Making gains with the OK™ mill

A positive economic outlook and an influx of foreign investments have driven up cement production in India and South Asia in recent times. While this creates opportunities for major cement manufacturers, many of whom are importing clinker to meet production demands, the rising need for increased capacity requires larger and more flexible grinding solutions. Manufacturers are increasingly turning to the vertical roller mill (VRM) as a highly productive solution to meet these increasing demands.

With VRMs already 30 to 50 percent more energy-efficient than conventional ball mills, the OK™ mill delivers even greater efficiencies. It uses around five-ten percent less power than other cement VRMs, which means producers can save millions of kilowatts each year.

The unique design elements in the roller and the table profile improve operating stability and reliability, resulting in a typical availability of 90 to 95 percent.

All-purpose flexibility

In 2016 and 2017, a total of 21 VRMs were sold in South Asia covering raw, coal and cement grinding applications. This demonstrates the industry’s shift in selecting an option that can be adapted to a plant's scale and needs. In Bangladesh, which is stepping up efforts to improve infrastructure bottlenecks by attracting foreign capital, four cement producers have ordered FLSmidth’s OK mill for expansion of their production lines. Among these is Shah Cement, which has ordered the world’s largest OK mill. The OK 81-6 mill features six rollers and an 8.1-metre diameter grinding table, boasting an installed power of 11,600 KW.

The trend towards larger OK mills in Bangladesh is helping cement producers keep up with the boom in infrastructure development. But they are also benefitting from greater flexibility thanks to the OK mill’s ability to produce multiple types of blended cement in each unit.

Smaller in Nepal

In Nepal, cement producers typically have smaller capacity requirements and use a single mill to produce a range of OPC and slag-based products. Although the demand on production is not as high as in Bangladesh, the OK mill remains a suitable option, with many Nepal-based plants having ordered the mill recently. An example is Nepal Shalimar Cement, who will shortly be using the smallest OK mill available on the market.

Installations in India

Since the installation of an OK mill at India’s Orissa Cement Limited in Midnapore, the plant has consistently met or exceeded the performance guarantees regarding capacity, fineness and specific power consumption.

The mill at Orissa Cement was guaranteed to produce 212 tonnes per hour of PSC at 3800 cm2/gm Blaine without the use of grinding aid and with a mill area power consumption of 39.3 kWh/tonne. However, as shown in table 1, its operational performance has exceeded this guarantee. Furthermore, the plant’s OK mill has the flexibility to adjust to changes in the feed composition and granulometry; a critical element for Orissa Cement as the plant grinds both PSC and PPC.

In Karnataka, India, Orient Cement Limited has implemented two OK mills into its integrated greenfield cement plant. Here, the mills produce a guaranteed capacity of 250 tph @ 3000 Blaine for OPC and 265 tph @ 4000 Blaine for PPC, but as shown in table 2, both mills exceed performance guarantees.