The present invention relates to an apparatus for thermally compacting waste material, particularly waste polypropylene in flexible sheet form.

Sheet polypropylene has huge number of uses. One such application is privacy curtains that are used in hospital type environments. Such curtains must be regularly replaced in order to maintain hygiene in the hospital. However, there remains a significant problem in recycling this type of material. A first problem is that sheet material occupies significant volume even when compacted into compressive bags, meaning that it expensive to transport to a location suitable for recycling. Secondly, processing the waste sheet material necessarily involves heating and melting for onward transportation and subsequent repurposing. A significant problem with sheet material, for example polypropylene sheet material is the significant volume occupied by a small weight and the associated difficulty in safely inputting the material into a machine capable of supplying heat sufficient to melt the sheet material. In the event the sheet material is transported in compressive bags, then expansion will occur again causing difficulty in ensuring the sheet material is appropriately loaded into the compaction machine. Furthermore, even when the sheet material is loaded into a compaction machine, the relative weight is low meaning it is difficult to ensure the sheet material enters the heating zone under gravity to effect melting. This has a number of implications. Firstly, processing times are very slow as a significant proportion of the sheet material does not appropriately enter the heating zone. Secondly, portions of the sheet material that contact the heated areas of the heating zone may bum and other areas out of the primary heating zone do not melt. This is a safety hazard and also results in a commercial impractical apparatus and method of processing.

Aspects of the present invention address the above-mentioned problems, or at least provide a useful alternative.

According to a first aspect of the present invention there is a thermal volumetric reduction apparatus for thermally reducing the volume of a polymer, the apparatus comprising a first and second heated plate inclined downwardly towards each other from an upper end to a lower end and provided with a first passage at their lower ends through which melted polymer may drain, and a third and fourth heated plate inclined downwardly towards each other and provided with a second passage at their lower ends through which melted polymer may drain, where an upper end of each of the second and third heated plates cooperate to define an apex.

The first and second plates preferably each comprise a first and second lower edge at their respective lower ends, where the first and second lower edges are preferably aligned to sit in a horizontal plane. The third and fourth plates also preferably each comprise a third and fourth lower edge at their respective lower ends, where the third and fourth lower edges are preferably aligned to sit in a horizontal plane, even more preferably the same horizontal plane of the first and second lower edges.

The first passage has a first passage width opening defined between opposing lower ends (even more preferably edges of the lower ends) of the first and second plate. The second passage has a second passage width opening defined between opposing lower ends (even more preferably edges of the lower ends) of the third and fourth plate. The first passage width opening is beneficially less than 20% of the width of the first or second plate when measured in the same axis. The second passage width opening is beneficially less than 20% of the width of the third or fourth plate when measured in the same axis. It will be appreciated therefore that the width of the passages is significantly less than width of the plates which is important for ensuring the sheet material is melted and does not block the passages.

A benefit associated with such a configuration is that the apex between the second and third heated plates acts as a cutting edge for the polymeric material. This is particularly the case when processing sheet polymeric material, such as sheet polyethylene or polypropylene. Such a configuration means that an increased volume of waste material can be processed at reduced cycles times, particularly waste sheet material such as hospital sheet material. This previously unrecyclable material can now be processed to provide a reusable material for various downstream applications. The heated surfaces are provided by heated plates. The plates may comprise a variety of surface profiles, however it is beneficial that the heated surfaces that contact the polymer to be volumetrically reduced are planar. Each of the first, second, third and fourth heated plate are inclined downwardly at an angle of between 25 degrees and less than 45 degrees relative to a vertical axis, even more preferably between 35 degrees and less than 45 degrees. Each of the heated plates preferably have substantially the same surface area.

The plurality of plates preferably each have one or more heating elements disposed therein. The one or more heating elements of the second and third heated plates are preferably configured such that the temperature profile of the second and third heated surfaces does not decrease from a midpoint between the upper and lower ends towards the upper end. It is beneficial that the volume of heating element increases towards the apex. It has been determined that it is beneficial to at least maintain (or even increase) the temperature of the heated surfaces in operation towards the apex in order to maintain cutting effectiveness. Accordingly, the temperature of the heated surfaces towards the apex is maintained at a more consistent temperature. It has been found that heat is lost more readily from the upper area of the heated surfaces having a detrimental effect on cutting effectiveness, and therefore increasing the volume of heating elements in the second and third heated plates towards the upper ends ensures cutting effectiveness.

