COAL ENERGY
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The Key of permanat solution for Pakistan energy crisis
lies with the reserves of the coal which is blessed with
the nation in Thar. So far the governments were reluctant
to recognize the importance of coal reserves Pakistan was
having and no intrest in investing on technology and infra
structure needed for such large project. Instead every body
was thinking the easy money making short cuts for developing
energy resources which were heavyly dependent on foreign
technology . Now it is good news that the coal is getting
momentum at least vocally, but unfortunately no serious
investment and project management is seen so far.
Every body must understand that the future of Pakista is
not with KalaBagh Dam but with small hydro projects on run
of river in north Pakistan and large fossile poer plants
at sea shore of Sind providing the chain of supply of the
coal fuel from Thur desert.
An argument is made that Pakistan coal is of poor quality
and difficult to burn. this argument is baseless and any
coal which is having some percentage of Carbon can be burnt
effectively.
Another reluctance is the current avilabilty of the coas
which may take years to develop the exploration and refining
arrangements to enable steadt supply to Power Plants.
Our suggestion is the procurement of 1000 MW power plants
on Sind shores near Thatta which have boiler capabilities
to burn poor coal. Presently the coal can be imported to
produce the energy and later when the steady supply of Pakistan
mines available then the foreign dependance can be curtailed
according to supply and demand requirements
DESCRIPTION
OF A TYPICAL PLANT
1.
Coal
Storage
The coal is brought to site and stored in a safe yard. Since
the coal itself is a fire hazard therefore storage facilities
should be equipped with normal fire deduction and fighting
capabilities.
The facility should be required to store at least 20,000
ton of coal all the time
Proper handling gear is needed for handling and shifting
the coal.
To transfer the coal to the crushing facilities conveyors
are needed for smooth flow of the fuel.
2.
Coal
Grinding Facility
The coal from the storage unit is brought here for crushing
and grinding to convert it to powdered form. The basis logic
for the conditioning of the coal is to clean burn the Coal
as far as possible. There are many other methods designed
at this stage to condition the coal and improve the combustion
at later stage. These are additional processes and can be
added at little extra cost depending on the quality of fuel
being used.
3.
Combustion
This is the most important issue of this project and need
careful study
Combustion is a chemical process where the fuels which constitute
various compounds and minerals heated to an elevated temperature
and in the process it eliminates the heat and various new
compounds and gases formed due to oxidation.
Excess quantity of air is provided and normally the furnace
pressures kept on atmospheric.
To get the maximum thermal efficiency this is utmost important
that more than 99% fuel is burned completely leaving only
the exhaust gases. To achieve this target burners are designed
carefully and adjusted according to available fuel. To get
an optimum air fuel ratio various controls are incorporated
which continuously monitors the flame condition and combustion
temperatures as well exhaust gases chemistry and regulate
the air fuel ratio continuously.
With the clean fuel like gas the combustion is not an issue.
The gas having high methane nr. ignite very easily and burn
most efficiently. With light diesel the combustion also
is very efficient and with heavy viscous fuel oil also the
oil is heated to get the required viscosity of 12-15 CST
and a perfect combustion is achieved.
However with the coal the situation is problematic. The
fuel obtained from each source is different is chemistry
and can constitute different compounds. When this coal is
burned at high temperatures then it can produce different
kind of harmful gases and solids.
Government regulatory Authorities are very much concerned
of clean air formation. The coal which consists of high
percentage of Sulpher will produce undesirable Sulpher-
di-Oxide which when combines with rain water produce Sulfuric-
Acid and hence cause the famous Acid Rain. The 2nd
most undesirable gas is the Nitrous Oxide the percentage
of which need to be controlled within permissible limits.
The solutions for these issues are readily available. Because
the most coal using power plants are located in USA and
the clean air act is much more forceful in USA than in 3rd
world countries.
Two major combustion technologies are available in the market
Pulverized Coal Combustion (PCC)
The coal is ground (Pulverized) to a fine powder, so that
less than 2% below 300 micro meter and 70-75% below 75 micro
meter size for a bituminous coal is achieved. The pulverized
(powdered) coal is blown through the burners with the air
and the combustion takes place 1300-1700 degree Centigrade
depending upon the quality of the coal.
The particle residence time in the furnace is 2-5 seconds
and this is most important that the particle sizes are small
enough to burn quickly and completely with out any unburned
fuel passing through the exhaust gases.
The technology is well developed and a large nr. Of power
plant which is around 90% of world coal generating capacity
is being used by this technology.
PCC is used for wide variety of coals and gives high thermal
efficiency but particularly not appropriate for the fuel
with high ash contents.
Fluidized Bed Combustion (FBC)
FBC technology is particularly suitable for the coals of
high ash content or of variable characteristics.
The relatively coarse particles of around 3 mm are fed in
to combustion chambers. Two formats are used
Bubbling beds (BBFC) and Circulating beds (CFBC)
Combustion takes place at around 800---900 degree centigrade,
resulting reduced production of NOX than PCC.
