The method of obtaining peroxide salts in the form of solid particles and device for its implementation

 

(57) Abstract:

The invention is intended for the chemical industry and can be used for washing substances. The apparatus comprises a mold (1) and classifier (2). The diameter of the classifier (2) less than the diameter of the mold (1). The mold (1) is divided by the grating (5) of the zone of formation and growth of crystals (3) and clarification (4). Zone (3) is equipped with a blade stirrer (6) with a hollow shaft (8) and dual coil (7). The classifier (2) equipped with a mixer (13). Concentrated solution of H2O2fed through the hollow shaft (8) of the agitator (6) in the lower part of the mould (1). This also serves a concentrated aqueous salt solution of an alkali metal containing wasalive agent and stabilizer. Solutions interact with the formation of a supersaturated solution of peroxide of salt. The supersaturated solution is kept in a regulated environment for the formation and growth of crystals. Through the zone of the formation and growth of crystals (3) passes upward flow of supersaturated solution and downward flow of solid particles peroxide salts. Excess clarified in the refining zone (4) of the solution is withdrawn from the upper part thereof, and fed into the classifier (2), where elutriate h the historical composition in a continuous mode. 2 C. and 7 C.p. f-crystals, 2 ill., table 2.

The invention relates to a method for peroxide salts in the form of solid particles and device for its implementation.

Solid particles peroxide salts, obtained by the method, used in various industries as a carrier of active oxygen in the solid state and, in particular, in industries of detergents.

Already known methods for producing peroxide salts by crystallization from supersaturated aqueous solution obtained at the offset in the mould of concentrated solutions of hydrogen peroxide and water-soluble salts (U.S. patent 2 986 448). This patent also States that as an option, you can use another type of mold in which the supersaturated solution is moving in an upward flow through the layer formed and growing crystals, which allows a certain classification of particles (mould type of Oslo).

However, these known methods have the disadvantage that receive peroxide salt, the particle size distribution which is always relatively wide and which are not very high stability. Moreover, Cree is part stick to the walls of the apparatus and form a crust, which must be periodically removed.

These disadvantages of the known methods are eliminated by using the method according to the invention, which allows you to get in economical conditions of stable peroxide salt with a narrow particle size distribution in continuous mode.

The invention relates to a continuous method for producing a peroxide salt of at least one alkali metal in the form of solid particles in the interaction of concentrated aqueous hydrogen peroxide solution with a concentrated aqueous solution of at least one salt of at least one alkali metal with the crystallization of the formed peroxide salt crystallizer-classifier that contains the refining zone above the zone of mixing, which passes through the rising stream of supersaturated solution of peroxide salts, in which particles peroxide salts are moved in the direction opposite to the direction of the solution, and the mold is located above the classifier, in which particles peroxide salts are subjected to decantation and collected in the lower part of the classifier, where they extract.

Under peroxide salt pony is em when dissolved in water, hydrogen peroxide and a salt of an inorganic acid. Examples of peroxide salts, corresponding to the method according to the invention are perborate, PEROXYDICARBONATE phosphates and peroxidation carbonates.

The method according to the invention is suitable, in particular, to obtain solid particles of perborates or peroxiderythromycin carbonates of alkali metals. He gives excellent results to obtain peroxiderythromycin carbonates of alkali metals.

The method is applicable for obtaining peroxide salts of any of the alkali metals. It is convenient to obtain peroxide salts of sodium or potassium. He gives excellent results when receiving peroxide sodium salt.

The method according to the invention is particularly applicable to obtain peroxidation sodium carbonate formula 2Na2CO33H2O2usually called percarbonate sodium.

The method is also applicable to obtain a mixture of several of peroxide salts, for example, a mixture of perborate and peroxidation carbonate of alkali metals. It can also be used to obtain a mixture of peroxide various salts of alkali metals such as, for example, peroxide salts of sodium and potassium.

Under salt delock hydrogen peroxide with the formation of compounds solid under normal conditions of temperature and pressure, called peroxide salt, such as defined above. Examples of such salts are the borates of alkali metals, phosphates of alkali metals and carbonates of alkali metals. Preferred are metaborate sodium or potassium and carbonate of sodium or potassium. Sodium carbonate leads to excellent results.

