US 4,400,183 A · Processes for separating the noble fission gases xenon and krypton from waste gases from nuclear plants

Abstract

Process for separating the noble fission gases xenon and krypton from a prepurified waste gas from a nuclear plant. The prepurified waste gas is brought into contact with liquid Cl.sub.2 CF.sub.2 as an absorption agent in a first column at an operating pressure which is less than or equal to normal pressure, whereby Xe, Kr, N.sub.2 O, CO.sub.2, O.sub.2 and N.sub.2 are absorbed by the agent. Subsequently, the liquid absorption agent containing the absorbed gases is heated to substantially the boiling temperature of Cl.sub.2 CF.sub.2 at the operating pressure for vaporizing part of the liquid absorption agent and desorbing the absorbed Kr, N.sub.2 and O.sub.2 to thereby separate the Kr and Xe from one another. The desorbed Kr, N.sub.2 and O.sub.2 gases are separated from the vaporized absorption agent. The liquid absorption agent which has not been vaporized is treated to recover Xe, N.sub.2 O and CO.sub.2. Waste gas containing Kr, N.sub.2 and O.sub.2 from the head of the first column is brought into contact with liquid Cl.sub.2 CF.sub.2 as an absorption agent in a second column, at an operating pressure which is less than or equal to normal pressure, whereby Kr, N.sub.2 and O.sub.2 are absorbed. Subsequently, the liquid absorption agent in the second column containing the absorbed Kr, N.sub.2 and O.sub.2 is heated to substantially the boiling temperature of the Cl.sub.2 CF.sub.2 at the operating pressure for vaporizing part of the liquid absorption agent and desorbing the absorbed N.sub.2 and O.sub.2. The liquid Cl.sub.2 CF.sub.2 which has not been vaporized is treated to recover Kr. An apparatus is provided for performing the process.

Claims13

Dependent claims

In a process for separating the noble fission gases xenon and krypton from a prepurified waste gas from a nuclear plant, the prepurified waste gas being substantially free of the main contaminating components, namely, aerosols, No.sub.x, CO.sub.2, water vapor, iodine and RuO.sub.4 and consisting essentially of Xe, Kr, N.sub.2 O, O.sub.2, N.sub.2 and small quantities of CO.sub.2, wherein:

(a) the prepurified waste gas is brought into contact with liquid Cl.sub.2 CF.sub.2 as an absorption agent, whereby Xe, Kr, N.sub.2 O and CO.sub.2 are absorbed by the agent and small quantities of O.sub.2 and N.sub.2 are absorbed and thus removed from the waste gas;
(b) subsequently the liquid absorption agent containing the absorbed gases is heated to substantially the boiling temperature of Cl.sub.2 CF.sub.2 for vaporizing part of the liquid absorption agent and desorbing an absorbed noble fission gas, the desorbed noble fission gas being carried along by the vaporized absorption agent;
(c) the noble fission gas which is carried along by the vaporized absorption agent is separated from the vaporized absorption agent by condensation of said vapor;
and
(d) the Cl.sub.2 CF.sub.2, which has been freed in step (c) from the absorbed noble fission gas and condensed, is circulated and reused;
the improvement comprising:
in step (a), absorbing Xe and Kr in liquid Cl.sub.2 CF.sub.2 at an operating pressure equal to or less than normal pressure;
in step (b), separating the Xe and Kr from one another at a temperature which corresponds substantially to the boiling point of Cl.sub.2 CF.sub.2 at said operating pressure, with the Kr being desorbed and carried along by the vaporized absorption agent;
in step (c), recovering the separated Kr;
and
desorbing and recovering the separated Xe.

8 more elements

Apparatus for separating the noble fission gases xenon and krypton from a waste gas from a nuclear plant, comprising:

