UA73684C2 - A method for producing the crystalline iodine and an apparatus for realizing the same - Google Patents

Abstract

The invention concerns with the chemical technology, particularly methods for producing crystalline iodine of reactive qualifications and devices for realizing the same. A method for producing the crystalline iodine of reactive qualifications, involving isolation of iodine out from solutions with obtaining paste iodine, paste iodine dehydration and iodine sublimation. The paste iodine dehydration is performed due to water vaporization at the first stage of the iodine sublimation process, before sublimation sodium carbonate is added to paste iodine at an amount providing pH of water condensate of no more than 4.0, the sublimation process of dehydrated iodine is performed at the temperature of iodine vapors of 114-184 DEGREE C, and the partial pressure of iodine vapors in the iodine-air mixture before sublimation is reduced due to diluting with air to the pressure which is lower than the pressure of saturated iodine vapors in the triple point. An apparatus for producing crystalline iodine of reactive qualifications involves iodine evaporator, iodine condenser with finished production receiving box, abgases catcher and tail fan. The iodine condenser is made of elastic film, stretched on the frame, internal space of condenser is under depression which prevents iodine vapors outlet, at that iodine receiving bin is simultaneously container for the finished product. Use of the invention provides an increase in the finished product quality, simplification and reduction of prices of the technological process and increase of the apparatus productivity.

Description

Description of the invention

The invention relates to methods of obtaining crystalline iodine of reactive qualifications and can be used for the production of iodine from highly concentrated solutions containing iodine of man-made origin, or from iodine concentrates obtained during the processing of natural waters containing iodine in their composition.

A known method of obtaining crystalline iodine of reactive qualifications from iodine obtained from industrial iodine concentrates by melting it under a layer of sulfuric acid at 120-1502C, crushing the cooled melt, washing with water to remove sulfuric acid and drying |V.I. Ksenzenko, D.S. Stasynevich. Chemistry and technology of bromine, iodine and their compounds. M., "Chemistry", 1995, pp. 356-357.| The main disadvantages of the method are the need to use a large amount of sulfuric acid (2-3t per 1t of iodine), large losses of iodine with spent acid, low quality of the finished product due to the presence of sulfates in it, difficult working conditions, due to direct contact of personnel with iodine and the presence other dangerous factors (concentrated sulfuric acid at high temperatures).

A known method of obtaining crystalline iodine of reactive qualifications by sublimation in a stream of carrier gas, which consists in the fact that carrier gas, mainly air heated to a temperature of 1114-4002, is blown through the iodine located in the evaporator, while the amount of carrier gas and its the speed is chosen so that the carrier gas saturated with iodine vapor at the outlet of the evaporator has a temperature below the melting point of iodine (90-1102С) 720 (Poland Patent, Mob68017, MKY СО187/14). A common feature of this method with the proposed one is the purification of iodine by the sublimation method and the supply of the carrier gas to the evaporator. The disadvantage of the method is the high temperature (300-350 2С) of the process, which necessitates the search for special stable materials, because the publicly available ones are chemically unstable in iodine (titanium), cannot withstand mechanical stress arising due to temperature differences of 25 °C (enamel), or melt ( fluoroplastic). The use of non-traditional materials (for example, an alloy of niobium with tantalum) for the manufacture of an evaporator greatly increases the cost of iodine purification. At a temperature of 90-110 2С of the carrier gas, (o) saturated with iodine, which leaves the evaporator, the equilibrium concentration of iodine vapor is 350-800g/m 3.

The specified concentration limits the productivity of the method. Maintaining the necessary ratio of the amount of sublimable iodine and the carrier gas is a rather difficult task of conducting the technological process, because later this ratio will change depending on the reduction of the effective contact area of the carrier gas and iodine, and therefore the decrease in the degree of saturation of the carrier gas with iodine, which will lead to the loss of iodine in the abgas trap and a decrease in the yield of the finished product. Gee)

