Method for improving metallization rate and dezincification rate of solid waste based on cascade distribution of coke oven gas

Abstract

The invention discloses a method for improving metallization rate and dezincification rate of solid waste based on cascade distribution of coke oven gas, which comprises the following steps: mixing a binder and iron-containing and zinc-containing solid waste according to a ratio, and feeding the mixture into a powerful mixer to form a mixture; the mixture enters a ball press machine to obtain green balls containing zinc and iron, and the green balls enter a rotary hearth furnace after being preheated, dried and screened; the green pellets sequentially pass through a heating area, a first reduction area, a second reduction area, a third reduction area, a fourth reduction area and a fifth reduction area which are sequentially arranged in the rotary hearth furnace in the trolley direction to form metallized pellets; and discharging the metallized pellets to a cylindrical cooling machine through a spiral discharging machine, and introducing nitrogen into the cylindrical cooling machine to obtain a final product. The method has the advantage that the metallization ratio of the carbon-containing pellets of the rotary hearth furnace is increased on the premise that the dezincification rate of the zinc-containing and iron-containing solid waste is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of pellet production, and in particular to a method for improving the metallization rate and dezincification rate of solid waste based on the step distribution of coke oven gas. Background Art

[0002] Generally speaking, the dust output of steel enterprises is about 8% to 10% of the steel output. These dusts contain a large amount of iron, and also contain zinc, potassium, sodium and carbon. Metallurgical dust should be reasonably recycled. If it is not handled properly, it will not only cause waste of resources, but also pollute the environment. Under normal conditions, steel enterprises collect metallurgical dust as sintering raw materials to produce sintered ore, but these dusts will affect the technical and economic indicators of sintering production, and will also cause zinc and alkali metals to be enriched inside the blast furnace, increase the zinc load of the blast furnace, and hinder the production of the blast furnace. The rotary hearth furnace process is one of the effective processes for steel enterprises to treat metallurgical dust. It has obvious advantages in solid waste recycling and environmental protection. The rotary hearth furnace has strong adaptability to raw materials and fuels, and the pellets are laid flat at the bottom of the furnace. There is no high requirement for the mechanical strength of the raw materials; and the dezincification rate is high, and the product has a wide range of uses. The dezincification rate can be obtained above 90%, and the iron content of the metallized pellets after reduction is more than 50%, and the zinc content of the reduced product zinc ash is more than 60%. Metallized pellets can replace scrap steel in electric furnaces and converters. Zinc ash is a raw material for zinc smelting, and its market price is about 6,000 yuan / t. Therefore, the rotary hearth furnace process can produce objective economic benefits.

[0003] For the carbon-containing pellets in the rotary hearth furnace, the main source of heat comes from the radiation heat transfer of the furnace wall and the furnace top, followed by the heat conduction inside the carbon-containing pellets and between the carbon-containing pellets, while the proportion of convective heat transfer is relatively small. Therefore, the current rotary hearth furnace process has the problems of low energy utilization and low production capacity, and the carbon-containing pellets use anthracite and coke powder as carbon sources, which are less reactive and harder, making them difficult to powder. At the same time, the use of carbon-containing materials such as carbon-containing blast furnace bag ash and coking dust removal ash ensures that the residual zinc in the rotary hearth furnace pellets meets the requirements, but due to process matching, there is insufficient carbon in the rotary hearth furnace pellets, and additional carbon-containing resources need to be found. The main reduction reactions of iron and zinc oxides occur in zinc-containing and iron-containing solid wastes. When the temperature is lower than 843K, the reduction conditions of iron oxides are better than those of zinc oxide. When the temperature is higher than 843K, the reduction of zinc oxide increases with the increase of zinc vapor in the gas phase (zinc has a low boiling point). In general, in most areas, the difficulty of the reaction ZnO+CO=Zn(g)+CO2 is greater than that of Fe3O4+CO=3FeO+CO2, and less than that of FeO+CO=Fe+CO2. Therefore, when the ambient temperature is higher than 1500K (for %V Zn <20), ZnO reduction is easy to FeO reduction, that is, as long as the reaction atmosphere can meet the production of metallic iron, ZnO will be reduced to generate zinc vapor, thus separated from the solid material. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the metallization rate and dezincification rate of solid waste based on the step distribution of coke oven gas. By setting different reduction zoning functions and the step distribution of the coke oven gas flow rate of hydrogen-rich gas for the rotary hearth furnace, efficient zoning reduction of iron oxides and zinc oxides can be achieved. Under the premise of ensuring the dezincification rate of zinc-containing and iron-containing solid waste, the metallization rate of carbon-containing pellets in the rotary hearth furnace is improved, and the pellets can be directly used as iron-containing raw materials for blast furnaces or converters.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas, characterized by comprising the following steps:

[0007] The binder and the iron- and zinc-containing solid waste are mixed in proportion and then enter into a high-power mixer to form a mixture;

[0008] The mixture enters the briquette press to obtain raw balls containing zinc and iron. The raw balls are preheated, dried and screened before entering the rotary hearth furnace.

