RU2725926C1 - Chemical absorber of carbon dioxide and method of production thereof - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to compositions of absorbers used in respiratory protection. Disclosed is a chemical carbon dioxide absorber which contains (wt. %): lithium hydroxide of not less than 84; lithium carbonate is not more than 6; potato dextrin 4–6; porous sheet substrate 6–4. To obtain a chemical carbon dioxide absorber of said composition, an impregnating composition is prepared in form of a liquid paste which is applied on a porous sheet substrate, which is a Spunlace nonwoven material, containing 50 % of viscose and polyester fibre. Liquid paste contains components at following ratio (wt. %): lithium hydroxide monohydrate, not less than 36–46; potato starch 6–8; water - balance up to 100, second paste of Spunlace material is applied on applied paste and subjected to thermal compression treatment at temperature of 220 ± 2 °C and pressure of 0.5–2 MPa for 0.5–10 minutes.EFFECT: invention provides high sorption capacity of absorber.2 cl, 4 tbl, 1 dwg

Description

The invention relates to compositions of absorbers used in respiratory protective equipment, and can be used in the manufacture of a chemical absorbent of carbon dioxide CO ₂ .

Chemical absorbers of carbon dioxide, as a rule, are produced in the form of granules with a diameter of 1-5 mm, consisting of hydroxides of calcium, potassium, sodium, lithium, as well as water. Chemical absorbent calcareous HP-I is made in accordance with GOST 6755-88 and contains at least 96 mass. % calcium hydroxide and 4 wt. % sodium hydroxide (in terms of dry matter).

The main disadvantage of granular absorbers is the low sorption capacity associated with the underdeveloped active surface of the granules, as a result of which chemisorbents absorb CO ₂ 2.2-3.1 times less than possible by stoichiometry (90-110 dm ³ / kg instead of 250- 280 dm ³ / kg).

Known technical solutions aimed at increasing the sorption capacity of granular absorbers. So, according to the copyright certificate SU 1840416, IPC B01J 20/04, 2007, calcium chloride in the amount of 5-10 mass is additionally added to the granular chemical carbon dioxide absorbent based on calcium hydroxide. % as an additive that increases the sorption capacity and crush strength of granules. Calcium chloride plays the role of a water-retaining additive, forming crystalline hydrates in the chemical absorbent, which contributes to an increase in sorption capacity due to the fact that the chemisorption of CO _{2 is} intensified in the presence of moisture in an amount sufficient to transfer ions to the surface of the calcium hydroxide molecule.

Despite the increase in sorption capacity, the granular chemical absorber has a disadvantage associated with the inconvenience of re-equipping the CO ₂ absorption apparatus. The loading of granules into the apparatus takes a lot of time, granules must be sieved and vibro-compacted before use, which can lead to dusting of the material.

In the granular layer of the absorber, the air passing through it looks for ways of least resistance of the layer. In this case, the air flow pattern may be random. Depending on the nature of the load, the operating time of the devices varies significantly.

These drawbacks are deprived of chemical absorbers in the form of sheet materials. Sheet materials in the form of a ribbon are rolled into a roll with a cross section in the form of a spiral, placed in a cartridge and used in its composition. Channels for the passage of air are created either by molded ribs on the material, or by the material forming the gas ducts, which is placed between the layers of the chemical absorber when it is rolled up. The channels create a controlled uniform air flow through the absorber layer, which leads to a more uniform development and more complete use of the capacity of the chemical absorber for carbon dioxide.

Also, the advantages of cartridges from sheet absorbers in comparison with a layer of granules are: lack of dust when placed in the apparatus, good shock and vibration resistance, ergonomic use, the instability of the protective action time is eliminated. As additives that provide the formability of the sheet material, use a polymer binder.

So, upon receipt of a sheet absorber according to US patent No. 5165399, IPC B01D 53/62, 1992, a fibrous material is used as a binder. The fibrous material is a polymer fiber made of substances such as polyolefins, polyesters, polyamides with a fiber length of 2.5-76 mm. The content of fibrous material in the chemical absorber is from 0.1 to 70 mass. %

But at the same time, the combination of particles of hydroxides of alkali and alkaline earth metals in the sheet material does not occur due to the low adhesion of hydroxides to the fibers. As a result, the chemical absorber has an unstable structure, there is no material continuity, as a result of which jamming occurs when the sheet material is placed in the cartridge, voids occur, and the air flow passing through the cartridge is inhomogeneous, which leads to inhomogeneity of the chemical absorber working and impossibility to achieve high sorption capacities.

