Patent GB-1049240-A (GB)
Title: Cold separation of gas mixtures
Inventor: MINKHORST JAN HENDRIK
IPC: F25J5/00
Filed: 1964-10-20
Abstract: 1,049,240. Cold separation of air. WERKSPOOR N.V. Oct. 20, 1964, No. 42728/64. Heading F4P. Air rectification apparatus for the production of either oxygen or nitrogen or both either in the gaseous or liquid phase or in both phases in any desired ratio comprises a column 31, 32, Fig. 5 (not shown), separated by an evaporatorcondenser 33 from the opposite sides of which product oxygen and nitrogen may be withdrawn, a main heat exchanger 52 serving to. cool at least apart of the feed air in a valved line 53 in heat exchange with reversely flowing separated gaseous oxygen and nitrogen, a cold gas refrigerator 47 for supplying cold to the column and a cooler evaporator having. the lower part of its evaporation space 39 connected by a duct 38 to a liquid container 34 of the condenserevaporator 33 having the upper part of evaporation space 39 connected by a duct 42 to the vapour space 43 of the condenser-evaporator 33 and having the cooling space 44 connected by a duct 55 to the main feed air inlet 53 and connected by a duct 57 to the column 31. When withdrawn products are wholly in the gaseous phase the refrigerator 47 merely condenses sufficient nitrogen to provide heat losses. On opening a valve 41 to discharge liquid oxygen at a rate p, k Mol/hr. a level-responsive means 64 increases the output of refrigerator 47 so that it condenses nitrogen at an increased rate of p, k Mol/hr. Since the total quantity of withdrawn products is maintained constant, opening of valve 41 results in a decrease in the output of gaseous oxygen and nitrogen in ducts 46, 51 which in turn results in a rise in temperature of the exchanger 52 which includes means 63 for increasing the by-pass feed air through duct 55 at the rate p 1  k Mol/hr. This results in evaporation of p, k Mol/hr. of liquid oxygen in containers 39, 34 and the resulting fall in level is followed by a further increase in the output of the refrigerator 47 to condense a further p 1  k Mol/hr. of nitrogen for supply to container 35 under which conditions equilibrium is attained with the refrigerator 47 condensing 2p 1  k Mol/hr. more than before valve 41 was opened. Similarly when a valve 37 is opened to discharge p 2 k Mol/hr. of liquid nitrogen the output of the refrigerator 47 is automatically, increased by 2P 2  k Mol/hr. before equilibrium is reached. The initial drop in level of the liquid nitrogen container results in further evaporation of liquid oxygen from container 34 at an increased rate P 2  k Mol/hr. and at the same time a rise in temperature at the base of column 31 due to the decrease in reflux flow results in means 66 adjusting a valve 57 in gaseous nitrogen duct 50 to decrease the discharge at the rate of p 2 ; k Mol/hr. The resulting temperature rise in exchanger 52 results in means 63 adjusting valve 54 so .as to increase the supply of air through duet 55 by an amount P 2  k Mol/hr. which in turn results in refrigerator 47 condensing nitrogen at a further increased rate of P 2  k Mol/hr. In a modification the refrigerator is connected to the oxygen side of the condenser-evaporator. The cooler-evaporator may be connected to the nitrogen side of said evaporator condenser.