Combustion gas separation process to produce nitrogen, argon and CO2

Abstract

Title: Flue Gas Separation Process for the Production of Nitrogen, Argon, and CO2 In a flue gas separation process for the production of nitrogen, argon, and CO2, CO2 is removed from the flue gas to a concentration of less than 5 mol% by solvent scrubbing, forming a CO2-rich gas and a CO2-poor gas. The CO2-poor gas is compressed and dried, forming a purified gas. The purified gas is then cooled and separated in a column system operating at cryogenic temperatures to produce nitrogen and / or argon. No figure

Description

Title of the invention: Process for separating combustion gases to produce nitrogen, argon and CO2

[0001] The present invention relates to a process for separating combustion gases to produce nitrogen, argon and CO2.

[0002] It is known from US5100635 to use an amine wash to separate an already dried flue gas to produce a CO2-rich stream and a CO2-depleted stream, the CO2-depleted stream then being separated to produce nitrogen and argon.

[0003] According to an object of the invention, there is provided a method for separating combustion gases to produce nitrogen, argon and CO2 in which

[0004] a) A combustion gas comes from an industrial process, burning hydrocarbons as fuel.

[0005] b) CO2 is removed from the combustion gas to a content of less than 5 mol% and preferably less than 2 mol% CO2 by scrubbing with

[0006] solvent forming a CO2-rich gas and a CO2-poor gas

[0007] c) At least a portion of the CO2-poor gas is compressed to a pressure greater than 2 bar abs., preferably greater than 5 bar abs., or even greater than 8 bar abs., forming a compressed gas

[0008] d) Water and residual CO2 are removed from the compressed gas forming a purified gas

[0009] e) The purified gas is then cooled and separated in a system of columns operating at cryogenic temperatures to produce nitrogen and / or argon and / or oxygen in gaseous and / or liquid form.

[0010] By drying the gas after washing, the water generated during washing is eliminated.

[0011] The invention will be described in more detail.

[0012] A flue gas comes from an industrial process, burning hydrocarbons (natural gas, oil, etc.) as fuel. This industrial process may be an H2 production plant, preferably comprising a methane steam reformer whose burners produce the flue gas. The oxygen content of the flue gas is less than 5%, preferably 3% and 1.5%, the percentages being molar and on a dry basis.

[0013] CO2 is removed from the combustion gas to a content of less than 5 mol% and preferably less than 2 mol% CO2 by solvent washing, for example amines, hot potassium, methanol, refrigerated ammonia or the like) forming a CO2-rich gas and a CO2-poor gas. At least a portion of the CO2-poor gas is compressed to a pressure greater than 2 bar abs., preferably greater than 5 bar abs., or even greater than 8 bar forming a compressed gas. Water and residual CO2 are removed from the compressed gas forming a purified gas. Water and CO2 are removed by pressure swing adsorption (PSA) or temperature swing adsorption or a combination of extraction solvent (e.g. triethylene glycol or TEG) and temperature swing adsorption.

[0014] The gas is then cooled and separated in a column system operating at cryogenic temperatures to produce nitrogen and / or argon and / or oxygen in gaseous and / or liquid form. The column system comprises a first column operating at a first pressure, supplied with the cooled gas, and a second column operating at a second pressure, lower than the first pressure. The bottom of the second column is thermally connected to the head of the first column by a nitrogen condenser. The system comprises a third column with a head condenser for producing argon supplied from an intermediate point of the second column. The second column may have an overhead condenser. A bottom liquid of the first column containing less

[0015] than 10 mol%, preferably less than 3.5 mol% of oxygen is sent to the condenser of the third column and to the second column. The gas feeding the third crude column contains less than 25 mol%, preferably less than 20 mol% of oxygen and more than 75 mol% Ar, preferably more than 80 mol% Ar

[0016] The crude argon column can produce either pure argon (depending on market specifications) or argon to be further purified (e.g. in a pure argon column to remove remaining nitrogen).

[0017] Gaseous and / or liquid nitrogen is withdrawn from one of the first and second columns. Gaseous and / or liquid oxygen can be produced in the bottom of the second column.

Claims

Claims

1. A method of separating flue gases to produce nitrogen, argon and CO2 wherein a) A flue gas comes from an industrial process, burning hydrocarbons as fuel. b) CO2 is removed from the flue gas to a content of less than 5 mol% and preferably less than 2 mol% CO2 by scrubbing with solvent forming a CO2-rich gas and a CO2-poor gas c) At least a portion of the CO2-poor gas is compressed to a pressure greater than 2 bar abs., preferably greater than 5 bar abs., or even greater than 8 bar abs., forming a compressed gas d) Water and residual CO2 are removed from the compressed gas forming a purified gas e) The purified gas is then cooled and separated in a column system operating at cryogenic temperatures to produce nitrogen and / or argon and / or oxygen in gaseous and / or liquid form.