A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace

Abstract

The present invention provides a method for reducing energy consumption in treating zinc-containing dust in a rotary hearth furnace. By adding a sufficient amount of calcium oxide and a small amount of a reducing agent, the zinc-containing dust is converted into calcium ferrite and elemental zinc through high-temperature roasting. High calcium and low carbon conditions promote the conversion of iron oxide into calcium ferrite, reducing both the heat absorbed by the iron oxide reduction reaction and the amount of flue gas generated and the heat removed by the flue gas. This, to a certain extent, alleviates the high energy consumption and large flue gas volume associated with treating zinc-containing dust in a rotary hearth furnace. Furthermore, the addition of lignin as a reducing agent not only effectively reduces zinc oxide but also reduces the consumption of non-renewable energy (pulverized coal), resulting in both environmental and social benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of treating zinc-containing dust in a rotary hearth furnace, and particularly relates to a method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace. Background Art

[0002] The steel industry is resource- and energy-intensive, generating significant amounts of industrial dust, such as zinc dust, during steel production. Zinc dust, high in elements like iron and carbon, holds considerable recycling and utilization value for steelmakers. However, zinc dust also contains zinc, potassium, and sodium, all of which can significantly negatively impact steel production, particularly in blast furnaces. Consequently, zinc dust from steel mills cannot generally be recycled directly within the plant, leading to significant accumulation and severe environmental pollution. Consequently, resource utilization of zinc dust has become a significant challenge for steelmakers.

[0003] Rotary hearth furnaces are a highly efficient and scalable method for treating zinc-containing dust and are a major resource for zinc-containing dust recovery in steel mills. The rotary hearth furnace process primarily utilizes self-reduction of carbon-containing pellets under high-temperature conditions to remove zinc, producing metallized pellets. The primary source of the reducing agent, carbon powder, is carbon from dust removal ash or added coke or coal dust. For example, patent publication number CN101386913A, published on March 18, 2009, discloses a method for recovering zinc oxide from zinc-containing dust using a rotary hearth furnace. The disclosed technical solution involves mixing zinc-containing dust with coal and additives, briquetting and drying it, and then feeding it into a rotary hearth furnace for direct reduction. Zinc in the dust is recovered from the exhaust gas. The zinc-removed briquettes are then cooled or briquetted for use after direct reduction in the rotary hearth furnace. This technology is widely applicable to zinc-containing raw materials and maximizes resource utilization. It requires low fuel calorific value, high flue gas temperature, and a high zinc removal rate. The treated dust is converted into direct reduced iron. However, the high reaction temperature of the rotary hearth furnace and the large amount of flue gas that carries away a lot of heat, resulting in low energy efficiency. Therefore, the rotary hearth furnace process still needs to be improved and perfected. Improving the energy efficiency of the rotary hearth furnace and reducing energy consumption are urgent issues that need to be addressed in the rotary hearth furnace process.

[0004] In addition to adding coal powder and coke powder, calcium oxide is added to the zinc-containing dust in order to lower the melting point of the slag when treating zinc-containing dust in other processes. For example, the patent with publication number CN 111647704 A published on September 11, 2020, discloses a zinc recovery method based on a HIsmelt smelting reduction furnace. By adding zinc-containing dust during the ironmaking process of the HIsmelt smelting reduction furnace and collecting the dust in the escaping furnace gas for cyclic injection, the zinc content in the atmosphere of the smelting reduction furnace is effectively increased, and the collected zinc-rich dust has a higher zinc content; and by wet-processing the zinc-rich dust, a higher-purity zinc oxide product is obtained, thereby achieving effective enrichment and recovery of zinc. The reduction reaction still mainly occurs during the treatment process, and the purpose of adding calcium oxide is to lower the melting point. Summary of the Invention

