PROCESS FOR REMOVING HYDROCARBONS FROM A LIQUID MIXTURE WITH A REGENERABLE FILTER

Abstract: There is provided a process for removing hydrocarbons from hydrophilic solutions in which the adsorbent is regenerated in situ. A solution containing at least one hydrocarbon impurity is passed through a resin bed and the hydrocarbon is retained by the resin. The solution passes from the resin bed substantially reduced of hydrocarbons. The filtration bed containing the resin is regenerated in situ by passing a second liquid therethrough such that the hydrocarbon is removed in the second liquid stream and the resin is available for reuse.

Description: PROCESS FOR REMOVING HYDROCARBONS FROM A LIQUID MIXTURE WITH A REGENERABLE FILTER FIELD OF THE INVENTION This invention relates to a process for removing hydrocarbons from a solution. More particularly, this invention relates to a process for absorbing hydrocarbons from a solution onto a medium and to the in si tu regeneration of the absorbing medium. Typically, the solutions are composed of polar solvents, such as alkanolamines, glycols, sulfolane, and their aqueous mixtures . BACKGROUND OF THE INVENTION The removal of acid gases (such as H 2 S and C0 2 ) from natural gases, enhanced oil recovery gases, petroleum gases and liquids, tail gases, ammonia plant gases, coke oven gases, and the like, is commonly accomplished by alkanolamine sweetening units. When alkanolamine amine solutions are used to absorb acid gases from gas and liquid streams, hydrocarbons may also be absorbed or entrained in the alkanolamine solution. The aqueous solutions of alkanolamines are contacted with streams containing H 2 S and CO;, the H 2 S and C0 2 dissolve into the alkanolamine solution to form solvated alkanolamine salts (e.g., protonated alkanolamine cation with HS " ar.a HC0 3 " anions; . The solution of water, unreacted alkanolamine, and alkanolamine salts is subjected to steam stripping to decompose the alkanolamine salts and remove K;S and CO 2 from the alkanolamine. Thiocyanate anion (SCN ~ ), for example, forms from the reaction of HCN with H 2 S or sulfides in the gases from crude units or catalytic reformers. Other typical alkanolamine salt anions include S;^' '- , S0 3 " ~ , SO, ? 2" , HC0 2 ~ , CH 3 C0; ~ , and the like. These alkanolamine salts cannot be removed by steam stripping. Thus, they are called heat stable salts and remain in the system where they accumulate in the alkanolamine solution, gradually depleting the e fectiveness of alkanolamine treatment. Generally, the heat stable salt anions are removed by exchange with hydroxide from an anion exchange resin and cations, such as sodium and potassium, are removed by exchange with hydrogen ion from a cation exchange resin. Ion exchange to remove heat stable salts from alkanolamine solutions has been a subject in the patent literature for many years, see for example, Taylor, U.S. Patent No. 2,797,188; Pearce, U.S. Patent No. 4,477,419; Keller, U.S. Patent No. 4,970,344; Yan, U.S. Patent No. 4,795,565; Veatch, U.S. Patent No. 5,006,258; and Cummings, U.S. Patent No. 5,162,C34. Unfortunately, hydrocarbons also cause problems for alkanolamine system operations even at very low concentrations (i.e., cleaning natural gas). Scrubbing efficiency and stripping efficiency are reduced, foaming can cause upsets and solvent loss, production may be curtailed, and environmental discharge limits may be exceeded. The situation is mirrored in other solvent extraction processes that employ r.ydrophilic solvents such as giycol dehydrators . C-irrent technology relies on - A - absorption onto activateα caroon granules to remove hydrocarbons from amine systems. For example, U.S. Patent 2,762,852, is directed to an adsorption process in which a hyαrocaroon is contacted with activated carbon. When saturated, the activated caroon must be separately regenerated or exchangee for new carbon. Thus activated carbon adsorption is expensive ana labor intensive. In another type of process, .S. Patent 2,963,519 uses a zeolitic molecular sieve as the adsorbent to remove small diameter nydrocarbons from petroleum refinery hydrocarbon streams. The molecular sieves are regenerated by heating and passing hot adsorbate through the bed. In another process, that disclosed in German Patent No. 155,036, aromatics are removeα from non-aqueous hydrocarbon mixtures by adsorption onto a cation ion- exchange resin that has been charged with silver ions. Adsorbed aromatics are desorbed by flowing water through the resin, then the adsorbed water is removed from the resin by evaporation or by flashing with a volatile solvent . In yet another type of process, U.S. patent 2,718,489 to Coonradt et al., αescrioes