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PROCESS SAFETY > TOXIC RELEASE AND DISPERSION > Flashcards

TOXIC RELEASE AND DISPERSION Flashcards

TOXIC RELEASE AND DISPERSION

1
Q

During an accident, _____can release _____ quickly and in significant enough quantities to spread in dangerous clouds throughout a plant site and the local community

A

Process equipment, toxic materials

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2
Q

Rupture of pressure vessel as a result of ?

A

excessive pressure caused by a runaway reaction

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3
Q

rupture of pipeline containing

A

toxic materials at a high pressure

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4
Q

rupture of a tank containing

A

toxic materials above its atmospheric boiling point

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5
Q

What serious accident emphasize the importance of planning emergencies and designing plants to minimize the occurrence and consequences of toxic release

A

Bhopal Tragedy

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6
Q

Are routinely used to estimate the effects of a release on the plant and community environments

A

Toxic release models

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7
Q

Why must chemical engineers understand all aspects of toxic release?

A
  1. To prevent the existence of release situations
  2. To reduce the impact of a release if one occurs
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8
Q

Understanding all aspects of toxic release of a ChE requires what?

A

Toxic release model

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9
Q

Describes the airborne transport of toxic materials away from the accident site and into the plant and community

A

Dispersion models

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10
Q

After a release of the airborne, toxic material is carried away by the wind in what characteristics?

A

Plume or Puff

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11
Q

Where does the maximum concentration of toxic material is located?

A

At the release point (may not be at ground level)

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12
Q

Concentrations downwind are ____ because of ______ and dispersion of the toxic substance with ____

A

less, turbulent mixing and air

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13
Q

What is the purpose of the toxic release model?

A

Provide a tool for performing release mitigation

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14
Q

Parameters affecting atmospheric dispersion of toxic materials: (5)

A
  1. Wind speed
  2. Atmospheric stability
  3. Ground conditions (buildings, water, trees )
  4. height of the release above ground level
  5. momentum and buoyancy of the initial material released
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15
Q

Are used to estimate the concentrations downwind of a release in which the gas is mixed with fresh air.

A

Neutrally Buoyant Dispersion Models

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16
Q

These models apply to gases at low concentrations, typically in ppm range

A

Neutrally Buoyant Dispersion Models

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17
Q

2 types of neutrally buoyant vapor cloud dispersion models

A
  1. Plume models
  2. Puff models
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18
Q

Describes the steady-state concentration of material released from a continuous source

A

Plume models

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19
Q

The release of a continuous puffs

A

Plume

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20
Q

Were originally developed for dispersion from a smoke stack

A

Plume models

21
Q

Plume can develop when ?

A

There is a leak in a large tank

22
Q

If there is a leak in a large tank what could develop?

A

Plume

23
Q

Describes the temporal concentration of material from a single release of fixed amount of material

A

Puff model

24
Q

Used when you have essentially an instantaneous release and the cloud is swept downwind

A

Puff model

25
Q

Describe a plume

A

Puff model

26
Q

Pasquill-Gifford or

A

Gaussian Dispersion Models

27
Q

Guassian Dispersion Model or?

A

Pasquill-Gifford

28
Q

Because of fluctuations and turbulence, _____ is constantly changing (PG Model)

A

Diffusivity

29
Q

These equations don’t do a good job in predicting dispersion

A

Traditional transport phenomena equations

30
Q

This assumes that the materials spread out in a normal Gaussian -type distribution

A

Pasquill-Gifford or Gaussian Dispersion Model

31
Q

According to Pasquill-Gifford Model, as the plume is swept downwind, the concentration profile?

A

spreads out and decreases

32
Q

This applies only to neutrally buoyant dispersion of gases in which turbulent mixing is the dominant featureof the dispersion

A

Pasquill-Gifford or Gaussian Dispersion Model

33
Q

Pasquill-Gifford or Gaussian Dispersion Model is valid only for a distance of ? from the release point

A

0.1 to 1 km

34
Q

Best suited for instantaneous or continuous ground-level releases of dense gases

A

Dense Gas Dispersion: Britter and McQuaid Model

35
Q

In this model, the release is assumed to occur at ambient temperature and without aerosol or liquid droplet formation

A

Dense Gas Dispersion: Britter and McQuaid Model

36
Q

Dense Gas Dispersion: Britter and McQuaid Model reuires specification of? (7)

A

Initial Cloud Volume
Initial Plume Volume Flux
Duration of release
Initial gas density
windspeed at a height of 10 m
distance downwind
ambient gas density

37
Q

Any gas whose density is greater than the density of the ambient air though which it is being dispersed

A

dense gas

38
Q

A gas with a molecular weight greater than that of air

A

dense gas

39
Q

A gas with low temperature resulting from autorefrigeration during release

A

Dense gas

40
Q

Lessening the risk of a release incident by acting on the source in a preventive and protective way

A

Release Mitigation

41
Q

Reducing the likelihood of an event that could generate a hazardous vapor cloud

A

preventive way

42
Q

reducing the magnitude of the release and/or exposure of local persons or property

A

Protective way

43
Q

6 Release Mitigation

A
  1. Inherent Safety
  2. Engineering Design
  3. Management
  4. Early Vapor Detection
  5. Countermeasures
  6. Emergency response
44
Q

Inventory reduction
chemical substitution
process attenuation

A

Inherent safety

45
Q

Physical integrity of seals and construction
Process Integrity
Emergency Control
Spill containment

A

Engineering design

46
Q

Policies and procedures
Training for vapor release
Audits and Inspections
Equipment testing
routine maintenance
management of change
Security

A

Management

47
Q

Sensors
Personnel

A

Early vapor detection

48
Q

Water sprays and curtains
steam or air curtains
deliberate ignition
foams

A

countermeasures

49
Q
A

PROCESS SAFETY (3 decks)

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