Molienda es un paso crítico en el procesamiento de minerales, donde las partículas de mineral se reducen en tamaño y los minerales objetivo se liberan a través de la coli, impacto y abrasión entre el medio y el mineral. Sin embargo, los molinos de bolas se basan principalmente en el impacto y la colide de los medios de molienda para descomponer los minerales, lo que resulta en una baja eficiencia de molienda, ya que sólo una parte de la energía se utiliza para la fragmentación de mineral y molienda. En consecuencia, los molinos de bolas generalmente sufren de baja eficiencia de molienda, alto consumo de energía, desgaste severo de la camisa, y bajo rendimiento en molienda ultrafina. Molinos agit, por otro lado, operan a través de la fricción abrasiva, ofreciendo ventajas tales como bajo consumo de energía, alta eficiencia de molienda, y una estrecha distribución de tamaño de partícula, por lo que son altamente eficientes equipos de molienda ultrafina. Debido al alto consumo de energía y bolas en operaciones de molienda fina, un número creciente de concentradores están adoptando molinos agitados para esta etapa.

Actualmente, los medios de molición utilizados en molinos agitincluyen bolas de acero, bolas de hierro fundido y bolas de cerámica, siendo las bolas de acero las más ampliamente aplicadas. Sin embargo, en la producción real de molienda, las bolas de acero exhialta pérdida de redondez, alta densidad, pobre rendimiento de molienda y corta vida útil. Además, tienden a causar sobremolide de minerales objetivo en la molienda ultrafina, limitando en gran medida su aplicación en molinos agitados. Las bolas nanocerámicas, hechas de materiales resistentes al desgaste como alúmina, zirconia o boride de sili, ofrecen ventajas tales como baja densidad, peso ligero, excelente resistencia al calor, resistencia al desgaste superior y fuerte resistencia a ácidos y álcalos. Por lo tanto, la adopción de bolas nanocerámicas representa una solución técnica promete, que atrae la atención de los investigadores. Por ejemplo, Sanxin New Materials Co., Ltd. desarrolló una bola de cerámica sub-nano resistente al desgaste a través de la calcina alta temperatura con la adición de óxidos y materiales de tierras raras, mejorando significativamente la uniformidad del material y la resistencia al desgaste. Las pruebas de resistencia al desgaste mostraron que estas bolas cerámicas sub-nano superan con creces a las bolas de acero, reduciendo el consumo de bolas en más del 84% con la misma eficiencia de molienda. Estudios comparativos sobre la eficiencia de molienda de bolas de nanocerámica y bolas de acero revelaron que mientras que la distribución de tamaño de partícula de los productos de tierra era similar, las bolas de nanocerámica exhimayor utilización de energía, menos sobremoli, y mejor rendimiento de molienda ultrafina.

El concentrde la mina de cobre no ferropulang de Diqing utiliza un molino de bolas vertical CSM-850 para la molide de concentrado grueso, que es beneficioso para mejorar la liberación de minerales que contienen cobre, reducir el sobremoli, y mejorar significativamente la tasa de recuperación y el grado de cobre en la flotación posterior. Sin embargo, durante la fase de producción inicial, el molino vertical emplebolas de acero como medio de molienda, y la finura de molienda fallconsistentemente en cumplir con el objetivo de diseño (± 0.049 mm > 86%). Por lo tanto, encontrar un nuevo medio de rectificado para reemplazar bolas de acero es crucial para mejorar la eficiencia de rectificado y reducir costos.

Este estudio aborda esta cuestión mediante la comparación del rendimiento de molienda de bolas de nanocerámica y bolas de acero en el afilado de concentrado grueso en la mina de cobre Pulang, con el objetivo de explorar enfoques técnicos para mejorar la eficiencia de molienda y reducir costos.

1 estado de producción actual

1.1 Brief Introduction to the Production Process

The concentrator of Diqing Nonferrous Pulang Copper Mine adopts the SABC + bulk flotation process. The SABC (SAG-Ball-Crush) process consists of a semi-autogenous grinding (SAG) mill, ball mill, and pebble crusher for ore crushing and grinding. The bulk flotation process follows a one-stage roughing – regrinding of rough concentrate – three-stage scavenging – two-stage cleaning circuit.

The regrinding of rough concentrate aims to further liberate target minerals, thereby improving the grade of the bulk concentrate and ensuring optimal flotation performance. The CSM-850 vertical mill is used for the regrinding of flotation rough concentrate.

1.2 Current Production Status with Steel Balls as Grinding Media

The CSM-850 vertical mill has an effective volume of 45.4 m³. In the initial production phase, the mill used Φ25 mm steel balls as grinding media. To ensure grinding efficiency, the initial ball loading was 75 t, with a filling rate of 34%. The daily ball replenishment was 1 t/d, resulting in a specific ball consumption of 42.56 g/t. The operating current of the mill was approximately 42 A, and the spiral liner lifespan was about 6 months, with 4–6 liners replaced per cycle.

