RU2290993C1 - Method of producing chemical absorber - Google Patents

Abstract

FIELD: nuclear power engineering.

SUBSTANCE: method comprises impregnating active coal with a ratio of sorbents to the total volume of pores equal to 0.6-0.8 by water solution made of triethylenediamine and iodide of one of metals, drying the absorber at 80-120°C with heating rate 0.5-3.0°C/min, and allowing the absorber to stand at drying temperature for 10-20 min.

EFFECT: enhanced efficiency.

1 cl, 4 tbl, 5 ex

Description

The invention relates to the field of sorption technology and can be used to obtain absorbers for cleaning vent emissions of nuclear power plants from radioactive isotopes of iodine and volatile ruthenium oxides.

A known method of producing an absorber (chemisorbent), including impregnation of activated carbon with nickel chloride, drying, heat treatment and sieving (see RF patent No.2019288, B 01 J, C 01 B 31/16, publ. 15.09.94).

The disadvantage of this method is the low absorption capacity of the resulting sorbent on the radioactive isotopes of iodine.

The closest in technical essence and the achieved result is a method of obtaining a chemical absorber, comprising impregnating activated carbon with a solution containing amine and metal iodide selected from the group of potassium, barium, zinc, lead, strontium, and drying at 80-120 ° C (see patent RU IP 2174722, 10/10/2001), which is taken as a prototype of the alleged invention. The method provides a sufficiently high efficiency for the removal of the radioactive isotope of iodine ( ¹³¹ J) and its methyl iodide.

The disadvantage of this method is the low degree of absorption of the radioactive isotope of iodine (J ¹²⁹ ) and volatile oxides of ruthenium ( ¹⁰⁶ RuO ₄ ).

The aim of the invention is to increase the absorption efficiency of hardly absorbed radioactive compounds of iodine ( ¹²⁹ J) and ruthenium tetroxide (RuO ₄ ) at relatively low temperatures of 5-30 ° C, i.e. ensuring the reliability of environmental protection, especially in emergency situations.

The goal is achieved by the proposed method, including the impregnation of activated carbon with a ratio of sorbing pore volume to the total equal to 0.6-0.8, the impregnation is carried out by stirring in a solution at 40-50 ° C for 40-80 minutes, and drying is carried out in the temperature range of 80-120 ° C when the temperature rises at a speed of 0.5-3.0 ° C / min, followed by exposure of impregnated coal at a drying temperature for 10-20 minutes, while the impregnation solution is taken with the content of ingredients,% (wt. .):

water 95-98 triethylenediamine 1.0-2.5 potassium iodide barium iodide zinc iodide lead iodide or strontium iodide 1.0-2.5

The difference of the proposed method from the known one is that coal is taken as a carbon base with a ratio of sorbing pores (v _mi + v _me ) to the total (total volume) of pores equal to 0.6-0.8.

Another difference is that in order to increase the efficiency of retaining absorbed substances, the impregnation is carried out by mixing coal in solution at 40-50 ° C for 40-80 minutes, and drying is carried out at a temperature rise of 0.5-3.0 ° C / min, impregnated carbon is maintained at a drying temperature for 10-20 minutes.

The use of activated carbons with a high content of sorbing pores with a minimum volume of transport (ballast) macropores in the production of impregnated absorbent sorbents is unknown to the authors of the scientific and technical literature.

Impregnation of coal by stirring it in a solution at a temperature of 40-50 ° C for 40-80 minutes is the same as drying coal with a slow heating rate of 0.5-3.0 ° C / min and keeping it at a drying temperature in similar technical decisions are unknown.

The essence of the proposed method is as follows.

Currently, active coals with large volumes of macropores, characterized by a relatively low (0.3-0.5) ratio of sorbing pores to the total pore volume, are used as the basis for the preparation of absorbers used in the treatment facilities of nuclear power plants, which does not provide effective absorption of difficultly sorbed substances such as iodine ( ¹²⁹ J) and ruthenium oxides, especially at relatively low temperatures (5-30 ° C), when the rates of chemical reactions slow down significantly. All this reduces the degree of environmental protection from harmful pollution of nuclear power plants, especially in emergency situations.

Our studies have shown that activated carbons obtained from compacted plant materials, such as fruit tree seeds, coconut shells granulated at elevated pressures of peat, wood processing products, etc., characterized by highly developed volumes of micro- and mesopores, meet the given requirements to the highest degree. with moderate development of transport (ballast) macropores.

It was also experimentally established that the determining parameters for the formation of active complex compounds of amines with metal iodides on such coals are:

- the duration and temperature of the impregnation of coal;

- the heating rate during drying from 80 to 120 ° C;

- holding time at a drying temperature.

The proposed method is as follows.

