Mercury speciation in gypsums produced from flue gas desulfurization by temperature programmed decomposition

[EN] Temperature programmed decomposition was used to identify mercury (Hg) species in gypsum samples produced from flue gas desulfurization in two Spanish power stations (A and B). As stricter emission control/reduction policies, particularly those focusing on Hg, are being implemented, wet flue gas desulfurization (FGD) technologies used for the removal of SO2 can result in the co-removal of highly-soluble oxidized Hg. The amount of Hg retained in FGD products may increase in the future if these units are optimized for co-capture. For this reason, it is important to identify the mercury species in FGD products not only to determine the potential risk when the wastes are finally disposed of, but also to understand the behaviour of mercury during combustion and therefore to improve the technologies for mercury removal. Different mercury species were identified in the gypsum samples. In power station A, HgS were the most probable Hg species, whereas in power station B the main compound was Hg halogenated compounds.This work was supported by the project ABETRAP (RFCR-CT-2006-00006). The authors would like to thank INCAR (CSIC), IJA/IDEA (CSIC) and ENDESA. S.A. for providing the samples employed in this study and the programme of postdoctoral contracts abroad by Ministerio de Ciencia e Innovacion.Peer reviewe

Mercury speciation in co-combustion by-products from full scale power stations

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Study of mercury in by-products from a Dutch co-combustion power station

[EN] Fly ashes and gypsum are one of the main wastes produced in coal-fired power stations which may be sent to landfills for their disposal. In this work, leaching and speciation of mercury in fly ashes and gypsum from a modern co-combustion power plant equipped with a selective catalytic reduction (SCR) unit in the Netherlands were studied. The mercury leachable contents were checked against different regulations, including Dutch, German and the Council Directive 2003/33/EC. The speciation of mercury in coal combustion products is essential not only to determine the risk when the wastes are finally disposed but also to understand the behaviour of mercury during combustion and therefore to select the appropriate mercury removal technology. A temperature-programmed decomposition technique was used in order to identify and quantify which mercury species are associated with coal combustion products. The main mercury species identified in fly ash samples was mercury sulphate, whereas in the gypsum sample the mercury present was mercury chloride. The quantitative mercury results carried out using the thermal desorption method may be considered accurate. The results obtained show that fly ash and gypsum samples from this power plant can be acceptable at landfills as a non-hazardous waste.The financial support for this work was provided by the project ABETRAP (RFCR-CT-2006-00006) and Ministerio de Ciencia e Innovacion (programme of postdoctoral contracts abroad).Peer reviewe

Speciation of Hg retained in gasification biomass chars by temperature-programmed decomposition

The development of elemental mercury (Hg0) capture technology for coal-fired power plants is essential for achieving the goal of zero emissions from coal derived flue gas. Sorbents such as biomass gasification chars have proved to be effective for mercury capture and offer the added advantage of their low cost since they are sub-products of the thermal conversion process. However, the mercury species captured on the sorbents have not yet been characterized. In this study, a temperature programmed decomposition technique was used to identify the mercury species captured on the sorbents and to clarify the mechanisms responsible for mercury retention. The mercury species formed were observed to be dependent on char characteristics and flue gas composition. The results showed that mercury chloride was the most likely mercury species in a simulated coal combustion atmosphere from the chars obtained from poultry litter, sunflower husks and paper and plastic waste, the last two containing small amounts of mercury sulphate. The mercury compounds identified in the char from the gasification of wood waste were mainly sulphide and sulphate species.The financial support for this work was provided by the project CTM2011-22921. The authors thank the Energy Research Centre of the Netherlands for supplying the chars employed in this study and the Spanish Research Council (CSIC) for awarding Ms. Aida Fuente-Cuesta a pre-doctoral fellowship and Ma. Antonia Lopez-Anton with a JAE-Doc contract (European Social Fund).Peer reviewe

Mercury policy and regulations for coal-fired power plants

Introduction Mercury is a high-priority regulatory concern because of its persistence and bioaccumulation in the environment and evidence of its having serious adverse effects on the neurological development of children. Discussion Mercury is released into the atmosphere from both natural and anthropogenic sources. Coal-fired utilities are considered to be one of the largest anthropogenic mercury emission sources. The period since the late 1990s has been marked by increasing concern over mercury emissions from combustion systems to the extent that a number of national governments have either already implemented or are in the process of implementing, legislation aimed at enforcing tighter control over mercury emissions and a reduction in mercury consumption. Conclusion This review examines the most important national and international policies and agreements for controlling mercury emissions from coal-fired combustion systems. To provide a global perspective, this study lists the countries with the largest estimated mercury emissions and regulatory efforts to reduce them.Peer reviewe

Unusual speciation and retention of Hg at a coal-fired power plant

An unusual and different speciation of Hg in the outgoing gaseous stream of the flue gas desulfurization (OUT-FGD) system was revealed at two Spanish power plants (PP1 and PP2) equipped with a forced oxidation wet FGD system with water recirculation to the scrubber. At PP1 and PP2, a high proportion of Hg escapes from the electrostatic precipitator in gaseous form, Hg2+ (75–86%) being the species that enters the FGD. At PP1 Hg0 (71%) was the prevalent Hg OUT-FGD species, whereas at PP2 Hg2+ was the prevalent Hg OUT-FGD species in 2007 (66%) and 2008 (87%). The unusual speciation of gaseous Hg OUT-FGD and the different Hg retentions between 2007 and 2008 at PP2 were attributable to the evaporation of HgCl2 particles from the aqueous phase of gypsum slurry in the OUT-FGD gas and the Al additive used at PP2, respectively. The Al additive induced the retention of Hg as HgS in the 2007 FGD gypsum, thus reducing gaseous emissions of Hg in the OUT-FGD gas