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This document provides an overview of the petroleum refining process. It begins with an introduction that defines an oil refinery and its purpose of transforming crude oil into useful products like gasoline and diesel. It then discusses the major components and processes within a typical refinery, including distillation units, cracking units, and hydrotreating units. Linear and nonlinear modeling approaches for refinery components are also covered. The document concludes with sections on refinery locations and environmental and safety considerations.
control report.docx
- 1. 1 Modeling Of Petrol Refining Process StudentName: 1-Ahmed Naseh Latif 2-Ibrahim Abdulla Ahmed Class: 4 Stage – Group:B CourseTitle: Control Department: Mechanic and MechatronicEngineering College of Engineering Salahaddin University-Erbil Academic Year 2020-2021
- 2. 2 Introduction An oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils. Petrochemicals feed stock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha. The crude oil feedstock has typically been processed by an oil production plant. There is usually an oil depot at or near an oil refinery for the storage of incoming crude oil feedstock as well as bulk liquid products. According to the Oil and Gas Journal in the world a total of 636 refineries were operated on the 31 December 2014 for a total capacity of 87.75 million barrels (13,951,000 m3). Oil refineries are typically large, sprawling industrial complexes with extensive piping running throughout, carrying streams of fluids between large chemical processing units, such as distillation columns. In many ways, oil refineries use much of the technology, and can be thought of, as types of chemical plants. Jamnagar Refinery is the largest oil refinery, since 25 December 2008, with a processing capacity of 1.24 million barrels (197,000 m3). Located in Gujarat, India, it is owned by Reliance Industries. Some modern petroleum refineries process as much as 800,000 to 900,000 barrels (127,000 to 143,000 cubic meters) of crude oil per day. An oil refinery is considered an essential part of the downstream side of the petroleum industry. Operation Raw or unprocessed crude oil is not generally useful in industrial applications, although "light, sweet" (low viscosity, low sulfur) crude oil has been used directly as a burner fuel to produce steam for the propulsion of seagoing vessels. The lighter elements, however, form explosive vapors in the fuel tanks and are therefore hazardous, especially in warships. Instead, the hundreds of different hydrocarbon molecules in crude oil are separated in a refinery into components that can be used as fuels, lubricants, and feedstocks in petrochemical processes that manufacture such products as plastics, detergents, solvents, elastomers, and fibers such as nylon and polyesters.Petroleum fossil fuels are burned in internal combustion engines to provide power for ships, automobiles, aircraft engines, lawn mowers, dirt bikes, and other machines. Different boiling points allow the hydrocarbons to be separated by distillation. Since the lighter liquid products are in great demand for use in internal combustion engines, a modern refinery will convert heavy hydrocarbons and lighter gaseous elements into these higher value products.il can be used in a variety of ways because it contains hydrocarbons of varying molecular masses, forms and lengths such as paraffins, aromatics, naphthenes (or cycloalkanes), alkenes, dienes, and alkynes. While the molecules in crude oil include different atoms such as sulfur and nitrogen, the hydrocarbons are the most common form of molecules, which are molecules of varying lengths and complexity made of hydrogen and carbon atoms, and a small number of oxygen atoms. The differences in the structure of these molecules account for their varying physical and chemical properties, and it is this variety that makes crude oil useful in a broad range of several applications.
- 3. 3 Major products Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. The majority of petroleum is converted to petroleum products, which includes several classes of fuels. Oil refineries also produce various intermediate products such as hydrogen, light hydrocarbons, reformate and pyrolysis gasoline. These are not usually transported but instead are blended or processed further on-site. Chemical plants are thus often adjacent to oil refineries or a number of further chemical processes are integrated into it. For example, light hydrocarbons are steam-cracked in an ethylene plant, and the produced ethylene is polymerized to produce polyethene. Because technical reasons and environment protection demand a very low sulfur content in all but the heaviest products, it is transformed to hydrogen sulfide via catalytic hydrodesulfurization and removed from the product stream via amine gas treating. Using the Claus process, hydrogen sulfide is afterwards transformed to elementary sulfur to be sold to the chemical industry. The rather large heat energy freed by this process is directly used in the other parts of the refinery. Often an electrical power plant is combined into the whole refinery process to take up the excess heat. According to the composition of the crude oil and depending on the demands of the market, refineries can produce different shares of petroleum products. The largest share of oil products is used as "energy carriers", i.e. various grades of fuel oil and gasoline. These fuels include or can be blended to give gasoline, jet fuel, diesel fuel, heating oil, and heavier fuel oils. Heavier (less volatile) fractions can also be used to produce asphalt, tar, paraffin wax, lubricating and other heavy oils. Refineries also produce other chemicals, some of which are used in chemical processes to produce plastics and other useful materials. Since petroleum often contains a few percent sulfur-containing molecules, elemental sulfur is also often produced as a petroleum product. Carbon, in the form of petroleum coke, and hydrogen may also be produced as petroleum products. The hydrogen produced is often used as an intermediate product for other oil refinery processes such as hydrocracking and hydrodesulfurization. Crude oil is separated into fractions by fractional distillation. The fractions at the top of the fractionating column have lower boiling points than the fractions at the bottom. The heavy bottom fractions are often cracked into lighter, more useful products. All of the fractions are processed further in other refining units.
