Insights and Commentaries
Opportunities for CCS in the Chinese steel industry
15th August 2015
Topic(s): Carbon capture, use and storage (CCUS)
Toshiba has released the results of a feasibility study, Applying carbon capture and storage to a Chinese steel plant commissioned by the Global CCS Institute into the application of carbon capture and storage (CCS) at a major steel plant in China. The results suggest that carbon capture in Chinese steel plants is a cost effective means of reducing carbon emissions compared with similar plants around the world. In this Insight the Institute's Senior Adviser for Carbon Capture, Asia-Pacific, Tony Zhang introduces the report and discusses some of the major findings. The full report is available on the Global CCS Institute website.
Schematic of CO2 capture plant applying to iron and steel plant (Case 1). Image courtesy of Toshiba
Steel production is a major contributor to carbon emissions, especially the iron making process. China has the world’s largest iron and steel industry which contributes a significant proportion of global anthropogenic CO2 (carbon dioxide), with estimates of around 1.5 billion tons in 2013. To address country-wide carbon emissions the Chinese government has established polices aimed at reducing emission intensities, including from industrial processes.
In response to the government's initiatives many steel companies have been actively looking for technologies to curb their CO2 emissions. Through an international collaboration project China Shougang Steel and Tsinghua TongFang Environment have worked with Toshiba on reducing emissions in the steel-making process. This collaboration was recognised as a model Demonstration Project at the 8th China-Japan Energy Saving Environment Protection General Symposium organised by China National Development and Reform Commission (NDRC), China Ministry of Commerce, Japan Ministry of Economy and Industry and the Japan China Economic Cooperation Society in December 2014.
Caofeidan Steel Plant
Shougang Group is one of the largest steel companies in China, producing more than 30 million tons of crude steel in 2013. Steel production is an energy intensive process and Shougang’s total CO2 emissions were over 61 million tons (Mt) in 2013. Carbon capture and storage is one way to reduce emissions. Transport and storage technologies are well advanced but the capture process represents the most cost-intensive and application-specific process. Therefore, this project aimed to evaluate the effectiveness of Toshiba's solvent-based capture technology on a Chinese steel manufacturing plant. The Shougang Jingtang Steel Plant at Caofeidian was selected for the study.
The main CO2 emissions sources and the volumetric CO2 concentrations at the Shougang Jingtang steel plant are:
| Process | Share of CO2 emissions |
|---|---|
| Lime kiln | 19.3% |
| Hot blast stove | 28.5% |
| Coke oven | 11.0% |
| Heating furnace | 10.0% |
| Thermal power plant | 9.9% |
The steel plant also has various waste heat for utilisation, including:
- Hot blast stove
- Coke oven
- Two Heating furnaces
Considering the demand for enhanced oil recovery (CO2-EOR) at a nearby oilfield, 300 tons per day (tpd) was chosen as the capture plant capacity. Two emission sources were studied: the lime kiln and hot blast stove. Both streams exhibit relatively high CO2 concentrations. The energy for solvent regeneration is extracted from the flue gas produced by the hot blast stove, which has a temperature of 258°C.
Pilot studies inform demonstration plant
Both case studies use solvent absorption methods to capture carbon dioxide. Pilot experiments were conducted at Toshiba’s Mikawa pilot plant in Japan. The results demonstrated the complex and highly coupled nature of a solvent capture system. The interconnectedness of the system components means that one cannot change a single parameter without affecting others. For example, the change of inlet CO2 concentrations requires corresponding changes to the rich/lean solvent pumps, heat exchanger loading and steam supply. Experiments also established an energy-CO2 concentration correlation curve which shows that capture from the lime kiln flue gas consumes 1.05 times the regeneration energy required for capture from the host blast stove.
Based on the parametric experiments at the Mikawa pilot, two 300-tpd capture plants were designed for the two streams at the Caofeidian site. The CO2 capture systems for the lime kiln and the hot blast stove are solvent-based, comprising:
- Flue gas pretreatment system
- Absorption system
- Regeneration system
- Steam generation system
- Compression and dehydration system
- CO2 Transport system
- Water supply system
- Waste water sump system
Demonstration plant parameters
The footprint for the Lime Kiln capture plant is 53.1 m(L) x 40.5m (W) x 51.7m (H) (absorber height). The Blast Stove capture plant is slightly lower (absorber height 51.5m). Impurities (SOx and NOx) in both gases are relatively low and their impacts are not covered by this work.
Steam consumption for the two cases are reported as 31 gigajoules per hour (GJ/h) and 29.26 GJ/h for the lime kiln and hot blast stove respectively, which may translate into a specific regeneration energy of 2.48GJ/t CO2 and 2.34 GJ/t CO2 (assuming 300 tpd CO2, 12.5 ton per hour).
The captured CO2 is compressed to 100 bar for transport and may be used to enhanced oil recovery in nearby oilfields.
The CAPEX(EPC cost) for the lime kiln capture plant is reported as USD$22.1 million and the CAPEX for the hot blast stove capture plant is USD$18.1 million. Taking into account both CAPEX and OPEX, the break-even CO2 price for lime kiln capture plant is USD$39.80 per tonne CO2, and the break-even CO2 price for the hot blast stove capture plant is USD$34.10 per tonne CO2. Flue gas with higher CO2 concentrations will result in a lower CAPEX and OPEX.
Results and key findings
The key operational learning from this report is that the installation of a carbon capture plant needs to minimise its impact on existing steel production, which is the main business of the project stakeholder. Adequate planning is key to overcoming this issue. The integration and heat utilisation require detailed technical investigation for each case.
Overall, the carbon capture cost at a steel plant in China is relatively competitive in comparison with other countries. The preliminary feasibility study reveals promising economics for carbon capture in steel industry which would help to facilitate the development of CCS deployment in the Chinese steel industry.