In 1858, Dr. Abraham Gesner, a Canadian physician and amateur geologist, devel­oped and patented the extraction of a lamp fuel from asphalt rock, which he named kerosene (Nova Scotia Museum 2008). At that time, kerosene, which was an ex­tremely high-value lighting fuel for lamps, was the primary product of petroleum refining. For a while, distillation of kerosene for lamps was the mainstay of the new petroleum industry. Gasoline was merely a byproduct of kerosene production from crude oil, and until the early 1900s there was no significant demand for it. The first petrochemical, aside from carbon black manufactured on an industrial scale, was isopropyl alcohol, made by Standard Oil of New Jersey in 1920.

When a mixture of two liquids of different boiling points is heated to its boiling point, the vapor contains a higher mole fraction of the liquid with the lower boiling point than the original liquid, i. e., the vapor is enriched in the more volatile com­ponent. If this vapor is now condensed, the resultant liquid has also been enriched
in the more volatile component. This is the principle of batch fractional distillation, and in a distillation column many, many such cycles are performed continuously, al­lowing almost complete separation of liquid components. A generalized distillation column is shown in Figure 7.4. The first step in the refining of crude oil, whether in a simple or a complex refinery, is the separation of the crude oil into fractions (fractionation or fractional distillation). These fractions are mixtures containing hy­drocarbon compounds whose boiling points lie within a specified range.

Crude oil is a complex mixture that is between 50 and 95% hydrocarbon by weight. The first step in refining crude oil involves separating the oil into different hydrocarbon fractions by distillation. An oil refinery cleans and separates the crude oil into various fuels and byproducts, including gasoline, diesel fuel, heating oil, and jet fuel. The main crude oil components are listed in Table 7.3. Since various components boil at different temperatures, refineries use a heating process called distillation to separate the components. For example, gasoline has a lower boiling point than kerosene, allowing the two to be separated by heating to different temper­atures. Another important job of the refineries is to remove contaminants from the oil, for example, sulfur from gasoline or diesel to reduce air pollution from the auto­mobile exhausts. After processing at the refinery, gasoline and other liquid products are usually shipped out through pipelines, which are the safest and cheapest way to move large quantities of petroleum across land (Demirbas 2009).

Uncondensed gases Figure 7.4 A generalized fractional distillation column

Table 7.3 Main crude oil fractions Component Boiling range, K Number of carbon atoms Natural gas < 273 C1 to C4 Liquefied petroleum gas 231-273 C3 to C4 Petroleum ether 293-333 C5 to C6 Ligroin (light naphtha) 333-373 C6 to C7 Gasoline 313-478 C5 to C12, and cycloalkanes Jet fuel 378-538 C8 to C14, and aromatics Kerosene 423-588 C10 to C16, and aromatics No. 2 diesel fuel 448-638 C10 to C22, and aromatics Fuel oils > 548 C12 to C70, and aromatics Lubricating oils > 673 > C20 Asphalt or petroleum coke Nonvolatile residue Polycyclic structures

The refining of heavy oil requires extracting and thorough chemical, engineering, and computing processes. Before the actual refining begins, the stored heavy crude oil is cleaned of contaminants such as sand and water.

Industrial distillation is typically performed in large, vertical, steel cylindrical columns known as distillation towers or distillation columns with diameters ranging from about 65 cm to 11m and heights ranging from about 6 to 60 m or more. To improve the separation, the tower is normally provided inside with horizontal plates or trays, or the column is packed with a packing material. To provide the heat re­quired for the vaporization involved in distillation and also to compensate for heat loss, heat is most often added to the bottom of the column by a reboiler. Large — scale industrial fractionation towers use reflux to achieve more efficient separation of products. Reflux refers to the portion of the condensed overhead liquid product from a distillation tower that is returned to the upper part of the tower. Inside the tower, the downflowing reflux liquid provides cooling and partial condensation of the upflowing vapors, thereby increasing the efficacy of the distillation tower. There are generally 25 to 45 plates or trays in a distillation tower. Each of the plates or trays is at a different temperature and pressure. The stage at the tower bottom has the highest pressure and temperature. Progressing upwards in the tower, the pressure and temperature decrease for each succeeding stage. Another way of improving the separation in a distillation column is to use a packing material instead of trays.

