A method for treating zinc oxide fume containing fluorine and chlorine at low temperature

Abstract

A method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine belongs to the technical field of resource recovery. A method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine includes the following steps: Low-temperature pretreatment step: Zinc oxide fume containing fluorine and chlorine is added with calcium oxide-containing material and calcium chloride-containing material, and the materials are heated and pretreated to obtain pretreated zinc oxide fume. In the pretreated zinc oxide fume, zinc mainly exists in the form of oxide, and lead mainly exists in the form of chloride; the heating pretreatment temperature is 150-450 °C; Microwave treatment step to obtain low-lead zinc oxide fume; Reduction and zinc recovery step: The low-lead zinc oxide fume is reduced and zinc is recovered through a reduction device. It can reduce the use of carbonaceous reducing agents, reduce carbon emissions and energy consumption, reduce water consumption, and the recovery rates of Pb and Zn can reach over 99%. The production cycle is short and the output is high.

Description

Technical Field

[0001] This application relates to the technical field of resource recovery, and specifically relates to a method for treating zinc oxide fume containing fluorine and chlorine at low temperature. Background Art

[0002] Due to its good physical and chemical properties, zinc is widely used in many industries. Although China has certain zinc mineral resources, with the rapid development of the national economy, it is far from meeting the economic development needs. The comprehensive utilization of secondary zinc resources (zinc oxide fume) has become an important way to solve the shortage of raw materials.

[0003] The sources of secondary zinc resources mainly include blast furnace dust, electric arc furnace fume, hot-dip galvanized slag, galvanized ash, etc., the leaching slag of zinc smelting and the blast furnace slag of lead smelting, and the production and recycling processes such as brass smelting. Among them, the disposal method of blast furnace dust is mostly carbothermal reduction, and zinc oxide dust is obtained through equipment such as rotary hearth furnaces and rotary kilns.

[0004] Affected by the raw material composition, the dust contains a certain amount of lead, and the reduction properties of lead and zinc are similar, making it difficult to separate them using pyrometallurgical processes. The hydrometallurgical process is relatively complex and has high material consumption. Microwave energy, as a radiation-type heating energy, can rely on the dielectric properties of the material itself to convert microwave energy and can selectively heat the material quickly. Using the microwave heating property, selective separation of different elements can be achieved.

[0005] In the prior art:

[0006] Prior art one: The authorized announcement number CN 103320623 B discloses a method and device for dechlorination of zinc oxide fume by steam activation / microwave roasting. This method roasts zinc oxide fume powder under closed conditions, blows air and passes steam under normal pressure, and discharges the generated gas. When the temperature of the zinc oxide fume powder rises to 500 - 750 °C, keep it warm for 20 - 180 min, and after natural cooling, obtain dechlorinated zinc oxide fume powder, and the dechlorination rate > 93 wt%.

[0007] Disadvantages of prior art one: The metal ions in the metal chlorides in the zinc oxide fume are not recovered, resulting in waste of resources.

[0008] Prior art two: The authorized announcement number CN 104593586 B discloses a method for removing fluorine and chlorine from zinc oxide fume by microwave low-temperature roasting and alkali washing. First, roast the zinc oxide fume under microwave conditions; add the zinc oxide fume roasted by microwave to Na 2 CO 3, and after stirring and dissolving, it is filtered to obtain an alkali washing solution and alkali washing residues. First, it rapidly removes low-melting and volatile fluorochlorides by microwave low-temperature roasting, and then deeply removes high-melting fluorochlorides in zinc oxide fume by means of alkali washing.

[0009] Disadvantages of the prior art two: Metal ions in metal chlorides in zinc oxide fume are not recovered, resulting in waste of resources, and the recovery rates of Pb and Zn in the fume are not high.

