Case Study: Preventing Distortion in Copper Smelting Equipment
An international process equipment manufacturer came to BMT WBM looking for a solution to a complex problem, which had been costing them millions of dollars per year over many years. Launders, used in their copper smelting equipment, were deforming during service. This deformation was causing two major problems: the bolted joints between sections of lauder were leaking molten copper, and launder support structures were being pulled out of the floor. Each time this happened extensive clean-up was required, the floor and support structure had to be repaired, and the launder itself had to be scrapped, remelted, and remanufactured. The designer had made several previous attempts to address the problem in a trial and error fashion, but those measures had not been effective.
A copper tapping launder is a solid copper chute used to transport molten copper between furnaces in a smelting plant. The launder does not melt because of a “skull” of low thermal conductivity material that forms on the inside surface of the launder as the molten material runs down. However, the launder does get very hot, causing it to both expand and weaken during use.
Figure 1: Basic launder geometry. Molten copper is poured in at the top (LHS) and runs out the bottom (RHS). Total length is approximately 12m. Total weight is approximately 15t.
BMT WBM was employed to carry out an investigation into the distortion of a copper tapping launder assembly, to determine the cause and then devise appropriate solutions. Several different phases to this work were considered as follows:
Determine the cause of distortion
BMT WBM built a finite element model of the launder in an attempt to reproduce the observed behaviour. The first step was to define the material properties of the copper alloy at very high temperatures. The model also included the cooling system and accounted for repeated usage cycles. Several analyses were run with different temperature distributions through the thickness. The analysis also studied a range of support scenarios to mimic the observed distortion.
Figure 2: FEA result showing upward distortion in a representative section of launder.
Optimise the design to minimize distortion
BMT WBM ran several optimization studies aimed at eliminating the permanent deformation in the launder. Primary areas considered for refinement were:
- profile of the launder cross sections
- arrangement of the water cooling system
- launder support arrangements
These studies required simulation of the heating cycle on multiple launder sections with differing levels of thermal conductivity. Detailed plots of the temperature-distribution time-history were produced.
Figure 3: FEA result showing temperature distribution in launder profile at different times during a tapping cycle.
Refine a new design concept
Based on BMT WBM’s optimisation studies, the client proposed a new launder design. To determine if the design would work, BMT WBM built a complex model of the entire launder assembly that included the material properties developed in the first phase and the thermal conductivity algorithms developed in the second phase. The temperature and deflection characteristics of this model showed excellent agreement with measurements taken on an actual launder of the same design, which validated the model for use in refinement studies. From there, BMT WBM was able to make further modifications to the shape, the cooling system, and the support arrangements to ensure that permanent deformation would not occur.
Figure 4: FEA result showing distortion in a launder during a tapping cycle.
BMT WBM’s investigation uncovered some fundamental design considerations necessary for distortion-free launder operation. A vastly improved understanding of the materials and mechanics involved in this highly complex process has perhaps been the most valuable outcome for the client. They have been able to use these insights in several other launder designs since this project was completed in 2008. Their launders now operate without incident, and their reputation in the marketplace has improved dramatically.
Through our complex problem solving techniques and advanced analytical expertise, BMT WBM was able to solve a long standing problem for our client. The in-service distortion of their copper tapping launders had cost them millions of dollars and had been troubling them for more than a decade. By leveraging BMT WBM’s expertise, they have now experienced 7+ years of problem-free operations.
An investment in a practical and robust engineering solution from BMT WBM has paid itself back over 100 times.