COMBINED DIRECT AND INDIRECT REGASIFICATION OF LNG USING AMBIENT AIR

Abstract

A process and apparatus for regasification of LNG to form natural gas using ambient air as the primary source of heat are described. LNG is directed to flow through an ambient air vaporizer to form a natural gas stream through direct heat exchange between the LNG and ambient air. The temperature of the natural gas stream is adjusted to suit a predetermined delivery temperature in a trim heater exchanging heat with a circulating intermediate fluid. The intermediate fluid is directed to flow through an ambient air heater such that the intermediate fluid exchanges heat with ambient air. Heat transfer between the ambient air and the LNG is assisted using one or more force draft fans to direct the flow of ambient air over the ambient air heater and the ambient air vaporizer in turn to dry the ambient air before it arrives at the ambient air vaporizer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a more detailed understanding of the nature of the invention several embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a flow chart illustrating a first embodiment of the regasification facility;

FIG. 2 is a flow chart illustrating a second embodiment of the regasification facility; and,

FIG. 3 is a flow chart illustrating an alternative embodiment of FIG. 1 for use in extremely cold weather conditions.

Claims

1. A process for regasification of LNG to form natural gas using ambient air as the primary source of heat, said process comprising: (a) directing LNG to flow through an ambient air vaporizer to form a natural gas stream through direct heat exchange between the LNG and ambient air;(b) adjusting the temperature of the natural gas stream to a predetermined delivery temperature in a trim heater by exchanging heat with a circulating intermediate fluid;(c) directing the intermediate fluid to flow through an ambient air heater such that the intermediate fluid exchanges heat with ambient air; and,(d) assisting heat transfer using one or more force draft fans to direct the flow of ambient air over the ambient air heater and the ambient air vaporizer, the ambient air heater being arranged in closer proximity to the forced draft fans than the ambient air vaporizer such that the air is directed to flow across the ambient air heater to cool and dry the air before the air arrives at the ambient air vaporizer.

2. The process of claim 1, wherein the one or more forced draft fans are installed above the ambient air heater which in turn is installed above the ambient air vaporizer and the air is caused to flow downwardly across the ambient air heater before arriving at the ambient air vaporizer.

3. The process of claim 1, wherein the ambient air heater and the ambient air vaporizer are arranged as a single system and share a common forced draft fan.

4. The process of claim 1, wherein the temperature of the intermediate fluid is maintained above zero degrees Celsius and the ambient air heater comprises a horizontal tube bundle.

5. The process of claim 1, wherein the ambient air heater comprises a horizontal tube bundle and the ambient air vaporizer comprises a vertical tube bundle.

6. The process of claim 4, wherein the temperature of the intermediate fluid is maintained above zero degrees Celcius using a source of supplemental heat.

7. The process of claim 6, wherein the source of supplemental heat is selected from the group consisting of an exhaust gas heater, an electric water or fluid heater, a propulsion unit of a ship, a diesel engine, a gas turbine propulsion plant, and an exhaust gas stream from a power generation plant.

8. The process of claim 1, further comprising directing a bypass stream of LNG to flow through an intermediate fluid vaporizer wherein the LNG exchanges heat with a portion of the circulating intermediate fluid.

9. The process of claim 1, wherein the intermediate fluid is selected from the group consisting of a glycol, a glycol-water mixture, methanol, propanol, propane, butane, ammonia, a formate, fresh water, and tempered water.

10. A regasification facility for regasification of LNG to form natural gas using ambient air as the primary source of heat, said apparatus comprising: an ambient air vaporizer to regasify LNG to natural gas;a trim heater to boost the temperature of the natural gas by exchanging heat with a circulating intermediate fluid;an ambient air heater to heat the intermediate fluid;a circulating pump to circulate the intermediate fluid between the trim heater and the ambient air heater; andone or more forced draft fans to direct the flow of ambient air over the ambient air heater and the ambient air vaporizer, the ambient air heater being arranged in closer proximity to the forced draft fans than the ambient air vaporizer such that the air is directed to flow across the ambient air heater to cool and dry the air before the air arrives at the ambient air vaporizer.

11. The apparatus of claim 10, wherein the ambient air heater is installed above the ambient air vaporizer in closer proximity to the forced draft fans such that the air is caused to flow downwardly across the ambient air heater before arriving at the ambient air vaporizer.

12. The apparatus of claim 10, wherein the ambient air heater comprises a horizontal tube bundle and the ambient air vaporizer comprises a vertical tube bundle.

13. The apparatus of claim 10, wherein the ambient air heater comprises a horizontal tube bundle, and the apparatus further comprises a control device to regulate the temperature of the intermediate fluid fed to the ambient air heater to a temperature greater than zero degrees Celsius using a source of supplemental heat.

14. The apparatus of claim 13, wherein the source of supplemental heat is selected from the group consisting of an exhaust gas heater, an electric water or fluid heater, a propulsion unit of a ship, a fired heater, a diesel engine, a gas turbine propulsion plant, and an exhaust gas stream from a power generation plant.

15. The apparatus of claim 13, wherein the regasification facility is provided onboard an LNG carrier and the source of supplementary heat is heat recovered from the engines of the LNG carrier.

16. The apparatus of claim 10, further comprising an intermediate fluid vaporizer to vaporize a bypass stream of LNG, wherein the LNG exchanges heat with a portion of the circulating intermediate fluid.