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Use Of Different Types Of Trays In A Column


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#1 Light

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Posted 26 July 2014 - 08:08 AM

Hello Everyone,

Is it true that in industrial practice a distillation column rarely consists of only a single type of trays throughout the column? What is the reason behind using different types of trays in the same column? Our design professor went to the extent of saying that even packings are sometimes used along with trays in the same column for some separations. Is this true? What can be the advantage of doing it?



#2 Bobby Strain

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Posted 26 July 2014 - 09:13 AM

Your professor knows. Pay attention to him. And use Google.

 

Bobby



#3 PingPong

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Posted 26 July 2014 - 10:40 AM   Best Answer

Is it true that in industrial practice a distillation column rarely consists of only a single type of trays throughout the column?

Your professor exaggerates a little.

Most new columns are designed with only one type of trays, although different sections in the column can have different tray spacing and/or different number of downcomers.

 

New columns designed with only packing can have the same packing througout the column, but it can also be the same sort, but different type number in different parts, for example: IMTP50 in the top and IMTP70 in the bottom, or Mellapak 350Y in the top and Mellapak 250Y in the bottom.

 

Through the years however certain sections in a column can become a bottleneck when the plant capacity is to be increased, and those sections can then be equipped with the latest type of trays or packing, which is different from the older stuff in the rest of the column. Sometimes corroded trays are to be replaced and it is decided that a newer type is to be used so as to make future capacity increase easier. As a consequence older columns have more chance of having different types installed than new columns.

 

Some new columns, like fractionators, are indeed designed from the start with different types of trays, or a combination of trays and packings, but those are a minority on the total number of columns in operation.

 

Choice for different tray and/or packing types in one column has to do with very different vapor and liquid loadings, different viscosity, different surface tension, different corrosivity, different fouling/coking tendency, different .... (whatever), in different sections of the column.


Edited by PingPong, 26 July 2014 - 10:46 AM.


#4 sukanta87

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Posted 27 July 2014 - 10:49 AM

I do agree with bobby strain.
In my academic we worked with a hybrid distillation coloumn, internals with both packing and trays. Checked the column efficiency and found better efficiency in the column than tray column. That time as far I knew both tray and packing are not usually used. Have no update yet.

#5 Padmakar Katre

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Posted 18 August 2014 - 04:43 AM

Hello Everyone,

Is it true that in industrial practice a distillation column rarely consists of only a single type of trays throughout the column? What is the reason behind using different types of trays in the same column? Our design professor went to the extent of saying that even packings are sometimes used along with trays in the same column for some separations. Is this true? What can be the advantage of doing it?

 

Hello,

Industrial columns have various internals (removable) such as,

1. Contact devices - these are cross flow and counter current flow

2. Other internals such distributors, support grids, support plates etc

 

Contact devices are mainly two types i.e. cross flow and counter flow based on the contact/flow pattern. Cross flow devices are trays and counter flow devices are packing. Use of these devices is purely based on experience and thorough understanding of system.

 

Yes your teacher is right in saying the columns have trays as well packing but these are in various sections of column and not alternatively. 

 

A single packed bed could be combination of two or more different packing types. Use of suitable devices is what is required to meet the intended capacity and efficiency.

 

There is plenty of open literature available on internet to understand these devices in detail.






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