Patent GB-693149-A (GB)
Title: Improvements in or relating to the concentration of solutions
Inventor: BERGER ELWOOD PAUL WENZEL
IPC: B01D9/04
Filed: 1951-05-15
Abstract: 693,149. Concentrating solutions by freezing. COMMONWEALTH ENGINEERING CO. OF OHIO. May 15, 1951. No. 11390/51. Class 29 [Also in Groups I and VI] Solutions and aqueous dispersons such as milk, fruit juices, wines, antibiotics, &c. are concentrated by subjecting the solution &c. to a series of separate freezing steps at different temepratures, removing from the solution at each freezing step those ice crystals which exceed a predetermined size and subjecting the crystals below this size, together with the concentrated solution, to further freezing in the next following step, until a solution of the desired concentration has been obtained. The larger crystals are transferred to the next preceding step to bring about further growth, and are washed by oncoming weak. solution. Three chambers 104, 106 with curved bottoms are arranged step-wise in a container 101 adapted to receive cooling brine supplied separately to the spaces surrounding the chambers by pipes 102, 103. Each chamber has a scraper 149-151 on rotating arms 140-142 which also carry grading screens 130-132 connected to a frame 133 pivoted at 134 to arm 136. The brine in the compartment of the container 101 surrounding the chambers 104-106 is kept at the temperatures indicated, the lowest chamber 104 being the coldest and the mother liquor is supplied from a tank 159 through a valve 161 to the upper chamber 106 and overflows to fill the other chambers. The valve 161 is then closed, and small ice crystals, e.g. one to two millimetres long, will form in the three chambers. Motor 158 is then started to rotate the scrapers 149-151 and screens 130-132 to push in front of them the crystals formed in the respective chambers. Those crystals able to pass through the screen will return to the respective chambers and are carried along by the mother liquor to the next following freezing chamber while the larger crystals will be transferred to the next preceding chamber. The larger crystals in the first chamber 106, which has the screen with the largest mesh, will be transferred to a centrifuge 117. The crystals transferred from the chamber 104 to the chamber 105 will be allowed to grow further in the chamber 105 and similarly in the chamber 106, and the crystals finally transferred to the centrifuge 117 may average one to two centimeters long. While the transfer of crystals is taking place the valve 161 is opened and the crystals are washed by the liquor. The centrifuged crystals are removed from the drum 117 while the liquid flows through pipe 123 and vessel 124 to a pump 126 which returns it by a pipe 129 to the chamber 106. The mixture of liquid and small crystals passes from the lowermost chamber 104 into a centrifuge 108 from which the concentrated solution passes to a collector 115. In a modification a series of separate tanks refrigerated to successively lower temperatures and each having a stirrer are connected by separate pipes with electromagnetically operated valves to a single centrifuge from which further pipes with electromagnetically operated valves return the liquor, together with the smaller crystals not centrifuged out, to the next succeeding tank, the valves being operated in sequence by a timer.