A continuous process for the cleavage of iodides, autolysis and separation of iodine, as well as equipment for carrying out such a process

Abstract

The present invention relates to a process for harvesting and purifying elemental iodine contained in an iodide solution, specifically comprising the steps of simultaneous iodide cleavage and iodine melting by reacting a preheated iodide solution with an oxidizing agent to produce elemental molten iodine directly, without the iodine passing through a crystalline state; and separating the elemental molten iodine from spent molten water by liquid-liquid separation, all of which are carried out in a single, continuously operating system.

Description

[Technical field]

[0001] The present invention relates to the recovery and purification of elemental iodine contained in concentrated iodide solutions by a continuous, economical, high speed process and using simplified equipment. The present invention also relates to equipment for carrying out said process. Summary of the Invention

[0002] Specifically, in the process of the present invention, iodide reacts "hot" with an oxidizing agent, a reagent for both operations, at specific temperature and pressure conditions in a reactor having specific geometric characteristics operated under conditions that determine that all the operations necessary for the recovery and purification of iodine, which are conventionally performed discontinuously and separately, are performed simultaneously, in a specific hydrodynamic regime, namely, iodide shearing, iodine melting and iodine separation, which utilize the reaction heat of shearing to produce liquid iodine instantly, all in a continuous process, allowing for an automatic control called Iodine Autogenous Fusion (IAF). [Brief description of the drawings]

[0003] [Figure 1] A conventional line for harvesting and purifying iodine. [Diagram 2] A complete system containing equipment to run the IAF iodine autolysis process, including iodide solution heater, oxidant feeder, and separation reactor equipment (liquid centrifuge). [Diagram 3] FIG. 1 is a portion of the system of the present invention detailing a pilot liquid centrifuge for a 20 L / min iodide IAF process example. [Figure 4] 1 is a temperature record of a 142 gpL iodide hot cut in a pilot liquid centrifuge. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0004] Industrial iodine extraction processes depend strongly on the iodine content from various mineral resources. The two largest reserves in the world (Non-Patent Document 1) are underground brines from natural gas wells in the eastern Tokyo area of ​​Japan, which contain iodine in the form of sodium iodide in concentrations of the order of 150-160 ppm (grams per tonne of dry product), and nitrate deposits (caliche) in the Tarapaca and Antofagasta regions of Chile, which contain iodate salts with typical concentrations of 300-400 ppm iodine (Non-Patent Document 2). The reserves of these sources are estimated at 5 million and 1.8 million tons of iodine, respectively, and the iodine production of both sources represents 55% of the current world production (Non-Patent Document 3).

[0005] Essentially, given the low iodine content of the derived resources, the current industrial process is structured as a sequence of two clearly characterized single operational lines, a first line called the "extraction line" intended to collect an aqueous concentrated brine of iodate or iodide (usually the latter), and then another line called the "purification line" devoted to the treatment of the concentrated brine in order to collect purified elemental iodine. This last process line is the concern of the present invention, as mentioned earlier in the technical field section of this specification. For example (Non-Patent Document 4), the extraction line of the process starts with the treatment of some kind of iodine solution, such as iodate or iodide, with an iodine content as low as 0.3 grams per liter (gpL), after concentration, 50-250 gpL. The process continues with a purification line, the operation of which is intended to process this concentrated solution to collect elemental iodine and purify it into a solid product with a purity of more than 99.5%.

[0006] Many of the patents and studies related to this subject can even be classified based on the two indicated lines. Most of the studies and prior art related to invention patents refer to a single operation of an extraction line concentrating some kind of iodine (generally iodate or iodide), among which are, inter alia: gas-liquid extraction by drawing or blowing air (blowout, Non-Patent Documents 4, 5, 6; Patent Documents CL35944, CL37655, CL34656, CL38613, US1853621, US1897031, US1922693, US2282289, US2143222), cold primary cleavage reaction (Non-Patent Documents 4, 5; Patent Documents CL34662, ... , US1897031, US2282289, US2143222), solid-liquid extraction using ion exchange resins (Non-Patent Document 5, Patent Document US33526419) or, for example, adsorption on activated carbon (Patent Documents US2028099, US1897031, US1922693), liquid-liquid extraction with organic or inorganic solvents (Non-Patent Documents 4, 5; Patent Documents CL38613, US1853621), reduction by SO2 absorption (Non-Patent Documents 4, 5, Patent Documents CL34662, CL37655, CL34656, US2143222), sublimation (Non-Patent Document 5, Patent Application US2010308261) and electrolysis (Patent Document US1853621). Currently widespread processes employ some of the above operations, primarily the first three, and often some combination of them, to harvest an aqueous brine containing iodine, generally in the form of iodide, with iodine concentrations typically ranging from 50 to 250 gpL. This concentrated iodide solution undergoes a charcoal filtration operation, known as polishing, and is finally collected in a tank before being sent to a processing line to harvest and purify the iodine. Generally, almost all of the unit operations described above are run continuously, and if not, it is relatively easy to convert them to continuous operation.

