Process for desulfurizing gasoline and hydrocarbon feedstocks

• US 5,730,860 A
• Filed: 08/14/1995
• Issued: 03/24/1998
• Est. Priority Date: 08/14/1995
• Status: Expired due to Fees

• Current Assignee: The Pritchard Corporation
• Original Assignee: The Pritchard Corporation
• Inventors: Irvine, Robert L.
• Primary Examiner(s): Myers, Helane
• Application Number:
  US08/514,948
• Time in Patent Office: 953 Days
• Field of Search: 208/210, 208/310, 208/213, 208/214, 208/251 H, 208/254, 208/306, 585/310 R, 585/822, 585/826
• US Class Current: 208/213
• CPC Class Codes: C10G 25/08 according to the "moving bed" method

Abstract

An apparatus and method for treating a liquid hydrocarbon stream useful as a precursor for transportation fuel and which contains an unacceptably high level of heteroatom compounds is provided for the removal of a significant portion of the heteroatom compounds from the hydrocarbon stream. The method and apparatus employ an adsorbent which is brought into countercurrent contact with a hydrocarbon stream in an adsorption zone to form a product hydrocarbon stream and a spent adsorbent stream. The adsorbent is recirculated to a desorption zone and is thereafter brought into cross-current contact with a reactivating medium, such as hydrocarbon gas, at elevated temperatures to form a reactivated adsorbent stream and a hydrogen/heteroatom stream. The regenerated adsorbent is recirculated back to the adsorption zone to form the adsorbent stream.

Claims

1. A method of treating a liquid hydrocarbon stream useful as a precursor for transportation fuel and which contains an unacceptably high level of heteroatom compounds, in order to remove a significant proportion of the heteroatom compounds from the hydrocarbon stream, said method comprising the steps of:

providing a hydrocarbon stream containing an unacceptably high level of heteroatom compounds;

providing an adsorbent in the form of a finely divided particulate adsorbent stream, the adsorbent particles being characterized by the property of adsorbing said heteroatom compounds from said hydrocarbon stream;

providing an adsorption zone with an inlet and an outlet;

introducing said adsorbent stream into said adsorption zone and causing said adsorbent stream to flow therethrough;

introducing said hydrocarbon stream into said inlet, causing said hydrocarbon stream to flow therethrough for bringing said hydrocarbon stream into counter-current contact with said adsorbent stream in the form of a moving fluidized bed for adsorption of a portion of said heteroatom compounds to form a hydrocarbon stream exiting said adsorption zone outlet and a spent adsorbent stream exiting said adsorption zone in the proximity of said inlet;

providing a desorption zone and a cool-down zone for the regeneration of the spent adsorbent stream;

transferring said spent adsorbent from said adsorption zone into said regeneration zone by means of a hydrocarbon fluid carrier;

providing a plurality of hot hydrogen gas streams;

introducing said hot hydrogen gas streams into said desorption zone at a plurality of spaced regeneration stages along the length of the desorption zone, said hot hydrogen gas streams each being brought into cross-current contact with said downwardly flowing spent adsorbent stream for the transfer of heat from respective heated hydrogen gas streams to said spent adsorbent stream, the transfer of heat from the hydrogen gas stream to the adsorbent stream collectively being sufficient to raise the temperature of said spent adsorbent stream to a level to cause desorption of a portion of said heteroatom compounds from said adsorbent to form a hot regenerated adsorbent stream and a hydrogen and heteroatom gas stream;

causing said regenerated adsorbent stream to exit said desorption zone and enter said cool-down zone;

discharging said hydrogen and heteroatom stream from said desorption zone;

cooling said hot regenerated adsorbent stream in said cool-down zone to a temperature sufficiently low to permit subsequent adsorption of heteroatoms by the adsorbent; and

recirculating said regenerated adsorbent stream from said cool-down zone to said adsorbent stream for introduction into said adsorption zone.

2. The method of treating a liquid hydrocarbon stream as set forth in claim 1, wherein is included the step of maintaining the temperature of the adsorbent stream and the hydrocarbon stream at about ambient temperature when said streams are brought into countercurrent contact in said adsorption zone.

3. The method of treating a liquid hydrocarbon stream as set forth in claim 1, wherein said adsorption zone includes six serially interconnected adsorption stages each having a lower inlet and an upper outlet, and presenting in said serial order thereof an initial adsorption stage and a final adsorption stage, said adsorption stages being located in disposition and interconnection in a manner such that the outlet of each stage is connected and communicates with the inlet of the next stage in the serial order thereof.

4. The method of treating a liquid hydrocarbon stream as set forth in claim 1, said adsorption stage reducing the heteroatom content of said hydrocarbon stream to less than 30 ppmw of sulfur.

5. The method of treating a liquid hydrocarbon stream as set forth in claim 1, said desorption zone including four serially interconnected regeneration stages, regeneration stage having an upper inlet and a lower outlet and presenting in said serial order thereof an initial regeneration stage and a final regeneration stage, each regeneration stage being located in disposition and interconnection in a manner such that the outlet of each stage is connected to and communicates with the inlet of the next adjacent stage in the serial order thereof.

