Synergistic Mercury Removal by Conventional Pollutant Control Strategies for Coal-Fired Power Plants in China

Abstract

China's 11th 5-yr plan has regulated total sulfur dioxide (SO 2 ) emissions by installing flue gas desulfurization (FGD) devices and shutting down small thermal power units. These control measures will not only significantly reduce the emission of conventional pollutants but also benefit the reduction of mercury emissions from coalfired power plants. This paper uses the emission factor method to estimate the efficiencies of these measures on mercury emission abatement. From 2005 to 2010, coal consumption in power plants will increase by 59%; however, the mercury emission will only rise from 141 to 155 t, with an increase of 10%. The average emission rate of mercury from coal burning will decrease from 126 mg Hg/t of coal to 87 mg Hg/t of coal. The effects of the three desulfurization measures were assessed and show that wet FGD will play an important role in mercury removal. Mercury emissions in 2015 and 2020 are also projected under different policy scenarios. Under the most probable scenario, the total mercury emission in coal-fired power plants in China will decrease to 130 t by 2020, which will benefit from the rapid installation of fabric filters and selective catalytic reduction.

Uncertainties in estimating mercury emissions from coal-fired power plants in China

“…As these parameters used in our new sub-module involve uncertainties, we establish probability distribution functions for them on the basis of the available data. Many of these were already collected and published in our previous papers (Streets et al, 2005(Streets et al, , 2008Wu et al, 2006), supplemented with other newly available test data from various researchers. To accomplish this, the data from each source type are read into Crystal Ball TM , a statistical software package, which, based on the number of data points and scatter of the data, attempts to fit a distribution about the data for that source type.…”

“…Hg emissions are speciated using technology-specific factors and gridded for use in atmospheric models. A detailed estimation of China's mercury emissions by province for the year 1999 is presented in Streets et al (2005), and the trends in anthropogenic Hg emissions in China from 1995 to 2003 are presented in Wu et al (2006). Hg emissions were stable at around 540 (±20) Mg during the period 1995-2000, but increased quickly to nearly 700 Mg in 2003.…”

“…Hg emissions were stable at around 540 (±20) Mg during the period 1995-2000, but increased quickly to nearly 700 Mg in 2003. Coal combustion and nonferrous metals production continue to be the two leading mercury sources in China, together contributing ∼80% of total mercury emissions over the past decade (Wu et al, 2006). However, many uncertainties still remain in our knowledge of primary anthropogenic releases of mercury to the atmosphere in China.…”

“…Based on a preliminary uncertainty analysis with coefficients of variation of various contributing factors and combining total uncertainties with quadrature average, approximately ±40% for power plants, ±60% for industrial coal use, and even larger uncertainty ranges for other sources were estimated for Hg emissions in China in 1999 (Streets et al, 2003a(Streets et al, , 2005. Further, the gap between Hg emission inventories and atmospheric observations (Friedli et al, 2004;Jaffe et al, 2005;Pan et al, 2006;Weiss-Penzias et al, 2007;Wu et al, 2006), has been driving an urgent need to better understand the uncertainties embedded in the Hg emission estimate.…”

“…In this paper, we present a new comprehensive sub-module within our previous Hg emission inventory (Streets et al, 2005;Wu et al, 2006) for estimation of Hg emissions from coal-fired power plants in China as an uncertainty case study. With this effort, stochastic simulation capability is incorporated into the model to address uncertainties.…”