title: Differential partitioning and speciation of Hg in wet FGD facilities of two Spanish PCC power plants.
abstract: This paper evaluates the speciation and partitioning of mercury in two Spanish pulverised coal combustion power plants (PP1 and PP2), equipped with wet limestone-based flue gas desulphurisation facilities (FGD) operating with forced oxidation and re-circulation of FGD water streams. These plants are fed with coal (PP1) and coal/pet-coke blends (PP2) with different mercury contents. The behaviour, partitioning and speciation of Hg were found to be similar during the combustion processes but different in the FGD systems of the two power plants. A high proportion (86-88%) of Hg escaped the electrostatic precipitator in gaseous form, Hg2+ being the predominant mercury species (68-86%) to enter the FGD. At this point, a relatively high total Hg retention (72% and 65%) was achieved in the PP1 and PP2 (2007) FGD facilities respectively. However, during the second sampling campaign for PP2 (2008), the mercury removal achieved by the FGD was much lower (26%). Lab-scale tests point to liquid/gas ratio as the main parameter affecting oxidised mercury capture in the scrubber. The partitioning of the gaseous mercury reaching the FGD system in the wastes and by-products differed. In the low mercury input power plant (PP1) most of the mercury (67%) was associated with the FGD gypsum. Moreover in PP2 a significant proportion of the gaseous mercury reaching the FGD system remained in the aqueous phase (45%) in the 2007 sampling campaign while most of it escaped in 2008 (74%). This may be attributed to the scrubber operating conditions and the different composition and chemistry of the scrubber solution probably due to the use of an additive.
authors.affiliation: Instituto Nacional del Carbón (INCAR-CSIC), Francisco Pintado Fé, 26, 33011 Oviedo, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Ochoa-González
authors.forename: P
authors.initials: P
authors.lastname: Córdoba
authors.forename: M
authors.initials: M
authors.lastname: Díaz-Somoano
authors.forename: O
authors.initials: O
authors.lastname: Font
authors.forename: M A
authors.initials: MA
authors.lastname: López-Antón
authors.forename: C
authors.initials: C
authors.lastname: Leiva
authors.forename: M R
authors.initials: MR
authors.lastname: Martínez-Tarazona
authors.forename: X
authors.initials: X
authors.lastname: Querol
authors.forename: C Fernández
authors.initials: CF
authors.lastname: Pereira
authors.forename: A
authors.initials: A
authors.lastname: Tomás
authors.forename: P
authors.initials: P
authors.lastname: Gómez
authors.forename: P
authors.initials: P
authors.lastname: Mesado
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000302:isolation & purification; D002119:Calcium Carbonate / Q000737:chemistry; D004784:Environmental Monitoring; D008628:Mercury / Q000032:analysis* / Q000302:isolation & purification; D010084:Oxidation-Reduction; D011210:Power Plants / Q000295:instrumentation*; D013030:Spain
chemical_list: D000393:Air Pollutants; D008628:Mercury; D002119:Calcium Carbonate