traceability research activities in the field of …...2015/04/14 · in iso 14644-1, the air...
TRANSCRIPT
Liu Junjie, Zhang Wenge, Song Xiaoping
Division of Nano metrology and Materials Measurement
National Institute of Metrology, China
Traceability research activities in the field of airborne particle number/ mass concentration measurement
• Division of Nano Metrology and Materials Measurement
Advanced Materials Laboratory
Focusing on the accurate measurement of particle characteristics, - Developing the traceable instruments and calibration procedures for particle number concentration and particle mass concentration. PM10/PM2.5 calibration standards particle counting in airborne calibration standards -Traceability study of particle size measurement methods in nano- and micro- scale meter, for example, SEM, TEM, AFM, DLS, NTA and DMA methods -Particle counting in liquid
Nanometrology Laboratory
Physical Chemistry Laboratory
Particle Measurement
Chemical composition analysis
particle mass concentration measurement
/ / /
Accurate measurement of PM2.5 mass concentration and calibration of
automatic PM2.5 monitors
Automobile exhaust particle number concentration measurement
Calibration of PM2.5 sampler/ monitor
Calibration of PM2.5 seperators
PM2.5 Calibration Plan
Standard sampling method
Next Step Condensation particle counter calibration
• Gravimetric standard for PM 2.5 mass concentration, development of calibration instrument for PM2.5 sampler (finished)
• Development of calibration instrument for PM2.5 impactors, National metrology calibration specification for PM10/PM2.5 impactors (finished)
• development of calibration instrument for online PM2.5 monitors (undergoing) • Condensation particle counter (CPC) calibration (undergoing)
Research activities in PM2.5 calibration(2013~2017)
Gravimetric standard for PM 2.5 mass concentration
A calibration instrument /standard have been designed and developed. • auto sampling • Membrance auto-balance and auto-weighting
Gravimetric standard for PM 2.5 mass concentration
Particle aerosol
PM2.5 impactor
Membrane
Flow controller
Pump
Barometer
Therometer
Balance
Therometer
Displayer/recorder
Uncertainty is less than 3%,k=2
Cut-point calibration standard for PM2.5 impactor/seperator
Cut point:
D50=10±0.5µm (PM10)
D50=2.5±0.2µm (PM2.5)
Impactor calibration, establish the curve of penetration and aerodynamic diameter
Series particle size standard polystyrene particles with nominal value (1.0— 4.0) um were prepared by dispersion polymerization method Standard deviation of particle size distribution is less than 3.0%
Cut-point calibration standard for PM2.5 impactor
Particle counting in airborne (particle number concentration ) Optical particle counter (OPC) and Condensation particle counter (CPC) calibration
China: GB18352.5-2013 limits and measurement methods for emission from light-duty vehicles standard was implemented.
EU: Euro 5 emissions regulations for light diesel vehicles and Euro 6 emission regulations for heavy-duty diesel vehicles
2. Characterization of exhaust particulate emissions for road vehicles
Particle counting efficiency calibration for OPC and CPC
Optical particle counter OPC
condensation particle counter CPC
Faraday-cup aerosol electrometer FCAE
Electrical current
In OPC calibration field, a widely recognized OPC traceability chain has already been established and described in several ISO document, where, OPC should be calibrated by CPC, if it has already been calibrated by Faraday cup aerosol electrometer (FCAE). Using this calibration method, it is possible to make the particle number concentration result of OPC trace to an international recognized primary unit-- electrical current.
1. Clean room classification monitoring In ISO 14644-1, the air cleanliness in cleanrooms is classified according to the particle number.
Calibration of Faraday-cup aerosol electrometer
y = 0.9321x + 0.1104 R² = 1
0102030405060
0 20 40 60
resp
onde
nt e
lect
rical
cu
rren
t of F
C /f
A
Standard electrical current /fA
respondent electrical current of FCAE is well calibrated, and the calibration uncertainty is less than 1% k=2 (>10fA).
