Introduction to tubular reactors
1.1 Difference between tubular
Reactor and kettle reactor
(1) Tubular reactors are flat push flow reactors with no return mixing, while kettle reactors are fully mixed flow reactors;
(2) The residence time of the medium in the reactor is shorter in the tubular reactor, while the residence time in the kettle reactor is unstable;
(3) The tube reactor has a stronger ability to dissipate reaction heat, while the kettle reactor has a poorer ability to dissipate reaction heat, and can be equipped with a jacket outside the kettle reactor or with coils inside the kettle to strengthen heat exchange;
1.2 Features of tubular reactors
1) equal reaction times for all parts of the reactant in the reactor, the concentration of reactants and the rate of chemical reaction at any point in the reactor do not change because of time
2) narrow working chamber, large specific surface area, internal and external heat transfer structure, high heat transfer efficiency, especially suitable for reactions with large thermal effects
3) as the tubular reactor is a flat push flow reactor, the material re-mixing in the tubular reactor is smaller and in this respect it has an advantage over the kettle reactor in that the fluid in the tubular reactor can be seen as an ideal fluid when the flux is small;
4) It is suitable for both gas-to-gas reactions and liquid-to-liquid reactions, which can also be carried out in pressurised environments, and is equally suitable for highly viscous materials;
5) extremely high control accuracy for the time control of the medium staying in the reactor, and also the operation of sectional temperature control;
6) the large capacity per unit volume of the tubular reactor makes it suitable for large continuous production with high reaction rates;
Types of tubular reactors
2.1 Horizontal tubular reactor
Horizontal reactors such as Figure 1 are composed of seamless steel tubes and u-tubes, which are connected to each other by flanges to form a whole. The structure is clear and simple, which is conducive to processing and manufacturing, and it is also very convenient to clean the reactor at a later stage, which is conducive to keeping the reactor clean. For high pressure reactions, the tubular reactor is still suitable and requires a standard slotted butt-weld
Steel Flange. For higher pressure reactions, lenticular steel flanges can be used. Horizontal reactors are suitable for gas-to-gas or liquid-to-liquid reactions.
2.2 Standpipe reactors
Vertical reactors are also more commonly used in production processes and are available in a wide range of types, shown in Figure 2 as a single programmed standpipe reactor, in Figure 3 as a centrally inserted tube reactor and in Figure 4 as a jacketed standpipe reactor [2].
Standpipe reactors are suitable for liquid reactions and can also perform reactions such as hydrogenation reactions, liquid phase oxidation reactions and liquid phase ammonification reactions.
Picture
2.3 Coil reactors
As the name suggests, a coiled tube reactor is one in which the pipes are coiled together, similar to a disc. This makes the tube reactor compact and takes up less space, but the small gap between the pipes is inconvenient when servicing and cleaning the pipes.
As shown in Figure 5, the semi-circular pipes meet in a spiral shape and the pipes are connected to each other by flanges, leaving a gap in the middle of the coil reactor, overcoming the difficulties of inconvenient installation and cleaning.
2.4 U-tube reactor
The larger diameter of the U-tube reactor increases the residence time of the material in the reactor, allowing the reactants to be mixed more fully in the reactor and therefore used for some reactions with slower reaction rates.
The U-tube reactor is equipped with a porous baffle or stirring device in the pipe to disperse the material in-line at high speed shear to improve the efficiency of mass transfer.
2.5 Multi-tube parallel tubular reactor
Multi-tube parallel tubular reactors allow more complex reactions to be carried out between gases and solids, e.g. hydrogen chloride gas and acetylene reacting in a multi-tube parallel reactor while a solid catalyst is placed to react to produce vinyl chloride.
2.6 Internal spiral tube reactor
Internal spiral tube reactors have the following characteristics:
(1) Adopting double heat transfer structure inside and outside, the hollow spiral plate structure shears and disperses the material as it passes through, making the material mix more fully, and used in conjunction with the outer jacket, making the inner spiral tube reactor more significant in its ability to transfer heat effects;
(2) For viscous liquids with the same mixture used, especially for fast exothermic reactions, heat to improve the circulation of the medium, such as nitrification reactions;
(3) Suitable for reaction processes in which solid products are generated by reaction between liquids or between gases and liquids.
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