RU2087569C1 - Installation for zinc oxide production - Google Patents

Abstract

FIELD: inorganic materials production. SUBSTANCE: zinc oxide (zinc white) is produced from metal zinc to be applied in rubber and varnish and dye industries. Installation contains apparatus for fusing metal zinc connected with zinc evaporation apparatus coaxially mounted inside zinc vapor oxidation apparatus. The latter is made in the form of parallel annular plates disposed in horizontal plane provided with inlet openings arranged radially along their generatrices and overflow openings in the bottom. Oxidation apparatus has air supply means disposed in side wall of chamber and additionally has gas and air supply means located in the center of upper end wall of its chamber. EFFECT: improved structure. 2 dwg, 1 tbl

Description

 The invention relates to the field of production of metal oxides by a gas-phase method followed by oxidation of metal vapors and can be used in the production of zinc oxide (zinc white) from zinc metal used in the rubber and paint industry.

 At present, muffle furnaces for producing zinc oxide are known, containing a heated chamber with muffles horizontally mounted in it, into which pig zinc is periodically charged, melted and evaporated. Vapors are oxidized in an oxidizing "well" into which air is supplied. Each of the muffles works periodically, but because in the furnace there are a large number of muffles and their loading with zinc is carried out sequentially, then the evaporation of zinc in the furnace proceeds continuously (Kozulin N.A. et al. Equipment of the paint and varnish industry plants. L. Chemistry, 1980, p. 376).

 The disadvantages of the known furnaces are high fuel consumption, rapid wear of the muffles and the lack of uniformity of their work along the length of the furnace, high consumption of zinc and environmental pollution with zinc oxide.

 Of the known devices for producing zinc oxide, the closest in technical essence is the installation for the production of zinc oxide from metal zinc taken by the authors for the prototype, including a device for melting zinc and installed behind it, connected by a collector of zinc vapor, a device for evaporating zinc and oxidizing its vapor, the latter of which it has air supply devices made in the form of tangential nozzles placed at an angle to the vapor stream in the side wall of the chamber (ed. St. USSR N 999231, class B 01 J 19/00, 1981).

 A disadvantage of the known device is that it does not provide sufficient efficiency and environmental friendliness of the process.

This is due to the fact that to obtain 1 kg of finished products in a known installation requires 1.23 kg of standard fuel, while the main heat consumption is accounted for by the evaporation of zinc (75%). The device for the evaporation of zinc is heated by the combustion products of natural gas, which at the outlet of the evaporation device fall into the burs of the installation and are released into the atmosphere. Due to the inevitable leaks of the device for evaporating the presence of cracks in plates and muffles and their frequent breakdowns, zinc vapors enter the flue gases and are lost with them in an average amount of 0.6 0.7 g / nm ³ . In this case, the resulting zinc oxide is scattered into the environment.

 The technical result provided by the invention is to reduce the consumption of raw materials and fuel per unit of production and to prevent losses of zinc from flue gases.

 The specified technical result is achieved by the fact that in the known installation for producing zinc oxide from metallic zinc, including a device for melting zinc and devices behind it for evaporating zinc and oxidizing its vapor, the last of which has devices for supplying air made in the form of tangential nozzles placed at an angle to the vapor flow in the side wall of the chamber, the device for evaporating zinc is coaxially mounted in the cavity of the device for oxidizing zinc vapor and is made in the form of parallel to the horizontal plane of the ring-shaped plates with outlet openings arranged radially along their generators and an opening in the bottom for overflowing molten zinc, and said oxidation device is additionally equipped with an air supply device located in the center of the upper end wall of its chamber.

 Comparative analysis with the prototype allows us to conclude that the inventive installation differs from the known mutual arrangement of the device for evaporation and the device for oxidation of zinc vapor, as well as the form and arrangement of elements of the said device for oxidation.

 Comparison of the claimed technical solution with the prototype made it possible to establish compliance with its criterion of "novelty." In the study of other well-known technical solutions in the art, the features that distinguish the claimed invention from the prototype were not identified, and therefore they provide the invention with the criterion of "inventive step".

 In FIG. 1 schematically shows the proposed installation; in FIG. 2 its cross section.

 The proposed installation includes a device for melting zinc 1, connected by an overflow channel 2 with a device for evaporating zinc 3. The latter is coaxially installed in the chamber of the device for oxidizing zinc vapor 4.