[0005] The present invention aims to provide a method for reducing energy consumption in treating zinc-containing dust in a rotary hearth furnace. By adding a sufficient amount of calcium oxide (referred to as high calcium) and a small amount of a reducing agent (referred to as low carbon), the zinc-containing dust is converted into calcium ferrite and elemental zinc through high-temperature roasting. The high calcium and low carbon conditions promote the conversion of iron oxide into calcium ferrite, reducing both the heat absorbed by the iron oxide reduction reaction and the amount of flue gas generated and the heat removed by the flue gas. This, to a certain extent, alleviates the high energy consumption and high flue gas volume associated with treating zinc-containing dust in a rotary hearth furnace. Furthermore, the addition of lignin as a reducing agent not only effectively reduces zinc oxide but also reduces the consumption of non-renewable energy (pulverized coal), resulting in both environmental and social benefits.

[0006] The specific technical solutions of the present invention are as follows:

[0007] The present invention provides a method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace, comprising the following steps:

[0008] 1) Mixing a reducing agent, zinc-containing dust and calcium oxide, and feeding the resulting mixture into a rotary hearth furnace, heating and keeping the mixture warm, and then cooling it down along with the furnace;

[0009] 2) Calcium ferrite pellets are discharged from the rotary hearth furnace, and the flue gas discharged from the rotary hearth furnace is subjected to heat exchange and zinc removal to obtain zinc powder containing zinc oxide.

[0010] The reducing agent accounts for 2-4% by mass in the mixture, preferably 2-3% by mass;

[0011] The reducing agent comprises the following raw materials in percentage by weight: 60% to 70% lignin, 20% to 25% anthracite powder, and the balance high-efficiency catalyst;

[0012] The particle size of the lignin is 200-18 mesh;

[0013] The high-efficiency catalyst comprises the following raw materials in 100% by mass: 10-20% cobalt oxide, 15-25% cerium oxide, 3-6% potassium chloride, and 49-72% nickel oxide, which total 100%.

[0014] The zinc-containing dust accounts for 70-73% by mass in the mixture, preferably 71%;

[0015] The zinc-containing dust is selected from blast furnace, converter or electric furnace dust, with a dust particle size of less than 0.1 mm and a moisture content of less than 6%;

[0016] The calcium oxide accounts for 23-28% by mass in the mixture, preferably 26-27%;

[0017] The particle size of the calcium oxide is 200-18 mesh;

[0018] The moisture content of the reducing agent, zinc-containing dust and calcium oxide is reduced to below 2% by drying, and then mixed;

[0019] Preferably, the reducing agent, zinc-containing dust and calcium oxide are mixed, sent to a high-pressure briquetting machine and pressed into green balls with a diameter of 10 to 40 mm, and then sent to a rotary hearth furnace;

[0020] The rotary hearth furnace is fueled by coke oven gas and protected by nitrogen atmosphere.

[0021] In step 1), the heating and heat preservation is specifically as follows: heating to 1250°C in a rotary hearth furnace, holding the temperature for 15-25 minutes, and then cooling with the furnace. Preferably, the temperature is 1250°C and the heat preservation time is 25 minutes.

[0022] In step 1), during the insulation period, nitrogen was first passed through for 15 minutes and then switched to air for 10 minutes;

[0023] Alternatively, during the holding period, nitrogen was passed through for 15 minutes and then switched to oxygen for 10 minutes;

[0024] Alternatively, nitrogen is always introduced during the holding period;

[0025] In step 2), after the insulation is completed, the calcium ferrite pellets are discharged from the rotary hearth furnace and can be used as additives for sintering and converters, and can also be used as raw materials for negative expansion materials and photocatalytic materials.

[0026] In step 2), zinc powder containing zinc oxide is obtained by heat exchange and zinc removal from the high-temperature flue gas discharged from the rotary hearth furnace. The high-temperature flue gas is first subjected to dust reduction, then heat is recovered using a heat exchanger. After the heat exchange, air is added to oxidize the zinc vapor to produce zinc oxide dust, which is then cooled using a cooler and finally recovered using a bag dust collector.

