Coal Advantages and Disadvantages – Pros of Coal Winning Despite Dangerous Cons

COAL

Coal is one of the most important sources of energy for mankind providing an easy way to generate energy in a cheap manner. The relative abundance and low costs of using Coal has made it the the first choice of Fuel for building Power Plants in the world. Coal has huge importance as an Energy source and  forms the most important raw material for Cement and Steel. Coal is also used in a variety of other industries like Paper, Aluminum, Chemical, Transportation and Pharma. However Coal also has huge negative consequences as it is the largest source of Carbon Emissions which happen during Coal Combustion.

Coal Mining despite two hundred years remain  as hazardous as ever resulting in thousands of deaths in India and China. Mercury, Arsenic and pollution of  other harmful substances into the environment causes diseases and many deaths as well. However for countries like India and China there  are little other alternatives and there is no conviction amongst policymakers to change their energy strategies as well. So the advantages of Coal are currently overpowering those of the Cons of Coal. This despite Coal being the dirtiest form of Energy and causing many deaths globally. The main reason for the cheapness of Coal is that the societal costs are not added on explicitly to the Price of Coal making it seem artificially cheap.

Advantages of Coal

1) Abundance – Coal is located almost universally, it can be found on every continent in over 70 countries, with the biggest reserves in the USA, Russia, China and India.

2) Continuous,Predictable,Reliable Source of Power – Coal Based Energy can be generated almost 24×7  unlike other forms of renewable energy like wind and solar that are intermittent in nature.

3) Low Capital Investment - The capital investment required for Coal based Power plants is relatively less at $1-2/watt of Thermal  Capacity. Note wind energy is slightly higher while Solar is even higher. Coal Mines are also quite cheap to build and Mine with Open Cast Mines providing Coal at a very Low Cost.

4) Low Cost – Coal is one of  the cheapest forms of energy making it the energy of choice in developing countries like India and China. In India its possible to get cheap coal at just $20/ton while international prices of coal range in the region of $100/ton. Note Coal based electricity can be produced at 2-4c/Kwh making it the cheapest electricity source.

5) High Load Factor - Thermal Power Plants have very high load factors in excess of 80%. They can generate power almost 24/7 and only require shutdown for periodic maintenance. Coal Based Plants which have become too old or have been shutdown due to environmental concerns can still be used for backup power.

6) Large  Potential compared to Oil – Coal  Energy Potential is quite large compared to other Fossil Fuels like Oil and Gas. Coal Reserves globally are estimated to be around 1 trillion tons which implies that Coal can be consumed at the current rates for another 200 years.

7) Big Industrial Base - Coal Energy has been present since the start of the Industrial Revolution with the development of the Steam Engine based on Coal. The technology and industry of the Coal Industry and Thermal Power Plants is well developed and mature. This allows a rapid deployment of Coal Power in most places in the world.

8) Coal to Liquids and Coal to Gases - Coal is now being looked upon as source of Transportation Fuels as Oil becomes scarce and increasingly costly. Coal to Liquid Plants are being constructed in India and China though the Technology is quite immature and the use of the technology is still questionable on environmental grounds.

Disadvantages of Coal

1) Greenhouse Gas Emissions - One of the biggest cons of Coal Energy is that it releases Carbon Dioxide which has been sequestered for millions of years in the dead bodies of plant and animals. This transfer the Carbon from the Earth to the Environment leading to the Global Warming Effect. Global Treaties have failed in putting a Cost on this, though individual countries are tying to account for this through Carbon Taxes and Cap and Trade.

2) Coal Mining Deaths - Coal Mining has resulted in thousands of deaths each year ever since man discovered coal. Note Coal Deaths happen not only in countries which don’t have good safety regulations like China but also in developed countries like USA and New Zealand.

