Valves for nickel autoclave high pressure acid leaching

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Improving reliability with optimal valves for nickel autoclave high-pressure acid leaching

Autoclaves are used in mining and minerals processing to extract metals from refractory ore bodies. A typical process for autoclaves is high-pressure acid leaching (HPAL), which is often used to extract nickel from laterite ore bodies, but it can also be applied in copper and cobalt production. HPAL is considered to be an efficient processing method, especially due to the shorter processing time and higher recovery rates compared to conventional leaching methods.

Autoclave HPAL is a challenging process requiring the toughest flow control solutions. Temperatures and pressures are extremely high, and acidic media and abrasive solids increase the wear and tear of the equipment. An optimal HPAL operation generally uses several different types of valves, such as slurry feed and discharge valves, pump isolation valves, depressurization valves, steam supply and steam drum isolation valves, as well as acid injection valves.

Valves for slurry feed

The conditions that valves face in the HPAL process require the highest possible resistance against corrosion and erosion as well as against deterioration caused by solids. Selecting the right material, seat and coating is vital in maintaining the sealing abilities of slurry feed valves. 

Valves for acid feed

Controlling the acid feed is essential in the HPAL process. Valves must provide absolute isolation. If unstable situations occur, the valves and other process equipment in the acid feed line must be able to resist very high concentrations of acid.

Valves for depressurization

Autoclave processes are occasionally depressurized as a result of operational disturbances, emergency situations or maintenance. During depressurization, a vent line is used to reduce pressure and temperature inside the autoclave. Careful consideration of valve materials and coatings are among the top priorities when selecting the valves for this service.