GB2525007A

GB2525007A - A method and system for heat recovery from high-temperature slag

Info

Publication number: GB2525007A
Application number: GB1406412.5A
Authority: GB
Inventors: Zhongfu Zhou; Qinglu Wang
Original assignee: FOREMOST INNOVATION Ltd
Current assignee: FOREMOST INNOVATION Ltd
Priority date: 2014-04-09
Filing date: 2014-04-09
Publication date: 2015-10-14
Also published as: GB201406412D0; CN105112575A

Abstract

Apparatus for recovering heat from hot slag comprises a heat exchanger having at least two concentric cylinders 6-8, 6-9 & 6-10 which are rotatable about their concentric axis. The first cylinder 6-8 comprises a slag inlet 6-11 and another 6-10 comprises a slag outlet 6-12. A slag transmission path 6-16 lies between the inlet 6-11 and the outlet 6-12 and passes through the first cylinder 6-8 in a first direction and through another cylinder 6-9 in the opposite direction. Also a method of recovering heat from hot slag by passing hot slag from an inlet 6-11 to an outlet 6-12 of a heat exchanger in a first direction along a first tubular part 6-8 of the heat exchanger and then in an opposite direction along second concentric tubular part 6-9 of the heat exchanger. While slag moves through the heat exchanger air is passed from the outlet 6-12 to the inlet 6-11.

Description

A METHOD AND SYSTEM FOR HEAT RECOVERY FROM HIGH-

TEMPERATURE SLAG

This invention rdates to heat recovery from high temperature stag discharged. In S particu'ar, but not exclusively, this invention relates to a system and method for achieving heat recovery in a closed system.

Slag is a by-product from industrial processes. For example, slag may be produced in the making of non-ferrous metals or in processes in the chemical industry, Due to the nature of these processes, slag if often produced at high temperatures, for example, between 1100°C and 1600°C.

Currently, there are a number of methods for heat recovery from high-temperature slag, such as air blast granulation, rotary roller granulation, heat recovery from steel slag, ctc. None of these methods can be used for both liquid and non liqiLid slag and they are generafly offly apphcable to stag produced from certain processes.

In air blast granulation, high-pressure air quenched liquid slag is crushed into a heat recovery chamber to collect heat radiation. However, air blast granulation is only suitable for liquid slag with a good fluidity and requires a relative long heat cycle.

In rotary roller granulation, slag is first injected between two rollers and extruded to form a thin layer of slag. The thin sheet of slag on the surface of the roller is rapidly cooled down by air blasting and the heat is taken away by the flow of air, The main drawback of rotary roller granulation is that sticky residue on the roller must be removed by a rake manually. In addition, both the efficiency of heat recovery and service life of the equipment is limited.

In heat recovery from steel stag. heat is coflected during the continuons modification of the stag surface, The heat is transferred to an aqueous medium by heat radiation and dynamic energy exchanging, thus generating superheated steam. However, this technique is not reliable with liquid slag, because the viscosity of the liquid slag is extremely uneven and the stability of heat transferring cannot be ensured. A'so. after the heat recovery, the temperature of the steel slag is too high for a secondary heat exchange, According to a first aspect of the invention, there is provided a heat recovery system for recovering heat from high temperature slag. The system has a heat exchanger that may comprise first, second and third cylinders arranged concentrically about an axis around which the cylinders are configured to rotate. The heat exchanger may further comprise a slag inlet provided in the first cylinder for receiving high temperature slag and a slag outlet provided in the third cylinder for discharging cooled slag. The system may also comprise a slag transmission path between the inlet and outlet, along which the slag is passed, the stag transmission path awning from the inlet, through the first cylinder in a first direction, through the second cylinder in a second direction, opposite the first direction, and through the third cylinder, in the first direction, to the outlet.

A device for heat recovery from high-temperature slag includes: a closed tilting device, a closed crushing apparatus, a high-temperature granulator, a non-crushing slag warehouse, a system for silo lifting and buffering, a main heat exchanger, and a closed circuit heat exchange system.

In this way, air can be heated to a temperature of between 300 °C and 450 °C from slag at a temperature between 1100 °C and 1600 °C. The heat recovery system is advantageous because it can be used for heat recovery from both liquid and non liquid high-temperature slag without any alteration. Furthermore, it applicable to slag that is discharged from a wide range of processes, such as the production of nonferrous metals and the chemical industry, The heat recovery system neither consumes water nor produces dust or any harmful gases. The system is highly efficient and simpler than previous system.

