Adjustment of product quality at atmospheric pressure

Everyone, please help me out. . .

The title is way too vague; is it atmospheric and vacuum distillation? I’ll send you a diagram of the atmospheric and vacuum distillation unit. 1. Control principle for the dry point of the initial distillate: It is controlled by adjusting the temperature at the tower top through reflux, with heat extraction from the overhead stream used as an auxiliary control method. Main influencing factor (high dry point): ⑴ Excessively high top temperature control ； ⑵The components of crude oil are becoming heavier ； ⑶Top pressure drops ； ⑷The initial liquid level is too high ； ⑸The crude oil contains a high amount of water. Adjustment method: (1) Increase the cold return flow rate at the tower top or the top circulation flow rate to reduce the temperature at the tower top ； ⑵Slightly increase the top pressure of the tower ； ⑶Reduce the feed rate to the initial distillation tower in a timely manner and increase the draw rate from the bottom of the tower to prevent carryover caused by an excessively high liquid level; switch liquid level control to manual mode and contact the instrumentation team for handling ； ⑷If the crude oil has a high water content, electrodesalination and dehydration should be intensified; if necessary, contact the dispatch team to reduce the volume of crude oil or change tanks. 2. Control principles for the dry point of the constant overhead product: The overhead temperature is controlled by adjusting the flow rate of the overhead cooling stream; heat is extracted using the overhead circulation, with the temperature of the first distillate stream serving as an auxiliary control parameter. Main influencing factor (often high dry point at the tower top): ⑴ Excessive control of the tower top temperature ； ⑵The composition of crude oil varies greatly, resulting in an overload of the vapor and liquid phases at the tower top ； ⑶Fluctuations in the operation of the initial distillation column affect the properties of the feed to the atmospheric distillation column ； ⑷The flow rate at the main line is often high, and the distillation temperature increases ； ⑸The liquid level in the primary stripping tower is too high, and the amount of stripping steam used is excessive ； ⑹The steam injection volume at the bottom of the tower is too high. Adjustment methods: (1) Appropriately increase the top reflux and top recycle flow rates, reduce the constant top temperature, and decrease the vapor-liquid load at the tower top ； ⑵Reduce the distillation temperature at the first stage by increasing the reflux at the first column or reducing the draw rate at that stage ； ⑶Stabilize the operation of the initial distillation tower and reduce the initial distillation yield ； ⑷Control the liquid level in the constant-pressure first-stage stripping tower; based on the performance of this stage, reduce the amount of steam used for stripping appropriately ； ⑸Reduce the steam injection at the bottom of the tower. 3. Control principle for the dry point of side-stream products: It is controlled through the side-stream distillation temperature, with the tower top temperature and the temperatures of adjacent side-stream distillates used as auxiliary controls. Main influencing factor (low dry point): ⑴ Too low side stream distillation temperature ； ⑵The tower top temperature or the distillate temperature of the adjacent side stream is too low ； ⑶The feed temperature is too low. Adjustment method: (1) Slightly increase the side-line extraction rate ； ⑵Appropriately increase the distillation temperatures at the tower top and on the upper and lower side streams, and increase the amount taken from these side streams ； ⑶Appropriately reduce the reflux flow at the tower top and in the middle section, and increase the temperature of the reflux returning to the tower ； ⑷Increase the outlet temperature of the atmospheric pressure furnace. 4. Control principles for the initial boiling point and flash point of side-stream products: These are controlled by adjusting the amount of stripping steam in the stripper, as well as the distillation temperatures of the current side stream and the previous side stream, as well as the temperature of the mid-stage reflux returning to the tower. Main influencing factors (low initial boiling point, low flash point): ⑴ The extraction temperature of the previous side stream is too low ； ⑵Insufficient stripping steam volume in the stripper ； ⑶This side line draws in the midstream return flow below, which has a high heat absorption capacity. Adjustment method: (1) Increase the extraction amount from the upper side line ； ⑵Control the liquid level in the side-line stripping tower and increase the amount of stripping steam used in the tower ； ⑶Increase the temperature of the mid-section reflux returning to the tower, and appropriately reduce the reflux volume. 5. Control principles for the initial boiling point and dry point of alkylbenzene feed: Control is achieved by adjusting the distillation temperature in the main column and the amount of steam used for stripping in that column; auxiliary control is provided by utilizing the temperature of the overhead vapor and the reflux streams from the main column and intermediate column. Main influencing factors (low initial boiling point, low dry point): ⑴ Low extraction volume from the primary distillation column, low distillation temperature ； ⑵The normal top temperature is controlled too low, and the extraction point of Line 1 in the atmospheric pressure tower is positioned improperly ； ⑶The components of crude oil become lighter ； ⑷High top reflux and low temperature at the constant middle reboiler level ； ⑸In the normal first-stage stripping tower, the liquid level is too high and the amount of stripping steam used is low ； ⑹The distillation temperature at the second stage is low ； ⑺The initial distillate volume is large, with light components. Adjustment method: (1) Increase the constant-line extraction volume and distillation temperature ； ⑵Slightly increase the constant top temperature. When the naphtha index is used for controlling the constant pressure top, the draw point of Line 1 is changed to the 50th stage of the constant pressure tower ； When the constant top pressure is controlled according to the reformation feed specifications, the draw point of Line 1 is changed to the 41st stage of the atmospheric tower ； ⑶Appropriately increase the temperatures of constant top circulation and constant middle return to the tower ； ⑷Slightly increase the temperature of the second normal distillation cut ； ⑸Control the level of the constant-pressure first-stage liquid properly, and increase the amount of steam used for stripping in the constant-pressure first stage ； ⑹Based on the composition of the primary fraction, appropriately increase the primary overhead temperature and reduce the amount extracted from the primary side.