According to the invention are in the crystallizer-classifier, i.e. the device that provides the generation of solid crystals and their exponential growth with obtaining particles with relatively narrow particle size distribution.

In the method according to the invention the solution of peroxide salt obtained by the reaction of hydrogen peroxide with an alkali metal salt, circulates in the crystallizer-classifier in the form of a stream which crosses from the bottom up layer formed and growing crystals peroxide salts. This solution of peroxide salt is kept in a crystallizer-classifier under controlled conditions of concentration and temperature to create a state of slight supersaturation.

Used concentrated aqueous hydrogen peroxide solution may contain various obratno to use aqueous solutions, containing at least 15 wt.%, preferably at least 20 wt.% of hydrogen peroxide. To ensure the safety of the method, it is desirable to use aqueous solutions of hydrogen peroxide containing not more than 80 wt.%, preferably, not more than 70 wt.% of hydrogen peroxide. Solutions of hydrogen peroxide with a concentration of 55-45 wt.% to give excellent results.

The concentration of the used aqueous solution of salts of alkaline metal depend on the water solubility and the nature of the salt used, the nature and quantity used vicalvaro agent, and the conditions of temperature and pressure existing in the mold. This concentration is usually adjusted to be obtained after the reaction with concentrated hydrogen peroxide solution supersaturated solution kristallisoituu peroxide salt.

According to the invention the solution of peroxide salts may contain at least one wasalive agent and at least one stabilizer. Under wycliffism agent see agent, which reduces the solubility of the peroxide salt in aqueous solution and which facilitates the crystallization of peroxide salts. Among the various possible Vasiliadi agents preferably IGNOU salt. In the case of obtaining percarbonate sodium convenient to use salt NaCl and Na2SO4that are not in aqueous solution total cation Na+with percarbonate sodium. Concentration vicalvaro agent in the hydrogen peroxide solution is usually selected not less than 4 g/100 g of solution, preferably not less than 9 g/100 g of solution. Usually it does not exceed 25 g/100 g of solution, preferably not greater than 19 g/100 g of solution. Concentration vicalvaro agent 16.5 g/100 g of the solution in the case of NaCl and 9 g/100 g of the solution in the case of application of Na2SO4to give excellent results.

Under the stabilizer understand any connection, is able to prevent hydrogen peroxide from decomposing, and, consequently, the loss of active oxygen. In General suitable conventional stabilizers aqueous alkaline solutions of hydrogen peroxide, in particular, silicates of sodium and potassium, soluble salts of magnesium, inorganic or organic complexing agents. Among the latter give a good organic phosphonates, in particular, sodium salt 1-oxetan-1,1-diphosphonic acid.

Concentrations used stabilizers vary depending on the effectiveness of these compounds for Stabia/kg used Na2CO3. More often, however, the concentration does not exceed 80 g of silicate/kg Na2CO3. In the case of complexing agents that are more effective products, the concentration does not exceed 1 g of agent/kg Na2CO3. For complexing agents amount of 20 g/kg Na2CO3be the upper limit, which is usually not transferred. It is also advisable to use a combination of stabilizers. Mix 40 g/kg Na2CO3for sodium silicate and 2.4 g/kg Na2CO3for the sodium salt of 1-oxetan-1,1-diphosphonic acid gives excellent results.

Wasalive agent and stabilizer can be entered at different points in the process. These products can be introduced in solid form or in aqueous solution, alone or in mixture. Introduction vicalvaro agent in a solution of salts of alkaline metal and stabilizer in the hydrogen peroxide solution gives excellent results.

In accordance with an advantageous variant of the method according to the invention is introduced into a solution of alkali metal salt crystallization agent additive. This term refers to a compound or composition which modifies the shape of the obtained crystals, turning igol aspati, such as sodium hexametaphosphate or ammonium pyrophosphate or sodium, and water-soluble Homo - or copolymers of acrylic acid.

