Senior Design

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• Senior Design
• Guest Lecture 3
• Process Safety Applications
• For Design Engineers
• CHEN 4470
• Spring 2007

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Importance of Process Safety

• The safety record of the chemical process
  industry is the responsibility of all of us in
  the profession.
• Process safety is important for employees, the
  environment, the general public, and its the
  law.
• As process design engineers we are tasked with
  reducing the risk of operating a chemical
  manufacturing process to a level acceptable to
  employees, regulatory authorities, insurance
  underwriters and the community at large.
• Recent chemical plant disasters underscore the
  importance of this point in terms of both human
  and financial losses.

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Importance of Process Safety

• Sonatrach LNG Plant - Skikda, Algeria, January
  2004
• Incident
• A defective, high pressure, steam boiler
  ruptured.
• The resultant explosion on rupture damaged nearby
  vessels containing flammables.
• Flammable loss of containment resulted in further
  fires and explosions.
• Result
• 23 workers were killed.
• Nine bodies never recovered.
• 74 were injured.
• 800,000,000 (U.S.) estimated property damage.

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Process Safety Terminology
Hazard vs. Risk

• HAZARD is a measure of the severity of the
  consequences of a catastrophic failure of a given
  process or system, regardless of the likelihood
  and without considering safeguards.

• RISK is the combination of both the severity of
  the worst case consequence and the likelihood of
  the initiating cause occurring.

• In short, for an EXISTING PROCESS, we have little
  influence on the HAZARD, but through the
  application of safeguards, we can reduce the RISK
  of operating the process.

How do we quantify the Hazards of a process????
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Process Hazard Analysis

• Process Hazard Analysis (PHA) is a technique for
  determining the RISK of operating a process or
  unit operation.
• PHAs are required by law for process handling
  threshhold quantities for certain listed Highly
  Hazardous Chemicals (HHC) or flammables.
• Various techniques have been approved for
  conducting PHAs
• HAZOP
• What If?
• FMEA
• In general, a PHA is conducted as a series of
  facilitated, team brainstorming sessions to
  systematically analyze the process.

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Mitigating Process Risk
The operating risk is mitigated through the
application of safeguards that reduce the risk to
an acceptable level.
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Layer of Protection Analysis

• LOPA is a quantitative technique for reducing the
  RISK of a process.
• The theory of LOPA is based on not putting all
  your eggs in one basket.
• The layers mitigate the process RISK as
  determined by the PHA.
• Each layer reduces the RISK of operating the
  process.

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LOPA Example

• Failure of Transfer Pump leading to overfill of
  Process Vessel.
• Potential release of material to the environment
  requiring reporting or remediation.
• Potential personnel injury due to exposure to
  material.
• Severity would be based on properties of the
  material released.

http//powerlink.powerstream.net/002/00174/051222b
p/BPAnimations.asx
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Inherently Safe Process Design

• Inherent safety is a concept based on eliminating
  the causes and/or reducing the consequences of
  potential process upsets.
• Inherently Safe Process Design is a technique
  applied during the conceptual phase of process
  design.
• Inherently Safe Process Design targets the
  HAZARD, rather than reducing the RISK after the
  fact.
• This technique is based on making inherently
  safer design choices at a point in the process
  development where the engineer has the most
  influence on the final design.

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Inherently Safe Process Design
Inherently safe process design can be grouped
into 5 categories

Category
Example
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Intensification
Continuous reactor vs. batch reactor
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Substitution
Change of feedstock
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Attenuation
Alternate technology
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Limitation of effects
Minimization of storage volume
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Simplification
Gravity flow vs. pumping
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Inherently Safe Process Design Example 1
Azeotropic Distillation vs. Pervaporation

Standard Process
Inherently Safer Process
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Conclusions

• Questions Comments