The single-spin voltage drop drops sharply and then recovers after 2 hours; what could be the cause?
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The catalytic cracking unit is of the coaxial type. Under normal conditions, the normal pressure drop during single rotation remains around 7.4 kPa; however, it suddenly dropped to 7.0 kPa before returning to normal after 2 hours. The solid content in the slurry is within normal limits, and the pressure of the pre-heated dry gas also fluctuates within the normal range. The pressure of the atomization steam increased slightly, but it is still within the specified limits. However, the amount of atomization steam is very small compared to the amount of feedstock, so the impact should not be significant. What other possible causes could there be?
Exploring the possible causes from the factors affecting the pressure drop in cyclone separators: 1. Flow rate, the main factor affecting pressure drop; 2. Gas density, a secondary factor affecting pressure drop; 3. Frictional resistance, which has a theoretical impact on pressure drop; 4. Properties of the particles and structural parameters, which also have a theoretical impact on pressure drop. Considering these influencing factors, the recovery after 2 hours allows us to rule out the effects of friction and structural parameters； The impact of particle properties is relatively small. Therefore, a possible factor is that the flow rate or gas density after a single rotation has changed. As for whether it is caused by changes in the atomized steam, we cannot provide an assessment here due to a lack of knowledge regarding the specific operating conditions. What passes through the single swirl fluid is not limited to the feed flow rate; it should be the sum of the pre-heated dry gas, the atomized steam, the feed material, the material after gasification, and the recycled catalyst. An increase in steam pressure means an increase in the amount of steam entering, and this steam expands due to being heated by the catalyst, resulting in an increase in volumetric flow rate. As for what this ratio is, the original poster can estimate it to determine its impact on the total flow rate. I made a rough estimate under certain assumptions: when the flow rate decreases by 4%, the pressure drop across the cyclone separator drops to 7.6%. Compared to the 5.4% decrease in pressure drop mentioned by the original poster, from 7.4 to 7, even a slight change in the flow rate results in a corresponding change in the pressure drop. The above description is not intended to prove that steam has an impact; rather, it shows that flow rate changes have a significant effect on pressure drop. As for the specific reason behind this, the original poster should analyze it based on the actual circumstances.
It may be that local coking occurred in the rise pipe within the centrifuge, and new coke was formed again after 2 hours……