[0007] However, the current practice in the entire industry, when it comes to the purification line, i.e. the harvesting of purified solid iodine, always consists of discontinuous and sequential independent operations, and is largely supported by one or more of the following patent documents with slight modifications: US1936553A, US1895929A, CL35944, US2010308261, the first two being the closest to the present invention. Patent document US1936553 describes a discontinuous batch process for harvesting and purifying iodine, consisting in treating a batch of an aqueous solution of soluble iodide, pure or mixed with iodate, with a batch of an oxidizing agent to precipitate solid elemental iodine. When mixed with iodate, it is reduced to iodide by the action of a reducing agent before oxidation. The oxidation is carried out with a reagent at room temperature, without preheating ("cold"), to precipitate solid crystalline iodine that remains suspended in the brine. The suspension is then heated to above 114°C to dissolve the iodine, which is separated by settling or siphoning. If the boiling point of the suspension is below 114°C, the heating must be carried out under pressure to prevent boiling, or, preferably, the boiling point can be increased by adjusting the high salt concentration in the suspension and the heating can be carried out at atmospheric pressure.

[0008] Patent document US1895929 describes a batch-by-batch device for purifying solid iodine obtained by cold cutting, according to the process described in patent document US1936553. Raw iodine crystals are stirred with a mineral acid solution and the mixture is then heated to a temperature slightly above the melting point of iodine. Finally, the molten iodine can be siphoned off or, alternatively, cooled and solidified within the device itself.

[0009] Then, mainly based on the mentioned patents (Non-Patent Documents 4, 5, Patent Documents US1936553, US1895929), a conventional purification line currently in the industry is described and is shown diagrammatically in FIG. 1. The first operation of this purification line is the so-called cutting, which is based on the oxidation reaction of iodide ions in solution with a stoichiometric amount of a strong oxidizing reagent, such as hydrogen peroxide or iodate salts, especially in aqueous solution, or gaseous chlorine, to produce elemental solid iodine. A defining feature of this operation is that the mixing of the reagents is carried out at room temperature or at temperatures generally below 50° C., thus determining the production of a solid iodine pulp, the latter (temperatures below 50° C.) constituting a substantial difference from the present invention, and is called "cold cutting". Thus, a quantity of iodide and clarified (activated carbon filtered) concentrated brine coming from the first concentration line of the process, containing iodide, hydroiodic acid, sulfuric acid and salts with iodine concentrations of 50-250 gpL, is placed in a stirred tank together with a stoichiometric amount of hydrogen peroxide (plus about 10% more), both at a temperature below 50°C, to produce elemental iodine in the form of a slurry of a paste-like consistency of crystalline solids suspended in the brine. This pulp then undergoes a solid iodine concentration operation, either by filtration, settling, flotation, or siphoning. The concentrated pulp then undergoes a melting operation in which it is heated in a melting tank by an external energy source until it reaches the melting temperature of the crystals (about 114°C). The higher relative density of the produced liquid iodine (specific gravity 3.9) compared to the exhausted brine (specific gravity about 1.2) allows its separation from it by settling and the consequent washing (by the concentrated brine itself and by the addition of sulfuric acid). Finally, the liquid iodine undergoes a cooling operation to solidify it in the form of a purified product with a given geometry (generally spherical, called prills).

[0010] The present invention proposal reduces and / or eliminates the problems faced by the conventional operation of the line for harvesting and purifying iodine, which is common to all currently implemented industrial iodine extraction processes (Non-Patent Document 5), regardless of the iodine source, namely: 1) cold cutting of the concentrated iodide solution produced in the iodide concentration line 1 to harvest a pulp of elemental solid iodine, 2) concentration of the pulp by filtration, flotation, sedimentation or siphoning to harvest a pulp with a higher concentration of solid iodine, 3) preheating of the concentrated pulp to promote melting of the crystals, 4) melting of the solid iodine and separation of the liquid iodine by gravity to harvest the spent brine-free purified iodine, and 5) cooling of the liquid iodine to harvest the solid purified iodine product.

[0011] The problems presented by the above conventional operations are explained in detail below. 1) "Cold" cutting Typically, a load of iodide solution containing 100 gpL of iodine is reacted with a stoichiometric amount of 30% (w / w) hydrogen peroxide (H2O2) solution in a stirred tank reactor called a "cutter" that is open to the atmosphere and operated for 30 minutes to an hour, plus an additional 30 minutes for loading and unloading. Due to the heat released by the exothermic reaction, the reaction mixture reaches a temperature of 40-50°C, but does not reach its melting point, about 114°C, resulting in a solid iodine pulp suspended in brine. The iodine pulp occludes part of the still unreacted iodide-containing brine, preventing contact with the peroxide and establishing a protective mechanism that has an apparent "passivating" effect on the reaction, i.e., manifests itself as a slowdown in the reaction rate, but what actually occurs is a physical separation of the reagents, some of which remain occluded in the spongy matrix of solid iodine, preventing the reaction and requiring more time to complete. This does not occur when the reaction is carried out hot, as is evidenced by the almost instantaneous rate at which liquid iodine is produced, as will be explained later. The generation of bubbles due to the agitation and thermal reaction, the sublimation of iodine, and the formation of floating flocs of pasty iodine and settling iodine crystals make cold cutting extremely difficult to control.