3) Devastation of Earth and Scenery Near Coal Mines – Open Cast Mining of Coal has resulted in destruction of the habitat and destruction of the scenery. It leads to removal of trees and pollution of air and water in areas surrounding the mines. Coal Mine Fires have burned for hundreds of year underground and make living in those areas hazardous. Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface fires as well.

4) Displacement of Humans due to Mining Destruction - In West Bengal,India people are being displaced in huge numbers as the hollowing of the earth due to underground coal mining has made those places unsafe as the  Land Caves in without warning.

5) Emission of Harmful Substances like Sulfur Dioxide,Carbon Monoxide, Mercury, Selenium, Arsenic, Acid Rain - Thermal Plants emit harmful substances such as Mercury and Sulfur Dioxide which cause health hazards among the surrounding population and Acid Rain. While modern equipment has reduced the emission of these harmful substances, it is still very harmful to humans.

http://www.greenworldinvestor.com/2011/04/11/coal-advantages-and-disadvantages-pros-of-coal-winning-despite-dangerous-cons/

Coal-Fired Power Plants

Electric power plants commonly use a pulverized coal steam-generating system, in which metal spheres or cylinders crush pieces of coal into a fine powder. Hot air blows the coal powder into a furnace, where it combusts at high temperatures and converts water to steam. The steam passes through a series of high-, mid-, and low-pressure turbines connected to a common shaft that spins a generator. This type of power plant requires high-grade (low ash content) coal.

Another type of coal-fueled power plant utilizes “fluidized bed combustion,” a method that involves burning coal in a layer (bed) of heated particles suspended in flowing air. [1] At sufficiently high air velocity, the bed acts as a fluid that thoroughly mixes coal particles with air, completely combusting the coal at relatively low temperatures. The advantage of fluidized bed combustion is that it can use almost any grade of coal, including coal rejected by power plants that use pulverized coal systems.

One more type of power generation from coal is an integrated gasification combined cycle (IGCC) system. This method does not combust coal directly, but first converts it to a gas called “syngas” composed of carbon monoxide (CO) and hydrogen (H2). This process involves some of the same reactions as hydrogen production from fossil fuels and Fischer-Tropsch synthesis.

Essentially, a gasification reactor introduces a limited amount of oxygen to burn some of the organic carbon material in the coal and release carbon monoxide (CO) and energy. This drives a second reaction that converts additional organic carbon material in the coal to CO and H2 and a

third reaction, in what is known as a water-gas shift converter, changes CO and steam to CO2 and H2. The H2 combusts directly in a gas turbine that spins an electrical generator. Heat from this combustion also generates steam that drives a steam turbine and another electrical generator.

IGCC power plants have several advantages over other types of coal-fired power plants. They release less sulfur dioxide (SO2) and nitrogen oxides (NOx) pollution because filters remove these compounds from the syngas before it combusts. They achieve high fuel efficiencies, from 38% to 56% [1], [2] They can capture CO2 more easily and more cheaply than other types of coal-fired plants because they generate it at high concentrations in the water-gas shift converter before combustion rather than emit it, diluted, in a large volume of flue gas after combustion.

The main problem with IGCC plants is their high capital costs. Construction of an IGCC plant costs from 15% to 20% more than construction of a conventional pulverized coal-fired plant. [2], [3] Currently, IGCC plants generate only 0.1% of the world’s electricity, [4] and only two IGCC plants are operating in the United States.

Water at temperatures above 374°C and at pressures above 22 Mega Pascales (MPa) transforms into a subcritical fluid that has properties of both a liquid and a gas. Supercritical water has a density that changes with temperature and pressure in a continuous manner, and so power plants designed to operate under supercritical conditions can scale to higher temperatures and pressures without having to accommodate two phases of water (liquid and gas) in various locations.

