PROPOSAL TOPIC :
NATURAL GAS
INTRODUCTION:
Natural gas is a gas consisting primarily of methane, typically with 0-20%
higher hydrocarbons[1] (primarily ethane). It is found associated with other
fossil fuels, in coal beds, as methane clathrates, and is an important fuel source
and a major feedstock for fertilizers.
Most natural gas is created by two mechanisms: biogenic and thermogenic.
Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills,
and shallow sediments. Deeper in the earth, at greater temperature and
pressure, thermogenic gas is created from buried organic material.[2]
Before natural gas can be used as a fuel, it must undergo processing to remove
almost all materials other than methane. The by-products of that processing
include ethane, propane, butanes, pentanes, and higher molecular weight
hydrocarbons, elemental sulfur, carbon dioxide, water vapor, and sometimes
helium and nitrogen.
Natural gas is lighter than air and is a mixture of methane, ethane, propane
and butane. Other component found in natural gas include carbon dioxide,
helium, hydrogen sulphide and nitrogen. It is highly inflammable and has no
odour and cannot be seen.
Natural Gas has widespread use in many of the areas. In this article we shall
discuss some of the uses of natural gas that has allowed for increase in the
quality of living.
Description of Uses of Natural Gas:
1.Natural gas is the cleanest burning fossil fuel as it gives off 50% of the carbon
dioxide released by coal and 25% less carbon dioxide than oil for the same
amount of energy produced.
2. It virtually gives no sulphur dioxide and only small amount of nitrous oxides.
Thus, natural gas is a environmental-friendly fuel.
3. Before it is sent to the pipe lines or storage tanks it is mixed with a chemical
that gives it a strong odour which is almost like that of rotten eggs. This makes
it easy to detect any leakage.
List of Uses of Natural Gas
1.It is used as a domestic and industrial fuel.
2.It is used as a fuel in thermal power plants to generate electricity.
3.It has been a source of hydrogen in the manufacture of fertilizers.
4.Compressed natural gas, which is in the liquid form, is used as a fuel i n
transport vehicles as being pollution free, it is a good alternative to petrol and
diesel.
Advantages of Using Natural Gas
1.It is a complete fuel land can be used directly for household and industrial
purposes.
2.There is no problem of transportation as it can be supplied directly through
the gas pipe lines. Vadodra city in Gujrat is supplied natural gas through a
network of pipe lines.
3.It has a high calorific value of about 55 KJ/g.
Natural gas is a gas that consist of methane. It is an important sources of fuel,
an important ferilizers and a greenhouse gas.
PROBLEM STATEMENT :
The electric power sector in Pakistan is growing faster (11 percent) than the
average growth rate of other developing countries (10 percent). However, the
demand in Pakistan is growing even faster than the supply and therefore
power shortage has become a serious problem. The problem is compounded
by inefficiency of electric power sector. Moreover there is underpricing,
subsidising, overstaffing and inadequate maintenance. Like many other
developing countries,
The report maintained that the difference between firm supply and peak
demand is estimated at 5,529 MW by the year 2009-10 when firm electricity
supply will stand at 15,055 MW against peak demand of 20,584 MW.
BACKGROUNDS:
At the time of independence in 1947, Pakistan inherited 60MW of power
generation capability for a population of 31.5 million, yielding 4.5 units per
capita consumption. The Government of Pakistan in 1952 by acquiring majority
shareholding took control of the Karachi Electric Supply Company (KESC)
engaged in generation, transmission and distribution of electric energy to the
industrial, commercial, agricultural and residential consumers of the
metropolitan city of Karachi and its suburbs.
In 1958, Water and Power Development Authority (WAPDA) was created as a
semi-autonomous body for the purpose of coordinating and giving a unified
direction to the development of schemes in water and power sectors, which
were previously being dealt with by the respective electricity and irrigation
department of the provinces.
In 1959, the generation capacity had increased to 119 MW and by that time
the country had entered the phase of development, which required a
dependable and solid infrastructure, electricity being its most significant part.
