Patent GB-864431-A (GB)
Title: Method and apparatus for separating components from gases
IPC: B01D53/32
Filed: 1959-04-01
Abstract: 864,431. Electrolysis. JANSEN, H. J. April 1, 1959 [April 1, 1958], No. 11123/59. Class 41. A method of separating gaseous components having an acid or alkaline reaction from a mixture of gases, e.g. CO 2  from air or SO 2  from crude oil cracking gases, comprises contacting the mixture of gases with a solution of an electrolyte 27 in which the components are absorbed and with which they form a chemical compound, the solution being electrolysed in a closed vessel 24 partitioned by a diaphragm 28 which separates the products of electrolysis, the mixture of gases being passed through the part of the vessel 24 containing the solution 27 capable of absorbing the components. In one embodiment, for the separation of acid components, e.g. CO 2 , the gas mixture enters the cathode chamber by a pipe 39, the electrolyte 27 being an aqueous solution of a partial salt, e.g. K 2 SO 4 , with excess KOH, which is circulated by a pump 35 between the chamber and a spray 37 which deposits it on a bed 38 of comminuted material from which the electrolyte drips back into the mass 27. The CO 2  combines with the KOH catholyte, which is continuously formed by electrolysis, to form K 2 CO 3  which is in turn electrolysed, the CO 2  going to the anode 31 for discharge at 43. Purified gas leaves at 44, where the component to be removed is basic, excess acid, e.g. H 2 SO 4 , is added to the K 2 SO 4  electrolyte instead of KOH being added, and the electrical connections are reversed, the basic component being discharged at 43. A wall having openings below liquid level may separate the electrode 29 from the rest of the interior of the vessel, a gas discharge exit being provided near the electrode 29, and a similar arrangement may be provided for electrode 31. Gasabsorbers, e.g. active carbon or silica gel, may be positioned in the path of the gases to be purified. In a modified apparatus, a central electrode depends in a gas-impermeable, porous vessel which is supported from the cover of a rectangular vessel near each side of which is supported an electrode of a polarity opposite to that of the central electrode. Partition walls, apertured below liquid level, separate the porous vessel from the side electrodes. Gas to be purified is delivered below liquid level to the space between the partitions and the porous vessel, purified gas escaping from this space through a duct in the cover. The component to be removed goes as ions to the central electrode through the porous vessel, as in the first embodiment, and escapes via a duct in the cover. Gas exit ducts are provided in the cover adjacent the side electrodes, and the central electrode may have a surrounding apertured wall and a gas outlet duct. This apparatus may be modified by providing one cylindrical apertured wall about the porous vessel and one cylindrical outer electrode. It is preferred to employ as electrolyte a salt which is derived from a stronger alkali or acid than that formed by the components. In an example in which CO 2  was separated from air the aqueous solution comprised 2% K 2 SO 4  and 25% KOH (parts by weight), and where NH 4  was separated from air the solution comprised 2% K 2 SO 4  and 10% of 99% H 2 SO 4  (parts by weight). In separating CO 2  from air K 2 SO 4  alone may be employed, in which case electrolysis must proceed prior to introduction of the air to produce KOH catholyte, or alternatively, KOH only may be employed.