I. Project Overview

1.1 Project Objective

To process waste glass (scrap glass, glass offcuts, glass cullet, etc.) into glass powder of specified fineness using a ball mill, for wide applications in building materials, coatings, ceramics, chemicals, electronic pastes, and other fields.

1.2 Scope of Application

This plan covers both laboratory‑scale small‑batch production (using planetary ball mills) and industrial‑scale large‑volume production (using industrial ball mills).

1.3 Raw Material Sources

• Waste glass bottles and jars, flat glass offcuts
• Rejected glass products and cullet from glass manufacturing
• Water‑quenched glass slag (obtained by quenching molten glass in water)

II. Complete Process Flow

The complete process for grinding glass powder consists of five stages: Pre‑treatment → Primary Crushing → Fine Grinding → Classification → Packaging.

Raw glass → Sorting & impurity removal → Washing & drying → Primary crushing (frantoio a mascelle)
    → Secondary crushing (hammer crusher) → Screening (≤15 mm) → Magnetic separation (iron removal)
    → Ball mill fine grinding → Screening/classification
    → Qualified (≤ target fineness) → Packaging & warehousing
    → Unqualified → Return to ball mill for re‑grinding

2.1 Sorting and Pre‑treatment

Sort waste glass by colour (colourless, brown, green, etc.), and remove impurities such as ceramics, stones, plastics, metal caps, etc. Wash thoroughly with clean water to remove surface dirt and label residues, then dry for later use.

2.2 Primary and Secondary Crushing

• Primary crushing: Break large glass pieces (>50 mm) to 10‑30 mm particles using a jaw crusher.
• Secondary crushing: Further reduce to ≤15 mm using a frantoio a martelli.
• Screening: Use a vibrating screen to separate; particles >15 mm are returned to the crusher for re‑crushing.

2.3 Iron Removal

Use a magnetic separator or electromagnetic iron remover to remove metallic impurities (nails, caps, etc.), preventing metal contamination of the finished glass powder and protecting the ball mill equipment.

2.4 Mulino a sfere Fine Grinding

Feed the screened glass (≤15 mm) into the ball mill for fine grinding to obtain glass powder.

2.5 Classification and Packaging

• Classify the ground glass powder through a screening machine.
• Pack qualified powder (meeting the target fineness) into bags and store.
• Return unqualified powder (coarser than the target) to the ball mill for further grinding.

III. Equipment Selection Plan

3.1 Complete Production Line Equipment Configuration

3.2 Ball Mill Type Comparison

Recommended options:

• Laboratory / small batches: Planetary ball mill (e.g., IM600 model, speed up to 2100 rpm)
• Industrial scale: Horizontal ball mill (grid type or overflow type)

3.3 Grinding Media Selection

• Grinding jars: Alumina jars, zirconia jars (metal‑free contamination)
• Grinding balls: Zirconia balls (recommended), alumina balls
• Ball size gradation: Use a mix of large, medium and small balls.

IV. Ball Mill Process Parameters

4.1 Dry Ball Milling (suitable where no water is allowed or when drying is required afterwards)

4.2 Wet Ball Milling (suitable for finer powders and dust reduction)

4.3 Grinding Ball Size Gradation

Gradation principle: Large balls provide impact for coarse breakage, medium balls perform intermediate crushing, small balls carry out fine grinding.

4.4 Typical Process Examples

Example 1: Glass powder for solar cell silver paste

• Equipment: Planetary ball mill
• Milling time: 4 hours
• Solid‑to‑liquid mass ratio: 1:0.8
• Charge‑to‑ball mass ratio: 1:2.5
• Ball gradation (large:medium:small) = 3:2:1

Example 2: Glass powder for aluminium back‑surface field of silicon solar cells

• Milling time: 10‑12 hours
• Volumetric ratio balls:charge:water = 1:1:2
• Screening: 400‑mesh screen
• Target particle size: <7 μm

Example 3: Powder from waste glass tubes for ceramic bond grinding wheels

• Speed: 450 r/min
• Ball‑to‑charge ratio: 3:1
• Ball gradation (large:medium:small) = 2:4:1

V. Detailed Operating Procedure

5.1 Pre‑start Inspection

1. Check that all connection bolts are tight.
2. Check that all lubrication points are properly lubricated.
3. Check that the transmission system is in good working order.
4. Check that all protective guards are in place.
5. Check that all electrical instruments are responsive.

