11 replies to this topic

[SivaChandra]

Dear people

we have a tube in tube heat exchanger, it is blocked with solids. we have a slurry 10% solids going through one side and the other side is also 10% solids.
the solids size is around 100 mesh. these heat exchangers are blocked really bad.

if some one is involves in such kind of work before, please post your comments.

thank you every one for reading this

Siva C

[breizh]

Hi ,
Let you consider to open the HX and do High pressure cleaning , which is an effective way to get your equipment back to operation . Make sure you have spare parts prior to dismantle the heads (gaskets,...) . An other point you may have hazardous chemicals traped inside the HX (safety first)
Hope it helps
Breizh

[Art Montemayor]

A double pipe heat exchanger is the wrong type of exchanger to be using on slurry streams. A spiral heat exchanger is the type of exchanger that is called for in this application.

[SivaChandra]

Thanks for the replies guys, i thought i need to give more info. the heat exchangers are tube in tube and are spiral in shape.
they are clean now. i have used a very low flow high pressure pump and it worked pretty good. But the question remains is how clean are the walls of the exchanger.

so I invite some discussion on this one

I hope we will have a good discussion

Siva C

[Art Montemayor]

A spiral heat exchanger is the type of exchanger that is called for in this application. You have a double pipe type of configuration (in a spiral layout), and this type of arrangement is prone to plug ups with solids. A spiral (flat plates) type of exchanger is called for - as long as the operating pressure is less than about 150 psig. You haven't stated any basic data so I have to assume your operating pressure is less than 150 psig.

If you insist on employing the existing type of exchanger, then prepare yourself for more operational problems and shutdowns. Simply put, you are employing a very difficult type of exchanger to clean out or to maintain - unless you have pure, solid-free fluids (which you do not).

[SivaChandra]

the operating pressures are 3500 psi, we thought having other type of heat exchangers, but because of high operating pressures we chose tube in tube exchanger.

when i say slurry, its the wood flour about 100-140 mesh size.

we are startup company working on biomass, the thermo chemical way. i mean there are people who are working on biological, chemical ways to convert biomass to useful products

Thanks

[djack77494]

With such a high pressure operation, a S&T exchanger is probably your only option. In any case, there's an old saying that I suspect applies to your situation. It is, "an ounce of prevention is worth a pound of cure." It will likely be far easier and more effective if you can avoid these pluggin problems than it is to use brute force to unplug the tubes. I'd suggest you develop some effective operational procedures to avoid ever developing the problem. Good luck.

[S.AHMAD]

Thanks for the replies guys, i thought i need to give more info. the heat exchangers are tube in tube and are spiral in shape.
they are clean now. i have used a very low flow high pressure pump and it worked pretty good. But the question remains is how clean are the walls of the exchanger.

so I invite some discussion on this one

I hope we will have a good discussion

Siva C

Hi,
For minimizing exchanger fouling, the higher the velocity is the better. But you are using low flow pump,this means low velocity so i think you will encounter fouling again very soon. The only reason to limit the velocity is to avoid erosion. So you should increase the velocity as much as possible as limited by erosion. Normally we set lower limit of 1 m/s velocity, but for your case need to consider higher probably 2.5 m/s

Regards

[Qalander (Chem)]

Dear Siva Hello/Good Afternoon,

Although much discussion has been made by our forum's stallwarts,with undoubtedtedly pertinent suggestions,however

I am not sure if a Scrapped surface Double Pipe Heat exchanger proves most suitable;on pressure concerns!
otherwise this could be the "best fit" most probably.

Hope this shows a way forward!

[fatimah]

Hi Siva

i'm never involved in spiral type HE but i think it is better if you install a screening mesh or filter at each inlet of the HE. you will be able to clean the filter instead of cleaning the double pipe. but if the HE is experiencing biological fouling, this won't help.

[SivaChandra]

Hi Siva

i'm never involved in spiral type HE but i think it is better if you install a screening mesh or filter at each inlet of the HE. you will be able to clean the filter instead of cleaning the double pipe. but if the HE is experiencing biological fouling, this won't help.

dear Fatimah,

Thats a very good idea, but is it feasible to have a filter at very high temperature and high pressure. we have soilds in the process, we deal with slurries, so thats the problem.

A spiral HE is nothing but a double pipe HE in a spiral shape.

I hope now you have enough info to give some inputs

Thanks

Siva C

[fatimah]

Dear Siva

OK. Idea to have filter may not able to work. Then, if you still want to go with cleaning the double pipe, as some of our friends here suggested to use high velocity flow. well, if you want to reconfirm that the double pipe is clean enough, would you mind of doing high velocity back flow flushing?

Edited by fatimah, 06 January 2010 - 09:35 PM.