Q & A > Question Details
We're experiencing an increasing loss of heat transfer efficiency in our shell and tube heat exchangers. Has anyone found any technologies for cleaning exchangers online that does not require a shutdown of the distillation unit at all? Something for both sticky/polymeric as well as water scaling would be most desirable.
20/06/2018 A: Russell Philion, ORANGE Ultrasonics, russ@orangeultrasonics.com
Often the difficulty with in situ chemical circulation is the contact-time of the chemicals and exchangers. But by reducing contact-time, even a leftover millimeter of fouling runs the risk of suboptimal performance.
A solution to consider for online fouling mitigation to the aforementioned fouling types would be ultrasonic scale prevention technology.
Ultrasonic transducers can be attached directly to a heat exchanger's tube sheet. They convert electrical energy into finely-calibrated mechanical energy, which disrupts fouling particles from settling and building up on both ID and OD tube surfaces. Ultrasonic cleaning occurs online continuously while exchangers are in operation, thereby maintaining OHTC and extending run-length.
02/06/2018 A: Muhammad Faisal, Oman Oil Refineries & Petroleum Industry (Orpic)-Oman, engr.faisalfraz@gmail.com
As stated earlier in above comments, classification of foulant is important. if these are metals (Ni,V,Fe amines) then "use of Metal removal aid OR acid aid will help to eliminate it. You may contact "Nalco/Suez/Dorf ketal/Kurita are main companies providing online solutions.
In all online treatments, care should be required as " foulant/salts will land up in column and may affect products especially JetA1. for example, to reduce TPA/Crude exchanger fouling rate, use of antifoulant will shift salts from one end to other.
If deposition is due to salts, then water shocks (pretrain/post train/water washing of column) can help.
01/06/2018 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Fouling is a result of deposition of contaminants on the tube surfaces. Generally Caustic is injected in Desalted Crude towards neutralizing the chlorides. This forms a sludge in the hot preheat train (water gets evaporated leaving the Caustic sludge) and the rust and dust ingressed into the Desalted Crude gets deposited in low velocity zones of heat exchanges. Once the deposition starts it will continuously increase and affect heat transfer efficiency adversely. Best is to avoid Caustic injection. If not possible, look into the option of injecting a mild acid to ensure the pH of the Crude (boosted by Caustic injection) is maintained below 7.0. This will prevent preheat fouling very effectively. Prevention is the best in case of preheat fouling.
30/05/2018 A: NS Murthy, Suez, murthy.ns.ext@suez.com
We need to look at the issue of fouling from three different perspective: - a) design aspects of exchangers wrt shear stress and TMT; b) Process conditions like crude mix incompatibility and presence of contaminants that add to fouling c) chemical solutions and optimization. The client is encouraged to set up a KPI on drop in crude heater inlet temp per month with least or no cleaning of preheat exchangers. Pl contact the nearest "Suez Water and Technology Solutions" team in your area and we shall be more willing to mitigate your pain points in exchangers.
29/05/2018 A: Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita.eu
A chemical cleaning method during operation is possible, but the performance is often a result of several influencing factors. It is always important to know, which kind of fouling is expected to be present. Based on the chemistry of the fouling material suitable cleaning programmes can be selected for an online cleaning. In general coke layers or polymerized materials are difficult to remove. The usage of suitable antifoulants is often the best choice to avoid that fouling. Already formed high molecular weight polymers are better removed during shutdowns with mechanical devices.
Kurita´s ACF technology shows excellent results, when sticky deposits are observed, which were formed by ammonium salts, corrosion debris and/or water scaling products. A combination of ACF and chemical cleaning agents for inorganic scale removal can provide very good results. An online cleaning is possible, where an aqueous cleaning solution can be added before the fouled heat exchangers. The temperature plays an important role. For that reason the cleaning solution should be injected below 180°C to avoid thermal degradation. Most cleaning agents are surfactants, which should be collected during an online cleaning. Kurita can provide powerful cleaning programmes that can be used by your local cleaning companies, who can provide the equipment and are well established at your plants.
29/05/2018 A: Marcello Ferrara, ITW SrL, mferrara@itwtechnologies.com
Yes we can do the job.
29/05/2018 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
If the fouling in pre-desalter train, we have used deminerized water injection/shots for limited time on the the tube side and got relief of higher pressure drop. Pressure gauges & the thermal safety valves on tube sides should be operational.
28/05/2018 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Yes. But it depends on working pressure, flow and temperatures.