[0009] The green balls are sequentially passed through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone arranged in sequence along the direction of the trolley in the rotary hearth furnace to form metallized balls. The heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone are all introduced with coke oven gas and combustion-supporting air. By adjusting the ratio of coke oven gas to combustion-supporting air, the first reduction zone is a weak hydrogen-rich atmosphere, the second reduction zone is a strong hydrogen-rich atmosphere, and the third reduction zone, the fourth reduction zone and the fifth reduction zone successively reduce the ratio of coke oven gas to form a stepped distribution;

[0010] The metallized pellets are discharged to a cylindrical cooler through a screw discharger, and nitrogen is introduced into the cylindrical cooler to obtain the final product.

[0011] Preferably, the iron-containing and zinc-containing solid waste includes dust removal ash water-washing filter cake, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash. The mass fraction of the water-washing filter cake is not less than 25%, and the mass fraction of the carbon-containing gravity dust removal ash is not less than 2%. The zinc oxide content in the iron-containing and zinc-containing solid waste is not higher than 3.5%, and the fixed carbon content is not less than 8.5%. The binder ratio is 4% to 6% of the mass of the iron-containing and zinc-containing solid waste, and the binder is selected from one of bentonite or water glass.

[0012] Preferably, the controlled size of the green ball is 28mm×25mm×15mm, the green ball is elliptical, the diameters of the ellipse are 28mm and 15mm respectively, and the thickness of the green ball is 25mm.

[0013] Preferably, the flue gas flow direction in the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone in the rotary hearth furnace is countercurrent to the running direction of the rotary hearth furnace, and a flue gas outlet is arranged at the heating zone.

[0014] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set to 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas flowing in countercurrent through the rear zone, and the atmosphere temperature is 800-900℃.

[0015] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the first reduction zone is 0.4:1, and the combustion air flow rate is 2800-3000m 3 / h, the coke oven gas flow rate is set to 1100-1200m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0016] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the second reduction zone is 0.8:1, and the combustion air flow rate is set to 4800-5000m 3 / h, the coke oven gas flow rate is set to 3800-4000m 3 / h, the center of the burner is 20cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature of the reduction zone II is set to 1100-1300℃, forming a strong hydrogen-rich atmosphere to accelerate the reduction of iron oxides.

[0017] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the third reduction zone is set to 1100-1350℃.

[0018] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100-1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

[0019] Preferably, the ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120-150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fifth reduction zone is set to 900-1000℃ through coke oven gas combustion.

[0020] In summary, the beneficial effects of the present invention are as follows: by setting different reduction zoning functions for the rotary hearth furnace and a step-by-step distribution of the coke oven gas flow rate of the hydrogen-rich gas, efficient zoning reduction of iron oxides and zinc oxides is achieved, and the metallization rate of the carbon-containing pellets in the rotary hearth furnace is improved while ensuring the zinc removal rate of zinc-containing and iron-containing solid wastes, so that the zinc removal rate of zinc-containing and iron-containing solid wastes reaches more than 93%, and the metallization rate reaches more than 68%, and the pellets can be directly used as iron-containing raw materials for blast furnaces or converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas. DETAILED DESCRIPTION

[0022] The specific implementation manner of the present invention is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the present invention.

[0023] Embodiment 1:

[0024] Table 1 Distribution ratio of each group in iron-containing and zinc-containing solid waste

[0025] materials Wet mix ratio carbon Moisture Zinc Dust removal ash water washing filter cake 25％ 35.4％ 25.8％ 3.4％ Steelmaking dust removal 25％ 8.0％ 5.6％ LT dust removal fine ash 48％ 1.0％ 2.7％ Carbonaceous gravity dust removal 2％ 28.7％ 2.6％ 0.4％

[0026] The washed filter cake of dust removal ash, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash are mixed according to the proportions in Table 1, with a zinc oxide content of 3.40% and a carbon content of 9.60%. 4.2% of bentonite as a binder is added. After strong mixing, the mixture enters the ball pressing process to obtain zinc-containing and iron-containing raw balls. The raw balls are preheated, dried and sieved before entering the rotary hearth furnace, and pass through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone respectively.

[0027] The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas passing through the rear zone in countercurrent flow, and the atmosphere temperature is 800-900℃.