[0010] Prior art three: Publication No. CN 105671314A discloses a direct smelting method and system for simultaneously producing metallic lead and zinc. The method includes: proportioning and granulating lead-zinc concentrate, lead-zinc oxide ore, and / or lead-zinc secondary materials with a solvent; adding the granulated furnace charge into the smelting zone of a two-zone oxygen-enriched side-blowing furnace, blowing oxygen-enriched air, controlling a weakly reducing atmosphere, and performing smelting to form a lead phase and a slag phase. The crude lead is discharged through a siphon port, and the high-zinc slag enters the fuming zone of the oxygen-enriched side-blowing furnace; adding coal required for zinc reduction to the fuming zone, blowing oxygen-enriched air, and controlling the fuming zone to be a strongly reducing atmosphere; the reduced zinc forms zinc vapor and enters a zinc vapor condenser with the furnace gas to form a zinc-containing lead liquid. After cooling, the zinc liquid is separated from the lead liquid to obtain crude zinc.

[0011] Disadvantages of the prior art three: Using coal as a reducing agent and fuel, the smelting temperature is above 1000 °C, resulting in relatively high energy consumption; the elemental mass ratio of the furnace charge is required to be Pb≥10% and Zn≥20%, and the types of raw materials that can be processed are limited.

[0012] Based on the above existing problems, the method for recycling zinc oxide fume needs to be improved urgently to reduce the use of carbonaceous reducing agents, reduce carbon emissions and energy consumption, reduce water consumption, increase the recovery rates of Pb and Zn, shorten the production cycle, and increase the output. Summary of the Invention

[0013] This application provides a method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine, which can reduce the use of carbonaceous reducing agents, reduce carbon emissions and energy consumption, reduce water consumption, increase the recovery rates of Pb and Zn to over 99%, shorten the production cycle, and increase the output.

[0014] The embodiments of this application are implemented as follows:

[0015] This application example provides a method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine, including the following steps:

[0016] Low-temperature pretreatment step: Adding calcium oxide-containing material and calcium chloride-containing material to zinc oxide fume containing fluorine and chlorine, heating and preprocessing the materials to obtain pretreated zinc oxide fume. In the pretreated zinc oxide fume, zinc mainly exists in the form of oxides, and lead mainly exists in the form of chlorides; the heating pretreatment temperature is 150 - 450 °C;

[0017] Microwave treatment step: The pretreated zinc oxide fume is transported to a microwave heating furnace for microwave heating treatment and stirring. After the lead existing in the form of chloride volatilizes, it is recovered to obtain low-lead zinc oxide fume.

[0018] Reduction and zinc recovery step: The low-lead zinc oxide fume is reduced and zinc is recovered through a reduction device.

[0019] Further, the zinc in the zinc oxide fume containing fluorine and chlorine includes ZnO, ZnF 2 and ZnCl 2 , and the lead includes PbSO 4 and PbCl 2 .

[0020] Further, the molar ratio of CaO in the calcium oxide-containing material to (ZnCl 2 +ZBF 2 ) in the zinc oxide fume containing fluorine and chlorine is 1.04 - 1.21, and the molar ratio of CaCl 2 in the calcium chloride-containing material to PbSO 4 in the zinc oxide fume containing fluorine and chlorine is 1.02 - 1.19.

[0021] Further, the heating pretreatment temperature in the low-temperature pretreatment step is: first heated to 301 - 450 °C, calcined for 20 - 30 min, then the temperature is reduced to 150 - 300 °C, and calcined for 10 - 20 min.

[0022] Further, first heat to 301 - 450 °C and add the calcium oxide-containing material; then reduce the temperature to 150 - 300 °C and add the calcium chloride-containing material.

[0023] Further, the average particle size of the calcium oxide-containing material is 2 - 6 mm, and the average particle size of the calcium chloride-containing material is 0.5 - 1.5 mm.

[0024] Further, in the microwave treatment step, the microwave frequency is 2350 - 2550 MHz, the output power is 1 - 10 KW, the heating rate is 50 - 100 °C / min, the heating temperature is 600 - 800 °C, and the holding time after reaching the heating temperature is 20 - 45 min.

