RU2274484C2 - Method of preparing silica gel-based gas drier - Google Patents

Abstract

FIELD: gas-treatment materials.

SUBSTANCE: invention relates to sorption engineering, particularly to process gas drying processes and to individual and collective respiratory apparatus protection systems. Proposed method comprises impregnation of silica gel with aqueous solution containing 380 g/L calcium chloride and 480 g/L lithium bromide at solution temperature 10-20°C and ratio of silica gel pore volume to solution volume 1:(0.9-1.0); stirring for 15-20 min; drying at 300-450°C for 0.8 h; screening and recovery of fraction with granule diameter 1.0-3.0 mm.

EFFECT: increased strength and workability of drier.

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Description

The invention relates to the field of sorption technology, in particular to processes for drying process gases and to individual and collective respiratory protection systems.

A known method of producing a desiccant of gases based on silica gel, comprising impregnating silica gel with a pore volume of at least 0.9 cm ³ / g lithium halide solution; obtaining tablets with a diameter of 3.8 mm; drying at a temperature of 140 ° C for 4 hours; firing at a temperature of 700 ° C for 2 hours; immersion of the tablets for 15 min in a solution containing 800 g / l of lithium bromide, and final drying at a temperature of 140 ° C for 3 hours (Japan Patent No. 55-39240, class B 01 D 53/28).

The disadvantage of this method is the high complexity of the process.

The closest to the proposed technical essence and the number of matching features is a method of producing a gas desiccant based on crushed silica gel bound into water-resistant granules with various mineral binders, including a single or double (which is more preferable) impregnation with an aqueous solution containing 5-25 wt.% Chloride calcium and 5-25 wt.% lithium chloride.

The temperature of the impregnating solution is 60-80 ° C, the ratio of the volumes of the sorbent base and the impregnating solution is 1.0: (0.8-1.20). (Patent RU 2174870 C2, B 01 J 20/10, 10.20.2001 (abstract). This method can be adopted as a prototype.

The disadvantage of the prototype is the high temperature of the impregnating solution and the high complexity of the process: the manufacture of granules from crushed silica gel and the preference for double impregnation of the base.

The claimed invention is aimed at increasing the strength of the desiccant without preliminary grinding and granulation of the base, increasing the manufacturability of the process, as well as at lowering the temperature of the impregnating solution, which is achieved by the proposed method, including the impregnation of silica gel brand SHSKG (GOST 3956-76) with a total pore volume of 0.8- 1.2 cm ³ / g of a solution of the halides of the elements of the first and second groups in one stage and drying, and the impregnation is carried out with an aqueous solution of calcium chloride and lithium bromide with a solution temperature of 10-20 ° C at a CaCl ₂ content of 380 g / l and LiBr - 480 g / l, while the ratio of pore volume of silica gel and impregnation solution is 1.0: (0.9-1.0).

The difference between the proposed method and the known one is that, firstly, silica gel with a total pore volume of 0.8-1.2 cm ³ / g is used as a base, and secondly, the temperature of the impregnating solution is much lower than in the above inventions , and is 10-20 ° C.

The method is as follows. 0.7-1.2 kg of silica gel with a total pore volume of 0.8-1.2 cm ³ / g is loaded into the mixing drum. While stirring, 0.65-1.2 L of a solution with a temperature of 10-20 ° C containing calcium chloride and lithium bromide is added to the mixing drum, while the concentration in the solution of calcium chloride is 380 g / l, lithium bromide is 480 g / l .

The mixing process after adding the solution is carried out for 15-20 minutes The impregnated silica gel is discharged from the mixing drum and dried at a temperature of 300-450 ° C. for 0.8 hours. The dried product is dispersed and a fraction with a granule diameter of 1.0-3.0 mm is taken.

Example 1. Take 1 kg of silica gel with a total pore volume of 1.0 cm ³ / g, load into the mixing drum and mix by adding 0.95 l of a solution with a temperature of 10 ° C and a concentration of calcium chloride 380 g / l, lithium bromide - 480 g / l After adding the solution, stirring is carried out for 15 minutes The impregnated silica gel is discharged from the mixing drum and dried at a temperature of 300-450 ° C. for 0.8 hours. The dried product is dispersed and a 1.0-3.0 mm fraction is taken. The mechanical strength of the obtained desiccant was 86%.

Example 2. The process, as in example 1, except for the temperature of the impregnating solution, which was 20 ° C. The mechanical strength of the obtained desiccant was 83%.

Example 3. The process, as in example 1, with the exception of the coefficient of impregnation, which amounted to 1.0 of the total pore volume of silica gel. The mechanical strength of the obtained product was 85%.

The results of the study of the influence of the coefficient of impregnation and temperature of the impregnating solution on the mechanical strength of the desiccant are presented in the table.

Note to the table. The strength of the desiccant was determined according to GOST 16188-70.

As follows from the data given in the table, the greatest strength is observed with an impregnation coefficient equal to 0.95-1.0 of the total pore volume of silica gel, and the temperature of the impregnating solution of 10-20 ° C. When the parameters go beyond the specified values, the strength of the desiccant decreases markedly.

The essence of the proposed method is as follows. The increase in the strength of the desiccant is associated with an optimal ratio and uniform distribution of components in the pores.

A decrease in the impregnation coefficient leads to an uneven filling of the pores: the bulk of the components goes deep, and closer to the surface the pores remain unfilled. This reduces the strength of the desiccant.

Table
Dependence of the strength of the desiccant on the temperature of the impregnating solution and the impregnation coefficient. Way The temperature of the impregnation solution, ° C Impregnation coefficient of the total pore volume Desiccant Strength,% Proposed 10 0.8 78 10 0.85 80 10 0.90 85 10 0.95 86 10 1,0 85 5 0.95 80 10 0.95 86 fifteen 0.95 85 twenty 0.95 85 25 0.95 75 thirty 0.95 60 Known (pat. RF №2081823 from 11.24.94) 70 0.7 75

At the temperature of the impregnating solution below 10 ° C, it is impossible to introduce the required number of components, which reduces the strength of the desiccant. At temperatures above 20 ° C, the granules of the desiccant crack.

Thus, the proposed method allows to obtain a desiccant of gases that exceeds the known process manufacturability while maintaining strength and adsorption characteristics.

Implementation of the proposed method will allow for efficient drying of gas streams.

From the foregoing, it follows that each of the signs of the claimed combination to a greater or lesser extent affects the achievement of the goal, namely, increasing the strength of the desiccant and improving the processability, and the entire population is sufficient to characterize the claimed technical solution.

Claims (1)

A method of producing a gas desiccant based on silica gel, comprising impregnating it with an aqueous solution of metal halides in one step and drying, the ratio of pore volume of silica gel and solution volume being 1.0: (0.9-1.0), characterized in that as the basics use silica gel with a total pore volume of 0.8-1.2 cm ³ / g, the temperature of the impregnating solution is 10-20 ° C.