6. The method of treating a liquid hydrocarbon stream as set forth in claim 1, said adsorption zone reducing the total heteroatom content of said hydrocarbon stream less than 0.5 ppmw.

7. The method of treating a liquid hydrocarbon stream as set forth in claim 1, said cool-down zone made up of a number of serially interconnected cool-down stages, each cool-down stage having an upper inlet and a lower outlet and presenting in said serial order thereof an initial cool-down stage and a final cool-down stage, each cool-down stage being located in disposition and interconnection in a manner such that the outlet of each cool-down stage is connected to and communicates with the inlet of the next adjacent cool-down stage in the serial order thereof.

8. The method of treating a liquid hydrocarbon stream as set forth in claim 7, wherein said cooling of hot regenerated adsorbent stream in said cool-down zone is to a temperature of about ambient temperature.

9. A method of treating a liquid hydrocarbon stream useful as a precursor for transportation fuel and which contains an unacceptably high level of heteroatom compounds, in order to remove a significant proportion of the heteroatom compounds from the hydrocarbon stream, said method comprising the steps of:

providing a hydrocarbon stream suitable for use as a motor fuel, said hydrocarbon stream containing a quantity of heteroatom compounds;

providing an adsorbent in the form of a finely divided particulate, fluidized bed adsorbent stream, the adsorbent particles being characterized by the property of adsorbing said heteroatom compounds from said hydrocarbon stream;

providing an adsorption zone made up of at least two serially interconnected adsorption stages each having a lower inlet and an upper outlet, and presenting in said serial order thereof an initial adsorption stage and a final adsorption stage,

said adsorption stages being located in disposition and interconnection in a manner such that the outlet of each stage is connected to an communicates with the inlet of the next stage in the serial order thereof;

introducing said adsorbent stream into said adsorbent zone in the proximity into of said final adsorbent stage outlet and causing said adsorbent stream to thereafter flow downwardly in serial order through said adsorbent stages, from the outlet of a respective stage to the inlet of the stage next adjacent thereto;

introducing said hydrocarbon stream into said adsorbent zone initial stage inlet and thereafter causing said hydrocarbon steam to flow upwardly in serial order through said stages from the outlet of each of said stage to the inlet of the stage next adjacent thereto, said hydrocarbon stream being brought into counter-current contact with said adsorbent stream in said adsorption zone in the form of moving fluidized beds for adsorption of a portion of said heteroatom compounds by said adsorption stream to form a product hydrocarbon stream that exits the outlet of said final adsorption stage and a spent adsorption stream that exits said adsorption stage in the proximity of said initial adsorption stage inlet;

providing a regeneration zone and a cool-down zone,

said regeneration zone made up of a number of serially interconnected regeneration stages, each having an upper inlet and a lower outlet and presenting in said serial order thereof an initial regeneration stage and a final regeneration stage, each regeneration stage being located in disposition and interconnection in a manner such that the outlet of each stage is connected to and communicates with the inlet of the next adjacent stage in the serial order thereof,

said cool-down zone made up of a number of serially interconnected cool-down stages, each cool-down stage having an upper inlet and a lower outlet and presenting in said serial order thereof an initial cool-down stage and a final cool-down stage, each cool-down stage being located in disposition and interconnection in a manner such that the outlet of each cool-down stage is connected to and communicates with the inlet of the next adjacent cool-down stage in the serial order thereof, and

said regeneration zone and said cool-down zone being located in disposition and interconnection in a manner such that the outlet of said final regeneration stage is connected to and communicates with the inlet of said initial cool-down stage;

introducing said spent adsorption stream into said initial regeneration stage upper inlet and causing said spent adsorption stream to flow downwardly into respective inlets of said regeneration stages and said cool-down stages;

introducing streams of heated hydrogen gas into said initial regeneration stage and into respective regeneration stages serially connected therewith, said heated hydrogen gas streams being brought into cross-current contact with said downward flowing spent adsorbent stream for the transfer of heat from said heated hydrogen streams to said downward flowing spent adsorbent stream, said heat transfer collectively being sufficient to raise the temperature of the spent adsorbent stream sufficiently high to cause the release of said heteroatom compounds from said spent adsorbent stream to form a hot regenerated adsorbent stream exiting said final regeneration stage outlet and a plurality of hydrogen and heteroatom gas streams exiting each regeneration stage;

introducing said hot regenerated adsorbent stream into said cool-down zone, causing said hot regenerated adsorbent stream to flow downwardly in serial order through corresponding cool-down stages, from the outlet of a respective stage to the inlet of the stage next adjacent thereto,

introducing streams of cool hydrogen gas into said initial cool-down stage and into respective cool-down stages serially connected therewith and bringing said cool hydrogen gas streams into cross-current contact with said downward flowing hot regenerated adsorobent stream for the transfer of heat from the hot adsorbent stream to the cool hydrogen gas stream, said heat transfer collectively being sufficient to lower the temperature of the regenerated adsorbent stream below a temperature to permit adsorption of heteroatom compounds by the adsorbent; and

recirculating said regenerated adsorbent to said adsorption zone.

