Please help check if there is a problem with the diesel stripping tower
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Our diesel stripping tower uses 500 kilograms of steam per hour, with a steam pressure of 1.0 MPa. In recent days, we have observed that the temperature at the bottom of the tower remains quite low, and there is a significant amount of water in the diesel. The temperature at the top of the tower is somewhat high. Previously, the lowest temperature at the bottom of the tower was 180 degrees; these days it has dropped to around 166 degrees. Occasionally, it rises to 180 degrees for half an hour before dropping again. Moreover, the level in the reflux tank at the top of the tower hardly increases. We use steam directly for stripping – could it be that there is a problem with the tray system, resulting in poor separation between water and oil? Urgent help needed! ! ! Some expert who is aware of this situation, please offer some guidance. The tank area is completely filled with water, and it’s impossible to remove the water quickly enough
1 I’m not sure what your processing volume is? The steam injection rate is generally 20 percent of the processing volume. 2 I don’t know what your steam temperature is; it should be at least 150 degrees higher than that of the feed material. The probability of problems occurring with the trays is low.
It seems that it is the condensation of steam that leads to excessive water content, as well as a decrease in the temperature at the bottom of the tower
In this case, the issue with the diesel stripping tower is not caused by the diesel stripping steam condensing into water; rather, it is due to a malfunction in the distillation tower. The likely reason is that the temperature and pressure at the top of the distillation tower are too low, resulting in steam from the upper part of the tower condensing into water, which then mixes with the diesel. The solution is to increase the temperature at the top of the distillation tower to ensure that no water is present in the vapor flowing upward, thereby resolving the problem.
1. What is the temperature at the top of your tower, and has it decreased? 2. What is your reflux rate, and has it increased? 3. What is your gasoline yield, and is it increasing? 4. What is your diesel flash point, and has it decreased? 5. What is the feed temperature of your stripping tower, and has it been reduced? Knowing this is necessary in order to specifically analyze what causes water to be present in your diesel and the low temperature at the bottom of the tower.
The temperature at the top of the tower is 130 degrees, and it continues to rise. The flow rate has increased from 1.5 tons to 3 tons. The quality of the diesel fuel was unsatisfactory for a few days, with very low standards, but it was satisfactory in most cases
The top of the tower temperature is 130 degrees, and it keeps rising. The reflux rate has increased from 1.5 tons to 3 tons. The quality of the diesel product was poor for a few days, but it was acceptable in most cases. From what you’ve described, it seems that your gasoline yield has also increased compared to before. The rise in the top of the tower temperature is caused by this increased gasoline yield, which leads to more heat being carried to the top of the tower. Since the total amount of heat entering the tower remains constant, an increase in heat at the top results in less heat at the bottom, which is why the bottom temperature is low. If you want to control the temperature at the top of the distillation tower and reduce the gasoline yield, you need to increase the reflux rate. This may result in the diesel flash point not meeting the requirements, or it may cause the steam coming from the upper part of the distillation tower to condense into water, which then ends up in the diesel and causes it to contain water. The solution is to raise the temperature at the top of the distillation tower and maintain an appropriate reflux rate; by not forcing the temperature at the top of the tower too low, you can prevent the diesel from containing water, although the temperature at the bottom of the tower might be lower. However, this does not affect the quality of diesel; if it is necessary to increase the bottom temperature of the tower, simply raising the temperature of the light fraction oil entering the stripping tower will suffice. The previous description states that you should prioritize ensuring that the stripping steam is superheated steam at 1.0 MPa, with a temperature of 230–250 degrees
It’s normal for the temperature at the bottom of the tower to be low; ours is at 170. It’s abnormal when there’s no level indication in the reflux tank. Let’s first increase the top temperature and see what happens
It was finally resolved today – our supervisor is really great. He said that the position at the top of the tower wasn’t accurate, which was definitely causing the water to flow back. We recalibrated that position yesterday; it was indeed the inaccurate positioning that led to the continuous backflow of water. Today we removed the wastewater, and now the temperature at the top of the tower is controlled at 140 degrees. The amount of water flowing back is 2 tons. The temperature at the bottom of the tower has risen by over 20 degrees, approaching 185 degrees now. There’s much less water at the bottom. Thank you all for your guidance and help; I hope what we’ve done can also be useful to other companies. Don’t rely entirely on the instruments :)