Take 100 g of activated carbon with a ratio of sorbing pores to the total pore volume equal to 0.6-0.8 (coal from fruit seeds or other compacted plant material), which is impregnated by stirring in a solution containing 95-98% (wt.) water, 1.0-2.5% triethylenediamine and 1.0-2.5% iodide of one of the metals (potassium, barium, zinc, lead or strontium) at 40-50 ° C and holding for 40-80 minutes. Then the coal is placed in a heating cabinet and drying is carried out at a rate of temperature rise of 0.5-3.0 ° C / min. At the drying temperature, the impregnated carbon is held for 10-20 minutes, after which it is cooled to room temperature and examined.

The following examples illustrate the invention.

Example 1. Take 100 g of activated carbon MeKS brand from stone raw materials with a ratio of sorbing pores to the total pore volume equal to 0.8:

and characterized by high adsorption energy E = 24 kJ / mol, which is impregnated with a solution prepared on the basis of% (wt.) water 95, triethylenediamine 2.5 and potassium iodide 2.5 by stirring in solution at 40 ° C for 40 minutes. After that, the coal is dried at a temperature rise of 0.5 ° C / min and incubated for 10 minutes. The resulting absorber has a degree of purification:

¹²⁹ J 99.99% ¹⁰⁶ RuO ₄ 99.98%

Example 2. The implementation of the process as in example 1, except that they take barium iodide, stirring is carried out at 45 ° C for 60 minutes, the temperature rise during drying is 1.5 ° C / min with a holding time of 15 minutes. The resulting absorber has a degree of purification:

¹²⁹ J 99.99% ¹⁰⁶ RuO ₄ 99.99%

Example 3. The implementation of the process as in example 1, except that they take zinc iodide, mixing is carried out at 50 ° C for 80 minutes, the temperature rise during drying is 3.0 ° C / min with an exposure of 20 minutes.

The resulting absorber has a degree of purification:

¹²⁹ J 99.99% ¹⁰⁶ RuO ₄ 99.99%

Example 4. The implementation of the process as in example 1, except that they take lead iodide.

The degree of purification of J ¹²⁹ is 99.99%, ruthenium tetroxide - 99.97%.

Example 5. The implementation of the process as in example 1, except that they take strontium iodide. The degree of absorption of the radioactive isotope of iodine (J ¹²⁹ ) and ruthenium tetroxide is 99.98%. Table 1 shows data describing the influence of the ratio of the micropore volume and mesopore (v + v _{E IU)} to the total pore volume (v _E + v + v _{ma IU)} on charcoal trapping percentage and ¹²⁹ J ruthenium tetroxide RuO ₄ of nuclear waste gases power plants. In this series of experiments, BaJ _{2 was} used as metal iodide. The product was impregnated at 45 ° C for 60 minutes, and drying was carried out in the temperature range of 80-120 ° C at a heating rate of 1.5 ° C / min.

Table 1
The influence of coal quality - the basics on the degree of capture of J ¹²⁹ and RuO ₄ The method of obtaining an absorber The ratio of the volume of sorbing pores to the total volume of pores The degree of capture,% J ¹²⁹ RuO ₄ Proposed 0.4 98.70 97.0 0.5 98.90 97.6 0.6 99,99 99,99 0.7 99,99 99,99 0.8 99,99 99,99 0.9 98.00 97.00 Famous Pat. RF №2174722 0.5 97.35 96.00

Note: Experiments to determine the efficiency of the degree of capture of J ¹²⁹ and RuO ₄ were carried out under the following conditions: - temperature, ° С 15 ÷ 30 - air humidity (relates),% 80 - linear gas velocity, m / s 0.3 - layer height, cm 5 - concentration of ¹²⁹ J and ¹⁰⁶ RuO ₄ , Ku / l 10 ^-7 ÷ 10 ^-10

The measurements were carried out using radiometric equipment, including a scintillation detector and a PSO recalculation device.

As follows from the data presented in Table 1, the quality of coal taken as a basis in the manufacture of effective amino-iodide absorbers J ¹²⁹ and RuO ₄ plays a significant role. The experiments showed that the maximum degree of purification, equal to 99.99%, is achieved only when using coal with the ratio of the sorbing pore volume to the total equal to 0.6-0.8.

A decrease in this ratio of less than 0.6 indicates the presence of large volumes of large pore macropores in coals, which are characterized by a small surface size (less than 5 m ² / g) and do not take part in the chemisorption process of absorption of harmful impurities, which in turn determines relatively low capture rates of ¹²⁹ J and RuO ₄ . The decrease in the protective properties of the absorber in the case of increasing the ratio of sorbing pores to the total pore volume of more than 0.8 is due to the deterioration of the kinetic properties of coal.

Table 2-4 shows the data allowing to justify the choice of parameters of the technological process of preparation of the absorber, providing a high adsorption capacity for iodine 129 and ruthenium tetroxide.

As a coal base, VSK grade activated carbon based on coconut carbonizate was used, which was characterized by a ratio of the sum of micro- and mesopores to the total pore volume of 0.75.