10. A method of treating a liquid hydrocarbon stream which contains an unacceptably high level of heteroatom compounds, in order to remove a significant proportion of the heteroatom compounds from the hydrocarbon stream, said method comprising the steps of:

providing a hydrocarbon stream, said hydrocarbon stream containing an unacceptably high level of heteroatom compounds;

providing an adsorbent in the form of a finely divided particulate adsorbent stream, the adsorbent particles being operable to absorb said heteroatom compounds from said hydrocarbon stream;

providing an adsorption zone with an inlet and an outlet;

introducing said adsorbent stream into said adsorption zone and causing said adsorbent stream to flow therethrough;

introducing said hydrocarbon stream into said inlet, causing said hydrocarbon stream to flow therethrough for bringing said hydrocarbon stream into counter-current contact with said adsorbent stream in the form of a moving fluidized bed for adsorption of a portion of said heteroatom compounds to form a hydrocarbon stream exiting said adsorption zone outlet and a spent adsorbent stream exiting said adsorption zone in the proximity of said inlet;

providing a desorption zone and a cool-down zone for the regeneration of the spent adsorbent stream;

transferring said spent adsorbent in a slurry form from said adsorption zone into said regeneration zone by a hydrocarbon fluid carrier;

providing a hot reactivating medium in the form of a plurality of gas streams from the group consisting of hydrogen, nitrogen, methane, ethane, propane, and butane, and mixtures thereof;

introducing said hot gas streams into said desorption zone at a plurality of spaced regeneration stages along the length of the desorption zone, said hot gas streams each being brought into cross-current contact with said downwardly flowing spent adsorbent stream for the transfer of heat from respective gas streams to said spent adsorbent stream, the transfer of heat from the gas streams to the adsorbent stream collectively being sufficient to raise the temperature of said spent adsorbent stream to cause desorption of a portion of said heteroatom compounds from said adsorbent to form a hot regenerated adsorbent stream and a hydrogen and heteroatom gas stream;

causing said hot regenerated adsorbent stream to exit said desorption zone and enter said cool-down zone;

cooling said hot regenerated adsorbent stream in said cool-down zone to a temperature sufficiently low to permit subsequent adsorption of heteroatoms by the adsorbent; and

recirculating by means of a hydrocarbon fluid carrier said regenerated adsorbent stream from said cool-down zone to said adsorption zone.

11. A method of treating a liquid hydrocarbon stream which contains heteroatom compounds, said method comprising the steps of:

providing a stream containing heteroatom compounds;

providing an adsorbent in the form of a finely divided particulate adsorbent stream, the adsorbent particles being of a size within the range of about 0.4 to about 1.6 mm and operable to absorb said heteroatom compounds from said stream;

providing a moving fluidized bed adsorption zone with an inlet and an outlet;

substantially continuously introducing said adsorbent stream into said adsorption zone and causing said adsorbent stream to flow therethrough;

substantially continuously introducing said liquid stream into said inlet, causing said liquid stream to flow therethrough for bringing said liquid stream into counter-current contact with said adsorbent stream in the form of a fluidized bed for adsorption of a portion of said heteroatom compounds to form a product liquid stream exiting said adsorption zone outlet and a spent adsorbent stream exiting said adsorption zone;

providing a desorption zone and a cool-down zone for the regeneration of the spent adsorbent stream;

transferring said spent adsorbent from said adsorption zone into said regeneration zone;

providing a hot reactivating medium in the form of a plurality of gas streams selected from the group consisting of hydrogen, nitrogen, methane, ethane, propane, and butane, and mixtures thereof;

introducing said hot gas streams into said desorption zone at a plurality of spaced regeneration stages along the length of the desorption zone, said hot gas streams being brought into cross-current contact with said downwardly flowing spent adsorbent stream for the transfer of heat from respective gas streams to said spent adsorbent stream, the transfer of heat from the gas streams to the adsorbent stream collectively being sufficient to raise the temperature of said spent adsorbent stream to cause desorption of a portion of said heteroatom compounds from said adsorbent to form a hot regenerated adsorbent stream and a hydrogen and heteroatom gas stream;

causing said hot regenerated adsorbent stream to exit said desorption zone and enter said cool-down zone;

causing said heteroatom gas stream to exit said desorption zone;

cooling said hot regenerated adsorbent stream in said cool-down zone to a temperature sufficiently low to permit subsequent adsorption of heteroatoms by the adsorbent; and

recirculating by means of a liquid carrier said regenerated adsorbent stream from said cool-down zone to said adsorption zone, said liquid carrier formed from a portion of said product liquid stream.