It will be appreciated that the apex is a join between the second and third heated plates, and there is beneficially no gap between the second and third heated plates through which melted polymer may drain. The apex is preferably linear.

The apparatus preferably further comprises one or more receivers disposed in a respective one or more receiving zones for receipt of melted polymer material from the first and optionally second passage. The one or more receivers may comprise receptacles for receipt of the melted polymer. There are beneficially first and second receivers disposed in first and second receiving zones beneath the first and second passages respectively. The receivers are beneficially portable and beneficially removable from the apparatus. The apparatus is therefore preferably arranged for the or each receiver to be received into a respective receiving zone and also be removed from the receiving zone. The apparatus preferably further comprises a cooling arrangement arranged to direct cooling gas into communication with the one or more receivers for cooling the molten material.

The or each receiver preferably comprises a base and one or more upstanding side walls and at least a partially open top opposing the base through which molten material is received.

The cooling arrangement is preferably arranged to direct cooling gas from one or more ports.

The one or more ports are preferably arranged such that cooling gas is directed towards the or at least one of the side walls and/or the base of the receptacle.

The receiving zone is preferably defined by a receiving zone base and at least one receiving zone wall upstanding from the receiving zone base, where the one or more ports are provided in the at least one receiving zone wall.

The receptacle and receiving zone are preferably arranged such that there is a cooling gas flow pathway intermediate the at least one receptacle wall and the at least one receiving zone wall, and preferably a further cooling gas flow pathway intermediate the receptacle base and the receiving zone base.

One or more spacers are preferably provided intermediate the receiving zone base and the receptacle base and/or between at least one receptacle wall and the at least one receiving zone wall.

The cooling arrangement preferably comprises a gas (air) compressor and a vortex tube.

Also according to the first aspect there is a method of thermally compacting polymeric materials comprising introducing polymeric material into a heating chamber, the heating chamber comprising a first and second heated surface inclined downwardly towards each other from an upper end to a lower end and provided with a first passage at their lower ends through which melted polymer may drain and the heating chamber further comprising a third and fourth heated surface inclined downwardly towards each other and provided with a second passage at their lower ends through which melted polymer may drain, where an upper end of each of the second and third heated surfaces cooperate to define an apex, and collecting the melted polymer from the first and second passages.

The method is particularly beneficial for thermally compacting polypropylene and/or polyethylene textile materials, preferably in sheet form.

Cooling cycles of known apparatus are long due to the requirement to melt the waste polymer material and subsequently solidify the waste polymer material in order that it can be safely removed from the apparatus by an operator. The cycle time of known apparatus can therefore be long, and it is desirable to reduce this time period. In order to address this, the speed of a fan driving the exhaust gas is typically increased in order to increase airflow to thus accelerate solidification of the molten waste polymer material. Whilst this works to an extent, it is desirable to further reduce cycle times.

According to a second aspect of the present invention there is a thermal volumetric reduction apparatus for thermally reducing the volume of a polymer comprising a heating chamber comprising first and second heated plates inclined downwardly towards each other from an upper end to a lower end and provided with a passage at their lower ends through which melted polymer may drain, the apparatus further comprising a receiver positioned to receive molten polymer from the passage, the apparatus further comprising a cooling arrangement arranged to direct cooling gas into communication with the receiver for cooling the molten polymer.

The receiver, preferably in the form of a receptacle, preferably comprises a base and one or more upstanding side walls and at least a partially open top opposing the base through which molten material is received. The cooling arrangement is preferably arranged to direct cooling gas from one or more ports. The one or more ports are arranged such that cooling gas is directed towards the or at least one of the side walls and/or the base of the receptacle. By directing the cooled gas (air) into contact with the receptacle itself rather than the material to be cooled safety is improved.

The receptacle is preferably removably received into a receiving zone. This means that after each processing cycle the receptacle is removed, the compacted material emptied from the receptacle and finally the receptacle replaced ready for a subsequent cycle.

The receiving zone is preferably defined by a receiving zone base and at least one receiving zone wall upstanding from the receiving zone base. The one or more ports are preferably provided in the at least one receiving zone wall. The receptacle and receiving zone are preferably arranged such that there is a cooling gas flow pathway intermediate the at least one receptacle wall and the at least one receiving zone wall, and preferably a further cooling gas flow pathway intermediate the receptacle base and the receiving zone base. In order to ensure appropriate spacing following positioning of a receptacle into the receiving zone, spacers may be provided intermediate the receiving zone base and the receptacle base and between at least one receptacle wall and the at least one receiving zone wall. Such spacers may for example be provided by projections in the form for example of dimples protruding from the receiving zone base and at least one wall. The provision of spacers in whatever form ensure a minimum spacing between the receptacle and base/wall(s) defining the receiving zone.

