Method and apparatus for the liquefaction of natural gas
AssigneeMobil Oil Corporation
InventorTsoung Y. Yan
Life of this patent
Estimating the term…
Abstract
A system and a process are provided for cooling a natural gas feed to an aluminum heat exchanger to protect it from mercury damage and increase productivity. A multi-stage vaporization system is employed wherein the last stage or lowest pressure heat exchanger is provided with a propane ejector. This allows the last stage heat exchanger to operate at a very low pressure without unduly reducing the pressure within other parts of the system. The last stage heat exchanger is accordingly able to sufficiently reduce the temperature of the feed to the aluminum heat exchanger to protect against mercury contamination. In addition, the decreased heat transfer load of the aluminum heat exchanger leads to an increase in the LNG production rate.
Claims31
A method for cooling a hydrocarbon fluid such as natural gas comprising the steps of:
- compressing a fluid refrigerant;
- passing said refrigerant successively through a plurality of heat exchangers, the pressure in each successive heat exchanger being less than the pressure in the preceding heat exchanger;
- passing a second fluid successively through each of said heat exchangers such that the temperature of said second fluid is successively reduced as it passes through each successive heat exchanger;
- and
- repressurizing said refrigerant near an output of the last of said successive heat exchangers, thereby lowering the operating pressure and working temperature within said last of said successive heat exchangers.
A system for reducing the temperature of a hydrocarbon gas such as natural gas, comprising:
- a compressor;
- a plurality of heat exchangers arranged in stages for sequential cooling of a fluid;
- means for conveying a refrigerant from said compressor to a first stage heat exchanger;
- means for conveying a refrigerant from said first stage heat exchanger to a last stage heat exchanger;
- means for conveying a fluid to be cooled from said first stage heat exchanger to said last stage heat exchanger;
- means for recirculating refrigerant from each of said heat exchangers back to said compressor;
- said last stage heat exchanger including a refrigerant outlet;
- and
- means for introducing a moving fluid near said outlet of said last stage heat exchanger, thereby reducing the pressure and working temperature within said last stage heat exchanger to promote cooling of said fluid.
Dependencies are inferred from the claim text.