Loading...

Saturday, January 25, 2020

Finding Clean, Efficient, Flexible, Reliable & Cost-competitive of Future Coal Power Plant

The Transformative Power Generation Program aims to advance science, engineering, and technology by inventing, integrating, maturing, and commercializing coal combustion power technologies and systems to enhance the nation’s energy production and protect the environment for future generations. The program develops technologies to improve performance and extend the life of existing power plants. Research also focuses on next generation modular coal-fired power plants providing stable power generation with operational flexibility and high efficiency, as well as oxy-combustion and chemical looping combustion – technologies that provide options for coal-fired power generation in a carbon-constrained future.

The program uses a multi-pronged and coordinated approach to identify and perform research through in-house research and development (R&D), as well as cost-shared R&D with external partners in academia, industry, and other national laboratories.

Transformative Power Generation technologies will be market-driven with the best technologies, increasing deployment opportunities in an increasingly challenging power generation market.

The program comprises three key technologies: Coal FIRST, Improvements for Existing Coal Plants, and Advanced Combustion.

CoalFIRST – Coal Plant of the Future

Research is developing coal combustion technology options for future deployment of flexible, reliable, and resilient plants.

This effort—the Coal FIRST (Flexible, Innovative, Resilient, Small, Transformative) initiative—will develop the coal plant of the future needed to provide secure, stable, and reliable power. This research and development (R&D) will underpin coal-fired power plants that are capable of flexible operations to meet the needs of the grid; use innovative and cutting-edge components that improve efficiency and reduce emissions; provide resilient power to Americans; are small compared to today’s conventional utility-scale coal; and will transform how coal technologies are designed and manufactured.

Changes to the U.S. electricity industry are forcing a paradigm shift in how the nation’s generating assets are operated. Coal-fired power plants optimized as baseload resources are being increasingly relied on as load-following resources to support electricity generated from intermittent renewable capacity, as well as to provide critical ancillary services to the grid. These fundamental changes to the operating and economic environment in which coal plants function are expected to persist into the next decade and beyond. In addition, wide-scale retirements of the nation’s existing fleet of coal-fired power plants— without replacement—may lead to a significant undermining of the resiliency of America’s electricity supply. Nevertheless, the need for considerable dispatchable generation, critical ancillary services, and grid reliability, combined with potentially higher future natural gas prices and energy security concerns, such as the importance of onsite fuel availability during extreme weather events, create the opportunity for advanced coal-fired generation for both domestic and international deployment.

Deployment of new coal plants will require a different way of thinking. Specifically, the Department of Energy envisions that the coal-fired fleet of the future may be based on power systems with the following characteristics:
  • High overall plant efficiency (40 percent or greater higher heating value (HHV) at full load, with minimal reductions in efficiency over the required generation range)
  • Small (unit sizes of approximately 50 to 350 megawatts (MW)), maximizing the benefits of high-quality, low-cost shop fabrication to minimize field construction costs and project cycle time
  • Near-zero emissions, with options to consider plant designs that inherently emit lower amounts of carbon dioxide (amounts that are approaching those of comparable natural gas technologies) or could be retrofitted with carbon capture without significant plant modifications
  • Capable of high ramp rates and minimum loads
  • Integration with thermal or other energy storage (e.g., chemical production) to ease intermittency inefficiencies and equipment damage
  • Minimized water consumption
  • Reduced design, construction, and commissioning schedules from conventional norms by leveraging techniques including but not limited to advanced process engineering and parametric design methods for modular design
  • Enhanced maintenance features including technology advances with monitoring and diagnostics to reduce maintenance and minimize forced outages
  • Integration with coal upgrading, or other plant value streams (e.g., co-production)
  • Capable of natural gas co-firing.
The Coal FIRST initiative will advance coal power generation beyond today’s state-of-the-art to make coal-fired power plants a critical contributor to the grid of the future and offer both “firm and flexible” operations—providing stable power with operational flexibility and high efficiency such that it can quickly meet the needs of the evolving grid for resiliency and reliability. The initiative will integrate critical R&D on power plant components with currently available technologies into a first-of-a-kind system. Through innovative technologies and advanced approaches to design and manufacturing, the initiative will look beyond today’s utility-scale power plant concepts (e.g. base-load units) in ways that integrate with the electrical grid in the United States and internationally.

Improvements for Existing Coal Plants

Research identifies impactful, near-term opportunities applicable to the needs of the existing fleet, leading to increased reliability, operational flexibility, and improved efficiency.

Technology Options to Improve the Efficiency, Longevity, and Competitiveness of the Existing Coal Fleet

The existing coal power generating fleet plays a critical role providing reliable power generation required for power grid stability. It is important that these existing units continue to operate in an efficient and reliable manner. Under the current energy landscape, power plants are often required to operate at low and/or variable loads. Since the plants are not designed to operate below baseload, operation at low-load results in lowered efficiency and increased wear on the plant components. Operation at variable loads requires ramping of the plant capacity, which adds to the lowered efficiency and increased wear on plant components. As a result, there is a need for rapid commercialization of technologies to improve the efficiency, reliability, and flexibility of existing coal-based power plants. Existing plant combustion technologies research and development (R&D) focuses on the identification of impactful, near-term opportunities applicable to the needs of the existing fleet.

