Problems with the naphtha hydrogenation stripping tower
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I have a naphtha hydrogenation unit that has been modified for diesel production; the raw material used is atmospheric naphtha. The main equipment in this unit has not been altered, and both the quality of the product and the processing capacity are satisfactory. However, there are currently two main issues: first, the yield of liquid product is relatively low, with an overall yield of around 92%, meaning that about 6-7% of the components go out as light gases or from the top of the stripping tower. Secondly, the naphtha contains a relatively high amount of water, with a water content of 0.2-0.5% as determined by testing. The likely cause of this issue is the stripping tower, as it was originally designed for diesel processing and no modifications were made. Both the feed temperature and the top temperature of the tower are lower than before, which prevents water from being separated at the tower top. Additionally, there is no reboiler at the bottom of the tower; currently, steam is being injected for stripping, and the presence of water may be due to this. May I ask what your stripping tower process is like? Analysis shows that C3 and C4 make up around 70% of the contents in the gas coming from the top of the stripping tower. Gas components in the reflux tank at the top of the desulfurization tower: hydrogen, C2 propane, H2S, isobutane, n-butane, C5N2; volume percentages: 17.66%, 4.81%, 13.31%, 1.73%, 20.49%, 17.33%, 3.61%, 1.38%. Gas components in the gas from the lower section of the tower: hydrogen, C2, C3, H2S, isobutane, n-butane, C5N2; volume percentages: 81.91%, 1.09%, 4.04%, 0.14%, 2.99%, 3.62%, 4.03%, 2.19%
1. Feed is introduced through the lower feed port; controlling the feed temperature reduces the amount of flashing； 2. Reduce the amount of stripping steam; as long as the sulfur content is within the specified limits ； 3. Increase the pressure in the reflux tank, while ensuring that the product meets quality standards ；
All these adjustments you mentioned have been made, but the yield remains low
1. Products with steam injected at the bottom of the tower tend to contain water; in diesel hydrogenation, a coalescer is used to remove water from the products exiting the unit； 2. What is the design operating pressure for the stripping tower? The design operating pressure at the top of our gasoline hydrogenation stripping tower is 0.55 MPa, while the normal operating pressure is 0.45 MPa ； 3. The feed temperature of the stripping tower should be no lower than 126 degrees; make appropriate adjustments to avoid affecting product quality.
Do you also use steam for stripping, or do you employ a reboiler?
Reboiler for gasoline hydrogenation stripping tower, stripping steam for diesel hydrogenation；
It is recommended to analyze the distillation range of the raw material, as well as the content of components below C5 in it； Contact the design institute to check whether the stripping tower is overloaded