There are various types of grinding mill operation, e.g., open-circuit ball mills, closed-circuit ball mills, air-swept mills, mills equipped with pre-grinders, vertical roller mills, etc. These mills consume nearly 35-40% of the total power required to manufacture one ton of cement. Mills' specific power consumption varies from 19 units to 35 units per ton of cement ground, depending upon the technology and the extent of optimization.

In the case of the cement industry, there are three main drivers of energy consumption:

• electrical power
• fuel
• customer demand for high-strength products that require a significant proportion of high-energy clinker as a component.

These factors significantly influence the producer's cost competitiveness, usually accounting for over 50 percent of total production costs. Therefore, accurately and continuously monitoring energy usage must be a way of life for any producer's technical team.

ICR research on Best Energy Consumption1, published in cementnet.com in February 2015, shows process-wise power consumption in a typical cement plant, as depicted below.

Typically, 2/3rds of power is consumed in the grinding process (raw and cement grinding combined). Hence, it is essential to use this grinding process efficiently.

Grinding mills have very low energy efficiency. It is accepted that approximately 1% of the electricity consumed to operate ball mills2 is effectively used to produce new material surfaces. The remaining 99% is wasted as noise, vibration, and heat. Some portions are also used to wear grinding media and mill internals. Grinding is an inefficient process.

While dissipation of heat is necessary for the drying and avoidance of partial dehydration of gypsum, excess heat leads to high mill temperature, which can affect cement quality if it is significantly above 120 deg C.

Due to significantly less energy conversion into effective size reduction, controlling the conditions that impact grinding performance is essential. Some crucial contributors are the quality of Input materials, the condition of mill internals (ball mill, VRM, Roll Press), grinding media, and the separator. As ball mills are the most common type of equipment used for grinding and are the most energy-consuming, we will emphasize primarily ball mill operation in the subsequent chapters.

Grinding is a crucial process in cement manufacturing, and its efficient operation determines the efficiency of the grinding process, the cost of production, and the quality of the finished product.

Suman Sarkar 31.07.2024