Clinker MakingTechnologies & Measures
|Technology or Measure||Energy Savings Potential||CO2 Emission Reduction Potential Based on Literature||Costs||Development Status|
|Cement Suspension Preheater Calcining Technology with High Solid-Gas Ratio|
Heat energy consumption for clinker making can be reduced below 2.85 GJ/t-clinker. Savings of 14.3 kg of standard coal per ton of clinker can be realized (NDRC, 2011. p.37)
In a Chinese plant with 2500 tpd capacity, the installation of this technology reduced annual energy consumption by 571.5 TJ (19 500 tce) (NDRC, 2011. p.37)
In a Chinese plant with 3000 tpd capacity, the installation of this technology reduced annual energy consumption by 633 TJ (21 600 tce) (NDRC, 2011. p.37)
Installation of this technology in a Chinese plant with 2500 tpd capacity required an investment of 35 million RMB, and took one year to complete. The economic benefits of saved energy was about 34.5 million RMB, resulting in a payback time of around 1 year (NDRC, 2011. p.37)
Installation of this technology in a Chinese plant with 3000 tpd capacity required an investment of 35 million RMB, and took one year to complete. The economic benefits of saved energy was about 37.2 million RMB, resulting in a payback time of 10 months (NDRC, 2011. p.37)
|Waste Heat Recovery for Power Generation|
Typically, 8–22 kWh/t-clinker can be produced without changes to kiln operation. Generation up 45 kWh/t clinker is possible by modifying kiln operations (e.g. less cyclone stages or by-passing upper stage(s) (CSI/ECRA, 2009. p. 31)
In China, production potential is reported to be around 24-32 kWh/t-clinker using domestic technology and 28-36 kWh/t-clinker using foreign technogly. 39 kWh/t-clinker is achieved in a Chinese plant using Japanese technology
Japanese technologies are reported to be able to produce 45 kWh/t clinker.
The potential for Indian plants are reported to be 20-24 kWh/t clinker.
48.5 GWh/y of net electricity production was projected for a 8 MW WHR unit installed at a 4500 tpd plant in China (UNFCC, 2008).
The 8 MW power plant installed by the Indian Cements Ltd. (for their 4500 tpd plant) has been reported to reduce the CO2 emissions by 45 000 tons per year (PCA, 2008).
With the installation of a 9 MW WHR plant to a plant with 5000 tpd capacity, annual CO2 emission reductions in excess of 52 000 ton year is planned (UNFCC, 2007)
41 000 t CO2/y reduction is expected with the installation of an 8 MW waste heat recovery unit in a 4500 tpd plant in China.
|For a plant with 2 millon t-clinker/y capacity, installation costs are estimated to be between € 15-25 million. Operational costs are estimated to decrease by €0.3–1.2/t-clinker (CSI/ECRA, 2009. p.32).
Investment per kW are estimated to be about 6000-10000 RMB (US $ 940 - 1570) for Chinese technology and 16,000 - 22 000 RMB (US $2500 to 3400) for foreign technology for China. Estimated payback periods are usually less than 3 years.
For China it was estimated that for a 2000 ton per day (730,000 annual ton) kiln capacity, about 20 kWh/t clinker of electricity could be generated for an investment of 20 to 30 million RMB (US $ 3.1 to 4.7 million).
For India, investment costs are given to be around $2.25 million per MW capacity. Indian Cements Ltd. has put up an up to 8 MW power plant using Japanese technology for its 4500 tpd plant for a total investment of US $ 18.7 million (PCA, 2008).
The installation cost of the 8 MW WHR unit in a 4500 tpd plant in China is reported to be RMB 58.8 million. The project is reported to have an IRR of 6.65% (the IRR value is stated to be 17.08% with carbon credits) [2008 values]. (UNFCC, 2008)
|Process Control and Optimization in Clinker Making|
Savings vary between 2.5 to 10% and typical values are estimated to be 2.5 to 5%.
For modern dry kilns with capacities more than 2500 tpd, savings are reported to reach 0.29 GJ/t-clinker (NDRC, 2012. p.66)
In a 4500 tpd Chinese plant, annual energy consumption was reduced by 395.6 TJ (13500 tce) with the installation of a process control and optimization system (NDRC, 2012. p. 66)
In a 4000 tpd Chinese plant, annual energy consumption was reduced by 351.7 TJ (12000 tce) with the installation of a process control and optimization system (NDRC, 2012. p. 66)
The costs of process control optimization measures/techniques vary widely and can be up to $6.8 million [1€=$1.35 US]
In a 4500 tpd Chinese plant, installation of a process control and optimization system required an investment of 980 thousand RMB, and took one month. The system provided annual savings of 8 million RMB, resulting in a payback time of 2 months (NDRC, 2012. p. 66).
