Method for inhibiting ring formation of coal-based rotary kiln by using zinc-containing dust sludge as main raw material

Abstract

The invention discloses a coal-based rotary kiln ring formation inhibition method taking zinc-containing dust sludge as a main raw material, which comprises the following steps: S1, performing ore blending on the zinc-containing dust sludge on the basis of multi-target control conditions of internal carbon content, binary alkalinity (CaO / SiO2), MgO / SiO2 mass ratio and alkali metal (K2O + Na2O) content to obtain a coarse-grain zinc-containing dust sludge material; s2, carrying out mechanical activation on the coarse-grain zinc-containing dust and mud material, carrying out strong mixing and pre-wetting on the activated zinc-containing dust and mud material, a composite binder and water, and then adding atomized water into the mixture for pelletizing to obtain green pellets; s3, the green pellets are dried and solidified in advance, and zinc-containing dust pellets with certain strength are obtained; and S4, the dried zinc-containing dust pellets and an external reducing agent are loaded together from the tail of the rotary kiln, the existence period of a FeO phase of the pellets is shortened by adopting the thermal regulation of rapid heating, the pellets form metal iron continuous crystals as soon as possible, and the zinc-containing dust and sludge reduced pellets are obtained. The pelletizing effect is enhanced and the heat stability of the pellets is improved in a manner of preparing enhanced raw materials and combining a composite binder with mechanical activation, and meanwhile, the pellets are promoted to cross a FeO phase valley region as soon as possible through a rapid heating and rapid reduction system, so that the low-temperature reduction degradation performance and the process strength of the pellets are improved, and the service life of the pellets is prolonged. Pellet pulverization and rotary kiln ring forming phenomena are effectively inhibited.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgical solid waste resource processing, and relates to a coal-based rotary kiln ring formation inhibition method taking zinc-containing dust and sludge as main raw materials, in particular to a ring formation inhibition technology for the reduction process of a rotary kiln for zinc-containing dust and sludge. BACKGROUND

[0002] The steel industry is an important basic industry for the economic development of China, but it is also a major emitter of solid waste. A large amount of dust is generated in the smelting process. According to statistics, the total amount of various types of dust generated by steel enterprises is generally 8% to 12% of the steel production, and the zinc-containing dust accounts for about 20% to 30% of the total. According to this estimate, the annual zinc-containing dust emissions of steel plants in China exceed 20 million tons. The pyrometallurgical process has the advantages of high zinc removal rate and high production efficiency, and is the main method for treating zinc-containing dust and sludge in steel plants at home and abroad. Among them, the rotary kiln and the rotary hearth furnace reduction and zinc removal processes are the most widely used. In China, only a few steel plants such as Baosteel and a few other steel plants have built less than 20 rotary hearth furnace reduction and zinc removal production lines, and most of the others have adopted the rotary kiln reduction and zinc removal process.

[0003] The traditional rotary kiln reduction and zinc removal process usually uses zinc-containing dust and sludge powder after blending and mixing directly into the kiln, which tends to treat low-zinc dust and aims to remove zinc and recover metallic iron. Generally, the zinc content of the mixed material is required to be 5%, and the iron content is required to be 30%, in order to meet the saleability of secondary zinc oxide (zinc grade 30%) and the recycling of iron components. Although subsequent improvements have been made to the traditional process, mainly by adopting the process of feeding the kiln after balling the zinc-containing dust and sludge, but in the actual production process, because the zinc-containing dust is of various types, complex composition, fine particle size, poor balling property, and poor ball stability, it often causes ring formation in the process of treating zinc-containing dust and sludge in the rotary kiln, which deteriorates the reduction and zinc removal effect of the rotary kiln and the product quality, and seriously affects the economic efficiency and popularization and application of the process. In production, Sumitomo Metal in Japan found that the dust green balls prepared by the traditional disc balling process have too high moisture content, slow drying, poor ball strength and poor thermal stability, which seriously deteriorate the production efficiency and product quality of the rotary kiln process, and new strengthening technology for balling zinc-containing dust must be developed to optimize the process parameters and improve the performance of green balls.