[0027] In step 2), the specific recovery process is:

[0028] The flue gas first enters a dust suppression chamber to allow large dust particles to fall. Heat is then exchanged through a heat exchanger, where the sensible heat in the flue gas preheats the combustion air in the rotary hearth furnace. Air is then added to oxidize the zinc vapor to produce zinc oxide dust, which is further cooled in a cooler. To increase the zinc oxide concentration in the finished product, the low-concentration zinc oxide dust collected at the bottom of the cooler is piped into the batching room for further batching, where it is recycled and enriched for reuse. The cooled exhaust gas is then fed to a dust collector, where zinc oxide is recovered and stored in a silo. An induced draft fan is installed at the dust collector outlet to achieve the required pressure drop in the flue gas system. The exhaust gas can also be used to dry materials in the system.

[0029] The operating temperature of the rotary hearth furnace is 1250-1350°C, and the main heat transfer method is radiation heat transfer. During the treatment process, the reduction reaction of iron / zinc oxides mainly occurs. The simultaneous reduction of iron and zinc causes a large amount of flue gas to take away a large amount of heat, resulting in low energy efficiency. How to improve the energy efficiency of the rotary hearth furnace and reduce energy consumption is an urgent problem to be solved in the rotary hearth furnace process. In view of the high energy consumption of the rotary hearth furnace process, the present invention provides a method for reducing the energy consumption of the rotary hearth furnace for treating zinc-containing dust. Coal powder is used as a reducing agent, which has a high carbon content, a low oxygen content, and a strong reducing effect, so the dezincification rate is high. However, due to the good reducing effect, more iron oxides are reduced, and the amount of calcium ferrite generated is reduced. Lignin is used as a biomass raw material. Compared with traditional carbonaceous reducing agents (coal powder), it has a lower carbon content and a higher oxygen content. Therefore, the reducing effect is slightly lower than that of coal powder, so the dezincification rate is lower than the dezincification rate using coal powder as a reducing agent. The combustion of lignin consumes some carbon elements, and the large porosity is conducive to the formation of calcium ferrite, so the calcium ferrite formation rate is high. Using a single reducing agent cannot effectively remove zinc oxide and generate calcium ferrite. Therefore, the present invention selects lignin as the main additive to the mixed reducing agent, and then adds some coal powder and a high-efficiency catalyst to promote zinc oxide removal. Zinc oxide removal requires ensuring that the residual zinc content in the pellets after roasting is below 0.5%. Calculations show that the zinc removal rate must reach above 93%, and the calcium ferrite production must remain above 90%, ensuring the subsequent utilization of the calcium ferrite pellets.

[0030] The present invention dries zinc-containing dust, a reducing agent, and calcium oxide, mixes them, compresses them into briquettes, and sends them to a rotary hearth furnace for high-temperature roasting. Zinc in the dust is recovered from the exhaust gas, and the calcium ferrite pellets obtained after zinc removal can be further utilized. Under high-calcium and low-carbon conditions, the present invention utilizes the high-temperature reduction process of the rotary hearth furnace to rapidly volatilize zinc from the zinc-containing dust, achieving a dezincification rate of up to 94.0%. Simultaneously, the iron oxides in the zinc-containing dust react with the calcium oxide to form calcium ferrite, with a calcium ferrite formation rate of up to 93.1%. This method successfully separates the iron and zinc elements from the zinc-containing dust, achieving the reduction of zinc oxide and the formation of calcium ferrite, while suppressing the reduction of iron oxides.

[0031] Compared with the traditional rotary hearth furnace process, the present invention has a higher pellet yield. The traditional rotary hearth furnace process only produces 585.97 kg of metallized pellets when processing 1 ton of zinc-containing dust and carbon-containing pellets. The new process of the present invention produces 930.79 kg of calcium ferrite pellets when processing 1 ton of zinc-containing dust and carbon-containing pellets, an increase of 58.85%. Moreover, under the same reaction temperature conditions (1250°C), the traditional rotary hearth furnace process has a heat expenditure of 6144.53 MJ when processing 1 ton of zinc-containing dust and carbon-containing pellets, while the heat expenditure of the present invention is 3542.25 MJ, saving 42.35% and greatly reducing energy consumption. From an economic perspective, the traditional rotary hearth furnace process costs 1135.97 yuan to process 1 ton of zinc-containing dust and carbon-containing pellets, while the present invention costs only 802.68 yuan to process 1 ton of pellets, reducing the cost per ton by 29.34%, greatly reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The effects of different reducing agents on the formation rate of calcium ferrite and the dezincification rate;