- 4. 4 Flow diagram of typical refinery The image below is a schematic flow diagram of a typical oil refinery that depicts the various unit processes and the flow of intermediate product streams that occurs between the inlet crude oil feedstock and the final end products. The diagram depicts only one of the literally hundreds of different oil refinery configurations. The diagram also does not include any of the usual refinery facilities providing utilities such as steam, cooling water, and electric power as well as storage tanks for crude oil feedstock and for intermediate products and end products. There are many process configurations other than that depicted above. For example, the vacuum distillation unit may also produce fractions that can be refined into end products such as: spindle oil used in the textile industry, light machinery oil, motor oil, and various waxes.
- 5. 5 Linear modeling Historically, models that have been used in refineries have been linear. The models have followed a black box approach, where the outputs were related to inputs through basic linear functions. For instance, in the hypothetical reactor in Figure below, the flow rate of product F2 would be related to the reactor feed by a simple function such as: F2=a2,1*F1 Eq. 1 Where α2,1 is a conversion factor. This allows the model to operate using simple, linear equations. What this type of model gains in simplicity, it loses in accuracy. Reactors often contain hundreds of different hydrocarbons undergoing many reactions at a wide range of temperatures and pressures. A simplified conversion factor cannot accurately account for multiple components undergoing multiple reactions for all conditions. Hypothetical reactor with 2 products and 1 feed stream. Linearity vs. Non-linearity Equations 2 and 3 are examples of the kerosene pretreating unit—showing the degree of nonlinearity. 𝐹𝑎𝑟 = 𝛼1𝐹total eq 2. 𝐹𝑎𝑟 = 𝑓𝑜 + 𝑊∗ 𝐿𝐻𝑆𝑉 ∗ ( 1000∗𝑃 𝑅∗𝑇 ) 𝐹total ∗ ( 1000 ∗ 𝑃 𝑅∗𝑇 ) ∗ ( 885000 𝐹total ) eq 3. Where Far is the flowrate of aromatics, α1 is alpha, Ftotal is the total flowrate, fo is the initial flowrate, W is the weight of the catalyst, LHSV is liquid hourly space velocity, P is pressure, R is the gas constant and T is temperature. The solution to nonlinearities is to linearize. This is done by discretizing the variables of the units. Discretizing the variables achieves linearity since it is variables existing in nonlinearities that create the problems. The discretization of the variables changes equation 4 into the following form: 𝑋 = 𝑓(𝑇, 𝐹, 𝑃) 𝑒𝑞.4 𝑋 = ∑𝑍(𝑇, 𝐹, 𝑃)∗ 𝑓(𝑇, 𝐹, 𝑃) 𝑒𝑞.5
- 6. 6 Where Z (a,b,c) is a binary variable that is used to choose the operation conditions. This reduces all variables present to zero, and therefore the model is run as a mixed integer program. A multi dimensional table was created X(a,b,c). This table was then uploaded into the model and equation 5 changed to equation 6 below. 𝑋 = ∑𝑍(𝑇, 𝐹, 𝑃)∗ 𝑋(𝑇,𝐹, 𝑃) eq 6 Galiasso determined that there were reaction orders for the removal of nitrogen, and aromatics. Below are the ordinary differential equations that show the rate of removal of the components based on their concentrations. 𝑟𝑁 = 𝑑𝐶𝑁 𝑑𝑊 = 𝑘𝑁𝐶𝑁 1.4 𝐶𝐻2 0.6 eq.7 𝑟𝐵𝑁 = 𝑑𝐶𝐵𝑁 𝑑𝑊 = 𝑘𝐵𝑁 𝐶𝐵𝑁 1.2 𝐶𝐻2 0.5 eq.8 𝑟 𝐴𝑟 = 𝑑𝐶𝐴𝑟 𝑑𝑊 = 𝑘𝐴𝑟 𝐶𝐴𝑟𝐶𝐻2 eq.9 Utility modeling The amount of each utility required for a unit is calculated based on specific operating conditions of temperature, pressure, and flow rate through each unit. This method is more accurate than modeling the demand equations as linear functions of a single variable (such as flow rate) through each unit. For example, when modeling a heat exchanger, basic equations for heat transfer are used. For a fluid that does not undergo a phase change, 𝑄 = 𝑚 ˙ 𝐶𝑝Δ𝑇 𝑒𝑞.10 Where 𝑚 ˙ is the mass flow rate and Cp is the specific heat of the fluid. For a fluid that undergoes an isothermal phase change, 𝑄 = 𝑚 ˙ 𝜆 𝑒𝑞. 11 Where𝑚 ˙ is the mass flow rate and λ is the latent heat of vaporization/condensation. For this model, heat exchangers are assumed to be adiabatic with their surroundings, and the heat transfer to the material of the heat exchanger itself is assumed to be negligible. This allows us to say that the heat lost by the process stream is equal to the heat gained by the utility stream or vice versa. Then, for steam-fed heat exchangers, we can say that: steam use = ∑ 𝑚𝑝 ˙ ∗𝐶𝑝𝑝∗Δ𝑇 𝜆steam eq.12 power can be calculated as a function of flow rate: power use = ∑ 𝐹𝑇∗ W𝐹𝑇 𝜂 eq.13 Fuel gas usage can then be related to refinery throughput by: Fuel gas usage= ∑ 𝑚𝑝 ˙ ∗𝐶𝑝𝑝∗Δ𝑇 Δ𝑀𝑓𝑔 eq.14
