Visit to Morenci Copper Ore Processing Plant, Arizona (USA)
From 12.02.20 to 02.14.2020, specialists of SPA RAKURS LLC as part of the working group (PrJSC Poltava GOK, Ferrostroy LLC, SV Tek LLC and Metso Company) visited Morenci mine, Arizona (USA) in order to familiarize themselves with the operation of the pilot installation for grinding copper ores using a semi-industrial press roll and industrial press roll HRC-3000 from Metso.
General information
The Morenci Copper Mine is owned by three companies:
- Freeport-McMoRan Inc. – 72%;
- Sumitomo Metal Mining Arizona Inc. – 15%;
- SMM Morenci Inc. – 13%.
Morenci Mine is located in Arizona, Greenlee County, 50 miles northeast of Safford.
Below is a general view of the pilot installation and the thin crushing site with the beneficiation factory.
The Morenci mine processes copper-porphyry ore with a copper content of 0.16%. By mineralogical composition, these ores mainly consist of the following ore minerals: chalcocyte, pyrite, chrysocolla, malachite and molybdenite. The hardness of ore minerals is shown in the table below.
| № | Name | Mohs material hardness |
|---|---|---|
| 1 | Chalcocyte | 2-3 |
| 2 | Pyrite | 6-6,5 |
| 3 | Chrysocolla | 2-4 |
| 4 | Malachite | 3-4 |
| 5 | Molibdenite | 1-1,5 |
Pilot installation
According to Metso, before the industrial introduction of thin crushing technology using press rolls in the territory of a copper mine, a pilot installation was designed and built to work out the regimes of thin crushing, classification and grinding.
The plant capacity is 50-70 t/h, the size of the initial ore varies between 11-16 mm. A press roll with roll sizes of 750×400 mm was mounted on a pilot installation.
At the pilot installation, 12 modes were worked out, 420,000 tons of ore were processed in 8800 hours.
The pilot installation includes the following technological operations:
- Reception of the original ore;
- Classification of source ore (primary);
- Classification of crushed ore after HPGR (secondary);
- Thin crushing of over grate products of primary and secondary classification;
- Classification in a hydrocyclone of under grate products of primary and secondary classification;
- Ball grinding in a vertical mill of hydrocyclone sands.
From the moment it was commissioned to the present day, this pilot installation is conducting research to optimize the operation of the industrial thin crushing site.
Thin crushing industrial site
According to the results of pilot studies at the facility in May 2014, an industrial section of thin crushing with a press roll НРС-3000 was built and commissioned.
The thin crushing industrial site is a technological complex that includes equipment for feeding the initial crushed ore after the second crushing stage to the НРС-3000 press roll, as well as a system for transporting crushed ore after the press roll to wet inertial screens and over grate product return (circulation) to press roll.
The size of the feed press roll is F80 from 26 to 50 mm. Thin crushing is carried out to a fineness of -8 + 0 mm. The classification of the crushed product is carried out on wet screens of the company FLSmidth in the class of 8 mm.
Over grate product is conveyed by conveyor transport to separate bins and then combined with the original dry product, after which it is sent to НРС-3000.
The under grate product is accumulated in sumps under wet screens and then pumped to the beneficiation area.
The design capacity of the НРС-3000 press roll is 5400 t/h. The actual recorded 30 minutes after the start of the site was 6045 t / h, taking into account the circulation of 2000 t/h.
Layout solutions for installing a press roll НРС-3000
The press roll НРС-3000 is installed in a separate case with a plan size of 36×30 m, the height of the case (approximately) is 35-40 m
Characteristics of the press roll НРС-3000 and design features
Specifications of the HPC-3000 press roll are shown in the table below. Overall dimensions are: height – 6264 mm, width – 4230 mm, length – 10800 mm.
| № | Name | Sizes of rolls (length) x (diameter), mm | Drive power, kW | Productivity, t/hour | Weight, t |
|---|---|---|---|---|---|
| 1 | HRC-3000 | 3000×2000 | 2×5700 | 2600-5400 | 900 |
A distinctive feature of Metso press rolls is the presence of end flanges on one of the two rolls of the press roll. A comparison of the designs of traditional Metso press rolls and press rolls is shown in the figure below.
According to the statements of Metso specialists, this solution made it possible to redistribute the wear of the rolls from the maximum in the central part and the minimum along the edges of the rolls, as is the case in traditional machines.
The following is a graph of roll zone wear for a traditional roll design and a new one from Metso.
The red line is the wear of the rolls of a traditional design (maximum wear in the middle of the roll, minimum – at the edges of the roll).
The green line is the roll wear according to Metso design (more uniform wear along the entire length of the roll).
However, when familiarizing ourselves with the operation of the HRC-3000 industrial press roll during inspection of the rolls, it was found that wear of the roll lining without a flange occurs in the central part, as in a traditional design.
HRC-3000 Press Roll Exploitation and Repair
According to the data provided by Metso, the press roll operating time until the band is completely worn out is up to 16,000 hours with thin crushing of Morenci copper ores.
To replace the bandage, additional equipment is required – an induction heating installation, which is shown in the figure below.
For maintenance and repair of the press roll, the following types of work and the timing of their implementation are provided:
Planned stops:
- 2 hours every week: scrap removal, measurements of rolls and bearings;
- 60-72 hours every 3 months: long shutdown of the factory.
Service duration:
- Replacing 2 rolls: 60 hours;
- Replacing the side blocks: 36 hours;
- Replacing Flange: 48 hours;
- Replacing Hopper: 14 hours.