Emission-limit-oriented strategy to control atmospheric mercury

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Emission-limit-oriented strategy to control atmospheric mercury emissions in coal-fired power plants towards the implementation of Minamata Convention Qingru Wu, Shuxiao Wang, Kaiyun Liu, Guoliang Li, and Jiming Hao Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b02250 • Publication Date (Web): 07 Sep 2018 Downloaded from http://pubs.acs.org on September 12, 2018

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Environmental Science & Technology

Emission-limit-oriented strategy to control atmospheric mercury emissions in coal-fired power plants towards the implementation of Minamata Convention Qingru Wu,†,‡ Shuxiao Wang,*,†,‡ Kaiyun Liu,† Guoliang, Li†, and Jiming Hao†,‡ †

State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of

Environment, Tsinghua University, Beijing 100084, China ‡

State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex,

Beijing 100084, China E-mail address: [email protected]

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TOC Art

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Abstract

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Emission limit is a significant index of pollution control in most countries. However, the

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determination of a reasonable limit value and corresponding supported technical paths is always

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a challenge during the implementation procedure. In this study, we developed an

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emission-limit-oriented strategy which links the emission limit with reduction amount via

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technical paths, so as to control the Hg emissions in the coal-fired power plants in China. Results

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indicate that tightening emission limit does not always guarantee the reduction of Hg amounts,

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especially when coal consumptions keep increasing during the economic growth period. By

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comprehensively considering the feasibility of different technical paths, the emission limit of 5

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µg/m3 is recommended to be executed in 2025. Under the guidance of this limit, the reduction

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amount of emitted Hg will reach as large as 63 t during 2015-2025 by primarily using

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multi-pollutant control measures. During 2025-2030, both alternative energy measures and

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specific Hg removal measures will be applied to achieve the emission limit of 1 µg/m3 in 2030.

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The assessment method developed in this study can be used to establish the

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emission-limit-oriented control strategies in other countries or industries, which will assist the

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success of the Minamata Convention on Mercury.

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19

1 Introduction

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Anthropogenic mercury (Hg) emissions have risked the global ecosystem and human health

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due to the toxicity, persistence, long-distance transport, and bioaccumulation of Hg in the

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environment.

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the Minamata Convention on Mercury (abbreviated as Convention) which has been effective

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since Aug 16, 2017. Coal-fired power plants (CFPPs) are the largest atmospheric Hg emission

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sources7 and have been listed as one of the key controlled targets.8

1-6

Therefore, reducing atmospheric Hg emissions has been a compulsive goal of

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To effectively control global atmospheric Hg emissions, five measures in the Convention

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are recommended, including 1) setting a quantified goal; 2) establishing multi-pollutant control

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measures; 3) adopting alternative measures; 4) using best available techniques and best

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environmental practices (BAT/BEP); and 5) defining emission limits.

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emission limit is generally applied as a significant index for pollution control. Such method is

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convenient for the supervision and inspection of emission control. But how to determine the

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value of the emission limit is always a problem. Loose emission limits might result in ineffective

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pollution control. Oppositely, both the governments and plants will suffer heavy financial burden

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or lack feasible technical paths. In addition, corresponding supporting measures to achieve the

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emission limits are also integrated parts to guarantee the success of pollution control.

8

In most countries, the

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To effectively control atmospheric Hg emissions, we develop an emission-limit-oriented

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strategy which links the emission limit with Hg reduction amount directly and is supported by

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the use of technical paths and alternative measures. This method is applied to control the

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atmospheric Hg emissions in the CFPPs of China. The detailed procedures are introduced in the

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methodology part. To be brief, this method includes the following steps. First, we evaluate

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current Hg emission limit (30 µg/m3) 9 for the CFPPs in China and determine future options for

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CFPPs by comparing international standards as well as using monitoring data and simulation

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results. Then we choose the technical paths for corresponding emission limits based on the Hg

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removal efficiency of each air pollution control device combinations (APCDs) in the technical 4


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paths. At last, future Hg emissions for CFPPs under different emission limit scenarios are

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developed, so as to identify the mitigation potential of the Hg and to determine the most effective

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limit. By using this method, both the future emissions and technical paths/alternative measures

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leading to the emissions are observable under different limit scenarios. Consequently, policy

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makers can reduce the emissions by determining a reasonable and effective emission limit.

50 51

2 Methodology 2.1 Technical paths for the emission limits

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We determine the technical paths to achieve different emission limits by the following steps.

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(1) Current limit evaluation

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The existing monitoring data in Chinese CFPPs are collected through literature review to

55

evaluate the gap between existing emission limit and actual emissions. Then we compare the air

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Hg emission limit of China’s CFPPs (GB 13223-2011)

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international level of existing limit in China (Table S1). These two works are done to warrant the

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necessity and possibility of limit revision.

