自動化溫室效應氣體分析系統之建立與應用

1

Speaker ： Ming-Xia Li

Advisor ： Prof. Jia-Lin Wang

Construction of an automated GC system for measuring atmospheric greenhouse gases

Introduction

2

GWP100： 1

364 ~ 408 ppm

GWP100： 298

303 ~ 326 ppb

GWP100： 25

1758 ~ 2133 ppb

Analytical Techniques

3

GHGs Instrument

CO2

Non-Dispersive Infra-Red (NDIR)

Gas Filter Correlation (GFC)

Cavity Ringdown Spectroscopy Fourier Transform Infrared Spectroscopy (FTIR)

Gas Chromatograph (GC) – methanizer - FID

CH4 Cavity Ringdown Spectroscopy

GC/FID

N2O

Quantum cascade laser (QCL) Tunable Diode Laser Infrared Absorption

Spectroscopy (TDLAS) Fourier Transform Infrared Spectroscopy (FTIR)

Ultraviolet (UV) GC/ECD

4

Our analytical system

Sampling system

• Sample automatically fills up to 700 torr

Oven ： 70℃

5

Column Configuration

CH4 & CO2

N2O

Injection

6

Back-Flush

ActionsO2, N2O,

other compounds

other compounds

O2, N2O

other compounds

Sampling

O2, N2O N2OO2

Channel switching

7

H2

Methanizer

• Composition ： 30 ~ 50% NiO (nickel(II) oxide) and 50 ~ 70% SiO2

• Function ： reduced CO2 into CH4

• Temperature : 375°C

CO2 + 4H2 → CH4 + 2H2O

CO2CH4

Chromatograms

8

CO2FID

ECD N2O

O2

CH4

Experimental

• Carrier gases

• Oxygen cutting or not

• Parameter optimization

9

Different carrier gases – N2 vs. CH4/Ar

10

N2

CH4/Ar

• When the carrier gas uses 5% CH4/Ar, the single of N2O will increase

N2O

Cutting oxygen or not

11

Not cut oxygenCut oxygen

• When cut oxygen, the single of N2O just increase slightly, but the analyze time will increase

N2O

O2

Optimize the parameters

12

Valve System Parameters

oven 70°C

V1

sample loop

pre-column

analytical column1

detector

CG1

CG2

Ni catalyst temperature

1.73 mL

1.5 m Porapack Q (80-100 mesh)

1.5 m Hayesep Q (80-100 mesh)

FID(250°C)

30 psi Nitrogen

20 psi Nitrogen

375°C

V2

sample loop

pre-column

analytical column1

detector

CG1

CG2

1.73 mL

1.5 m Hayesep Q (80-100 mesh)

1.5 m Porapack Q (80-100 mesh)

ECD(330°C)

30 psi 5% CH4/Ar

20 psi 5% CH4/Ar

Results and discussion

• Linearity

• Limit of Detection

• Reproducibility

13

Connecting with Vacuum System

14

vacuum system

• When system connects with vacuum system, makes sure samples are not be contaminated.

Quantitative – Working Standard

15

CO2 CH4 N2O

Standard 15.3 16250.4

Standard concentrations 1788 ppb 10 ppm

Working standard signal 3276 16.03 647.31

Working standard concentrations

372.66 ppm 1873 ppb 398 ppb

3000 3200 3400 3600 3800 4000 4200 4400 4600 4800300

350

400

450

500

550

f(x) = 0.115131960252174 x − 5.4220693669721R² = 0.999959983240925

signal

conc

. (pp

m)

Calibration curve - CO2

• Using NOAA standards to make calibration curves

Linearity

16

• Pressure range ： 4 ~ 44 psi

0 5 10 15 20 25 30 35 40 45 500

100020003000400050006000700080009000

f(x) = 187.3142857 xR² = 1

CH4

Pressure (psi)

Con

c. (p

pb)

0 5 10 15 20 25 30 35 40 45 500

200400600800

10001200140016001800

f(x) = 37.26609 xR² = 1

CO2

Pressure (psi)

Con

c. (p

pm)

0 5 10 15 20 25 30 35 40 45 500

200400600800

100012001400160018002000

f(x) = 39.8337448 xR² = 1

N2O

Pressure (psi)

Con

c. (p

pb)

Limits of Detection

CO2 CH4 N2O

D.L.Concentration

3.42 ppm364 ~ 408 ppm

138.34 ppb1758 ~ 2133 ppb

2.30 ppb303 ~ 326 ppb

Reproducibility

CO2 CH4 N2O

RSD 0.96% 0.86% 0.45%

17

• Based on 3 times standard deviation 

N = 7

N = 7• Pressure ： 4 psi

• Pressure ： 10 psi

18

Canister Analysis

Canister sampling in Taipei area in 2012

• Sampling time ： 2012/02/14 05:00~06:00 am

18:00~19:00 pm

• 53 sampling sites

• Sampling time less than 1 min

• Monitoring compounds ：CFCs, CO2, CH4, N2O, NMHCs

• Look for emissions hot spots – sources of GHGs.

19Ref. Chemosphere 1998, Vol.36, No. 10, 2391-2400

Ref. Analytica Chimica Acta 2006, 576, 91-99

20Evening (18:00 ~ 19:00)Morning (05:00 ~ 06:00)

CO2

Concentration range ：387.04 ~ 578.12 ppmv

21Evening (18:00 ~ 19:00)Morning (05:00 ~ 06:00)

CH4

Concentration range ：1837.57 ~ 4496.74 ppbv

22Evening (18:00 ~ 19:00)Morning (05:00 ~ 06:00)

N2O

Concentration range ：392.06 ~ 421.88 ppbv

Conclusions

The system measures CH4 、 CO2 、 N2O in 10 minutes for each sample.

It has very good reproducibility (RSD < 1%), and linearity (R2 = 0.9999).

The limits of detection for CH4 is 138.34 ppb (vs. ~1.7 ppm), CO2 is 3.42 ppm (vs. >360 ppm), and N2O is 2.3 ppb (vs. >300 ppb).

23

24

Thanks For Your Attention