GB2524127A

GB2524127A - Asphalt production

Info

Publication number: GB2524127A
Application number: GB1415398.5A
Authority: GB
Inventors: Jerome Robert Aloysius Smyth
Original assignee: Individual
Current assignee: JEROME ROBERT ALOYSIUS SMYTH
Priority date: 2014-03-11
Filing date: 2014-09-01
Publication date: 2015-09-16
Anticipated expiration: 2034-09-01
Also published as: GB201415398D0; GB2524127B; GB201404256D0

Abstract

The apparatus 10 comprises first and second vessels 14, 28 a heat exchanger 18 and an outlet 16 for exhaust gases. Virgin aggregate is heated in the first vessel 14 and transferred into and mixed with RAP in the second vessel 28 to form a combined aggregate. The second vessel is spaced from the first and an outlet 16 for exhaust gas from the first vessel extends into the heat exchanger. The heat exchanger is configured to reduce the temperature of the exhaust gas from the first vessel. The heat exchanger may be located between the first vessel and a filter. Also claimed is a method of asphalt production comprising: a) heating virgin aggregate to a required temperature in a first vessel to provide heated aggregate and exhaust gas; b) passing exhaust gas through a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas and c) mixing the heated virgin aggregate with RAP to form a combined aggregate.

Description

Asphalt Production This invention concerns apparatus and a method for producing asphalt, and particularly where the asphalt includes a proportion of Recycled Asphalt s Planings (RAP).

An asphalt plant is a plant used for the manufacture of asphalt, macadam and other forms of coated road stone. There are three main types of asphalt plant: batch heater plants, semi-continuous plants, and continuous plants.

Asphalt comprises a combination of aggregate, filler (such as stone dust) and binder, which is usually bitumen. There is increasing legislative and commercial pressure to use high levels of RAP in the production of asphalt, as a partial and valuable substitute for virgin aggregate and bitumen.

The production of asphalt containing a proportion of RAP is achieved by running batch heater plants at greater operating temperatures than they were originally designed to operate at. This results in exhaust gas from the production process also being at a greater temperature. The increased temperature of the exhaust gas can cause damage to components of the batch heater plant, often causing the plant to shut down.

According to a first aspect of the present invention there is provided apparatus for producing asphalt, the apparatus comprising a first vessel in which virgin aggregate is heated, a second vessel into which the heated virgin aggregate is transferred and mixed with RAP to form a combined aggregate, the second vessel being spaced from the first vessel, and an outlet for exhaust gas from the first vessel extending to a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas from the first vessel.

The heat exchanger may be positioned between the first vessel and a filter, and may be connected to the outlet of the first vessel by a first duct and to the filter by a second duct, such that the exhaust gas passes from the first vessel to the heat exchanger through the first duct, and from the heat exchanger to the filter through the second duct. The exhaust gas may be vented directly to the atmosphere following passage through the filter.

The heat exchanger may be an air to air heat exchanger, and may comprise a plurality of air filled plates, such that the exhaust gas passed through the heat exchanger is cooled by the air filled plates, and the air in the air filled plates is heated. The heat exchanger may be connected to an inlet duct through which air enters the heat exchanger, and an outlet duct through which air warmed by the transfer of heat from the exhaust gas exits the heat exchanger. A fan may be used to propel the air through the heat exchanger.

The virgin aggregate may be heated in the first vessel to a temperature of between 140 and 250°C, and may be heated to a temperature of between 160 and 230°C, and may be heated to a temperature of 220°C. A burner may be used to heat the virgin aggregate in the first vessel.

In a first arrangement the warmed air exiting the heat exchanger is vented directly to the atmosphere.

In a second arrangement the outlet duct of the heat exchanger is connected to the second vessel such that warmed air exiting the heat exchanger passes through the outlet duct to the second vessel to apply heat thereto, which second vessel contains RAP.

In a third arrangement the outlet duct of the heat exchanger is connected to the burner, such that warmed air exiting the heat exchanger passes through the outlet duct to the burner, and the outlet duct may be connected to a primary air fan of the burner.

In a fourth arrangement the outlet duct of the heat exchanger extends to the first vessel such that the warmed air exiting the heat exchanger passes through the outlet duct to the first vessel to apply heat thereto.

s The heat exchanger may be configured such that the flow rate and pressure of the exhaust gas entering and exiting the heat exchanger is substantially unchanged. The heat exchanger may be configured to prevent contaminants contained in the exhaust gas from entering the heat exchanger.

