Notes on Industrial Chemicals and Environment
Notes on Industrial Chemicals and Environment
Q-1 : What are industrial gasses? How can you classify them? What are the areas of use of these gases?
Solution:
A gas or a mixture of gasses which in general remain in
gaseous state at ambient temperature and pressure specifically manufactured for
industry is (are) called industrial gasses.
Classification:
Industrial gasses can be
classified based on their uses such as medical gasses, fuel gasses, refrigerant
gasses, welding gasses, breathing gasses, etc.
Elementary gasses:
Gasses like H2, N2, O2, F2, noble
gasses etc. which are or can be obtained from natural gasses are collectively
called as elementary gasses.
Liquefied gasses:
Gasses which are produced from air: LIN (Liquefied Nitrogen), LOX (Liq. Ox.), LAR (Liq. Argon)
Gasses which are produced from other
sources: Liq. CO2. Liq. H2, Liq. He
Gas mixture from hydrocarbon
Feedstock: LNG (Liq. natural gas), LPG (Liq.
Petroleum Gas)
Compound Gasses: NH3, CO, N2O, SO2, Ethene, Ethane, Butane, Propane,
HCl, NH3, SF6 etc.
Areas of use of industrial gasses:
Aerosol propellants, Fire fighting
gasses, Laboratory and instrumentation, refrigerant, industrial water treatment,
lifting gasses, cryogenics, Coolants, food processing, medical gasses, welding
gasses, metallurgy
Q-2: Discuss the Manufacture, properties, uses and hazards of Oxygen, nitrogen and Argon.
Solution: Manufacture, properties, uses and
hazards of Oxygen:
Two mostly used methods of
preparation are: Electrolysis
of an aq. solution of dilute sulphuric acid and the fractional distillation of
liquid air.
Mfg. of O2 from liquefied Air:
Liq. air broadly contains N2 and O2.
Since nitrogen is more volatile due to lower B.P evaporates first out of the
liq. mixture. As because the B.Ps of the two gasses are closer they are
separated through fractional distillation.
The evolved mixture of gasses (N2 + O2) is passed through a rectifying column. O2 condenses and almost pure N2 leaves at the top of column.
Properties of Oxygen: It is:
- colourless gas
- slightly heavier than air
- sparingly soluble in water
- difficult to liquefy due to very
low B.P of - 183 degree centigrade
- pale blue col and appreciably
magnetic
Uses of oxygen:
- In combustion and respiration
- as dissolved oxygen for aquatic
life
- as hydrogen or coal gas
- as a component of anesthetic gas
along with N2O
Hazards of O2:
- since it is inflammable, pressure
and temperature should be monitored in safest range.
- During transfer from one vessel to
another vessel monitoring is almost essential to avoid adiabatic heating and
fear of fire.
Manufacture, properties, uses and
hazards of Nitrogen:
Nitrogen can be manufactured by any
one of the following methods:
Mfg. from fractional distillation:
Pure nitrogen gas is obtained from
the fractional distillation of liquid air. Nitrogen being most volatile is
obtained at the top of the rectifying column. Purity of nitrogen obtained in this
method is up to 99.99%.
Pressure swing adsorption method
(PSA) :
In this method an adsorbent is
chosen or which the desired gas is adsorbed. The adsorbent may be any materials
like zeolite, activated charcoal, molecular sieves etc, which can trap the
desired gas preferentially at high pressure.
Polymeric membrane separation:
A permeable membrane made of polymer
so designed that it selectively separate (allows) gasses to pass through on
their rates of diffusion. the lighter gas pass faster thus N2 gets separated
sooner.
Properties of N2:
-Its boiling point is - 196
degree centigrade.
- it a col.less odourless and
tasteless gas.
Uses of N2:
It is used to:
- prepare fertilizers
- prepare ammonia
- provide inert atmosphere
- preserve food
- be used as refrigerant.
Hazards of N2:
- Its an irritant and high
concentration of it causes inflammation in the air ways.
