Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
1999-02-08
2001-02-20
Doerrler, William (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
C062S903000, C165S111000, C165S114000
Reexamination Certificate
active
06189338
ABSTRACT:
The present invention relates to a brazed-plates condenser, of the type comprising an exchanger body which has at least one condensation passage which is flat in shape and delimited between two substantially vertical parallel plates, this passage containing, over most of its height, a heat-exchange spacer corrugation with substantially vertical generatrices; an inlet box for a gas that is to be condensed, this box being located at the upper end of the passage; an outlet box for the liquid condensate, this box being located at the bottom end of the passage; a distributor spacer corrugation, the generatrices of which are at an angle to the direction of the generatrices of the heat corrugation and which direct the liquid condensate from the bottom end of the heat-exchange corrugation to the outlet box.
The invention applies, for example, to the main vaporizer-condensers of double air-distillation columns.
Brazed-plates cryogenic condensers are in widespread use. In general, they condense a first fluid flowing downward through the exchanger body by the vaporization of a second fluid flowing through passages adjacent to the condensation passages.
In certain applications, the gas being condensed contains a small proportion of constituents which have a low boiling point and are known as “uncondensables”, that cannot be condensed at the temperature of the exchange. In the case of the main vaporizer-condensers of double distillation columns, the fluid condensed is nitrogen, and the uncondensables are hydrogen, helium and neon.
When the gas that is to be condensed flows downward through the exchanger body, the uncondensables are carried toward the bottom by the speed at which the liquid formed flows and are then deflected by the distributor corrugation toward the outlet box. The latter generally comprises, at the bottom, a liquid discharge nozzle which opens into a liquid reservoir, and at the top generally comprises a nozzle for discharging the gas phase containing the uncondensables at a predetermined rate.
However, in practice, complete discharge of the uncondensables is difficult to achieve because, in the bottom of the condensate passages, the lower region of the distributor corrugation which opens into the heat-exchange zone furthest from the outlet box, is sometimes flooded with liquid. Gas, containing the uncondensables, therefore stagnates in this zone, and this reduces the efficiency of the condenser and disturbs the equilibrium of the heat transfers. This is because the zones in which the uncondensables accumulate participate less in vaporizing the liquid causing heat exchange to be concentrated into the other parts of the condenser.
The object of the invention is to supply a brazed-plates condenser in which the discharge of the uncondensables is encouraged.
To this end, the subject of the invention is a brazed-plates condenser of the aforementioned type, characterized in that, in cross section, that part of the outlet box which lies between its lowermost point and the point of a liquid-outlet pipe connected to this box, lies completely at a level that is lower than the level of the lowermost point of the distributor corrugation.
The condenser according to the invention may have one or more of the following features, taken separately or in any technically feasible combination thereof:
the distributor corrugation has generatrices which are inclined downward from the lower end of the heat-exchange corrugation to the outlet box;
the outlet box is located completely beside the body of the exchanger, and the plates are extended downward as far as the lowermost point of the outlet box;
in a lower region of the passage remote from the outlet box, the passage contains a stiffening spacer corrugation which possibly has a construction and/or corrugation spacing and/or an orientation that differs from the corresponding characteristics of the distributor corrugation;
the spacer corrugation and the distributor corrugation are made from one and the same corrugated sheet;
the outlet box straddles a lower edge of the heat-exchanger body and is connected to this body along an upper longitudinal line running along a lateral face of the body and along a lower longitudinal line running along the underside of said body;
the outlet box is connected to the exchanger body along an upper longitudinal line running along a lateral face of the body and along a lower longitudinal line which runs along the same lateral face or along the corresponding lower edge of said body;
the outlet box is connected to the exchanger body along two longitudinal lines running along the underside of this body, one of these lines possibly following a lower edge of the body;
the outlet box is equipped with a liquid-discharge duct which starts from near its lowermost point and with a gas-discharge duct which starts from near its uppermost point;
the outlet box is equipped with fluid-discharge pipework, the axis of which passes outside the overall axis of the outlet box with respect to the body;
said pipework has an essentially vertical axis (X—X); and
said pipework is extended upward beyond the outlet box, to form a gas-discharge duct.
The following are also subjects of the invention:
a vaporizer-condenser for a double air-distillation column, intended to vaporize oxygen by the condensing of nitrogen, characterized in that the condenser part of this vaporizer-condenser is as defined hereinabove;
a double air-distillation column, characterized in that it comprises a vaporizer-condenser so defined; and
a method of condensing a fluid in a brazed-plates condenser, of the type comprising an exchanger body which has at least one condensation passage which is flat in shape and delimited between two substantially vertical parallel plates, this passage containing, over most of its height, a heat-exchange spacer corrugation with substantially vertical generatrices; an inlet box for a gas that is to be condensed, this box being located at the upper end of the passage; an outlet box for the liquid condensate, this box being located at the bottom end of the passage; a distributor spacer corrugation, the generatrices of which are at an angle to the direction of the generatrices of the heat corrugation and which direct the liquid condensate from the bottom end of the heat-exchange corrugation to the outlet box, characterized in that the free surface of the liquid is permanently kept at a level below that of the lowermost point of the distributor corrugation.
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Doerrler William
L'Air Liquide, Societe Anonyme pour l'Etude et l'
Young & Thompson
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