Waste heat recovery system

Abstract

A waste heat recovery system includes a hot product, a conveyor that conveys the slab from a first position to a second position, an enclosure that partially encloses the slab between the first position and the second position, a fan disposed outside of the enclosure and operable to deliver a flow of air into the enclosure at a first temperature, the flow of air being heated by the slab as the slab moves from the first position to the second position to produce a flow of heated air, the flow of heated air having a second temperature higher than the first temperature, a discharger formed as part of the enclosure and operable to discharge the flow of heated air from the enclosure, and a heat exchanger coupled to the discharger to receive the flow of heated air to produce a flow of heated fluid.

Description

WASTE HEAT RECOVERY SYSTEMBACKGROUND

[0001] In steel manufacture plants, hot molten steel is poured into a mold to form slabs or other forms, like billets, etc. in continuous casting. This semi solid slabs are moved forward on roller conveyors for cutting and cooling. Conventionally, the hot metal slabs are cooled down with water sprays increasing water consumption of the steel plant and / or allowed to cool naturally in the storage yard with or without water spray. Waste heat of the slabs is not recovered and is dissipated into atmosphere.BRIEF SUMMARY

[0002] In one aspect, a waste heat recovery system is provided. The waste heat recovery system includes a hot product, a conveyor that conveys the slab from a first position to a second position, an enclosure that partially encloses the slab between the first position and the second position, a fan disposed outside of the enclosure and operable to deliver a flow of air into the enclosure at a first temperature, the flow of air being heated by the slab as the slab moves from the first position to the second position to produce a flow of heated air, the flow of heated air having a second temperature higher than the first temperature, a discharger formed as part of the enclosure and operable to discharge the flow of heated air from the enclosure, and a heat exchanger coupled to the discharger to receive the flow of heated air to produce a flow of heated fluid. The heat exchanger is coupled to the fan to recirculate a flow of exhaust air from the heat exchanger back to the enclosure.

[0003] In one aspect, a method for recovering waste heat from a hot product is provided. The method includes conveying the hot product from a first position to a second position,enclosing a portion of the hot product between the first position and the second position by an enclosure, delivering a flow of air into the enclosure at a first temperature, heating the flow of air with the hot product as the hot product moves from the first position to the second position to produce a flow of heated air, the flow of heated air having a second temperature higher than the first temperature, discharging the flow of heated air from the enclosure to a heat exchanger, passing the flow of heated air through the heat exchanger to produce a flow of heated fluid, and recirculating a flow of exhaust air from the heat exchanger back to the enclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0005] FIG. 1 illustrates a schematic diagram of a waste heat recovery system.

[0006] FIG. 2 illustrates a schematic piping and instrumentation diagram of a waste heat recovery system of FIG. 1.

[0007] FIG. 3 illustrates a schematic section view of the waste heat recovery system along section line 3-3 of FIG. 2.

[0008] FIG. 4 illustrates a schematic piping and instrumentation diagram of another waste heat recovery system of FIG. 1.DETAILED DESCRIPTION

[0009] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in thefollowing drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0010] Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0011] It should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including”, “having”, and “comprising”, as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and / or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard toone embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0012] Although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0013] In addition, the term “adjacent to" may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of twenty percent would fall within the meaning of these terms unless otherwise stated.

[0014] FIG. 1 illustrates a schematic diagram of a waste heat recovery system 100. The waste heat recovery system 100 includes a hot product In the embodiment shown in FIG. 1 , FIG. 2, FIG. 3, and FIG. 4, the hot product is slab 102, for example slabs provided by a caster 104 in a steel manufacture plant. In other embodiments, the hot product may include slags produced by the steel manufacture plant or any other types of products having a high temperature.

[0015] The slab 102 is transferred to a conveyor 106. The conveyor 106 moves in directions as indicated by the arrow lines and transports the slab 102 from a first position to a second position. The conveyor 106 is made of heat resistant materials and includes a plurality of rollers disposed on a roller bed. The roller bed is made of heat resistant materials and includes a plurality of air channels built into the roller bed. In otherembodiments, the rollers and roller bed may be replaced with any other beam transport system, such as walking beam transport system or slat chain transport system, etc.

