Patent EA-004127-B1 (EA)
Title: Method of denitration and liquefaction of natural gas and gases obtained after separation thereof
Inventor: PARADOVSKY HENRY
IPC: F25J1/02
Filed: 2002-07-03
Abstract: 1. A method of denitration and liquefaction pressurized natural gas (1), comprising methane, C2 hydrocarbons and higher hydrocarbons and nitrogen for obtaining liquefied natural gas purified substantially from gaseous nitrogen, hydrocarbons, comprising the first step at which natural gas flux is cooled, expanded and liquefied in a first fractionator, comprising a plurality of steps, into a first head fraction, relatively more volatile enriched with nitrogen which is collected at the last step of said fractionator and the first bottom fraction, relatively less volatile with reduced nitrogen content, characterized in that comprises a second step at which the first head fraction is cooled and liquefied, separated to a second head fraction, more volatile with very high nitrogen content, and to a second bottom fraction, less volatile, relatively less enriched with nitrogen, wherein the second head fraction is introduced to the last step of said fractioner, the second head fraction is heated to obtain gaseous nitrogen, and the first bottom fraction is cooled to obtain natural liquefied gas, purified, substantially from nitrogen, wherein thermal power which permits to cool and liquefy the first head fraction id supplied using the third cooling cycle. 2. The method according to claim 1, characterized in that cooling medium is used for the third cycle, which is cooled and/or, at least, condensed using the second cooling cycle. 3. The method according to claim 2, characterized in that cooling flowing medium is used for the second cooling cycle, which is cooled and/or, at least, partially is condensed using the first cooling cycle, for which another cooling flowing medium is used. 4. The method according to claim 3, characterized in that either pure C3 hydrocarbon or a mixture, comprising mainly C3 hydrocarbons are used as cooling flowing medium of the first cooling cycle. 5. The method according to claim 5, characterized in that or a mixture, comprising mainly C2 and C1 hydrocarbons are used as the cooling flowing medium of the second cooling cycle. 6. The method according to claim 3 or 4, characterized in that or a mixture, comprising mainly C2 hydrocarbon is used as the cooling flowing medium of the second cooling cycle. 7. The method according to any one of claims 2 to 6, characterized in that or a mixture, comprising mainly C1 hydrocarbons and nitrogen are used as the cooling flowing medium of the third cooling cycle. 8. The method according to claim 7, characterized in that or a mixture, comprising mainly C1 hydrocarbon is used as the cooling flowing medium of the third cooling cycle. 9. The method according to any one of claims 2 to 8, characterized in that the cooling flowing medium(s) is (are) compressed using (K1-K6) compressors. 10. The method according to claim 9, characterized in that said compressors are driven by electrical motors. 11. The method according to any one of claims 1 to 10, characterized in that comprises a third step at which, prior to cool the first bottom fraction, to obtain liquefied natural gas, substantially purified from nitrogen it is cooled, expanded and introduced into a relatively cold step of the second fractioner, wherein prior to heat the second fraction to obtain gaseous nitrogen, it is cooled, liquefied, expanded and introduced into a relatively cold second step of said second fractioner. 12. Liquefied natural gas, substantially purified from nitrogen, obtained according to any one of the preceding claims.