[0025] Further, in the microwave treatment step, the first stage: the microwave frequency is 2451 - 2550 MHz, the output power is 8 - 10 KW, the heating rate is 75 - 100 °C / min, and the heating temperature reaches 600 - 745 °C; the second stage: the microwave frequency is 2350 - 2450 MHz, the output power is 1 - 7 KW, the heating rate is 50 - 70 °C / min, and the heating temperature reaches 746 - 800 °C.

[0026] Further, in the microwave treatment step, the stirring rate of the material is 14 - 20 r / min.

[0027] Further, in the step of reducing and recovering zinc, the low - lead zinc oxide fume is reduced and zinc is recovered through a carbothermal reduction device, and the reduction temperature is above 1000 °C.

[0028] The beneficial effects include:

[0029] By adding specific calcium - oxide - containing materials and calcium - chloride - containing materials as pretreatment auxiliary aids in the low - temperature pretreatment step, the conversion effect of pretreatment is achieved, in which zinc in the zinc oxide fume mainly exists in the form of oxides and lead mainly exists in the form of chlorides at low temperatures. This provides better material conditions for the subsequent separation of Pb and Zn in the process, can significantly improve the recovery rates of Pb and Zn in the fume, and can greatly reduce the use of carbonaceous reducing agents. Through the low - temperature pretreatment step, the microwave treatment step, and the step of reducing and recovering zinc, a three - step dry - process treatment for efficiently recovering and utilizing zinc oxide fume containing fluorine and chlorine without wet treatment is realized, which can reduce energy consumption, reduce water consumption, and the recovery rates of Pb and Zn can reach more than 99%. The production cycle is short and the output is high. Specific embodiments

[0030] The following will describe the implementation scheme of the present application in detail in combination with embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0031] Zinc oxide fume containing fluorine and chlorine mainly comes from ① blast - furnace dust, ② electric - arc - furnace fume, ③ hot - dip galvanized slag, galvanized ash, etc., ④ leaching slag in zinc smelting and blast - furnace slag in lead smelting, ⑤ production and recovery processes such as brass smelting. Among them, the secondary zinc - oxide powder obtained from the above - mentioned dust or slag through pyrometallurgical or hydrometallurgical processes is also used as the zinc oxide fume containing fluorine and chlorine mentioned in the present invention. Zinc in the zinc oxide fume containing fluorine and chlorine mainly exists in the forms of ZnO, ZnF 2 and ZnCl 2 forms, and lead mainly exists in the forms of PbSO 4 and PbCl 2 forms. Through a method for treating zinc oxide fume containing fluorine and chlorine at low temperature of the present application, the full recovery and utilization of Zn and Pb in the zinc oxide fume containing fluorine and chlorine are realized.

[0032] The following will describe in detail the method for treating zinc oxide fume containing fluorine and chlorine at low temperature in the embodiments of the present application.

[0033] The present application example provides a method for treating zinc oxide fume containing fluorine and chlorine at low temperature, comprising the following steps:

[0034] Low-temperature pretreatment step: Zinc oxide fume containing fluorine and chlorine is added with calcium oxide material and calcium chloride material, and the materials are heated and pretreated to obtain pretreated zinc oxide fume. Zinc in the pretreated zinc oxide fume mainly exists in the form of oxide, and lead mainly exists in the form of chloride; the heating pretreatment temperature is 150 - 450 °C (examples are: 150 °C, 163 °C, 178 °C, 187 °C, 196 °C, 201 °C, 234 °C, 257 °C, 279 °C, 298 °C, 331 °C, 346 °C, 364 °C, 375 °C, 398 °C, 406 °C, 413 °C, 427 °C, 432 °C, 439 °C, 442 °C, 446 °C, 448 °C, 450 °C, etc.).

[0035] It can be understood that: the calcium oxide material is lime, limestone, etc.; the calcium chloride material is a powder mainly composed of calcium chloride. The equipment for heating and pretreating the materials is not specifically limited and can be a rotary kiln, tunnel kiln, rotary hearth furnace and other heating treatment equipment. Preferably, it is a rotary kiln. By rotating to provide material stirring, the reaction can be promoted to proceed fully.