Three major refinery processes change crude oil into finished products: (1) sep­aration, (2) conversion, and (3) purification. The first step is to separate the crude oil into its naturally occurring components. This is known as separation and is ac­complished by applying heat through a process called distillation. Separation is per­formed in a series of distillation towers. The conversion processes have focused on reducing the length of some hydrocarbon chains. The primary purpose of con­version is to convert low valued heavy oil into high valued petrol. For example, catalytic reforming is a conversion process. The purpose of the reformer is to in­crease the octane number of the petrol blend components. Once crude oil has been through separation and conversion, the resulting products are ready for purification, which is principally sulfur removal. Common process units found in an oil refinery are presented in Table 7.4.

Petroleum refining is somewhat analogous to biorefining. Although biorefineries utilize different processing technologies, they separate and isolate components of biomass for the production of energy fuels, chemicals, and materials. Biorefiner­ies can be designed and built to produce desired outputs from the processing of a wide variety of biorenewable materials. These biorefineries will adopt and inte­grate a range of materials handling and preprocessing equipment, thermochemical and biochemical conversion technologies, and new extraction and purification sci­ences to produce a range of intermediate products, while using less energy and re­ducing effluents and emissions. The scale of the biorefining operations will range from medium-sized to very large (equivalent in size to existing chemical plants and pulp and paper mills). Adoption of biorefineries and related processes and product technologies depends on available research, development, and prevailing regulations during design and construction.

In some ways, biorefineries are analogous to oil refineries. Oil refineries take crude oil and fractionate it into many different useful parts. This is done using a sim­ple chemical distillation process. Biomass, like oil, consists of many different frac­tions that are separated and made into useful products in biorefineries. However, the processes involved in fractionating biomass are more complex than those used in oil refineries. Another important difference between biorefineries and oil refineries is their size. The term biorefinery was coined to describe future processing complexes that will use renewable agricultural residues, plant-based starch, and lignocellulosic materials as feedstocks to produce a wide range of chemicals, fuels, and bio-based materials. Biorefineries will most likely be limited in size, because biomass must be produced and transported economically from a limited catchment area. In contrast, oil is drilled and transported all over the world for processing.

Biomass can be processed into plastics, chemicals, fuels, heat, and power in a biorefinery. High-value components, for example essential oils, drugs, or fibers, can be recovered as a preprocessing step, with the remaining materials then pro­cessed downstream. Processing technologies are most advanced for chemicals and fuels. Biorefineries vary from small single-process plants to large multiprocess sites. Larger biorefineries will be able to integrate different technologies to obtain maxi­mum value from biomass feedstocks.

A biorefinery is an integrated plant producing multiple value-added products from a range of renewable feedstocks. This innovative approach responds to chang­ing markets for traditional forest products as well as new products such as energy, chemicals, and materials. The range of feedstocks, processes, and potential prod­ucts is large; each combination of feedstock, process, and product is characterized by its own unique combination of technical and economic opportunities, emerging technologies, and barriers.

Table 7.5 shows the classification of biorefineries based on their feedstocks. A forest biorefinery will use multiple feedstocks including harvesting residues, ex­tracts from effluents, and fractions of pulping liquors to produce fiber, energy, chem­icals, and materials. A lignocellulosic-based biorefining strategy may be supported

Table 7.4 Common process units found in an oil refinery Unit Treatment 1 Desalter Washes out salt from the crude oil before it enters the atmospheric distillation unit 2 Atmospheric distillation IDdistills crude oil into fractions 3 Vacuum distillation Further distills residual bottoms after atmospheric distillation 4 Naphtha hydrotreater Uses hydrogen to desulfurize naphtha from atmospheric distillation 5 Catalytic reformer Used to convert the naphtha-boiling-range molecules into higher — octane reformer product (reformate) 6 Distillate hydrotreater Desulfurizes distillates (such as diesel) after atmospheric distilla­tion 7 Fluid catalytic cracker (FCC) Upgrades heavier fractions into lighter, more valuable products 8 Hydrocracker Uses hydrogen to upgrade heavier fractions into lighter, more valu­able products 9 Visbreaking Upgrades heavy residual oils by thermally cracking them into lighter, more valuable reduced-viscosity products 10 Merox Treats LPG, kerosene, or jet fuel by oxidizing mercaptans into or­ganic disulfides 11 Coking Converts very heavy residual oils into gasoline and diesel fuel, leav­ing petroleum coke as a residual product 12 Alkylation Produces high-octane component for gasoline blending 13 Dimerization Converts olefins into higher-octane gasoline blending components 14 Isomerization Converts linear molecules into higher-octane branched molecules for blending into gasoline 15 Steam reforming Produces hydrogen for hydrotreaters or hydrocracker 16 Liquefied gas storage For propane and similar gaseous fuels at pressure sufficient to main­tain in liquid form 17 Storage tanks For crude oil and finished products, usually cylindrical, with some sort of vapor emission control 18 Amine gas and tail gas treatment For converting hydrogen sulfide from hydrodesulfurization into elemental sulfur 19 Utility units Such as cooling towers for circulating cooling water, boiler plants for steam generation 20 Wastewater collec­tion and treating Converts wastewater into water suitable for reuse or for disposal 21 Solvent refining Uses solvent such as cresol or furfural to remove unwanted, mainly asphaltenic materials from lubricating oil stock 22 Solvent dewaxing For removing the heavy waxy constituents of petroleum from vac­uum distillation products

