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At our unit we have observed polymer on the tubes of reboiler, the reboiler being stab in, requires shutdown and tube bundle removal and cleaning. Looking for any online chemical injection continuous that could avoid the scaling or polymer formation.
 
Answers
09/10/2014 A: Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita-water.com
Without knowing details about the fouled process unit it is difficult to give recommendations. The kind of polymerization reaction and fouling material should be known. Of course it is always better to avoid polymerization that no further mechanical cleaning is required. Polymer fouling in reboiler tubes of petrochemical process units is quite common, if no antifoulant programs are used.
Traces of dissolved oxygen or radicals can cause unwanted polymerization reactions with olefins and other hydrocarbons. Powerful antifoulants can significantly reduce or stop the polymerization process, which is initiated by radicals or oxidation. The selection of the best performing antifoulant is the key element. Powerful antifoulants are often blends of oxygen scavenger, radical catcher, metal deactivator and dispersant.
07/10/2014 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
First of all the deposit should be analysed. It may be from carry over of water/emulsion from reflux drum along with naphtha. The source should be addressed before coming to any treatment for solution.
26/09/2014 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Firstly, it is highly likely that our technology can clean this bundle In situ, without the cost of having to remove it from the shell in order to clean (if it is the tube side you're looking to clean)
If the shell side requires cleaning, then providing it is square pitch, tube tech international can achieve as new cleanliness, back to bare metal, no matter how severe the external fouling, however deep into the exchanger fouling sits. Case study on the website.
We are however in the process of developing a system to mechanically clean external fouling whilst the bundle is in situ i.e. without pulling.
Being polymer, it is likely current mechanical cleaning methods can leave certain levels of fouling on the tube. Any "key way" encourages future fouling to build more quickly. Hence this needs to be removed back to bare metal. Our enhanced tube polishing system achieves this (case study on our website tubetech.com)
Once experience has been cleaned from off-line cleaning the next stage is to modified heat exchanger, so it can be cleaned online during production and prevent fouling from occurring in future
26/09/2014 A: Kavirayani R Murthy, K R Murthy Consultants, krmurthy_ipcl@yahoo.com
In the Arimatics plant of Indian petrochemical Corporation Ltd now taken over by Reliance Industries at Vadodara Location in India we had faced a similar problem in the feed /effluent exchangers in the reforming section . There were 4 exchangers to heat the naphtha feed with the out going reformate.The 2nd and 3rd heat exchangers were getting choked more in the 3rd exchanger with carbon thereby tripping the feed pump.
We identified the problem to the dissolved oxygen present in the naphtha coming from the naphtha feed tanks .This dissolved oxygen acting as an initiater for polymerization of unsaturates present in the naphtha creating the polynuclear aromatics.These unsaturates and polynuclear aromatics were getting carbonised mostly in the 3rd exchanger as temperatures were ideal in the range of 325 to 350 deg C.
To get rid of this problem we blanketed the Naphtha feed tanks with Nitrogen to get rid of dissolved oxygen. that problem never appeared.
You may look for such a possibility in your unit.
26/09/2014 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Most of the major chemical suppliers have antifoulants that are intended to prevent polymerization reactions. I don't know how effective they will be in this service. If the polymer is coming from a trace contaminant it may be more effective to figure out how to reduce the contaminant. Often these reactions are strongly temperature dependent. I know of one case where switching from a thermosyphon to a one pass trap out tray design to feed an FCC debutanizer reboiler lowered the reboiler temperature enough to eliminate a severe fouling problem that was being caused by polymer formation on the outside of the tubes.
25/09/2014 A: keith bowers, B and B Consulting, kebowers47@gmail.com
You will have to analyze the deposits and figure out exactly what molecules are polymerizing. Your question does not provide nearly enough fundamental information for me to develop a credible answer.
You will likely discover the only feasible solution is to change the reboiler to a high circulation rate (thermo-syphion or high rate pump-around) shell and tube unit to keep the tube wall temperature as low as possible.