PROCESSES FOR SEPARATING CHLORINE FROM A GAS STREAM CONTAINING CHLORINE, OXYGEN AND CARBON DIOXIDE
Processes are disclosed which include: (a) providing a gas comprising chlorine, oxygen, and carbon dioxide; (b) feeding the gas to a distillation column having a head, a bottom, a rectifying section and a stripping section, wherein the gas is fed to the distillation column at an introduction point between the rectifying section and the stripping section; (c) distilling the gas in the column at a pressure of 8 to 30 bar and at a column head temperature of −10° C. to −60° C., to form liquid chlorine and a head mixture comprising carbon dioxide and oxygen; (d) removing the liquid chlorine from the distillation column at the bottom of the column; and (e) removing a first portion of the head mixture from the head of the distillation column, and refluxing a second portion of the head mixture in the column.
1 . A process comprising:
(a) providing a gas comprising chlorine, oxygen, and carbon dioxide, wherein the gas is a product of a hydrogen chloride oxidation process;
(b) feeding the gas to a distillation column having a head, a bottom, a rectifying section and a stripping section, wherein the gas is fed to the distillation column at an introduction point between the rectifying section and the stripping section;
(c) distilling the gas in the column at a pressure of 8 to 30 bar and at a column head temperature of −10° C. to −60° C., to form liquid chlorine and a head mixture comprising carbon dioxide and oxygen;
(d) removing the liquid chlorine from the distillation column at the bottom of the con; and
(e) removing a first portion of the head mixture from the head of the distillation column, and refluxing a second portion of the head mixture in the column.
2 . The process according to claim 1 , further comprising feeding the first portion of the head mixture into the hydrogen chloride oxidation process.
3 . The process according to claim 1 , wherein the head mixture is substantially free of chlorine.
4 . The process according to claim 1 , further comprising drying the gas prior to distilling the gas.
5 . The process according to claim 1 , wherein the hydrogen chloride oxidation process comprises a gas phase oxidation with oxygen at an elevated temperature in the presence of a catalyst.
6 . The process according to claim 1 , further comprising feeding at least a portion of the liquid chlorine to an HCl-generating process selected from the group consisting of isocyanate production processes, and organic compound chlorination processes.
7 . The process according to claim 1 wherein the hydrogen chloride oxidation process is supplied with hydrogen chloride from an HCl-generating process selected from the group consisting of isocyanate production processes, organic compound chlorination processes and combinations thereof; and wherein the process further comprises feeding at least a portion of the liquid chlorine to the HCl-generating process.
8 . The process according to claim 1 , wherein the distillation is carried out at a pressure of 10 to 25 bar and at a column head temperature of −25° C. to −45° C.
9 . The process according to claim 1 , wherein the liquid chlorine is substantially free of low-boiling compounds selected from the group consisting of oxygen, carbon dioxide, nitrogen, noble gases, and hydrogen chloride.
10 . The process according to claim 1 , wherein the head mixture further comprises hydrogen chloride.
11 . The process according to claim 1 , wherein all low-boiling compounds selected from the group consisting of oxygen, carbon dioxide, nitrogen, noble gases, and hydrogen chloride are present in the head mixture after distillation and wherein the head mixture is substantially free of chlorine.
12 . The process according to claim 1 , further comprising adding hydrogen chloride gas to an addition point selected from the gas prior to introduction into the distillation column, a condenser proximate to the column head, and combinations thereof.
13 . The process according to claim 12 , wherein up to 30 vol. % of the hydrogen chloride gas supplied to the first hydrogen chloride oxidation process is diverted prior to oxidation and is reintroduced into the gas prior to the distillation.
14 . The process according to claim 1 , the carbon dioxide in the first portion of the head mixture is 20 to 70 vol. %.