The heat exchanger may be selectively removable from the remainder of the apparatus. The apparatus may include a housing which selectively locates the heat exchanger. The heat exchanger may be in the form of a cartridge, which cartridge may be selectively locatable in the housing.

According to a second aspect of the present invention there is provided a method of production of asphalt, the method comprising: a) heating virgin aggregate to a required temperature in a first vessel to provide heated aggregate and exhaust gas; b) passing the exhaust gas through a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas; c) mixing the heated virgin aggregate with RAP to form a combined aggregate.

The heated virgin aggregate may be mixed with RAP in a second vessel to form the combined aggregate, which vessel may be spaced from the first vessel.

The combined aggregate may be mixed in the second vessel with a filler and a binder. The filler may be stone dust. The binder may be bitumen.

The exhaust gas may be passed from the heat exchanger to a filter.

The exhaust gas may be vented directly to the atmosphere following passage through the filter.

Exhaust gas passing through the heat exchanger may be cooled by the transfer of heat to air in the heat exchanger, and the air in the heat exchanger may be warmed by the transfer of heat from the exhaust gas. The air may be propelled through the heat exchanger by a fan.

The virgin aggregate may be heated in the first vessel to a temperature of between 140 and 250°C, and may be heated to a temperature of between and 230°C, and may be heated to a temperature of 220°C. A burner may be used to heat the virgin aggregate in the first vessel.

Warmed air exiting the heat exchanger may be vented directly to the atmosphere through an outlet duct of the heat exchanger, or may pass through an outlet duct of the heat exchanger to the second vessel to apply heat thereto, or may pass through an outlet duct of the heat exchanger to a burner, which burner is used to heat the virgin aggregate in the first vessel, or may pass to the first vessel to apply heat thereto The method may use apparatus according to any of the preceding paragraphs.

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:-Fig. 1 is a block diagram showing a first apparatus for producing asphalt according to the invention; Fig. 2 is a perspective view of part of the apparatus of Fig. 1; Fig. 3 is a block diagram showing a second apparatus for producing asphalt according to the invention; Fig. 4 is a block diagram showing a third apparatus for producing s asphalt according to the invention; Fig. 5 is a block diagram showing a fourth apparatus for producing asphalt according to the invention; and Fig. 6 is a similar view to Fig. 2 but of part of a fifth apparatus according to the invention.

Figs. 1 and 2 shows a first apparatus 10 for producing asphalt. The apparatus 10 includes a first vessel 14 which is connected via an outlet (not shown) to a first duct 16. The first duct 16 is connected to an air to air heat exchanger 18 and the heat exchanger 18 is connected to a second duct 24.

The second duct 24 is connected to an exhaust plant filter 26. A burner 12 with a primary air fan 13 is positioned adjacent to the first vessel 14, and is configured to heat the contents of the first vessel. The apparatus 10 also includes a second vessel 28 which is located at a position away from the first vessel.

In use virgin aggregate is heated to an approximate temperature of 220°C in the first vessel 14 by the burner 12 using a 4000kW flame. Hot exhaust gas from the heating process passes through the outlet of the first vessel 14 and along the first duct 16 to the heat exchanger 18. The exhaust gas passing through the heat exchanger 18 is cooled by the transfer of heat to air in the air to air heat exchanger 18. The exhaust gas then passes through the second duct 24 to the exhaust plant filter 26, which vents the exhaust gas to the atmosphere. The flow of exhaust gas through the apparatus 10 is depicted by arrows 30.

As shown in greater detail in Fig. 2 of the drawings, the heat exchanger 18 is positioned between the first duct 16 and the second duct 24 such that warmed exhaust gas is passes through the heat exchanger 18 towards the filter 26. The air to air heat exchanger 18 includes a plurality of spaced air s cooled plates or fins (not shown in the drawings), as is conventional. The hot exhaust gas passes over the plates or fins, as shown by arrows 30, with a proportion of the heat of the hot exhaust gas transferred by conduction to the air in the plates or fins. The exhaust gas therefore exits the heat exchanger 18 through the second duct 24 at a lower temperature than the exhaust gas entering the heat exchanger 18 through the first duct 16.