The downside of supercritical operation is that higher temperatures and pressures demand stronger, more corrosive-resistant materials, tighter tolerances, and more complex control systems, which add about 7% to the cost of construction and maintenance. [2] Nevertheless, supercritical plants are more efficient, and their lower fuel costs eventually compensate for higher costs. Currently, more than 400 supercritical power plants are in service worldwide, [1] and a few ultra-supercritical plants, which operate at even higher temperatures and pressures, are beginning operations in Europe and Japan. [2]

http://www.eoearth.org/view/article/160420/

How electricity is generated through coal

A coal power station turns the chemical energy in coal into electrical energy that can be used in homes and businesses.

First the coal (1) is ground to a fine powder and blown into the boiler (2), where it is burned, converting its chemical energy into heat energy. Grinding the coal into powder increases its surface area, which helps it to burn faster and hotter, producing as much heat and as little waste as possible.

As well as heat, burning coal produces ash and exhaust gases. The ash falls to the bottom of the boiler and is removed by the ash systems (3). It is usually then sold to the building industry and used as an ingredient in various building materials, like concrete.

The gases enter the exhaust stack (4), which contains equipment that filters out any dust and ash, before venting into the atmosphere. The exhaust stacks of coal power stations are built tall so that the exhaust plume (5) can disperse before it touches the ground. This ensures that it does not affect the quality of the air around the station.

Burning the coal heats water in pipes coiled around the boiler, turning it into steam. The hot steam expands in the pipes, so when it emerges it is under high pressure. The pressure drives the steam over the blades of the steam turbine (6), causing it to spin, converting the heat energy released in the boiler into mechanical energy.

A shaft connects the steam turbine to the turbine generator (7), so when the turbine spins, so does the generator. The generator uses an electromagnetic field to convert this mechanical energy into electrical energy.

After passing through the turbine, the steam comes into contact with pipes full of cold water. In coastal stations this water is pumped straight from the sea (8). The cold pipes cool the steam so that it condenses back into water. It is then piped back to the boiler, where it can be heated up again, turn into steam again, and keep the turbine turning.

Finally, a transformer converts the electrical energy from the generator to a high voltage. The national grid uses high voltages to transmit electricity efficiently through the power lines (9) to the homes and businesses that need it (10). Here, other transformers reduce the voltage back down to a usable level.

http://www.edfenergy.com/energyfuture/coal-generation

How Coal Power Plants Produce ElectricityThe conversion from coal to electricity takes place in three stages.

Stage 1The first conversion of energy takes place in the boiler. Coal is burnt in the boiler furnace to produce heat. Carbon in the coal and Oxygen in the air combine to produce Carbon Dioxide and heat.

Stage 2The second stage is the thermodynamic process.

1. The heat from combustion of the coal boils water in the boiler to produce steam. In modern power plant, boilers produce steam at a high pressure and temperature.

2. The steam is then piped to a turbine. 3. The high pressure steam impinges and expands across a number of sets of blades in the turbine. 4. The impulse and the thrust created rotates the turbine. 5. The steam is then condensed and pumped back into the boiler to repeat the cycle.Stage 3In the third stage, rotation of the turbine rotates the generator rotor to produce electricity based of Faraday’s Principle of electromagnetic induction.Check out this series describing the layout of thermal power plants.

Key Facts About Coal-Fired Electricity ProductionIn practice to effect these three stages of conversion, many systems and sub systems have to be in service. Also involved are different technologies, like combustion, aerodynamics, heat transfer, thermodynamics, pollution control, and logistics.

As an example consider these facts for typical coal fired power plant of capacity 500 MW.

Around 2 million tons of coal will be required each year to produce the continuous power. Coal combustion in the boiler requires air. Around 1.6 million cubic meter of air in an hour is

delivered by air fans into the furnace. The ash produced from this combustion is around 200,000 tons per year. Electrostatic precipitators capture almost all of this ash without dispersing this to the atmosphere.

Pollutants from coal power plants like carbon dioxide, sulphur dioxide, and nitrogen oxide can also affect the environment. Thermal power plants are the biggest producers of Carbon Dioxide.

