Vertical roller mills have long been recognised as the industry standard for raw mills – and are quickly gaining ground as cement grinders.
The vertical roller mill (VRM) is well known as the preferred mill for grinding of raw materials. Its grinding efficiency combined with its ability to dry, grind and classify within a single unit gives it a decided advantage over other systems, such as the ball mill or roll press. For the same reasons, the VRM is also developing as the preferred solution for cement grinding.
This can be explained by issues such as cost of installation, ease of operation and maintenance, energy efficiency and product quality. At the same time, there is greater demand for cement grinding capacity as more producers look to increase use of clinker substitute materials and import clinker to meet localised increases in cement demand for example during short-term infrastructure development projects.
Positive market development
Overall vertical roller mill sales in 2016 were above the long-term market trend, highlighting the importance of FLSmidth’s position as a lead supplier for VRMs in the cement industry. The strong market for VRMs is mostly driven by ongoing emphasis on energy efficiency in the global cement industry and continuing growth in developing markets.
The ever-increasing global focus on energy reduction naturally brings more attention onto vertical mills. Grinding systems in cement production make up approximately 85 to 90 percent of total plant electrical energy consumption. As vertical mills are 30 to 50 percent more efficient than other grinding solutions, they give cement plant owners a great opportunity to maximise productivity and minimise operating costs. The high energy efficiency is especially beneficial in countries with power generating capacity or where electricity availability is limited.
Bigger than ever
Capacity growth can be seen in regional markets around the world with a mix of new clinker production lines and standalone grinding units. Vertical mills are the standard grinding equipment in both types of installations. While many smaller mills with 3,000 kilowatts or less installed power were sold in 2016, the largest-ever VRM was sold with 11,600 kilowatts installed power.
Capacity requirements for new cement plants and grinding units are consistently increasing. Ongoing advances in manufacturing and decades of design experience make it possible to produce reliable mills of ever-larger size and potential capacity.
This also reflects a trend of building larger capacity cement plants serving wide geographical areas, according to Carsten Schoessow, Vice President of Global Product & Upgrades Sales in FLSmidth:
“Acknowledging of course that regional differences exist, there are a number of contributing factors to the demand for larger grinding mills. First, there is greater general acceptance of economic benefits of larger single mill installations. Second, VRM development over several decades has shown that they are mechanically reliable. And third, there are now a sufficient number of VRM references, referring to the production of all cement types, such that the global industry knows they meet or exceed quality requirements.”
The growing size trend is reflected by the 2016 sale of the largest-ever VRM, the FLSmidth OK™ 62-6 cement mill, in Bangladesh and the recent start of the largest VRM for raw grinding installed, the FLSmidth OK 54-6 raw mill in Indonesia. Increasing the size of the mills not only
takes advantage of economies of scale, but also reduces the CAPEX investment or total installed costs, while also increasing total plant productivity.
Maintenance strategyGrowing mill sizes have an impact on the peripheral equipment and operating practices, too. These include, for example, the need for larger gears and drives, as well as maintenance planning and procedures with larger components. This highlights the importance of a solid maintenance strategy, according to Morten Østergaard, Technical Manager at FLSmidth Operation & Maintenance.
“A plant’s ability to maintain equipment is vital for the performance of the mill. The biggest issues are not down to equipment, but more related to how well the maintenance of the mills is understood and how they are looked after, after commissioning. To increase the reliability of equipment, we recommend a preventive maintenance approach. Furthermore, it is essential to have easy access to equipment and allow it to be easily and quickly maintained during production shutdowns.”
With ever-larger VRMs increasingly showing their muscle for raw materials and cement grinding, it appears that cement producers take advantage of the ideal opportunity to benefit from the VRM’s reduced energy consumption and reliable high grinding capacity.