Nutsche filters mechanized

The saponification of organotriethoxysilane is carried out in enameled reactor 14 with an agitator and a water vapour jacket. First the reactor is filled from batch box 13 with 42% caustic soda and with a metered amount of water. After the dissolution is complete, the alkali solution receives organotriethoxysilane from batch box 12 at a temperature below 60 °C. The contents of the apparatus are agitated for 1 hour the mixture is sampled to determine the NaOFl content, solid residue and density. The prepared liquid is filtered through brass mesh in nutsch filter 15 into settling box 16. In the settling box the product is separated from mechanical impurities (it is settled for at least 24 hours), filtered in pressure filter 17 and poured into containers. 

Tetrabutoxytitanium from the vacuum distillation tank is sent into nutsch filter 12, where it is filtered from residual ammonia chloride and mechanical impurities. The filtered product is collected in receptacle 13. 

After alcohol has been distilled, the tank receives a necessaiy amount of toluene or xylene to prepare a 50-55% solution of polybutoxytitaniumox-ane. After the solvent has been introduced, the mixture in the tank is agitated approximately for 15 minutes and then sent into nutsch filter 12. From there the finished product, filtered from mechanical impurities, enters container 13. 

Nutsch filters are equipped with supporting perforated partitions covered with the filtering cloth. The washed cake is removed by turning each unit over. Sometimes a shaker mechanism is included to ensure more complete cake removal. 

Smaller Nutsche filters require a manual cake discharge while larger machines generally employ mechanical ploughs or rakes. Fully automated versions of the vacuum Nutsche filter are available and some include cake smoothing devices to minimise the problems of cake cracking. A range of filter media can be accommodated with filter areas up to a maximum of 10 m. ... 

The essence of the purification method used in the production of diamond nanopowders is to dissolve impurities of metals and their compounds and oxidize nondiamond forms of carbon by chromic anhydride in the presence of sulfuric acid. The use of such a strong oxidant in the presence of a strong acid makes it possible to combine in one stage the purification of diamonds both from nondiamond carbon forms and from metal impurities. The suspension of the nanodiamond-containing mixture is filtered through a set of sieves to remove mechanical impurities, the metal part is removed by magnetic treatment, and the solid phase is concentrated by nutsch filters. Dissolution of impurities of metals and their compounds and oxidation of nondiamond forms of carbon is carried out in a reactor (further on, this operation is called oxidation ). One run of oxidation to purify 3.3-3.7-kg solid phase of the mixture requires 24-27-kg sulfuric acid and 6.9-7.5-kg chromic anhydride. In the oxidation, when a solution of chromic anhydride is added, the temperature in the reactor reaches 125-130°C the mixture is kept in the reactor with sulfuric acid and chromic anhydride for 3-4 h. Following the oxidation, the reaction mixture is washed with water to remove chromium and sulfuric-acid salts. The yield is a nanodiamond suspension that contains 2.3-2.5-kg solid phase. 

Pressure filters are usually operated batch-wise. The batch pressure filters can be classified as tank (pressure vessel) filters or presses. Tank filters have filter elements of different types mounted in pressure vessels. Tank filters are divided into pressure nutsches, leaf filters, candle or tubular filters, bag filters, and cartridge filters. Presses (see Figure 22.38) consist of a series of filter surfaces (plates). The elements are mounted on a frame and are pressed together mechanically. 

These filters, often called mechanized Nutsches , are circular vessels provided with a cover, through which passes a shaft carrying a stirrer. The stirrer can sweep the whole area of the filter cake and it can be lowered or raised vertically as required. During the filtration process the stirrer is in the top position, if necessary in motion in order to prevent the formation of an... 

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