The cooling arrangement is preferably arranged to supply cooled air to cool the receptacle. The cooling arrangement preferably comprises a compressor and a vortex tube. Vortex tubes are commercially available and capable of separating an airflow into hot and cold air, where the cold air is directed towards the receptacle. The compressor is arranged to force compressed air into the vortex tube. The heated surfaces are provided by plates. The plates may comprise a variety of surface profiles, however it is beneficial that the heated surfaces that contact the polymer to be volumetrically reduced are planar.

Also according to the second aspect of the present invention there is a method of thermally compacting polymeric material comprising introducing polymeric material into a heating chamber comprising first and second heated surfaces inclined downwardly towards each other from an upper end to a lower end and provided with a passage at their lower ends through which melted polymer may drain, collecting the molten polymeric material from the passage in a receiver and directing cooling gas into communication with the receiver for cooling the molten material.

Further preferred features applicable to both first and second aspects of the present invention will now be described.

The apparatus preferably further comprises an electrostatic precipitator downstream of the melt chamber.

The apparatus preferably further comprises a filter arrangement downstream of the electrostatic precipitator. The filter arrangement preferably comprises a first and second filter, the first filter downstream of the electrostatic precipitator, and the second filter downstream of the first filter. The first filter preferably comprises a bag filter, and the second filter preferably comprises a carbon filter. The bag filter filters any residual oil, moisture and particulate material from smoke, and the carbon filter filters odours.

The passage preferably comprises a longitudinal length and a width, where the width is in the range 15mm to 75mm.

The heated surfaces are each preferably inclined at less than 45 degrees to a vertical axis. The heated surfaces are preferably inclined to a vertical axis of between 25 degrees and less than 45 degrees. The heated surfaces are preferably arranged to be heated to a temperature in the range 250°C to 3 KFC, and more preferably between 275°C and 295°C and even more preferably at substantially 285°C. This temperature is present in operation adjacent the upper ends of the heated plates.

The apparatus preferably further comprises a housing for housing the heated surfaces and the receiver.

Aspects of the present invention will now be described by way of example only with reference to the accompanying Figures where:

Figure 1 is a schematic representation of an apparatus according to an illustrative embodiment of the present invention.

Figure 2a is a schematic cross sectional representation of the heating elements in a plate in plan view of the plate and Figure 2b is a cross sectional representation of the same heating plate at ninety degrees to the viewing direction of Figure 2a according to an illustrative embodiment of the present invention.

Figure 3 is a schematic representation of a perspective view of an illustrative embodiment of the present invention showing the heating chamber in which the heated plates are located.

Figure 4 is a schematic perspective view of an illustrative embodiment of the present invention.

Referring to Figure 1 there is a schematic representation of an illustrative embodiment of the present invention. The apparatus is shown without a door which would be closed during use and hides the internal components provided within the housing 2 and provides a seal for when the apparatus is in use. The housing 2 provides a chamber 3 comprising first, second, third and fourth heated plates 4,6,8,10 therein which are beneficially formed from cast aluminium and are heated by electrical heating elements. A detailed representation of the heating elements in the respective plates is presented in Figure 2.

The first and second plates 4,6 are inclined downwardly relative to one another and the third and fourth plates 8,10 are also inclined downwardly relative to one another. Both pairs of plates are configured to funnel waste material such as molten synthetic polymeric textile material downwardly toward a channel 12 provided between the lower ends of the plates 4, 6 and 8, 10.

An upper end of each of the second and third plates 6,8 providing the second and third heating surfaces cooperate to define an apex 14. The apex 14 between the second and third heated plates acts as a cutting edge for the polymeric material. The apex 14 is a join between the second and third heated surfaces, and there is no gap between the second and third heated surfaces through which melted polymer may drain. The apex is preferably linear. Accordingly, the apex 14 acts as a heated knife for cutting through the polymeric material added for processing and has particular benefit when the material is sheet polymeric material.

It will be appreciated that in the illustrative embodiment four heated plates have been presented, however it will be apparent to the skilled address that additional heated plates may be provided in the same housing thereby providing increased processing capability.