The flow of air through the heat exchanger is depicted by arrows 32.

Air from the atmosphere passes into the heat exchanger 18 through an inlet duct 20. A fan (not shown) is used to propel the air through the heat exchanger 18. Warmed air exits the heat exchanger through an outlet duct 22. In this example, the warmed air is vented directly to the atmosphere.

The spaced internal plates or fins (not shown) are configured to allow exhaust gas to pass through the heat exchanger 18 without affecting the flow rate or pressure of the exhaust gas. The flow rate and pressure of the exhaust gas entering the heat exchanger 18 through the first duct 16 and exiting the heat exchanger 18 through the second duct 24 is therefore substantially the same. The first duct 16 and the second duct 24 have a diameter of approximately 1 m diameter.

Once the virgin aggregate is at the correct temperature in the first vessel 14 it is transferred to the second vessel 28 and mixed with RAP, and dry filler (such as stone dust). RAP maintains a coating of flammable binder and cannot therefore be mixed with virgin aggregate in the first vessel 14 because the virgin aggregate in the first vessel is exposed to a naked flame.

There would be a considerable risk therefore that RAP would catch fire if it were heated in the first vessel 14.

The RAP is therefore mixed with the super heated virgin aggregate in the second vessel 28. In this example the RAP is at an ambient temperature, and is therefore significantly cooler than the pre-heated virgin aggregate, which is at an approximate temperature of 220°C.

The mixing in the second vessel 28 of super heated virgin aggregate at an approximate temperature of 220°C with RAP at an ambient temperature provides a combined aggregate at an approximate temperature of 150°C, which in this example is the required temperature for further processing of the combined aggregate.

As would be clear to a person skilled in the art the end temperature of combined aggregate in the second vessel 28 is dependent on the temperature/moisture content of the RAP, the percentage by weight of RAP in the combined aggregate in the second vessel 28, and the temperature to which the virgin aggregate is heated to in the first vessel 14.

In this instance RAP is not heated prior to being mixed with pre heated virgin aggregate in the second vessel 28. The virgin aggregate is therefore heated to a greater temperature than would be necessary without the addition of a proportion of RAP. In the example described above, the virgin aggregate is heated to an approximate temperature of 220°C in the first vessel 14 to provide a combined aggregate at a temperature of 150°C in the second vessel 28. Without the addition of a proportion of RAP it would only be necessary to heat the virgin aggregate to an approximate temperature of 160°C in the first vessel 14 to provide an approximate temperature in the second vessel 28 of 150°C.

The amount of virgin aggregate heated in the first vessel 14 is reduced to take into account the amount of RAP added in the second vessel 28. In the present example, the aggregate in the second vessel 28 consists of 95 % w/w virgin aggregate and S % w/w RAP. Accordingly, the quantity of virgin aggregate in the first vessel 14 is reduced by 5 % w/w.

Figs. 3, 4 and 5 of the drawings show second 100, third 200 and fourth 300 apparatus for producing asphalt according to the invention. Many features of the second 100, third 200 and fourth 300 apparatus are similar to those previously described, and where features are the same or similar the s same reference numeral have been used and these feature will not be described again for the sake of brevity.

As shown in Fig. 3 of the drawings the second apparatus 100 is similar to the first apparatus 10 but in this instance the outlet duct 22 from the heat exchanger 18 includes an additional section of duct 34 which passes the warmed air to the second vessel 28 to warm the RAP prior to mixing with the heated virgin aggregate.

The temperature of the combined aggregate in the second vessel is approximately 150°C, which in this example is the required temperature for further processing of the combined aggregate. The warmed air from the heat exchanger provides some or all of the heat necessary to reduce the moisture content and provide warming of the RAP in the second vessel 28, and therefore reducing production costs.

As shown in Fig. 4 of the drawings the third apparatus 200 is similar to the first apparatus 10 but in this instance the outlet duct 22 from the heat exchanger 18 includes an additional section of duct 34 which passes the warmed air to the burner primary air fan 13.

The energy requirements to heat the virgin aggregate in the first vessel 14 to approximately 220°C are significant. The warmed air from the heat exchanger 18 is directed through the burner primary air fan 13, instead of cold air from the atmosphere. The energy requirements to heat already warmed air to the required temperature are less than to heat cold air from the atmosphere to the required temperature, therefore reducing production costs.