[0016] An enclosure 108 at least partially encloses the conveyor 106 and the slab 102 between the first position and the second position. Only one enclosure 108 is illustrated in FIG. 1. In other embodiments, two or more enclosures 108 may be used to at least partially enclose the conveyor 106 and the slab 102 between the first position and the second position. The enclosure 108 includes an entrance 110 to receive the slab 102 into the enclosure 108 and an exit 112 to exit the slab 102 out of the enclosure 108. A first seal 114 is disposed at the entrance 110 and a second seal 114 is disposed at the exit 112 to minimize heat leakage from the enclosure 108. The first and second seals 114 are air curtains created by air nozzles. In other embodiments, the first and second seals 114 may be any other types of seals that can minimize heat leakage.

[0017] A plurality of fans 116 are disposed outside of the enclosure 108 and are operated to deliver a flow of air 118 into the enclosure 108. The flow of air 118 has a first temperature. The flow of air 118 passes the conveyor 106 and flows around and is heated by the slab 102 as the slab 102 moves with the conveyor 106 from the first position to the second position to produce a flow of heated air 120. The flow of air 118 includes flow of ambient air 122. The flow of ambient air 122 is controlled by a plurality of dampers 218. The plurality of dampers 218 may reduce or stop the flow of ambient air 122 flowing into the enclosure 108 after stabilization of cooling in the enclosure 108. The plurality of fans 116 can be disposed under the enclosure 108 and mounted on sides of the enclosure 108.

[0018] The flow of heated air 120 has a second temperature that is higher than the first temperature. The flow of heated air 120 is delivered to a heat exchanger 124 containing a flow of fluid. The flow of fluid is heated by the heated air 120 to produce a flow of heated fluid. In the embodiment shown in FIG. 1, FIG. 2, FIG. 3, and FIG. 4, the fluid is water, and the heated fluid is steam and water mixture 126. In other embodiments, the fluid may be any other types of heat transfer fluids, such as synthetic hydrocarbon, silicone-based fluids, molten salts, molten metals, nitrogen, argon, helium, hydrogen, mineral oils, etc. The flow of steam and water mixture 126 is delivered to a tank 128 to produce a flow ofsteam 132. The tank 128 may be a steam drum. The flow of steam 132 is delivered to a unit 130 for utilizing the flow of steam 132.

[0019] FIG. 2 illustrates a schematic piping and instrumentation diagram of a waste heat recovery system 200. The enclosure 108 includes at least one discharger. The enclosure 108 including the discharger may be a membrane panel or plane sheet metal with refractory lining. In the embodiment shown in FIG. 2, the discharger includes a first discharger 202 and a second discharger 204. The first discharger 202 is disposed at an upstream side of the enclosure 108 and the second discharger 204 is disposed at a downstream side of the enclosure 108 with respect to the moving direction of the slab 102. The heated air 120 in the upstream side of the enclosure 108 has a temperature that is higher than the heated air 120 in the downstream side of the enclosure 108.

[0020] The first discharger 202 is operatively coupled to the heat exchanger 124. The heat exchanger 124 contains water. A first portion of the heated air 120 is discharged from the first discharger 202 to the heat exchanger 124 to produce a flow of steam and water mixture 126. The first portion of the heated air 120 is from the upstream side of the enclosure 108. The flow of steam and water mixture 126 is delivered to the tank 128 to separate the steam and water mixture 126 to steam and water. The flow of steam and water mixture 126 is delivered to the tank 128 from an upstream side of the heat exchanger 124 with respect to a flow direction of the heated air 120. A flow of water 206 is delivered from a downstream side of the heat exchanger 124 to the tank 128. The heat exchanger 124 has a countercrossflow configuration in which the flow of heated air 120 flows in a counter crossflow direction to heat the fluid in the heat exchanger 124. A flow of cold fluid is delivered to the downstream side of the heat exchanger 124 and is heated by the flow of heated air 120 and the flow of heated fluid is discharged from the upstream side of the heat exchanger 124. In other embodiments, the heat exchanger 124 may have any other configurations as desired.