An impregnating solution was prepared from the calculation,% (wt.) 98 - water, 1.0 - triethylenediamine, 1.0 - barium iodide.

table 2
The influence of the temperature of impregnation of coal on the degree of purification of emissions of nuclear power plants The method of obtaining the absorber Impregnation temperature, ° С The degree of capture,% The temperature of the experiment, ° C ¹²⁹ J ¹⁰⁶ RuO ₄ Proposed 35 97.85 95.62 5-30 40 99,99 99,99 - "- 45 99,99 99,99 - "- fifty 99,99 99,99 - "- 55 97.00 96.10 - "- Famous Pat. - 97.35 96.00 30-90 RF №2174722 - 96.00 95.80 5-30

From the data of table 2 it follows that the temperature range of impregnation equal to 40-50 ° C, to the greatest extent ensures the achievement of the goal of the invention. With a decrease in temperature (below 40 ° C), a partial crystallization of the added additives occurs, leading to a decrease in the active sorbing surface of coal and a decrease in the degree of capture of pollutants. An increase in the aging temperature leads to the blocking of small micropores, which also reduces the absorption efficiency of the studied substances. It was also shown that high results are maintained at relatively "low" temperatures from +5 to + 30 ° C, while the prototype noted a deterioration at these temperatures.

Table 3
The influence of the duration of coal impregnation on the degree of purification of ventilation emissions of nuclear power plants Duration of impregnation, min The degree of capture,% J ^{129 106} RuO ₄ thirty 97.00 96.00 40 99,99 99,99 fifty 99,99 99,99 70 99,99 99,99 80 99,99 99,99 90 96.50 95.30

As follows from the data presented in Table 3, a decrease in the impregnation time of less than 40 minutes leads to a deterioration in the absorption of iodine and ruthenium due to the inhomogeneous distribution of amine and metal iodide (barium) additives. An increase in the duration of impregnation facilitates the penetration of some water molecules into ultrathin micropores, which are not removed during subsequent heat treatment, reducing the sorption component of this absorber.

The optimal time for impregnation, ensuring an even distribution of chemical additives, is 40-80 minutes.

Table 4
The effect of the rate of temperature rise during drying in the range of 80-120 ° C on the degree of purification of NPP emissions The rate of temperature rise, ° C / min The degree of capture,% J ¹²⁹ RuO ₄ 0.3 97.15 96,99 0.4 97.60 96.00 0.5 99,99 99,99 1,0 99,99 99,99 1,5 99,99 99,99 2.0 99,99 99,99 3.0 99,99 99,99 3,5 96.50 96.50 4.0 96.00 96.50

Studies have shown that the rate of temperature rise during drying of coal is of great importance, because water removal determines the uniformity of the formation of the barium-iodide complex and its distribution in the volume of micro- and mesopores. At a fast rate of removal of water vapor (temperature rise rate of more than 3.0 ° C / min), most of the additives are distributed on the outer surface of the coal particles, which leads to a decrease in the adsorption capacity of the adsorbent. At a slow heating rate, part of the solution penetrates into the small pores and blocks their surface. The optimal rate of temperature rise, judging by the data obtained, is 0.5-3.0 ° C / min.

The series of experiments determined that the maximum degree of purification of gas emissions equal to 99.99 is achieved when a solution of triethylenediamine and iodide of one of the metals (K, Ba, Zn, Pb or Sr) in an amount of 1.0-2.5%. With a decrease in the amount of chemical additives below 1.0%, the degree of purification decreases to 96.00%, and an increase in additives of more than 2.5% does not lead to an increase in the degree of purification of the generated gases of nuclear power plants.

It was also found that the resulting absorber stably works under conditions of increased values of concentrations of radioactive substances and humidity, as well as a wide temperature range, including in the range from +5 to 30 ° C, whereas the known method (see table 2) while reducing the degree of purification (up to 96.00% and 95.80%).

The proposed absorber is universal, because provides protection from another heavier isotope of iodine ¹³¹ J, as well as iodine methyl iodide CH ₃ ¹³¹ J.

As follows from the foregoing, each of the signs of the claimed population to a greater or lesser extent affects the achievement of the goal, and the entire population is sufficient to characterize the claimed technical solution, i.e. increase the efficiency of cleaning gas emissions of nuclear power plants from hard to remove components.

Claims (2)

1. A method of obtaining a chemical absorber used to clean the gas emissions of nuclear power plants, comprising impregnating activated carbon with a solution containing amine and metal iodide from the series: potassium, barium, zinc, lead, strontium and drying at 80-120 ° C, characterized in that active carbon is subjected to impregnation, characterized by the ratio of the sum of the micropore and mesopore volumes to the total pore volume of coal equal to 0.6-0.8, the impregnation is carried out by mixing the coal in solution at 40-50 ° C for 40-80 minutes, and drying carried out when raising tempera urs at a speed of 0,5-3,0 ° C / min and maintaining the impregnated carbon at a drying temperature for 10-20 min. 2. The method according to claim 1, characterized in that the solution is taken with the following content of ingredients, wt.%: Water 95-98 Triethylenediamine 1.0-2.5 Cadmium iodide, barium iodide, zinc iodide, lead iodide or strontium iodide 1.0-2.5