hg emissions from a coal-fired power plant in north ... emissions from a coal-fired power plant in...

Hg emissions from a coal-fired power plant in North China and its

environmental impacts

Zhonggen Li1, Taishan Li2, Haiyu Yan1,

Guangle Qiu1, Xinbin Feng1

1. Institute of Geochemistry, CAS, Guiyang 550002, China;

2. Tangshan Environmental Monitoring Center, Tangshan 063000, Hebei, China

Wik Castle, Uppsala, SwedenMay 19, 2014

OutlineEmissions and controls of Hg from the power plant1

Hg in soils and air2

Hg in the lake system 3

Conclusions4

Dai et al., 2012 , Int. J. Coal Geol.

Background

3.5 billion tons/yr

coal consumption in China:

50% of the world; 50% by power plants

coal combustion (45%)

Hg national emissions

BackgroundFGD

Fly ash: since 1980s, use electrostatic

precipitator (ESP) to replace wet dust collector,

and cyclone; by 2010, 96% power plant use ESP,

and 6% with ESP+FF (fabric filter)

FGD: Flue gas desulfurization begin in 1990s,

increased rapidly in the past 10 years (2005-

2010), now almost 100% power plants installed

FGD, with >90% in wet FGD

De-NOx: flue gas denitrification in 2010 is 14%,

and projected to be 83% by 2015 (rapid growth in

2011-2015), of which, 90% is SCR (Selective

Catalytic Reduction).Tian et al., 2010, ACP; 2014 EST

WFGD+SCR installation in 2010

Great changes in the air pollution control device (APCDs) for CFPP in the past 30 year!

Basic information about the CFPP studied

Totally 1550 MW, with 8 units, started into operation in 1970s

Unit #3 studied, with 250 MW

Pulverized coal-fired boiler

Bituminous coal

APCDs: SCR+CS-ESP-FF+WFGD

Tangshan Unit 3

Sampling and analysis

Hgp Hg2+ Hg0

Ontario Hydro Method (OHM) for flue gas，

ASTM Method 6784-02

Flue gas sampling sites(each site>3 runs)

Solid/liquid sampling sites

Sampling date: August 13-17, 2013


Lab workWFGDoutlet

ESPinlet

FFoutlet

SCR inlet Sampling

Results: Hg in solid and liquid samples

Compared with the feed coal (139 ng/g), Hg was much enriched in fly ash, gypsum and desulfurization wastewaters

But Hg depleted in bottom ash and lime stone

Feed coal Bottom ash ESP fly ash FF fly ash Lime stone Gypsum

0

200

400

600

800

1000

1200

Hg

co

nte

nt

(ng

/g)

Sample type

Desulfurization wastewater Slag flushing water

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Hg

co

nce

ntr

atio

n (

ng

/L)

Water types

Solid samples Waste water

Hg concentrations in the flue gas

Total Hg dropped from 21μg/m3 to 0.87 μg/m3.

Hg removal efficiency is 96%.

Much lower than the emission standard (30 μg/m3 in China and 1.7 μg/m3 in USA )

Results: Hg in the flue gas

SCRinlet ESPinlet FFoutlet WFGDoutle

0

2

4

6

8

10

12

14

16

18

20

22

24

Sampling locations

Hg

conce

ntr

atio

ns

in t

he flu

e g

as

(g/m

3)

Hgp

Hg0

Hg2+

THg

SCR inlet ESP inlet FF out let FGD outlet0

10

20

30

40

50

60

70

80

90

100

Pe

rce

nta

ge

of

diff

ere

nt

Hg

sp

eci

es

in t

he

flu

e g

as

(%)

Sampling locations

Hgp

Hg0

Hg2+

Hg species in the flue gas

SCR oxidization 90% of Hg0 in to Hg 2+

ESP-FF removed 99.8% of Hgp

WFGD absorbed 97% of Hg2+.

SCR

ESP-FF WFGD

SCR ESP-FF WFGD

Results: Mass balance of Hg in Unit #3

Most Hg was removed by ESP+FF (77%)

A lesser extent was removed by WFGD (17%)

A small portion (4%) was discharged into atmosphere through the stack, with 86% in Hg0, 13% in Hg2+, and 1% in Hgp

Results: Hg emission factor of Unit #3

Hg emission factor of this unit is 6.3 mg Hg/t coal or 3.1 μg Hg/ kW.h, much lower than other power plants that just installed ESP or ESP+WFGD

PP#1 PP#2 PP#3 PP#4 PP#5 PP#6 this study0

20

40

60

80

100

120

140

SC

R+

ES

P-F

F+

WF

GD

SC

R+

ES

P+

WF

GD

ESP+CFB-FGD+FF

ES

P+

WF

GD

ES

P+

WF

GD

ES

P+

WF

GD

ES

P+

WF

GD

Hg e

mis

sio

n fact

or

(mg H

g/t c

oal)

Power plant

this study

Comparison of Hg emission factors with 6 other power plants in China.

