【Weekly Topic】Production Technology: Briefly explain the interrelationships between changes in the key parameters of distillation operations? 05.02~05.08

Here’s a hint: for example, 1. If the steam temperature rises, how should other parameters be adjusted? If the steam temperature drops, how should other parameters be adjusted? 2. As pressure increases, how should other parameters be adjusted? With the pressure reduced, how should other parameters be adjusted? 3. As the reflux ratio increases, how should other parameters be adjusted? If the reflux ratio is reduced, how should other parameters be adjusted?

This post was last edited and replied to by Refinery Operator on 2011-5-2 at 11:34. Reply 1# sun-rock: I’m sorry; I found this information in a book. The control objective of a distillation tower is to achieve the highest recovery rate and the lowest energy consumption, while ensuring that the product quality meets the required standards. In distillation operations, various factors can affect its proper functioning. The main factors that influence distillation include the following: ① The temperature and pressure of the tower ； ②Feeding status ； ③Feed rate ； ④Feed composition ； ⑤Feed temperature ； ⑥Return flow ； ⑦Heating capacity of the reboiler ； ⑧Temperature and pressure of the tower top cooling water ； ⑨Top of tower yield ； ⑩Bottom tower yield. Now that we know the factors affecting distillation operations, we should monitor these factors in real time to ensure that the relevant parameters remain within normal ranges. During the production process, the evaporation rate at the bottom of the tower is proportional to the gas flow rate, and the flow rate is in turn proportional to the pressure difference across the tower. Therefore, by controlling the pressures at the top and bottom of the tower, a certain level of evaporation can be ensured. In operation, the pressure at the top of the tower can be adjusted stably using a pressure control system; hence, it is particularly important to maintain stable tower pressures. When the temperature of the heat transfer oil rises suddenly, the amount of volatile components evaporating at the bottom of the tower increases, and the temperature of the sensitive plate goes up. It is necessary to increase the reflux rate or reduce the flow rate of the heat transfer oil in order to control the temperature of the sensitive plate and ensure the quality of the product at the top of the tower ； However, in practical operation, if the evaporation rate is too high, foam entrainment will occur, which reduces the mass transfer between the gas and liquid phases and severely affects the quality of the product ； In severe cases, flooding may also occur ； When the temperature of the heat transfer oil drops suddenly, the amount of volatile components evaporating at the bottom of the tower decreases, and the temperature of the sensitive plate falls. If the flow rate of return fluid is not reduced in a timely manner, the temperature of the sensitive plate will drop significantly, allowing volatile components to easily reach the bottom of the tower and leading to a decline in the quality of the products produced later on ； Three types of equilibrium must also be observed during distillation operations; the first is material balance ； The second is vapor-liquid equilibrium ； Third is heat balance; only by achieving these three balances can a qualified product be obtained, thereby maximizing the yield of the product.

Reply to 3# zhuyitou8: I. Changes in the temperature at the top of the tower can cause: 1. Changes in the reflux flow rate or reflux temperature; 2. Changes in the diesel reflux flow rate or reflux temperature, as well as changes in the flow rates and temperatures of various side streams; 3. Changes in the pressure at the top of the tower; 4. Fluctuations in the temperature at the furnace outlet. II. Changes in the feed volume and temperature can cause: 1. Changes in the temperature and volume of the oil and gas entering the distillation tower; 2. Changes in the wax oil reflux flow rate and temperature; 3. Changes in the liquid level and temperature at the bottom of the tower; 4. Changes in the temperature at the furnace outlet; 5. Changes in the temperature and pressure at the top of the distillation tower; 6. Changes in the temperature of the diesel distillate; 7. Changes in the temperatures and flow rates of various reflux streams

For a distillation column, any change in any parameter, from the feed composition and flow rate to reboiling, reflux, product withdrawal, and column pressure, will affect the operation of the column. To ensure stable operation of a tower, it is necessary to maintain stable tower pressure; all designs are based on a fixed value for this pressure. Any fluctuations in tower pressure can lead to changes in the composition of the material at the top and bottom of the tower. For example, as the column pressure decreases, the relative volatility increases; however, under all current operating parameters, this may lead to the upward movement of heavier components. At lower pressures, the boiling points of various components decrease, making them easier to vaporize. Therefore, the appropriate adjustment is to increase the reflux rate slightly, so as to prevent excessive reboiling and to accommodate changes in column pressure, thereby ensuring that the product meets quality standards. This is just my personal opinion; please give me your guidance.

Reply 1# sun-rock: The control objective of the distillation tower is to achieve the highest recovery rate and the lowest energy consumption, while ensuring that the product quality meets the required standards. In distillation operations, various factors can affect its proper functioning. The main factors that influence distillation include the following: ① The temperature and pressure of the tower ； ②Feeding status ； ③Feed rate ； ④Feed composition ； ⑤Feed temperature ； ⑥Return flow ； ⑦Heating capacity of the reboiler ； ⑧Temperature and pressure of the tower top cooling water ； ⑨Top of tower yield ； ⑩Bottom tower yield. Now that we know the factors affecting distillation operations, we should monitor these factors in real time to ensure that the relevant parameters remain within normal ranges. During the production process, the evaporation rate at the bottom of the tower is proportional to the gas flow rate, and the flow rate is in turn proportional to the pressure difference across the tower. Therefore, by controlling the pressures at the top and bottom of the tower, a certain level of evaporation can be ensured. In operation, the pressure at the top of the tower can be adjusted stably using a pressure control system; hence, it is particularly important to maintain stable tower pressures. When the temperature of the heat transfer oil rises suddenly, the amount of volatile components evaporating at the bottom of the tower increases, and the temperature of the sensitive plate goes up. It is necessary to increase the reflux rate or reduce the flow rate of the heat transfer oil in order to control the temperature of the sensitive plate and ensure the quality of the product at the top of the tower ； However, in practical operation, if the evaporation rate is too high, foam entrainment will occur, which reduces the mass transfer between the gas and liquid phases and severely affects the quality of the product ； In severe cases, flooding may also occur ； When the temperature of the heat transfer oil drops suddenly, the amount of volatile components evaporating at the bottom of the tower decreases, and the temperature of the sensitive plate falls. If the flow rate of return fluid is not reduced in a timely manner, the temperature of the sensitive plate will drop significantly, allowing volatile components to easily reach the bottom of the tower and leading to a decline in the quality of the products produced later on ； Three types of equilibrium must also be observed during distillation operations; the first is material balance ； The second is vapor-liquid equilibrium ； Third is heat balance; only by achieving these three balances can a qualified product be obtained, thereby maximizing the yield of the product.

1. As the steam temperature rises, the evaporation rate increases; increasing the return flow appropriately will suffice； As the steam temperature drops, increase the steam flow slightly to ensure an adequate rate of evaporation. 2. Pressure changes, as well as changes in evaporation rate and temperature, can generally be addressed by adjusting the pressure control valve. 3. Increasing the reflux ratio reduces the amount of evaporation, thereby reducing heat consumption ； Reduce the reflux ratio and increase the steam volume.

Hehe, this is a basic question!