The method of obtaining crystalline iodine of reactive qualities using the sublimation of raw iodine (V.Y. Ksenzenko, o 35 D.S. Stasynevich. Chemistry and technology of bromine, iodine and their compounds) is the closest in terms of technical essence and achievable result to the intended invention. M., "Chemistry", 1995, pp. 355-356). According to this method, iodine is isolated from concentrates in the form of elemental iodine crystals, which are separated from the mother solution with the help of a centrifuge or a notch filter, obtaining the so-called iodine paste. Then the iodine paste is dried with heated air. Raw iodine is subjected to sublimation. Sublimation of iodine is carried out in special furnaces (evaporators), where steel cuvettes or ceramic crucibles with iodine are loaded. Furnaces have gas heating. Iodine vapors leaving the furnace are condensed in refrigerators (condensers) made of ceramic, asbestos-cement or fluoroplastic pipes, cooled by air. In the evaporator, the temperature is maintained above the melting point of iodine (114-1802С). The process is carried out so that the temperature of iodine vapors during desublimation "" is below its melting temperature (113.622), in the opposite case, strong adhesion of iodine to the walls of the condenser occurs, because iodine vapors in this case do not desublimate, but first condense with the formation of liquid iodine, which then crystallizes into a dense solid mass. The removal of iodine crystals from the condenser is carried out manually using special scrapers or a chisel with a hammer. The disadvantage of this method is the need to dehydrate (dry) the iodine paste before sublimation, heavy manual labor at high levels of gas in workplaces at the stages of dehydration and sublimation of iodine, low quality of the finished product and (o) large irreversible losses of iodine (5-1095). In order to obtain reactive iodine of the "Ch" grade, iodine sometimes has to be subjected to repeated sublimation.

The purpose of the claimed invention is to simplify and reduce the cost of the technological process, to improve the conditions

I" of labor, improvement of the quality of the finished product, reduction of iodine loss, improvement of device productivity.

The claimed method and device for its implementation are characterized by the following features: - isolation of iodine from solutions and preparation of iodine paste; - dehydration of iodine paste; - sublimation of iodine; o - the use of an iodine evaporator, an iodine condenser with a receiver of the finished product and a tail fan; and with new features: 60 - dehydration of iodine paste is carried out due to evaporation of water at the first stage of the iodine sublimation process; - addition of sodium carbonate to the iodine paste before sublimation in an amount that ensures the pH of the water condensate is not lower than 4.0; - carrying out the process of sublimation of dehydrated iodine at the temperature of iodine vapors of 114-184 C and reducing the partial pressure of iodine vapors in the iodine-air mixture by 65 before desublimation due to dilution with air to a pressure below the pressure of saturated iodine vapors at the triple point;

- production of an iodine capacitor from an elastic film stretched on a frame, the internal space of the capacitor is under vacuum, which ensures the exclusion of iodine vapors, while the iodine receiver is at the same time a container for the finished product.

The achievement of the set task is achieved by the fact that the iodine paste obtained when isolated from iodine concentrates and separated from the mother solutions is immediately sent to sublimation, without prior drying, dehydration of the iodine paste is carried out due to the evaporation of water at the initial stage of sublimation, before sublimation into iodine paste a small amount of sodium carbonate is added, the process of sublimation of dehydrated iodine is carried out at an iodine temperature of 114-1842C, the partial pressure of iodine vapors in the iodine-air mixture before desublimation is reduced to 7/0 below the pressure of iodine vapors at the triple point, and the sublimation of iodine paste is carried out on the device, the diagram of which shown in Fig.

The device for obtaining crystalline iodine consists of an evaporator 1, which is an enameled container with a jacket, inside which there is a heat carrier heated by thermoelectric heaters. The evaporator is covered with a lid, in which holes are provided for the installation of two tubes: 75 one for bubbling molten iodine with air, the other for supplying air for diluting the iodine-air mixture. The attachment of the bubble tube provides for the possibility of adjusting its depth under the layer of liquid iodine.

The inner space of the evaporator is connected to condenser 2 by means of a fluoroplastic tube. Condenser 2 is a frame on which an elastic film resistant to iodine is stretched. An iodine receiver Z is attached to the lower part of the condenser, which is also a container for the finished product. The internal space of the condenser 2o is under rarefaction, due to the operation of the tail fan 5, connected to each other through the abgas trap (scrubber) 4.