As shown in Fig. 5 of the drawings the fourth apparatus 300 is similar to the first apparatus 10 but in this instance the outlet duct 22 from the heat exchanger 18 includes an additional section of duct 34 which includes an opening 36 adjacent to the first vessel 14. In this example, the warmed air from the heat exchanger 18 provides heating to the first vessel 14, in addition to the heat provided by the burner 12. Accordingly, the energy requirements s of the burner 12 are reduced, which in turn reduces production costs.

Fig. 6 shows a similar view to Fig. 2 but of a fifth apparatus 110 which is similar to the first apparatus 10 except for the arrangement of the heat exchanger 118. In this instance the heat exchanger 118 is in the form of a cartridge 120. The form of the heat exchanger 118 is similar to the heat exchanger 18 but the plates or fins are mounted on a square frame 122. The frame 122 is selectively locatable in a housing positioned between the first duct 16 and second duct 24.

This cartridge arrangement means that the heat exchanger 118 can be selectively removed as required for repair, cleaning or maintenance, or if it is not required to include a heat exchanger in the apparatus during use.

There are thus described apparatus for producing asphalt with a number of advantages.

There is increasing legislative and commercial pressure to use increased levels of RAP in the production of asphalt. As described with reference to Fig. 1, to obtain a combined aggregate (i.e. virgin aggregate plus RAP) at a required temperature for further processing, the virgin aggregate is heated to a greater initial temperature prior to mixing with the RAP. This increase in temperature is proportional to the amount of RAP in the combined aggregate, and would generally be calculated on a case by case basis.

In conventional batch heater plants the requirement to heat the virgin aggregate to a greater temperature can cause damage to components of the plant, and particularly the filter 26, often causing the plant to shut down. This problem is compounded because the quantity of virgin aggregate heated in each batch is reduced, to take into account the amount of RAP content of the combined aggregate. As a result voids are created in the material in the first vessel 14. Hot air passes directly though the voids to the filter 26.

The inclusion of a heat exchanger 18 cools the exhaust gas and restores the asphalt plant to a normal operating temperature, thereby preventing damage to the filter 26. Asphalt containing increased levels of RAP can therefore be manufactured using conventional batch heater plants modified to include a heat exchanger 18 as claimed.

The invention also provides numerous environmental benefits, as detailed below. An increased usage of RAP reduces the amount of RAP which would otherwise be placed in landfill. Furthermore, increasing the quantity of RAP in asphalt reduces the amount of virgin aggregate in asphalt, which in turn results in less virgin aggregate being quarried.

Furthermore, as described with reference to the second 100, third 200 and fourth 300 apparatus of Figs. 3 to 5, warmed air from the heat exchanger can be recycled to reduce the overall costs and energy usage for manufacturing asphalt.

