A method for producing single-crystal fused zirconium dioxide

Abstract

This invention relates to zirconium dioxide production technology, and particularly to a method for producing single-crystal fused zirconium dioxide. The method includes the following steps: Step 1, adding a reducing agent to zircon sand raw material and smelting to obtain fused zirconium dioxide; Step 2, adding a degranulating agent to the fused zirconium dioxide and continuing smelting; Step 3, casting, demolding, and transferring the resulting zirconium dioxide ingot to a pulverizing chamber for thorough pulverization; Step 4, the pulverized material obtained in Step 3 is washed with water, acid-washed, dehydrated, dried, calcined, and graded to obtain single-crystal fused zirconium dioxide. The beneficial effects of this invention are: unlike existing technologies, this invention provides a method for producing fused zirconium dioxide products without crushing or pulverizing, and the product is in a single-crystal state with a wide particle size distribution, capable of producing fused zirconium dioxide single-crystal products from 10 mesh to 1000 mesh.

Description

[0001] This case is a divisional application based on the invention patent with the application date of April 27, 2021, application number 2021104614360, and title "A method for producing single crystal fused zirconium dioxide". Technical Field

[0002] This invention relates to zirconium dioxide production technology, and particularly to a method for producing single-crystal fused zirconium dioxide. Background Technology

[0003] Industrially produced zirconia is widely used in refractory materials, ceramic glazes, and sponge zirconium. The main production methods are chemical and electrofusion. The electrofusion method involves desilication of zircon sand with a carbon reducing agent at high temperatures in an electric arc furnace. The molten zirconia is then shaped by compressed air blowing or casting to obtain fused zirconia products. Subsequent finishing processes yield granules or powders of appropriate particle size for application in relevant fields.

[0004] Zirconia granules or fine powder obtained by crushing or grinding have irregular appearances, with larger particles having more pronounced edges and corners. Processing them into fine powder requires a lot of energy. For example, using an air jet mill to process fine powder with a D50 of about 6μm costs about 2,500 yuan. However, by electro-melting, single-crystal zirconia particles or fine powder of different particle sizes can be obtained directly. This results in defect-free granular products as well as smaller micro powders, without the need for subsequent crushing and grinding processes, thus greatly reducing processing costs.

[0005] Fused zirconia particles are single-crystal in shape, which can maximize the advantages of the material in specific applications, such as brake pads, surface sandblasting, and refractory products. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a simple and low-cost method for producing single-crystal fused zirconium dioxide.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for producing single-crystal fused zirconium dioxide, comprising the following steps:

[0008] Step 1: Put the zircon sand raw material into the electric arc furnace that has been ignited, and at the same time add a reducing agent accounting for 6-10% of the mass of the zircon sand raw material, and melt for 60-120 minutes;

[0009] Step 2: Add a degranulating agent of 5-20% (by mass) of zircon sand to the material obtained in Step 1, and continue smelting for 100-180 minutes; the degranulating agent is sulfur or calcined coke.

[0010] Step 3: The molten liquid obtained in Step 2 is poured into a mold assembled from graphite plates for cooling; after cooling for 24 hours, it is demolded, and the resulting zirconia ingot is transferred to a pulverization chamber for full pulverization; the pulverization time is 50-70 days.

[0011] Step 4: The pulverized material obtained in Step 3 is washed with water, acid-washed, dehydrated, dried, calcined, and classified to obtain single-crystal fused zirconium dioxide.

[0012] Preferably, in the above-described method for producing single-crystal fused zirconium dioxide, the reducing agent has a fixed carbon content > 80% and a mineral impurity content < 0.5%.

[0013] Preferably, in the above-described method for producing single-crystal fused zirconium dioxide, the degranulating agent is sulfur, and the sulfur content of the degranulating agent is ≥98%.

[0014] Preferably, in the above-described method for producing single-crystal fused zirconium dioxide, the degranulating agent is calcined coke, and the C content of the degranulating agent is ≥98%.

[0015] Preferably, in the above method for producing single-crystal fused zirconium dioxide, step 4 specifically comprises: the pulverized material obtained in step 3 is washed once with water, acid-washed with sulfuric acid at a mass percentage of 3-5% for 30 minutes, and then washed three times with water; dehydrated using a centrifuge; dried in a rotary kiln; calcined in a vertical kiln at 800-1200℃ for 0.5-3 hours; and finally sieved into products of different particle sizes using a linear sieve to obtain single-crystal fused zirconium dioxide.

