RU2594934C2 - Installation for production of zinc oxide - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to production of zinc oxide from zinc metal. Plant includes device for melting zinc and installed after it device for evaporation of zinc and device for oxidation of zinc vapors, which is made in the form of chamber, containing arranged in the center of the upper end wall the device for supply of natural gas and air. Device for evaporation of zinc coaxially installed inside the chamber cavity of the device for oxidation of zinc vapor and is made in the form of parallel located in horizontal plane ring-shaped disks with arranged radially along generating lines of outlet orifices and an orifice in the bottom for overflow of melted zinc. In the inner formed by ring-shaped disks vertical cavity along the axis and along the whole height the rod with a gap is installed. Ring-shaped disks are made as notched located on inner and outer surfaces at an angle to 90° to the vertical axis, and ratio of inner diameter of ring-shaped disks to their outer diameter is equal to 0.1-0.99.

EFFECT: uniform distribution of zinc vapors and their combustion with formation of zinc oxide crystals with similar structure of the crystal lattice is provided, as well as optimum aerosol speed at which there is no sticking of zinc oxide on walls of disks and lining is provided.

1 cl, 2 dwg

Description

The invention relates to the field of production of metal oxides by a gas-phase method from metal zinc 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 installed in it, into which the 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, quick wear of the muffles and the lack of uniformity of their operation along the length of the furnace, the need for frequent maintenance of the installation, high consumption of zinc and environmental pollution with zinc oxide.

Also known is a plant for producing zinc oxide from metal zinc, 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 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 (ed. St. USSR N 999231, class B01J 19/00, 1981). A disadvantage of the known device is that it does not provide sufficient reliability, since zinc oxide adheres to the walls of the furnace, which reduces heat transfer between the zinc oxide aerosol and liquid zinc in the plates, and as a result forces personnel to stop the furnace for maintenance.

Of the known devices for producing zinc oxide, the closest in technical essence is taken by the authors as a prototype device for producing zinc oxide from metal 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 air supply placed in the side wall of the chamber. The zinc evaporation device is coaxially mounted in the chamber cavity of the zinc vapor oxidation device and is made in the form of ring-shaped plates parallel to the horizontal plane with outlet openings arranged radially along the generatrix and an opening in the bottom for overflowing molten zinc (ed. St. RU 2087569 C1 IPC С22В 19/34). A disadvantage of the known device is the low heat transfer efficiency, which reduces the productivity of the installation. The low speed of the movement of the aerosol of zinc oxide leads to its sticking to the walls of the chamber and the need for its frequent stop to clean the internal surfaces. This leads to a decrease in plant productivity and difficulties in its operation.

The technical result provided by the claimed invention is to increase the productivity of the installation, facilitate maintenance, and ensure uninterrupted operation for a long period of operation without stopping the furnace.

The specified technical result is achieved by the fact that in the proposed installation for producing zinc oxide from metallic zinc, a rod is additionally installed in the cavity between the plates along their entire length, the diameter of which is less than the internal diameter of the plates by the amount of clearance, which ensures full operation when the material expands in the operating temperature range installation and its integrity. The core creates an aerosol velocity, which should be at least 15 m / s, and there is no overgrowing of the living gas cross section, prone to zinc oxide particles sticking to the walls. Also, plates having a ratio of internal diameter to external equal to 0.1-0.99 are located in the oxidation chamber, additionally equipped with notches of any shape. The notches are located on the inner and outer surfaces of the plate at an angle of 0-90 ° to the vertical axis of the furnace. This solution ensures uniform distribution of the zinc vapors leaving the channels and their combustion with the formation of zinc oxide crystals with the same crystal lattice structure, the optimal aerosol movement speed at which zinc oxide does not adhere to the walls of the plates and the furnace lining in contact with zinc oxide aerosol.

