This roadmap defines R&D pathways for reducing or eliminating the adverse environmental impacts of fossil power generation, encompassing air emissions and process discharges (solid, liquid) as well as freshwater consumption.
For existing and new plants, innovations are being pursued in the following areas:
- Sensing, monitoring, and process control for multimedia emissions
- Control of NOx, SOx, acid gases, particulates, mercury, and other air toxics through primary (combustion) and secondary (after-combustion) means
- Control of mercury, arsenic, selenium, nitrates, bromine, and other water-borne contaminants
- Treatment of process wastewaters and degraded water resources
- Dry and hybrid cooling systems
- Cost, reliability, and operations & maintenance
As limits on environmental releases from coal-fired power plants and other fossil sources are ratcheted down, these innovations can support continued operations of existing generating assets and long-term deployment of future fossil plants by enabling cost-effective compliance with existing and anticipated air and water quality standards.
Advanced thermoelectric cooling and water reclamation technologies that reduce freshwater consumption while improving plant performance can help alleviate the water-related constraints that face a growing population of operating plants and challenge the siting of new fossil generating capacity.
- Top Innovators: EPRI’s Kirk Ellison and Jeffery Preece
- 2019 Integrated Environmental Controls Workshop
- Power Plant Water Management Workshop and User Group Meeting
- Wastewater Encapsulation: Development of Fundamental Science, Process Designs, and Operational Guidance
- Cooling System and Heat Transfer R&D Test Center
KEY INDUSTRY DRIVERS
Near Zero Emissions
As the public seeks improved environment and health and governments around the world impose increasingly stringent standards, power producers face growing technical and economic challenges. New requirements and stricter limits on air emissions increase costs, can lead to fuel switching, and can create downstream wastewater treatment or by-product management issues. In many instances, the costs of environmental control system upgrades are a key driver of early coal plant retirements. Uncertainty regarding future regulations increases business risks.
Power plant cooling can result in significant freshwater consumption, depending on site-specific characteristics. In many areas of the world, coal-fired assets and combined-cycle gas plants face operating and siting restrictions and cost pressures due to freshwater availability limitations and the performance characteristics of current wet and dry cooling technologies. Novel dry and hybrid dry/wet cooling systems promise to reduce water consumption while maintaining or improving plant productivity across all seasons.
Power producers are challenged to meet environmental standards while maintaining cost-competitiveness for each fossil asset and across entire fleets. At the same time that regulatory limits become more restrictive, the use of lower-cost, lower-quality fuels may make compliance even more difficult. Flexible operation adds to the challenge because standards must be achieved across the load range, including at lower turndown levels and during increased cycling. Fuel constituents and process additives must be managed and controlled holistically. New learning and innovative technologies are needed to address all air, water, and solids emissions while minimizing impacts on plant performance, reliability, and cost.
For coal- and oil-fired power plants, pre-combustion and combustion-based controls can affect fuel conversion efficiency and boiler reliability, while selective catalytic reduction (SCR), flue-gas desulfurization (FGD), electrostatic precipitation (ESP), and other post-combustion systems can increase pressure drop and add to a plant’s parasitic energy consumption. A similar systems perspective is needed in gas turbine combined cycles between fuel, combustion, emissions, and reliability for key components of combustor, turbine, HRSG, duct burners, and NOx and CO catalysts.
Current dry cooling technology can reduce or eliminate freshwater needs for cooling but imposes seasonal performance penalties. Minimizing the adverse impacts of environmental control and water conservation systems on net heat rate and other key parameters is essential.
Diversity of Generation
Due to gas prices, renewables deployment, and other factors, many coal plants designed for baseload service are experiencing flexible operations and switching to lower-quality fuels. Gas-fired units also are facing dynamic new mission profiles. Fossil plants must meet air emission limits across the duty range, which can involve more frequent and faster startups, faster ramping, more frequent load changes and minimum-load operation, and longer reserve shutdowns. Emission control systems can be challenged at low load and by transients, since they’re designed for and perform best during steady-state, full-load operation. Tighter limits and changed fuels exacerbate the compliance issues created by flexible operations.
Transformation of the Power Industry
Innovations in and reductions in the cost of sensors, computing processing, and in general, digital connectivity—embodied today by handheld electronics and tomorrow by wearable computers and broadly distributed wireless sensors—provide access to information resources addressing real-time plant status and historical operations. Collecting and applying Big Data to improve situation awareness, tune combustion conditions, and adjust process chemistry creates opportunities to optimize the performance of environmental controls on a site-specific basis.
By the mid-2020s, fossil power plants owned by EPRI members will be meeting all existing and anticipated environmental control requirements for air, water, and solids while maintaining reliability and cost-effectiveness across diverse mission profiles. In addition, existing units and new builds will have the capability to achieve near-zero emissions and reduced on-site freshwater consumption with decreased cost-performance impacts.