The boiler for typical 500 MW units produces around 1600 tons per hour of steam at a temperature of 540 to 600 degrees Centigrade. The steam pressures is in the range of 200 bar. The boiler materials are designed to withstand these conditions with special consideration for operational safety.

Heat transfer from the hot combustion gases to the water in the boiler takes place due to Radiation and convection.

The Electrical generators carry very large electric currents that produce heat and are be cooled by Hydrogen and water.

The steam leaving the turbine is condensed and the water is pumped back for reuse in the boiler. To condense all the steam it will require around 50,000 cubic meter per hour of cooling water to be circulated from lakes, rivers or the sea. The water is returned to the source with only an increase of 3 to 4 degrees centigrade to prevent any effect to the environment.

Apart from the cooling water the power plant also requires around 400 cubic meter per day of fresh water for making up the losses in the water steam cycle.

Details of Generating Electricity from CoalThese are some of the facts to highlight the complexities of the working of a Coal Fired Power Plant generating Electricity.

For more details, discover how coal is blended to the right mix to maximize energy production or learn about the specific caloric energies of coal and how moisture in the coal can affect a power plant's efficiency. Also learn how the coal is prepared to be fired in the boiler.You may also learn about the parts of a thermal power plant and site selection.

http://www.brighthubengineering.com/power-plants/18082-coal-fired-thermal-power-plant-the-basic-steps-and-facts/

How is Coal Converted to Electricity?

Steam coal, also known as thermal coal, is used in power stations to generate electricity.

Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverised coal combustion (PCC) systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature (see diagram below). The hot gases and heat energy produced converts water – in tubes lining the boiler – into steam.

The high pressure steam is passed into a turbine containing thousands of propeller-like blades. The steam pushes these blades causing the turbine shaft to rotate at high speed. A generator is mounted at one end of the turbine shaft and consists of carefully wound wire coils. Electricity is generated when these are rapidly rotated in a strong magnetic field. After passing through the turbine, the steam is condensed and returned to the boiler to be heated once again.

The electricity generated is transformed into the higher voltages (up to 400,000 volts) used for economic, efficient transmission via power line grids. When it nears the point of consumption, such as our homes, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market.

Efficiency Improvements

Improvements continue to be made in conventional PCC power station design and new combustion technologies are being developed. These allow more electricity to be produced from less coal - known as improving the thermal efficiency of the power station. Efficiency gains in electricity generation from coal-fired power stations will play a crucial part in reducing CO2 emissions at a global level.

Efficiency improvements include the most cost-effective and shortest lead time actions for reducing emissions from coal-fired power generation. This is particularly the case in developing countries where existing power plant efficiencies are generally lower and coal use in electricity generation is increasing. Not only do higher efficiency coal-fired power plants emit less carbon dioxide per megawatt (MW), they are also more suited to retrofitting with CO2 capture systems.

Improving the efficiency of pulverised coal-fired power plants has been the focus of considerable efforts by the coal industry. There is huge scope for achieving significant efficiency improvements as the existing fleet of power plants are replaced over the next 10-20 years with new, higher efficiency supercritical and ultra-supercritical plants and through the wider use of Integrated Gasification Combined Cycle (IGCC) systems for power generation.

A one percentage point improvement in the efficiency of a conventional pulverised coal combustion plant results in a 2-3% reduction in CO2 emissions.

http://www.worldcoal.org/coal/uses-of-coal/coal-electricity/

Diesel Power Plantan electrical installation equipped with one or several electric current generators driven by diesel engines.

Diesel power plants are divided into two main classes: stationary and mobile. Stationary diesel power plants use four-stroke diesel engines (less frequently, two-stroke diesel engines), with power ratings of 110, 220, 330, 440, and 735 kilowatts (kW). Stationary diesel power plants are classed as average in their power rating if the rating does not exceed 750 kW; large diesel power plants can have a power rating of 2,200 kW or more. The advantages of a diesel power plant are favorable economy of operation, stable operating characteristics, and an easy and quick start-up. The main disadvantage is the comparatively short interval between major overhauls. Diesel power plants are used mainly for servicing areas remote from transmission lines or areas where sources of water supply are limited and where the construction of a steam power plant or of a

hydroelectric power plant is not feasible. Stationary diesels are usually equipped with synchronous generators.