[0033] Figure 2 Comparison of thermal dezincification rates between a conventional rotary hearth furnace and process example 6 of the present invention;

[0034] Figure 3 Heat expenditure of conventional rotary hearth furnace process and embodiment 6 of the present invention;

[0035] Figure 4 Thermal cost expenditure of the conventional rotary hearth furnace process and Example 6 of the present invention. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0038] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0039] The dust treated by the present invention has a particle size of less than 0.1 mm and a moisture content of less than 6% and is electric furnace dust.

[0040] The moisture content of the reducing agent, zinc-containing dust and calcium oxide is reduced to below 2% by drying before use.

[0041] Example 1

[0042] A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace comprises the following steps:

[0043] 1) According to mass percentage, 71% zinc-containing dust, 2% reducing agent, and 27% calcium oxide are mixed to obtain a mixture. The reducing agent includes 69% lignin, 25% anthracite powder, and the balance is a high-efficiency catalyst. The specific raw materials and proportions are shown in Table 2. The lignin and calcium oxide are sieved through an 18-mesh sieve, and the particle size is less than 18 mesh. The mixture is sent to a high-pressure briquetting machine to be pressed into green balls of 10 to 40 mm, and then sent to a rotary hearth furnace. The rotary hearth furnace uses coke oven gas as fuel and is protected by a nitrogen atmosphere. The mixture is heated to 1250° C. in the rotary hearth furnace and maintained for about 25 minutes. During the holding period, nitrogen is first passed for 15 minutes and then switched to air for 10 minutes. The temperature is then cooled with the furnace.

[0044] 2) Calcium ferrite pellets discharged from the rotary hearth furnace; Zinc powder containing zinc oxide can be obtained by heat exchange and zinc removal from the high-temperature flue gas discharged from the rotary hearth furnace. The high-temperature flue gas is first dusted, then heat is recovered using a heat exchanger. After heat exchange, air is added to oxidize the zinc vapor to produce zinc oxide dust, which is cooled using a cooler and finally recovered using a bag dust collector.

[0045] Comparative Example 1

[0046] A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace comprises the following steps:

[0047] 1) According to mass percentage, 71% zinc dust, 2% coal powder, and 27% calcium oxide are mixed to obtain a mixture. The coal powder and calcium oxide are sieved through an 18-mesh sieve to obtain a particle size of less than 18 mesh. The mixture is fed into a high-pressure briquetting machine to be pressed into green balls of 10 to 40 mm, and then fed into a rotary hearth furnace fueled by coke oven gas and protected by a nitrogen atmosphere. The mixture is heated to 1250° C. in the rotary hearth furnace and maintained at this temperature for about 25 minutes. During the holding period, nitrogen is first passed through for 15 minutes and then switched to air for 10 minutes. The mixture is then cooled with the furnace.

[0048] 2) Same as Example 1.

[0049] Comparative Example 2

[0050] A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace comprises the following steps:

[0051] 1) According to mass percentage, 71% zinc dust, 2.5% biomass carbon powder, and 26.5% calcium oxide are mixed to obtain a mixture. The biomass carbon powder and calcium oxide are sieved through an 18-mesh sieve to obtain a particle size of less than 18 mesh. The mixture is fed into a high-pressure briquetting machine to be pressed into green balls of 10 to 40 mm. The mixture is then fed into a rotary hearth furnace fueled by coke oven gas and protected by a nitrogen atmosphere. The mixture is heated to 1250° C. in the rotary hearth furnace and maintained at this temperature for about 25 minutes. During the holding period, nitrogen is first passed through the furnace for 15 minutes and then switched to air for 10 minutes. The mixture is then cooled with the furnace.

