9 replies to this topic

[rocky]

Can any body help in understanding and in designing of Demister Tray? Only thing I know about it is that "Demister Tray is used to stop the carry over of the liquid droplet along with the gas in the distillation column."

[Padmakar Katre]

Dear Rocky,
Fisrt of all let me clear you that the element which is used in knock out drums or flash drums/vessels is demister pad and not the demister tray.Demister pads are porous blankets of wire or plastic knitted mesh, designed and constructed for efficient & economical removal of entrained liquid droplets from vapour streams.I am doubtful if it is used in top of the distillation columns.These are placed where liquid carryover can create upsets in the associated system e.g.if any vessel or equipment overhead is going to compressor suction then to avoid the carryover liquid droplets in compressor suction which will potentially damage the machine.

Demister pads or mist eliminators are used within a process where these particles can cause problems such as corrosion of equipment, contamination of product, fouling of heat exchangers and catalysts and damage to instruments. When released to the atmosphere, these mist particles can cause violations of air pollution emission standards or of opacity regulations.

[pleckner]

If you want more information, Google "demister pad". Also if you have Perry's Chemical Engineeing Handbook around, look them up in that resource.

And if don't have Perry's, at least go to your university library and look at it. I would strongly suggest you make an effort to purchase a copy as it will serve you well for many years to come. It can be expensive but as a student you should be able to find a copy with a huge student discount.

[Milutin]

Hi all,

Demister pad is regularly used on refinery vacuum distillation columns, to avoid entrainment of LVGO product to vacuum system.

Regards,

[Padmakar Katre]

Dear Milutin,
Thanks for the information regarding the demister pads in refinery distillation columns which I was not aware.I found those mainly in KODs.

[rocky]

Thanks for the information..

[Profe]

Hi Rocky

Attached I send you a Mesh blanket article in PDF format, with a sample problem.

Please read it and understand the complete article for apply the sample problem.

Additionally, look at: http://www.acsseparations.com/, the "Mist Eliminator Design Manual" . to ACS


Good luck

[Profe]

Hi All Cheresources' People

Attached you find the the complete article that I had sent in 2007.
And additionally the excel spreadsheet.

Good luck.

Attached Files

•  Mesh Blankets.pdf   705.84KB   51 downloads
•  Mesh Blankets.xls   114.5KB   48 downloads

Edited by Profe, 02 April 2012 - 02:48 PM.

[kkala]

Working in Fertilizers in the past, we had received a proposal to install a mist eliminator pad (OK, it looks like a tray) at the exit of a spray column, treating gases from phosphoric fertilizer autoclaves to retain fluorides and ammonia. We had problem of entrained droplets, yet we did not install the mist eliminator since we supposed it would be often clogged by the scales created in the column. I had also the information that mist eliminators are installed at the gas exit of SO3 absorption tower in sulfuric acid plants.
http://www.amistco.c.../MeshVaneSM.pdf looks a good guide for mist eliminator design, although the supplier of it usually selects type of mist eliminator and exact location of it (*). Flow rates, components, gas and liquid temperature, should be specified by the Process Engineer of the Plant, being aware of potential corrosion or plugging problems. Diameter of entrained particles can be difficult to specify (we did not in the case of Fertilizers), but supplier could make a rough estimate out of general conditions (e.g. spray data of the said column along with gas rate); or you can base the mist eliminator on another one installed and successfully operating.
ΔP through the mist eliminator is given by supplier.

(*) Location can be also specified by Plant Engineer, according to design practices (e.g. for drums).

Edited by kkala, 28 June 2011 - 01:08 AM.

[kkala]

Hi ZYPeng
I think that this class of commentaries are not well received in this Forum!
Its a waste of time.

Probably this is not voluntarily sent by ZYPeng, it might be some kind of malware / virus spread over. I have seen this automatic sending of e-mails in my work computer. I remember a similar "advertisement" propagated in our forum in the past (most probably in Jan 2010), which was soon cleared off. Same is expected to be done now.