Decantation, continuous

Continuous decanter Continuous Continuous screw conveyor To 54,000 gal/h... 

The adsorbers are usually built of steel, and may be lagged or left unlagged the horizontal type is shown in Figure 28. The vapor-laden air is fed by the blower into one adsorber which contains a bed of 6- to 8-mesh activated carbon granules 12 to 30 inches thick. The air velocity through the bed is 40 to 90 feet per minute. The carbon particles retain the vapor only the denuded air reaches the exit, and then the exhaust line. The adsorption is allowed to continue until the carbon is saturated, when the vapor-laden air is diverted to the second adsorber, while the first adsorber receives low-pressure steam fed in below the carbon bed. The vapor is reformed and carried out by the steam. The two are condensed and if the solvent is not miscible with water, it may be decanted continuously while the water is run off similarly. After a period which may be approximately 30 or 60 minutes, all the vapor has been removed, the adsorbing power of the charcoal has been restored, and the adsorber is ready to function again, while adsorber No. 2 is steamed in turn. 

Scroll/decanter Continuous 5-50,000 200 1. Continuous solid discharge 2. High-feed solid concentration 1. Turbulence created by scroll 2. Low centrifugal force Antibiotic production... 

Leaving the refinery, jet fuel has generally no free water and contains only a small quantity of dissolved water. But humidity from the air and tank breathing result in continuous intrusion of water that must be then removed by decanting and filtration. This is why jet fuel needs to be tested for its ability to separate the contained water. 

Add 101 g. (55 ml.) of concentrated sulphuric acid cautiously to 75 ml. of water contained in a 1 htre beaker, and introduce 35 g. of finely-powdered wi-nitroaniline (Section IV,44). Add 100-150 g. of finely-crushed ice and stir until the m-nitroaniUne has been converted into the sulphate and a homogeneous paste results. Cool to 0-5° by immersion of the beaker in a freezing mixture, stir mechanically, and add a cold solution of 18 g. of sodium nitrite in 40 ml. of water over a period of 10 minutes until a permanent colour is immediately given to potassium iodide - starch paper do not allow the temperature to rise above 5-7° during the diazotisation. Continue the stirring for 5-10 minutes and allow to stand for 5 minutes some m-nitrophenjddiazonium sulphate may separate. Decant the supernatant Uquid from the solid as far as possible. 

Into a 1-litre beaker, provided with a mechanical stirrer, place 36 - 8 g. (36 ml.) of aniline, 50 g. of sodium bicarbonate and 350 ml. of water cool to 12-15° by the addition of a little crushed ice. Stir the mixture, and introduce 85 g. of powdered, resublimed iodine in portions of 5-6 g, at intervals of 2-3 minutes so that all the iodine is added during 30 minutes. Continue stirring for 20-30 minutes, by which time the colour of the free iodine in the solution has practically disappeared and the reaction is complete. Filter the crude p-iodoaniline with suction on a Buchner funnel, drain as completely as possible, and dry it in the air. Save the filtrate for the recovery of the iodine (1). Place the crude product in a 750 ml. round-bottomed flask fitted with a reflux double surface condenser add 325 ml. of light petroleum, b.p. 60-80°, and heat in a water bath maintained at 75-80°. Shake the flask frequently and after about 15 minutes, slowly decant the clear hot solution into a beaker set in a freezing mixture of ice and salt, and stir constantly. The p-iodoaniline crystallises almost immediately in almost colourless needles filter and dry the crystals in the air. Return the filtrate to the flask for use in a second extraction as before (2). The yield of p-iodoaniline, m.p. 62-63°, is 60 g. 

Decant the ethereal solution from the yellow aldimine stannichloride which has separated, rinse the solid with two 50 ml. portions of ether, and transfer the solid to a 2-5 litre flask fitted for steam distillation and immersed in an oil bath at 110-120°. Pass steam through a trap (compare Fig. 11,40, 1,6) to remove condensed water, then through a superheater heated to 260° (Fig. I, 7, 2), and finally into the mixture (2). Continue the passage of y steam until the aldehyde is completely removed (4-5 litres 8-10 hours). Filter the white soUd at the pump, and dry in the air. The resulting p-naphthaldehyde, m.p. 53-54°, weighs 12 g. It may be further purified by distillation under diminished pressure (Fig. II, 19, ) -, pour the colourless distillate, b.p. 156-158°/15 mm., while hot into a mortar and powder it when cold. The m.p. is 57- 58°, and the recovery is over 90 per cent. 