In FIG. 1 shows a diagram of an apparatus for producing zinc oxide a) in general form, b) a transverse section, c) a longitudinal section, in FIG. 2 - plate in a) general view, b) top view, c) cross section

The device comprises a device for melting solid zinc (1), air ducts (2), distribution manifolds (3), an air heater (4), horizontally arranged plates (5), openings (6), white pipe (7), an oxidation chamber (8), a rod in the oxidation chamber (9), air supply to the air heater (10), from the air heater (11), a nozzle for supplying liquid zinc (12), notches on the inner and outer surfaces of the plates (13), nozzles for the release of zinc vapor from the plates ( 14), overflow holes in the plates for the flow of zinc from one plate to another (fifteen).

The device operates 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 through the air ducts 2 to the distribution manifolds 3. Combustion products pass through the air heater 4, wash the zinc melting device 1 and are emitted through the filters into the atmosphere. In this case, the solid metal zinc located in the device for melting zinc 1 is heated, melted, and heated to a temperature of 550–600 ° C, after which liquid zinc flows by gravity through channel 12 onto plates 5 located in the oxidation chamber 8. For oxidizing zinc vapors with air oxygen air ducts 2 air heated to 300-400 ° C is supplied. As a result, an intense exothermic oxidation reaction of zinc vapor occurs. This process is carried out at a temperature of 1250– 1500 ° C (the adiabatic temperature of the oxidation reaction of zinc vapor in air is 2900 ° C).

When a stable process of evaporation and oxidation of zinc vapor is achieved, the gas is turned off, 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.

Liquid zinc from melting chamber 1 through pipe 12 enters the upper plate 5 and through overflow openings 15 liquid zinc from the upper plate enters all others, liquid zinc is heated and evaporated in the plates 5 turns into zinc vapor and through nozzles 14 enter the oxidation chamber 8 representing the gap between the plates and the lining on the one hand and the plates and the rod 9 on the other hand.

). Из камеры окисления 8 аэрозоль окиси цинка через проемы 6 поступает в белилопровод 7 и, продвигаясь по последнему, отдает свое тепло на подогрев воздуха в воздухоподогревателе 4 и на плавление твердого металлического цинка в устройстве для плавления цинка 1. При этом аэрозоль охлаждается до температуры 100-150°C и подается на фильтрационную аппаратуру (не показано).The red-hot products of the oxidation reaction (zinc oxide aerosol) create a temperature of 1100-1800 ° C around plates 5 at which boiling and evaporation of liquid zinc ( $$t_{\mathrm{to}\mathrm{and}P}^{Zn}907.5°C$$

) From the oxidation chamber 8, the zinc oxide aerosol through the openings 6 enters the belilovod 7 and, moving along the latter, gives its heat to heat the air in the air heater 4 and to melt the solid metal zinc in the device for melting zinc 1. The aerosol is cooled to a temperature of 100- 150 ° C and fed to filtration equipment (not shown).

Claims (1)

Installation for producing zinc oxide from metal zinc, containing a device for melting zinc and a device for evaporating zinc and an apparatus for oxidizing zinc vapor, which is arranged in the form of a chamber containing a device for supplying natural gas and air, located in the center of the upper end wall, wherein the device for the evaporation of zinc is coaxially mounted in the chamber cavity of the device for oxidizing zinc vapor and is made in the form of a ring parallel to the horizontal plane different plates with radially arranged outlet openings and an opening in the bottom for overflowing molten zinc, characterized in that it is provided with a rod mounted along the axis and along the entire height in the inner cavity formed by the ring-shaped plates of the vertical cavity with a gap and made with a diameter smaller than the inner diameter of the ring-shaped plates on the size of the gap, ensuring the speed of movement of the aerosol of zinc oxide is not less than 15 m / s, while the ring-shaped plates are made with notches located and inner and outer surfaces at an angle of 90 ° to the vertical axis and the ratio of the inner diameter of annular tareli to their outer diameter is equal 0,1-0,99.

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