9

with foreign limits to evaluate the

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(2) Control technologies investigation

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The BAT/BEP guidance under the article 8 of the Convention provides a draft database of

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APCDs. Then both commercial and potential APCDs used in China’s CFPPs are collected

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mainly through literature review and expert judgments to enrich the database. During this

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process, both Hg removal efficiencies and the range of emitted Hg concentrations from field

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experiments of each APCD combination are also collected. If there is no tested data of a certain

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APCD combination, we will split the APCD combination to several tested sub-combinations of i

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and calculate the Hg removal efficiency according to equation (1).

η = 1 − ∏ (1 −ηi )

67 68 69

(1)

where η and ηi is the Hg removal efficiency of the type of APCD combination and the i sub-combination. 5



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(3) Technical paths determination

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Relationship between Hg removal efficiency of APCDs and the final emitted Hg

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concentration is established by the following equations.

ρ gas =

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Ccoal × γ × (1 − η ) V

η =1-

(2)

ρ gas ×V Ccoal × γ

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That is

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where ρgas is the simulated Hg concentrations in the exhausted gas, µg/m3. Ccoal is the Hg

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contents of coal, mg/kg. The Hg contents of coal are reported in our previous studies. 4, 10-13 We

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further improve the database by collecting data from Chinese Academy of Sciences. Batch fit of

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the Hg concentrations in the 763 coal samples indicates that the Hg concentrations fit lognormal

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distribution and the mean concentration is 0.18±0.24 mg/kg. V is the gas volume required to

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combust 1 t coal, m3/t. In China, the value of V is generally in the range of 8500-12000 m3/t coal

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combusted. To be conservative, we use the lowest value of 8500 m3/t to promote a higher

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requirement of Hg removal efficiency. γ is the release rate of Hg from coal to the flue gas, %.

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The Hg release rate is generally more than 99% according to previous field experiments in

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CFPPs. 13-18 Therefore, the requirement for the Hg removal ability of APCDs will mainly depend

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on the Hg concentrations in the exhaust gas once the range of Hg contents of coal is determined.

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Based on both step (2) and step (3), we can classify the APCDs to three technical paths so as to

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achieve different Hg emission limits by using the parameter of Hg removal efficiency as a link.

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The three technical paths will be detailed introduced in section 3.2.

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2.2 Estimation of Hg emissions

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(1) Estimation method

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(3)

Hg emissions in 2015 are regarded as a basic scenario. The detailed calculation procedure 19

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has been described in our recent study.

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scenarios, we follow our previous estimation method,

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Carlo simulations to estimate future Hg emissions.

To evaluate Hg reduction potential in different 4, 10, 19

6


which is embedded with Monte

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E s = As Ccoal (1 − f s w) ∑ γ j (1 − Pj , sη j )

(4)

j

95

where Es is the Hg emissions under scenario s, t. A is coal consumption, Mt (See section

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2.2.2). j is the type of APCD combinations (Table 1). Ccoal is the distribution characteristics of

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Hg contents of coal, mg/kg. Future Hg contents of the consumed coal are assumed to be

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unchanged. f is the proportion of washed coal used in China, %. The proportion of f is

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approximately 1.5% in 2015, 20 which is assumed to reach 3% in 2025 and 5% in 2030. w is the

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probabilistic distribution of the Hg removal efficiency of coal washing, %. We assume that the

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removal efficiency of coal washing has a normal distribution and the value is 30%±10%.7γ is

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Hg release rate, %. P is the application rate of different APCD combinations, % (See section 3.2).

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η is the probabilistic distribution of Hg removal efficiency of a certain type of APCD

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combination, % (Table 1). The Hg removal efficiency of ESP+WFGD fits Weibull distribution

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and we assume that Hg removal efficiencies of other APCD combinations fit normal distribution.

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(2) Uncertainty analysis

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Hg removal efficiency of a certain APCD is assumed to be unchanged during 2015-2030.

We use the Monte Carlo simulations to calculate the uncertainty.

11

We run the simulations

109

for 10,000 times and get the results in the form of a statistical distribution. Key characteristics of

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the simulation curves include P20, P50, and P80 values. The P20, P50, and P80 mean that the

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probabilities of actual results less than corresponding values were 20%, 50%, and 80%,

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respectively. We calculate the uncertainty range according to equation (5) following our previous

113

study. 11

±

u =

Mo − σ s±σ k±

P50

(5)

−1

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where u is the uncertainty. Mo is the mode value. σs+ and σs- are the distances between Mo

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and the values where the probability equal to f(Mo)/2; σk+ and σk- are the distances between Mo

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and P20 or P80. 7



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(3) Projection of future coal consumption in CFPPs

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Coal consumption in CFPPs reached 1884 Mt in 2015. Future coal consumptions in CFPPs

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are predicted mainly based on the development of electricity production, clean energy power and

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standard coal consumption by using electricity elasticity coefficient method (Table 2). Two

