Method for preparing chlorine dioxide

FIELD: inorganic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for preparing chlorine dioxide from chlorate ions and hydrogen peroxide in small scales. Chlorate ions, sulfuric acid and hydrogen peroxide are fed into reactor as aqueous solutions wherein they are mixed. Chlorate ions are reduced to chlorine dioxide. Chlorine dioxide-containing product flow is formed in reactor. Flowing water is fed into ejector fitted by jet by spiral or helically. The product flow from reactor passes into ejector and mixed with water and chlorine dioxide diluted solution is formed. Invention provides preparing chlorine dioxide aqueous solution of high concentration and high output.

EFFECT: improved preparing method.

18 cl, 3 dwg, 1 tbl, 1 ex

 

The scope of the invention

The present invention relates to a method for producing chlorine dioxide from chlorate ions, acid and hydrogen peroxide.

Prior

Chlorine dioxide is used in various applications, such as pulp bleaching, whitening, fat, water purification and removal of organic materials from industrial waste. Because chlorine dioxide is unstable during storage, it must be obtained on-site (locally).

Chlorine dioxide is usually produced by interaction of alkali metal chlorate or charnawati acid with a reducing agent in an aqueous reaction medium. Chlorine dioxide can be removed from the reaction medium in the form of gas, as described in the methods of U.S. patent No. 5091166, 5091167 and in EP No. 612686. Usually dioxyphenyl gas then absorb into the water with the formation of its aqueous solution.

To obtain chlorine dioxide in small scale installations, such as water purification plants or small plants for bleaching, it is advantageous not to yield gaseous chlorine dioxide from the reaction medium and to extract data directly from the reactor solution containing chlorine dioxide, optionally after dilution with water. Such methods are described in U.S. patent No. 2833624, 4534952, 5895638 and in WO 00/76916 and in recent years they have become commercial. However, there is still a need for further usovershenstvovaniju particular, it was found that to obtain solutions with high concentration of chlorine dioxide, as required for some applications, such as the bleaching of pulp, bleaching of sugar cane or small-scale bleaching of pulp, is difficult. High concentration of chlorine dioxide can also be useful for any application in which it is important to minimize the flow of water.

The invention

The aim of the invention is the provision of means providing direct get in an aqueous solution of chlorine dioxide in high concentrations.

Another objective of the invention is the provision of a method for direct production of chlorine dioxide in aqueous solution with high performance.

Another objective of the invention is the provision of a device for implementing the method.

Brief description of the invention

Was suddenly found the ability to perform these goals by providing methods of continuous receipt of chlorine dioxide, comprising the stage of:

feed to the reactor in the form of aqueous solutions of chlorate ions, acid and hydrogen peroxide;

recovery chlorate ions in the reactor until the chlorine dioxide with the formation thereof in the reactor product stream containing chlorine dioxide;

supply running water to the ejector containing the nozzle;

the implementation of the ing the flow of running water through the nozzle and call its subsequent flow through the ejector, at least partially, preferably essentially in a spiral or helical;

the flow of product from the reactor in the ejector and mixing it with running water and education as a result of a diluted aqueous solution containing chlorine dioxide;

removal of a diluted aqueous solution containing chlorine dioxide from the ejector.

Ions, chlorate can be fed into the reactor in the form of an aqueous solution containing chlorobutyl acid and/or metal chlorate, preferably the alkali metal chlorate. The alkali metal may be present, for example, sodium, potassium or mixtures thereof, of which the most preferred is sodium. If chlorobuta acid is not used, the reactor must be filed another acid, preferably a mineral acid such as sulfuric acid, hydrochloric acid or nitric acid, of which the most preferred is sulfuric acid. The molar ratio of N2About2to ClO3-fed to the reactor, suitably is from about 0.2:1 to about 2:1, preferably from about 0.5:1 to about 1.5:1, most preferably from about 0.5:1 to about 1:1. The metal chlorate and Chlorophyta acid always contains as an impurity a certain amount of chloride, but it is also possible to apply to the reactor more chloride, such as is lorid metal or hydrochloric acid. However, to minimize the formation of chlorine, it is preferable to maintain the amount of chloride ions fed to the reactor, low, suitably below about 1 mol.%, preferably below about 0.1 mol.%, more preferably less than about 0.05 mol.%, most preferably less than about 0.02 mol.% Cl-relatively ions ClO3-.

