In this Copper Electrorefining CFD Analysis tutorial, we explore the final step in producing very pure copper for electrical wires. In this process, we take impure copper (99%) and dissolve it in an acid bath to make high-purity copper (99.99%). This happens in a large tank called a cell. Electricity moves copper ions from the anode to the cathode. Understanding the movement of the liquid electrolyte is very hard because the gap between plates is small. Real experiments are difficult because the acid is dangerous. Therefore, engineers use CFD simulation to see inside the tank. We use ANSYS Fluent to simulate the chemical reactions and fluid flow. This software helps us predict where the copper ions go. By using a UDF fluent code, we can calculate the exact rate of copper deposition. This Copper Electrorefining fluent simulation helps factories save energy and improve metal quality.

In this report, we perform a detailed CFD study of the purification process. We track the concentration of copper and acid. We also look at how density changes cause the liquid to move naturally. For more details on chemical processes, please explore our Chemical Engineering tutorials.

• Reference [1]: Leahy, Martin J., and M. Philip Schwarz. “Flow and mass transfer modelling for copper electrowinning: Development of instabilities along electrodes.” Hydrometallurgy147 (2014): 41-53.

Figure 1: Diagram of the purification process showing the movement of Copper ions (Cu²⁺) from the impure anode to the pure cathode in the electrolyte.

Simulation process: Species Transport Modeling and UDF Integration

For this CFD simulation, we created a full 3D geometry of a single anode-cathode pair. The gap between them is about 30 mm. We generated a detailed Unstructured Mesh with 979,794 cells. We used prisms and tetrahedra to fit the shape perfectly. We refined the mesh very closely near the electrode walls. This is necessary to catch the thin boundary layers where mass transfer happens. We activated the Species Transport Model in ANSYS Fluent to track Copper ions (Cu²⁺) and Sulfuric Acid (H₂SO₄).

To make the simulation realistic, we wrote a custom UDF fluent code (User-Defined Function) in C language. This code uses Faraday’s Law to calculate how much copper dissolves at the anode and deposits at the cathode based on the current density. We applied this UDF as a source term at the boundaries. The code also changes the density of the liquid based on how much copper is in it. This setup allows ANSYS Fluent to simulate natural convection, where heavy fluid sinks and light fluid rise. This makes the Species Transport simulation physically accurate.

Figure 2: 3D Computational Domain representing the inter-electrode gap with refinement near the walls for the CFD simulation.

Post-processing: Copper Electrorefining CFD Analysis of Mass Transfer

This section analyzes the engineering data to understand how copper moves in the cell. We examine the concentration profiles and 3D contours to evaluate the efficiency of the process. First, we analyze the Copper Mass Fraction Profile in Figure 3. This graph shows how copper concentration changes from the anode (left) to the cathode (right). At the anode surface, the copper concentration is extremely high (near 100%) because the metal is dissolving rapidly. The curve drops very sharply within just 2-3 millimeters. This is the anode boundary layer. In the middle of the gap, the line is flat at about 5%. This means the bulk electrolyte is well-mixed. At the cathode on the right, the concentration drops to nearly zero. This is the depletion layer. Engineering Insight: This result is critical for the designer. If the concentration at the cathode stays near zero, it limits how fast we can produce copper. This profile proves that mass transfer is the limiting factor in the process.

Next, we evaluate the 3D Contours of Natural Convection in Figures 4 and 5. Figure 5 shows the copper concentration. We see a strong vertical gradient. The bottom of the tank is red/orange, meaning it has high copper concentration (0.046 mass fraction). The top is blue, meaning low copper concentration (0.040 mass fraction). This happens because water with more copper is heavier. The UDF fluent code correctly simulates gravity pulling this heavy fluid down. Conversely, Figure 4 shows the sulfuric acid. The acid concentration is highest at the top. This is because when copper leaves the solution at the cathode, the remaining liquid is lighter and floats up.

Figure 3: Copper mass fraction profile between anode and cathode obtained from the Copper Electrorefining CFD Analysis, showing the boundary layer drops.

Figure 4: 3D contour of sulfuric acid (H₂SO₄) mass fraction in the electrorefining cell showing lighter acid accumulating at the top.

Figure 5: 3D contour of copper (Cu) mass fraction in the electrorefining cell showing heavier copper-rich fluid sinking to the bottom.

Finally, we consider the impact on Manufacturing Quality. The simulation shows that the bottom of the cell has a different chemical makeup than the top. This uneven distribution can cause the copper plate to grow unevenly, making it thicker at the bottom. The ANSYS Fluent results suggest that the factory might need to increase the pumping speed of the electrolyte to mix the tank better. By using this Copper Electrorefining CFD Analysis, engineers can optimize the flow rate to prevent this separation, ensuring the entire copper plate is pure and smooth.