EP0141890B1 - Waste gas circulation method and system for sintering apparatus - Google Patents
Waste gas circulation method and system for sintering apparatus Download PDFInfo
- Publication number
- EP0141890B1 EP0141890B1 EP19830402210 EP83402210A EP0141890B1 EP 0141890 B1 EP0141890 B1 EP 0141890B1 EP 19830402210 EP19830402210 EP 19830402210 EP 83402210 A EP83402210 A EP 83402210A EP 0141890 B1 EP0141890 B1 EP 0141890B1
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- EP
- European Patent Office
- Prior art keywords
- heat
- zone
- heat exchanging
- waste gases
- sintering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/16—Sintering; Agglomerating
- C22B1/20—Sintering; Agglomerating in sintering machines with movable grates
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B21/00—Open or uncovered sintering apparatus; Other heat-treatment apparatus of like construction
- F27B21/06—Endless-strand sintering machines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/004—Systems for reclaiming waste heat
Definitions
- the present invention relates generally to an on-strand type sintering apparatus having a sintering zone and a cooling zone extending along a horizontal strand and, more particularly, to both a waste gas circulation method and a waste gas circulation system for heat recovery of the on-strand type sintering apparatus.
- the sintering apparatus existing in the art is generally divided into two types, namely, a separate type, in which a sintering machine and a cooling machine are so separately arranged that the sintered ore product discharged from the former is introduced into and cooled by the latter after it has been crushed, and an on-strand type in which a sintering zone and a cooling zone immediately following the former zone are formed to extend along a horizontal strand.
- the water has to be preheated in case the waste gases coming from the intermediate and downstream portions of the sintering machine are to be subjected to a heat exchanging process. This is because those waste gases contain such a considerable amount of SO X that condensation of sulfuric acid is undesirably invited.
- the heat recovery is conducted only from the waste gases coming from the cooling zone while allowing the sensible heat of the hot waste gases to uselessly dissipate into the atmosphere.
- the waste gases coming from the cooling zone are sufficiently hot as to permit the heat recovery therefrom. This is because the sinter in the cooling zone shrinks to generate fine cracks all over the section of the cooling zone so that its effective surface area to be cooled can be so increased as to reduce the flow rate of the cooling air and to shorten the cooling time period.
- an object of the present invention to provide a waste gas circulation method for effectively recovering the heat which might otherwise be released from an on-strand type sintering apparatus having its sintering and cooling zones extending continuously along a horizontal strand.
- Another object of the present invention is to provide a waste gas circulation system for putting the above-specified method into practice by repeatedly circulating the waste gases through a charge mixture of ore, solid fuel and flux being sintered and through the sintered ore product thereby to effectively recover the heatwhich might otherwise be carried away by the waste gases discharged.
- the present invention is based upon the aforementioned differences between the separate type and on-stand type sintering apparatus and has been conceived in view of the facts that the waste gases discharged from the sintering apparatus take their maximum temperature at a point where the sintering reaction is completed in the actual run of the sintering apparatus, namely, where the cooling operation is started, and that the point and its neighborhood act an an important zone for recovering that sensible heat.
- the gist of the present invention resides in that the hottest waste gases arising at the final stage of the sintering zone and at the front stage of the cooling zone, in which the sintering reaction is completed, are subjected to heat recovery, and in that the problem, which naturally takes place in the case of the heat recovery, namely, the condensation of sulfur oxides SO x of the waste gases in the form of droplets of sulfuric acid is prevented by preheating the water, which is supplied for the purpose of that heat recovery, with the waste gases coming from the downstream half of the cooling zone.
- a waste gas circulation method for heat recovery of on-strand type sintering apparatus which includes: a sintering zone having a plurality of wind boxes; and a cooling zone extending just downstream of said sintering zone and having a plurality of wind boxes, comprising: a first step of exchanging the heat of still hot waste gases coming from the wind boxes belonging to both the intermediate stage and at least a portion of the final stage of said cooling zone with cold water to recover said heat thereby to heat said cold water into hot water; and a second step of exchanging the heat of the hot waste gases coming directly from the wind boxes belonging to a mixed zone consisting of the final stage of said sintering zone and the front stage of said cooling zone with the hot water, which has been heated at the first-named heat exchanging step, to recover the second-named heat thereby to heat said hot water into steam, whereby the heat generated by the sintering action of a charge mixture of ore, solid fuel and flux can be efficiently recovered as said steam
- the second heat exchanging step comprises; a first sub-step of exchanging the heat of the hottest waste gases coming directly from the wind boxes (163) belonging to a mixed zone consisting of the final stage of said sintering zone and the front stage of said cooling zone with steam to recover the second-named heat thereby to heat said steam into superheated steam, and a second sub-step of exchanging the heat of the waste gases, which have been subjected to the first heat exchanging sub-step, with the hot water, which has been heated at the first heat exchanging step, thereby to heat said hot water into the steam which is to be heated at the first heat exchanging sub-step.
