Adjustment of product specifications for reactive distillation

The diesel pour point is controlled by the diesel extraction temperature, the flash point is adjusted by the amount of steam used for stripping, and the gasoline dry point is regulated by the tower top temperature

For the most basic questions, check out the Q&A section on catalytic cracking technology – it explains everything in detail. I have an electronic version here

Personally, I think catalyzed diesel should not have its freezing point controlled; it would be better to control its boiling range instead. It would be better to address the dew point of diesel by using diesel hydroprocessing.

The last edit to this post was made by lijianhuai on 2011-8-12 at 15:17. Reply 1# YBH13590663069 1. Control of the 95% point for light diesel: A. Influencing factors: 1) An increase in the temperature at the light diesel extraction point in the distillation tower leads to an increase in the 95% point； 2) An increase in the circulation volume in Stage 1 or a decrease in the temperature returning to the tower results in a drop in the 95% point ； 3) The raw materials become lighter, the reaction depth increases, and the 95% point decreases ； 4) Changes in the heat balance and material balance in the upper part of the distillation tower result in a decrease in the amount of gasoline extracted, an increase in the amount of diesel extracted, and a decline in the 95% cut point ； 5) The liquid level in the light diesel stripping tower is full; light diesel cannot be drawn out, and the 95% point of light diesel decreases ； 6) An increase in the amount of lightly contaminated oil reused, or a decrease in temperature, results in a drop in the 95% point ； 7) An increase in the flow rate of oil reabsorbed in tower 27 of the reflux distillation column or a decrease in temperature results in a drop in the 95% point. B. Control method: 1) Under normal circumstances, a medium-temperature control valve (TIC304) is used to adjust the flow rate of the air-cooled cooling bypass, thereby regulating the temperature in the middle return column and thus controlling the extraction temperature of light diesel (at the 21st liquid phase stage) in order to manage the 95% point of light diesel ； 2) When the temperature at the return point of Unit 1 approaches the upper or lower limit of the specified range, while ensuring that the stabilizer has sufficient heat supply, adjust the circulation volume of Unit 1 appropriately to regulate the 95% point of light diesel ； 3) When the circulation volume in section 1 is unstable, light diesel can be used to supplement it, but the amount of light diesel used for this purpose should be kept as low as possible, provided that the circulation volume in section 1 remains stable. At the same time, the heat extraction amounts from the lower, middle, and upper sections of the distillation tower should be adjusted appropriately to ensure proper material balance and heat balance, thereby maintaining an appropriate load in the middle section of the distillation tower ； 4) Control the liquid level in the stripping tower, adjust the output volume of light diesel and the amount of reabsorbed oil to maintain stability. 2. Control of the flash point of light diesel: The flash point of light diesel is an important indicator reflecting its safety properties; diesel fractions containing more light components have a lower flash point and a lower initial boiling point. The flash point specification is ≮57°C (during the dehydrorefining of diesel, flash point is not used as a quality control parameter). A. Influencing factors: 1) A decrease in the temperature at the top of the distillation tower leads to a reduction in the amount of gasoline extracted, an increase in the amount of diesel produced, and a decrease in the flash point ； 2) An increase in the amount of stripping steam or an increase in temperature leads to an elevation in the flash point ； 3) The extraction temperature of light diesel rises, and its flash point increases ； 4) The pressure in the stripping tower increases, and the flash point decreases ； B. Control methods: 1) Under normal circumstances, when the flash point is low, increase the amount of stripping steam to bring it within acceptable limits; however, the amount of stripping steam should not be too large to avoid gas blockages and to prevent issues with the operation in the upper part of the distillation tower ； 2) Appropriately increase the light diesel extraction temperature or the stripping steam temperature to adjust the flash point so that it meets the requirements ； 3) Appropriately increase the extraction temperature or amount in the top circulation, and reduce the flow rate of cold return fluid, thereby decreasing the internal return flow in the upper part of the tower and improving the distillation efficiency. 