RU2542245C2 - Method of obtaining dry zinc white and installation for method realisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of obtaining dry zinc white includes zinc evaporation in evaporation furnace at temperature 1200-1350°C and vacuum in the system furnace-exhaust fan 50-100 Pa from the surface of zinc melt 3-5 m² with thickness of zinc melt 250-350 mm. Removal of zinc vapours from the evaporation zone is realised at the height 450-55 mm from the melt surface. Layer of zinc melt is heated from both sides of furnace due to combustion of natural gas in zones of heating, separated from zinc melt with brickwork of refractory bricks. Zones of heating are divided into 1200-1350 mm long sections. After that, oxidation of zinc vapours in reactor of dry zinc white synthesis is carried out with air oxygen heated to 180-300°C. Air intake is performed from the height of 10-15 m. Mixing of zinc vapours and air is carried out for not less than 2 s in mode of tangential introduction of their flows from the opposite sides of reactor. Obtained aerosol of dry zinc white is transported by whitewash line into section of zinc white and air separation. After that, collection of zinc white in tanks and discharge into packing containers are carried out.

EFFECT: invention makes it possible to reduce loss of zinc, dry zinc white and natural gas consumption, increase output of product, obtain finely disperse dry zinc white of high quality in continuous mode for 2-3 months.

6 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of metallurgical and chemical industries and can be used for the production of dry zinc oxide consumed in the manufacture of rubber products and tires, paints and varnishes, artificial leather and plantar rubbers, electrical cables, dental, medicinal substances and other materials.

A known muffle method for producing dry zinc oxide, including loading zinc ingots into muffles heated to 1250-1450 ° C, evaporating zinc, transporting zinc vapors from muffles to an oxidizing chamber due to rarefaction in the oxidizing chamber - exhaust fan system, where zinc vapor is oxidized by oxygen air with the formation of an aerosol of dry zinc oxide, which is transported as a result of rarefaction along the boron, aluminum oxide pipe through the equalization chamber to the filter compartment, where air is separated and zinc oxide, which accumulate in bunkers, from which they are periodically unloaded into packaging containers (Orlova OV, Fomicheva TN, Okunchikova A.3., Kursky GR “Technology of varnishes and paints”, Study guide for technical schools, M., Chemistry, 1980, p. 211-212, 371-372).

The known muffle method for the production of dry zinc oxide has the following disadvantages:

- significant laboriousness, harmful working conditions associated with loading zinc ingots into hot muffles as they evaporate, replacing muffles that have fallen out of order with new ones;

- high operating costs associated with the purchase of heat-resistant muffles.

A known method for the production of dry zinc oxide, in which the loading of zinc in the muffle is carried out in the form of a melt obtained in the prefixes to the muffle at a temperature of 500 ° C (copyright certificate SU 53566, class F27B, 5 / 00.1938 g).

This known method has the same disadvantages, with the exception of the inconvenience of loading zinc ingots into muffles heated to a temperature of 1250-1450 ° C.

A known muffle method for producing dry zinc oxide, taken by us as a prototype, which differs from the above in that the muffle furnace is divided into two autonomously working sections. The loading of zinc in the muffle is carried out in the form of a melt obtained in the prefixes to the muffle. Replacement of failed muffles is carried out during the stop of one of the sections and cooling of the furnace and muffles. This greatly improves the production conditions of dry zinc oxide, however, this method also has disadvantages:

- the stability and continuity of the furnace depends on the serviceability of the muffles, which often fail due to cracking;

- the replacement of the muffles is the reason for the prolonged shutdown of the furnace section and, consequently, leads to a decrease in furnace productivity, as well as to additional costs for the purchase of expensive muffles, which leads to an increase in the cost of dry zinc oxide (RF patent No. 2398802, published September 10, 2010, Bulletin No. 25)

The objective of the proposed method for producing dry zinc oxide, not inferior in quality to muffle, is to eliminate the above disadvantages of the muffle method for producing dry zinc oxide, to reduce the loss of zinc and dry zinc oxide, to increase the yield of dry zinc oxide in high quality, to eliminate labor-intensive and harmful production conditions, to create a process production of dry zinc oxide in continuous mode for two to three months with a stop for routine inspection and repair of process equipment one week, reducing operating costs and cost of dry zinc oxide.

A method of obtaining dry zinc oxide is as follows.