- a waste gas circulation system for heat recovery of on-strand type sintering apparatus which includes: a sintering strand arranged generally in a horizontal direction; conveying means for conveying a charge mixture of ore, solid fuel and flux along said sintering strand; feeding means for feeding said conveying means with said charge mixture; ignition means for igniting the solid fuel in said charge mixture at the surface thereof so that the sintering of said charge mixture may be started; and a plurality of wind boxes arranged on line below and opened toward said charge mixture through the pallets of said sintering strand, said wind boxes being so grouped as to belong to an ignition zone, which underlies said ignition means, a sintering zone, in which the sintering reaction of said charge mixture proceeds until it is completed, and a cooling zone in which a sintered ore product resulting from said sintering reaction is cooled down, comprising: first heat exchanging means for exchanging the heat of still hot waste gases coming from the wind
- reference numeral 10 Indicated at reference numeral 11 is a sintering strand which is arranged to extend in a horizontal direction.
- the sintering strand 11 supports a plurality of not-shown pallets which are driven to travel in series therealong so that they are successively fed with a hearth layer and a charge mixture of ore, solid fuel and flux from a hearth layer hopper 12 and a mixture surge hopper 13, respectively.
- the charge mixture is ignited at its surface by the action of an ignition furnace 14 so that the sintering reaction of the charge mixture may be started.
- the suction system 17 is composed of a corresponding number of branch ducts or downcomers 17 1 , which are respectively connected with the wind boxes 16 (i.e., Nos.
- a trunk duct or collector main 17 2 which is connected with the downcomers 17, in a merging manner and which has its downstream portion extending through the electrostatic precipitator 18 1 , the suction blower 15 and the desulfurating and denitrating device 18 2 .
- the downcomers 17, are respectively equipped with valves 17 3 for controlling the respective flow rates of the waste gases therethrough.
- the waste gases thus cleared of the dust and the SO X and NO x are discharged from the collector main 17 2 to the atmosphere by way of a stack 19.
- the pallets are driven to travel on rails 21, which are mounted on the sintered strand 11, by the rotations of a charge side sprocket 22 and a discharge side sprocket 23.
- the charge mixture is ignited at its surface by the action of the ignition furnace 14.
- the solid fuel in the charge mixture thus ignited sinters the ore more deeply into the charge mixture as this mixture is conveyed from the feed end to the discharge end.
- the resultant sinter or the sintered ore product is crushed by means of a crusher 24.
- the crushed sinter is fed to a not-shown cooling machine in which it is cooled down. In this meanwhile, dust resulting from the crushing operation is so much that it has to be carried by suction to a not-shown dust collector (which may be of electrostatic type).
- FIG. 2 an on-strand type sintering apparatus, which is indicated generally at reference numeral 20 and which is equipped with a waste gas circulation system 30 according to the present invention, will be described.
- like reference numerals indicate like or corresponding parts of the sintering apparatus 10 of the prior art shown in Fig. 1.
- wind boxes are divided into a first group of wind boxes 16 i (which are numbered at 1 to 6), a second group of wind boxes 16 2 (which are numbered at 7to 11), a third group of wind boxes 16 3 (which are numbered at 12 to 16), and a fourth group of wind boxes 16 4 (which are numbered at 17 to 20).
- the first group wind boxes 16 are further grouped into the wind boxes Nos. 1 and 2, which belong to the ignition zone underlying the ignition furnace 14, and into the wind boxes Nos. 3 to 6, which belong to the front stage of the sintering zone where the sintering reaction of the charge mixture proceeds.
- the second group wind boxes Nos. 7 to 11 belong to the intermediate stage of the sintering zone where that sintering reaction further proceeds.
- the third group wind boxes Nos. 12 to 16 belong to the final stage of the sintering zone, where that sintering reaction is completed, and to the front stage of a cooling zone where the sintered ore product is cooled down.