[0021] A flow of steam 132 is delivered from the tank 128 to the unit 130 for utilizing the steam 132. The unit 130 may be a turbine using the steam 132 to generate power, or a furnace using the steam 132 to generate heat, or other power cycle equipment, such as organic Rankine cycle or supercritical CO2 cycle turbines, etc. The unit 130 is operativelycoupled to a feed water pump 208. A flow of condensate 210 from the unit 130 is pumped back to the downstream side of the heat exchanger 124 through the feed water pump 208. The flow of condensate 210 is produced after the steam 132 performs the desired functions.

[0022] The heat exchanger 124 is operatively coupled to the plurality of fans 116. A flow of exhaust air 212 from the heat exchanger 124 is recirculated back to the enclosure 108 through the plurality of fans 116 as a portion of the flow of air 118. The flow of exhaust air 212 is produced after the heated air 120 passing through the heat exchanger 124 to produce the steam and water mixture 126. In the embodiment shown in FIG. 2, the flow of exhaust air 212 is split into a first portion and a second portion and controlled by dampers 218. The first portion of the flow of exhaust air 212 is recirculated back to the downstream side of the enclosure 108 and the second portion of the flow of exhaust air 212 is delivered to a stack 220 through the fan 116 and discharged from the stack 220. The fan 116 may be an induced draft fan 116. In other embodiments, the first portion of the flow of exhaust air 212 or the entire flow of exhaust air 212 may be recirculated back to any desired locations of the enclosure 108 or the entire flow of exhaust air 212 is discharged from the stack 220. The plurality of fans 116 are disposed under the enclosure 108 and above the enclosure 108.

[0023] The second discharger 204 is operatively coupled to the plurality of fans 108. A second portion of the heated air 120 is discharged from the second discharger 204 and is recirculated back to the enclosure 108 through the plurality of fans 116 as a further portion of the flow of air 118. The second portion of the heated air 120 is from the downstream side of the enclosure 108. In the embodiment shown in FIG. 2, the second portion of the heated air 120 is recirculated back to the upstream side of the enclosure 108. In other embodiments, the second portion of the heated air 120 may be recirculated back to any desired locations of the enclosure 108. The second portion of the heated air 120 has a temperature that is lower than the first portion of the heated air 120.

[0024] A first portion of a flow of exhaust water 214 from the tank 128 is recirculated back to the downstream side of the heat exchanger 124. A second portion of the flow of exhaust water 214 from the tank 128 is recirculated back to a pipe 304 (shown in FIG. 3) through arecirculation pump 216. The pipe 304 is disposed within the enclosure 108. The second portion of the flow of exhaust water 214 is heated by the heat generated by the slabs 102 and the heated air 120 to produce a further flow of steam and water mixture 126. The further flow of steam and water mixture 126 is delivered to the tank 128 to produce the flow of steam 132. The recirculation pump 216 and the feed water pump 208 may be the same type of pump. In other embodiments, a first portion of a flow of exhaust fluid from the tank 128 is recirculated back to the downstream side of the heat exchanger 124, and a second portion of the flow of exhaust fluid from the tank 128 is recirculated back to the pipe 304 to produce a further flow of heated fluid and is delivered to the tank 128. The fluid may be any other types of heat transfer fluids, such as synthetic hydrocarbon, silicone-based fluids, molten salts, molten metals, nitrogen, argon, helium, hydrogen, mineral oils, etc.

[0025] FIG. 3 illustrates a schematic section view of the waste heat recovery system 200 along section line 3-3 of FIG. 2. The plurality of fans 116 are disposed on two sides of the enclosure 108 to deliver the flow of air 118 around the slab 102. For illustration purpose, the discharger shown in FIG. 3 is labeled as the first discharger 202. It is understood that the discharger includes the second discharger 204. It is also possible that the enclosure 108 may have only one discharger.

[0026] The enclosure 108 includes a wall 302. The wall 302 is insulated from an outer side to minimize heat loss from the enclosure 108. The wall 302 is made of heat resistant materials and may have refractory lining. The pipe 304 is attached to an inner side of the wall 302 to cool the wall 302 and to produce the further flow of steam and water mixture 126 which is delivered to the tank 128.

