Optimization method for co-processing zinc-containing iron fine powder and lime powder through dezincification rotary kiln

Abstract

The invention relates to the technical field of solid waste treatment, in particular to an optimization method for synergistically treating zinc-containing iron fine powder and lime powder through a dezincification rotary kiln, which comprises the following steps: (1) preparing raw materials; (2) zinc-containing iron fine powder is added, specifically, the proportion of the zinc-containing iron fine powder is increased in a stepped mode by stages according to the proportion of 5%-10%-15%-20%, and after each stage is stabilized for 2-4 days, the next stage is started; and (3) dynamically adjusting the ratio of the lime powder to the zinc-containing iron fine powder to be stabilized at 12%, increasing the alkalinity from 1.2 to 1.8, and continuously monitoring the alkalinity of the kiln slag and the ring formation condition during the period. According to the optimization method, the high-zinc iron fine powder is introduced and matched with the scientific proportion of the coke powder and the lime powder, so that the overall zinc content and reducibility of the raw materials are effectively improved, and sufficient reduction and volatilization of zinc in a high-temperature area are promoted. By optimizing the dezincification raw material ratio and the thermal regulation, the synergistic effect of improving the production load and the yield of the secondary zinc oxide powder is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste treatment, and particularly relates to an optimization method for rotary kiln cooperative treatment of zinc-containing iron concentrate powder and lime powder. BACKGROUND

[0002] With the continuous development of the steel industry, a large amount of iron-containing solid waste is generated in the metallurgical production process, such as blast furnace dust, converter sludge, electric furnace dust and rolling sludge. These solid wastes usually contain high-value metal elements such as iron, zinc and lead. If they are directly discarded, not only the resources will be wasted, but also the environment will be polluted. In order to realize the resource recycling and green production of steel enterprises, the use of zinc removal production line for resource treatment of zinc-containing solid waste has become a key technical path recognized by the industry. Through the processes of thermal reduction, volatilization enrichment and flue gas condensation, zinc is volatilized and separated from the solid waste, forming a by-product of secondary zinc oxide powder, and realizing the simultaneous recovery of iron and zinc resources.

[0003] In the existing production system, the raw materials of the zinc removal production line are mainly derived from the dust and sludge generated in the production process of the enterprise itself. These solid wastes have the advantages of concentrated source, convenient treatment and low transportation cost, but they have two significant problems: first, the production of self-produced solid waste is limited, which cannot support the full-load operation of the zinc removal production line for a long time, resulting in insufficient equipment utilization and high energy consumption; second, the zinc content in the self-produced solid waste is generally low (usually only 5% to 10%), which leads to limited production of secondary zinc oxide powder by-product in the zinc removal process and unsatisfactory economic benefits. In order to improve the production line load and zinc recovery rate, some enterprises try to mix in high-zinc iron concentrate powder or zinc-containing dust and sludge mixture to improve the overall raw material grade and processing capacity.

[0004] However, this outsourcing raw material blending strategy also introduces new technical challenges. The outsourced high-zinc iron concentrate powder usually comes from electric furnace steelmaking dust, galvanized dust or hydrometallurgical residues, etc. Such materials not only contain a high content of ZnO, but also often contain a high content of SiO2, Al2O3 and alkali metal elements (K, Na). The addition of these components significantly affects the charge composition and thermal stability of the dezincing process. In particular, the increase in SiO2 content will reduce the basicity of the mixture, making the charge system acidic, thereby promoting the formation of low-melting iron olivine (such as Fe2SiO4). When the temperature in the kiln is in the range of 900-1100℃, this phase is easy to react with FeO, Fe2O3, etc. to form a viscous liquid phase, causing the kiln inner wall or refractory brick surface to appear ring phenomenon. Ringing not only reduces the effective cross section of the kiln, hinders the flow of materials, but also causes temperature fluctuations, material retention and local overburning in the kiln, and in severe cases, even leads to production interruption. At the same time, alkali metal elements K and Na will volatilize at high temperatures and react with oxides or silicates to form low-melting salts. These salts are easy to deposit, scale or block in the flue and dust removal system, increasing the difficulty of system cleaning and operation risk, further affecting the stable operation of the dezincing production line.

