|Title of Invention||
" A PROCESS FOR PACKAGING BITUMEN"
|Abstract||A process for packaging bitumen, in large-volume disposable packaging units for transporting bitumen in cold state, wherein the disposable packaging units arc made of flexible plastic having a melting point of between 20 degrees and 50 degrees centigrade above the bitumen softening point and that, prior to filling in, the bitumen is cooled down nearly to the softening point of the bitumen being processed, a plate heat exchanger (6) is provided for cooling the bitumen, in which the temperature difference between the coolant and bitumen at the heat exchanger exit is between 10 and 25°C, preferably 15 to 25°C. Fig. 1|
|Full Text||The Present invention relates to a process for packaging bitumen.
The invention relates to a process for packaging bitumen, especially road bitumen, in bulk one-way transportation units for the transportation of bitumen in cold state.
The processing of bitumen is very temperature-dependent as bitumen is liquid at higher temperatures and a rigid solid at low temperatures, in between, there is a wide transitional range of physical states, including viscous and pasty states, with viscoelastic bitumen properties highly varying while the physical state changes from solid to liquid.
For the transportation of bitumen over long distances, it is inefficient to use heated trucks for that purpose as this necessitates to permanently keep the bitumen at a temperature above its softening point. Moreover, these haulage cars require extensive safety precautions for protecting the environment as leaking bitumen is a hazard to the environment. With a view to environmental hazards and the high energy consumption for transportation, there has been a trend towards reducing the transportation of bitumen in liquid form.
If bitumen has to be transported over long distances, it is common to pour the bitumen in hot liquid form into sheet metal barrels and allow them to cool down, which are then either cut apart on site just to remove the cold bitumen from them or heated to be poured out in liquid form. Both approaches are unsatisfactory as disposable containers are left as waste material, which are very hard to dispose of because they are polluted with bitumen.
So in the case of special bitumen, e.g. roof and industrial bitumen, there has been a change to packaging bitumen in small units having a capacity of e.g. 30kg, filled in plastic films which are then melted down and processed together with this bitumen These films are put into special moulds which will then receive hot bitumen for solidifying. This procedure is, however, difficult to use for large amounts of bitumen as used m the case of road bitumen since lots of such containers are required in which bitumen can cool down. Moreover, the plastic film customarily used is not applicable for road bitumen owing to its higher softening point.
As large amounts of bitumen are needed particularly in road construction, attempts have been made to find larger packaging units than conventional portable ones. Apart from greater ease of filling in, such larger packaging units have the advantage that the ratio of plastic melted and bitumen is distinctly shifted in favour of bitumen, in comparison with
conventional small packaging units. Large packaging units usually failed because bitumen with its viscoelastic properties cannot be filled into large-volume plastic containers without a great risk that of the plastic material of being melted away or softening to such a degree that they will lose their stability of shape and the material will expand so that it will start to tear.
It is also already known how to package road bitumen in multilayered plastic bags, which are then melted down with the bitumen. Known packages (U.S. patent 5,452,800 A) are small units where nothing is written in this publication about the type of filling or special filling parameters. Such small packages are efficient only for packaging minor amounts, as packaging and transporting major bitumen amounts requires relatively large amounts of packaging material. In addition, there is a considerable portion of packaging material in the bitumen after melting.
When bitumen is processed, it should be basically taken into account that it has no definite melting point, but rather a wide thermal range of transition from solid via pasty to viscous and finally liquid states, which, as mentioned initially, makes the viscoelastic properties of bitumen highly temperature-dependent
This invention is based on the task of creating a process of the type mentioned at the beginning where a package may be selected also for large amounts of bitumen that can be melted down with the bitumen without.adversely affecting the quality of bitumen.
In accordance with this invention, the task is accomplished by making the disposable packaging units of flexible plastic having a melting point of between 20 degrees and 50 degrees above the bitumen softening point and, prior to filling in, cooling the bitumen down nearly to the softening point of the bitumen being processed. This causes the bitumen to be in a state where it is already viscous, but can still be pumped. In this state, bitumen quickly cools on contact with the cold plastic external layer, which is a good thermal conductor and causes the bitumen to quickly assume the ambient temperature, this results in a layer of bitumen already cooled down directly next to the plastic film. In this way, the disposable packaging unit is not damaged, on the one hand, and the bitumen rapidly forms a stable body at the side after it was filled into the cold packaging material, on the other hand. In its interior, bitumen is left to cool down slowly.
In road construction, bitumen qualities having different softening points RaB ranging between 45 degrees centigrade and a maximum of 60 degrees centigrade is usually used,
which are commonly stored in liquid state at about 140 to 160°C. Each quality of bitumen used is cooled down to an exactly specified filling temperature defined for each respective actual softening temperature where the bitumen is already viscous, but is still pumpable. IVtoreover, there is a clear relation between the melting temperature of the plastic material used for packaging and the processing temperature or softening point of the bitumen to be processed, where abiding by this relation of plastic material melting temperature and the temperature of the bitumen pumped in enables the desired effect regarding "cooling down" to be achieved by means of bitumen for protecting the packaging unit.
Packaging material is typically selected from a range of plastics melting at 115°C to 130°C and, at filling-in temperature, still being sufficiently dimensionally stable for receiving the bitumen without being deteriorated. When a plastic material is selected, it also has to be considered that it will completely melt at the conventional processing temperature, so at about 140 to 160°C without leaving any fibrous residues because this would seriously interfere with further processing.