[0052] 2) Same as Example 1.

[0053] Comparative Example 3

[0054] A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace comprises the following steps:

[0055] 1) 71% zinc dust, 2.5% lignin, and 26.5% calcium oxide are mixed according to mass percentage to obtain a mixture. The lignin and calcium oxide are sieved through an 18-mesh sieve to a particle size of less than 18 mesh. The mixture is fed into a high-pressure briquetting machine to form green balls of 10 to 40 mm in size. The mixture is then fed into a rotary hearth furnace fueled by coke oven gas and protected by a nitrogen atmosphere. The mixture is heated to 1250° C. in the rotary hearth furnace and maintained at this temperature for approximately 25 minutes. During this holding period, nitrogen is first passed through the furnace for 15 minutes, then switched to air for 10 minutes, and then the temperature is lowered along with the furnace.

[0056] 2) Same as Example 1.

[0057] After the treatment of Example 1 and Comparative Examples 1-3, the calcium ferrite generation rate and the dezincification rate were statistically analyzed. The results are as follows: Figure 1 shown.

[0058] In Example 1, a mixed reducing agent was selected as the reducing agent. Compared with coal powder, biomass carbon powder and lignin, the calcium ferrite generation rate and the zinc removal rate were significantly improved, and the calcium ferrite generation rate and the zinc removal rate were 93.7% and 92.95% respectively.

[0059] In Comparative Example 1, pulverized coal was used as the reducing agent, and the generation rate of calcium ferrite was low, only 86.5%. This was because the pulverized coal had a strong reducing effect, resulting in more iron oxides being reduced and a low calcium ferrite generation rate. At the same time, the pulverized coal participated in the reaction slowly, requiring a longer reaction time, and therefore the dezincification rate did not meet the requirements.

[0060] In Comparative Example 2, biomass carbon powder was used as the reducing agent, the amount of calcium ferrite generated and the zinc removal rate were not high, and the reaction effect was poor.

[0061] In Comparative Example 3, lignin was selected as the reducing agent, and the calcium ferrite generation rate was higher. Compared with the biomass carbon powder, the generation amount of calcium ferrite was increased, but the zinc removal rate still could not meet the requirements.

[0062] The present invention selects to add lignin, coal powder and a high-efficiency catalyst and mix them in a certain proportion to prepare a high-efficiency reducing agent. When lignin is used as the reducing agent, the calcium ferrite generation rate is high, but the dezincification rate is not high. The coal powder has a strong reducing effect. The addition of coal powder can promote the reduction of zinc oxide, but the coal powder has the problem of slow participation in the reaction. Therefore, a small amount of high-efficiency catalyst is added to catalyze the reduction of lignin, coal powder and zinc oxide.

[0063] The experiment was carried out in accordance with Example 1, with the raw material ratio, holding temperature, holding time and the gas introduced during holding being changed. The results are shown in Table 1.

[0064] Table 1 Experimental results under different experimental conditions

[0065]

[0066]

[0067] Table 1 shows that:

[0068] In Comparative Example 4, at a reaction temperature of 1150° C., a reaction time of 25 min, and a nitrogen atmosphere, the formation rate of calcium ferrite and the dezincification rate were only 87.2% and 58.7%, respectively, because the reaction temperature was too low and the reaction could not be fully achieved.

[0069] In Comparative Example 5, the reaction temperature was raised to 1200°C, while other reaction conditions remained unchanged. The formation rate of calcium ferrite increased to 88.7%, and the zinc removal rate increased to 77.8%, indicating that increasing the reaction temperature is beneficial to the formation of calcium ferrite and the removal of zinc oxide.

[0070] In Example 2, the reaction temperature was further increased to 1250°C, while other reaction conditions remained unchanged. The calcium ferrite formation rate increased to 90.1%, and the zinc removal rate increased to 92.6%. However, if the temperature is further increased, the calcium ferrite will decompose due to the high temperature, so the reaction temperature needs to be controlled at around 1250°C.

