Pump design for circulating supercritical carbon dioxide

• US 6,986,647 B2
• Filed: 11/21/2003
• Issued: 01/17/2006
• Est. Priority Date: 11/21/2003
• Status: Expired due to Fees

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Jones, William Dale, Spilsbury, Hugh Gybbon, Seegers, Bryan J.
• Primary Examiner(s): Koczo, Jr., Michael
• Application Number:
  US10/718,964
• Publication Number:
  US 20050112003A1
• Time in Patent Office: 788 Days
• Field of Search: 310/43, 310/86, 310/87, 310/90, 310/254, 310/261, 417/357, 417/366, 417/369, 417/370, 417/423.7
• US Class Current: 417/357
• CPC Class Codes: F04B 15/08 the liquids having low boiling points
• CPC Class Codes: F04D 13/0633 Details of the bearings
• CPC Class Codes: F04D 13/064 Details of the magnetic circuit
• CPC Class Codes: F04D 29/026 especially adapted for liquid pumps
• CPC Class Codes: F04D 7/02 of centrifugal type
• CPC Class Codes: F05D 2300/2283 of silicon
• CPC Class Codes: F05D 2300/436 Polyetherketones, e.g. PEEK

Abstract

In accordance with an embodiment of the present invention, a pump assembly for circulating a supercritical fluid is disclosed. The pump assembly comprises an impeller for pumping fluid between a pump inlet and a pump outlet; a rotating pump shaft coupled to the impeller, wherein the pump shaft is supported by corrosion resistant bearings; a rotor of a DC motor potted in epoxy and encased in a non-magnetic material sleeve; and a stator sealed from the fluid via a polymer sleeve. The pump can be of centrifugal type. The bearings can be made of silicon nitride balls combined with bearing races made of Cronidur® and can operate without oil or grease lubrication. The polymer sleeve can be a PEEK™ sleeve which forms a casing for the stator. The non-magnetic material sleeve encasing the rotor of the DC motor is preferably made of stainless steel. A portion of the fluid passing through the pump assembly can be diverted over the bearings and/or the rotor and stator.

Claims

1. A pump assembly for circulating a supercritical fluid, comprising:

an impeller for pumping fluid between a pump inlet and a pump outlet;

a rotating pump shaft coupled to the impeller, wherein the pump shaft is supported by non-lubricated bearings;

a rotor of a DC motor potted in epoxy and encased in a stainless steel sleeve, the stainless steel sleeve being welded to the pump shaft such that torque is transferred through the stainless steel sleeve; and

a stator sealed from the fluid via a Polyetheretherketone sleeve, the rotor and the stator defining an alternative flow path used to divert a portion of the supercritical fluid through the pump assembly and then back to the pump inlet through an outer flow path.

2. The pump assembly of claim 1, further including an electrical controller suitable for operating the pump assembly, wherein the electrical controller comprises a commutation controller for sequentially energizing windings of the stator.

3. The pump assembly of claim 1, wherein the pump is of centrifugal type.

4. The pump assembly of claim 1, wherein the impeller has a diameter between 1 inch and 2 inches.

5. The pump assembly of claim 1, wherein the rotor has a diameter between 1.5 inches and 2 inches.

6. The pump assembly of claim 1, wherein the rotor has a maximum speed of 60,000 rpm.

7. The pump assembly of claim 1, wherein an operating pressure of the pump assembly is in the range 1,500–

3,000 psi.

8. The pump assembly of claim 1, wherein the supercritical fluid operates in the range 40–

100 degrees Celsius.

9. The pump assembly of claim 1, wherein the supercritical fluid is supercritical carbon dioxide.

10. The pump assembly of claim 1, wherein the supercritical fluid is supercritical carbon dioxide admixed with an additive or solvent.

11. The pump assembly of claim 1, wherein the bearings are selected from the group consisting of ceramic bearings, hybrid bearings, full complement bearings, foil journal bearings and magnetic bearings.

12. The pump assembly of claim 1, wherein the motor is a variable speed motor.

13. The pump assembly of claim 1, wherein the motor is an induction motor.