[0004] Previous studies have shown that when ordinary iron ore concentrate is added with 4% zinc-containing dust, the green ball burst temperature is reduced by 30C; and the thermal stability of the ball prepared by 100% zinc-containing dust is extremely poor, and the green ball burst temperature is generally lower than 250C. The rotary kiln ring formation phenomenon is usually closely related to the physical and chemical properties of the raw materials, the poor ball strength of the high-temperature process, the excessive generation of low-melting-point liquid phase caused by unreasonable kiln temperature and atmosphere control, and other factors. In addition, due to the differences in chemical composition and phase characteristics of metallurgical solid waste raw materials from different sources, as well as the large fluctuations in output and properties, many domestic steel plants lack attention in raw material preparation, and there are often problems such as randomness of "eating as much as coming" and excessive reliance on experience for ore blending. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a coal-based rotary kiln ring formation inhibition method using zinc-containing dust and sludge as the main raw material. By strengthening the preparation of raw materials, using a composite binder combined with mechanical activation, the balling effect is enhanced and the thermal stability of the pellets is improved. At the same time, through the rapid heating and rapid reduction system, the pellets are prompted to quickly pass through the FeO phase low valley region, thereby improving their low-temperature reduction pulverization performance and process strength, effectively inhibiting pellet pulverization and rotary kiln ring formation.

[0006] The inventor revealed through sampling analysis of the ring formation in each part of the rotary kiln that excessive powder in the kiln, the reaction of a large amount of FeO phase in the powder (iron-containing materials, coal ash, etc.) with gangue to form low-melting-point solid and liquid phase bonding, and local temperature being too high or improper atmosphere control are important causes of rotary kiln "ring formation". The zinc-containing dust and sludge have fine particle size and are rich in iron, silicon and other components, which are more likely to generate low-melting-point liquid phases such as olivine at high temperatures, thereby forming a large amount of binding materials in the rotary kiln, leading to poor material layer bonding and material flowability, and further exacerbating the ring formation problem.

[0007] The technical idea of the present application is to build a systematic raw material preparation and reduction optimization path around the two core objectives of "improving the thermal stability and reduction process strength of the pellets" and "inhibiting the ring formation of the rotary kiln".

[0008] The present application provides a coal-based rotary kiln ring formation inhibition method using zinc-containing dust and sludge as the main raw material, comprising the following steps:

[0009] S1. Based on the multi-objective control conditions of internal carbon content, binary basicity (CaO / SiO2), mass ratio of MgO / SiO2, and alkali metal (K2O+Na2O) content, the zinc-containing dust and sludge is matched to obtain a coarse-grained zinc-containing dust and sludge material;

[0010] S2. The coarse-grained zinc-containing dust and sludge material obtained in step S1 is mechanically activated, and the activated zinc-containing dust and sludge material is strongly mixed and pre-wetted with a composite binder and moisture, and then the mixture is balling with misty water to obtain green balls;

[0011] S3. The green balls obtained in step S2 are pre-dried and solidified to obtain zinc-containing dust pellets with certain strength;

[0012] S4. The zinc-containing dust pellets obtained in step S3 are loaded together with an externally matched reducing agent from the tail of the rotary kiln, a rapid heating thermal regime is adopted to shorten the FeO phase existence period of the pellets, so that the pellet ore forms metallic iron intercrystalline as soon as possible, and zinc-containing dust reduction pellets are obtained.

[0013] Preferably, in step S1, the coarse granular zinc-containing dust and sludge material includes zinc-containing dust and sludge, iron-containing dust and sludge, converter dust and sludge, electric dust and sludge, blast furnace bag dust, steelmaking dust, CDQ dust, coke foam, etc.

[0014] Further preferably, the coarse granular zinc-containing dust and sludge material further includes iron concentrate and flux; by adding iron concentrate, the softening temperature of the mixture is increased, and the risk of ring formation is reduced from the source.

[0015] Preferably, in step S1, the internal carbon content is controlled to be 5-15%, the binary basicity (CaO / SiO2) of the pellets is less than 0.3 or greater than 1.6, the mass ratio of MgO / SiO2 is greater than or equal to 0.45, and the content of alkali metal (K2O+Na2O) is less than 2.0%.

[0016] The CaO and MgO components in the coarse granular zinc-containing dust and sludge material act as basic flux, which mainly functions to increase the melting temperature of the pellet component system, inhibit excessive liquid phase generation, and reduce the rotary kiln ring formation phenomenon.

[0017] Further preferably, the CaO and MgO are derived from the basic components carried by the zinc-containing dust and sludge itself, as well as additional limestone, dolomite, etc.

