REVIEW OF CARBON CAPTURE TECHNOLOGIES FOR COAL-FIRED POWER PLANT

CO2 Emissions from Coal-Fired Power Plant

According to the IEA report, the biggest sectoral increase in emissions in 2022 came from electricity and heat generation, whose emissions were up by 1.8% or 261 Mt. In particular, global emissions from coal-fired electricity and heat generation grew by 224 Mt or 2.1%, led by emerging economies in Asia.

Emissions from electricity generation vary by type of fuel/energy source and by type and efficiency of electric power plants. The amount of CO2 produced per kWh during any period of time will vary according to the sources of electricity supplied to the electric power grid during that time. Therefore, electricity-related CO2 emissions and CO2 emission factors will vary hourly, daily, monthly, and annually.

Whilst estimates vary, the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) has provided a median value among peer-reviewed studies of CO2?equivalent/kWh associated with types of fuel/energy sources.

Table 1-1 shows the representative concentration of post-combustion flue gas for coal-power plants. There is additional variation around these values depending on the exact composition of the fuel, the efficiency of the plant, types of emission controls installed, and other factors, but for purposes of CO2 capture, 10-15% CO2 for coal is quite representative.

Overview of CO2 Capture Implementation in Coal-Fired Power Plant

Although applicable to the decarbonization of many industrial processes, the 25% of manmade CO2 emissions which derive from the combustion of coal for power generation is a principal target for CCS technologies, which hold the potential to both curb future emissions from existing coal plants and enable sustainable use of a low-cost source of dispatchable energy. Projections by the IEA have therefore determined that up to 17% of global CO2 abatement should come from CCS by 2035 under a lowest cost scenario for decarbonization. However, despite significant technological developments since the turn of the century, the application of CCS to power stations has yet to reach the necessary uptake rate, with the first few facilities only recently beginning to see deployment in North America and a pilot project in China. Meanwhile, a CCS power plant in Europe has yet to be realized despite numerous projects reaching advanced design and planning stages.

The major large-scale Power Plant CCS Projects Worldwide are listed in Table 1.2.

With large-scale carbon capture from coal now demonstrated as technically feasible, the main barrier to its deployment is the significant economic cost of CCS compared to a conventional, unabated coal plant. Whilst some form of CO2 pricing or other clean energy subsidy will always be necessary for the operation of such a plant to be viable, the cost of CO2 capture using current CCS technologies, estimated to be at least $60/t CO2 captured, is considered too great for the process to be economic based on carbon prices in the near term. In the absence of such compensation, the additional costs incurred by a CCS-equipped coal plant are associated with an increase in the cost of electricity (COE) by around 80%, which is too great to encourage investment in most energy markets. Early CCS plants have therefore tended to only be feasible in regions where other favorable conditions apply, including the possibility of revenue from CO2 sales for enhanced oil recovery (EOR), a low-cost, long-term coal supply, or an uncompetitive energy market.

As a result, research worldwide has sought to make CCS more competitive by developing carbon capture technologies. In particular, the US Department of Energy (DOE) has funded a wide-reaching research program into new concepts at all levels of technical readiness, but research is also active at several academic institutes and private sector companies throughout the developed world, commonly setting cost targets as low as $2030/t CO2 or a 3040% cost of electricity (COE) reduction on existing technologies.

State-of-Art of CO2 capture technologies

• Pre-combustion carbon capture occurs before combustion (through fuel gasification with oxygen, e.g., integrated IGCC coal gasification technology).
• Post-combustion carbon capture occurs after the combustion process (capturing CO2 from flue gas, e.g., using chemical absorption, physical adsorption, membrane separation, or the use of a chemical loop).
• Oxy-combustion carbon capture occurs after the combustion process in an oxygen atmosphere by separating CO2 generated during the oxy-combustion process, e.g., using an oxygen gas turbine. Oxygen atmosphere can be obtained by removing nitrogen from the air before the combustion process.Below Figure? illustrates the challenges and development progress of the three CO2 capture approaches.

Post-combustion capture for coal-fired power plants

The post-combustion capture (PCC) methods produce a pure CO2 stream in several ways and flexible technology with high adaptability. The post-combustion capture technology can be applied to the existing large point source of fossil fuel-based power plants, refineries, and cement manufacturing industries, as these are the main sources of carbon dioxide emission in the atmosphere.

Post-combustion CO2 capture methods are based on removing carbon dioxide from flue gas. The capture unit is placed after the purification systems, such as desulphurization, de-nitrogenation, and dedusting installations.

