CN110951976A - Oxidizing furnace for aluminum surface treatment - Google Patents

Abstract

The invention relates to an oxidation furnace for surface treatment of aluminum materials, which comprises a tunnel furnace body constructed by a furnace wall, a furnace top and a furnace bottom; a hearth space is arranged above the inside of the tunnel furnace body; a cement hearth, a hearth seat and a movable hearth are arranged below the hearth space, and traveling wheels of the movable hearth travel on rails laid in the hearth so that a cement hearth cylinder body can move relative to the hearth space; the invention has the characteristics of large treatment capacity, low energy consumption, convenient replacement of the hearth cylinder body, hard cement hearth and difficult cracking.

Description

Oxidizing furnace for aluminum surface treatment

Technical Field

The invention relates to the technical field of nonferrous metallurgy smelting, in particular to an oxidation furnace for surface treatment of aluminum materials; the method is mainly used for purifying and enriching gold and silver alloy noble metals.

Background

The alloy containing noble metal is obtained by carrying out enrichment, reduction, smelting and melting on the gold and silver-containing materials such as anode mud, the noble metal alloy is generally purified by fire refining, and at present, domestic large-scale production enterprises generally use oxidation furnaces. On day 09/08 1999, chinese patent grant publication no: CN2337500Y discloses a lead blast oxidation furnace, which comprises a heating stove, a lead melting pot and a stirrer, a sealing cover sleeved with the lead melting pot, the cover and the surface of lead liquid together enclose a sealed chamber, an air blower capable of blowing air into the sealed chamber is arranged outside the sealed chamber, and a sealing part is arranged between the stirrer shaft and the sealing cover. Although the stirrer and the sealing cover adopted by the technical scheme overcome the problems of low production efficiency and poor lead oxidation degree caused by the fact that the air inlet and the air inlet are both arranged above the oxidation pot and oxygen in gas cannot completely reach the surface of the lead liquid, the stirrer works in a high-temperature environment, the service life is short, and the production cost is high; and molten lead oxide liquid stirred and raised by the stirrer is easy to gasify and volatilize, so that the recovery rate of lead oxide is low, and the environment is polluted.

Disclosure of Invention

The invention aims to provide an oxidation furnace for surface treatment of aluminum materials, which has the characteristics of large treatment capacity, low energy consumption and high automation level; by using the oxidation furnace, the direct yield of gold and silver can be improved to 97.5-99%, and the oxidation furnace is environment-friendly and safe.

The invention relates to an oxidation furnace for surface treatment of aluminum material; comprises a tunnel furnace body constructed by a furnace wall, a furnace top and a furnace bottom; a hearth space is arranged above the inside of the tunnel furnace body; a flue leading to the hearth space is arranged on one side of the furnace wall, and an outlet of the flue is connected with a dust collector through a condensing system; a blast hole leading to the hearth space is formed in the other side of the furnace wall, and a blower is connected outside the blast hole; the furnace top is provided with a natural gas combustion nozzle; a cement hearth, a hearth seat and a movable hearth are arranged below the hearth space, travelling wheels of the movable hearth can travel on rails laid in the bottom of the furnace below the inside of the tunnel furnace body, a cement hearth cylinder body is arranged in the hearth seat, and the hearth seat is built on a steel plate bed surface of the movable hearth so that the cement hearth cylinder body can move relative to the hearth space;

preferably, the furnace roof and the furnace wall are built by clay refractory bricks;

preferably, the hearth seat consists of a protective frame and a frame bottom, the protective frame is built by high-alumina bricks or clay bricks, the frame bottom is built on a steel plate bed surface of the movable hearth by flat magnesia bricks, loess of 20 meshes is filled into the lower part of the protective frame and is pounded into a pot-shaped pit foundation with the thickness of 200-300 mm, the depth of the pot-shaped pit foundation is 100-200 mm, and the area of the pot-shaped pit foundation is matched with the appearance of a cement hearth cylinder body.