The number of crystallization additives, which are used in the method according to the invention, which largely depends on various parameters, such as, for example, the nature of the additive, the conditions of temperature and mixing that exist in the mould, and the residence time of the solution in the crystallizer. Typically this amount will not be less than 2 g/kg Na2CO3and preferably not lower than 5 g/kg used Na2CO3. Most often, the number of auxiliary additives does not exceed 50 g/kg NaCO3preferably it does not exceed 30 g/kg Na2CO3. Sometimes it is advisable to combine several different auxiliary additives.

According to the invention, solutions of hydrogen peroxide and alkali metal salt is injected continuously in the zone of formation and growth of crystals located in the lower part of the mould, which functions simultaneously as a reactor to obtain a supersaturated solution of peroxide of salt and as the mold for separating the formed particles of this peroxide salt from the rest of the solution. The area about which nucleate and grow crystals, forming particles of peroxide salt.

An advantageous variant of the method according to the invention is to regulate the density of the suspension of particles growing in the area of education and growth, so that she was never less than 25 wt.% solids, preferably at least 30 wt.%, solid substances.

In addition, it is generally inadvisable to exceed the density of the suspension equal to 60 wt. % solids in the area of education and growth, prefer not to exceed a density equal to 50 wt.% solid substances.

The temperature in the mold is adjusted so as to maintain the conditions of slight supersaturation of the solution of peroxide of salt, given the nature and amount of various additives, in particular vicalvaro agent. Usually she at least is 5oC, and preferably at least equal to 8oC. most Often, this temperature does not exceed 40oC, preferably it does not exceed 35oC. the Temperature from 10 to 30oC give excellent results.

According to the invention the area of education and growth is an area with stirring. This mixing can be carried out using any known device, ensure that the industrial agitators well suited rotary agitators. It is noted that for the experienced small-size installation (the crystallizer volume of 50 l) is usually suitable rotation speed of not less than 40 rpm, preferably not less than 50 rpm Often experienced in such installation, the mixer rotation speed does not exceed 120 rpm, preferably 100 rpm rotation Speed from 60 to 90 rpm to give good results on the experimental setup.

In accordance with the method according to the invention the upward flow of the liquid then flows into supermasive zone, located in the upper part of the mould, where it is asserted (lightened) in a quiet area called the refining zone.

Because the peroxide crystals of salt grow in the area of education and growth, there comes a moment when the form of particles whose size becomes large enough, in which they have no passion for upward flow or movement of fluid caused by mixing. Then, these particles begin to move in the direction opposite the upward movement of the fluid crossing the area of education and growth, and sedimentation of particles towards the bottom of the mould.

In accordance with the method according to the invention these ossification, located under the mold (area classification). In this zone, the particle peroxide salts are subjected to decantation in an upward flow of liquid.

According to the invention desantiruemaya liquid introduced into the lower portion of zone classification represents the portion of the liquid withdrawn from the upper part of the clarification zone of the mold. This liquid is injected under pressure into the lower part of the classifier.

The flow rate selected in the refining zone and re-introduced under pressure into the lower part of the classifier should be adjusted depending on the average particle size of peroxide salts, which want to receive. For classification of a certain diameter is directly proportional to the speed of rise of the liquid in the classifier. Usually arrange so that the rate of rise of liquid in the classifier is not less than 5 m/HR, preferably not less than 10 m/h. Often choose the lifting speed of the fluid, which does not exceed 100 m/h, preferably it does not exceed 80 m/h. Speed of lifting liquids from 20 to 50 m/hour give good results.

The excess fluid flowing over the upper part of the classifier, re-injected into the loop process is ora, select using shagivaleva device located at the bottom of the zone classification.

According to an advantageous variant of the method, the particles that cross the zone classification, is subjected to the stirring inside the liquid rising in the classifier. Preferably this mixing is carried out at lower energy cost than the mixing, which is carried out in the area of education and growth of crystals. Usually it does not exceed 70% of the energy consumed by stirring in the area of education and growth, is preferably 50% from it.

Specifically, the invention relates to a method for peroxidation carbonate of an alkali metal, in particular peroxidation sodium carbonate.