Known chemical absorber of carbon dioxide in the form of a sheet material based on hydroxides of alkali and alkaline earth metals, containing as a binder additive polyethylene in an amount of 1.5-4 mass. %, 13-19 mass. % water, the rest is calcium hydroxide (US patent No. 5964221, IPC B01D 053/14, 1999). Polyethylene is introduced into the chemical absorber in the form of a melt and, upon further solidification, binds the particles of the absorbing component, forming a strong monolithic structure. The material is molded in the form of a sheet with ribs on the surface. When forming a cartridge from sheet material, ribs create channels whose size allows you to adjust the air flow entering the apparatus for cleaning.

However, polyethylene, being a hydrophobic material with low gas permeability, blocks the access of gas to absorbing particles and does not retain moisture in the structure of the chemical absorber necessary for the successful chemisorption process, resulting in a decrease in the sorption capacity and the degree of development of the chemical absorber.

Known adopted as a prototype for the object “substance” is a chemical absorber of carbon dioxide (US Pat. RF 2591167, IPC B01J 20/04 (2006.01) B01J 20/28 (2006.01), publ. 10.07.2016), consisting of calcium hydroxide and / or hydroxides of alkali metals, water and a polymer binder, as a polymer binder contains polyvinyl alcohol and a porous sheet substrate in the following ratio of components (wt.%):

- calcium hydroxide and / or alkali metal hydroxides 64 ÷ 72; - polyvinyl alcohol 8.5 ÷ 13; - porous sheet substrate 2.5 ÷ 5; - water 10 ÷ 25.

The disadvantage of the absorber is the low sorption capacity associated with a lower stoichiometric capacity of calcium hydroxide, which absorbs CO ₂ 1.5 times less than lithium hydroxide.

Also known is a chemical absorber of carbon dioxide adopted as a prototype for the “production method” (Pat. RF 2610611, IPC 01J 20/04 (2006.01), B01J 20/30 (2006.01), published on 02/14/2017). A method of obtaining a chemical absorbent of carbon dioxide consists in preparing a suspension of alkali and / or alkaline earth metal hydroxides by dissolving alkali metal hydroxides in water, followed by the addition of alkali and / or alkaline earth metal hydroxides. After suspension of alkali metal hydroxides, a modifying agent is introduced into the suspension in the form of halides of alkali and / or alkaline earth metals or a mixture thereof in an amount of 1-3 mass. % The suspension is treated with a substrate of fibrous material, forming and drying. The resulting absorber has high mechanical strength and good absorption kinetics of carbon dioxide.

The disadvantage of this method is also the low sorption capacity of the absorbent obtained from it, since calcium hydroxide is used as the main substance.

The purpose of the present invention is to improve the prototypes by increasing the content of the basic substance, i.e. lithium hydroxide in a nonwoven material with a decrease in the concentration of the polymer binder, as well as in an increase in the absorption capacity in gas media and insulating breathing apparatus due to the higher stoichiometric capacity of the absorber.

The technical result is an increase in the sorption capacity of the chemical absorber.

The technical result for the object "substance" is achieved by the fact that the chemical carbon dioxide absorber containing alkali metal hydroxides, water and a polymeric binder, according to the invention, contains lithium hydroxide as an alkali metal hydroxide, starch and a porous sheet substrate as a polymeric binder " Spanlace ”in the following ratio of components (wt.%):

lithium hydroxide, not less 84 lithium carbonate, no more 6 potato dextrin 4-6 Spunlace porous sheet substrate 6-4

The technical result of the object “production method” is achieved by the fact that upon receipt of a chemical absorbent of carbon dioxide, including the preparation of an impregnating composition in the form of a paste, which is applied to a porous substrate, according to the invention, the Spunlace non-woven sheet material containing 50 mass. % viscose and polyester fiber, the impregnation is carried out by applying to the first sheet of Spanlace material an impregnating composition in the form of a paste containing the following components in the ratio (wt.%):

lithium hydroxide monohydrate 36-46 potato starch 6-8 water - the rest is up to 100,

a second sheet of Spanlace material is applied to the applied paste and the resulting assembly is subjected to heat compression treatment at a temperature of 220 ± 2 ° C and a pressure of 0.5-2 MPa for 0.5-10 minutes.

The invention consists in the thermal removal of water from the substances that make up the impregnating composition: technological paste for preparation, crystallization paste contained in lithium hydroxide monohydrate, natural moisture in starch. The result is a monolithic sheet absorber, in which the main substance (anhydrous lithium hydroxide) is enclosed between two sheets of substrate (Spanlace nonwoven fabric) and all elements of the monolithic sheet absorber are bonded using a polymer binder (potato dextrin).

