Precautions for heating and reducing synthetic catalysts
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This year, our plant replaced the catalyst in the synthesis tower. The reduction process proceeded normally at the beginning, but later on there was a sudden increase in water vapor concentration, which caused blockages in the sampling tubes. We were forced to wait at a constant temperature, which extended the reduction time. The likely reason for this is that the temperature in the water cooler where the sampling tubes are located is low, leading to condensation that causes blockages and results in inaccurate analysis data during the initial stages. I wonder what new opinions everyone has? ?
What is the temperature at the outlet of the water cooler? How can it get blocked by water? It might be caused by an incomplete system purge!
The areas that tend to get clogged are usually behind the heat exchanger; when the temperature is below the freezing point of the mixed solution, the likelihood of ice formation and resulting blockages increases. There is a blockage behind the water cooler; I agree with the opinion of the moderator from floor 2.
Reply to 3# sun0225: This phenomenon occurs because the sampling tube is too far away from the analysis site. In cold weather, especially during winters in the north, when sampling is done behind the water cooler, the temperature is low, and some water vapor condenses inside the sampling tube. Over time, this condensed water can cause blockages in the tube, leading to a sudden increase in water vapor concentration. It is recommended to insulate the sampling tube and also adjust the sampling valve to an appropriate setting, so as to obtain an accurate reading of the water vapor concentration.
Reply 4# HZG: This phenomenon generally does not occur in summer, unless the opening degree of the sampling valve is too small.
This post was last edited by 517306015 on 2010-7-3 at 16:30. Ammonia can be added to the system before raising the temperature (by adding it to the ammonia stream), so that the gas circulating at elevated temperatures contains a certain concentration of ammonia. This ammonia, together with the water produced by the catalyst, forms dilute ammonia solution, thereby reducing the freezing point. Of course, the pipeline must be thoroughly purged.
This post was last edited by yh521 on 2010-7-3 at 17:38. 1. The system has not been thoroughly purged; there may be welding slag from previous welding processes, rust inside the system, or catalyst powder. 2. It’s the length of the sampling tube – this is something that many factories tend to overlook. Sometimes, to facilitate sampling for analysts, the sampling tube is made quite long. It’s important to pay attention to its length, as an overly long tube can cause some of the water to condense during sampling. If necessary, insulation can be added to the sampling tube. 3. It is the sampling skill of your sampling personnel; this is very crucial and requires careful control. 4. At the current temperature, and since it is located after the water cooler, the possibility of ice blockage is basically ruled out. One question remains: why is your sampling point placed after the water cooler? How is the water vapor concentration at the outlet of the synthesis tower analyzed? Is it calculated?
Was ammonia not poured into the system before restoration?
Thank you all for your enthusiastic answers! It’s not an ice blockage; it’s a water blockage. It gives the impression that the water volume suddenly becomes extremely large. The temperature behind the water cooler is around 80 degrees. The opening degree of the sampling valve is fine, and the sampling tube is insulated; it’s true that the tube is quite long. Later, it was forced to wait at a constant temperature until the water volume decreased before resuming the reduction process. Of course, I personally think that the sampling location isn’t very good; if it were at the outlet of the synthesis tower, where the temperature is around 180 degrees, there should be no condensate water. At present, it can only be concluded that the low temperature is causing the water to condense. Would it be better to use sampling from the outlet of the synthesis tower next time the catalyst is replaced?
Yes, that’s exactly as you analyzed it; our sampling points for vapor concentration analysis are located at the exit of the synthesis tower, and there has never been any issue of water blockage (not even in winter). The low temperature at the sampling point, combined with a long sampling pipeline, is what causes water blockage.
As a supplementary point, the water vapor concentration measured through such sampling analysis also yields inaccurate results. It may seem that the measured concentration meets the process requirements, but in reality it has already exceeded the allowed limits; this is why water blockages occur in the sampling tubes.