It is to be realised that a wide range of variations may be made without departing from the scope of the invention. For instance, the process could be adapted to be carried out in different types of asphalt plant, for example semi-continuous and continuous plants. A different type of heat exchanger could be used, for example the spaced internal plates or fins could be cooled by a suitable liquid rather than air from the atmosphere.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims 1. Apparatus for producing asphalt, the apparatus comprising a first vessel in which virgin aggregate is heated, a second vessel into which the heated virgin aggregate is transferred and mixed with RAP to form a combined aggregate, the second vessel being spaced from the first vessel, and an outlet for exhaust gas from the first vessel extending to a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas from the first vessel.
2. Apparatus according to claim 1, in which the heat exchanger is positioned between the first vessel and a filter.
3. Apparatus according to claim 2, in which the heat exchanger is connected to the outlet of the first vessel by a first duct and to the filter by a second duct, such that the exhaust gas passes from the first vessel to the heat exchanger through the first duct, and from the heat exchanger to the filter r" 15 through the second duct. Co
4. Apparatus according to any of the preceding claims, in which the exhaust gas is vented directly to the atmosphere following passage through the filter.
5. Apparatus according to any of the preceding claims, in which the heat exchanger is an air to air heat exchanger.
6. Apparatus according to claim 5, in which the heat exchanger comprises a plurality of air filled plates, such that the exhaust gas passed through the heat exchanger is cooled by the air filled plates, and the air in the air filled plates is heated.
7. Apparatus according to any of the preceding claims, in which the heat exchanger is connected to an inlet duct through which air enters the heat exchanger, and an outlet duct through which air warmed by the transfer of heat from the exhaust gas exits the heat exchanger.
8. Apparatus according to any of the preceding claims, in which a fan is used to propel air through the heat exchanger.
9. Apparatus according to any of the preceding claims, in which the virgin aggregate is heated in the first vessel to a temperature of between 140 and 250°C.
10. Apparatus according to claim 9, in which the virgin aggregate is heated in the first vessel to a temperature of between 160 and 230°C.
11. Apparatus according to claim 10, in which the virgin aggregate is heated in the first vessel to a temperature of 220°C.
12. Apparatus according to any of the preceding claims, in which a burner is used to heat the virgin aggregate in the first vessel.
13. Apparatus according to any of the preceding claims, in which the C\J warmed air exiting the heat exchanger is vented directly to the atmosphere. r
14. Apparatus according to any of claims ito 12, in which the outlet duct of 0 15 the heat exchanger is connected to the second vessel such that warmed air exiting the heat exchanger passes through the outlet duct to the second vessel to apply heat thereto, which second vessel contains RAP.
15. Apparatus according to any of claims ito 12, in which the outlet duct of the heat exchanger is connected to the burner, such that warmed air exiting the heat exchanger passes through the outlet duct to the burner, and the outlet duct may be connected to a primary air fan of the burner.
16. Apparatus according to any of claims ito 12, in which the outlet duct of the heat exchanger extends to the first vessel such that the warmed air exiting the heat exchanger passes through the outlet duct to the first vessel to apply heat thereto.
17. Apparatus according to any of the preceding claims, in which the heat exchanger is configured such that the flow rate and pressure of the exhaust gas entering and exiting the heat exchanger is substantially unchanged.
18. Apparatus according to any of the preceding claims, in which the heat exchanger is configured to prevent contaminants contained in the exhaust gas from entering the heat exchanger.
19. Apparatus according to any of the preceding claims, in which the heat exchanger is selectively removable from the remainder of the apparatus.
20. Apparatus according to claim 19, in which the apparatus includes a housing which selectively locates the heat exchanger.
21. Apparatus according to any of the preceding claims, in which the heat exchanger may be in the form of a cartridge.C\J
22. Apparatus according to claim 21 when dependent on claim 20, in which r. . . the cartridge is selectively locatable in the housing. Co0 15
23. A method of production of asphalt, the method comprising: a) heating virgin aggregate to a required temperature in a first vessel to provide heated aggregate and exhaust gas; b) passing the exhaust gas through a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas; c) mixing the heated virgin aggregate with RAP to form a combined aggregate.
24. A method according to claim 23 in which the heated virgin aggregate is mixed with RAP in a second vessel to form the combined aggregate.
25. A method according to claim 24, in which the second vessel is spaced from the first vessel.
26. A method according to claims 23 to 25, in which the combined s aggregate is mixed in the second vessel with a filler and a binder.
27. A method according to claim 26, in which the filler is stone dust.
28. A method according to claims 26 or 27, in which the binder is bitumen.
29. A method according to any of claims 23 to 28, in which the exhaust gas is passed from the heat exchanger to a filter.
