In the fields of electronic materials, conductive pastes, powder metallurgy, and high-end metallic materials, nanometer- and micrometer-sized copper powders are increasingly becoming essential raw materials. In particular, particle size 300–500 nm In the production of copper powder, solid–liquid separation and washing are often critical process steps that significantly impact product quality, production efficiency, and cost control.

Compared with conventional micron-sized powders, nano- and sub-micron-sized copper powders exhibit Large specific surface area, high particle activity, and excellent suspension stability. These characteristics pose significant challenges to conventional sedimentation and centrifugation technologies in practical production. This paper, drawing on typical operating conditions, analyzes the technical difficulties inherent in the solid–liquid separation of nanometer- and micrometer-scale copper powders, and explores the application pathways and technical advantages of a novel nanometer- and micrometer-scale powder filtration machine in such processes.

I. Background and Typical Operating Conditions of Nanometer- and Micrometer-Scale Copper Powder Separation Processes

In certain nanometer- and sub-micron-scale copper powder production processes, surface oxides are typically removed by using Pickling and Multi-Stage Washing Process . The typical process is as follows:

1. Prepare a copper powder suspension.
2. Use 10% sulfuric acid solution Perform oxide washing
3. Perform a secondary wash with alcohol.
4. Wash until the system conductivity is controlled at Around 30 μS/cm
5. Ultimately achieve solid–liquid separation and obtain dry copper powder.

During this process, the slurry exhibits the following typical characteristics:

On the surface, this processing capacity does not qualify as ultra-large scale; however, due to the extremely fine particle size, the system complexity is significantly higher than that of conventional powders.

II. Core Issues with Traditional Separation Methods

Currently, the more common solid–liquid separation methods in this type of process include:

• Natural Sedimentation Method
• Centrifugal separation
• Multi-stage washing and dilution

However, in nanometer- and micrometer-scale copper powder systems, these methods often encounter significant bottlenecks.

1. Natural sedimentation is highly inefficient.

The sedimentation behavior of nanoscale particles in liquids is significantly influenced by Brownian motion.

When the particle size is reduced to 300–500 nm At such times, the settling velocity of particles is extremely slow, often requiring a considerable amount of time to form a distinct sedimentary layer.

Typical issues include:

• Long settling time
• Difficulty in clarifying the supernatant
• The system takes up a lot of space.
• Production takt is difficult to control.

Especially when the solid content reaches 25–40% At this point, the viscosity of the system increases, and the settling velocity decreases further.

2. Centrifugal separation involves a trade-off between energy consumption and efficiency.

Although centrifuges can enhance separation speed, they also present challenges in nanofluid and micropowder applications:

(1) Particles are too fine

Nanoscale particles are easily formed:

• Stable Suspension System
• Colloidal structure
• Secondary dispersion

This leads to a decrease in centrifugal separation efficiency.

(2) High water consumption for washing

To achieve a low conductivity (e.g., 30 μS/cm), it is often necessary to:

• Multi-stage dilution
• Large amounts of wash water
• Multiple centrifugations

This directly leads to:

• Increased water consumption
• Increased alcohol consumption
• Rising post-processing costs

(3) Unstable powder recovery rate

Nanometer-scale powders are prone to:

• Lost with the mother liquor
• Forming a fine suspended tail liquid

It affects the final yield.

III. Core Technical Challenges in the Filtration of Nanoscale and Micron-Scale Copper Powders

From an engineering perspective, the main challenges of such systems are concentrated in three areas:

1. Particle size is close to the nanoscale.

Particles in the 300–500 nm range are already close to the typical filtration limit.

Its manifestation is:

• Particles can penetrate ordinary filter media.
• Prone to clogging of the filter layer
• Rapid increase in filtration resistance

This places higher demands on filtration equipment.

2. Large fluctuations in slurry solids content (25–40%)

High-solids slurry has:

• High viscosity
• Easy agglomeration
• Prone to forming a compacted filter cake

If the filter structure is poorly designed, the following issues are likely to arise:

• Filter cake densification
• Difficult to wash
• Difficult to dry

3. The multi-media washing system is complex.

The system involves:

• Sulfuric acid system
• Alcohol system

Therefore, the equipment must meet:

• Corrosion-resistant
• Organic solvent resistance
• Good sealing performance

Otherwise, the following is likely to occur:

• Leakage Risk
• Safety hazard
• Product Contamination

IV. Technical Approach for the New Nano- and Micropowder Filtration Machine

In response to the aforementioned issues, the new nano- and micro-powder filtration machine utilizes Structural Design + Filtration Mechanism Optimization , enabling efficient separation and washing of nanometer- and micrometer-scale powders.

Its core approach is not simply “filtering,” but rather:

Establish a stable and controllable nanometer-to-micrometer filtration system.

1. Nanometer- and Micrometer-Scale Filtration Structure Design

This device employs a multi-stage filtration structure, enabling the system to:

• High retention capacity
• Stable filtration channel
• Low particle penetration rate

Even in 300–500 nm In powder systems, relatively stable solid–liquid separation can also be achieved.