In a particularly preferred embodiment, the alkali metal chlorate and hydrogen peroxide was fed into the reactor in the form of a pre-mixed aqueous solution, for example in the form of a mixture, as described in WO 00/76916 included in this description by reference. This mixture may submit an aqueous solution containing from about 1 to about 6.5 mol/l, preferably from about 3 to about 6 mol/l of alkali metal chlorate, from about 1 to about 7 mol/l, preferably from about 3 to about 5 mol/l of hydrogen peroxide and at least one substance of the protective colloid, acceptor radicals or complexing agents based on phosphonic acid, if the pH of an aqueous solution suitably is from about 0.5 to about 4, preferably from about 1 to about 3.5, most preferably from about 1.5 to about 3. Preferably there is at least one complexing agents based on phosphonic acid preferably in an amount of from about 0.1 to about 5 mmol/l, most preferred is compulsory from about 0.5 to about 3 mmol/L. If there is a protective colloid, its concentration is preferably from about 0.001 to about 0.5 mol/l, most preferably from about 0.02 to about 0.05 mol/L. If the acceptor radicals, its concentration is preferably from about 0.01 to about 1 mol/l, most preferably from about 0.02 to about 0.2 mol/L. particularly preferred mixtures contain at least one complexing agents based on phosphonic acid selected from the group consisting of 1-hydroxyethylidene-1,1-diphosphonic acid, 1-aminoethane-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), hexamethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and 1-aminoalkyl-1,1-diphosphonic acids, such as morpholinobutyrophenone acid, N,N-dimethylaminomethylphenol acid, aminomethylphosphonic acid, or their salts, preferably sodium salts. Suitable protective colloids include tin compounds such as stannat alkali metal, in particular stannate sodium (Na2(Sn(OH)6). Suitable acceptors radicals include pyridineboronic acid, such as 2,6-pyridinedicarboxylate acid. The number of chloride ions on Hadasha is less than about 50 mmol/l, preferably less than about 5 mmol/l, most preferably less than about 0.5 mmol/L.

In the case when the quality of raw materials used sulphuric acid, it preferably has a concentration of from about 70 to about 96 wt.%, most preferably from about 75 to about 85 wt.%, and the temperature is preferably from about 0 to about 80°S, most preferably from about 20 to about 60°With, in this case, the process can be done essentially o adiabatically. Preferably served from about 2 to about 6 kg H2SO4most preferably from about 3 to about 5 kg H2SO4per kg received ClO2. Alternatively, it may be used an equivalent amount of another mineral acid.

The net reaction, which leads to the generation of chlorine dioxide, can be represented by the following equation:

2ClO3-+2H++H2O2→2ClO2+2H2O+O2

The exact mechanism is complex and it is assumed that it includes a first reaction between chlorate and chloride (even if it is not added separately, it is always present in sufficient quantities in the chlorate as an impurity) to produce chlorine dioxide and chlorine and the subsequent reaction of chlorine with hydrogen peroxide with the formation of chloride again. However, it should be taken into account that the Chi is the reaction of hydrogen peroxide is generally regarded as the reducing agent, reactive ion chlorate.

Restoration of chlorate ions to chlorine dioxide leads to the formation in the reactor, the product stream comprising normally as a liquid, and foam, and containing chlorine dioxide, oxygen and, in most cases, some amount of the remaining unreacted source of chemicals. Chlorine dioxide and oxygen may be present both in the liquid in a dissolved state and in the form of gas bubbles. When as a source of chemical reagents used a metal chlorate and a mineral acid, the product stream will then contain, in addition to chlorine dioxide and oxygen, the metal salt of the mineral acid and usually also a certain amount of the remaining metal chlorate and a mineral acid. It has been found that it is possible to achieve the degree of conversion of chlorate ions to chlorine dioxide, from about 75% to 100%, preferably from about 80% to 100%, most preferably from about 95% to 100%.

