WO1994023279A1

WO1994023279A1 - Device for determining the binder content of a bituminous construction material sample

Info

Publication number: WO1994023279A1
Application number: PCT/EP1994/001031
Authority: WO
Inventors: Joachim Hutter; Manfred Pflanz; Franz Laubenthal
Original assignee: Strassentest Acs Baustoff-Prüfsysteme Vertriebs Gmbh
Priority date: 1993-04-07
Filing date: 1994-04-01
Publication date: 1994-10-13
Also published as: AU6564494A; DE9317009U1; DE4491893D2

Abstract

A device for determining the binder content of bituminous construction material samples, in particular asphalts, has a furnace (14, 100) provided with a heating and a sample chamber (56, 58, 105, 112), as well as a weighing device (30, 104) for determining the weight of the sample. In order to check several samples at short intervals, a cold wall furnace which can be controllably cooled is used. In order to obtain reproducible results, it is further provided that the samples are surface heated.

Description

description

Device for determining the binder content of a sample of a bituminous building material

The invention relates to a device for determining the binder content of samples of bituminous building materials by thermal decomposition, in particular of asphalts, comprising an oven which receives a sample, has a closable opening and a weighing device for determining the weight of the sample.

DE 38 08 888 AI or DD 113 407 discloses a method for determining the binder content of bituminous building materials, in particular asphaltene, in which a sample of the building material is weighed, the binder is removed from the sample, the sample is weighed again and the binder content is selected the weight loss of the sample due to the removal of the binder. In order to ensure that the samples with relatively large masses can be analyzed with comparatively little expenditure of time, the binder is removed from the sample by its thermal degradation. The samples can be placed in an oven, which is connected via a hanger to a scale below the oven for continuous weight measurement (EP 0 333 063 A2).

A method and a device for determining the weight ratios of the assembled components of asphalt are described in DE-OS 2 107 058. Bitumen is separated using solvents.

The present invention is based on the problem of providing a device of the type mentioned at the beginning, with the aid of which the binder content is very precise can be determined, while at the same time ensuring that different samples can be tested within short time units. At the same time, errors caused by equipment in particular are to be eliminated.

According to the invention, the task is among others solved in that the oven has at least one controllable coolable outer jacket (cold wall oven). In this case, the heater, which heats the surface of the specimen, is preferably arranged in the cold-wall furnace, at least above the surface of the specimen receiving the specimen.

Due to the cold-wall furnace, the teaching according to the invention enables structurally simple measures to be used to evaluate samples one after the other in short time intervals. Reproducible results are also ensured, in particular, by the fact that a spatially uniform temperature field is generated in the sample material itself by the areal effective heating.

In particular, it is provided that there is a clear distance X between the surface of the sample and the facing flat heater, which is approximately 1.5 to 5 times the sample layer thickness. The clear distance X can be approximately 50-100 mm.

Furthermore, the invention is characterized in that the supply of the reaction gases (combustion air) as well as the removal of the gaseous reaction products takes place via a transverse flow in the head region of the furnace, that is to say above the sample material. This results in an equalization of the reaction conditions. The air supply during the heating of the samples is preferably regulated in such a way that ignition of the combustible gases formed during the thermal decomposition is prevented.

The sample itself is preferably distributed flat on a sieve insert of the sample holder and covered on the outside with a cover sieve.

To load and unload the sample holder, it can be decoupled from the weighing system using a mechanical system and pulled out of the furnace chamber horizontally using a guide become. For this purpose, the furnace has a closable opening in a side wall or a side wall itself can be designed as a closure opening.

Alternatively, it is possible to close the furnace with a hinged lid or a lid that can be raised.

The sample temperature is continuously measured by temperature measuring points in the sample or by representative measuring positions on the sample holder in order to be able to provide sufficiently reliable information about the relevant temperatures of the sample or the sample material.

In an embodiment of the invention, the sample receptacle can be designed as a cup-shaped sample container, in which at least one sample dish or a plurality of sample dishes spaced apart from one another can be introduced, which in turn run at a distance from the inner wall of the sample container.

In particular, however, it is provided that the sample holder is designed as a sieve set, which consists of a closed bottom, several sieves of different mesh sizes and empty rings running between them, which are provided with perforations on the circumference in order to improve the ventilation during the combustion process. The parts are plugged into each other and are transported using a bracket that is pushed into tabs on the floor.