[0018] Preferably, in step S2, the mechanical activation is one or a combination of wet grinding and high-pressure roller grinding. Through mechanical activation treatment such as wet grinding, the coarse granular zinc-containing dust and sludge material is dispersed, which can improve the surface activity of the zinc-containing dust and sludge particles, promote the bonding between particles, increase the physical contact and chemical reaction interface, and improve the strength and thermal stability of the zinc-containing dust and sludge pellets.

[0019] Preferably, in step S2, the composite binder is a bentonite-based binder, which includes 50-90% bentonite and 10-50% sodium humate, and the addition amount is 1.0%-3.0%.

[0020] The composite binder can improve the balling property of the zinc-containing dust and sludge, improve the thermal stability of the green pellets, and prevent the green pellets from breaking and pulverizing during drying and pellet reduction through capillary attraction, chemical bonds, etc., thereby maintaining the stability of the pellet structure.

[0021] Preferably, in step S2, the green pellets obtained by pelletizing have a particle size of 8-14 mm and a moisture content of 15%-20%.

[0022] Preferably, in step S2, the water required for pelletizing the zinc-containing material is added in two parts, of which the water added in the intensive mixer accounts for 80-90% of the total water added, and the remaining 10-20% is added during the pelletizing process.

[0023] Preferably, in step S3, the green balls are dried and dehydrated at 200-350C and a wind speed of 0.6-1.0 m / s, so that the water content is less than 1%, and the compressive strength of the dried balls is greater than 200 N / P; the heat system of low temperature and low wind speed is used to pre-dry and consolidate the green balls, promote the outward migration of water in the green balls, reduce the drying stress, and avoid the bursting of the green balls.

[0024] Preferably, in step S4, the atmosphere for the reduction of the zinc-containing dust pellets mainly relies on the carbon in the zinc-containing dust and the added reducing agent; the total carbon content is controlled to be 20-45% according to the iron grade, wherein the internal carbon content accounts for 20-40%, and the external carbon content accounts for 60-80%.

[0025] Preferably, in step S4, the kiln head uses gas fuel such as blast furnace gas or mixed gas for heating, which avoids the use of coal powder combustion that aggravates the ring formation of the rotary kiln due to the low coal ash melting point, and is more conducive to the control of the kiln temperature; by controlling the maximum temperature in the rotary kiln, optimizing the air inlet amount and mode, maintaining a strong reducing atmosphere in the kiln, improving the efficiency of the reducing agent, reducing the combustion loss, and ensuring the deep reduction of iron oxides and the reduction and volatilization of zinc components in the zinc-containing dust pellets.

[0026] Further preferably, by optimizing the temperature distribution in the rotary kiln, the maximum temperature in the rotary kiln is controlled to be 1100-1150°C, and the heating rate is 8-15°C / min; the liquid phase amount is controlled to be less than 20%, the low-temperature reduction and pulverization performance and process intensity are improved; the excessive generation of liquid phase is prevented, and the risk of rotary kiln ring formation is reduced.

[0027] Preferably, in step S4, through the application of the method, the proportion of the zinc-containing dust pellet +8 mm is more than 60%, the Fe metallization rate is more than 80%, the Zn removal rate is not less than 90%, and the Pb removal rate is not less than 95%.

[0028] The present application improves the thermal stability and strength of the pellets by developing and applying the combined technology of optimizing the ore proportioning of the zinc-containing dust based on the composition, synergistically strengthening the balling of the zinc-containing dust by using the composite binder and mechanical activation, putting the dried and consolidated zinc-containing dust pellets into the kiln, optimizing the temperature distribution in the rotary kiln, and strictly controlling the atmosphere; at the same time, the pellets quickly pass through the FeO phase low valley region by using the rapid heating and rapid reduction system, avoiding the reduction and pulverization at low temperature, the excessive generation of liquid phase, and the rotary kiln ring formation, and finally improving the removal rates of zinc and lead and ensuring the efficient recovery of iron resources.

[0029] The idea and technical measures of the present application effectively realize the linkage optimization of raw material adaptation-pellet stability-process intensification, effectively inhibit the rotary kiln ring formation phenomenon, and provide key technical support for the efficient and stable operation of the zinc-containing dust rotary kiln reduction and zinc removal process.

