Method for preparing alumina hollow sphere thermal insulation material from waste slag generated in production of chromium

Abstract

A method for preparing alumina hollow sphere heat-insulating material from chromium production waste residue, relates to a smelting waste residue comprehensive utilization method.The method uses the way of replacing the furnace shell, and lets the liquid of the reduced chromium oxide into the lower part of the furnace shell, and the upper layer covers the alumina melt, which avoids the possibility of the metallic chromium contacting air and being oxidized, and improves the efficiency of the aluminum-chromium residue refining metallic chromium.The invention converts the residue produced in the production of metallic chromium by aluminum thermal method into two products, one is alumina hollow sphere, one is high-grade heat-insulating material; the other is metallic chromium. The two products are both high-priced products, and realize the high-value utilization in the resource comprehensive utilization of aluminum-chromium residue waste residue.

Description

Technical Field

[0001] The present invention relates to a comprehensive utilization method of smelting waste residue, in particular to a method for preparing alumina hollow ball thermal insulation material by using waste residue generated in chromium production. Background Art

[0002] The aluminothermic process is a major method for producing metallic chromium. It involves a reduction reaction between aluminum and chromium oxide, reducing the chromium oxide to chromium metal and oxidizing the aluminum to aluminum oxide. The aluminum oxide forms the slag of this reaction, floating on the surface; the chromium metal sinks to the bottom. Due to the incomplete reaction, some chromium oxide may be mixed with the molten aluminum oxide. Upon solidification, the slag forms a co-solvent of aluminum oxide and chromium oxide, resulting in the aluminothermic slag. This slag typically contains approximately 80% to 90% aluminum oxide and 10% to 20% chromium oxide. Currently, this slag is used solely as a raw material for primary refractory materials. This byproduct is not further processed, resulting in low added value.

[0003] Currently, this slag is used to separate alumina from chromium oxide in order to obtain metallic chromium. The alumina obtained after separation is only used as sub-white corundum, which is a primary refractory raw material with low added value. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing alumina hollow sphere insulation material using waste slag generated in the production of chromium. The present invention melts the slag generated in the process of producing metallic chromium in a plasma electric melting furnace, purifies the alumina melt, and blows it into alumina hollow spheres. The slag generated in the process of producing metallic chromium by the aluminothermic method is converted into high-end alumina hollow sphere insulation material with high added value, thereby realizing high-value utilization of waste slag resources.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing alumina hollow sphere insulation material using waste residue generated in chromium production, the method comprising the following preparation steps:

[0007] (1) firstly, the aluminum-chromium slag is mixed with a carbon reducing agent in a ratio of 100:8 to 100:4 by weight of the slag to the carbon reducing agent;

[0008] (2) The mixture of aluminum-chromium slag and carbon reducing agent is melted in a plasma electric melting furnace. During the melting process, the chromium oxide in the slag is reduced to metallic chromium and deposited at the bottom of the furnace, while the aluminum oxide melt is on the upper layer, thus achieving the separation of aluminum oxide and metallic chromium;

[0009] (3) one furnace melting cycle after the end of the molten aluminum oxide blowing into the hollow ball way out of the furnace; inclined furnace body molten aluminum oxide from the nozzle left out, with compressed air blowing molten aluminum oxide, so that the molten aluminum oxide into small droplets, into the hollow ball;

[0010] (4) blowing hollow ball in the process, the oxygen in the air will burn off the residual carbon in the molten aluminum oxide, to achieve the purification of alumina; alumina hollow ball is a thermal insulation material products;

[0011] (5) by adjusting the pressure of compressed air, air volume, viscosity of molten aluminum oxide, further realize the different particle size of hollow ball;

[0012] (6) process continuous production of 3 furnace, namely the third furnace blowing ball after the replacement of the furnace shell; unloading this furnace shell has achieved the enrichment of metallic chromium, namely the accumulation of 3 furnace melting reduction separation of metallic chromium in the lower part of the furnace shell, covered with molten aluminum oxide, preventing air contact with the liquid metal chromium, to prevent the separation of the metal chromium is oxidized;

[0013] (7) then install a empty furnace shell on the plasma electric furnace, start production again;

[0014] (8) with the cooling of the furnace shell, the inside of the solidification of the excavated, the lower part is the metal chromium, the upper part is the alumina block; alumina block back to the process cycle to participate in the blowing of alumina hollow ball; prepared into this waste slag into two products, alumina hollow ball and metal chromium.

