JP2014025601A - Exhaust gas recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide exhaust gas recovery system capable of improving power generation efficiency.SOLUTION: The exhaust gas recovery system includes: a first exhaust flow path 14 where a blast furnace gas discharged from a furnace body 6 flows; a wet type dust removal part 18 for removing dust in the blast furnace gas led from the furnace body to the first exhaust flow path 14; a second exhaust flow path 20 where the blast furnace gas from which the dust is removed by the wet type dust removal part flows; a power generator 22 for generating power using the blast furnace gas flowing in the second exhaust flow path; and a heat medium circulation device which has a first heat exchange part provided in the first exhaust flow path and a second heat exchange part provided in the second exhaust flow path 20, circulates a heat medium between the first heat exchange part and the second heat exchange part, and exchanges heat through the heat medium between the exhaust gas flowing in the first exhaust flow path and the exhaust gas flowing in the second exhaust flow path.

Description

  The present invention relates to an exhaust gas recovery system that generates power using high-temperature exhaust gas discharged from a heating furnace.

  Heating furnaces such as blast furnaces, reduction furnaces, melting furnaces, and combustion furnaces are equipped with an exhaust gas recovery system that generates power using the high-temperature exhaust gas discharged from the furnaces, so that the energy efficiency of the entire plant equipment is improved. Improvements are being made. In such exhaust gas recovery systems, dry dust removal parts such as cyclones and bag filters and wet dust removal parts such as rings, slits and washers for washing exhaust gas are provided to remove dust in the exhaust gas. The exhaust gas after the dust is removed by the dry dust removing unit and the wet dust removing unit is guided to the power generation device.

  In the power generation device, a turbine such as a gas turbine, an expansion turbine, or a steam turbine is provided. The turbine shaft is rotated by the kinetic energy or thermal energy of the fluid generated by the exhaust gas, and power is generated by the rotational energy of the turbine shaft. ing. At this time, the higher the temperature of the exhaust gas guided to the turbine and the higher the flow rate, the higher the power generation efficiency. However, as described above, the exhaust gas washed with water by the wet dust removal unit is guided to the turbine, so The temperature of gas will be cooled and power generation efficiency will fall.

  Therefore, as in the exhaust gas recovery system disclosed in Patent Document 1, the exhaust gas before the dust is removed by the dry dust removing unit and the wet dust removing unit and the exhaust gas after the dust is removed are converted into a heat exchanger. It is possible to adopt a configuration in which heat is exchanged and guided to the turbine. Thus, if heat exchange is performed between the exhaust gases before and after dust removal, the exhaust gas cooled by the wet dust removing unit can be heated again and guided to the turbine, and the power generation efficiency can be improved.

JP-A-8-28353

  However, in the exhaust gas recovery system disclosed in Patent Document 1, heat is directly exchanged between exhaust gases before and after dust removal. Therefore, there is a need to extend the exhaust gas pipe after dust removal to the exhaust gas pipe before dust removal, and a need for pipe shape change and pipe subdivision to ensure the surface area of the heat exchange section. As a result, the pressure loss increases due to the increase and complexity of the long exhaust gas piping and the bent portion of the piping. In addition, because of heat exchange in the pipe containing a large amount of dust, there is a high risk of pressure loss due to dust clogging in the complicated shape portion and wear of the pipe. For these reasons, there has been a problem of a decrease in power generation efficiency due to an increase in pressure loss and a problem of difficulty in stable operation of the plant due to fear of wear of the heat exchanger.

  An object of the present invention is to provide an exhaust gas recovery system capable of further improving power generation efficiency and realizing stable operation of a plant.

  In order to solve the above problems, according to the exhaust gas recovery system of the present invention, a furnace body, a first exhaust passage through which exhaust gas discharged from the furnace body flows, and the furnace body to the first exhaust passage. Using a wet dust removing unit that removes dust in the guided exhaust gas, a second exhaust channel through which the exhaust gas from which dust has been removed by the wet dust removing unit flows, and an exhaust gas that flows through the second exhaust channel A power generation device that generates power, a first heat exchange section provided in the first exhaust flow path, and a second heat exchange section provided in the second exhaust flow path, the first heat exchange section and the second heat exchange section Heat that circulates a heat medium between the heat exchange section and performs heat exchange between the exhaust gas flowing through the first exhaust flow path and the exhaust gas flowing through the second exhaust flow path via the heat medium. And a medium circulation device.

