Distillation: processes – separatory – With measuring – testing or inspecting – Of temperature or pressure
Patent
1996-07-08
1999-11-02
Cain, Edward J.
Distillation: processes, separatory
With measuring, testing or inspecting
Of temperature or pressure
B01D 342
Patent
active
059763230
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to a method and a device for automatic control of a distillation or condensation apparatus comprising a boiling vessel, a heating device, and a condenser.
When a solution or suspension is heated or distilled by refluxing a mixture is heated to boiling in a reaction flask above a heating device, e.g. a magnetic stirrer with heating device, a heating mantle, an electric hot plate or the like. The vapour generated in this process is condensed in a cooling device which is flown through by a cooling agent and collected in a receiver flask in case of a distillation. While reflux-heating the vapour or gas just condenses and runs back into the reaction flask.
A chemical reaction can be run at a constant temperature with the latter process.
In most cases, a temperature sensor integrated in the heating device is used to monitor the temperature. Advanced magnetic stirrers with heating device are equipped with an extra thermometer for exact temperature stabilization of the mixture to be stirred. This may be either a mercury contact thermometer or a semiconductor-rsp. resistance-based thermometer that points directly into the mixture to be stirred or into the heating bath surrounding the reaction flask. This thermometer can be connected to the electronic circuitry of the magnetic stirrer by a plug-and-socket connection.
Distillation or condensation devices such as Liebig condensers, downflow reflux condensers or Allihn, Friedrichs, Graham, and Dimroth condensers are regularly connected to a cooling water feed valve by tubing while the cooling water that passes through the condenser is directly discharged into the sink through another piece of tubing. The appropriate flow of cooling water is adjusted manually to match the size of the condenser. The amount of drinking water consumed varies from 0.6 l/min to an excess of 3 l/min depending on the size of the condenser used.
Safety questions are another aspect to be considered in addition to the high consumption of drinking water. In many cases, in particular by inexperienced experimenters, only an insufficient amount of cooling water is supplied. This has resulted in explosions and laboratory fires causing severe personal injury and material damage.
One problem frequently occuring in this regard is swelling of seals of the usually available cooling water feed valves. This gradually decreases the net flow so that the cooling water supply may be sometimes insuffincient. No help as well are so-called "water flow controllers" which scan a rotating ball in a flow indicator optically and turn out the heating device connected to the condenser when the cooling agent flow is disturbed or drops below a variable value (e.g. 1 pulse/s). This known facility may help to prevent many accidents. However, it is unsatisfactory from an ecological point of view as the cooling water continues to flow.
Furthermore, it doesn't prevent water damages resulting from defect tubings. Moreover, swelling of seals or a temporary pressure drop in the cold water pipes may result in an unnecessary switch-off of the experimental set-up. The latter has been compensated only by setting the cooling water supply to high values which would be unnecessary otherwise.
Also known in laboratory practice are "thermostats" which can be connected with the condensation apparatuses. Thermostats using methanol or other organic solvents such as R134a as a cooling agent have a closed circuit which entails the disadvantage that a heat exchanger is required to facilitate the desired cooling effect.
This results in high energy lose. In addition, these facilities do not have adequate safety devices. They are bulky anyway requiring a major part of the laboratory or production space available.
Leaks which may occur when the condensation devices are inaccurately assembled cause big problems. The solvent evaporates slowly, and the evaporated residue decomposes or is polymerized. Occasionally there are explosions, in particular when the residue tends to form peroxides (e.g. tetrahydrofurane). The s
REFERENCES:
patent: 4344826 (1982-08-01), Smith
Milde Eckhardt
Muller Gunnar
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