electrical generation from coal, oil and gas

3ed lecture
Electricity Generation from Coal
All three fossil fuels can be used for electricity generation, but petroleum is used mostly in other sectors (petrochemicals and transportation fuels), and coal tends to be the dominant fossil fuel source for electricity generation. There are many possible reasons, however, why a nation (such as Germany or Japan) might wish to use natural gas or even oil to generate electric power instead of coal, even though coal in the past has been the cheaper alternative—ignoring “external” (environmental) costs. These reasons include concern for the environment !!!??? and human health, lack of abundant domestic coal reserves, and greater ease of transport of oil and gas through existing pipelines or nearby ports.




Figure 2.7 Basic components of a coal-fired power plant.


Example
Total consumption of gas, oil, and coal in the United States in 2004 measured 23.8, 42.6, and 24.0 EJ of energy content, respectively. (A) Calculate the ratio of reserves to energy consumption
for the United States for these three resources. (B) Discuss the validity of this calculation.
Solution
From Table 5-4, the total reserves for the United States are 195, 115, and 6750 EJ, respectively. Therefore the ratios are 8.5, 2.8, and 301 for the three fuels. This calculation implies that at current rates, without considering other circumstances, the gas reserves will be consumed in 8.5 years, and the oil reserves in 2.8 years, while the coal reserves will last for more than three centuries.




Question
can you represent the above figure in any heat cycle (eg. Carnot…etc)? How?


Apart from steam-powered locomotives powered by coal, transportation fuels are generally either liquids or gases. A gaseous fu“syngas” (short for synthetic gas, which is a mixture of carbon monoxide and hydrogen) can be produced from coal by heating it under high pressure in the presence of water vapor. The syngas reaction known as coal gasification is
Coal +O2 + H2O=H2 + CO
Although syngas can be used on its own as a transportation fuel, its energy content is only about half that of natural gas, so that normally it is converted instead into a more energy-rich liquid fuel similar to gasoline or else the hydrogen component is extracted and used to power fuel cells. The conversion to a liquid akin to gasoline or diesel can be done through
the Fischer–Tropsch (F–T) process, which involves a series of chemical reactions starting with syngas and resulting in the production of a variety of liquid hydrocarbons. The process is still being used by South Africa today to make synthetic gasoline from coal—a process that accounts for 30% of their fuel needs. In most other nations, production of synthetic fuels usually starts from natural gas rather than coal—this currently being the more economical alternative????How?. In fact, one recent study has projected that producing liquid fuels from coal could become economically viable in coal-rich nations as early as 2015.

Atmospheric Emissions from Coal Power Plants
Coal-fired power plants are prodigious emitters of pollution, although newer plants using “scrubbers” to filter the exhaust as it travels up the smoke stacks have significantly reduced some emissions. Nevertheless, as can be seen from Table 2.2, coal is still the dirtiest of the fossil fuels. For example, compared to gas-fired power plants, coal plants emit 1200 times more particulates and nearly double the CO2.


PETROLEUM AND NATURAL GAS
Petroleum or crude oil is a liquid hydrocarbon consisting of many kinds of complex molecules. Its elemental composition includes 83%–87% carbon, 10%–14% hydrogen, 0%–6% sulfur, and under 2% nitrogen and oxygen. Natural gas is a gaseous hydrocarbon, primarily methane, CH4, with up to 20% higher hydrocarbons, primarily ethane.
API Gravity
The gravity of crude oil determines its price commercially. It is generally
expressed as API gravity defined as:
API = (141.5/S.G)-131.5

Table below is a classification of crude


Products of oil
1-Liquefied Petroleum Gas (LPG)
Liquefied petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation. They include thane, ethylene, propane, propylene, normal butane, butylene, isobutane and isobutylene. For convenience of transportation, these gases are liquefied through pressurization.

2. Gasoline
Gasoline is classified by octane ratings (conventional, oxygenated and
reformulated) into three grades: Regular, Midgrade and Premium.
-Regular gasoline: Gasoline having an antiknock index, i.e. octane
rating, greater than or equal to 85 and less than 88.
- Mid-grade gasoline: Gasoline having octane rating, greater than or
equal to 88 and less than or equal to 90.
-Premium gasoline: Gasoline having octane rating greater than 90.
Premium and regular grade motor gasoline are used depending on the
octane rating. In addition, aviation gasoline, which is a complex mixture
of relatively volatile hydrocarbons, is blended with additives to form suitable
fuel for aviation engines

3.Kerosene
Kerosene is a light petroleum distillate that is used in space heaters, cook stoves and water heaters and which is suitable for use as a light source. Kerosene has a maximum distillation temperature of 204 C (400F) at the 10% recovery point, a final boiling point of 300 C (572 F), and a minimum flash point of 37.8 C (100 F). The two grades are recognized by ASTM Specification D3699. A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10% recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655.