[0015] The method for preparing alumina hollow ball thermal insulation material from waste slag generated in the production of chromium, wherein the carbon reducing agent in step (1) is petroleum coke or semi coke or charcoal or briquettes or metal aluminum.

[0016] The method for preparing alumina hollow ball thermal insulation material from waste slag generated in the production of chromium, wherein the melting time in the ion electric furnace in step (2) is 4-5 hours.

[0017] The advantages and effects of the present application are:

[0018] 1. The present application adopts the replacement of the furnace shell, so that the reduced chromium oxide is left in the lower part of the furnace shell, and the upper layer is covered with molten aluminum oxide, which avoids the possibility of oxidation of the metal chromium and improves the efficiency of the extraction of metal chromium from aluminum chromium slag.

[0019] 2. The slag generated during the production of metal chromium is converted into two products, one is alumina hollow ball, a high-grade thermal insulation material, and the other is metal chromium. These two products are high-priced products, realizing the high-value utilization of the resource comprehensive utilization of aluminum chromium slag waste slag. DETAILED DESCRIPTION

[0020] The application will be described in detail below in connection with the illustrated embodiments.

[0021] The application uses a plasma electric furnace, and aluminum-chromium slag is added into the electric furnace, and is spread on the furnace bottom with a thickness of about 300 mm. Carbon blocks are laid on the slag, which can be petroleum coke blocks or graphite blocks, and the size of the blocks is 30-50 mm. After the electrode is electrified, the descending electrode approaches the carbon blocks, so that a plasma arc is generated between the electrode and the carbon blocks. The heat of the arc melts the aluminum-chromium slag. When the slag forms a molten pool and the current of the electric furnace is stable, a mixture of the aluminum-chromium slag and the carbon reducing agent is added into the electric furnace. The weight ratio of the aluminum-chromium slag to the carbon reducing agent is in the range of 100 / 4 to 100 / 8. The reducing agent can be petroleum coke, semi-coke, charcoal, graphite blocks, etc., or metal aluminum, etc., and carbon is generally used as the reducing agent. The carbon reducing agent reduces the chromium oxide in the aluminum-chromium slag into metal and deposits on the furnace bottom, so as to purify the aluminum oxide. The electric furnace is electrified during the feeding process, and the feeding and melting are simultaneously performed until the liquid level in the electric furnace reaches a level close to the nozzle, and no more feeding is performed. The melting is continuously performed for 3 hours, and the melting cycle of one furnace is ended. The upper layer of the molten liquid in the furnace is aluminum oxide molten liquid, and the lower layer is chromium metal molten liquid. The melting cycle of one furnace is 4-5 hours. About 40 minutes before the end of the melting cycle of one furnace, the reaction degree of the molten liquid is tested by the dipping method, and if the reaction degree is found to be insufficient, carbon is supplemented into the furnace. After the melting cycle of one furnace is ended, the furnace body is tilted, the upper aluminum oxide molten liquid in the electric furnace flows out from the nozzle, and at the same time, compressed air is used to blow the flow of the aluminum oxide molten liquid, so that the aluminum oxide molten liquid is dispersed into small droplets to form hollow spheres; at the same time, the residual carbon in the aluminum oxide molten liquid is oxidized by the oxygen in the air, so that the aluminum oxide is purified. When there is still a small amount of aluminum oxide molten liquid in the electric furnace, the tilting of the furnace is stopped, and the furnace body is returned to the normal position, i.e., the state in which the furnace body is not tilted. The aluminum oxide hollow spheres fly in the air under the action of the compressed air, which is also the process of cooling, and finally the spheres fall into a hopper. Then, different particle sizes of the spheres are obtained through screening, which are the products. By controlling the flow rate of the flow and the pressure of the compressed air, different particle sizes of the hollow spheres can be realized. After the same process is repeated twice, after the third time of blowing the spheres, the furnace shell of the electric furnace is removed, is moved to a designated place, and after the material in the furnace shell is cooled, the remaining material in the furnace is dug out. The upper layer of the remaining material is aluminum oxide, and the lower layer is chromium metal. The upper layer of the material is returned to repeat the above process, and the lower layer of the chromium metal is the product. After the last furnace shell is removed, the next empty furnace shell is moved to be connected with the furnace body, and the above process is repeated. Example 1

[0022] Using 1800KVA plasma electric furnace, add aluminum chromium slag into the electric furnace, spread on the furnace bottom, thickness about 300mm, these slag material on the carbon block, carbon block can be petroleum coke block, also can be graphite block, block size 30-50mm.