[0016] The beneficial effects of this invention are as follows: Unlike the prior art, this invention provides a method for producing fused zirconia products without crushing or pulverizing, and the product is in a single crystal state with a wide particle size distribution, capable of producing fused zirconia single crystal products from 10 mesh to 1000 mesh. Detailed Implementation

[0017] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0018] Example 1

[0019] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0020] Step 1: Add zircon sand raw material into the electric arc furnace that has been ignited, and add 6-10% carbon powder as a reducing agent. The zircon sand reacts with carbon at the high temperature of the electric arc to carry out desiliconization treatment.

[0021] The aforementioned zircon sand raw material can be fused zircon dioxide, and no carbon powder reducing agent needs to be added during electric arc furnace smelting;

[0022] The aforementioned carbon powder reducing agent includes: calcined coke, carbon powder, etc. with a fixed carbon content >80% and a mineral impurity content <0.5%; the aforementioned electric arc furnace is equipped with a dust removal system, and the exhaust gas must be desulfurized and decarbonized before being emitted;

[0023] Step 2: Add 5-20% (by mass) of a degranulating agent to the material obtained in Step 1, and continue smelting for 100-180 minutes. The degranulating agent is sulfur or calcined coke. Add 5-20% of the degranulating agent. The sulfur degranulating agent is required to have an S content ≥98%. The calcined coke degranulating agent is required to have a C content ≥98%. Continue smelting for 100-180 minutes to allow the degranulating agent and zirconium dioxide to react fully at high temperature.

[0024] The above reaction mechanism is that at high temperature, sulfur or carbon reacts with zirconium dioxide to generate zirconium sulfide or carbide. The reaction equation is: ZrO2 + 2S(C) → ZrS2(ZrC) + SO2(CO2). SO2 or CO2 is absorbed through desulfurization and decarbonization treatment.

[0025] Step 3: The molten liquid obtained in Step 2 is poured into a mold assembled from graphite plates for cooling;

[0026] The above molds are graphite assembly molds or cast iron molds; water-cooled molds are not applicable. After casting, the molten liquid is rapidly cooled in the early stage to form a zirconia shell, while the interior is cooled slowly. After cooling for 24 hours, the material block is demolded and transferred to the pulverization chamber for spraying. The pulverization time is 1-3 months.

[0027] The above-mentioned pulverization mechanism involves the reaction of zirconium sulfide (ZrS2) with water, and the reaction equation is as follows:

[0028] ZrS2+ H2O —— ZrO2+ H2S, with H2S gas being absorbed by an alkaline spray tower;

[0029] Step 4: After the material is fully pulverized, it is washed with water, acid washed, dehydrated, dried, calcined, and graded to obtain a single-crystal fused zirconium dioxide product.

[0030] The acid used for the above pickling is sulfuric acid with a concentration of 3-5%;

[0031] The aforementioned dewatering equipment includes plate and frame filter presses, centrifuges, etc.

[0032] The aforementioned drying equipment includes rotary kilns, shuttle kilns, flash dryers, etc.

[0033] The above-mentioned calcination equipment includes rotary kilns, shuttle kilns, vertical kilns, and pusher kilns, with calcination temperatures of 800-1200℃ and calcination times of 0.5-3 hours.

[0034] The above grading uses a linear screen or an air classifier.

[0035] Example 2

[0036] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0037] The amount of zircon sand used is 1500 kg, the amount of calcined coke used is 90 kg, and the furnace is smelted for 60 minutes using a 3200 KVA electric arc furnace. 50 kg of sulfur is added and the smelting continues for another 60 minutes. Finally, the molten liquid is poured into a mold assembled from graphite plates for cooling.

[0038] After cooling for 24 hours, the zirconia ingot is demolded and transferred to the pulverization chamber for full pulverization.

[0039] Powdering time: 60 days;

[0040] Wash once with water, then acid wash with 3% sulfuric acid for 30 minutes, and wash three times with water.

[0041] Dehydration is performed using a centrifuge;

[0042] Drying in a rotary kiln;

[0043] Then it is calcined in a vertical kiln at 800℃ for 1 hour;

[0044] Finally, the products are sieved into different particle sizes using a linear sieve.

[0045] Example 3

[0046] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0047] The amount of zircon sand used is 1500 kg, the amount of calcined coke used is 100 kg, and the furnace is smelted for 60 minutes using a 3200 KVA electric arc furnace. 90 kg of sulfur is added and the smelting continues for another 60 minutes. Finally, the molten liquid is poured into a mold assembled from graphite plates for cooling.

[0048] After cooling for 24 hours, the zirconia ingot is demolded and transferred to the pulverization chamber for full pulverization.

[0049] Powdering time: 60 days;

[0050] Wash once with water, then acid wash with 3% sulfuric acid for 30 minutes, and wash three times with water.

