Idea Transcript
Design of a compact dilution sampler for stationary combustion sources
Xinghua Li, Shuxiao Wang, Lei Duan and Jiming Hao Department of Environmental Science and Engineering Tsinghua University, Beijing, China A&WMA International Specialty Conference: Leapfrogging Opportunities for Air Quality Improvement May 10-14, 2010, Xi’an, China
Outline Background Tsinghua’s compact dilution sampler Conclusion
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
Background US 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
Background US 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 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
CIT Dilution Sampling System (Hidemann et al., 1989)
Background
DRI Dilution System Based on CIT design
Background
US EPA’s conditional method CTM 39
Background Compact dilution sampler
GE Energy Compact Dilution Samplers (England et al., 2007)
Tsinghua’s compact dilution sampler Inlet part First dilution system
Cyclone
Pressurized air First diluter Venturi flowmeter Valve
Pressurized air
First diluter Venturi
Second dilution system
Dilution air Venturi flowmeter Second diluter valve
Second diluter
redundant gas Valve Dilution air
Residence chamber Sampling part
Residence chamber
Stack
Sampling part
redundant gas
Dilution sampler First diluter
Dekati Diluter DIDI-100 The operation principle of the diluter is based an ejection type dilution. Pressurized dilution air is conducted into the diluter through an ejector cavity. The underpressure caused by the dilution air flow draws the sample through the nozzle.
Dilution sampler 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.
sampling gas from first diluter Dilution air
Dilution air
Mixing zone
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 Calibration of the venturi flowmeter
Dilution sampler Sampling gas and dilution gas were mixed well
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%
Dilution sampler Particle loss
Hildemann, et al. 1989
Flow chart for measurement emissions from biofuel combustion stack
Flue gas analyzer
ELPI
Aethalo meter
Dilution sampler
PM2.5 sampler （Teflon） ）
PM2.5sample r（ （Quartz） ）
1L Tedlar bag CO2、CO、 、CH4、NMTHCs and N2O analysis
20L Tedlar bag
DNPH
Impinger
Canister
NMHCs analysis
Carbonyls analysis
SO2, NOx and NH3
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.
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