Industrial Chemistry - Coal and Petroleum Processing PDF

# Industrial Chemistry ## Chapter 1: Coal and Petroleum Processing ### Unit Introduction This chapter deals with coal and petroleum processing. It covers: * **Basic terms:** Provides the basic concept of coal and petroleum processing. * **Origin of coal:** Explains the origin of coal, its rankin...

# Industrial Chemistry ## Chapter 1: Coal and Petroleum Processing ### Unit Introduction This chapter deals with coal and petroleum processing. It covers: * **Basic terms:** Provides the basic concept of coal and petroleum processing. * **Origin of coal:** Explains the origin of coal, its ranking, gasification, and hydrogenation. * **Petroleum origin:** Covers the origin, classification, and mining of petroleum. * **Petroleum processing:** Discusses distillation, rating of petrol and diesel, cracking, alkylation, hydrotreating, and reforming. ### Learning objective of the unit After completing this unit, students will be able to: * **Define important terms:** Coal, carbonization of coal, gasification of coal, hydrogenation of coal, petroleum oil, and distillation of petroleum oil. * **Mention the origin and common ranking of coal.** * **Give examples for classification of petroleum.** * **Explain the difference between carbonization and gasification of coal.** * **Compare and contrast the rating of petrol and diesel.** * **Explain the difference among Cracking, Alkylation, Hydrotreating, and Reforming in petroleum processing/refinery.** ### 1.1 Coal: Its origin and its ranking #### Learning task 1.1 * **Define coal.** * **Explain how coal is formed.** * **List the major composition of coal.** * **List the common ranking of coal.** * **Mention the major uses of coal.** Coal is a readily combustible black or brownish-black sedimentary rock found in rock strata as layers or veins (coal beds). The harder forms (e.g., anthracite coal) are classified as metamorphic rock, formed from mineralized vegetative material deposited over a long period of time. These factors contribute to coal formation: 1. **Initiation, maintenance, and repetition of environments** that favor large-scale accumulation and preservation of vegetal sediment. 2. **Conditions within this depositional environment** that favor biological degradation and alteration of the vegetal sediment to peat (peatification). 3. **Geochemical processes** that induce chemical coalification of the peat to higher-rank coal. Coal primarily consists of carbon (>50%), alongside other components: * **Volatile matter:** * **Sulphur** * **Chlorine** * **Phosphorus** * **Nitrogen** * **Trace amounts of dirt and other elements** as impurities. Coal, a fossil fuel, is a major source of energy for electricity generation worldwide. It is also a significant anthropogenic source of carbon dioxide emissions. While coal usage emits slightly more carbon dioxide than petroleum, it emits about double the amount from natural gas. #### Types of coal These types of coals are formed due to geological processes applying pressure to dead biotic material over time. * **Peat:** A precursor of coal. It is a highly effective absorbent for fuel and oil spills on land and water. * **Lignite (brown coal):** The lowest rank of coal, primarily used as fuel for electric power generation. * **Sub-bituminous coal:** Its properties range from those of lignite to those of bituminous coal. It is used for steam-electric power generation and as a source of light aromatic hydrocarbons for the chemical synthesis industry. * **Bituminous coal:** Dense mineral, black or dark brown, often with well-defined bands of bright and dull material. Used for steam-electric power generation, heat and power in manufacturing, and to make coke. * **Steam coal:** A grade between bituminous coal and anthracite. Once widely used as a fuel for steam locomotives, it is now primarily used for domestic water heating. * **Anthracite:** The highest rank. A hard, glossy, black coal used for residential and commercial space heating. * **Graphite:** Technically the highest rank. It is difficult to ignite and is not often used as fuel but is commonly used in pencils and, when powdered, as a lubricant. The classification of coal is based on the content of volatiles, but the exact classification varies between countries. ### 1.1.1 Carbonization of coal #### Learning task 1.1.1 * **Define carbonization of coal.** * **Explain the advantage of carbonization of coal.