Abstract
In pressure hydrometallurgy, unplanned shutdowns associated with autoclave operation result in significant downtime and substantial economic impact. Equipment downstream of the autoclave is particularly susceptible to damage due to the severe operating conditions in the discharge line. The two block valves and the level control valve (LCV) that are part of the slurry control in the discharge line are vulnerable to erosive wear and hydraulic shock from flashing flow, while the LCV faces additional risks of ceramic fracture caused by thermal transients and crushing of scale.
Autoclave startups and shutdowns represent the highest-risk operating periods for this equipment. Valve sequencing downstream of the autoclave, along with the thermal soak time of the discharge line, strongly influences the magnitude and rate of thermal stresses imposed on the LCV. In this work, computational fluid dynamics and heat transfer models, validated against experimental data, are used to evaluate flow behavior, thermal response, and thermal shock risk in the autoclave discharge line during startup and shutdown. The results demonstrate how optimized operational procedures can reduce thermal, hydraulic, and erosive damage, improve valve reliability, and minimize costly unplanned downtime.