The invention also relates to an industrial plant producing a peroxide salt by crystallization of classification, including the capacity for crystallization of cylindrical shape, provided with a rotary stirrer and cooling system, the tank contains a separation between mixed bottom area, which is the mixer, and an upper zone in which the stirrer is missing, and which is designed for the clarification of liquids, the situation is, predstavlyayushikh a source products to obtain peroxide salts; the installation also includes a cylinder of diameter less than the diameter of the vessel, the cylinder is located under the tank, and with it connected and provided in its lower part supply system solution that came with nanyavshego pump for discharging pipe, the beginning of which is at the top of nepremerimoj zone capacity, and this cylinder is the area classification by decanting particles coming from the stir zone capacity, and the device for removal of particles is connected with the lower part of the specified cylinder.

Preferably the cylinder to classify features in such a way that its axis coincides with the axis of the crystallization vessel.

In addition, particularly suitable to perform cylinder for classification rigidly connected to the bottom of the vessel for crystallization.

Expedient variant of the industrial installation according to the invention lies in the use of stirrers, which, in addition to its function of homogenization in the area of education and growth of crystals implements the input and distribution of one of the two aqueous concentrated solutions, namely solution perox is defined by the hollow axle, which is located inside the pipe, the bottom of which communicates with the hollow pipelines along the entire length of the lower blades of the agitator and which end at the ends of these blades.

Another preferred variant of the industrial installation according to the invention is to provide a zone classification stirrer. Can be used different types of mixers.

In addition, more detailed installation disclosed in the following description with reference to the attached drawings, which show schematically a preferred form of the installation according to the invention.

The installation consists (Fig. 1) in the General form of a cylindrical tank 1, which serves as a mold, and a cylindrical riser 2, employee classification, the diameter of which is smaller than the diameter of the tank 1 and made integral with the bottom of the tank 1. Riser 2 communicates with the bottom of the tank 1 and is located on the same axis, and that this capacity.

The tank 1 is divided into two zones 3 and 4, respectively, the area of formation and growth of crystals and the refining zone, divided by the grid 5. Zone 3 contains impeller mixer 6 and a double metal coil 7, which circulates the coolant. Axis 8 mesh is the target of hydrogen peroxide. The pump 10 delivers under pressure in the bottom 11 of the tank 1 concentrated aqueous salt solution of an alkali metal supplied through the pipeline 12.

The front of the classifier 2 is equipped with a blade stirrer 13, driven by a motor 14. A pressure pump 15 can apply pressure to the bottom of the truncated cone 16, which is located under the cylinder 2, the solution taken from the upper section 17 is situated in a tranquil area of clarification. The device 18 for removal of particles is connected with the lower part of the cylinder classifier 2. It can be derived from the installation of classified particles through the pipeline 19.

In Fig. 2 shows the crystallizer-classifier together with the connected other devices necessary to obtain particles of peroxide salt.

The pipeline 12 feed of salt solution of an alkali metal goes from the tank to dissolve the reactants 20, equipped with a mixer 21 and the heating coil 22. In this capacity serves a mixture of Na2CO3containing stabilizer and possible crystallization additive through the pipeline 23. The pipe 24 can regulate the pH of the solution using 2H NaOH to maintain a pH of about 10-10,5 in the mould. Overflow from Kristiania.

Solid particles peroxide salt, abstracted from classifier 2 to line 19, is temporarily stored in a buffer tank 29 to their suction and washing in the centrifuge 30. The mother liquor and wash water emerging from the centrifuge 30, is directed through the conduit 31 into the buffer tank 26, where they Recuperat. Installation is also equipped with a flow meter 32, 33 and 34, denoted by F1 (flow Indicator), as well as device registration and regulation of level 35, called LRC (control-level indicator) flow 36, called FRC (Controller-pointer stream) and the density of the suspension 37, called DRC (Controller-pointer-density).

The following examples are given to illustrate the invention without limiting it.

Example 1R (not according to invention)

In the tank for dissolving a volume of 25 l continuously dissolved under stirring to 110 rpm and at a temperature of 42oC adjustable number of Na2CO3to obtain a solution containing 120 g of Na2CO3/kg solution. To it add two stabilizer in the form of sodium silicate concentration 40oBe (molar ratio SiO2/Na2O = 3,4) at the rate of 20 g/kg Na2CO3available in solution, and sodium hexametaphosphate havemy by the company BASF, at the rate of 10 g/kg Na2CO3. The solution flow rate Na2CO3containing stabilizers, maintain a constant and equal to 5 kg and Na2CO3/hour.