The following are the characteristics of the components used in the manufacture of a chemical carbon dioxide absorber.

Technical lithium hydroxide according to GOST 8595-83 (lithium hydroxide). This standard applies to technical lithium hydroxide, which is lithium hydroxide monohydrate used in the manufacture of water-resistant lubricants, as an additive to electrolyte for alkaline batteries, in air conditioning systems, in analytical chemistry, as a feedstock for various lithium compounds and other goals, and establishes requirements for lithium hydroxide, manufactured for the needs of the national economy and for export delivery. The formula LiOH⋅Н ₂ O. The molecular mass (for international atomic masses of 1985) is 41.96. Lithium hydroxide is made of two grades: LGO - 1 and LGO - 3. According to the physicochemical parameters, lithium hydroxide must meet the standards specified in table. 1.

Potato starch in accordance with GOST P 53876-2010. This standard applies to potato starch obtained by the mechanical processing of potatoes. Potato starch is used in various sectors of the food industry (confectionery, concentrate, meat and dairy, baking, etc.) as a consumer product; in the chemical and pharmaceutical industry as a filler in tablet medicines and powders, as well as for technical purposes (dextrin production, in the textile, paper and other industries). According to physico-chemical parameters, potato starch must comply with the requirements and standards specified in table. 2.

Spanlace according to TU 8390-001-50030680-09 is a non-woven fabric obtained by tightly bonding fibers (threads) with high-pressure water jets, without the use of adhesive compositions. Properties: soft lint-free material with high absorbency. It is used as a cleaning material in everyday life and in the form of napkins. High barrier properties of the material, inhibiting the penetration of microorganisms to anything, make it possible to use it in medicine and cosmetology, as a material that less infects human skin compared to traditional fabrics made of cotton and linen. The material, if necessary, is well sterilized.

Distilled water according to GOST 6709-72 This standard applies to distilled water obtained in distillation apparatus and used for the analysis of chemical reagents and the preparation of reagent solutions. Distilled water is a clear, colorless, odorless liquid. Formula H ₂ O. The molecular weight (according to international atomic masses of 1971) is 18.01. According to physico-chemical indicators, distilled water must meet the requirements and standards specified in table. 3.

The essence of the claimed invention is illustrated by an example of a specific implementation, where in FIG. 1 is a flow chart of a carbon dioxide absorber.

The list of items shown in FIG. 1:

1 - packaging with lithium hydroxide;

2 - a container with distilled water;

3 - capacity;

4 - packaging with potato starch;

5 - a roll of Spanlace material;

6 - table;

7 - capacity;

8 - scales;

9 - capacity;

10 - scales;

11 - sealed container;

12 - laboratory mill;

13 - capacity;

14 - table;

15 - a backing sheet;

16 - thermal press;

17 - technological packaging;

18 - transport packaging.

Chemical absorber is prepared as follows.

The manufacturing process for a chemical carbon dioxide absorber is shown in the diagram of FIG. 1 and consists of the following main stages:

- preparation of a solution of potato starch in an amount of 1 DM ³ ;

- preparation of a solution of lithium hydroxide using LGO-1 according to GOST 8595-83 with a basic substance content of at least 56.7 mass. % in examples 2 and 4 and LGO-3 according to GOST 8595-83 with a lithium hydroxide content of at least 53 mass. % in examples 1 and 3;

- preparation of the substrate, applying the solution to the substrate;

- thermal pressing of the sheets of the absorber.

The cooking process is periodic. 50 ml of distilled water are measured and poured into a container 7. On the scales, potato starch is weighed, 50 g are poured into a container 7 and mixed until it is completely dissolved. With a measuring cylinder, 1 dm ^{3 of} hot distilled water is measured and poured into a container 9. The water temperature should be at least 90 ° C. The solution from the container 7 is poured into a container 9 with hot water and mixed until a uniform colloidal solution is formed. To prepare a lithium hydroxide solution, lithium hydroxide is weighed on a scale of 10 and poured into an intermediate tightly closed container 11. Then, in small portions, lithium hydroxide is poured into a laboratory mill 12 and ground for 30 s. After that, pour it into the intermediate tightly closed container 13.