[0012] The long hold times (1 / 2 to 1 hour) required for the reaction require large cutters, or alternatively some of these cutters, operated open to the atmosphere, would result in losses of iodine by sublimation with environmental problems when temperatures of 40-50°C are reached. For example, in a typical plant producing 20 tons of iodine per day, 20,000 / 100 = 200m 3 100 gpL of iodide solution should be cut off per day. Due to the stirring force, the effective volume is 4 m 3 (4 useful m 3)It is convenient to use cutter tanks of the order, whose operating cycle is 1 hour (considering that the reaction time is only 30 minutes), i.e. each cutter could ideally perform 24 cuts / day. Therefore, each cutter would have a capacity of ([4 / 0.8=]) 5 m 3 Two cutters (≒[200 / 4 / 24]) are required (taking into account 80% of the useful capacity). The conditions of temperature, acidic environment and concentrated halogens require special equipment such as Pfaudler (a German brand of glass reactor) or the use of special alloys for the construction of the equipment, such as Hastelloy C. The loss of iodine by sublimation in the reactor open to the atmosphere amounts to about 1.5% of the iodine produced in the batch, which is already present in the working environment. 2 Parts per million levels are dangerous to life and health.

[0013] 2) Pulp thickening This operation is carried out to produce a pulp with a high content of solid iodine and eliminates part of the contained brine, reducing the size and operating times of the equipment used downstream in the line, such as pumps, heat exchangers, and melting tanks.

[0014] However, the crystalline solid iodine precipitated by cold cutting is embedded in various brine ratios, so that the crystalline solid iodine exhibits a paste-like consistency, which tends to precipitate and accumulate in parts of the equipment, resulting in blockages, thus hindering transportation and pumping.More serious is the fact that once the pulp is completely separated from the brine, it becomes difficult to standardize the iodine concentration of the pulp.The iodine concentration in the pulp determines the values ​​of the operating parameters of many downstream equipment, such as retention time, reagent ratio, energy amount and its supply rate, operating temperature, pumping and recirculation rate, stirring power, etc., and the fluctuation of the iodine concentration in the pulp causes many operational problems, and ultimately makes it difficult to achieve the standard purity of the refined product.

[0015] The most practical operation seen so far is the brine siphon, an artisanal operation carried out in the reactor itself after the cutting reaction, resulting in a pulp with a highly variable iodine content, typically between 250 and 1300 gpL, due to fluffy solids occluding various amounts of brine. Control of these concentrations is not easy, and in the example of the plant type mentioned above in the preceding paragraph, using 100 gpL of iodide solution to produce 20 tons of iodine per day, the daily amount of pulp was [20000 / 250=]80 m 3 and [20000 / 1300=]15m 3 This variability is carried forward to all downstream operations in the process, particularly the heat exchangers and melt tanks, which are faced with processing pulp inputs with highly dissimilar characteristics and require highly variable retention times to meet their requirements. One way to deal with this variability is to over-size the equipment, resulting in reduced efficiency as well as increased investment costs. 、 Operational costs , and maintenance costs Furthermore, the siphoning operation added at least 30 minutes to the open-wide operation of the reactor, resulting in loss of iodine and contamination by sublimation.

[0016] Similarly, other alternatives for pulp thickening, such as filtration, settling and flotation operations, are also extremely laborious and difficult to control due to the characteristics of pulp, i.e., its paste-like consistency makes it difficult to handle and transport, requires a lot of manual labor, and frequent settling of solid iodine and clogging of filters, pipes, valves and pumps, which requires maintaining high pumping recirculation rates of the solution to keep the solids in suspension, and often requires blowing with pressurized air over 100 psi to unclog equipment, resulting in reduced efficiency, increased operating and investment costs, and safety risks. In addition to these problems, there is the corrosion and wear suffered by equipment and accessories due to the corrosive and abrasive nature of solid iodine crystals, which requires the use of special alloys for construction, such as Hastelloy C276, or rare metals such as tantalum, which nevertheless require frequent maintenance, repair and replacement with associated costs.

[0017] 3) Preheating the concentrated pulp to promote melting of the crystals Solid iodine crystals have a low thermal conductivity (0.4581 W / m / K at 24.4°C), 3-5 times lower than common refractory materials, and a very low melting point, but its heat of fusion is comparable to that of iron. Liquid iodine also has a low heat capacity (0.077 cal / g / °C between 114-160°C), 13 times lower than that of water, and twice as viscous. All these physical properties of solid iodine combine to produce a high resistance to heat transfer, which results in extremely slow heating and melting. The long holding times require the specification of large equipment for preheating. All this makes it extremely inconvenient to produce solid iodine and process it in such a state, considering the need to smelt it for subsequent purification, and then to solidify it again to obtain a purified solid product, which is the cause of the extremely slow and at the same time proven energy inefficiency of these alternate heat treatments.

