Various kettle-type reactors, reaction principles, and structural components.

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Chemical reactions are everywhere! ! When we stand under the blue sky and breathe in fresh air, a chemical reaction takes place: the O2 we inhale is converted into CO2, and our bodies serve as the \"reactors\" for this reaction. What would you like to know about the reactor? 　　A reactor is the medium for chemical reactions, providing the necessary space and conditions for them to take place; wherever there are reactions, reactors are essential. The reactors in chemical plants are even more diverse. 　　Today, we bring you an overview of the reaction principles and structural components of kettle-type reactors. Let’s take a look! 　　A kettle-type reactor is also known as a tank-type or pot-type reactor. The reaction principle is shown in the figure: Classification of batch reactors 1. Water-heated reaction reactor This heating method can be used when high temperature requirements are not necessary. Its heating systems come in open and closed types. 　　The open-type design is simpler; it consists of a circulation pump, a water tank, pipes, and regulators for controlling the valves. When high-pressure water is used, high mechanical strength is required for the equipment. Coils are welded to the outer surface of the reaction tank; the gap between these coils and the tank wall increases the thermal resistance and reduces the heat transfer efficiency. 　　2 Steam-heated reaction kettle: When the heating temperature is below 100°C, steam at a pressure lower than one atmosphere can be used for heating ； When the heating range is 100–180°C, use saturated steam ； At higher temperatures, high-pressure superheated steam can be used. 　　3 Reactors heated by other media If the process requirements dictate operation at high temperatures, or if it is desired to avoid using high-pressure heating systems, other media can be used in place of water and steam, such as mineral oil (275–300°C), biphenyl ether mixtures (boiling point 258°C), molten salts (140–540°C), liquid lead (melting point 327°C), etc. 　　4 Electric heating reaction kettle: By winding resistance wires around the insulation layer of the reaction kettle’s cylinder, or by installing them on specialized insulators at a certain distance from the kettle, it is possible to use electricity to heat the reaction. To achieve high temperatures using the first three methods, it is necessary to add a jacket to the reactor vessel; due to the large amplitude of temperature changes, the jacket and shell of the reactor are subjected to thermal stress resulting from these temperature differences. 　　When electric heating is used, the equipment is lightweight and simple; the temperature is easy to control. Moreover, no pumps, furnaces, chimneys, or other such devices are required, making it very simple to operate. The level of risk is low, and the costs are relatively low. However, the operating expenses are higher compared to other heating methods, and the thermal efficiency is below 85%. Therefore, it is suitable for applications where the heating temperature is below 400°C and electricity is inexpensive. 　　5-carbon steel reaction kettle Suitable for environments without corrosive liquids, such as in the processing of certain oils. 　　6 Stainless steel reaction kettle: It possesses excellent mechanical properties, can withstand high operating pressures, and is also able to resist the impacts associated with handling solid materials in bulk. 　　It has excellent heat resistance and a wide operating temperature range (-196–600°C); it does not peel off due to oxygen at high temperatures, allowing it to be used with direct flame heating. 　　It has high wear and corrosion resistance. 　　It has excellent heat transfer performance, with fast heating and cooling speeds. 　　It has excellent machinability, allowing reaction vessels of various shapes and structures to be manufactured according to different processing requirements; it can also be polished. 　　7. Glass-lined reaction vessels are made by lining the inner surface of a steel container with glass containing high levels of silica; upon heating at high temperatures, this glass adheres firmly to the metal surface, resulting in a composite material product. Therefore, glass-lined reactors combine the stability of glass with the strength of metal, making them excellent corrosion-resistant equipment. 　　8 Steel-lined reaction vessel: A steel substrate is used as the base, with an outer layer of steel pipe; inside, materials such as rubber or plastic can be used for lining, in order to address issues that are inherent to pure steel, such as exposure to corrosive substances or extreme temperatures. Common types include PE-lined steel reaction vessels and ETFE-lined steel reaction vessels. 　　Steel-lined PE reactor, with polyethylene as the lining material, suitable for the processing of liquid foods and pharmaceuticals. 　　Steel-lined ETFE reactor, with the lining material being an ethylene-tetrafluoroethylene copolymer. This type of reactor has excellent corrosion resistance, capable of withstanding acids, bases, salts, strong oxidizing agents, organic compounds, and other highly corrosive chemical substances at various concentrations. 　　Structure of a kettle-type reactor A kettle-type reactor is mainly composed of a reactor vessel, heat transfer devices, stirring devices, drive mechanisms, shaft sealing devices, and various process connections. 　　1. Reactor vessel The reactor vessel provides the space necessary for the reaction to take place. It consists of a shell and upper and lower end caps, with a height-to-diameter ratio generally ranging from 1 to 3. During pressurization, the upper and lower end caps are usually hemispherical or ellipsoidal in shape ； During normal-pressure operation, the upper and lower end caps can be made as flat lids. For easier discharge, the bottom can also be made conical. 　　