[0030] Compared with the prior art, the present application has the beneficial technical effects:

[0031] (1) Improve the strength and thermal stability of the pellets: By optimizing the balling process and rapid heating, the compressive strength and burst temperature of the pellets are significantly improved, ensuring the structural integrity of the pellets at high temperatures, reducing the burst and pulverization of the pellets after entering the kiln. After taking the above technical measures, the proportion of +8mm particle size after reduction of zinc-containing dust and sludge pellets can still be maintained at more than 60%.

[0032] (2) Effectively inhibit the phenomenon of ring formation: By "improving the thermal stability and strength of the reduction process of the pellets" and "optimizing the temperature distribution and atmosphere control in the rotary kiln", the phenomenon of ring formation in the rotary kiln is effectively inhibited, and the process efficiency and reduction and dezincification effect are improved.

[0033] (3) Improve the efficiency of reduction and dezincification: By rapid heating and rapid reduction system, the pellets can quickly pass through the FeO phase low valley area, and the Fe metallization rate of the reduced pellets can reach more than 80%, the Zn removal rate is not less than 90%, and the Pb removal rate is not less than 95%, thereby improving the quality of kiln slag and secondary zinc oxide. DETAILED DESCRIPTION

[0034] The present application will be described in detail below in conjunction with examples, but the scope of protection of the present application is not limited to the following examples:

[0035] Comparative Example 1

[0036] The reference ore blending scheme is "52% zinc-containing dust and sludge + 20% blast furnace bag dust + 15% return material + 5% steelmaking dust + 5% CDQ powder + 3% coke foam", the carbon content in the pellets is 25% (97% of the total reducing agent mass), the total iron content is 22.85%, the ZnO content is 9.87%, the binary basicity is 1.4, the mass ratio of MgO / SiO2 is 0.32, the alkali metal (K2O+Na2O) content is 2.77%, and the softening temperature of the mixed material is 1183°C.

[0037] The coarse-grained zinc-containing dust and sludge material is directly balling without mechanical activation treatment, without adding binder and with a fixed balling time of 12 min. The average particle size of the green ball prepared is 10.98 mm, the moisture content is 19.0%, the drop strength is 4.4 times / (0.5 m), the green ball compressive strength is only 8.8 N / P, and the burst temperature is lower than 230°C. After the green ball is dried by hot air at 300°C and 1.2m / s for 5min, the residual moisture content is 3.3%, and the +10mm particle size integrity rate is only 50%.

[0038] Example 1

[0039] The reference ore blending scheme is "52% zinc-containing dust and sludge + 20% blast furnace bag dust + 15% return material + 5% steelmaking dust + 5% CDQ powder + 3% coke foam", the carbon content in the pellet is 25% (97% of the total reducing agent mass), the total iron content is 22.85%, the ZnO content is 9.87%, the binary basicity is 1.4, the mass ratio of MgO / SiO2 is 0.32, the alkali metal (K2O+Na2O) content is 2.77%, and the softening temperature of the mixed material is 1183°C.

[0040] The coarse-grained zinc-containing dust and sludge material is pre-treated by wet grinding for 5 minutes, but without adding a binder, and the pelletizing time is 12 minutes, to obtain green pellets with an average particle size of 10.76 mm, a moisture content of 17%-19%, a drop strength of 9-13 times / (0.5 m), and a compressive strength of 11-14 N / P. After drying the green pellets at 400°C and a hot air speed of 1.2 m / s for 5 minutes, the residual moisture content of the pellets is less than 1%, and the +10 mm particle size is 70-90%. After drying the pellets at 500°C and a hot air speed of 1.2 m / s, the +10 mm particle size is only 25-55%.

[0041] Example 2

[0042] The reference ore blending scheme is "52% zinc-containing dust and sludge + 20% blast furnace bag dust + 15% return material + 5% steelmaking dust + 5% CDQ powder + 3% coke foam", the carbon content in the pellet is 25% (97% of the total reducing agent mass), the total iron content is 22.85%, the ZnO content is 9.87%, the binary basicity is 1.4, the mass ratio of MgO / SiO2 is 0.32, the alkali metal (K2O+Na2O) content is 2.77%, and the softening temperature of the mixed material is 1183°C.