[0018] Therefore, in conventional processes, to speed up the melting process and therefore reduce the size and / or number of melting tanks, the concentrated pulp is preheated and heated through indirect heat exchangers, concentric tubes, or plate exchangers at least 10000 rpm before being charged into the melting tank. 16663kgf / m 2 ( 23.7psia ) Using the example given in section 1) cold cutting, in a typical cold cutting plant processing 100 gpL of iodine to produce 20 tonnes of iodine / day, the amount of pulp to be processed, according to the calculations in the preceding section, is 15-80 m 3 / day range, which leads to reduced efficiency and increased capital and operational costs due to the need to oversize equipment to meet capacity targets, as shown in the following paragraphs:

[0019] Given the long term exposure to high surface temperatures and the presence of iodine, unreacted peroxides and strong mineral acids, this equipment is particularly susceptible to corrosion, wear and clogging, problems inherent in pulping solid crystalline iodine as described above.

[0020] 4) Solid iodine melting and gravity liquid iodine separation The pulp charge, preheated to a temperature of 50-90°C in the above-mentioned heat exchangers, is fed to a Pfaudel or Hastelloy type melting tank called "Knockout", where the solid iodine melts when it reaches a temperature of 114°C, and at the same time the depleted brine is separated by gravity from the liquid iodine (which is at the top) for a variable period of 4-20 hours depending on the high or low content of solid iodine in the pulp feed, after which the liquid iodine is transferred to a melting tank called "Transfer" for the completion of purification and awaiting a cooling operation to obtain purified iodine.

[0021] Usually, when the processing volume is large, the 2m 3 A series of knockout tanks are used in parallel, each with a depth of 1.5m3 (taking into account 80% of the usable capacity). Both units are equipped with indirect heating by a 120°C steam jacket and are of Pfaudler type or made of Hastelloy.

[0022] The number of melting tanks in the series mentioned above depends on the production capacity of the plant and the required residence time in each melting tank (30 minutes for loading and unloading, in practice 4-20 hours). Continuing with the same example given in the cold cut in item 1), calculate the number of melting tanks required for a typical plant processing 100 gpL of iodine iodide to produce 20 tons of iodine / day. Using a 4-hour retention time for melting in each reservoir (a conservative estimate, since the number of units or their size will increase over time), each unit can perform only [24 / 4.5≒] 5 cycles per day. Producing 20 tonnes / day of iodine requires a total of [200 / 2 / 0.8=]125 cycles, so there is a minimum requirement of [125 / 5=]25 knockout melting tanks. Another series of 25 knockout melting tanks in series, known as "transfer melting furnaces", are also used, so a total of 50 melting tanks are required, for a total of [25×(2+1.5)=]87.5 m 3 Thus, 24 daily operations of each of the two cutting reactors will produce a total of 10 m 3 (according to calculations carried out in the same paragraph 1), which must be linked with 125 daily cycles of 50 melting tanks, resulting in a total of up to 87.5 m 3 This produces 20 tonnes of iodine per day. If the holding time for melting in each melting tank were to be 20 hours instead of 4 hours, as was sometimes necessary, then 125 cycles per day would be required for the 250 melting tanks, resulting in a total of 437.5 m 3 Faced with this situation, for design purposes, an average retention time of [(4+20) / 2=] 12 hours should be considered, which includes the 12 hour increase in retention time alone. 5 125 cycles of melting tanks per day, i.e., the number of melting tanks is [125 / 50=]2.5 times (total capacity of melting furnace is218.75 m 3 ) needs to be increased.

[0023] The above diagram illustrates the size and amount of equipment, as well as the complexity and laboriousness of the operations involved in a conventional iodine extraction and purification line. Moreover, in practice, the useful life of a melting tank is only 1-2 years, given the long exposure to high temperatures and the presence of iodine, unreacted peroxides, and strong mineral acids.

[0024] In addition, there are published documents reinforcing the problems of the conventional process regarding purification by melting with sulfuric acid, specifying residence times for melting of more than 3 hours. On the other hand, quantitative methods for continuously feeding iodine to the reactor (patent document US8268284) have the disadvantages of supplying iodine at its melting point. These disadvantages include the need for external thermal energy for heating, the natural tendency of iodine to sublime, and corrosion of the equipment.

[0025] 5) Cooling the liquid iodine to obtain a solid purified iodine product. The purified liquid iodine is pumped from the transfer melt tank to the top of the prilling tower, a vertical cylinder with a liquid iodine distributor at the top, where it falls by gravity and is cooled by air and water streams injected at various points along its length, solidifying into the shape of spheres that constitute the purified solid product. Operating in the open with iodine at its melting point would result in losses of iodine by sublimation, resulting in costs and environmental pollution. Additionally, it would be necessary to send off-spec material for reprocessing and to separate the product to standardize the sphere size.

