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

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

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

Background

DRI Dilution SystemBased 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

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

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

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.

Thanks for your attention!