When using steel balls as grinding media, the regrinding fineness in the second stage of the vertical mill was approximately 84% passing 300 mesh (−0.049 mm), slightly below the required technical parameter. Additionally, the following drawbacks were observed in actual production:

1. Steel balls are prone to deformation and loss of roundness, leading to accumulation and compaction at the bottom of the mill, reducing the effective grinding volume.

2. "Dented" surfaces develop on steel balls (as shown in Figure 1), causing inefficient grinding and reducing overall grinding efficiency.

2 Results and Discussion

2.1 Overall Performance of Nano-Ceramic Balls in Industrial Application

To improve grinding efficiency and reduce costs, the Pulang Copper Mine concentrator replaced steel balls with nano-ceramic balls as grinding media in the regrinding of rough concentrate. The initial filling rate of ceramic balls was increased from 30% to 34%, with a total loading of 39 t. The initial ball size distribution was set at m(Φ10 mm) : m(Φ15 mm) : m(Φ20 mm) = 3:4:3, corresponding to:

• Φ10 mm ceramic balls: 12 t

• Φ15 mm ceramic balls: 15 t

• Φ20 mm ceramic balls: 12 t

2.2 Impact on Pulp Density and Grinding Fineness

Pulp density and grinding fineness are key indicators of grinding efficiency. Therefore, a comparative analysis was conducted on the cyclone overflow density and fineness when using ceramic balls versus steel balls. The results are summarized in Table 1.

The comparison revealed that:

• Overflow pulp density was similar for both media, falling within the required range (17%–24%).

• However, when steel balls were used, pulp density fluctuated significantly (17.27%–23.62%).

• In contrast, with ceramic balls, pulp density stabilized at around 20%, facilitating better control of downstream cleaning operations.

Moreover, replacing steel balls with ceramic balls significantly improved grinding fineness, demonstrating a clear enhancement in grinding efficiency.

2.3 Impact on Grinding Efficiency

Particle size distribution and grinding selectivity are critical parameters for evaluating grinding performance. A comparative particle size analysis was conducted on ground products using both steel balls and ceramic balls as grinding media, with the results presented in Table 2. It should be noted that the previously mentioned "-0.049 mm content" in the study on pulp density and grinding fineness refers to the particle size distribution of cyclone overflow products, whereas the grinding fineness discussed in this section pertains to the particle size of the ground product discharged directly from the outlet of the vertical ball mill.

The results in Table 2 demonstrate that when ceramic balls were used as grinding media, the content of coarse particles (+300 mesh) in the ground product significantly decreased. Specifically, the content and generation rate of fine particles (-300 mesh) markedly increased, with the -300 mesh fraction content rising by nearly 8 percentage points. Notably, the content of the -400 mesh fraction increased by approximately 10 percentage points, indicating a substantial improvement. These findings confirm that using ceramic balls as grinding media can effectively enhance grinding efficiency.

2.4 Impact on Grinding Media Consumption

In actual production, based on feed characteristics and product particle size distribution, we optimized the diameter and replenishment rate of grinding media. The final determined ceramic ball replenishment rate was 150 kg/d, with a replenishment diameter of Φ20 mm. Details of the media replenishment are shown in Table 3.

As evident from Table 3, after replacing steel balls with ceramic balls as grinding media, the daily replenishment quantity of grinding media decreased significantly. This indicates that ceramic balls can substantially reduce grinding media consumption. For instance:

• The specific consumption of ceramic balls was 7.91 g/t, compared to 42.79 g/t for steel balls.

• After switching to ceramic balls, the specific media consumption decreased by 34.88 g/t, representing an 82.32% reduction.

Furthermore, visual inspection of the grinding media inside the vertical mill cylinder revealed that ceramic balls effectively maintained their spherical shape, with virtually no out-of-roundness observed (Figure 2). This demonstrates that ceramic balls can significantly reduce media wear and consumption.

2.5 Impact on Energy Consumption Reduction

While maintaining grinding efficiency, the vertical mill's operating current significantly decreased to 31 A when using ceramic balls as grinding media, compared to the previous 42 A with steel balls. Detailed power consumption data is presented in Table 4.

Key findings from Table 4 show:

• The mill's operating current dropped from 42 A (steel balls) to 31 A (ceramic balls)

• Specific power consumption decreased from 0.69 kW·h/t to 0.52 kW·h/t

• This represents a 25.71% reduction in energy usage

These results demonstrate that adopting ceramic balls as grinding media can substantially reduce grinding energy consumption while maintaining processing efficiency.

2.6 Impact on Spiral Liner Service Life

The wear and consumption of mill liners represent a significant portion of grinding costs. We conducted a comparative analysis of liner replacement frequency between ceramic ball and steel ball grinding media, with results presented in Table 5.

Key findings demonstrate:

1. Extended service life:

2. Cost reduction:

3. Reduced replacement quantity:

This data confirms that ceramic balls significantly reduce liner wear and associated maintenance costs while maintaining grinding efficiency.