Catalyst metal passivation agent line blockage
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Recently, two of our unit’s catalytic passivation agent lines have become clogged one after another, and dealing with this situation has been quite difficult. Passivation agent lines are usually small DN15 wires that tend to get clogged easily. We tried many methods one after another, but none of them worked. In the end, the pipeline had to be sawed off and cleared using wire. By observing the cross-section of the pipeline, it was found that the pipeline was severely scaled; in the DN15 pipe, there was less than 5 mm of open space left in the middle. Could everyone help analyze why scaling occurs (brown in color, turning gray after drying)?
When passivators and scale inhibitors are added, if air pumps are used together, there is a possibility of mixed scaling. Or someone added the wrong additive. Strengthen the management of additives.
This post was last edited by ljx5210 on 2012-12-21 09:08. We haven’t encountered the situation you mentioned here; instead, the sulfur transfer agent became clogged after not being used for a long time. Slurry scale inhibitors have been in use all along, and there has never been any clogging. The pipeline is also around DN15; does this thing need heating in winter? The scale inhibitor is an oily, black liquid with a strong, pungent odor. Oh, you’re a metal passivator; we don’t use slag here, we haven’t added this stuff. There are only slurry scale inhibitors and sulfur transfer agents. I’m asking, did you not add diesel as a diluent? It’s not going to be directly pumped in by the metering pump, right? :dizzy:
Is the passivator water-soluble or oil-soluble? Could we try increasing the amount of diluent, raising the flow rate of the metering pump to increase the flow speed? Additionally, the colloidal properties of the additive are very important; we’ve used one additive that caused sedimentation, especially at points where the flow direction changes, which makes clogging more likely. It was later found that the colloid was unstable and prone to decomposition and deposition in the presence of impurities.
Generally, there is a root valve at the main feed inlet, and a vent should be installed in front of the valve. It has also gotten clogged here; to resolve the issue, we close the root valve, open the vent valve, and connect a pressure pump to the outlet of the passivation agent pump – this usually helps to clear the blockage.
Our passivation agent is water-soluble. There is heat tracing in winter; the water temperature is around 100°C. Will this have any impact?
1. Dilution: Use water to dilute water-soluble substances, and use oil for oil-soluble substances; add them according to the specified dilution ratio. 2. For modifications, small pipelines can be equipped with spare lines; flange connections facilitate disassembly and assembly, require minimal investment, and are easy to operate. 3. Insulate and provide heat tracing; of course, be careful not to set the heat tracing temperature too high, as this can have the opposite effect.
Initially, water heating was adopted to avoid excessively high temperatures from steam heating. What is the thermal stability of metal passivators? Are there any materials on this topic? It is best to add a water flushing system to clean the pipelines regularly, using medium-pressure water preferably.
It’s probably because the viscosity is too high and the flow rate is too low
It seems that the passivator tends to decompose when the temperature exceeds 200 degrees. Additionally, the injection point should be angled toward the center of the oil pipe, following the flow of the fluid. We have run into this problem before as well; the passivating agent should not be diluted with water. Since the passivator is Ce carbonate, it tends to hydrolyze easily when water is added.
We are also water-soluble, and blockages have occurred as well. However, we observed white gel-like substances, with the blockage being most severe at the check valve. Our analysis is similar to that of the 4th floor, and we believe it may be caused by decomposition. Heating is not recommended, as the passivator tends to degrade at temperatures above 220 degrees.