How can atmospheric and vacuum distillation units reduce the residue yield?

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In oil refining and chemical production, the operation of vacuum towers is crucial for product yield and quality. Below are some key measures for reducing the yield of residue oil: 1. Increasing the vacuum level in the tower. 1. Lowering the post-cooling temperature at each stage of the condensers at the top of the tower allows the vapors there to condense more completely, thereby reducing the amount of non-condensable gases and ultimately increasing the vacuum level within the tower. For example, reducing the post-cooling temperature to an appropriate range by optimizing the flow rate and temperature of the cooling medium or by replacing it with a more efficient cooling device can effectively improve the vacuum level. 2. Increasing the number of ejectors (when multiple ejectors are installed in multiple stages) Ejectors are crucial equipment for maintaining the vacuum level in a vacuum distillation column. Increasing the number of ejectors can enhance the vacuum pumping capacity, allowing for the rapid removal of non-condensable and condensable gases from the tower. However, note that after adding more injectors, it is necessary to monitor steam consumption and equipment load to ensure the stable operation of the system. 3. Adjust ejectors that are not functioning properly (e.g., those with steam leakage). Steam leakage can significantly impair the pumping efficiency of the ejectors. The steam inlet, outlet, and internal structure of the ejector should be carefully inspected. Parameters such as steam pressure, flow rate, and injection angle should be adjusted to restore the ejector to its normal operating condition and improve the vacuum level. II. Appropriately raise the outlet temperature of the vacuum furnace to increase the amount of steam used for stripping at the bottom of the tower. 1. Raising the outlet temperature of the vacuum furnace: Appropriately increasing this temperature can enhance the vaporization degree of the oil products, allowing more heavy components to vaporize and enter the tower; this in turn helps to improve the yield of distillates. However, the temperature increase should be moderate; excessively high temperatures may cause the oil to decompose, affecting product quality. Therefore, adjustments must be made appropriately based on the properties of the raw materials and the equipment’s tolerance limits. 2. Increase the amount of stripping steam at the bottom of the tower. Stripping steam can reduce the partial pressure of oil vapors in the tower, thereby promoting the vaporization of the oil. Increasing the amount of steam stripped at the bottom of the tower allows more light components to be stripped from the bottom and enter the distillate, thereby improving the product yield. At the same time, care must be taken to control the temperature and flow rate of the stripping steam, to prevent excessive amounts of steam from carrying heavy components into the top of the tower, which could affect product quality and subsequent processing. III. Optimize the distribution of products and the proportion of heat recovery from the middle section of the column 1. Optimize the product distribution by adjusting appropriately the amount and temperature at which products are withdrawn from various side streams in the column. This ensures that the product quality meets the required standards, while also promoting a more uniform distribution of gas and liquid within the column. It prevents certain tray sections from having excessive or insufficient loads, thereby reducing the pressure drop across those trays and increasing the vacuum level in the vaporization section. 2. Adjust the heat extraction ratio of the middle-section reflux. Heat extraction from the middle-section reflux can control the temperature distribution and heat balance within the tower. By adjusting the flow rate and heat extraction location of the middle-section reflux, the heat distribution within the tower can be made more reasonable, thereby reducing unnecessary heat loss and improving the fractionation efficiency. For example, appropriately increasing the proportion of heat removal via mid-section reflux can make the temperature gradient within the tower more uniform, facilitating the entry of heavier components into the distillate and thus improving the product yield. In summary, to improve the performance of vacuum distillation towers, it is necessary to consider multiple factors such as vacuum level, furnace outlet temperature, amount of stripping steam, product distribution, and heat removal via intermediate reflux. These factors must be finely adjusted based on actual production conditions in order to enhance the yield of distillates and the quality of the products. As experts in refining and chemical processing skills, I hope that everyone can master these key points during actual operations, thereby ensuring the efficient operation of vacuum towers.