The proposed method of iodine sublimation on the device is carried out as follows. Iodine paste in the amount of up to 1.0-1.5 tons is loaded into evaporator 1, which is an enameled container with a jacket, 8-10 kg of sodium carbonate is loaded on top of the iodine paste. The evaporator jacket is filled with a high-temperature coolant with a boiling point of at least 2502 (for example, PMO-100 polymethylsiloxane), which is heated

Heaters up to a temperature of 150-2002C. When the iodine paste is heated to the boiling point of water, the distillation of i) water begins. At the same time, water vapor is saturated with iodine vapor. The mixture of water vapor and iodine condenses on the surface of the condenser 2, which is made of an elastic film (for example, from fluoroplastic or varnished fabric based on fluoroplastic and fiberglass). Water flows from the surface of the condenser, and iodine crystals are periodically shaken (by lightly tapping the polymer film) into receiver 3. Water flows out through the hole in the lower part of the receiver and collects in the collector, while iodine remains in receiver 3, which as it fills iodine is removed and replaced with a new one. The pH of the water flowing out of the receiver is controlled so that its value is not (Ce) higher than 4.0. The obtained wet iodine is used for loading in the next sublimation operation.

After the distillation of the water ends, and the remaining iodine in the evaporator melts (practically, in about 35%, depending on the amount and humidity of the iodine paste being loaded, this is achieved after 1-2 days), in the evaporator h-1 begin supply air Part of the air is bubbled through the iodine melt (or blown over the surface of the iodine melt) to saturate it with iodine vapors. Another part of the air is supplied to the upper part of the evaporator to dilute the concentration of iodine vapors. The mixture of air and iodine vapor enters the condenser, where iodine is desublimated on the surface of the film and is periodically shaken into the receiver, which is also a container for the finished product. Distillation of 70 dry iodine continues for 2-3 days. For one operation, 0.7-1.2 tons of dry finished product are obtained. - with Productivity of the device 50-7Otonn/year. a The air from the condenser is sucked by the fan 5 through the abgas trap 4. With the help of the fan in the evaporator-condenser system, a small rarefaction of 2-5 mm H2O is maintained, which excludes gassing of the room with iodine vapors.

The process of sublimation of dry iodine is carried out at a temperature of iodine vapors of 114-1842C. At a temperature below 113.69 °C, iodine becomes a solid substance and the process of its evaporation slows down dramatically. It is impossible to reach a temperature higher than 184 ss s, because iodine boils at this temperature under conditions of atmospheric pressure.

Dilution with air of the concentration of iodine vapors obtained by bubbling air through molten iodine or by blowing the surface of molten iodine is done in such a way that the partial pressure of iodine vapors in the resulting mixture does not exceed the pressure of saturated iodine vapors at the triple point by 50 (87 mm Hg .) In the opposite case, during the condensation of vapors, not crystals are formed, but molten iodine, which upon solidification turns into a shapeless mass that does not meet the criteria of crystalline iodine reactive qualifications.

Distinctive features of this invention from the prototype are: 1. Dehydration of iodine paste is carried out due to evaporation of water at the first stage of the sublimation process

Iodine

Gee! 2. Addition of sodium carbonate to the iodine paste before sublimation in an amount that ensures the pH of the water condensate is not lower than 4.0. If the water condensate is more acidic, the quality of the finished product is reduced due to the acids present in the iodine paste getting into it.

C. Carrying out the process of sublimation of dehydrated iodine at the temperature of iodine vapors of 114-184 C and reducing the partial pressure of iodine vapors in the iodine-air mixture by 60 before desublimation due to dilution with air to a pressure below the pressure of saturated iodine vapors at the triple point (87 mm Hg), which provides high-quality crystals of the finished product, which are easily removed from the condensation surface. 4. Production of an iodine capacitor from an elastic film stretched on a frame, the internal space of the capacitor is under vacuum, which ensures the exclusion of iodine vapors, while the iodine receiver is at the same time a container for the finished product. This provides the possibility of easy shaking of iodine crystals from the cooled surface, facilitates working conditions, improves the quality of the finished product and reduces its losses due to the exclusion of direct contact of personnel with the finished product, reducing the gassing of the room with iodine vapors.

Examples of concrete implementation.

