Upgradation of VRPM Cement Grinding

After the upgradation of VRPM circuit at Maihar Cement Limited, Satna, cement grinding capacity increased from 170 TPH PPC to 226 TPH PPC at blaine of 3300 cm2/gm and savings were witnessed in specific power consumption of 3.17 kwh/t.
In recent years, there have been success stories associated with VRPM for upgradation of the existing Ball Mill system for capacity enhancement and reduced specific power consumption in clinker grinding. The upgradation of the VRPM system at Maihar Cement Limited is one such example of a successful installation. AMCL has been supplying VRPM from the past 18 years based on technology supplied by Nihon Cement Company, Japan. VRPM machines are very sturdy and proven for stable operations.

At Maihar Cement, VRPM was installed along with Vibrating Screen in pre-grinding mode with the existing Ball Mill system. The vibrating screens were prone to heavy maintenance, hence these circuits have now been converted to semi-finish mode by installing Static Separator.

VRPM in pre-grinding mode
At Maihar Cement, the VRPM project was commissioned with VRPM in pre-grinding mode. The Vibrating Screen was used in close circuit with VRPM. The average particle size of (-) 3mm clinker was sent to the Ball Mill. The circuit is shown in figure 2.1. After installation of VRPM, the increase in capacity was around 30-40 per cent and reduction in specific power consumption was 3 – 4 kwh/ton. The Vibrating Screen was prone to heavy maintenance which also affected the availability of the plant.

Upgradation of VRPM system
With a view to improve the existing grinding capacity and to increase the availability of the plant; Maihar Cement has contacted AMCL to carry out a feasibility study for converting VRPM system from pre-grinding mode to semi-finish mode. The scheme finalised by AMCL in semi-finish mode is shown in figure 2.2.

Figure 2.1

In the upgradation project, the vibrating screen was removed, and in place of that, static separator system was added. The details of additions and deletions of major equipment are given below in Table 1:

Engineering and layout
With the efforts of both Maihar Cement and AMCL, the layout was developed wherein it was possible to fit new a static separator in the existing building. For the Cyclone Separator and Circulating Fan, a new civil structure was made near the existing building.

Figure 2.2

Project Management
The downtime was curtailed to a maximum of 14 days.

Upgradation Results
After upgradation, the capacity of Ball Mills has increased by 30 per cent and additional savings in specific power consumption is around 3.17 kwh/tonne. The results are tabulated in Table 4;

Conclusion
After upgradation of grinding circuit from pre-grinding mode to semi-finish mode, Maihar Cement Limited has achieved the desired results. Further improvement in Cement Mill no.2 is possible.

It has been clearly demonstrated that by the proper co-ordination between the user and the supplier it is possible to make best use of existing equipment to achieve substantial savings in power consumption and increase in production capacity. Plant availability has been increased due to elimination of downtime on account of maintenance on the vibrating screen.

This article has been authored by R K Vaishnavi (President, Works – Maihar Cements Limited), U K Sharma (DGM, Process – AMCL Machinery Limited), and Niketan Nagpure (Sr Engineer – AMCL Machinery Limited).

Table 1

Table 3

Table 4