Air distillation plant and corresponding cold box

Details Air distillation plant and corresponding cold box Air distillation plant and corresponding cold box

1999-04-30

2001-02-06

Doerrler, William (Department: 3744)

Refrigeration

Cryogenic treatment of gas or gas mixture

Separation of gas mixture

C062S900000

Reexamination Certificate

active

06182470

ABSTRACT:

The present invention relates to an air distillation plant of the type comprising a double column and a mixing column for mixing a gas and a liquid, the double column itself comprising a medium-pressure column, a low-pressure column and a reboiler for bringing the gas at the top of the medium-pressure column into heat-exchange relationship with the liquid at the bottom of the low-pressure column, the plant furthermore comprising means for sending gaseous air into the bottom of the mixing column, means for sending an oxygen-rich liquid into the top of the mixing column and a production line for gaseous impure oxygen withdrawn from the top of the mixing column.
The invention applies particularly to the supply of impure oxygen, for example for feeding blast furnaces in the iron and steel industry.
In order to provide such a supply of impure oxygen, it is known to use a plant of the aforementioned type. The mixing column operates at a pressure approximately equal to or less than the medium pressure. It is fed at the bottom with purified and compressed air and at the top with impure liquid oxygen removed from the bottom of the low-pressure column and brought by pumping to the pressure of the mixing column. The impure gaseous oxygen to be supplied is withdrawn from the top of such a mixing column approximately at the pressure of the mixing column.
In general, the low-pressure column sits on top of the reboiler, which itself sits above the medium-pressure column. The double column then forms a first structure erected on site and the mixing column is placed beside the double column, forming a second erected structure. Each erected structure is surrounded by a thermal insulation jacket which holds perlite around the erected structure forming a cold box.
Moreover, it is desirable to prefabricate air distillation plants in packets which each comprise a structure and the thermal insulation jacket of a cold box. Each packet is transported onto a site and then erected. Next, the erected structures are functionally connected and the cold boxes filled with perlite in order to complete the construction of the air distillation plant.
Such a method of construction makes it possible to limit the construction operations on the site, where on the one hand, all the necessary infrastructures may not be available and, on the other hand, the environmental conditions may impede the construction operations.
The object of the invention is to provide an air distillation plant of the aforementioned type, in which the degree of prefabrication may be higher.
For this purpose, the object of the invention is an air distillation plant of the aforementioned type, characterized in that the medium-pressure column, the low-pressure column and the mixing column are placed one on top of another, forming a single erected structure.
Depending on the particular embodiments, the plant may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:
the plant furthermore comprises means for sending gaseous air into the bottom of the mixing column, means for sending an oxygen-rich liquid into the top of the mixing column and a production line for gaseous impure oxygen withdrawn from the top of the mixing column;
the erected structure also comprises the reboiler;
the mixing column is placed under the medium-pressure and low-pressure columns;
the medium-pressure column is placed under the low-pressure column; and
the reboiler is placed at least partly at a level intermediate between the top of the medium-pressure column and the bottom of the low-pressure column.
The subject of the invention is also a cold box intended for the construction of such a plant as defined above, characterized in that it comprises the said erected structure and a thermal insulation jacket surrounding the said structure.


REFERENCES:
patent: 4883517 (1989-11-01), Rathbone
patent: 5341646 (1994-08-01), Agrawal et al.
patent: 5471843 (1995-12-01), Chretien
patent: 5865041 (1999-02-01), Agrawal et al.
patent: 0 567 047 (1993-10-01), None
patent: 2 143 986 (1973-02-01), None
patent: 2 677 667 (1992-12-01), None

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