removing ionic mercaptans from non-aqueous hydrocarbon mixtures using ion exchange resins. After tne ion exchange capacity of the resins is consumed, typical ionic regeneration of the resin is done. This patent has for its purpose a method of activating fresh or regenerateα ion-exchange resin by contacting with one or a mixture cf lower molecular weight mononydric alconols prior to cleansing a hydrocarbcr fluid. The activaticr is said to improve the effectiveness of the resm at removing mercaptans from nydrocarbon liquids. Another type of process, U. S. Patent 4,775,475 to Johnson, αescπbes removing Hydrocarbons from an aqueous feed stream by contacting the stream with an adsorbent whereby the spent adsoroent is regenerated by means of an elution solvent. Examples of suitable adsorbents include molecular sieves, amorpnous silica-alumina gel, silica gel, activated carbon, activated a_umma and clays. Examples of elution solvents include naphtha, kerosene, diesel fuel and gas oil. It has been discovered that h ydrocarbon impurities can be removed from hyαrophillic solvent solutions by means of water-wet resins and that these resins can be regenerated without the use of hyαrocarbon solvents. It is, therefore, the genera-, object of the present invention to provide a process for absorbing hydrocarbons from an alkanolamine-, glycol-, or other polar solvent- containing solution onto an ion exchange resm and to the in si tu regeneration of the ion exchange resm. Anotner object of this invention is to provide a process for regenerating a filter oed of ion exchange resm having a hydrocarbon adsorbeα thereon. SUMMARY OF THE T VENTION In accordance with the prese n t invention, there is provided a process for removing r^drocarbons from liquid streams sαci as an amme-contammg solution or a glycol- contain g solution by passing t r e solution through an ion excharαe resm m a filtratic bed, whereby the hydrocaroc-s are retained o tne ced. The resm is either cation or anion exchange resm. The liquid stream passes through the ion excnange resm and leaves the filtration bed substantially reduced in hydrocarbon content . The ion exchange resm may be regenerated m situ by removing the hydrocarbons from the resm bed oy flowing water therethrough, such that the nydrocarbon is carried away in tnat liquid. The ion excnange resm may be reused to remove hydrocarbons from a liquid stream. BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be apparent from t e following detailed description taken in conjunction with the drawings. Figure 1 is a schematic flow diagram which illustrates a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in v.πich preferred e*nboαιments of the invention are shown. Tms invention may, however, be emoodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, ana will fully convey the scope of tne invention to those skilled in the art. The process of the present invention is used to remove hydrocaroons from liquid streams such as an amine- containmg section or a glyccl-containing solution by passing the solution through an ion exchange resm, whereby the hydrocarbons are retained by the resm bed. The ion exchange resm is then regenerated in si tu by removing tne hydrocarbons from the ion exchange resm by flowing water therethrough, such tnat the hydrocarbon is carried away in that liquid. An example of one system in which the process of the present invention may be used is shown m Figure 1, wherein hydrocarbons are removed from a first liquid stream 12, such as an alkanolamme-contammg solution and/or glycol-contammg solution, as they separate from the liquid stream as it passes through filtration bed 10, composed of resm beads. The resm is a polymeric material, such as cation or anion exchange resm. When the first liquid stream is from an alkanolamine system it generally enters the filtration bed at a temperature of between about 0°F. and about 130°F. and a pressure of about 15 to 600 p.s.i. The liquid stream 14 passes from the resm bed substantially reduced in hydrocarbon content. In the case of an amme stream it is returned to the system. The hyαrocarbons ray oe removed from the filtration bed by flowing a second liquiα stream 16, such as water, through the resm bed, such that the hydrocarbon is carried away in the second liquid stream 18 to disposal. Although it is not necessary to the operation of the process, the second liquid (backwash water) may be introduced to the filtration oed 10 at a temperature of between about 100°F. and 250°F. , and a pressure of about 5 to 150 p.s.