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Air Dispersion Modelling with Building Wakes Assessment in Jurong Island

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ESC was commissioned by a global leading chemical manufacturing company to conduct Air Quality Impact Assessment in 2015.  

About the Project

As part of the design optimisation to minimise the potential air quality impacts experienced by onsite workers, the client proposes to extend the height of the existing vent combustor stack from 15m to 45m above ground level. On behalf of the client, ESC prepared a report for the proposed stack extension works to the vent combustor. This study is performed to assess the changes of potential air quality impacts arising from the existing Phase I and Phase II processes when the stack height is increased from 15m to 45m and discuss measures adopted to minimise such air quality impacts.

Our Approach

ESC conducted the air quality impact assessment of emissions from a vent combustor and emergency blowdown drum vent at a Chemical Facility at Jurong Island, Singapore. The study modelled for carbon monoxide (CO), oxides of nitrogen (NOx), PM10, PM2.5, sulphur dioxide (SO2), methanol and hexane and assessed onsite and offsite impacts of these pollutants by comparison of the model predictions with long term Singapore ambient air quality targets set by NEA and permissible exposure limits (PELs) specified in the Workplace Safety and Health (General Provisions) Regulations. 

ESC took the following approach: 

  • Identification of nearby air-sensitive receptors 
  • Determination of the quality, rates and quantities of air emissions from the vent combustor with a new stack height 
  • Potential impact assessment of the air emissions from the vent combustor with a new stack height 
  • Determination of measures to control potential air pollution and ensure compliance with emission standards and requirements in the COPPC 
  •  Establishing of monitoring programme after stack extension of vent combustor 


ESC effectively proved that the air emission concentrations emitted from the vent combustor with a new stack height of 45m remain the same from a stack height of 15m. However, the new stack height will ensure a better upward dispersion of air pollutants. With the existing abatement measures to control air pollution, the emissions of pollutants from the vent combustor after stack extension will remain in compliance with the EPMA and COPPC. 

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