- 7. 7 The crude oil distillation unit The crude oil distillation unit (CDU) is the first processing unit in virtually all petroleum refineries. The CDU distills the incoming crude oil into various fractions of different boiling ranges, each of which are then processed further in the other refinery processing units. The CDU is often referred to as the atmospheric distillation unit because it operates at slightly above atmospheric pressure. Below is a schematic flow diagram of a typical crude oil distillation unit. The incoming crude oil is preheated by exchanging heat with some of the hot, distilled fractions and other streams. It is then desalted to remove inorganic salts (primarily sodium chloride).Following the desalter, the crude oil is further heated by exchanging heat with some of the hot, distilled fractions and other streams. It is then heated in a fuel-fired furnace (fired heater) to a temperature of about 398 °C and routed into the bottom of the distillation unit.The cooling and condensing of the distillation tower overhead is provided partially by exchanging heat with the incoming crude oil and partially by either an air-cooled or water-cooled condenser. Additional heat is removed from the distillation column by a pumparound system as shown in the diagram below.As shown in the flow diagram, the overhead distillate fraction from the distillation column is naphtha. The fractions removed from the side of the distillation column at various points between the column top and bottom are called sidecuts. Each of the sidecuts (i.e., the kerosene, light gas oil and heavy gas oil) is cooled by exchanging heat with the incoming crude oil. All of the fractions (i.e., the overhead naphtha, the sidecuts and the bottom residue) are sent to intermediate storage tanks before being processed further. Schematic flow diagram of a typical crude oil distillation unit as used in petroleum crude oil refineries.
- 8. 8 Location of petroleum refineries A party searching for a site to construct a refinery or a chemical plant needs to consider the following issues: The site has to be reasonably far from residential areas. Infrastructure should be available for supply of raw materials and shipment of products to markets. Energy to operate the plant should be available. Facilities should be available for waste disposal. Refineries which use a large amount of steam and cooling water need to have an abundant source of water. Oil refineries therefore are often located nearby navigable rivers or on a sea shore, nearby a port. Such location also gives access to transportation by river or by sea. The advantages of transporting crude oil by pipeline are evident, and oil companies often transport a large volume of fuel to distribution terminals by pipeline. Pipeline may not be practical for products with small output, and rail cars, road tankers, and barges are used. Petrochemical plants and solvent manufacturing (fine fractionating) plants need spaces for further processing of a large volume of refinery products for further processing, or to mix chemical additives with a product at source rather than at blending terminals. Safety and Enviroment The refining process releases a number of different chemicals into the atmosphere and a notable odor normally accompanies the presence of a refinery. Aside from air pollution impacts there are also wastewater concerns, risks of industrial accidents such as fire and explosion, and noise health effects due to industrial noise. Many governments worldwide have mandated restrictions on contaminants that refineries release, and most refineries have installed the equipment needed to comply with the requirements of the pertinent environmental protection regulatory agencies. In the United States, there is strong pressure to prevent the development of new refineries, and no major refinery has been built in the country since Marathon's Garyville, Louisiana facility in 1976. However, many existing refineries have been expanded during that time. Environmental restrictions and pressure to prevent construction of new refineries may have also contributed to rising fuel prices in the United States. Additionally, many refineries (more than 100 since the 1980s) have closed due to obsolescence and/or merger activity within the industry itself.Environmental and safety concerns mean that oil refineries are sometimes located some distance away from major urban areas. Nevertheless, there are many instances where refinery operations are close to populated areas and pose health risks. In California's Contra Costa County and Solano County, a shoreline necklace of refineries, built in the early 20th century before this area was populated, and associated chemical plants are adjacent to urban areas in Richmond, Martinez, Pacheco, Concord, Pittsburg, Vallejo and Benicia, with occasional accidental events that require "shelter in place" orders to the adjacent populations. A number of refineries are located in Sherwood Park, Alberta, directly adjacent to the City of Edmonton. The Edmonton metro area has a population of over 1,000,000 residents.
- 9. 9 References James G, Speight (2006). The Chemistry and Technology of Petroleum (Fourth ed.). CRC Press. 0-8493-9067-2. "Exxon starts world's 1st crude-cracking petrochemical unit". Reuters. 2014-01-08. Retrieved 13 April 2018. "Converting Crude to Ethylene Technology Breakthrough". 2016-08-02. Retrieved 13 April 2018. Gary, J.H. & Handwerk, G.E. (1984). Petroleum Refining Technology and Economics(2nd ed.). Marcel Dekker, Inc. ISBN 978-0-8247-7150-8. Leffler, W.L. (1985). Petroleum refining for the nontechnical person (2nd ed.). PennWell Books. ISBN 978-0-87814-280-4.