As electricity has become a significant factor in the economic and social development of all countries, electricity management has therefore become the main policy of each government as it indicates the welfare of the people.

However, in electricity generation, it is necessary to have a plan for the use of fuel appropriately in the context of economic situation, geographical condition, and demand for electricity of the country. The organization responsible for electricity has an important role in setting policies which take into account the sufficiency, good quality, and reasonable price of electricity, as well as environmental protection. Thus, it has to consider carefully the benefit and disadvantage of each type of fuel to be used in electricity generation.

Natural Gas

Natural gas is, the same as oil, petroleum energy. In fact, oil, natural gas, and coal are formed from the remains of plants and animals which were accumulated and buried under the ground for hundreds of millions of years and transformed naturally into fossils from which crude oil, natural gas, and coal are derived. Thus, this kind of fuel is called fossil fuel.

Scientifically a plant, animal, and human body have cells which compose mainly of hydrogen and carbon. When oil, natural gas, and coal are formed from the accumulation of the remains of plants and animals, they compose mainly of hydrocarbon molecules. When burnt, the hydrocarbon, like wood, produces energy, but fossil fuels such as oil, natural gas, or coal gives more energy.

Composition

Natural gas is a hydrocarbon gas mixture consisting of methane, ethane, propane, butanes, etc. In general, the main composition is methane of 70% or more. Before being used, this hydrocarbon gas mixture has to be separated for maximum benefit.

Apart from hydrocarbon gas, natural gas may have other kinds of gas, such as carbon dioxide, hydrogen sulfide, nitrogen, and water which can be separated for further use by the separation process at the gas separation plant.

Natural Gas Acquisition for Electricity Generation

In acquiring natural gas for electricity generation, EGAT takes into account the cost of production coupled with the quality and security of the power system.

The acquisition of natural gas, the main fuel for electricity generation, must be conducted cautiously by experts who understand the process of planning, electricity generation, management of project, as well as the process of gas acquisition and transfer. Moreover, they must have abilities in commercial negotiation, analysis of energy economics, and financial condition of purchase, as well as price structure of natural gas. 

Coal

Coal is a combustible brown or brownish black sedimentary rock, a type of mineral fuel which has a bright or dull surface and is light in weight. Coal consists of carbon, hydrogen, nitrogen, and oxygen, and may have a small amount of other elements or substances such as sulfur. Coal that is high in carbon content and low in other elements generate higher heat when burnt and is classified as high quality.

Coal Classification

Coal is classified into five types as follows:
          1. Peat is a precursor of coal with some decomposed plant remains and can be used as fuel. 
          2. Lignite has a bit of plant remains left with high inherent moisture content and can be used as fuel. 
          3. Subbituminous is a black coal and is suitable for use in electricity generation.
          4. Bituminous is a dense, sedimentary rock; it is typically hard, with well-defined layers of shiny black coal within the seams and is suitable for use in iron smelting. 
          5. Anthracite is a glossy black coal with a brilliant luster; it breaks with a conchoidal fracture into sharp fragments and is nonflammable.

Coal Mining

Coal production or excavating coal for utilization is called coal mining. Generally, there are two types of coal mining:    

Open Pit Mine

Open-pit mining is a surface mining technique which extracts minerals from an open pit in the ground. It is the most common method and does not require expensive capital. It is used when mineral or ore deposits are found relatively close to the surface of the earth. The depth of the pit depends on the size of the area and the cost-benefit of the investment. Generally, the depth ranges from the earth surface to 500 m below the surface.

Underground Coal Mine

In the area where ore body is too deep for open pit mine, it is necessary to use underground coal mining by excavation of a tunnel in order to use special equipment to extract and transport coal to the surface by belt conveyor. Underground coal mining involves high investment and an extremely careful mining plan to prevent mine explosion from the accumulation of gas in the coal seams and a collapse of rock. It is necessary to study geology and engineering geology of the area in details.

Apart from coal mining, at present, there are several studies to reduce the impact from the use of coal such as coal gasification, coal liquid mixture to reduce pollutant and to facilitate transportation, and the use of methane in the coal layer as fuel. 

Coal Benefits

Coal has been used widely as there are available reserves all over the world with abundant supply. Moreover, coal mining is not a complicated business. As it is cheaper than oil, coal is commonly used in industries which involve the use of boiler in production such as electricity generation, metal smelting, cement production, tobacco curing, and food industry.

Moreover, coal is used in the production of activated carbon to absorb odor, carbon fiber, and coal liquefaction or coal gasification. In coal gasification, impurities and by-products which are removed from the coal can be used for various purposes, such as sulfur for making sulfuric acid and gypsum, ammonia for agricultural fertilizer, ash for construction materials, etc.

Oil Shale

Oil shale is fine-grained sedimentary rock formed millions of years ago from organic matter and sediment buried in wetlands. Being brown or dark brown in color, oil shale contains a compound called kerogen from which oil and hydrocarbons can be extracted by heating at 500˚C. The refined products can be used for the same purpose as those derived from crude oil.

