2 replies to this topic

[deltaChe]

I have a PDT(pressure differential transmitter) on the ethoxylated scrubber and
working pressure is Atm(refer from atach 1.pdf).

My question is following:

N1. From the attached file(2.pdf) , I found out the the pressure on bed 1 and bed 2 are the
same (atm or 1.02 bara).But from the p=density*g*height rule, the lower tapping poit seems
has higher pressure. What is the reason for this? Is that mean scrubber contain much more vapor
than vapor?

N2. From the attached file(2.pdf), there is a column marked by red cloud(turn up and turn down ratio),
what is that mean?

Thank you very much.

Attached Files

•  2.pdf   38.27KB   18 downloads
•  3.pdf   36.22KB   13 downloads

Edited by hswang2, 17 June 2010 - 07:05 AM.

[Dacs]

I have a PDT(pressure differential transmitter) on the ethoxylated scrubber and
working pressure is Atm(refer from atach 1.pdf).

My question is following:

N1. From the attached file(2.pdf) , I found out the the pressure on bed 1 and bed 2 are the
same (atm or 1.02 bara).But from the p=density*g*height rule, the lower tapping poit seems
has higher pressure. What is the reason for this? Is that mean scrubber contain much more vapor
than vapor?

N2. From the attached file(2.pdf), there is a column marked by red cloud(turn up and turn down ratio),
what is that mean?

Thank you very much.

If you're going to attach documents, make sure that you remove any markings that will identify you and your client. Your company/client won't surely be happy that you share confidential docs over the internet.

To answer your question, normally you should expect a lower pressure on top of the tray due to pressure drop across the bed. But in this case, it's possible that the pressure drop is small, hence the apparent exactness of the pressure on top and bottom of the PDT. BTW, for most processes, static head for vapors is quite small that it's neglected.

Anyway, the PDT is installed to tell you (well the operator that operates the plant) that there's an operation malfunction in the column (most likely due to column flooding, that will result in a higher pressure drop across the beds).

Turn up and turn down ratio mean the operating flexibility of your process. Only that (anyone correct me if I'm wrong) that turn up should be above 100% and turn down should be below 100%. Anyway it means that your scrubber (which has nothing to do with your PDT, and the topic in general) is expected to operate from 50 to 110% of design capacity.

Hope this helps

[deltaChe]

Thank you very much for your kindly help and reminding.
You make a very great point that I didn't see.
Thanks again.

I have a PDT(pressure differential transmitter) on the ethoxylated scrubber and
working pressure is Atm(refer from atach 1.pdf).

My question is following:

N1. From the attached file(2.pdf) , I found out the the pressure on bed 1 and bed 2 are the
same (atm or 1.02 bara).But from the p=density*g*height rule, the lower tapping poit seems
has higher pressure. What is the reason for this? Is that mean scrubber contain much more vapor
than vapor?

N2. From the attached file(2.pdf), there is a column marked by red cloud(turn up and turn down ratio),
what is that mean?

Thank you very much.

If you're going to attach documents, make sure that you remove any markings that will identify you and your client. Your company/client won't surely be happy that you share confidential docs over the internet.

To answer your question, normally you should expect a lower pressure on top of the tray due to pressure drop across the bed. But in this case, it's possible that the pressure drop is small, hence the apparent exactness of the pressure on top and bottom of the PDT. BTW, for most processes, static head for vapors is quite small that it's neglected.

Anyway, the PDT is installed to tell you (well the operator that operates the plant) that there's an operation malfunction in the column (most likely due to column flooding, that will result in a higher pressure drop across the beds).

Turn up and turn down ratio mean the operating flexibility of your process. Only that (anyone correct me if I'm wrong) that turn up should be above 100% and turn down should be below 100%. Anyway it means that your scrubber (which has nothing to do with your PDT, and the topic in general) is expected to operate from 50 to 110% of design capacity.

Hope this helps