R&D has been initiated on cost-effective technologies expected to bring about near-term (three to five years) benefits for incorporation into commercial plants that will continue to operate on coal into the future. Currently, the National Energy Technology Laboratory (NETL) supports several Existing Plant Combustion Technologies projects in collaboration with academia, industry, and NETL’s Research and Innovation Center (RIC), ranging from bench-scale testing to validation testing in actual coal-fired power plants.

Reliability Improvements

To alleviate reliability impacts, the Transformative Power Generation Program is investigating technologies that could improve reliability and availability, as well as reduce maintenance costs. Innovative technologies being researched include online sensors, instrumentation, algorithms, and failure mode detection systems to monitor key plant components and inform possible repairs. One such concept is condition-based monitoring, a maintenance philosophy that actively monitors the condition of equipment to predict failures and schedule maintenance to maximize availability and generating capacity while saving cost. R&D is also being performed on tools for predicting the life of critical equipment to ensure long-term safety and reliability of existing plants.

Operational Flexibility

For a significant fraction of the existing coal-fired fleet, flexible operation (i.e., low-load operation and frequent deep cycling) has become the normal operating condition. Technology development efforts are focusing on rapid cycling and methods for responding to load changes. Advanced control methods for monitoring coal pulverizer operation and controlling steam and gas temperatures at low loads are being studied to improve the performance and economics of existing power plants. The implementation of neural networks and sensor technologies enables intelligent control for optimal combustion system performance and can improve flexible operation capability.


Efficiency Improvements

Improving plant efficiency is critical to the economic viability of a coal-fired power plant. Technology solutions are being investigated to improve efficiency of existing plants during both transient and steady-state operation, leading to reductions in operating cost and emissions. The Transformative Power Generation Program is identifying plant upgrades and areas for potential R&D to improve boiler and steam cycle efficiency, as well as to reduce auxiliary power. Improvements to the steam cycle efficiency involve additional steam generation, pump and cooling tower upgrades, and advanced ultra-supercritical (A-USC) retrofit options that include increased steam temperature and use of advanced materials for enhanced heat transfer efficiency. Efficiently recycling resources such as waste heat and water also presents advantages for increasing plant efficiency and reducing costs.


Advanced Combustion

Research on chemical looping and pressurized oxy-combustion technologies is developing options for CO2 capture

Research on chemical looping and pressurized oxy-combustion technologies is developing options for CO2 capture.

Advanced combustion power generation combusts coal in an oxygen-rich environment rather than air. This eliminates most of the nitrogen found in air from the combustion process, resulting in flue gas composed largely of carbon dioxide (CO2) and water, as well as contaminants from the fuel (including coal ash). The high concentration of CO2 and absence of nitrogen simplify separation of CO2 from the flue gas for storage or beneficial use. Thus, oxygen-fired combustion is an alternative approach for carbon capture and storage (CCS) for coal-fired systems. However, the appeal of oxygen-fired combustion is tempered by several challenges, namely the capital cost, energy consumption, and operational challenges of supplying oxygen to the combustion system, air infiltration that dilutes the flue gas with nitrogen, and purification processes to remove pollutants and excess oxygen from the concentrated CO2 stream. Consequently, advanced combustion research and development (R&D) is exploring technologies that can lower the cost of oxygen supplied to the system and/or increase the overall system efficiency. Cost-shared R&D is being performed both externally, by industry, research organizations, and academic institutions, and internally, through the National Energy Technology Laboratory’s (NETL) Research and Innovation Center (RIC), to develop oxy-combustion and chemical looping combustion (CLC) technologies to overcome these challenges.

Oxy-Combustion

The combustion of fossil fuels in nearly pure oxygen, rather than air, presents an opportunity to simplify CO2 capture in power plant applications.

In pressurized oxy-combustion, higher temperature latent heat is recoverable, heat transfer rates are increased, equipment size is reduced, and there is no air in-leakage, increasing efficiency and decreasing capital cost.

Alstom's 3-MWth Boiler Simulation Facility

The combustion of fossil fuels in nearly pure oxygen, rather than air, presents an opportunity to simplify carbon dioxide ( CO2) capture in power plant applications. Oxy-combustion power production provides oxygen to the combustion process by separating oxygen from air. However, the capital cost, energy consumption, and operational challenges of oxygen separation are a primary challenge of cost-competitive oxy-combustion systems. Oxy-combustion system performance can be improved by two means:

  1. by lowering the cost of oxygen supplied to the system and
  2. by increasing the overall system efficiency. The research and development (R&D) within the National Energy

Technology Laboratory’s (NETL) Transformative Power Generation Program is aimed at strategies to improve oxy-combustion system efficiency and reduce capital cost, offsetting the challenges of oxygen production.

