GB1157816A - Improvements in and relating to Evaporators - Google Patents

Abstract

1,157,816. Evaporators, vapour compression type; automatic control. P. RIVA and G. RIVA..18 July, 1966 [13 April, 1966], No. 32200/66. Heading B1B. An evaporator of the . vapour-compression type, openated by mechanical compressor I driven by motor M, is provided with auxiliary heaters R 1 , R 2 , R 3 in the heatinig chamber D, and with a by-pass from the pipe N so that the vapours may pass from the heating chamber in to the condenser B without going through the compressor. The opening and closing of the by-pass is gradually controlled by motorised valve EV2 and thermometer K, which has contacts for maximum and minimum values, associated with electrical relays, servomotors, and a programmed switch. The solution to be evaporated is supplied from tank G4 which is under reduced pressure. The evaporator is equipped with a 'magnetic contact G1 responsive to liquid-level therein, a compressor purge valve EV3, and a concentrate discharge valve EV4. The control system operates so that the supply of solution to the evaporator, 'the preheating of the solution, the starting-up of the compressor, operation of the evaporator under steady state conditions, and shutting down of the evaporator are automatically and successively controlled. The distillate and residual non-evaporated solution (concentrate) are withdrawn from the evaporator through heat-exchangers E and H, respectively. Heaters R 1 , R 2 , R 3 may be electrical resistance heaters, or they may 'be coils supplied with heating-vapour. On closure of the contact of the programmed switch, the valve EV 1 which controls the supply of solution of tank G 4 is opened; and the servomotor of valve E v2 is put in operation. The solution flows from tank G 4 through heat exchangers E, H, and then through chamber D before it enters the tubes of the heatercondenser B. When the solution reaches the level determined by magnetic contact G 1 , the auxiliary heaters R 1 , R 2 , R 3 are put into operation. When the solution boils, the vapours flow into the compressor and heat it until the thermometer K reaches its maximum contact; the valve E v2 is then opened, and heater R 2 is made inoperative. Valve E v2 then closes. After steady state operation for a predetermined time, the programmed switch opens its contact, and the evaporator is shut down. 'If, during operation, a condition of excess vacuum arises in the evaporator, detector device V energises a relay which puts the evaporator out of action, and a signal lamp indicates the reason.