate to a digester; e. separating the catalyst fines of the backwash feed from the low boiling point solvent and slurry oil of the backwash feed; f. decanting the solvent/slurry oil portion from the digester; g. isolating the solvent from the slurry oil; h. delivering solvent-moist catalyst fines from the digester to a dryer; and i. drying the catalyst fines.

25. The method of claim 1 wherein the drying step comprises drying the catalyst such that the catalyst is less than about 0.25% solvent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic flow diagram of the current method.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] While the invention is susceptible of embodiment in many different forms, there is described in detail preferred embodiments of the claimed invention. It is to be understood that the present disclosure is to be considered only as an example of the principles of the claimed invention. This disclosure is not intended to limit the broad aspect of the claimed invention to the illustrated embodiments. The scope of protection should only be limited by the claims.

[0026] The present method typically includes eight (8) stages or steps, as follows: [0027] 1. Continuous Filtration of the FCC Slurry Oil Run-Down Stream; [0028] 2. Backwash of catalyst from the respective filtration system with a low boiling point solvent; [0029] 3. Digestion of the backwash mixture by mixing and subsequent settling of the catalyst; [0030] 4. Decanting of the upper, hydrocarbon layer containing LBPS and extracted FCC Slurry Oil; [0031] 5. Filtration of the decanted hydrocarbon layer; [0032] 6. Evaporation of LBPS from the FCC Slurry Oil; [0033] 7. Fluffing of the solvent-moist catalyst; [0034] 8. Condensation & Recovery of vaporized LBPS resulting from both the fluffing process and Evaporation of LBPS from the recovered FCC Slurry Oil.

[0035] In a broad overview of the present invention the resolution of the components of the back washing exercise, i.e. FCC slurry oil, catalyst retentate and solvent, are sent to a Digester vessel. The inorganic catalyst constituent, the solvent used for the filter backwash and extraction of FCC slurry oil from the catalyst surface and pores and the extracted residual FCC slurry oil are mixed/digested. After digestion, the solvent/catalyst-retentate/heavy-oil mixture is left to settle. The hydrocarbon layer is then decanted and filtered. The solvent is then distilled from the heavy oil with minimal thermal requirements. After decanting the hydrocarbon layer from the digester, the remaining settled catalyst, moist with solvent, is transferred to a heated conveyor where total vaporization of the solvent is assured and achieved in a procedure referred to as fluffing. The LBPS vapor product of evaporation, fluffing and heated transport is condensed, recovered and finally recycled back into the K-170 Resolution Process.

[0036] The flow of FCC Slurry oil from the FCCU Fractionator 10 in accordance with my SORDS Purification by K-170 Resolution method is shown schematically in the flow diagram of FIG. 1. The FCC Slurry Oil Run-down Stream (SORDS) is initially delivered to a bank of in line filter assemblies 12 by way of piping 14 and is directed to one of those filter assemblies. The FCC slurry oil from the FCCU fractionator 10 can be about 800 ppm to about 1200 ppm (about 0.08% to about 0.12%) catalyst. While only one filter assembly is needed, preferably, there are at least two filter assemblies 12 because the SORDS process is continuous and the filter assemblies must be periodically backwashed (requiring that the filter assemblies temporarily stop filtering the SORDS). The filter assemblies 12 separate FCC catalyst solids (cat' fines) from the FCC slurry oil. The filtrand (i.e., the cat' fines) from the SORDS is trapped and collected in the filter assemblies 12. The filtered FCC slurry oil exits the filter assemblies 12 to be delivered to an FCC slurry oil storage tank 16 over piping 18. The filtered FCC slurry oil sent to storage tank 16 is substantially free of catalyst solids, i.e., less than about 200 ppm (about 0.02%) catalyst, and potentially as low as about 20 ppm (about 0.002%). Stated differently, the FCC slurry oil exiting the filter assemblies 12 through piping 18 is at least 99.9% (and preferably about 99.98% to about 99.998%) FCC slurry oil. The SORDS retentate (which is trapped by the filter assembly) comprises cat' fines and FCC slurry oil.