At current fossil plants, innovations in sensing, monitoring, and pre-combustion, combustion-based, and post-combustion technologies—handling both air emissions and wastewaters—will ensure reliable control performance at lower loads, during system transients and startup/shutdown cycles, and in the face of reduced fuel quality. Impacts on net plant heat rate and overall production cost will be minimized through advanced operations and maintenance (O&M) practices and holistic, multimedia strategies reflecting the sum of all resource inputs, processes, systems, and environmental requirements—including CO2 limits and controls.
Advances in dry cooling, hybrid cooling, and water reclamation technologies will allow power producers to lower freshwater consumption and tap alternative sources. By and after 2025, breakthrough concepts for dramatically reducing or eliminating water use for steam condensation are expected to be ready for commercial demonstration. These innovations also promise to increase thermal efficiency and thus provide further economic and environmental benefits.
Site-specific and fleet-wide decisions to invest in environmental control and cooling system technologies will reflect capital, operations, and maintenance costs, weighted to account for remaining plant life, hours of operation, dispatch, and other factors.
AREAS OF FOCUS
The 5-year Generation Sector program plans address immediate R&D priorities for mitigating environmental impacts from central-station power plants while reducing costs, risks, and adverse effects on performance and reliability. Near- and mid-term solutions also are being pursued under EPRI’s research imperatives (RI) related to Flexible Operations, Integrated Modeling, and Sensor Systems.
This roadmap defines collaborative R&D pathways for controlling primary air pollutants and multimedia releases, reducing freshwater consumption, and accelerating commercialization of advanced environmental resource management technologies and strategies over a timeframe 5 to 10 years out, and beyond. Areas of focus are introduced below.
Relevant R&D is under way or anticipated across the Generation Sector’s base programs. This roadmap also encompasses ongoing and planned work through EPRI’s Technology Innovation (TI) program.
- AIR QUALITY CONTROL
- FLEXIBLE OPERATION FOR AIR, WATER AND SOLIDS
- WATER & WASTEWATER TREATMENT AND CONSUMPTION
- ADVANCED I&C AND PROCESS CONTROL OF EMISSIONS CONTROL SYSTEMS
Air Quality Control
State-of-the-art knowledge, advanced O&M practices, and innovations in pretreatment, combustion-based, and post-combustion technologies are needed to reduce the costs and adverse impacts of meeting existing standards and achieving near-zero emissions of primary pollutants such as NOx, SO2, particulates, mercury, other metals, and additional air toxics. This includes current and future power plants firing lower-quality fuels and blends and undergoing flexible operations.
Ongoing and planned R&D activities address the following topics:
- First Principles. Improved understanding and predictive modeling of the effects of fuel quality and processing, combustion parameters, and additives on chemical speciation and partitioning across combustion and environmental control systems and in flue gas, aqueous discharges, and solid wastes and by-products.
- Integrated Control: Guidance and tools to support development and implementation of optimal site-specific emission control strategies based on fuel and plant characteristics, existing and anticipated air and water quality standards, by-product disposal and use considerations, and other factors.
- Intelligent Systems: Sensors, model-based controls and data analytics for optimization of full operations range with dynamic flexibility with high performance and minimum costs.
- Coal Cleaning: Advanced technologies and practices for cost-effective processing and treatment of individual coals and blends to produce beneficiated fuels with improved heat rate and reduced levels of mercury, SOx, and other contaminants.
- NOx: Advanced tools and best practices, SCR technologies, and process monitoring and control capabilities for cost-effectively minimizing NOx levels at the SCR outlet while tuning reaction chemistry to optimize downstream capture and removal of mercury and acid gases.
- SOx & Other Acid Gases: Advanced tools and practices, wet and dry FGD and sorbent injection technologies, and process monitoring and control capabilities for cost-effectively minimizing SOx and acid gas emissions, capturing trace metals, avoiding mercury re-emission and downstream selenium removal challenges, maintaining by-product marketability, and controlling parasitic energy consumption.
- Mercury & Other Air Toxics: Advanced tools and practices, sorbent injection technologies, and process monitoring and control capabilities for optimizing reaction chemistry to minimize the costs of capturing and managing mercury, selenium, and other trace elements in FGD and particulate control systems and in liquid and solid by-products.
- Particulates & Opacity: Advanced tools and practices, ESP and baghouse technologies, and process monitoring and control capabilities for cost-effectively minimizing emissions of filterable and condensable particulate matter and maximizing capture of mercury and other contaminants while maintaining by-product marketability and reducing parasitic energy consumption.