** **Carbonization** is the conversion of an organic substance into carbon (coke) and liquid and gaseous carbon-containing residues (coal gas and coal tar), using pyrolysis or destructive distillation. Coke is used in the iron and steel industry and as a domestic smokeless fuel. Bituminous rank coals produce acceptable metallurgical cokes. A significant development in understanding carbonization processes was the discovery of mesophase in the plastic stage of this process. Mesophase leads to graphitizable carbons, as observed by optical microscopy. During carbonization, dehydrogenative polymerization of aromatic molecules occurs, increasing the average molecular weight. The final coke structure is related to the properties of mesophase at the time of solidification, which are dependent on the chemical properties of the parent material. ### 1.1.2 Gasification of coal #### Learning task 1.1.2 * **Define gasification of coal.** * **Mention some of the major products produced during gasification of coal.** * **Explain the advantage of gasification of coal.** **Coal gasification** is the process of producing coal gas or "synthesis" gas (syngas), a mixture of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), and water vapor (H2O), from coal. Syngas can be converted into transportation fuels like gasoline and diesel through the Fischer-Tropsch process. Hydrogen obtained from gasification can be used for various purposes, such as powering a hydrogen economy, making ammonia, or upgrading fossil fuels. During gasification, coal is mixed with oxygen and steam (water vapor) while being heated and pressurized. Oxygen and water molecules oxidize the coal into carbon monoxide (CO) while also releasing hydrogen (H2) gas. Note: Gasification is not combustion. **(Coal) + O2 + H2O → H2 + CO** **The partial oxidation process:** * **C + O2 + H2O → CO + H2** * **(CHn)n + O2 → H2 + CO** #### Figure 1.1.2: Gasification of coal and its products **Coal--> Coal Gasification --> Syngas --> Fischer-Tropsch -->** * **Ammonia Fertilizers** * **Methanol/DME/Propylene** * **Electricity (IGCC)** * **Diesel Fuel/Kerosene/Jet Fuel** * **Naphtha/Gasoline/Detergents** * **Waxes/Lubricants** * **Steam/Electricity** * **Synthetic Natural Gas** * **Hydrogen** * **Carbon Dioxide** Coal gasification is considered the cleanest coal technology as it produces syngas. This method inherently produces lower SOx, NOx, particulate matter, collateral solid wastes, and wastewater. It also provides an environmentally friendly way to remove mercury and sequester CO2. ### 1.1.3 Liquefaction of coal #### Learning task 1.1.3 * **Define hydrogenation of coal.** * **Mention some of the major products obtained during hydrogenation of coal.** **Hydrogenation of coal** is the direct conversion of coal to liquids. One process called the "Bergius process," developed by Friedrich Bergius in 1913, involves mixing dry coal with heavy oil from previous cycles, and heating the mixture between 400 °C (752 °F) to 5,000 °C (9,030 °F) at 20 to 70 MPa hydrogen pressure in the presence of catalyst. **n C + (n + 1) H2 → CnH2n+2** #### 1.1.3.2 Fisher-Tropsch process The Fisher-Tropsch process is an indirect process used to convert syngas into light hydrocarbons (e.g., ethane) in the presence of Fischer-Tropsch catalysts. This method was initially used on a large technical scale in Germany between 1934 and 1945, and is currently used by many countries. Ethane produced here is further processed into gasoline and diesel. Coal liquefaction methods involve carbon dioxide (CO2) emissions in the conversion process. Different processes have diverse lifecycle carbon footprints, dependent on the processes and environmental controls employed. ### 1.1.4 Environmental Effects of coal mining Coal mining and burning have numerous environmental effects: * **Generation of hundreds of millions of tons of waste products:** Including fly ash, bottom ash, flue gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals. * **Acid rain:** From high sulfur coal. * **Interference with groundwater and water table levels.** * **Contamination of land and waterways.** * **Destruction of homes from fly ash spills.** * **Impact of water use on flows of rivers.** * **Dust nuisance** * **Subsidence above tunnels** Coal-fired power plants without effective fly ash capture are one of the largest sources of human-caused background radiation exposure. They also release mercury, selenium, and arsenic, which are harmful to human health and the environment. The release of carbon dioxide, a greenhouse gas, contributes to climate change and global warming. #### Potential environmental and health effects of coal include: * **Effluent discharges to water:** Can affect water quality and the health of aquatic organisms. * **SO2 emissions:** Result in the acidification of lakes, rivers, and soil, and can have severe respiratory effects in humans. * **Metal emissions from smelters:** Include human carcinogens and affect terrestrial and aquatic ecosystems. ### 1.2 Petroleum: Its origin, classification, and mining #### Learning task 1.2 * **Define petroleum and list the most common forms of petroleum.