Use the mold has a cylindrical shape (with a volume of 50 liters and equipped with a stirrer. The stirrer of the mold represents the stirrer vane type EKATOMIG . In the mold is continuously fed through the axis of rotation of the agitator 40% solution of H2O2containing 22 g NaCl/100 g of the solution as vicalvaro agent, and with a flow rate of 5 kg Na2CO3/hour of a solution of Na2CO3containing stabilizers and vasilevousa agents coming from the vessel for dissolution. The flow rate of the feed solution H2O2maintain a constant and equal to 5 l/h.

During the whole experience support the density of 20% solids in the crystallizer.

The rotation speed of the stirrer of the mold is 70-75 rpm

After the installation mode in a solution of Na2CO3extending from the tank to dissolve, set the residual content of H2O21 g H2O2/100 g of solution and NaCl content equal to 20 g NaCl /100 g of solution.

From the bottom h of the solid substances.

The obtained particles percarbonate sodium have the following characteristics:

The average diameter, mm 780

Index of grain-size variation - 1,2

Apparent specific weight kg/l - 0,82

The content of active oxygen, % - 14,1

NaCl content, % - 5,5

The content of SiO2, % - 0,3

The content of PO4, % - 0,16

Granulometric characteristics, namely, the average diameter and the intermediate index of dispersion were determined using a laser granulometer. The average diameter is an average diameter of 50% (D50) on the combined gradation curve, which corresponds to 50 wt.% particles. The index of the particle size of the dispersion is a measure of the breadth of granulometric distribution of the particles. It is calculated from the average diameters of D90D10and D50then there are the average diameters of the combined particle size distribution curve, i.e. respectively 90, 10 and 50 wt.% particles having a smaller diameter. Analytical expression index particle size of the dispersion is as follows:

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Example 2 (according to the invention)

In the tank for dissolving a volume of 25 l setup like the one described in the drawings 1 and 2 continuously dissolve when peremeshivaniya 120 g of Na2CO3/kg solution. Add two stabilizer in the form of sodium silicate with a concentration of 40oBe (molar ratio SiO2/Na2O = 3,4) at the rate of 20 g/kg Na2CO3available in solution, and sodium hexametaphosphate based on 6 g/kg Na2CO3. Then there enter polyacrylate ammonium brand PIGMENTVERTEILERA , sold by the company BASF, the rate of 10 g/kg Na2CO3. The solution flow rate Na2CO3containing stabilizers, maintain a constant and equal to 4.2 kg Na2CO3/hour.

Use the mold has a cylindrical shape (volume 50 l), is provided in the bottom of the riser-classifier without stirring, also of cylindrical shape (diameter 9 cm, height 46 cm). The stirrer of the mold represents an impeller type agitator EKATOMIG . In the mold is continuously fed through the axis of rotation of the agitator 40% solution of H2O2containing 16.5 g NaCl /100 g of the solution as vicalvaro agent. The flow of injectate H2O2is 5 l/h.

Continually select solution with a flow rate of 300 l/h zone lightening and again served under pressure into the lower portion of zone classification. Overflow from cristalli the amounts of the substances in the reaction zone and growth of the mould.

The rotation speed of the stirrer of the mold is 70-75 rpm

After the installation mode in a solution of Na2CO3extending from the tank to dissolve, set the residual content of H2O20.5 g of H2O2/100 g of the solution and the contents NCl equal to 15 g NaCl/100 g of solution.

Continuously withdrawn from the lower portion of the classifier suspension of particles of percarbonate sodium with a density of about 40 wt.% solid substances.

After 4 hours of work appear inlays in the mould near the device for selection of particles. Experience break after 10 hours of work due to crust formation in the riser of the classifier.