[0071] In Comparative Example 6, at a reaction temperature of 1250° C., a reaction time of 5 min, and a nitrogen atmosphere, the calcium ferrite formation rate and the dezincification rate were only 89.4% and 74.9% respectively. This was because the reaction time was too short and the reaction was not complete, resulting in a low calcium ferrite formation rate and a low dezincification rate.

[0072] In Example 3, the reaction time was extended to 15 min, the formation rate of calcium ferrite increased to 89.9%, and the dezincification rate increased to 85.2%.

[0073] In Example 2, the reaction time was extended to 25 minutes, and the formation rate of calcium ferrite increased to 90.1%, and the dezincification rate increased to 92.6%. The reaction time of a rotary hearth furnace is generally around 25 minutes. Too long a holding time will lead to high energy consumption, so the reaction time should be controlled at around 25 minutes.

[0074] In Comparative Example 7, the amount of reducing agent was reduced. At a reaction temperature of 1250°C, a reaction time of 25 min, and a nitrogen atmosphere, when the amount of high-efficiency reducing agent added was 1%, the formation rate of calcium ferrite and the dezincification rate were 92.6% and 51.6% respectively. This is because the amount of reducing agent added was too low and zinc oxide could not be completely reduced.

[0075] In Example 2, increasing the reducing agent dosage to 2% reduced the calcium ferrite formation rate to 90.1%, but increased the zinc removal rate to 92.6%. This is because increasing the reducing agent dosage promoted the reduction reaction of iron oxide and zinc oxide. The increased degree of iron oxide reduction reduced the amount of iron oxide involved in the calcium ferrite formation reaction, thus reducing the calcium ferrite formation rate.

[0076] In Comparative Example 8, the amount of reducing agent added was increased to 3%, the formation rate of calcium ferrite decreased to 77.3%, but the dezincification rate increased to 94.5%.

[0077] Comparative Examples 9 and 10, along with Examples 1 and 4-6, attempted to promote the formation of calcium ferrite and the removal of zinc oxide by changing the reaction atmosphere. Because an oxidizing atmosphere favors the formation of calcium ferrite but hinders the reduction of zinc oxide, changing the reaction atmosphere significantly impacts the formation of calcium ferrite and the removal of zinc oxide. Taking all factors into consideration, the optimal conditions were a 15-minute nitrogen cycle followed by a 10-minute air cycle (air is less expensive than oxygen), a 3% reducing agent, 71% zinc dust, and 26% calcium oxide reaction temperature at 1250°C for 25 minutes, achieving a calcium ferrite formation rate of 93.1% and a zinc removal rate of 94%, respectively.

[0078] Comparative Example 11-Comparative Example 13

[0079] The process was carried out in accordance with Example 1, except that the catalyst raw materials and proportions were different, and the specific control was as shown in Table 2.

[0080] Table 2 High-efficiency catalyst composition and its effect on calcium ferrite formation rate and dezincification rate

[0081] Reaction conditions Cobalt oxide (%) Cerium oxide (%) Potassium chloride (%) Nickel oxide (%) Calcium ferrite formation rate (%) Dezincification rate (%) Example 1 14 17 4 65 93.7 92.95 Comparative Example 11 14 17 1 68 92.5 78.65 Comparative Example 12 5 10 2 83 86.5 76.25 Comparative Example 13 30 30 10 30 81.5 73.25

[0082] Compared with Example 1, Comparative Examples 11 to 13 show that the raw materials and proportions of only one or several high-efficiency catalysts do not meet the requirements of the present invention, which leads to a significant decrease in the calcium ferrite formation rate and the dezincification rate.

[0083] A conventional rotary hearth furnace processes zinc-containing dust, and the final product is metallized pellets. The specific method is as follows: 87% zinc-containing dust and 13% coal powder are prepared into carbon-containing pellets, and the pellets are added to the rotary hearth furnace to realize resource utilization of the zinc-containing dust. The atmosphere is always maintained at nitrogen. Other experimental conditions are the same as those in step 1 of Example 1.