  In addition, an inner wall that defines the first exhaust flow path and an outer wall that is provided in a radially outward direction of the inner wall while maintaining a gap, and a heat medium is formed by the gap between the inner wall and the outer wall. It is preferable that the first heat exchanging portion through which is distributed is partitioned.

  The first heat exchanging unit may circulate the heat medium along an outer periphery of the first exhaust passage.

  The second heat exchange unit may be provided inside a wall surface that defines the second exhaust flow path, and the heat medium may be circulated along a longitudinal direction of the second exhaust flow path.

  The heat medium circulation device may circulate the heat medium in a direction opposite to a flow direction of the exhaust gas flowing through the first exhaust flow path in the first heat exchange unit.

  The heat medium circulating device may circulate the heat medium in a direction opposite to a flow direction of the exhaust gas flowing through the second exhaust flow path in the second heat exchange unit.

  Also, a dry dust removing unit that removes dust in the exhaust gas flowing through the first exhaust channel and sends it to the wet dust removing unit is provided between the first exhaust channel and the wet dust removing unit. Good.

  The dry dust removing unit may remove dust in the exhaust gas by gravity settling.

According to the present invention, the first heat exchanging unit and the second heat exchanging unit are provided before and after the wet dust removing unit, and through the heat medium circulating between the first heat exchanging unit and the second heat exchanging unit. Since heat exchange is performed, the shape of the piping through which the exhaust gas flows can be simplified. As a result, the pressure loss generated in the exhaust gas and the risk of wear of the piping are reduced, and the power generation efficiency can be improved and the plant can be stably operated.
The power generation efficiency can be further improved.

It is a conceptual diagram for demonstrating a blast furnace plant. It is a conceptual diagram for demonstrating an exhaust-gas collection | recovery system. It is a figure explaining the structure of 1st piping, (a) is a side view, (b) is the III (b) arrow directional view of (a), (c) is in the III (c) line of (a). It is a figure which shows a cross section. It is a figure explaining the structure of 2nd piping, (a) is a side view, (b) is a IV (b) arrow directional view of (a), (c) is in IV (c) line of (a). It is a figure which shows a cross section.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  The exhaust gas recovery system of the present embodiment is widely applicable to heating furnaces that generate high-temperature exhaust gas such as blast furnaces, reduction furnaces, melting furnaces, combustion furnaces, etc. The collection system will be described.

  FIG. 1 is a conceptual diagram for explaining a blast furnace plant. A blast furnace plant 1 shown in FIG. 1 melts iron ore which is a metal raw material to produce pig iron, a reducing agent serving as a fuel such as iron ore and coke, limestone to remove impurities (hereinafter referred to as iron ore). , A mixture of a reducing agent, limestone and the like is simply referred to as a raw material). The raw material stored in the raw material tank 2 is transported to the top of the furnace body 6 by the charging conveyor 4 and charged into the hopper 8 provided in the furnace body 6 from the top.

  Below the hopper 8, there is provided a charging chute 10 that receives the raw material falling from the hopper 8 on an inclined surface and causes the raw material to slide downward on the inclined surface. The charging chute 10 is arranged so that one end is located directly below the center of the hopper 8, the one end is located most vertically above the charging chute 10, and the other end is located vertically below. It rotates in the direction of the arrow indicated by the broken line in the figure with the one end side as the central axis. As a result, the raw material dropped from the hopper 8 falls while sliding on the inclined surface of the charging chute 10 and is dispersed and dropped over the entire periphery of the furnace body 6.

