*3.3. The Scaled-Up Dismantling Process*

The experimental results obtained for the dismantling of the four types of WPCBs were used to design a conceptual recycling plant at higher scale of production for the dismantling of 100 kg/h of WPCBs. It was assumed that the WPCBs fed into the recycling plant have the metallic composition of Table 8, which presents an average composition calculated based on the data from Table 2.


**Table 8.** Metallic composition (wt.%) of WPCBs feed into the recycling plant.

The dismantling process was modeled and simulated using process flow modeling software ChemCAD 7.1.5 in order to evaluate the contribution of all steps and equipment to the performance of the overall process and to provide the necessary data for the environmental assessment. Chemical and phase equilibrium were assumed based on Gibbs free energy minimization model. Other or complementary input data and assumptions used for modelling and simulation of the dismantling process are presented in Table 9.



Figure 3 shows that the recycling plant designed for the dismantling of WPCBs with the simultaneous recovery of copper includes two main subsystems: Phase 1 for the dissolution of the accessible metallic parts from the surface of WPCBs along with the separation of the obtained material fractions and Phase 2, where copper is electrodeposited and the leaching solution is regenerated. In addition, Phase 1 deals with the processing of the chips, small EC, and boards, considering that these fractions have high copper content and low concentration in other metals. In the model, these material fractions are ground to a fine powder in order to enhance the dissolution reaction; then, the obtained material is contacted in a second chemical reactor with the leaching solution generating two streams: (i) the electrolyte solution used for copper and leaching agent production and (ii) polymers and fiberglass that exit the system as byproduct. According to Figure 3, the solution obtained in the ER is only partially recirculated into the process, due to the fact that it contains other metals besides copper that need to be extracted, after which it can be reused in the dissolution step. This is the reason why, in this model, new reagents are feed into the system, which, in a complete recovery plant, would be significantly, or possibly entirely, reduced.

**Figure 3.** Recycling plant process flow diagram.

The overall mass balance (Table 10) of the scaled-up dismantling process indicates that the WPCBs were completely dismantled and processed into different materials fractions. Based on the initial amount of copper feed into the system with the WPCBs and the amount of obtained copper deposit, it is evident that more 90% of the copper is extracted during the dismantling process. As was expected, the organic matter, consisting of plastic and epoxy resin, represents the most important solid fraction obtained in the dismantling process, followed by fiber glass. It can also be seen that the amount of solution evacuated from the system is slightly higher than at the inlet due to the presents of the dissolved metals.


**Table 10.** Overall mass balance of the scaled-up dismantling process.

In accordance with the mass balance data (Table 10), equipment types, and operating conditions, the overall energy balance of the scaled-up dismantling process was established (Table 11). The results indicate that the highest energy consumption is associated with the electrochemical process followed by the separation of different material fractions during the dismantling process. Combining the mass and energy balance data, it was determined that the dismantling of 1 kg of WPCBs requires 0.48 kWh, while the total specific energy consumption for copper production is 2.59 kWh/kg. It is also important to note that the overall energy balance data reveals that the process generates 47% more energy that it consumes. However, the potential usability of the generated energy is discussible, considering that it is low grad heat generated during the dissolution processes in comparison to the consumed electrical power. However, if the energy would be valorized for heating purposes, then the process would be useful for energy production in parallel with the dismantling of WPCBs and recovery of copper.


**Table 11.** Overall energy balance of the scaled-up dismantling process.