The economic efficiency of a diesel power plant is improved considerably if the waste heat of the engine (55 to 60 percent of total heat release in currently available engines) can be used for preheating of fuel and oil or for domestic heating within the power station building or adjacent premises. In diesel power plants with a high power rating (above 750 kW) the waste heat can be used in a heating system serving a whole block or a whole town area in proximity to the power station.

Automatic protection against exceeding maximum or minimum limits for the temperature of cooling water and oil, the oil pressure, and the rotational speed (rpm) is built into diesel power plants; protection is also provided in the event of a short circuit in the line. Three levels of automation for stationary diesels are used: automatic regulation of the rotational speed (rpm) and of the temperature of the cooling water and oil, along with automatic emergency signaling and protection in the event of a breakdown; automatic or remotely controlled start-up and shutdown of the diesel engines, an automatic check of conditions required for connecting load to the line, synchronization with other units and with the power system, and a load connection and load distribution with units operating in parallel; and automatic refilling of the feeder tanks for fuel, oil, and water and of the air feed vessels, an automatic (trickle) charging of start-up batteries and of batteries used in auxiliary operations, and automatic control of the auxiliary equipment.

Mobile diesel power plants are widely used in agriculture and forestry and by expeditions involved with geological exploration. In these applications, diesel power plants can be used as a source of electricity for energy or lighting networks; they can be used as the main, auxiliary, or standby power source. In transportation, diesel power plants are a basic power source (for instance, in diesel-electric locomotives and in diesel ships). In mobile diesel power plants, the high-speed diesels serve as prime movers. A mobile diesel power plant includes the diesel-electric unit itself, spare parts, instruments and accessories, a set of cables for making connections to the load, and fire-fighting equipment. Automated diesel power plants with a power rating up to 10 kW are often mounted on a single-axle truck trailer; power plants rated 20 kW or more are usually installed on two-axle, covered trailers. Such a mobile station comprises not only the diesel-electric unit but also the power distribution cabinet (or panel), a cabinet containing the automatic controls, the remote control console, heating and ventilation equipment, rectifiers, and the storage batteries that feed the automatic controls or automated systems.

The first mobile diesel power plants in the USSR were built in 1934 and were known as diesel trains. Such diesel trains have all the power plant equipment installed on platforms or in cars. The power ratings of diesel trains are 1, 2.5, 4.5, and 10 megawatts.

The electric part of the power plant of a diesel train consists of a synchronous generator delivering a voltage of 3–10 kilovolts, assembled or unitized compartments containing high-voltage leads (overhead leads or cables), distribution equipment for voltages of 230–380 volts (required for lighting and for auxiliary motors of the power plant), the storage battery, and operating power circuits and the battery charger.

REFERENCESAlekseev, A. P., and E. E. Chekmenov. Peredvizhnye dizel’nye elektrostantsii. Moscow, 1966.Mikhalin, G. I. Ekspluatatsiia dizel’nykh elektricheskikh stantsii. Moscow, 1968.Kuznetsov, A. V., and K. A. Achkasov. Ustroistvo, ekspluatatsiia i remont dizel’nykh stantsii. Moscow, 1969.

K. A. ROZANOV

http://encyclopedia2.thefreedictionary.com/Diesel+Power+Plant

The Operation of Diesel Power Plants Diesel-powered generators can supply an electric load ranging from approximately 10 to 5,000 kilowatts of power. They function primarily as backup generators, emergency municipal power supplies and power houses on ships or construction sites.

