The pH value of the quench water is low
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I have installed a newly replaced low-temperature hydrogenation catalyst. The passivation process proceeded normally; the hydrogen content in the exhaust gas from the quench tower was around 3%. The temperature rise in the catalyst bed was within normal limits, and the space velocity met the required specifications after calculation. However, the pH of the quench water was around 5, requiring continuous addition of alkali to maintain it at that level. Even after increasing the reaction temperature, no improvement was observed. Please help analyze the reasons for this and suggest what measures should be taken.
The newly installed low-temperature hydrogenation catalyst should be presulfided before being put into operation. If the normal operating procedure has already been adopted, with the reactor inlet temperature raised above 250°C and the hydrogen ratio at the upper limit specified, presulfidization should be carried out for an additional period of time.
““The passivation process is normal” — this is a shutdown, not normal operation.
First, please verify whether the actual measured value of the pH is the same as the indicated value. Here, certain deviations occur over time, so regular measurements are carried out to ensure the accuracy of the indications.
That’s because the air supply during pre-vulcanization was too high.
Was sampling and analysis done at the outlet of the hydrogenation reactor?