[0028] The first reduction zone sets the combustion air flow rate at 2800~3000m 3 / h, the ratio of the internal coke oven gas flow rate to the combustion air flow rate is 0.4:1, and the coke oven gas flow rate is set at 1100-1200m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0029] The second reduction zone is set as a strong reduction zone, the ratio of the coke oven gas flow rate to the combustion air flow rate is 0.8:1, and the combustion air flow rate is set to 4800-5000m 3 / h, the coke oven gas flow rate is set to 3800~4000m 3 / h, the center of the burner is 20 cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the second reduction zone is set to 1100-1300℃.

[0030] The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm away from the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature in the third reduction zone is set to 1100-1350℃.

[0031] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100~1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

[0032] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120~150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fourth reduction zone is set to 900-1000℃ through coke oven gas combustion.

[0033] After the zinc- and iron-containing solid waste passes through the rotary hearth furnace, the zinc removal rate reaches 93.2% and the metallization rate reaches 68.5%.

[0034] Comparative Example 1:

[0035] Table 2 Distribution ratio of each group in iron-containing and zinc-containing solid waste

[0036] materials Wet mix ratio carbon Moisture Zinc Dust removal ash water washing filter cake 20％ 35.4％ 25.8％ 3.4％ Steelmaking dust removal 30％ 8.0％ 5.6％ LT dust removal fine ash 48％ 1.0％ 2.7％ Carbonaceous gravity dust removal 2％ 28.7％ 2.6％ 0.4％

[0037] The washed filter cake of dust removal ash, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash are mixed according to the proportions in Table 2, with a zinc oxide content of 3.5% and a carbon content of 8.7%. 4.5% of a binder bentonite is added. After strong mixing, the mixture enters the ball pressing process to obtain zinc-containing and iron-containing raw balls. The raw balls are preheated, dried and sieved before entering the rotary hearth furnace, and pass through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone respectively.

[0038] The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas passing through the rear zone in countercurrent flow, and the atmosphere temperature is 800-900℃.

[0039] The first reduction zone sets the combustion air flow rate at 2800~3000m 3 / h, the ratio of the internal coke oven gas flow rate to the combustion air flow rate is 0.4:1, and the coke oven gas flow rate is set at 1100-1200m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0040] The second reduction zone is set as a strong reduction zone, the ratio of the coke oven gas flow rate to the combustion air flow rate is 0.8:1, and the combustion air flow rate is set to 4800-5000m 3 / h, the coke oven gas flow rate is set to 3800~4000m 3 / h, the center of the burner is 20 cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the second reduction zone is set to 1100-1300℃.

[0041] The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm away from the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature in the third reduction zone is set to 1100-1350℃.

[0042] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100~1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

[0043] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120~150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fourth reduction zone is set to 900-1000℃ through coke oven gas combustion.

[0044] After the zinc- and iron-containing solid waste passes through the rotary hearth furnace, the zinc removal rate reaches 90.5%, the metallization rate is 65.2%, and the zinc removal rate and metallization rate are reduced.

[0045] Comparative Example 2:

[0046] Table 3 Distribution ratio of each group in iron-containing and zinc-containing solid waste

[0047] materials Wet mix ratio carbon Moisture Zinc Dust removal ash water washing filter cake 25％ 35.4％ 25.8％ 3.4％ Steelmaking dust removal 25％ 8.0％ 5.6％ LT dust removal fine ash 48％ 1.0％ 2.7％ Carbonaceous gravity dust removal 2％ 28.7％ 2.6％ 0.4％

[0048] The washed filter cake of dust removal ash, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash are mixed according to the proportions in Table 3, with a zinc oxide content of 3.40% and a carbon content of 9.60%. 4.2% of bentonite as a binder is added. After strong mixing, the mixture enters the ball pressing process to obtain zinc-containing and iron-containing raw balls. The raw balls are preheated, dried and screened before entering the rotary hearth furnace, and pass through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone respectively.

[0049] The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas passing through the rear zone in countercurrent flow, and the atmosphere temperature is 800-900℃.

[0050] The first reduction zone sets the combustion air flow rate at 2800~3000m 3 / h, the ratio of the internal coke oven gas flow rate to the combustion air flow rate is 0.4:1, and the coke oven gas flow rate is set at 1100-1200m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0051] The ratio of the coke oven gas flow rate to the combustion air flow rate in the second reduction zone is 0.4:1, and the combustion air flow rate is set at 4800-5000m 3 / h, the coke oven gas flow rate is set to 1900~2000m 3 / h, the center of the burner is 20 cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the second reduction zone is set to 1000-1200℃.