[0026] In summary, the conventional practices of iodine harvesting and purification operations in current industrial processes suffer from the following problems: a) Limited generating capacity Long retention times in major equipment due to discontinuous operation of equipment: 30 minutes in cutter (plus 1 hour for loading, unloading and siphoning), 4 to 20 hours in knockout and transfer melt tanks (plus 30 minutes for loading and unloading). For example, assume a plant with a capacity of 20 tons of iodine per day operates with a total of 6 equipment (each with a retention time of 4 hours) connected in series. If the retention time in one of them increases to 8 hours due to operational problems ("bottleneck" effect), the daily production capacity will be limited to [20 x 24 / 28 ≒] 17 tons / day.

[0027] Furthermore, the inherent fragmentation of discontinuous operations prevents, impedes or even negates automation of the process.

[0028] b) Excessive energy consumption Due to the very slow transfer of heat from the solid iodine contained in the pulp, the pulp is first preheated and then melted, which ensures long heating times in both operations, resulting in heat losses. Moreover, the cyclic solidification-melting-solidification operations that the iodine undergoes in cold cutting, and the subsequent melting and prilling, respectively, Use of indirect heat (through the surface) exacerbated by wasted cutting reaction heat This constitutes an inherent source of thermal inefficiency.

[0029] c) Excessive difficulty in controlling and standardizing operating conditions Due to the complex phenomenon of crystallization and agglomeration of the pasty solid iodine produced by cold cutting under mechanical agitation (always introducing air into the reaction mass), the pulp is obtained with occluded brine in ever-changing amounts, making regularization and automation unmanageable not only from cutting but also from subsequent melting. The crystalline solid iodine has a tendency to settle and to float when trapped in air, causing clogging of pumps, pipes and valves. This requires cumbersome solutions such as forced air blasts and high-speed pulp recirculation to keep the solid in suspension, in addition to the time and processing required to deal with frequent contingencies.

[0030] d) Inefficiency in the operation of major equipment The solid iodine produced by cold cutting reduces the efficiency of the reaction due to the separation or shielding effect of the reagents, which requires an increase in the retention time and / or the cutter capacity or the number of cutters. Fluctuations in the concentration of the solid iodine in the treated pulp are carried downstream and hinder all subsequent operations due to the excessive equipment capacity that is inevitably generated to take into account said fluctuations. The solid nature of the produced iodine has a high resistance to heat transfer and low mobility, which requires excessive heating times, i.e., a longer retention time, and therefore a larger capacity melting tank or multiple tanks for the same flow rate to be treated.

[0031] e) Excessive difficulty in homogenizing and regularizing product quality The variability in iodine concentration in pulp requires that the operating conditions of each piece of equipment being processed be varied. In the conventional process Molten iodine dissolves significant amounts of salts present in the brine containing it, a situation that is exacerbated with longer retention times in the melt-separation step, adversely affecting product purity.

[0032] f) Excessive number and capacity of equipment The fluctuating operating conditions faced by the equipment, especially in terms of retention times or flows to be processed, constantly necessitate an increase in the capacity of the equipment and / or an increase in the number of pieces of that equipment to maintain a given production capacity. In the case of melt tanks, the problem is exacerbated by both the varying ratio of iodine in the pulp and its high resistance to heat transfer.

[0033] g) Excessive requirements for maintenance, repair and replacement of equipment In general, the exposure time and / or amount of surface area exposed to corrosion and abrasion by solid crystalline iodine and acid solutions, especially at elevated temperatures, increases with the duration of operation, the volume or number of equipment and accessories, or the transportation activity or handling activity(b) To the extent that the repair and replacement of equipment and accessories is increased by either an increase in the need for repair or maintenance, the repair and replacement of equipment and accessories shall be increased proportionately.

[0034] h) Excessive iodine loss For the same reasons as in points d) and f) above, the greater the amount of transportation and handling, the greater the iodine sublimation losses, as well as with extended periods of operation in discrete equipment with long retention times and open to atmosphere, or with a larger number of equipment or their increased capacity.

[0035] i) Excessive operational risks due to environmental pollution and safety Due to these higher losses, the iodine limit of 0.1 ppm established by the American agency OSHA (Occupational Safety and Health Administration) highlights safety and contamination risks in the working environment (Non-Patent Document 5).

[0036] The present invention provides improved methods and systems for the preparation of medicaments, as more fully described below, along with corresponding claims, the accompanying drawings, and the following description, which set forth some of the various ways in which the present invention may be used. process FIG. 2 shows a configuration suitable for carrying out the present invention. System and Represents a device.

[0037] The present invention aims to solve the aforementioned problems of the prior art in the process of extracting elemental iodine and purifying it through the implementation of continuous operations of both shearing and autolysis, as well as separation of exhausted brine, regardless of the source of origin of iodine, the extraction process used, and the iodide concentration.

