Raw Material Preparation

Raw material preparation aims to preare a mixture that has the right chemical composition and particle size necessary for the clinker production. For plants that receive their raw materials already crushed, this stage usually involves grinding (milling), classification, mixing and storage.  Ball mills, tube mills, vertical or horizontal roller mills are commonly used for grinding. The production of one ton of portland cement requires more than 1.5 ton of raw materials.  

Raw material preparation is an electricity intensive stage, typically requiring 25 to 35 kWh of electricity per ton of processed raw material, although the energy consumption can be as low as 11 kWh/t.

Raw Material PreparationTechnologies & Measures

Technology or MeasureEnergy Savings PotentialCO2 Emission Reduction Potential Based on LiteratureCostsDevelopment Status
High-Efficiency Roller Mills

By replacing ball mills with vertical or horizontal roller mills in raw material preparation, energy savings of 6-10 kWh/t-raw materials (depending on grindability of raw material) can be achieved.

Chinese flag For Chinese context, reductions are estimated to be 4.7 to 5.5 kg-CO2/t-raw material (assuming 0.79 kg CO2/kWh electricity)
Indian flag For Indian context, reductions are estimated to be 4.9 to 5.7 kg-CO2/t-raw material (assuming 0.81 kg CO2/kWh electricity)

Chinese flag Investments are estimated to be US $5.5/t annual raw material processed.

Indian flag For India investment costs are reported to be $10 - 20 million (or $25 000 to $30 000 per t/h capacity) depending upon the type & size. 

Chinese flag In a 2500t/d clinker production line, installation of a VRM costed 14 million RMB and took eight months to complete. The technology provided annual savings of 4 million RMB in electricity costs and resulted in a payback period of 3-4 years (NDRC, 2008. p.51).

Chinese flag In China, installation of a vertical mill for raw material grinding in a plant with with 5000t/d production is reported to require an investment of around 50 million RMB, and has operating and maintenance expenses of approximately 17 million RMB /year. When working with raw material with medium grindability, a saving of about 10kwh per ton of raw material can be achieved. If material consumption factor is 1.55 and production days are 300 days per year, the technology can save 22.5 million kWh per year and result in a payback period between 3 and 5 years, based only on savings on electricity costs (MIIT, 2012. p.19).

Commercial
High-Efficiency Separators and Classifiers

Case studies have shown that the specific electricity use in material preparation can be reduced by 2.8-3.7 kWh/t-raw material. 

Chinese flag For Chinese context, reductions are estimated to be 2.2 to 2.9 kg-CO2/t-raw material (assuming 0.79 kg CO2/kWh electricity)
Indian flag For Indian context, reductions are estimated to be 2.3 to 3.0 kg-CO2/t-raw material (assuming 0.81 kg CO2/kWh electricity)

Chinese flag Investments are estimated to be US $5.5/t annual raw material processed.

Indian flag For India investment costs are reported to be $10 - 20 million (or $25 000 to $30 000 per t/h capacity) depending upon the type & size. 

Commercial
Efficient Mechanical Transport Systems

2.0 kWh/t-raw material can be saved.

Japanese flag In a Japanese plant (of 300 tpd capacit) energy used for raw material transport was reduced by up to 80% - depending on the distance. (APP, 2010. p. 75)

Indian flag In Indian context this technology is reported to provide savings in the range of 0.6-0.8 kWh/t material/100m (with typical energy consumption of around 0.41 kWh/t-100m). 

Chinese flag For Chinese context, reductions are estimated to be 1.58 kg-CO2/t-raw material (assuming 0.79 kg CO2/kWh electricity)
Indian flag For Indian context, reductions are estimated to be 1.62 kg-CO2/t-raw material (assuming 0.81 kg CO2/kWh electricity)

Costs are estimated to be around $2.2 per annual ton of raw material processed. 

Indian flag In India, implementation costs are reported to be around  0.5-0.7 million, or around $20 000 per t/h capacity, depending upon the capacity. 

Commercial
Gravity Type Blending Silos

1.0 to 2.5 kWh of electricity can be saved for each ton of raw meal processed. 

Chinese Flag In China, for every ton of raw material processsed, 0.8 to 2.5 kg of CO2 can be saved with this technology

Indian Flag For every ton of raw material processsed, 0.8 to 2 kg CO2 can be saved in India. 

Retrofitig costs are estimated to be US $3.7/t-raw material  (assuming US$550 thousand per silo and an average capacity of 150,000 tonnes annual production).  

Indiann Flag In India, retrofiting costs are reported to be around $35 per ton of silo capacity

Commercial
Automation of Raw Material Mixing Control

Better control of raw material composition helps reduce overall energy consumption.

X-ray fluorescence spectrometer of the glass bead method: $1.3 to 2.6 million (US$=¥77.4)

Commercial
Vibration Control in Vertical MillsEnergy savings are estimated at around 6%, or 0,8 to 1.0 kWh/t-raw material

Chinese flag For Chinese context, reductions are estimated to be 0.63 to 0.79 kg-CO2/t-raw material (assuming 0.79 kg CO2/kWh electricity)
Indian flag For Indian context, reductions are estimated to be 0.65 to 50.81 kg-CO2/t-raw material (assuming 0.81 kg CO2/kWh electricity)

Commercial
Pre-grinding to ball mills

 In a Japanese plant, specific energy consumption was reduced by 7.7 kWh/t-raw materia (22% reduction) 

 In India savings of 20% are reported. 

Chinese flag For Chinese context, reductions are estimated to be 6.1 kg-CO2/t-raw material (assuming 0.79 kg CO2/kWh electricity)
Indian flag For Indian context, reductions are estimated to be 6.2 kg-CO2/t-raw material (assuming 0.81 kg CO2/kWh electricity)

 Installing a pre-grinder for a ball mill with 180 t-raw material/h original capacitycosted US $7.3 million [1US$=¥110]. 

 For India investment costs are reported to be around $30 000 - 40 000 per t/h capacity. 

Commercial
Separate Grinding of Raw Material Components

Electricity use can be decreased by 1.4 kWh/t-clinker. 

EU flag Reduction potential is estimated to be between 0.7 to 1.0 kg CO2/t-clinker

EU flag Investment cost for both retrofit and new installation is estimated to be € 40 million and 35 million respectively. The operational costs are estimated to increase by €0.9/t-clinker.
The cost estimation is based on a clinker capacity of 2 million t/a, constant specific costs over time. Replacement of an existing vertical roller mill by ball mill (40 t/h) and high pres-sure grinding rolls (360 t/h). If raw material grinding is processed with 2 existing ball mills, the investment can be much lower (about 10 Million EUR or 13.6 million USD). Also for greenfield plants the in-vestments will be less than 40 Million EUR ($54.4 million) if operation of 2 raw mills is planned from the beginning.

 
Commercial