In an embodiment of the invention to be observed, this includes e.g. Weighing device on the underside of the oven has an adapter which can be spaced apart from the weighing cell of the weighing device and in turn can be connected to the carrier element like a stamp. This results in the possibility that, in the absence of an active connection between the adapter and the load cell, the former can be set in vibration in such a way that the sample holder undergoes a shaking movement. This can significantly reduce the analysis time.

In order to generate corresponding vibrations, an oscillating device is provided which comprises an oscillating magnet with a lifting cylinder, which is mounted elastically relative to the furnace or a frame receiving the latter, and that the lifting cylinder is indirect or is directly connected to the adapter. The lifting cylinder passes through a base plate that receives the load cell, which in turn is preferably arranged centrally. As a result, the carrier element penetrates the furnace floor itself centrally.

In order to provide combustion gases to a sufficient extent, a gas distribution element can be provided which starts from the inside of the head of the furnace and is preferably designed as a gas distribution ring. There may be an excess supply of combustion gases to accelerate the thermal decomposition of the binder.

In order to ensure that when the flue gases are removed, sample particles, which may be in the form of dust, are not whirled up and / or sucked away, a further development of the invention provides that the interior of the oven is connected via a bypass to a flue gas duct which emanates from a flue gas blower.

The cold wall furnace itself has a double jacket, to the interior of which at least one or more cooling fans are connected. The cooling fans are preferably operated in suction mode.

Instead of flat heaters above or below the sample surface, resistance elements, preferably in the form of a meander heater, can be arranged concentrically around the inner wall of the furnace. In order to reduce the radiation to the outside of the furnace, a circumferential radiant panel is provided within the double jacket.

Further details, advantages and features of the invention result not only from the claims, the features to be extracted from them - individually and / or in combination - but also from the following description of a preferred exemplary embodiment which can be seen from the drawing.

Show it:

1 shows a section through a first embodiment of a thermal analysis device intended for bituminous building materials, 2 shows a section through the thermal analysis device according to FIG. 1 along the line BB,

3 shows a section through the thermal analysis device according to FIG. 2 along the line C -

C,

4 shows a second, preferred embodiment of an arrangement for binder

Thermal analysis and

4a-4b variants of the embodiment of FIG. 4th

1 to 3 show various sectional representations of a first embodiment of a thermal analysis device (10) for determining the binder content of bituminous building materials, in particular asphalt. The weight of the sample should be tracked during the thermal degradation of the originally present binder or the initial weight of a pre-dried sample and its weight after the thermal decomposition of the binder should be determined.

The thermal analysis device (10) comprises a housing (12), in the center of which a cold wall oven (14) is arranged, in which the samples (not shown) are introduced and their weight or weight changes during the thermal decomposition of the binders are to be determined.

The cold wall furnace (14) of cylindrical shape comprises an inner wall (16) and an outer wall (18) which delimit an annular space to which cooling fans (20) and (22) are connected in order to allow the cold wall furnace (14 ) ensure. The cooling air flows out through an exhaust pipe (24).

A circumferential radiant panel (26) is arranged in the annular space formed by the inner and outer walls (16) or (18), around which radiation from a resistance element in the form of a meandering heater (28) arranged along the inner wall (16) enters the interior of the oven (14) to reflect. In order to be able to determine or continuously track the weight of the sample, a load cell (30) is provided, which is arranged below the furnace (14). The load cell is attached to a holding plate (32), which in turn starts from an oven frame (34). Above the load cell (30) there is also a holder (36) which can be pushed through by an adapter (38) which acts on the load cell (30) to determine the weight. The adapter (38) can be spaced apart from the load cell (30) by means of a lifting frame (40) so that the oscillating or vibrating movement caused by an oscillating magnet (50) cannot be transmitted to the load cell (30).

The lifting cylinder (42) is mounted in a plate (44) which is connected to a base plate (48) of the furnace frame (34) via elastic spacer elements (46). An electromagnet (50) emanates from the base plate (48), via which the lifting cylinder (42) is set in vibration.