The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a front view a heat recovery system according to the invention; Figure 2 shows a front view of the closed titling device of Figure 1; Figure 3A shows a side view of the closed crushing apparatus of Figure 1; Figure 3B shows a sectional view of the front of the dosed crushing apparatus of Figure 1; Figure 4 shows a sectional view of the front of the high-temperature granulator; Figure 5 shows a front view of the silo lifting and buffering system of Figure I; Figure 6A shows a front view of the main heat exchanger; Figure 6B shows a sectional view of the cylinders of the heat exchanger of Figure 6A; S and Figure 6C shows a left view of the main heat exchanger of Figure 1: The Figures show a heat recovery system 100 for recovering heat from high temperature stag. The system comprises a closed tilting device I, a closed crushing apparatus2, a high-temperature granulator 3, a non-crushing materials warehouse 4, a system for silo lifting and buffering 5. a main heat exchanger 6, and a closed circuit heat exchange system 7.

The air is circulated through the system 100 by closed circuit heat exchange system 7, The closed circuit heat exchange system comprises air duets 7-1. 7-2, 7-3. 7-4. electric valves 7-5, 7-6, 7-7 and high-temperature electric fans 7-8. The system a'so indudes temperature and air quality sensors (not shown).

Figures 2 to 4 shows the elements of the system 100 used to process high temperature slag before it is provided to the main hcat exchanger 6.

High temperature slag, with a temperaturc of between 1100°C and 1600°C. is poured into the closed tilting device 1 shown in Figure 2. The closed tilting device comprises a closed box 1-3 provided with a movabk cover 1-I on its top. The cover is driven by a hydraulic cylinder or electric plunger (not shown) and is moved between an open and closed position when slag is poured in.

A hydraulic motor or electric motor-driven device 1-2 that can contain and dump the high-temperature slag is provided in the box 1-3, Slag h&d in the box 1-3 is discharged through outlet 1-4 into the closed crushing apparatus 2 shown in figures 3A and 3B, The slag is discharged at a constant speed.

The closed crushing apparatus 2 comprises a container 2-9 with an entrance 2-6 at its top and outlets for both crushed slag 2-7 and non-crushing stag 2-8 at the bottom, The closed crushing apparatus separates the slag into crushing slag and non-crushing slag.

The centre of the crushing apparatus 2 is equipped with fixed jaw plate 2-2, rigid grate 2-4 and movable jaw plate 2-1, The movable jaw 2-I moves around an eccentric shaft 2-3 and interacts with fixed jaw plate 2-2 to crush the slag.

The fixed jaw plate 2-2 is moveable between an open position and a closed position and the moveabk jaw plate is driven by a hydrauhc motor or electric motor, The fixed jaw plate 2-2 is mounted on a locking device 2-5, The locking device comprises a hydraulic cylinder or an electric push rod driver and fitting pins (not shown). The fitting pins lock the fixed jaw plate into the closed position and can be disengaged with the fixed jaw p'ate 2-2 is moved.

When the fixed jaw plate is in the closed position, as shown in Figure 2 crushed materia' faDs through outlet 2-7. When the fixed jaw plate is moved away from the moveable jaw, to the open position, non-crushing slag falls along rigid grate and into the non-crushing materials warehouse 4 through outlet 2-S.

Materials warehouse 4 is a box-type hopper that can endure high temperature. It has an opening on the top, provided with a hook and is p'aced on a steel or concrete platform.

The closed crushing apparatus 2 also indudes an outlet 7-9 for preheated air, received from the high temperature granulator 3. The outlet 7-9 is provided on the side of the closed crushing apparatus 2.

Crushed material falling through outlet 2-7 enters the high-temperature granulator 3, shown in Figure 4, The high temperature granulator 3 is a vertical cylindrical device, with multiple sets of ring shaped baffles 3-3 on its interior wall, In the centre of the granulator, a shaft 3-1 is mounted, The shaft has multiple sets of rotary spoiler blades 3-2.

The spoiler blades 3-2 decrease the falling speed of slag passing through the granulator. The baffles serve to disperse the stag uniform'y in the spofler blades 3-3.

such that no slag passes directly down the interior wall of the cylinder.

Crushed slag enters through an irfiet 3-5 for crushed slag at the top of the granu'ator 3.