[0005] To suppress the problem of ring and sticking, the existing technology usually takes measures such as increasing the basicity of the mixture, reducing the kiln temperature or optimizing the reducing atmosphere. For example, by increasing the proportion of limestone or dolomite to increase the basicity, to neutralize the acidic components of SiO2, thereby inhibiting the formation of low-melting phases; or by controlling the amount of reducing agent and temperature, to slow down the formation rate of liquid phase. However, these methods often have a dilemma: if the basicity is too high, it will dilute the effective zinc content in the mixture, reducing the dezincing rate and the production of secondary zinc oxide powder; if the temperature is too low, the reduction reaction is not complete, and the zinc volatilization is not sufficient, affecting the resource recovery efficiency. Therefore, maintaining stable kiln conditions while increasing production load and zinc grade has become a core problem that existing dezincing production technology cannot balance. SUMMARY

[0006] In view of the technical problem that the existing dezincing rotary kiln is difficult to maintain stable kiln conditions while increasing production load and zinc grade, the present application provides a synergistic optimization production method for a dezincing rotary kiln for synergistically processing zinc-containing iron concentrate powder and lime powder, which can increase the load of the dezincing production line to full load, increase the kiln slag production, increase the zinc content of the raw material, increase the production and income of secondary zinc oxide powder, and avoid the problem of rotary kiln ring and material sticking caused by high proportion of zinc-containing iron concentrate powder, and ensure stable kiln conditions.

[0007] The technical solution of the present application is as follows: A method for optimizing the dezincing rotary kiln for synergistically processing zinc-containing iron concentrate powder and lime powder, specifically comprising the following steps: (1) Prepare raw materials: select zinc-containing iron concentrate powder and lime powder, select zinc-containing iron concentrate powder and lime powder, and zinc-containing iron concentrate powder includes the following mass percentage of chemical components: TFe 40%~42%, SiO218%~20%, ZnO 3%~4%; the particle size of lime powder is ≤3mm, and the mass percentage of CaO is 85%~90%; (2) Add zinc-containing iron concentrate powder: increase the proportion of zinc-containing iron concentrate powder in stages by 5%→10%→15%→20%, and after 2~4 days of stable operation in each stage, proceed to the next stage; (3) Dynamically adjust the lime powder: when the proportion of zinc-containing iron concentrate powder is stable at 12%, increase the alkalinity from 1.2 to 1.8, and continuously monitor the kiln slag alkalinity and ring formation during the period.

[0008] By introducing high-zinc iron concentrate powder and scientifically matching coke powder and lime powder, the overall zinc content and reducibility of the raw materials are effectively improved, and the full reduction and volatilization of zinc in the high-temperature zone are promoted. By optimizing the proportion of zinc removal raw materials and the thermal system, the synergistic effect of increasing the production load and the yield of secondary zinc oxide powder is achieved.

[0009] Further, the zinc-containing iron concentrate powder includes the following chemical components in mass percentage: TFe 40%~42%, SiO218%~20%, CaO 3%~4%, MgO 1%~2%, Al2O33%~4%, K 0.5%~1%, Na 0.5%~1%, ZnO 3%~4%, Pb 1%~2%, Cl 0.05%~0.1%, H2O 10%~11%, and the rest are inevitable trace impurities; the lime powder includes the following chemical components: CaO 85%~90%, MgO 4%~5%, SiO21%~2%, Al2O31%~2%, S 0.05%~1%, and the rest are inevitable trace impurities.

[0010] Further, the zinc-containing iron concentrate powder includes the following chemical components in mass percentage: TFe 40.46%, SiO219.5%, CaO 3.8%, MgO 1.7%, Al2O33.45%, K 0.68%, Na 0.665%, ZnO 3.01%, Pb 1.69%, Cl 0.063%, H2O 10.88%, and the rest are inevitable trace impurities; the lime powder includes the following chemical components: CaO 87.67%, MgO 4.35%, SiO21.68%, Al2O30.61%, S 0.07%.

[0011] Further, the temperature in the kiln is controlled at 1150~1250℃ throughout the process, and the basic calorific value is controlled at 960~1020kcal / kg.