[0038] In addition to being a continuous process, the process of the present invention is faster, simpler, more compact, safer and non-polluting. and susceptible to automationThe need for chopped-stirred tank type reactors, pulp thickener systems or equipment, and bulky pulp preheaters are eliminated, avoiding corrosion and wear on all these equipment and the transfer systems between them. The melting tanks with excessive melting periods are eliminated, homogenizing the purity of the refined product and increasing the production capacity of the plant. By replacing several pieces of equipment (reaction tanks, pulp separation systems, pulp heat exchangers, pulp melting tanks) with two simple conventional pieces of equipment (conventional design heat exchangers for preheating the solution and centrifugal and / or gravity separators) of smaller size and less investment, subject to non-abrasive and less corrosive conditions, the requirements for heating steam, the level of maintenance, repairs, replacements, as well as the associated operational risks due to iodine sublimation losses and environmental pollution and safety are reduced.

[0039] Indeed, the conversion of a discontinuous process to a continuous process by the autolysis automatic control of the present invention significantly reduces investment, operating costs (especially energy consumption), team maintenance, repair and replacement, reduces iodine losses, contamination and occupational hazards, facilitates the transportation and handling of all process streams, eliminates the need for contingencies and frequent handling, allows automatic control of operations and efficient standardization of product characteristics and quality.

[0040] Unlike what is known in the prior art, the process for harvesting and purifying elemental iodine of the present invention is an automatically controlled continuous process, which consists in treating a given flow rate of an aqueous soluble iodide solution with a stoichiometric flow rate of an oxidizer that is "hot", i.e. with an iodide flow that is preheated to such a temperature upon contact with the oxidizer flow, that thanks to the released reaction heat, the reaction product reaches a temperature of 114° C. or higher, thus producing a continuous flow of liquid iodine, which represents a relative advantage compared to the prior art and can lead to an important competitive advantage in the iodine industry.

[0041] In fact, the "hot" shearing carried out as described above makes it possible to obtain elemental iodine, which is generated at practically theoretical rates, for example by iodide oxidation with hydrogen peroxide, and it takes only a few seconds to complete the shearing and produce iodine in liquid form, which is relatively easy to separate from the spent liquid brine thanks to the difference in specific gravity of [3.9-1.2=] 2.7. In this way, the retention time is reduced from [1×1 / 2+4.5=] 6 hours of shearing and melting of the conventional discontinuous process (according to a conservative scenario for the typical example of a 20 ton / day capacity plant described in item 4), and it is estimated that the continuous IAF process will increase the plant capacity to 34 ton / day with a retention time of less than 1 minute. Among other advantages of this last process, a reduction in energy consumption equivalent to 10 hours of operation per day of a conventional plant can be foreseen, as well as automatic control and standardization of the operating conditions, which will allow regularization of production and homogenization of product quality.

[0042] On the other hand, the oxidation reaction of the present invention takes place at the inlet of a reactor, which may be in the form of a liquid centrifuge or settling tank with specially designed hydrodynamics to drive the reaction to completion and separate the liquid iodine from the supernatant by either centrifugal and / or gravitational forces, the iodine flow exiting at the bottom and the supernatant flow exiting at the top, the entire operation being carried out at a pressure above the boiling point of the supernatant.

[0043] According to what is described in the prior art, the differences and advantages of the present invention can be understood. Table 1 summarizes the comparison between the IAF process and the conventional process for harvesting and purifying elemental iodine currently in the industry.

[0044] [Table 1-1] [Table 1-2]

[0045] [Details of the invention] The present invention makes it possible to carry out simultaneously and continuously a process for obtaining purified elemental iodine through controlled operations and conditions for the reaction of an iodide solution with an oxidizing agent (such as H2O2), melting, and separation of the resulting liquid iodine. That is, the present invention makes it possible to realize a process in which the steps described in the description of the prior art (Figure 1), which have so far been carried out discontinuously, are converted into a continuous, stable, large-scale process carried out substantially in a single equipment element (reactor-furnace-separator) designed to achieve the conditions required for the process.

[0046] The present invention relates to a process for obtaining purified elemental iodine, which is the result of extremely fast exothermic reactions occurring in a multiphase, non-isothermal, hydrodynamic system, specifically referring to 1) preheating an iodide solution flow to a specific temperature prior to subsequent operations, 2) carrying out a cleavage reaction of said preheated solution, which comprises intimately mixing said preheated solution to a specific temperature with a solution of an oxidizing agent (e.g. hydrogen peroxide) at room temperature, proceeding away from the crystalline state and directly producing molten iodine in its self-generated form, and 3) separating spent brine from purified liquid iodine, validating these last two operations in a single liquid-liquid separation device.

[0047] The preheating of the iodide solution flow is done in a continuous shell-and-tube or plate heat exchanger of standard design to a specific temperature between 40 and 120 °C depending on the iodine content of the iodide solution flow, so that when it is mixed and reacted with the oxidant flow in an in-line mixer, thanks to the heat generated by the exothermic reaction, both the product and the reactant reach the melting temperature of iodine, 113.6 °C, and molten iodine can be obtained directly, avoiding iodine crystallization. The reaction rate is theoretically instantaneous and does not change substantially when carried out "hot", since no solid iodine is produced that occludes the iodide solution, as in the case of "cold" cutting, and no separation of reagents that would cause an obvious reduction occurs. Thus, the fluid dynamics are established to make the continuous separation feasible, and the resulting iodine is separated from the wasting brine by centrifugal and / or gravitational action in a device such as a liquid centrifuge, which ensures the purity of the iodine obtained.