[0052] The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm away from the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature in the third reduction zone is set to 1100-1350℃.

[0053] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100~1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

[0054] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120~150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fourth reduction zone is set to 900-1000℃ through coke oven gas combustion.

[0055] After the zinc- and iron-containing solid waste passes through the rotary hearth furnace, the dezincification rate reaches 93.0%, the metallization rate is 60.1%, and the metallization rate is reduced.

[0056] Comparative Example 3:

[0057] Table 4 Distribution ratio of each group in iron-containing and zinc-containing solid waste

[0058]

[0059]

[0060] The washed filter cake of dust removal ash, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash are mixed according to the proportions in Table 4, with a zinc oxide content of 3.6% and a carbon content of 8.3%. 4.5% of binder water glass is added, and after strong mixing, they enter the ball pressing process to obtain zinc-containing and iron-containing raw balls. The raw balls are preheated, dried and screened before entering the rotary hearth furnace, and pass through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone respectively.

[0061] The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas passing through the rear zone in countercurrent flow, and the atmosphere temperature is 800-900℃.

[0062] The first reduction zone sets the combustion air flow rate at 2800~3000m 3 / h, the ratio of the internal coke oven gas flow rate to the combustion air flow rate is 0.4:1, and the coke oven gas flow rate is set at 1100-1200m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0063] The second reduction zone is set as a strong reduction zone, the ratio of the coke oven gas flow rate to the combustion air flow rate is 0.8:1, and the combustion air flow rate is set to 4800-5000m 3 / h, the coke oven gas flow rate is set to 3800~4000m 3 / h, the center of the burner is 20 cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the second reduction zone is set to 1100-1300℃.

[0064] The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm away from the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature in the third reduction zone is set to 1100-1350℃.

[0065] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100~1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

[0066] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120~150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fourth reduction zone is set to 900-1000℃ through coke oven gas combustion.

[0067] After the zinc- and iron-containing solid waste passes through the rotary hearth furnace, the zinc removal rate reaches 88.1%, the metallization rate is 68.1%, and the zinc removal rate is reduced.

[0068] Comparative Example 4:

[0069] Table 5 Distribution ratio of each group in iron-containing and zinc-containing solid waste

[0070] materials Wet mix ratio carbon Moisture Zinc Dust removal ash water washing filter cake 25％ 35.4％ 25.8％ 3.4％ Steelmaking dust removal 25％ 8.0％ 5.6％ LT dust removal fine ash 48％ 1.0％ 2.7％ Carbonaceous gravity dust removal 2％ 28.7％ 2.6％ 0.4％

[0071] The washed filter cake of dust removal ash, steelmaking dust removal ash, LT dust removal fine ash and carbon-containing gravity dust removal ash are mixed according to the proportions in Table 5, with a zinc oxide content of 3.40% and a carbon content of 9.60%. 4.2% of binder water glass is added. After strong mixing, the mixture enters the ball pressing process to obtain zinc-containing and iron-containing raw balls. The raw balls are preheated, dried and screened before entering the rotary hearth furnace, and pass through the heating zone, the first reduction zone, the second reduction zone and the third reduction zone respectively.

[0072] The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas passing through the rear zone in countercurrent flow, and the atmosphere temperature is 800-900℃.

[0073] The first reduction zone sets the combustion air flow rate at 2800~3000m 3 / h, the ratio of the internal coke oven gas flow rate to the combustion air flow rate is 0.30:1, and the coke oven gas flow rate is set at 1100-1200m 3 / h, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

[0074] The ratio of the coke oven gas flow rate to the combustion air flow rate in the second reduction zone is 0.30:1, and the combustion air flow rate is set at 4800-5000m 3 / h, the coke oven gas flow rate is set to 1400~1500m 3 / h, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the second reduction zone is set to 1000-1200℃.

[0075] The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.20:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1200m 3 / h, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the third reduction zone is set to 1000-1350℃.

[0076] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.20:1, and the combustion air flow rate is set to 4500m 3 / h, the coke oven gas flow rate is set to 900m 3 / h, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the fourth reduction zone is set to 1000-1350℃.

[0077] The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.20:1, and the combustion air flow rate is set to 1000m 3 / h, the coke oven gas flow rate is set to 200m 3 / h, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the fifth reduction zone is set to 900-1000℃.

[0078] After the zinc- and iron-containing solid waste passes through the rotary hearth furnace, the dezincification rate reaches 92.0% and the metallization rate is 54.1%, both of which are lower than before.