The shaft 3-1. driven by a motor 3-8 mounted on the underside of the granulator 3.

drives the rotation of the blades 3-2, which interact with the ring shaped baffles 3-3 to granulate the slag. The granulated high temperature slag is discharged through outlet 3-7 at the bottom of the granulator 3.

An inlet for air 3-6 is also provided at the bottom of the granulator 3. This is controfled by valve 3-4. Slag passing through the granu'ator exchanges heat with room-temperature air, generating a preheated air in a primary heat exchange stage.

The preheated air is discharged throlLgh the slag inlet 3-5. into the closed crushing apparatus 2 and out through oufiet 7-9 into duct 7-1.

High temperature granulated slag discharged through outlet 3-7 is provided into the system for silo lifting and buffering 5, shown in Figure 5, Slag grains fall into the bucket elevator 5-1 from the outlet 3-7 of the high-temperature slag granulator 3, and are lifted and sent into a heating resistant buffer sUb 5-3.

The heat resistant buffer silo 5-3 is mounted with an entrance 5-5 for granulated slag at the top and an exit 5-6 at the bottom, through which the stag passes into a reciprocating feeder or vibrating feeder 5-4.

The bucket elevator 5-1 is mounted with a number of sets of air outlets 5-2 for room temperature air. The air outlets 5-2 allow for adjustment of air pressure in the bucket elevator 5-1, The structures of bucket elevator 5-1 and reciprocating feeder 5-4 are known in the art.

From the system for sUo Ufting and buffering 5, the high temperature crushed and granulated slag is passed to the main heat exchanger 6 for secondary heat exchange.

Figures 6A to 6C shows the main heat exchanger 6, The main heat exchanger 6 includes feedstock device 6-1. roller heat exchanger 6-2, output device 6-3 and reciprocating or vibrating feeder 6-4.

The feedstock device 6-1 is a horizontal cylinder with an inlet 6-5 for granulated slag at its top and outlets for granulated slag 6-6 and high-temperature air 6-7.

Rofler heat exchanger 6-2 is a cylindrical device comprising three concentric roflers of different diameters 6-8, 6-9, 6-10, At one end, it is equipped with an inlet 6-11 for granulated slag and the other end with a low-temperature slag outlet 6-12, To direct stag through the roller heat exchanger, the rofler heat exchanger 6-2 rotates around the centre of the cylinder driven by motor groups (not shown). In addition, the diameter of the rollers are tapered, narrowing in the direction slag is intended to travel and the interna' walls of the cylinders are provided with deflectors 6-17 to direct the slag.

The first roller 6-8 is the innermost roller and is at least partially within the second 6- 9 and third 6-10 rollers. At a first end, the first roller 6-8 is open and coupled to the exterior of the roller heat exchanger 6-2, through an aperture in an end waD of the third roller, by the inlet 6-11.

The first end of the first roller 6-8 protrudes from the second rofler 6-9, The second, opposite, end of the first roller 6-8 is open and received within the first end of the second roller 6-9, The second roller 6-9 is fully encased in the third roller 6-10. The first end of the second roHer. is closed and extends beyond the first roller 6-8 but does not extend to the end of the third rofler 6-10, The second, opposite, end of the second rofler 6-9 is open inside the third roller 6-10, The third rofler 6-10 forms the exterior of the rofler heat exchanger 6-2. The interior of the third rofler 6-10 is coupled to the exterior of the roller heat exchanger 6-2 by outlet 6-12, Output device 6-3 is a liorizonta cylinder with an entrance 6-13 for low-temperature slag and an outlet 6-14 for low temperature slag. Also, it has the duct 6-15 at the top, where preheated air can enter, Slag grains pass from the reciprocating or vibrating feeder 5-4 to thc feedstock device 6-1 and enter into the roller heat exchanger 6-2 through an are chute (not shown).At the same time, valve 7-5 is opened so preheated air is provided via duct 7-1, into duet 6-15 and into the output device 6-3, Slag moves along the path indicated by the arrow 6-16. High temperature slag that has been crushed and granulated is provided through inlet 6-11, into the interior of the first roller 6-8. As a result of the rotation, deflectors and tapering, the slag is directed along the length of the roller to the open second end, where it enters the second roller 6-9.

The rotation. deflectors and tapering then causes the slag to move between the exterior of the first roller 6-8 and the interior of the second roller 6-9. from the first end of the second roller 6-9 to the second end, The slag then moves through the open end of the second roller 6-9 into the third roller 6-10.