[0012] Further, in step (2), the specific operation of gradually increasing the proportion of zinc-containing iron concentrate is as follows: First stage: the proportion of zinc-containing iron concentrate is 5% by mass fraction, and the proportions of the remaining materials are bag dust 17%, sludge 70%, and zinc-containing iron concentrate 5%. The cycle is 2 days.

[0013] Second stage: the proportion of zinc-containing iron concentrate is 10% by mass fraction, and the proportions of the remaining materials are bag dust 17%, dezincing sludge 65%, and zinc-containing iron concentrate 10%. The cycle is 3 days.

[0014] Third stage: the proportion of zinc-containing iron concentrate is gradually increased from 10% to 20% by mass fraction, and the proportions of the remaining materials are bag dust 17%, sludge 50%-60%, and converter secondary dust 5%. The cycle is 3 days.

[0015] Further, during the first stage, the properties of the materials are observed, and the contents of K2O and Na2O in the secondary zinc oxide and PbO in the kiln slag are monitored to ensure stable kiln conditions. During the second stage, due to the increase in SiO2 content leading to a decrease in alkalinity, the temperatures and pressures at the kiln head and tail are closely monitored, and parameters are adjusted in time to inhibit ring formation. During the third stage, the combustion state is adjusted according to the thickness of the material layer and the adhesion of the kiln wall, and the ring formation trend is alleviated by optimizing the kiln speed and air supply position.

[0016] Further, in step (3), lime powder is added in four stages to increase the alkalinity: in the first stage, the proportion of lime powder is 2%, and the target alkalinity is 1.5; in the second stage, the proportion of lime powder is 3%, and the target alkalinity is 1.6; in the third stage, the proportion of lime powder is 4%, and the target alkalinity is 1.7; in the fourth stage, the proportion of lime powder is 5%, and the target alkalinity is 1.8.

[0017] Further, in the first stage, the material composition is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 59%, zinc-containing iron concentrate 12%, lime powder 2%, and coke powder 6%. The CaO content in the kiln slag and the improvement of ring formation are monitored. In the second stage, the material composition is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 58%, zinc-containing iron concentrate 12%, lime powder 3%, and coke powder 6%. The temperature field distribution in the kiln and the fluidity of the materials are observed. In the third stage, the material composition is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 57%, zinc-containing iron concentrate 12%, lime powder 4%, and coke powder 6%. The TFe content in the kiln slag and the cost changes are continuously monitored. In the fourth stage, the material composition is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 56%, zinc-containing iron concentrate 12%, lime powder 5%, and coke powder 6%. The stability of the kiln conditions and the product quality are evaluated, and the optimal proportion of lime powder is determined.

[0018] Further, when the ring is formed, the kiln speed is adjusted to reduce by 5-10%, and the air supply position is moved up by 10-15 cm, so as to disperse the high temperature point through temperature fluctuation and slow down the development of ring.

[0019] The present application has the advantages of: 1. The optimization method for the de-zinc rotary kiln for processing zinc-containing iron concentrate powder and lime powder provided by the present application improves the processing capacity of the rotary kiln system for high-zinc and high-silicon materials by increasing the proportion of zinc-containing iron concentrate powder in stages, effectively avoiding the working condition fluctuation caused by the dramatic change of raw materials. On this basis, the lime powder proportion is dynamically adjusted to gradually and stably increase the alkalinity from 1.2 to 1.8, which fundamentally changes the slag phase melting point and actively inhibits the generation of low-melting-point substances, thereby solving the core technical problem of the easy ring formation of the rotary kiln caused by high-zinc iron concentrate powder, ensuring the long-term stable and smooth operation of the kiln, and greatly extending the stable operation period.

[0020] 2. The optimization method significantly improves the production load and resource recovery benefit under the premise of ensuring system stability. The rotary kiln can achieve full-load operation, and the kiln slag daily output breaks through 450 tons, and the equipment utilization rate increases by more than 30%. At the same time, the increase of the zinc content of the raw materials makes the by-product secondary zinc oxide daily output increase by more than 2.7 tons, combined with the value-added utilization of the kiln slag, the comprehensive benefit is improved by 20%-30%. Finally, through the significant increase of the output and the reduction of the loss during shutdown, the overall operating cost is reduced by 10%-15%, realizing the double improvement of environmental and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0022] Figure 1 The figure is a process flow diagram of the optimization method for the de-zinc rotary kiln for processing zinc-containing iron concentrate powder and lime powder. DETAILED DESCRIPTION