Preferably, the cement hearth is in a round pot bottom shape.

The invention relates to a small tunnel furnace, wherein the furnace wall, the furnace top, the furnace bottom and a flue leading to a hearth space are all fixed; the cement hearth cylinder body, the hearth seat and the movable hearth are movable; the cement hearth cylinder body is convenient to replace; in particular, the disposable cement hearth is used, and the lead oxide absorbed by the lead oxide can be recycled, so that the operation is simpler and more convenient. The production benefit is remarkable, and the direct yield of the gold and silver is improved to 97.5-99%.

Compared with the prior art, the invention adopts the cement hearth with the round pot bottom shape, and the cement is a cheap common material; the cement furnace hearth is hard and not easy to crack. The invention does not need a stirrer, greatly reduces the gasification and volatilization of the molten lead oxide liquid, and actually measures that the lead oxide volatilized from the gas only accounts for 1.5 percent of the total lead oxide weight, thereby reducing the environmental pollution.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a block diagram of the process of the present invention.

In the drawings: 1, furnace wall; 2, furnace top; 3, furnace bottom; 4, a hearth space; 5, a flue; 6, a blast port; 7 a combustion nozzle; 8, a cement hearth; 9, a furnace cylinder base; 10 moving the hearth; 11 a running wheel; 12 tracks.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Reference is made to FIG. 1

An oxidation furnace for surface treatment of aluminum material; comprises a tunnel furnace body which is constructed by a furnace wall (1), a furnace top (2) and a furnace bottom (3); the method is characterized in that: a hearth space (4) is arranged above the inside of the tunnel furnace body; a flue (5) leading to the hearth space (4) is arranged on one side of the furnace wall (1), and an outlet of the flue is connected with a dust collector through a condensing system; a blast hole (6) leading to the hearth space (4) is formed in the other side of the furnace wall (1), and a blower is connected outside the blast hole (6); a natural gas combustion nozzle (7) is arranged on the furnace top (2); a cement hearth (8), a hearth seat (9) and a movable hearth (10) are arranged below the hearth space (4), a traveling wheel (11) of the movable hearth can travel on a track (12) laid in the furnace bottom (3) below the inside of the tunnel furnace body, a cement hearth (8) cylinder body is arranged in the hearth seat (9), and the hearth seat (9) is built on a steel plate bed surface of the movable hearth (10), so that the cement hearth (8) cylinder body can move relative to the hearth space (4);

the furnace top (2) and the furnace wall (1) are built by clay refractory bricks;

the hearth seat (9) is composed of a protective frame and a frame bottom, the protective frame is built by high-alumina bricks or clay bricks, the frame bottom is built on a steel plate bed surface of the movable hearth (10) by flat magnesium bricks, loess of 20 meshes is filled into the lower part of the protective frame and is tamped into a pot-shaped pit base with the soil layer thickness of 200-300 mm, the depth of the pot-shaped pit base is 100-200 mm, and the area is matched with the outer surface of a cement hearth (8) cylinder body;

the cement furnace hearth (8) is in a round pot bottom shape.

Adding water which is 8-12% of the cement in parts by weight into 400# or 500# Portland cement for the cement hearth, and uniformly stirring; pouring the mixture on a hearth (8) mould, and pressing the mixture into a vessel by using a press; the Portland cement comprises, by weight, 60-70% of CaO, 12O 34-10% of A12, 219-24% of SiO 219 and 32-6% of Fe 2O.

The oxidation furnace for enriching gold and silver alloy is a tunnel furnace for burning natural gas. The furnace wall (1), the furnace top (2), the furnace bottom (3) and the flue (5) are all fixed. The movable hearth (10) and the cement hearth (8) are movable. The damaged cement hearth (8) can be replaced.

