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英语翻译
Lesson 10
Gas Absorption
Gas absorption is an important unit operation chemical engineering,particularly in the heavy chemical industry.In the purification of coal gas and synthetic gas as well as in the manufacture of hydrochloric acid,sulphuric acid,metric acid,soda ash and bleaching lyes,to mention only the most striking examples,gas absorption is the essential feature of the process.Since the twenties extensive research has been carried out with the result that the knowledge of this unit operation has increased considerably.
The essential element in gas absorption is the mass transfer between two fluid phases,if necessary,combined with chemical reactions.The latter are mainly restricted to the liquid phases although,for instance in the manufacture of nitric acid,the chemical reaction may also occur in the gas phase.
It will be understood that in such a heterogeneous process as gas absorption a large contact area is a primary requisite for rapid transfer.
There are three ways in which a large contact area can be established:
1.The liquid is brought in contact with the gas in the form of thin films(film scrubbers).
2.The liquid is dispersed in the gas in the form of minute drops(spray scrubbers).
3.The gas is dispersed in the liquid in the form of small bubbles(bubble scrubbers).
All apparatus applied in gas absorption practice is based on one of these three principles or on a combination of them.
Here serious problems are encountered which have only been partly solved.The first things to discover when dealing with a process of mass transfer are the size of the contact area and the way in which this size depends on the various condition of the experiment.The most complete answer to this question can be even for apparatus of type 1.The simplest representative of this type is the wetted wall column,the contact area of which may be determined with great accuracy.For packed column the question cannot be answered so easily,since it cannot be exactly ascertained which part of the packing will be wetted.For the sake of simplicity the contact area may be considered to be equal to the total area of the packing material.In apparatus in which gases or liquids are dispersed,type 2 and 3,determination of the contact area is almost impossible.
Only in the last few years has insight been obtained into the conduct of gas bubbles during their formation in an ascension through liquids,although much work is still to be done in this field.
Absorption,or gas absorption,is a unit operation used in the chemical industry to separate gases by washing or scrubbing a gas mixture with a suitable liquid.One or more of the constituents of the gas mixture will dissolve or be absorbed in the liquid and can thus be removed from the mixture.In some systems,this gaseous constituent forms a physical solution with the liquid or the solvent,and in other cases,it reacts with the liquid chemically.
Lesson 10
Gas Absorption
Gas absorption is an important unit operation chemical engineering,particularly in the heavy chemical industry.In the purification of coal gas and synthetic gas as well as in the manufacture of hydrochloric acid,sulphuric acid,metric acid,soda ash and bleaching lyes,to mention only the most striking examples,gas absorption is the essential feature of the process.Since the twenties extensive research has been carried out with the result that the knowledge of this unit operation has increased considerably.
The essential element in gas absorption is the mass transfer between two fluid phases,if necessary,combined with chemical reactions.The latter are mainly restricted to the liquid phases although,for instance in the manufacture of nitric acid,the chemical reaction may also occur in the gas phase.
It will be understood that in such a heterogeneous process as gas absorption a large contact area is a primary requisite for rapid transfer.
There are three ways in which a large contact area can be established:
1.The liquid is brought in contact with the gas in the form of thin films(film scrubbers).
2.The liquid is dispersed in the gas in the form of minute drops(spray scrubbers).
3.The gas is dispersed in the liquid in the form of small bubbles(bubble scrubbers).
All apparatus applied in gas absorption practice is based on one of these three principles or on a combination of them.
Here serious problems are encountered which have only been partly solved.The first things to discover when dealing with a process of mass transfer are the size of the contact area and the way in which this size depends on the various condition of the experiment.The most complete answer to this question can be even for apparatus of type 1.The simplest representative of this type is the wetted wall column,the contact area of which may be determined with great accuracy.For packed column the question cannot be answered so easily,since it cannot be exactly ascertained which part of the packing will be wetted.For the sake of simplicity the contact area may be considered to be equal to the total area of the packing material.In apparatus in which gases or liquids are dispersed,type 2 and 3,determination of the contact area is almost impossible.
Only in the last few years has insight been obtained into the conduct of gas bubbles during their formation in an ascension through liquids,although much work is still to be done in this field.
Absorption,or gas absorption,is a unit operation used in the chemical industry to separate gases by washing or scrubbing a gas mixture with a suitable liquid.One or more of the constituents of the gas mixture will dissolve or be absorbed in the liquid and can thus be removed from the mixture.In some systems,this gaseous constituent forms a physical solution with the liquid or the solvent,and in other cases,it reacts with the liquid chemically.
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