Preconcentration with X-ray sorting technology

Hildebrand Wilhelm, Ore processing manager at Navachab Gold Mine

What is your position at Navachab?

Hildebrand Wilhelm: My name is Hildebrand Wilhelm. I am Metallurgist by profession and the ore processing manager at Navachab responsible for engineering, maintenance, obviously the operations of the plants and the quality control or the laboratories fall under me as well. I have 195 people working for me in the department. I am obviously interfacing a lot with the mining teams and so forth because of that role and have several inputs that have to be communicated to them.

How long have you been working in the mining industry?

Hildebrand Wilhelm (laughing): That might be embarrassing – 34 years. I started in 1986.

How long have you been working with Steinert?

Hildebrand Wilhelm: I think with Steinert the relationship is about 6 years. I have been involved in the concept of sorting for much longer. In fact, for the last 20 years we have been looking at this.

What made you decide to go with Steinert?

Hildebrand Wilhelm: I think the most important issue is relationships. I think it is an issue to pursue new technologies in a very conservative mining environment. It is very important that you are confident in the people that you work with. It is extremely important that one is at ease with the technological know-how of those people. And that those people can interface with you as a person directly and efficiently. It is very important that the relationships are under control.

What makes Steinert special?

Hildebrand Wilhelm: Certainly, as I said already the relationships are very important. Steinert had a very experienced team that I had worked with before. They are very confident in their capability and it was well-established relationships. That was one of the important things. The other important thing is that Steinert had partnerships with the larger industry, which had a big impact on our decision-making. We felt very confident that they were using this X-ray technology which was really well established globally. It is seen as being a much lower risk for us to take while understanding that the whole sensor technology was really industry wide already.  This made us very confident to work with Steinert. The other thing is that Steinert was the first company that was interested in building wider machines than that what was at that stage  in the market. Other companies had only 1 meter wide sorters where Steinert was quite happy to pursue 2 meter wide sorters. And I always had the feeling that Steinert was interested in our well-being, in my understanding and looking after us as a customer much more that the other companies that were available to us.

Which problem were solved using Steinert sorting machines?

Hildebrand Wilhelm: It is important to understand that the mining industry has to reinvent itself at certain intervals. My feeling is that every 15 years you have to make a technological change of what you are doing. Because the cost margins reduce and are eating away at your profits. The interesting thing about the sorting technology is that is runs at 1/5 of our conventional operating plants operating costs. Because Navachab is a low grade mine and we had a lot of low grade stock piles lying around in the mine, it was very important for us that we could recover gold out of those low grade stock piles. We never looked at treating high-grade material through the XRT plants. We were interested in being able to scavenge these low-grade dumps for rich material. What we do with the machines here on site is we treat our material that falls below the CIP Plant cut-off grade. We treat them to the XRT machines and in general we double the grade of our input material and that is where the value is generated because then with the doubled grade the material can be profitably treated by the processes that come after that.

What is the profit of preconcentration?

Hildebrand Wilhelm: Firstly, it is an upgrading in terms of gold grades and secondly obviously you remove a lot of material. We have set up the plants such that we get about a 25% mass-pull to concentrate and we get an average of 70% gold recovery with this kind of set up – that make sense to us. That is a profitable operation. The only real operating costs of the machine is obviously the compressed air requirement, that is the big cost component, and if one has power available that is then a very cheap operating cost; certainly in my environment.

What has amazed you about Steinert machines?

Hildebrand Wilhelm: It is incredibly robust for being the first sorting machines installed in a hard rock gold mining environment. We were very unsure how robust this technology was but because of the huge operating cost advantage, we were happy to take the chance. What has amazed us that the machine is very robust. We are getting good reliability on the units and so 80-90% running time is absolutely possible. An important aspect is the feed preparation to these machines. If you have that under control, it is very reliable machine.

What is special about your relationship to Steinert people in Southern Africa?

The team in Southern Africa and now in Namibia is a team I have known for a very long time. I am very aware of their capabilities and they have been willing to help. Even at a very silly 3 o’clock in the morning phone call “Hey guys please phone into the machine there is something going wrong. Help us”. And that relationship has been always well established and that is the A and O of making the success obviously. Steinert was prepared to train our operators and our foreman that are in the field. That was also very advantageous that they had that kind of information available that could be shared with my very lowest level operating team in the mine. That helps a lot. But the relationships are good and long may it run.

Watch interview with Hildebrand Wilhelm here: Videointerview