Oil shale is found mostly in the North of Thailand particularly in the Mae Sod source which is presently the largest oil shale source of the country. From the survey during 1974–1983, nine oil shale sources have been discovered with a total reserve of not less than 11,000 million metric ton.

Oil Shale Benefits   

1. Oil shale can be crushed, sprayed, and burnt in a specially designed oven. The energy obtained from the burning can be used in electricity generation.
2. Oil can be extracted from oil shale for use. 
3. The by-product of burnt oil shale, as in No.1, can be developed as a construction material, such as a mixture in cement or brick.

At present, oil shale is not widely used in the industry. However, after the Oil Crisis in 1973, more attention has been given to oil shale as an alternative energy. In electricity generation, EGAT, in cooperation with the Department of Mineral Resources, is making a feasibility study of using oil shale in electricity generation.

EGAT’s survey and evaluation of resources section is in the process of exploring the oil shale source according to the cabinet resolution on December 11, 2007, which gave approval to the following proposal of the Ministry of Energy:

1. Allocation of the area of 104 km² in Ban Huay Kraloke, Mae Sod District, Tak Province as an area for exploration for oil shale source development

2. Department of Mineral Fuels and EGAT would jointly conduct a survey and prepare guidelines for oil shale development of the designated area for four years from the date of approval by the cabinet.

Coal and Electricity Generation

At present, local coal reserves for use in electricity generation is rather limited. The developed coal source will not be able to sufficiently cope with the future demand. Moreover, there is a limitation in terms of quality. The newly developed source is not cost effective.

Therefore, if EGAT has a plan to construct new power plants according to the Power Development Plan, it is possible that EGAT has to import coal to meet the demand of the power plant’s lifespan. As there are a large amount of global reserves, EGAT has the choice to use coal of the desired property. From the world export statistics in 2003-2007, the top countries which has potential to produce coal for export are countries in the Asia Pacific region, such as Australia, Indonesia, and China. The location of these countries is not so far from Thailand, particularly Indonesia which the transportation cost will be comparatively lower than from other countries.

The coal which is proper for electricity generation is coal of good quality with high heating value and relatively low content of impurities. Thus, the suitable coal for electricity generation of EGAT’s new power plant is subbituminous or bituminous as it is of good quality and the global reserves are available in a large amount.

Petroleum (Crude Oil)

The word “petroleum” comes from the Latin words “petra” (rock) and “oleum” (oil). The term “petroleum” is used to refer to mineral oil. In general, petroleum includes carbon, hydrogen, sulfur, and nitrogen.

Scientists believe that the earth originated some 4,500 million years ago. The large quantities of dead organisms were mixed with other sediments and settled to the ocean floor. As a result of pressure, some sediment layers transformed into shale and some became limestone and sandstone. The remains of the organisms which were buried or trapped in the rock are known as fossils. Crude oil and natural gas are mostly found in the area where there are remains of the organisms or buried sediments. Dead organic matter becomes crude oil and natural gas by high temperature, bacteria (microbe), radiation, or other processes.

Classification of Crude Oil

There are different types of crude oil with different specific gravity and different names and properties. In general, crude oil is classified into three types as follows:

1.  Asphalt-base crude oil or naphthenic-base crude oil is commonly found in the Middle East, Gulf of Mexico and Venezuela. In appearance, it is a sticky and highly viscous liquid. Asphalt–base crude oil such as fuel oil give higher distillation residue. It is easy for transportation as it is not solidified. The distillation residue is mostly asphaltic material. It is believed that the formation of asphalt-base crude oil is from the dead organisms on the ocean floor.

2.  Paraffin-base crude oil is crude oil of better grade with a high API value (The American Petroleum Institute gravity). It gives higher yield of benzene and lubricating oil and kerosene. Paraffin-base crude oil yield paraffin wax from refining. It is more difficult to transport as the oil becomes solidified at the temperature lower than 30˚C. In Thailand, the crude oil found in the Sirikit oil source in Kamphaeng Phet Province is of this classification.

3.  Mixed-base crude oil is crude oil with properties between asphalt–base crude oil and paraffin-base crude oil. It is believed that it is formed from the remains of the organisms which lived on the ground which used to be the ancient sea. After the refining process, the oil gives asphalt and/or paraffin wax.

Moreover, each classification has different chemical formulae and properties. The asphalt–base crude oil gives high octane value in distillation whereas the paraffin-base crude oil gives higher viscosity index. However, with the technological advance of the oil refining industry, it is possible to conduct treatment with additives to obtain the desired property.          

In trade, crude oil is classified into three types, namely light crude oil, medium crude oil, and heavy crude oil according to the API gravity which is the gravity scale commonly used in the world trade developed by The American Petroleum Institute.

Oil Acquisition for Electricity Generation

In the acquisition of oil for electricity generation, as a state enterprise, EGAT has to comply with the rules and regulations on procurement of EGAT, the cabinet resolutions, and related laws.