- the fourth group wind boxes Nos. 17 to 20 belong to the intermediate and final stages of the cooling zone where the sinter or sintered ore product is sufficiently cooled down for the subsequent crushing operation resorting to a crusher 24'.
- the first group wind boxes 16 1 i.e., Nos. 1 to 6, are connected with the stack 19 through an electrostatic precipitator 18, and a blower 15, by way of the downcomers 17 11 and the collector main 17 21 -
- the second group wind boxes 16 2 i.e., Nos. 7 to 11, are made to merge into the collector main 17 2 , through a desulfurating and denitrating device 18 2 and a blower 15 2 by way of the downcomers 17 12 and the collector main 17 22 .
- the third group wind boxes 16 3 i.e. Nos.
- the fourth group wind boxes 16 4 are connected through the downcomers 17 14 and the collector main 17 24 with a waste-heat boiler 27 so that the waste gases may be circulated, after they have exchanged their heat with the water flowing through a water pipe, to a mixed zone hood 28 by the action of a blower 15 4 .
- reference numeral 29 indicates a fresh air guide hood which extends above the pallets travelling over the wind boxes Nos. 17 to 20 of the intermediate and final stages of the cooling zone and above the discharge end of the sintering apparatus 20 for guiding fresh air into the sinter. Since the fresh air guide hood 29 forms such a compartment as is opened toward the discharge end for allowing the dust, which might otherwise drop down to the outside, to be returned together with the fresh air to the particular sinter.
- Pure water is supplied from the outside to flow through the water pipe of the waste-heat boiler 27 until the resultant hot water flows into a steam drum 31, as better seen from Fig. 3.
- the hot water reserved in the lower portion of the steam drum 31 is pumped out by the action of a pump 32 to the evaporator portion 25 2 of the waste-heat boiler 25 so that it is heated into steam, which is to be returned to the steam drum 31.
- the steam thus reserved in the upper portion of the steam drum 31 is guided through the superheater portion 25, of the waste-heat boiler 25, in which it is heated into superheated steam. This superheated steam is then discharged to the outside so that its energy may be recovered as an electric power by driving a steam turbine or the like.
- reference numerals 33, and 33 2 indicate dampers which are connected, respectively, between the downcomers 17" and 17 12 leading from the wind boxes 16, and 16 2 of the front and intermediate stages of the sintering zone and between the downcomers 17, 2 and 17 13 leading from the wind boxes 16 2 of the intermediate stage of the sintering zone and the wind boxes 16 3 of the mixed zone.
- the dampers 33, and 33 2 thus connected are adjusted so as to obtain a smooth sloping variation in the pressure difference at each boundary portion between the adjacent groups of wind boxes.
- Fig. 4 there is shown another embodiment of the present invention, in which the water pipe of the waste-heat boiler 27 is also divided into two portions, i.e., an evaporator portion 27, and an economizer portion 27 2 both connected with the steam drum 31.
- the remaining construction is absolutely the same as the first embodiment shown in Fig. 3, and the description to be made in the following is accordingly directed only to the different portion of the construction.
- the pure water is supplied at a flow rate, which corresponds to the steam generation rate of the waste-heat boilers 25 and 27, first to the economizer portion 27 2 of the waste-heat boiler 27, in which it is preheated until it flows into the steam drum 31.
- the hot water reserved in the lower portion of the steam drum 31 is pumped out by the actions of the pumps 32 and 32', respectively, to the evaporator portions 25 2 and 27, of the waste-heat boilers 25 and 27, in which it is heated until it is returned to the steam drum 31.
- the steam thus separated by the steam drum 31 is then introduced into the highest- temperature portion of the superheater portion 25, of the water pipe of the waste-heat boiler 25 until it is discharged as the superheated steam to the outside of the heat exchanging system under discussion.
- Fig. 5 illustrates the sintering zone temperature distribution and the NOx and SO x concentration patterns along the strand in accordance with the present Example.
- the point at which the sintering reaction is completed is located at the wind box No. 14. More specifically, the instant when the temperatures A of the waste gases reach their maximum in an actual running operation is found to occur approximately three minutes after the temperature of the combustion zone of the lowermost layer has reached the maximum temperature. That instant is referred to as the "Burn Through Point" which is indicated at reference letters BTP.
- BTP the mixed zone extending from the wind box No. 12 to the wind box No.
- the high-temperature combustion zone C reaches the lowermost surface at the end of the second group wind boxes 16 2 .
