GB2089507A

GB2089507A - A Combustion Calorimeter

Info

Publication number: GB2089507A
Application number: GB8133677A
Authority: GB
Original assignee: MORAT KG FRANZ
Current assignee: MORAT KG FRANZ
Priority date: 1980-11-11
Filing date: 1981-11-09
Publication date: 1982-06-23
Also published as: JPS57156547A; DE3042496A1; FR2495323B1; FR2495323A1; CH654927A5; GB2089507B

Abstract

A combustion calorimeter comprises a pressure-resistant pressure vessel or tank (10), a combustion vessel (11) of a corrosion resistant material, an oxygen supply and combustion gas discharge pipe (19) extending into the combustion vessel, and a valve (22,38) connected into said line and serving to control the oxygen supply or the combustion gas discharge (exhaust), respectively. For the ignition of a sample in the vessel (11) hot-wire 33 is provided. Electric power to the wire is supplied through the pipe (19) or through a valve control element (31) passing through the pipe. The other end of the wire is connected to the vessel 11. With this arrangement only one aperture in the pressure vessel 10 is required. <IMAGE>

Description

SPECIFICATION A Combustion Calorveter The present invention relates to a combustion calorimeter, comprising a pressure-resistant pressure vessel or tank, a combustion vessel made of a corrosion resistant material and adapted to be placed into said tank, an oxygen supply and combustion gas discharge line extending into the combustion vessel, and a valve connected into said line and serving to control the oxygen supply or the combustion gas discharge (exhaust), respectively.

The measurement or detection of the combustion energy under a constant volume has been known for a long time. The first values were measured by Berthelot already in 1881.

The apparatus technology in the combustion calorimeter field remained almost without any improvement or development for many years.

A significant improvement is the adiabatic calorimeter. Nowadays, the conventional manner of temperature detection by means of a mercury thermometer must be considered critically, because the employment of modern electronics not only facilitates the operation, but primarily also provides for more accurate and reliable operation. The troublesome test preparations of the present commercially available instruments no longer satisfy the advanced requirements or standards. A particular drawback of the conventional method can be found when it is necessary, owing to the inhomogeneities of material or for similar reasons, to repeadedly perform the measurements with statistic evaluation (analysis).

Recently, the combustion calorimetry has found novel and interesting fields of application, such as, for instance, the ecology or studies regarding the photosynthesis, such that, to a certain degree, it may be spoken of a revival of the classical method.

Now, the inventor made it his object to provide a calorimeter whichallows performance of a completely automatic measuring or detection operation in which only the sample to be measured has to be inserted (manually), such that this calorimeter may be operated or handled in an extremely easy manner. In particular, the present invention is intended to provide a constructional solution which is as simple and uncomplicated as possible.

According to the present invention, this object is solved in that a glow wire or hot-wire adapted to be connected to a power source is provided to ignite a sample interiorly of said combustion vessel, and that power may be supplied through the oxygen supply and combustion gas discharge line or through a valve control element passing through said line.

The calorimeter according to the invention is safe in operation, easy to operate or handle, and further, has the simplest construction conceivable. Separate electrical current conductors are unnecessary.

The combustion calorimeter according to the invention is handled or operated as follows: The sample to be measured is placed into the combustion vessel, and the latter is thereafter closed with a cover or the like. This closed unit is then placed into the pressure vessel or tank, preferably threaded into the latter. Thereupon, oxygen is introduced into the combustion vessel through an oxygen line opening in the combustion vessel, by turning, for example, an operating knob.

Subsequently, the sample is ignited and burnt.

Completion of the measuring process is indicated preferably by a lighting signal lamp or an acoustic signal. Before a new sample is inserted, the energy of the preceding combustion may be read in Joules on a digital display or the like. After the measuring process, the combustion gases are automatically allowed to escape from the combustion vessel. Still further, the pressure vessel or tank is cooled to its initial temperature.

Upon ignition, the temperature detection instrument is electrically zeroed (temperature difference between the sensors and zero), such that after a completed measuring process the measured value already forms a differential value.

Elimination of the errors caused by heat exchange between the calorimeter and the environment (diathermic process) is performed by an electric correction circuit on the basis of an electric imitation of simulation of the heat exchange, with continuous control of the varying temperature gradient between the calorimeter and the environment, wherein the residual heat of the cover (thread) is detected and-I F NEEDED- used for correction of the measured values. (The heat of said cover may trail or lead with respect to the temperature of the vessel or tank).

Preferred structural further developments of the invention are disclosed in the subclaims.

In the following, the present invention is explained in greater detail by referring to an embodiment illustrated schematically in the enclosed drawing. The figure shows a sectional view of a combustion calorimeter.