1. Purposeo Diesel power plants produce energy though the combustion of chemical fuel, in

most cases diesel derived from petroleum, into mechanical energy. This energy is then used to power an alternator which in turn generates electricity. Diesel is preferred to other fuel types as these engines have a higher thermal efficiency than other commercial generators of equivalent size.

Processo Most modern generators harness mechanical energy through the process of

electromagnetic induction. In this system, the mechanical energy produced by the diesel engine moves an electrical conductor, such as a magnetically charged wire, in a magnetic field. The movement of the conductor creates a difference in voltage between the two ends of the charged wire, creating a flow of electric charges and thereby generating electricity.

Trainingo As the State of Alaska generates a large portion of its energy with diesel power

plants, the Alaska Institute of Technology offers a training program in diesel power plant operation. Students spend 60 percent of their time maintaining and operating diesel generators, with the remaining 40 percent in formal classes. The program results in a power plant operator certification.

References Alaska Institute of Technology: Power Plant Operation Program U.S. Army Corps of Engineers: Diesel Engine Power Plant Operation How Does a Generator Create Electricity? How Generators Work

http://www.ehow.com/facts_7322543_operation-diesel-power-plants.html

Diesel power plant

Lets discuss about diesel power plants in this post.

Applications of diesel power plant1. Diesel power plant’s is in the range of 2 to 50 MW capacity. They are used as central station for

small or medium power supplies.2. They can be used as stand-by plants to hydro-electric power plants and steam power plants for

emergency services.3. They can be used as peak load plants in combinations with thermal or hydro-plants.4. They are quite suitable for mobile power generation and are widely used in transportation

systems such as automobiles, railways, air planes and ships.5. Now-a-days power cut has become a regular feature for industries. The only solution to tide

over this difficulty is to install diesel generating sets.

Layout diesel engine power plant:

Diesel engine:Diesel engines or compression ignition engines as they are called are generally classified as two stroke engine and four stroke engines. In diesel engine, air admitted into the cylinder is compressed, the compression ratio being 12 to 20. At the end of compression stroke, fuel is injected. It burns and the burning gases expand and do work on the position. The engine is directly coupled to the generator. The gases are then exhausted from the cylinder to atmosphere.

Engine strating system:This includes air compressor and starting air tank. The function of this system is to start the engine from cold supplying compressed air.

Fuel system:Pump draws diesel from storage tank and supplies it to the small day tank through the filter. Day tank supplies the daily fuel need of engine. The day tan is usually placed high so that diesel flows to engine under gravity.

Diesel is again filtered before being injected into the engine by the fuel injection pump. The fuel is supplied to the engine according to the load on the plant.

Air intake system:Air filters are used to remove dust from the incoming air. Air filters may be dry type, which is made up of felt, wool or cloth. In oil bath type filters, the sir is swept over a bath of oil so that dust particles get coated.

Exhaust system:In the exhaust system, silencer (muffler) is provide to reduce the noise.

Engine cooling system:The temperature of burning gases in the engine cylinder is the order of 1500 to 2000’C. to keep the temperature at the reasonable level, water is circulated inside the engine in water jackets which are passage around the cylinder, piston, combustion chamber etc. hot water leaving the jacket is sent to heat exchanger. Raw water is made to flow through the heat exchanger, where it takes up the heat of jacket water. It is then cooled in the cooling tower and recirculates again.

Engine lubrication system:It includes lubricating oil tank, oil pump and cooler. Lubrication is essential to reduce friction and wear of engine parts such as cylinder walls and piston.Lubricating oil which gets heated due to friction of moving parts is cooled before recirculation. The cooling water used in the engine is used for cooling the lubricant also.

Advantages of diesel power plant:

1. Plant layout is simple. Hence it can be quickly installed and commissioned, while the erection and starting of a steam power plant or hydro-plant takes a fairly long time.

2. Quick starting and easy pick-up of loads are possible in a very short time.3. Location of the plant is near the load center.4. The load operation is easy and requires minimum labors.5. Efficiency at part loads does not fall so much as that of a steam plant.6. Fuel handling is easier and no problem of ash disposal exists.7. The plant is smaller in size than steam power plant for same capacity.8. Diesel plants operate at high overall efficiency than steam.

