RU2077944C1 - Method for production of air drier - Google Patents

Abstract

FIELD: sorption technique. SUBSTANCE: method is carried out by impregnation of granules of sorbent with solution of halogenids of alkali or alkali-earth metals, ratio of said sorbent and solution being 1:0.3-0.5 respectively. Concentration of said solution is 20-40 mass %, the process takes place at 80-100 C. The process is followed by drying at 180-230 C, then impregnation and drying are repeated at the same regime. EFFECT: increased sorption ability of desired sorbent. 1 tbl

Description

 The invention relates to a sorption technique, and in particular to a method for producing a moisture absorbent sorbent for drying gas-air flows. The primary area of application is individual and collective respiratory protection.

The closest in technical essence and the achieved results is a method of obtaining an impregnated desiccant, which consists in mixing 5 to 15 wt. polyacrylamide and 85 to 95 wt. Aerosil with V beats 100 - 200 m ² / g, granulation, heat treatment at 160 180 ^o C for 2 to 4 hours. impregnation with a solution of halides of alkali and alkaline earth metals. The volume of the impregnating solution is taken equal to the pore volume of the sorbent, followed by drying.

 The disadvantage of this method is the low sorption capacity of the resulting desiccant in water vapor, which does not allow the use of such desiccants in respiratory protection.

 The aim of the invention is to increase the sorption ability of the resulting desiccant in water vapor.

 One of the main purposes of a desiccant in protective equipment is to prevent a hopcalite humidifier that effectively absorbs carbon monoxide only in the dry state. The use of a desiccant in the frontal layer can significantly increase the absorption capacity of hopcalite and increase the time of the protective effect of the charge on carbon monoxide. Therefore, the criterion for evaluating the effectiveness of the desiccant can be the time of the protective action of the charge;

The goal is achieved by the proposed method, including the impregnation of the sorbent granules with a solution of halides of alkali or alkaline-earth metals and their drying, and the impregnation is carried out with a solution with a concentration of 20 to 30 wt. at t 80 100 ^o C with a ratio of sorbent and solution of 1: 0.3-0.5, and drying is carried out at 180 230 ^o C with subsequent repetition of impregnation and drying under these conditions.

 When sorbents are modified by hygroscopic salts (alkali and alkaline earth metal halides), the impregnation and drying stages are crucial for the formation of the drying ability.

 Numerous experiments have shown that for uniform application of hygroscopic salt on the surface of the sorbent, it is important to maintain the temperature regime of impregnation and the ratio of the components of the sorbent-solution, as well as to ensure optimal conditions, which favors the formation of dehydrate complexes of the introduced salt. To apply a sufficient amount of a hygroscopic additive to a porous base, it is advisable to impregnate sequentially in two stages with intermediate drying. Two-stage impregnation and drying allow evenly applying the maximum possible amount of additive to all types of pores.

The method is as follows. Take a sorbent (activated carbon, silica gel, active alumina) with a diameter of granules of 0.5 to 3.5 mm and a total pore volume of 0.6 to 1.3 cm ³ / g and place it in an impregnation apparatus. Then in a separate reactor prepare an aqueous solution of the applied salt (calcium chloride, lithium chloride, lithium bromide) with a concentration of 20 to 30 wt. by dissolving in industrial water or condensate when heated to 80 100 ^o C. Turn on the impregnation apparatus and add a salt solution to the sorbent at the rate of 0.3 0.5 solution per 1 kg of carrier, which corresponds to the introduction of a 15% hygroscopic additive into the sorbent 8. The impregnation is carried out for 8-15 minutes at t 80 100 ^o C. Then the impregnated sorbent is discharged and sent to the fluidized bed furnace, where the air-gas mixture is dried at a temperature of 180 230 ^o C, the feed rate of the sorbent during drying is 600 800 kg / h. Then, the resulting product is fed into the impregnation apparatus and a second impregnation and heat treatment are carried out in a fluidized bed furnace with the same technological parameters, to a moisture content of the finished desiccant of not more than 1% as in the first.

 After the second stage of the process, the content of absorbent salt on the sorbent reaches 15 to 35 wt.

