CALCULATION OF ADSORPTION UNIT FOR P-XYLENE CAPTURE

Contents

Introduction

1 Status of the question

2 Technical Descriptions and Calculations

2.1 Description of the operating principle of the process diagram

2.2 Isotherm of p-xylene vapour adsorption on active carbon

2.3 Diameter and height of adsorber

2.4 Mass transfer coefficient

2.5 Duration of adsorption. Output curve. Concentration profile in adsorbent layer

2.6 Material Balance

2.7 Calculation of component equipment

2.8 Hydraulic calculation of product line and selection of delivery equipment

Conclusion

List of sources used

Introduction

Adsorption means the process of absorbing one or more components from a gas mixture or solution with a solid adsorbent. The substance to be absorbed is called an adsorbate or adsorbent.

Adsorption processes are selective and generally reversible. Due to their reversibility, it becomes possible to separate absorbed substances from the adsorbent, or to carry out a desorption process.

The mechanism of the adsorption process differs from the absorption mechanism due to the fact that the recovery of substances is carried out by a solid rather than a liquid absorber.

Adsorption is mainly used at low concentrations of the adsorbent in the feed when substantially complete recovery of the adsorbent is desired. Where the concentration of the absorbed substance in the starting mixture is high, it is generally more advantageous to use absorption.

Distinguish between physical and chemical adsorption. Physical adsorption is due to the mutual attraction of adsorbate and adsorbent molecules under the influence of VanderWaals forces and is not accompanied by the chemical interaction of the adsorbed substance with absorbers. Chemical adsorption, or chemisorption, results in a chemical reaction between the molecules of the absorbed substance and the surface molecules of the scavenger.

Adsorption processes are widely used in industry in the purification and drying of gases, purification and clarification of solutions, separation of mixtures of gases and vapors, in particular in the extraction of volatile solvents from their mixture with air or other gases (recovery of volatile solvents), etc. Adsorption is used to purify ammonia before contact oxidation, dry natural gas, extract and purify monomers in the production of synthetic rubber, resins and plastics, extract aromatic hydrocarbons from coke gas and for many other purposes. In some cases, after adsorption, the absorbed substances are separated (desorbed) from the absorber.

The importance of adsorption processes has increased greatly in recent times due to the increased need for high purity substances.

Technical Descriptions and Calculations

2.1 Description of the operating principle of the process diagram

Adsorption unit is intended for cleaning of abgases leaving washing column of abgases before their release into atmosphere. The adsorption unit is a gas purification unit subject to the Operating Rules of Gas Purification Units. It consists of three adsorbers A13, each of which is a horizontal cylindrical apparatus.

The adsorber is filled into three layers:

bottom layer - gravel, layer height 110 mm;

middle layer - activated carbon, layer height 500 mm;

the upper layer is gravel, the height of the layer is 40 mm.

Between the layers of gravel and activated carbon, a grid is laid that prevents the particles of activated carbon from being carried away from the adsorber.

Abgases enter the adsorber through the corresponding inlet valves BP8,10,12 and pass under the grate from below upwards through the activated carbon layer. In this case, p-xylene is adsorbed by coal. Purified gases are discharged to atmosphere through corresponding outlet valves BP7,9,11. Adsorption is carried out in two parallel adsorbers, the third adsorber at this time is on regeneration. Coal regeneration is carried out by acute steam at a pressure of 0.25 MPa supplied to the adsorber from top to bottom. Steam is supplied to adsorber through valves BP1,3,5. At the same time adsorbed p-xylene is distilled off together with water steam, it enters condensers K1.2 through valves BP2,4,6. In K1.2 condensers, the vapors are condensed, then cooled in distillate cooler O and supplied to water separator O. From the water separator, the upper layer (p-xylene) is discharged to the pxylene tank, and the lower layer (water) to the barometric water tank or to the waste water tank.

After the regeneration (steaming) is completed, the adsorber is switched to absorption. The abgases, passing through the layer of heated gravel, slightly warm up, drying the activated carbon. At the same time the adsorber is cooled. Chilled coal again absorbs p-xylene.

The adsorption unit is controlled by an automatic software device. The software device automatically conducts a cycle: absorption → steaming → drying → cooling → absorption according to the program for each adsorber.

Actuation of the software device is possible both in automatic mode, when switching of the adsorber is performed in the specified sequence without operator's participation, and in manual mode, when switching of adsorption is performed by the operator himself using buttons on the main control panel. Residual concentration of p-xylene in abgas released into atmosphere is less than 20 mg/m 3.

Conclusion

During the course project on "Calculation of the adsorption plant for pxylene capture," I got acquainted with the principles of its operation and purpose.

She gained skills in the calculation and design of an adsorption plant. In the design part, a horizontal adsorber was calculated according to the given parameters. An acute steam flow rate for adsorbent regeneration was calculated. The Ts14030 centrifugal fan was also selected. A drawing of the general view of the designed adsorber was drawn, and a drawing of the general view of the centrifugal fan was also made