In an oxy-combustion process, a pure or enriched oxygen stream is used instead of air for combustion. In this process, almost all the nitrogen is removed from the air, yielding a stream that is approximately 95 percent oxygen. Hence, the volume of flue gas, which is approximately 70 percent CO2 by volume, from oxy-combustion is approximately 75 percent less than from air-fired combustion. The lower gas volume also allows easier removal of the pollutants (sulfur oxide [SOx], nitrogen oxide [NOx], mercury, particulates) from the flue gas. Another benefit is that because nitrogen is removed from the air, NOX production is greatly reduced.

Oxy-combustion power production involves three major components: oxygen production (air separation unit [ASU]), the oxy-combustion boiler (fuel conversion [combustion] unit), and CO2 purification and compression. These components, along with different design options, are shown below. Oxy-combustion systems can be configured differently with these components, resulting in different energetic and economic performances.

Advanced oxy-combustion systems can be configured in either low- or high-temperature boiler designs. In low-temperature designs, flame temperatures are like that of air-fired combustion (~3,000°F), while flame temperatures exceed 4,500°F in the advanced high-temperature design. Low-temperature designs for new or retrofit applications recycle combustion products to lower the flame temperature to approximate the heat transfer characteristics of air-fired boilers. In high-temperature oxy-fuel combustion processes, fuel and oxygen are mixed at the burner undiluted with recycled flue gas, except to motivate coal for coal-fired systems. This process can result in a high flame temperature (>4,500°F), which enhances heat transfer in the radiant zone of the boiler. This process also results in more viable heat in the radiant zone of new or existing boilers and can result in a reduction in fuel demand at constant steam generation rates. High-temperature designs in new construction applications use increased radiant heat transfer to reduce the size and capital cost of the boiler. Furthermore, advanced emissions control systems for the removal of acid gases can enable recovery of latent heat in the flue gas.

Today’s state-of-the-art oxy-combustion systems would use a cryogenic process to supply oxygen; atmospheric-pressure combustion for fuel conversion in a conventional supercritical pulverized-coal boiler; substantial flue gas recycle; conventional pollution control technologies for SOx, NOx, mercury, and particulates; and mechanical CO2 compression. The Transformative Power Generation Program is developing advanced technologies to reduce the cost and improve the performance associated with current systems. R&D efforts are focused on developing pressurized oxy-combustion power generation systems. Currently, NETL supports several oxy-combustion projects in collaboration with industry and academia, ranging from lab- and bench-scale testing to verification testing at pilot scale. These projects are focused on understanding oxy-fuel combustion at high temperatures and pressures, verifying system design and operation concepts, and improving performance of ancillary system components.


Chemical Looping Combustion

CLC is oxy-fuel combustion without the need to separate oxygen from air prior to combustion, reducing energy demand and system costs while capturing CO2.

n chemical looping combustion, oxygen is created in-situ, eliminating the need to separate oxygen from air, reducing energy demand and system costs.

NETL-ORD Chemical Looping Pilot-Scale Reactor

The combustion of fossil fuels in nearly pure oxygen, rather than air, presents an opportunity to simplify carbon dioxide (CO2) capture in power plant applications. Oxy-combustion power generation provides oxygen to the combustion process by separating oxygen from air. However, chemical looping systems produce oxygen internal to the process, eliminating the large capital, operating, and energy costs associated with oxygen production.

In chemical looping combustion (CLC) systems, oxygen is introduced to the system via reduction-oxidation cycling of an oxygen carrier. The oxygen carrier is usually a solid, metal-based compound. It may be in the form of a single metal oxide, such as an oxide of copper, nickel, or iron, or a metal oxide supported on a high-surface-area substrate (e.g., alumina or silica), which does not take part in the reactions. For a typical CLC process, combustion is split into separate reduction and oxidation reactions in multiple reactors. The metal oxide supplies oxygen for combustion and is reduced by the fuel in the fuel reactor, which is operated at elevated temperature.

This reaction can be exothermic or endothermic, depending on the fuel and the oxygen carrier. The combustion product from the fuel reactor is a highly concentrated CO2 and water stream that can be purified, compressed, and sent for storage or beneficial use. The reduced oxygen carrier is then sent to the air reactor, also operated at elevated temperature, where it is regenerated to its oxidized state. The air reactor produces a hot spent gas stream, which is used to produce steam to drive a turbine, generating power. Then the oxygen carrier is returned to the fuel reactor, re-starting the reduction-oxidation cycle.


Current CLC research and development (R&D) efforts are focused on developing and refining oxygen carriers with sufficient oxygen carrying capacity, durability, and production cost to minimize one of the primary CLC operating costs; developing effective solids circulation and separation techniques; improving reactor design to support fuel and oxygen carrier choices; effective heat recovery and integration; and overall system design and optimization.


Advertisement

The 10 largest coal producers and exporters in Indonesia:

  1. Bumi Resouces
  2. Adaro Energy
  3. Indo Tambangraya Megah
  4. Bukit Asam
  5. Baramulti Sukses Sarana
  6. Harum Energy
  7. Mitrabara Adiperdana 
  8. Samindo Resources
  9. United Tractors
  10. Berau Coal

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...