The temperature in the reactor is suitably supported below the boiling point of the reactants, preferably from about 20 to about 80°S, most preferably from about 30 to about 60°and the overwhelming pressure of the stream of product. Supported in the reactor pressure is eligible slightly below atmospheric and preferably absolute pressure is from about 30 to about 100 kPa, the most preference is sustained fashion from about 65 to about 95 kPa.

The reactor may contain one or more vessels, for example, installed vertically, horizontally or inclined. The reagents can be fed directly into the reactor or through a separate mixing plant. The reactor preferably is essentially tubular vessel or pipe with longitudinal flow, most preferably contains means for mixing reagents essentially homogeneous. Such means may include a drive or a similar tool, provided with holes and installed inside the reactor where the metal chlorate and hydrogen peroxide serves downstream relative to the disk, whereas the acid serves upstream relative to the disk and is forced to flow through the holes and then mixed with metal chlorate and hydrogen peroxide. It has been found that such a system provides a homogeneous mixing and sustainable mode of the process, as well as the ability to change performance while maintaining high chemical efficiency, particularly in reactors mounted essentially vertically, where the main flow direction is the direction it up. However, you can also just submit one of the reagents, such as acid, a nutrient pipeline for another reagent or mixture of reagents, for example a mixture of a metal chlorate and hydrogen peroxide.

Length (mainly n the Board of thread) used reactor is preferably from about 50 to about 800 mm, most preferably from about 350 to about 650 mm Was found that is a beneficial use of essentially tubular reactor with an inner diameter of from about 25 to about 300 mm, preferably from about 70 to about 200 mm, particularly favorably used essentially tubular reactor, having a preferred ratio of length to inner diameter of from about 12:1 to about 1:1, most preferably from about 8:1 to about 4:1. A suitable average residence time in the reactor in most cases is from about 1 to about 1000 seconds, preferably from about 2 to about 40 seconds.

The ejector creates a suction force that forces flow of the product, including any liquid, foam and gas, to flow into the ejector and mixed with the flowing water with the formation of a diluted solution containing chlorine dioxide. Flowing water is forced to flow at least partially in a spiral or helical any appropriate means, such as helical blade, the system of internal rifling, or similar means, which may be in the form of a single nozzle or separately from the nozzle and installed inside or in front of him. The nozzle may be of any suitable type and may contain one or more holes.

The ejector suitably further comprises, in the direction of flow from the nozzles is, the suction chamber, which moves the flow of product from the reactor, and a Venturi tube through which in this case, remove the dilute aqueous solution containing chlorine dioxide. Can also be used ejectors with more than one nozzle.

It was found that at least partially spiral or helical flow of the flowing water increases the productivity of the production of chlorine dioxide in the stream of flowing water, thereby obtaining a solution with a higher concentration of chlorine dioxide than the concentration that was possible before allocating deoxidising gas from the reaction medium and subsequent absorption into the water, there are stages that are not necessary to implement the present invention. Therefore, it is possible to obtain aqueous solutions containing from about 1 to about 4 g/l of chlorine dioxide, preferably from about 1.5 to about 3.5 g/l of chlorine dioxide.

The method of the invention is particularly suitable for obtaining chlorine dioxide in small scale, for example in amounts of from about 0.1 to 100 kg/hour, preferably from about 0.1 to about 50 kg/hour in a single reactor. In many applications the preferred performance of the process of obtaining chlorine dioxide is from about 0.1 to about 25 kg/hour, most preferably from okolo,5 to about 10 kg/hour in a single reactor. A typical production unit on a small scale usually includes only one reactor, although you can set up several parallel, for example up to about 15, or more reactors, for example, in the form of bundles of pipes.

The invention additionally relates to apparatus for producing chlorine dioxide in accordance with the above method. The device includes a reactor equipped with a nutrient pipelines for ion chlorate, hydrogen peroxide and acid, while the reactor is connected to the ejector equipped with a nozzle for flowing water and means causing flow of running water through the ejector, at least partly, in a spiral or helical.

Preferred variants of the device is apparent from the above description of the method and the following description with reference to the drawings. However, the invention is not limited to the options shown in the drawings, and covers many other options that are included in the scope of the claims.

