Dispersion models describe the airborne transport of toxic material away from th
ID: 107820 • Letter: D
Question
Dispersion models describe the airborne transport of toxic material away from the accident site and into the plant and community. A wide variety of parameters affect atmospheric dispersion of toxic material for example, atmospheric stability and momentum and buoyancy of the initial material released. Explain the following conditions: Atmospheric stability relates to vertical mixing of the air. Compare the vertical mixing for day and night. Atmospheric stability is classified according to three stability classes unstable, neutral, and stable. Describe the THREE (3) classes. The buoyancy and momentum of the material released changed the effective height of release. Explain on what will happen to the released gas if the gas has a density greater than air. A safety officer at Petronas Refinery Plant. Sungai Udang, Malsees is responsible to evaluate each gas stacks in the plant. Due to the changes in normal operations, he needs to evaluate one of the slacks that release carbon monoxide (CO) to the environment m order to ensure it is safe. The stack has an effective height of 65 m and only operated from 20:00 PM to 05:00 AM. Additionally, the onsite technician reported that the indicator located in the stack shows that CO is released at the rate of 75 g/s. Moreover, the average wind speed is recorded at 5 m/s with low cloud. State the assumption clearly and help him to determine: The mean concentration of CO on the ground 500 m downwind. The mean concentration on the ground 500 m downwind and 50 m crosswind The location of the maximum concentration.Explanation / Answer
b)Given the effective height of stack=65m
Rate of CO release=75g/s
Average wind speed=5m/s
i)The mean concentration of CO on ground 500m downwind is calculated as follows:-
Mean concentration of CO=(rate of release of CO*500)/average wind speed
=(75*500)/5=7500g
ii)Mean concentration of CO at 500m downwind and 50m crosswind is as follows:-
Wind direction=500-50=450m
Mean concentration=(rate of CO release*450)/average wind speed)
=75*450/5=6750g
iii)The location of maximum concentration would be present above 500m in downwind direction.
a)i)Atmospheric stability refers to the constant level maintainance in amount of air blowing. It also refers to temperature changes. At morning it would be hot and at night it would be cold. Thus the temperature in the air must also be maintained constant.
ii)Stable state is that when the temperature level is said to be constant over a period of time and the blowing of wind is at a stable velocity.
Unstable is that when the temperature level changes widely and the velocity of blowing wind also does not remain constant.
Neutral state is that when no change takes place in the temperature level as well as in velocity of wind.
iii)If the gas has density greater than air,there are possibilities for the gas to suppress certain matter with its density and it could cause some breathing problems as its density may block air from getting in the nossils.