Wang SX et al., 2010, ACP

Hg removal efficiency by different types of APCDs.

Zhang L. et al., 2012, EST

PC+SCR+CS-ESP-FF+WFGD 96% This study


Hg in the soils and air2


Conclusions4


Sampling sites for the surrounding soils and ambient air

Results: total Hg in the surface soil

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

0

10

20

30

40

TH

g (

ng/g

)

Sample No.

THg

THg vs distance

0 2 4 6 8 105

10

15

20

25

30

35

40

45

TH

g (

ng/g

)

Distance (km)

R=-0.50, p=0.015

Agricultural soil: 0-20 cm

Range: 9.2-43.5 ng/g, mean:20.7±10.0 ng/g

Less than the national (65 ng/g) and provincial (36 ng/g) background

Closer sites (<4 km) are significantly higher than the remote ones (26.7 vs 16.1 ng/g)

Results: SOM and pH in the surface agricultural soil

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

3

4

5

6

7

8

9

10

pH

Sample No.

pH

SOM are low in most sites

pH are low (around 6) in closer sites than remote sites (~8)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Org

anic

matter

(%)

Sample No.

SOM

60

50

40

30

20

10

0

De

pth

(cm

)

SP#1 SP#2

0 10 20 30 40 50 60

THg (ng/g)

THg in the soil profile

Results: Total in the soil profile

THg Hg in surface layer (ca. 50 ng/g) are higher than the bottome part

Local background is about 10 ng/g

Soils within 10 km to the CFPP has accumulated 0.59 t Hg, account for 3.47% of the total emitted

Results: GEM in the ambient atmosphere

GEM: 1.5-9.0 ng/m3

Less than the ambient air standard (GB 3095-2012) for Hg (50 ng/m3)

No trend with distance to the CFPP

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

0

1

2

3

4

5

6

7

8

9

GE

M (

ng/m

3)

Sample No.

GEM




Conclusions4


Waters Sediments Fishes, shrimp, spiral shell

Mercury in lake waters

THg<4 ng/L, in the natural background range, below the class-I surface water standard in China (50 ng/L)

DHg ≈PHg

0

1

2

3

4

5

6

0.0 1.0 2.0 3.0 4.0

水深

（m）

陡河库心汞含量（ng/L）

THg

DHg

PHg

Hg in water column at KX (ng/L)

Dep

th (m

)

0

5

10

15

20

25

30

0.00 0.50 1.00 1.50

沉积

物深

度（cm

）

陡河沉积物中甲基汞含量（ng/g.dw）

DHKX

DHXZ

DHDZ

0

5

10

15

20

25

30

0.0 50.0 100.0 150.0

沉积

物深

度（cm

）

陡河沉积物总汞含量（ng/g.dw）

DHKX

DHXZ

DHDZ

Mercury in sediments

THg in sediment cores (ng/g, dw) MeHg in sediment cores (ng/g, dw)

Dep

th (cm

)

Dep

th (cm

) Both THg and MeHg are higher in surface layer than the bottom

THg in sediment(up to 100 ng/g) are higher than the surrounding soils, indicating other inputs (such as influent)

Hg in fishes

B C D E

-20

0

20

40

60

80

100

120

140

160

杂食性肉食性滤食性底栖

鱼的食性

TH

g (

ng

.g-1,

ww

)

y = 0.207x + 4.1622R² = 0.4212

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

0.0 50.0 100.0 150.0

MeH

g

THg

OmnivorousCarnivorousFiltering-feeding Benthal

Feeding type

THg content in fish are low (<140 ng/g), and MeHg% is 28%

THg in fish decreased with feeding types, Carnivorous> Omnivorous>Filtering-feeding




Conclusions4

Conclusions

The installation of conventional pollutant control devices (SCR+CS-ESP-FF+WFGD) has high synergistic mercury removal efficiency (96%), and Hg in the discharged flue gas is lower the emission standard

Hg in the surrounding environmental compartments indicates slightly impacts by the coal-fired power plant

Acknowledgements

The Major State Basic Research Development Program ofChina (973 program) (No. 2013CB430001)

Science & Technology Research and Development Plan ofTangshan (No. 12130215A)

Ji Chen Guangyi Sun Xu YangZhuo Lu Qiongzhi YouMingmeng Wang

Thanks for your attention！

[email protected]

@WPS官方微博

@kingsoftwps

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