- the sintering reaction at this point is not completed yet, as has been touched in the above, so that the SO x is still generated at such a considerable rate as will invite the mixing of the SO x with the waste gases coming from the third group wind boxes 16 3 belonging to the mixed zone. Therefore, one might deduce that sulfuric acid would condense in the form of droplets on the water pipes of the waste-heat boiler 25 and would cause corrosion of the evaporator and superheating pipes.
- the pure water has already been heated in the waste-heat boiler 27 so that at least the warm water will flow through those pipes of the waste-heat boiler 25, there is no danger of the pipe corrosion due to the condensation of sulfuric acid.
Description
- The present invention relates generally to an on-strand type sintering apparatus having a sintering zone and a cooling zone extending along a horizontal strand and, more particularly, to both a waste gas circulation method and a waste gas circulation system for heat recovery of the on-strand type sintering apparatus.
- In the prior art, there have been proposed a variety of waste-heat recovering methods for a sintering apparatus, all of which have not succeeded in providing an efficient one. In other words, the methods thus far proposed have failed to reach the level of the so-called "energy generating process" in which such energy is generated as can sufficiently cover that to be consumed for driving the sintering apparatus itself.
- The sintering apparatus existing in the art is generally divided into two types, namely, a separate type, in which a sintering machine and a cooling machine are so separately arranged that the sintered ore product discharged from the former is introduced into and cooled by the latter after it has been crushed, and an on-strand type in which a sintering zone and a cooling zone immediately following the former zone are formed to extend along a horizontal strand.
- In the separate type sintering apparatus, heat radiation takes place while the sintered ore product, which is still hot, is being crushed, and pallets of the sintering machine, which have conveyed both the charge mixture of ore, solid fuel and flux to be sintered and the sintered ore product, are returned back in a still hot state to receive a fresh charge mixture while allowing its heat to radiate to the surrounding atmosphere. This make it rather difficult to effectively recover the heat which remains conserved in the cooling machine. Another heat loss is caused while the sintered ore product is being transferred from the sintering machine to the cooling machine. In the cooling machine, moreover, the sinter supplied has been so roughly crushed that it has a limited surface area to be effective for the cooling operation. As a result, the sintered ore product or sinter cannot be sufficiently cooled down unless the flow rate of cooling air is increased. This inevitably lowers the temperature of the waste gases coming from the downstream half of the cooling machine, thus making it difficult to recover the heat from the relatively cool waste gases. Therefore, no separate type sintering apparatus of the prior art has endeavored to recover any heat from the downstream half of its cooling machine. Even if, on the other hand, it is intended to recover the heat from the waste gases coming from the upstream half of the cooling machine, it is unnecessary to preheat a heat transferring medium such as water because those waste gases contain no suflur oxides SOx. On the contrary, the water has to be preheated in case the waste gases coming from the intermediate and downstream portions of the sintering machine are to be subjected to a heat exchanging process. This is because those waste gases contain such a considerable amount of SOX that condensation of sulfuric acid is undesirably invited.
- In the latter type, i.e., on-strand type sintering apparatus having its sintering and cooling zones formed along the common strand, the heat recovery is conducted only from the waste gases coming from the cooling zone while allowing the sensible heat of the hot waste gases to uselessly dissipate into the atmosphere. In this respect, more specifically, the waste gases coming from the cooling zone are sufficiently hot as to permit the heat recovery therefrom. This is because the sinter in the cooling zone shrinks to generate fine cracks all over the section of the cooling zone so that its effective surface area to be cooled can be so increased as to reduce the flow rate of the cooling air and to shorten the cooling time period.
- It is, therefore, an object of the present invention to provide a waste gas circulation method for effectively recovering the heat which might otherwise be released from an on-strand type sintering apparatus having its sintering and cooling zones extending continuously along a horizontal strand.
- Another object of the present invention is to provide a waste gas circulation system for putting the above-specified method into practice by repeatedly circulating the waste gases through a charge mixture of ore, solid fuel and flux being sintered and through the sintered ore product thereby to effectively recover the heatwhich might otherwise be carried away by the waste gases discharged.
- The present invention is based upon the aforementioned differences between the separate type and on-stand type sintering apparatus and has been conceived in view of the facts that the waste gases discharged from the sintering apparatus take their maximum temperature at a point where the sintering reaction is completed in the actual run of the sintering apparatus, namely, where the cooling operation is started, and that the point and its neighborhood act an an important zone for recovering that sensible heat.