The burners are turned on in the zones of heating of the melting furnaces (Fig. 1, pos. 3) and the longitudinal zinc evaporation furnace (Fig. 2, pos. 21), the furnaces are heated to a temperature of 700-800 ° C, then in the melting furnace (Fig. 1, 2, item 1) zinc ingots containing not more than 0.5% impurities are loaded, zinc ingots are loaded in the melting furnace continuously as they are melted and zinc melt flows into the evaporation furnace through a heat-resistant ceramic pipe (Fig. 1, 2, pos. . 8).

The composition of the proposed technological equipment for the installation of dry zinc oxide is shown in Fig. 1 (side view) and fig. 2 (top view).

Fig. 1. Installation for obtaining dry zinc oxide (side view)

No. of positions:

1. A furnace for smelting zinc ingots made of refractory bricks with a metal casing and covers made of heat-resistant steel, having a thickness of 20 mm. and lined with reinforced heat-resistant concrete.

2. The crucible of furnaces, laid out of refractory bricks, the thickness of the masonry is 120 mm .. the internal diameter of the crucible of the melting furnace is 300-350 mm, the height of the crucible is 1000-1200 mm.

3. The heating zones of the furnaces, the width of the zones 200-250 mm, the heating zones are divided into sections by brickwork, the length of the plot is 1200-1300 mm.

4. Gas burners having a tangential input, operating in automatic mode with the ability to maintain the set temperature in the crucible of the furnace.

5. The gas pipeline has a security system and automatic provision for switching on and off the supply of natural gas to the burners.

6. Heat-resistant ceramic pipe to remove natural gas combustion products from the crucible heating zone of the furnace into a discharge system into the atmosphere.

7. Zinc melt having a temperature of 600-700 ° C.

8. Heat-resistant ceramic pipe having an inner diameter of 100-150 mm for loading the zinc evaporation furnace with its melt.

9. Furnace for the evaporation of zinc from a melt having a temperature of 1200-1350 ° C.

10. Zinc melt in the evaporation zone, having dimensions (450-500) mm × (7000-9000) mm, the melt thickness is maintained in the range of 250-350 mm, the melting rate of the zinc ingots in the furnace, pos. one.

11. Heat-resistant ceramic pipe having an inner diameter of 350-400 mm, to remove zinc vapor in the synthesis reactor of aggregates of dry zinc oxide crystals.

12. The reactor for the synthesis of aggregates of crystals of cubic form of dry zinc oxide, laid out of refractory bricks on a refractory mortar and having dimensions: the inner diameter of the horizontal drawer is 1500 mm, the length of the drawer is 1700 mm.

13. The tangential introduction of zinc vapor through a refractory ceramic pipe having an inner diameter of 350-400 mm.

14. The tangential introduction of air having a temperature of 180-300 ° C, through a steel pipe having an inner diameter of 100-150 mm.

15. Refractory ceramic pipe having an internal size of 400-500 mm, for the exit of the aerosol of dry zinc oxide in the burs.

16. Hog, laid out of refractory brick on a refractory mortar having internal dimensions: width 600-800 mm, height 600-800 mm, length 5000 mm.

17. Beliloprovod - steel pipe, having dimensions: pipe wall thickness 12 mm, inner diameter 450-500 mm, length 90-100 m.

18. A recuperator that provides heating of air to a temperature of 180-300 ° C, taken by a pressure fan from a height of 10-15 m.

19. Air inlet from the pressure fan to the recuperator.

20. The outlet of heated air from the recuperator to the synthesis reactor of dry zinc oxide through a steel pipe having an inner diameter of 100-150 mm

Fig. 2. Installation for obtaining dry zinc oxide (top view)

No. of positions:

1. Zinc ingots melting furnaces.

2. Crucible furnaces.

3. The zones of heating crucible furnaces as a result of natural gas combustion.

8. Refractory ceramic pipes for feeding zinc melt from smelting furnaces to a zinc evaporation furnace.

9. Zinc evaporation furnace.

11. Refractory ceramic pipe having an inner diameter of 350-400 mm, for the exit of the stream of zinc vapor from the zone of evaporation of the furnace into the reactor for the synthesis of dry zinc oxide.

12. The synthesis reactor of dry zinc oxide, laid out of refractory bricks on a refractory mortar, having internal dimensions: the diameter of the horizontal drawer 1500 mm, the length of the drawer 1700 mm.

15. Refractory ceramic pipe for the release of an aerosol of dry zinc white in the burs.

16. Hog, laid out of refractory bricks on a refractory mortar.

17. Beliloprovod.

18. A recuperator for heating the air supplied to the synthesis reactor of dry zinc oxide.

19. Air supply by pressure fan to the recuperator.

21. Section of the heating zones of the zinc melt in the zone of its evaporation.

22. The partition dividing the heating zone and the evaporation zone of zinc, laid out of refractory bricks on a refractory mortar, the thickness of the masonry is 120 mm.

