Chemistry of inorganic compounds – Nitrogen or compound thereof
Patent
1987-10-09
1990-01-23
Doll, John
Chemistry of inorganic compounds
Nitrogen or compound thereof
166268, 1663051, 422170, B01D 5000, C01B 2100, E21B 4316
Patent
active
048957100
DESCRIPTION:
BRIEF SUMMARY
The present application is related to a method and a system for production of nitrogen for application at high pressure, preferably for pressure injection in submarine or subterranean oil or natural gas wells.
With recovering of oil and gas, in particular from submarine wells, it is in certain cases of importance to perform a pressure injection of nitrogen gas into the well in question to increase the operational pressure and prevent the well from collapsing. Such a situation is present for the Ekkofisk field in the North Sea, and in order to generate the necessary large amounts of nitrogen gas in this connection, it is suggested to produce nitrogen by combustion of natural gas in air for binding of the oxygen content of the air in carbon dioxide, which then is removed from the flue gas by absorption, whereas the remaining nitrogen is pressurized to a predetermined high pressure suitable for said application. In the suggested system the combustion takes place partly in gas turbines and partly through direct combustion of gas in boiler systems at atmospheric conditions. The system is then very space-demanding, unpractical and heavy.
This implies very great disadvantages when mounted on an off-shore platform, and it is then an object of the invention to provide a method as stated above, but in which the indicated disadvantages are overcome.
Thus, the invention concerns a method for production of nitrogen for application at high pressure, preferably for pressure injection in submarine or subterranean oil or natural gas wells, by combustion of natural gas in air, which is compressed prior to the combustion, for binding of the oxygen content of the air in carbon dioxide to be removed from the flue gas by absorption, whereas the remaining nitrogen is pressurized to a predetermined high pressure suitable for said application.
A compression of the combustion air for the present purpose is known in principle from British Patent Specification No. 1.440.476, and in view of this known prior art, the unique features of the method according to the invention are that the compression of the combustion air prior to the combustion is made to a preselected, operationally optimum intermediate pressure between said predetermined high pressure and the atmospheric pressure, and substantially above the latter pressure, the heat energy developed by the combustion being heat exchanged at the intermediate pressure with water for production of steam, which subsequently is utilized for mechanical work, preferably in steam turbines for compression to the intermediate pressure and maintenance of said predetermined high pressure.
As the injection pressure in this connection would be of the order of magnetude 100-500 bars, an immediate pressure of 10-60 bars, normally 25-40 bars, is preferably applied.
The residual oxygen in the flue gas is preferably removed by addition of hydrogen for wet combustion with the oxygen while the flue gas is guided past a catalyst at said intermediate pressure.
By compressing the combustion air to e.g. 25-40 bars before the combustion and performing the gas combustion and energy recovering at this pressure, the gas volumes under treatment are reduced in the corresponding proportion, i.e. with a factor at 1/25-1/40, and at the same time the heat transfer conditions are dramatically improved.
The invention also concerns a system for production of nitrogen by the method indicated above, the system comprising a combustion chamber for combustion of natural gas in air, which is compressed prior to the combustion, for binding of the oxygen content of the air in carbon dioxide to be removed from the flue gas in an absorption device, and an outlet compressor for pressurizing the remaining nitrogen to a predetermined high pressure suitable to said application.
In view of prior art the system of the invention is then characterized by the feature that it further comprises an inlet compressor disposed and adapted for said compression of the combustion air to a preselected, operationally optimum intermediate pressure betw
REFERENCES:
patent: 914279 (1909-03-01), Hurford
patent: 3145085 (1964-08-01), Breault
patent: 3388973 (1968-06-01), Marquardt et al.
Gran Helge G.
Hartmann Gotfred
Doll John
Gran Helge G.
Langel Wayne A.
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