[0037] The filter assemblies 12 preferably filter the FCC slurry oil run-down stream via porous metal filtration and/or electrostatic attraction (using charged glass or ceramic beads). A porous metal filter has a void size in the range of 0.5 micron to about 2 microns, which is smaller than the cat' fines (which have an average particle size or APS of about 30 microns). In addition, the filter assemblies 12 can have a diameter of about 24 to about 48, and preferably, about 24 to about 36, and a height of about 8 feet to about 9 feet (to define a filtering volume of about 250 gallons to about 300 gallons). Such a filter assembly would need to be purged (cleaned) of the entrapped cat' fines, for example, 2-3 times/day. As can be appreciated, the frequency with which the filter assemblies 12 need to be purged or backwashed, will be affected by the size of the filter assemblies (smaller or larger filter assemblies could be used) and by the volume of FCC slurry oil run-down stream passing through the filter assemblies.

[0038] To purge or backwash the filter assemblies, a low boiling point solvent (LBPS) is delivered from a LBPS storage 20 over an LBPS line 22 to the filter assemblies 12 to backwash the filter assemblies and remove trapped cat' fines from the filter assemblies 12. The solvent is preferably dimethyl formaldehyde, which has a boiling point of about 132.8 F. (56 C.). Although, as noted above, other solvents can be used. For example, petroleum ether and chloroform would also work. For the filter assemblies 12 to filter the cat' fines from the FCC slurry oil run-down stream (and thus separate or isolate the cat' fines from the FCC slurry oil), the FCC slurry oil run-down stream must have a low viscosity. This is typically met, because the FCC slurry oil run-down stream is hot when it exits the FCC unit. For example, the FCC slurry oil run-down stream can be in excess of 300 F. when it enters the filter assemblies 12. This is substantially above the boiling point of the solvent. The preferred solvent, dimethyl formaldehyde, has a boiling point of about 133 F. Thus, the filter assemblies must be cooled prior to introducing the solvent into the filter assemblies. The filter assemblies can be cooled in any desired manner.

[0039] To backwash the filter assemblies, the filter assemblies 12, once cooled, are filled with solvent (the backwash medium). The SORDS retentate may increase in viscosity as the filter assemblies are cooled. However, the solvent introduced into the filter assemblies 12 will reduce the viscosity to enable the retentate to be backwashed from the filter assemblies. When the filter assembly is filled with solvent, the ratio of the solvent to catalyst is at least 2:1 by volume, and can be 4:1, 6:1 or even as high as 8:1 by volume. Thus, the solvent:catalyst ratio can be from about 2:1 to about 8:1, from about 2:1 to about 6:1, from about 2:1 to about 4:1, from about 4:1 to about 6:1 from about 4:1 to about 8:1, or from about 6:1 to about 8:1.

[0040] Once the filter assembly is filled with solvent, the filter assembly vents are closed, and the filter assembly is pressurized under a nitrogen atmosphere to about 60 psi to about 80 psi. A valve (not shown) at a bottom of the filter assembly is opened to allow the backwash feed (i.e., the solvent, cat' fines and FCC slurry oil retained on or in the cat' fines) to exit the filter assembly.

[0041] Vendors of in-line slurry oil filter assemblies have shown to be proficient in developing automated backwash software and actuated valves that efficiently provide for transfer of the SORDS from one filter assembly to another and back again over the course of back wash cycles.

