How to clean fouling in shell and tube heat exchangers
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Dear sea friends, in our compressors, the inter-stage heat exchanger features water flowing in the shell side and gas flowing in the tube side. The quality of our circulating water is poor, and cooling inefficiencies occur frequently. During maintenance, after removing the water cooler, it was found that the tubes inside were very dense. The sludge and rust on the surface of the tube bundle could be removed using a high-pressure water gun, but the sludge inside the tube bundle could not be cleared. The result after assembly is not good at all. I would appreciate it if you could share any valuable experiences you have for removing dirt; please feel free to give your advice.
First, improve the quality of the circulating water by reducing turbidity, adding corrosion inhibitors, scale removers, and disinfectants, enhancing wastewater discharge from the water treatment plant, and increasing the concentration ratio. Secondly, replace the cooler with a plate heat exchanger (it’s not clear what the pressure of the medium is; one with a pressure up to 4.0 MPa will suffice). It offers high heat exchange efficiency and occupies less space (provided that water quality is improved). Third, adjust the flow process: gas flows through the shell side, while water flows through the tube side (taking pressure considerations into account), in order to increase the water flow rate and reduce dead zones.
Thank you for the answer from above, but circulating water is not within the scope of management of our company, so the water quality will not improve in the short term. Replacing the cooler and changing the process are both impossible; we have seven compressors, and all of them use four-stage water coolers following this same process. The investment is too large. All we can do now is to regularly remove the core for cleaning. Is there any good solution?
The key is to find the cause of the problem. Since 7 similar devices of yours are all experiencing the same issue, it proves that the water quality is no longer suitable for these units. It is recommended that you establish separate cooling systems for these units – including water storage tanks, water pumps, cooling towers, and supply and return piping – using demineralized water (or softened water). You pay too little attention to the operation management of the units; in particular, the requirements regarding the selection and quality of cooling water are far too low. Do you think just having water is enough?
I agree with you, but there’s nothing we can do. The recirculated water system is not under our control, and we don’t have the funds to set up one separately; moreover, the discharge of external wastewater is also restricted. All we can do is clean it regularly and replace it periodically. How to clean it has left us puzzled.
Is the cooler floating-head type or U-tube type? If it’s these two types of cleaning, they are relatively convenient, but regular shutdowns are required. If it’s a fixed tube sheet, that’s troublesome! What is the material of the tube bundle? It’s carbon steel, right? If that’s the case, even the lifespan of your tube bundles won’t be long (the water quality is poor, and corrosion under scale is severe!) ) It is recommended that you apply a coating for corrosion protection.
If your company is unable to manage the circulating water on its own. The following suggestions are proposed: 1. Modify the process so that, taking factors such as pressure and heat transfer efficiency into account, the circulating water flows through the tube side while the fluid flows through the shell side ； 2. Measure the flow rate of the circulating water to check if it is too low. Among them, the flow velocity of the circulating water in the tube side should not be less than 0.5 meters per second, and that in the shell side should not be less than 0.3 meters per second; otherwise, backwashing facilities must be installed. Therefore, the flow rate of the circulating water should be increased as much as possible, by fully opening the circulating water valves, increasing the number of tube passes, enlarging the outer diameter of the tubes, and adding pipeline pumps. 3. Install filtering facilities on the circulating water pipes. 4. If other methods are ineffective and regular cleaning is necessary, it is imperative to do so. Consider redesigning the arrangement of the pipes, such as in a square or corner-square pattern, to facilitate cleaning.
Online cleaning can be carried out using efficient and environmentally friendly cleaners, which yield good results without causing any corrosion to the equipment itself. Contact is needed.
Your water quality must be very poor. Simply trying to clean it up isn’t enough; it’s necessary to identify the source of the problem. The money that needs to be spent must be invested, otherwise, if it turns out that the standards aren’t met, it won’t have been enough to fix the issue.:)
Follow the procedure on the 8th floor; using online chemical cleaning is more effective than using you.
Online chemical cleaning is not necessarily very effective against inert substances such as scale!