A carrier element or pin (52) extends from the adapter (38) and passes through the bottom (54) of the furnace (14) centrally and carries a sample container (56) in which an embodiment example has several sample trays (59) spaced apart from one another. are arranged to accommodate the samples to be analyzed. The sample trays (59) are, on the one hand, spaced apart from one another in the sample tray container and, on the other hand, also run at a distance from the inner wall thereof. The sample container (56) is open on the furnace lid side.

The sample container (56) preferably consists of a closed bottom surface and sieves of different mesh sizes arranged one above the other, which enable a pre-classification. There are empty rings between the sieves, the peripheral walls of which have openings to improve the combustion process. The sample container is closed on the lid side with a close-meshed mesh to prevent it from jumping out or being sucked off with sample particles.

The furnace (14) has a cover (58) which comprises a radiant panel (60) and an insulating plate (62) for thermal insulation. In order to keep the lid (58) in the open position, a gas spring (64) is also provided. In order to introduce the necessary combustion gases into the interior of the furnace, a gas distributor device (66) is provided, which starts from the cover (58) and is designed in a ring shape. The gas distributor device (66) is to be connected to compressed air via a line (68) via a coupling (70). In the compressed air line (68) there is also a shut-off valve (72) and a variable area compressed air meter (74) which is intended to regulate the supply of combustion air via the air distribution device (66). Preferably there should be an excess supply of combustion gases in the furnace (14).

In order to remove the flue gases from the oven (14) without the risk that sample particles are also sucked off, a connection, a so-called bypass (76), emanates from the inside of the oven and opens into a channel (78) that leads from one Flue gas fan (80) goes out.

Thermocouples (82) and (84) are provided to determine the temperature both inside and outside the furnace (14).

Measuring and display devices, by means of which the weight of the samples are determined or ascertained, are arranged on the housing (12), in the exemplary embodiment a monitor (86), a computer (88), a printer (90) and a control unit with a temperature controller (92) and a main switch (94).

The cover (58) can be locked via an electromagnetic door closer (94). A limit switch (96) is also arranged, which interrupts the power supply for the meander heating when the cover (58) is open.

Because the furnace (14) is designed as a cold-wall furnace, several samples can be analyzed in a short time sequence. The samples themselves can be easily removed from the oven (14) because the load cell (30) is not a hindrance. Because of the possibility of decoupling between the load cell and the punch (52) which penetrates the furnace floor (54) and which holds the sample pan container (46), there is also the possibility that the samples are subjected to a shaking movement, whereby the thermal decomposition of the binder can be accelerated.

The entire thermal analysis device (10) has a compact structure and can be connected with the exhaust pipes (24) and (78) to a stationary or also to a mobile filter device which could be flanged to the housing (12).

4, 4a and 4b show, purely schematically, an arrangement for binder thermal analysis that is particularly noteworthy and has its own inventive character, and the associated peripheral units are shown purely schematically. The centerpiece of the arrangement is a cold-wall flat oven (100), which - according to the exemplary embodiment in FIGS. 1 to 3 - is penetrated on the bottom by a coupling rod (102) via which a connection between a weighing device (104) is located below the bottom (100) is arranged, and a cup-shaped sample holder (106) is produced. The weighing device (104) can be lowered via a lifting device (108) so that the sample holder (106) is decoupled.

Alternatively, there would be the possibility of arranging a weighing device laterally, so that weighing beams are guided through at least one side wall.

A sample tray (110) can be introduced within the sample holder (106), which is designed as a sieve insert and runs at a distance from the bottom surface of the sample holder (106).

The sample to be analyzed is spread over the bottom surface of the sieve insert. The sieve insert (110) is covered by a further sieve (112).

1 to 3, the cold-wall flat furnace (100) according to FIG. 4 can be closed or opened via a closure element (114) provided in a side wall, the closure element (114) with the sample holder (106 ) can be connected in order - as the right part of FIG. 4 illustrates - to be able to pull the closure (114) together with the sample holder (106) via horizontally extending guides. In this way it is easy to remove or insert the sieve insert (110) possible in the sample holder (106).

According to the variants of FIGS. 4a and 4b, it is provided to close the furnace with a hinged cover (FIG. 4a) or a cover that can be raised or lowered as a unit (FIG. 4b).

In order to ensure a spatially uniform temperature field in the sample, at least above the sample holder (106) a heater (116) e.g. arranged in the form of radiant heaters, which are surrounded by reflectors facing away from the sample. If necessary, a corresponding surface heating (118) can also be provided below the sample holder (106).