Example 1. In the device for obtaining crystalline iodine of reactive qualifications, which contains an iodine evaporator, an iodine condenser with a receiver of the finished product, an abgas trap and a tail fan, 7b8kg of iodine paste with the content of the main substance 8595, obtained during the isolation of iodine from waste from the production of single crystals, was loaded. and 192 kg of wet iodine from the previous operation with a moisture content of 1095 in the evaporator, which is an enameled tank with a jacket, with a capacity of 1000 ml. 2 kg of sodium carbonate was loaded on top of the iodine paste. 7/0 Evaporator heating is turned on. As the iodine paste heats up, water and iodine begin to evaporate from it, entering the condenser, which is a device in the form of a surface cooling chamber with an area of 7 m², made of an elastic fluoroplastic film stretched over a metal frame. The water condensed in the condenser flows into the receiver, where periodically, with light taps on the film, the iodine is shaken. From the receiver, the water flows through the hole into the collector, where its quality is controlled by the pH value. The value of pH in the process of distillation of 75 Water varies from 7.0, at the beginning of the process of water distillation, to 6.0 at the end of water distillation.

Uncondensed water and iodine vapors in the condenser enter the abgas trap with the help of a tail fan, where they are absorbed by an alkaline solution. After the complete distillation of water from the evaporator, air is introduced into the evaporator for the distillation of dry iodine as a finished product, for which part of the air in the amount

BmU/hour is supplied through the iodine melt, and the other part is supplied to the upper part of the evaporator, to dilute the concentration of iodine vapors, with a consumption of 20mU/hour. The temperature of iodine vapor at the outlet of the evaporator is maintained at 16092F0. In the distillation process, the ratio between the amount of air supplied through the melt and the amount of air supplied for dilution is controlled so that the partial pressure of iodine vapor in the iodine-air mixture before desublimation is below the pressure of saturated iodine vapor at the triple point. They also monitor the ratio between the air supply to the evaporator and the suction of iodine vapors from the condenser by the tail fan through the abgas trap, and the CM should be such that a small vacuum is maintained in the evaporator-condenser system (15 mm of water at room temperature), which ensures that the output is excluded iodine vapors outside the capacitor in the event of a leak in it or a violation of continuity. Dry iodine enters the receiver, which is a container for the finished product, which is changed to a new one as it fills. After complete distillation of iodine, the heating is turned off. The remaining salts formed in the evaporator, after cooling, are unloaded and sent for separation and crystallization of iodine paste. The solution from the abgas trap is also directed there. When loading into the sublimator 768 kg of iodine paste with a mass fraction of iodine of 8590 and 192 kg of wet iodine from the previous operation, containing 1095 moisture, the following was obtained: - 616.7 kg of the finished product, or 614.5 kg in terms of 10095 iodine; so - 192.Okg of wet iodine, or 172.8kg in terms of 10095 iodine; so - 111 kg of condensate containing 0.3 kg of iodine;

Zo - 16.8 kg of salts containing 12.3 kg of iodine; o - 150,000 kg of solutions, from the abgas trap, containing 23,1 kg of iodine.

At the same time, irreversible losses (mechanical losses, emissions into the atmosphere, etc.) amounted to 33.5 kg.

The output of the product in relation to iodine loaded with iodine paste is 94965.

Reversible losses of iodine aimed at the separation and crystallization of iodine paste amount to 5.595.

Irreversible losses are 0.495 of the amount of iodine loaded with iodine paste. The duration of one operation is 110 hours, of which water distillation is 45 hours, distillation of the finished product is 60 hours, heating and cooling of the evaporator is 5 hours. Productivity of the device in the dry iodine distillation mode is 15 kg/hour.

Comparative characteristics of the quality of the finished product, obtained by the sublimation method, and the raw material with quality indicators according to GOST 4159 are presented in Table 1. -I c

F so 5 t

Example 2. The process of iodine distillation on a device for obtaining crystalline iodine of reactive qualifications was carried out as in example 1, which differed in that different amounts were added to the iodine paste before sublimation

GF! of sodium carbonate and determined the range of changes in the pH of the water condensate. Depending on the pH value of the condensate, the quality of the finished product was determined. The results of the determinations are presented in Table 2. Name) "iodine paste, kg of water condensate of monocrystals of sulfates in o81111110111toyayu 0 Answered////// 1.0 7.0-6.0 Corresponds to the sulfate industry and

Tires are only LI Ovi Turkmen sulfate

Table 2 shows that, regardless of the type of iodine paste, the consumption of sodium carbonate should ensure that the pH of the water condensate is not lower than 4.0. Thus, when the pH of the water condensate changes from 7.0 to 4.0, the quality of the finished product meets the requirements of GOST 4159, a decrease in the value of pH below 4.0 leads to a discrepancy in the quality of GOST products.