  A blower opening 12 is provided in the lower part of the furnace body 6, and hot air is introduced into the furnace body 6 from the blower opening 12. The hot air introduced into the furnace body 6 ascends the furnace body 6, but when coke in the raw material falling from the charging chute 10 burns with the hot air, carbon monoxide (reducing agent) is generated, and the carbon of the coke is iron. It takes oxygen out of it and produces carbon dioxide and heat, and this reaction becomes a heat source to melt iron ore. In the process of dropping the raw material, such a reaction is continuously performed, and the combustion temperature reaches its maximum when it reaches the lower part of the furnace body 6, and high-temperature liquid pig iron is obtained at the bottom of the furnace body 6.

  A first exhaust passage 14 is connected to the top of the furnace body 6, and high-temperature blast furnace gas (exhaust gas) is discharged from the furnace body 6 to the first exhaust passage 14. A dry dust removing unit 16 and a wet dust removing unit 18 are connected to the first exhaust passage 14 in order from the upstream side in the flow direction of the blast furnace gas. The dry-type dust removing unit 16 removes dust in the blast furnace gas guided from the first exhaust passage 14 from the blast furnace gas by gravity settling. In addition, the structure of this dry-type dust removal part 16 is not specifically limited, For example, you may comprise with a bag filter, a cyclone, etc.

  The blast furnace gas from which dust has been removed by the dry dust removing unit 16 is sent from the dry dust removing unit 16 to the wet dust removing unit 18. The wet dust removing unit 18 rinses the blast furnace gas with water and further removes dust in the blast furnace gas. The specific configuration of the wet dust removing unit 18 is not particularly limited as long as it removes dust in the blast furnace gas by washing with water, but here, it is assumed that it is configured with a so-called ring, slit, and washer. To do.

  The second exhaust passage 20 is connected to the wet dust removing portion 18, and the blast furnace gas from which dust has been removed by washing in the wet dust removing portion 18 is sent to the second exhaust passage 20. The second exhaust passage 20 is connected to a power generation device 22 that generates power using blast furnace gas flowing through the second exhaust passage 20. The power generation device 22 includes a steam turbine, a gas turbine, an expansion turbine, and the like, and generates power by converting the kinetic energy and thermal energy of the blast furnace gas flowing through the second exhaust passage 20 into the rotational motion of the turbine shaft. .

  Further, a gas holder 26 for storing blast furnace gas is connected to the downstream side of the power generation device 22 in the second exhaust flow path 20 via a connection pipe 24, and the furnace body 6 is connected via a connection pipe 28. The hot air furnace 30 which produces | generates the hot air introduce | transduced into is connected. The blast furnace gas introduced into the hot stove 30 is exhausted from the chimney 32 to the atmosphere after the inside of the hot stove 30 is heated. A blower 36 is connected to the hot stove 30 via an introduction pipe 34, and air supplied by the blower 36 is supplied to the hot stove 30 while recovering exhaust heat of the blast furnace gas in the exhaust heat recovery unit 38. Led. Then, the air guided to the hot stove 30 is further heated in the hot stove 30 to become hot air, and is introduced into the furnace body 6 from the air blowing port 12.

  In the gas cycle in the blast furnace plant 1, power generation is performed in the power generation device 22. At this time, the power generation efficiency is increased as the blast furnace gas guided to the power generation device 22 is at a higher temperature and the flow rate of the blast furnace gas is higher. Becomes higher. However, since the blast furnace gas discharged from the furnace body 6 contains a large amount of dust, the blast furnace gas cannot be guided to the turbine of the power generator 22 unless the dust is removed. As a result, the blast furnace gas guided to the power generation device 22 inevitably undergoes a decrease in flow rate due to pressure loss and a decrease in temperature mainly due to the wet dust removing unit 18, resulting in a decrease in power generation efficiency. Therefore, in the blast furnace plant 1 of the present embodiment, the exhaust gas recovery system that increases the flow rate and temperature of the blast furnace gas guided to the power generation device 22 is provided to improve the power generation efficiency. Hereinafter, the exhaust gas recovery system will be described in detail.