5.2 Charging Operation

1. Weigh the glass cullet, grinding balls (and liquid medium, if wet) according to the prescribed ratio.
2. Start the ball mill under no‑load (never start under load).
3. After the mill runs steadily, feed the material evenly through the feeder.
4. Ensure total filling volume does not exceed 3/4 of the mill volume.

5.3 Running Monitoring

1. Monitor bearing temperature; normally it should not exceed 70 °C.
2. Listen for abnormal operating noises.
3. Check discharge particle size and adjust parameters in time.

5.4 Shutdown and Discharge

1. Stop feeding and allow the material inside the mill to be discharged completely.
2. Turn off the ball mill power.
3. After the mill has come to a complete stop, discharge the ground material.
4. Clean any residual material from the mill interior.

5.5 Trial Operation Requirements

For newly installed or overhauled ball mills, a no‑load continuous trial run of no less than 12‑24 hours is required. Any problems found must be resolved promptly.

VI. Quality Control

6.1 Particle Size Control

• Regularly sample and test the particle size distribution of the glass powder.
• Adjust grinding time, rotation speed, and charge‑to‑ball ratio to control fineness.
• Use classifiers to separate qualified and unqualified products in time.

6.2 Purity Control

• Thoroughly remove iron before milling.
• Use non‑metallic grinding media (zirconia, alumina) to avoid metal contamination.
• Regularly test the metal impurity content in the final glass powder.

6.3 Common Problems and Solutions

VII. Safety and Environmental Protection

7.1 Key Safety Operating Points

1. Never start the ball mill under load.
2. Never insert hands or tools into the mill during operation.
3. Operators must wear dust masks and safety goggles.
4. All electrical equipment must be properly grounded.
5. Do not use glass containers for grinding hard and brittle materials (risk of shattering and injury).

7.2 Environmental Protection Measures

1. Install dust collection equipment such as bag filters.
2. Wet milling can effectively reduce dust emission.
3. Wastewater should be treated by sedimentation and either recycled or discharged after meeting standards.
4. Use a closed‑line production system to minimise dust leakage.

VIII. Investment and Economic Analysis (Example: 1000 t/year glass powder production line)

8.1 Estimated Main Equipment Investment

Note: Laboratory planetary ball mills cost about 10‑25 (10,000 CNY).

8.2 Revenue Sources

• Low raw material cost for waste glass (may even be negative cost if disposal fees are charged).
• Market price of glass powder: 500‑3000 CNY/tonne (depending on fineness and purity).
• Annual output value: 0.5‑3 million CNY (for 1000‑tonne scale).

IX. Plan Summary

This plan adopts a complete process flow of “Crushing pre‑treatment → Screening & iron removal → Ball mill fine grinding → Classification & packaging”. By selecting the appropriate ball mill and optimising grinding parameters (time, speed, ball‑to‑charge ratio, ball size gradation, etc.), waste glass can be processed into glass powder meeting the required specifications.

Key success factors:

1. Keep feed size ≤15 mm.
2. Optimise milling parameters (time 4‑12 h, speed depending on mill type) according to the target fineness.
3. Use non‑metallic grinding media to avoid contamination.
4. Use a classification system to promptly separate qualified products.
5. Install a dust collection system to ensure environmental compliance.

It is recommended that, before full‑scale production, small‑scale trials be conducted to determine the optimal process parameters, which can then be scaled up to industrial production.