23. Masonry made of refractory bricks, dividing the heating zones of the zinc evaporation furnace into sections with a length of 1200-1350 mm.

24. The zone of evaporation of zinc from the melt, having dimensions: width 450-500 mm, length 7000-9000 mm, melt thickness 250-300 mm.

25. Supply of air heated in a recuperator to a dry zinc oxide synthesis reactor.

After reaching the temperature in the furnaces (Fig. 1, 2, item 1) 600–700 ° C and the zinc melt entering the furnace for evaporation (Fig. 1, 2, item 9), the evaporation zone is purged with nitrogen for 2–5 min every hour until the zinc reaches its boiling point in the evaporation furnace, then nitrogen purge is stopped. The intensity of loading the zinc melt into the evaporation furnace (Fig. 1, 2, item 9) is controlled so that the thickness of the zinc melt layer in the evaporation furnace (Fig. 1, item 10) is 250-300 mm. The temperature of the zinc melt in the evaporation zone is brought to 1350 ° C, the vacuum in the system of the evaporation furnace - exhaust fan is maintained in the range of 50-100 Pa, by adjusting the suction of the dry zinc oxide aerosol on the pressure fan. The resulting zinc vapors in an evaporation furnace, which have a surface of an evaporating zinc layer of 3-5 square meters, a thickness of an evaporating zinc melt layer of 250-350 mm, a zinc melt layer width of 450-500 mm, are sent to a synthesis reactor (Fig. 1, 2, item 12) of dry zinc oxide through a ceramic refractory pipe (Fig. 2, item 11), which has an internal diameter of 350-400 mm and is located at a height of 450-550 mm from the surface of evaporating zinc. At the same time, air heated in the recuperator (fig. 1, 2, pos. 18) to a temperature of 180-300 ° C is sent to the synthesis reactor of dry zinc oxide (Fig. 1, 2, item 12) through a steel pipe (Fig. 2 , item 25), having an internal diameter of 100-150 mm, the ratio of zinc vapor and air, calculated on their mass, is 1.94: 1.0. The synthesis reactor for dry zinc oxide is a tsar, lined with refractory bricks on a refractory mortar and having dimensions: inner diameter 1500 mm, length 1700 mm. Intensive mixing of zinc and air vapors takes place in the dry zinc oxide reactor, where the flows of zinc and air vapors are directed by tangential inlet. The volume of the dry zinc oxide synthesis reactor allows mixed zinc and air vapors to remain in it for 2 seconds, and the temperature of the mixed gases 1100-1200 ° C ensures the complete oxidation of zinc and the formation of zinc oxide, as well as the formation of fine crystals of dry zinc oxide with dimensions 0.5-5.0 microns. The dry zinc oxide aerosol from the synthesis reactor enters through a heat-resistant ceramic pipe (Fig. 1, 2, pos. 15) into the boron (Fig. 1, 2, pos. 16), lined with refractory brick, where the aerosol temperature drops to 600-800 ° C, then along the white line (Fig. 1, 2, item 17), the dry zinc oxide aerosol enters the area of the installed recuperator (Fig. 1, 2, item 18), where its temperature drops to 300-400 ° C, then passing through the belly pipe to the exhaust fan, the aerosol temperature decreases to 200-300 ° C, the aerosol entering the cyclone is cooled to 150-200 ° C, after the cycle bosom, passing through the bell pipe to the bag filters, the temperature of the aerosol is reduced to 100-150 ° C, which is acceptable for the bag filter material and that ensures removal through the bag filters along with air and moisture introduced into the aerosol along with air at the stage of synthesis of dry zinc white . Air intake for the synthesis of dry zinc oxide at a height of 10-15 m prevents pollution of zinc oxide with industrial dust.

After continuous operation of the plant for two to three months, the zinc ingots in the melting furnace are stopped melting, the zinc melt in the evaporation furnace is fully developed, then the gas burners are turned off, the processing equipment is cooled and its preventive inspection and repair are carried out for a week. To stop the installation for routine inspection, cleaning and repair, the crucibles of the zinc melting furnaces are purged with nitrogen and hermetically sealed with covers. After the charged zinc is fully developed in the melting furnace and the evaporation furnace, the gas burners are turned off, the lids of the crucibles of the melting furnaces are removed, the manholes are opened in the ceiling of the zinc evaporation zone, and after the furnaces are cooled, preventive inspection, cleaning and repair are performed. After conducting a routine inspection and repair of technological equipment, the installation is again launched into continuous work on the production of dry zinc oxide, as described above.