  FIG. 2 is a conceptual diagram for explaining the exhaust gas recovery system. In FIG. 2, the flow of the blast furnace gas is indicated by a broken line arrow, and the flow of a heating medium described later is indicated by a solid line arrow. As shown in FIG. 2, the furnace body 6 of the blast furnace plant 1 and the dry dust removal unit 16 are connected by a first pipe 50, and the first blast furnace gas discharged from the furnace body 6 is guided to the dry dust removal unit 16. The exhaust passage 14 is partitioned by the first pipe 50. In addition, the wet dust removing unit 18 and the power generation device 22 are connected by a second pipe 52, and the second exhaust passage 20 that guides the blast furnace gas sent from the wet dust removal unit 18 to the power generation device 22 is a second pipe. A partition 52 is formed.

  A heat medium flow path through which the heat medium flows is partitioned from the first exhaust flow path 14 in the first pipe 50, and a heat medium flow path through which the heat medium flows in the second pipe 52. Is partitioned from the second exhaust flow path 20. The first pipe 50 and the second pipe 52 are connected by connecting pipes 100 and 101. When the pump P is driven, the heat medium is sucked and discharged from the tank T, and the heat of the first pipe 50 and the second pipe 52 is obtained. The heat medium circulates in the direction of the solid line arrow in FIG.

  In the first pipe 50, heat exchange is performed between the high-temperature blast furnace gas immediately after being discharged from the furnace body 6 and the heat medium, and the heat medium heated by this heat exchange causes the connection pipe 100 to pass through. To the second pipe 52. In the second pipe 52, heat exchange is performed between the blast furnace gas cooled in the wet dust removing unit 18 and the heat medium, and the blast furnace gas is heated by this heat exchange and sent to the power generator 22. As described above, the exhaust gas recovery system of the present embodiment includes the heat medium circulation device A having the first pipe 50, the second pipe 52, the connection pipes 100 and 101, the pump P, and the tank T.

  By this heat medium circulation device A, the heat medium is circulated between the first pipe 50 and the second pipe 52, and the blast furnace gas flowing through the first exhaust flow path 14 and the blast furnace flowing through the second exhaust flow path 20. By performing heat exchange with the gas via a heat medium, the following effects are realized. That is, in the first pipe 50, the heat of the blast furnace gas flowing through the first exhaust flow path 14 is taken away by the heat medium, and the blast furnace gas whose flow rate is reduced due to the temperature drop is introduced into the dry dust removal unit 16. . In this way, by introducing the blast furnace gas having a reduced flow rate into the dry dust removal unit 16, the dust removal rate in the dry dust removal unit 16 can be increased. In the second pipe 52, the blast furnace gas flowing through the second exhaust passage 20 is heated again by the heat medium, and the blast furnace gas whose flow rate is increased by the temperature rise is sent to the power generator 22. The power generation efficiency in the power generation device 22 can be improved.

  In addition, in the 1st piping 50 and the 2nd piping 52, the improvement of the heat exchange rate of a heat carrier and blast furnace gas is desired. In particular, blast furnace gas containing a large amount of dust circulates in the first pipe 50, and the first pipe 50 is installed at a high place, so that maintenance is difficult, and wear due to dust is less likely to occur. There is a need to. Therefore, in the present embodiment, the first pipe 50 and the second pipe 52 are configured as follows.

  FIGS. 3A and 3B are diagrams for explaining the configuration of the first pipe 50, in which FIG. 3A is a side view, FIG. 3B is a view taken along line III (b) in FIG. 3A, and FIG. It is a figure which shows the cross section in the (c) line. The first pipe 50 is configured by connecting a plurality of first pipe members 50a in the longitudinal direction. The first piping member 50a is composed of a double pipe, and as shown in FIG. 3 (c), an inner wall 60 that defines the first exhaust passage 14 on the inner side, and a radially outward direction of the inner wall 60. The outer wall 62 is provided with a gap maintained between the inner wall 60 and the outer wall 62, and the first heat exchange section 64 is formed by the gap formed between the inner wall 60 and the outer wall 62.