-_. The flow rate is aoout 1 to 10 gallons/min/ft' . The resin may be used again to remove undesirable hydrocarbons from a liquid stream. The hydrocarbons in question include a variety of aliphatic and aromatic hydrocarbons such as those common to petroleum production, syngas production, steel production and chemical processing. Among the hydrocarbons are aliphatic and aromatic hydrocarbons, petroleum hydrocarbons, gasoline, kerosene, gas oil, waxes, and the like. These hydrocarbons are often present as mixtures of hydrocarbons. Ion exchange resins exhibit the desired property for removing hydrocarbons from alkanolamine solutions and glycol solutions. Cation and anion exchange resins are similarly effective. Thus, one can assume it is not the ionic exchange capability that is important, rather it is the polymer structure, or perhaps a physical surface phenomenon that is responsible for effecting the desired separation . Examples of resins include anion exchange resins of the strong base, weak base, strong cation and weak cation varieties. Examples of strong base anion exchange resins include styrene-divinylbenzene resins with quaternary alkanolamine groups attached to the polymer framework, such as Resintech™ SBG-2, Sybron lonac™ ASB-2 , Rohm and Haas Amberlite© IRA-410; styrene-divinylbenzene resins having quaternary amine functional groups, such as Dow SBR, Dow MSA-1, Rohm and Haas IRA-900 and IRA-400, ResinTech S3G1, SBMP1, and the like. Examples of strong acid cation resins include suifonated stryrene- divinylbenzene resins, such as Dow HCR, ResinTech CG8 and CG10, Sybron C250, and Rohm and Haas IR-120. Examples of weak base anion exchange resins include stryrene- divmylbenzene resins with tertiary amine functional groups, such as Rohm and Haas IRA93/94, ResinTech WBMP, Sybron AFP-329, and Dow MWA-1. Examples of weak acid cation exchange resins ciude acrylic resins such as Sybron CC, Rohm and Haas IRC84, Dow CCR-2 and ResinTech WACMP. The preceding resms are not intended to limit the resm which may be used in carrying out the process of tnis invention. Alkanolamine-containing solutions from petroleum production refining, gas production, syn-gas production and the like typically contain 30 to 85% water by weight. The alkanolamine solutions commonly used include, for example, monoethanolamme, methylethanolamme, dietnanoiamme, methyldiethanolamme, diisopropanolamme, tπethanolamme, diglycolamme, proprietary hindered ammes, proprietary mixtures of ammes, and mixtures with physical solvents, like sulfolane, and various other mixtures . Glycol-contammg solutions typically contain from about 2% to about 80% water. Typical glycols used in dehyαratcr service and hydrate inhibition include monoetny_ene glycol, diethylene glycol, tπethylene glycol and tetraethylene glycol. The following examples are presented as illustrations of the invention. Example 1 To illustrate the adsorption of the resms used in the process of this invention kerosene was adαed to a 50% /50% mef-vldiethanolamine/water solution such that the kerosene concentration in the solution was about 100 ppm. The solution was passed through 100 ml. of strong base ion exchange resin. The effluent from the filtration bed was collected and the amount of unabsorbed kerosene was determined. The kerosene concentrations were: Original solution 105 ppm 1 st pass effluent 80 ppm 2 nd pass effluent 11 ppm This means that the adsorption of hydrocarbons from the alkanolamine-containing solution was 90% effective. Example 2 A monoethanolamine solution from a petroleum refinery amine system was run through a bed of strong base anion exchange resin. The hydrocarbon concentrations in the amine were analyzed by gas chromatography as follows: Original solution 19 ppm 1 st pass effluent <5 ppm Example 3 An anion exchange resin bed was used for 3 weeks removing heat stable salts from a refinery amine system. The amine solution also contained varying amounts of petroleum hydrocarbons. A heavy goo of hydrocarbon developed at and near the top of the resin bed that eventually severely reduced the ion exchange function of the resin. The resin was slurried with water and removed from the service vessel. The resin that came from most near the top of the vessel was most heavily coated with waxy goo and could not participate in the ion exchange. However, after flushing the resm in a column with hot water while agitating with nitrogen gas, the goo and resm separated. The recovered resm was tested and found to have acceptable ion exchange capacity. The hydrocarbon could also oe separated from the resm with the aid of a detergent in water. Example 4 A cation exchange resm was used for several weeks removing cations from a refinery amine system. Upon opening the vessel, a greasy substance was observed on the top of the resm. Subsequently the resm was slurried with water and flushed from the