Its manifestation is:

• Improved clarity of the supernatant
• Reduced fine powder loss
• Increased recovery rate

2. Mechanism of Stable Filter Cake Formation

During the filtration process, a stable filter cake layer gradually forms within the system.

This filter cake serves not only as a separation medium but also as:

Secondary filtration layer.

Its advantages include:

• Enhance filtration accuracy
• Improve washing efficiency
• Reduce fine powder loss

This is particularly critical for copper powder systems.

V. Significant Improvement in Multi-Stage Washing Efficiency

In traditional centrifugal systems, washing typically relies on:

• Multiple dilutions
• Multi-stage centrifugal

In the nano-micropowder filtration machine, the following can be achieved:

Filter Cake Washing Technology

Achieve a more efficient washing process.

1. Improved removal efficiency of residual acid solution after pickling

After washing with 10% sulfuric acid, the residual acid solution often requires extensive rinsing to reduce its conductivity.

The filtration and washing method can achieve:

• Directed Liquid Displacement
• Uniform penetration washing
• Lower residual liquid volume

Therefore, upon reaching:

Electrical conductivity: 30 μS/cm

When targeting, the amount of washing solution required is significantly reduced.

2. Improved alcohol washing efficiency

During the alcohol washing stage, the filter cake structure remains stable, allowing the alcohol to pass uniformly through the filter cake layer.

The results include:

• Shorter washing time
• Improved alcohol utilization
• Improved drying efficiency

This is particularly important for easily oxidizable copper powder.

VI. Analysis of the Alignment Between Dry Material Acquisition Capability and Production Capacity

Under the target operating condition:

120 kg of dry material / 8–12 hours

This processing capacity falls within the typical range for pilot-scale to small-scale industrial production.

The new nano- and micro-powder filtration machine can:

• Filter Area Design
• Differential Pressure Control
• Washing Cycle Optimization

Achieve stable operation.

Annual Production Capacity Expansion Analysis

Future Goals:

10 tons of dry material per year

Estimated as follows:

If run daily:

• 1 batch
• Approximately 120 kg

Then:

Approximately 80–90 batches per year

The design objectives can thus be achieved.

Explanation:

This equipment demonstrates good compatibility with current production capacity and offers room for future expansion.

VII. Optimization Analysis of Water Consumption and Operating Costs

In traditional centrifugal systems:

Water consumption for cleaning is typically high.

The reasons include:

• Uneven washing
• Fine powder is hard to remove.
• Multiple iterations are required.

And in the filtration and washing system:

Water consumption can be significantly reduced.

Typical conservation pathways include:

1. Reduce the number of washes
2. Improve single-wash efficiency
3. Reduce the volume of residual liquid

The result is manifested as:

• Reduced water consumption
• Reduced alcohol consumption
• Reduced waste liquid treatment costs

From a long-term operational perspective, this is often a key source of system cost-effectiveness.

VIII. Process Stability and Product Quality Improvement

The quality stability of nanometer- and micrometer-scale copper powder directly affects:

• Electrical conductivity
• Sintering performance
• Final Product Consistency

After the filtration system has been operating stably, product quality typically manifests as:

1. More stable powder purity

Through efficient washing:

• Residual acid reduction
• Impurities reduced

Helps with:

Enhance the consistency of powder quality.

2. Controllable moisture content

Stabilizing the filter cake structure can achieve:

Lower residual liquid volume.

This means:

The load is reduced during the drying phase.

3. Particle size distribution remains stable

Compared with the strong centrifugal process:

The filtration method causes relatively little damage to the particles.

Helps with:

Maintain the integrity of the nano- and microstructure.

IX. Future Development Trends in Nanomicro Powder Filtration

With the development of the electronic materials and new energy industries, the applications of nano- and micro-powders are continuously expanding.

Includes:

• Nano copper powder
• Nano nickel powder
• Silver powder
• Conductive material
• Catalytic materials

Their common characteristics are:

Particle size is becoming increasingly fine, and purity requirements are rising accordingly.

This means:

Traditional sedimentation and centrifugation techniques will gradually reach their technological limits.

Meanwhile, filtration technologies specifically designed for nanoscale and microscale systems will become one of the critical pieces of equipment.

Conclusion: Nanometer- and micrometer-scale solid–liquid separation is entering an era of specialized equipment.

Regarding particle size 300–500 nm In copper powder systems, although conventional sedimentation and centrifugation remain in use, they have gradually revealed limitations in terms of efficiency, resource consumption, and operational stability.

The new nano- and micro-powder filtration machine achieves:

• High-precision filtration structure
• Stable filter cake formation
• Efficient washing mechanism

It is currently providing a more controllable, energy-efficient, and stable technological approach for the separation of nanoscale particulate materials.

As future production capacity shifts to 10 tons per year level With continued development, such equipment will play an increasingly important role in the production processes of nanoscale and micrometer-scale metal powders, serving as one of the critical foundational technologies for advancing the manufacturing processes of high-end materials.

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