Concept of Nuclear power plants and Uranium

Concept of Nuclear power plants and Uranium

-         Natural uranium contains 0.7% U 235. Uranium with an increased concentration of U 235 is called enriched uranium.

-         Nuclear weapons require uranium enriched to 90% or more U 235. Fuel used in nuclear power plants use Uranium enriched to 3-5% U-235.

-         U235 is the only isotope that is found in nature which can be fissioned by thermal neutrons.

-         Natural Uranium has 99.284% 238U isotope and 235U constitutes 0.711% of its weight.

-         Percentage composition of U235 is increased through isotope separation.

-         Highly enriched uranium is mostly produced for nuclear weapons, naval propulsion and a small quantity for nuclear power plants out of the total 2000 Tonnes.

      -     Depleted Uranium: 238 U remaining after enrichment. It is less radioactive than natural uranium.   Presently 5% in use for armor penetrating weapons as it is highly dense.

Facts about Hydroelectric Power plants

Facts about Hydroelectric Power plants:

- It generates 24%of world's electricity
- Approximately 2000 hydroelectric power plants operating in United States
- Turbine that is most often used in hydroelectric power plants is Francis Turbine.
- More the water flow and head, more will be electricity generated.
- Hoover dam in USA generates 2000 MW consisting of 17 generators each generating 133 MW at Nevada, Arizona.
- Biggest hydroelectric power plant is Itaipu power plant jointly owned by Brazil and Paraguay. It produces 12,600 MW. Second largest hydroelectric power plant is Guri power plant at Caroni river Venezuela generating 10,300 MW.
- Largest hydroelectric power plant in USA is Grand Coulee at Columbia river in Washington. It can produce 7,600 MW.

Some nice facts about coal

Some nice facts about coal

- Some coals after release of volatile matter become soft and pasty and form agglomerates. They are called caking coals. Extent of caking of coal is determined by swelling index. On the contrary, free burning fuels have high swelling index, expand in volume during combustion.
- Grindability index is inversely proportional to power required to grind coal. Grindability of a standard coal is defined as 100.
- Phosphorous in coal should be <0.01% as it can react with iron to form hard, brittle iron phosphide.
- Sulphur occurs in coal as a) Pyrites: FeS2 b) Organic sulphur coupled with carbon atom of coal molecule. c) In form of gypsum Ca SO4.
- Fixed carbon in proximate analysis is a hypothetical term and not a precise constituent of fuel. It is obtained from subtracting from 100 sum of % of moisture, volatile matter and ash content of fuel sample.
- Moisture can be present in coal as surface moisture(Formed during washing, scrubbing of coal), inherent moisture(Absorbed moisture through water absorbed in capillaries in coal), Combined moisture
- As moisture increases, free hydrogen for combustion decreases as 1/8th of weight of oxygen content is consumed as moisture.
- Organic Sulphur is inseparable from coal. Only pyritic sulphur can be removed.
- Basic contents of volatile matter are a) Gases containing: CO, H2, CH4, C2H6 and H2S
b) Tar: Complex mixture of benzene, toluene, napthalene, xylene, phenols, free carbon, anthracite and cresols.
c) Ammoniacal liquor: Aqueous condensate of nitrogen and sulphur compounds plus cynides.

Heat rate of a reheat turbine

Heat rate of a reheat turbine
= ( ( Main steam flow at ESV inlet x (Enthalpy of main steam - Enthalpy of feed water ) + ( Reheat steam flow x ( Enthalpy of hot reheat - Enthalpy of cold reheat ) ) ) / New power output in MW.

Steam turbine

Steam turbine shaft vibration is calculted as per ISO 7919.

Plant heat rate

Plant heat rate = Turbine heat rate / Boiler efficiency

Heat rate of steam turbine

Heat rate of Steam Turbine = Steam Flow at Turbine inlet x (Enthalpy of steam at inlet to turbine - Enthalpy of feed water at HP heater outlet) / MW generation

Unit of heat rate = kcal/kWhr

India Power- December 2008 Statistics

Total power generation increased by 1.53% in December 2008 as compared to December 2007
%age increase in thermal and nuclear generation = 3.36%
%age increase in hydel generation = 10.58%
Total power generation 50.14 billion units.
Share of central sector --> ~ 25 billion units
Share of state sector -- > ~ 29 billion units

Coal as a fuel

Worldwide, coal is right now the most widely used primary fuel, accounting for approximatley 36% of global electricity production. It is expected to remain same till at least 2020.
----> South Africa:
- About 77% of country's primary energy needs are provided by coal.
- Produces an average of 224 million tonnes of marketable coal annually.
- 5th largest coal producing country in the world
- Coal reserves expected to be 53 billion tonnes
----> India:
- Around 63% of electric generation through thermal power (90,000 MW of 1,41,000 MW)
- Indian Coal is generally with low GCV, high ash content.