In a container 13 with milled lithium hydroxide, a potato starch solution is poured from the container 9 and mixed until a homogeneous pasty mixture is obtained. To apply a paste-like mixture to the blank of Spanlace material on a table 14, a backing sheet 15 of 0.5–0.8 mm thick fluoroplastic is laid on which a sheet of Spanlace material is laid, a paste-like solution of lithium hydroxide is applied to it and the trowel is evenly distributed over the entire surface of the workpiece. After that, a second sheet of Spanlace material is placed on the first sheet coated with a paste-like solution and placed in a thermoforming press, in which the absorber is pressed by heating. During heating, the water introduced into the solution from the resulting paste evaporates, the water contained in the potato starch is removed, and lithium hydroxide monohydrate under the action of heating loses crystallization water. Due to this, the specific content of lithium hydroxide in the absorber sharply increases.

The following are examples of the proposed method.

Example 1

Preparation of potato starch solution. A solution of potato starch was prepared with a volume of 1.0 DM ³ . The cooking process is periodic. 0.05 dm ^{3 of} distilled water was measured with a measuring cylinder and poured into a container 7. On a scale, 50 g of potato starch was weighed, poured into a container 7 and mixed until it was completely dissolved. 0.664 dm ^{3 of} distilled water was measured with a measuring cylinder at a temperature of 95 ° C and poured into a container 9. A solution from a container 7 was poured into a container 9 with hot water and mixed until a uniform colloidal solution was formed.

Preparation of lithium hydroxide solution. A portion of lithium hydroxide LGO-3 according to GOST 8595-83 with a lithium hydroxide content of at least 53 mass. % in an amount of 360 g was placed in an intermediate tightly closed container 11. In small portions, lithium hydroxide was poured into a laboratory mill 12 and milled for 30 s. Received 246 ml of dispersed powder. After that, they poured into the intermediate tightly closed container 13, into which then a solution of potato starch was poured from the container 9 and mixed until a uniform paste-like mixture was obtained in an amount of 1 dm ³ .

Preparing the substrate, applying the solution to the substrate. To apply a paste-like solution of lithium hydroxide to the blank of Spanlace material on table 14, a Teflon backing sheet with dimensions of 400 × 500 mm and a thickness of 0.6 mm was laid on which a sheet of Spanlace material with dimensions of 400 × 500 mm and a thickness of 0 was laid. 4 mm, 0.25 dm ³ of lithium hydroxide paste was applied to it and a spatula was evenly distributed over the entire surface of the workpiece. After that, a sheet of Spanlace material coated with a layer of paste was covered with a second sheet of Spanlace material and subjected to heat pressing.

Example 2

The preparation of potato starch solution was carried out similarly to that described in example 1. At the same time, hot distilled water with a temperature of 94 ° C was taken. The solution from tank 7 was poured into a tank 9 with hot water in an amount of 0.667 ml and stirred until a uniform colloidal solution was formed.

Preparation of lithium hydroxide solution. A portion of lithium hydroxide LGO-1 according to GOST 8595-83 with a lithium hydroxide content of at least 56.7 mass. % in an amount of 340 g was placed in an intermediate tightly closed container 11. In small portions, lithium hydroxide was poured into a laboratory mill 12 and ground for 40 s. Received 233 ml of dispersed powder. After that, they poured into an intermediate tightly closed container 13, into which then a solution of potato starch was poured from the container 9 and mixed until a homogeneous mixture was obtained. Got an impregnating solution in the form of a paste in an amount of 1 DM ³ .

Preparing the substrate, applying the solution to the substrate. To apply a paste-like solution of lithium hydroxide to the blank of Spanlace material on table 14, a Teflon backing sheet with dimensions of 400 × 500 mm and a thickness of 0.4 mm was laid on which a sheet of Spanlace material with dimensions of 400 × 500 mm and a thickness of 0 was laid. 4 mm, 0.25 dm ^{3 of a} paste-like lithium hydroxide solution was applied to it and a spatula was evenly distributed over the entire surface of the workpiece. After that, a sheet of Spanlace material coated with a layer of paste was covered with a second sheet of Spanlace material and subjected to heat pressing.

Example 3

The preparation of a solution of potato starch was carried out similarly to that described in example 1. In this case, hot distilled water with a temperature of 93 ° C was taken. The solution from vessel 7 was poured into vessel 9 with hot water and mixed until a uniform colloidal solution was formed.

Preparation of lithium hydroxide solution. A portion of lithium hydroxide LGO-3 according to GOST 8595-83 with a lithium hydroxide content of at least 53 mass. % in an amount of 360 g was placed in an intermediate tightly closed container 11. In small portions, lithium hydroxide was poured into a laboratory mill 12 and milled for 30 s. Received 246 ml of dispersed powder. grove. After that, they poured into an intermediate tightly closed container 13, into which then a solution of potato starch was poured from the container 9 and mixed until a homogeneous mixture was obtained. Got an impregnating solution in the form of a paste in an amount of 1 DM ³ .

