Changes in light and heavy components during distillation
Thread Content
For the light-end and heavy-end distillation columns, distillation is carried out first on the light-end column and then on the heavy-end column. Currently, the content of light components in the heavy-end column has increased, resulting in defective products at both the top and bottom of this column. So, is it more beneficial to lower the feed temperature or to increase the reflux rate in order to obtain qualified products?
It would be best to include a schematic diagram to facilitate discussion. It is recommended to return to the basis of distillation at the time the device starts up. It should be a qualified liquid, for reference.
Generally, one should focus on the source; first, ensure proper control of the light-end stripping tower, otherwise it will be difficult to meet the requirements
Increasing the degasification reflux certainly helps to obtain qualified overhead product, but I believe that since the feed already contains too many light components, increasing the reflux further will cause the light phase in the tower to exceed its processing capacity. This in turn increases the load on the stripping section as well, raising the content of light components in the bottom of the tower and resulting in substandard product there. I’m not sure if this is correct; I hope for your guidance
The operability flexibility of the stripping column is quite high. Of course, in order to understand the impact of the feed temperature to the stripping column, pressure tests were conducted with both increased and decreased pressures; it was found that when the light components (relative to the stripping column) increase, reducing the pressure in the column is more effective than increasing it, and the overhead product meets the required standards more easily when the column flow rate remains constant. So now I think it is the fact that the light component content in the degassing tower exceeds the designed level, which results in the top and bottom products from the degassing tower not meeting the specifications
A PID is still needed to make an accurate judgment! Possible reason: The increase in the light main fraction in the degassing tower is due to the fact that the degassing unit failed to remove all of the light main fraction; this fraction entered the degassing tower from its bottom. Therefore, adjusting the reflux ratio of the degassing tower alone is meaningless, as it is not possible to restore the purity levels at both ends. It may be caused by an increase in the light components entering the light-end tower. Samples should be taken to analyze the composition of the feed and the composition of the product obtained from the bottom of the light-end removal tower, in order to verify the above possibilities. If verification is successful, it is recommended to: 1. Increase the heating capacity of the light-end tower reboiler separately and appropriately ； 2. Appropriately increase the draw rate of the light-end tower separately. After the light-end stripping column is adjusted, then adjust the heavy-end stripping column.
The light components have entered the degassing tower; as a result, more and more product accumulates at the top of the tower. Raising the degassing temperature helps to remove this product more quickly. Additionally, it is possible to empty the material in the bottom of the tower and feed it in again. It is important to first get the light-end stripping tower up to standard.
This post was last edited by flymxcao on 2020-11-12 08:45. It should be the light-material reflux, not the heavy-material reflux.
The light component content in the dewaxing tower is high because the light-component removal tower fails to remove the light components completely; once they enter the dewaxing tower, they inevitably end up together with the product and are incorporated into it. If this situation persists for a long time, it is recommended to replace the degassing tower; contact me if necessary.