Scholarlink

Purpose <p>China dominates global NdFeB magnet production (90%), and yet its resource-intensive processes pose sustainability challenges. To guide the industry towards high resource-efficiency sustainable development, this study employs cumulative exergy demand (CExD) to quantify and compare the natural-resource efficiency of primary NdFeB production and three recycling routes.</p> Methods <p>A comprehensive CExD framework is applied to evaluate four routes: primary production from rare earth ores, scrap magnet recovery, hydrometallurgical recovery from oil sludge and calcium reduction-diffusion (RD) recovery from oil sludge. The analysis integrates the exergy value of upstream resources (including a novel estimation for Bayan Obo rare earth minerals) and the process-specific energy/material flows, using 1 tonne of NdFeB magnet as the functional unit.</p> Results and discussion <p>Results show large differences in resource efficiency: Primary production exhibits the highest CExD (936.28 GJ/t), primarily driven by exergy-intensive ore smelting (68%) and complex material transformations. In contrast, scrap magnet recovery achieves the lowest CExD (125.76 GJ/t, 86.6% reduction), because it avoids mining and refining and re-uses the existing component of Nd<sub>2</sub>Fe<sub>14</sub>B. For high-volume oil sludge waste, the CExD value of calcium RD route outperforms that of hydrometallurgy route by 21% (376.21 GJ/t vs. 477.05 GJ/t). This advantage stems from RD’s thermodynamic efficiency in rare earth oxide reduction (utilizing calcium’s high affinity for oxygen and CaCl<sub>2</sub> molten salt medium) and lower energy demand, despite challenges with ethanol degreasing (52% of CExD by RD). Hydrometallurgy shows higher exergy consumption due to intensive consumption of reagent (e.g., HCl, ammonia) and multi-stage separation processes.</p> Conclusions <p>This study establishes a CExD framework for evaluating resource depletion across the life cycle of NdFeB. It demonstrates that high-efficiency recycling, particularly scaling scrap magnet recovery for immediate resource savings and advancing RD technology (focusing on calcium recycling and low-exergy cleaning agents), is necessary for reducing China’s rare earth resource footprint. Prioritizing these pathways, alongside clean energy integration in primary production, offers a strategic roadmap for enhancing the sustainability and circularity of the NdFeB magnet industry.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Exergy-based resource efficiency evaluation of NdFeB magnet production and recycling in China

  • 期刊论文

  • 发表日期：

    2026年3月11日

查看全文
  • Duan Zhang,
  • Boxue Sun,
  • Suping Cui,
  • Lingqin Meng,
  • Shiwei Du,
  • Zuoren Nie

摘要

Purpose

China dominates global NdFeB magnet production (90%), and yet its resource-intensive processes pose sustainability challenges. To guide the industry towards high resource-efficiency sustainable development, this study employs cumulative exergy demand (CExD) to quantify and compare the natural-resource efficiency of primary NdFeB production and three recycling routes.

Methods

A comprehensive CExD framework is applied to evaluate four routes: primary production from rare earth ores, scrap magnet recovery, hydrometallurgical recovery from oil sludge and calcium reduction-diffusion (RD) recovery from oil sludge. The analysis integrates the exergy value of upstream resources (including a novel estimation for Bayan Obo rare earth minerals) and the process-specific energy/material flows, using 1 tonne of NdFeB magnet as the functional unit.

Results and discussion

Results show large differences in resource efficiency: Primary production exhibits the highest CExD (936.28 GJ/t), primarily driven by exergy-intensive ore smelting (68%) and complex material transformations. In contrast, scrap magnet recovery achieves the lowest CExD (125.76 GJ/t, 86.6% reduction), because it avoids mining and refining and re-uses the existing component of Nd2Fe14B. For high-volume oil sludge waste, the CExD value of calcium RD route outperforms that of hydrometallurgy route by 21% (376.21 GJ/t vs. 477.05 GJ/t). This advantage stems from RD’s thermodynamic efficiency in rare earth oxide reduction (utilizing calcium’s high affinity for oxygen and CaCl2 molten salt medium) and lower energy demand, despite challenges with ethanol degreasing (52% of CExD by RD). Hydrometallurgy shows higher exergy consumption due to intensive consumption of reagent (e.g., HCl, ammonia) and multi-stage separation processes.

Conclusions

This study establishes a CExD framework for evaluating resource depletion across the life cycle of NdFeB. It demonstrates that high-efficiency recycling, particularly scaling scrap magnet recovery for immediate resource savings and advancing RD technology (focusing on calcium recycling and low-exergy cleaning agents), is necessary for reducing China’s rare earth resource footprint. Prioritizing these pathways, alongside clean energy integration in primary production, offers a strategic roadmap for enhancing the sustainability and circularity of the NdFeB magnet industry.