RU2245843C2 - Installation for production of granular sodium percarbonate - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: the invention is intended for a chemical industry and may be used in production of bleaching agents and washing agent, household chemical goods. The reactor (1) is fed with soda ash, for example in the form of a solution, through sleeves(5) and a link (7) and hydrogen peroxide solution through a link (6). The sleeves (5)allow to move the reactor (1) along the auger of the mixer (2). Humid granules of sodium percarbonate produced in the mixer (2) are removed through a connecting pipe (9) into a dryer (3) supplied with a gas-distributing lattice (10). One part of the dried granules through a connecting pipe (8) is fed back into the mixer (2), and other part through link (15) is fed into the qualifier (4). A commercial fraction of sodium percarbonate is removed through link (16) into a pneumatic classifier (20). The fine fraction through link (22) and through the cyclone separator (13) and link (14) is fed back into the mixer. The coarse fractions of sodium percarbonate from the qualifier (4) is fed through link (17) into the grinding machine (18). Crushed sodium percarbonate is mixed with the fine fractions and through the cyclone separator (13) and through link (14) is fed back into the mixer (2). The invention allows to decrease the share of a dust faction down to 0.10 - 0.63 % and losses at drying, to increase the share of active oxygen up to 13.91-14.01 % and stability of the finished product.

EFFECT: the invention ensures reduction of the share of a dust faction up to 0.10 - 0.63 % and losses at drying, an increase of the share of active oxygen up to 13.91-14.01 % and stability of the finished product.

4 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of inorganic chemistry, and in particular to installations for the production of granular sodium percarbonate, which is used as a component of detergents and bleaches, and can be used in the chemical industry in the production of household chemicals.

A known plant for producing granular sodium percarbonate containing a calcined soda solution preparation unit, a soda ash solution filtration unit, a soda ash supply line, a hydrogen peroxide solution supply line, and a reactor, auger mixer, dryer, and classifier comprising a product fraction outlet line of the target product are connected in series , a line for withdrawing coarse fractions to the mill and a line for returning the coarse fractions to the mixer as a reture (see RU 2164215).

The objective of the invention is to increase the productivity of the installation, as well as improving the quality of the resulting target product.

The problem is solved by the installation for producing granular sodium percarbonate containing a calcined soda solution preparation unit, a soda ash solution filtration unit, a soda ash supply line, a hydrogen peroxide solution supply line and a reactor, auger mixer, dryer and classifier containing a product fraction withdrawal line the target product, the line of removal of the coarse fraction to the mill and the line of return of the coarse fraction to the mixer as a retur, while p The reactor is movable along the auger of the mixer, and the supply lines are provided with flexible hoses.

In private embodiments of the invention, the calcined soda solution preparation unit and / or the filtration unit and / or the soda solution supply line are equipped with ultrasonic radiation units, and an additional pneumatic classifier is installed on the outlet line for the product fraction.

The drive motors of the auger of the mixer and mill can be equipped with a frequency regulator.

The drawing shows a diagram of an installation for producing granular sodium percarbonate.

The apparatus for producing granular sodium percarbonate includes a calcined soda solution preparation unit, a soda ash solution filtration unit (not shown), a supply system connected in series

reagents in the form of a reactor 1, a mixer 2, a fluidized bed dryer 3 and a means for separating granules into fractions according to particle sizes - classifier 4. The reactor 1 is installed directly on the mixer 2.

The mixer 2 is a twin-screw conveyor, equipped with an engine with an adjustable number of revolutions of the screws, and consists of a housing in which two screws are placed, rotating in opposite directions. A frequency regulator (not shown in the drawing) can be installed on the auger motor, which allows varying the auger performance for finer adjustment of the formation of granules of a given composition.

The upper part of the screw conveyor of the mixer 2, on which the reactor is mounted, is closed with removable metal plates in sections about 400 mm long. Flexible metal hoses 5 connect the hydrogen peroxide supply line 6 and the soda ash supply line 7 to the reactor 1. Line 7 is connected to the nodes for preparing the soda ash solution and its filtration (not shown in the drawing). These nodes and the soda ash supply line may preferably be equipped with ultrasonic radiation units — either one of the nodes, or both, or line 7, or a line in combination with one or both nodes. The most effective option is when an ultrasonic installation of the USP-900 type is mounted on the unit for preparing a solution of soda ash, and an ultrasonic installation of the USP-300 type is mounted on the solution supply unit (not shown in the drawing).

The mixer 2 is in communication with the dryer 3 with a nozzle 8 for introducing dried granules located in the lower part of the mixer 2 in the zone of output of granules into the classifier 4, and a nozzle 9 for discharging wet granules located in the upper part of the mixer 2. The dryer 3 has a rectangular cross section and a gas distribution grill 10 with gaps of 6, 5, 4, 3 mm.

