Patent GB-895215-A (GB)
Title: Improved method and apparatus for continuous heating of liquids
IPC: F28B3/06
Filed: 1960-01-28
Abstract: <PICT:0895215/IV (a)/1> In a method and apparatus for instantaneously and uniformly heating a liquid for a selected time at a selected temperature, starch slurry from tank 107 is pumped at 12 through restriction 113 and relief valve 7 to a mixing chamber 31 at the top of a detention tank 11 while steam is delivered through valve 30, pipe 15 and regulating valve 14 to mix with the slurry and condense, the slurry then falling on a baffle 36, collecting to form liquid level 38 and being withdrawn at 26 through spring-loaded diaphragm-actuated flow regulating valve 16 to a flash chamber 28, whence steam escapes at 52 and paste flows into storage tank 54. To counter heat loss in the tank, steam is also admitted from the top of pipe 4 and, to prevent clogging, from the bottom of pipe 4 through orifice 48 and pipe 33.  Air passes valve 13 and pressure regulating valve 6 to manifold 49 through bleed 46 and line 42 to the space above level 38 and through bleed 40 and line 43 to the bottom of the tank, the air bubbles aiding slurry flow in the tank and providing means for detecting the level at 38 by the pressures at the top and bottom of the tank, which are led from lines 42, 43 to a differential pressure controller 21.  The sensed pressure difference is multiplied and sent to a reverse acting pressure controller 25, where the signal is inverted and amplified and directed via line 52 and solenoid valve 23 to adjust valve 16, e.g. to open when the level 38 rises.  On the level in storage tank 54 covering probe 55, electric relay 27 via wire 57 and master manual switch 29 closes solenoid valve 51 and shuts off air pressure loading, via regulating valve 50, and a diaphragm relief valve 8, whereby slurry from pump 12 is returned through 8 to tank 107 and flow into tank 11 stops.  Relay 27 through wire 65 also moves three-way solenoid valve 23 to disconnect valve diaphragm 16 from controller 25 and connect it to pressure regulating valve 66 via three-way solenoid valve 24, from which air pressure corresponding to equilibrium flow in tank 11 holds valve 16 open to allow paste to drain from tank 11 at a rate ensuring correct detention time.  When level 38 approaches the tank bottom, pressure diaphragm switch 22 moves solenoid valve 24 to relieve valve diaphragm 16 via 32, 23, 67, 114, whereby valve 16 opens wide to allow residual paste to blow out and produce a momentary pressure drop in tank 11 which is transmitted via 42, 72 to pressure switch 20 to move solenoid valve 23 to reconnect valve diaphragm 16 to controller 25 which, being responsive to low pressure in tank 11, closes valve 16.  Switch 20 through wire 74 also closes normally open solenoid air valve 3, allowing diaphragm valve 70 to vent steam from tank 11 to a steamtrap. The apparatus is then ready to resume operation and, when the level in storage tank 54 reaches probe 56, valve 51 opens to close valve 8 and start slurry flowing.  Air bleeds at 79 and 115 co-operating with check valve 10 and valves 7, 8 and 50 prevent clogging of pipe 9 between valve 7 and 8 and also ensures smooth building up to equilibrium slurry flow.  Temperature and steam pressure in tank 11 are determined by pressure regulating valve 14, the diaphragm pressure of which is regulated, via line 58 and restriction 110 for slow closing, and via line 111 anc check valve 109 for quick opening, from controller 17 having a reference pressure at 61 opposing and tank pressure at 62 aiding the spring loading, the output pressure being fed back to two opposed diaphragms, one being via a restriction.  If a master stop-start switch 29 is open, valve 8 is opened and a locking relay 19 renders pressure switch 20 ineffective to close valve 3, and valve 70 is opened to drain the tank.  Flow through restriction 113 is kept constant by downstream pressure via 76, restriction 115 and regulating valve 50 acting on the diaphragm of bypass valve 8.