** * **Mention some of the main origin and classification of petroleum.** * **State the mining process of petroleum.** Petroleum (crude oil) is a naturally occurring, flammable liquid found in rock formations in the Earth. It is a complex mixture of various molecular weights hydrocarbons and other organic compounds. The term petroleum comes from the Latin stems _petra_ ("rock") and _oleum_ ("oil"), describing hydrocarbons found in gas, liquid, or solid forms beneath the earth's surface. Petroleum is found in many parts of the world, including: * **The Middle East** * **Southern United States** * **Mexico** * **Nigeria** * **The former Soviet Union** Crude oil varies in appearance, depending on its composition. Usually, it is black or dark brown, but it can also be yellowish, reddish, or greenish. In the reservoir, it is typically found in association with natural gas, which forms a gas cap over the petroleum, and saline water, which is heavier and sinks beneath it. Crude oil can also be found in semi-solid form mixed with sand and water, known as crude bitumen. #### 1.2.2 Origin of Petroleum The origin of petroleum is explained by two theories: * **Biogenic theory:** The majority of geologists view crude oil, like coal and natural gas, as the product of compression and heating of ancient vegetation over geological time scales. Decayed remains of prehistoric marine animals and terrestrial plants are buried under thick sedimentary layers over many centuries. * **Abiogenic theory:** In 1866, Berthelot proposed that carbides formed by the action of alkali metal on carbonates react with water to give rise to large quantities of acetylene, which can be converted in to petroleum at elevated temperatures and pressures. #### 1.2.3 Mining of petroleum Mining of petroleum is not a simple task; it requires the knowledge of various disciplines. The vast majority of oil is found in oilfields or reservoirs below the earth's surface. While some oilfields have high pressure and can flow to the surface without pumping, most require induced pressure using water, carbon dioxide, natural gas, or steam to bring the oil to the surface. #### 1.2.4 Composition and classification of Petroleum Petroleum is principally a mixture of various hydrocarbons, such as: * **Alkanes:** (linear or branched) * **Cycloalkanes** * **Aromatic hydrocarbons** * **Heavier hydrocarbons** It also contains trace amounts of nitrogenous and sulfurous compounds, nickel, vanadium, and other elements. Crude oil is classified according to: * **Geographic location of production** * **API gravity (oil's industry measure of density):** Light if low density, heavy if high density * **Sulfur content:** Sweet if low sulfur content, sour if high sulfur content Each petroleum variety has a unique mix of molecules, which define its physical and chemical properties, like color and viscosity. #### 1.2.5 Petroleum refining (Distillation of Petroleum) and Processing #### Learning task 1.2.5 * **What are the common process units' distillations of petroleum?** * **List the major steps/processes in petroleum refining.** * **What are the major products during distillation of crude oil?** Raw oil (unprocessed crude oil) is not very useful in its initial form. It needs to be broken down and refined before use in a solid material (plastics and foams) or as petroleum fossil fuels (automobile and airplane engines). **An oil refinery** is a process plant where crude oil is separated into different hydrocarbon fractions by distillation: * **Ethane and other short-chain alkanes:** Used as fuel. * **Liquid petroleum gas (LPG)** * **Naphtha** * **Gasoline (petrol)** * **Jet fuel** * **Kerosene** * **Diesel oil** * **Lubrication oils** * **Fuel oils** * **Other hydrocarbons** Each fraction is a complex mixture. For example, the gasoline fraction contains more than 500 different hydrocarbons. **Figure 1.2.5 - Schematic of the distillation of crude oil** * Crude oil enters a fractionating column where different hydrocarbons are separated based on their boiling points, with the lightest fractions (e.g., gases) at the top and heaviest fractions (e.g., bitumen) at the bottom). * The distillation process produces various products, including liquefied petroleum gas, chemicals, petrol for vehicles, jet fuel, kerosene, diesel fuels, lubricating oils, waxes, polishes, fuel oil for ships, factories, and central heating, and bitumen for roads and roofing. Petroleum refining has been continuously evolving due to changing consumer demand for better products: * **Original requirement:** Produce kerosene as a cheaper and better source of light than whale oil. * **Internal combustion engine:** Led to the production of gasoline and diesel fuels. * **Airplane:** Created the need for high-octane aviation gasoline and jet fuels. * **Present-day refineries:** Produce a variety of products, including feedstock for the petrochemical industry: gasoline, liquefied refinery gas, still gases, kerosene, aviation fuel, distillate fuel oil, residual fuel oil, lubricating oils, asphalt, coke, and petrochemical feed stocks. #### Learning task 1.2.5.1 * **Define Cracking, Alkylation, Hydro treating, and Reforming in terms of oil refining.