Using the oxidative refining process of the present invention:

placing the 45-55% crude gold-silver alloy obtained after the separation in the vacuum furnace into a cement hearth (8), controlling the temperature to 950-1100 ℃ for oxidation refining, wherein the molten lead is contacted with oxygen in the air to become lead oxide, most of PbO is absorbed by the porous cement hearth (8) due to the action of surface tension, a small part is volatilized, gold and silver are not oxidized, and the gold and silver are formed into particles and are left in the cement hearth (8). According to the metallurgical aspect, the oxidation smelting process above the melting point of the metal oxide is called oxidation refining, so we call this separation means oxidation refining process.

Oxidation refining is an important means for separating lead from noble metals in lead alloys. During oxidation refining, the cement hearth (8) is preheated at a high temperature of 800-900 ℃, organic matters, water, carbon dioxide and other volatile substances in the cement hearth (8) are removed, and then the crude gold-silver alloy with the content of 45-55% is put on the red hot cement hearth (8). If the cement hearth (8) is preheated for a short time and the coarse gold-silver alloy with the content of 45-55% is put on, residual gas in the cement hearth (8) escapes, breaks through the liquid surface of molten lead and throws small lead drops, and the phenomenon is called spitting. After the coarse gold-silver alloy with the content of 45-55% is melted, the surface of the molten lead is oxidized by air to form a layer of lead oxide film. The surface tension of the molten lead oxide is different from that of the molten lead, the molten lead oxide can be wetted by the surface of the cement hearth (8) and absorbed in the porous cement hearth (8) (capillary action), and the cohesive force of the molten lead is large and is not absorbed by the cement hearth (8). The molten lead oxide slides down from the surface of the molten lead to infiltrate into the cement hearth (8), a new surface is exposed and oxidized, and the molten lead oxide generated immediately is absorbed by the cement hearth (8), and the steps are repeated until the lead is completely oxidized into lead oxide and absorbed by the cement hearth (8). In the process, only about 1.5 percent of lead oxide is volatilized into the air in the form of steam, and about 98.5 percent of lead oxide is absorbed by the cement hearth (8). The gold and silver are not oxidized. After the lead is converted into lead oxide and absorbed by the cement hearth (8), the gold and silver are gradually concentrated, and after the process is finished, the gold and silver are left in the center of the concave part of the cement hearth (8). Impurities in the crude gold-silver alloy with the content of 45-55% are oxidized in the oxidation refining process, and the sequence of the oxidation is related to the heat formation and the free energy of various metal oxides. The zinc, tin, iron, nickel, cobalt, arsenic and antimony are oxidized in sequence before the lead is oxidized, wherein the zinc is firstly oxidized into zinc oxide and the tin is secondly … …. After lead is oxidized, bismuth, copper and tellurium are oxidized. Oxides formed during the oxidation refining of these impurities are released As gas (for example, As2O3, Sb2O 3), and some oxides are dissolved in lead oxide (for example, copper oxide) and removed As the lead oxide is also absorbed into the cement hearth (8).

In the oxidation refining process, gold and silver are separated from lead, and impurities entering the coarse gold and silver alloy with the content of 45-55% can be removed. Therefore, the finally obtained gold and silver particles are shorter than pure oxidation refining process time, the oxidation refining is carried out at the speed of 0.8-1.0 g/min, the oxidation refining method is quick, simple and convenient, the separation effect is good, and the direct recovery rate is high. This is an advantage not found in other oxidative purifications. The oxidative refining process can be divided into three stages: charging and melting the coarse gold-silver alloy with the content of 45-55%; oxidizing and absorbing the coarse gold-silver alloy with the content of 45-55%; glare and sparkle;

