FOG exam qestions.gdoc

1. Present the classification of fuels. Chemical Fuels: ​ primary/natural -solid (wood, coal, lignite) -liquid (crude oil) -gaseous (natural gas) ​ secondary/derived -solid (coke, petroleum, coal) -liquid (karosene, diesel, petrol) -gaseous (co...

1. Present the classification of fuels. Chemical Fuels: ​ primary/natural -solid (wood, coal, lignite) -liquid (crude oil) -gaseous (natural gas) ​ secondary/derived -solid (coke, petroleum, coal) -liquid (karosene, diesel, petrol) -gaseous (coal gas, bio gas, oil gas) Motor Fuels: ​ conventional (petrol , diesel fuel) ​ alternative -renewable (biogas, syngas, vegetable oil, spirits, methyl esters of vegetable oils) - non-renewable (natural gas, LPG, synfuels) 2. Present the classification of oils and greases. Oils: ​ compressor oils ​ gear oils ​ turbine oils ​ machine oils ​ cylinder oils ​ oils for pneumatic devices ​ oils for hydraulic drives and controls ​ for heat treatment of metals ​ metal plastic treatment ​ roller bearing oils ​ oily heat transfer media Greases: ​ gaseous ​ liquid -synthetic -mineral -vegetable and animal oils -inorganic ​ plastic ​ solid -organic -inorganic 3. Present the classification of crude oil. Crude oil is the only natural liquid fuels, the origin of oil are organic Classification: ​ sulphur content -low sulphur oils 2% ​ density  -light < 0.87 kg/m3 -medium 0.87–0.91 kg/m3 -heavy > 0.91 kg/m3 ​ paraffins -low paraffin oils 10% 4. Present the classification of gaseous fuels. Gaseous fuels- multi-component mixture of flammable and nonflammable gases of natural or artificial origin General: ​ natural (natural gas, LPG, mine gas) ​ artificial (hydrogen, coke oven, town gas) Energy value: ​ rich (high-metal, calorific value 39MJ/m3 ​ poor (nitrogenous, calorific value 27 MJ/m3 Public utility: ​ artificial ​ natural ​ LPG (liquefied petroleum gas) ​ mixture of technical propane-butane with air Transport: ​ LPG (liquefied petroleum gas) ​ CNG (compressed natural gas) ​ LNG (liquefied natural gas) 5. Present the classification of liquid petroleum fuels. General: ​ fossil (crude oil) ​ synthetic (alcohols, vegetable oils) Classification of liquid petroleum fuels: ​ gasoline -aviation gasoline -unleaded gasoline 98 -unleaded gasoline 95 ​ diesel -diesel ON ​ aviation kerosene -jet A -jet B ​ heavy fules -IFO180 -IFO380 6. Characterize coal as a fuel. The origin of coal is organic; it belongs to the bioliths. Carbony matter was formed from plant material, which was enriched in the element C in the process of transformation. These transformations are referred to as coalification. The process of coalification of organic matter is divided into two phases: biochemical and geochemical. Coal, a solid fossil fuel, is rich in carbon and hydrogen, with impurities like sulfur, nitrogen, and ash. It’s classified by origin (natural), state (solid which is easy to handle, transport, and store), and calorific value (low-grade lignite to high-grade anthracite). Coal combustion releases significant energy but produces greenhouse gases (CO₂), pollutants (SO₂, NOₓ), and ash. Its uses include power generation and industrial processes, but environmental challenges like emissions and waste disposal limit its sustainability. Burning is less controllable compared to liquid or gaseous fuels.Coal as a fuels provides high energy output, making it suitable for power generation Periods of coal formation: ​ Hard coal before 300-200 million years ​ Brown coal (hard) before 100 million years ​ Lignites (soft) before 70-2 million years ​ Peat from 2 million years ago to now Coal consists of: ​ organic (combustible) matter, (substance that was formed during the growth of living organisms and then died transformed (carbonised). ​ mineral matter, ​ moisture. 7. Describe the origin and occurrence of crude oil and natural gas. The most probable origin of natural gas is organic. Natural gas can occur: separately, diluted in oil, diluted in water, diluted in rocks (in coal). 8. Explain the terms: flash point, self ignition temperature, clouding point and solidification temperature. Flash point- the "lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture Self ignition temperature-often called spontaneous ignition temperature or minimum ignition temperature and formerly also known as kindling point, of a substance is the lowest temperature in which it spontaneously ignites in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical ignites decreases as the pressure is increased. Clouding point-temperature at which dissolved waxes in a liquid start to precipitate as visible solid particles, making the liquid appear hazy or cloudy. Solidification temperature-is the temperature at which the fuel stagnates. For heavy oils it is about +5℃, for light diesel it is about. -20℃. If the fuel temperature is close to the solidification temperature, the fuel is unfit for pumping and requires heating. 9. Explain the terms: density (relative and absolute), viscosity (relative and absolute) with units and scales used. The density- An increase in the amount of hydrogen in the fuel causes a decrease in density, and vice versa. Density decreases with increasing temperature. Absolute density - is the ratio of the mass of a homogeneous body to the volume it occupies expressed in g/cm3 or any other units of mass and volume (e.g. kg/m3). Specific gravity (relative density) - an unmeasured quantity that is the ratio of the absolute density of the test body to the absolute density of the reference body. Scale: Api ° Absolute viscosity- the amount of resistance that occurs when two adjacent layers of a liquid are moved relative to each other Relative viscosity- the ratio of the viscosity of a fluid to the viscosity of a reference fluid Engler degrees [ °E]. 