a first absorption column and a second absorption column, the two columns each having three column sections, upper, intermediate and lower, each section having a mass exchange zone with means for mass exchange, the apparatus further including absorption agent evaporators, a first cooling device connected upstream of the first column and means for circulating the absorption agent, wherein
(a) the first absorption column is connected in series at its head with the second essentially identically designed absorption column through the intermediary of a second cooling device, the connection being made by means of a gas line;
(b) the first absorption column is separated at the gas side at its transition between its intermediate and lower sections, and is provided with a siphon means to permit liquid flow between its intermediate and lower sections, and the second absorption column is separated at the gas side at its transition between its intermediate and lower sections, and is provided with a siphon means to permit liquid flow between its intermediate and lower sections;
(c) the first absorption column has a line for Cl.sub.2 CF.sub.2, which includes a heating device, the line being disposed between the lower portion of its upper section and its intermediate section, for transfer of charged absorption agent into its intermediate section, and the second absorption column has a line for Cl.sub.2 CF.sub.2, which includes a heating device, the line being disposed between the lower portion of its upper section and its intermediate section, for transfer of charged absorption agent into its intermediate section;
(d) the first absorption column has an additional heating device disposed in its intermediate section below the opening of its Cl.sub.2 CF.sub.2 line into its intermediate section and below the mass exchange zone of its intermediate section;
and the second absorption column has an additional heating device disposed in its intermediate section below the opening of its Cl.sub.2 CF.sub.2 line into its intermediate section and below the mass exchange zone of its intermediate section;
(e) the lower section of the first absorption column is provided with a cooling device in its upper portion and with a heating device above its lower end;
and the lower section of the second absorption column is provided with a cooling device in its upper portion and with a heating device above its lower end;
and
(f) the first absorption column is equipped with means for circulating absorption agent from the lower end of its lower section to the head of its upper section, which means includes a pump and at least one heat exchanger;
and the second absorption column is equipped with means for circulating absorption agent from the lower end of its lower section to the head of its upper section, and which means includes a pump and at least one heat exchanger.

8 more elements

A process for separating the noble fission gases xenon and krypton from a prepurified waste gas from a nuclear plant, the prepurified waste gas being substantially free of the main contaminating components, namely, aerosols, No.sub.x, CO.sub.2, water vapor, iodine and RuO.sub.4 and consisting essentially of Xe, Kr, N.sub.2 O, O.sub.2, N.sub.2 and small quantities of CO.sub.2, comprising:

(a) bringing the prepurified waste gas into contact with liquid Cl.sub.2 CF.sub.2 as an absorption agent in a first column at an operating pressure which is less than or equal to normal pressure, whereby Xe, Kr, N.sub.2 O and CO.sub.2 are absorbed by the agent and small quantities of O.sub.2 and N.sub.2 are absorbed and thus removed from the waste gas;
(b) subsequently, heating in the fisrt column the liquid absorption agent containing the absorbed gases to substantially the boiling temperature of Cl.sub.2 CF.sub.2 at the operating pressure for vaporizing part of the liquid abbsorption agent and desorbing the absorbed Kr, N.sub.2 and O.sub.2 gases, the desorbed Kr, N.sub.2 and O.sub.2 gases being carried along by the vaporized absorption agent to the prepurified waste gas, to thereby separate the Kr and Xe from one another;
(c) separating the desorbed Kr, N.sub.2 and O.sub.2 gases which are carried along by the vaporized absorption agent from the vaporized absorption agent by condensation of said vapor;
(d) vaporizing a part of the liquid absorption agent which has not been vaporized in step (b) and which contains Xe, N.sub.2 O and CO.sub.2, and from which Kr, N.sub.2 and O.sub.2 have been desorbed, to desorb the Xe, N.sub.2 O and CO.sub.2, with the desorbed Xe, N.sub.2 O and CO.sub.2 gases being carried along by the vaporized absorption agent;
(e) separating the desorbed Xe, N.sub.2 O and CO.sub.2 from the vaporized absorption agent by condensation of the vapor;
(f) removing the desorbed Xe, N.sub.2 and O.sub.2 gases from the head of the first column and bringing them, as feed gas, into contact with liquid Cl.sub.2 CF.sub.2 as an absorption agent in a second column, at an operating pressure which is less than or equal to normal pressure, whereby Kr, N.sub.2 and O.sub.2 are absorbed;
(g) subsequently, heating in the second column the liquid absorption agent containing the absorbed Kr, N.sub.2 and O.sub.2 to substantially the boiling temperature of the Cl.sub.2 CF.sub.2 at the operating pressure for vaporizing part of the liquid absoprtion agent and desorbing the absorbed N.sub.2 and O.sub.2, the desorbed N.sub.2 and O.sub.2 gases being carried along by the vaporized absorption agent to the feed gas for the second column;
(h) vaporizing a part of the liquid Cl.sub.2 CF.sub.2 which has not been vaporized in step (g) and which contains Kr and from which N.sub.2 and O.sub.2 have been desorbed, to desorb the Kr, with the desorbed Kr being carried along by the vaporized absorption agent;
and
(i) separating the desorbed Kr of step (h) from the vaporized Cl.sub.2 CF.sub.2 by condensation of the vapor.

7 more elements

Dependencies are inferred from the claim text.

Processes for separating the noble fission gases xenon and krypton from waste gases from nuclear plants

Life of this patent

Processes for separating the noble fission gases xenon and krypton from waste gases from nuclear plants

Life of this patent

Abstract

Claims13