Disadvantages of diesel power plant:

1. Plant capacity is limited to about 50 MW of power.2. Diesel fuel is much more expensive than coal.3. The maintenance and lubrication costs are high.4. Diesel engines are not guaranteed for operation under continuous, while steam can work under

25% of overload continuously.

http://mechanical-engineering-info.blogspot.com/2011/12/diesel-power-plant.html

How diesel power station work?A diesel engine converts the energy contained in the diesel fuel into mechanical energy in the form of rotation of a shaft. The shaft turns a generator which is essentially a magnet contained within a coil of wire. The generator converts the rotational energy into a voltage across the coil - electrical energy.

Diesel plants are used primarily in two applications:

1. There is a need for an emergency source of backup electrical power, and the relatively low 'first cost' of diesel generation combined with its ability to start up rather rapidly (often in 10 sec or less) are attractive features.

Incidentally, there is a special case of this 'emergency' application - in the entertainment industry, it is common for diesel gensets to be used to power lights and sound for special events. For example, rock musicians often bring in special diesel power plants to support their performances rather than relying on the available commercial supplier.

Another special case is that for the past several cycles, NBC's broadcasts of the Olympics have been powered by diesel gensets. Olympics venues are often in remote areas where the existing power infrastructure is limited and it doesn't make economic sense to expand those facilities for games lasting only two-three weeks. Also, that has allowed NBC to design one set of broadcast equipment so that they don't have to deal with the fact that the frequency of indigenous power infrastructure varies from one host country to the next.

2. There is a need for a base-load source of modest size and low first cost. This is most often the case in areas where there is no commercial power supplier, and the amount of capacity that is needed is relatively small.

The downside of diesel plants include: 1. They are very noisy. 2. They are not very efficient - diesel engines produce a lot of waste heat. Practical economies exist only if there are no local sources of fuel, and the cost of transporting diesel fuel is favorable compared with

the cost of bringing in the fuels required for alternative technologies. 3. Diesel fuel has to be transported to and stored on the site. Diesel power plants that have operated for a number of years in developing areas are typically horrible examples of environmental contamination. 4. The airborn effluent from diesel plants is noxious. 5. Diesel engines require a lot of maintenance.

https://answers.yahoo.com/question/index?qid=20081122041042AAfpIke

Component s of Diesel Power Plants

1. Engine

2. Air Intake System

3. Engine Starting system

4. Fuel System

5. Exhaust System

6. Cooling System

7. Lubricating System

Engine:

· It’s the main component of plants which develops power.

· Types : Two stroke, Four strokes.

· Air is passed into the cylinder, fuel is also injected.

· The fuel is burned and bring gases expand and do work on piston.

· Shaft of engine is coupled to generator. Burned gases are exhaust to atmosphere.

Air intake system:

· Removes dust from atmospheric air & supplies fresh air to engine.

· Types of filters :

1. Dry or oil bath filter.

2. Oil immersed type of filter.

Precaution’s for location:

1. Should not be located inside engine room.

2. Air intake line should not be too small or too long.

3. Air should not be taken from a confined space.

Engine Starting System:

Used to start the engine in cold conditions by supplying air.

Starting methods:

1. Auxiliary engine.

2. Self-starters

3. Compressed air system.

Auxiliary engine:

Auxiliary engine located close to main engine and driven through clutch and gears. Clutch is disengaged and engine is started.

Self-Starters:

Used in small diesel engines. Motor draws heavy current & designed to work continuously for 30sec after which it is cooled.

Compressed Air System:

Used in large diesel engines.

Compressed air supplied from air tank.

