What is a Continuous Distillation Tower?

A continuous distillation tower is a crucial chemical equipment, primarily used for the separation and purification of liquid mixtures. Its working principle involves vaporizing a portion of the liquid mixture and then partially condensing the resulting vapor, repeatedly performing the processes of vaporization and condensation to sequentially separate the components of the mixture.

Specifically, a continuous distillation column typically consists of a rectifying section and a stripping section, with the feed plate marking the boundary. The portion above the feed plate is referred to as the rectifying section, while the portion below the feed plate (including the feed plate) is called the stripping section. During operation, the raw liquid is heated to a predetermined temperature in a heat exchanger and then added to the column from the upper layer of the stripping section, which is the feed plate. The liquid material on this plate combines with the reflux from the rectifying section, then flows downward layer by layer to the bottom of the column. As it descends, the more volatile (low boiling point) components are continuously vaporized from the liquid, resulting in a liquid at the bottom of the column containing a higher concentration of less volatile (high boiling point) components. A portion of the bottom liquid is continuously transferred to a storage tank, while the other portion is directed to the bottom of the column's evaporator (reboiler) for vaporization. The vapor produced in the evaporator rises layer by layer from the bottom, gradually concentrating the more volatile components in the vapor, which then enters the top condenser. A portion of the vapor condenses in the condenser, and the resulting liquid is returned to the top of the column as reflux.

The continuous distillation tower features various structural characteristics, such as the innovative two-phase continuous sieve tray, which includes gas outlet holes on the trays with various types of caps arranged above them, along with downcomer pipes. Its operating principle involves gas-liquid flow contact in a jet-like state, where the gas phase and liquid droplets froth and separate within the tray spaces. The gas phase rises to the next tray level, while the liquid droplets ejected from the caps collide with each other, causing some small droplets to merge into larger ones, which then fall onto the tray along with the original large droplets. Some of these are reabsorbed into the caps for further film formation and fragmentation. The remaining portion flows with the liquid on the tray to the next row of caps or circulates within a cap before being directed through the downcomer to the lower tray.

The applications of continuous distillation towers are extensive, encompassing petrochemicals, organic chemicals, and food industries. In the petrochemical sector, they are commonly used in processes such as refining, cracking, reforming, and purification; in the organic chemicals field, they are applied in refining compounds, separation and purification, and recycling processes; within the food industry, they are typically utilized for extracting specific food components, such as edible oils, spices, and nutrient extracts.

In summary, the continuous distillation tower is a crucial chemical equipment with a broad application prospect.