Blending Control System for Maintaining Consistent Kiln Feed Quality

Background

The Kiln is the heart of a Cement plant. The steady and continuous operation of the Kiln is essential for producing good quality Clinker, higher level of output and lower energy consumption. To ensure this, consistent quality of kiln feed is a pre-requisite. This can be achieved only if the raw meal fed to the silo is consistent. The raw meal is produced by grinding various raw materials such as limestone, bauxite, iron-ore, etc,. The quality of these raw materials varies from time-to-time. Hence, the quality of the raw meal is analysed every hour and the percentage of the mix is varied to maintain the raw meal quality. In the old plants, the mix percentage is varied manually from hour to hour. This manual method of adjustment is inaccurate and generally leads to fluctuation in the quality of raw meal and hence the kiln-feed.

In the latest plants, the hourly chemical analysis is performed and the data is fed to the computer. A Software included in the system, varies the raw mix proportion so that the required mix quality is maintained. This has been retrofitted in many plants with substantial benefits.

Previous status

In a 3000 TPD dry process pre-calciner plant operating with a VRM and a continuous blending cum storage silo, the raw meal was being produced by grinding Limestone, bauxite and iron-ore. The raw meal was being analysed every hour through an X-ray analyser and the mix varied manually.

Energy saving project

A new blending software based control system was introduced. The new system had a separate PC which could be linked to the existing control system. The X-ray analysis was fed to the blending control system, which automatically varied the raw mix proportion.

Implementation methodology & time frame

The raw mix proportioning was done manually in the initial days and the blending control was put into operation in a phased manner. The system was checked for the extreme conditions (e.g. limestone of maximum and minimum LSF) by both the supplier and the plant team, so that the system is functional at all conditions.

Benefits of the project

There was a marginal increase in the output of the Kiln, reduction in feed cuts on account of quality of kiln feed, better quality of clinker and steady operation of the Kiln.

The benefits achieved are as below.

• Increase in kiln output by 10 to 15 tpd.
• Reduction in LSF variation in Kiln feed from 0.4 % to 0.2 %.
• Reduction in Thermal Energy Consumption
  

Financial analysis

The implementation of this project resulted in an annual saving of Rs. 18 lakhs (Increased Production and thermal energy saving). The investment made was around Rs. 15.0 lakhs. The simple payback period was 10 months.

Benefits of blending control system

• Fine and accurate control of raw mix
• Reduced Kiln feed - L.S.F. variation
• Lower thermal consumption

Cost benefit analysis

• Annual Savings - Rs. 18.0 lakhs
• Investment - Rs. 15.0 lakhs
• Simple payback - 10 months