[0023] In order to make the person skilled in the art better understand the technical solutions in the present application, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0024] As Figure 1As shown, the present application proposes an optimization method for treating zinc-containing iron concentrate powder and lime powder in a dezincing rotary kiln, which specifically includes the following steps: (1) Prepare raw materials: select appropriate zinc-containing iron concentrate powder and lime powder, and the selection criteria of the zinc-containing iron concentrate powder are as follows: in terms of mass percentage, TFe accounts for 40% to 42%, SiO2 accounts for 18% to 20%, and ZnO accounts for 3% to 4%; the particle size of the lime powder is ≤3 mm, and the mass percentage of CaO is 85% to 90%; (2) Add zinc-containing iron concentrate powder: increase the proportion of zinc-containing iron concentrate powder in stages by 5%→10%→15%→20%, and after stabilizing for 3 to 4 days in each stage, proceed to the next stage; (3) Dynamically adjust the lime powder: when the proportion of zinc-containing iron concentrate powder is stabilized at 12%, increase the alkalinity from 1.2 to 1.8, and continuously monitor the kiln slag alkalinity and ring formation during this period.

[0025] The following are some specific embodiments of the present application.

[0026] Example 1 An optimization method for treating zinc-containing iron concentrate powder and lime powder in a dezincing rotary kiln, which specifically includes the following steps: (1) Raw material preparation: the chemical components of the zinc-containing iron concentrate powder and the lime powder are shown in Tables 1 and 2, and the remaining basic raw materials include bag dust, sludge, converter secondary dust, and coke powder.

[0027] Table 1 Chemical composition of zinc-containing iron concentrate powder

[0028] Table 2 Main chemical components of lime powder

[0029] (2) Ladder type addition of zinc-containing iron concentrate powder According to the adaptability of the kiln condition, gradually increase the proportion of zinc-containing iron concentrate powder, and implement it in three stages, with the kiln temperature controlled at 1150 to 1250℃ throughout the process, and the basic heat value regulated at 960 to 1020kcal / kg: In the first stage, the material composition is: bag dust 17%, sludge 70%, and zinc-containing iron concentrate powder 5%; in this stage, the properties of the material are observed, the contents of K2O and Na2O in the secondary zinc oxide and PbO in the kiln slag are monitored, and the kiln condition is ensured to be stable, with a cycle of 2 days; In the second stage, the material composition is: bag dust 17%, dezincing sludge 65%, and zinc-containing iron concentrate powder 10%; in this stage, the increase of SiO2 content leads to a decrease of alkalinity, and the temperature and pressure changes at the kiln head and tail are closely observed, and parameters are adjusted in time to inhibit ring formation, with a cycle of 2 days; Third stage: the ratio of zinc-containing iron concentrate is gradually increased from 10% to 20%, and the remaining material composition is: bag dust 17%, sludge 50%~60%, converter secondary dust 5%; In this stage, the burning state is adjusted according to the thickness of the material layer and the adhesion of the kiln wall, and the trend of ring formation is relieved by optimizing the kiln speed and the air supply position, with a cycle of 3 days; At the initial stage of material adhesion, the kiln speed is accelerated, the material residence time is reduced, the accumulation is prevented, the feeding speed is avoided to be suddenly changed, the stable thermal regime in the kiln is maintained, and the kiln speed is simultaneously increased by 0.2~0.3r / min, so as to accelerate the material passing through the high temperature zone.

[0030] (3) Lime powder dynamic adjustment stage When the ratio of zinc-containing iron concentrate is stable at 12%, the basicity of the mixture is reduced to about 1.2 due to the increase of SiO2 content, and the basicity needs to be increased by adding lime powder, which is implemented in four stages: First stage: lime powder ratio 2%, target basicity 1.5; Material composition: blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 59%, zinc-containing iron concentrate 12%, lime powder 2%, coke powder 6%; At the same time, the CaO content in the kiln slag and the improvement of ring formation are monitored; Second stage: lime powder ratio 3%, target basicity 1.6; Adjust the sludge ratio to 58%, and the ratio of the remaining materials remains unchanged; Pay attention to the temperature field distribution in the kiln and the fluidity of the material; Third stage: lime powder ratio 4%, target basicity 1.7; The sludge ratio is reduced to 57%, and the TFe content in the kiln slag and the cost change are continuously monitored; Fourth stage: lime powder ratio 5%, target basicity 1.8; The sludge ratio is reduced to 56%, and the stability of the kiln condition and the product quality are evaluated to determine the optimal lime powder ratio.

