Semen Indonesia gains newest OK™ mill

October 20, 2014 Klaus Bøgeskov Hansen

Amidst a buoyant cement industry in Indonesia, South East Asia’s largest cement supplier, Semen Indonesia, is continuing to raise the bar on cement production capacity and efficiency. 

FLSmidth’s newest version of the OK mill has been commissioned at Semen Indonesia’s Tuban cement plant in east Java as part of its plans to use advanced, high-quality technology that delivers the lowest possible energy consumption and the minimum possible environmental impact. 

FLSmidth’s new OK vertical roller mill, featuring an updated mechanical package and structural design, will provide the required boost to Tuban’s grinding capacity, helping to make the plant more effective and energy-efficient.

Based on market data
This latest version has been developed using the performance data from other FLSmidth OK mills as well as the practical know-how and experience gained from working with them. Important parameters included reducing maintenance requirements and maintaining competitive pricing. 

The update included reviewing and evaluating the complete mechanical package and structural design of the mill. 

Of the many updates applied to the mill, the most significant included optimising the grinding pressure needed for grinding ordinary and high-Blaine cement. The grinding profile of the roller and table enable a narrow wedge-shaped grinding area, without compromising the peak pressure, which is the highest of any mill in the market. The table profile ensures uniform bed thickness, which eliminates the need for additional rollers or rolling scrapers to remove material accumulated inside the dam ring.

The new OK mill includes the latest version of the ROKSH separator, which is an updated version of the standard OKS separator. Requiring extremely low power, the ROKSH is a low-wear, highly efficient separator and is one of the most durable ‘top seals’ in the market.

Optimal airflow
Fluid dynamics played a vital role in the development of the new OK mill. The airflow through the nozzle ring and inside the mill was carefully analysed to ensure the right amount of material was lifted into the separator. To minimise wear, it was also important to know the air velocity required in the mill to optimise the load on the guide vanes and rotor.

Fluid dynamics was applied to achieve the airflow conditions necessary to optimise performance and reduce wear       

Increasing demands for cement
Indonesia’s economic growth in recent years, resulting in continuing investments in infrastructure development, has had a significant influence on the country’s cement production demands. As Indonesia’s leading cement supplier, PT Semen Indonesia has played a major role in servicing the cement demands. The company’s Tuban plant is located in East Java and has a total output of 33,600 tpd. Tuban’s four lines have all been supplied by FLSmidth. Tuban required extra grinding capacity at two of its lines. Even though the plant operates with many ball mills, it needed more effective and energy-efficient mills. This was a key reason for the choice of an OK mill. 

The OK mill was put into service in 2013 as an Ordinary Portland Cement (OPC) finish grinder. The mill was fitted to grind clinker from the older but updated production lines Tuban 1 & 2. However, Tuban also needed to use it for Portland Pozzolana Cement (PPC) finish grinding for cement containing trass, a volcanic tuff that is harder than the normal Pozzolane and has a higher level of moist content. The upgrade project started in 2010, and the new OK mill 42-4 with a capacity of 250-300 tph, began operations in October 2013.

“We often face challenges in space limitations when installing new equipment. It was no different at Tuban Cement plant as the OK mill had to be squeezed between two existing mills.” - Klaus Bøgeskov, 
Project Manager at FLSmidth


Beating performance requirements
Klaus Bøgeskov, Project Manager at FLSmidth, explains how some of the installation and commissioning challenges were tackled: “We often face challenges in space limitations when installing new equipment. It was no different at Tuban Cement as the OK mill had to be squeezed between two existing mills. We solved it by modifying the mill’s design to fit the plant’s layout.”

Klaus Bøgeskov explains that the OK 42-4 mill was guaranteed to 250 tph OPC according to ASTM C-150 Type 1 (Standard Specification for Portland Cement). “But when the PGT certificate was signed, the mill was running 253tph at a Blaine value of 3559cm2/g,” he says, adding, “The total power consumption goals for the main motor, separator and fan motor were 26.8 kWh/t, and we achieved a figure of 24kWh/t.”

FLSmidth’s OK mill
FLSmidth’s OK mill is a vertical roller mill designed for cement and slag grinding. It combines drying, grinding and separation processes into just one unit and can provide savings of approximately 40 percent in power consumption compared with traditional ball mills. This latest version has been commissioned at cement plants in Brazil, Indonesia and India, joining the more than hundred FLSmidth OK mills in operation around the world.

Read more about the OK vertical roller mill here >>

Read more about ball mills here >>

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