New FGD and DeNOx Approaches was the Hot Topic on Thursday April 7, 2011

The CAIR replacement rule, the regional haze rule, the NAAQS revisions, GHG regulations and the utility MACT will all push fossil fuel power plants to reduce NO_x and SO₂ even more, while at the same time achieving compliance with the limits for HCl, total particulates, and mercury in the Utility MACT proposed by the U.S. Environmental Protection Agency on March 16, 2011.  SCRs and FGD systems will be a primary method employed to achieve the reductions mandated by these rules. Yesterday five very knowledgeable speakers discussed the latest technology under development for meeting the MACT requirements and gave specific advice on the selection and application of SCR catalysts.

Shiaw Tseng, Marketing Manager at Graymont, Inc., described a multi-pollutant control system for existing coal-fired power plants using lime-based Circulating Dry Scrubbers (CDS) to remove SO₂, SO₃, HCl, and HF.  He presented the results of performance guarantee tests conducted at the AES Greenidge Station Unit #4 (107 MW) burning eastern bituminous coal (2.5 to 3 percent sulfur) with a CDS and baghouse. These tests showed pretty impressive reductions of SO₂, SO₃, Hg and HCl to levels that were well under the limits in the proposed utility MACT. Advantages of this system include a relatively small footprint, fuel flexibility (including biomass), low water consumption and dry byproducts (no wet sludge). Interestingly, the CDS system achieved better mercury reduction than using ACI under the same operating conditions, indicating that ACI is not required. These systems are currently operating at 14 plants in the U.S.

Dr. Sebastian Hirschberg, Manager of R&D Energy and Environment, Mixing and Reaction Technology at Sulzer Chemtech Ltd, called in from Switzerland describing how power plant operators can improve SCR reactor performance and save money by installing and using Sulzer static mixers. The primary point of his presentation was that properly designed static mixers with CFD modeling can eliminate the need for injection lances with their problems, while increasing catalyst life, improving NO_x reduction and reducing pressure drop.  An arc wire coating is also available to increase the service life in highly abrasive environments. There are over 35 plants in the U.S. using these Sulzer mixers.

Robert (Bob) Crynack, Business Development Manager for the Peroxygen Division of FMC Corporation, described a process under development by FMC that utilizes hydrogen peroxide to control NO_x from combustion sources and industrial processes. Injection of peroxide into existing ducts oxidizes the NO_x, primarily NO, to other nitrogen species that can be captured by existing downstream equipment such as wet scrubbers, CFB scrubbers, spray dryer absorbers or dry injection (lime/trona) with ESP or FF. The technology is intended for coal-fired power plants that desire NO_x reductions of 40-80 percent with minimal capital investment and low operating and maintenance cost. While it has been proven that hydrogen peroxide will oxidize NO, NO₂ and even mercury, the ability of downstream equipment to capture the NO_x and mercury are still being evaluated.

Ken Jeffers, SCR Applications Engineer at Johnson Matthey Catalysts LLC, gave a good overview of SCR technology and described new developments to improve the life and performance of catalysts. Advances include ammonia slip control catalysts to allow higher injection rates and extend the useful life of catalysts while achieving up to 95 percent NO_x reduction, catalysts being developed with enhanced Hg oxidation capability while preserving performance on deNO_x and SO₂ oxidation, and catalysts for high as well as lower temperature operation. He also discussed the major problems with SCR catalysts particularly flyash plugging and deactivation. Potential solutions include tail end applications. He said that there was a tradeoff between the cost to install and operate a flue gas reheat system and the potential longer life of the catalyst in a tail end position. Ken stated that there are now three units operating successfully on plants firing Texas lignite.

Brian Adair, Director of Technology at CoaLogix, coined a new term in his presentation calling SRCs “Multi-Pollutant Reduction Reactors” or MPRRs because they should now be looked at as devices to control SO₃ and mercury as well as NO_x. The focus of his talk was why an operator should treat a catalyst as an asset rather than a consumable. He stated that operators need to balance the different goals of deNO_x, SO₂ conversion, NH₃ usage, pressure drop and mercury oxidation and to have a different way of long term planning. When a catalyst layer is no longer optimum for the operating conditions, it can be traded in for a different type or formulation or sold to another plant where it will achieve their objectives.

Bios, Abstracts and Photos are shown below.

BIOS, ABSTRACTS, PHOTOS - April 7, 2011.htm