CH637211A5 - Device for isothermic measurement of reaction heat - Google Patents

Description

The invention relates to a device for the isothermal measurement of heat of reaction and in particular to a device in which heat of reaction can be measured at constant temperatures.

Isothermal calorimeters have already been recommended and used to determine the heat during reactions.

Such a system (see «Chemical apparatus», Vol. 91 (1967), pages 915-921) consists of a reaction vessel and a heat expansion vessel, between which a heat exchange liquid circulates, which is kept at temperature in the heat expansion vessel. For use, when the heat exchange fluid flows around the reactor and a thermal equilibrium of the system has been reached, the reactor is provided with the reagents of the chemical reaction to be checked.

The temperature of the circulating liquid flowing around the reactor is automatically monitored and any change in heat of the liquid is continuously compensated for and maintained, so that the reaction and the entire system can be kept under isothermal, constant conditions. With the help of the automatically monitored and registered temperatures and flow velocities of the circulating liquid, it is possible to record the degree of heat compensation in relation to the reaction time, the amounts of heat compensation being in the opposite sense to the heat of reaction.

However, such systems have the disadvantage that they do not provide correct records of the development of the chemical reaction to be investigated, because the system is based only on the principle of maintaining a thermal equilibrium which, as it turns out, cannot always be achieved.

In this regard it is important that good heat exchange can take place between the reactor and the circulating solution circulating around it. Although better heat exchange could be achieved by circulating the heat exchange liquid at a sufficiently high speed, the high circulation speeds result in very small differences between the temperature of the incoming and outgoing liquid, which results in large experimental errors in the automatic monitoring of this temperature difference.

The aim of the invention is now to reduce the disadvantages mentioned above. The invention relates to a Vorrich2

device for the isothermal measurement of heat of reaction, which consists of a calorimeter, in the form of a reaction vessel which is provided with a jacket which contains a heat exchange liquid which can flow around the vessel via a first and second circuit, characterized in that the first circuit is set up for a relatively slow circulation of the heat exchange liquid through a heat expansion vessel in order to compensate for the heat gained or lost during the reaction, and the second circuit is designed for a relatively faster circulation of the heat exchange liquid through the jacket.

The first circuit is advantageously bridged by the second. In practice, this means that the flow rate of the heat exchange fluid in the first circuit is in the 15 order of 10 to 500 liters per hour, mainly in the order of 50 to 200 liters and particularly advantageously around 100 liters per hour.

The flow rate of the second heat exchange fluid is generally 10 to 30 times greater than that of the first circuit, in practice the flow rate of the second circuit is of the order of 500 to 5,000 liters per hour, mainly between 1,000 and 3,000 liters per hour and advantageous by about 2,000 liters per hour.

In the preferred form of the calorimeter system of the invention, the reaction vessel and the envelope for the circulating heat exchange fluid are assembled, i.e. that the cavity in the jacket provided for the circulation of the heat exchange liquid is open to the inside and that the reaction vessel and jacket are assembled in such a way that this cavity is closed inwards by the outer wall of the reaction vessel. The cavity should be as narrow as possible.

Furthermore, the calorimeter should be in the form of a Dewar-Fla-35 see, i.e. the envelope provided for the circuit is double-walled with a hermetically sealed and evacuated space between the walls.

In particular, the incoming and outgoing liquids to the first circuit are advantageously in contact with a second circuit assembled therewith.

In the event that chemical reactions have to be carried out under reflux cooling, the vessel provided for the chemical reaction is provided with a reflux cooler, in such a way that the temperature and the flow rate of the incoming and outgoing coolant can be regulated automatically.

When using the calorimetric system according to the invention, all temperature measurements are advantageously carried out using temperature measuring devices which emit electrical temperature signals, e.g. with resistance thermometer or with heat probes.

Furthermore, the device is advantageously used in combination with a data processing device which measures the incoming data of the various temperatures in writing 55 and records written records of incoming and / or process-related information.

A particular embodiment of the invention is described below - with reference to the accompanying drawing, which shows a schematic representation of a device for isothermal measurement of heat of reaction.

The device for the isothermal measurement of heat of reaction, which is recorded in the accompanying drawing, consists of a calorimeter (1), a first heat exchange stream (2) and a second heat exchange stream (3). 65 The calorimeter (1) consists of a chemical reaction vessel (la) assembled with a casing (lb), which enables the exchange of heat, being between the reaction vessel (la) and the casing (lb)

637 211

there is a narrow cavity (le), which is ring-shaped in cross-section and allows the circulation fluids to flow through.