Table 7.5 Classification of biorefineries based on their feedstocks Feedstocks Products Green biorefinery Grasses, green plants Ethanol Cereal biorefinery Starch crops, sugar crops, grains Bioethanol Oilseed biorefinery Oilseed crops, oil plants Vegetable oils, biodiesels Forest biorefinery Forest harvesting residues, barks, sawdust, pulping liquors, fibers Fuels, energy, chemicals, materials Lignocellulosic Agricultural wastes, crop Lignocellulosic ethanol, biorefinery residues, urban wood wastes, industrial organic wastes bio-oil, gaseous products

by biomass reserves, created initially with residues from wood product processing or agriculture. Biomass reserves should be used to support first-generation biorefin­ing installations for bioethanol production, development of which will lead to the creation of future high-value coproducts (Mabee et al. 2006).

Biorefineries can be classified based on their production technologies: first — generation biorefineries (FGBRs), second-generation biorefineries (SGBRs), third- generation biorefineries (TGBRs), and fourth-generation biorefineries.

The FGBRs refer to biofuels made from sugar, starch, vegetable oils, or animal fats using conventional technology. Table 7.6 shows the classification of biorefiner­ies based on their generation technologies. SGBRs and TGBRs are also called ad­vanced biorefineries. SGBRs made from nonfood crops, wheat straw, corn, wood, and energy crop using advanced technology.

Sugar and vegetables are used and converted into bioalcohols and biodiesel in FGBRs. The transition from FGBRs to SGBRs will mark a qualitative leap. Ligno — cellulosic residues such as sugar cane bagasse and rice straw feedstocks are used and converted into SGBs in SGBRs.

The first TGBR demonstration plant in the world was commissioned in Oulu, Finland, by Chempolis Oy. As far as is known, the world’s first TGBR producing paper fiber, biofuel, and biochemicals from nonwood and nonfood materials was launched in Finland. TGBRs start with a mix of biomass feedstocks (agricultural or forest biomass) and produce a multiplicity of various products, such as ethanol for fuels, chemicals, and plastics, by applying a mix of different (both small — and

Table 7.6 Classification of biorefineries based on their generation technologies Generation Feedstocks Examples First Sugar, starch, vegetable oils, animal fats Bioalcohols, vegetable oil, biodiesel, biosyngas, biogas Second Non food crops, Wheat straw, Corn, Wood, Solid waste, Energy crop Bioalcohols, bio-oil, bio-DMF, bio­hydrogen, bio-Fischer-Tropsch diesel Third Algae Vegetable oil, biodiesel, jet fuel Fourth Vegetable oil, biodiesel Biogasoline

large-scale) technologies such as extraction, separation, and thermochemical or bio­chemical conversion. However, large integrated TGBRs are not expected to become fully established until around 2020. Increasing quantities of agricultural residues will be needed to make paper in the future, as insufficient wood is available locally in the world’s growing paper markets, forest resources are declining, and growing environmental pressures are being put on the use of wood. Vegetable oil is used and converted into biogasoline in fourth-generation biorefineries.

Biorefineries can also be classified based on their conversion routes: biosyngas — based biorefineries, pyrolysis-based biorefineries, hydrothermal-upgrading-based biorefineries, fermentation-based biorefineries, and oil-plant-based biorefineries. Table 7.7 shows the classification of biorefineries based on their conversion routes. Biosyngas is a multifunctional intermediate for the production of materials, chemi­cals, transportation fuels, power, and heat from biomass.

Table 7.7 Classification of biorefineries based on their conversion routes Biorefinery Products Biosyngas-based Syngas, hydrogen, methanol, dimethyl ether, FT diesel Pyrolysis-based Bio-oil, diesel fuel, chemicals, oxygenates, hydrogen Hydrothermal-upgrading-based Cx Hx, diesel fuel, chemicals Fermentation-based Bioethanol Oil-plant-based Biodiesel, diesel fuel, gasoline