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Dry Covers Applied to Coal Tailings

Trockenabdeckung von Abfallkohle

Coberturas secas aplicadas a los relaves de carbón

煤矸石堆的干式盖层

Abstract

Covering coal mining tailings with layers of soil reduces the generation of acid mine drainage. These layers are designed to minimize water seepage and the flow of oxygen into tailing deposits. In Brazil, tailings from mineral coal processing are rich in pyrite, are often stored in piles, and are covered with layers of soil on the surface. This study provides results on the performance of four experimental soil cover models on tailings resulting from coal mining in southern Brazil. Pilot-scale physical models were constructed on-site, and the water balance of the covers, suction, volumetric moisture content, temperature in the tailings/cover layers, and quality of released effluent were measured. The covers designed with soil and bottom ash significantly reduced the volume of water seepage through the tailings and improved the quality of the generated effluents. Moreover, the results demonstrated that the performance of the cover depends on climate variations, and its behavior varies seasonally.

Zusammenfassung

Die Abdeckung von Abfallkohle mit Boden verringert die Entstehung von saurem Grubenwasser. Diese Schichten sollen das Versickern von Wasser und den Zufluss von Sauerstoff in die Abfallkohle minimieren. In Brasilien sind die Abfälle aus der Steinkohleverarbeitung reich an Pyrit, werden häufig in Halden gelagert und an der Oberfläche mit Boden bedeckt. Diese Studie liefert Ergebnisse über die Leistungsfähigkeit von vier experimentellen Bodenabdeckungsmodellen für Abfallkohlehalden aus dem Kohlebergbau in Südbrasilien. Modellhalden wurden im Pilotmaßstab vor Ort gebaut, und der Wasserhaushalt der Abdeckungen, die die Saugspannung, der volumetrische Feuchtigkeitsgehalt, die Temperatur in den Abfallkohle-/Abdeckungsschichten und die Qualität des freigesetzten Abwassers wurden gemessen. Die Abdeckungen mit Boden und Schlacke verringerten das Volumen des durch die Halde versickernden Wassers erheblich und verbesserten die Qualität der entstehenden Abwässer. Darüber hinaus zeigten die Ergebnisse, dass die Leistung der Abdeckung von Klimaschwankungen abhängt und ihr Verhalten saisonal variiert.

Resumen

La cobertura de los residuos de la minería del carbón con capas de tierra reduce la generación de drenaje ácido de la mina. Estas capas están diseñadas para minimizar la filtración de agua y el flujo de oxígeno en los depósitos de estériles. En Brasil, los relaves del procesamiento del carbón mineral son ricos en pirita, suelen almacenarse en pilas y se cubren con capas de suelo en la superficie. Este estudio proporciona resultados sobre el rendimiento de cuatro modelos experimentales de cobertura del suelo en relaves resultantes de la minería del carbón en el sur de Brasil. Se construyeron modelos físicos a escala piloto in situ y se midió el balance hídrico de las cubiertas, la succión, el contenido volumétrico de humedad, la temperatura en las capas de relaves/cubiertas y la calidad del efluente liberado. Las cubiertas diseñadas con tierra y cenizas de fondo redujeron significativamente el volumen de filtración de agua a través de los relaves y mejoraron la calidad de los efluentes generados. Además, los resultados demostraron que el rendimiento de la cubierta depende de las variaciones climáticas y su comportamiento varía estacionalmente.

抽象的

煤矸石的土层覆盖技术可以减少酸性矿山废水排放。覆盖土层设计的目的是减少水流和氧气流进入煤矸石尾矿堆。在巴西, 煤洗选产生的矸石 (尾矿废物) 富含黄铁矿, 多堆积存放, 用土层覆盖矸石堆表面。研究给出了巴西南部煤矿尾矿的四个覆盖土层的试验模型运行结果。现场搭建了小型物理模型, 测量了覆盖土层水平衡、吸力、体积含水率、尾矿/覆盖土层温度和释出水水质。盖层的土层和底灰设计显著地减少了穿过尾矿的渗水量, 提高了出流水质量。另外, 研究表明, 盖层性能还依赖于气候变化, 随季节而变。

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Data availability

The water balance, physical–chemical and geochemical, waterflow, and weather data that support the findings of this study are available from the corresponding author.

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Acknowledgements

The authors thank the Brazilian Ministry of Science and Technology (Finep) for financial support, and Carbonifera Criciúma S/A and Tractebel Energia S/A for providing the ash from coal combustion.

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Correspondence to Marcos Fábio Porto de Aguiar.

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Soares, A.B., Possa, M.V., de Souza, V.P. et al. Dry Covers Applied to Coal Tailings. Mine Water Environ 41, 666–678 (2022). https://doi.org/10.1007/s10230-022-00883-6

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Keywords

  • Acid mine drainage (AMD)
  • Dry covers
  • Unsaturated water flow