In a 4000 tpd Chinese plant, installation of a process control and optimization system required an investment of 990 thousand RMB, and took one month. The system provided annual savings of & million RMB, resulting in a payback time of 1.5 months (NDRC, 2012. p. 66).
|Combustion System Improvements|
Specific fuel savings up to 8% have been realised in plants using Gyro-Therm technology.
Another technique developed in the UK for flame control resulted in fuel savings of 2 to 10% depending on the kiln type.
The payback times for Gyro-Therm technology is expected to be less than one year.
Costs are estimated to be around $1.0/annual ton clinker capacity, with estimated payback periods of 2-3 years.
|Dry Kilns with Multistage Pre-heaters and Pre-calcination|
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).
Emission reductions are estimated to be:
284 kg CO2/t-clinker in Chinese context.
297 kg CO2/t-clinker in Indian context
233 kg CO2/t-clinker in the United States.
|Conversion of Long Dry Kilns to Preheater/Precalciner Kilns|
Up to 1.4 GJ/t-clinker can be saved.
For every ton of clinker, following amounts of CO2 reductions are estimated:
132.4 kg in Chinese context;
138.5 kg in Indian context;
108.8 kg in the United States.
Upgrading costs are reported to be between US $8.6 to $29 per annual ton of clinker capacity.
|Kiln Shell Heat Loss Reduction|
Fuel consumption is estimated be reduced by around 0.12 to 0.4 GJ/t of clinker.
in China, switching to better refractories may reduce CO2 emissions by 11 to 38 kg per ton of clinker.
Switching to higher quality refractories may cost around US $0.25/annual tonne clinker capacity. Estimated payback period is approximately 1 years.
|Addition of Pre-Calcination to Kilns with Preheaters|
In an Italian plant, the conversion reduced specific fuel consumption from 3.6 to 3.1-3.2 GJ/t clinker, resulting in savings of 11 to 14%, and enabled a capacity increase of 80 to 100% (from 1100 tpd to 2000 to 2200 tpd).
For Chinese context, this option holds the potential to reduce CO2 emissions by 38 to 47 kg for every ton of clinker produced.
Investments in the range of US $9.4-28 per annual ton clinker may be required. Payback times are usually less than 5 years.
In India, the payback times are reported to be less than 3 years.
|Replacing Vertical Shaft Kilns|
Savings up to 2.4 GJ/t clinker can be obtained.
Savings of 1.6-2.0 GJ/t clinker are reported from India depending on pre-heater/pre-calcination system configuration
In China, CO2 emissions can be reduced by 227 kg/t clinker by converting VSKs to pre-heater/pre-calciner kilns.
Costs of such conversions can be between US $28-41 per annual ton of clinker production.
|Low Pressure Drop Cyclones for Suspension Preheaters|
Power savings in the range of 0.7-4.4 kWh/t clinker depending upon feasibility of cyclone modification and fan efficiency.
In India, average savings are reported to be 1.5 kWh/t clinker.
Use of this option may reduce CO2 emissions by 0.5 to 3.5 kg per ton of clinker produced.
Based on the average savings of 1.5 kWh/t clinker, use of this technology reduces CO2 emissions by 1.2 kg per ton of clinker produced.
The cost of a low-pressure drop cyclone system is assumed to be US $3 per annual ton clinker capacity. Installation of the cyclones can be expensive, since it may often entail the rebuilding or the modification of the preheater tower, and the costs are very site specific.
|Additional Preheater Cyclone Stages|
Moving from 4 stage to 5 stage, or from 5 stage to 6 stage can reduce the specific heat energy consumption between 0.08 to 0.1 GJ/t clinker
In India reductions between 0.06 to 0.1 GJ/t clinker are reported.
CO2 emissions can be reduced by 7.6 – 9.5 kg/t-clinker.
CO2 emissions can be reduced by 7.9 – 9.9 kg/t-clinker.
|High Efficiency Fans for Preheaters|
0.7 kWh of electricity can be saved for each ton of clinker produced.
In India savings in the range of 0.3-.0.5 kWh/ton clinker are reported depending on generation of existing fan.
CO2 emissions can be reduced by:
0.55 kg CO2/t-clinker
0.57 kg CO2/t-clinker
Capital costs of US $0.01 per annual ton of clinker capacity are reported.
|Bucket Elevators for Kiln Feed|
Following savings in electricity consumption are reported in literature:
In India savings in the range of 1.0-1.3 kWh/t of clinker are reported.
Following cost informatin is provided in the literature:
In India Installation costs of this technology is reported to be US $4000-5000 per meter.