[0023] Plasma electric furnace power down electrode, electrode and slag on the carbon block between the arc, the arc to the slag heating to make it melt, at this time the voltage: 170V, current: 5000A. This stage time for 20-30 minutes, the current fluctuation at the beginning, 20-30 minutes or so current in a stable state.

[0024] Add slag and coking coal reducing agent mixed with the mixture into the electric furnace. The proportion of the mixture: the weight of the slag and the weight of the coking coal reducing agent is 100 / 5. The size of the coking coal block is 30-40mm.

[0025] Melting while feeding, until the liquid level close to the level of the nozzle, stop feeding. The voltage of this process: 170V, current: 6000A. The melting time of this stage is 2 hours. This stage is reduced to metal chromium deposited to the bottom of the furnace shell, the upper layer is aluminum oxide melt.

[0026] An hour before the furnace, test the reaction degree of the melt with dip probe method, if the reaction degree is not enough, add carbon to the furnace.

[0027] After adding carbon, continue to melt for 30 minutes, then adjust the voltage to 190V, current 4500A, melt for 30 minutes, this furnace melting is finished.

[0028] After the melting cycle of a furnace is finished, tilt the furnace body, the upper layer of aluminum oxide melt in the furnace flows out from the nozzle, at the same time, use compressed air to blow the stream of aluminum oxide melt, so that the aluminum oxide melt is dispersed into small droplets, forming hollow spheres; at the same time, the residual carbon in the aluminum oxide melt is oxidized by the oxygen in the air, realizing the purification of aluminum oxide. The aluminum oxide hollow spheres fly in the air under the action of compressed air, which is also the process of cooling. Finally the spheres fall into a hopper.

[0029] When there is still a small part of aluminum oxide melt in the furnace, stop tilting the furnace and let the furnace body return to the normal position, i.e. the state of the furnace body not being tilted.

[0030] By controlling the flow rate of the stream and the pressure of the compressed air during blowing, different particle sizes of hollow spheres can be realized.

[0031] The hollow spheres are sieved by a screening machine to obtain different particle sizes of spheres, and the hollow spheres are the products.

[0032] After repeating the same process twice, the furnace shell is replaced after the end of the third blow. The furnace shell of the electric furnace is removed and moved to a designated place. After the material in the furnace shell is cooled, the remaining material is excavated. The upper layer of the remaining material is aluminum oxide, and the lower layer is metallic chromium. The upper layer of material is returned to repeat the above process, and the lower layer of metallic chromium is the product.

[0033] After the previous furnace shell is removed, the next empty furnace shell is moved to the furnace body and connected. The previous process is repeated. Example 2

[0034] A 3600 KVA plasma electric furnace is used to add aluminum-chromium slag to the electric furnace. The slag is spread on the furnace bottom with a thickness of about 400 mm. Carbon blocks are placed on the slag, and the carbon blocks are graphite blocks with a size of 30-50 mm.

[0035] The plasma electric furnace is powered and the electrode is lowered. An electric arc is generated between the electrode and the carbon blocks on the slag, heating the slag to melt it. At this time, the voltage is 170 V and the current is 8000 A. The time for this stage is 30 minutes. At the beginning, the current may fluctuate, and after about 30 minutes, the current is stable.

[0036] The electric furnace is added with a mixture of aluminum-chromium slag and graphite blocks. The proportion of the mixture is that the weight ratio of the total weight of aluminum-chromium slag to the weight of graphite blocks is 100 / 5, and the size of the graphite blocks is 20-30 mm.

[0037] The material is added while melting until the liquid surface is close to the level of the nozzle, and the addition is stopped. The voltage for this process is 180 V, the current is 10000 A, and the time is 3 hours. This process allows the reduced metallic chromium to deposit on the furnace bottom, and the upper layer is aluminum oxide melt.

[0038] An hour before the furnace is discharged, the reaction degree of the melt is tested by the dipping method. If the reaction degree is insufficient, carbon is added to the furnace.

