Rotary evaporator

Rotary evaporator (Figure 22-10) is used to continuously distill a large amount of volatile solvents under reduced pressure, and is widely used in the concentration of reaction extracts and the distillation and concentration of chromatographic separation receivers

(1) Basic principles

The basic principle of the rotary evaporator is thin-film vacuum distillation

Rotary evaporator unit is more than one combination of instruments, comprising a rotation system, a heating system, vacuum system, the condensed water circulation system of FIG.

(Two) use

Follow the instruction manual

(3) Maintenance

(1) Check the instrument carefully before use.

(2) Wipe each interface with a soft cloth (can be replaced by a paper towel), and then apply a little vacuum grease

(3) Each interface should not be screwed too tightly, and should be loosened regularly to avoid long-term locking and causing the connector to seize

(4) Turn on the power switch first, and then let the machine run from slow to fast; when shutting down, keep the machine in a stopped state, and then turn off the switch

(5) Teflon switches everywhere should not be tightened with excessive force, which may damage the glass

(6) After each use, a soft cloth must be used to clean all kinds of oil stains, stains, and residual solvents on the surface of the machine

(7) Loosen the PTFE switches after the machine is stopped, and the PTFE piston will be deformed if it is in the working state for a long time

(8) Clean the sealing ring regularly by removing the sealing ring and checking whether there is dirt on the shaft.

(4) Safety instructions

(1) The glass parts should be handled gently before assembly, and they should be cleaned and wiped or dried before assembly

(2) Each grinding port, sealing surface, sealing ring and joints need to be coated with a layer of vacuum grease before installation, but be careful not to contaminate the product

(3) Water must be added to the water bath before it is energized

(4) Adjust the speed of rotary steaming, and the speed should not be too fast, otherwise the shaft will break easily and the water in the water bath will easily slosh out

(5) Do not concentrate explosive materials
.
A R&D personnel violated the operating specifications of the rotary evaporator and concentrated the azide in the rotary evaporator
.
With a huge muffled noise, the water bath was blown over, and the entire water bath rose and fell into the bucket next to it, as shown in Figure 22-11
.

(6) The water temperature should not be too high to avoid rapid evaporation
.
When the temperature exceeds 80°C, an oil bath should be used instead
.

(7) After adjusting the height of the distillation flask, fix the entire rotating shaft device firmly
.

In addition, the distillation flask and the rotating shaft must be tightly inserted and clamped with stainless steel clamps, otherwise the distillation flask may loosen and fall off due to shaking, and fall into the water bath
.
The distillation flask falls off, the organic solvent enters the water bath to volatilize, the poor contact between the power output of the aviation plug, and the thyristor of the rotary steam speed control plate is broken down to produce sparks are the direct causes of the fire and combustion of the rotary evaporator, see Figure 22-12
.

Figure 22-12 Screenshot of the accident video

(5) Use little common sense

(1) The rotary evaporator is composed of multiple operating systems.
Any system or part of the problem cannot complete the set task.
Once the rotation is not smooth or there are abnormal noises, heating, vacuum and other problems should be repaired in time to prevent it from becoming ill.
Homework
.

(2) Once it is found that the distillation flask has fallen off and the organic solvent has flowed into the pot, it is necessary to immediately turn off the main power source at a distance and replace the water immediately
.
Do not leave it alone, nor close the control switch of the rotary steaming instrument, so as not to cause a fire, because the safety distance is not enough
.
When the nearby space reaches the explosive limit, it will cause a fire triggered by the electric spark in the instrument, as shown in the first fireball in Figure 22-12(b), it can be seen that the organic vapor is sinking
.

(3) If the evaporating flask is not easy to remove, you can use a wooden hammer to gently tap the evaporating flask opening along the inclined direction of the rotating shaft or use a flask ejector to return the evaporating flask, so that the evaporating flask is not only easy and safe to remove, and the rotating shaft is not easy to break
.

(4) When selecting an evaporating flask over 3L, it should be operated at a low speed.
The depth of the evaporating flask should be such that its gravity and buoyancy are balanced to avoid damage to the shaft due to excessive force
.

(5) When the rotary steamer is raised and lowered, the locking device must be released first, and then the lifting shall be carried out, otherwise the operating handle will be easily broken
.

(6) When the rotary evaporator is not in use, remove the filling plug (or bleed plug) to prevent the vacuum grease from drying up and unable to rotate the filling plug
.

(7) When the temperature is lower than 0℃ in winter, empty the water in the condenser coil after work to prevent the condenser from cracking due to water freezing
.

(8) Heat the water bath.
Don’t turn it on from morning to work.
First, it’s difficult to adjust the vacuum balance and easy to flush when feeding.
Second, the room is full of steam, which increases the electrical load and wastes electrical energy, and also increases the indoor temperature.
Especially in summer, the efficiency of air conditioning will be reduced
.

(9) Changing the water in the water bath frequently can prolong the service life of the electric heating tube
.

(10) After using the instrument, unplug the power and clean the exterior
.