Flexible Operation for Air, Water and Solids
Best practices and innovative strategies and technologies are needed to ensure cost-effective compliance with air quality standards during startups, rapid ramps, and cycling, as well as to relax the limits on minimum turn-down levels imposed to avoid catalyst plugging in SCR systems. The effects of variations in fuel quality and co-firing gas and biofuels with alternative blending ratios also need to be addressed.
Improved knowledge and advanced technologies and operational practices are needed to maximize the effectiveness of combustion optimization as the least-cost approach for controlling multimedia emissions—primarily NOx but also mercury and other air toxics, sulfur trioxide (SO3), carbon monoxide, and unburned carbon—from both existing and future fossil generation technologies, operating on a range of fuels and blends.
- Flexibility: Improved understanding of the flexing capabilities and limitations—and associated performance, cost, and reliability impacts—for combustion-based and post-combustion control technologies.
- Operations & Maintenance: Advanced practices, strategies, and technologies for controlling process conditions, optimizing performance tradeoffs, implementing condition-based maintenance, including Big Data and data analytics, and optimizing staffing and investment to increase flexibility and environmental competitiveness at specific plants and across fleets.
- NOx Control: Guidance, tools, and primary control (combustion) technologies for optimizing fuel-air mixing to maximize combustion efficiency and minimize NOx formation while controlling fireside corrosion and deposition and avoiding boiler tube failure. In addition, SCR systems will implement best practices and protocols to ensure reliable operation at lower and transient loads.
- Sensors: Advanced sensors for real-time monitoring of fuel quality, combustion parameters, species concentrations, additive levels, control and treatment processes, and ambient conditions.
- Integrated Control: Guidance, tools, and technologies for tuning combustion conditions to optimize post-combustion NOx removal (SCR, selective non-catalytic reduction), minimize SO3 formation and promote mercury oxidation across the SCR, and improve FGD chemistry, ESP performance, and other environmental control equipment to achieve ever better environmental performance with low capital and O&M costs.
Water & Wastewater Treatment and Consumption
Advanced analytical tools, O&M practices, and technologies are needed for cost-effective treatment of process wastewaters to meet tightening discharge permit standards. Reuse, treatment, and desalination innovations create the opportunity to reduce freshwater withdrawal and consumption by power plants by enabling reliance on alternate water resources for thermoelectric cooling and other needs.
Innovations in dry cooling and hybrid wet/dry cooling systems are needed to alleviate power plant operating and siting restrictions imposed due to freshwater availability limitations while avoiding the seasonal performance penalties and high parasitic energy consumption associated with current air-cooled condenser technology. Breakthrough steam cooling and condensation concepts are required to dramatically reduce future freshwater use for thermoelectric cooling while also improving heat rates.
Ongoing and planned R&D activities address the following topics:
- Integrated Control: Understanding, predictive modeling, and control of reaction conditions in combustion, SCR, FGD, and other environments to optimize control of trace metals across all media.
- Wastewater Treatment: Guidance, tools, and technologies for cost-effective physical/chemical removal, biological processing, and zero-liquid-discharge treatment to control nutrients, mercury, selenium, arsenic, and other trace elements in wet FGD, ESP, and other plant wastewaters.
- Alternative Sources: Guidance, tools, and innovative technologies for reducing freshwater consumption by recycling and reusing on-site process wastewaters and treated municipal effluents, treating and desalinating degraded water sources, and recovering moisture from exhaust stacks and cooling systems.
- Technology Assessment: Engineering, cost, and performance analysis to inform site-specific evaluation and implementation of existing and advanced cooling technologies
- Near-Term Deployment: Guidance, tools, integration strategies, and demonstrated technologies for cost-effective addition of dry cooling capacity to reduce freshwater use at existing plants and new builds.
- Breakthrough Cooling: Laboratory testing, process simulation, and scale-up demonstration to accelerate commercialization of innovative concepts and systems promising greatly reduced water use and improved productivity for future power plants.
Advanced I&C (Instrumentation & Control) and Process Control of Emissions Control Systems
Advanced I&C and process control will be needed to better optimize combustion and pollutant control system performance, and thereby reduce overall operating costs while maintaining emissions compliance. One example is use of tunable diode laser (TDL) technology, which has the potential for diagnostic measurements of O2/CO and NH3/NO, as well as SO3 and other species, in coal-fired boiler flue gas streams. Spatially resolved measurements of the former species (e.g. O2/CO) can enable improved fuel/air balance and reduced excess oxygen set points with resultant heat rate benefits. Another example is measurements of NH3/NO, which can provide continuous tuning capability and diagnostic information regarding the operation of SCR systems.
Ongoing and planned R&D activities address the following topics:
Advanced I&C and process control: Development and demonstration of advanced sensors and integration into plant process control to lower emissions throughout the load range while reducing overall operating and maintenance costs.