Introduction

Absorption is called absorption process gases or vapors from the gas or vapor-gas mixtures by liquid (absorbent).

When physical absorption absorbable gas (absorptive) does not chemically react with the absorbent. If absorptive forms chemical compound with the absorbent, the process is called chemisorptions.

The physical absorption is reversible in most cases. On this property, absorption processes based allocation of absorbed gas from the solution - desorption.

The combination of absorption desorption allows repeatedly use the absorber and release the absorbed component in pure form. In many cases, to carry out the desorption is not necessary, as the absorbent and absorptive are cheap or of off-products, which, after absorption can not be used again (for example, gas cleaning).

In industry absorption processes are used mainly for the recovery of valuable components from gaseous mixtures or for the purification of these mixtures of contaminants.

Absorption processes are common in chemical engineering and are the main process step a number of major industries (for example, absorption of nitrogen oxides with water in nitric acid absorption ammonia, benzene vapor, hydrogen sulphide and other components from the coke oven gas, absorption of vapors of various hydrocarbons from gas refining and etc.). In addition, the absorption process are the main processes in sanitary cleaning of exhaust gases released into the atmosphere from harmful impurities (eg, cleaning of flue gases from carbon dioxide and etc.).

Devices in which the absorption process, called absorbers. Like other mass transfer processes, absorption occurs at the interface. Therefore absorbers should have a developed contact surface between gas and liquid. By the method of formation of the surface of the absorbers can be roughly divided into the following groups:

1. Surface and foil;

2. packing;

3. Bubble;

4. spattering.

Widespread industry as absorber received columns filled with packing - solids of different shapes.

The packed column liquid flows through the nozzle element is mainly in the form of a thin film, so the phase contact surface is substantially wetted surface nozzles, and packed devices may be considered as a kind of film. However, in the past the liquid film flow occurs over the entire height of the machine, and packed absorbers - only packing element height. When the liquid overflow from one packing element to another liquid film is destroyed and a new film is formed on the underlying element. In this part of the fluid passes through the layers located below the nozzle in the form of jets, droplets and sprays. Part of the nozzle surface is wetted with a fixed (stagnant) liquid.

1. Justification of choice construction the designed

1.1. Design Consideration

The term absorption came from the Latin word absorbere that in translation means "to absorb". In fact, it is process of complete or partial absorption of gas (which is capable to be dissolved almost entirely in it) a liquid absorber (scientists gave it the name "absorbent"). The return process is called a desorption, in case of it, on the contrary, there is a liberation of gas from solution.

For separation of gases from each other in their mixes, for the purpose of cleaning or receipt of valuable components there are also other methods: deep chilling, adsorption, etc., but the absorption method because complete extraction of such components is required seldom is most often used.

Process of absorption or desorption always takes place liquid and gas phases during which there is a transformation of substance from gas in liquid in case of process of absorption and, on the contrary, from liquid in gas in case of process of a desorption. For this reason processes of absorption are called one of mass transfer methods (exchange of masses by means of an interface or through a permeable wall in the course of two phases or between two substances).

In practice gas mixes, but not any separate types of gases are exposed to process of absorption. Such compound shares are called components, and those parts which aren't absorbed have the name inert gas. Together with an absorber this gas represents the component carrier in liquid and gas phases.

The liquid phase includes an absorber and a component of process of absorption. The absorber is, in fact, solution of an active component which enters chemical reaction with the absorbed its analog, and substance in which the active component is dissolved call the solvent.

Absorption happens two types:

1. Physical. (In the course of physical absorption the absorber and inert gas don't take part in the course of transition of a component from a phase in a phase and aren't dissipated.)

2. Chemical. (Chemical absorption assumes reaction which results from chemical interaction of an absorber with a component of sanitary purification of gases, waste solution which after a neutralization stage is usually merged in the sewerage is as a result formed.)

The special device is necessary for successful carrying out absorption. Such devices have the conditional classification depending on a type of a surface of contact.

Absorbers. Description and types

1. Superficial

Here in turn subspecies enter:

o superficial absorbers (in them the surface of contact of two phases is a mirror of liquid);

o film absorbers (the liquid film surface participates in process);

o nozzle absorbers (they have a special nozzle, on which of bodies of different forms (lumpy material, rings etc.) flows down liquid.);

o film mechanical absorbers.

In general, the surface of contact for such type of absorbers is defined by geometrical parameters of a surface of elements (for example, the same nozzle), but isn't equal to it in many cases.