Synthesis Gas. James G. Speight

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СКАЧАТЬ general difference is that extra heavy crude oil, which may have properties similar to tar sand bitumen in the laboratory but, unlike tar sand bitumen in the deposit, has some degree of mobility in the reservoir or deposit (Table 1.1) (Delbianco and Montanari, 2009; Speight, 2014a). Extra heavy crude oils can flow at reservoir temperature and can be produced economically, without additional viscosity-reduction techniques, through variants of conventional processes such as long horizontal wells, or multilaterals. This is the case, for instance, in the Orinoco basin (Venezuela) or in offshore reservoirs of the coast of Brazil but, once outside of the influence of the high reservoir temperature, these oils are too viscous at surface to be transported through conventional pipelines and require heated pipelines for transportation. Alternatively, the oil must be partially upgraded or fully upgraded or diluted with a light hydrocarbon (such as aromatic naphtha) to create a mix that is suitable for transportation (Speight, 2014a, 2017).

      Tar sand (referred to as oil sand in Canada) deposits are found in various countries throughout the world, but in vast quantities in Alberta and Venezuela. There have been many attempts to define tar sand deposits and the bitumen contained therein. In order to define conventional crude oil, heavy crude oil, and bitumen, the use of a single physical parameter such as viscosity is not sufficient. Other properties such as API gravity, elemental analysis, composition, and, most of all, the properties of the bulk deposit must also be included in any definition of these materials. Only then will it be possible to classify crude oil and its derivatives.

      In fact, the most appropriate and workable definition of tar sand is found in the writings of the United States government (US Congress, 1976), which is not subject to any variation in chemical or physical properties that can vary depending upon the method of property determination and the accuracy of that method (Speight, 2014), viz.:

      Tar sands are the several rock types that contain an extremely viscous hydrocarbon which is not recoverable in its natural state by conventional oil well production methods including currently used enhanced recovery techniques. The hydrocarbon-bearing rocks are variously known as bitumen-rocks oil, impregnated rocks, oil sands, and rock asphalt.

This definition speaks to the character of the bitumen through the method of recovery (Speight, 2014, 2016). Thus, the bitumen found in tar sand deposits is an extremely viscous material that is immobile under reservoir conditions and cannot be recovered through a well by the application of secondary or enhanced recovery techniques.

      By inference and by omission, conventional crude oil and heavy crude oil are also included in this definition. Extra heavy oil can also be accommodated under this definition because the oil approximates the properties and behavior of tar sand bitumen at ambient conditions but is mobile because the reservoir temperature is higher than the pour point of the oil (Table 1.1). Crude oil is the material that can be recovered by conventional oil well production methods whereas heavy crude oil is the material that can be recovered by enhanced recovery methods. Tar sand currently recovered by a mining process followed by separation of the bitumen by the hot water process. The bitumen is then used to produce hydrocarbon derivatives by a conversion process.

1.3 Other Energy Sources

      All fossil fuels are non-renewable, and as such they will get eventually depleted. Since they are based on finite resources and their distributions are heavily localized in certain areas of the world, they will become expensive. Further, energy generation from fossil fuels requires combustion, thus damaging the environment with pollutants and greenhouse gas emission (Speight and Lee, 2000). In order to sustain the future of the world with clean environment and non-depletive energy, renewable energy is a right choice. Renewable energy sources include solar energy, wind energy, geothermal energy, biomass, and hydrogen. Most renewable energy except geothermal energy comes directly or indirectly from sun. Benefits of renewable energy are numerous and they include: (i) environmental cleanness without pollutant emission, (ii) non-depletive nature, (iii) availability throughout the world, (iv) no cause for global warming, (v) waste reduction, (vi) stabilization of energy cost, and (vii) creation of jobs.

      Alternate fuels produced from sources other than crude oil are making some headway into the fuel demand. For example, diesel from plant sources (biodiesel) is similar in performance to diesel from crude oil and has the added advantage of a higher cetane rating than crude oil-derived diesel. However, the production of liquid fuels from sources other than crude oil has a checkered history. The on-again-off-again efforts that are the result of the inability of the political decision-makers to formulate meaningful policies has caused the production of non-conventional fuels to move slowly, if at all (Yergin, 1991; Bower, 2009; Wihbey, 2009; Speight, 2011a, 2011b, Yergin, 2011; Speight, 2014a).

      Non-fossil fuels are alternative sources of energy that do not rely on continued consumption of the limited supplies of crude oil, coal, and natural gas. Examples of the non-fossil fuel energy sources include: (i) biomass, wind, solar, geothermal, tidal, nuclear, and hydrogen sources (Nersesian, 2007; Speight, 2008, 2011c). Such resources are considered to be extremely important to the future of energy generation because they are renewable energy sources that could be exploited continuously and not suffer depletion. In addition, energy production using non-fossil-based sources is claimed to generate much less pollution than the fossil fuel energy sources. This is considered crucial by many governments who are looking for ways to reduce the amount of pollution produced by their countries. The advantages of fossil fuel resources are often considered to include the know-how and ease of production, many opponents of fossil fuel use cite the adverse effects on the environment (Speight, 2008, 2013a, 2013b, 2014a) and consider non-fossil fuels as a much better way to generate energy.

While there are now methods of burning gas and similar products very efficiently, as clean fossil fuels, a certain amount of pollution is still generated. Accordingly, various initiatives now exist, especially in Western countries, to encourage corporations and energy companies to invest in methods of producing energy from renewable (non-fossil fuel).

      1.3.1 Coal

      Coal of various types (Table 1.2) is an organic sedimentary rock that is formed from the accumulation and preservation of plant materials, usually in a swamp environment (Speight, 2013a, 2013b). Coal is a combustible rock and along with crude oil and natural gas it is one of the three most important fossil fuels, such as for the generation of electricity and provides approximately 40% of electricity production on a worldwide basis. In many countries these data are much higher: Poland relies on coal for approximately 94% of its electricity; South Africa relies on coal for approximately 92% of its electricity; China relies on coal for approximately 77% of its electricity; and Australia relies on coal for approximately 76% of its electricity.

      Table 1.2 Types of coal.

Coal type	Description
Lignite	Also referred to as brown coal.
	The lowest rank of coal.
	Used almost exclusively as fuel for steam-electric power generation.
	Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
Sub-bituminous coal	The properties range from those of lignite to those of bituminous coal.
	Primarily as fuel for steam-electric power generation.
Bituminous coal	A dense coal, usually black, sometimes dark brown, often with well-defined bands of brittle and dull material,
	Used primarily as fuel СКАЧАТЬ В начало < 9 10 11 12 13 14 15 16 17 18 > В конец