[0042] The backwash feed from the filter assemblies 12 is delivered to a digester 24 over backwash piping 26. The digester can be sized to receive all of the backwash from the filter assemblies 12, such that the digester is operated on a batch basis. The backwash feed contains catalyst (cat' fines) backwashed from the filter assembly, residual FCC slurry oil that has been retained in the pores or on the catalyst surface, and the LBPS that acts as the back wash medium. Additional low boiling point solvent may be delivered to the digester 24 by means of piping 28. This additional solvent delivered to the digester, if used, is the same solvent used to backwash the filter assemblies 12. As noted above, the LBPS dissolves and extracts FCC slurry oil retained on the surface and in the pores of the cat' fines to thereby extract the FCC slurry oil from the catalyst into the LBPS. If a sufficient amount of solvent is used during the backwash of the filter assembly 12, the solvent introduced into the filter assembly should be sufficient to substantially remove or separate the FCC slurry oil in the retentate from the cat' fines. For example, additional solvent should not be necessary if the solvent:catalyst ratio is at least 4:1 by volume.

[0043] As seen in the FIGURE, the digester 24 has an upper portion and a lower, cone-shaped portion. The backwash feed is preferably introduced into the digester upper portion. In the digester 24, the backwash feed from the filter assemblies 12 (and any additional LBPS, if added) are agitated using an impeller or agitator 30. The backwash solution generally need not be agitated for very long. Fifteen minutes of agitation is sufficient to ensure that the desired amount of the FCC slurry oil in or on the catalyst in the backwash is extracted from the catalyst. Although an impeller is used to agitate the backwash/LBPS solution in the digester, other methods could be used to agitate the solution in the digester.

[0044] After the agitated mixing, the impeller 30 is deactivated and the catalyst constituent is allowed to settle out of the hydrocarbon portion into the lower conical portion of the digester 24. This results in a lower catalyst layer and an upper hydrocarbon layer in the digester. Preferably, the catalyst that settles out is not 100% free of FCC slurry oil. Rather, the catalyst that settles out in the digester contains about 2-4% FCC slurry oil. The upper hydrocarbon layer is comprised primarily of LBPS containing dissolved FCC slurry oil. As can be appreciated, even after the catalyst portion has settled out of the hydrocarbon portion, catalyst particles and ultra-fines may remain in the hydrocarbon portion, and are part of the hydrocarbon layer. Preferably, the cat' fines settle out of the hydrocarbon portion under gravity. The digester can be provided with a second impeller 32 or auger to help force the catalyst from the digester 24 after the catalyst particles have settled. This second impeller 32 or auger is operated to rotate in a direction opposite that of the agitating/mixing impeller 30.

[0045] After the catalyst has settled out of the hydrocarbon portion (LBPS and FCC slurry oil), the upper hydrocarbon layer is decanted from the digester. The hydrocarbon layer is initially delivered to a filtration system 34 to remove any unsettled cat' fines. The filtered hydrocarbon layer is then sent to an evaporator 36 where a reboiler provides heat to evaporate (and isolate) the solvent from the FCC slurry oil. The solvent, as noted, is a low boiling point solvent. The preferred solvent, dimethyl formaldehyde, has a boiling temperature of 132.8 F. (56 C.). Thus, the energy requirements to evaporate the solvent are not great. The evaporated LBPS (i.e., LBPS vapor) exits the evaporator over a line 38 and is directed to a chiller 40 where the LBPS vapor is condensed. The liquid LBPS is then sent to the LBPS storage vessel 20 to be reused in the filter assemblies 12 and the digester 24. The FCC slurry oil is removed from the bottom of the evaporator 36 and is delivered to the FCC slurry oil storage tank 16 over piping 42.

[0046] Returning to the digester 24, the cat' fines that settle at the bottom of the digester 24 are solvent-moist, and can have a solvent content of about 20% to about 40%. The solvent-moist, settled cat' fines exit the digester 24 through piping 44 which delivers the solvent-moist, settled cat' fines to a drying unit 46. Piping 44 can, for example, incorporate an auger to deliver the solvent-moist cat' fines to the dryer. The drying unit 46 can, for example, be a heated conveyor or auger. In view of the fact that the boiling point of the solvent is low, the drying unit need not heat the solvent-moist cat' fines to a high temperature to evaporate the solvent from the cat' fines (i.e., to dry the cat' fines). For the preferred solvent, dimethyl formaldehyde, the conveyor need only heat the solvent-moist catalyst to a temperature of, for example, 160 F. The residence time of the cat' fines in the dryer depends on the volume of cat' fines being dried, the moisture content, and the dryer temperature. For example, for solvent-moist cat' fines (in which the cat' fines have a moisture content of about 20%) to about 40%), the residence time in the dryer rated to handle about 1666 lbs/hr is about 25 minutes. Obviously, the residence time of the cat' fines in the drying conveyor can be varied by altering the temperature of the drying unit, the solvent content of the cat' fines entering the drying unit, and the thickness of the layer of cat' fines being dried. However, the drying time is sufficient to evaporate substantially all the solvent from the cat' fines, such that the dried cat' fines have a solvent content of less than about 2%, and preferably less than about 0.25%, and even more preferably, about 0%.