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scenarios are developed to predict future coal consumption, including a reference scenario (R)

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and an alternative policy scenario (A). The R scenario is based on the implementation status of

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current legislations (until the end of 2015) and forecast coal consumption in CFPPs according to

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a conservative economy developing trend. In the A scenario, we assume that the implementation

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of the Convention, the strict requirement of domestic pollution control, as well as the carbon

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reduction pressure will reduce the coal consumption by promoting alternative measures such as

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energy-saving and structural transformation measures. Thus, the comparison of these two

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scenarios aims to reflect the control effect by using alternative measures. In 2015, total electricity

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production reached 5740 TWh. The aim of annual growth rate of gross domestic product (GDP)

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is above 6.5% during 2015-2020.

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China, the GDP growth rate is expected to decrease to 6.0%/5.5% in 2025 and 5.0%/4.5% in

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2030 under the R/A energy scenarios, respectively (Table 1). The electricity elasticity coefficient

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has decreased from 1.41 in 2010 to 0.76 in 2015. With the industrial upgrading and urbanization

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process, the electricity elasticity coefficient is assumed to be decreased to the range of 0.65-0.70.

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21

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0.53/0.40 in 2025/2030 under the A energy scenario, respectively. Based on the above

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information, the total electricity production is to be 8139/8898 TWh in in 2025/2030 under A

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energy scenario, respectively. The penetration of clean energy power is expected to increase

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rapidly in the coming future and the proportion of coal-fired electricity will decrease. By

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completely considering the recent released development plan for power plants

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pollution control action plan 23, future standard coal consumption will decrease from 297 g/kWh

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in 2015 to 280 g/kWh in 2030. Therefore, coal consumptions for R/A scenarios will be

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Considering the end of industrialization around 2020 in

We assume that the trend will keep to 2030 and the electricity elasticity coefficient will be

8


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and air

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2208/1888, and 2038/1622 Mt in 2025 and 2030, respectively.

3 Results and discussions 3.1 Evaluation of existing Hg emission limit

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Figure 1(a) shows the emitted atmospheric Hg concentrations of 56 CFPPs which are tested

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in China after 2010 (See Table S2 for detailed data). The type of coal consumed in these plants

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covers bituminous coal, anthracite, lignite, and blended coal. The boiler type includes both

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pulverized coal furnace (PC) and circulating fluidized bed, the two dominant coal combustion

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boilers in China.

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APCD configurations and locations of CFPPs. 19 The average emitted Hg concentration from the

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CFPPs of China is 3.3 µg/m3 (0.1-12.8 µg/m3). Approximately 75% of the tested CFPPs can

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achieve the emission limit of 5 µg/m3 and emitted Hg concentrations in 34% CFPPs are lower

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than 1 µg/m3. The overall emitted Hg concentrations in these CFPPs are quite lower than current

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emission limit of 30 µg/m3 for the CFPPs in China.

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The tested plants are also chosen by considering the representativeness of

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From a national perspective, the distribution of simulated Hg concentrations in the exhaust

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gas of CFPPs of China is calculated according to equation (2) and the result is presented in Fig.

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1(b). The simulated Hg concentrations fit the lognormal distribution, which are characterized

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with “long tail” and the maximum value deviates far away from the median value. Therefore, to

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avoid irrationally too strict emission limit, we use P95 instead of the maximum value to

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determine the Hg emission limit. Correspondingly, the minimum value is replaced with P5 value.

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The P5 and P95 means the probabilities of 5% and 95% that the actual results are no more than

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corresponding values read from the curve. Therefore, the emitted Hg concentrations in the

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exhaust will be in the range of 2-68 µg/m3 (P5-P95) when there are no APCDs applied (curve

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ρno). Under this situation, there is a chance that the emitted Hg concentrations will be larger than

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current emission limit when the Hg contents of coal are higher than 25 mg/kg. To make the P95

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value decrease from 68 to 30 µg/m3 (curve ρ30), the maximum Hg removal efficiency of APCDs

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should be no less than 56%. Actually, the average Hg removal efficiency of the installed APCDs 9



4

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in the power plants has reached 73% in 2014.

Thus, we assume that the existing APCDs in

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China’s CFPPs can reach the emission limit of 30 µg/m3.

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However, the existing emission limit for the CFPPs in China is much higher than those in

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Canada and USA (Fig.1(a) and Table S2). The emission limit for new CFPPs in the USA

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designed for non- low rank virgin coal even reaches as low as approximately 0.4 µg/m3, which is

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only 0.013 times of the present value in China. The emission limits for the existing CFPPs in the

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USA are further divided according to the coal quality. The emission limit for CFPPs designed for

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low rank virgin coal (subbituminous coal and anthracite) is approximately 5.08 µg/m3, under

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which the tested CFPPs in China using anthracite can achieve standard emission. However, the

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average Hg concentration in the CFPPs using bituminous coal, which is the most popular coal

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type consumed in China’s CFPPs, is about 4.0 (0.2-11) µg/m3. This is approximately 2.2 times of

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that for the existing USA’s CFPPs designed for non-low rank virgin coal (bituminous coal and

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lignite). The emission level in the CFPPs of China using bituminous coal is also higher than the

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new emission limit of 2.3 µg/m3 for the new CFPPs using bituminous coal or blends in Canada.