[0031] The temperature in the kiln is controlled at 1150~1250℃ throughout the process, and the basic heat value is controlled at 960~1020kcal / kg. When ring formation occurs, the kiln speed is adjusted to decrease by 5~10% and the air supply position is moved up by 10~15cm, so as to disperse the high temperature point through temperature fluctuation and slow down the development of ring formation.

[0032] After the above method is implemented, the load of the zinc removal production line is 100%, the kiln slag daily output is 460t, the secondary zinc oxide daily output is 17.5t, and the kiln ring formation cycle is 25 days.

[0033] Example 2 An optimization method for a zinc removal rotary kiln to cooperatively treat zinc-containing iron concentrate and lime powder, specifically comprising the following steps: (1) Raw material preparation, the chemical components of zinc-containing iron concentrate and lime powder are shown in Tables 3 and 4, and the remaining basic raw materials include bag dust, sludge, converter secondary dust, and coke powder.

[0034] Table 3 Chemical composition of zinc-containing iron concentrate

[0035] Table 4 Main chemical composition of lime powder

[0036] (2) Zinc-containing iron concentrate powder stepwise addition stage According to the adaptability of the kiln, the proportion of zinc-containing iron concentrate powder is gradually increased, which is implemented in three stages. The temperature in the kiln is controlled at 1150-1250℃ throughout the process, and the basic heat value is regulated at 960-1020kcal / kg: In the first stage, the material composition is: bag dust 17%, sludge 70%, and zinc-containing iron concentrate powder 5%. In this stage, the properties of the material are observed, and the contents of K2O and Na2O in the secondary zinc oxide and PbO in the kiln slag are monitored to ensure the stability of the kiln, with a cycle of 2 days; In the second stage, the material composition is: bag dust 17%, dezincing sludge 65%, and zinc-containing iron concentrate powder 10%. The decrease in alkalinity caused by the increase in SiO2 content requires close attention to the temperature and pressure changes at the kiln head and tail, and timely adjustment of parameters to inhibit ring formation, with a cycle of 3 days; In the third stage, the proportion of zinc-containing iron concentrate powder is gradually increased from 10% to 20%, and the remaining material composition is: bag dust 17%, sludge 50%-60%, and converter secondary dust 5%. In this stage, the combustion state is adjusted according to the thickness of the material layer and the adhesion of the kiln wall, and the ring formation trend is alleviated by optimizing the kiln speed and air supply position, with a cycle of 3 days. In the initial stage of material adhesion, the kiln speed is increased to reduce the residence time of the material, prevent accumulation, avoid sudden changes in the feeding speed, maintain the stability of the kiln thermal regime, and simultaneously increase the kiln speed by 0.2-0.3r / min to accelerate the passage of the material through the high-temperature zone.

[0037] (3) Dynamic adjustment stage of lime powder When the proportion of zinc-containing iron concentrate powder is stable at 12%, the alkalinity of the mixed material decreases to about 1.2 due to the increase in SiO2 content, and lime powder needs to be added to increase the alkalinity, which is implemented in four stages: In the first stage, the proportion of lime powder is 2%, and the target alkalinity is 1.5. The material composition is: blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 59%, zinc-containing iron concentrate powder 12%, lime powder 2%, and coke powder 6%. The CaO content in the kiln slag and the improvement of ring formation are monitored; In the second stage, the proportion of lime powder is 3%, and the target alkalinity is 1.6. The proportion of sludge is adjusted to 42%, and the proportions of the remaining materials remain unchanged. The temperature field distribution in the kiln and the fluidity of the material are focused on; In the third stage, the proportion of lime powder is 4%, and the target alkalinity is 1.7. The proportion of sludge is reduced to 41%, and the TFe content in the kiln slag and the cost changes are continuously monitored; In the fourth stage, the proportion of lime powder is 5%, and the target alkalinity is 1.8. The proportion of sludge is reduced to 40%, and the stability of the kiln and the quality of the product are evaluated to determine the optimal proportion of lime powder.