[0043] The coarse-grained zinc-containing dust and sludge material is pre-treated by wet grinding for 5 minutes, but without adding a binder, and the pelletizing time is 12 minutes, to obtain green pellets with an average particle size of 10.76 mm, a moisture content of 17%-19%, a drop strength of 9-13 times / (0.5 m), and a compressive strength of 11-14 N / P. After drying the green pellets at 400°C and a hot air speed of 1.2 m / s for 5 minutes, the residual moisture content of the pellets is less than 1%, and the +10 mm particle size is 70-90%. After drying the pellets at 500°C and a hot air speed of 1.2 m / s, the +10 mm particle size is only 25-55%.

[0044] The dry pellets are externally carbonized (3% of the total reducing agent mass), and the dry pellets are reduced at a reduction temperature of 1150°C (the heating rate is 10°C / min) and a reduction time of 75 minutes, to obtain reduced pellets with an iron metallization rate of 73.03%, a Zn content of less than 0.1%, a zinc removal rate of 99.36%, and a lead removal rate of 99.99%. However, the compressive strength of the reduced pellets is only 26 N / P.

[0045] By comparing Comparative Example 1, Example 1 and Example 2, it can be seen that by pre-treatment of wet grinding, addition of composite binder and low-temperature and low-wind-speed drying, the balling of the zinc-containing dust and sludge mixture is significantly strengthened, the green ball strength and thermal stability are greatly improved, and good reduction and dezincing and deleading effects can be achieved, but the strength of the reduced pellets is low and the pellets are prone to pulverization in the kiln.

[0046] Example 3

[0047] For the ore blending scheme "52% zinc-containing dust and sludge + 2% blast furnace bag dust + 3% return material + 43% steelmaking dust", the carbon content in the pellets is 15% (60% of the total reducing agent), the total iron content is 34.34%, the ZnO content is 6.60%, the binary basicity is 2.2, the mass ratio of MgO / SiO2 is 0.75, the alkali metal (K2O+Na2O) content is 1.66%, and the softening temperature of the mixture is 1236°C.

[0048] The coarse-grained zinc-containing dust and sludge material is pre-treated by wet grinding for 5 minutes, 1.0% bentonite-based binder (90% bentonite, 10% sodium humate) is added, and the balling is carried out under the condition that the balling time is 12 minutes. The average particle size of the obtained green balls is 11.12 mm, the moisture content is 17%-19%, the drop strength is 5.0 times / (0.5 m), the compressive strength is 13.5 N / P, and after the green balls are dried at 300°C and 0.8 m / s hot air for 8 minutes, the +10 mm particle size is 100%, and the dry ball compressive strength is 223 N / P.

[0049] Under the conditions of 10% external reducing agent (40% of the total reducing agent), a reduction temperature of 1150°C (heating rate of 10°C / min), and a reduction time of 90 minutes, the above dry balls are reduced to obtain reduced pellets with an iron metallization rate of 77.06%, a Zn content of less than 0.1%, a dezincing rate of 99.46%, and a deleading rate of 99.12%, but the compressive strength of the reduced pellets is 84.6 N / P.

[0050] Example 4

[0051] For the ore blending scheme "37% zinc-containing dust and sludge + 43% steelmaking dust + 20% iron ore concentrate", the carbon content in the pellets is 10% (40% of the total reducing agent), the total iron content of the mixed ore is 34.22%, the ZnO content is 3.99%, the binary basicity is 2.0, the mass ratio of MgO / SiO2 is 0.74, the alkali metal (K2O+Na2O) content is 1.56%, and the softening temperature of the mixture is 1257°C.

[0052] The coarse particle zinc-containing dust and sludge material is pre-treated by wet grinding for 5 minutes while adding 1.0% bentonite-based binder (90% bentonite, 10% sodium humate), and then is pelletized under the condition that the pelletizing time is 12 minutes, to obtain green pellets with an average particle size of 10.65 mm, a moisture content of 17%-19%, a drop strength of 6.3 times / (0.5 m), and a compressive strength of 15.7 N / P. After the green pellets are dried by hot air at 300°C and 0.8 m / s for 8 minutes, the +10 mm particle size is 100%, and the dry pellet compressive strength is 235 N / P.