Preparing the substrate, applying the solution to the substrate. To apply a lithium hydroxide solution to the blank of Spanlace material on table 14, a Teflon backing sheet with dimensions of 400 × 500 mm and a thickness of 0.6 mm was laid on which a sheet of Spanlace material with dimensions of 400 × 500 mm and a thickness of 0.4 was laid mm, 0.25 dm ³ of lithium hydroxide paste was applied to it and a spatula was evenly distributed over the entire surface of the workpiece. After that, a sheet of Spanlace material coated with a layer of paste was covered with a second sheet of Spanlace material and subjected to pressing under heat.

Example 4

The preparation of a solution of potato starch was carried out similarly to that described in example 1. In this case, hot distilled water with a temperature of 96 ° C was taken. The solution from tank 7 was poured into a tank 9 with hot water in an amount of 0.667 ml and stirred until a uniform colloidal solution was formed.

Preparation of lithium hydroxide solution. A portion of lithium hydroxide LGO-1 according to GOST 8595-83 with a lithium hydroxide content of at least 56.7 mass. % in an amount of 340 g was placed in an intermediate tightly closed container 11. In small portions, lithium hydroxide was poured into a laboratory mill 12 and ground for 40 s. Received 233 ml of dispersed powder. After that, they poured into an intermediate tightly closed container 13, into which a solution of potato starch was then poured from the container 9 and mixed until a homogeneous mixture was obtained. Got an impregnating solution in the form of a paste in an amount of 1 DM ³ .

Preparing the substrate, applying the solution to the substrate. To apply a paste-like solution of lithium hydroxide on a Spanlace blank, a Teflon backing sheet with dimensions 400 × 500 mm and a thickness of 0.8 mm was laid on table 14, onto which a Spanlace sheet with dimensions of 400 × 500 mm and a thickness of 0.5 was laid mm, 0.25 dm ³ of lithium hydroxide paste was applied to it and a spatula was evenly distributed over the entire surface of the workpiece. After that, a sheet of Spanlace material coated with a layer of paste was covered with a second sheet of Spanlace material and subjected to heat pressing.

The chemisorption properties of the absorber obtained according to examples 1-4 were studied in a dynamic tube with a diameter of 39 ± 0.5 mm and a height of 220 mm, through which a gas-air mixture (GVS) was passed under the following conditions:

DHW flow rate 7.0 ± 0.3 dm ³ / min carbon dioxide volumetric flow 0.280 ± 0.005 dm ³ / min volume fraction of carbon dioxide in hot water 4.0 ± 0.2% DHW temperature plus 23 ± 1 ° C dhw relative humidity 70 ± 10% mass of chemical absorber in a dynamic tube 100 + 2 g test time 40 min

The tests of the absorber were carried out until the carbon dioxide content in the hot water supply was reached behind the layer of the chemical absorber equal to 3.0% vol. After testing, the amount of carbon dioxide absorbed was determined. The research results are presented in table. 4

As can be seen from table 4, the proposed chemical absorber has a higher sorption capacity than known.

The active particles of the absorber are fixed in the polymer frame, due to which the chemical absorber does not dust and does not collapse.

Claims (5)

1. A chemical carbon dioxide absorber containing alkali metal hydroxides, water and a polymer binder, characterized in that it contains lithium hydroxide as an alkali metal hydroxide, and it contains starch and a porous sheet substrate in the following ratio of components (% wt. .): lithium hydroxide not less than 84 lithium carbonate no more than 6 potato dextrin 4-6 porous sheet substrate 6-4 2. A method of obtaining a chemical absorber of carbon dioxide, comprising preparing an impregnating composition, which is impregnated with a porous sheet substrate, characterized in that as a porous sheet substrate using non-woven material "Spanlace" containing 50 wt. % viscose and polyester fiber, the impregnation is carried out by applying to the first sheet of the porous sheet substrate an impregnating composition in the form of a paste containing the following components in a ratio (% wt.): lithium hydroxide monohydrate no less than 36-46 potato starch 6-8 water - the rest is up to 100 a second sheet of a porous sheet substrate is applied to the applied paste and subjected to thermocompression treatment at a temperature of 220 ± 2 ° C and a pressure of 0.5-2 MPa for 0.5-10 minutes.

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