[0048] FIG. Process operations Appropriate for carrying out system The iodide flow is preheated to a temperature determined by its iodine concentration and then co-fed in stoichiometric ratio with the oxidant flow to a reactor-separator unit where they react to produce molten iodine and a depleted solution that are separated by centrifugal and / or gravitational action.

[0049] The oxidizing agents used in the present invention can be, inter alia, chlorine, bromine, nitrous acid, hydrogen peroxide, chlorates, iodates. The flow ratio between the oxidizing agent and iodide solutions is a crucial characteristic of the process, and is typically added at a ratio slightly higher than the stoichiometric ratio, usually between 1% and 10%. On the other hand, the process is capable of treating solutions with a wide concentration range for both iodide and oxidizing agent, always maintaining the stoichiometric ratio between the reactive species they contain.

[0050] Separation of the produced iodine can be carried out, for example, in liquid centrifuges designed for liquid-liquid separation of molten iodine and spent brine, which requires very specific characteristics related to the design (size and shape) and process conditions (applied flow rates, temperatures and pressures).

[0051] The size and shape of the liquid centrifuge can impart the necessary fluid dynamics to the reactant flows to drive the reaction to completion and separate the liquid iodine from the spent brine, while the operating conditions of temperature and pressure can ensure that the reaction takes place in the liquid phase while melting the iodine and avoiding boiling of the spent brine.

[0052] [Proof of concept for discontinuous IAF operations] Using a laboratory-scale reactor (80 mL) operated in batch mode, a conventional process of the prior art was reproduced from fundamental research to study the technical feasibility of producing liquid iodine by utilizing the heat of reaction between iodide and H2O2. Table 2 shows some experimental results of this proof of concept. It shows that for all iodide solutions processed, covering the iodine concentration range from 61 gpL to 242 gpL, the maximum temperature reached was higher than 113.6 °C in all cases, resulting in molten iodine. It was observed that the magnitude of the released reaction heat, in addition to the heat required for melting, is involved in the allocation of the heat required for the final reached temperature of the depleted brine and the iodine produced, the participation of which is more substantial for iodine solutions of higher concentration.

[0053] [Table 2]

[0054] Based on the evidence of the feasibility of batch operation, a continuous process was designed to simultaneously perform iodine melting and separation virtually instantaneously in the same reactor. This process, which the inventors term IAF (Iodine Autogenous Fusion), was implemented on a pilot scale to study the thermodynamic and hydrodynamic behavior of "hot" IAF cleavage, as well as the conditions required for subsequent phase separation, through continuous operation. EXAMPLES

[0055] The IAF process for producing elemental iodine and iodine refinery can process aqueous iodide streams with iodine content in a wide range of concentrations, for example, from about 50 to about 250 gpL, but with substantially less restriction on the concentration of the iodide solution than previous operations may have had. For that concentration range, the temperature and pressure of the iodide solution should be between 50° C. and 130° C. and 100 to 500 kPa (1.0 to 5.0 bar), respectively, while the concentration of the hydrogen peroxide solution can be between 15% and 70% (w / w).

[0056] As an example, Figure 3 shows the dimensions of a pilot liquid centrifuge designed to cut 20 L / min of iodide solution according to the IAF process. The production capacities of this pilot equipment, operating at a flow rate of 20 L / min of iodide solution, vary depending on the iodine concentration in the iodide being processed and are 86; 130; and 181 tonnes of iodine per month for iodine concentrations of 100; 150; and 210 gpL, respectively.

[0057] The centrifuge was used to cut off a 20±1% L / min flow rate of iodide from 142 gpL of iodine preheated to temperatures between 50 and 110°C with a stoichiometric flow rate of 0.62±1% L / min (including 2% excess) of 70% (w / w) hydrogen peroxide, which was fed into an in-line mixer located just at the centrifuge inlet. Figure 4 shows the temperature record of the centrifuge during the experiment, which shows that the temperature rose from 85°C to 114°C (the melting temperature of iodine) in 75 seconds after peroxide injection was started, with a transient due to line temperature regulation, reached a steady state at 121±2°C in 94 seconds after peroxide delivery began, and maintained continuous operation for more than 4 minutes (total operating time was limited to less than 10 minutes in all tests to avoid corrosion damage to the iodide delivery pump).

[0058] The top outlet of the hydrostatic centrifuge gave exhausted brine with a flow rate of 19.04 L / min, while the bottom outlet of the hydrostatic centrifuge gave liquid iodine with a flow rate of 0.69 L / h at a temperature of about 120° C. (which was collected in the iodide solution to prevent the escape of sublimated iodine vapor). After 4 minutes of steady operation, exhausted brine and molten iodine samples containing 7.71 gpL of iodine were extracted, showing a purity of 99.6% (w / w), indicating the formation of molten elemental iodine in autogenous form and its separation from the exhausted brine, and indicating the production of a high purity product in liquid form.