- The gist of the present invention resides in that the hottest waste gases arising at the final stage of the sintering zone and at the front stage of the cooling zone, in which the sintering reaction is completed, are subjected to heat recovery, and in that the problem, which naturally takes place in the case of the heat recovery, namely, the condensation of sulfur oxides SOx of the waste gases in the form of droplets of sulfuric acid is prevented by preheating the water, which is supplied for the purpose of that heat recovery, with the waste gases coming from the downstream half of the cooling zone.
- According to a feature of the present invention, there is provided a waste gas circulation method for heat recovery of on-strand type sintering apparatus which includes: a sintering zone having a plurality of wind boxes; and a cooling zone extending just downstream of said sintering zone and having a plurality of wind boxes, comprising: a first step of exchanging the heat of still hot waste gases coming from the wind boxes belonging to both the intermediate stage and at least a portion of the final stage of said cooling zone with cold water to recover said heat thereby to heat said cold water into hot water; and a second step of exchanging the heat of the hot waste gases coming directly from the wind boxes belonging to a mixed zone consisting of the final stage of said sintering zone and the front stage of said cooling zone with the hot water, which has been heated at the first-named heat exchanging step, to recover the second-named heat thereby to heat said hot water into steam, whereby the heat generated by the sintering action of a charge mixture of ore, solid fuel and flux can be efficiently recovered as said steam from a sintered ore product, and whereby sulfur oxides, which are carried in the mixture of the hot waste gases having passed through both the wind boxes belonging to the final stage of said sintering zone and wind boxes belong to the front stage of said cooling zone, can be maintained at a relatively high temperature during the second-named heat exchanging step by the hot water, which has recovered the heat of said still hot waste gases, so that said sulfur oxides can be prevented from condensing in the form of droplets of sulfuric acid while ensuring substantially corrosion-free operation of the second-named heat exchanging step.
- According to another feature of the present invention, the second heat exchanging step comprises; a first sub-step of exchanging the heat of the hottest waste gases coming directly from the wind boxes (163) belonging to a mixed zone consisting of the final stage of said sintering zone and the front stage of said cooling zone with steam to recover the second-named heat thereby to heat said steam into superheated steam, and a second sub-step of exchanging the heat of the waste gases, which have been subjected to the first heat exchanging sub-step, with the hot water, which has been heated at the first heat exchanging step, thereby to heat said hot water into the steam which is to be heated at the first heat exchanging sub-step.
- According to still another feature of the present invention, there is provided a waste gas circulation system for heat recovery of on-strand type sintering apparatus which includes: a sintering strand arranged generally in a horizontal direction; conveying means for conveying a charge mixture of ore, solid fuel and flux along said sintering strand; feeding means for feeding said conveying means with said charge mixture; ignition means for igniting the solid fuel in said charge mixture at the surface thereof so that the sintering of said charge mixture may be started; and a plurality of wind boxes arranged on line below and opened toward said charge mixture through the pallets of said sintering strand, said wind boxes being so grouped as to belong to an ignition zone, which underlies said ignition means, a sintering zone, in which the sintering reaction of said charge mixture proceeds until it is completed, and a cooling zone in which a sintered ore product resulting from said sintering reaction is cooled down, comprising: first heat exchanging means for exchanging the heat of still hot waste gases coming from the wind boxes belonging to both the intermediate stage and at least a portion of the final stage of said cooling zone with cold water to recover said heat thereby to heat said cold water into hot water: first waste gas circulating means for sucking and supplying fresh air to the sintered ore product at both the intermediate stage and at least a portion of the final stage of said cooling zone, and for circulating the still hot waste gases, which have passed through said wind boxes of said intermediate and final stages of said cooling zone, through said first heat exchanging means to the charge mixture, which is being and has been sintered at a mixed zone consisting of the final stage of said sintering zone and the front stage of said cooling zone; second heat exchanging means for exchanging the heat of the waste gases coming directly from the wind boxes belonging to said mixed zone with steam to recover the second-named heat to heat said steam into superheated steam; third heat exchanging means disposed in tandem downstream of said second heat exchanging means for exchanging the heat of the hottest waste gases, which have passed through said second-named heat exchanging means, to recover the third-named heat thereby to heat said hot water into the steam which is to be heated by said second-named heat exchanging means; second waste gas circulating means for sucking and supplying said hottest waste gases to the second-named heat exchanging means and then to the third-named heat exchanging means and for circulating the waste gases, which have passed through said second- and third-named heat exchanging means, to the charge mixture which is to be sintered at the front and intermediate stages of said sintering zone.