The heated surfaces are provided by plates. The plates may comprise a variety of surface profiles, however it is beneficial that the heated surfaces that contact the polymer to be volumetrically reduced are planar.

The plurality of plates that provide the heated surfaces preferably each have one or more heating elements 20 disposed therein as more clearly shown in Figures 2a and b. The one or more heating elements 20 are configured such that the temperature profile of the heated surfaces does not decrease from a midpoint between the upper and lower ends 22,24 towards the upper end. It is beneficial that the volume of heating element in plates two and three 6,8 at least increases towards the apex 14 as is apparent in Figure 2. It has been determined that it is beneficial to at least maintain (or even increase) the temperature of the heated surfaces in operation towards the apex in order to maintain cutting effectiveness. Accordingly, the temperature of the heated surfaces towards the apex 14 is maintained at a more consistent temperature. It has been found that heat is lost more readily from the upper area of the heated surfaces having a detrimental effect on cutting effectiveness, and therefore increasing the volume of heating elements in the second and third heated plates towards the upper ends 24 ensures cutting effectiveness.

In the examples shown the first and second plates have identical angles relative to the vertical axis. It will be appreciated, however, that the angle of the first and second plates may be different to each other. The incline angle of the heated surfaces to the vertical is beneficially less than 45 degrees and is beneficially in the range 25 degrees to less than 45 degrees. This is to ensure that the material melts and collapses and subsequently flows through the first and second channels 12a and 12b.

Figure 3 is a schematic representation of a perspective view of the chamber 3 showing the heated plates 4,6,8,10 and the apex 14. It will be appreciated to the skilled addressee that the illustrative embodiment has been described with four heated plates. For the purposes of the manner of cooling of the molten material according to the second aspect of the present invention it is not essential to have third and fourth heated plates 8,10, and instead the apparatus may comprise for example first and second heated plates 4,6 only. There could of course be more than four heated plates and the second aspect of the invention is not limited in that regard.

The first and second plates 4,6 each comprise a first and second lower edge 13a, 13b at their respective lower ends, where the first and second lower edges are preferably aligned to sit in a horizontal plane. The third and fourth plates also each comprise a third and fourth lower edge at their respective lower ends, where the third and fourth lower edges are aligned to sit in a horizontal plane, even more preferably the same horizontal plane of the first and second lower edges. The first passage 12a has a first passage width opening defined between opposing lower edges 13a, 13b of the first and second plate. The second passage also has a second passage width opening defined between opposing lower ends (even more preferably edges of the lower ends) of the third and fourth plate. The first passage width opening which is represented by arrow 15 is beneficially less than 20% of the width of the first or second plate when measured in the same axis as represented by arrow 17. The second passage width opening is beneficially less than 20% of the width of the third or fourth plate when measured in the same axis. It will be appreciated therefore that the width of the passages is significantly less than width of the plates which is important for ensuring the sheet material is melted and does not block the passages 12a, 12b. In the embodiment as schematically presented in Figure 1, the passage width openings are approximately 10% of the width of any of the first to fourth plates measured in the same axis. Less than 20% has been found beneficial for the purposes of processing sheet polymeric material.

The apparatus further comprises one or more receivers 26 disposed in a respective one or more receiving zones 28 for receipt of melted polymer material from the first and optionally second passage 12. The one or more receivers 26 may comprise receptacles 28 for receipt of the melted polymer. There are beneficially first and second receivers 26 disposed in first and second receiving zones beneath the first and second passages 12 respectively. The receivers 26, preferably in the form of receptacles, each comprise a base 30 and upstanding opposing side walls 32 and opposing end walls with at least a partially open top opposing the base. Molten material is received through the top.

A cooling arrangement 34 is arranged to direct cooling gas through a duct 36 into communication with the receivers 26 for cooling the molten material via one or more ports 38. The ports 38 in the illustrative embodiment are arranged such that cooling gas is directed towards the end walls of the receptacle 26. By directing the cooled gas (air) into contact with the receptacle itself rather than the material to be cooled safety is improved.

The cooling arrangement 34 supplies cooled air to cool the receptacle walls and may comprise a compressor and a vortex tube. Vortex tubes are commercially available and capable of separating an airflow into hot and cold air, where the cold air is directed towards the receptacle. The compressor is arranged to force compressed air into the vortex tube.

