Information Destruction And Recycling Of The Storage Medium In Waste Computers

Electronic waste recycling is an important part for the development of circular economy and achievement of sustainability. There are all kinds of electronic waste with large quantity and complex compositions. More and more researchers pay attention to this research area. As the storage medium in computers, waste hard disk drive and internal memory are both typical and special electronic waste, which not only need destruction but also recycling. The method for waste hard disk drive destruction was designed. The size distribution model and dynamic model for waste internal memory destruction were established. The separation mechanism of the pneumatic separator was identified by computational fluid dynamics method. These models and simulation provide theoretical foundation for the destruction and recycling of storage medium. The production line for internal memory destruction and recycling was established. Health risk assessment was carried out in the production line workshop and improving measures were proposed. Economic assessment was carried out to evaluate the economic performances. Life cycle assessment was conducted to identify the significant environmental impact category and guide the decision making.According to the analysis of storage principle for hard disk drive, degaussing was used for the waste hard disk drive destruction. It is concluded that the direction of the hard disk drive should be parallel with that of the magnetic field direction. The degaussing was completed in 10 seconds. The high-intensity magnetic field was good for destruction when the magnetic field intensity was less than 5000 Gs.The G-S distribution and R-R distribution models both could be used to describe the size distribution of internal memory after crushing destruction. The crushing dynamic model could guide the parameter adjustment during the destruction.To improve the traditional cyclone for removing small particles, the computational fluid dynamics method was used to simulate the pneumatic separator. It indicated that the fluid pattern of the pneumatic separator was axisymmetric with small fluctuation at the two sides. The dust hopper flow pattern swirled up and down along with some local second vortex. The bottom inlet flow enhanced the inner upward flow that could effectively avoided the materials plugging during operation. The charge model for electrostatic separation was established which provides support for the theory of electrostatic separation.The production line for internal memory destruction and recycling was established. Health risk assessment was conducted which showed that the main noise sources in the workshop were the crushing equipments. After taking noise reduction measures, the noise level was reduced from 96.2 dB to 78.2 dB. The Cu, Cr and Cd did not have non-carcinogenic risk. But the hazardous quotient for Pb by ingestion was 1.41 times higher than the reference value. Among the three exposure pathways, ingestion presented the largest health risk.Economic assessment indicated that the profit rate for the production line project was 25%. The profit and tax rate was 37%. The internal rate of return was 43%. The break-even analysis results showed that the capacity at the break-even point was 18 t/a. The sales revenue was the most sensitive factor, the change of which brought tremendous changes of net present value and payback period.Life cycle assessment results suggested that the target metals leaching in the refining stage posed most of the environmental impact in the recycling chain, which contributed to 83% for the global warming potential, 91% for the eutrophication potential, and 80% for the terrestrial aquatic eco-toxicity potential. After normalization and weighting, global warming potential was the most significant environmental impact category. The energy source and the consumption of chemical reagents in the refining stage had a great effluence on the environmental performance of the recycling chain.This study provided the theoretical basis for the destruction and recycling of waste hard disk drive and internal memory and supported the industrialization of recycling technologies and equipments from the viewpoint of health risk, engineering economy, and environmental impact.