Regarding the timing of putting the mid-section reflux into use?
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The fractionator of our newly built hydrocracking unit is equipped with two mid-stage reflux streams; since we have no prior experience with this, we lack expertise in putting it into operation at startup. I also looked at some information from other departments; it mainly focused on temperature. I’m not sure how everyone went about making their submissions Especially regarding practical experience, I would appreciate your advice!
The mid-section reflux is primarily intended for heat removal to facilitate distillation efficiency. Since the main locations where the backflow is interrupted are on either side of the sensitive tray, its control directly affects the efficiency of distillation. Based on the top-to-bottom temperature gradient of the tower, its optimal operating temperature can be calculated for control purposes. However, the sensitivity board should prioritize stability. At the same time, depending on the raw materials, the distribution of the products varies, and the temperature at this point will differ to some extent~~
You can add a cross-connected pipe at the mid-section between the outlet and the return port; initially, carry out external circulation around the tower, and once the temperature rises, slowly open the inlet and outlet valves to gradually replace the water in the oil collection tank, so that the pump won’t keep drawing air. Great, that’s how we’ll do it.
We have a fully pull-out design; there is no oil collection tank
The normal operating principle for mid-section reflux should be to appropriately reduce the amount of cold reflux, in order to decrease the cooling load at the tower top and increase the heat output from the lower reflux. During operation, do not adjust the mid-stage reflux frequently, and do not use it to control product quality; the goal is to maintain a stable balance in the distribution of vapor and liquid loads in the atmospheric pressure tower. The mid-stage reflux is adjusted only when there are significant changes in the refining volume, variations in the density of crude oil, or alterations to the product mix. This helps maintain a good heat balance throughout the entire tower ； Adjust the internal recirculation to suit the product design; the product must be of satisfactory quality. The principle for heat extraction is to make full use of the heat in the middle section, by extracting more heat from the lower part of this middle section at higher temperatures. But at the same time, it is necessary to avoid excessive temperature differences during withdrawal, as this can affect the efficiency of the return tray; therefore, there should be lower and upper limits!