Distillation tower
Distillation towers are used to separate liquid mixtures into their individual components based on differences in boiling points. Based on the principles of heat and mass transfer, distillation towers heat the feed mixture to partially vaporize it, causing the more volatile components to rise in the tower while the heavier components condense and fall. The tower is equipped with trays or packing to promote repeated contact between gas and liquid, thereby achieving multi-stage high-purity separation. Key components include reboilers (bottom heat source), condensers (top cooling devices), feed ports, and reflux systems, which return partially condensed overhead products to improve separation efficiency. Distillation towers have a wide range of applications, from crude oil refining and ethanol purification to pharmaceutical production and wastewater treatment, and can operate under atmospheric pressure, vacuum or pressurized conditions depending on the thermal sensitivity of the substances being processed. Today, advanced designs focus on energy efficiency, automation, and high-performance internals to improve the productivity and sustainability of chemical processing.
| Equipment type | Classification method | Features | Application scenario |
| Plate tower | Classification by tower structure | The tower is equipped with several layers of tower plates (or trays), the liquid flows on the tower plates, and the gas contacts the liquid through the holes or valves on the tower plates to achieve gas-liquid mass transfer. | Suitable for occasions with large processing volume and low liquid viscosity, such as petroleum distillation, alcohol distillation, etc. |
| Packed tower | Classified by the structure inside the tower | The tower is filled with packing, which has a large specific surface area and high porosity, and can provide a large amount of gas-liquid contact area to promote mass transfer. | Suitable for occasions with small processing volume, high liquid viscosity or high mass transfer efficiency, such as fine chemicals, biochemicals, etc. |
| Spray tower | Classification by tower structure | The liquid is sprayed into the tower through the nozzle to form droplets or mist, which are fully in contact with the gas to achieve mass transfer. The spray tower has high mass transfer efficiency, but requires a higher liquid injection pressure. | It is suitable for occasions with small processing volume and low liquid viscosity, such as certain absorption processes. |
| Atmospheric distillation tower | Classification by operating pressure | The operating pressure is close to atmospheric pressure, the structure is simple, and the cost is low, but the separation efficiency may be limited. | It is suitable for occasions with large boiling point differences and low separation requirements, such as alcohol distillation. |
| Pressure distillation tower | Classification by operating pressure | The operating pressure is higher than atmospheric pressure, which can improve the separation efficiency and reduce the height of the tower, but requires high-pressure resistant equipment. | Applicable to mixtures with higher boiling points, such as petroleum distillation, synthetic ammonia distillation, etc. |
| Vacuum distillation tower | Classification by operating pressure | The operating pressure is lower than normal pressure, which can reduce the operating temperature and reduce the decomposition of heat-sensitive substances, but a vacuum system is required. | Applicable to the separation of heat-sensitive substances, such as some fine chemical products, biological products, etc. |
| Separation tower | Classification by tower purpose | Mainly used to separate liquid mixtures into different components. By controlling the temperature, pressure and feed position of the tower, the separation of different components is achieved. | For example, the petroleum distillation tower separates crude oil into different fractions such as gasoline, kerosene, and diesel. |
| Purification tower | Classification by tower purpose | Mainly used to improve the purity of a certain component. Through multiple distillations, impurities are removed and the purity of the target product is improved. | For example, when producing high-purity ethanol, impurities are removed through a purification tower to improve the purity of ethanol. |
| Absorption tower | Classification by tower purpose | Mainly used to absorb certain components in the gas. The absorption of certain components in the gas is achieved by contacting the liquid absorbent with the gas. | For example, in waste gas treatment, alkaline solution is used to absorb acidic gases (such as sulfur dioxide, hydrogen chloride, etc.) in the waste gas. |
| Desorption tower | Classification by tower purpose | Mainly used to desorb the absorbed components in the absorbent and recover the useful components. | For example, in some solvent recovery processes, the solvent is desorbed from the absorbent to achieve solvent recovery. |
