Continuous Vacuum Drying

The main features in which the Radford process differs from the batch operation are in thermal dehydration and compounding. Water-wet nitrocellulose on a continuous vacuum belt filter is vacuum-dried followed by hot air transfusion (80°C) to reduce the moisture to less than 2%. After cooling, alcohol is sprayed on the nitrocellulose to a concentration of 15—20%. The alcohol-wet nitrocellulose is then transferred from a surge feeder to a compounder by a continuous weigh-belt along with the other ingredients of the composition, which are also weighed and added automatically. 

Vacuum Treatment. Milk can be exposed to a vacuum to remove low boiling substances, eg, onions, garlic, and some silage, which may impart off-flavors to the milk, particularly the fat portion. A three-stage vacuum unit, known as a vacreator, produces pressures of 17, 51—68, and 88—95 kPa (127, 381—508, and 660—711 mm Hg). A continuous vacuum unit in the HTST system may consist of one or two chambers and be heated by Hve steam, with an equivalent release of water by evaporation, or flash steam to carry off the volatiles. If Hve steam is used, it must be cuUnary steam which is produced by heating potable water with an indirect heat exchanger. Dry saturated steam is desired for food processing operations. 

Sodium anthraquinone-l,5-disulfonate (HjO) [853-35-0] M 412.3. Separated from insoluble impurities by continuous extraction with water. Crystd twice from hot water and dried under vacuum. 

Sodium di(ethylhexyl)sulfosuccinate (Aerosol-OT) [577-11-7] M 444.6. Dissolved in MeOH and inorganic salts which ppted were filtered off. Water was added and the solution was extracted several times with hexane. The residue was evaporated to one fifth its original volume, benzene was added and azeotropic distillation was continued until no water remained. Solvent was then evaporated. The white solid was crushed and dried in vacuum over P2O5 for 48h [El Seoud and Fendler J Chem Soc, Faraday Trans I 71 452 /9751. 

Figure 18. Process flow scheme for continuous vacuum drying in the food processing industry.

B. Amalgamated, Zinc [Mercury alloy (Hg, Zn)]. Zinc powder (206 g., 3.15 moles) is placed in a 1-1. beaker, covered with 250 ml. of aqueous 10% hydrochloric acid, and stirred for 2 minutes. The acid is then decanted and replaced by distilled water, the mixture is stirred, and the supernatant is decanted. Washing is continued in this way until the water is neutral to litmus. A warm solution of 40 g. (0.15 mole) of mercuric chloride [Mercury chloride (HgCl2)] in 250 ml. of distilled water is then poured onto the zinc, and the mixture is stirred gently for 10 minutes. After filtration, the powder is washed with 250 ml. of distilled water, five 250-ml. portions of 95% ethanol, and five 250-ml. portions of anhydrous ether. Drying under vacuum gives 196 g. of zinc amalgam. 

Polycondensation At room temperature, 0.4% mass of Sn(II) chloride dihydrate (SnCl2-2H20) and 0.4% mass of p-toluenesulfonic acid monohydrate (p-TSA) are introduced into the mixture. The mixture is heated to 180°C under mechanical stirring. The pressure is reduced stepwise to reach 13 mbar, and file reaction is continued for 20 h. The reaction system becomes gradually viscous, and a small amount of L-lactide is formed and refluxed through the reflux condenser. At file end of the reaction, the flask is cooled down, file product is dissolved in chloroform and subsequently precipitated into diethyl ether. The resulting white fibrous solids are filtered and dried under vacuum (average yield 67%). 

SPE purification was carried out continually after the SEE procedure. The SPE tube was mounted on a vacuum manifold and preconditioned with 2 mL acetone and 2 mL of acetone-water (2 1, v/v) successively. The tube was connected with a 25-mL reservoir into which the extract was transferred. After percolation, the tube was rinsed with 10 mL of water-acetone (2 1, v/v) and the sorbent was dried under vacuum for 15 min. The residue was eluted with 5 mL of acetone into a volumetric flask. As well as water-acetone (2 1, v/v), 2 mL of acetonitrile-water (1 1, v/v) were also used for rinsing. ... 

The diamine was dissolved in N,N-dimethyl-acetamide by stirring under a nitrogen stream. After the diamine was completely dissolved, equal moles of isophthaloyl chloride was added all at once. Stirring was continued for about three hours after which the reaction mixture was poured into hot water and magnetically stirred. The polymer was washed with hot water at least three times and then extracted with acetone to remove low molecular weight species. The polymer was dried in vacuum oven at about 70°C overnight. 

To the clear solution is gradually added 1 L of ethyl acetate (Note 4) over 1 hr with continual stirring. The product slowly crystallizes during the addition of ethyl acetate. At the end of the addition, the product slurry is cooled to 5°C by immersing the reaction flask in an ice bath. The product is filtered and washed twice with 100 mL of cold ethyl acetate. Upon drying under vacuum at 50°C for 24 hr, 38.6 g of the product is recovered as a white solid (96% yield, mp 128-131 °C) (Note 5). 

Borax decahydrate is produced from borate ores, primarily colemanite and also from dry lake brines. When produced from its ore, the ore is crushed and then blended with B2O3. The blend is mixed with hot recycle liquor in a dissolving plant. Rock and clay particles from the liquor are removed over vibrating screens. The hquor is then fed to thickeners for settling of insolubles after which the underflow mud is washed with water. The strong liquor of borax hydrates is then pumped into continuous vacuum crystallizers for the separation of the pentahydrate first and then the decahydrate. The products are dried in rotary or fluid bed driers. 

To a suspension of D-glucose (59.8 g, 332.0 mmol) and dibenzylamine (64.0 mL, 332.0 mmol) in absolute ethanol (350 mL) was added acetic acid (57.0 mL, 995.7 mmol). The mixture was heated to reflux with an oil bath (temperamre not exceeding 90 °C) and stirred continuously for 3 h. After cooling to 0°C, the mixture was filtered, washed to white with ethanol, and dried under vacuum to give the rearranged product as a white solid (98.4 g, 83 %). 

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