With the continuous development of chemical production processes, tower equipment has also developed a wide range of structures and types in order to meet various process requirements. In order to facilitate research and comparison, the tower equipment is classified from different perspectives.
For example: by operating pressure into pressurised towers, atmospheric towers and reduced pressure towers;
distillation towers, absorption towers, desorption towers, extraction towers, reaction towers and drying towers by unit operation;
According to the formation of inter-phase contact interface is divided into the way with a fixed phase interface and the flow process to form the phase interface of the tower and so on, the following is the conventional classification of several tower equipment.
1. According to the use of classification
(1)
Distillation Tower The use of liquid mixtures in each component of the volatility of the difference to separate its various liquid components of the operation known as distillation, repeated multiple distillation process known as distillation, to achieve the distillation operation of the tower equipment known as distillation tower. Such as normal decompression device in the atmospheric pressure tower, decompression tower, crude oil can be separated into gasoline, paraffin, diesel and lubricants, etc.; platinum reforming device in a variety of distillation tower, can be separated out of benzene, toluene, xylene, etc..
(2) Absorption towers, desorption towers
The process of separating gases by absorbing liquid using the different solubilities of the components in the solution is called absorption; the process of releasing the dissolved gases from the absorbing liquid by heating is called desorption. The process of absorption and desorption is known as absorption and desorption towers. Such as catalytic cracking plant in the absorption, desorption tower, recovery of gasoline from the refinery gas, recovery of ethylene and propylene from the cracking gas, and gas purification, etc. need absorption, desorption tower.
(3)
Extraction Tower For the components of the boiling point difference between the liquid mixture, the use of general fractionation method is difficult to work, then the liquid mixture can be added to a higher boiling point of the solvent (called extractant); the use of the components in the mixture in the extractant solubility differences, they will be separated, this method is called extraction (also known as extraction), to achieve the extraction operation of the tower equipment called extraction tower. Such as the extraction tower in the propane deasphalting plant. Extraction tower to pulsating tower and turntable tower used more.
(4) scrubber tower
The process of removing useless components or solid dust particles from the gas with water is called water washing or dust removal, and the tower equipment used is called a scrubber tower or dust removal tower.
Here in particular, some equipment in terms of its shape is a tower equipment, but the essence of its work is not separation but heat exchange or reaction. Such as cool water tower is a cooler, ammonia synthesis plant in the synthesis tower is a
Reactor.
2. According to the operating pressure classification
Tower equipment according to its completion of the process operation is different, its pressure and humidity are not the same. However, when the phase equilibrium is reached, there is a certain relationship between pressure, temperature, gas phase composition and liquid phase composition. In actual production, the composition and requirements of raw materials and products are determined by the process and cannot be changed at will, the pressure and temperature have a choice, but the two are interrelated, if one is determined first, the other can only be derived from the phase equilibrium relationship. From the point of view of operational convenience and equipment simplicity, the best choice of atmospheric pressure operation, from the source of coolant point of view, it is generally desirable to control the condensing temperature at the top of the tower at 30 ~ 40 ℃, in order to use cheap water or air as coolant. So the tower equipment according to the specific process requirements, equipment and operating costs to consider, sometimes can be operated under atmospheric pressure, sometimes need to operate under pressure, sometimes also need to reduce pressure operation. The corresponding tower equipment is called atmospheric tower, pressurised tower and reduced pressure tower respectively.
3. According to the structure of the classification
Tower equipment, although its use varies, operating conditions also vary, but its structure is basically similar, mainly by the tower body, support, internal components and accessories. According to the structure of the internal components of the tower can be divided into two categories: plate towers and packed towers.
In the plate tower, the tower is equipped with a certain number of discs, the gas in the form of bubbles or jets through the liquid layer on the disc so that the two phases in close contact, mass transfer. The concentration of the components of the two phases varies in a stepwise manner along the tower height. In packed towers, the tower is filled with a certain height of the packing layer, the liquid is sinking downwards along the surface of the packing in the form of a film, while the continuous phase of the gas flows from bottom to top, and the liquid counter-current mass transfer. The concentration of the components of the two phases is continuously changing along the tower height. People also according to the plate tower tower plate structure and packing tower packing used, can be subdivided into different tower type.
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