|
 What is Natural Gas, PNG, CNG & LNG?
How LNG is stored and handled?
What is Rich gas and Lean gas?
Why is natural gas processed?
What is associated and non-associated gas?
What is sweet & sour gas?
What is PNGRB and what is its role in awarding CNG projects?
Where the LNG terminals are located in India ?
Can Natural gas be stored?
How natural gas is generally traded?
Natural
gas as its name indicates is a Gaseous fuel, consisting of 87-92% of Methane
with a small percentage of other higher hydrocarbons.
PNG,
CNG & LNG are different forms of Natural gas under varied temperature &
pressure.
is generally under atmospheric temperatures but
the pressure can up to as high as 90 Kg/cm2 in transmission lines
and limited to less than 24 Kg/cm2
in City Gas grids due to risk involved in movement of high pressure gas inside
crowded cities/towns .
means natural gas used as fuel for vehicles,
typically compressed to the pressure ranging from 200 to 250 kg/cm2
in the gaseous state
It
is used pre-dominantly for automotive purpose as the energy requirement for running
a car (for 150-200 km) can be packed in a container of size, which can fit in
to the luggage compartment or boot space when pressurized gas volume reduces by
nearly 300 times. There are few instances of CNG being used for industrial
purposes for shipping desired quantities through cylinder cascades .However in
such cases pressure reduction at the end use is inevitable.
(Refer
OISD-179 for Safety Requirements for Compression, storage & refueling
stations for CNG in Automotive sector)
is liquid form of Natural gas, generally intended
for transportation of large volumes
through ships, where cross country pipelines are not feasible. There will be
high degree of economy in transportation logistics due to large scale of operations
involved.
Natural
gas can be reduced to liquid state by cooling to 160 C so that it
will occupy 1/600th of its gaseous volume and it is called as Liquefied
Natural Gas which eliminates more space for gas transportation. In fact during
the process of liquefaction of NG to LNG lot of impurities are eliminated.
Hence
LNG is the purest form of Natural Gas.
LNG
is stored in large insulated tanks that are specially designed for this
purpose. The tanks are so-called "full containment" tanks. Each tank
consists of a special nickel-steel inner tank and a (roughly 80-cm thick)
concrete outer tank. The space between the walls of the two tanks is filled
with a thick layer of special insulating material that ensures that virtually
no heat can get into the inner tank. However, even with the most efficient
insulation, some ambient heat will always reach the inner tank. This slight
quantity of heat will cause a very small amount of the LNG (approximately
0.065% a day) to turn back into a gas. All of this so-called evaporation loss
in the tank is collected, so that none of it is released into the atmosphere.
It is again condensed into LNG and added to the tank as LNG liquid. It may also
be used at the terminal as a fuel to heat up the LNG.
At
receiving terminals (like Dahej, Hazira), LNG is re-gasified and transmitted
for further usage in NG form. These receiving terminals are also known as Re-Gasification
terminals
LNG
vessels (Ships) are also there to carry 2,50,000 m3 of Gas at a time
In
India we have LNG import-cum-re-gasification terminals and we do not have
liquefaction plants, as India is not a gas-exporting nation.
Rich
gas contains 5 or 6 gallons or more of recoverable liquid hydrocarbons per
thousand cubic feet. Whereas Lean gas contains less than 1 gallon of
recoverable liquid hydrocarbons per thousand cubic feet.
Natural
gas is processed in LPG fractionator plant to separate it into different
fractions as it is required by different applications. The following shows the
different applications
Methane - fuel
and feedstock for urea plants and fuel for power plants
Ethane - Production of petrochemicals
Propane - LPG and industrial fuel
Butane - Production of LPG
C5 and heavier - Production of solvents and pentane
Based
on the type of source Natural gas is classified as associated and non-associated
gas and there is of no significance when end use is concerned.
- Associated gas is
natural gas found in crude oil reservoirs either dissolved or in conjunction
with crude oil deposits and it is also called as Oil well gas.
- Non-associated gas
is Natural gas found in reservoirs separate from crude oil wells and it is
also called as Dry gas.
Based
on the sulphur content the natural gas is classified as sweet & sour gas.
Sour gas contains higher level of sulphur content in its composition and sweet
gas has very little or nil sulphur.
Petroleum and Natural Gas Regulatory Board (www.pngrb.gov.in)
(PNGRB) was formed on 1st Oct-2007 to
- Protect the
interest of consumers by fostering fair trade and competition amongst the
entities
- Regularize and
authorizing entities involved in the business
CGD
projects will be awarded to entities based on bidding process wherein
weightages for different qualifying parameters will be given for entities
participating in the bid.
As of Nov. 2008, India has
1. Petronet LNG Limited (PLL), Dahej (Gujarat)
2. Shell Hazira, Hazira (Gujarat)
3. Dhabol , Ratnagiri for Captive usage of Power
plant at Ratnagiri
Generally
natural gas is stored only in CNG outlets and in LNG terminals. Apart from that
natural gas will not be stored and it is in continuous flow through pipelines.
There
are few Natural Gas underground caverns in some parts of the world.
Gas
trade is based on $/MMBTU (Million British Thermal Units)
What
is the composition of natural Gas:
Composition
of Natural gas varies widely from source to source.
Natural
gas is a combustible mixture of hydrocarbon gases. While natural gas is formed
primarily of methane, it can also include ethane, propane, butane and pentane.
Depending on the application the buyer/user can seek pure form of Methane (as
high as 95%)
The
thermal efficiency varies from 9000 k.cal to 13500 K.cal per Kg based on the
composition of Gas.
1
MMBTU is 252000 K.cal
1 MMBTU (Million British
thermal unit) = 19 to 23 kg or 23 to 30 SCM approx. based on the composition of
the gas.
|