[0059] Table 3 shows the set of operating conditions in continuous operation and the results of various pilot tests. [Table 3]

[0060] The final yields for the batch and continuous IAF processes are shown in Tables 2 and 3, respectively, and are similar, however the continuous IAF process is significantly superior in comparison as it exhibits virtually all of the technical advantages shown in Table 1 and eliminates the need for discontinuous application for both "cold" and "hot" cutting.

[0061] [Non - Patent Literature] (1) USGS (2013) Mineral Commodities Summary. Iodine. (2) Chilean Copper Commission (2013) Monitoring of Industrial Minerals of Chile. Analysis of saline resources. (3) Krukowski, ST (2004) Iodine, Min. Engng. 56: 27 - 28. (4) SQM, DIP, PV (1989), Iodine Plant Operations Manual No. 3. (5) Tatsuo Kaiho (ed., 2015) Iodine Chemistry and Applications, John Wiley, USA. (6) Johnson KS and Gerber WR (1998). Iodine geology and extraction in northwestern Oklahoma. In: Johnson KS, (ed., 1999) Proceedings of the 34th Forum on the Geology of Industrial Minerals, Vol 102, Oklahoma Geological Survey Circular; pp 73 - 79. (7) Cosayach Nitrates S.A. (2012). Emissions, discharges and residues. In: Environmental impact statement increase in iodine production Cala - Cala. Tarapaca, Chile. Retrieved from http: / / seia.sea.gob.cl / archivos / CAPITULO_III_Emisions_descargas_y_residuos.pdf

Claims

1. A continuous process for the steps of iodide cleavage with an oxidizing agent, iodine melting, and separation for the harvesting and purification of elemental iodine contained in an iodide solution, comprising: said iodide severing step comprising reacting a preheated iodide solution flow with an oxidant flow to directly produce elemental molten iodine; separation of said elemental molten iodine from the spent molten water occurs by liquid-liquid separation; 11. A process characterized in that the iodide cleavage step occurs without iodine going through a crystalline state, and the steps described above are carried out in a single system where a rapid cleavage reaction takes place in an in-line mixer just prior to entering a liquid-liquid separator, thereby allowing time for separation of liquid iodine from spent brine.

2. 2. The process according to claim 1, characterized in that the cleavage step is carried out continuously above the melting temperature of iodine (113.6° C.) and that said temperature is maintained only by mixing the reacting flows, without the need to add additional heat during the reaction.

3. 2. The process of claim 1, wherein the scission temperature is reached using the heat of the scission reaction, which is called autogenous.

4. 10. The process of claim 1, wherein the iodide cleavage step directly produces purified iodine in a liquid state.

5. 2. The process of claim 1, wherein the oxidizing agent used in the cleavage reaction is selected from chlorine, bromine, nitrous acid, hydrogen peroxide, chlorates, and iodates.

6. 6. The process of claim 5, wherein the oxidizing agent is hydrogen peroxide.

7. 7. The process according to claim 1, characterized in that, before cleavage, the iodide solution is preheated to a temperature depending on its iodine content and on the nature of the oxidizing agent.

8. 8. The process of claim 7, wherein the preheating temperature is between 50° C. and 130° C. for iodide with an iodine content of 50 to 250 gpL when the oxidizing agent is hydrogen peroxide.

9. 9. The process according to any one of claims 1 to 8, characterized in that the cleavage is carried out in a stoichiometric ratio of the reactive species contained in the iodide flow and the oxidant flow, the latter being in excess.

10. 10. The process of claim 9, wherein when the oxidizing agent is hydrogen peroxide, the cleavage step is carried out using an excess of oxidizing agent between 1% and 7% above the stoichiometric ratio.

11. 2. The process of claim 1, characterized in that the concentration range is 50-250 gpL iodine for the iodide solution and 15% w / w to 70% w / w for hydrogen peroxide for the oxidizer solution.

12. 12. The process of claim 11, wherein the iodide solution is subjected to a pressure of 100 to 500 kPa (1.0 to 5.0 bar).

13. 13. The process according to any one of claims 1 to 12, characterized in that it is carried out by liquid-liquid separation equipment purposefully designed for centrifugal and / or gravitational action, such as liquid centrifuges or settling tanks, of a size and geometry determined to provide the necessary fluid dynamics in the continuous operation required to complete the reaction and carry out the separation of purified liquid iodine and spent brine at a temperature equal to or higher than the melting point of iodine or 114°C and at a pressure higher than the pressure corresponding to the boiling point of the spent brine.

14. 1. A system for carrying out a continuous process for harvesting and purifying elemental iodine contained in an iodide solution, comprising: an iodide solution heater; an oxidant flow feeder and an iodide solution flow feeder, both flows being simultaneously directed to a mixing point of the in-line mixer where iodide shedding occurs to instantaneously produce elemental liquid iodine and spent solution; a separation reactor located immediately downstream of said mixing point, which makes it possible to complete the cleavage reaction and to carry out a separation of the purified molten iodine and said spent solution streams; A system comprising:

15. 15. The system of claim 14, wherein the separation reactor is a hydrostatic centrifuge.

Images