Waste heat recovery system

Abstract

A waste heat recovery system 100 includes a conveyor 104 for conveying a slag 102 from a first position to a second position. An enclosure 106 partially encloses the slag between the two positions, an

Description

BACKGROUND

[0001] Steel slag from steel manufacture plant is a by-product of steelmaking process. Most slags are used for manufacturing of cement, building materials, aggregates of road construction and fertilizer, etc. Some slags are dumped in waste disposal sites or landfills. The dumped slags can have a temperature up to 1700°C and contain a considerable amount of energy. Conventionally, this wasted heat from slags is treated by water quenching which uses water to cool down the slags. However, it consumes a huge amount of water and fails to recover any usable heat from the slags. BRIEF SUMMARY

[0002] In one aspect, a waste heat recovery system is provided. The waste heat recovery system includes a slag, a conveyor that conveys the slag from a first position to a second position, an enclosure that partially encloses the slag 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 slag as the slag 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.

[0003] In one aspect, a method for recovering waste heat from a slag is provided. The method includes conveying the slag from a first position to a second position, enclosing a portion of the slag between the first position and the second position, delivering a flow of air into the enclosure at a first temperature, heating the flow of air with the slag as the slag 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, and passing the flow of heated air through the heat exchanger to produce a flow heated fluid. 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 diagram of another waste heat recovery system.

[0007] FIG. 3 illustrates a schematic diagram of a yet another waste heat recovery system. DETAILED DESCRIPTION

[0008] 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 the following 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.

[0009] 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.

[0010] 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 to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0011] 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.

[0012] 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.

[0013] 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, and FIG. 3, the hot product is slag 102, for example slags produced by a steel manufacture plant. In other embodiments, the hot product may include slabs from a steel manufacture plant or any other types of products having a high temperature.

[0014] The slag 102 is transferred to a conveyor 104. The conveyor 104 moves in directions as indicated by the arrow lines and transports the slag 102 from a first position to a second position. The conveyor 104 is made of heat resistant materials and includes a plurality of air channels built into the conveyor 104.

[0015] An enclosure 106 at least partially encloses the conveyor 104 and the slag 102 between the first position and the second position. A plurality of fans 108 are disposed outside of the enclosure 106 and are operated to deliver a flow of air 110 into the enclosure 106. The flow of air 110 has a first temperature. The flow of air 110 passes the conveyor 104 through the plurality of air channels and flows around and is heated by the slag 102 as the slag 102 moves with the conveyor 104 from the first position to the second position to produce a flow of heated air 112. The flow of heated air 112 has a second temperature that is higher than the first temperature. The flow of air 110 includes flow of ambient air 114. The flow of ambient air 114 is controlled by a plurality of dampers 136. The plurality of dampers 136 may reduce or stop the flow of ambient air 114 flowing into the enclosure 106 after stabilization of cooling in the enclosure 106.

[0016] The enclosure 106 includes at least one discharger. In the embodiment shown m FIG. 1, the discharger includes a first discharger 116 and a second discharger 118. The first discharger 116 is disposed at an upstream side of the enclosure 106 and the second discharger 118 is disposed at a downstream side of the enclosure 106 with respect to the moving direction of the slag 102. The heated air 112 in the upstream side of the enclosure 106 has a temperature that is higher than the heated air 112 in the downstream side of the enclosure 106.

[0017] The first discharger 116 is operatively coupled to a heat exchanger 120. The heat exchanger 120 contains a flow of fluid. A first portion of the heated air 112 is discharged from the first discharger 116 to the heat exchanger 120 to produce a flow of heated fluid. The first portion of the heated air 112 is from the upstream side of the enclosure 106. In the embodiment shown m FIG. 1, FIG. 2, and FIG. 3, the fluid is water, and the heated fluid is heated water 122. 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 heat exchanger 120 has a countercrossflow configuration in which the flow of heated air 112 flows in a counter crossflow direction to heat the fluid in the heat exchanger 120. A flow of cold fluid is delivered to a downstream side of the heat exchanger 120 with respect to a flow direction of the heated air 112 and is heated by the flow of heated air 112 and the flow of heated fluid is discharged from an upstream side of the heat exchanger 120. In other embodiments, the heat exchanger 120 may have any other configurations as desired.