- N2 along with O2 forms NOx gas which
creates health hazards.
- These NOx gas are also responsible
for smog formation and acid rain.
Manufacture, properties, uses and
hazards of Argon:
Mfg. from liq. Air:
Argon is extracted industrially by
the fractional distillation of liq. air. A cryogenic distillation makes the
purity of argon to very high grade.
The mfg of Ar form Kellog Ammonia
production process:
Natural gas is processed to have
synthetic gasses like CO, CO2, H2 etc. and then N2 gas is added to form ammonia
gas. Ar being inert accumulates and hence is separated out.
Properties of Argon:
- Its a colourless, odourless &
tasteless gas.
- Its nontoxic and present in
atmosphere at a concentration below m1% by volume.
- Its B.P (- 185.9 degree
centigrade) is quite close to that of oxygen.
- It is approximately 1.4 times
heavier than air and is slightly soluble in water.
- Interestingly its B.P and F.P (-
199.3 degree cent.) are quite closer too.
Uses of Ar:
It is used to:
- create complete inert atmosphere
- sealed atmosphere from other gas in various types of
welding process such as TIG (tungsten inert gas in tungsten arc welding)
and MIG (metal inert gas or metal arc
welding).
- maintain desired percentage of
carbon in steel manufacturing by blowing into the molten metal.
- remove dissolved hydrogen form
molten aluminium.
- avoid oxidation and avoid reaction
with nitrogen in the mfg. of titanium.
- help in the mfg. of zirconium.
- provide high purity inert shield
in the mfg. of Si and Ge crystals in semiconductor industry.
- avoid oxidation (displace oxygen)
in beverage industry.
- perform cryosurgery (to destroy
small area of infected tissues).
Hazards of Ar:
- Argon can act as asphyxiant
by displacing in air to a level lower than required to support life.
- Inhalation of argon in excess may
cause dizziness, nausea, vomiting.
Manufacture of Helium: It is mainly produced from the natural gas deposits and next
to it by fractional distillation.
Natural Gas Extraction: Helium is typically extracted from natural gas deposits. It
is a byproduct of the natural decay of radioactive elements, such as uranium
and thorium, within the Earth's crust.
Fractional Distillation: Once extracted, helium is separated from natural gas through
a process called fractional distillation, which involves cooling the gas
mixture to extremely low temperatures, causing it to liquefy. The different
components of the gas can then be separated based on their boiling points, with
helium being one of the first to vaporize.
Storage of Helium:
Helium is usually stored in
specialized containers designed to withstand the extremely low temperatures at
which it becomes liquid. These containers are often double-walled and heavily
insulated to minimize heat transfer. Helium is also stored in high-pressure
cylinders as a gas for various applications.
Uses of Helium:
Cryogenics:
Helium is widely used as a cryogenic agent due to its extremely low boiling
point (-268.9°C or -452°F). It is used to cool superconducting magnets in MRI
machines, particle accelerators, and other scientific equipment.
Welding and Cutting: Helium is used as a shielding gas in welding processes, especially for
non-ferrous metals. Its inert properties help prevent oxidation and improve
weld quality.
Pressurizing and Purging: Helium is employed to pressurize and purge fuel tanks,
rocket engines, and other aerospace systems due to its inertness and low
density.
Balloons:
Helium is perhaps most famously known for its use in filling balloons,
including party balloons, weather balloons, and blimps. Its low density makes
it an excellent choice for providing buoyancy.
Leak Detection:
Helium is used as a tracer gas in leak detection processes because of its small
atomic size and inertness, making it easy to detect even the smallest leaks.
Breathing Mixtures: In certain diving situations and medical applications, helium is mixed
with oxygen to reduce the risk of nitrogen narcosis and decompression sickness.
Cooling in Electronics: Helium is used for cooling certain high-power electronic
devices, such as semiconductors and superconductors, where traditional cooling
methods are inadequate.
