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

1. Modeling of fugitive dust emission and control measures in stone crushing industry 專題討論 碩一 79842001 劉昱麟

2. 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.

3. 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 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 模式模擬預測

4. TSPM 總懸浮顆粒物 Study area RSPM 可吸入懸浮顆粒物

5. 風速 風向 氣溫 • 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 氣壓 降雨 濕度

6. Modeling of fugitive dust emissions(1/3) • FDM(揚塵擴散模式) • Computerized Gaussian plume air quality dispersion model • Three basic types of sources: point, line, and area • Designed for estimation of concentrations and deposition impacts from fugitive dust sources. • Gravitational settling velocity and deposition velocity are calculated.

7. Modeling of fugitive dust emissions(2/3) • ISCST3(工業污染短期模式) • Based on the straight line, steady state Gaussian plume equation. • Three basic types of sources: point, volume, and area. • 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. • Includes a new wet deposition algorithm and also incorporates the COMPLEX1 screening model algorithms.

8. Modeling of fugitive dust emissions(3/3) • AERMOD(美國環境保護逸散模式) • It serves as a complete replacement for ISCST3. • 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. • 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.

9. Model prediction • Emission rate • Particle size distribution of dust • Meteorology • Source-receptor geometry • Treatment for deposition • Scavenging effect

10. 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 source Dust concentration around stone crushing units

11. 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

12. Air quality monitoring (Dust concentration at source)

13. Air quality monitoring (Dust concentration around stone crushing units)

14. Particle size analysis PM30 73.5％ PM15 45％ PM2.5 14.3％

15. Emission rate estimation micro-meteorological condition location of source and receptor upwind and downwind direction 3.89g/s2.778g/s(USEPA) ＞

16. EXCESS • Assessment of occupational exposure level 職業安全與健康機構 (15mg/m3 for total) Occupational Safety and Health Administration National Institute of Occupational Safety and Health 國家安全與健康協會 (10mg/m3 for TSPM) American Conference of Governmental Industrial Hygienists 美國政府工業衛生聯盟 (10mg/m3 for TSPM & RSPM) Indian Factory Act. 印度工業法規

17. Model prediction

18. Model prediction

19. Control measures

20. 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 Control measures • Dust containment cum suppression system for the equipment • Construction of wind breaking walls • Construction of metalled roads within the premises • Regular cleaning and wetting of the ground within the premises • Reducing drop heights • Spray nozzle for periodical wetting of dust • Collection of fine powder below ground level and completem covering • Covering of loaded trucks using tarpaulins while transportation • Arresting re-entrainment of settled dust from surfaces

21. N N 風向 風向 E E W W S S Impact zone

22. 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.