The technological parameters of the known (RF patent No. 2398802, bull. No. 25, 05/27/2010) and the proposed methods for producing dry zinc oxide are presented in table 1

Example

The composition of the ingots of zinc, wt. %:

Zinc metal - 99.5

Impurities - 0.5

As follows from table 1, the technological parameters of the proposed method for producing dry zinc oxide is superior to the same parameters by a known method.

Claims (6)

1. A method of producing dry zinc oxide by evaporation of zinc at high temperature and vacuum in the furnace-exhaust fan system, oxidizing zinc vapor with air oxygen to form an aerosol of dry zinc oxide, transporting them through the piping line to the separation unit of zinc oxide and air, collecting zinc oxide in hoppers, unloading in packaging containers, characterized in that the evaporation of zinc is carried out at a temperature of 1200-1350 ° C and with a vacuum in the furnace-exhaust fan system, equal to 50-100 Pa, from the surface of the zinc melt, Commercially area 3-5 m ² and a thickness of the molten zinc layer, equal to 250-350 mm, removal of the zinc vapor from the vaporization zone it is carried out at a height of 450-550 mm from the surface of molten zinc, molten zinc surface has a width of 450-500 mm, a length of 7000 -9000 mm, the zinc melt layer is heated on both sides of the furnace by burning natural gas in the heating zones separated from the zinc melt by refractory brick masonry, the heating zones are divided into sections having a length of 1200-1350 mm, the zinc vapor is oxidized in the synthesis reactor aggregates of crystals of dry zinc filled with atmospheric oxygen heated to a temperature of 180-300 ° C, air intake is carried out from a height of 10-15 m, zinc and air vapors are mixed in the mode of tangential entry of their flows from opposite sides of the reactor, air is heated in a recuperator mounted on the line of the white line immediately after boron, the mixing of zinc vapor and air in the reactor is carried out for at least two seconds, while finely dispersed aggregates of crystals of dry zinc oxide of white cubic form are formed. 2. The method according to p. 1, characterized in that the loading of zinc into the evaporation zone is carried out continuously by melting the ingots of zinc in furnaces installed at the ends of the evaporation furnace, the temperature of the zinc melt supplied to the evaporation zone is 600-700 ° C. 3. The method according to p. 1 characterized in that the production of dry zinc oxide is carried out continuously for 2-3 months, then the loading of the zinc melt in the evaporation furnace is stopped, the remaining zinc melt in the evaporation furnace is fully developed, the burners in the heating sections are turned off and Perform routine inspection and repair of the furnace. 4. Installation for implementing the method of producing dry zinc oxide according to paragraphs. 1-3, characterized in that the zinc evaporation furnace consists of natural gas heating sections located on both sides of the zinc evaporation zone, in which the zinc melt has an evaporation surface of (450-500) mm × (7000-9000) mm and the melt thickness is 250-350 mm, the length of each section of the heating zone is 1200-1350 mm, the output of the zinc vapor stream is mounted by a refractory ceramic pipe having an inner diameter of 350-400 mm and located at a height of 450-550 mm from the surface of the zinc melt, at the ends of the furnace two vertical furnaces installed To melt the zinc ingots and load the zinc melt into the furnace for its evaporation through refractory ceramic pipes having an inner diameter of 100-150 mm and installed at the bottom of the furnaces, the crucibles of the zinc melting furnaces have an inner diameter of 300-350 mm and a height of 1000-1200 mm and lined with refractory bricks on a refractory mortar, masonry thickness 120 mm, furnace crucible heating zones have a width of 200 mm, gas burners in the heating zones are located in the upper part, and the combustion products of natural gas are removed using refractory ceramic their tubes mounted at the bottom of the heating zone. 5. The installation according to claim 4, characterized in that it has a separately installed dry zinc oxide synthesis reactor having the following dimensions: the inner diameter of the horizontally laid collet is 1500 mm, the length inside the collet is 1700 mm, the reactor has a tangential entry of refractory zinc vapor flows a ceramic pipe with an internal diameter of 350-400 mm and air - a steel pipe with an internal diameter of 100-150 mm, the introduction of zinc and air vapors was carried out from opposite sides of the cylindrical reactor, the introduction of zinc vapors was made in the upper Asti, and air - into the bottom of the reactor, the reactor outlet formed aerosol of dry zinc oxide in burs formed refractory ceramic tube having an inner diameter of 400-500 mm. 6. Installation according to claim 4, characterized in that the heating of the air for supplying dry zinc oxide synthesis to the reactor is carried out in a recuperator mounted on the line of the gas pipeline directly after the hog.

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