The receptacles 26 are removably received in the receiving zone 28. This means that after each processing cycle the receptacle 26 is removed, the compacted material emptied from the receptacle 26 and finally the receptacle 26 replaced ready for a subsequent cycle.

The receiving zone 28 is defined by a receiving zone base 40 and at least one receiving zone wall 42 upstanding from the receiving zone base. The one or more ports 38 are provided in the receiving zone wall 42. Cooled air is directed from the ports 38 into direct contact with the wall of the receptacle. Furthermore, there is a cooling gas flow pathway 44 intermediate the receptacle walls 32 and the receiving zone walls 42, and a further cooling gas flow pathway 46 intermediate the receptacle base and the receiving zone base. In order to ensure appropriate spacing following positioning of a receptacle into the receiving zone, spacers 48 such as projections are provided to ensure a minimum spacing between the receptacle and base/wall(s) defining the receiving zone.

Referring to Figure 4, the receiving zone 28 is shown without the receiver 26 being present for clarity purposes. Ports 38 are shown in a receiving zone wall 42 configured to direct cool air to the receptacle wall when a receptacle is located into the receiving zone 28.

Use of a vortex tube, beneficially in combination with directing the output towards a wall/base of the receptacle together with the spacing between the receptacle 26 and receiving zone walls/base has been found to be particularly beneficial in the present application for reducing cycles times as effects fast cooling and solidifying of the molten polymer.

Vortex tubes are commercially available devices and are beneficially used in harsh environments as require no moving parts. In the present application this is particularly beneficial due to the requirement for high reliability whilst performing multiple heating and cooling cycles as fast as possible to maximise speed of processing of the material to be compacted. A vortex tube creates cold air and hot air by forcing compressed air through a generation chamber, which spins the air at a high rate of speed (1,000,000 rpm) into a vortex. The high-speed air heats up as it spins along the inner walls of the tube toward the control valve. A percentage of the hot, high speed air is permitted to exit at the valve. The remainder of the (now slower) air stream is forced to counterflow up through the centre of the high-speed air stream in a second vortex. The slower moving air gives up energy in the form of heat and becomes cooled as it spins up the tube. The inside counterflow vortex exits the opposite end as extremely cold air. Vortex tubes generate temperatures as much 56°C) below the inlet air temperature.

Thermocouples are beneficially provided on the heated plates 4,6,8,10 to monitor temperature. Temperature information from the thermocouples is transferred to a control arrangement 50. The control arrangement 50 includes a control panel and serves to control the electrical supply to the heating elements within the heated plates, operation of an exhaust arrangement 52 which includes an electrostatic precipitator 56 and filter arrangement 58, and operation of the cooling arrangement 34.

The exhaust arrangement comprises a fan 54 for drawing hot gas from the chamber 3 via the electrostatic precipitator 56 and filter arrangement 58, where the electrostatic precipitator 56 is downstream of the chamber 3 and filter arrangement 58 is downstream of the electrostatic precipitator. Hot fumes including oil molecules and smoke transfer from the chamber 3 to the electrostatic precipitator 56 where the oil molecules are charged and attracted to collecting plates where they are retained for onward disposal. Particulate matter is also partially removed at this stage. The filter arrangement preferably comprises a first and second filter, the first filter comprising a bag filter and the second filter comprising a carbon filter. The bag filter filters any residual oil, moisture and particulate material from smoke, and the carbon filter filters odours.

The apparatus as hereinbefore described according to either aspects of the invention follows a predetermined operating cycle for effecting fast and safe processing of the waste polymeric material. As a first step, the waste polymeric material is input into the housing 2 through an opening which may be provided in the top or in the side of the housing 2 such that the material falls into contact with the plates 4,6,8,10. This is completed at ambient temperature. The apparatus is switched on, and heating of the plates commences. A heating cycle is completed to melt the polymeric material, following which the current to the heating plates is switched off. At this time the fan 54 is turned on which opens a backdraft valve (not shown) which allows air to enter the chamber 3. At a similar time, a solenoid valve is opened to open the compressor and introduce air into the vortex tube thereby causing cold air to be blown into communication with the receptacle 26. After a predetermined time or when a predetermined temperature is reached the doors of the housing can be opened and the full receptacles removed, emptied and reloaded for a further operating cycle.

Aspect of the present invention have been described by way of example only and it will be appreciated to the skilled addressee that modifications and variations may be made without departing from the scope of protection afforded by the appended claims.