[0036] Zinc in the zinc oxide fume containing fluorine and chlorine mainly exists in the forms of ZnO, ZnF 2 and ZnCl 2 forms, and lead mainly exists in the forms of PbSO 4 and PbCl 2 forms. Through heating pretreatment, pretreated zinc oxide fume is obtained. Zinc in the pretreated zinc oxide fume mainly exists in the form of oxide, and lead mainly exists in the form of chloride; this is mainly achieved through the following reactions.

[0037] CaO reacts with ZnCl 2 , ZnF 2 to generate ZnO. The reaction is as follows:

[0038] ZnCl 2 +CaO = ZnO + CaCl 2 ΔG θ =-92.77 KJ (at 150 °C)

[0039] ZnF 2 +CaO = ZnO + CaF 2 ΔG θ =-179.131 KJ (at 150 °C)

[0040] In addition, the reaction of PbCl 2 in the fume with CaO is as follows:

[0041] PbCl2 +CaO = PbO + CaCl 2 ΔG θ = -20.353 KJ (at 150 °C)

[0042] Due to the relatively low reactivity of PbCl 2 when reacting with CaO, CaO preferentially reacts with ZnCl 2 and ZnF 2 .

[0043] PbSO 4 reacts with CaCl 2 to form PbCl 2 , and the reaction is as follows:

[0044] PbSO 4 +CaCl 2 = PbCl 2 +CaSO 4 ΔG θ = -77.79 KJ (150 °C)

[0045] The preheating treatment temperature is 150 - 450 °C. Below 150 °C, the reaction rate is insufficient to complete the material transformation. Above this temperature, the possibility of the reaction between PbCl 2 in the soot and CaO may increase, forming PbO that cannot be removed subsequently, reducing the recovery rate of Pb in the soot.

[0046] By adding calcium oxide-containing materials and calcium chloride-containing materials as pretreatment auxiliary aids in the low-temperature pretreatment step, ZnF 2 , ZnCl 2 , and PbSO 4 in the soot are transformed at low temperature. There is no requirement for the Zn and Pb contents in the soot, and wet treatment is not required. This pretreatment transformation enables zinc in the zinc oxide soot to mainly exist in the oxide form and lead to mainly exist in the chloride form at low temperature, providing favorable conditions for the subsequent separation of zinc oxide and lead chloride in the process, significantly improving the recovery rates of Pb and Zn in the soot, and greatly reducing the use of carbonaceous reducing agents.

[0047] The molar ratio of CaO in the calcium oxide-containing material to (ZnCl 2 + ZnF 2 ) in the zinc oxide soot containing fluorine and chlorine is 1.04 - 1.21 (preferably: 1.06 - 1.13, 1.07 - 1.11; examples are 1.04, 1.06, 1.08, 1.09, 1.11, 1.13, 1.15, 1.18, 1.19, 1.21, etc.). Below this ratio, in the zinc oxide soot containing fluorine and chlorine (ZnCl 2 + ZnF2 ) The reaction is incomplete. Above the above ratio, the materials are prone to caking, resulting in the inability to proceed with the reaction smoothly. Beyond the above ratio range, higher recovery rates of Pb and Zn in the soot cannot be achieved.