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Therefore, current emission limit for the CFPPs in China can be revised for better pollution

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control.

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3.2 Technical paths to support the emission limits

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We set future scenarios of Hg emission limits in China into three levels by comprehensively

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considering the Hg concentrations in the exhaust gas and the international standards. That is 15,

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5, and 1 µg/m3, respectively. To achieve these limits, corresponding technical paths will be

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required. We use the Hg removal efficiency as a criterion for technology selection. Based on

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equation (3), the Hg removal efficiencies of the APCDs will fit minimal extreme value

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distribution characteristics due to the various Hg concentrations in the coal (Fig. 2). The

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corresponding P95 values of the Hg removal efficiencies of the technical paths will be 69.2%,

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92.7%, and 98.5% for the emission limits of 15, 5, and 1 µg/m3, respectively. Thus, at least one

194

type of APCD combination in each technical path should achieve the P95 values. But the higher 10


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requirement of Hg removal may imply higher cost. Thus, we regard that the APCD combination

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which can achieve the P95 value of Hg removal efficiency is the best technology in each

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technical paths at the beginning. Likewise, the P5 value is regarded as the basic requirement of

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the technical paths. Therefore, type (1-3), type (1-6), and type (2-11) of the APCD combinations

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in Table 1 can be regarded as preliminary technical paths to support the corresponding emission

200

limits of 15, 5, and 1 µg/m3, respectively. It should be noticed that although the Hg removal

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efficiencies of type (7), type (8), and type (9) are higher than that of type (6), the cost of the

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former three APCD combinations is lower or similar to the latter one. Therefore, we recommend

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the former three APCD combinations as technologies to support the emission limit of 5 µg/m3. In

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addition, PC with electrostatic precipitator (ESP) + wet flue gas desulfurization system (WFGD),

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fabric filter (FF) + WFGD, and ESP-FF+WFGD are not choices to support the emission limit of

206

5 and 1 µg/m3 because selective catalytic reduction (SCR) technology is required to be applied in

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plants using PC in order to achieve “ultra-low emissions” of NOx. At last, the technical paths of

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type (1-3), type (2-3, 5-7, 9-10), and type (2-3, 5-7, 9-12) are classified as the technical paths to

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support the emission limit of 15, 5, and 1 µg/m3, which are donated as TP15, TP5, and TP1,

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respectively. The emission limit value for a certain year is the actual implementation time of the

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limit. However, the issued date of a standard is generally earlier than the effectiveness of a

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revised emission limit so as to ensure enough time for technical transformation during the actual

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operational procedure. For example, the standard for China’s CFPPs was issued four years before

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the execution of the Hg emission limit (30 µg/m3) in 2015.9 Thus, the three scenarios of TP15,

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TP5, and TP1 for a certain year indicate that the potential technical paths will be applied before

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the inspected year.

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Then we further determine the application proportion of the various APCD combinations in

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each technical path according to future technology developing trend. Overall speaking, the

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APCD combinations targeted to other pollutants synergically removed 75% of total Hg input to

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the CFPPs of China in 2015, which is even higher than the P95 value of the Hg removal 11



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efficiencies to reach emission limit of 15 µg/m3. Therefore, we recommend similar technical path

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in 2025 and 2030 as that in 2015 under the TP15 scenario. Under the TP5 scenario, the

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“ultra-low emissions” will be fully implemented during 2015-2020

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the emitted concentrations of PM2.5, SO2, and NOx should be no more than 10, 35, and 50 mg/m3

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in the public CFPPs with the scale of no less than 300 MW (non-small-scale CFPPs) and owned

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CFPPs (excluding W-type flame and circulating fluidized bed boilers), respectively. The

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requirement of “ultra-low emissions” in CFPPs will promote the application of WESP, ESP-FF,

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and LT-ESP in PC and ESP-FF in circulating fluidized bed boilers during 2015-2020. Recently, a

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series of regulatory documents

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governments to take emission control measures, especial in the Beijing-Tianjin-Hebei region and

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around cities (also called as “2+26 cities”), Yangtze River Delta, and Pearl River Delta, etc. Thus,

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we assume that all CFPPs in these key regions will fully install these multi-pollutant control

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technologies before 2020. In other regions before 2020, the transformation of multi-pollutant

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control technologies will take place in the non-small scale CFPPs and the small-scale CFPPs will

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follow before 2025. In 2030, all CFPPs in China will apply the multi-pollutant control

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technologies. The TP1 scenario will speed up the implementation of the multi-pollutant control

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technologies. Before 2025, we assume that specific mercury removal (SMR) measures will be

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evaluated and demonstrated in some large CFPPs whereas SMR measures will popularize in

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CFPPs in 2030. Based on the above assumption, the share of each APCD combination is shown

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in Table 1.

