Calculation of packing absorber - exchange rate

Contents

Task

Contents

Legend List

Introduction

1 Theoretical foundations of the process

2 Selection of main equipment installation and design type, material selection

3 Process calculation

Determination of the mass of the substance to be absorbed and the flow rate of the absorber

Calculation of driving force

Calculation of gas velocity and absorber diameter

Calculation of light liquid layer height

Calculation of mass recovery factors

Calculation of absorber trays

Selection of distance between trays and determination of absorber height

Hydraulic calculation

Heat calculation

4 Mechanical calculation

Calculation of absorber shell thickness

Calculation of bottom and absorber cover thickness

Calculation of apparatus supports

5 Calculation and selection of auxiliary equipment

Calculation of fan for gas mixture supply

Calculation of pump for adsorbent supply

Calculation of capacity for adsorbent reception

6 Process intensification methods

List of sources used

Introduction

Mass exchange processes are those in which the main role is played by the transfer of matter from one phase to another. The driving force of these processes is the difference in chemical potentials. It characterizes the degree of deviation of the system from the state of dynamic equilibrium. Mass exchange processes are widely used in industry to solve the problems of separating liquid and gas homogeneous mixtures, concentrating them, as well as protecting the environment.

The following processes have become most widespread: absorption, rectification, extraction, adsorption, drying, crystallization, etc.

Consider the absorption process. Absorption is the process of absorbing gases or vapors from gas or vapor-gas mixtures with liquid absorbers (absorbers).

Physical absorption and chemosorption are distinguished. When physically absorbed, the dissolution of the gas in the liquid is not accompanied by a chemical reaction, or at least the effect of this action on the speed of the process can be neglected. As a result, physical absorption is not accompanied by a thermal effect.

Physical absorption is reversible in most cases. This property of absorption processes is based on the separation of the absorbed gas from the solution - desorption.

In industry, absorption processes are mainly used to extract valuable components from gas mixtures or to purify these mixtures of harmful impurities.

Absorption processes are widespread in chemical technology and are the main technological stage of a number of important industries (for example, absorption in the production of sulfuric acid; absorption of HCl to obtain hydrochloric acid; absorption of other components from coke gas). In addition, absorption processes are the main processes in the sanitary purification of exhaust gases released into the atmosphere from harmful impurities (for example, cleaning flue gases from; purification from fluorine compounds of gases released in the production of mineral fertilizers, etc.). Process devices are called absorbers.

Methods of intensification and efficiency improvement

The absorption process is most often carried out by countercurrent flow of gas and liquid used for substances emitted from the mixture and called absorbent. In industrial installations, absorption is combined with desorption - the release of absorbed substance. This enables production of the end product and reuse of the absorbent.

At a certain speed, the gas begins to entrain liquid droplets, which are formed when the bubbles exit the surface of the bubble layer break; Note here that said drops fall with gas flow onto said above plate. Liquid entrainment by gas flow leads to reduction of motive force of moss transfer process, increase of liquid load of drain devices, loss of absorbent with gas leaving absorber. The amount of spray should not exceed 510% of the total amount of liquid supplied to the absorber. The amount of entrainment increases as the gas velocity in the column increases and the height of the equipment space decreases.

Analysis of the calculation results shows that the main diffusion resistance of mass transfer in this process is concentrated in the liquid phase. Therefore, it is possible to intensify the absorption process by increasing the liquid velocity. To do this, either increase the consumption of the absorbent or reduce the diameter of the absorber. An increase in absorbent consumption would lead to a significant increase in capital and energy costs. A decrease in the diameter of the absorber leads to a decrease in the operating speed of the gas, which will cause a corresponding increase in the hydraulic resistance. Another method of intensifying the process may be to introduce an ultra sound field into the absorption process. The application of UZ oscillations on a two-phase system causes local turbulization due to the occurrence of cavitation. In addition, a shear wave system is created that increases the interface.

The resulting apparatus is rather small, which indicates a reduction in the costs associated with applying additional forces to relieve external loads, since it is most likely to be in the room.