Direct-heat drying continuous, rate

Employing wood chips, Cowan s drying studies indicated that the volumetric heat-transfer coefficient obtainable in a spouted bed is at least twice that in a direct-heat rotaiy diyer. By using 20- to 30-mesh Ottawa sand, fluidized and spouted beds were compared. The volumetric coefficients in the fluid bed were 4 times those obtained in a spouted bed. Mathur dried wheat continuously in a 12-in-diameter spouted bed, followed by a 9-in-diameter spouted-bed cooler. A diy-ing rate of roughly 100 Ib/h of water was obtained by using 450 K inlet air. Six hundred pounds per hour of wheat was reduced from 16 to 26 percent to 4 percent moisture. Evaporation occurred also in the cooler by using sensible heat present in the wheat. The maximum diy-ing-bed temperature was 118°F, and the overall thermal efficiency of the system was roughly 65 percent. Some aspec ts of the spouted-bed technique are covered by patent (U.S. Patent 2,786,280). 

Rate of Drying for Continuous Direct-Heat Driers... 

The hottest part of the tube, which is near the middle of the heated section, is maintained at 550° 10° while dry oxygen-free nitrogen is passed successively through a flowmeter and the tube at about 150 ml. per hr. for at least 30 minutes (Note 6). The dropping funnel is charged with 56 g. (0.67 mole) of diketene (Notes 7 and 8), which is then introduced into the hot tube at a rate of about 0.5 ml. per min. while the nitrogen flow continues. Essentially pure ketene (Note 9), yield 26-31 g. (46-55%) (Note 10), collects in the dry-ice trap as a colorless or nearly colorless liquid. The ketene is distilled directly from this trap for use in reactions. 

The other method. of conducting the evaporation of vat liqiiors is by means of iron pans, with the fire and, heated air applied beneath. These—named fishing pans —are of considerable size, and shaped somewhat similar to a boat. They may bo heatad by a fire used solely for the purpose in which case to prevent injury to the pan, the arch of the furnace should be continued for some distance beneath, or the pan may be placed at the end of the black-ash furnace farthest from the fire, just as with the salting pan, except that the heated air is mads to pass under instead of over the pan. The evaporation is rapidly conducted by this method and when the lie becomes concentrated to a certain strength, small crystals of mo nob yd rated carbonate of soda— Na 0, COa, HO—constantly fall to the bottom, and as quickly as thoy fall are raked together to tho end of the pan farthest from the source of heat, and then Scooped or fished out by moans of perforated iron shovels. After being allowed some time to draiD, the salta so obtained are washed with fresh vat liquor, and then removed a reverberatory furnace, and all worked about until sufficiently dry. The deep-red mother liquor is either applied to the production of caustic soda or evaporated, and the residue heated with sawdust as before directed. 

The catalyst chosen was packed into a hard glass combustion tube, heated to the desired temperature, and the gases, measuring some 1500 e.c. in toto, were continuously circulated throughout the system. Any combination to form water was measured by observing the fall in pressure. The majority of the experiments were carried out with porcelain 1 as catalyst., and it was found that the rate of combination of hydrogen and oxygen in electrolytic gas is directly proportional to the pressure of the dry gas. 

In the continuous drying of BALL POWDER, dewatered powder is fed into a series of vibrating pan conveyors. Fresh air is preheated and blown into an air distribution manifold where tubes direct the air flow into the powder. An aerated bed is obtained by controlling the powder flow rate, the pan conveyor vibration speed, and the heated air supply. The air supplies the heat for evaporating the water. The water vapor is removed with the exhaust air by vacuum transfer. 

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