Finally, the rotation. deflectors and tapering causes the slag to move between the exterior of the second roller 6-9 and the interior of the third roller 6-10 to outlet 6-12 and into output device 6-3, Air enters the roller heat exchanger 6-2 through the slag outlet 6-12, and follows the reverse path of the slag i.e. from the third roller, to the second to the first and out through slag inlet 6-11. As the slag and air move along these paths, they exchange heat to heat the air and coot the slag.

The cooled grains enter into the feeding device 6-3 and are discharged by feeder 6-4.

A further arc chute (not shown) directs slag from the roller heat exchanger to the feeder 6-4.

The heated air is output at outlet 6-7 into duct 7-2. Heated air is carried through duct 7-2 to electric fan 7-8 and discharged through duct 7-4, Temperature sensors (not shown) in duct 7-4 detect the temperature of the air. The air quality is also detected.

The action of electric fan 7-8 and valves 7-4, 7-5, 7-6, 3-6 is used to control the pressure in the system 100. The pressure is controlled such that there is a negative pressure difference over the heat exchanger 6-2 to draw air along the desired path.

A negative pressure difference may also be used to draw air through granulator 3 when preheating the air.

If the temperature of the high-temperature heated air meets the required standard, valve 7-7 wifl be opened and valve 7-6 shut and the air provided for downstream use.

Otherwise, valve 7-7 will be shut and valve 7-6 opened and the air will return into the rollcr hcat cxchangcr 6-2 by air duct 7-3 and air duct 7-1.

The required standard can be varied depending on the downstream use. In one example. the required standard will be for the air to be between 300°C and 450°C.

The heat recovery system 100 may make use of asbestos or other insulating materials for heat insulation. For example, the closed tilting device 1 and/or the closed crushing apparatus 2 and/or the outer waD of the buffer silo 5-3 and/or the air ducts 7-I, 7-2, 7- 3. 7-4 may be attached to asbestos or other insulating materials.

The heat recovery system 100 may also make use of a water cooling system (not shown). For example, the moveable jaw plate 2-1 and/or the fixed jaw plate 2-2 and/or the eccentric shaft 2-3 and/or the shaft 3-1 in the granulator 3 and/or the bucket elevator 5-1 and/or bearing groups associated with the rotating parts may be protected by a vater cooling system.

At least the reciprocating or vibrating feeder 5-4, the feedstock device 6-1 and roller heat exchanger 6-2 are made from steel or another heat resistant material.

It will be appreciated that although it has been described with the first roller 6-8 being the innermost roller, it may be the outermost roHer and slag may enter the main heat exchanger at the outer most roller and move to the inner most roller, following the reverse transmission path described above.

It wifl dso be appreciated that afthough the roflers have on'y been described as having S deflectors on their inner surfaces, the first 6-8 and second 6-9 roller may have deflectors on their outer surface also.

In the illustrated examples, seven baffles and eight rotary spoiler blades are provided in the granulator. This is for iflustration only and different numbers may be used.

Similarly, more than three concentric rollers may be used in the roller heat exchanger 6-2. It is simply preferable to have a path that doubles back on itself In the above examples, high temperature air with a temperature between 300 00 and 450 00 is produced from stag with a temperature between 1100 °C and 1600 °C. It will be appreciated that the temperature of air produced is a function of the temperature of the slag and hotter slag will produce hotter air and cooler slag will produce cooler air.

The method and system described above can be used for liquid and non-liquid slag without any adaptation of the system. Furthermore, the above method and system can be used for slag that is a by product in the product of non-ferrous metals or a by product in the chemical industry. The above system and method is not applicable to slag that is a by product from steel production.