Example 3. The process of iodine distillation on a device for obtaining crystalline iodine of reactive qualifications 75 was carried out as in example 1, which differed in that the process of sublimation of dehydrated iodine was carried out at different temperatures, the results are presented in table 3. ой 1116 с о

Table C shows that the performance of the device decreases when the temperature of iodine vapors decreases below 11496. It is impossible to reach a temperature above 1842, because iodine boils at this temperature and at atmospheric pressure.

Example 4. The process of iodine distillation on a device for obtaining crystalline iodine of reactive qualifications - was carried out as in example 1, which differed in that in the process of sublimation of dry iodine, the air supply to the so bubbling and dilution was done in different ratios, which is presented in table 4. (Se)

Id

Air consumption for bubbling, Air consumption for dilution, Iodine vapor pressure before desublimation, mm Iodine quality in PURPOSES routine put x product

A drank PI PI PON NNYA lani KI s product

I" 415 product -- with product (95)

It can be seen from Table 4 that an increase in the partial pressure of iodine vapor in the iodine-air mixture before (22) desublimation to a pressure above saturated iodine vapor at the triple point (87 mm Hg) leads to the formation of liquid iodine by 50 during condensation, deterioration of its commercial form and consumer properties.

Thus, the examples given above show that the use of this technical solution, which consists in dehydrating the iodine paste due to the evaporation of water at the first stage of the iodine sublimation process, adding sodium carbonate to the loaded iodine paste in an amount that ensures pH water condensate not lower than 4.0, carrying out the sublimation process in a wide temperature range from 114 to 1842С with a partial pressure of iodine vapors of 22 in an iodine-air mixture before desublimation below the saturation pressure at the triple point (87 mm Hg) according to

F! due to their dilution with air on the device for obtaining crystalline iodine of reactive qualifications, the capacitor of which is made of an elastic film stretched on a frame, the internal space of the capacitor is under vacuum, which ensures the exclusion of the release of iodine vapors, with the iodine receiver, which is also a container for the finished product, allows to simplify and reduce the cost of the process of obtaining iodine, improve working conditions, improve the quality of the finished product, reduce losses of iodine and increase the productivity of the equipment. b5

Compressed air and them

Iodine paste F 5

I shd 4 - 9 9 2

Y i-y , x

IT 5 g Kh

IN pjsj

And I M

Worked | 2 solution

Iodine wet 3 o flax no other and cash otTovyIy p

Condensate product, sch 29 Fig. Gee)

Claims (2)

The formula of the invention « 30 1. The method of obtaining crystalline iodine of reactive qualifications, which includes the isolation of iodine from solutions with its preparation of iodine-paste, dehydration of iodine-paste and sublimation of iodine, which differs in that the dehydration of iodine-paste is carried out due to the evaporation of water on the first at the stage of the process of sublimation of iodine, sodium carbonate is added to the iodine paste before sublimation in an amount that ensures the pH of the water condensate is not lower than 4.0. the pressure of iodine vapors in the iodine-air mixture before desublimation is reduced due to air dilution to a pressure lower than the pressure of saturated iodine vapors at the triple point. 2. A device for obtaining crystalline iodine of reactive qualifications according to the method according to claim 1, which includes an iodine evaporator, an iodine condenser with a receiver of the finished product, an abgas trap and a tail fan, which is characterized by the fact that the iodine condenser is made of an elastic film stretched over a frame , -about 70 the inner space of the condenser is under rarefaction, which prevents the release of iodine vapors, while the iodine receiver is at the same time a container for the finished product. ;" Official bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2005, M 8, 15.08.2005. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. -1 In r (95) (o) ge» SHY s» ime) 60 b5