  The first heat exchange unit 64 functions as a heat medium flow path through which the heat medium flows. The first heat exchange unit 64 includes a plurality of fins extending along the flow direction of the heat medium and the blast furnace gas. 66 are provided at equal intervals in the circumferential direction. Thereby, the heat of the blast furnace gas flowing through the first exhaust flow path 14 is transmitted to the heat medium flowing through the first heat exchanging section 64 via the inner wall 60 and the fin 66, and between the blast furnace gas and the heat medium. In this case, heat exchange is performed.

  Further, flange portions 68a and 68b are provided in the vicinity of both ends of the first piping member 50a. As shown in FIG. 3B, the flange portion 68a is provided with a plurality of connection holes 70 at equal intervals in the circumferential direction. Each of the connection holes 70 communicates with the first heat exchange unit 64, and the heat medium guided to the first piping member 50 a from each connection hole 70 joins at the first heat exchange unit 64. . In addition, although the flange part 68a was demonstrated here, the same number of connection holes 70 are provided also in the flange part 68b.

  A plurality of the first piping members 50a are arranged in the longitudinal direction, and the adjacent first piping members 50a are fixed by welding or the like to constitute the first piping 50. At this time, of the adjacent first piping members 50a, the connecting hole 70 formed in the flange portion 68a of one first piping member 50a and the connecting hole formed in the flange portion 68b of the other first piping member 50a. 70 is connected by a flexible tube or the like. Thereby, a heat medium will distribute | circulate the 1st heat exchange part 64 provided in the 1st piping member 50a sequentially.

  According to said 1st piping 50, the 1st exhaust flow path 14 is division-formed inside the double pipe, and the 1st heat exchange part 64 is divided-formed outside the double pipe. That is, the pipe and wall for partitioning the first heat exchange section 64 do not protrude into the first exhaust flow path 14, that is, on the flow path of the blast furnace gas containing a large amount of dust. A first heat exchanging portion 64 is provided along the outer peripheral surface of the first exhaust passage 14. Thereby, the risk that the first pipe 50 is worn can be reduced. Further, as shown in FIG. 2, in the present embodiment, the heat medium is circulated in the direction opposite to the flow direction of the blast furnace gas flowing through the first exhaust flow path 14 so that the blast furnace gas and the heat medium are opposed to each other. Thus, the heat exchange rate can be further improved.

  4A and 4B are diagrams illustrating the configuration of the second pipe 52, where FIG. 4A is a side view, FIG. 4B is a view taken along the line IV (b) in FIG. 4A, and FIG. It is a figure which shows the cross section in the (c) line. The second pipe 52 is configured by connecting a plurality of second pipe members 52a in the longitudinal direction. As shown in FIG. 4C, the second piping member 52a is disposed along the longitudinal direction of the second piping member 52a, that is, the flow direction of the blast furnace gas, in the wall portion defining the second exhaust flow path 20. A plurality of plate members 80 extending are provided. The plate member 80 is provided with a second heat exchange part 82 functioning as a heat medium flow path through which the heat medium flows, and the heat of the heat medium flowing through the second heat exchange part 82 It is transmitted to the blast furnace gas flowing through the second exhaust flow path 20 via the member 80, and heat exchange is performed between the blast furnace gas and the heat medium.

  Further, as shown in FIGS. 4A and 4B, the same number of protruding pipes 84 as the plate members 80 (second heat exchanging portions 82) are provided in the vicinity of both ends of the second piping member 52a. ing. As shown in FIG. 4B, the projecting pipe 84 is provided with a connection hole 86 communicating with the second heat exchanging portion 82, and the projecting pipe 84 provided on one end side of the second piping member 52a. After the heat medium guided from the connection hole 86 to the second piping member 52a flows through the second heat exchange portion 82 of each plate member 80, the protruding pipe 84 provided on the other end side of the second piping member 52a It is configured to flow out from the connection hole 86.

  Then, a plurality of the second piping members 52a are arranged in the longitudinal direction, and the adjacent second piping members 52a are fixed by welding or the like to constitute the second piping 52. At this time, of the adjacent second piping members 52a, the connecting hole 86 formed in the protruding tube 84 of one second piping member 52a and the connecting hole formed in the protruding tube 84 of the other second piping member 52a. 86 is connected by a flexible tube or the like. Thereby, a heat medium will distribute | circulate the 2nd heat exchange part 82 provided in the 2nd piping member 52a sequentially.