- For further particular embodiments of the invention reference is made to the claims.
- Other objects, features and advantages of the present invention will now become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
- Fig. 1 is a schematic view showing the arrangement of an example of a separate type sintering apparatus according to the prior art;
- Fig. 2 is also a schematic view but shows the arrangement of an on-strand type sintering apparatus which is equipped with a waste gas circulation system embodying the present invention;
- Fig. 3 is an enlarged flow chart showing an essential portion of the waste gas circulation system of Fig. 2 for regeneratively cooling the sintered ore product so as to effectively recover its heat through heat exchanging operations;
- Fig. 4 is similar to fig. 3 but shows another embodiment of the waste gas circulation system according to the present invention; and
- Fig. 5 is a graphical presentation illustrating the patterns of both temperatures and NOX and SOx concentrations in the sintering zone, which are plotted against the distance taken along the strand.
- Before entering into detailed description of the present invention, cursory review will now be made upon the separate type sintering apparatus of the prior art, which is indicated generally at
reference numeral 10. Indicated atreference numeral 11 is a sintering strand which is arranged to extend in a horizontal direction. - The
sintering strand 11 supports a plurality of not-shown pallets which are driven to travel in series therealong so that they are successively fed with a hearth layer and a charge mixture of ore, solid fuel and flux from ahearth layer hopper 12 and amixture surge hopper 13, respectively. As the pallets on thesintering strand 11 travel, the charge mixture is ignited at its surface by the action of anignition furnace 14 so that the sintering reaction of the charge mixture may be started. At the same time, fresh air is sucked by the action of asuction blower 15 through the charge mixture by way of a plurality ofwind boxes 16, which are arranged on line below thesintering strand 11 and which are consecutively numbered at 1 to 14 and through asuction system 17 so that the resultant waste gases may be introduced into an electrostatic precipitator 18, and subsequently into a desulfurating and denitrating device 182. Thesuction system 17 is composed of a corresponding number of branch ducts ordowncomers 171, which are respectively connected with the wind boxes 16 (i.e., Nos. 1 to 14), and a trunk duct or collector main 172 which is connected with thedowncomers 17, in a merging manner and which has its downstream portion extending through the electrostatic precipitator 181, thesuction blower 15 and the desulfurating and denitrating device 182. Moreover, thedowncomers 17, are respectively equipped withvalves 173 for controlling the respective flow rates of the waste gases therethrough. The waste gases thus cleared of the dust and the SOX and NOx are discharged from the collector main 172 to the atmosphere by way of astack 19. Incidentally, the pallets are driven to travel onrails 21, which are mounted on thesintered strand 11, by the rotations of a charge side sprocket 22 and adischarge side sprocket 23. - As those pallets travel along the
sintering strand 11, the charge mixture is ignited at its surface by the action of theignition furnace 14. The solid fuel in the charge mixture thus ignited sinters the ore more deeply into the charge mixture as this mixture is conveyed from the feed end to the discharge end. The resultant sinter or the sintered ore product is crushed by means of acrusher 24. The crushed sinter is fed to a not-shown cooling machine in which it is cooled down. In this meanwhile, dust resulting from the crushing operation is so much that it has to be carried by suction to a not-shown dust collector (which may be of electrostatic type). - Turning now to Fig. 2, an on-strand type sintering apparatus, which is indicated generally at
reference numeral 20 and which is equipped with a wastegas circulation system 30 according to the present invention, will be described. Incidentally, like reference numerals indicate like or corresponding parts of thesintering apparatus 10 of the prior art shown in Fig. 1. Below thestrand 11 of thesintering apparatus 20, there are arranged on line a number of, e.g., twenty wind boxes. These wind boxes are divided into a first group of wind boxes 16i (which are numbered at 1 to 6), a second group of wind boxes 162 (which are numbered at 7to 11), a third group of wind boxes 163 (which are numbered at 12 to 16), and a fourth group of wind boxes 164 (which are numbered at 17 to 20). - More specifically, the first
group wind boxes 16, are further grouped into the wind boxes Nos. 1 and 2, which belong to the ignition zone underlying theignition furnace 14, and into the wind boxes Nos. 3 to 6, which belong to the front stage of the sintering zone where the sintering reaction of the charge mixture proceeds. The second group wind boxes Nos. 7 to 11 belong to the intermediate stage of the sintering zone where that sintering reaction further proceeds. The third group wind boxes Nos. 12 to 16 belong to the final stage of the sintering zone, where that sintering reaction is completed, and to the front stage of a cooling zone where the sintered ore product is cooled down. The fourth group wind boxes Nos. 17 to 20 belong to the intermediate and final stages of the cooling zone where the sinter or sintered ore product is sufficiently cooled down for the subsequent crushing operation resorting to a crusher 24'. - The first
