Calculation of rectification column by separation of binary mixture.

Contents

Introduction

2. Engineering calculations

2.1 Process calculations

2.1.1 Equilibrium data

2.1.2 Material Balance

2.1.3 Calculation of steam and liquid flow rates at the top and bottom of the column

2.1.4 Calculation of heat balance of the unit and heating steam flow rate

2.2 Hydraulic calculation of rectification column with cap trays

2.2.1 Hydraulic calculation at constant steam load

2.2.1.1 Determination of steam velocity and column diameter

2.2.1.2 Check of tray free cross-section margin

2.2.1.3 Hydraulic resistance of tray

2.2.1.4 Interrail liquid entrainment

2.2.1.5 Check of overflow device operation

2.2.2 Column height calculation

2.2.2.1 Determination of kinetic parameters (mass transfer factors, number of transfer units)

2.2.2.2 Determination of local tray efficiency

2.2.2.3 Determination of the number of valid trays

2.2.3 Determination of height and hydraulic resistance of the column

2.3 Calculation of heat exchanger

Conclusions

4 List of used literature

Introduction

Rectification is one method of separating liquid mixtures based on the different distribution of the components of the mixture between the liquid and steam phases. Rectification columns are used as rectification devices - consisting of the column itself, where the countercurrent contact of steam and liquid is carried out, and devices in which the liquid evaporates and the vapor-cube and reflux condensation occur. The column is a vertically standing hollow cylinder, inside of which there are so-called trays (contact devices of various designs) or a shaped piece material - a nozzle - is placed. The cube and dephlegmator are usually shell and tube heat exchangers (tubular furnaces and evaporator cubes are also used).

The purpose of the trays and the nozzle is to separate the interfacial surface and improve contact between liquid and steam. The trays are typically provided with a liquid overflow device. Rings whose diameter is equal to their height are commonly used as the packing of distillation columns.

In both packing and poppet columns, the kinetic energy of steam is used to overcome the hydraulic resistance of contact devices and create a dynamic dispersed system of steam - liquid with a large interfacial surface. There are also rectification columns with the supply of mechanical energy, in which a disperse system is created when the rotor installed along the axis of the column rotates. Rotary machines have a smaller pressure drop in height, which is especially important for vacuum columns.

According to the method, continuous and periodic rectification is distinguished. In the first case, the separated mixture is continuously fed to the distillation column, and two or more fractions enriched in one component and depleted in the other are continuously withdrawn from the column. The complete column consists of two sections: reinforcing and exhaustive. The feed mixture (usually at boiling point) is fed to a column where it is mixed with the so-called recovered liquid flowing through the contact devices (trays or packing) of the exhaustive section countercurrent to the rising steam stream. Reaching the bottom of the column, the liquid is enriched with heavy volatile components. At the bottom, the liquid partially evaporates as a result of heating by the supplied heat carrier, and steam again enters the exhaustive section .

Enriched with volatile components, steam enters the reflux condenser, where it is usually completely condensed with a suitable refrigerant. The resulting liquid is divided into two streams - distillate and reflux. Distillate is a product stream, and reflux is supplied to the irrigation of the strengthening section, through the contact devices of which it flows. Part of the liquid is withdrawn from the bottom of the column as a so-called bottom residue (also a product stream).

If the initial mixture is to be divided in a continuous manner into a number of fractions greater than two, then a sequential or parallel - sequential column connection is used.

During periodic rectification, the initial liquid mixture is simultaneously loaded into the column cube (a tank that corresponds to the desired capacity). The vapors enter the column and rise to the reflux condenser, where they condense. In the initial period, all condensate is returned to the column, which corresponds to the complete reflux mode. The condensate is then divided into distillate and reflux. As the distillate is withdrawn (either at constant reflux or with its change, first volatile components are removed from the column, then medium volatile, and so on). The desired fraction (or fractions) is collected in a suitable collector. The operation continues until the initially charged mixture is fully processed.

The main areas of industrial application of rectification are the production of individual fractions and individual hydrocarbons from oil raw materials in the oil refining and petrochemical industries; ethylene oxide, acrylonitrile, acrylchlorosilanes - in the chemical industry. Rectification is widely used in other sectors of the national economy: coke chemical, forest chemical, food, chemical and pharmaceutical industries.

Specification No. 52x

Topic: rectification - separation of methyl alcohol-water mixture.

List of engineering calculations: calculate the diameter, height and hydraulic resistance of the distillation column. Calculate heat balance and heating steam flow for rectification column. The pressure in the column is 1 atmosphere. Calculate and select the heater of the initial mixture with heating steam.

List of works performed on the computer: determine the heat exchange surface of the heater.

Composition and volume of the graphic part: heat exchanger drawing for heating the initial mixture with heating steam. Process diagram.

Basic data: consumption of vat balance,,,. The temperature of the initial mixture - C, the temperature of the cooling water - C, the pressure of the heating steam - select .

2 Engineering calculations

2.1 Process calculations

For technological calculations of the plant, it is necessary to know the properties of substances at certain temperatures. The main diagrams for determining these properties are diagrams: steam composition - liquid composition, and the dependence of boiling temperature on composition. Annex 2 shows diagrams of these properties of the chloroform 1.2 dichloroethane binary system.

Conclusions

In this course design, a distillation column was calculated to separate the methyl alcohol-water mixture at atmospheric pressure. A column apparatus with cap trays was chosen to provide countercurrent phase motion. The diameter of the apparatus is 1.8 m, the height of the apparatus is 10.2 m.

A standard two-way shell-and-tube heat exchanger according to GOST 1512079 was also selected for heating the initial mixture with heating steam. Heat exchanger characteristics:

total number of pipes = 166,

heat exchange surface at length of pipes = -.

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