[0038] The temperature in the kiln is controlled at 1150-1250℃, and the basic heat value is controlled at 960-1020 kcal / kg. When ring formation occurs, the kiln speed is adjusted to reduce by 5-10%, and the air supply position is moved up by 10-15 cm, to disperse the high temperature point through temperature fluctuation, and slow down the development of ring formation.

[0039] After the above method is implemented, the dezincification production line load is 100%, the kiln slag daily output is 455 t, the secondary zinc oxide daily output is 17.2 t, and the kiln ring formation period is 24 days.

[0040] Example 3 An optimization method for a dezincification rotary kiln to cooperatively process zinc-containing iron concentrate powder and lime powder, specifically comprising the following steps: (1) Raw material preparation, the chemical components of zinc-containing iron concentrate powder and lime powder are shown in Table 3 and Table 4, and the remaining basic raw materials include bag dust, sludge, converter secondary ash, and coke powder.

[0041] Table 5 Chemical components of zinc-containing iron concentrate powder

[0042] Table 6 Main chemical components of lime powder

[0043] (2) Staged addition of zinc-containing iron concentrate powder The proportion of zinc-containing iron concentrate powder is gradually increased according to the kiln condition, and is implemented in three stages, and the temperature in the kiln is controlled at 1150-1250℃ throughout the process, and the basic heat value is regulated at 960-1020 kcal / kg: In the first stage, the material composition is: bag dust 17%, sludge 70%, and zinc-containing iron concentrate powder 5%; In this stage, the properties of the material are observed, the contents of K2O and Na2O in the secondary zinc oxide and PbO in the kiln slag are monitored, and the kiln condition is ensured to be stable, and the period is 2 days; In the second stage, the material composition is: bag dust 17%, dezincification sludge 65%, and zinc-containing iron concentrate powder 10%; The decrease of alkalinity caused by the increase of SiO2 content, the changes of temperature and pressure at the kiln head and tail are closely observed, and the parameters are adjusted in time to inhibit ring formation, and the period is 3 days; In the third stage, the proportion of zinc-containing iron concentrate powder is gradually increased from 10% to 20%, and the remaining material composition is: bag dust 17%, sludge 50%-60%, and converter secondary ash 5%; In this stage, the combustion state is adjusted according to the material layer thickness and kiln wall adhesion, and the ring formation trend is alleviated by optimizing the kiln speed and air supply position, and the period is 3 days; The kiln speed is accelerated at the initial stage of material adhesion, the material residence time is reduced, the accumulation is prevented, the feeding speed is avoided to be suddenly changed, the kiln thermal system is kept stable, and the kiln speed is simultaneously increased by 0.2-0.3 r / min to accelerate the material passing through the high temperature zone.

[0044] (3) Lime powder dynamic adjustment stage When the ratio of zinc-containing iron concentrate is stable at 12%, the basicity of the mixture is reduced to about 1.2 due to the increase of SiO2 content, and lime powder needs to be added to increase the basicity, which is implemented in four stages: First stage: lime powder ratio 2%, target basicity 1.5; material composition: blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 59%, zinc-containing iron concentrate 12%, lime powder 2%, coke powder 6%; at the same time, monitor the CaO content of the kiln slag and the improvement of the ring formation; Second stage: lime powder ratio 3%, target basicity 1.6; adjust the sludge ratio to 58%, and the rest of the material ratio remains unchanged; focus on the temperature field distribution in the kiln and the fluidity of the material; Third stage: lime powder ratio 4%, target basicity 1.7; sludge ratio reduced to 57%, continuously monitor the TFe content of the kiln slag and cost changes; Fourth stage: lime powder ratio 5%, target basicity 1.8; sludge ratio reduced to 56%, evaluate the stability of the kiln and the product quality, and determine the optimal lime powder ratio.

[0045] The temperature in the kiln is controlled at 1150-1250°C throughout the process, and the basic heat value is controlled at 960-1020 kcal / kg. When ring formation occurs, adjust the kiln speed to reduce by 5-10% and the air supply position to move up by 10-15 cm, disperse the high temperature point through temperature fluctuation, and slow down the development of ring formation.