vessel into an open container. A hydrocarbon layer appeared on top of the water as it separated from the resm below. Example 5 A five-foot diameter vessel was filled with anion exchange resm. Flow was taken from a circulating refinery amine system known to contain paraffins, including waxes, and passed througn the resm bed at 60 to 90 gallons per minute for several days. Amine flow was stopped, the amine rinsed from the resm bed with ambient temperature water, and the resm bed was back- flushed with water at 150°F. to 160°F. at about 30 gpm, and the flushed material was collected in a settling tank. The cycle was repeated twice more. At the conclusion of the test, the flushed material was found to have a layer of wax on it, indicating transfer of wax from amme to tne resm bed and from the resm bed to the settling tank. Many modifications and other embodiments of the invention will come to mind to one skilled m the art to which this invention pertains navmg the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims: THAT WHICH IS CLAIMED: 1. A process for absorption of a hydrocarbon in a filtration bed containing a resm and m si tu regeneration of said filtration bee comprising: (a) passing a first liquid containing at least one hydrocarbon through said resm bed; (b) aosorbmg said hydrocarbon from said first liquid onto said resin; (c) passing said first liquid from said res substantially reduced of hydrocarbon; and (d) removing said hyαrocarbons from said resin by passing a second liquid therethrough such that the hydrocarbon is substantially removed in said second liquid stream. 2. The process according to Claim 1 wherein said first liquid is an alkanolamme/water solution and said hydrocarbon is selected from the group consisting of gasoline, kerosene, other petroleum hydrocarbons, or other aromatic or aliphatic hydrocarbons. 3. Tne process according to Claim 1 wherein said first liquid is a glycol/water solution and said hydrocarbon is selected from the group consisting of gasoline, kerosene, other petroleum hydrocarbons, and other alipnatic or aromatic hydrocarbons. 4. The process according to Claim 1 wherein said resm is an. ion exchange resm. 5. Tne process according to Claim 1 wherein said ion exchange resin is an anion excnange resm. 6. The process according to Claim 1 wherein said ion exchange resm is a cation exchange resm. 7. The process according to Claim 1 wherein said second liquid is water. 8. The process according to Claim 1 wherein said second liquid is passed through said resm at a temperature between about 100°F and about 250°F at a pressure from about 5 p.s.i. to about 150 p.s.i. 9. The process according to Claim 2 wherein said alkanolamine is selected from the group consisting of monoethanolamme, methylethanolamme, diethanoiamme, methyldiethanolamme, diisopropanolamme, tπethanolamme, diglycolamme, proprietary hindered am es and their mixtures. 10. The process according to Claim 3 wherein said glycol is selected from the group consisting of monoethylene glycol, diethylene glycol, trietnylene glycol, tetraethylene glycol and analogues. 11. The process according to Claim 1 wherein said first liquid is recirculated through the resm bed, each pass reducing the hydrocarbon content of said first liquid. 12. The process according to Claim 1 wherein said steps are repeated cyclically. 13. A process for treating a" amine-containing solution in a filtration bed containing an ion exchange resm and m si tu regeneration of said filtration bed comprising: (a) passing said amme-contammg solution containing at least one hydrocarbon through an ion exchange resin; (b) adsorbing said hydrocarbon from said amme- contammg liquid onto said ion exchange resin; (c) passing said amine-contammg solution from said ion exchange resm substantially reduced of hydrocarbons; and (d) removing said hydrocarbons from said ion exchange resm by passing a liquid therethrough such that the hydrocarbon is substantially removed in said liquid stream. 14. The process according to Claim 13 wherein said alkanolamine is selected from the group consisting of monoethanolamme, methylethanolamme, diethanoiamme, methyldiethanolamme, diisopropanolamme, tπethanolamine, diglycolamme, proprietary hindered ammes and their mixtures. 15. A process for regenerating a filter bed of ion exchange resm having a hydrocarbon adsorbed thereon comprising passing water therethrough such that said ion exchange resm is substantially reduced of the hydrocarbons.

Inventors: CUMMINGS ARTHUR L, CUMMINGS, ARTHUR, L.
Applicants: CUMMINGS ARTHUR L, MPR SERVICES INC, CUMMINGS, ARTHUR, L., MPR SERVICES, INC.
Application year: 2000
Main classification: B01D15
IPC codes: B01D15, B01D17, B01J20, B01J49, C02F1