Patent GB-711067-A (GB)
Title: Process and apparatus for the recovery of vapours of organic compounds diluted in a gas
Filed: 1951-08-01
Abstract: <PICT:0711067/III/1> In a process for the separation of condensible components from a gaseous composition by contacting the gas countercurrently with a cold liquid in a (first) contacting chamber wherein partial condensation of the condensible components takes place, and then passing the gas through a refrigerating zone wherein further condensation is effected, the liquid to be supplied to the first contacting chamber is cooled by contacting it in a second contacting chamber with the cold exhaust gas from the refrigerating zone.  There is a continuous circulation of the auxiliary liquid between the two contacting chambers; condensate being separated from the liquid before it is returned from the first to the second chamber.  The condensation in the refrigerating zone is effected in the presence of a second auxiliary liquid, which entrains or dissolves the condensate. The process may be carried out at super-atmospheric pressure.  The process may be applied to gas mixtures containing hydrocarbons or alcohols, and is particularly suitable for the removal of benzol from illuminating gas.  It may be employed in the treatment of air which has served for the ventilation of workshops where cellulose, varnishes and paints are applied, and in the treatment of cracking gases containing gasoline, butanes and butylenes.  The circulating auxiliary liquid may be an aqueous solution of calcium chloride or of a nitrate, or it may be a gycol or glycol ether. If the auxiliary liquid and the condensate are immiscible, they are separated by decantation; if however they are miscible, then distillation or solvent extraction may be employed for the separation.  In the case of benzol vapour, the second auxiliary may be an aromatic hydrocarbon fraction boiling above xylene; paracymene, tetrahydro- and decahydro-naphthalene are also referred to.  Illuminating gas at a temperature of 20 DEG  C., containing 55 g. benzole per cubic meter and saturated with water vapour, is supplied through pipe 11 into the base of plate column C1; and auxiliary liquid at -30 DEG  C. from vat 8 is pumped through pipe 5 into the top of the column.  The liquid withdrawn from the base of column C1 is passed to decanter 6 where the condensed benzene (31 g. per cubic metre of fresh gas) separates as an upper layer, and the auxiliary liquid as a lower layer.  The auxiliary liquid is collected in vat 7.  The gas leaving the head of column C1 is passed through pipe 12 into refrigerating unit 13, which is cooled by circulating refrigerant from refrigerator 17 through jacket 16.  While in unit 13, the gas is emulsified with a second auxiliary liquid by means of high-speed agitator 15.  Part of the liquid is continuously withdrawn from unit 13, benzene is separated therefrom and the residual second auxiliary liquid is returned to unit 13.  Exhaust gas at -30 DEG  C. is withdrawn from unit 13 through insulated pipe 14, and is introduced into the base of plate column C2, which is also insulated. Auxiliary liquid at 20 DEG  C. from vat 7 is pumped (if necessary after concentration or dilution) through pipe 3 into the top of column C2.  Cooled auxiliary liquid is withdrawn at the base of column C2, and is collected in vat 8 for recirculation to the head of column C1.  Columns C1 and C2 both contain plates of sintered metal which cause the rising gas to be divided into a large number of small bubbles while traversing the layer of auxiliary liquid on each plate. In order to insulate groups of plates from one another, thick joints of asbestos may be placed between the flanges of consecutive column sections.  The refrigerating unit may also comprise a column of the same type as C1 and C2; in which case, pipe 12 opens into the base of the column, and the second auxiliary liquid is sprayed in at the top.