[0018] The flow of heated water 122 is discharged from the upstream side of the heat exchanger 120 and delivered to a tank 124 to produce a flow of steam 126. The tank 124 may be a steam drum. The flow of steam 126 is delivered from the tank 124 to a unit 128 for utilizing the steam 126. The unit 128 may be a turbine using the steam 126 to generate power or a furnace using the steam 126 to generate heat, other power cycle equipment like but not limited to organic Rankine cycle or supercritical CO2 cycle turbines, etc. The unit 128 is operatively coupled to a pump 130. A flow of exhaust water 132 from the unit 128 is pumped back to the downstream side of the heat exchanger 120 through the pump 130. The flow of exhaust water 132 is produced after the steam 126 performs the desired functions.

[0019] The heat exchanger 120 is operatively coupled to the plurality of fans 108. A flow of exhaust air 134 from the heat exchanger 120 is recirculated back to the enclosure 106 through the plurality of fans 108 as a portion of the flow of air 110. The flow of exhaust air 134 is produced after the heated air 112 producing the heated water 122 in the heat exchanger 120. In the embodiment shown in FIG. 1, a damper 136 is operatively coupled to the heat exchanger 120 to control the flow of exhaust air 134 to split into a first portion and a second portion. The first portion of the flow of exhaust air 134 is recirculated back to the downstream side of the enclosure 106 and the second portion of the flow of exhaust air 134 is delivered to a stack 138 through the fan 108 and discharged from the stack 138. The fan 108 may be an induced draft fan 108. In other embodiments, the first portion of the flow of exhaust air 134 or the entire flow of the 134 may be recirculated back to any desired locations of the enclosure 106 or the entire flow of the exhaust air 134 is discharged from the stack 138.

[0020] The second discharger 118 is operatively coupled to the plurality of fans 108. A second portion of the heated air 112 is discharged from the second discharger 118 and is recirculated back to the enclosure 106 through the plurality of fans 108 as a portion of the flow of air 110. The second portion of the heated air 112 is from the downstream side of the enclosure 106. In the embodiment shown in FIG. 1, the second portion of the heated air 112 is recirculated back to the upstream side of the enclosure 106. In other embodiments, the second portion of the heated air 112 may be recirculated back to any desired locations of the enclosure 106. The second portion of the heated air 112 has a temperature that is lower than the first portion of the heated air 112.

[0021] FIG. 2 illustrates a schematic diagram of another waste heat recovery system 200. In this embodiment, the first portion of the heated air 112 is discharged from the first discharger 116 to a first location of the heat exchanger 120. The second portion of the heated air 112 is discharged from the second discharger 118 to a second location of the heat exchanger 120 that is downstream of the first location with respect to a flow direction of the heated air 112. The flow of exhaust air 134 from the heat exchanger 120 is recirculated back to the enclosure 106 through the plurality of fans 108 as a portion of the air 110. In other embodiments, the first portion of the heated air 112 and the second portion of the heated air 112 may be delivered to the same location of the heat exchanger 120.

[0022] FIG. 3 illustrates a schematic diagram of yet another waste heat recovery system 300. In this embodiment, the flow of the heated air 112 is discharged from the first discharger 116 and the second discharger 118 to the same location of the heat exchanger 120. The flow of exhaust air 134 from the heat exchanger 120 is delivered to a stack 138 through the plurality of fans 108 and discharged from the stack 138. In other embodiments, the enclosure 106 may have only one discharger to discharge the flow of the heated air 112, or the first portion of the heated air 112 discharged from the first discharger 116 and the second portion of the heated air 112 discharged from the second discharger 118 may be delivered to different locations of the heat exchanger 120.

[0023] A first portion of the ambient air 114 is delivered by the plurality of fans 108 to the upstream side of the enclosure 106 and a second portion of the ambient air 114 is delivered by the plurality of fans 108 to the downstream side of the enclosure 106. In other embodiments, the ambient air 114 may be delivered to any desired locations of the enclosure 106 by the plurality of fans 108.

[0024] In operation, the flow of air 110 is delivered to the enclosure 106 by the plurality of fans 108. The flow of air 110 passes the conveyor 104 through the plurality of air channels built into the conveyor 104 and flows around and is heated by the slag 102 as the slag 102 moves from the first position to the second position to produce a flow of heated air 112. The slag 102 is air quenching cooled and breaks into smaller pieces during this process which may eliminate a need of big slag crusher. The flow of heated air 112 is discharged from the enclosure 106 to the heat exchanger 120. The flow of water in the heat exchanger 120 is heated by the flow of heated air 112 to produce a flow of heated water 122. The flow of heated water 122 is delivered to the tank 124 to generate a flow of steam 126. The flow of steam 126 is delivered to the unit 128 to utilize the steam 126, such as to generate power or perform any other desired functions. The exhaust water 132 from the unit 128 is recirculated back to the heat exchanger 120 by the pump 130. The exhaust air 134 from the heat exchanger 120 is recirculated back to the enclosure 106 by the plurality of fans 108.

