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CHBE 370 (Fundamentals of Sustainable Engineering) > Chapter 7: Sustainable engineering applications for process industries > Flashcards

Chapter 7: Sustainable engineering applications for process industries Flashcards

1
Q

What are categories of pollution prevention for unit operations?

A
  • Material
    selections and substitutions
    – Chemical reactors
    – Separators and heat exchangers
    – Fugitive emissions
    – Storage, transport and loading/unloading operations
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2
Q

What are examples of pollution prevention in industrial processes?

A

-Use of less hazardous materials and design of
safer/benign chemicals

-Use of high quality raw materials with less
impurities or elimination of feedstock impurities

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3
Q

What do chemical reactors do?

A

Chemical reactors convert raw materials into desired products.

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4
Q

What is an environmental concern about chemical reactors and how will improving the performance of the reactor help the environment?

A

-Wastes or byproduct may be produced and
propagate into downstream processing units.
-Improving the chemical reactors’
performance will directly lead to the reduction or
elimination of waste streams.

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5
Q

What are the general measures of performance for chemical reactors?

A

-Conversion
-Selectivity
-Yield
-Atom Economy

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6
Q

Define conversion

A

How much feed is converted

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7
Q

What is selectivity?

A

How much converted feed becomes the
product

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8
Q

Yield

A

How much product collected for each unit of
feed into the reactor

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9
Q

What is atom economy?

A

the ratio of the molecular weight of
the desired product and the molecular weight of all
materials generated from the transformation

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10
Q

What are general approaches for improving the performing of a chemical reactor?

A

-Maximize atom economy in the design
of a reaction pathway
- Maximize selectivity toward the desired
product

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11
Q

What property difference does distillation/absorption exploit?

A

Vapor pressure

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12
Q

What property difference does adsorption use?

A

Chemical and physical surface sorption

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13
Q

What property difference does condensation use?

A

Boiling point

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14
Q

What property
difference do membranes use?

A

Diffusivity and solubility

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15
Q

What propery difference do reverse osmosis/micro-and ultrafiltration use?

A

Molecular size

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16
Q

What property difference does crsytallization use?

A

Melting point

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17
Q

What property difference does liquid-liquid extraction use?

A

Distribution between immiscible phases

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18
Q

What property does sedimentation exploit?

A

Particle size and density

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19
Q

What are options for waste minimization from unit operations?

A
  • Improve separation efficiencies

-Reduce waste generation from reboiler

– Insulate or preheat the column feed to reduce the load on the
reboiler.

– Reduce pressure drop over the column or reduce the pressure
in the distillation column (vacuum distillation) to lower the
load on the reboiler.

– Reduce fouling by the use of on-line cleaning techniques,
antifoulants, specially designed heat exchange tubes or heat
exchangers.

– Improve cleaning techniques for heat exchangers

– Redesign of the reboiler to avoid the unnecessary shut-down.

  • Good process control and maintenance to avoid
    unstable operation
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20
Q

How much do fugitive emissions from synthetic organic chemical manufacturing industry facilities account for?

A

1/3 of the total organic emissions.

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21
Q

How can fugitive emissions be reduced?

A

-Regularly
monitoring and maintaining facilities. Greater frequency = more emissions reduction

-Reduce the number of equipment components

  • Replace low quality components with high
    quality components
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22
Q

How does leaking result from connectors?

A

Leaking mainly results from
aging and damage of the flange gaskets
after exposure to high temperature/pressure
and corrosive fluids environment.

23
Q

Where does leaking come from when it comes to valves?

A

Leaking mostly comes from the movable stem
due to the worn or damaged packing sealant.

24
Q

Where does leaking come from when it comes to pumps and compressors?

A

Leaking comes from the
sealing surrounding the pump or compressor shaft.

25
Q

How to prevent leaks from valves?

A

Use high quality valves with dual-packing or dual valves.

– Use leakless valves like bellow and diaphragm valves in
places with little tolerance

26
Q

How to prevent leaks from pumps and compressors?

A

Use packing sealant, mechanical seal, tandem seal and double
seal and the leakless diaphragm pump.

27
Q

How to prevent leaks from pressure relief devices?

A

Use rupture disks rather than relieve valves.

28
Q

How to prevent open-ended valves and lines from leaking?

A

Install pipe plugs, caps or blind flanges, dual-valves.

29
Q

What are some common equipment that can be modified to reduce fugitive emissions?

A

-Connectors
-Valves
-Pumps and compressors
-Pressure relief devices
-Open-ended valves and lines
-Sampling systems

30
Q

What are some options for minimizing waste/emissions from storage tanks?

A

-Using mixers and emulsifying agent to reduce tank
bottoms which are sludge accumulating at the
bottom of large storage vessels.