3. Control of the dry point of gasoline: The dry point of the gasoline is controlled by regulating the dry point of the crude gasoline; as the dry point of the crude gasoline rises, so does the dry point of the gasoline. Under normal circumstances, the dry point of crude gasoline is several degrees higher than that of stabilized gasoline. Dry point is an important indicator of gasoline’s combustion performance. A. Influencing factors: 1) Increase in the temperature at the top of the distillation tower, resulting in an increase in the dry point ； 2) The temperature in the middle section of the distillation column rises, and the dry point increases ； 3) The pressure at the top of the distillation tower increases, and the dry point decreases ； 4) The vapor pressure at the top of the distillation column increases, causing the dry point to rise ； 5) The raw material becomes heavier, the reaction depth decreases, and the dry point rises ； 6) Salt deposition on the upper trays of the distillation column, with an increase in the dry point ； 7) Mist entrainment at the top of the distillation tower, with an increase in the dry point. B. Control method: 1) Under normal conditions, adjust the TIC303 three-way valve – specifically the flow rates of cold fluid to tower 303 and the cold bypass at 1.2 times the normal level – in order to regulate the temperature of the reflux stream from the top of the tower. This allows for control of the temperature at the top of the distillation column, and thereby control of the dry point of the crude gasoline ； 2) When the top temperature of the distillation column cannot be controlled due to it being outside the adjustment range of TIC303, adjust the top circulation flow rate of FIC310 in order to control the dry point of the crude gasoline ； 3) When top circulation is not possible due to the inability of both pumps to operate or equipment issues, or when the amount of top circulation is insufficient, FIC311 can be adjusted appropriately to regulate the temperature at the top of the fractionation tower and thereby control the dry point of the crude gasoline. The flow rate of the cold return stream should not be increased too rapidly; it should be kept as low as possible to prevent pressure buildup at the top of the tower, which could lead to pressure issues in the reaction process ； 4) Appropriately adjust the load in the middle section of the distillation tower to improve the separation efficiency in that area ； 5) When the heat load at the top of the fractionation tower is too high, it is possible to contact the reactor to appropriately reduce the steam supplied to the riser and settler systems, as well as to decrease the amount of steam used for stripping light diesel ； 6) During operation, factors that cause mist entrainment at the top of the distillation tower should be reduced to maintain operational stability. 4. Control of the saturated vapor pressure and 10% point of gasoline: The saturated vapor pressure and 10% point are important indicators that reflect the volatility of gasoline, as well as its anti-knock properties and starting performance. A low saturated vapor pressure and a 10% increase indicate good anti-knock properties of the gasoline, but poor starting performance. A. Factors affecting the decrease in the saturated steam pressure and the rise in the 10% point: (1) An increase in the bottom temperature of the stabilizer leads to a decrease in the steam pressure ； ⑵If the stabilizer tower pressure drops, the vapor pressure also drops ； ⑶If the feed temperature rises or the flow rate decreases, the vapor pressure drops ； ⑷The vapor pressure of water in the feed decreases ； ⑸Malfunctions in instruments and pump equipment. Control method: (1) Under normal circumstances, the temperature at the bottom of the stabilizer is adjusted by using TIC402 to regulate the intercooler circuit in 403, thereby controlling the steam pressure in the stabilizer as well as the 10% point ； ⑵When there is a shortage of heat source, the reflux flow rate at the top of the stabilizer can be appropriately reduced to lower the vapor pressure of gasoline ； ⑶When the reflux rate is high, appropriately reduce the reflux flow at the top of the stabilizer to lower the vapor pressure of gasoline ； ⑷Timely analyze, address, and contact regarding failures of relevant pumps, equipment, or instruments.

The diesel pour point is controlled by the diesel extraction temperature, the flash point is adjusted by the amount of steam used for stripping, and the gasoline dry point is regulated by the tower top temperature