In China energy use for coking has decreased from 5.6 GJ/t-coke to 4.9 GJ/t-coke between 1995 and 2000, and further decreased to 4.2 GJ/t-coke by 2004, thanks to installation of more than ten coke dry quenching and other advanced quenching technologies.
In Europe equipment costs for a 2 million ton-coke/year plant are estimated to be €70 million. Depending on the electricity costs, the payback time can be 3 years - if all the steam is used for electricity generation. (IPPC BREF, p. 276)
In Japan, installation of a CDQ for a 450 000 t-coke/y capacity plant required ¥ 3 billion in equipment and ¥ 500 million in construction costs. With an electricity price of ¥17.99/kWh, approximate payback time was 3.6 years [1 ¥ = US $0.1257] (NEDO, 2008. p.67)
http://www.epa.gov/nsr/ghgdocs/ironsteel.pdf
Coke Making
Coke is a material with high carbon content and porosity. It has high resistance to breakage and low reactivity with gases, particularly CO2. Coke production is an important part of the integrated iron and steel plants using BF-BOF route, acting as a reducing agent, as a source of thermal energy, and providing physical support for the burden in blast furnace. In modern blast furnaces 460 - 480 kg of total reductant /t-hot metal is needed, and global average is 500 kg/t-hot metal (IEA, 2007. p.117). In modern blast furnaces with supplementary fuel injection, coke consumption can be less than 300 kg/t-hot metal.
Coke is produced by heating coking coals up to 1000 to 1200 °C for several hours in coke ovens to drive off volatile compounds and moisture. For every ton of coke around 3.5 to 5.0 GJ of energy (IEA, 2007. p.110) and around 1.6 ton of coking coal is used (IEA, 2009, p.52). Coke production accounts for around 10% of the energy demand in a BF-BOF plant (IEA, 2007. p. 110). Coal characteristics play an important role on the coke consumption and thus the energy demand. A 1% increase in the ash content of coke may increase the coke demand by 2%. This is an important factor for countries like India where the coal ash content is high.
In China energy use for coking has decreased from 5.6 GJ/t-coke to 4.9 GJ/t-coke between 1995 and 2000, and further decreased to 4.2 GJ/t-coke by 2004, thanks to installation of coke dry quenching and advanced coke quenching technologies in Chinese plants (old behive coke ovens that account for one fifth of Chinese coke production are not included in these statistics) (IEA, 2007).
Coke MakingTechnologies & Measures
| Technology or Measure | Energy Savings Potential | CO2 Emission Reduction Potential Based on Literature | Costs | Development Status |
|---|---|---|---|---|
| Coke Dry Quenching |
The most efficient coke ovens use CDQ and may use up to 40% less energy. Approximately 1.5 GJ heat/t-coke (as ~ 400 - 500 kg high temperature steam/t-coke) and 0.55 GJ electricity/t-coke can be recovered. For a plant with 450 000 t/y coke capacity (~1 million t/y BF capacity), 450 GWh/y of steam and around 150 GWh/y of electricity can be produced.
|
CO2 savings in excess of 100 000 t/y are estimated by converting two 25 t/h capacity quenching systems from wet to dry (Climatetech Wiki, 2011) Given about 300 Mt coke production without CDQ and savings of 600 g CO2/kWh, global CO2 emissions reduction potential is about 25 Mt CO2.(IEA, 2007) |
Retrofit capital costs are 109.5$/ton coke. The cost of a 3-chamber plant can be estimated to be in the range of €60-70 million including equipment and installation costs.