Capacities

----> Total installed power plant capacity in World: 28,12,000 MW
----> Total installed power plant capacity in India: 1,41,000 MW
----> % of Nuclear power in Total installed power stations in world: 14%
----> % of Hydor-electric power power plants in Total installed power stations in world: 24% (Around 6,75,000 MW)
----> Total installed power plant capacity in US: 5,00,000 MW
----> % of Nuclear power power plants in Total installed power stations in US: 20% (Around 1,00,000 MW

----> Largest Hydro-electric power station in the world: Itaipu power plant, Jointly owned by Brazil and Paraguay, producing 12,600 MW
----> Second largest Hydro-electric power station in the world: Guri Power plant, Caroni River Venezuela, producing 10,300 MW
----> Largest Hydro-electric power station in US: Grand Coulee power station, Columbia River, Washington, producing 7,600 MW being upgraded to 10,080 MW.

Hydropower

Hydropower
---> 24% of world's electricity
Combined total of 6,75,000 MW
More than 2000 Hydroelectric power plants operating in United states
Largest Hydroelectric power plant: Itaipu Power plant, Jointly owned by Brazil and Paraguay, can produce 12,600 MW.

Nuclear Power

Watts Bar1: Came online on Feb7 1996, last commercial nuclear reactor to go on-line.
----> Quoted as evidence of succesful worldwide campaign of nuclear power phase-out.
In US, 104 nuclear plants generate 1,00,000 MW approximatley 20% of nation's total electric consumption.
---->It's the largest suppier of nuclear power.

Calculate fuel flow

Fuel flow to a boiler is calculated as,

Fuel flow = (Heat duty x 1000 x 3.6) / (4.2 x GCV x Efficiency /100)

Dulongs formula for GCV calculation

If we know the ultimate analysis of fuel, we can easily calculate its GCV.
The basic principle is that there are only 3 components in a fuel which generate heat. These are:
Carbon, Hydrogen and Sulphur.
According to Dulong's formula gross calorific value of a fuel is;
GCV = ((35.5 x C + 114.8 x H + 9.5 x S – 14.5 x O) x 1000) / (100 x 4.1868)
Each multiple of carbon, hydrogen and sulphur represents heat generated by its one mole.
The formula gives GCV in kcal/kg. Simple isnt it !

Boiler Heat Duty

Boiler heat duty = Tonnes per hour of steam generated x (Enthalpy of main steam - Enthalpy of feed water)

Various systems of a coal fired power plant

•Coal Handling System: Consisting of crushers, conveyors, belts etc.
•Water treatment plant: Consisting of RO system, cation and anion exchangers, DM system, mixed bed system.
•Boiler package: PF, AFBC, CFBC etc.
•Turbine package: Consisting of turbine, generator, condensor (Air cooled or water cooled)
•Condensate system: With water cooled or air cooled condensor.
•Plant air system: Consisting of compressors, receivers
•Ash handling system: Slurry system or dense phase pneumatic ash handling system
•Electrical system including generation and distribution: Consisting of busbars, transformers, circuit brakers, MCC etc.
•Control and instrumentation along with DCS.: Consisting of transmitters, guages, PLC, DCS with the associated communication cables.
•Civil: With or without piling
•BOP package ( Air conditioning, ventilation, fire fighting, Public address system, plant illumination)

Types of steam Generators

Steam Generator Basics

Steam Generator is based on Rankine cycle

•Definition: Equipment which produces steam from water with heat from fuel. Steam generator is also conventionally known as boiler.

•Fuel analysis:
•a) Proximate analysis: Includes Fixed carbon, Volatile matter, Moisture and Ash %ages by mass.
•B) Ultimate analysis: Gives respective C, H, O, N, S, M, Ash %ages by mass.