In many chemical processes, liquid hasto be fed into laboratory reactors gradually, rather than immediately. There are two ways to do this: the most common method for feeding liquid substances into the reactors is with the help of a dropping funnel, and in pilot reactors, a dosing tank is used.
Glass chemical drip funnels are designed for chemical processes where it is necessary to slowly add liquid to a vessel with a reaction mixture. They are produced, like reactors, of a wide variety of volumes – from several milliliters to liters, with and without a measuring scale.
The dropping funnel for regulating the supply of liquid to the container has a tap on the drain spout. Outwardly it resembles a dividing one, but has some differences:
• the tap is located directly under the vessel;
• they are thinner and lighter;
• have a longer nose.
Drip funnels are usually included in the finished laboratory reactor as part of the kit. Attach them to the reaction vessel on a grinding joint, if any, or with a cork or rubber stopper.
Liquid from the dropping funnel flows down into the reaction flask, provided the device is open. In reactions when the liquid must be isolated from the external environment, the dropping device is closed with a stopper. In these cases, a pressure balancing model is used, which is achieved by a side tube on the separating funnel. This type of device is needed if the chemical process takes place under vacuum or reduced pressure.
A liquid reagent from a dosing tank or funnel is fed into the reactor through a glass tube, sometimes a Teflon tube is used instead. Initially, the liquid is loaded into the fixture using a vacuum.
Types of reaction tanks for laboratory chemical reactors
Reactors, from the point of view of heat exchange, aredivided into three types: without a jacket, with one or with two. The shirt is a little larger than the reaction vessel, the container in which it is placed. A smooth steel jacket can be welded to the reaction flask, glass is fixed in another way. The main purpose is to carry out heat exchange: heating or cooling, as well as maintaining a constant temperature.
Industrial reactors are:
• with dents;
• frame shirts.
For chemical laboratory reactors, such designs are usually not used.
Types of laboratory reactor vessels
Classic with shirt
The temperature regime is provided by supplying a heat carrier with a given rate of a certain t. A conventional smooth jacket is effective when the speed of movement in the heat exchange layer has little effect on heat transfer, for example, when heating with steam. When using a liquid coolant, a spiral is welded to the metal reactors to increase the speed of its movement. Laboratory or industrial thermostats are often used with glass.
Double (vacuum) jacketed
At especially low negative temperatures, three-walled reactors with two jackets are used. Coolant circulates inside the first, and the second creates an additional barrier to the external environment, thereby reducing heat loss.
Such a laboratory reactor can maintain temperatures from minus 40 ° C to +200 ° C. To obtain lower temperatures, down to minus 90 ° C, additional thermal insulation is used.
Units with triple walls can have both laboratory (on thin sections) and semi-industrial (on flanges) execution.
With shirt and ring baffles
This design is quite rare and is used for particularly accurate temperature maintenance.
Glass ring baffles force the coolant to circulate evenly over the entire area of the tank. High accuracy of maintaining t is achieved due to the increased contact time with the coolant and its distribution over the entire surface without “dead zones”.
The choice and use of a reaction vessel is primarily determined by the temperature at which the reaction is to proceed and the importance of maintaining it accurately.
• Vessels without jackets are used when it is not necessary to maintain a certain temperature of the reaction mixture.
• Double-wall reactor is used for organic synthesis, distillation, refluxing, polymerization. Wherever it is important to maintain the temperature of the mixture.
• The apparatus with annular baffles is used for applications where very precise temperature control is required, for example, for the oxidation of aromatic hydrocarbons. However, in most cases this quality can be achieved using a good quality thermostat and a “normal” reaction vessel.
• Three-walled laboratory reactors are used more often for low-temperature processes. This design prevents the formation of frost during reactions at low temperatures and allows you to monitor the progress of the reaction.
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