The task of power development was undertaken by WAPDA for executing a
number of hydel and thermal generation projects, a transmission network and
a distribution system, which could sustain the load of the rapidly increasing
demand of electricity.
After the first five years of its operation by 1964-65, the electricity generation
capability rose to 636 MW from 119 MW in 1959, and power generation to
about 2,500 MKWH from 781 MKWH. At the inception of WAPDA, the number
of electrified villages in the country was 609 which were increased to 1882
villages (688,000 consumers) by the year 1965. The rapid progress witnessed a
new life to the social, technical and economic structures of the country.
Mechanized agriculture started, industrialization picked up and general living
standards improved.
The task of accelerating the pace of power development picked up speed and
by the year 1970, the generating capability rose from 636 MW to 1331 MW
with installation of a number of thermal and hydel power units. In the year
1980 the system capacity touched 3,000 MW which rapidly rose to over 7,000
MW in 1990-91.
However, electricity consumption in Pakistan has been growing at a higher
pace compared to economic growth due to the increasing urbanization,
industrialization and rural electrification. From
1970 to the early 1990s, the supply of electricity was unable to keep pace with
demand that was growing consistently at 9-10% per annum.
In the early 1990s, the peak demand exceeded supply capability by about 1525%, necessitating load shedding of about 1,500 - 2,000 MW. On the demand
side, there was a weak link between the electricity price and demand, which
failed to manage the demand. On the supply side, the main reason behind this
capacity shortage was the inability of the public budget to meet the high
investment requirement of the power sector, despite the allocation of a high
share to this sector. During the 1990s, the economic growth rate of Pakistan
declined to a level of 4-5% per annum from a level of 6% per annum in the
1980s.
In order to eliminate power shortage/load shedding in the minimum possible
time, the Government constituted an Energy Task Force in 1993 to devise a
consolidated and comprehensive policy for revamping the energy sector. On
the recommendations of the Energy Task Force, the Government announced a
“Policy Framework and Package of Incentives for Private Sector Power
Generation Projects” in March 1994 for a large scale induction of private sector
in power development. The said policy offered a fix levelized tariff of USD
5.57/kWh to the prospective investors (USD 6.1/kWh average for 1-10 years)
and a number of other incentives to attract foreign investment in the power
sector.
The Power Policy 1994 helped in overcoming load shedding in the country.
Rather, it resulted in surplus power as the actual load growth was much less
than that projected and the projects were contracted beyond requirement.
Moreover the Policy attracted only thermal projects resulting in reversal of the
hydel/thermal generation mix.
In the year 2000, the vertical disintegration of WAPDA started as part of the
country’s new electricity market restructuring and liberalisation program. Since
then WAPDA has been broken down into fourteen separate units: four thermal
power generating companies, nine distribution companies and a transmission
and distribution company.
In November 2005, the Government of Pakistan privatised (74.35%) the
Karachi Electric supply Company (KESC). At present, KESC and WAPDA operate
their own networks and are interconnected through 220 KV double circuit
transmission lines and can supply power to each other.
On June 30’ 2008, the total generation capacity from WAPDA’s own hydel and
thermal sources plus generation from two nuclear power plants, KESC and
Independent Power Procedures (IPPs) stood at 19,420 MW.
LITERATURE SURVEY:
The electricity generation sector in Pakistan is a mixed industry of hydro,
thermal and nuclear power plants.
About 33.3 percent power is generated through hydel system, 64.13 percent
through thermal system and the rest 2.57 percent is generated through
nuclear and renewable power generation systems.
The country meets its energy requirement around 41% by indigenous gas, 19%
by oil, and 37% by hydro electricity. Coal and nuclear contribution to energy
supply is limited to 0.16% and 2.84% respectively with a vast potential for
growth.
Hydel Generation:
As a consequence of partition of the Indo-Pakistan Sub-Continent in 1947,
India and Pakistan became two independent sovereign states. Hydel
generation capacity of only 10.7 MW (9.6 MW - Malakand Power Station & 1.1
MW - Renala Power Station) existed in the territory of Pakistan. With the
passage of time, new hydel power projects of small and medium capacities
were commissioned including the first water storage dam and power house at
Warsak due to which country's hydel capability rose to about 267 MW up till
1963.
