SU466186A1 - The method of desilicating alkaline aluminate solutions - Google Patents

Description

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The invention relates to the production of alumina, in particular, to the stage of cleaning solutions from silica impurities.

The known method of desilicating sodium aluminate solutions, in which the desiliconization of aluminum solutions is carried out at 135 ° C with the addition of relatively small amounts of seed - calcium metasilicate (2.5-5 g / l). However, inlaid walls of autoclaves during operation are noted.

According to the proposed method, the process is carried out with vigorous stirring and in the presence of 5-10 g / l nepheline with a ratio of calcium metasilicate to nepheline 1: 2.

A mixture of calcium metasilicate and nepheline or a chemical concentrate in the ratio of 1: 2, used as a seed in the desilination of aluminate solutions, protects the surface of the apparatus from precipitating the newly formed alkaline aluminosilicate on it. The seed of a mixture of calcium metasilicate and a chemical concentrate can be returned three or four times to the process of desalinization without rinsing and drying, while retaining both its desilicating ability and the protective properties of the equipment surface from incrustation.

Chemical concentrate (sodium or potassium) is obtained by autoclaving the treatment of nepheline syenite for 1.5 hours at a temperature of 230 ° C with alkaline solutions containing the corresponding, g / l: 1) 300 NaOH and 2) 225 COP and 125 NaOn. Chemical concentrates are crystalline sodium or potassium aluminosilicates with the inclusion of dark-colored minerals. Pagriya chemical concentrate contains,%: 42 SiOs; 25 AbOg; 3.7 Fe2Oz; 3.4 CaO; 1.4 CgO; 16.3 NasO; 7 loss on ignition (PPP) -Lvlaga. The crystals have a refractive index. Potassium chemical concentrate contains,%: 38.7 SiOs; 27.6 HOP; 4.4 FesOs; 3.9 CaO; 20.1 K2O; 2.3 NasO; 1,4 ppp-bvlaga. Crystal refractive index, 52. Calcium metasilicate is obtained by preparing limestone for limescale dilution of alkaline – siliceous – earth solutions (50–60 g / l. 5Ю2) emitted during the washing of chemical concentrates from mother liquors. Calcium metasilicate is a dispersed

a substance with a highly developed surface, oi has adsorption properties, does not coagulate, does not clot. Calcium metasilicate contains,%: 33 SiOa; 39 CaO; 7 SOA; 0.4 NajO; 18.8 moisture. Example i. Sodium aluminate solutions (NaA2Ototal 100 g / l; A12Oz 86 g / l; 1.70; Okremn. 23) in laboratory modular moduli are stirred in an autoclave with a root agitator at 135 ° C for 2 hours with the addition of a mixture of calcium metasilicate ( 2.5 g / l) and sodium chemical concentrate (5 g / l). After desiliconization, aluminate solutions with silicon modules 330-360 are obtained, the loss of AlaOs from solution into the solid phase is 3.2-3.9%. The incrustation of the surface of the autoclaves after the 60 hours of work specified for testing is not observed. Example 2. Predominantly sodium aluminate solutions (CgO total. On Na2O) 92 g / l; g / l, "caustic. 1.47, creyn. 33) stirred under laboratory conditions. In an autoclave with a root mixer at a temperature of 135 ° C for 2 hours in the presence of a two-component seed, consisting of calcium metasilicate (5 g / l) and sodium chemical concentrate (or natural nepheline) (10 g / l). When the process is carried out under these conditions, the silicon modules of aluminate solutions reach 250–270, the loss from solution to the solid phase is 3–3.5%. After 60 hours of operation of the autoclave, its surface inlay is not observed. Example 3. Preimush, naturally potassium aluminate solutions (R2Oo6m; (K2O) 152 g / l; g / l; 1.70; silica, 23, CsO:) are mixed. Under laboratory conditions in an autoclave with a root agitator 135 ° C for 3 hours with priming, consisting of calcium metasilicate (5 g / l) and potassium chemical concentrate (10 g / l). After that, the pulp is additionally unscrewed at a temperature of 95- 98 ° C for 3 more hours. As a result of the process, the silicon module of aluminate solutions rises to 100-130, the loss from solution to the solid phase is 2.5-3.0%. Inlaid surface of the autoclave after 60 hours of work is not observed. Example 4. Under factory conditions, the predominantly potassium aluminate solutions (K20 total (K2O) 149 g / l; A12Oz 90 g / l; caustic 1.52; Okremn. 28; CsO:, 8: module: 1), resulting when leaching potassium nepheline cake, mix in factory autoclaves with a root mixer at 135 ° C for 3 hours with a seed consisting of calcium metasilicate (at the rate of 5 g / l) and potassium chemical concentrate (at the rate of 10 g / l). Aluminate solutions are obtained with silicon modules 102-110. Loss from solution to the solid phase 3-3.2%. The incrustation of the autoclave surface after 70 hours of continuous operation under the specified conditions is not observed. Example 5. Under factory conditions, predominantly potassium aluminate solutions (K20 total (K2O) 147 g / l; g / l; a; av. 1.55; Scremn. 26; K2O:, 8: module: 1) resulting from leaching of potassium. nepheline cake with the addition of a mixture of calcium metasilicate (at the rate of 5 g / l) and potassium chemical concentrate (at the rate of 10 g / l) in heat exchangers of the type "pipe in pipe, heated at 135 ° C with a pulp passing rate of 30 mm / seconds for 120 hours A visual study of the internal surface of the heat exchangers after 120 hours of continuous operation under the specified conditions shows a complete absence of surface incrustation. The subject of the invention is a method of desilicating alkaline aluminas: tny solutions by introducing into them 2.5-5 g / l of calcium metasilicate seed at a temperature, characterized in that, in order to eliminate incrustation of the apparatus, the process is carried out with vigorous stirring and in the presence of g / l nepheline at a ratio of calcium metasilicate to nepheline 1: 2.