course design secondary distillation of gasoline

Introduction. 3 1 Theoretical Part 4 1.1 the Device and the principle of action of a column of redistillation of gasoline 1.2 Bases of process of rectification 1.3 Operation and service of a column of rectification 1.4 Comparative characteristic 2 Settlement Part 2.1 Calculation of pressure above and in the bottom of a column 13 2.2 Material balance 2.3 Calculation of temperature of top 16 2.4 Calculation of temperature of a bottom of a column 17 2.5 Calculation of a share of distillation on an entrance to a column 18 2.6 Calculation of thermal balance 19 2.6.1 Calculation of an enthalpy of a steam and liquid phase of raw materials 2.6.2 Calculation of amount of heat, output with distillate 21 2.6.3 Calculation of amount of heat carried away with residue 2.6.4 Calculation of enthalpy of vapor and liquid phase at distillate temperature and reflux 2.7 Calculation of rectification column diameter 2.8 Hydraulic calculation of tray List of used sources Introduction Oil refining industry - heavy industry, covering the processing of oil and gas condensates and the production of high-quality commercial oil products: motor and energy fuels, lubricating oils, bitumen, petroleum coke, paraffins, solvents, elemental sulfur, thermogasoil, petrochemical raw materials and consumer goods. Industrial processing of oil and gas condensates at modern oil refineries (refineries) is carried out through complex multi-stage physical and chemical processing at separate or combined large-capacity technological processes (installations, workshops) designed to obtain various components or assortments of commercial oil products. To obtain these oil products, the oil is first prepared, that is, purified from undesirable impurities, and then sent to primary processing. Primary distillation of oil is the first stage of studying its chemical composition. After primary distillation, broad fractions are sent to secondary processing to obtain narrower fractions. The purpose of the course work is the project of a column for the secondary distillation of gasoline, designed to divide gasoline into fractions by boiling points, oil production of 3 million tons per year, the number of working days 350. To achieve this goal, the following tasks are set: - to study the basics of the rectification process; - to study the structure and principle of operation of the secondary gasoline distillation column; - to compare contact devices of different types; - to study safe methods of operation and maintenance of rectification columns; - to perform the technological calculation of the secondary gasoline distillation column (make a material balance, determine the temperature regime, the fraction of the spur, make a heat balance, calculate the main dimensions (diameter, height); - select a standard tray according to GOST; - perform hydraulic calculation of the tray; - develop a general drawing in the format A1 of the secondary distillation columns of gasoline, compile a table of nozzles, technical characteristics, specification.1 Theoretical part 1.1 The structure and operation of the distillation column The design of the rectification apparatus depends on how the whole process is organized and how the phases are contacted. The simplest design of rectifiers when moving liquid from one contact stage to another under the influence of gravity. The rectification column is a vertical cylindrical apparatus of the column type with fractionating trays equipped on it in the amount of no more than 40 pieces, nozzle nozzles for introducing raw materials and withdrawing products, manholes for inspection and repair and installation work. The injection point into the distillation column of the heated distillable feedstock is referred to as the feed section or zone. Flash evaporation is performed here. The part of the column located above the feed section serves for rectification of the steam flow and is called concentration (strengthening), and the other - the lower part in which the rectification of the water flow is carried out - stripping, or exhaustive, sections. Contact of steam and liquid flows can be carried out either continuously (in packing columns) or stepwise (in plate distillation columns). At interaction of opposite flows of steam and liquid at each stage of contact (tray or nozzle layer), heat and mass exchange occurs between them due to system zeal to equilibrium state. As a result of each contact, ingredients are redistributed between phases: steam is somewhat enriched with low-boiling, and liquid with high-boiling components. With long enough contact and high efficiency of the contact device, the steam and liquid leaving the tray or nozzle layer can achieve an equilibrium state, then the temperatures of the flows will become the same and their compositions will be connected by equilibrium equations. Such contact of liquid and steam, culminating in the achievement of phase equilibrium, is commonly called an equilibrium stage, or a theoretical plate. By selecting the number of contact stages and the characteristics of the process (temperature mode, pressure, flow ratio, reflux number, etc.), it is possible to provide the required clarity of fractionation of oil mixtures. In order to ensure normal operation of the distillation column, it is necessary to always have an upflow of steam and a downflow of reflux. A heating system is provided at the bottom of the column to produce steam. The rectification process can be carried out at atmospheric pressure, under vacuum, under excessive pressure at a reduced temperature. Basically, the rectification process is carried out at a pressure close to atmospheric. Vacuum rectification is subjected to mixtures of substances prone to thermal decay or polymerization at high temperatures. Low temperature rectification is used to separate solutions having a low boiling point. 1.2 Fundamentals of the rectification process In some cases, the fractions obtained during the primary distillation must be divided into narrower cuts, each of which is then used for its intended purpose. Units or independent units for the secondary distillation of gasoline are built at almost all refineries. The secondary distillation of gasoline distillate is either a stand-alone process or part of a combined unit that is part of an oil refinery. In modern plants, gasoline distillate secondary distillation plants are designed to obtain narrow fractions from it. Rectification is a method of separating a mixture into pure components, carried out by repeatedly alternating the processes of evaporation of the liquid phase and condensation of vapors. The physical essence of the process consists in bilateral mass and heat exchange between non-equilibrium flows of steam and liquid with high turbulisation of the surface of the contacting phases. As a result of mass exchange, steam is enriched with low-boiling, and liquid with high-boiling components.With a certain number of contacts, vapors consisting mainly of low boiling components and a liquid consisting mainly of high boiling components can be obtained. In a step-by-step rectification process, vapor-liquid contact can occur in countercurrent, cross current, and direct flow. If the rectification is continuous throughout the column, the vapor-liquid contact during the movement of both phases can only occur in countercurrent. With a sufficiently large number of stages in this way, it is possible to obtain a liquid or vapor phase with a sufficiently high concentration of the component by which it is enriched. However, the yield of this phase will be sufficiently small with respect to its amount in the feed. In addition, such plants are bulky and operate with large heat losses to the environment. A much more economical, complete and clear separation of mixtures into components is achieved by conducting rectification processes in more compact apparatus - fractionation columns. 1.4 Comparative characteristic Main elements of the valve tray - lifting valves of round or rectangular shape covering the holes in the tray. Structurally, the valve is designed so that its lifting is possible only by a certain amount. At a certain rate of vapor in the hole, the valves are balanced by steam flows and with a further increase in load, they begin to rise so that the steam velocity in the section between the valve and the tray web remains approximately constant. This results in uniform distribution of steam across the tray area, reduced liquid entrainment and lower hydraulic resistance. The wide range of stable operation, low weight and simple design make the use of valve trays promising. Diameter of disc valves is 50-100 mm, total lifting height is 8-15 mm. In extreme lower position there is clearance of 1-1.5 mm between valve and plate plane. Valve trays are manufactured with disk and rectangular valves; plates operate in direct-flow or cross-flow phase movement mode. On the valve straight-flow plate in staggered order there are holes in which self-regulating disk valves with a diameter of 50 mm are installed, which can be raised during movement of steam (gas) to a height of 6-8 mm. Efficiency of valve straight-flow trays: efficiency = 0.70-0.85, F ≤ 2.5 (m/s) (kg/m3) -0.5, stable operation range 3.5. In the field of self-regulating operation, the trays have relatively little hydraulic resistance. The main advantages of these trays are the ability to provide efficient mass transfer in a large range of workloads, ease of design, low metal consumption and low cost.