** * **What is the difference among Cracking, Alkylation, Hydro treating, and reforming in oil refining?** These are common process units in petroleum refinery processes: * **Cracking:** Produces light products (e.g., LPG and gasoline) from heavier crude oil distillation fractions (e.g., gas oils) and residues. * **Fluid Catalytic Cracking (FCC):** High yield of gasoline and LPG. * **Hydrocracking:** Major source of jet fuel, gasoline components, and LPG.. * **Thermal cracking:** Upgrades very heavy fractions or produces light fractions, distillates, burner fuel, and/or petroleum coke. * **Steam Cracking:** High-temperature process (750-900 °C or more), producing valuable ethylene and other feedstocks for the petrochemical industry. * **Delayed coking:** Milder temperature (500°C) which produces valuable needle coke, a highly crystalline petroleum coke used in the production of electrodes for the steel and aluminum industries. * **Hydrocracking:** A catalytic cracking process assisted by an elevated partial pressure of hydrogen, producing saturated hydrocarbons. * Products range from ethane, LPG to heavier hydrocarbons comprising mostly of isoparaffins. * Requires a bifunctional catalyst to rearrange and break hydrocarbon chains and add hydrogen to aromatics and olefins (producing naphthenes and alkanes). * **Alkylation:** Transfers an alkyl group from one molecule to another. * The alkyl group is transferred as a carbocation, a free radical, or a carbanion. * In standard oil refinery processes, alkylation involves low-molecular-weight olefins (primarily a mixture of propylene and butylenes) with isobutene in the presence of a catalyst (sulfuric acid or hydrofluoric acid). * Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning. * **Hydro treating:** A process where a petroleum faction is reacted with hydrogen to remove impurities. This process is typically used to remove sulfur. * **Catalytic reforming:** Improves the quality of naphtha from the crude distillation unit. * It uses a catalyst to allow chemical reactions to take place under reasonable temperatures and pressure, and to encourage the desired hydrocarbons to be produced. * **Steam cracking:** A petrochemical process where saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. The principal industrial method for producing lighter alkenes (olefins), including ethane (ethylene) and propene (propylene). ### Table 1.2.5 - Common Process Units in an Oil Refinery | Unit Process | Function | |-------------------------|---------------------------------------| | Atmospheric Distillation Unit | Distills crude oil into fractions. | | Vacuum Distillation Unit | Further distills residual bottoms after atmospheric distillation. | | Hydro-treater Unit | Desulfurizes naptha from atmospheric distillation, before sending to a Catalytic Reformer Unit. | | Catalytic Reformer Unit | Reformate paraffins to aromatics, olefins, and cyclic hydrocarbons, which are having higher octane number. | | Fluid Catalytic Cracking | Break down heavier fractions into lighter, more valuable products - by means of catalytic system. | | Hydro-cracker Unit | Break down heavier fractions into lighter, more valuable products - by means of steam. | | Alkylation Unit | Produces high octane component by increasing branching or alkyl. | | Dimerization Unit | Smaller olefinic molecules of less octane number are converted to molecules of higher octane number by dimerization of the smaller olefins. | | Isomerization Unit | Straight chain normal alkanes of less octane number are isomerized to branched chain alkane of higher octane number. | ### 1.2.6 Gasoline/petrol and Diesel: Production, composition, properties, and rating #### Learning Task 1.2.6 * **Compare and contrast the rate of petrol and diesel in our country.** * **What is octane rating?