Dry Kilns with Multistage Pre-heaters and Pre-calcination

Multistage preheaters and pre-calciners make use of the waste heat from the kiln and clinker cooler to pre-heat and pre-process the kiln feed, and thereby allow for considerable energy savings. Whenever economically feasible a wet process kiln can be converted to a state-of-the art dry process production facility that includes either a multi-stage preheater, or a multi-stage pre-heater and a pre-calciner. Such transformations are usually feasible for new plants and major upgrades.  Kiln systems with five cyclone preheater stages and precalciner are considered standard technology for ordinary new plants. Typical efficiency values that can be obtained with the use of multi-stage preheaters and precalcination is provided in the table below:

Heat Consumption of Different Cement Kiln Technologies (IEA, 2007. p.145))
Process Fuel Consumption (GJ/t-clinker)
Wet processes 5.9 – 6.7
Long dry processes 4.6
1 stage cyclone preheater 4.2
2 stage cyclone preheater 3.8
3 stage cyclone preheater 3.3
4 stage cyclone preheater 3.1
5 stage cyclone preheater 3.0 – 3.1
6 stage cyclone preheater 2.9

Chinese Flag As of 2007, only 45% of the Chinese cement production capacity was employing dry kilns with multi-stage preheaters and precalcination. (Tshinghua University, 2008)

 Majority of the cement plants in In India already have pre-heater pre-caliner systems in place. 

Development Status Products
Commercial
clinker, Cement

Dry Kilns with Multistage Pre-heaters and Pre-calcinationCosts & Benefits

Parent Process: Clinker Making
Energy Savings Potential

Fuel savings up to 3.0 GJ/t-clinker can be realized. Electricity consumption can increase by around 9 kWh/ton clinker.

In a case in UK, two wet process kilns with a total heat requirement of 5.65 GJ/t-clinker were replaced with a single pre-heater/pre-calciner kiln resulting in energy saving of 36% (down to 3.5 GJ/t-clinker).

CO2 Emission Reduction Potential

Emission reductions are estimated to be:

Chinese flag 284 kg CO2/t-clinker in Chinese context.

Indian flag 297 kg CO2/t-clinker in Indian context

US flag 233 kg CO2/t-clinker in the United States.

Costs
Parent Process:
Energy Savings Potential
CO2 Emission Reduction Potential

N/A

Costs
Parent Process:
Energy Savings Potential
CO2 Emission Reduction Potential

N/A

Costs
Parent Process:
Energy Savings Potential
CO2 Emission Reduction Potential

N/A

Costs

Dry Kilns with Multistage Pre-heaters and Pre-calcinationSchematic

Dry Kilns with Multistage Pre-heaters and Pre-calcination Standards

Reference Document on Best Available Techniques in the Cement, Lime and Magnesium Oxide Manufacturing Industries

This is a reference document for Best Available Technologies available for Cement, Lime and Magnesium Oxide manufacturing industries and that have high relevance within the scope of the European Integrated Pollution Prevention and Control (IPPC) Directive (now titled as Industrial Emissions Directive following the 2010 recast). 

Page Number: 

103

Dry Kilns with Multistage Pre-heaters and Pre-calcination Publications

Page Number: 

9