[0047] The dryer is outfitted with an overhead manifold 48 which receives the LBPS vapors and which directs the LBPS vapor over piping 50 to the chiller 40 for condensation. The now liquid LBPS is directed to the LBPS Storage Vessel 20. The dryer conveyor 46 is shown to slope upwardly from its inlet end 46a where solvent-moist catalyst is fed into the conveyor to its exit end 46b where the dried solvent exits the conveyor. The slope is not so great that it will impede the transport of the catalyst along the conveyer, yet is sufficiently steep to facilitate the collection of LBPS vapors near the top (exit end) of the conveyer. The manifold is positioned toward the upper exit end of the conveyor. This allows for the solvent vapors to flow upwardly through the conveyor, and reduces the possibility of solvent vapors remaining in the conveyor (dryer) housing.

[0048] The dried catalyst exits the conveyor at the exit end, and is collected in a hopper

[0049] 52. The dried catalyst is, as noted above, substantially solvent free, and, as noted above, has a solvent content of less than 2%, and preferably less than about 0.25%, and even more preferably, about 0%. Thus, the dried catalyst is powder-like. With an average size of about 30 microns, the dried catalyst can be handled and transported pneumatically. As noted above, the dried catalyst, although substantially solvent free, contains up to about 4% by weight FCC slurry oil. The slight amount of FCC slurry oil facilitates transportation of the dried catalyst and helps reduce catalyst dust levels. The reclaimed, dry catalyst is preferably returned to the FCCU at a point just upstream of the FCC regenerator. This allows the catalyst to undergo regeneration thereby reactivating the catalyst for service in the FCC conversion process. Alternatively, the catalyst can be transported for disposal.

[0050] Importantly, other than the filter assemblies 12, the components of the SORDS purification system operate at ambient pressure. Additionally, the filter assemblies and the digester operate at ambient temperatures. As noted above, the FCCU fractionator 10 operates continuously. However, the filter assemblies 12 need only be back-flushed periodically. Thus, the purification system (i.e., the separation of the FCC slurry oil component and catalyst component of the SORDS retentate, and then the separation of the solvent from the FCC slurry oil and the catalyst) is conducted as a batch operation.

[0051] Although not disclosed, one of ordinary skill in the art will recognize that the disclosed system will also include necessary pumping equipment to move the various solutions through the system.

[0052] While the specific embodiments have been described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection should only be limited by the scope of the accompanying claims. For example, the additional solvent that is introduced into the digester (over line 28) could be introduced into the backwash feed passing though piping 26, such that the backwash and additional solvent enter the digester together. Depending on the amount of solvent used to backwash the filter assemblies 12, it may not be necessary to add the additional solvent to the backwashed retentate (feed) to extract and/or separate a desired amount of the FCC slurry oil from the cat' fines in the digester. If the piping delivering the backwash from the filter assemblies 12 to the digester sufficiently agitate the backwash, there may not be any need to mix or agitate the backwash in the digester, and the catalyst portion of the backwash can simply be allowed to settle out of the hydrocarbon portion of the backwash. Although heat is preferred as the method to dry the cat fines, the dryer 46 could rely on vacuum pressure to remove the solvent from the cat fines which exit the digester. These examples are merely illustrative.