In the year 1967 & 1977, Mangla Dam on Jhelum River and Tarbela Dam on
Indus River having the provision of power generation were commissioned
respectively. However, their capacities were subsequently extended in
different phases.
Hydel Generation Capacity: The total capacity of existing 13 hydel stations as of
today is 6,480 MW including 36 MW hydel generation of AJKHEB. During the
year 2007-2008, aggregate energy sharing of the hydel power plants was
33.30%.
. Thermal Generation:
Bulk of Pakistan’s power generation is based on thermal resources mainly
furnace oil and natural gas as fuel; coal is almost non-existent. The total
installed capacity of thermal power plants in the country as on June 30’ 2008
was 12,478 MW. As per Energy Yearbook 2008, share of thermal power
generation during 2007-08 was recorded at 64.13 percent.
Nuclear Power Generation:
The share of nuclear power in the total power generation capacity of Pakistan
is just 2.37 percent. At present, only two nuclear power plants are established
in Pakistan with a total generation capacity of 462 MW. The third nuclear
power plant is under construction.
Alternative / Renewable Energy:
Pakistan has abundant available and inexhaustible renewable energy (RE)
resources, which if tapped effectively can play a considerable role in
contributing towards energy security and energy independence of the country.
In May 2003, Alternative Energy Development Board – AEDB ( www.aedb.org )
was established to act as a central agency for development, promotion and
facilitation of renewable energy technologies, formulation of plans, policies
and development of technological base for manufacturing of renewable energy
equipment in Pakistan.
The Government of Pakistan has tasked the AEDB to ensure 5% of total
national power generation capacity to be generated through renewable energy
technologies by the year 2030. In addition, under the remote village
electrification program, AEDB has been directed to electrify 7,874 remote
villages in Sindh and Balochistan provinces through renewable energy
technologies.
At present, total Renewable Energy produced in the country accounts at
40MW which is about 0.21% of total installed generation capacity of all sorts.
The investment potential for the renewable energy sector of the country from
short to medium term is over USD 16 billion dollars.
OBJECTIVES:
Pakistan has rich resources of natural gas like the coal .By the small
effort of government of pakistan ,they can find alot of resources of
natural gas to overcome their recent crisis of electrical power.
 To convert most of natural gas energy into electrical energy to
overcome electricity shotage for the industrial sector.
 To make awareness about proper use of natural gas on
domestic level.
 To deliver information about the working of natural gas power
plant.
Methodology:
Schematic Arrangement of Gas Turbine Power Plant:
(i)Compressor (ii)Regenerator (iii)Combustion Chamber (iv)Gas
Turbine(v)Alternator (vi) Starting motor.
(i)Compressor
The compressor used in the plant is generally of rotatory type.The air at
atmospheric pressure is drawn by the compressor via the filter which removes
the dust from the air.The rotatory blades of the compressor push the air
between stationary blades to raise its pressure.Thus air at high pressure is
available at the output of the compressor.
(ii)Regenerator
A regenerator is a device which recovers heat from the the exhaust gases of
the turbine.The exhaust is passed through the regenerator before wasting to
atmosphere.A regenerator consists of a nest of tubes contained in ashell.the
compressed air from the compressor passes through the tubes on its way to
the combustion chamber.In this way compressor is heated by the hot exhaust
gases.
(iii)Combustion Chamber
The air at high pressure from the compressor is led to the combustion chamber
via the regenerator.In the combustion chamber,heat is added to the air by
burning oil.The oil is injected through the burner into the chamber at high
pressure ensure atomisation of oil and its through mixing with air.The result is
that the chamber attains a very high temperature(about 3000F).The
combustion gases are suitably cooled to 1300F to 1500F then delivered to gas
turbine.
(iv)Gas Turbine
The products of combustion consisting of a mixture of gases at high
temperature and pressure are passed to the gas turbine.These gases in passing
over the turbine blades expand and thus do the mechanical work.The
temperature of the exhaust gases from the turbine is about 900 F.