By converting two 25 t/h capacity quenching plants from wet to dry systems with 15 MW electricity generaton connected to each, US $9 million savings in electricity, and US $1 million in water related costs are estimated. (Climatetech Wiki, 2011) |
Commercial |
| Additional Use of Coke Oven Gas |
Coke oven gas with a heating capacity of 6 to 8 GJ can be recovered for every ton of coke produced. (IEA, 2007)
|
|
By using COG as supplementary fuel in blast furnace, a steel mill in the US was able to save US $6 million annually. The project required an investment of around US $6.1 million, and had a payback time of just over one year. |
Commercial |
| Automation and Process Control System | This technology can lead to fuel savings of about 10%. Estimated energy savings therefore are calculated to be 0.15 MBtu/ton (0.17 GJ/tonne) coke. | The technology leads to emissions reduction of 3.8 Kg CO2/tonne coke. | Retrofit capital costs are US $0.37/tonne coke. | Commercial |
| Coal Stamp Charging Battery |
This technology conserves coking coal due to use of higher proportion of high volatile & poor coal in the blend. It also increases the yield in the coke plant and may help improve the performance in heat recovery systems. |
Emissions reduction is unlikely. |
Investment and operational costs are reported to be reduced, due to reduced oven compartments and ability to use lower grade coal. |
Commercial |
| Coal Moisture Control |
|
Commercial | ||
| Non-Recovery Coke Ovens | Electrical power of about 630-700 kWh/t-coke can be produced. | VOC and particulate matter emissions are mostly eliminated. SOx emissions are reduced but NOx emissions are likely to increase. | Investment cost of a US coking plant producing 1.2 million tons of coke per year was $365 Million – including coke oven facilities, coke handling/blending and power plant in 1998. For the energy facility, investment costs of only USD 140 million are reported for 1998 (IPPC, 2009). | Commercial |
| Variable Speed Drive Coke Oven Gas Compressors | Variable Speed Drive System on a compressor at a coke plant at Corus in The Netherlands saved 6 to 8 MJ/t-coke. | Emissions can be reduced by 0.12 kg CO2/t-coke. | Retrofitting cost is 0.47 $/tonne coke. The payback time was estimated as 21 years (US EPA, 16) | Commercial |
| Coke Stabilization Quenching | The technique can reduce coke consumption by 1-2% and may also reduce energy consumption in BF. | Dust emissions are reduced in Coke making. CO2 emissions may be reduced if the good quality coke results in energy savings in BF. | Cost data has not been provided. | Commercial |
| Single Chamber System |
SCSs offers an improvement in thermal efficiency from 38% to 70%. |
The larger dimension ovens decrease the specific environmental emissions because fewer pushing operations are required per tonne coke. Emissions are directly proportional to number of pushes. |
Demonstration | |
| COURSE 50 | Research | |||
| SCOPE 21 - Next Generation Coke Making Technology | Coke-making energy consumption can be reduced by 21% (NEDO, 2008. p. 70). | For a plant with 1 million t/y capacity, CO2 reduction of 400,000 t-CO2/year are anticipated (NEDO, 2008. p. 70). | Production costs are 82% and construction costs are 84% of conventional coke oven. | Demonstration |
Coke Making Publications
Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Iron and Steel Industry
Page Number:
9, 16-17
Energy Efficiency Improvement and Cost Saving Opportunities for the U.S. Iron and Steel Industry
The U.S. Environmental Protection Agency’s (EPA) energy guide, Energy Efficiency Improvement and Cost Saving Opportunities for the U.S. Iron and Steel Industry, discusses energy efficiency practices and technologies that can be implemented in iron and steel manufacturing plants. This guide provides current real world examples of iron and steel plants saving energy and reducing cost and carbon dioxide emissions.
http://www.energystar.gov/ia/business/industry/Iron_Steel_Guide.pdf?25eb-abc5
Page Number:
79-82
The State–of-the-Art Clean Technologies (SOACT) for Steelmaking Handbook
Date:
Dec
2010
Source:
Format:
PDF
Type:
Publications
The State–of-the-Art Clean Technologies (SOACT) for Steelmaking Handbook is developed as part of the Asia-Pacific Partnership on Clean Development and Climate program and seeks to catalog the best available technologies and practices to save energy and reduce environmental impacts in the steel industry. Its purpose is to share information about commercialized or emerging technologies and practices that are currently available to increase energy efficiency and environmental performance.
http://asiapacificpartnership.org/pdf/Projects/Steel/SOACT-Handbook-2nd-Edition....
Page Number:
29-39
Global Warming Countermeasures: Japanese Technologies for Energy Savings / GHG Emissions Reduction
Date:
2008
Source:
Format:
PDF
Type:
Publications
This revised 2008 version of the publication from New Energy and Industrial Technology Development of Japan includes information on innovative Japanese technologies for energy efficiency and for the reduction of CO2 emissions.
Page Number:
67-70