[0084] Figure 2 The zinc removal rates of the conventional rotary hearth furnace and the process (new process) of Example 6 of the present invention were compared. The mass fraction of zinc in the raw material was detected, and the mass of zinc in the pellets before the reaction was calculated based on the mass of the pellets. The zinc content in the product was measured again after the reaction, and the zinc removal rate was calculated by subtracting the mass of zinc in the pellets after the reaction from the mass of zinc in the pellets after the reaction, divided by the mass of zinc in the pellets before the reaction.

[0085] Figure 3 Heat expenditure of the conventional rotary hearth furnace process and Example 6 of the present invention (new process); Figure 4 Thermal cost expenditure of the traditional rotary hearth furnace process and Example 6 of the present invention. The material and energy consumed by the traditional rotary hearth furnace process and the new process Example 6 when treating 1 ton of zinc-containing dust and carbon-containing pellets at the same reaction temperature were calculated by the material balance method, and the energy and mass balance of the new process and the traditional rotary hearth furnace process were compared and analyzed. By calculating the cost required for treating 1 ton of zinc-containing dust and carbon-containing pellets by the new process and the traditional rotary hearth furnace process, the economic feasibility of the new process was analyzed. Under the same reaction temperature conditions (1250°C), the heat expenditure of the traditional rotary hearth furnace process for treating 1 ton of zinc-containing dust and carbon-containing pellets is 6144.53MJ, while the heat expenditure of the present invention is 3542.25MJ, saving 42.35%, greatly reducing energy consumption. From an economic perspective, the traditional rotary hearth furnace process costs 1135.97 yuan to treat 1 ton of zinc-containing dust and carbon-containing pellets, while the present invention only costs 802.68 yuan to treat 1 ton of pellets, reducing the cost per ton by 29.34%, greatly reducing the processing cost. The zinc removal rate of the present invention is not inferior to that of the traditional process, and the economic efficiency is superior.

[0086] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for reducing energy consumption of treating zinc-containing dust in a rotary hearth furnace, characterized in that: The method comprises the following steps: 1) Mix the reducing agent, zinc-containing dust and calcium oxide, and send the resulting mixture into a rotary hearth furnace, heat and keep it warm, and then cool it down with the furnace; 2) Calcium ferrite pellets are discharged from the rotary hearth furnace, and the flue gas discharged from the rotary hearth furnace is subjected to heat exchange and zinc removal to obtain zinc powder containing zinc oxide; The reducing agent includes the following raw materials in mass percentage: 60% to 70% lignin, 20% to 25% anthracite powder, and the balance high-efficiency catalyst; the high-efficiency catalyst includes the following raw materials in mass percentage: 10% to 20% cobalt oxide, 15% to 25% cerium oxide, 3% to 6% potassium chloride, and 49% to 72% nickel oxide.

2. The method according to claim 1, characterized in that The zinc-containing dust accounts for 70-73% by mass in the mixture.

3. The method according to claim 1, characterized in that The reducing agent accounts for 2-4% by mass in the mixture.

4. The method according to claim 1, wherein The calcium oxide accounts for 23-28% by mass in the mixture.

5. The method according to claim 1, wherein The heating and heat preservation is specifically as follows: heating to 1250° C. in a rotary hearth furnace, keeping the temperature for 15-25 minutes, and then cooling with the furnace.

6. The method according to claim 5, characterized in that During the insulation period, nitrogen was passed through for 15 minutes and then switched to air for 10 minutes.

7. The method according to claim 5, characterized in that During the insulation period, nitrogen was passed through for 15 minutes and then switched to oxygen for 10 minutes.

8. The method according to claim 5, characterized in that Nitrogen was always introduced during the insulation period.

9. The method according to claim 1, characterized in that In step 2), the high-temperature flue gas discharged from the rotary hearth furnace is subjected to heat exchange and zinc removal to obtain zinc powder containing zinc oxide.

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