[0027] A hopper 306 is disposed under the conveyor 106 to collect scraps from the slab 102. The hopper 306 includes fluid cooled plates and is locked by rotary air. The fluid in the fluid cooled plate of the hopper 306 is heated by the scraps to produce a further flow of heated fluid which is delivered to the tank 128. The fluid may be water and the heated fluid is steam and water mixture 126. The fluid may also be any other types of heat transfer fluids, such as synthetic hydrocarbon, silicone-based fluids, molten salts, molten metals, nitrogen, argon, helium, hydrogen, mineral oils, etc. The hopper 306 includes erosionresistant lining and is connected to a fluid supply pipe by welding or any other types of connection methods. In other embodiments, the hopper 306 may not include fluid cooled plates.

[0028] A heat reflector 308 is attached to the wall 302 to reflect the radiation generated by the slab 102. The reflected radiation is used to heat the flow of air 118. In the embodiment shown in FIG. 3, the heat reflector 308 is placed on the inner side of the wall 302 and below the slab 102 in a trench between the conveyor 106 and the wall 302. In other embodiments, the heat reflector 308 may be placed on any inner locations of the wall 302.

[0029] FIG. 4 illustrates a schematic piping and instrumentation diagram of another waste heat recovery system 400. In this embodiment, the flow of heated air 120 is discharged from the enclosure 108 to the heat exchanger 124. In the embodiment shown in FIG. 4, the flow of heated air 120 is discharged from the first discharger 202 and the second discharger 204 to the heat exchanger 124. In other embodiments, the enclosure 108 may have one discharger to discharge the flow of heated air 120 to the heat exchanger 124. The flow of exhaust air 212 from the heat exchanger 124 is delivered to a stack 220 and discharged from the stack 220.

[0030] In operation, the flow of air 118 is delivered to the enclosure 108 by the plurality of fans 116. The flow of air 118 passes the conveyor 106 through the plurality of air channels built into the conveyor 106 and flows around and is heated by the slab 102 as the slab 102 moves from the first position to the second position to produce a flow of heated air 120. The slab 102 is air quenching cooled. The flow of heated air 120 is discharged from the enclosure 108 to the heat exchanger 124. The water in the heat exchanger 124 is heated by the flow of heated air 120 to produce a flow of steam and water mixture 126. The flow of steam and water mixture 126 is delivered to the tank 128 to generate a flow of steam 132. The flow of steam 132 is delivered to the unit 130 to utilize the steam 132, such as to generate power or heat, or any other types of equipment that uses the steam 132 to perform desired functions. The condensate 210 from the unit 130 is recirculated back to the downstream side of the heat exchanger 124 by the feed water pump 208. The exhaust air212 from the heat exchanger 124 is recirculated back to the enclosure 108 by the plurality of fans 116.

[0031] The second portion of the heated air 120 from the downstream side of the enclosure 108 is discharged from the enclosure 108 and is recirculated back to the upstream side of the enclosure 108 which reduces an overall consumption of the ambient air 114 during the waste heat recovery process and increases the temperature of the heated air 120 discharged from the enclosure 108.

[0032] The pipe 304 cools the wall 302 of the enclosure 108 and recovers more heat from the slab 102. The water cooled hopper 306 with rotary air lock collects scraps and recover heat from the scraps by conduction to the water cooled plates of the hopper 306. The heat reflector 308 reflects the radiation to further enhance the heat transfer. The waste heat recovery systems 100 and 400 recover and utilize the waste heat from the slab 102 which improves efficiency of the steel manufacturing process and reduces energy consumption.

[0033] Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form.