Numeral 10 designates a pressure-resistant pressure vessel or tank. A relatively thin-walled combustion vessel 11 made of a corrosion resistant material is adapted to be placed into this pressure-resistant tank. The combustion vessel 11 has a pot-like configuration. The tank 10 and the combustion vessel 11 inserted therein are adapted to be closed by means of a tank closure 1 5 which may be threaded into the tank, with a sealing ring 28 positioned on the inner periphery of the combustion vessel 11 acting to seal a combustion space or chamber 26 to the exterior.

At the bottom of the combustion vessel 11, a substantially centrally disposed aperture 1 7 is provided. A cylindrical sleeve 20, fixidly and sealingly connected to the bottom 1 6 of the combustion vessel 11, is positioned above this aperture, with a portion 21 of an oxygen supply and exhaust gas discharge exhaust line 19 extending above the bottom 18 of the tank being adapted to be introduced into such sleeve when the combustion vessel 11 is placed into tank 10 or into the vessel reception space of tank 10, respectively. Said line 1 9 and its portion 21 are electrically insulating at least at their interior wall.

Along the inner periphery of the sleeve 20, a sealing ring 30 is disposed, which, when inserted, sealingly engages the outer surface of the line portion 21 extending into the sleeve 20. In this way, the sleeve 20 is sealedly connected with the line portion 21.

Sleeve 20 has disposed therein a valve stem 37 which carries on its upper end a valve body 22. Said valve body 22 seals, together with a valve seat 38, the interior of the sleeve 20 and therefore also the line 1 9 with respect to the combustion chamber 26. With the pressure vessel inserted, the valve stem 37 may be controlled from the exterior by means of a control plunger 31. The control plunger 31 is mounted for reciprocating movement in the oxygen supply and combustion gas discharge line 1 9 in such a manner that a flow passage is defined between the control plunger 31 and the inner wall of the oxygen supply and combustion gas discharge (exhaust) line 19.

The control plunger 31 simultaneously serves as an electrically insulated ignition current terminal or connector. Upward and downward movement of the control plunger 31 is controlled by a pneumatically operated pistoncylinder unit 51. Said unit 51 is divided into two separate chambers 40, 41 by a membrane 42. Each of said chambers may-as desired-be connected via a line 43 and 44, respectively, and via a double valve 12 with a source of oxygen. Thus, the membrane can displace the control plunger 31 for opening and closing the valve 22, 38.

Introduction of oxygen or exhaust of combustion gases, respectively, as well as operation of the pneumatic unit 51 are controlled by the dual valve 12. This valve is actuated by means of an operating control knob. In this way, the entire measuring process may be initiated and terminated by means of a single operating knob.

Positioned above the sleeve 20 is a combustion crucible or pot 23 into which the sample is placed. A glow wire or hot-wire 33 extends above the combustion pot for ignition of the probe in said pot. An electrical connector 34 of the glow wire 33 is connected with a support 52, which is held at the top of the sleeve 20; the sleeve is electrically connected with said combustion vessel 11, and, thus, with the vessel 10. The other electrical connector 35 of the glow wire 33 leads via an electrical isolator 36 into the interior of said support 52 and is electrically connected with the valve body 22 and, thus, via the valve stem 37 with the control plunger 31. Said plunger 31 is connected with an electric wire 39 which leads from the interior of the chamber 41 to the outside of the chamber.

Thermistors or thermocouples 6, 9 are used as temperature sensors. One (9) of which is built into the wall of the vessel 10. The other (6) is built into the wall of the metallic jacket 25. Both thermistors or thermocouples 6, 9 are connected with lines 5 and 8, respectively, which lead to the exterior where they may be connected via terminals 4 and 7 with a measuring and evaluation circuit (not shown). During the measuring the temperature difference between both sensors is detected. Said temperature difference is caused by the combustion of the probe. From said temperature difference the combustion energy or enthalpy of the combustion process may be derived.

The temperature error caused by heat exchange or by probably existing residual heat is corrected by means of control electronics. After a few minutes, the requisite measuring temperature is reached, and the sample is ignited automatically. Completion or termination of the measurement is indicated by the flashing of a not illustrated signal lamp and/or by an acoustic signal. Depending on the required accuracy of the measurement, two (different) measuring or detection periods may be set. Additionally the water 49 may be heated or cooled by a heat exchanger 47 located inside the water. Said heat exchanger 47 is connected via a line 46 with a heat source 48.

Cooling of the tank 10 is effected by supplying cold water 49 to a calorimetric vessel 24. Said vessel 24 surrounds the major part of the outside of the vessel 10. Reference number 45 denotes the water level. Incidentally, the cooling water consumption in the above-described calorimeter is so low that under normal circumstances a continuous cold water supply can be dispensed with. The water continuously circulates in order to avoid any temperature gradients. Said circulation is caused by a stirring apparatus 3 driven via a drive 2 by a motor 1.

The calorimetric vessel 24 is enclosed by a metallic jacket 25, the temperature of which is controlled to be kept constant. Between the metallic jacket 25 and the calorimetric vessel 24 there is air, which may be under vacuum.

