Published Sep 20, 2016

Six-fold moisture content reduction in iron ore concentrate with gigantic Metso rotary dryer

At Olenegorsky GOK (Olcon), a multi-stage iron ore concentration process has been implemented to produce a high-quality concentrate – from the drilling and production of the ore to crushing, grinding, and dewatering. In the winter, the production process ends with drying the concentrate in order to limit the moisture content in the solid material. This is important under the conditions that take place north of the Arctic Circle. The predominantly low ambient temperatures can affect the characteristics of the concentrate: under the impact of the cold external factors, products with a high moisture content will freeze during transportation and storage

Olenegorsky Mining and Metallurgical Integrated Works is one of the oldest companies north of the Arctic Circle. The production operations were set up here in the middle of the twentieth century. In 1954, iron ore concentrate was produced at the concentration plant for the first time. The following year, Cherepovets Metallurgical Works produced its first lot of iron made with the Olenegorsk concentrate. During the Soviet era, scientists conducted research to find the optimal composition of the raw materials used to produce cast iron. Given the easy access transport vehicles have between these sites, along with various other factors, these two companies became reliable partners.

“It is very important for us to ensure a stable production of high-quality iron ore concentrate. Any shutdowns of the equipment or any shipment of low-grade raw materials presents a significant loss for any industrial enterprise,” says Kirill Markin, Head of the Commercial Department at the Design Institute LLC “SPb-Giproshakht”.

“Furthermore, without the Olenegorsky concentrate, no cast iron can be produced at the Cherepovets Mining and Metallurgical Integrated Works. Back in Soviet times, the flow charts and ratios were elaborated to produce the best quality iron with the raw materials supplied from different deposits. To this day, the integrated works still operate according to this proven technology,” continues Kirill Markin.

Reasons for the renewal of the drying system

“One of the problems we had with our previous rotary package had to do with the concentrate escaping with the exhaust steam during its operation. This created an acidic environment in the drying room. The doses of concentrate were small, but they affected not only the structural elements of the plant but also the well-being of the service personnel,” added Kirill Markin.

“The domestic rotary dryers had reached their wear limit, and the infrastructure of the entire drying plant was worn out and obsolete. Therefore, we had to work out a solution that would result in an optimal ratio of the price and the quality of the drying process,” adds Aleksey Smirnov, the JSC Olcon Project Manager responsible for the construction of the new iron ore concentrate drying system.

The Production Capacity Upgrade Plan, approved by the company in 2007, covers many of the plant’s assemblies and processes, including the drying package. As with most of the equipment operating in the plant at that time, the 13 rotary dryers had a high degree of physical wear. For this reason, the company management decided to replace them.

Metso solution to replace 13 old dryer drums with a single line of operations

In 2012, following the results of a tender, a highly efficient system designed by Metso and featuring a single line of operations that would replace all 13 dryer drums in the drying area was chosen as the best solution. The scope of the project included a rotary dryer that would operate with a direct heating system, with various other processes and equipment included in the design (a hot gas generator, bag filter, instrumentation system and an automated control system). Metso’s specialists supervised the assembly, the startup and the commissioning of the system.

At the request of Olcon, the Design Institute “SPb-Giproshakht” expanded the project to integrate Metso’s equipment into the company’s existing process flow. Acting as the General Designer, the Saint-Petersburg Institute prepared detailed design documents, as well as performed the state expert examination and the supervision of the assembly. During the design stage, special attention was paid to verifying the compliance of the new drying system with the production-related requirements, such as ensuring a suitable moisture content of the concentrate: With Metso’s solution, the moisture content of the materials leaving the concentration area can be reduced from 8-9% to 1.5%. 

“The moisture content of the concentrate is an important issue. If a product with a high moisture content is loaded into wagons, it will freeze when it is transported the 1500 km to Cherepovtsy. Unloading such raw materials then takes additional effort, time, and costs,” says Kirill Markin.

“Metso’s equipment is designed to minimize the levels of the concentrate escaping with the exhaust gases. This enables us to reduce the amount of product that is lost during the drying process,” adds Nikolay Palamarchuk, Head of the Engineering Solution Department at Metso.

Joint effort of Metso’s experts produces a unique solution tailored to the customer’s needs

Metso’s rotary dryer, designed for Olcon, is the largest equipment used to dry iron ore above the Arctic Circle. The overall dimensions of the new dryer drum are unique: 39.6 m long and 6.4 m in diameter. The system has a unit capacity of 625 t/hour (of dry solid material) and a max. temperature of 1177 °C. As a result, the total six-month capacity of the system is 2.6 mln tons of dry concentrate.

This drying system design and manufacturing project was completed through the joint efforts of Metso’s experts located all over the world: the dryer drum was manufactured at the company’s plant in China; the bag filter in Ukraine; the drive in Brazil; the burners, tire and drive gear in France; and the control system and instrumentation in the USA. The size of the components made it difficult to transport them to the installation site. Therefore, a plan was prepared in which all of the components were first shipped to the port of Antwerp (Belgium), and transported by sea to the port of Murmansk. Then, the equipment was delivered to the plant using special low platforms.

“The drying system created by the experts at Metso allowed us to fully decommission the old equipment. In addition to the resulting economic efficiency, the equipment assembled in the open site has enabled us to improve the performance of the company and the environmental friendliness of our iron ore concentration process,” notes Aleksey Smirnov.

The assembly process required several issues to be solved. For instance, given the significant size of the equipment, high accuracy of the connections had to be ensured as nine separate elements were welded into a single system. However, the fact that the structural elements of the rotary dryer were designed as a single line of operations enabled the engineers to reduce the consumption rate of the construction materials. This made the assembly of the one large piece of equipment more economically efficient compared to other packages made up of several small units.

“Under the current space limitations, we nonetheless managed to assemble the rotary dryer within just 4-5 months. The efforts put into the development of this unique project were indeed impressive,” shares James Rupert, Metso’s Service Engineer who worked at the site throughout the assembly period.

Metso solution reduces the plant’s operating and maintenance costs

Metso’s drying system not only meets the latest requirements, it also enables better production performance, thanks to the implementation of unique technologies for gas purification, ignition and the control of the burner. This ensures lower fuel consumption and minimizes harmful emissions. In addition, the solution reduces the plant’s operating and maintenance costs.

“Despite its technological complexity, the equipment is easy to operate and to service. For example, all of the drying parameters are displayed on a large screen in the main dispatch room,” notes Nikolay Palamarchuk.

“One rotary dryer supplied by Metso has replaced 13 drying units that were previously used at Olcon. Such an approach has significantly cut the capital costs for producing the iron ore concentrate,” concludes Metso’s expert.

 

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