RU2393064C1 - Method of producing finely dispersed zinc powder for antirust paints and plant to this end - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to production of zinc powder and can be used in production of antirust paints from zinc-containing stock. Zinc, not containing metal oxide admixtures, is heated, melted and evaporated in furnace at boiling temperature and above it in atmosphere of nitrogen. Zinc vapors are transferred via steam line by rarefaction produced by blower and equal to 50-150 Pa and cooled in steam line abrupt-cooling zone to produce powder. Zinc powder, in getting into magnetic trap built in dust duct, downstream of steam line abrupt-cooling zone, is purified of intermetallic compounds. Pure finely-dispersed zinc powder containing 99.95% of metallic zinc and with dispersity of 0.5-5 mcm comes into cyclone to get settled on hopper, while more fine zinc powder is entrapped by sleeve filter mounted downstream of exhaust blower. ^ EFFECT: higher powder quality, expanded application, perfected production hardware. ^ 4 cl, 2 tbl, 1 dwg

Description

The invention relates to the production of pigmented zinc powder and can be used in the production of zinc-containing raw materials that do not contain metal oxides as impurities, finely dispersed high-purity zinc powder for anticorrosion paints.

A known method of producing zinc dust (pigment powder) by the method of rapid condensation of zinc vapor in an inert medium (carbon dioxide or nitrogen), selected as a prototype. To obtain zinc vapor, muffle furnaces are used, similar to those used to produce zinc oxide. Instead of an oxidizing well, these furnaces are equipped with steel sheet capacitors. Zinc vapor is transported to the capacitors by an inert gas supplied to the muffle. During vapor condensation, particles of 10-20 microns in size are formed, which fall on the bottom of the capacitor and are collected by the screw.

The content of zinc metal in such powders usually does not exceed 94% -95%, the main part of the impurities is zinc oxide (E.F. Belenky, I.V. Riskin, Chemistry and technology of pigments. Publishing house "Chemistry", Leningrad branch. 1974, p. 535-536).

The disadvantages of this method are:

- complex loading of raw materials into hot muffles, while air does not get into capacitors, which will lead to oxidation of zinc vapors to zinc oxide;

- inefficient cooling of zinc vapor in the space of the condenser, which leads to the coarsening of particles of zinc dust to 20 microns;

- the oxidation of zinc vapor by partially entering the air into the condenser is the reason for the low quality of zinc dust - the content of zinc metal is 94-95%;

- difficulty in replacing spent muffles with new ones;

- limited scope of zinc powder due to its low pigment properties.

A known method of producing fine zinc powder for the paint and varnish industry, including the evaporation of zinc, characterized by a low content of impurities, at a boiling point or higher than the boiling point in a nitrogen medium as an inert medium, the transportation of zinc vapor, their rapid cooling (from 1470 - 1570K to 520 - 670K ) and powder collection (Non-ferrous metal powders edited by S.S. Naboychenko, Moscow, Metallurgy, 1997, pp. 431-439).

The installation for implementing this method of producing zinc powder contains a furnace for the evaporation of zinc in a nitrogen medium as an inert medium, a steam-dust pipe for transporting zinc vapor and zinc powder, having a zone of rapid cooling of zinc vapor (condenser) to a temperature below the melting point of zinc, a cyclone for powder collection, exhaust fan and bag filter.

The disadvantage of this method is the inability to clean the resulting zinc powder from impurities in the form of intermetallic compounds, which can reduce the anticorrosive properties of zinc powder. The objectives of the proposed method for producing fine zinc powder for anticorrosion paints and installation for implementing the method are to create a method for the production of fine zinc powder of high quality (impurity content not more than 0.05%), expand the scope of zinc powder for pigment purposes, improve hardware design of the zinc powder production process .

These tasks are achieved in that the zinc powder is cleaned of impurities in the form of intermetallic compounds by separating them from the zinc powder stream in a magnetic field, and the process of obtaining finely dispersed zinc powder is carried out during rarefaction in the furnace-vapor-dust-pipe-cooling chamber of zinc vapor-magnetic trap - a cyclone equal to 50-100 Pa.

The apparatus for producing fine powder, in addition to known parts, contains a magnetic trap with a hopper for collecting intermetallic compounds, installed in the steam and dust pipe system to the cyclone, the steam line to the chamber for the sharp cooling of zinc vapor is made of refractory non-metallic materials.

Installation for implementing the method for producing fine zinc powder for anticorrosion paints is shown in the drawing.

The installation contains the following equipment:

item 1. The furnace is mounted from refractory non-metallic material, such as fireclay bricks. Heating of the furnace can be achieved by burning natural gas or electricity. The furnace has: a cover made of silicon carbide (pos. 2), a ceramic pipe (pos. 3) with a stopper (pos. 4) for loading the furnace with zinc ingots, a pipe for draining zinc melt (pos. 5) with a stopper made of refractory clay (pos.6) for the case of repair of the furnace, a fitting for supplying nitrogen to the furnace (pos.7). Zinc is melted in a furnace at a temperature of 500-600 ° C to a melt layer height of 300 mm (pos. 8). After that, the temperature of the zinc melt is raised to a boiling point and above. To transport zinc vapors, a steam line (pos. 9) made of refractory non-metallic material adjoins directly to the furnace. The steam line at a distance of 2-3 m from the furnace has a zone of sharp cooling to a temperature below the melting point of zinc, for example, to a temperature of 400 ° C (item 10).

For abrupt cooling of zinc vapor in the cooling zone, a refrigeration unit (pos. 11) is mounted, in the zone of abrupt cooling of zinc vapor, a steam pipe made of refractory non-metallic material goes into a dust pipe (item 12) made of steel.