For carrying out a measurement, at first a sample is placed into the combustion pot 23, and the combustion vessed is placed into the tank 10.

The tank 10 is then closed by means of the threaded closure 1 5. Then a main (power) switch is turned on, whereupon the measuring temperature control becomes effective. It is intended to bring the whole system into a steady state with respect to its temperatures. It is desired that in this steady state both sensors 6 and 9 have the same temperature. By turning an operating knob to the position "oxygen inlet", the tank or the interior space of the combustion vessel 11, respectively, is charged with oxygen.

The operating knob cooperates with the dual valve 1 2. By turning the operating knob to the next position "measurement", the automatic measuring or detecting process is initiated.

Completion of the measurement is indicated by the flashing of a signal lamp. Valve 22, 38 is then opened by actuating the double valve 12 for allowing the exhaust gases to automatically flow from the combustion chamber. Prior to placing a new sample into the apparatus, the combustion energy-of the preceding measurement-may be read in Joules on a digital display. Then the tank closure 1 5 is unthreaded by means of a socket wrench, and simultaneously the combustion vessel 11 is removed from the tank.

Reference may further be made to the fact that the wall of the combustion vessel 11, when the latter is in its position in the tank 10, snugly contacts the inner wall of tank 10.

The temperature comparison is made along a temperature curve which is normally fully written before the comparison is made.

Conventionally, however, writing or plotting of the temperature curve takes at least approximately 5 to 10 minutes. Therefore, in a particularly advantageous further development or embodiment of the present invention, a microprocessor may be provided which is coupled to the temperature measuring instrument and which, upon starting of the temperature curve, calculates this curve in advance, such that the relatively time-cosuming writing or plotting of the temperature curve may be omitted and the comparison value may be available after a period of only approximately 20 to 30 seconds.

A combustion calorimeter according to the present invention can thus have the following advantages: easy handling or operation extromely low energy and cooling water consumption maximum independence of ambient temperature fully automatic measuring or detection operation ready installation and construction, particularly as far as the hot-wire 33 and its electrical connection are concerned service is simple.

Claims

1. A combustion calorimeter, comprising a pressure-resistant pressure vessel or tank, a combustion vessel made of a corrosion resistant material and adapted to be placed into said tank, an oxygen-supply and combustion-gas discharge line extending into the combustion vessel, and a valve connected into said line and serving to control the oxygen supply or the combustion gas discharge (exhaust) respectively, a glow wire or hot wire adapted to be connected to a power source to ignite a sample interiorly of said combustion vessel, the power being arranged to be supplied through the oxygen supply and combustion gas discharge line or through a valve control element passing through said line.

2. A combustion calorimeter according to claim 1, in which said hot wire is formed of a noble metal.

3. A combustion calorimeter according to claim 1 or 2, in which said tank is inserted into a cooling vessel, or calorimetric vessel, containing a cooling medium, preferably water, wherein the outside of the vessel is continuously surrounded by flowing cooling medium.

4. A combustion calorimeter according to claim 3, in which said calorimetric vessel comprises a closed system which communicates with the environment, such as ambient atmosphere, via one or more vent lines only.

5. A combustion calorimeter according to claim 3 or 4, in which said calorimetric vessel is connected to a cooling medium circuit, whereby a cold medium is introduced into said cooling vessel after a measurement or a combustion of a sample has been performed.

6. A combustion calorimeter according to any one of claims 1 to 5, in which in the bottom of the combustion vessel an aperture is provided, with a sleeve being disposed above said aperture, which sleeve, when the combustion vessel is placed in said tank is adapted to receive a portion of the oxygen supply and combustion gas discharge line extending above the tank bottom into the vessel reception space of said tank, in such a manner that the combustion space or chamber is sealed with respect to the exterior environment.

7. A combustion calorimeter according to claim 6, in which said sleeve has mounted therein a valve which, when said vessel is inserted, is adapted to be controlled from the exterior through said oxygen supply and combustion gas discharge line.

8. A combustion calorimeter according to claim 7, in which said valve is adapted to be controlled by means of a control plunger passing through said oxygen supply and combustion gas discharge line and mounted in said line for reciprocating movement.

9. A combustion calorimeter according to claim 8, in which said control plunger is adapted to be moved by a pneumatically or hydraulically operated piston-cylinder unit.

10. A combustion calorimeter according to claim 1, 8 or 9, in which power is supplied to the hot wire via said control plunger, with said oxygen supply and combustion gas discharge line being formed of an electrically non-conductive material.

11. A combustion calorimeter according to any one or several of claims 1 to 10, in which said valve is of the self-closing and self-opening type, said valve being electrically insulated from said sleeve.

12. A cumbustion calorimeter according to claim 10 or 1 in which power is supplied to said hot wire via said control plunger and the valve cooperating therewith.

1 3. A combustion calorimeter substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.