SU1527167A1 - Method of producing sodium monochromate solution - Google Patents

Abstract

The invention relates to the chemical field of industry, the technology of chromium compounds, allows to increase the filtration rate of the target product by leaching the cake with a circulating solution with the addition of production in an amount that provides the content of 80-270 g / g of solid in suspension. Leaching is carried out for 6–20 minutes, followed by separation of the suspension by condensation to a concentration of 850–1,200 g / l of solid in the thickened part and filtration. 1 tab.

Description

This invention relates to the technology of chromium compounds and can be used to produce sodium monochromate.

The purpose of the invention is to increase productivity.

Example 1. (by a known method), A mixture of 42 g of ground chromite (52.5%), 23 g of conditioned soda (97%) and 68 g of ground dolomite (33% CaO and 18% MgO) are calcined for 30 minutes at atmosphere 100 g of chromium and 26% of hexavalent chromium, including 21% in the form of sodium chromate and 5% in the form of calcium chromate.

The grinded speculum is extruded with 150 ml of a working solution containing 44 g / l of NaCrO and 32 g / l of NaCOeV for 30 minutes at 70 ° C. The suspension is filtered under vacuum of 0.4 atm for 106 s on a funnel “5 98 mm, thus obtaining 160 ml of filtrate containing 259.2 g / l and 8.8 g / l of free alkali in terms of, and 102 2 g of sediment with a moisture content of 30%. The capacity of the filtration equipment is 115 kg / m.

EXAMPLE 2. Sinter from calcining furnaces is leached in a tank for 11 minutes, obtaining 300 liters of suspension with a solid concentration of 330 g / l and a CgO concentration of 180 g / l, the resulting suspension is sent to a tank, where it is diluted with 600 a production solution with a concentration of J80 g / l and heated, thus obtaining 900 l of suspension with a solid content of 110 g / l and temperature. The resulting suspension is concentrated by condensation into a tank thickener with a deposition surface of 1.5 m, where the suspension is thickened for 400 minutes, the resulting discharge in an amount of 787.5 liters is a product with a CrOj concentration of 180 g / l, part of which return at the stage of diluting the suspension.

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The condensed part in the amount of 112.5 l with a concentration of solid 880 g / l is fed to filtration on an industrial Zh-1.6 belt vacuum filter with a filtering surface, 6 m. The filtrate after filtration and preliminary drying, which is a production solution, is Fr, The amount of 48 liters with a concentration of 180 g / l is sent to the tank to dilute the suspension after the wet grinding mills.

The sludge with a moisture content of 30% goes to the wash where 90 liters of water of the first circulating cycle are subsequently washed with a CgO concentration of 5 g / l and dried with air, then 10 liters of hot industrial water with T 75 C. Filtrates after washing and drying steps This gives 110.4 liters of filtrate with a CrOj concentration of 60.5 g / l, which is sent to wet grinding mills to improve the cake, the filtration process, drying and washing, takes 8.2 minutes.

After filtration, 132 kg of mud are obtained with a moisture content of 25%. The sludge, which is a waste, contains in dry matter up to 0.15% hexavalent

water soluble chromium. The capacity of the filter equipment is 452.7 kg / mH in terms of dry sludge.

The results of example 2 and another example are given in the table.

Leaching for 6–20 minutes gives an optimum suspension from the point of view of the dispersion of the precipitate. The leaching duration of less than 6 minutes leads to an increase in the number of speck particles with sizes greater than 250 microns, which, in turn, significantly reduces the degree of extraction of Cr. An increase in the duration of desalting more than 20 minutes leads to overgrinding of the cake, an increase in the specific weight of fractions with a particle size of less than 40 microns, which significantly reduces the productivity of the filtration equipment, significantly reduces the sedimentation rate of the suspension, and also reduces the amount of thickening agents.

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The high concentration of solid particles in suspension within 850-1200 g / l ensures the highest productivity of the filter equipment. The decrease in the concentration of the supplied suspension below 850 g / l of solid leads to an increase in the load on the filters in phase and, accordingly, to a decrease in the performance of the filters. Increasing the concentration of solids in suspension above 1200 g / l makes it difficult to unload the thickened part and supply the thickened suspension to the filter.

Claims (1)

Dilution of the suspension to 80–270 g / l of solid in wet grinding mills ensures that the cake remains in the wet grinding mills for 6–20 min, which gives a high degree of leaching and the necessary dispersion of the precipitate, and also ensures an optimal rate of sedimentation of solid particles in a thickener. x Dilution of the suspension to less than 80 g / l of solid leads, by reducing the residence time in the mill, to an increase in the size of the grind, which reduces the degree of extraction of hexavalent chromium and the degree of removal of slime. A dilution of more than 120 g / l of solids increases the duration of leaching in the mill, which leads to overgrinding of solid particles, to a decrease in the rate of sedimentation of solid particles and to a decrease in the degree of sludge removal from water-soluble Cr. Invention Formula A method of producing a solution of sodium monochromat, which includes the improvement of the spectra & working solution in the wet grinding mill, separation of the suspension by condensation and filtration to obtain a production solution, washing the sludge on the filter, characterized in that, in order to increase productivity by increasing the filtration rate, 80- 270 g / l of solid in suspension, leaching is carried out for 6–20 min, and thickening is carried out up to 850-1200 g / l of solid solid condensed portion. eleven 14 20 thirty More than 250 nhm 250-75 microns 75-41 microns 40-10 microns Less than 10 nkm More than 250 microns 250-75 microns 75-41 microns 40-10 microns Less than 10 microns More than 250 microns 250-75 microns 75-41 microns 40-10 microns Less than 10 microns More than 250 microns 250-75 microns 75-41 microns 40-10 microns Less than 10 microns More than 250 microns 250-75 microns 75-40 microns 40-10 microns Less than 10 microns More than 250 microns 270-75 microns 75-40 µm 40-10 µm Less than 10 µm sixteen 66 13 five ABOUT eight 69 sixteen 7 ABOUT four 57 32 17 ABOUT one 64 nineteen sixteen ABOUT ABOUT 24 48 27 I About i 37 60 2 105 40 1155451,20,17 80 40850 441,70,14 110 40880 452,70,15 120 401200458,30,15 270 85770 205 0.21 330 100730 115 0.7 Editor N. Yatsola Compiled Oh, Zobnin Tehred M. Khodanich Proofreader L. Patay Order 7470/29 Circulation 435 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab., 4/5 Subscription