The obtained particles percarbonate sodium have the following characteristics:

The average diameter, Ám - 900

Index of grain-size variation - 1,1

Apparent specific weight kg/l - 0,85

The content of active oxygen, % - 14,3

NaCl content, % - 3

The content of SiO2, % - 0,15

The content of PO4, % - 0,45

Stability in the dry state, the loss of active O, % - 12

Granulometric characteristics determined in the same manner as in example 1R.

Measurement of stability in a dry status is Cafu at 105oC. the Content of active oxygen determined in the usual iodometry in an acidic environment.

Examples 3-5 (according to the invention)

Repeat example 2 after installing the riser-classifier mixer with flat-bars, perpendicular to the axis of rotation, which rotates at a speed of 20 rpm, the Following working conditions are changed in comparison with example 2 (see tab. 1).

The stabilizer DEQUEST2010 is a sodium salt of 1-hydroxyethane-1,1-diphosphonic acid.

Used ammonium polyacrylate is a product brand PIGMENTVERTEILERA sold by the company BASF.

The resulting percarbonate sodium has the following characteristics (see tab. 2).

Measurement of particle size distribution characteristics and stability during drying is conducted according to the same methods as in the previous examples.

1. Continuous method for the production of solid particles of at least one peroxide salt of at least one alkali metal, including interaction of the concentrated aqueous solution of hydrogen peroxide and concentrated aqueous solution of at least one salt of at least one alkali metal and crystallizer contains calm, supermasive, the refining zone which is located above the area of education and growth, which impose solutions of hydrogen peroxide and alkali metal salt, reacting to each other with the formation of a supersaturated solution of peroxide salts, and the area of education and growth is stirred by means of intended for mixing devices and through it passes upward flow of supersaturated solution of peroxide salt and downward flow of particles peroxide salts formed by crystal growth peroxide salts, while the mold is located above the classifier, in which particles peroxide salt is subjected to elutriation and collect in the lower part of the classifier, where they extract.

2. The method according to p. 1, wherein the supersaturated solution of peroxide salts containing at least one wasalive agent and at least one stabilizer, kept in controlled conditions of supersaturation and carry out an upward circulation of the supersaturated solution through a layer of the above-mentioned crystals peroxide salts, which are formed and grow in the area of education and growth, and the resulting particles peroxide salt in the classifier is subjected to elutriation in ascending stream of clarified races who ICEM excess supersaturated solution of peroxide salt is withdrawn from the upper part of the zone of lightening and reinjection in the path of dissolution of salts of alkaline metal.

3. The method according to p. 2, characterized in that the particles that cross the zone classification is subjected to mixing, which carry less energy than mixing in the area of education and growth.

4. The method according to p. 2 or 3, characterized in that a concentrated solution of salts of alkaline metal is injected crystallization additive.

5. The method according to any of paragraphs.1 to 4, characterized in that the density of the suspension in the area of education and support growth at the level of at least 25% solids.

6. Device for producing peroxide salts by crystallization-classification according to any one of paragraphs.1 to 4, comprising a container for crystallization of cylindrical shape, provided with a rotary stirrer and cooling system containing a separation between the lower mixing zone, which is a mixer, and the top of the refining zone without agitators designed for the clarification of liquids, consisting of the mother liquor of crystallization, and the agitation zone in the lower part is equipped with a feeding system reagents, consisting of raw materials to obtain a peroxide salt, the lower part of the vessel for crystallization directly connected to the cylinder with OGA solution, supplied by a pressure pump through the pipeline to filter the clarified solution is withdrawn from the upper part of the zone lighten the vessel for crystallization, and forms a zone classification, carried out by elutriation particles out of the zone mixing device for the escape of particles connected to the bottom of the specified cylinder.

7. Installation according to p. 6, characterized in that the zone classification equipped with a mixer.

8. Installation under item 6 or 7, characterized in that the stirrer vessel for crystallization is a paddle stirrer, equipped with a hollow axle, which is located inside the pipe, the bottom of which communicates with the hollow pipelines along the entire length of the lower blades of the agitator and ending at the ends of these blades.

9. Installation according to any one of paragraphs.6 to 8, characterized in that the cylinder for classification is located on the axis of the capacity of crystallization and connected with him.

 

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