30. A method according to claim 29, in which the exhaust gas is vented -15 directly to the atmosphere following passage through the filter. (431. A method according to any of claims 23 to 30, in which exhaust gas CO passing through the heat exchanger is cooled by the transfer of heat to air in O the heat exchanger.32. A method according to claim 31, in which the air in the heat exchanger is warmed by the transfer of heat from the exhaust gas.33. A method according to any of claims 23 to 32, in which the air is propelled through the heat exchanger by a fan.34. A method according to any of claims 23 to 33, in which the virgin aggregate is heated in the first vessel to a temperature of between 140 and 250°C.35. A method according to claim 34, in which the virgin aggregate is heated in the first vessel to a temperature of between 160 and 230°C.36. A method according to claim 35, in which the virgin aggregate is heated in the first vessel to a temperature of 220°C.s 37. A method according to any of claims 23 to 36, in which a burner is used to heat the virgin aggregate in the first vessel.38. A method according to any of claims 23 to 36, in which warmed air exiting the heat exchanger is vented directly to the atmosphere through an outlet duct of the heat exchanger.39. A method according to any of claims 23 to 37, in which warmed air exiting the heat exchanger passes through an outlet duct of the heat exchanger to the second vessel to apply heat thereto. *-15(%j 40. A method according to any of claims 23 to 37, in which warmed air 1 exiting the heat exchanger passes through an outlet duct of the heat CO exchanger to a burner, which burner is used to heat the virgin aggregate in 0 the first vessel.41. A method according to any of claims 23 to 37, in which warmed air exiting the heat exchanger passes to the first vessel to apply heat thereto 42. A method according to claim 41, in which the method uses apparatus according to any of claims 1 to 22.43. Apparatus substantially as hereinbefore described and with reference to Figs. 1 and 2 of the accompanying drawings.44. Apparatus substantially as hereinbefore described and with reference to Fig. 3 of the accompanying drawings.45. Apparatus substantially as hereinbefore described and with reference to Fig. 4 of the accompanying drawings.46. Apparatus substantially as hereinbefore described and with reference s to Fig. 5 of the accompanying drawings.47. Apparatus substantially as hereinbefore described and with reference to Fig. 6 of the accompanying drawings.48. A method substantially as hereinbefore described and with reference to Figs. 1 and 2 of the accompanying drawings.49. A method substantially as hereinbefore described and with reference to Fig. 3 of the accompanying drawings. *-15(%j 50. A method substantially as hereinbefore described and with reference to Fig. 4 of the accompanying drawings. Co0 51. A method substantially as hereinbefore described and with reference to Fig. 5 of the accompanying drawings.52. A method substantially as hereinbefore described and with reference to Fig. 6 of the accompanying drawings.53. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWSClaims 1. Apparatus for producing asphalt, the apparatus comprising a first vessel in which in use virgin aggregate is heated, a second vessel into which in use the heated virgin aggregate is transferred and mixed with RAP to form s a combined aggregate, the second vessel being spaced from the first vessel, and an outlet for exhaust gas from the first vessel extending to a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas from the first vessel, wherein the heat exchanger is positioned between the first vessel and a filter.2. Apparatus according to claim 1, in which the heat exchanger is connected to the outlet of the first vessel by a first duct and to the filter by a second duct, such that in use the exhaust gas passes from the first vessel to the heat exchanger through the first duct, and from the heat exchanger to the filter through the second duct.* 15 3. Apparatus according to any of the preceding claims, in which the exhaust gas is vented directly to the atmosphere following passage through the filter.::::. 4. Apparatus according to any of the preceding claims, in which the heat exchanger is an air to air heat exchanger.5. Apparatus according to claim 4, in which the heat exchanger comprises a plurality of air filled plates, such that the exhaust gas passed through the heat exchanger is cooled by the air filled plates, and the air in the air filled plates is heated.6. Apparatus according to any of the preceding claims, in which the heat exchanger is connected to an inlet duct through which air enters the heat exchanger, and an outlet duct through which air warmed by the transfer of heat from the exhaust gas exits the heat exchanger.7. Apparatus according to any of the preceding claims, in which a fan is used to propel air through the heat exchanger.8. Apparatus according to any of the preceding claims, in which the virgin aggregate is heated in the first vessel to a temperature of between 140 and 250°C.9. Apparatus according to claim 8, in which the virgin aggregate is heated in the first vessel to a temperature of between 160 and 230°C.10. Apparatus according to claim 9, in which the virgin aggregate is heated in the first vessel to a temperature of 220°C.11. Apparatus according to any of the preceding claims, in which a burner is used to heat the virgin aggregate in the first vessel.12. Apparatus according to any of the preceding claims, in which the warmed air exiting the heat exchangeris vented directly to the atmosphere.13. Apparatus according to any of claims Ito 11, in which the outlet duct of :. 