Reasons affecting the temperatures and pressures in the initial distillation tower and the atmospheric distillation column, as well as key operating points

Thread Content

The temperature and pressure at the top of the initial distillation tower and the atmospheric distillation column are key parameters for controlling the dry point of gasoline, ensuring effective fractionation, and maintaining stable operation of the plant. In actual production, fluctuations in the temperature and pressure at the top of the tower are often a direct reflection of changes in the material balance, heat balance, and gas-phase load of the plant. If these fluctuations are not adjusted in a timely manner, it can lead to poor quality of the product at the tower top, pressure fluctuations, and even issues such as tower overpressure or vacuum conditions. Based on actual on-site operations, the main factors affecting this phenomenon are summarized as follows: First, changes in the temperature at the outlet of the heating furnace. An increase in the temperature at the furnace outlet leads to a significant rise in the amount of gasification within the tower, with both the temperature and pressure at the top of the tower increasing accordingly. Treatment: Appropriately increase the reflux rate and reasonably raise the top temperature to ensure that the dry point of gasoline meets the specifications. II. Changes in the properties of crude oil and feedstock: The crude oil becomes lighter, with an increase in light components; this leads to an increase in the pressure at the top of the tower, necessitating an appropriate increase in the temperature at that location ； The crude oil becomes heavier, with fewer light components; the top pressure of the tower decreases, so the top temperature needs to be appropriately lowered. III. Influence of feed water content and stripping steam: Water present in the crude oil, as well as an increased amount of steam supplied at the bottom of the tower or via side streams for stripping, will increase the vapor load at the top of the tower, resulting in higher pressure and temperature there. Treatment: The top temperature of the tower can be appropriately reduced, while the top pressure must be strictly controlled; if the pressure remains high, it is not advisable to increase the reflux rate indiscriminately. IV. Water carried back in the tower top: The water that returns to the tower top causes a significant drop in the temperature at the tower top. Meanwhile, the vaporization of this water leads to a sudden increase in the gas-phase load, resulting in a noticeable rise in the pressure at the tower top. Treatment: Strengthen water cutting in the reflux tank, and promptly investigate any malfunctions in the dewatering equipment and instruments. V. Feed rate and changes in tower load: As the feed rate increases, the gas-phase load within the tower rises, resulting in an increase in the top pressure of the tower ； If the feed rate is too high and the liquid level at the bottom of the tower is excessively high, or even flooding occurs, the temperature and pressure at the top of the tower will rise sharply. Treatment: Adjust the processing volume in a timely manner, control the liquid level at the bottom of the tower, and strictly prevent the tower from becoming full or experiencing overflow. VI. Effects of the backflow and gas discharge system: Obstructions in the low-pressure gas discharge pipelines or clogs in the burners can cause gas to build up under pressure, leading to an increase in the pressure at the top of the tower. An excessively high liquid level in the overhead product tank, a malfunctioning extraction pump, or faulty instruments can cause blockages in the downstream path of gasoline, which in turn raises the pressure at the top of the tower. Action taken: The rear path was cleared immediately, additional extraction pumps were activated to lower the liquid level in the product tank, and pressure was restored to normal levels. VII. Changes in the amount and pressure of steam blown into the tower: As the amount of steam blown at the bottom of the tower increases and its pressure rises, the gas-phase load also increases, leading to a rise in the pressure at the top of the tower ； The steam flow decreases, the pressure drops, and as a result the pressure at the top of the tower also falls. Treatment: Adjust the steam injection volume flexibly based on the temperature and pressure at the top of the tower to avoid significant fluctuations.