group wind boxes 161, i.e., Nos. 1 to 6, are connected with thestack 19 through an electrostatic precipitator 18, and ablower 15, by way of thedowncomers 1711 and the collector main 1721- On the other hand, the secondgroup wind boxes 162, i.e., Nos. 7 to 11, are made to merge into the collector main 172, through a desulfurating and denitrating device 182 and ablower 152 by way of thedowncomers 1712 and the collector main 1722. On the contrary, the thirdgroup wind boxes 163, i.e. Nos. 12 to 16, are connected through thedowncomers 1713 and the collector main 1723 with a waste-heat boiler 25 so that the waste gases may be circulated, after they have exchanged their heat with hot water or steam flowing through water pipes, to asintering zone hood 26 by the action of ablower 153. Moreover, the fourthgroup wind boxes 164, i.e., Nos. 17 to 20, are connected through thedowncomers 1714 and the collector main 1724 with a waste-heat boiler 27 so that the waste gases may be circulated, after they have exchanged their heat with the water flowing through a water pipe, to a mixedzone hood 28 by the action of ablower 154. Incidentally,reference numeral 29 indicates a fresh air guide hood which extends above the pallets travelling over the wind boxes Nos. 17 to 20 of the intermediate and final stages of the cooling zone and above the discharge end of thesintering apparatus 20 for guiding fresh air into the sinter. Since the fresh air guide hood 29 forms such a compartment as is opened toward the discharge end for allowing the dust, which might otherwise drop down to the outside, to be returned together with the fresh air to the particular sinter. - Pure water is supplied from the outside to flow through the water pipe of the waste-
heat boiler 27 until the resultant hot water flows into asteam drum 31, as better seen from Fig. 3. On the other hand, the hot water reserved in the lower portion of thesteam drum 31 is pumped out by the action of apump 32 to theevaporator portion 252 of the waste-heat boiler 25 so that it is heated into steam, which is to be returned to thesteam drum 31. The steam thus reserved in the upper portion of thesteam drum 31 is guided through thesuperheater portion 25, of the waste-heat boiler 25, in which it is heated into superheated steam. This superheated steam is then discharged to the outside so that its energy may be recovered as an electric power by driving a steam turbine or the like. - Reverting to Fig. 2, incidentally, reference numerals 33, and 332 indicate dampers which are connected, respectively, between the
downcomers 17" and 1712 leading from thewind boxes downcomers wind boxes 162 of the intermediate stage of the sintering zone and thewind boxes 163 of the mixed zone. The dampers 33, and 332 thus connected are adjusted so as to obtain a smooth sloping variation in the pressure difference at each boundary portion between the adjacent groups of wind boxes. - Turning now to Fig. 4, there is shown another embodiment of the present invention, in which the water pipe of the waste-
heat boiler 27 is also divided into two portions, i.e., anevaporator portion 27, and aneconomizer portion 272 both connected with thesteam drum 31. The remaining construction is absolutely the same as the first embodiment shown in Fig. 3, and the description to be made in the following is accordingly directed only to the different portion of the construction. - The pure water is supplied at a flow rate, which corresponds to the steam generation rate of the waste-
heat boilers economizer portion 272 of the waste-heat boiler 27, in which it is preheated until it flows into thesteam drum 31. On the other hand, the hot water reserved in the lower portion of thesteam drum 31 is pumped out by the actions of thepumps 32 and 32', respectively, to theevaporator portions heat boilers steam drum 31. The steam thus separated by thesteam drum 31 is then introduced into the highest- temperature portion of thesuperheater portion 25, of the water pipe of the waste-heat boiler 25 until it is discharged as the superheated steam to the outside of the heat exchanging system under discussion. - Fig. 5 illustrates the sintering zone temperature distribution and the NOx and SOx concentration patterns along the strand in accordance with the present Example. With close reference to Fig. 5, it will be understood that the point at which the sintering reaction is completed is located at the wind box No. 14. More specifically, the instant when the temperatures A of the waste gases reach their maximum in an actual running operation is found to occur approximately three minutes after the temperature of the combustion zone of the lowermost layer has reached the maximum temperature. That instant is referred to as the "Burn Through Point" which is indicated at reference letters BTP. In the present Example, the mixed zone extending from the wind box No. 12 to the wind box No. 16, the latter of which belongs to the cooling zone downstream of the Burn Through Point, allows heat recovery of the waste gases at a high temperature of 400 to 500°C. Furthermore, the waste gases in that mixed zone, which consists of the final stage of the sintering zone and the front state of the cooling zone, still has an oxygen concentration as high as 19 to 20% and a moisture content as low as 1.0 to 1.5% so that the particular waste gases can be advantageously reused as the burning air. Thus, this reuse is conducted for the wind boxes Nos. 3 to 11, which belong to the front and intermediate stages of the sintering zone, so that generation of NOx can be restricted to 15 to 20%. Incidentally, reference letter C appearing in Fig. 5 indicates the high-temperature zone at 1200°C or higher, namely, the combustion zone where the charge mixture is being burned.