Claims

Claims 1 A heat recovery system for recovering heat from high temperature slag, the system having a heat exchanger comprising: at least first and second cylinders arranged concentrically about an axis around which thc cylinders arc configured to rotate; a slag inlet provided in the first cylinder for receiving high temperature slag; a slag outlet provided in the second cylinder for discharging cooled slag; and a slag transmission path between the inlet and outlet, along which the slag is passed, the slag transmission path running from the inlet, through the first cylinder in a first direction and through the second cylinder in a second direction, opposite the first direction, to the outlet.
2. A heat recovery system as claimed in claim 1 wherein the heat exchanger comprises a third cylinder arranged concentrically with the first and second cylinders, the slag transmission path running through the third cylinder in the third direction, to the outlet.
3, A hcat recovery system as claimed in claim 1 or claim 2, wherein the slag outlet forms an air inlet for receiving air into the heat exchanger and the slag inlet forms an air outlet for heated air such that air is passed from the slag outlet to the slag inlet, and wherein thc slag exchanges heat with the air as the slag moves along the slag transmission path.
4, A heat recovery systcm as claimed in any preceding claim, wherein the internal walls of the cylinders are provided with deflectors to direct the slag along the slag transmission path.
5, A heat recovery system as claimed in any preceding claim, wherein the cylinders are tapered to direct the slag along the slag transmission path.
6. A heat recovery system as claimed in claim 5. wherein the cylinders arc tapered such that they narrow in the direction of the slag transmission path.
7. A heat recovery system as claimed in any preceding claim, further comprising a closed circuit air circu'ation system for feeding air to the stag outlet and taking air away from the slag inlet.
8, A heat recovery system as claimed in daim 6 wherein the air is circulated through the air circulation system by fans.
9. A heat rccovcry systcm as claimcd in claim 8 whcrein the fan is arranged to providc a negative pressure differential through the heat exchanger to draw the air through the heat exchanger.
10. A heat recovery system as claimed in claim 8 or claim 9. wherein the air circu'ation system comprises a temperature sensor arranged to detect the temperature of heated air discharged by the heat exchanger.
11. A heat recovery system as claimed in claim 10, wherein the air circu'ation system is arranged such that if the detected air temperature exceeds a threshold value, the air is provided for downstream use and if the air is below the threshold value, the air is recycled to the slag outlet.
12. A heat recovery as daimed in claim I I. wherein the high temperature slag is at a temperature between 1100 °C and 1600 °C.
13. A heat recovery as claimed in claim 12 wherein the threshold temperature is between 300°C and 45 0°C.
14. A heat recovery system as claimed in any preceding claim comprising a high-temperature granulator for granulating high temperature slag prior to its introduction to the heat exchanger, the high temperature granu'ator comprising a vertical cyhnder with an inlet for high temperature slag at the top, an inlet for air at the bottom and an outlet for granulated slag at the bottom.
15. A heat recovers' system from high-temperature slag as claimed iii claim 14, in which the high-temperature granulator is mounted with shaft driven by a hydrauhc motor or electric motor in the underside of the equipment.

16, A heat recovery system as claimed in caini 15, in which the shaft of the high-temperature granulator is installed with a plurality of sets of rotary spoiler blades, arranged to decrease the falling speed of the crushed high-temperature stag.