The reactor 1, mixer 2 and dryer 3 are interconnected so that they are a single module that provides minimal transport paths and the return of hot retur, which can significantly reduce energy costs for moving granules and heating the retur.

The dust collection unit is connected to the dryer 3 by line 11 and includes a cascade of dust gas purification devices (cyclones 12 and 13), from which dry dusty sodium percarbonate after collection is returned to mixer 2 along the fine fraction return lines 14 and used as a retur, and purified air emitted into the atmosphere.

Classifier 4 is a two-stage vibrating screen, which is connected by line 15 to dryer 3 in the zone of entry of dried granules and from which the middle (marketable) target fraction is selected as the target product on line 16, the coarse fraction is fed to mill 18 along the coarse fraction withdrawal line 17, and the fine fraction is combined with the fraction after grinding and is sent back through line 19 to mixer 2 as a retura. On line 16 there is a pneumatic type classifier 20 connected to compressed air line 21 and line 22.

Installation for producing granular PKN works as follows.

Granulation of sodium percarbonate (PCN) is carried out by building up layers of PCN on the seed particles with which the mixer 2 and dryer 3 are filled. As seed particles, retur granules and fine particles (dust) of PCN are used that are returned to the mixer 2 - dryer 3 module.

In dryer 3, moisture is removed from the PCN particles by the heat carrier fluid in the fluidized bed mode. The exhaust air through the duct - line 11 enters the dust collection unit. From cyclone 12, purified air is discharged into the atmosphere, and the captured dust is returned via line 14 to the inlet of mixer 2.

The input of the mixer 2 also receives crushed PKN from an additional cyclone 13 along line 14.

Reagents 1 from the feed lines of soda ash 7 and hydrogen peroxide enter the reactor 1 through the sleeves 5. The solution of soda ash undergoes preliminary ultrasonic treatment in the unit for preparing the solution of soda ash, which reduces the dissolution time to obtain a concentration of 19.0-22.5% in 2 -4 times and reduces power consumption to 0.8 kW / h. The use of an ultrasonic installation on the pipeline significantly reduces salt deposits, which allows to increase the overhaul period by 3-5 times.

Hydrogen peroxide on the supply line is connected with a stabilizer of soda ash, for example sodium sulfate. Such a supply of reagents helps to prevent the pipelines from overgrowing with magnesium silicates and reduce equipment pollution, which, in turn, will increase the productivity of the process, and also allows to increase product stability (see table).

Streams of appropriately prepared aqueous solutions of soda ash and hydrogen peroxide are combined in the reactor 1 in the reaction mass. Obtained during their mixing, the reaction mass through line 23 through a film-type sprinkler-distributor enters the mixer 2.

Flexible metal hoses 5 allow you to move the reactor 1 along the mixer 2 by removing the corresponding metal installation in this section of the reactor 1.

The ability to move the reactor 1 along the mixer 2 allows you to change the feed location of the reaction mass and thereby control the humidity, particle size and, accordingly, adjust the productivity and increase the number of granules of the target fraction. This makes it possible to conduct the process in an optimal mode with minimal energy consumption.

At the entrance to the mixer 2 is a mixture of pulverized and powdered sodium percarbonate, forming seed particles. The ability to move the reactor along the mixer allows you to adjust the humidity, part size and, accordingly, to regulate the performance and increase the number of particles of the target fraction.

In mixer 2, the reaction mass is distributed over the surface of the seed particles and wetts small particles of PCN on their surface. The wet mixing process lasts no more than 30-40 seconds, after which the wet granules through the pipe 9 are discharged into the dryer 3.

Through the gas distribution grid 10 of the dryer 3 at the inlet section (from the pipe side) 7, additional flue gas blowing occurs, which contributes to the rapid distribution of the moistened material across the width of the dryer 3. The increased live section of the gas distribution grid 10 at the inlet section of the dryer 3 prevents the accumulation of large product particles at the entrance to dryer 3.

One part of the dried granules PKN from the dryer 3 through the pipe 8 is returned to the mixer 2, and the other part through line 15 enters the classifier 4.

Commodity fraction of medium size (from 0.1 to 1.0 mm) contains up to 15% of particles with particle size distribution from 0.1 to 0.16 mm. Particles with this size have minimal stability.

To improve stability indicators, the product fraction from the intermediate part of the classifier 4 through line 16 enters the pneumatic classifier 20.

Pneumatic classifier 20 is intended for cooling percarbonate and blowing out fine particles from it when packing from the main classifier 4 into containers.

The pneumatic classifier 20 is a vertical cylindrical vessel, inside of which, in a checkerboard pattern, plates are welded at a 45 ° angle to the horizontal.