2 Heat transfer devices Heat transfer devices are used to achieve the temperature required for reactions, and there are various types of them. 　　Jacketed heat transfer A jacket refers to an outer covering added outside the wall of a container. The material inside the container (or pipeline) can be heated by adding a heat medium such as steam, hot water, or hot oil, while it can also be cooled by introducing a cooling medium such as cooling water or other cooling fluids. 　　Coiled tube heat transfer is suitable for reaction vessels with a large heat transfer area, where the heat transfer area provided by the jacket alone is insufficient, or for reaction vessels whose interior is lined with rubber. 　　Tube heat transfer: For large reactors where high-speed heat transfer is required, a tube heat exchanger can be installed inside the reactor. It has the advantages of a large heat exchange area, good heat transfer performance, simple structure, and high operational flexibility. 　　External circulating heat transfer: When the heat transfer area provided by the jacket and coiled tubes is insufficient to meet the process requirements, or when it is not possible to install coiled tubes or a jacket inside the reactor and thus the heat transfer area remains inadequate, the liquid inside the reactor can be pumped out, cooled in an external heat exchanger, and then recycled back into the reactor. 　　Reflux condensation heat transfer: The steam generated within the reactor is condensed using an external condenser, and the condensed liquid is returned to the reactor. 　　3 Mixing device Includes mixers, mixing shafts, etc. 　　Stirrer: It moves the stationary liquid, maintaining the fluid flow state required for the stirring process in order to achieve the purpose of stirring. There are many types of mixers; the image below shows common styles of mixers. 　　Selection of mixing equipment 1. Selection based on the viscosity of the material For liquids with low viscosity, mixers with a small diameter and high rotational speed should be used, such as impeller-type or turbine-type mixers ； 　　For high-viscosity liquids, stirrers with large diameters and low rotational speeds are used, such as anchor, frame, and paddle stirrers. 　　2. Selection based on the mixing purpose For mixing low-viscosity homogeneous liquids, circulation flow rate is the key factor to consider; the circulation flow rates of various agitators, from highest to lowest, are: propeller type, turbine type, and paddle type. 　　For heterogeneous liquid-liquid dispersion processes, shear stress is considered first, along with the requirement for a high circulation flow rate. The shear effects of various agitators, in order from greatest to least, are: turbine type, propeller type, and paddle type. 　　4. Transmission mechanism: Its function is to provide the power for mixing. 　　The reaction vessel requires a motor and a transmission mechanism for operation; the agitator’s transmission mechanism is generally located at the top of the vessel, usually in a vertical arrangement, as shown in the figure. The motor has a high speed; this speed can be reduced to the mixing speed required by the process through a reducer, and then the coupling is used to drive the mixing shaft to rotate. 　　5-axis sealing device: A device whose function is to ensure sealed conditions during operation, thereby preventing the medium from leaking out. It can be divided into stuffing box sealing and mechanical sealing. 　　Packing box seal Structure: It consists of a bushing, a packing box body, packing rings, a gland, compression bolts, etc. 　　Principle: The packing, which is placed in the annular gap between the stirring shaft and the stuffing box, exerts a radial compressive force on the surface of the stirring shaft under the pressure exerted by the gland. The lubricant in the filler is forced out under radial compression, forming an extremely thin liquid film on the surface of the stirring shaft. This liquid film lubricates the stirring shaft on one hand, and on the other hand prevents the fluid inside the equipment from leaking out or external fluid from entering, thereby achieving axial sealing. 　　Mechanical seal A mechanical seal is a relatively new type of sealing structure. It has low leakage, a long service life, low frictional power loss, no wear on the shafts or bushings, and good vibration resistance; it is commonly used in environments with high or low temperatures, as well as in situations involving flammable, explosive, or toxic media. However, it has a complex structure, high requirements for the machining precision of the sealing rings, specific installation requirements, is inconvenient to assemble and disassemble, and comes with high costs. 　　Operating conditions of the sealing device: Packing seals are typically used under normal or low pressure conditions, with pressures generally below 2 kilograms. 　　Mechanical seals are used under normal medium pressures or in vacuum conditions; the pressure is usually negative or 40 kilograms. 　　Magnetic sealing is used under high pressure or when the volatility of the medium is high, typically when the pressure exceeds 14 kilograms. 　　Except that magnetic seals all use water cooling, other types of seals require additional cooling jackets when the temperature exceeds 120 degrees. 　　6 Process connections: Raw material inlet pipe (gray), Purging air inlet pipe (blue), Purging nitrogen inlet pipe (black), Cleaning water inlet pipe (green), Solid material inlet pipe (raw materials, solid catalysts, etc.), Product outlet pipe (gray), Heat exchange medium inlet and outlet pipes (steam pipes are red)