17, A heat recovery system as claimed in claim 16, in which the internal wall of the high-temperature granulator is installed with several sets of ring shaped baffles, arranged to uniformly disperse slag in the spoiler blades (3-2) to avoid slag fall direcfly a'ong the cylinder walL iS. A heat recovery system as claimed in claim 17, in which the shaft (3-1) inside the high temperature granulator is protected bya\'ater cooling system.19, A heat recovery system as claimed in any of claims 14 to 18 wherein the air is drawn from the air inlet to the air outlet by a negative pressure differential, and is heated as it is drawn.20, A heat recovery system as claimed in claim wherein the granulated slag from the granulated slag outlet is provided to the slag inlet of the heat exchanger.21, A heat recovery system as daimed in any of claims 14 to 20, comprising a crushing apparatus for crushing high temperature slag and providing crushed high temperature slag to the high temperature granulator.22, A heat recovery system as claimed in 21, in which the crushing apparatus comprises a container that can separate high temperature slag into crushed high temperature slag and non-crushing slag.23, A heat recovery system as claimed in daim 22, wherein the crushing apparatus comprises a first oudet for providing crushed slag to the high temperature granulator and a second outlet for discharging non-crushing slag.24. A heat recovery system as daimed in claim 22 or claim 23, in which the crushing apparatus comprises a fixed jaw plate and a movable jaw p'ate, wherein the movable jaw plate is driven by a hydraulic cylinder or electric plunger and moves around an eccentric shaft and interacts with the fixed jaw plate for crushing high-temperature slag, A heat recovery system as daimed in claim 24, in which the fixed jaw p'ate is arrange to move horizontafly, such that non-crushing stag faH along a rigid grate to the second outlet.26. A heat recovery system as claimed in claim 25, wherein the fixed jaw plate is mounted with a locking device, comprising a hydraulic cylinder or an electric push rod driver, arranged to lock the fixed jaw in place.27. A heat recovery system as claimed in any of claims 24 to 26, in which the movable jaw plate, the fixed jaw plate and the eccentric shaft are protected by water cooling system 28. A heat recovery system as claimed in any of claims 21 to 27, wherein the closed crushing device is arranged to receive preheated air from the high temperature granulator, the closed crushing device comprising an outlet for preheated air.29. A heat recovery system as claimcd in claim 28 wherein the preheated air from the air outlet of the crushing device is provided to the slag outlet of the heat exchanger.30. A heat recovery device as claimed in any of claims 14 to 29, comprising a tilting device to provide high temperature stag into the crushing apparatus, the tilting device arranged to receive 31. A heat recovery system as claimed in any preceding claim, in which the slag inlet comprises a feedstock device for the main heat exchanger.32. A heat recovery as claimed in claim 31, in which the feedstock device of the main heat exchanger comprises an inlet for granulated slag, an outlet for granulated slag and an outlet for high-temperaturc air.33. A heat recovery system as claimed iii claim 32 in which the feedstock device of the main heat exchanger comprises a cylinder with the granulated stag inlet in the top, the granulated slag outlet at one end and the air outlet at the other end.34. A heat recovery system as claimed in daim 31 or 32, in which the feedstock device of the main heat exchanger is provided with arc chute inside, arranged to direct the high-temperature slag into the first cylinder.35. A heat recovery system as daimed in any preceding claim wherein the rotation of the cylinders is driven by a motor group.36. A heat recovery system as claimed claim 35 in which the cylinders are driven in the same direction.37. A heat recovery system as claimed in claim 35 or claim 36, wherein the cylinders are driven at substantiafly the same speed.38, A heat recovery system as claimed in any preceding claim, comprising a slag output device of the main heat exchanger, the slag output device of the main heat exchanger comprising a low-temperature slag outlet and a preheated air inlet.39. A heat recovery system as claimed in claim 38 in which the outlet comprises a cylinder with the slag inlet at one end, the slag outlet at the other and the air inlet in the top.40, A heat recovery system as claimed in claim 38 or claim 39 in which the output is provided with an arc chute inside, arranged to lead the low-temperature slag into a reciprocating or vibrating feeder.41, A heat recovery system as claimed in any preceding claim, wherein the first cylinder is within the second cylinder. and wherein the second cylinder is within the third cylinder. wherein the slag transmission path rlLns through the first cylinder in the first direction, between the exterior of the first cylinder and the interior of the second cylinder in the second direction, and between the exterior of the second cyhnder and the interior of the third cylinder in the first direction.42, A heat recovery system as claimed in claim 41 wherein the slag passes from the first cylinder to the second cylinder via an open end of the first cylinder and from the second cylinder to the third via an open end of the second cylinder.43 A heat recovery system as claimed in claim 41 or 42 wherein the second cylinder is longer than the first cylinder and shorter than the third cylinder.44, A heat recovery system as claimed in any of daims 41 to 43 in which the first and second cylinder are wholly received in the third cylinder, and the first cylinder projects from the open end of the second cylinder, and wherein the exterior of the third cylinder forms the exterior of the heat exchanger.45. A method of heat recovery from high-temperature slag comprising: passing high temperature slag along a transmission path between a slag inlet of a heat exchanger and an oufiet, the path passing in a first direction through a first concentric cyhnder and in a second direction, opposite the first direction, through a second concentric cylinder, to the slag outlet; and passing air from the slag outlet to the slag inlet, the slag heating the air as they pass through the heat exchanger.46. A method of heat recovery as claimed in claim 45, the slag transmission path passing through a third cylinder, in the first direction, to the slag outlet.47. A method of heat recovery from high-temperature slag as claimed in claim 45 or 46 comprising crushing and granulating the slag prior to heat exchange.48. A method of heat recovery from high-temperature slag as claimed in claim 47, in which the granu'ating and/or crushing step(s) further comprise(s) preheating air, the preheated air provided to the slag outlet, 49. A method of heat recovery from high-temperature slag as claimed in any of claims 44 to 48 comprising: detecting the temperature of heated air discharged at the slag outlet; if the detected air temperature exceeds a threshold value providing for down stream use; and if the air is below the threshold value, providing the air to the slag outlet.50, A method of heat recovery as claimed in daini 49, wherein the high temperature slag is at a temperature between 1100 CC and 1600 °C.51 A method of heat recovery from high-temperature slag as claimed in 50, wherein the threshold temperature is between 300°C and 450°C.