(v)Alternator
The gas turbine is coupled into the alternator.The alternator converts the
mechanical energy of the turbine into electrical energy.The output of the
alternator is given to the bus-bars through transformers,isolators and circuit
breakers.
(vi) Starting motor
Before starting the turbine,compressor has to be started.For this purpose,an
electric motor is mounted on the same shaft as that of the turbine.The motor
is energised by the batteries.Once the unit starts, a part of the mechanical
power of the turbine drives the compressor and there is no need of the motor
now.
(vii)Performance
More than Fifty percent of the energy converted is used by the compressor.
Only around 35 % of the energy input is available for electric power generation
in the generator. The rest of the energy is lost as heat of the exhaust gases to
the atmosphere.
Three parameters that affect the performance of a of gas turbine are
•The pressure of the air leaving the compressor.
•The hot gas temperature leaving the Combustion chamber.
•The gas temperature of the exhaust gases leaving the turbine.
The gas turbine power plant has to work continuously for long period of time
without output and performance decline. Apart from the main sections there
are other important Auxiliaries systems which are required for operating a Gas
Turbine Power Plant on a long term basis.
Air Intake System
Air Intake System provides clean air into the compressor. During continuous
operation the impurities and dust in the air deposits on the compressor blades.
This reduces the efficiency and output of the plant . The Air Filter in the Air
Intake system prevents this.
A blade cleaning system comprising of a high pressure pump provides on line
cleaning facility for the compressor blades.
The flow of the large amount of air into the compressor creates high noise
levels. A Silencer in the intake duct reduces the noise to acceptable levels.
Exhaust System
Exhaust system discharges the hot gases to a level which is safe for the people
and the environment. The exhaust gas that leaves the turbine is around 550 °C.
This includes an outlet stack high enough for the safe discharge of the gases.
Silencer in the outlet stack reduces the noise to acceptable levels.
In Combined Cycle power plants the exhaust system has a ‘diverter damper’ to
change the flow of gases to the Heat Recovery Boilers instead of the outlet
stack.
Starting System
Starting system provides the initial momentum for the Gas Turbine to reach
the operating speed. This is similar to the starter motor of your car. The gas
turbine in a power plant runs at 3000 RPM (for the 50 Hz grid - 3600 RPM for
the 60 Hz grid). During starting the speed has to reach at least 60 % for the
turbine to work on its on inertia. The simple method is to have a starter motor
with a torque converter to bring the heavy mass of the turbine to the required
speed. For large turbines this means a big capacity motor. The latest trend is to
use the generator itself as the starter motor with suitable electrics. In
situations where there is no other start up power available, like a ship or an
off-shore platform or a remote location, a small diesel or gas engine is used.
Fuel System
The Fuel system prepares a clean fuel for burning in the combustor. Gas
Turbines normally burn Natural gas but can also fire diesel or distillate fuels.
Many Gas Turbines have dual firing capabilities.
A burner system and ignition system with the necessary safety interlocks are
the most important items. A control valve regulates the amount of fuel burned
. A filter prevents entry of any particles that may clog the burners. Natural gas
directly from the wells is scrubbed and cleaned prior to admission into the
turbine. External heaters heat the gas for better combustion.
For liquid fuels high pressure pumps pump fuel to the pressure required for
fine atomisation of the fuel for burning.
These are the main Aiuxiliary systems in a Gas Turbine Power Plant. Many
other systems and subsystems also form part of the complex system required
for the operation of the Gas Turbine Power Plant.
Location:
The following is a list of factors that influence the selection of site for
constructing a Steam power station:
1. Supply of fuel:
The station must be located close to coal mines to reduce transportation cost
of fuel.
2. Availability of water:
The station must be located near a river bank or canal for continous water
supply.
3. Transportation facilities:
The station must be well connected to major transport routes eg Rail or Road.
4. Cost & type of land:
The land must have a good bearing capacity for heavy equipment and yet be
cheap enough to purchase.
5. Distance from populated areas:
The station must be located as far away from populated areas as possible due
to air pollution.
REFERENCES:
Wikipedia.com
Google.com
Wikianswers.com
Youtube.com
en.wikiversity.org