[0046] After the implementation of the above method, the zinc removal production line load is 100%, the kiln slag daily output is 465 t, the secondary zinc oxide daily output is 17.8 t, and the kiln ring formation period is 26 days.

[0047] Comparative Example 1 The traditional zinc removal rotary kiln process was used for the experiment. This process uses bag dust, sludge and a small amount of coke powder as the main raw materials, without adding zinc-containing iron concentrate and lime powder. The material ratio is as follows: bag dust 20%, sludge 75%, coke powder 5%. The rotary kiln operating temperature is controlled at 1100-1200°C, the basic heat value is about 920 kcal / kg, the kiln speed and air supply parameters are fixed and unchanged, and no targeted temperature zoning adjustment and basicity dynamic control measures are set.

[0048] Under this condition, the SiO2 content in the mixture is high and the CaO content is low, the material layer has strong adhesion, and high-temperature adhesion and local ring formation are easy to occur during operation. Usually, the kiln needs to be stopped and the ring needs to be cleaned after about 15 days of operation, and the production stability is poor. At the same time, due to insufficient zinc content in the raw materials and insufficient reduction and volatilization, the re-oxidation efficiency of zinc vapor and fly ash in the cooling zone is low, resulting in low secondary zinc oxide powder yield. After testing, the average load of the production line is maintained at about 80%, the kiln slag daily output is about 380 t, the secondary zinc oxide daily output is about 14.8 t, and the Zn comprehensive recovery rate is less than 70%.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that the raw material ratio is as follows in mass percentage: bag dust 17%, sludge 60%, converter secondary dust 5%, zinc-containing iron concentrate 12%, coke powder 6%, and no lime powder is added, and the temperature in the kiln is controlled at 1150-1250°C throughout, and the basic calorific value is regulated at 960-1020 kcal / kg.

[0050] The kiln condition is relatively stable at the initial stage of the process, but as the proportion of zinc-containing iron concentrate increases, the SiO2 content in the raw material increases, causing the overall alkalinity of the mixture to decrease. After about 7-10 days of operation, local ring formation occurs on the kiln wall, and the ring thickness gradually increases. After 20 days, the kiln needs to be stopped for cleaning. Analysis of the ring sample shows that the main components are fayalite and part of potassium and sodium silicate, with a melting point of about 1150°C, which is easy to melt and form a ring in the high temperature zone. Due to the formation of local ring, the heating of the material is uneven, and the unit heat consumption increases by about 5%. At the same time, the temperature distribution of the material layer is uneven, the reduction and volatilization rate of ZnO decreases to about 70%, and the yield of secondary zinc oxide also decreases significantly.

[0051] During the stable operation stage, the average load of the production line is about 90% of the rated load, the daily output of the kiln slag is about 420 t, and the daily output of secondary zinc oxide is about 16.2 t. Compared with the traditional process, it has improved, but the kiln condition is still unstable, the ring formation frequency is high, and the continuous operation period is short.

[0052] As can be seen from the above comparison, although the addition of zinc-containing iron concentrate can improve the zinc recovery rate, the low alkalinity of the mixture caused by the increase of SiO2 and the lack of neutralization by alkaline materials leads to the formation of low-melting substances and frequent ring formation, making it difficult to achieve stable and long-period operation. However, by using the stepwise addition of zinc-containing iron concentrate and dynamically adjusting the alkalinity of lime powder, the contradiction between production load and kiln stability is successfully solved, and the production efficiency and zinc recovery rate are significantly improved.

[0053] Although the present application has been described in detail with reference to the preferred embodiments thereof, it is apparent that various equivalent modifications and changes can be made thereto without departing from the spirit and scope thereof. Any modifications and changes made to the embodiments of the present application by those skilled in the art within the technical scope disclosed by the present application shall be covered by the protection scope of the present application.