| Sieve plate tower | Classification by the internal structural characteristics of the tower | There are many small holes on the tower plate, and the gas is dispersed into the liquid through the small holes to form bubbles, realizing gas-liquid mass transfer. | Suitable for occasions with large processing volume and low liquid viscosity. |
| Float valve tower | Classified by the internal structure characteristics of the tower | The float valve on the tower plate can automatically adjust the opening according to the gas flow rate, making the gas distribution more uniform and improving the mass transfer efficiency. | Suitable for occasions with large processing volume and high requirements for mass transfer efficiency. |
| Bubble tower | Classification by the internal structure characteristics of the tower | The tower plate is equipped with bubbles, and the gas enters the liquid through the bubbles to form bubbles, realizing gas-liquid mass transfer. | Suitable for occasions with large processing volume and low liquid viscosity. |
| Packed tower | Classification by the internal structure characteristics of the tower | The tower is equipped with packing, which has a large specific surface area and high porosity, and can provide a large amount of gas-liquid contact area to promote mass transfer. | Suitable for occasions with small processing volume, high liquid viscosity or high mass transfer efficiency. |
| Regular packing tower | Classified by the internal structure characteristics of the tower | The tower is equipped with regular packing, such as corrugated packing, mesh packing, etc., with high mass transfer efficiency and small pressure drop. | Suitable for occasions with small processing volume and high mass transfer efficiency requirements. |
| References | Authors | Abstract | DOI |
| A review of research on distillation tower control and energy-saving optimization | Xue Meisheng, Qi Fei, Wu Gang, Sun Demin | Based on the analysis of the principles of distillation process and the basic structure of distillation towers, the current research status of distillation tower control and energy-saving optimization at home and abroad is reviewed, the shortcomings of current research are pointed out, and possible research directions in the future are proposed. | 10.3969/j.issn.1000-3932.2006.06.001 |
| Dynamic process simulation and its application in the operation analysis of distillation tower | Wang Liang, Lv Wenxiang, Huang Dexian | The HYSYS process simulation software is used to simulate the dynamic process of the propylene propane distillation tower. The dynamic response change process of the propylene propane distillation tower when the operating conditions, feed flow rate, feed component interference, etc. are changed is analyzed. The problems existing in the conventional PID control scheme and the common advanced control scheme are studied, providing a basis for designing an improved control scheme integrating real-time optimization and advanced control. | 10.3969/j.issn.1001-4160.2006.01.016 |
| Application of ASPEN Plus in Fault Diagnosis and Parameter Optimization of Industrial Distillation Towers | Sun Wei, Li Lin, Chen Xiaochun | ASPEN Plus software is used to simulate the actual production process in production practice to diagnose possible faults in actual operation; on the basis of serialized process simulation optimization, guided by theoretical calculation, targeted operation parameter adjustment schemes and distillation tower internal maintenance strategies are proposed. The actual operation results show that the best transformation effect is achieved with the minimum cost investment, and the fault diagnosis and parameter optimization are successful. | 10.3321/j.issn:1000-6613.2005.08.025 |
| Linear Mixed Model for Distillation Columns | Carlos Rodriguez, Prashant Mahaskar, Vladimir Mahalek | In this study, the authors proposed a steady-state mixed model consisting of a simplified first-principles model (SFPM) and an error correction model. The SFPM represents the internal structure of the plant and the linear correction model, which is different from recent studies that used a simpler form of the SFPM and a nonlinear data-driven model. Preserving the distillation column structure in SFPM allows accurate calculation of sensitivities, the composition correction model is linear, and the errors due to changes in column efficiency can be corrected by additional linear corrections. This study uses multiplicative correction terms and shows that additive corrections often lead to negative concentrations calculated by the mixture model. Due to the structure of the model, PLS is used to estimate the parameters because PLS predictions are more accurate than neural networks. The correction model is linear, easy to iteratively update, and ensures accurate prediction of up to 10% changes in column efficiency without updating the SFPM parameters. | 10.1016/j.compchemeng.2023.108160 |
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