 The mentioned device for the evaporation of zinc 3 is made in the form of ring-shaped plates 5 parallel in parallel to the horizontal plane and divides the chamber of the device for oxidation into two parts, internal 6 and external 7. The plates 5 have outlet openings 8 for zinc vapors arranged radially along their generatrices and openings 9 in the bottom for overflow of molten zinc. The outer and inner parts of the chamber of the oxidation device in the lower part are connected by openings 10 with a white lead 12, which is also a heat exchanger for heating air and heating and melting zinc metal in the melting device 1.

 The aforementioned zinc vapor oxidation device 4 has two air supply devices 13 diametrically disposed in the side wall of the chamber and an air-gas mixture supply device 14 located in the center of the upper end wall of the chamber, connected to the air duct 15 and the gas pipe 16 with a shut-off device 17. the air supply is made in the form of tangentially arranged tuyeres connected by an air duct 18 with an air heater 19 having an air duct 20.

 The proposed installation works as follows.

Solid metal zinc is supplied to the melting device 1. During the start-up of the installation, natural gas and air are supplied via gas line 16 and pipe 15 to the inner part 6 of the chamber of the oxidation device 4. Combustion products pass through the air heater 19, wash the device for melting zinc 1 and through filters are emitted into the atmosphere. In this case, the solid metal zinc in the device is heated, melted and heated to a temperature of 550,600 ^° C, after which the liquid zinc flows by gravity through channel 2 onto the plates 5 of the zinc vaporization device 3, where zinc vapor is generated. The latter through holes 8 enter the inner 6 and outer 7 parts of the chamber of the oxidation device 4. To oxidize zinc vapor with air oxygen, tuyeres 13 and 14 are heated up to 300 400 ^o C. As a result, an intense exothermic oxidation reaction of zinc vapor occurs. This process is carried out at a temperature of 1250 1500 ^o C (adiabatic temperature of the oxidation reaction of zinc vapor in air 2900 ^o C).

 When a stable process of evaporation and oxidation of zinc vapors is achieved, the gas is turned off using the shut-off device 17, and the process is carried out due to the heat of the exothermic reaction.

 The oxidation temperature is controlled by the amount of air supplied and its temperature.

The red-hot products of the oxidation reaction (zinc oxide aerosol) create a temperature of 1000 1100 ^o C in the device for evaporation 3, at which boiling and evaporation of liquid zinc (t $\genfrac{}{}{0ex}{}{\text{Zn}}{\text{bale}}$ 907.5 ^o C). From the chamber of the device for oxidation 4, a zinc oxide aerosol having a temperature of 1000 - 1100 ^o C, through the openings 10 enters the bell pipe 12 and, moving along the latter, gives its heat to heat the air in the air heater 19 and to melt the solid metal zinc in the melting device zinc 1. In this case, the aerosol is cooled to a temperature of 100 to 150 ^o C and fed to the filter equipment (not shown).

 The heat balance of the proposed installation (per 1 kg of zinc oxide) is shown in the table.

что почти в десять раз выше, чем у всех известных действующих цинкобелильных печей.Thus, the thermal efficiency of the proposed installation is equal to
Efficiency

which is almost ten times higher than all known operating zinc-white furnaces.

 The proposed mutual arrangement of devices for the evaporation and oxidation of zinc vapors, as well as the execution of ring-shaped plates of the evaporation device with outlet openings arranged radially along their generators, and the provision of the device for oxidation with a gas and air supply device located in the center of the upper end wall of its chamber allows minimal heat loss and bleached into the environment.

The implementation of the proposed furnace in industry provides a saving of natural gas of 1000 m ³ per ton of zinc oxide produced from metal zinc. This is equivalent to 1.23 tons of fuel equivalent per tonne of product.

Claims (1)

 Installation for producing zinc oxide from metallic zinc, including a device for melting zinc and devices behind it for evaporating zinc and oxidizing its vapors, the last of which has air supply devices located in the side wall of the chamber, characterized in that the device for evaporating zinc coaxially installed in the chamber cavity of the device for oxidizing zinc vapor and is made in the form of ring-shaped plates with outlet openings parallel to the horizontal plane, arranged nnym forming radially, and the opening in the bottom for the overflow of the molten zinc, and said apparatus further oxidation is provided a device for supplying gas and air is disposed in the center of the upper end wall of its chamber.

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