CHAPTER 5 - TOXIC RELEASE AND DISPERSION MODEL Flashcards
A ________ is defined as any gas whose density is greater than the density of the ambient air through which it is being dispersed.
b. Dense gas
The dense cloud slumps toward the ground under the influence of ________, increasing its diameter and reducing its height.
a. Gravity
A model that was developed by performing a dimensional analysis and correlating existing data on dense cloud dispersion.
c.Britter and McQuaid Model
With Eq. 5-64, if the group has a value greater than or equal to 2.5, then the dense gas release is considered as?
a. Continuous
With Eq. 5-64, if the group value is less than or equal to 0.6, then the release is considered as?
b. Instantaneous
What assumption was made in the Britter-Mcquaid Model about the release of dense gases?
a. occurs at ambient temperature and without aerosol or liquid droplet formation.
What was found to have little effect on the results and is not a part of the Britter-Mcquaid model.
d. Atmospheric Stability
What is the area that most data of the dispersion tests came from?
c. rural area on flat terrain
The model requires a specification of the wind speed, distance downwind, and ambient gas density. At what elevation is required for the wind speed?
b. 10 m
As a dense gas moves downstream the concentration ________.
c. Decreases
This case is the same as case 2 but with eddy diffusivity as a function of direction. The applicable conditions are:
-Puff release (Qm= constant)
-No wind ((uj)=0), and
- Each coordinate direction has a different but constant eddy diffusivity( Kx,Ky,andKz)
d. Case 5: Puff with No Wind and Eddy Diffusivity Is a Function of Direction
This case is the same as case 5 but with wind.he applicable conditions are,
-Puff release (Qm= constant)
-Wind blowing in x direction only (uj)=(ux)=u=constant, and
-Each coordinate direction has a different but constant eddy diffusivity( Kx,Ky,andKz)
b. Case 7: Puff with Wind
This case is the same as case 4 but with eddy diffusivity a function of direction. The applicable conditions are:
-Continuous release (Qm= constant)
-Steady State (d(c)/dt=0),
-Wind blowing in x direction only ((uj)=(ux)=u=constant
-Each coordinate direction has a different but constant eddy diffusivity( Kx,Ky,andKz)
a. Case 6: Steady-State Continuous Point Source Release with Wind and Eddy Diffusivity Is a Function of Direction
The EPA9 suggests that F stability can exist with wind speeds as low as ____.
a. 1.5 m/s
Pasquill-Gifford or Gaussian dispersion applies only to neutrally buoyant dispersion of gasses in which the turbulent mixing is the dominant feature of the dispersion. It is typically valid only for a distance of ______ km from the release point.
a. 0.1–10 km
In the Gaussian plume model, what does a “puff” refer to?
b. An instantaneous release of gas in a single, compact cloud.
In the Gaussian puff model, what primarily determines the size and shape of the puff over time?
b. Atmospheric stability and wind speed.
When applying the Gaussian puff model, what factor is critical in determining the dispersion of the puff over time?
c. The wind speed and direction at the time of release.
In dispersion modeling, what does the term “dense gas” specifically refer to?
a. A gas that is heavier than air and tends to stay close to the ground
In the context of the Gaussian plume model, what does the term “steady-state” imply?
d. Both the wind conditions and the rate of gas release are constant over time.
A process equipment can release toxic materials quickly and in significant enough quantities to spread in dangerous clouds throughout a plant site and the local community during?
b. An Accident
Which statement correctly describes the impact of wind speed on the dispersion of a plume or puff according to the Gaussian dispersion models?
a. Higher wind speeds lead to greater dispersion and lower concentrations at a given point.
What is the primary effect of atmospheric stability on gas dispersion according to the Gaussian dispersion model?
a. Unstable conditions lead to faster vertical dispersion.
Toxic release models are routinely used to _________the effects of a release on the plant and community environments.
a. Estimate
Chemical engineers must ___________ all aspects of toxic release to prevent the existence of release situations and to _______ the impact of a release if one occurs
c. Understand ; reduce
The toxic release model represents the first ________ steps in the consequence modeling procedure.
b. 3
_______________ describe the airborne transport of toxic materials away from the accident site and into the plant and community
c. Dispersion Models
Concentrations downwind are ________, because of turbulent mixing and dispersion of the toxic substance with air.
b. Less
___________________ relates to vertical mixing of the air.
a. Atmospheric Stability
The momentum of a__________ jet will carry the gas higher than the point of release, resulting in a much higher effective release height.
c. Medium-velocity
Emergency response planning guidelines (ERPGs) for air contaminants was issued by?
c. AIHA
What does TLV stands for?
a. Threshold limit value
It is the maximum airborne concentration below which almost everyone believes People could be exposed for up to an hour without feeling or developing permanent or additional severe health consequences or symptoms that might limit their capacity to act in a protective manner.
b. ERPG-2
To date, an AIHA peer review task force has produced ____ and is currently reviewing, updating, and expanding them.
a. 47 ERPGs
An ____ exposure condition is defined as a condition “that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment.”
a. IDLH
Since the _____, the National Research Council’s Committee on Toxicology has provided Emergency Exposure Guidance Levels (EEGLs) for ____ chemicals to the Department of Defense.
a. 1940s ; 44
For smokestack releases Turner suggested using the empirical ______ formula to compute the additional height resulting from the buoyancy and momentum of the release.
b. Holland
- Risk is composed of both _______ and probability.
b. Consequences
Toxic endpoints promulgated by the Environmental Protection Agency (EPA) as part of the _______.
b. RMP
They define an _____ toxic concentration as the level of a toxic gas or vapor that could lead to acute health effects
b. Acute
