Patent GB-1435875-A (GB)
Title: Drying apparatus
IPC: F26B23/02
Filed: 1974-06-11
Abstract: 1435875 Drying STAR-KIST FOODS Inc 11 June 1974 [14 June 1973] 25838/74 Heading F4G  A drying apparatus for drying fish meal or granular vegetable matter comprises an elongated dryer with a drying chamber having an inlet at one end and an outlet at the other end; an incinerator 21 adjacent and connected to the dryer inlet, a burner 23 in an upstream end of the incinerator remote from the dryer inlet, a fuel controller 65 for controlling the supply of fuel to the burner, an exhaust conduit 28 leading from the incinerator and a recirculation system for recirculating gases from the dryer to the incinerator and responding to the temperature of the gases by controlling the gas recirculation to maintain a predetermined temperature in the dryer. The dryer comprises a rotary dryer 15 with a rotary seal 67 at the inlet between tube 65A connected to the incinerator and a rotary seal 68 at the exit to a discharge bore 71. A motor 37 drives a pinion 39 engaging a gear 41 on the dryer which rotates on rollers 36. A temperature sensor 33 in the exhaust conduit connected to the fuel supply controlled and responsive to predetermined high and low temperatures of the sensor to reduce or increase the rate of fuel supply to the burner 21. A cyclone separator 75 in the recirculation system separates particles of the material and a scrubber 81 for the vapour. The recirculation system comprises a reheat conduit 27 connected to the incinerator 21 and a residual heat conduit 29. A blower 73 in a conduit 74 of the system blows gases therethrough, a valve 91, 93 in a respective conduit 27, 29 controls gas flow therethrough, a controller 30 adjacent the dryer outlet for the vapour expelled is connected to the valves with a pneumatic actuator operative in response to a first predetermined temperature by a sensor 105 to move the reheat valve towards its open position and the residual heat valve 93 towards its closed position and also responsive to a second predetermined temperature to move the valves to the reverse directions whereby the recirculation of the vapour from the dryer maintains the temperature at the sensor between the two temperatures. Cookers 115, 117 are supplied with fish from a conveyer 113 and the fish is conveyed to presses 122, 123 and from them conveyed to a conveyer 13 connected to the inlet of the dryer 15. Liquid from the presses is pumped to holding tanks 136 for feeding to centrifuges to separate the oils. Vapour emitted is conveyed through a scrubber 147 and by a blower to a burner 23 for incineration before exhaust to the atmosphere. The incinerator 21 has an outer refractory shell 45 with an annular pressure drop ring 51 and vortex grid 55. The inner shell is surrounded by an outer shell 57 to provide an annular counter flow chamber 59. A second dryer 15<SP>1</SP> aligned with the first dryer operates in series or in parallel or independently. In operation, for processing fish or fish parts the fish is conveyed by the screw conveyer 113 to the cookers 115, 117 the cooked fish is then passed through perforated drain conveyers 119, 121 to the presses 123, 125 where 50% of the moisture is removed. The fish is then conveyed by conveyers 131, 13 to the inlet of the rotatable dryer 15. The fish is tumbled by longitudinal fins which project within the dryer. The blower 73 draws air and gases through the dryer and directs them to recirculate. The finer meal is blown into the cyclone separators 75 and from there to the scrubber 81. The fine fish meal is collected in the hopper 77 and conveyed to grinders 80. The recirculating gases pass through the scrubber 81, jets 81, a demister 85 and then to the reheat and residual heat conduits 27, 29 in a ratio according to the setting of the valves 91, 93 therein the gases then pass to the incinerator 21. The heavier fish meal falls from a discharge box 71 and is conveyed by conveyer 13 to the inlet of the second dryer 15<SP>1</SP>. The temperature of the incinerator controlled by the exhaust chimney sensor 33 connected to a fuel controller 65 maintains the temperature of the chimney 28 at 1200 F. and the temperature of the dryer inlet at 550 F. The dryer temperature controller 30 responds to the sensor 105 in the discharge bore 71 to maintain the valves 91, 93 so that the outlet temperature is 220 F. The moisture content of the fish meal discharged from the dryer 15 contains approximately 25% moisture and is then passed through the second dryer 15<SP>1</SP> for reducing to 8% moisture. The dryer 15<SP>1</SP> is the same as the dryer 15 but has only one cyclone separator 75<SP>1</SP>. The liquid pressed from the presses is centrifuged to remove the oil and the vapour released is burnt.