Several problems should be paid attention to when choosing glass reactor and temperature control equipment

1. Reactor and insulation measures
1) Selection of inlet and outlet of circulating media At present, the import and export of circulating medium reactors for domestically produced jacketed glass reactors mainly include two kinds of pagoda heads and flanges, and most of them are pagoda heads. The author thinks that although the pagoda head interface is convenient, it has many drawbacks: Firstly, the shape gradually reduced on the outer shape is easy to produce resistance affecting the flow velocity of the circulating medium, and the high-speed flowing liquid will thus form a force against the glass to form a jacket. The pressure is potentially destructive to the glass reactor; secondly, the pagoda shape and the brittleness of the glass determine that it can only be directly connected to the hose, because the current temperature resistance of soft rubber materials does not exceed 250 ° C, so the use of the pagoda head The interface means that the temperature of the product you choose is difficult to exceed 210 ° C. For the pilot-grade reactor above 20 liters, the heat transfer resistance is greater, the achievable temperature value will be lower; and the rubber hose is used. It is also impossible to avoid the problem that the rubber will age. Therefore, the author recommends the use of the flange interface, which is also a common interface for foreign counterparts, it can avoid many of the drawbacks of the pagoda head interface, the only drawback is that the loading and unloading is more cumbersome. There are also quick-open connections, but it is also very convenient and quick to use. It is more labor-saving than the connection between the pagoda head and the rubber hose. The jacketed glass reactor developed by the author's company all uses the flange interface, and no user has put forward different opinions.
2) Built-in corrosion-resistant coil This accessory can also function as a heating and cooling device. It can also act as a flexible temperature measuring probe for supporting the skeleton. It does not affect the amplification of the stirring paddle. It can be said that there are many functions. As a heater, it can pass steam, hot water or hot oil; as a cooler, it can pass water, cold alcohol and water mixture and cold oil or even liquid nitrogen. Common manufacturing methods are thin-walled PTFE coated metal pipes. Many people reject the use of the built-in coil, which is considered to be inconvenient to clean. In fact, the metal pipe coated with thin-walled PTFE is different from the coil fixed on the large metal reaction vessel. The former is easy to disassemble and clean, and the cost is Not high, can be used interchangeably. It should be noted that the method of spraying PTFE on stainless steel is not desirable, not only because the layer is too thin and easy to peel off, but also because of the high cost of spraying. The most important reason is that the mesh coating with fine mesh is formed after the spraying is completed. It acts to prevent chemical corrosion.
3) The principle of vacuum interlayer is to eliminate the air convection factor in heat conduction, just like the vacuum flask vacuum. When the glass reaction vessel adopts a three-layer design, the outer jacket is vacuumed and closed to form a vacuum interlayer, so that the reaction heat preservation effect is good. Moreover, when the temperature is low, the surface of the outer glass will not form frost, and the reaction will be clearly visible; when the temperature is high, the surface of the outer glass is not hot, and the danger of burns can be avoided. However, the three-layer glass reactor has many stress points, and the firing rate is not high, and the larger the volume, the more the reactor.
4) Thermometer and temperature measurement point Most glass reactors on the market currently use a fixed thermometer glass tube to measure the temperature of the material. The sleeve is fixed from the fixed position on the cover to a certain depth in the kettle. There are many disadvantages to this: 1) The stir bar may have strong resonance in a certain speed range, which may hit the thermometer glass casing; 2) The pilot-stage reactor (20~50 liters) of the glass casing is in the stirring shaft and In the center of the inner wall, it is easy to be hit by the sheet when using the turbine type paddle, so that the blade can not be made as large as possible and affect the stirring effect; 3) when the material is loaded much, the casing is stressed and easily broken. When the material is loaded less, the casing may not be in contact with the material and cannot be measured. We have developed a thermowell with adjustable insertion depth to compensate for the third drawback. An optional bendable temperature probe that can be used with the built-in heat exchange coil has also been developed so that the temperature measurement point can be placed at any depth close to the inner wall of the reactor without affecting the paddle with a larger agitation radius. page. Of course, the premise of this application is that the built-in heat exchange coil must be used at the same time. In addition, foreign countries have built a temperature probe from the central protruding part of the bottom valve to carry out digital measurement of temperature. The highest point of the protruding part is 1~2cm higher than the bottom of the tank. This method measures the temperature of the bottom material and is suitable for small reactors and liquids that should be stirred and mixed, which is not suitable for larger reactors or materials with high viscosity. Moreover, for larger reactors, the height of the jacket is also large, because the high temperature fluid density is small, and the low temperature fluid density is high, and generally the temperature of the circulating medium in the lower portion of the jacket is lower than the upper portion. Therefore, for large reactors, the bottom temperature measurement method determines that the material temperature is low. If the flow rate of the circulating medium is sufficiently fast, the deviation is smaller, but the high-speed fluid also imposes higher requirements on the strength of the reactor, which is precisely where the large glass reactor jacket is not as good as the small glass reactor.
5) Insulation measures Glass reactors generally use instrument-level temperature control equipment, which is of great value. Therefore, users do not choose to heat equipment with excessive cooling power. The use of the outer layer insulation jacket and the circulating medium pipe insulation sleeve can effectively reduce the heat exchange between the equipment and the outside air, thereby improving the temperature rise and fall, and avoiding the selection of equipment with higher power and higher price. The area of ​​the glass reactor in contact with the air is large, and the temperature rise and fall cannot be sacrificed because the visualization of the reaction process is required. The outer layer of the outer layer of the kettle can be selected to solve this contradiction.