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3.3 Hg reduction potential under different technical paths

26-28

22, 24, 25

, which requires that

aimed at air quality improvement also promote the local

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Current Hg emissions from the CFPPs in China and future trends as well as the uncertainty

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ranges are calculated in Figure 3. The bars represent the P50 value of the emissions and the short

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lines superimposed on each bar represent the uncertainty range. The best estimate for Hg

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emissions from CFPPs in China is approximately 76 t in 2015 with the uncertainty range of

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(-19%, 20%). Under the R energy scenario, the Hg emissions will increase by 16%/4% in 12


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2025/2030 for the TP15 scenario compared to that in 2015. However, the emissions will decrease

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by 76%/81% and 87%/96% in2025/2030 for the TP5 and TP1 scenarios, respectively. Under the

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A energy scenario, Hg emissions will decrease in all expected scenarios.

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For the TP15 scenarios where control technologies remain unchanged, Hg emissions are

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impacted by future energy consumption. Coal consumption in the CFPPs will keep increasing

252

during 2015-2025 and Hg emissions will increase by 16% in 2025 under the R energy scenario.

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Therefore, if we choose the emissions in 2015 as a benchmark, revising the emission limit from

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30 µg/m3 to 15 µg/m3 actually cannot achieve pollution control purposes in 2025. In 2030, we

255

will encounter similar predicament under the R energy scenario although the coal consumption

256

will decrease compared to that in 2025. Under the A scenarios, Hg emissions will decrease by 2%

257

and 17% in 2025 and 2030.

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For the TP5 scenarios where the “ultra-low emission” technologies are the dominant choices,

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Hg emissions will significantly decrease in all scenarios. In 2025, Hg emissions will be 18 t

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under the R scenario, which are 76% lower than the emissions in 2015. The A energy scenario

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where alternative energy measures (new energy substitution) are promoted will further reduce

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approximately 2 t of Hg emissions compared to the emissions in R energy scenario. The large

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reduction potential of Hg emissions during 2015-2025 when coal consumptions keep increasing

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reveal the huge benefit of Hg control from traditional air pollutants control, which also reflect the

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ambitious determination of air pollutant control of Chinese government under the guidance of

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Action Plan of National Air Pollution Prevention and Control. 23 After 2025, with the penetration

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of “ultra-low emissions” technologies in most CFPPs, the synergic Hg reduction potential in

268

CFPPs will decrease in the following five years and almost exhaust in 2030. For the TP1

269

scenarios, the application of SMR technologies will further enhance the Hg removal reduction

270

potential in addition to TP5 scenarios. The Hg emissions will be 9/3 t in 2025/2030 under the A

271

energy scenario. The emissions under the A-TP1 scenarios reflect the largest reduction potential

272

in the CFPPs of China. 13



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3.4 Emission- limit-oriented strategy for the CFPPs in China and global implication

274

The comparison of R-TP15 and A-TP15 scenarios in 2025 indicates that although the

275

alternative energy measures are more vigorously promoted in the A scenario, the increased coal

276

demand in this period will still lead to an increase of atmospheric Hg emissions unless using

277

powerful and effective technical paths. By comparing A-TP15 and A-TP5 in 2025,

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approximately 63.0 t of atmospheric Hg emissions can be reduced by using TP5 technical paths,

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which indicates that stricter requirement on the control of traditional pollutants will be effective

280

for Hg emission reduction. Although the TP1 scenario can further contribute to 6.9 t of Hg

281

emissions in 2025, it generally will take several years to demonstrate, evaluate and promote a

282

new technology. Therefore, it will be difficult to adopt the SMR technology in the TP1 technical

283

paths before 2025 in China. During 2025-2030, with the slowdown of economic development

284

and the continuous promotion of alternative energy measures, coal consumptions in CFPPs will

285

decrease. This will be an alternative support on Hg emission control, contributing to 1.8 t of

286

atmospheric Hg reduction in this period. Simultaneously, reduction potential of the

287

multi-pollutant control measures will almost exhaust and contribute to only 2.6 t of atmospheric

288

Hg reduction. If we further adopt the TP1 technical paths, approximately 9.1 t of atmospheric Hg

289

emissions can be reduced. Therefore, the emission limit is recommended to be 5 µg/m3 in 2025

290

supported by primarily using multi-pollutant control measures. During 2025-2030, both

291

alternative energy measures and SMR technologies can further be applied to achieve the

292

emission limit of 1 µg/m3 in 2030 (Fig. 4). However, considering the economic performance of

293

SMR, whether the SMR can be large-scale applied in CFPPs or not also depends on the national

294

overall action plan for the Convention.