[0051] Dehydration is performed using a plate and frame filter press;

[0052] Drying in a flash dryer;

[0053] It is then calcined in a rotary kiln at 1000℃ for 1.5 hours;

[0054] Finally, the particles are processed into products of different particle sizes using a linear sieve and an air classifier.

[0055] Example 4

[0056] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0057] The amount of fused zirconium oxide used is 1500 kg, with 80 kg of sulfur added. It is smelted in a 3200 KVA electric arc furnace for 120 minutes, and the molten liquid is poured into a cast iron mold for cooling.

[0058] After cooling for 24 hours, the zirconia ingot is demolded and transferred to the pulverization chamber for full pulverization.

[0059] Powdering time: 60 days;

[0060] Wash once with water, then acid wash with 5% sulfuric acid for 30 minutes, and wash three times with water.

[0061] Dehydration is performed using a centrifuge;

[0062] Drying in a rotary kiln;

[0063] Then it is calcined in a pusher kiln at 1000℃ for 1.5 hours;

[0064] Finally, the products of different particle sizes are separated by a circular vibrating screen.

[0065] Example 5

[0066] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0067] The amount of fused zirconium oxide used is 1500 kg, and 150 kg of calcined coke is added. It is smelted in a 3200 KVA electric arc furnace for 120 minutes. The molten liquid is then poured into a cast iron mold for cooling.

[0068] After cooling for 24 hours, the zirconia ingot is demolded and transferred to the pulverization chamber for full pulverization.

[0069] Powdering time: 60 days;

[0070] Wash once with water, then acid wash with 3% sulfuric acid for 30 minutes, and wash three times with water.

[0071] Dehydration is performed using a centrifuge;

[0072] Drying in a rotary kiln;

[0073] Then it is calcined in a shuttle kiln at 1100℃ for 1 hour;

[0074] Finally, the products are separated into different particle sizes by linear sieve.

[0075] Example 6

[0076] A method for producing single-crystal fused zirconium dioxide includes the following steps:

[0077] The amount of fused zirconium oxide used is 1500 kg, and 100 kg of calcined coke is added. It is smelted in a 3200 KVA electric arc furnace for 120 minutes. The molten liquid is then poured into a cast iron mold for cooling.

[0078] After cooling for 24 hours, the zirconia ingot is demolded and transferred to the pulverization chamber for full pulverization.

[0079] Powdering time: 60 days;

[0080] Wash once with water, then acid wash with 5% sulfuric acid for 30 minutes, and wash three times with water.

[0081] Dehydration is performed using a centrifuge;

[0082] Drying in a rotary kiln;

[0083] Then it is calcined in a shuttle kiln at 1100℃ for 1 hour;

[0084] Finally, the products are separated into different particle sizes by linear sieve.

[0085] Table 1 below compares the production costs of the new process and the traditional process using Examples 1 and 4 as examples.

[0086] Table 1

[0087]

[0088] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing single-crystal fused zirconium dioxide, characterized in that, Includes the following steps: Step 1: Put the zircon sand raw material into the electric arc furnace that has been ignited, and at the same time add a reducing agent accounting for 6-10% of the mass of the zircon sand raw material, and melt for 60-120 minutes; Step 2: Add a degranulating agent of 5-20% (by mass) of zircon sand to the material obtained in Step 1, and continue smelting for 100-180 minutes; the degranulating agent is sulfur or calcined coke. Step 3: The molten liquid obtained in Step 2 is poured into a mold assembled from graphite plates for cooling; after cooling for 24 hours, it is demolded, and the resulting zirconia ingot is transferred to a pulverization chamber for full pulverization; the pulverization time is 50-70 days. Step 4: The pulverized material obtained in Step 3 is washed with water, acid-washed, dehydrated, dried, calcined, and classified to obtain single-crystal fused zirconium dioxide.

2. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The reducing agent is calcined coke or carbon powder with a fixed carbon content >80% and a mineral impurity content <0.5%.

3. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The degranulating agent is sulfur, and the sulfur content of the degranulating agent is ≥98%.

4. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The degranulating agent is calcined coke, and the C content of the degranulating agent is ≥98%.

5. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The acid used for pickling is sulfuric acid with a concentration of 3-5%.

6. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The dehydration equipment is a plate and frame filter press or a centrifuge.

7. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The drying equipment is a rotary kiln, a shuttle kiln, or a flash dryer.

8. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The calcination equipment is a rotary kiln, shuttle kiln, vertical kiln or pusher kiln, with a calcination temperature of 800-1200℃ and a calcination time of 0.5-3 hours.

9. The method for producing single-crystal fused zirconium dioxide according to claim 1, characterized in that, The grading process uses a linear screen or an air classifier.

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