Brief description of drawings

Figure 1 shows the process flowchart of the method of the present invention. Figure 2 shows schematically the reactor. Figa and 3b schematically show the ejector and means causing a flow of running water, at least partially, in a spiral or helical.

Detailed description of drawings

Figure 1 shows the vertical pipes of Aty reactor 3 for the longitudinal flow, fed sulfuric acid through a nutritious pipeline 1 and pre-mixed aqueous solution of sodium chlorate and hydrogen peroxide through the pipeline 2. In the reactor 3 feed streams are mixed and interact with the formation of the product stream consisting of liquid, foam and gas including chlorine dioxide, oxygen, sodium sulfate and the remaining sulfuric acid and sodium chlorate. The ejector 6 is fed by running water through nutrient pipeline 5 and creates a pressure slightly below atmospheric, causing the flow of product to flow from the reactor 3 through line 4 into the ejector 6, where it is mixed with the flowing water with the formation of a diluted aqueous solution of the product. The obtained diluted solution contains chlorine dioxide, and another component from the reactor 3, and it is removed as a final product through the pipeline 8. The process control system including a programmable logic controller (PCR) (PLC), chlorine dioxide analyzer 9, the pressure sensor (DD) (PT) and the sensor flow rate (PDA) (FT)regulates the supply pump 10, intended for supply of chemicals to the reactor 3 and the flowing water in the ejector 6.

Figure 2 shows the distribution disk 21 with holes and placed in the lower part of the reactor 3, but above the inlet from the feed pipe 1 for sulfuric acid. Pete is part of the pipeline 2 to a pre-mixed solution of sodium chlorate and hydrogen peroxide ends in the distribution nozzle 20, established in the mid cross-section of the reactor just above the distributor disc. Then a solution of sodium chlorate and hydrogen peroxide is sprayed on the cross section in the reactor 3, whereas sulfuric acid flows up through the holes in the distribution disk and mixed with sodium chlorate and hydrogen peroxide above the distributor disc 21. When mixing, the reaction begins generating chlorine dioxide, and creates a product stream consisting of liquid, foam and gas, which are removed through the discharge opening 22 in the upper part of the reactor 3.

Presented at Figo and 3b ejector 6 includes the suction chamber 25, a single nozzle with a hole 26 with the insert 27 (shown in fig.3b)containing helical blade 28 and the Venturi 29. Flowing water is fed from the feed pipe 5 through the nozzle 26 and the insert 27. Helical blade 28 of the insert 27 to cause the flow of water, at least partially, in a spiral or screw through the suction chamber 25 where it is mixed with the product stream flowing through conduit 4 from the reactor 3 (see figure 1) forming a dilute solution containing chlorine dioxide, pour out of the ejector 6 through the Venturi 29. Flowing through the ejector flow creates a pressure below atmospheric, sufficient to discharge the product stream from the reactor to the prot is Chania in the ejector.

Technological equipment, including the reactor 3 and the ejector 6, made of materials resistant to hydrogen peroxide, sodium chlorate, sulfuric acid and chlorine dioxide. Such materials include, for example, glass, tantalum, titanium, plastic, reinforced with fiberglass, fluorine-containing plastics, such PVDF (polyvinylidene fluoride), CPVC (chlorinated polyvinyl chloride), PTFE (polytetrafluoroethylene), PFA (PerformancePoint), ECTFE (ethylenchlorhydrine) or FEP (fluorinated ethylene propylene), or these materials are used as cladding material for construction material like steel or stainless steel. Suitable fluorine-containing plastics sold under the trade name Kynar®, Teflon® or Halar®.

Further, the invention is illustrated by the following example.

Example: chlorine Dioxide was obtained in accordance with the invention in the apparatus shown in the drawings. A vertical tubular reactor 3 with an inner diameter of 75 mm and a length of 610 mm continuously fed 78 wt.% sulfuric acid and an aqueous solution of 40 wt.% sodium chlorate and 10 wt.% hydrogen peroxide, stabilized by complexing agents based on phosphonic acid. The reactor was maintained at a temperature of about 40-50°and an absolute pressure of about 84 kPa (below atmospheric approximately 17 kPa), while the vacuum pressure is tion (below atmospheric) was created by the power of the ejector 6 running water at an absolute pressure of 790 kPa.

