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process Safety > 4 > Flashcards

4 Flashcards

1
Q

Effects of air pollution

A

Health
Acidification
Eutrophication
Climate change

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2
Q

PRIMARY SOURCES of AIR POLLUTION

A

These are emitted directly into the atmosphere.
- SO2
- CO
- NOx
- SOx
- Particulates
- Hydrocarbons
- Metals

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3
Q

SECONDARY SOURCES of AIR POLLUTION

A

These pollutants are formed in the atmosphere by chemical reactions either with water or by reaction with sunlight. These include:
- O3 (ozone)
- Other photochemical oxidants
- Oxidised hydrocarbons

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4
Q

UK Clean Air Strategy,
2019

A

Plans for dealing with all sources of air pollution, making our air healthier to breathe, protecting nature and boosting the economy

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5
Q

UK Clean Air Strategy Aim, Emission targets for 5 key pollutants:

A

Aim to cut harm to human health by half.

Emission targets for 5 key pollutants:
* Fine particulate matter (PM 2.5
* Ammonia (NH 3
* Nitrogen oxides (NO x
* Sulphur dioxide (SO 2
* Non methane volatile organic compounds (NMVOCs)

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6
Q

What can we do on a personal level?

A

Reduce vehicle usage

Turn off your engine when parked or in traffic

Switch to electric vehicle

Reduce how much you burn in your home and garden

Insulate your home

Reduce number of deliveries needed

Reduce exposure by:
Opening windows when cleaning or doing DIY
Choose quieter routes when walking or cycling

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7
Q

Air pollution categories

A

Primary: Emitted directly into the atmosphere
e.g. particles from diesel engines

Secondary: Formed by reaction with atmosphere
e.g. sulphuric acid from sulphur
dioxide

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8
Q

Sources of industrial emissions

A
  • Continuous:
    Stacks
    Chimneys
    General ventilation
    Vacuum pumps
  • Routine:
    Equipment cleaning
    Start up /shutdown
    Materials handling
  • Irregular:
    (The most difficult to control!)
    Plant failure
    Spillages
    Leaks
    Demolition
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9
Q

CRITERIA POLLUTANTS identified by the EC and WHO are:

A
  • CO
  • NO2
  • O3 (Ozone)
  • SO2
  • PM-10 (particulate matter with diameter <10μm)
  • Lead
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10
Q

CLIMATE CHANGE

A

Climate change is the long-term change in average weather conditions, including temperature, precipitation and wind.

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11
Q

PARIS AGREEMENT, 2015

A

Key elements:
*To limit global temperature increase to 1.5 C
*To limit GHG emissions by humans to the same levels that
trees, soil and oceans can absorb naturally (Net
*Achieve this between 2050 and 2100
*Rich countries to help poor

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12
Q

IMPACT OF AIR POLLUTION – BHOPAL DISASTER

A

The Bhopal gas tragedy is considered the world’s worst industrial disaster.
Over 500,000 people were exposed to methyl isocyanate Methyl isocyanate and other chemicals Long term health effects

These gases caused long term health effects:
- Eye damage – cataracts, corneal opacities
- Respiratory issues
- Neurological impairments
- Children’s health – many children of parents exposed have birth defects

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13
Q

UK Net zero targets

A

Requires UK to bring all greenhouse gas emissions
to net zero by 2050
First

First major economy to pass net zero emissions law
Part of the Climate Change Act

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14
Q

net zero meaning

A

Net zero means any emissions balanced by schemes to off
set equivalent amount of GHG from atmosphere
E.g. by planting, more trees, carbon capture and storage

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15
Q

Waste minimisation hierarchy
air pollution

A

Reduction at source: Efficient design
Recycling/reuse: Collection & Recycling
Treatment:
- Incineration
- Adsorption
- Absorption
Disposal: to air

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16
Q

Characterisation

A

so the emissions should be fully characterised for:
- Concentration
- Flow and Variation
- Physical Properties
- Chemical Properties
- Temperature & Pressure

17
Q

REDUCTION AT SOURCE

A

Changing or eliminating a process that produces air pollution is often easier than trying to trap the effluent.

Change process

Change raw materials

Containment

Housekeeping

18
Q

Air pollution treatment methods

A

Cooling
Cyclones
Filtration
Scrubbers
ESP
Flaring
Specific contaminant removal

19
Q

Collection

A

Big challenge for mobile
sources
Process emissions from
stacks easier to collect
Impact of fugitive emissions

20
Q

Cooling

A

For gases too hot for treatment
Cooling may drop below condensation point
Removes some particulates and
gases
Can produce liquid effluent

21
Q

Cyclones

A

Very common for pre-cleaning
Use centrifugal forces to remove particles
Cheap to install
No moving parts
Small
Work best on large particles

22
Q

Fabric filters

A

Operate like a vacuum cleaner
Removes particulates
Filter elements collect the dust
Removed periodically
Not suitable for high temperatures or wet gases
Solid residue reuse/disposal
Explosion risk

23
Q

Wet collection
scrubbers

A

Examples are spray towers, venturi scrubbers, packed scrubbers

Effectively remove particles >
5 µm and some gaseous pollutants using water

Use a large amount of liquid

Not ideal where water supplies are limited

Expensive to construct and operate

Alternative liquids can be used to collect gaseous pollutants (absorption)

24
Q

ELECTROSTATIC PRECIPITATORS

A

Electrostatic precipitators (ESP) are widely used to trap fine particulate matter in applications where a large volume of gas needs treatment and where a wet scrubber is not appropriate.

25
Q

Adsorption

A

Effective for low concentrations
Several different techniques
available
Activated carbon, alumina, silica gel
Adsorption material has finite
capacity so needs regeneration /disposal

Adsorption – gas is contacted with a solid
Absorption – gas is contacted with a liquid

26
Q

Incineration or flaring
Used

A

Used when a pollutant can be oxidised to CO 2 and water, or in oxidising H 2 S to SO 2

Catalytic combustion can allow for lower temperature flare

Common in oil and gas

Can be designed with no visible flame

27
Q

Control of sulphur oxides (SO x)

A

Before
*Low sulphur fuel

During
*Fluidised bed combustion
*Gasification

After
*Flue gas de sulphurisation

28
Q

Flue gas desulphurisation
Common treatment methods:

A

Largest source of SO2 is burning fossil fuels

Common treatment methods:
*Wet scrubbing with an alkaline
*Wet sulphuric acid process
*Dry sorbent injection

FGD may remove 95 % or more of SO 2

29
Q

Control of nitrogen oxides (NOx)

A

Burner design (low NOx burners)
Low excess air
Recirculate flue gas
Inject water into combustion
chamber
Staged combustion
Inject ammonia

30
Q

Control of VOCs and odour

A

Incineration or combustion is common for low concentrations

Catalysts achieve 95-99 % destruction of VOCs

Condensation and absorption used for high concentrations of VOCs

31
Q

Odour treatments:

A

-Biofilters
-Ozone treatment
-Masking/neutralising

32
Q

Control of CO2

A

CO2 produced by oxidation of organic compounds

Combustion

Respiration

Oxidative decay

Substitute fossil fuels with other fuels or energy providers

33
Q

Carbon capture and storage (CCS)

A

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process Safety (8 decks)

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