[0048] The calcium chloride-containing material contains CaCl 2 and the molar ratio of the lead sulfate in the zinc oxide soot containing fluorine and chlorine to 4 is 1.02 - 1.19 (preferred: 1.02 - 1.05; examples are 1.03, 1.05, 1.07, 1.09, 1.12, 1.14, 1.16, 1.17, 1.19, etc.). Below the above ratio, the reaction of lead sulfate in the zinc oxide soot containing fluorine and chlorine is incomplete; above the above ratio, the air permeability of the materials becomes poor, resulting in a decrease in the reaction rate. Beyond the above ratio range, higher recovery rates of Pb and Zn in the soot cannot be achieved. In addition, the molar ratio of CaO in the calcium oxide-containing material to (ZnCl 4 ) in the zinc oxide soot containing fluorine and chlorine is greater than the molar ratio of CaCl in the calcium chloride-containing material 2 to the lead sulfate in the zinc oxide soot containing fluorine and chlorine, which can further improve the recovery rates of Pb and Zn in the soot. The reason may be that: the appropriate decrease of CaCl in the calcium chloride-containing material does not affect the promotion of the reaction of lead sulfate in the zinc oxide soot containing fluorine and chlorine to a certain extent, and at the same time, it also promotes the reaction of (ZnCl 2 ) in the zinc oxide soot containing fluorine and chlorine with calcium oxide. 2 and the lead sulfate in the zinc oxide soot containing fluorine and chlorine 4 The molar ratio of can further improve the recovery rates of Pb and Zn in the soot. The reason may be that: the appropriate decrease of CaCl in the calcium chloride-containing material does not affect the promotion of the reaction of lead sulfate in the zinc oxide soot containing fluorine and chlorine to a certain extent, and at the same time, it also promotes the reaction of (ZnCl 2 in the zinc oxide soot containing fluorine and chlorine. 4 The reaction while also promoting the reaction of (ZnCl 2 +ZnF 2 ) in the zinc oxide soot containing fluorine and chlorine with calcium oxide.

[0049] In some embodiments: the heating pretreatment temperature of the low-temperature pretreatment step is: first heated to 301 - 450 °C (examples are: 301 °C, 314 °C, 325 °C, 334 °C, 365 °C, 378 °C, 384 °C, 396 °C, 401 °C, 405 °C, 418 °C, 424 °C, 433 °C, 437 °C, 442 °C, 445 °C, 449 °C, 450 °C, etc.), calcined for 20 - 30 min, and then the temperature is reduced to 150 - 300 °C (examples are: 150 °C, 153 °C, 167 °C, 176 °C, 184 °C, 212 °C, 237 °C, 248 °C, 254 °C, 261 °C, 278 °C, 284 °C, 292 °C, 296 °C, 298 °C, 300 °C, etc.), and calcined for 10 - 20 min. By treating at a high temperature for a long time, it is more beneficial for CaO in the calcium oxide-containing material to react with (ZnCl 2 +ZnF 2) The rapid progress of the reaction shortens the reaction time, improves the reaction efficiency, and at the same time, the generated CaCl 2 can react with PbSO 4 reaction, reducing the dosage of CaCl 2 ; then lower the treatment temperature to ensure that while the PbSO 4 reaction occurs, the PbCl 2 reaction is inhibited. Through the above temperature control, the recovery rates of Pb and Zn in the soot can be further improved.

[0050] In some embodiments: First, heat to 301 - 450 °C and add the calcium oxide-containing material; then lower the temperature to 150 - 300 °C and add the calcium chloride-containing material. By heating the calcium oxide-containing material at the high temperature stage, it is more conducive to the rapid progress of the reaction between CaO in the calcium oxide-containing material and (ZnCl 2 + ZnF 2 ) in the zinc oxide soot containing fluorine and chlorine, shortening the reaction time and improving the reaction efficiency. At the same time, the generated CaCl 2 can react with PbSO 4 reaction, reducing the dosage of CaCl 2 ; at the same time, reducing the inhibition of the reaction by the addition of CaCl 2 , promoting the reaction between CaO and (ZnCl 2 + ZnF 2 ) in the zinc oxide soot containing fluorine and chlorine. Adding CaCl 2 at a lower treatment temperature ensures the PbSO4 reaction while inhibiting the PbCl 2 reaction. Through the separate addition of the above-mentioned auxiliaries, the reaction conversion process can be further improved, and the recovery rates of Pb and Zn in the soot can be increased.

[0051] In some embodiments: The average particle size of the calcium oxide-containing material is 2 - 6 mm (examples are 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, etc.), and the average particle size of the calcium chloride-containing material is 0.5 - 1.5 mm (examples are 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, etc.). The relatively large average particle size of the calcium oxide-containing material has little effect on the reaction between CaO and (ZnCl 2 + ZnF 2 ) in the zinc oxide soot containing fluorine and chlorine at high temperature, but it will inhibit the reaction between PbCl 2 and CaO at high temperature. The relatively small average particle size of the calcium chloride-containing material can promote the progress of the PbSO 4 reaction at low temperature, reduce the influence of temperature reduction on the reaction process, and further inhibit the occurrence of the reaction between PbCl 2 and CaO, thereby increasing the recovery rates of Pb and Zn in the soot.