Respondent electrical current calibration
Particle counting in airborne (particle number concentration)
eQI
etQqC ==
Calibration method for Faraday-cup aerosol electrometer (FCAE) was developed, by comparing the respondent electrical current of FCAE with reference electrical current.
Electromagnetic shielding box
resistance
FCAE Controller
Calibration of counting efficiency
In the range of (3600~39000)particles/cm3, uncertainty of counting efficiency calibration is less than2.5%(k=2)
Zero calibration, flow rate calibration, respondent electrical current calibration
FCE
R
eQII
etQqC
)( 0−== %100×=
CCFCE
FCEη
Condensation particle counter calibration
%100)202()153()101(
)101(
321
11 ×
++=
CCCC
φ
%100)202()153()101(
)153(
321
22 ×
++=
CCCC
φ
%100)202()153()101(
)202(
321
33 ×
++=
CCCC
φ
∑=
××××
=3
1pPFCE
FCE
CPCCPC P
CfC
φηβ
η
Particle counting in airborne (particle number concentration)
Correction for multiply-charged effect
In CPC counting efficiency calibration, a differential mobility analyzer was used to achieve monodisperse particle surface with only single charge. But actually, in the aerosol from the outlet of DMA, some large particles surface with multiply charges might be involved, because those large particles have the same electrical mobility in DMA chamber as single-charged particles. And if this multiply-charged effect in aerosol is actually existed, particle number concentration recorded by FCAE would not represent the real aerosol particle concentration, because the respondent electrical current caused by multiply-charged large particles will not be proportional to the aerosol concentration. On account of this, in CPC counting efficiency calibration multiply-charged effect should be corrected,
stable and single-charged particles aerosol were firstly produced by using DMA, and then after through a flow splitter, particles aerosol is equivalently separated into two ways, and pumped into FCAE and CPC separately , where FCAE counting efficiency has already been well calibrated.
CPC and calibration
Calibration points 1 2 3 4 5
/(particles/cm3) 6937 7013 6952 6915 6845
/(particles/cm3) 6770.7 6844.9 6977.2 6749.2 6680.9
Dilution factor f 1 2 5 10 20
CCPC/(particles/cm3) 6689 3380 1373 670 328
CPC counting
efficiency/(%) 98.79 98.76 98.39 99.27 98.19
FCEC
Particle counting in airborne (particle number concentration)
Condensation Particle Counter
(CPC)
Optical
Particle Counter (OPC)
10 nm 100 nm 1000 nm
Aerosol Electrometer
(AE)
1 cm-3
10 cm-3
100 cm-3
1000 cm-3
10000 cm-3
1 nm
Part
icle
Con
cent
ratio
n
Particle Size
T-tube Designed dilutor Dilutor from commercial
FCAE
CPC dilutor
splitter
Using calibrated FCAE as top standard of particle number concentration, and by comparing the results of FCAE and under-tested CPC, counting efficiency of CPC can be verified and calibrated. In the range of (200~16000) /cm3, uncertainty of CPC calibration result is about 5% (k=2).
OPC calibration
Calibration points 1 2 3 4
CCPC/f(particles/L) 1575.8 5182.4 16121.9 31228.6
OPC value(particles/L) 1478.9 4980.1 15545.6 29462.1
Particle counting in airborne (particle number concentration)
Condensation Particle Counter
(CPC)
Optical
Particle Counter (OPC)
10 nm 100 nm 1000 nm
Aerosol Electrometer
(AE)
1 cm-3
10 cm-3
100 cm-3
1000 cm-3
10000 cm-3
1 nm
Part
icle
Con
cent
ratio
n
Particle Size
dilutor
splitter
Filter
Using calibrated CPC as standard of particle number concentration, and by comparing the results of CPC and under-tested OPC, counting efficiency of OPC can be verified and calibrated. In the range of (1500~30000) particles/L, uncertainty of OPC calibration result is about 8% (k=2).
summarize
• PM2.5 sampler and monitors comparison. • Increasing the accuracy of CPC calibration results, especially in the
low particle number concentration range (less than 100/cm3). • Carrying out CPC comparison.
Thank you very much