Slurry circulation rate
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How is the circulation rate of the slurry determined? How is the amount of slurry returning to the tower determined? How is the temperature at the bottom of the distillation tower selected?
It is determined during the design of the device, and is generally 100–150 degrees lower than the extraction temperature.
Removing the high-temperature residual heat and washing away the catalyst contained within it is key to the heat balance of the distillation tower.
So how do you determine whether a catalyst for washing is good?
According to the data provided by the design institute, the low temperature in the fractionation tower is controlled at 340–360 depending on the quality of the product, and it is closely related to the properties of the raw materials
The circulation rate of the slurry should be set higher, provided that the requirements for distillation are met (such as the gas-liquid phase load distribution in the top reflux and intermediate sections, as well as the efficiency of catalyst powder separation). However, it is necessary to ensure that the absorption stabilization system has sufficient heat source~~~ The amount of slurry flowing back up the tower is also adjusted based on the above considerations (our plant generally does not use slurry flowing back down the tower). The temperature at the bottom of the tower should be controlled according to the density of the feed oil in order to reduce coking
The function of the oil slurry flowing upward is to remove catalyst dust from the high-temperature oil and gas as well as to remove excess heat, while its function of flowing downward is to regulate the temperature at the bottom of the tower; the amount of such slurry used is adjusted according to the temperature at the bottom of the tower. The temperature at the bottom of the tower in our current catalytic reforming units is generally not higher than 345 degrees. This value is based on empirical data, as too high a temperature at the bottom of the tower can lead to severe coking there, as well as an increase in the solid content within the oil slurry
So what is the typical design value for your slurry circulation rate?
In our production process, these values are determined by the temperature at the oil and gas inlet as well as the temperature at which the slurry returns upward. The temperature at which the slurry returns upward is kept above 270 degrees, while the temperature at the oil and gas inlet is kept below 405 degrees. Generally, high flow rates and high temperatures are used for operation, with the circulation rate being between 80% and 90% of the slurry pump’s rated flow rate. If conditions permit, it is better to have a larger slurry circulation volume.