** Petroleum is refined to produce petrol and diesel. The Fractional Distillation process is used for refining petroleum. At various temperatures, different byproducts are formed. * **Petrol:** Produced at a temperature between 35 degrees to 200 degrees. * **Diesel:** Produced at a boiling point of 250-350 degrees. After distillation, blending with other elements is necessary to create commercially acceptable petrol and diesel. Petrol is produced first because it is produced at a lower temperature than diesel. #### 1.2.6.2 Composition and properties of petrol vs diesel * **Diesel:** Composed of about 75% saturated hydrocarbons (including n, iso, and cycloparaffins) and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). The average chemical formula for common diesel fuel is C12H23. * **Petrol:** Consists of hydrocarbons with between 5 and 12 carbon atoms per molecule, but it is blended for various uses. A typical petrol sample is predominantly a mixture of paraffins (alkanes), naphthenes (cycloalkanes), aromatics, and olefins (alkenes). The ratios vary on a variety of factors. **Petrol is more volatile than diesel** because of the base constituents and the additives put into it. Diesel contains about 38.6 megajoules per litre (MJ/l) while diesel contains about 34.6 megajoules per litre. This gives a higher power to diesel. #### 1.2.6.3 Rating of petrol vs diesel **Octane number:** A figure of merit representing the resistance of gasoline to premature detonation when exposed to heat and pressure in the combustion chamber of an internal combustion engine. Premature detonation is wasteful of the energy in the fuel and potentially damaging to the engine, indicated by knocking or ringing noises that occur as the engine operates. The octane number is determined by burning the gasoline in an engine under controlled conditions: *Spark timing* *Compression* *Engine speed* *Load* The engine is then operated on a fuel blended from a form of isooctane (octane number 100), which is very resistant to knocking, and a form of heptane (octane number 0), which knocks easily. When a blend is found that duplicates the knocking intensity of the sample under test, the percentage of isooctane by volume in the blended sample is taken as the octane number of the fuel. Octane numbers higher than 100 are determined by measuring the amount of tetraethyl lead that must be added to pure isooctane so as to duplicate the knocking of a sample fuel. *Factors which can increase the octane number are more branching:* 2-methylbutane is less likely to auto ignite than pentane. *Shorter chains:* Pentane is less likely to autoignite than heptane. Petrol and diesel are both petroleum-derived liquid mixtures used as fuels, but they have different properties and usage. ### 1.2.7 Uses of petroleum Most of the crude oil is used in the production of fuels such as gasoline, kerosene, and fuel oil. Non-fuel uses include petroleum solvents, industrial greases and waxes, or as raw materials for the synthesis of petrochemicals. Petroleum products are used to produce synthetic fibers such as nylon and other polymers (polystyrene, polyethylene, and synthetic rubber). They also serve as raw materials in the production of pharmaceuticals, fertilizers, refrigerants, aerosols, antifreeze, detergents, dyes, adhesives, alcohols, explosives, and pesticides. The H2 given off in refinery operations can be used to produce a number of inorganic petrochemicals, such as ammonia, ammonium nitrate, and nitric acid, from which most fertilizers as well as other agricultural chemicals are made. ### Chapter Summary * **Coal and Petroleum Processing** is an industrial process that can be used for the manufacturing of coal and petroleum in the desired quality. * **Coal** is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. * **There are different types of coal:** Peat, lignite, bituminous coal, Steam coal or Anthracite, sub-bituminous coal, and graphite. * **Carbonization** is defined as "The destructive distillation of some organic substances in the absence of air accompanied by the production of carbon and liquid and gaseous products." * **Coal gasification** can be used to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H2) gas. * **Hydrogenation of coal** is the direct conversion of coal to liquids. For example, the Bergius process is one of the main methods of direct conversion of coal to liquids by hydrogenation. * **Petroleum** is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds. * **The two most common forms of petroleum are natural gas and crude oil.** Petroleum is a combination of gaseous, liquid, and solid mixtures of many alkanes. It consists principally of a mixture of hydrocarbons, with traces of various nitrogenous and sulfurous compounds. * **An oil refinery** is an industrial process plant where crude oil is processed in three ways in order to be useful petroleum products. * **Cracking, Alkylation, Hydro-treating, and reforming** are processes in petroleum refining which can be used for distillation or refining petroleum in to different desired products.