During the iron and steel metallurgical process, a significant amount of dust is generated. According to relevant statistics, total dust production generally accounts for 8%–12% of the steel output. Specifically:
During sintering: the produced dust is 8–15 kg per ton of sinter.
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In blast furnace: the dust is 20–30 kg per ton of iron.
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In converter: the produced dust is 8–20 kg per ton of steel.
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In electric furnace: dust is 10–20 kg per ton of steel.
The steel industry produces a large volume of dust, which often holds considerable value for recycling. How should the dust be processed? We will explore the classification and potential applications of dedusting ash in this article.
What is Dedusting Ash?
Dedusting ash can be broadly categorized into two types based on the requirements and nature of the dust collection system: flue gas dedusting ash and environmental dedusting ash.
Flue gas dedusting ash is generated as an essential part of the production process, such as from the high-temperature flue gas emitted by the sintering machine head or the dust collected in blast furnace and converter gas systems using technolies such as baghouse filter and wet scrubber.
Environmental dedusting ash is collected during the air pollution control system in industrial process. The purpose of dedusting is to reduce environmental pollution and air pollution. The dust is collected using technologies like electrostatic precipitators. Usually, environmental dedusting ash accumulates at room temperature, undergoes minimal changes in composition, thus becomes easier to recycle with little impact on production.
Dedusting ash from steelmaking usually contains high iron content (3-50%). If we can extract the iron content from the dedusting ash, it holds significant economic value.
Use of Dedusting Ash: As an Ingredient for Cold-Pressed Mixtures
Dedusting ash can be proportionally mixed with other iron-rich solid waste materials, such as converter sludge and iron oxide scale, and then briquetted using cold-pressing technology for recycling. Proper operation and coordination are crucial for this method, including orderly ash discharge and precise proportioning. You can also do pre-moistening to improve briquetting performance.
Advantages: Simple method, low processing cost.
Disadvantages: Risk of harmful element residues, potential deficiencies in metallurgical performance.
Use of Dedusting Ash: Using Rotary Hearth Furnace Technology for Zinc Removal and Ironmaking
The above method, when applied to sintering, still results in the internal circulation of dust and sludge within the process, leading to the accumulation of harmful elements. For example, the average Zn and Pb content in dedusting ash from a certain steel plant is 1.1% and 0.3%, respectively, while the sintering machine head flue gas dust contains K (17.75%), Na (2.25%), and Cl (18.94%), posing significant risks to steel production. To address this issue, their circulation within the production system must be eliminated.
Currently, the rotary hearth furnace (RHF) is a viable technology for processing metallurgical dust and sludge. Originating from the steel billet annular heating furnace, RHF technology has been successfully adopted in developed countries like Japan and the U.S. for the efficient utilization of metallurgical dust. This technology separates iron from potassium, sodium, zinc, lead, and chlorine, producing metallized pellets. Industrial practices by Nippon Steel (Japan) demonstrate that RHF processing achieves over 90% recovery rates for zinc and lead, with the direct reduction metallization rate of pellets reaching about 70%, making them high-quality raw materials for blast furnace ironmaking.
Jianjie Group’s Solutions for Dedusting Ash
With nearly 20 years of industry experience, Jianjie Group has fully mastered the technology of producing metallized briquettes using rotary hearth furnaces.
The basic RHF direct reduction process is as follows:
Mixing: Mix Iron ore powder, dedusting ash, sludge, or other iron-containing waste in correct proportion with coal powder (work as a reducing agent) and a binder specially designed for RHF as adhesive.
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Pelletizing: The mixture is processed in a mixing mill and then pressed into carbon-containing pellets using a roller press.
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Drying: The pellets are dried to remove moisture and evenly distributed on the RHF hearth via a vibrating feeder.
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Reduction: As the hearth rotates, the pellets are heated by radiant combustion, passing through preheating and reduction zones. At 1000–1300°C, they undergo metallization in 15–20 minutes, with zinc being vaporized simultaneously.
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Discharge & Cooling: After one rotation, the metallized pellets are discharged via a screw conveyor, cooled to below 100°C, and sent to storage.
The RHF can use gas as fuel. High-temperature exhaust gas is first directed to a boiler to generate steam via waste heat recovery, then passes through a heat exchanger to preheat combustion air. The remaining heat is used for drying raw pellets before being released through a dust collector and chimney. The zinc-enriched dust can be recovered as raw material for zinc metallurgy.
For dust and sludge with low iron content or high levels of harmful impurities, pre-treatment can enhance the efficiency of RHF production.
Are you interested in recycling dedusting ash? Contact us now for comprehensive and cutomized solutions.
Post time: Mar - 26 - 2025