  According to said 2nd piping 52, since the 2nd heat exchange part 82 is arrange | positioned in the 2nd exhaust flow path 20, the contact area of a heat medium and blast furnace gas can be ensured large. As shown in FIG. 2, in the present embodiment, also in the second pipe 52, the heat medium is circulated in the direction opposite to the flow direction of the blast furnace gas flowing through the second exhaust flow path 20, and the blast furnace gas and the heat medium are circulated. Is a counter flow, and a high heat exchange rate can be realized. In the second pipe 52, the dust in the blast furnace gas is removed by the dry dust removing unit 16 and the wet dust removing unit 18, and therefore the risk of wear due to dust is extremely low. Therefore, in the 2nd piping 52, even if it provides the 2nd heat exchange part 82 in the inside, a special trouble will not arise.

  As described above, according to the exhaust gas recovery system of the present embodiment, pressure loss is achieved by avoiding complication of the exhaust gas flow path shape while reducing the risk of pipe wear and realizing stable operation. As a result, the dust removal rate and power generation efficiency can be improved.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above embodiment, the dry dust removing unit 16 and the wet dust removing unit 18 are provided. However, the dry dust removing unit 16 is not an essential configuration, and only the wet dust removing unit 18 may be provided.

  INDUSTRIAL APPLICABILITY The present invention can be used in an exhaust gas recovery system that generates power using high-temperature exhaust gas discharged from a heating furnace.

6 ... Furnace body 14 ... 1st exhaust flow path 16 ... Dry-type dust removal part 18 ... Wet dust removal part 20 ... 2nd exhaust flow path 22 ... Power generator 60 ... Inner wall 62 ... Outer wall 64 ... 1st heat exchange part 82 ... 2nd heat Exchanger A ... Heat medium circulation device

Claims (8)

A furnace body;
A first exhaust passage through which exhaust gas discharged from the furnace body flows;
A wet dust removing unit for removing dust in the exhaust gas led from the furnace body to the first exhaust flow path;
A second exhaust passage through which exhaust gas from which dust has been removed by the wet dust removing section flows;
A power generator that generates power using the exhaust gas flowing through the second exhaust flow path;
A first heat exchange section provided in the first exhaust flow path, and a second heat exchange section provided in the second exhaust flow path, the first heat exchange section and the second heat exchange section, A heat medium circulating between the exhaust gas flowing through the first exhaust flow path and the exhaust gas flowing through the second exhaust flow path through the heat medium. And an exhaust gas recovery system.   An inner wall defining and partitioning the first exhaust flow path; and an outer wall provided with a gap maintained radially outward of the inner wall, and the heat medium flows through the gap between the inner wall and the outer wall. The exhaust gas recovery system according to claim 1, wherein the first heat exchanging section is partitioned. The first heat exchange unit is
The exhaust gas recovery system according to claim 1 or 2, wherein the heat medium is circulated along an outer periphery of the first exhaust passage. The second heat exchange unit is
4. The heat medium is provided inside a wall surface defining the second exhaust flow path, and the heat medium is circulated along a longitudinal direction of the second exhaust flow path. Exhaust gas recovery system. The heating medium circulation device is
4. The exhaust gas recovery system according to claim 2, wherein in the first heat exchange unit, the heat medium is circulated in a direction opposite to a flow direction of the exhaust gas flowing through the first exhaust flow path. The heating medium circulation device is
5. The exhaust gas recovery system according to claim 4, wherein in the second heat exchange unit, a heat medium is circulated in a direction opposite to a flow direction of the exhaust gas flowing through the second exhaust flow path.   A dry dust removing unit is provided between the first exhaust channel and the wet dust removing unit to remove dust in the exhaust gas flowing through the first exhaust channel and send the dust to the wet dust removing unit. The exhaust gas recovery system according to any one of claims 1 to 6.   The exhaust gas recovery system according to claim 7, wherein the dry dust removing unit removes dust in the exhaust gas by gravity sedimentation.

Images