Process and apparatus for treating and utilizing vaporized gas in a ship for transporting liquified gas

• US 3,885,394 A
• Filed: 12/10/1973
• Issued: 05/27/1975
• Est. Priority Date: 12/11/1972
• Status: Expired due to Term

• Current Assignee: Christian Trepp, Karel Witt
• Original Assignee: Christian Trepp, Karel Witt
• Inventors: Witt, Karel, Trepp, Christian
• Primary Examiner(s): Perlin, Meyer
• Assistant Examiner(s): Capossela, Ronald C.
• Application Number:
  US05/423,122
• Time in Patent Office: 533 Days
• Field of Search: 114/74A 62/7,50,51,54,240 60/651,671
• US Class Current: 60/651
• CPC Class Codes: B63H 21/00 Use of propulsion power plant or units on vessels
• CPC Class Codes: B63J 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: F17C 2265/03 Treating the boil-off
• CPC Class Codes: F17C 9/04 Recovery of thermal energy
• CPC Class Codes: F25J 1/0025 Boil-off gases "BOG" from storages
• CPC Class Codes: F25J 1/004 by flash gas recovery F25J1/0267 takes precedence
• CPC Class Codes: F25J 1/0202 in a quasi-closed internal refrigeration loop F25J1/0208, F25J1/0219, F25J1/0224 take precedence
• CPC Class Codes: F25J 1/023 for the combustion as fuels, i.e. integration with the fuel gas system
• CPC Class Codes: F25J 1/0277 Offshore use, e.g. during shipping
• CPC Class Codes: F25J 2220/62 Separating low boiling components, e.g. He, H2, N2, Air
• CPC Class Codes: F25J 2230/30 Compression of the feed stream
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or a mixture of hydrocarbons

Abstract

The vaporized gas is first heated and then compressed. Thereafter, the gas is divided into two component flows with one component flow being sent to the ship'"'"''"'"'s propulsion plant as a source of fuel. The second component flow is then further compressed and cooled in heat exchange relation with the continued flow of vaporized gas from the gas tanks. The cooled gas is then liquified and returned to the gas tanks.

Claims

1. A process of treating and utilizing vaporized gas from a liquified gas tank of a ship for transporting liquified combustible gas comprising the steps of drawing off a flow of vaporized gas from at least one gas tank;

compressing said flow of vaporized gas;

dividing the compressed flow of gas into at least two component flows;

feeding one of said gas component flows to a propulsion unit of the ship;

compressing a second of said gas component flows;

passing said compressed second gas component flow into heat exchange relation with a continued flow of said flow of vaporized gas to heat said continued flow of vaporized gas prior to compressing of said continued flow of vaporized gas; and

thereafter reducing the pressure of said second gas component flow and feeding a liquid part of the reduced pressure gas component flow to at least one gas tank.

2. A process as set forth in claim 1 which further comprises the step of cooling said flow of compressed gas prior to dividing into said component flows.

3. A process as set forth in claim 1 wherein the full flow of said vaporized gas from one tank is compressed to a pressure demanded by the propulsion unit.

4. A process as set forth in claim 1 which further comprises the step of separating volatile constituents from said reduced pressure gas component flow.

5. A process as set forth in claim 4 wherein said step of reducing the pressure of said second gas component flow includes expanding said second gas component flow to a pressure corresponding to a delivery pressure of said vaporized gas from the tank and wherein the separated volatile constituents pass in heat exchange relation with said flow of vaporized gas and are added to said one gas component flow.

6. An apparatus for treating anD utilizing vaporized gas from a liquified gas tank of a ship for transporting liquified combustible gas comprising at least one gas tank;

means for drawing off a flow of vaporized gas from said tank;

a first compressor connected to said for drawing off means for compressing the flow of vaporized gas;

a first branch line connected to said compressor to deliver one component flow of the compressed gas flow to a propulsion unit of the ship;

a second compressor connected to said first compressor to receive and compress a second component flow of the compressed gas flow from said first compressor;

a heat exchanger connected with said means and to said second compressor to receive the flow of vaporized gas from said tank and the flow of the compressed second gas component flow from said second compressor in heat exchange relation to heat the flow of vaporized gas and cool the second gas component flow; and

a pressure reducing means connected to said heat exchanger and said tank to deliver the second gas component flow to said tank in at least partly liquified form.

7. An apparatus as set forth in claim 6 which further comprises a second branch line between said first compressor and said second compressor to convey the second gas component therebetween.

8. An apparatus as set forth in claim 6 which further comprises an after-cooler downstream of said first compressor for cooling the compressed flow of vaporized gas.

9. An apparatus as set forth in claim 6 which further comprises a separator connected to said heat exchanger to receive the cooled second gas component flow, a cooling passage in said heat exchanger, a line between said separator and said cooling passage for passing separated volatile gas constituents from the second gas component flow through said cooling passsage, a line between said cooling passage and said first branch line to deliver the volatile gas constituents thereto and a line between said separator and said gas tank to deliver liquified gas thereto.