295

With the ratification of the Convention, new and tighter emission limits have been or will be

296

required soon in some countries or regions. The emission-limit-oriented strategy developed for

297

the CFPPs in China will provide a reference scheme for other regions, but the potential

298

diversities of relative parameters between regions should be noticed. First, there is a huge 14


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difference in the status of monitoring data such as tested Hg concentrations in the flue gas and

300

Hg content of the coal in different regions. Thus, policy maker can adjust the formulation

301

procedure of emission limits according to country-specific situations. For the countries with

302

relatively complete monitoring data, Hg concentrations in the flue gas can be used to determine

303

the emission limits directly. For example, the emission concentrations in the flue gas achieved by

304

the best performing 12% of sources is defined as the emission limit for the existing sources in the

305

United States. In Sweden, each plant will get its own emission limit in the environmental permit

306

implied with BAT requirement. On the contrary, Hg concentrations in the flue gas can be

307

estimated based on the Hg contents of coal and APCDs applied, as what we have done for the

308

CFPPs in China. The United States Geological Survey has provided a preliminary data of Hg

309

contents in different countries (Table S3), which can be used as database for calculation. The

310

global BAT/BEP guidance has evaluated different APCD combinations. Policy makers can

311

decide a preliminary emission limit based on these databases. Second, the potential measures to

312

support the development of the emission limit will be various between countries, mainly

313

depending on the development level of a specific country. When a country is experiencing an

314

upswing or rapid development of economy, large consumption of energy and raw materials

315

generally will lead to huge emissions of multiple pollutants. Therefore, multi-pollutant control

316

measures and energy substitution measures will be the dominant choice. When the economic

317

development is relatively stable, SMR will be an alternative.

318

ACKNOWLEDGEMENT

319

This work was funded by National Key Research and Development Program of China

320

(2017YFC0210401, 2017YFC0210404), Natural Science Foundation of China (21077065).

321

SUPPORTING INFORMATION AVAILABLE

322

S1, Exiting Hg emission limits in the world (Table S1); S2, Detailed information of the

323

tested CFPPs (Table S2); S3, Hg contents of coal in different countries (Table S3). This 15



324

information is available free of charge via the Internet at http://pubs.acs.org/.

325

REFERENCES

326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360

(1) Nriagu, J. O.; Pacyna, J. M. Quantitative Assessment of Worldwide Contamination of Air, Water and Soils by Trace-Metals. Nature 1988, 333 (6169), 134-139. (2) Horowitz, H. M.; Jacob, D. J.; Amos, H. M.; Streets, D. G.; Sunderland, E. M. Historical mercury releases from commercial products: Global environmental implications. Environ. Sci. Technol. 2014, 48 (17), 10242-10250. (3) Streets, D. G.; Devane, M. K.; Lu, Z. F.; Bond, T. C.; Sunderland, E. M.; Jacob, D. J. All-time releases of mercury to the atmosphere from human activities. Environ. Sci. Technol. 2011, 45 (24), 10485-10491. (4) Wu, Q. R.; Wang, S. X.; Li, G. L.; Liang, S.; Lin, C.-J.; Wang, Y. F.; Cai, S. Y.; Liu, K. Y.; Hao, J. M. Temporal trend and spatial distribution of speciated atmospheric mercury emissions in China during 1978–2014. Environ. Sci. Technol. 2016, 50 (24), 13428-13435. (5) Li, L.; Wang, F. Y.; Meng, B.; Lemes, M.; Feng, X. B.; Jiang, G. B. Speciation of methylmercury in rice grown from a mercury mining area. Environ. Pollut. 2010, 158 (10), 3103-3107. (6) Meili, M. Fluxes, pools, and turnover of mercury in swedish forest lakes. Water Air Soil Pollut. 1991, 56, 719-727. (7) Arctic Monitoring and Assessment Programme and United Nations Environment Programme (AMAP/UNEP): Technical background report for the global mercury assessment; AMAP/UNEP: Geneva, Switzerland, 2013. (8) United Nations Environment Programme (UNEP): Minamata Convention on Mercury; UNEP: Minamata, Japan, 2013. (9) Ministry of Environmental Protection (MEP); State Administration for Quality Supervision and Inspection and Quarantine (AQSIQ): Emission standard of air pollutants for thermal power plants; MEP&AQSIQ: Beijing, China, 2011. (10) Wang, S. X.; Zhang, L.; Zhao, B.; Meng, Y.; Hao, J. M. Mitigation potential of mercury emissions from coal-fired power plants in China. Energ. Fuel. 2012, 26 (8), 4635-4642. (11) Zhang, L.; Wang, S. X.; Wang, L.; Wu, Y.; Duan, L.; Wu, Q. R.; Wang, F. Y.; Yang, M.; Yang, H.; Hao, J. M.; Liu, X. Updated emission inventories for speciated atmospheric mercury from anthropogenic sources in China. Environ. Sci. Technol. 2015, 49 (5), 3185-3194. (12) Hui, M. L.; Wu, Q. R.; Wang, S. X.; Liang, S.; Zhang, L.; Wang, F. Y.; Lenzen, M.; Wang, Y. F.; Xu, L. X.; Lin, Z. T.; Yang, H.; Lin, Y.; Larssen, T.; Xu, M.; Hao, J. M. Mercury flows in China and global drivers. Environ. Sci. Technol. 2017, 51, 222-231. (13) Zhang, L.; Wang, S. X.; Meng, Y.; Hao, J. M. Influence of mercury and chlorine content of coal on mercury emissions from coal-fired power plants in China. Environ. Sci. Technol. 2012, 46 (11), 6385-6392. 16


