The missing link in the Comminution Island concept

HPGR’s are designed to reduce the ore rock supplied from the other comminution equipment down to a more manageable material

HPGR’s are designed to reduce the ore rock supplied from the other comminution equipment down to a more manageable material

With subsequent global interest in High Pressure Grinding Rolls (HPGR) technologies, FLSmidth engineers have been developing and testing HPGR solutions and introducing this specialised equipment into minerals applications.

FLSmidth moves forward in high pressure grinding rolls
With subsequent global interest in High Pressure Grinding Rolls (HPGR) technologies, FLSmidth engineers have been developing and testing HPGR solutions and introducing this specialised equipment into minerals applications. The FLSmidth mineral HPGR is the missing link in its comminutioncircuit. The realised benefits of utilising FLSmidth HPGR technology is that it can easily be bundled with complementary FLSmidth crushing and grinding equipment. This offers customersmultiple options when it comes to their specific comminution circuit requirements. Whether customers require full flowsheets, or sections of the flowsheet (often referred to as islands), the HPGR optimises their comminution results by providing energy-efficiency, high-throughput and metallurgically optimised ore treatment in both concentrators and hydrometallurgical plants.

HPGRs are not new to FLSmidth as the technology is actually taken from the legacy FLSmidth® High Pressure Roll Press (HRP) operating successfully in the cement industry. We have been involved with HRP’s since the early 1980’s with over 90 units sold to the industry thus far. However, these units are in cement applications. To introduce this sizing technology into the minerals industry, the product name has been changed to HPGR to distinguish it fromits sister in cement. 

Manageable material
HPGR’s are designed to reduce the ore rock supplied from the other comminution equipment down to a more manageable material that can be fed into the grinding circuit. As the name states, the ore is fed through rolls that exert high pressure on the rock to break it down. The HPGR process is a little bit more complicated than similar purpose equipment when it comes to sizing; the main contributing factor is that we do not dictate the gap as you would with a mechanical crusher. We calculate the optimal compression force for best comminution, micro fracture and/or liberation. This means that the ore dictates the gap size, which determines the throughput rates. This creates a problem with calculating the machine throughput for different ores. Calculations and test work is very important. There are 3 ways to determine the size.

  1. Calculations alone: This was the original way to calculate machine requirements. Ores were categorised, iron ore, gold…etc. Then relative ore averages were applied to set formulas. However, averages could have a 40% to 60% variation than actual throughputs. So it is a very rough way to calculate. We do still make use of this today as it gives us a ball park machine size to open discussions. This would lead to test work if the client wished to pursue it.
  2. Laboratory test work: Currently about 75 percent of sizing and subsequent sales are conducted this way. Basically 3000kg of material is sent to a laboratory for test work. With this actual sample, we can very accurately determine the nature of the ore. From this we can determine gap sizes and wear rates. This then translates into machine size determination and performance guarantees.
  3. Onsite pilot test work: Pilot test work is becoming more and more popular. With laboratory test work the supplier is comfortable with the results obtained, and will stand surety to the performance guarantees. Though, there have been some cases where the actual results have not matched the laboratory results. By re-conducting the test work we have found that the samples may vary. Which means that we as supplier are no longer accountable. The biggest problem we have with the laboratory test work is that the machine sizing and performance guarantee hinges on 3000kg’s of ore. But saying that, we cannot move hundreds of tons to the lab due to logistics. So the new approach is on site multiple test campaigns with a larger lab machine.

The majority of HPGR machines will be similar in size to those used in current Cement applications. There is some slight variation due to power draw and press force requirements. Below is a table of the current development range.

Implementation of HPGR
Even though the machine is still in development stage, we have made some monumental steps towards implementation into the market. This of course has been assisted by the strong FLSmidth client base and current market interest. It is currently envisaged that FLSmidth will be in the position to supply larger industrial machines (which are more sought after) in the second quarter of 2012. We are also looking into development of larger concept machines, which currently are not available from our competitors. The HPGR team is currently engaged in development projects at Rio Tinto and Anglo Platinum mine sites. The equipment at the Rio Tinto plant is currently in operation and the Anglo plant is to follow next year.

FLSmidth will also be installing a pilot HPGR and Wear Analysis equipment at its Salt Lake City Technologies centre. This equipment will help in sizing industrial machines and evaluating surface wear. The equipment will be supported by a dedicated team that can also be dispatched to sites where pilot test plants are in operation.

CONTACT: James Pownell