The casing is double-walled, which makes it possible to create a hermetically sealed and evacuated cavity between the walls in order to provide good thermal insulation protection.

The calorimeter is also provided with an inlet opening (8) and an outlet opening (9) through which the heat exchange liquid of the second circuit (3) flows in and out, which is connected to the primary circuit (2).

The first circulation system (2) contains a rapidly functioning heat exchanger (4), which contains a cooling device (4a) and a heating device (4b), a flow meter (G) and a counting pump (5).

The circulatory system is equipped or provided with temperature monitoring sensors in the form of thermal resistors (Tx) and T2, which measure the temperatures of the incoming and outgoing circulating liquids, always in relation to the liquids in the casing.

The second circuit (3) contains a powerful centrifugal pump (3a) for high speeds. The chemical conversion system (reactor) is also equipped with a reflux cooler (6), which is connected to a water level indicator, and with automatic temperature monitoring sensors (not shown), in the form of thermal resistors in the inlet and outlet pipes in this system, also with a flow meter. A thermometer (TC) is built in so that every temperature change in the reactor contents is recorded automatically.

A tap (7) is attached to the underside, which enables the reactor vessel to be emptied in a simple manner.

The various measuring devices are connected to a data processing device in which the necessary inputs are programmed and which is able to record the corresponding data in writing.

When the system described above is put into operation, the entire system is started by the circulation of the heat exchange fluid in the first and second heat circulation systems, the speed of the circulation being approximately 100 liters per hour in the first circulation system and approximately 2,000 liters per hour in the second circulation system . The reagents are prepared by bringing them to an appropriate temperature.

The way in which the reagents are used and in which phase they are to be used naturally depend on the type of reaction.

In most cases, the reaction solution and a

Reagent is added to the reaction vessel while the other is kept on standby, stirring the contents of the reaction vessel well. Once the system has reached thermal equilibrium, e.g. If the temperature recorders at (Tj) and T2) show the same temperature and the temperature remains constant, the prepared second reagent is added, and the various parameters are then automatically monitored and recorded from the beginning.

During the reaction, any heat, whether developed or absorbed, is immediately absorbed or compensated for. This is done with the help of the rapidly flowing liquid in the heat exchange jacket, which for the most part flows through the second circulatory system.

At the same time, circulation solution 15 is branched off relatively slowly through the first circuit with the aid of a measuring pump (5), the original temperature being set and monitored automatically at (T2). The solution then flows through the heat exchanger (4) in order to bring the temperature back to the original value, and in order to maintain the isothermal conditions, the temperature of the heat exchange liquid which flows back to the enveloping vessel is automatically at the point (T. ,) set and monitored.

25 The heat exchanger (4) works by first automatically changing the heat exchange liquid, e.g. is cooled to 10-15 ° C in the cooling device (4a) and then the temperature of the cooled liquid is brought to the originally set temperature equilibrium value with the help of the fast functioning heating device.

The separate cooling circulation system for the reflux cooler works according to known methods, the temperature of the inlet and outlet cooling system being automatically set, regulated and monitored, and the flow speed is also set and monitored automatically.

All automatically recorded information is recorded by a data processing machine, which calculates and at the same time graphically displays the total heat which is required to maintain the entire system at a constant temperature as a function of time.

In a modified embodiment, a measuring counter pump is used, which works with a constant flow rate, so that the use of a flow meter (G) is unnecessary.

45 With the measuring counter pump the flow rate of the solution can be calibrated (adjusted) so that the amount of the pumped solution can be measured over a given period of time.

C.

1 sheet of drawings

Claims (3)

637 211 o PATENT CLAIMS 1. Device for the isothermal measurement of heat of reaction, which consists of a calorimeter, in the form of a reaction vessel which is provided with a jacket which contains a heat exchange liquid which can flow around the vessel via a first and second circuit, characterized in that the first circuit is designed for a relatively slow circulation of the heat exchange liquid through a heat compensation vessel in order to compensate for the heat gained or lost during the reaction, and the second circuit is set up for a relatively faster circulation of the heat exchange liquid through the jacket. 2. Device for the isothermal measurement of heat of reaction according to claim 1, characterized in that the second circuit bridges the first. 3. Device for the isothermal measurement of heat of reaction according to claim 1, characterized in that the cavity provided for the circulation of the heat exchange liquid in the jacket is open to the inside and that the reaction vessel and jacket are assembled such that this cavity inwards through the outer wall of the Reaction vessel is complete.