[0052] Microwave treatment step: The reacted zinc oxide fume mixture enters a microwave heating furnace. The ability of a substance to absorb microwave heating depends on the dielectric loss factor. Different substances have different loss factors, and when heated by microwaves, it exhibits the characteristic of selective heating. PbCl 2 has strong wave absorption performance, while ZnO has weak wave absorption performance. By using microwave roasting, PbCl 2 can be rapidly heated, while the temperature of ZnO basically does not change. The pretreated zinc oxide fume is transported to a microwave heating furnace for microwave heating treatment and stirring. The microwave frequency is 2350 - 2550 MHz (examples are 2350 MHz, 2367 MHz, 2378 MHz, 2386 MHz, 2432 MHz, 2457 MHz, 2476 MHz, 2483 MHz, 2494 MHz, 2507 MHz, 2512 MHz, 2523 MHz, 2534 MHz, 2541 MHz, 2550 MHz, etc.), the output power is 1 - 10 KW (examples are 1 KW, 2 KW, 3 KW, 4 KW, 5 KW, 6 KW, 7 KW, 8 KW, 9 KW, 10 KW, etc.), the heating rate is 50 - 100 °C / min (examples are 50 °C / min, 62 °C / min, 74 °C / min, 88 °C / min, 93 °C / min, 100 °C / min, etc.), the heating temperature is 600 - 800 °C (examples are 600 °C, 623 °C, 634 °C, 647 °C, 653 °C, 667 °C, 682 °C, 691 °C, 701 °C, 714 °C, 728 °C, 735 °C, 748 °C, 759 °C, 768 °C, 779 °C, 783 °C, 794 °C, 800 °C, etc.), and the holding time after reaching the heating temperature is 20 - 45 min; PbCl 2 is a low melting point and volatile substance. When roasted in an air atmosphere, PbCl 2 will not react with O 2 and H 2 O in the air. It will only undergo a volatilization reaction and become gaseous; and as the roasting temperature increases, the vapor pressure of PbCl 2 increases accordingly, and the volatilization is significant. Therefore, increasing the roasting temperature can promote the forward progress of the volatilization reaction. Below the above temperature, the volatilization of PbCl 2 is insufficient and there is a lot of residue. Above the above temperature, components such as impurities in the material volatilize, affecting the product quality.

[0053] The stirring rate of the material is 14 - 20 r / min (examples are 14 r / min, 15 r / min, 16 r / min, 17 r / min, 18 r / min, 19 r / min, 20 r / min, etc.). Stirring the material helps PbCl 2After absorbing heat, it volatilizes. The lead existing in the form of chloride volatilizes and is recovered through an air extraction device, obtaining low-lead zinc oxide fume dust. The stirring device is not specifically limited and can be a stirring device such as a stirring paddle.

[0054] In the microwave treatment step, the first stage: the microwave frequency is 2451 - 2550 MHz, the output power is 8 - 10 KW, the heating rate is 75 - 100 °C / min, and the heating temperature is up to 600 - 745 °C; the second stage: the microwave frequency is 2350 - 2450 MHz, the output power is 1 - 7 KW, the heating rate is 50 - 70 °C / min, and the heating temperature is up to 746 - 800 °C. In the first stage, high power and high frequency are adopted to achieve a high heating rate, which can promote the volatilization of PbCl 2 Volatilization. In the second stage, low frequency, low power, and low heating rate are adopted to avoid excessive vapor pressure of PbCl 2 Volatilization, which affects the volatilization process.

[0055] Step of reducing and recovering zinc: The low-lead zinc oxide fume dust is reduced and recovered zinc through a carbothermal reduction device, and the reduction temperature is above 900 °C (examples are 954 °C, 1091 °C, 1112 °C, 1239 °C, 1342 °C, etc.).