  • Vapor-recovery devices that trap and condense
    escaping vapors for return to the tank can be used
    to reduce emissions from fixed-roof storage tanks.
  • Breathing losses can be prevented by using
    variable-vapor-space tanks with a telescoping roof
    or a flexible diaphragm or by floating a roof on the
    surface of the liquid in the tank.
31
Q

What are some options for minimizing wastes/emissions from loading/unloading operations?

A

Using off-loading devices to completely empty
shipping containers

-Using dedicated service containers to avoid cleaning
residual materials

  • Using reusable containers
  • Using appropriate-sized containers
32
Q

Which type of recycling is favoured to reduce the impact associated with waste handling and transportation?

A

On-site recycling

33
Q

What are the four principles of natural ecosystems?

A
  1. Roundput
  2. Diversity
  3. Locality
  4. Gradual changes
34
Q

Explain the “roundput” principle of natural ecosystems

A

Waste equals food, and the only input to the
system is the solar energy from the sun.

35
Q

Explain the “diversity” principle in natural ecosystems

A

Ecosystem survival is based on diversity,
diversity in species, in organisms, in interdependency, in
“cooperation” and in information.

36
Q

Explain the “locality” principle in natural ecosystems?

A

The “actors” in the ecosystem adapt to the local
environmental conditions and cooperate with their
surroundings in diverse interdependent relationships.

37
Q

Explain the “gradual changes” principle in natural ecosystems?

A

Ecosystem survival relies on the flow
resource from the sun, and the evolution respects the
renewal rate of the ecosystem.

38
Q

How would an ideal industrial ecosystem be constructed?

A

The system would be constructed from two
systems: the industrial subsystem and the natural/mother
ecosystem in which the industrial ecosystem is embedded.

39
Q

What would be the only input and output to the ideal industrial ecosystem AS A WHOLE?

A

Input: Solar energy

Output: Waste heat

40
Q

What would be the inputs to the industrial system in the ideal industrial ecosystem?

A

The renewable resources and recycling of matter as
cascading of energy would then happen between the
industrial actors of the system.

41
Q

What would be the outputs from the industrial system to the natural system in an ideal industrial ecosystem?

A

Only such things that nature can tolerate or
perhaps re-use and recycle in its own operation.

42
Q

What are the important goals of food webs analysis?

A

-To study the flows of resources in ecosystems

-To analyze ecosystems for dynamic interactions

43
Q

Why are food web studies in biological systems formed?

A

They are formed as opportunistic
responses to local
resource
availability and
desirability.

44
Q

What is species richness?

A

The number of different types of
organisms within the system

45
Q

What is connectance?

A

Degree of interactions

46
Q

What does metabolic analysis focus on and what is identified as a result of the analysis?

A

Metabolic analysis focuses on what enters a facility/system, what
leaves, and to what degree entering material is utilized usefully
or is lost. Opportunities for substantially improving
environmental performances can often be identified.

47
Q

What is the emphasis of elemental flow analysis?

A

The atom (Ex. gold, silver, lead)

48
Q

What is the emphasis of molecular flow analysis?

A

Focus on molecules

49
Q

What are disadvantages and obstacles to eco-industrial parks (EIPs)?

A

-Inflexibility in the use of resources

-Uncertainty in the supply of raw materials

-Obstacles to technological innovations

-Limits imposed by the management, funds, organization
etc.

50
Q

How can pollution prevention be implemented for chemical reactors?

A
  • Selection of less toxic and high quality raw materials

– Pre-purification of raw materials

– Optimization of selectivity and conversion

– Recycling of unconverted raw materials

– Development of new catalyst for new reaction pathways

51
Q

How can pollution prevention be achieved in chemical processes?

A

By optimizing the energy and matrial
efficiency of individual unit operations.

52
Q

What are ways to prevent pollution in separation units?

A

-Selection of suitable separation process

– Enhancing separation efficiency and energy efficiency

– Minimizing the sludge generation from reboilers

– Prolonging the operation of separation units.

53
Q

What are potential opportunities for eco-industrial parks?

A

-Build EIPs to make optimal use of mass flux, energy flux
and information flux

– EIPs can promote green development via developing green
links between industries or groups of industries

– EIPs can create R&D opportunities for new processes and
equipments

54
Q

How can secondary emissions be reduced?

A

-Alteration of waste treatment equipment

– Pretreatment of the waste streams to remove VOCs

– Modification of waste streams.

– Switch from conventional “dirty” fuels to “clean”
and/or renewable fuel sources

– Combustion modifications.

CHBE 370 (Fundamentals of Sustainable Engineering) (11 decks)

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