In the process, granules from the pneumatic classifier 4 enter the upper fitting of the pneumatic classifier 20 with a mass supply of 600-900 kg / h.

Compressed air is supplied to the lower part of the pneumatic classifier 20 through a lateral fitting, in a countercurrent flow of sodium percarbonate strewn across the plate cascade.

Air with PKN dust through lateral outlets from the pneumatic classifier housing 20 through line 22 enters cyclone 13, from which the separated dust is returned to the auger mixers 2 via line 14 using gateway feeders.

The compressed air supply is controlled so that the vacuum in the dust suction line is within (-30) ~ (-40) mm water column.

Cooled and dust-free PCN is poured into the container through the lower nipple of the classifier.

Coarse fractions from classifier 4 are sent to mill 18 via line 17. A frequency regulator is installed in the mill to control the particle size distribution of the crushed particles returned to the mixer.

The crushed percarbonate is mixed with small fractions and enters the injector 23, from where it is sent by a stream of compressed air through line 21 to an additional cyclone 13 and after that it returns to mixer 2 via line 14.

With a selected rotation speed of mixer 2 (screw conveyor) of 66 rpm, providing a dryer productivity of 800 kg / h, reture residence time in screws is 55 sec, and the contact time of the sodium percarbonate solution with the mass changes from the position of reactor 1 relative to the discharge window retura in a state of mixing without boiling in the fluidized bed. Since in the mixer 2 the retur of sodium percarbonate has a temperature of 55-62 ° C, and in the dryer 3 with a fluidized bed 68-72 ° C, the process of formation, growth of granules and the initial stage of drying occurs in the mixer 2 uniformly and under milder conditions, which allows you to get a larger amount of the required size and strength. In the fluidized bed dryer 3, the product is brought to a residual moisture content of not more than 3% (according to the TU standard), as a result of which part of the granules is destroyed, and the yield of the target product decreases. Since the target product is a mixture of granules of various sizes from 0.1 to 1.6 mm, where the most preferred is a range from 450 to 950 microns, the component of the product with a granule size of less than 400 microns significantly affects such indicators as product stability, average grain size, bulk density and final moisture content of the product. Since the dust fraction collected on the vibrating screen is recycled and fed into the lower part of mixer 2 as retur, its quantity proportionally affects the moisture content of the product in mixer 2 after reactor 1. The optimal product humidity at the discharge window to dryer 3 (for the above

conditions) is determined at the level of 7 ± 2%. With a decrease in humidity, the proportion of small granules increases, and when exceeded, it is possible to “bite” the mass and terminate the process.

The table shows examples of the operation of the installation at different positions of the reactor 1 relative to the discharge window from the mixer 2 to the dryer 3.

Table Indicators No. L mm Wed Granule size μR ** Bulk density g / cm ^{3 *} Contents dust fraction 0.1 mm,% * Contents active oxygen% * Humidity (% loss on drying) IKP Stability Conv. units. * (% oxygen loss **) 1 1000 580 1.25 1.80 13.84 2,30 4.05 2 1500 701 1.23 0.63 13.91 1.95 3.99 3 2000 728 1.21 0.35 13,99 1.78 3.84 4 2500 763 1.19 0.10 14.01 1.71 3,51 5 3000 716 1.20 0.56 13.78 1.86 3.70 * - Data on average values for 10 days of continuous operation in a stationary mode of operation of the circuit with regulatory parameters.
** - 15 hours 65 ° C, 100% humidity.
L is the distance from the reactor to the discharge window in millimeters.

When changing the rotation speed of the mixer 2, the productivity of the dryer 3 (load of solutions on the reactor 1), the optimal position of the reactor 1 must be selected again to achieve the required product performance (the highest value of active oxygen and stability of the product with minimal moisture and bulk density).

Claims (4)

1. Installation for producing granular sodium percarbonate containing a supply line of soda ash, a supply line of a solution of hydrogen peroxide and series-connected reactor, auger mixer, dryer and classifier connected to the withdrawal line of the commercial fraction of the target product and the withdrawal line of the coarse fraction to the mill, and a line returning the fine fraction to the mixer as a retur, characterized in that the reactor is arranged to move along the mixer screw, and the supply line of soda ash and raster ora hydrogen peroxide are provided with flexible hoses. 2. Installation according to claim 1, characterized in that it is equipped with a unit for preparing a solution of soda ash and a unit for filtering a solution of soda ash, while the unit for preparing a solution of soda ash, and / or a unit for filtering a solution of soda ash, and / or a supply line for soda ash ultrasonic radiation installations 3. Installation according to claim 1, characterized in that an additional classifier of a pneumatic type is installed on the discharge line of the product fraction. 4. Installation according to claim 1, characterized in that the drive motors of the auger of the mixer and mill are equipped with a frequency controller