Fuel System:

Contains:

· Storage Tank

· Fuel pump

· Strainers

· Meters

· Day Tanks (Supplies daily fuel need of engines and contains min 8hours of oil requirement)

1.Fuel Injection system:

Functions:

1. Filters fuel.

2. Measures correct quantity of fuel to be injected.

3. Time the fuel injection.

Types:

1. Individual pump injection system.

2. Common rail injection system.

3. Distributor.

Individual Pump Injection System:

· Individual pump is connected to each fuel nozzle.

· Nozzles contain delivery value actuated by oil pressure.

· High cost of manufacture.

Common rail injection system:

· Single pump supplies fuel to header.

· Control valve is present to set the amount & time of injection of fuel.

Distributor System:

There os a pressure pump which meters the fuel & time of injection. Fuel enters the distributor blocks. From there fuel is distributed to cylinders in correct order.

2.Fuel Pump :

· Measures & delivers correct quantity of fuel at high pressure to injector.

· It consists of plunger. When it moves down , oil comes into the barrel through ports SP & Y when it moves up, fuel gets compressed and lifts delivery value & fuel flows to injected through passage (p).

3.Fuel Injection:

· Delivers fuel into combustion chamber where fuel is mixed with air.

· Fuel from pump enters through passage and lifts nozzle value. Fuel travels down nozzle & injected to cylinder. The injection pressure can be adjusted by adjusting the screw present above the spring.

Exhaust System:

Discharge engine exhaust to atmosphere. Includes silencers & connecting ducts.

Lubricating System:

It is used to reduce friction of moving parts & reduce wear & tear of the engine.

Contains:

· Oil pumps

· Oil tanks

· Filters

· Coolers & pipes.

Types:

1. Wet sump lubrication system

i)Splash System

ii)Semi pressure system

iii)Fuel pressure system

2. Dry sump lubrication system.

3. Mist sump lubrication system.

Splash System:

· Used in 4 stroke stationary engines.

· Bottom of sump contains lubricating oil. Scoop is located at the bottom which splashes oil from all the parts.

· Suitable for low & medium speed engines.

Semi pressure System:

· Combination of splash & pressure systems.

· Oil is pumped from the sump through a filter and fed to main bearings.

· Less cost.

Full pressure system:

· Oil is pumped from sump through filter under pressure to various parts for lubrication.

· Oil is supplied to big end & small end bearings.

Dry sump lubrication system:

· Used in two stroke cycle engines.

· Mixture of oil & fuel is induced through carburetor & is vaporized.

Cooling System:

Carries heat generated inside engine cylinder.

Methods:

1. Air cooling

2. Liquid cooling

i)Thermo-syphon cooling

ii)Forced or pump cooling

iii)Cooling with thermostatic regulator.

iv)Pressurized water cooling.

Air cooling:

· Engine is cooled by atmospheric air, which flows around engine.

· Used in scooters , motor cycles.

Advantage:

1. No danger of coolant leakage.

2. Simple design.

3. Less weight.

4. Easy installation.

Disadvantage:

1. Non uniform cooling.

2. Less output.

3. More maintenance.

4. Used in small engines only.

5. Noisy operation.

6. More maintenance.

Liquid Cooling:

Thermo Siphon Cooling:

· Hot water goes up and cold water comes down due to density without any pump.

· Top of radiator is connected to top of water jacket by a pipe & bottom of radiator to bottom of water jacket.

· Water travels down the radiator across which air is passed to coal it. Simple, Cheap , but slow cooling.

Forced cooling by pump:

· Pump forces water to circulate to engine.

· It may cause over cooling which causes corrosion.

Thermostatic Cooling:

· Thermostat maintains desired temperature to increase heat transfer in radiator.

Pressurized water cooling:

High water pressure is maintained to increase heat transfer in radiator.

Evaporative Cooling:

Water is allowed to evaporate by absorbing latent heat of evaporation from the cylinder walls.

The temperature of cooling water is allowed to reach 100c.

Governing System:

It is used to regulate the speed of the engine. This is done by varying the fuel supply according to the engine load.

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