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361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398


(14) Li, Z. G.; Feng, X. B.; Li, G. H.; Yin, R. S.; Yu, B. Mass Balance and Isotope Characteristics of Mercury in Two Coal-fired Power Plants in Guizhou, China. Advances in Environmental Science and Engineering, Pts 1-6 2012, 518-523, 2576-2579. (15) Wang, J.; Wang, W. H.; Xu, W.; Wang, X. H.; Zhao, S. Mercury removals by existing pollutants control devices of four coal-fired power plants in China. J. Environ. Sci. 2011, 23 (11), 1839-1844. (16) Li, W. J. Characterization of atmospheric mercury emissions from coal-fired power plant and cement plant. Southwest University, Chongqing, China, 2011. (17) Wang, Y. J.; Duan, Y. F.; Yang, L. G.; Zhao, C. S.; Xu, Y. Q. Mercury speciation and emission from the coal-fired power plant filled with flue gas desulfurization equipment. Canadian journal of chemical engineering 2010, 88 (5), 867-873. (18) Wang, S. X.; Zhang, L.; Li, G. H.; Wu, Y.; Hao, J. M.; Pirrone, N.; Sprovieri, F.; Ancora, M. P. Mercury emission and speciation of coal-fired power plants in China. Atmos. Chem. Phys. 2010, 10 (3), 1183-1192. (19) Liu, K. Y.; Wang, S. X.; Wu, Q. R.; Wang, L.; Ma, Q.; Zhang, L.; Li, G. L.; Tian, H. Z.; Duan, L.; Hao, J. M. A highly resolved mercury emission inventory of Chinese coal-fired power plants. Environ. Sci. Technol. 2018, 52 (4), 2400-2408. (20) China Electric Power Association (CEPA): China Electric Power Yearbook; CEPA: Beijing, China, 2016. (21) The 18th Central Committee of the Communist Party of China (CCCPC): The 13th five-year plan for China's national economic and social development; CCCPC: Beijing, China, 2016. (22) National Development and Reform Commission (NDRC); National Energy Administration (NEA): The 13th development plan for power plants; NDRC&NEA: Beijing, China, 2016. (23) State Council of the People's Republic of China (SC): Action plan of national air pollution prevention and control; SC: Beijing, China, 2013. (24) Ministry of Environmental Protection (MEP): Working plan of fully implementing the ultra-low emissions and energy-saving transformation program in coal-fired power plants; MEP: Beijing, China, 2015. (25) National Development and Reform Commission (NDRC): Special plan for the construction and operation of owned coal-fired power plants; NDRC: Beijing, China, 2018. (26) Ministry of Environmental Protection (MEP): Ambient air quality standards; MEP: Beijing, China, 2012. (27) Environmental Protection Agency of Beijing (EPAB): Action plan of clean air in Beijing; EPAB: Beijing, China, 2013. (28) Environmental Protection Agency of Shanghai (EPAS): Action plan of clean air in Shanghai; EPAS: Shanghai, China, 2013.

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TABLES Table 1. Projection of future technical paths Application rate of different APCD combinations (%) Type

