×

METHOD FOR PROCESSING A STREAM OF LNG OBTAINED BY MEANS OF COOLING USING A FIRST REFRIGERATION CYCLE AND ASSOCIATED INSTALLATION

  • US 20070095099A1
  • Filed: 10/09/2006
  • Published: 05/03/2007
  • Est. Priority Date: 10/10/2005
  • Status: Active Grant
First Claim
Patent Images

1. Method for processing a stream of LNG obtained by means of cooling using a first refrigeration cycle, the method being of the type comprising the following steps:

  • (a) the stream of LNG which has been brought to a temperature of less than −

    100°

    C. is introduced into a first heat-exchanger;

    (b) the stream of LNG is sub-cooled in the first heat-exchanger by means of heat-exchange with a refrigerating fluid in order to form a stream of sub-cooled LNG; and

    (c) the refrigerating fluid is subjected to a second semi-open refrigeration cycle which is independent of the first cycle, characterised in that the method comprises the following steps;

    (d) the stream of sub-cooled LNG is expanded in a dynamic manner in an intermediate turbine, maintaining this stream substantially in the liquid state;

    (e) the stream from the intermediate turbine is cooled and expanded and then introduced into a distillation column;

    (f) a stream of denitrogenated LNG at the bottom of the column and a stream of gas at the top of the column are recovered; and

    (g) the top stream of gas is compressed in a stage compressor, and, at an intermediate pressure stage of the compressor, a first portion of the top stream of gas which is brought to an intermediate pressure PI is extracted in order to form a stream of combustible gas;

    and in that the second refrigeration cycle comprises the following steps;

    (i) an initial stream of refrigerating fluid is formed from a second portion of the top gas which has been compressed at the intermediate pressure PI;

    (ii) the initial stream of refrigerating fluid is compressed to a high pressure PH which is greater than the intermediate pressure PI in order to form a stream of compressed refrigerating fluid;

    (iii) the stream of compressed refrigerating fluid is cooled in a second heat-exchanger;

    (iv) the stream of compressed refrigerating fluid from the second heat-exchanger is separated into a primary cooling stream and a sub-cooling stream of the LNG;

    (v) the sub-cooling stream is cooled in a third heat-exchanger, then in the first heat-exchanger;

    (vi) the sub-cooling stream from the first heat-exchanger is expanded to a low pressure PB which is lower than the intermediate pressure PI in order to form a substantially liquid sub-cooling stream of the LNG;

    (vii) the substantially liquid sub-cooling stream is evaporated in the first heat-exchanger in order to form a reheated sub-cooling stream;

    (viii) the main cooling stream is expanded substantially to the low pressure PB in a main turbine and the cooling stream from the main turbine is mixed with the reheated sub-cooling stream in order to form a mixed stream;

    (ix) the mixed stream is reheated successively in the third heat-exchanger, then in the second heat-exchanger in order to form a reheated mixed stream; and

    (x) the reheated mixed stream is introduced into the compressor at a low pressure stage located upstream of the intermediate pressure stage.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×