[0056] The features and performance of the present application are further described in detail below in combination with embodiments:

[0057] Example 1

[0058] A method for treating zinc oxide fume dust containing fluorine and chlorine at low temperature, comprising the following steps: Low-temperature pretreatment step, zinc oxide fume dust containing fluorine and chlorine is added with calcium oxide-containing material and calcium chloride-containing material, and the materials are heated and pretreated. The heating pretreatment temperature is 403 °C. The molar ratio of CaO in the calcium oxide-containing material to (ZnCl 2 +ZnF 2 ) in the zinc oxide fume dust containing fluorine and chlorine is 1.07, and the molar ratio of CaCl 2 in the calcium chloride-containing material to PbSO 4 in the zinc oxide fume dust containing fluorine and chlorine is 1.18.

[0059] Microwave treatment step: The microwave frequency is 2457 MHz, the output power is 8 KW, the heating rate is 93 °C / min, the heating temperature is 797 °C, and the holding time is 20 - 45 min after reaching the heating temperature; the stirring rate of the materials is 16 r / min.

[0060] Step of reducing and recovering zinc: The low-lead zinc oxide fume dust is reduced and recovered zinc through a carbothermal reduction device, and the reduction temperature is 1001 °C.

[0061] It is measured that the volatilization rate of Pb in the microwave stage is 99.0%, and the recovery rate of Zn in the ZnO dust is 99.3%.

[0062] Example 2

[0063] The process parameters are basically the same as those in Example 1, except that: in the low-temperature pretreatment step, the heating pretreatment temperature is: first heated to 448 °C, calcined for 27 min, then the temperature is reduced to 216 °C, and calcined for 10 - 20 min. After measurement, the volatilization rate of Pb in the microwave stage is 99.2%, and the recovery rate of Zn in the ZnO dust is 99.4%.

[0064] Example 3

[0065] The process parameters are basically the same as those in Example 2, except that: in the low-temperature pretreatment step, the heating pretreatment temperature is: the molar ratio of CaO in the calcium oxide-containing material to (ZnCl 2 +ZnF 2 ) in the zinc oxide fume and dust containing fluorine and chlorine is 1.06, and the molar ratio of CaCl 2 in the calcium chloride-containing material to PbSO 4 in the zinc oxide fume and dust containing fluorine and chlorine is 1.03. After measurement, the volatilization rate of Pb in the microwave stage is 99.3%, and the recovery rate of Zn in the ZnO dust is 99.6%.

[0066] Example 4

[0067] The process parameters are basically the same as those in Example 3, except that: in the low-temperature pretreatment step, the heating pretreatment temperature is: first heated to 448 °C, the calcium oxide-containing material is added, calcined for 27 min, then the temperature is reduced to 216 °C, the calcium chloride-containing material is added, and calcined for 10 - 20 min. After measurement, the volatilization rate of Pb in the microwave stage is 99.5%, and the recovery rate of Zn in the ZnO dust is 99.5%.

[0068] Example 5

[0069] The process parameters are basically the same as those in Example 1, except that: the average particle size of the calcium oxide-containing material is 4 mm, and the average particle size of the calcium chloride-containing material is 0.8 mm. After measurement, the volatilization rate of Pb in the microwave stage is 99.2%, and the recovery rate of Zn in the ZnO dust is 99.4%.

[0070] Example 6

[0071] The process parameters are basically the same as those in Example 4, except that: the average particle size of the calcium oxide-containing material is 5 mm, and the average particle size of the calcium chloride-containing material is 0.6 mm. After measurement, the volatilization rate of Pb in the microwave stage is 99.6%, and the recovery rate of Zn in the ZnO dust is 99.7%.