SO2 emission is controlled by injecting the sorbent in to
the bed and subsequent removal of ash with the reacted sorbent.
CFBC technology is designed for the particular coal to be
used. The method is only feasible for low grade fuel which
is difficult to pulverize, or co-generation systems where
waster material is being used.
The direct injection of limestone gives an economic solution
of removing sulpher products.
Thermal efficiency is 2-3% lower than PCC
4.
BOILERS
In boilers the thermal energy produced by the combustion
process is transferred to the water which is passing in
the tubes. The water changes its state and converts in to
high pressure steam. This steam further heated to become
superheat which is more advantageous and efficient to run
the turbines.
Boiler are of many design, they may be of tower shape or
horizontal. The flue gases can pass single passage or they
may have two or three passes. In water tube boilers the
water which is called feed water is heated at high temperature
and pass through the tubes. In surrounding high temperature
flue gases passing through and hence raising the steam pressures.
Various mountings are accommodated in the boiler which is
required for automatic controls as well as for the approval
of Government agencies.
5.
TURBINES
Turbines convert thermal energy in to kinetic energy. When
high pressure steam passes through the rotor of turbine
it starts driving the turbines with high speed. The turbines
at drive end are connected to a gear box and then to the
genset which start revolving at required speed. The electrical
power is produced which is transferred to end user through
cables and switch gear.
The exhaust steam from the turbines is first pass through
the condensers where it changes its state in to water again.
The same water is re-circulated to the boilers and hence
the high pressure steam is formed.
CAPITAL COST
The cost of the equipment varies considerable with the country
of manufacturing and quality of the equipment chosen. However
as a budgetary guide line 1000 Euro/KWHR is a general rule
of thumb.
For 36 MW power plant the capital cost is expected 36 Million
Euro and in Pak Rs. 2520 Million Rs.
Foe comparison purposes with a diesel engine power plant
the capitol cost is around 50% higher.
FUEL COST
As a standard practice the good quality 1 pound coal produce
1 KW energy and low quality one kg fuel can produce 1 KWHR
energy. Translating this amount in Pak RS.
If imported fuel cost 5000 RS/ton at site
Energy Cost
2.20 RS/unit
For comparison purposes the Gas present day costing same
amount
However with 50% increase in capital cost the pay back time
is 50 % higher.
Steam turbine power plants have longer life than diesel
engines and the maintenance cost is lower.
EQUIPMENT MANUFACTURERS.
Boilers
There are many boiler manufacturers in the world which are
producing high pressure boilers with latest technologies
to burn low quality fuel.
One of them is in India with the name Thermax Babcock Wilcox
boilers, situated in Pune India they claim to burn worst
quality of coal. The supplier need to be further explored.
Turbines
The following are some of the manufacturers of turbines
·
Alstom
from France
·
Peter
Brother Hood from England
·
MAN
from Germany
Cooling Towers
Chinese cooling towers with low cost can be selected.
High Pressure Feed Pumps
The pumps are a vital auxiliary
and should be imported from any renowned pump manufacturer.
Piping and Valves
The high pressure steam pipes and valves should be imported
with the valid certificates from the manufacturers.
Electrical Switch Gear
Complete switch gear is available in Pakistan by Siemens
or Alstom
Coal Handling Facility and grinding unit
Local facility to be explored to fabricate the complete
system.
Installation and Erection
Local facilities to be explored
CONCLUSION
1.
With
the current prices coal plants are more or less compatible
with the gas plants.
2.
With
the projected fuel prices coal prices are being forecast
as more stable than crude and gas prices.
3.
Looking
for the future the coal is one the best alternate solution
for the power generation.
4.
Clean
burning of the low quality fuel is possible and technology
is available today..
5.
This
is suggested that the plant to be ordered for low quality
fuel but the option for high grade coal to be kept.
6.
Initially
the plant to be fired with good quality fuel and then the
low quality fuel is mixed with gradual increase in proportions.
7.
The
problems which come across by increasing low quality fuel
can be solved one by one.
8.
High
cost of consultants and brokers as well as middle man should
be curtailed.
9.
All
equipment to be ordered to well known manufacturers with
the performance warranties coming directly from the manufacturer.
The equipment may be ordered in following order
·
Turbines
·
Boilers
for matching turbines
·
Combustion
equipment for the available fuel
·
Auxiliaries
like heat exchangers and cooling towers
·
Coal
handling units
·
Electrical
switch gear
·
Pumps
and pumping system
·
Piping
cables and valves etc.
PROJECT DURATION
18 months is expected when the project will start commercial
productions.
PROJECT MANAGEMENT
1.
Approval
from the top Management for the go-ahead of the project
2.
Appointing
a project manager
3.
Selecting
the site of the plant
4.
Selecting
the suppliers
5.
Commercial
Agreements with the suppliers
6.
Ordering
the equipment
7.
Civil
Work
8.
Local
fabrication
9.
Ordering
the mechanical and electrical equipments
10.
Selecting
local erectors
11.
Awarding
the contract
12.
installation
of main and auxiliary equipments
13.
Trials
and tests
14.
Commercial
Production