For comparison, chlorine dioxide was obtained in the same way, except only that the ejector does not contain the insert in the nozzle, causing the flow of running water, at least partially, in a spiral or helical.

The results are shown in the following table.

Type ejectorThe stream of running water (l/min)The performance of the process of obtaining ClO2(kg/h)The concentration of ClO2in the final product (mg/l)
With insert (invention)48,19,13135
Without inserts (for comparison)to 45.4a 3.91450

It is clear that the method of the invention provides both a significant increase in performance of the process of obtaining ClO2and the concentration of ClO2in the solution of the final product, remote from the ejector.

1. Method for continuous receipt of chlorine dioxide, which includes stages

feed to the reactor in the form of aqueous solutions of chlorate ions, acid and hydrogen peroxide;

recovery chlorate ions in the reactor in the chlorine dioxide with the formation thereof in the reactor product stream containing chlorine dioxide;

supply running water in the ejector, the content is of ASI nozzle;

implementation of a leakage flow of water through the nozzle and subsequent flow through the ejector, at least partly, in a spiral or helical;

the flow of product from the reactor in the ejector and mixing it with running water and education as a result of a diluted aqueous solution containing chlorine dioxide, and

removal of a diluted aqueous solution containing chlorine dioxide from the ejector.

2. The method according to claim 1, in which flowing water is passed through the ejector essentially in a spiral or helical.

3. The method according to claim 2, in which flowing water is passed at least partially in a spiral or screw-shaped by means of representing the helical blade, placed inside the nozzle in the ejector or in front of the nozzle in the ejector.

4. The method according to claim 2, in which flowing water is passed at least partially in a spiral or screw-shaped by means of representing a system of internal rifling inside the nozzle in the ejector or in front of the nozzle in the ejector.

5. The method according to any one of claims 1 to 4, in which the ejector further comprises in the direction of flow from the nozzle suction chamber into which the flow of product is moved from the reactor, and a Venturi tube through which removes dilute aqueous solution containing chlorine dioxide.

6. The method according to claim 5, in which the torus ions, chlorate fed into the reactor in the form of aqueous solution, containing a metal chlorate and acid fed into the reactor in the form of a mineral acid.

7. The method according to claim 6, in which the mineral acid is sulfuric acid.

8. The method according to claim 6 in which the alkali metal chlorate and hydrogen peroxide was fed into the reactor in the form of a pre-mixed aqueous solution.

9. The method according to claim 8, in which a pre-mixed aqueous solution contains from about 1 to about 6.5 moles/liter of alkali metal chlorate, from about 1 to about 7 mol/l of hydrogen peroxide, at least one connection of the protective colloid, acceptor radicals or complexing agents based on phosphonic acid and has a pH of from about 0.5 to about 4.

10. The method according to any one of claims 1 to 9, in which the number of chloride ions fed to the reactor is less than about 1 mol. % Cl-relatively ClO3-.

11. The method according to any one of claims 1 to 4, in which the flow of product in the reactor containing chlorine dioxide, contains the liquid and foam.

12. The method according to any one of claims 1 to 4, in which the temperature in the reactor is maintained within the range from about 30 to about 60°C.

13. The method according to any one of claims 1 to 4, in which the absolute pressure in the reactor is maintained within the range from about 30 to about 100 kPa.

14. the procedure according to any one of claims 1 to 4, in which the reactor is essentially tubular vessel or pipe for flowing stream.

15. The method according to 14, in which the reactor has essentially vertically.

16. The method according to item 15, in which the reactor comprises a disk or a similar tool, provided with holes and installed in the reactor, and a metal chlorate and hydrogen peroxide serves downstream relative to the disk, whereas the acid serves upstream relative to the disk and through the holes and then mixed with metal chlorate and hydrogen peroxide.

17. The method according to item 15, in which the main flow is directed upwards.

18. Apparatus for producing chlorine dioxide comprising a reactor equipped with a nutrient pipelines for ion chlorate, hydrogen peroxide and acid, while the reactor is connected to the ejector equipped with a nozzle for flowing water and means for subsequent transmission flow of water through the ejector, at least partly, in a spiral or helical.



 

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26 cl, 1 dwg, 1 ex

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