[0053] Under the condition that 15% reducing agent (60% of the total reducing agent) is externally added, the reduction temperature is 1150°C (the heating rate is 10°C / min), the reduction time is 75 minutes, and the liquid phase amount is controlled to be less than 20%, the above dry pellets are reduced to obtain reduced pellets with a +8 mm particle size of about 70%, an iron metallization rate of 80.31%, a Zn content of less than 0.1%, a de-zinc rate of 99.12%, a de-lead rate of 99.14%, and a reduced pellet compressive strength of 184.7 N / P.

[0054] As can be seen from the comparative example 1 and the examples 2-4, by optimizing the ore blending and controlling the carbon content of the pellets, the strength of the reduced pellets is significantly improved, the risk of ring formation in the rotary kiln is reduced, and good de-zinc and de-lead effects are also achieved.

[0055] The above describes the preferred embodiments of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust as the main raw material, characterized in that, Includes the following steps: S1. Zinc-containing dust and sludge were blended under the multi-objective control conditions of internal carbon content, binary basicity (CaO / SiO2), MgO / SiO2 mass ratio and alkali metal (K2O+Na2O) content to obtain coarse-grained zinc-containing dust and sludge material. S2. Mechanically activate the coarse zinc-containing dust and sludge material obtained in step S1. Then, vigorously mix and pre-wet the activated zinc-containing dust and sludge material with composite binder and water. Finally, add mist water to the mixture to form pellets and obtain green pellets. S3. The green pellets obtained in step S2 are pre-dried and consolidated to obtain zinc-containing dust pellets with a certain strength; S4. The zinc-containing dust pellets obtained in step S3 are loaded together with the externally prepared reducing agent from the tail end of the rotary kiln. A rapid heating thermal regime is adopted to shorten the existence period of the FeO phase in the pellets, so that the pellet ore can form metallic iron crystals as soon as possible, and zinc-containing dust and sludge reduced pellets are obtained.

2. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S1, the coarse zinc-containing dust and sludge material includes one or more of the following: zinc-containing dust and sludge, iron-containing dust and sludge, converter dust and sludge, electrostatic precipitator dust and sludge, blast furnace bag filter ash, steelmaking ash, dust collector coke ash (CDQ), and coke dust. The coarse-grained zinc-containing dust and sludge material also includes iron concentrate and flux.

3. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S1, the internal carbon content is controlled at 5-15%, the binary basicity of the pellet (CaO / SiO2) is less than 0.3 or greater than 1.6, the MgO / SiO2 mass ratio is ≥0.45, and the alkali metal (K2O+Na2O) content is <2.0%.

4. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 3, is characterized in that... CaO and MgO originate from the alkaline components inherent in zinc-containing dust and sludge, as well as from one or more of limestone and dolomite.

5. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S2, the mechanical activation is one or a combination of two of the following: lubrication grinding and high-pressure roller grinding.

6. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S2, the composite binder is a bentonite-based binder, comprising 50-90% bentonite and 10-50% sodium humate, with an addition amount of 1.0%-3.0%.

7. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S2, the green pellets obtained by pelletizing have a particle size of 8-14 mm and a moisture content of 15%-20%. The water required for pelletizing zinc-containing materials is added in two parts. The water added in the high-intensity mixer accounts for 80-90% of the total water added, and the remaining 10-20% is added in the pelletizing process.

8. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S3, the green pellets are dried and dehydrated at 200~350°C and wind speed of 0.6~1.0m / s to reduce the moisture content to less than 1% and the compressive strength of the dried pellets to greater than 200N / P.

9. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... In step S4, the atmosphere for reducing zinc dust pellets mainly relies on the carbon inherent in the zinc dust sludge within the pellets and the added reducing agent. Regarding the proportion of reducing agent added, the total amount of carbon is controlled at 20% to 45% depending on the iron grade, of which the internal carbon accounts for 20% to 40% and the external carbon accounts for 60% to 80%.

10. The method for suppressing ring formation in a coal-based rotary kiln using zinc-containing dust and sludge as the main raw material, as described in claim 1, is characterized in that... By optimizing the temperature distribution inside the rotary kiln, the maximum temperature inside the kiln is controlled at 1100~1150℃, and the heating rate is 8~15°C / min; the liquid phase content is controlled to be below 20%. The zinc-containing dust and sludge reduction pellets have a particle size ratio of +8mm and above of over 60%, while the Fe metallization rate is over 80%, the Zn removal rate is not less than 90%, and the Pb removal rate is not less than 95%.