The major challenges in PCC revolve around the relatively large parasitic load CCS imposes on a power plant, the majority of which is due to capture, especially the energy needed to regenerate the solvent. Energy required for compression, though important, is less than that required for capture and is closer to its thermodynamic limit than capture is to its thermodynamic limit. Hence, developing new chemistry, new process designs, and novel power plant integration schemes aimed at reducing the parasitic load of CCS are the focus of virtually R&D in PCC.

Figure? shows a general block diagram of the post-combustion capture technique.

Post-combustion technologies can be divided into four types of processes used for capturing carbon dioxide, including the absorption process, membrane process, and adsorption process.

Market Available Solvent-based Technology

Some solvent-based carbon capture systems have successfully completed the early stages of commercial deployment for post combustion carbon capture. These technologies have an advantage concerning large-scale deployment by 2030.

There are five technology providers entered into the Demonstration Stage. They are: Mitsubishi Heavy Industry, Shell, Fluor, Carbon Clean Solution, and Aker Carbon Capture.

1. Mitsubishi Heavy Industry (MHI)

The MHI’s KM CDR Process is an amine process using the KS-1 solvent. The new technology uses KS-21, which is a new amine solvent formulation from MHI. Their targeted industry sector is in the Post-combustion capture (PCC) flue gas applications. MHI’s amine KS-1 solvent was used at the 4700 tpd Petra Nova project in Texas, USA. MHI’s next-generation solvent is KS-21. The new solvent and process improvements are anticipated to offer incremental improvements over plants using KS-1.

2. Shell Cansolv

Shell’s Cansolv technology utilises the next generation of their proprietary Cansolv advanced amine-based solvent and targeted in the Post combustion capture (PCC) flue gas applications.

3. Fluor

The Fluor’s technology utilises their next generation proprietary Econamine FG Plus advanced solvent. Fluor have also developed a water-lean amine solvent. Their targeted industries are the Post combustion capture (PCC) flue gas applications.

Fluor claims that the Fluor has carbon capture experience with over 30 licenced plants and is the only technology to be commercially proven for CO2 recovery from gas-turbine exhausts.

4. Carbon Clean

Carbon Clean’s technology utilises their proprietary Amine-Promoted Buffer Salts (APBS) advanced solvent. Additionally, Carbon Clean has offerings of bespoke large-scale carbon capture plants and smaller modular carbon capture units and they targeted in the Post combustion capture (PCC) flue gas applications.

Tuticorin Alkali Chemical & Fertilizers Plant Coal-Fired Boiler project in Tamil Nadu, India, with a design capacity of 60,000 tpa CO2 capture are in operation since 2016.

Tata Steel Jamshedpur Plant Blast Furnace in India with a design capacity of 5 tpd CO2 Capture was commissioned in 2021. Carbon Clean & Tata Steel have stated they have plans to develop a larger scale unit, but no details are available. Carbon Clean has captured over 1 million tonnes of CO2 across its projects since 2009.

5.?Aker Carbon Capture

Aker’s ‘Just Catch’ technology utilises their proprietary amine S26 advanced solvent. Aker offers large-scale carbon capture plants termed ‘Big Catch’ and smaller modular carbon capture units termed ‘Just Catch’. Aker Carbon Capture targeted in the Post combustion capture (PCC) flue gas applications.

Aker Carbon Capture designed and delivered the 80,000 tpa CO2 capture amine plant at the TCM facility which has been in continuous operation since its opening in 2013. They further performed testing of their capture technology at TCM.

Technology Providers

Evaluating the opportunity level of Carbon Capture Technology Providers or OEMs for coal-fired power plants involves assessing various criteria to determine their suitability and potential to deliver effective carbon capture solutions. The following primary concerns are evaluated for the mentioned solvent .

• Technical Readiness - The OEM's Technical Readiness Level in carbon capture technology development and deployment.
• Commercial Readiness – Evaluate the maturity of the technology provider, indicating its readiness for commercial deployment and market launch.
• Size of the Organization - The OEM's history of successful projects and installations related to carbon capture, especially in coal-fired power plants.
• Cost-Effectiveness - Consider the cost competitiveness of the OEM's carbon capture solutions and their ability to provide cost-effective options for power plants.
• Process warranties - The OEM's commitment to advancing and improving carbon capture technologies, including any innovations or breakthroughs they have introduced. The assurance and warranty provided by OEMs regarding the performance, reliability, and longevity of their carbon capture technology.
• Integration Capabilities - The OEM's ability to seamlessly integrate carbon capture technologies into existing power plant infrastructure without causing disruptions.
• Regional Presence - Consider whether the OEM has a regional presence, which can facilitate project implementation and support.

Based on the analysis outcomes, the high opportunity technology providers are Mitsubishi Heavy Industry, Shell Cansolv, and Fluor who have demonstrated a strong potential for successful deployment in commercial-scale coal-fired power plants.?