Design of a compact dilution sampler for stationary combustion sources
Xinghua Li, Shuxiao Wang, Lei Duan and Jiming Hao
May 10-14, 2010, Xi’an, China
Department of Environmental Science and Engineering
Tsinghua University, Beijing, China
A&WMA International Specialty Conference: Leapfrogging Opportunities for Air Quality Improvement
Background� PM emitted from combustion sources are an
important contributor to urban ambient PM, especially for PM2.5.
� Contribution to urban ambient PM from combustion sources can be generally categorized as consisting of primary and secondary particles.
� Primary particles are emitted directly from sources
• According to source-level sampling methods, PM from source
can be classifed as filterable and condensible particles.
� Secondary particles form in the atmosphere through
the reaction of numerous compounds, such as
SO2,NOx and VOCs
BackgroundBackgroundBackgroundBackgroundUS EPA method 17 and
method 5 collect filterable particles
�Using an in-stack filter according to method 17, solid and liquid particles present at the stack T are captured on the filter.
�Chinese national standard GB/T 16157-1996 for PM sampling from stationary sources is similar to method 17
BackgroundUS EPA method 202 collects
condensible particles.
� The amount of material collected in a series of impingers in an ice bath downstream of an in-stack filter and includes both fine particles which pass through the filter and vapors that condense at the T of the gas leaving the impingers.
� It tends to overestimate condensible particles.
� The combination of method 17 and method 202 can collect both filterable and condensible particles
Background
CIT Dilution Sampling System (Hidemann et al., 1989)
Dilution sampling methods
are widely used to simulate
the cooling and dilution processes after hot flue gas leaving the stack
�In dilution sampling methods, hot emissions are rapidly cooled and mixed with cleaned ambient air after leaving a stack.
�The rapid cooling and dilution promote gases to nucleate homogeneously and heterogeneously or condense on pre-existing particles, as in the ambient environment.
�It can collects both filterable and condensible particles
Tsinghua’s compact dilution sampler
Dilution air
Stack
Pressurized air
First diluter
Second diluter
Residencechamber
Cyclone
Venturi
Sampling part
Valve
redundant gas
�Inlet part
�First dilution system
�Pressurized air
�First diluter
�Venturi flowmeter
�Valve
�Second dilution system
�Dilution air
�Venturi flowmeter
�Second diluter
�valve
�Residence chamber
�Sampling part
redundant gas
Dilution sampler
First diluter� Dekati Diluter DIDekati Diluter DIDekati Diluter DIDekati Diluter DI----100100100100� The operation principle of the diluter is based an The operation principle of the diluter is based an The operation principle of the diluter is based an The operation principle of the diluter is based an
ejection type dilution. ejection type dilution. ejection type dilution. ejection type dilution. � Pressurized dilution air is conducted into the diluter Pressurized dilution air is conducted into the diluter Pressurized dilution air is conducted into the diluter Pressurized dilution air is conducted into the diluter
through an ejector cavity. The underpressure through an ejector cavity. The underpressure through an ejector cavity. The underpressure through an ejector cavity. The underpressure caused by the dilution air flow draws the sample caused by the dilution air flow draws the sample caused by the dilution air flow draws the sample caused by the dilution air flow draws the sample through the nozzle.through the nozzle.through the nozzle.through the nozzle.
Dilution sampler
sampling gas from first diluter
Dilution airDilution air
Mixing zone
Second diluter� The second diluter is an
enclosed cylinder with a perforated cone inside.
� The sample gas from the first diluter is introduced into the inside of the cone.
� The dilution air is forced through the apertures of the cone into the inside and then mixes with the sample flow.
Dilution sampler
� The dilution ratio (DR) of the first diluter is 8
� The DR of second diluter is 2.5~6
� The total DR of the two stage diluters ranges from 20 to 50.
� A regulator valve, attached at the exhaust pipe of the first diluter, is used to regulate gas flow rate of outlet into the second diluter.
� A regulator valve, attached at pipeline of the second dilution air, is used to regulate dilution air rate of the second diluter
Dilution sampler
� Residence time, 100L/min, about 80s
� Temperature, cooling unit, less than 40oC
� RH is less than 60%, dilution air is dryed by
desiccant.
Dilution sampler
Check the DR
� In the field measurement, DRT=DR1xDR2
• DR1
DR1 of the first diluter was according to the sheet supplied by Dekati
• DR2
Q1 sampling gas of the outlet of the first diluter,
Q2 second dilution air
� In the lab, we use standard gas (NO2992ppm))))to check the DR, flue gas analyzer was used to masure NO2 in the chamber
� RSD The results is 7.4%
stack
Flue gas analyzer
Dilution sampler
20L Tedlar bag
PM2.5
sampler
((((Teflon))))
1L Tedlar bag
PM2.5sampler((((Quartz))))
CO2、、、、CO、、、、CH4、、、、NMTHCsand N2O analysis
ELPI Aethalometer
Canister
DNPH
NMHCsanalysis
Carbonylsanalysis
Impinger
SO2, NOx
and NH3
Flow chart for measurement emissions from biofuel combustion
Conclusions
� The combination of two stage diluters shortens the length of mixing section. The size of the residence chamber is reduced by decreasing the nominal flow rate through the aging section to 100 L/min. The decreased size of the sampler is suitable for field test.
� The sampling gas is pressured into the residence chamber and the air pressure in the chamber is micro-positive. The un-collected redundant gas was discharged through pressure-equalizing port attached at the lower part of chamber automatically, which will keep the unit stable.