The reaction gases are led via a cross flow above the sample from an inlet (120) to a flue gas outlet (122), from which the flue gas or the gaseous reaction products are sucked off by a fan (126) via a filter (124) and e.g. then, if necessary, be released into the environment via a further filter device. The air supply during the heating of the sample is preferably regulated in such a way that ignition of the combustible gases formed during the thermal decomposition is prevented.

The temperature inside the oven (100) is monitored e.g. Via temperature measuring points (120) which are in the sample or through representative measuring positions on the sample holder (106) or inside the furnace. A corresponding measuring point is identified by way of example with the reference symbol (128).

The cold-wall flat furnace (100) is - according to the embodiment of FIGS. 1 to 3 - designed in a double jacket design, with cooling air flowing through the jacket. This is indicated by the dashed lines. The cooling air flowing through the double jacket is fed via a closure flap (130) into the line carrying the flue gas in order to be sucked off via the fan (126).

In order to achieve a fast and homogeneous heating of the sample, the clear distance between the sample surface and the flat or flat radiating heater should be (116) be approximately 1.5 to 5 times the layer thickness of the sample, which in turn should be spread out over the entire area of the sample pan (110). The layer thickness is preferably between 20 and 30 mm and the distance to the heater (116) is between 50 and 100 mm.

Claims

Device for determining the binder content of samples of bituminous building materials by thermal decomposition, in particular of asphalts, comprising an oven (14, 100) which receives a sample (56, 58, 105, 112) and a weighing device (30, 104) ) for determination of the weight of the sample, characterized in that the oven (14, 100) has at least one controllable coolable outer jacket (16, 18) (cold wall oven).

Apparatus according to claim 1, characterized in that in the cold-wall furnace (14, 100) at least above the sample receptacle (56, 58, 106) which receives the sample flatly, the surface heating the sample

Heater (116, 118) is arranged, the heater being arranged areally above and / or below the sample holder.

Device according to claim 1 or 2, characterized in that the furnace is a cold wall flat furnace (100).

Device according to at least one of the preceding claims, characterized in that that in the furnace (100) above the sample holder (106) a reaction gas or exhaust air leading transverse flow is formed.

5. The device according to at least one of the preceding claims, characterized in that a closable opening is formed in a side wall of the furnace (100) or this is or the furnace head can be closed via a pivotable or detachable cover (58), the cover preferably inside an example with a compressed air source (70) connectable gas distributor element (66) such as gas distribution ring.

6. The device according to at least one of the preceding claims, characterized in that the furnace interior is connected via a bypass (76) with a flue gas discharge line (78) having a fan.

7. The device according to at least one of the preceding claims, characterized in that the side wall of the cold wall furnace (14) consists of a double jacket (16, 18), the interior of which is connected at least to a cooling fan (20, 22), which can preferably be operated in suction mode is.

8. The device according to at least one of the preceding claims, characterized in that between the surface of the sample and facing flat heater (116) is a clear distance X, which is approximately 1.5 to 5 times the sample layer thickness, preferably the clear distance X is approximately 50-100 mm.

9. The device according to at least one of the preceding claims, characterized in that that the sample holder comprises a pot-shaped sample container (56, 106) with at least one sample shell (56, 110) which can be arranged therein, the sample shell (58, 106) preferably running at a distance from the inner wall of the sample container.

10. The device according to at least one of the preceding claims, characterized in that the sample container consists of sieves of different mesh sizes arranged one above the other, which are spaced apart by perforations having empty rings.

11. The device according to at least one of the preceding claims, characterized in that a circumferential blasting element such as radiant sheet (26) is arranged within the annular space surrounding the double jacket (16, 18) of the cold wall furnace (14).

12. The device according to at least one of the preceding claims, characterized in that the oven (14, 100) has at least one controllable coolable outer jacket (16, 18) (cold wall oven) that in the cold wall oven (14, 100) at least above the sample the sample heater (116, 118) which heats the sample areally is arranged, the heater being arranged areally above and / or below the sample receptacle that between the surface of the sample and the facing areal heater (116 ) is a clear distance X, which is approximately 1.5 to 5 times the sample layer thickness and that can be supplied to the furnace during the thermal decomposition of the binder to an extent that ignition of gases produced during the decomposition is excluded.