(1) melting and desquamation

Putting the crude gold-silver alloy with the content of 45-55% into a cement hearth (8) preheated at 900 ℃ for 30min, closing the furnace door, and if the cement hearth (8) is fully preheated, immediately melting the crude gold-silver alloy with the content of 45-55%. A layer of dark black floating slag is firstly arranged on the surface, if the temperature in the furnace is proper, the black floating slag disappears after 10-20 min, the molten lead starts to shine, and the bright molten lead surface appears for a moment, which is called peeling. If the peeling is not carried out after the delay of 20-30 min, the temperature of the high-temperature furnace is too low, the cement hearth (8) is not fully preheated, the atmosphere in the furnace is strongly oxidized, or a large amount of impurities such as tin, nickel and the like exist in the coarse gold-silver alloy with the content of 45-55%. Tin and nickel oxides have a high melting point and cover the surface of the molten lead. If the impurities in the crude gold-silver alloy with the content of 45-55% are too much, the oxidation refining is only carried out at the elevated temperature, but the loss of gold and silver is increased. If the coarse gold-silver alloy with the content of 45-55% is pure, only because the furnace temperature is too low, a small amount of reducing atmosphere generated by the reducing furnace is added to reduce lead oxide into metallic lead, so that the coarse gold-silver alloy with the content of 45-55% is peeled;

(2) oxidation and absorption

After peeling, air enters a hearth, the furnace temperature can be reduced to 950 ℃, and the temperature of the molten lead is obviously improved compared with the ambient temperature, which is caused by the fact that the lead is oxidized to generate heat, so that the surface of the molten lead is bright. The melted lead oxide penetrates into the cement hearth (8), and a small part of the lead oxide is volatilized as gas and rises from the cement hearth (8) like smoke. As the lead oxide is absorbed by the cement hearth (8), a ring appears around the cement hearth (8) which is positioned just above the molten lead. If the ring is bright red, it indicates that the oxidative refining temperature is too high. If the temperature of the oxidation refining is too low and the temperature on the surface of the molten lead is lower than the melting point of the lead oxide, the molten lead oxide is completely solidified, the molten lead is enclosed, the molten lead is not oxidized due to the exclusion of air, and the oxidation refining is stopped, which is called freezing. The freezing phenomenon often occurs in the latter stages of the oxidation refining because the lead is now very small, the heat generated by the oxidation of the lead is greatly reduced compared to the earlier stages, and the temperature on the molten lead is reduced. If the furnace temperature does not rise at this time, much cool air enters the furnace and is easily frozen. After freezing, if the furnace temperature is again raised to the temperature at which the oxidation refining is resumed, the analysis results obtained are often too low due to the temperature being too high. The remedy method is that the frozen cement hearth (8) is taken out, a few grams of lead sheet is added immediately, and the furnace is put into the furnace again for oxidation refining;

(3) glare and flash

The temperature must be raised just before the oxidative refining process is completed. Because the surface of the molten lead is greatly reduced, the amount of ignition heat generated by oxidation is correspondingly reduced, and because the proportion of gold and silver in the lead is increased as the amount of the molten lead is reduced, the alloy is more difficult to melt. To remove the last drop of lead, the final temperature should reach 1100 ℃, but not rise too high, which would result in a high loss of gold and silver. The higher the silver content, the more swirling and iridescent, continuous color, a phenomenon known as flare. The glare lasts only a few seconds, after the color disappears, the particles darken, and after a few seconds, the particles finally shine a glow, which is called glitter, because latent heat of fusion in the particles suddenly releases and reappears. The flash phenomenon shows that the oxidation refining work is finished, and the crude silver in the cement hearth (8) can be taken out.

Factors affecting oxidative refining.

(1) Temperature of oxidative refining

The influence of temperature on the oxidation refining is large, and the temperature is generally controlled to be 950 ℃ to 1100 ℃, if the temperature is too low, freezing can be generated, and if the temperature is too high, the loss of the gold and silver in the oxidation refining process is increased. Generally, gold and silver are difficult to oxidize, but the oxidation degree of gold and silver increases with the increase of temperature. After the gold and silver are oxidized, the oxide of the gold and silver is absorbed into the cement hearth (8) along with lead oxide or is scattered on the surface of the cement hearth (8), which is the main factor of gold and silver loss, and the loss amount of the gold and silver accounts for about 90 percent of the total loss. Another reason is that the evaporation of gold and silver at high temperatures increases with increasing temperature.