10. Explain the terms: heat of combustion, calorific value, incomplete and no-total combustion. Heat of combustion-is the amount of heat obtained from the complete and total combustion of a unit of mass or volume of fuel, after cooling the products of combustion to the initial temperature and complete condensation of the water vapor contained in the products of combustion. Examples of units are [kJ/kg],[kJ/m3]. Calorific value- is the amount of heat obtained from the complete and total combustion of a unit of mass or volume and fuel, after cooling the products of combustion to the initial temperature, assuming that the water contained in the products of combustion remains in the form of steam. Examples of units are [kJ/kg],[kJ/m3]. Incomplete combustion-if there are solid combustibles in the products (such as coke or soot) No-total combustion- if there are flammable gases in the products (CO, CH4 , H2) 11. Explain the terms: Octane Number, Cetane Number and CCAI. Octane Number-a number that determines the resistance to uncontrolled spontaneous ignition of engine fuel for spark-ignition engines, which can cause its knock (detonation) combustion.The exact value of the octane number is equal to the volume percentages of iso-octane (ON 100) content of such a mixture of iso-octane and n-heptane (ON 0) that causes an identical number of knocks in the test engine as the analyzed fuel. Cetane Number-is used to evaluate the ignition properties of fuels used in diesel engines. The best fuels in terms of ignition properties are those that show the smallest time lag, ignition delay, that is, the period that passes from the beginning of injection to the moment of self-ignition. CCAI- Carbonated Carbon Aromaticity Index characterizes the ignition properties of residual fuels for which the cetane number cannot be used, due to the completely different conditions of their combustion in marine engines than in a CFR reference engine. 12. Describe the fractional structure of crude oil. The fractional composition is obtained by distilling crude oil. Depending on the boiling point, the following fractions are obtained: ​ light gasoline: 313–433 K, ​ heavy gasoline: 433–473 K, ​ kerosene: 473–590 K, ​ Diesel oil: 590–633 K, ​ light residual oil: 633–813 K, ​ heavy residual oil: above 813 K. Fractional composition affects the self-ignition capability and regularity of the combustion process. This composition, in the case of motor fuels, should be characterized by a high content of light fractions, which make it easier to start the engine at low temperatures. 13. Describe the chemical structure of crude oil. Crude oil primarily contains hydrocarbons like alkanes, cycloalkanes, and aromatic hydrocarbons, along with organic compounds containing nitrogen, oxygen, sulfur, and trace metals (e.g., iron, nickel, copper, vanadium). The four main types of hydrocarbons in crude oil, which vary in proportion and determine oil properties, are: ​ Saturated hydrocarbons (alkanes) – Straight or branched chains (paraffins). ​ Cycloalkanes (naphthenes) – Monocyclic saturated hydrocarbons. ​ Aromatic hydrocarbons – Ring-shaped structures, typically derivatives of benzene. ​ Alkenes (olefins) – Unsaturated hydrocarbons with one double bond, rare in crude oil and typically formed during processing. Additionally, crude oil contains: Hetero Organic compounds (e.g., sulfur, nitrogen, oxygen). Asphaltenes – Complex molecules found with resins, aromatics, and saturates. 14. Describe the elemental structure of crude oil. Elementary composition: Pure hydrocarbons are composed of two elements only, carbon C and hydrogen H. In crude oil there are also other three important elements: O, S, N. Other elements in crude oil, like: vanadium, iron, manganese, cobalt, phosphor and microelements, are present in concentration of order of 10-3–10-5 %. 16. Describe the effect of the presence of paraffins in fuel on engine performance. The meaning of paraffins for engine operation: 1)​ Normal paraffins (with a straight chain) are preferable in diesel fuel - they cause soft engine operation. 2)​ Isoparaffins (with a branched structure) give greater resistance to knocking combustion in gasoline. 3)​ Paraffinic hydrocarbons have a high solidification temperature (54-60oC) which is a negative property 17. Describe the effect of the presence of aromatic hydrocarbons in fuel on engine performance.  ​ They support the knock-free combustion of gasoline. ​ They are not desirable in diesel fuel because they cause auto-ignition delay and hard engine operation. 18. Describe the effect of the presence of olefinic hydrocarbons in fuel on engine performance. ​ Double bonds are impermanent, so olefins oxidize easily even at low temperatures to form oxides and organic acids. ​ Oxides and organic acids promote corrosion, and are very harmful. 19. Describe the effect of the presence of sulfur and nitrogen in fuel on engine performance. Sulphurs: The corrosive effect increases when the engine is cold. Presence of sulfur in fuel can contributing to air pollution. Importance of nitrogen species and other compounds for engine operation: ​ These compounds are highly corrosive and toxic and should be removed in the refinery. ​ Nickel, vanadium, and copper can also severely affect the activities of catalysts and result in lower quality products. 20. Describe briefly 3 selected processes of oil processing. Cracking : it breaks or cracks heavier, higher-boiling point petroleum fractions into more valuable products. The basic types of cracking: thermal cracking, catalytic cracking, hydrocracking. Vacuum distillation: Distillation involves separating crude oil into boiling fractions at different temperature ranges, in two stages: at atmospheric pressure and in a vacuum. Starting from the lowest temperatures (