Prepare a solution of 41 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (as in A). Add all at once 60 ml. of 6iV-sulphuric acid to a rapidly stirred, hot (80°) solution of 63 1 g. of A.R. crystallised barium hydroxide in 600 ml. of water contained in a 2-htre beaker. Add more 6iV-sulphuric acid to render the suspension just acid to htmus (5). Introduce the palladium chloride solution and 4 ml. of 37 per cent, formaldehyde solution into the hot mechanically stirred suspension of barium sulphate. Render the suspension slightly alkaline with 30 per cent, sodium hydroxide solution, continue the stirring for 5 minutes longer, and allow the catalyst to settle. Decant the clear supernatant hquid, replace it by water and resuspend the catalyst. Wash the catalyst by decantation 8-10 times and then collect it on a medium - porosity sintered glass funnel, wash it with five 25 ml. portions of water and suck as dry as possible. Dry the funnel and contents at 80°, powder the catalyst (48 g.), and store it in a tightly stoppered bottle. 

To a suspension of a tinc-copper couple in 150 ml of 100 ethanol, prepared from 80 g of zinc powder (see Chapter II, Exp. 18), was added at room temperature 0.10 mol of the acetylenic chloride (see Chapter VIII-2, Exp. 7). After a few minutes an exothermic reaction started and the temperature rose to 45-50°C (note 1). When this reaction had subsided, the mixture was cooled to 35-40°C and 0,40 mol of the chloride was added over a period of 15 min, while maintaining the temperature around 40°C (occasional cooling). After the addition stirring was continued for 30 min at 55°C, then the mixture was cooled to room temperature and the upper layer was decanted off. The black slurry of zinc was rinsed five times with 50-ml portions of diethyl ether. The alcoholic solution and the extracts were combined and washed three times with 100-ml portions of 2 N HCl, saturated with ammonium chloride. 

Novolak Resins. In a conventional novolak process, molten phenol is placed into the reactor, foHowed by a precise amount of acid catalyst. The formaldehyde solution is added at a temperature near 90°C and a formaldehyde-to-phenol molar ratio of 0.75 1 to 0.85 1. For safety reasons, slow continuous or stepwise addition of formaldehyde is preferred over adding the entire charge at once. Reaction enthalpy has been reported to be above 80 kj /mol (19 kcal/mol) (29,30). The heat of reaction is removed by refluxing the water combined with the formaldehyde or by using a small amount of a volatile solvent such as toluene. Toluene and xylene are used for azeotropic distillation. FoHowing decantation, the toluene or xylene is returned to the reactor. 

Solvent Process. In the solvent process, or solvent cook, water formed from the reaction is removed from the reactor as an a2eotropic mixture with an added solvent, typically xylene. Usually between 3 to 10 wt % of the solvent, based on the total charge, is added at the beginning of the esterification step. The mixed vapor passes through a condenser. The condensed water and solvent have low solubiUty in each other and phase separation is allowed to occur in an automatic decanter. The water is removed, usually to a measuring vessel. The amount of water collected can be monitored as one of the indicators of the extent of the reaction. The solvent is continuously returned to the reactor to be recycled. Typical equipment for this process is shown in Figure 2. The reactor temperature is modulated by the amount and type of refluxing solvent. Typical conditions are ... 

Another nickel cataly2ed process is described ia a Tolochimie patent (28). Reaction conditions claimed are 1—2.4 MPa (150—350 psi) at 100°C minimum. The combination continuous stirred reactor and gravity decanter uses density-driven circulation between the two vessels to recirculate the catalyst to the reaction 2one without the use of filters or pumps. Yield and catalyst usage can be controlled by varying the feed rates. 

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

Gravity Settlers Decanters These are tanks in which a liqmd-liquid dispersion is continuously settled and coalesced and from wriich the settled liquids are continuously withdrawn. They can be either horizontal or vertical. Figure 15-24 shows some typical horizontal decanters. For an uninstrumented decanter the height of the heavy-phase-liquid leg above the interface is balanced against the height of the hght-hquid phase above the interface, Eq. 15-50. 

Control philosophies applied to continuous countercurrent decantation (CCD) thick eners are similar to those used for thickeners in other applications, but have emphasis on maintaining the CCD circuit in balance. It is important to prevent any one of the thickeners from pumping out too fast, otherwise an upstream unit could be stai ved of wash liquor while at the same too much underflow could be placed in a downstream unit too quickly, disrupting the operation of both units as well as reducing the circuit washing efficiency. Several control configurations have Been attempted, and the more successful schemes... 

Washing in a continuous decanter is fairlv effective on solid particles larger than 80 jlrn (200 mesh), provided the particles are reasonably uniform in size with porous structure, Othenvise, the vv ash tlovvvs across the cake surface with little penetration because the pores at the cake surface are plugged bv fines. Rinsing efficiency, the proportion of soluble impurities displaced from the solids, is in the range of 50 to 80... 

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