The degree of gold and silver loss during the entire oxidation refining process is not the same. The loss is small at the beginning, the lead content is gradually reduced along with the progress of the oxidation refining, the concentrations of gold and silver in the lead are correspondingly increased, the loss of the gold and silver is increased, and particularly, the loss is maximum near the end of the oxidation refining.

(2) Effect of base metals on oxidative refining losses

When the alloy is smelted, besides the precious metals entering the coarse gold-silver alloy with the content of 45-55%, some elements which are easy to reduce or are easy to dissolve in lead, such as copper, bismuth, selenium, tellurium, arsenic, antimony, nickel and the like, also enter the coarse gold-silver alloy with the content of 45-55%. After the base metals enter the coarse gold-silver alloy with the content of 45-55%, the coarse gold-silver alloy with the content of 45-55% becomes hard and is easy to crack when being hammered. Not only the physical properties of the crude gold-silver alloy with the content of 45-55% are changed, but also the difficulty is brought to the oxidation refining, and the loss of noble metal is increased;

copper and copper enter the crude gold-silver alloy with the content of 45-55% to different degrees, the copper is oxidized into copper oxide during oxidation refining, the copper oxide is easily dissolved in lead oxide, and the copper oxide and the lead oxide are absorbed in a cement hearth (8) together. After copper enters into the coarse gold-silver alloy with the content of 45-55%, the surface tension of molten lead is reduced, and the loss of gold and silver in oxidation refining is increased. When the content of copper in the crude gold-silver alloy with the content of 45-55% reaches 8.0%, the loss of gold and silver is obviously increased, and particularly, the loss of gold is more obviously influenced. When the copper content reaches 10.0%, oxidation refining cannot be carried out;

the nickel-nickel oxide has low solubility in lead oxide, when a small amount of nickel exists in the coarse gold-silver alloy with the content of 45-55%, dark green floating slag is formed, one part of the floating slag is left at the upper part of the cement hearth (8), the other part of the floating slag enters the cement hearth (8), and the cement hearth (8) is slightly green. When the content of nickel in the crude gold-silver alloy with the content of 45-55% is more than 0.1%, the nickel oxide covers the whole surface of the molten lead, and the oxidation refining is stopped;

antimony and lead are mutually soluble in liquid state, so that the crude gold-silver alloy with a content of 45-55% may contain a large amount of antimony. At the beginning of the oxidation refining, it initially gives off a dense smoke of Sb2O3, and when the content of antimony in the crude gold-silver alloy of 45-55% is not less than 1%, a yellow slag is formed. This slag is composed of oxides of lead and antimony, a portion of which floats on the surface of the molten lead and a portion of which penetrates into the cement hearth (8). This slag expands in volume as it solidifies. If a large amount of antimony is present, the cement hearth (8) is cracked by the expansion, and the lead liquid is drained. Even the presence of small amounts of antimony causes the cement hearth (8) to crack slightly and leaves a special relief of yellow dross;

arsenic has similar properties to antimony, but arsenic does not readily enter into crude gold-silver alloys containing 45-55% and at oxidative refining temperatures, As2O3 has a much higher vapor pressure than Sb2O3 and is readily removed. Due to these two factors, dross consisting of arsenic and lead oxides is not easily generated;

the iron and iron are not incorporated into the coarse gold-silver alloy in the content of 45-55%. The small amount of iron oxide from the outside dissolves in the lead oxide, leaving a dark red stain on the cement hearth (8);