[0079] The present invention sets different reduction partition functions and a step-by-step distribution of the coke oven gas flow rate of hydrogen-rich gas on the rotary hearth furnace. The specific process is as follows: Figure 1 As shown, the efficient zoning reduction of iron oxides and zinc oxides is achieved, and the metallization rate of carbon-containing pellets in the rotary hearth furnace is improved while ensuring the zinc removal rate of zinc-containing and iron-containing solid wastes. The zinc removal rate of zinc-containing and iron-containing solid wastes reaches more than 93%, and the metallization rate reaches more than 68%, which can be directly used as iron-containing raw materials for blast furnaces or converters.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas, characterized in that: The steps include: The binder and the iron- and zinc-containing solid waste are mixed in proportion and then enter into a high-power mixer to form a mixture; The mixture enters the briquette press to obtain raw balls containing zinc and iron. The raw balls are preheated, dried and screened before entering the rotary hearth furnace. The green balls are sequentially passed through the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone arranged in sequence along the direction of the trolley in the rotary hearth furnace to form metallized balls. The heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone are all introduced with coke oven gas and combustion-supporting air. By adjusting the ratio of coke oven gas to combustion-supporting air, the first reduction zone is a weak hydrogen-rich atmosphere, the second reduction zone is a strong hydrogen-rich atmosphere, and the third reduction zone, the fourth reduction zone and the fifth reduction zone successively reduce the ratio of coke oven gas to form a stepped distribution; The metallized pellets are discharged to a cylindrical cooler through a screw discharger, and nitrogen is introduced into the cylindrical cooler to obtain the final product.

2. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The iron-containing and zinc-containing solid waste includes dust ash water-washing filter cake, steelmaking dust ash, LT dust ash fine ash and carbon-containing gravity dust ash. The mass fraction of the water-washing filter cake is not less than 25%, and the mass fraction of the carbon-containing gravity dust ash is not less than 2%. The zinc oxide content in the iron-containing and zinc-containing solid waste is not higher than 3.5%, and the fixed carbon content is not less than 8.5%. The binder ratio is 4% to 6% of the mass of the iron-containing and zinc-containing solid waste, and the binder is selected from one of bentonite or water glass.

3. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The controlled size of the green ball is 28mm×25mm×15mm. The green ball is elliptical, the diameters of the ellipse are 28mm and 15mm respectively, and the thickness of the green ball is 25mm.

4. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The flue gas flow direction of the heating zone, the first reduction zone, the second reduction zone, the third reduction zone, the fourth reduction zone and the fifth reduction zone in the rotary hearth furnace is countercurrent to the running direction of the rotary hearth furnace, and a flue gas outlet is arranged at the heating zone.

5. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the heating zone is 0.3:1, and the combustion air flow rate is set at 1000m 3 / h, coke oven gas flow rate is set at 300m 3 / h, with high-temperature flue gas flowing in countercurrent through the rear zone, and the atmosphere temperature is 800-900℃.

6. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the first reduction zone is 0.4:1, and the combustion air flow rate is 2800-3000m 3 / h, the coke oven gas flow rate is set to 1100-1200m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature in the first reduction zone is set to 1000-1200℃.

7. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the second reduction zone is 0.8:1, and the combustion air flow rate is set at 4800-5000m 3 / h, the coke oven gas flow rate is set to 3800-4000m 3 / h, the center of the burner is 20cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature of the reduction zone II is set to 1100-1300℃, forming a strong hydrogen-rich atmosphere to accelerate the reduction of iron oxides.

8. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the third reduction zone is 0.30:1, and the combustion air flow rate is set to 6000m 3 / h, the coke oven gas flow rate is set to 1800m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent, and the atmosphere temperature of the third reduction zone is set to 1100-1350℃.

9. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the fourth reduction zone is 0.25:1, and the combustion air flow rate is set to 4500-5000m 3 / h, the coke oven gas flow rate is set to 1100-1250m 3 / h, the center of the burner is 30cm above the material surface, the flame spraying angle is 45° downward to the vertical direction, and the high-temperature flue gas passes through the back zone countercurrent. The atmosphere temperature of the fourth reduction zone is set to 1200-1250℃.

10. The method for improving the metallization rate and dezincification rate of solid waste based on the cascade distribution of coke oven gas according to claim 1, characterized in that: The ratio of the coke oven gas flow rate to the combustion air flow rate in the fifth reduction zone is 0.15:1, and the combustion air flow rate is set to 800-1000m 3 / h, the coke oven gas flow rate is set to 120-150m 3 / h, the burner center is 30cm above the material surface, the flame spraying angle is 90° to the vertical direction, and the atmosphere temperature in the fifth reduction zone is set to 900-1000℃ through coke oven gas combustion.

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