[0034] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.LISTING OF DRAWING ELEMENTS100 waste heat recovery system102 slabcaster conveyor enclosure entrance exit seal fan air heated air ambient air heat exchanger steam and water mixture tank unit steam waste heat recovery system first discharger second discharger water feed water pumpcondensate exhaust air exhaust water recirculation pump damper stack wall pipe hopper heat reflector waste heat recovery system

Claims

CLAIMSWhat is claimed is:

1. A waste heat recovery system comprising: a hot product; a conveyor that conveys the slab from a first position to a second position; an enclosure that partially encloses the slab between the first position and the second position; a fan disposed outside of the enclosure and operable to deliver a flow of air into the enclosure at a first temperature, the flow of air being heated by the slab as the slab moves from the first position to the second position to produce a flow of heated air, the flow of heated air having a second temperature higher than the first temperature; a discharger formed as part of the enclosure and operable to discharge the flow of heated air from the enclosure; and a heat exchanger coupled to the discharger to receive the flow of heated air to produce a flow of heated fluid, wherein the heat exchanger is coupled to the fan to recirculate a flow of exhaust air from the heat exchanger back to the enclosure.

2. The waste heat recovery system of claim 1, wherein the flow of exhaust air is recirculated back to a downstream side of the enclosure with respect to a moving direction of the hot product.

3. The waste heat recovery system of claim 1, wherein the enclosure comprises a first discharger disposed at an upstream side of the enclosure and a second discharger disposed at a downstream side of the enclosure with respect to a moving direction of the hot product.

4. The waste heat recovery system of claim 3, wherein the first discharger is operable to discharge a first portion of the heated air from the enclosure to the heat exchanger, and wherein the second discharger is operable to recirculate a second portion of the heated air from the enclosure back to the enclosure through the fan.

5. The waste heat recovery system of claim 4, wherein the second portion of the heated air is recirculated back to the upstream side of the enclosure.

6. The waste heat recovery system of claim 1, wherein the flow of heated fluid comprises a flow of steam and water mixture, and wherein the waste heat recovery system further comprises a tank coupled to the heat exchanger to receive the flow of steam and water mixture and to produce a flow of steam.

7. The waste heat recovery system of claim 6, further comprising a pipe attached to an inner side of the enclosure, wherein the tank is coupled to the pipe to deliver a flow of exhaust water from the tank to the pipe to produce a further flow of steam and water mixture which is delivered to the tank to produce the flow of steam.

8. The waste heat recovery system of claim 1, further comprising a hopper disposed under the conveyor to produce a further flow of heated fluid.

9. The waste heat recovery system of claim 1, further comprising a first seal disposed at an entrance of the enclosure and a second seal disposed at an exit of the enclosure.

10. The waste heat recovery system of claim 1, further comprising a stack coupled to the heat exchanger to discharge a flow of exhaust air.

11. A method for recovering waste heat from a hot product, the method comprising: conveying the hot product from a first position to a second position; enclosing a portion of the hot product between the first position and the second position by an enclosure; delivering a flow of air into the enclosure at a first temperature; heating the flow of air with the hot product as the hot product moves from the first position to the second position to produce a flow of heated air, the flow of heated air having a second temperature higher than the first temperature; discharging the flow of heated air from the enclosure to a heat exchanger; passing the flow of heated air through the heat exchanger to produce a flow of heated fluid; and recirculating a flow of exhaust air from the heat exchanger back to the enclosure.

12. The method of claim 11, further comprising recirculating the flow of exhaust air from the heat exchanger back to a downstream side of the enclosure with respect to a moving direction of the hot product.

13. The method of claim 11, further comprising discharging a first portion of the heated air from an upstream side of the enclosure to the heat exchanger and discharging and recirculating a second portion of the heated air from a downstream side of the enclosure back to the enclosure with respect to a moving direction of the hot product.

14. The method of claim 13, further comprising recirculating the second portion of the heated air back to the upstream side of the enclosure.

15. The method of claim 11, wherein the flow of heated fluid comprises a flow of steam and water mixture, and wherein the method further comprises delivering the flow of steam and water mixture from the heat exchanger to a tank to produce a flow of steam.

16. The method of claim 15, wherein the enclosure comprises a pipe attached to an inner side of the enclosure, and wherein the method further comprising delivering a flow of exhaust water from the tank to the pipe to produce a further flow of steam and water mixture and delivering the further flow of steam and water mixture to the tank to produce the flow of steam.

17. The method of claim 11, further comprising producing a further flow of heated fluid by a hopper disposed under the conveyor.

18. The method of claim 11, further comprising sealing an entrance and an exit of the enclosure.

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