[0039] After the carbon is added, the melting continues for 30 minutes, then the voltage is adjusted to 190 V and the current is 7500 A, and the melting of this furnace is completed after 30 minutes.

[0040] After the melting cycle of a furnace is completed, the furnace body is tilted, and the upper layer of aluminum oxide melt in the furnace flows out from the nozzle. At the same time, compressed air is used to blow the stream of aluminum oxide melt, so that the aluminum oxide melt is dispersed into small droplets to form hollow balls. At the same time, the residual carbon in the aluminum oxide melt is oxidized by the oxygen in the air, achieving the purification of aluminum oxide. The aluminum oxide hollow balls fly in the air under the action of compressed air, which is also the process of cooling. Finally, the balls fall into a hopper.

[0041] When there is still a small amount of aluminum oxide melt in the furnace, stop tilting the furnace and return the furnace body to its normal position, i.e. the state where the furnace body is not tilted.

[0042] By controlling the flow rate of the stream and the pressure of the compressed air, the blowing of hollow spheres of different sizes is achieved.

[0043] The hollow spheres are sieved through a sifter to obtain spheres of different sizes. The hollow spheres are the product.

[0044] After repeating the same process twice, after the third furnace is used to blow the spheres, the furnace shell is removed and moved to a designated place. After the material in the furnace shell is cooled, the remaining material in the furnace is excavated. The upper layer of the remaining material is aluminum oxide, and the lower layer is metal chromium. The upper layer of material is returned to repeat the above process, and the lower layer of metal chromium is sold as a product.

[0045] After the previous furnace shell is removed, the next empty furnace shell is moved and connected to the furnace body, and the previous process is repeated.

[0046] The furnace shell of the plasma electric furnace used in the present application can be removed, and the furnace body remains unchanged, achieving the replacement of the furnace shell.

[0047] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be included in the scope of the claims of the present application.

Claims

1. A method for preparing alumina hollow ball insulation material using waste residue generated in chromium production, characterized in that: The method comprises the following preparation steps: (1) firstly, the aluminum-chromium slag is mixed with a carbon reducing agent in a ratio of 100:8 to 100:4 by weight of the slag to the carbon reducing agent; (2) The mixture of aluminum-chromium slag and carbon reducing agent is melted in a plasma electric melting furnace. During the melting process, the chromium oxide in the slag is reduced to metallic chromium and deposited at the bottom of the furnace, while the aluminum oxide melt is on the upper layer, thus achieving the separation of aluminum oxide and metallic chromium; (3) After the melting cycle of a furnace is completed, the alumina melt is blown into hollow balls and taken out of the furnace; the furnace body is tilted to allow the alumina melt to flow out from the furnace nozzle, and compressed air is used to blow the alumina melt to disperse the alumina melt into small droplets, forming hollow balls; (4) During the process of blowing the hollow balls, the oxygen in the air burns off the residual carbon in the alumina melt, thereby purifying the alumina; the hollow alumina balls are thermal insulation materials. (5) By adjusting the pressure and air volume of the compressed air and the viscosity of the alumina melt, the different particle sizes of the hollow balls can be further achieved; (6) The process continuously produces three furnaces, that is, after the third furnace is finished blowing, the furnace shell is replaced; the removed furnace shell has already achieved the enrichment of metallic chromium, that is, the metallic chromium after the accumulation of melting, reduction and separation in the three furnaces is accumulated in the lower part of the furnace shell, which is covered with alumina melt, preventing the contact between air and liquid metallic chromium and preventing the separated metallic chromium from being oxidized; (7) Install an empty furnace shell on the plasma electric melting furnace and restart production; (8) After the furnace shell with the material cools down, the solidified body inside is dug out. The lower part is metallic chromium and the upper part is alumina melt. The alumina melt returns to the previous process cycle to participate in the blowing of alumina hollow balls. The waste slag is converted into two products: alumina hollow balls and metallic chromium.

2. The method for preparing alumina hollow sphere insulation material using waste residue generated in chromium production according to claim 1, characterized in that: The carbon reducing agent in step (1) is petroleum coke, blue charcoal, charcoal, graphite block or metallic aluminum.

3. The method for preparing alumina hollow sphere insulation material using waste residue generated in chromium production according to claim 1, characterized in that: In the step (2) of melting in the ion electric melting furnace, the melting cycle of one furnace is 4 to 5 hours.