[0072] Example 7

[0073] It is basically the same as the process parameters of Example 1, with the differences being: in the microwave treatment step, in the first stage, the microwave frequency is 2496 MHz, the output power is 9 KW, the heating rate is 83 °C / min, and the heating temperature is up to 730 °C; in the second stage, the microwave frequency is 2378 MHz, the output power is 5 KW, the heating rate is 62 °C / min, and the heating temperature is up to 799 °C. After measurement, the volatilization rate of Pb in the microwave stage is 99.4%, and the recovery rate of Zn in the ZnO dust is 99.2%.

[0074] Example 8

[0075] It is basically the same as the process parameters of Example 6, with the differences being: in the microwave treatment step, in the first stage, the microwave frequency is 2487 MHz, the output power is 9 KW, the heating rate is 91 °C / min, and the heating temperature is up to 735 °C; in the second stage, the microwave frequency is 2380 MHz, the output power is 6 KW, the heating rate is 59 °C / min, and the heating temperature is up to 800 °C. After measurement, the volatilization rate of Pb in the microwave stage is 99.8%, and the recovery rate of Zn in the ZnO dust is 99.6%.

[0076] The above are only specific embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine, characterized in that, it comprises the following steps: Low-temperature pretreatment step: Zinc oxide fume containing fluorine and chlorine is added with calcium oxide-containing material and calcium chloride-containing material, and the materials are heated for pretreatment to obtain pretreated zinc oxide fume. In the pretreated zinc oxide fume, zinc mainly exists in the form of oxide, and lead mainly exists in the form of chloride; the heating pretreatment temperature is 150 - 450 °C; Microwave treatment step: The pretreated zinc oxide fume is transported to a microwave heating furnace for microwave heating treatment and stirring. After lead existing in the form of chloride volatilizes, it is recovered to obtain low-lead zinc oxide fume; Reduction and zinc recovery step: The low-lead zinc oxide fume is reduced and zinc is recovered through a reduction device; The zinc in the zinc oxide fume containing fluorine and chlorine includes ZnO, ZnF 2 and ZnCl 2 , and the lead includes PbSO 4 and PbCl 2 ; the molar ratio of CaO in the calcium oxide-containing material to (ZnCl 2 +ZnF 2 ) in the zinc oxide fume containing fluorine and chlorine is 1.04 - 1.21, and the molar ratio of CaCl 2 in the calcium chloride-containing material to PbSO 4 in the zinc oxide fume containing fluorine and chlorine is 1.02 - 1.19; the heating pretreatment temperature in the low-temperature pretreatment step is: first heated to 301 - 450 °C, calcined for 20 - 30 min, then the temperature is reduced to 150 - 300 °C, and calcined for 10 - 20 min; first heated to 301 - 450 °C, and the calcium oxide-containing material is added; then the temperature is reduced to 150 - 300 °C, and the calcium chloride-containing material is added.

2. The method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine according to claim 1, characterized in that, the average particle size of the calcium oxide-containing material is 2 - 6 mm, and the average particle size of the calcium chloride-containing material is 0.5 - 1.5 mm.

3. The method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine according to claim 1, characterized in that, in the microwave treatment step, the microwave frequency is 2350 - 2550 MHz, the output power is 1 - 10 KW, the heating rate is 50 - 100 °C / min, the heating temperature is 600 - 800 °C, and the holding time after reaching the heating temperature is 20 - 45 min.

4. The method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine according to claim 3, characterized in that, in the microwave treatment step, the first stage: the microwave frequency is 2451 - 2550 MHz, the output power is 8 - 10 KW, the heating rate is 75 - 100 °C / min, and the heating temperature reaches 600 - 745 °C; the second stage: the microwave frequency is 2350 - 2450 MHz, the output power is 1 - 7 KW, the heating rate is 50 - 70 °C / min, and the heating temperature reaches 746 - 800 °C.

5. The method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine according to claim 1, characterized in that, in the microwave treatment step: the stirring rate of the material is 14 - 20 r / min.

6. The method for low-temperature treatment of zinc oxide fume containing fluorine and chlorine according to claim 1, characterized in that, reduction and zinc recovery step: The low-lead zinc oxide fume is reduced and zinc is recovered through a carbothermal reduction device, and the reduction temperature is above 1000 °C.