The total yield of the finished product 87 92%
Example 1. Take 10 kg of activated carbon AG-3 (GOST 20464-75) with a diameter of granules of 1.8 mm and a total porosity of 0.88 cm ³ / g, place it in an impregnation apparatus. The finished solution of calcium chloride with a concentration of 20 wt. obtained by dissolving CaCl ₂ in the condensate at t 90 ^o C, served in the supply unit at the rate of 4 kg (or 3.4 l) of solution per 10 kg of coal. The impregnation is carried out for 10 minutes Then, the impregnated coal is discharged and sent to a fluidized bed furnace, where it is dried with a gas-air mixture at 180 ^° C in order to remove excess moisture. Next, the resulting product is again fed into the air supply unit and a second impregnation is carried out with a solution of calcium chloride prepared as for stage 1. The ratio of the components of coal: solution, mixing time, temperature conditions are the same as in stage 1. Then the impregnated product is again fed into the fluidized bed furnace and dried at 180 ^° C. to a residual moisture content of not more than 1%
The resulting desiccant had a CaCl ₂ content of coal of 14.5 wt. the protective action time of the standard hopcalite by CO in combination with the obtained desiccant was 141 minutes.

The time of the protective effect of hopcalite on carbon monoxide when tested with a desiccant is determined under the following conditions:
total layer height 5.0 ± 0.1 cm (2.5 cm of desiccant in the frontal layer and 2.5 m of hopcalite in the closing layer);
specific consumption of gas-air mixture (0.32 ± 0.01) dm ³ / min • cm ² ;
the internal cross-sectional area of the dynamic tube 3.15 ± 0.15 cm ² ;
test temperature 23 ± 5 ^o C;
absolute humidity of the air-gas mixture 8.6 ± 0.3 mg / l;
carbon monoxide concentration of 6.2 ± mg / l;
when testing the used GFH hopcalite with a maximum clay content (12–13%), humidity not more than 1% with a protective action time of 45 ± 3 min.

 Example 2. The process as in example 1, except that they take a solution of calcium chloride with a concentration of 18 wt.

The resulting desiccant had a CaCl ₂ content _of 12.5% and the protective action time was 116 minutes.

The table presents examples 1 to 38, obtained analogously to example 1, showing the influence of the impregnation and drying modes on the absorption capacity of the desiccant, which is quite indicative of the protective time of the hopcalite charge on carbon monoxide under standard test conditions mentioned above, as well as the possibility of obtaining a desiccant on different carriers (activated carbon, silica gel, active alumina) with CaCl ₂ , LiBr, LiCl salts.

As follows from the table, when sorbent is impregnated with a solution of halides of alkaline and alkaline-earth materials with a concentration of 20-30 wt. at 80-100 ^o C and a sorbent: solution ratio of 1: 3 ^o C0.5, drying with a gas-air mixture at 180 230 ^o C, followed by repeated impregnation and drying under the indicated conditions, an increase in the absorbent capacity of the desiccant in water is achieved, which is characterized by an increase in the dynamic activity of hopcalite by carbon monoxide 20 50%
The salt content (CaCl ₂ , LiBr, LiCl) in the solution of less than 20% does not ensure the application of a sufficient amount of a hygroscopic additive on the sorbent, which leads to a high absorption capacity; on the other hand, a high solution concentration of more than 30 wt. leads to a significant increase in the density and viscosity of the solution and dramatically affects the absorption of the solution by the sorbent.

If the temperature of the salt solution is below 80 ^o C, its viscosity increases and the solution is poorly absorbed, the amount of the applied component on the carrier decreases, and therefore, the dynamic activity worsens.

Experimentally established the optimal ratio of sorbent: solution 1: 0.3 ^o C0.5.

 The introduction of a smaller amount of solution leads to a heterogeneous product, because the volume of the solution is insufficient to uniformly impregnate all grains of the sorbent, and a larger amount of the solution is poorly absorbed by the carrier, the salt crystallizes on its surface and, when dried in a fluidized bed furnace, is carried away with dust, which drastically worsens the quality of the desiccant.

At a drying temperature below 180 ^o C it is not possible to completely remove moisture, which significantly reduces the capacity of the desiccant in water, and at a temperature above 230 ^o C there is a surface burning of the carrier and the destruction of its porous structure, which leads to a decrease in the sorption capacity of the desiccant.

 From the foregoing, it follows that each of the features of the claimed combination to a greater or lesser extent affects the achievement of the goal, and the entire set of features is sufficient to characterize the claimed technical solution.

Claims (1)

A method of obtaining an air dryer, including the impregnation of the sorbent granules with a solution of halides of alkali or alkaline earth metals and their drying, characterized in that the impregnation is carried out in a solution with a concentration of 20 to 30 wt. at 80-100 ^° C with a ratio of sorbent and solution of 1 0.3 0.5, and drying is carried out at 180-230 ^° C, followed by repeated impregnation and drying under the indicated conditions.

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