Claims

1. An optimized method for co-processing of zinc-containing iron concentrate fines and lime fines in a dezincofication rotary kiln, characterized in that, Specifically comprising the following steps: (1) preparing raw materials: selecting zinc-containing iron concentrate powder and lime powder, the zinc-containing iron concentrate powder contains the following chemical components in percentage by mass: TFe 40%~42%, SiO2 18%~20%, ZnO 3%~4%; the lime powder has a particle size of ≤3 mm, and the mass percentage of CaO is 85%~90%; (2) adding zinc-containing iron concentrate powder: increasing the proportion of zinc-containing iron concentrate powder in stages by 5%→10%→15%→20%, and entering the next stage after 2~4 days of stabilization in each stage; (3) dynamically adjusting lime powder: when the proportion of zinc-containing iron concentrate powder is stabilized at 12%, the alkalinity is increased from 1.2 to 1.8, and the kiln slag alkalinity and ring formation are continuously monitored during the period.

2. The optimization method of claim 1, wherein, The zinc-containing iron concentrate powder contains the following chemical components in percentage by mass: TFe 40%~42%, SiO2 18%~20%, CaO 3%~4%, MgO 1%~2%, Al2O3 3%~4%, K 0.5%~1%, Na 0.5%~1%, ZnO 3%~4%, Pb 1%~2%, Cl 0.05%~0.1%, H2O 10%~11%, and the rest are inevitable trace impurities; the lime powder contains the following chemical components: CaO 85%~90%, MgO 4%~5%, SiO2 1%~2%, Al2O3 1%~2%, S 0.05%~1%, and the rest are inevitable trace impurities.

3. The optimization method of claim 2, wherein, The zinc-containing iron concentrate powder contains the following chemical components in percentage by mass: TFe 40.46%, SiO2 19.5%, CaO 3.8%, MgO 1.7%, Al2O3 3.45%, K 0.68%, Na 0.665%, ZnO 3.01%, Pb 1.69%, Cl 0.063%, H2O 10.88%, and the rest are inevitable trace impurities; the lime powder contains the following chemical components: CaO 87.67%, MgO 4.35%, SiO2 1.68%, Al2O3 0.61%, S 0.07%.

4. The optimization method of claim 1, wherein, The temperature in the kiln is controlled at 1150~1250℃ throughout the process, and the basic heat value is controlled at 960~1020kcal / kg.

5. The optimization method of claim 1, wherein, The specific operation of increasing the proportion of zinc-containing iron concentrate powder in stages and in steps is as follows: First stage: the proportion of zinc-containing iron concentrate powder is 5% in percentage by mass, and the proportions of the rest of the materials are bag dust 17%, sludge 70%, and zinc-containing iron concentrate powder 5%, with a cycle of 2 days; Second stage: the proportion of zinc-containing iron concentrate powder is 10% in percentage by mass, and the proportions of the rest of the materials are bag dust 17%, dezincing sludge 65%, and zinc-containing iron concentrate powder 10%, with a cycle of 3 days; Third stage: the proportion of zinc-containing iron concentrate powder is gradually increased from 10% to 20% in percentage by mass, and the proportions of the rest of the materials are bag dust 17%, sludge 50%~60%, and converter secondary dust 5%, with a cycle of 3 days.

6. The optimization method of claim 1, wherein, Step (3), lime powder is added in four stages to increase the alkalinity: in the first stage, the lime powder ratio is 2%, and the target alkalinity is 1.5; in the second stage, the lime powder ratio is 3%, and the target alkalinity is 1.6; in the third stage, the lime powder ratio is 4%, and the target alkalinity is 1.7; in the fourth stage, the lime powder ratio is 5%, and the target alkalinity is 1.

8.

7. The optimization method of claim 5, wherein, The material composition of each stage is as follows: The material composition of the first stage is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 59%, zinc-containing iron concentrate powder 12%, lime powder 2%, and coke powder 6%; The material composition of the second stage is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 58%, zinc-containing iron concentrate powder 12%, lime powder 3%, and coke powder 6%; The material composition of the third stage is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 57%, zinc-containing iron concentrate powder 12%, lime powder 4%, and coke powder 6%; The material composition of the fourth stage is blast furnace bag dust 16%, blast furnace gravity dust 5%, sludge 56%, zinc-containing iron concentrate powder 12%, lime powder 5%, and coke powder 6%.

8. The optimization method of claim 1, wherein, When the ring appears, the kiln speed is adjusted to decrease by 5-10%, and the air supply position is moved up by 10-15 cm.

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