Bitumen may cool down through thermo-oil which benefits from the fact that the oil temperature can be selected so as to be precisely equal tc the final bitumen temperature and stabilized at this value during processing.
In summary, the advantage of the process according to this invention is that a precisely defined temperature state is present during filling in as the average temperature inside the bitumen mass is kept constant within ±2°C tolerance. The constancy of filling-in temperature for the individual bitumen qualities can thus be maintained throughout the entire filling process typically continuing many days; thus, on the one hand, the risk of inadvertently melting the packaging plastic is minimised and job safety is implemented by using a controlled low temperature; on the other hand, the continuing filling-in is not interrupted by supercooling and thus solidifying the material. This enables economic automated packaging of large volumes (e.g. 50,000 - 100,000 TPA) in large-volume packaging units (about 1m3) to be realized.
In a preferred embodiment for implementing this procedure, a plate heat exchanger is provided for cooling the bitumen where the temperature difference between the cooling medium and bitumen at heat exchanger exit is between 10 degrees and 25 degrees centigrade, preferably 15 to 20 degrees centigrade. The temperature across such a plate heat exchanger can be well be kept constant which allows efficient and rapid temperature adaptation owing to
the large heat transmission area. For thermostatting the late heat exchanger can be equipped with a heating system, e.g. electric heating elements. This can be used as a precaution against the solidification of bitumen inside the heat exchanger during a brief plant standstill, which would entail the complete dismantling of the plate heat exchanger prior to further bitumen processing. Moreover, at the filling head, a return pipe can be provided which branches off near the filling valve and leads back to the storage bin. In this way, bitumen can be continuously circulated even when the filling process is inteirupted and thus prevented from solidifying. The filling head can be kept, through the use of heating elements, particularly electric heating elements, at the filling temperature so that the bitumen present inside the filling head always remains in liquid state and will not solidify even when the filling process stops.
The general layout of the filling plant is shown in the drawing.
1 denotes a storage bin where bitumen is kept at a storage temperature of ca. 140 -160°C using a heating device 2. From the storage bin 1, a feed pump 3 pumps bitumen into the bitumen pipe 5 and, in case no bitumen can be drawn off, bitumen is pumped back into the bin via the return pipe 4. Pipe 5 leads to heat exchanger 6 where bitumen is cooled and then led, via filling pipe 7, to filling head 8. Bitumen is filled through filling head 8 into the containers 9 for transportation.
Through a coolant circulation pipe 10, the heat exchanger is charged by pump 11 with a coolant, in this case thermo-oil, the temperature of which is kept at the desired value by means of cooler 12, with the temperature difference between coolant and bitumen at heat exchanger exit being between 10 and 25°C, preferably between 15 and 20°C.
13 denotes a transportation container in empty state prior to filling and 14 a filled container after filling. The temperature of the whole plant is monitored using conventional thermocouples and controlled by a centralized computer. The thermocouples and the control computer are not shown in this representation.
Filling is done under electronic control through filling valves on filling scales. A
special suspension arrangement for accommodating the ears of disposable transportation units
is provide on pallete particularaly steel pallet Disposable transportation units are supported
by means of the holding device until the bitumen sufficiently stable and doed not require
support any more The filled containers 14 are then parked at a coverd but well ventilated
place to allow the bitumen to cool down to ambient temperature also mside. As bitumen is a good insulator, the cooling time may be between 4 and 7 days, depending on the ambient temperature, for containers having a capacity of about 1 cubic metre.
The containers filled in this way can then be conventionally transported by rail, ship or truck without any thermostatting device and, on site, can be melted down together with the disposable packaging and processed further.
1. A process for packaging bitumen, in large-volume disposable packaging
units for transporting bitumen in cold state, wherein the disposable packaging
units are made of flexible plastic having a melting point of between 20 degrees
and 50 degrees centigrade above the bitumen softening point and that, prior to
filling in, the bitumen is cooled down nearly to the softening point of the
bitumen being processed, characterised in that a plate heat exchanger (6) is
provided for cooling the bitumen, in which the temperature difference between
the coolant and bitumen at the heat exchanger exit is between 10 and 25°C,
preferably 15 to 25°C.
2. A process as claimed in claim 1, wherein that the bitumen is cooled in heat exchange against thermo-oil.
3. A process as claimed in claim 1, wherein the plate heat exchanger (6) is provided with a heating device (2), electric heating elements for thermostatting.
4. A process as claimed in claim 1, wherein on the filling head (8), a return pipe (4) is provided that branches off near the filling valve and leads back to the storage bin.
5. A process as claimed in claim 1, wherein the filling head (8) is kept at a constant filling temperature through the use of heating elements, particularly electric heating elements.
|Indian Patent Application Number||2123/DELNP/2005|
|PG Journal Number||52/2010|
|Date of Filing||18-May-2005|
|Name of Patentee||BITUMEN APPLIED RESEARCH LIMITED|
|Applicant Address||147/1 ST. LUCIA STREET, VALLETTA, MALTA,|
|PCT International Classification Number||B65B 63/05|
|PCT International Application Number||PCT/AT2003/000347|
|PCT International Filing date||2003-11-19|