15 the heat exchanger is connected to the second vessel such that warmed air exiting the heat exchanger passes through the outlet duct to the second vessel to apply heat thereto which second vessel contains RAP.14. Apparatus according to any of claims Ito 11, in which the outlet duct of the heat exchanger is connected to the bumer, such that warmed air exiting the heat exchanger passes through the outlet duct to the burner, and the outlet duct may be connected to a primary air fan of the burner.* 15. Apparatus according to any of claims 1 to 11, in which the outlet duct of the heat exchanger extends to the first vessel such that the warmed air exiting the heat exchanger passes through the outlet duct to the first vessel to apply heat thereto.* . 19 16. Apparatus according to any of the preceding claims, in which the heat exchanger is configured such that the flow rate and pressure of the exhaust gas entering and exiting the heat exchanger is substantially unchanged.17. Apparatus according to any of the preceding claims, in which the heat s exchanger is configured to prevent contaminants contained in the exhaust gas from entering the heat exchanger.18. Apparatus according to any of the preceding claims, in which the heat exchanger is selectively removable from the remainder of the apparatus.19. Apparatus according to claim 18, in which the apparatus includes a housing which selectively locates the heat exchanger.20. Apparatus according to any of the preceding claims, in which the heat exchanger may be in the form of a cartridge.21. Apparatus according to claim 20 when dependent on claim 19, in which the cartridge is selectively locatable in the housing. 0**is 22. A method of production of asphalt, the method comprising: a) heating virgin aggregate to a required temperature in a first vessel to provide heated aggregate and exhaust gas; b) passing the exhaust gas from the first vessel through a heat exchanger, the heat exchanger being configured to reduce the temperature of the exhaust gas, wherein the heat exchanger is positioned between the first vessel and the filter; c) mixing the heated virgin aggregate with RAP in a second vessel to zs form a combined aggregate, the second vessel being spaced from the first vessel. * 2023. A method according to claim 22, in which the combined aggregate is mixed in the second vessel with a filler and a binder.24. A method according to claim 23, in which the filler is stone dust.25. A method according to claims 23 or 24, in which the binder is bitumen.26. A method according to any of claims 22 to 25, in which the exhaust gas is passed from the heat exchanger to a filter.27. A method according to claims 22 to 26, in which the exhaust gas is vented directly to the atmosphere following passage through the filter.28. A method according to any of claims 22 to 27, in which exhaust gas * is passing through the heat exchanger is cooled by the transfer of heat to air in the heat exchanger.14*ss* * S 29. A method according to claim 28, in which the air in the heat exchanger *4*s is warmed by the transfer of heat from the exhaust gas.30. A method according to any of claims 22 to 29 in which the air is propelled through the heat exchanger by a fan.
31. A method according to any of claims 22 to 30, in which the virgin aggregate is heated in the first vessel to a temperature of between 140 and 250°C.
32. A method according to claim 31, in which the virgin aggregate is heated in the first vessel to a temperature of between 160 and 230°C.
33. A method according to claim 32, in which the virgin aggregate is heated in the first vessel to a temperature of 220°C. * 2134. A method according to any of claims 22 to 33, in which a burner is used to heat the virgin aggregate in the first vessel.s 35. A method according to any of claims 22 to 33, in which warmed air exiting the heat exchanger is vented directly to the atmosphere through an outlet duct of the heat exchanger.36. A method according to any of claims 22 to 34, in which warmed air exiting the heat exchanger passes through an outlet duct of the heat exchanger to the second vessel to apply heat thereto.37. A method according to any of claims 22 to 34, in which warmed air exiting the heat exchanger passes through an outlet duct of the heat * * is exchanger to a burner, which burner is used to heat the virgin aggregate in the first vessel.*.**** * * *. 38. A method according to any of claims 22 to 34, in which warmed air U..exiting the heat exchanger passes to the first vessel to apply heat thereto 39. A method according to claim 38, in which the method uses apparatus . according to any of claims ito 21.40. Apparatus substantially as hereinbefore described and with reference to Figs. I and 2 of the accompanying drawings.41. Apparatus substantially as hereinbefore described and with reference to Fig. 3 of the accompanying drawings.42. Apparatus substantially as hereinbefore described and with reference to Fig. 4 of the accompanying drawings.* * 22 43. Apparatus substantially as hereinbefore described and with reference to Fig. 5 of the accompanying drawings.44. Apparatus substantially as hereinbefore described and with reference s to Fig. 6 of the accompanying drawings.45. A method substantially as hereinbefore described and with reference to Figs. 1 and 2 of the accompanying drawings.46. A method substantially as hereinbefore described and with reference to Fig. 3 of the accompanying drawings.47. A method substantially as hereinbefore described and with reference to Fig. 4 of the accompanying drawings.48. A method substantially as hereinbefore described and with reference to Fig. 5 of the accompanying drawings.49. A method substantially as hereinbefore described and with reference to r 20 Fig. 6 of the accompanying drawings. * .. * * * *. . * * * *.