[0025] The second portion of the heated air 112 from the downstream side of the enclosure 106 is discharged from the enclosure 106 and is recirculated back to the upstream side of the enclosure 106 which reduces an overall consumption of the ambient air 114 during the waste heat recovery process and increases the temperature of the heated air 112 discharged from the enclosure 106.

[0026] The waste heat recovery systems 100, 200, and 300 air quench the slags 102 produced by the steel manufacture plants and breaks the slags 102 into smaller pieces which ensure uniform cooling of the slags 102 and eliminate the need of water spay. The waste heat recovery systems 100, 200, and 300 recover and utilize the waste heat from the slags 102 which improves efficiency of the steel manufacturing process and reduces energy consumption.

[0027] 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.

[0028] 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 ELEMENTS 100 waste heat recovery system 102 slag 104 conveyor 106 enclosure 108 fan 110 air 112 heated air 114 ambient air 116 first discharger 118 second discharger 120 heat exchanger 122 heated water 124 tank 126 steam 128 unit 130 pump 132 exhaust water 134 exhaust air 136 damper 138 stack 200 waste heat recovery system 300 waste heat recovery system

Claims

What is claimed is:

1. A waste heat recovery system comprising:a slag;a conveyor that conveys the slag from a first position to a second position;an enclosure that partially encloses the slag 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 slag as the slag 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; anda heat exchanger coupled to the discharger to receive the flow of heated air to produce a flow of heated fluid.

2. The waste heat recovery system of claim 1, wherein the heat exchanger is coupled to the fan to recirculate a flow of exhaust air from the heat exchanger back to the enclosure.

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

4. 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 slag.

5. The waste heat recovery system of claim 4, 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.

6. The waste heat recovery system of claim 5, wherein the second portion of the heated air is recirculated back to an upstream side of the enclosure with respect to the moving direction of the slag.

7. The waste heat recovery system of claim 4, 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 discharge a second portion of the heated air from the enclosure to the heat exchanger.

8. The waste heat recovery system of claim 7, wherein the second portion of the heated air is discharged to the heat exchanger at a location that is downstream of the first portion of the heated air with respect to a flow direction of the heated air.

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

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

11. The waste heat recovery system of claim 1, further comprising a damper coupled to the heat exchanger to control a flow of exhaust air from the heat exchanger to split into a first portion and a second portion, and wherein the first portion of the flow of exhaust air is recirculated back to the enclosure and the second portion of the flow of exhaust air is delivered to a stack.

12. A method for recovering waste heat from a slag, the method comprising: conveying the slag from a first position to a second position;enclosing a portion of the slag 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 slag as the slag 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; and passing the flow of heated air through the heat exchanger to produce a flow heated fluid.

13. The method of claim 12, further comprising recirculating a flow of exhaust air from the heat exchanger back to the enclosure.

14. The method of claim 13, 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 slag.

15. The method of claim 12, wherein the enclosure comprises an upstream side and a downstream side with respect to a moving direction of the slag, and wherein the method further comprises discharging a first portion of the heated air from the upstream side of the enclosure to the heat exchanger and recirculating a second portion of the heated air from the downstream side of the enclosure back to the enclosure.

16. The method of claim 15, further comprising recirculating the second portion of the heated air back to the upstream side of the enclosure.

17. The method of claim 12, wherein the enclosure comprises an upstream side and a downstream side with respect to a moving direction of the slag, and wherein the method further comprises discharging a first portion of the heated air from the upstream side of the enclosure to a first location of the heat exchanger and discharging a second portion of the heated air from the downstream side of the enclosure to a second location of the heat exchanger, wherein the second location is downstream of the first location with respect to a flow direction of the heated air.

18. The method of claim 12, wherein the flow of heated fluid comprises a flow of heated water, and wherein the method further comprises delivering the flow of heated water from the heat exchanger to a tank to produce a flow of steam.

19. The method of claim 12, further comprising delivering a flow of exhaust air from the heat exchanger to a stack.

20. The method of claim 12, further comprising splitting a flow of exhaust air from the heat exchanger into a first portion and a second portion, recirculating the first portion of the flow of exhaust air back to the enclosure, and delivering the second portion of the flow of exhaust air to a stack.15

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