Lab-scale evaluation of possible mercury speciation in flue gas and mercury emission from combustion of pulverised solid fuels

Maciej Cholewiński,Wiesław Rybak

doi:10.1051/epjconf/201920106001

Abstract

In this work a new lab-scale method dedicated to the evaluation of both concentration and oxidation level of mercury in flue gases from pulverised fuel fired boiler was proposed. To detect the abovementioned parameters, 2 main steps need to be evaluated. Firstly, a calorimeter bomb is utilised - by a proper implementation of mass balance of mercury within substrates and products, the quantity of oxidised mercury in gaseous products can be evaluated. Then, to simulate solid fuel fired power unit and to calculate mercury concentrations in flue gases, one of the stoichiometric mathematical models of combustion process must be applied. Early validation of the method showed considerable differences between solid fuels in mercury oxidation efficiencies and concentrations in flue gasses. Four examined fuels (lignite, hard coal and 2 types of solid biomass) was investigated. Calculated mercury concentrations in raw flue gas (>700°C) varied between 4 and 75 µg/m3ref. The lowest quantity of oxidised forms ofHg in flue gases were identified in the case of investigated lignite (27% of total Hg), while significantly higher – for selected hard coal (72%) and one type of biomass (with high chlorine concentration; up to 98%).

Highlights

Mercury, a chemical element with an extremely negative impact on living organisms, has been classified by the European Union as a dangerous industrial pollutant and, as a result, included into the pro-environmental EU energy policy
While mercury speciation is affected by the composition of solid fuel, combustion working parameters of combustion chamber and pollutant control devices, the economy of mercury capture depends significantly on the type of fuel used in power plant [6,7]
The procedure presented in this paper, dedicated to pulverised fired power plants, highlights the significant variations in mercury oxidation levels in flue gases from different solid fuels

Summary

Introduction

A chemical element with an extremely negative impact on living organisms, has been classified by the European Union as a dangerous industrial pollutant and, as a result, included into the pro-environmental EU energy policy. This fact becomes important in the Polish power sector, where several new atmospheric emission standards (i.a. Directive 2010/75/EU) will affect significantly the economy of coal-based both electricity and heat generation activities in few years. While mercury speciation is affected by the composition of solid fuel, combustion working parameters of combustion chamber and pollutant control devices, the economy of mercury capture depends significantly on the type of fuel used in power plant [6,7]. To prove its functionality and prove the existence of substantial differences in mercury oxidation for different solid fuels, the first results for 4 materials are presented as well

Materials and methods

Results

Conclusions