US-EPA reports a US $0.17/ton-portland cement reduction in operating costs.
|Fluidized Bed Advanced Cement Kiln System|
Thermal energy use can be decreased by around 0.4 GJ/t-clinker (NEDO, 2006), while the electricity consumption increases by around 9 kWh/t-clinker (ECRA, 2009)
20% more heat can be recovered in the cooling system, as compared to conventional methods (APP, 2009)
CO2 reductions in the range of 10% can be realized (NEDO, 2006).
|Efficient kiln drives|
0.5 – 1% reduction in electricity use of the kiln drive can be achieved by replacing a DC motor with AC motor.
Using high-efficiency motors to replace older motors, or instead of re-winding old motors, may reduce power costs by 2 to 8%.
Electricity savings are 0.55-3.9 kWh/t clinker
The capital cost for single pinion drive with an air clutch and a synchronous motor is around 6% higher than standard kiln drive.
|Improved Burnability Using Mineralizers|
Based on the modelling results, thermal energy consumption can be reduced by between 0.05 to 018 GJ/t clinker.
CO2 emissions can be reduced by 4 to 16 kg per ton of clinker
Additional costs of mineralizers has to be considered and may outweigh the fuel cost savings. Espeically CaF2, which is commonly used, is an expensive material. Use mineral wastes containing flourides can be economically viable, however, such materials have a limited availability.
|Alkali Bleed (alkali by-pass) Systems||Commercial|
|Oxygen enrichment technology|
Thermal energy use can be decreased by 0.1 - 0.2 GJ/t clinker but electricity use increases by 10 - 35 kWh/t clinker
While this technology may reduce direct CO2 emissions by 10 to 20 kg per ton of clinker due to reduced fuel consumption, the indirect emissions are estimated to rise by 15 to 25 kg/t clinker due to increased electricity use.
|Using modern multi-channel burners|
Depending on the secondary air temperature, reduction of the primary air ratio by 5-10% will lead to a fuel energy saving of 0.05-0.08 GJ/t-clinker at conventional kilns and about half of this at precalciner kilns. The electrical energy demand will remain almost unchanged as the higher consumption for control fittings and air delivery channels can be offset by the reduction of the primary air.
Four channel pulverized coal injection burner is expected to reduce primary air usage by 4% and reduce kiln energy consumption by 0.020 GJ/t-clinker (NDRC, 2009. p.44).
By replacing the existing burner in a 2500 tpd kiln with a four channel pulverized coal injection burner and making necessary adjustments in their fan, Hunan Yintaishan Cement Co. Ltd. reduced its annual energy consumption by 16.2 TJ (553 tce) (NDRC, 2009. p. 45)
By retrofitting a more efficient burner in a 2500 tpd kiln, Ningxia Qingtongxia Cement Co. Ltd., reduced its energy consumption by 17 TJ/y (583 tce/y) (NDRC, 2009. p. 45)
By retrofitting a more efficient burner in a 5500 tpd kiln, Hebei Yanzhao Cement Co. Ltd., reduced its energy consumption by 35.7 TJ/y (1218 tce/y) (NDRC, 2009. p. 45)
Four channel pulverized coal injection burner is expected to reduce NOx emissions by 41% (NDRC, 2009. p.44).
In Hunan Yintaishan Cement Co. Ltd., retrofitting a four channel pulverized coal injection burner and making necessary fan adjustments in a 2500 tpd kiln took three days and costed 0.5 million RMB. The retrofit provides annual savings of 0.44 million RMB and had a payback time of 1.1 years (NDRC, 2009. p.45).
In Ningxia Qingtongxia Cement Co. Ltd., retrofitting a new burner in a 2500 tpd kiln took one month and costed 0.47 million RMB. The retrofit provides annual savings of 0.47 million RMB and had a payback time of 1.2 years (NDRC, 2009. p.45).
In Hebei Yanzhao Cement Co. Ltd., retrofitting a new burner in a 5500 tpd kiln took three days and costed 0.6 million RMB. The retrofit provides annual savings of 0.83 million RMB and had a payback time of 9 months (NDRC, 2009. p.45).
|Stabilization of Kiln Coating|
Radiation heat losses will be reduced leading to energy savings.
Assuming a reduction of excess air between 20% and 30%, indirect firing may lead to fuel savings of 0.015 -0.022 GJ/t clinker.
The advantages of improved combustion conditions will lead to a longer lifetime of the kiln refractories and reduced Nox emissions. These co-benefits may result in larger cost savings than the energy savings alone.
US $5 million for an annual production capacity of 680,000 ton clinker, or US $7.4/t annual clinker capacity.