Stable growth in steel pellets quality at Poltava Mining

New approach to crushing and separation

In 1960, the exploration of Kremenchug Magnetic Anomaly started on the left bank of the Dnieper River, Ukraine. At that time, the foundation of the future Poltava Mining refinery was laid, and 10 years later the plant produced its first batch of concentrate.

There were several phases of plant construction: In 1980, after launching the pelletizing plant the company presented a new type of product to the market - iron ore pellets. To stimulate the demand for this product, the company needed to improve the product's quality, i.e. increase the iron content in the concentrate. 

Keeping this in mind, the company’s managers decided to upgrade the ore pretreatment operations: reduce the fragmentation size to cut the costs of further ore degradation. Due to space constraints at the crushing plant, the company was in need of new equipment with the exact dimensions of the current foundation structures. At that time, Svedala* engineers suggested testing the Barmac vertical shaft impact crusher.

“The conventional crusher-based closed cycle of check screening was not an option for us, so we were offered inertial crushers for coarse lumps. And this proved to be a good technical solution,” says Vladimir Khovanets, Chief Concentrating Engineer at Poltava Mining.

“Metso always does lots of research and testing to offer us an integrated solution, i.e. technology that gives us exactly what we want,” says Alexander Lysenko, Poltava Mining's Chief Technical Officer.

After the pilot testing, the middle and small fraction crusher lines were upgraded with Barmac crushers.  That project was a success, so both companies decided to expand further joint activities: Two double-drum separators were installed instead of eight locally manufactured triple-drum separators with no loss in productivity.

Introduction of flotation technology for processing the low-grade ore

These earlier projects to upgrade the crushing and magnetic concentration processes laid the foundation for further improvement in the concentrate quality.

“It's common knowledge that our ore is quite lean, and the market was in demand of high-quality iron ore pellets containing 62-65% iron,” says Alexander Lysenko.

Two methods are used for concentration of lean ores: magnetic and flotation concentration. During the engineering study of these methods, Metso installed a pilot plant with laboratory mills, flotation cells, magnetic separators and hydrocyclones.

“The pilot results proved that 67-68% iron content in the pellets manufactured from Poltava Mining ores was quite possible after the flotation upgrading,” says Igor Grebeniuk, Regional Sales Manager at Metso.

In 2002, the company launched Flotation Plant 1 equipped with Metso RCS130. It was the first project in the former Soviet Union to use flotation upgrading in the ferrous industry. Keeping this in mind, the engineers at Poltava Mining ran a detailed preliminary analysis of the new technology, studying the cases of Metso equipment supplied to the concentration plants in the USA and Canada.

“Metso explained all the benefits and the hidden risks. And we saw that the technology works. It's friendly to the environment and commercially feasible,” says Alexander Lysenko.

10 points reduction in grain size after mill replacements

Commissioning of the new flotation plant entailed the modification of the crushing lines, since super-fine grain is required for efficient magnetic upgrading of concentrate.

“While working with Flotation Plant 1, we gained the insight that Flotation Plants 2 and 3 need to be constructed for the strategic development of the company. And conventional drum mills were not so good for that process,” recalls Vladimir Khovanets.

“Thanks to flotation, we were able to increase the yield of iron from quite lean ores, but we couldn’t get enough homogeneous product using the conventional crushing line,” says Alexander Lysenko.

Metso engineers suggested Vertimill for high-quality and fine milling of the product. In coordination with Ferrexpo engineers, a concentration line with vertical mills for all flotation cells was developed.

“After magnetic concentration, we get about 85-89% of below 44 microns grade. Vertimill machines help to bring up the fineness of grinding, i.e. up to 90% of ground materials are minus 33 microns,” says Vladimir Khovanets.

“Vertmill machines offer a new design. A conventional drum mill operates in the horizontal position, while Vertimill is installed vertically. The space needed of such equipment is much smaller, and it provides proper crushing grade,” says Vladimir Khovanets.

3% increase in iron content of pellets

Two additional flotation cells were commissioned in 2014. These additional cells gave a step change in the concentration technology. Today ore from different fields is processed separately at Flotation Plants 1 and 2, while Flotation Plant 3 is used for iron recovery from froth.

“Before commissioning the plant, we produced pellets with 62% iron content. Due to flotation upgrading we now have 67% concentrate, and this brings the product's quality to a new level. I mean pellets with 65% iron content,” says the CTO of Poltava Mining.

Introduction of the new iron ore concentration technologies entails upgrading the next downstream process, namely filtration. After the equipment upgrade, it will be possible to reach the maximum dehumidification of concentrate to gain additional quality.

“But we go the extra mile. To increase production, we're now constructing two additional plants, a crushing plant and filtration plant,” says Igor Grebeniuk about the current projects.

A tough market requires high-grade product rich in iron and with minimum impurities. After the process upgrade, Poltava Mining was able to improve the pellet quality, which also means more investments in the infrastructure of its hometown.

“We want to offer benefits to as many people in the city as possible,” says Ruslan Klimenko, Chief Communication Officer of Poltava Mining.

*Metso Outotec was formed July 1, 2020 when Metso and Outotec merged into one company. This case study has been written prior to the merger under the old company name.