This study evaluated the properties and processing of cemented paste backfills (CPBs) for potash mining through loop tests. The CPBs were made with steel slags as the binder, granulated potash tailings as the aggregate, and waste brine water as the liquid phase. The effects of solid concentration and steel slag dosage on the transport and mechanical properties of CPBs were assessed. The loop test demonstrated that all CPB slurries performed well, exhibiting strong long-distance pipeline transport capabilities. The 28-day compressive strength of the backfills exceeded 1 MPa, meeting the design requirements for backfill strength. The key rheological parameters, including yield stress (τ₀) and viscosity coefficient (η), were comprehensively and theoretically analyzed based on the variations in pressure loss per unit distance of the filling slurry measured during the loop test. The empirical formulas for CPB pressure loss, accounting for varying flow rates and pipeline diameters, were derived with an error margin under 2%. The response surface analysis showed that the affecting extents of factors on pressure loss in CPB slurry were ranked as follows: solid concentration > cementing agent content > flow rate. This study offered valuable guidance for the processing of potash mine backfill operations.

Utilizing potassium salt aggregates and waste brine to produce underground cemented filling materials can address the waste storage issue. However, it is essential for the backfill materials to meet specific transport characteristics. This paper examines the transportation characteristics of lime-cemented mine backfill for a potash mine. The parameters were optimized for the cemented backfill process of potash mines through loop experiments and model simulations. Results indicate that the slump and fluidity of the backfill slurry diminished with increasing lime content and solid concentration. Additionally, the growth rate of pressure loss at the bent pipe and the pressure loss per unit distance in a horizontal pipe increased rapidly over transportation time, indicating a decline in the flowability of the backfill slurry. The lime dosage and solid concentration must align with the backfill requirements. When the lime dosage is 0.5%, the solid content is 70–75%; conversely, with a lime dosage of 0.7% and solid content of 65%, the maximum pumpable time extends to 1 h. The compressive strength of the cured backfill material after 28 days exceeds 1.01 MPa, meeting the transportation requirements for 300 m vertical pipes and 5000 m horizontal pipes. In the case study, the actual flow rate of backfill slurry surpasses the calculated critical flow rate. The estimated and measured values of on-site pressure loss per unit distance in a horizontal pipe exhibit a strong correlation. As the pressure loss per unit distance in a horizontal pipe rises, the discrepancy between the calculated and measured values also increases. When the solid content exceeds 65%, the loop test slightly enhances the compressive strength of the lime-cemented backfill. The findings from this article can aid in determining the on-site backfill process parameters with lime as a binder.

This paper investigates the flow performance and mechanical properties of underground gelled filling materials made from potash mine tailings, using lime as a gel. It demonstrates the feasibility of using lime as a gel, potash mine tailings as aggregate, and replacing water with potash mine tailings to create filling materials that meet design requirements for flow and compressive strength. The role of lime in the hardening process is explored through X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and infrared analysis. Results show that hydration products vary with lime dosage. With 9% lime (L9), the products are primarily ghiaraite (CaCl₂·4H₂O) and carnallite (KMgCl₃·6H₂O); with 5% lime (L5), tachyhydrite (CaMg₂Cl₆·12H₂O) predominates, along with minor amounts of antarcticite (CaCl₂·6H₂O) and korshunovskite (Mg₂Cl(OH)₃·4H₂O); and with 2.6% lime (L2.6), the products include tachyhydrite, ghiaraite, bischofite (MgCl₂·6H₂O), and korshunovskite. These hydration products form a dense, interwoven structure, enhancing the strength of the filling material. This study offers a theoretical foundation for using lime gel as a filling material in potash mining, with significant implications for sustainable mining practices.

This study was based on the status of the recycling industry of spent activated carbon (SAC) in China. By integrating national and industry standards (GB/T 7701.1-3, GB/T 13803.1-5, LY/T 3284-2021, etc.) with pollution control regulations (GB 34330-2017, GB 5085.7-2019, etc.), a quality and hazardous composition indicators system for regenerated activated carbon (RAC) used for industrial organic waste gas purification was constructed. The applicability of the indicators was verified by collecting test data from 10 effective samples of typical recycling enterprises nationwide, including iodine adsorption value, wear resistance strength, carbon tetrachloride adsorption rate, and 11 heavy metal limits. Furthermore, a comparative carbon footprint analysis was conducted based on industrial project data, quantifying the carbon reduction benefits of regeneration. The results showed that the physical properties (moisture content ≤ 2.85%, abrasion resistance ≥ 96%) and adsorption properties (iodine number 782---860 mg/g) of RAC met the overall standards, but the carbon tetrachloride adsorption rate (44.9% - 46.82%) only met the requirements for qualified products. The hazardous components (such as mercury 0.013---0.088 mg/kg, lead 1.4---10.1 mg/kg) were significantly lower than the limit values. Critically, the carbon footprint of RAC (1.632---2.736 tCO₂e/t) was 46.5% - 68.1% lower than that of activated carbon (5.112 tCO₂e/t), demonstrating a substantial climate mitigation benefit. This study provides a comprehensive technical support, encompassing quality, safety, and environmental benefits, for the standardized application and market promotion of RAC products, which is expected to promote the high-quality development of SAC resource utilization industry.