Modeling of fugitive dust emission and control measures in stone crushing industry

專題討論碩一

79842001劉昱麟

Abstract

• A cluster of 72 stone crushing units located at Trisoolam in Chennai is a source of high levels of dust generation in the vicinity of the crushers and in the communities surrounding them.

• FDM, ISCST3 and AERMOD were employed for prediction of dust emission from stone crushers on the surrounding areas.

• The control measures adopted at these stone crushing units are not sufficient enough to bring down the concentration within the stipulated limits.

Materials and methods

• Weather monitoring• Ambient air quality monitoring network design

• Air quality monitoring• Particle size analysis• Emission rate estimation• Assessment of occupational exposure level

• Modeling of fugitive dust emissions• Data requirements of the models• Model prediction

氣象監測鄰近空氣品質監測系統

空氣品質監測粒徑分析

模式模擬預測

估算排放率職業性暴露性層級評估

模式應用模式參數設定

Study areaRSPM 可吸入懸浮顆粒物

TSPM 總懸浮顆粒物

• Weather monitoring Wind speed

Wind direction

Temperature

Pressure

Rainfall

Humidity

• Ambient air quality monitoring network design 17 sites across the area

10 location at stone crushing units

7 in ambient air

風速

氣溫風向

氣壓

濕度降雨

Modeling of fugitive dust emissions(1/3)

• FDM(揚塵擴散模式 ) 1. Computerized Gaussian plume air quality dispersion model

2. Three basic types of sources: point, line, and area

3. Designed for estimation of concentrations and deposition impacts from fugitive dust sources.

4. Gravitational settling velocity and deposition velocity are calculated.

• ISCST3(工業污染短期模式 )

1. Based on the straight line, steady state Gaussian plume equation.

2. Three basic types of sources: point, volume, and area.

3. Estimates the concentration or deposition value for each source and receptor combination for each hour of input meteorology, and calculates user selected short term averages.

4. Includes a new wet deposition algorithm and also incorporates the COMPLEX1 screening model algorithms.

Modeling of fugitive dust emissions(2/3)

• AERMOD(美國環境保護逸散模式 )

1. It serves as a complete replacement for ISCST3.

2. It assumes the concentration distribution to be Gaussian in both the vertical and horizontal in the stable boundary layer (SBL), but the vertical distribution is described to bi- Gaussian probability density function in the convective boundary layer.

3. The major improvements that AERMOD brings to applied dispersion modeling is its ability to characterize the Planetary Boundary Layer (PBL) through both surface and mixed layer scaling.

Modeling of fugitive dust emissions(3/3)

Model prediction

1. Emission rate

2. Particle size distribution of dust

3. Meteorology

4. Source-receptor geometry

5. Treatment for deposition

6. Scavenging effect

Result and discussion

• Weather monitoring• Air quality monitoring• Particle size analysis• Emission rate estimation• Assessment of occupational exposure level• Model prediction• Control measures• Impact zone

Dust concentration at sourceDust concentration around stone crushing units

• Weather monitoring direction in southwest 19%

direction in west 18.5%

direction in west of southwest 14%

wind speed in 5~10kmph 25%

wind speed in 10~15kmph 15%

ave. wind speed is 9.65kmph

Air quality monitoring (Dust concentration at

source)

Air quality monitoring (Dust concentration around stone crushing units)

Particle size analysis

PM30

PM15

PM2.5

73.5 ％

14.3 ％

45 ％

• Emission rate estimation micro-meteorological condition

location of source and receptor

upwind and downwind direction

3.89g/s 2.778g/s(USEPA)

＞＞

• Assessment of occupational exposure level

Occupational Safety and Health Administration

National Institute of Occupational Safety and Health

American Conference of Governmental Industrial Hygienists

Indian Factory Act.

職業安全與健康機構 (15mg/m3 for total)

印度工業法規

國家安全與健康協會 (10mg/m3 for TSPM)美國政府工業衛生聯盟 (10mg/m3 for TSPM & RSPM)

EXCESSEXCESS

Model prediction

Model prediction

Control measures

Control measures

1. Dust containment cum suppression system for the equipment2. Construction of wind breaking walls3. Construction of metalled roads within the premises4. Regular cleaning and wetting of the ground within the premises

1. Reducing drop heights2. Spray nozzle for periodical wetting of dust3. Collection of fine powder below ground level and completem cover

ing4. Covering of loaded trucks using tarpaulins while transportation5. Arresting re-entrainment of settled dust from surfaces

Implementation of following pollution control measures at source

Growing of a green belt along the periphery

In addition the following good house keeping were also implemented to further reduce the dust emissions

Impact zone

N

W E

S

風向N

W E

S

風向

Conclusion

• The adequacies of the control measures is not sufficient enough to bring down the concentration within stipulated limits in residential areas located less than 300 m from stone crushing activity in the eastern direction.

• There is a scope for further improvement of control measures at these stone crushing units in Trisoolam area.