NETL’s Power Plant Water Management R&D
In order to address issues related to water use in the generation of electricity, NETL is pursuing an aggressive R&D effort directed at developing technologies and approaches to better manage how coal-fired power plants use and impact freshwater resources. The overall goal is to reduce the amount of freshwater needed for power plant operations and to minimize potential impacts on water quality.
The research encompasses laboratory and bench-scale activities through pilot- and full-scale demonstrations and is built upon partnership and collaboration with industry, academia, technology developers, and other government organizations. The program is built around three specific areas of research: nontraditional sources of process and cooling water, innovative water reuse and recovery, and advanced cooling technology.
Nontraditional Sources of Process and Cooling Water Research. This research area seeks to develop innovative technologies to utilize lower-quality water for power plant cooling and related process needs. For example, one of the projects being conducted is titled "Reuse of Produced Water from CO2 Enhanced Oil Recovery, Coal-Bed Methane, and Mine Pool Water by Coal-Based Power Plants." The Illinois State Geological Survey is evaluating the feasibility of reusing three types of nontraditional water sources for cooling or process water for existing and planned coal-fired power plants in the Illinois Basin. The three types of nontraditional water sources are:
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Produced water from CO2 -enhanced oil recovery (EOR).
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Coal-bed methane recovery.
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Active and abandoned underground coal mines.
Increasing public resistance to the withdrawal or consumption of freshwater for industrial purposes suggests that the use of nontraditional water sources in power plants may alleviate the expected increase in water demand. Power plant usage of water produced by CO2 -EOR may be an environmentally sustainable alternative for "closing the CO2 -water loop," as illustrated in Figure 4.
4. Closing the CO2-water loop. CO2 is produced in the generation of electricity and then it is injected into depleted oil and gas reservoirs to enhance oil recovery. Water produced in the process is treated and returned to the power plant for cooling and other purposes. Source: U.S. Department of Energy’s National Energy Technology Laboratory
Innovative Water Reuse and Recovery Research Area. This research area focuses on development of advanced technologies to recover and reuse water from such power plant processes as coal dewatering and flue gas dehumidification. One of the projects in this research area is called "Water Extraction from Coal-Fired Power Plant Flue Gas." Coal naturally contains water (3% to 60% by weight), and the combustion process releases additional water as hydrogen as the coal is reacted with oxygen. The amounts of water that can be recovered from flue gas are sufficient to substantially reduce the need for off-plant sources of water. Currently, there is no practiced method of extracting the water from power plant stack gas.
The University of North Dakota Energy and Environmental Research Center is conducting a project to capture water from flue gas in both PC and IGCC applications. This research uses liquid desiccant – based dehumidification technology to efficiently extract water from the power plant flue gas. It requires minimal heat rejection equipment, can function across the entire ambient range, and has minimal impacts on power plant efficiency.
The liquid desiccant – based system is placed at the exhaust end of a coal-fired power plant and utilizes low-grade heating and cooling sources available in the plant. The flue gas is cooled and then subjected to a liquid desiccant absorption process, which removes water from the flue gas. Once the water is removed from the flue gas, the desiccant is heated to remove the water, and the water vapor is condensed and can be used in other plant processes.
Advanced Cooling Technology. This component of the EPEC program is working to develop advanced wet, dry, and hybrid cooling systems. One of the projects under way in this research area is called "Air2Air Technology to Reduce Freshwater Evaporative Cooling Loss." For this project, SPX Cooling Technologies is investigating the use of an air-to-air heat exchanger above a wet cooling tower, as shown in Figure 5. It takes warm, humid air from the cooling tower and contacts it with cooler, dry air from outside to condense and recover a portion of the water that just evaporated from the cooling tower.
5. Air2Air cooling technology. The tower on the far left of the photo includes Air2Air technology. Note that the steam plume coming from the other towers is effectively eliminated in the Air2Air tower. Source: U.S. Department of Energy’s National Energy Technology Laboratory
This system has the potential to condense as much as 20% of the cooling water that would have been lost to evaporation. If this technology were applied to all wet recirculating cooling towers in the U.S., the water savings could reach 1.56 bgd. In addition, these units are very effective at steam plume abatement. Initial tests of the technology produced positive results, and now follow-up work is focused on analysis of improved geometries of airflow through the units as well as improved seals to enhance liquid capture.
Looking Ahead
The production of electricity, the deployment of CCS, and water use all raise a wide variety of societal issues, policy and regulatory debates, environmental questions, and technological challenges. Water in particular is emerging as a significant factor in economic development activities. Given the extent to which CCS may increase water withdrawal and consumption, the impact of CCS on water resources must be considered and better understood in order to accommodate future energy and water needs.
Planning efforts must consider the availability and quality of water resources in a given locality or region in order to ensure that supplies are available to accommodate existing and future water consumers. Failure to do so can result in growth limitations, inequitable development, heated public debate, and litigation regarding usage priorities. In order for the energy industry to be environmentally responsible, technologically ready, and economically stable, advanced research to explore and resolve water issues and their relationship to CCS is imperative.
—J.P. Ciferno (jared.ciferno@netl.doe.gov) is technology manager, existing plants, Emissions & Capture, Office of Coal and Power R&D, National Energy Technology Laboratory, U.S. Department of Energy. R.K. Munson (ronald.munson@lt.netl.doe.gov) and J.T. Murphy (james.murphy@lt.netl.doe.gov) are senior engineers with Leonardo Technologies Inc. B.S. LaShier (brian.lashier@ba.netl.doe.gov) is a scientist for Booz Allen Hamilton.
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