Valves for gold autoclave pressure oxidation (POX)

Autoclave pressure oxidation (POX) is an effective pre-treatment option when extracting gold from refractory ore bodies, such as pyrite and arsenopyrite. While gold processing plants are the most common utilizers of POX technology, the process can also be applied to other metals, like copper, zinc and uranium. Neles™ has a wide range of valves and services for POX process.

Benefits

Higher recovery rates and lower total cost of ownership

Over a century of experience in the mining sector

Higher resistance against abrasive media, corrosion and erosion

400+ service professionals in over 40 countries around the world

Valves control various flows in gold autoclave pressure oxidation process

Autoclave POX operations include several different types of valves to control both liquid and gaseous flows. Slurry feed and discharge valves, pump isolation valves, depressurization valves, steam supply and steam drum isolation valves, as well as oxygen feed valves, among others, make sure that the POX process works optimally and efficiently.

In the autoclave, valves are subjected to a high-temperature and an oxygen-rich environment, so the right selection of valves can potentially make a significant positive impact on the operation’s reliability.

Valves for slurry feed

The conditions that valves face in the POX process require the highest possible resistance against corrosion and erosion as well as against the deterioration caused by solids. The right material, seat and coating choices play an important role in maintaining the sealing abilities of slurry feed valves.

Valves for oxygen feed

Controlling oxygen feed is one of the essential jobs in the POX process. In the event they are called upon, these valves need to provide absolute isolation. Valve materials need to be carefully selected, and cleanliness is of paramount importance because of the inherent danger of oxygen reacting with any grease, oil, or combustible material left in a piping system. The evaluation of valves for an oxygen application requires an understanding of metallurgy as well as valve geometries.

Valves for depressurization

In an operational disturbance, emergency or maintenance event, autoclave processes are sometimes depressurized. During depressurization, a vent line is used to reduce the pressure and temperature inside the autoclave. When selecting the right valve for this service, Neles combines the knowledge of experts in process technology, metallurgy and field service to deliver the most reliable and economical solution.

Valve products and services

Control valves

On-off valves

Knife gate valves

Valve controllers

Valves services

Autoclave POX for the extraction of refractory gold

In the POX process, the ore is crushed and mixed with water to create aqueous slurry that is then heated and fed into an autoclave.

Oxygen is added to the vessel to react with the slurry. The POX process uses high temperatures (approximately 200 °C/400 °F) and high pressures (10-35 bar/150-500 psi) to facilitate the leaching process.

After the autoclave processing step, the slurry is returned to atmospheric condition by taking it through two or more flashing letdown stages.

Once at atmospheric condition, the slurry is washed and separated, at which point the metal can be recovered from the liquid portion in the downstream processing circuits.

Insights into mining, metals and steel

Valve management service provides production reliability for maintenance shutdowns at Outokumpu’s steel plant

The Outokumpu steel plant is an impressive sight next to the Gulf of Bothnia in Tornio. Despite being Outokumpu’s largest plant, it is very compact with everything close by. The plant produces stainless steel, and its history dates back to the 1960s. Its cooperation with Neles has spanned decades. “Cooperation has always been key,” says Aleksi Korteniemi, Category Manager, Outokumpu.

Read the success story

How does Neles partner with customers in the mining, metals & steel industries?

Valves are needed in minerals and metals processing industries. We asked Heikki Kärki, Industry Manager for the mining, metals & steel industries at Neles, to tell us more about the importance of valves in mining, and how we partner with our customers.

Correct valve installations double the operational lifespan at Tarkwa mine

Seemingly minor details can make a major difference in unplanned costs. Valves are small, yet essential part of mining industry processes, and if problems with the valves should occur, it can lead to unplanned downtime and the equivalent losses in output.

Availability service guarantees the delivery of valves to Terrafame mine in six hours

Availability service is a service format developed by Neles to guarantee that the client receives the necessary components within the required timeframe. Based on its agreement, Terrafame’s multi-mineral mine in Sotkamo gets new valves delivered within six hours.