APCD combinations 1

Hg

removal

efficiency (%) 3

2025

2030

2015 TP15

TP5

TP1

TP15

TP5

TP1

1

(PC+)ESP+WFGD

60.3±21.6

2.4

2.4

0.0

0.0

2.4

0.0

0.0

2

(CFB+)ESP+CFGD 2

68.0±1.4

10.2

10.2

2.0

1.5

10.2

0.0

0.0

3

(PC+)SCR+ESP+WFGD

70.2±20.9

64.4

64.4

2.4

1.7

64.4

0.0

0.0

4

(PC+)FF+WFGD

86.0±10.2

0.2

0.2

0.0

0.0

0.2

0.0

0.0

5

(PC+)SCR+FF+WFGD

87.8±16.3

3.6

3.6

0.2

0.2

3.6

0.0

0.0

6

(PC+)SCR+ESP(FF)+WFGD+WESP

93.9±6.7

2.8

2.8

29.3

0.6

2.8

29.1

0.0

7

(CFB+)ESP-FF+CFGD 2

95.1±2.7 4

0.0

0.0

7.8

7.7

0.0

10.9

0.0

8

(PC+)ESP-FF+WFGD

95.1±2.7

0.5

0.5

0.0

0.0

0.5

0.0

0.0

9

(PC+)SCR+ESP-FF/LTESP+WFGD

97.0±1.9

15.1

15.1

58.3

6.0

15.1

58.2

0.0

10

(CFB+)SCR+ESP+CFGD+FF

97.0±1.9 5

0.8

0.8

0.0

8.5

0.8

1.8

12.7

11

(PC+)SCR+SMR+ESP(FF)+WFGD+WESP

98.8±1.4 6

0.0

0.0

0.0

24.6

0.0

0.0

29.1

12

(PC+)SCR+SMR+ESP-FF/LTESP +WFGD

99.4±0.5 7

0.0

0.0

0.0

49.2

0.0

0.0

58.2

Note: APCD – air pollution control device; PC – pulverized coal furnace; CFB – circulating fluidized bed; ESP – electrostatic precipitator; WFGD – wet flue gas desulfurization; CFGD –circulating fluidized bed desulfurization; SCR – selective catalytic reduction; SNCR – selective non-catalytic reduction; FF – fabric filter; WESP – wet electrostatic precipitator; LTESP – low temperature electrostatic precipitator; SMR – 19



specific mercury removal. 1 Nearly all CFPPs have installed low nitrogen oxide burner and some plants (especially CFB) have used the SNCR technology. Plants with these two technologies are not distinguished with those without de-NOx technology due to the little synergic Hg removal effect of these two technologies. 2 All plants using these two technologies also applied SNCR in the future scenarios due to the ultra-low emission requirement of NOx. 3 Most of the Hg removal efficiencies of APCDs refer to Wu et al. (2016) except those specially noted. 4 Estimated value by referring to the Hg removal efficiency for (PC+)ESP-FF+WFGD. 5 Estimated value by referring to the Hg removal efficiency for (PC+)SCR+ESP-FF+WFGD. 6 Estimated value by referring to the Hg removal efficiency for (PC+)SCR+ESP(FF)+WFGD+WESP and considering additional 90% Hg removal of SMR. 7 Estimated value by referring to the Hg removal efficiency for (PC+)SCR+SMR+ESP-FF/LTESP+WFGD and considering additional 90% Hg removal of SMR.

20


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Table 2. Projection of future coal consumptions in CFPPs R energy scenario

A energy scenario

2025

2030

2025

2030

Annual average growth rate of GDP (%)

6.0

5.0

5.5

4.5

GDP (103 billion USD)

19.56

24.96

19.10

24.37

Population (billion)

1.45

1.47

1.45

1.47

GDP per capita (USD)

13488

16980

13173

16580

Elasticity of electricity

0.61

0.45

0.53

0.40

Electric growth rate (%)

3.63

2.25

2.89

1.80

Total electricity (103 GWh)

8890

9936

8139

8898

Percentage of coal-fired electricity (%)

53.6

45.0

50.0

40.0

Coal-fired electricity (103 GWh)

4760

4471

4070

3559

Standard coal consumption (g/kWh)

285

280

285

280

Coal consumption (Mt)

2208

2038

1888

1622

Parameters

Note: R energy scenario – reference energy scenario; A energy scenario – alternative energy scenario; GDP – gross domestic product.

21



Page 22 of 25

FIGURES (a)

3

Tested Hg concentration (µg/m )

30

China/Germany/Malaysia/India 30

25 20 15

Canada(1) 11.6

10 5

USA(1) 5.08

USA(2) 1.8

Canada(2) 2.3

0 Anthracite Blends Bituminous coal

USA(3) 0.4

Lignite Unknown type

Figure 1 . Evaluation of existing Hg emission limit in China. (a) Tested Hg concentrations. USA(1), (2), and (3), is the emission limits for CFPPs using low rank coal, existing CFPPs using non-low rank coal, and new CFPPs using non-low rank coal, respectively. Canada (1) and (2) are the emission limits for new CFPPs using lignite and blends (or bitumite), respectively. The emission limit of USA and Canada in the figure is the approximate data after unit conversion, which is introduced in Table S1. The detailed information of the tested CFPPs is listed in Table S2. (b) The distribution of simulated Hg concentrations.

22


Page 23 of 25


Figure 2. Simulated Hg removal efficiencies of APCD combinations.

23



Figure 3. Future Hg emission trends.

24


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Figure 4. Emission-limit-oriented control strategy for CFPPs in China

25


Emission-limit-oriented strategy to control atmospheric mercury

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