under the condition of lead alloy, tin in the sample is not easily reduced into metal, but because tin is easily dissolved in lead, part of tin enters into the crude gold-silver alloy with the content of 45-55%. During the oxidation refining, tin in the crude gold-silver alloy with the content of 45-55% is quickly oxidized into SnO 2. When the tin content is more than 10.0 percent, a layer of yellow dross of insoluble lead stannate is formed to cover the surface of the molten lead, so that the oxidation refining is stopped;

bismuth is easy to enter the coarse gold-silver alloy with the content of 45-55%, bismuth in the coarse gold-silver alloy with the content of 45-55% is not easy to oxidize during oxidation refining, and after all lead is oxidized, bismuth still stays with particles until being oxidized finally and is absorbed by a cement hearth (8). An orange-yellow ring was formed around the particles. When the content of bismuth in the crude gold-silver alloy of 45-55% is below 0.8%, no influence is caused; when the content of the bismuth exceeds 0.8 percent, the loss of gold and silver is increased along with the increase of the content of the bismuth, and the loss is mainly in a cement hearth (8);

tellurium selenium has strong affinity to gold and silver, and causes great loss to gold and silver in the smelting and oxidation refining processes. Tellurium can easily enter into the crude gold-silver alloy with the content of 45-55 percent, is not easy to oxidize during oxidation refining, and is not easy to blow clean when the amount is large. When the total content of tellurium and selenium in the sample is below 0.6 percent, the loss of gold and silver in the smelting and oxidation refining processes is not obviously influenced. When the tellurium and selenium content is high, tellurium can be remained in the gold and silver particles after oxidation refining. When the content of tellurium and selenium in the crude gold-silver alloy with the content of 45-55% reaches 3.5%, oxidation refining cannot be carried out.

While there have been shown and described the fundamental principles and essential features of the invention and advantages thereof, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof; the present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, and any reference signs in the claims are not intended to be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (2)

1. An oxidation furnace for surface treatment of aluminum material; comprises a tunnel furnace body which is constructed by a furnace wall (1), a furnace top (2) and a furnace bottom (3); the method is characterized in that: a hearth space (4) is arranged above the inside of the tunnel furnace body; a flue (5) leading to the hearth space (4) is arranged on one side of the furnace wall (1), and an outlet of the flue is connected with a dust collector through a condensing system; a blast hole (6) leading to the hearth space (4) is formed in the other side of the furnace wall (1), and a blower is connected outside the blast hole (6); a natural gas combustion nozzle (7) is arranged on the furnace top (2); a cement hearth (8), a hearth seat (9) and a movable hearth (10) are arranged below the hearth space (4), a traveling wheel (11) of the movable hearth can travel on a track (12) laid in the furnace bottom (3) below the inside of the tunnel furnace body, a cement hearth (8) cylinder body is arranged in the hearth seat (9), and the hearth seat (9) is built on a steel plate bed surface of the movable hearth (10), so that the cement hearth (8) cylinder body can move relative to the hearth space (4); the furnace top (2) and the furnace wall (1) are built by clay refractory bricks; the hearth seat (9) is composed of a protective frame and a frame bottom, the protective frame is built by high-alumina bricks or clay bricks, the frame bottom is built on a steel plate bed surface of the movable hearth (10) by flat magnesium bricks, loess of 20 meshes is filled into the lower part of the protective frame and is tamped into a pot-shaped pit base with the soil layer thickness of 200-300 mm, the depth of the pot-shaped pit base is 100-200 mm, and the area is matched with the outer surface of a cement hearth (8) cylinder body; the cement furnace hearth (8) is in a round pot bottom shape.

2. An aluminum material surface treatment oxidation furnace as set forth in claim 1, wherein: the cement hearth (8) is prepared by adding water which is 8-12% of cement in parts by weight into 400# or 500# Portland cement, and uniformly stirring; pouring on a hearth mould, and pressing into a dish by using a press; the Portland cement comprises, by weight, 60-70% of CaO, 78-10% of A12O 34, 219-24% of SiO 219 and 32-6% of Fe 2O.

Images