After 2-3 meters from the zone of quenching, a magnetic trap (pos. 13) is mounted in the dust pipe to separate intermetallic compounds that are collected in the hopper (pos. 14) from the stream of finely dispersed zinc powder. Further, a cyclone (pos. 15) is built into the dust pipe to deposit the bulk (99%) of fine zinc powder into the hopper (pos. 16). From the cyclone, the purified gas stream enters the exhaust fan, which is connected to the bag filter to completely clear the gas stream of zinc dust (not shown in the drawing). The set of features of the proposed technical solution - a method for producing finely dispersed zinc powder for anticorrosive paints and an installation for implementing the method has differences from the prototype and should not be explicitly studied from the prior art, therefore, the authors believe that the method is new and has an inventive step.

The method of producing finely dispersed zinc powder and the installation for implementing the method can increase the dispersion and purity of zinc powder, expand the scope of finely dispersed zinc powder for anticorrosion paints. A method of obtaining a fine zinc powder for anticorrosion paints is as follows.

The exhaust fan is turned on, the furnace is heated to a temperature of 500-600 ° C, nitrogen is supplied to the furnace, and the air in the furnace – exhaust fan system is completely displaced. Make sure that the vacuum in the furnace is 50-100 Pa (5-10 mm century). Then, through the loading pipe (drawing, item 3), zinc ingots are started to be loaded into the furnace. After loading zinc ingots into the furnace, the loading tube is closed with a stopper (item 4).

After deposition of a zinc melt in a furnace to a height of 300 mm, the temperature in the furnace begins to increase, but not more than up to 1250 ° C. A refrigeration unit (pos. 11), a magnetic trap for intermetallic compounds (pos. 13) are included in the operation. Every hour, the magnetic trap is automatically turned off for 5-10 s to reset intermetallic compounds into the hopper (pos. 14). As fine-grained zinc powder accumulates in the bunker (pos. 16) of the cyclone (pos. 15), heating of the furnace is turned off, when the temperature in the furnace decreases to 600-700 ° C, the exhaust fan is turned off and zinc powder is unloaded from the hopper (pos. 16) and intermetallic compounds from the hopper (key 14). Then the bunkers pos.16 and pos.14 tightly closed, include increased heating of the furnace, include an exhaust fan.

After about a month, the internal state of the furnace and steam line are inspected. To do this, the zinc melt in the furnace is maximally produced, the remaining zinc melt is poured into the molds through the pipe (pos. 5), the furnace is turned off, the refrigeration unit, the magnetic trap, the exhaust fan, the furnace cover is removed using a crane beam (pos. 2) and the furnace is left to cool; after cooling, the furnace is inspected and, if necessary, cleaned. After cleaning the oven, the lid is replaced and the installation is started as described above. The data of the technological parameters of the well-known (EF Belenky, IV Riskin. Chemistry and technology of pigments. Publishing house "Chemistry", Leningrad branch, 1974, p. 535-536) and the proposed methods are presented in table 1.

Example

The composition of zinc, wt.%

Mass fraction of zinc - 99.5

Mass fraction of impurities - 0.5

The results of the technological process of the proposed method for producing fine zinc powder for anticorrosion paints with the parameters and boundary parameters indicated in the claims are presented in table 2

table 2 No. of experiments Name of process parameters Units Parameter Values Process results one. The content of impurities (intermetallic compounds) in the initial zinc-containing raw materials
Oven temperature
System vacuum
oven - exhaust fan The content of impurities in finely divided zinc powder - 0.04% % 0.5 The content of zinc metal in the powder is 99.96% ° C 1200 Pa fifty 2. The content of impurities (intermetallic compounds) in the source of zinc-containing raw materials
Oven temperature
Depression in the system furnace - exhaust fan The content of impurities in finely divided zinc powder - 0.05% % 0.7 The content of zinc metal in the powder is 99.95% ° C 1200 Pa fifty 3. The content of impurities (intermetallic compounds) in the source of zinc-containing raw materials The content of impurities in finely divided zinc powder - 0.04% Oven temperature % 0.5 Metal content Depression in the system furnace - exhaust fan ° C 1200 zinc powder - 99.96% Pa one hundred four. The content of impurities (intermetallic compounds) in the source of zinc-containing raw materials The content of impurities in finely divided zinc powder - 0.04% Oven temperature % Metal content Depression in the system furnace - exhaust fan ° C zinc powder - 99.96% Pa 0.5
1200
35

Claims (4)

1. A method of producing finely dispersed zinc powder for anticorrosion paints, including heating, melting and evaporating zinc, not containing impurities in the form of metal oxides, at a boiling point or higher than the boiling point in a nitrogen medium as an inert medium, transporting zinc vapors with a nitrogen stream, their rapid cooling to a temperature below the melting point of zinc to obtain a powder and collecting powder, characterized in that the zinc powder is purified from impurities in the form of intermetallic compounds m separating them from the flow of zinc powder in a magnetic field. 2. The method according to claim 1, characterized in that it is carried out at a vacuum of 50-100 Pa. 3. Installation for producing fine zinc powder for anticorrosion paints, containing a furnace for heating, melting and evaporating zinc in a nitrogen medium as an inert medium, a steam line for transporting zinc vapor in a nitrogen stream having a quench zone to a temperature below the zinc melting temperature to obtain powder, dust pipe for transporting the obtained zinc powder, a cyclone for collecting zinc powder, an exhaust fan and a bag filter, characterized in that it contains magnetic fishing Ku for cleaning powder from impurities in the form of intermetallic compounds through their separation from the resulting powder stream, upstream of the cyclone. 4. The installation according to claim 3, characterized in that the furnace and the steam line to the zone of rapid cooling of the zinc vapor are made of refractory non-metallic materials.

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