Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet FGD Systems

Abstract

This document is the final technical report for Cooperative Agreement DE-FC26-04NT41992, "Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet FGD Systems," which was conducted over the time-period January 1, 2004 through December 31, 2010. The objective of this project has been to demonstrate at pilot scale the use of solid catalysts and/or fixed-structure mercury sorbents to promote the removal of total mercury and oxidation of elemental mercury in flue gas from coal combustion, followed by wet flue gas desulfurization (FGD) to remove the oxidized mercury at high efficiency. The project was co-funded by the U.S. DOE National Energy Technology Laboratory (DOE-NETL), EPRI, Great River Energy (GRE), TXU Energy (now called Luminant), Southern Company, Salt River Project (SRP) and Duke Energy. URS Group was the prime contractor.The mercury control process under development uses fixed-structure sorbents and/or catalysts to promote the removal of total mercury and/or oxidation of elemental mercury in the flue gas from coal-fired power plants that have wet lime or limestone FGD systems. Oxidized mercury not adsorbed is removed in the wet FGD absorbers and leaves with the byproducts from the FGD system.The project has tested candidate materials at pilot scale and in a commercial form, to provide engineering data for future full-scale designs. Pilot-scale catalytic oxidation tests have been completed for periods of approximately 14 to19 months at three sites, with an additional round of pilot-scale fixed-structure sorbent tests being conducted at one of those sites. Additionally, pilotscale wet FGD tests have been conducted downstream of mercury oxidation catalysts at a total of four sites. The sites include the two of three sites from this project and two sites where catalytic oxidation pilot testing was conducted as part of a previous DOE-NETL project. Pilot-scale wet FGD tests were also conducted at a fifth site, but with no catalyst or fixed-structure mercury sorbent upstream.This final report presents and discusses detailed results from all of these efforts, and makes a number of conclusions about what was learned through these efforts.

Oxidation Catalysts for Elemental Mercury in Flue Gases—A Review

“…An uneven distribution of the gas flow and the small channel width of 3.2 mm of the honeycomb catalyst contributed to the blocking. In summary it can be said that lab-scale, pilot-scale and full-scale mercury oxidation investigations show that gold-based catalysts are not subjected to fast deactivation under flue gas conditions [37,40,46]. One measurement campaign with respect to the SO 2 conversion did not result in an appreciable increase of the SO 3 content over the Au catalysts layer.…”

“…Recently, the potential use of gold-based catalysts in mercury pollution control applications has attracted much interest from academia as well as industry [29,30,37,40,46,47]. The studies have concentrated on the temperature range between 140 and 225 °C with, in most cases, 1 wt.-% gold on alumina and in one case with Au on a Teflon-coated quartz filter.…”

“…Pilot [39,46] and full scale [40,47] investigations were conducted with the main objective to demonstrate the effectiveness and deactivation properties of a commercial gold catalyst wash coated on γ-alumina honeycomb substrate in promoting Hg el oxidation in flue gases from coal combustion. The catalyst modules were located downstream of a particulate control device [47] and in the flue gas scrubber inlet duct [40].…”

Chemistry of Trace Inorganic Elements in Coal Combustion Systems: A Century of Discovery

“…Another method to enhance the removal of gaseous Hg is to oxidize the elemental mercury using a Pd- or Au-based catalyst with subsequent adsorption. − The URS method developed by Blythe and co-workers employs a fixed catalyst bed, while the method developed by Seames et al coats the catalyst on the clean side of a fabric filter. , …”

Tuning the Adsorption of Elemental Mercury by Small Gas-Phase Palladium Clusters: First-Principles Study

“…To increase the efficiency of the mercury-removal processes, various sorbents or catalysts may be used to capture and/or oxidize Hg 0 including activated carbon, metal oxides, metal sulfides, and pure metals . Transition and noble metals such as copper, silver, gold, and palladium have been outlined as suitable sorbents for Hg removal because of their thermodynamic and regeneration stabilities. − A pilot-scale study of Hg oxidation in flue gas conducted by Blythe et al suggested that the higher cost of precious metals (Au or Pd) can be offset by requiring less metal (44% less in volume) and a potential longer life compared to carbon-based sorbent catalysts. Recent studies have also predicted Pd to be the most promising candidate for Hg removal. , The catalytic reactivity of bulk Pd surfaces may be enhanced significantly in the form of nanoparticles (NPs) through deposition onto various support materials, including oxide supports. − Some recent studies − have shown that the presence of catalytic noble metal NPs such as Pd, Pt, and Ag on the surface of some metal oxides, specifically, ZnO, TiO 2 , and SnO 2 , can enhance the gas-sensing performances.…”