- The high-temperature combustion zone C reaches the lowermost surface at the end of the second
group wind boxes 162. Despite of this fact, the sintering reaction at this point is not completed yet, as has been touched in the above, so that the SOx is still generated at such a considerable rate as will invite the mixing of the SOx with the waste gases coming from the thirdgroup wind boxes 163 belonging to the mixed zone. Therefore, one might deduce that sulfuric acid would condense in the form of droplets on the water pipes of the waste-heat boiler 25 and would cause corrosion of the evaporator and superheating pipes. However, since the pure water has already been heated in the waste-heat boiler 27 so that at least the warm water will flow through those pipes of the waste-heat boiler 25, there is no danger of the pipe corrosion due to the condensation of sulfuric acid. -
- Thanks to the construction thus far described, according to the present invention, it is possible to achieve heat recovery of regenerative type while assuring that the boiler components will not be corroded by the waste gases.
Claims (13)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8383402210T DE3371412D1 (en) | 1983-11-16 | 1983-11-16 | Waste gas circulation method and system for sintering apparatus |
EP19830402210 EP0141890B1 (en) | 1983-11-16 | 1983-11-16 | Waste gas circulation method and system for sintering apparatus |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19830402210 EP0141890B1 (en) | 1983-11-16 | 1983-11-16 | Waste gas circulation method and system for sintering apparatus |
Publications (2)
Publication Number | Publication Date |
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EP0141890A1 EP0141890A1 (en) | 1985-05-22 |
EP0141890B1 true EP0141890B1 (en) | 1987-05-06 |
Family
ID=8191463
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Application Number | Title | Priority Date | Filing Date |
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EP19830402210 Expired EP0141890B1 (en) | 1983-11-16 | 1983-11-16 | Waste gas circulation method and system for sintering apparatus |
Country Status (2)
Country | Link |
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EP (1) | EP0141890B1 (en) |
DE (1) | DE3371412D1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0646140B2 (en) * | 1987-02-16 | 1994-06-15 | 住友重機械工業株式会社 | Sintered exhaust heat recovery device |
CN106370019B (en) * | 2016-11-24 | 2018-07-03 | 山东钢铁股份有限公司 | A kind of sintering flue gas capturing device and method |
CN114485178B (en) * | 2022-01-11 | 2022-12-20 | 北京科技大学 | Sintering bed of material drying system of multi-process utilization waste heat in coordination |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
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FR2297922A1 (en) * | 1975-01-15 | 1976-08-13 | Siderurgie Fse Inst Rech | Sinter, plant for iron ore - with agglomeration using steam obtd. by recovering heat from cooling fluid |
AT352408B (en) * | 1978-03-24 | 1979-09-25 | Voest Ag | METHOD OF BURNING PELLETS ON A WALKING GRATE |
FR2444720A1 (en) * | 1978-12-22 | 1980-07-18 | Delattre Levivier | Gas circulation system for endless ore sintering belt - where gas collected in suction boxes in first baking zone is purified and fed into last cooling zone |
JPS5666683A (en) * | 1979-11-02 | 1981-06-05 | Sumitomo Heavy Industries | Sintering equipment |
-
1983
- 1983-11-16 DE DE8383402210T patent/DE3371412D1/en not_active Expired
- 1983-11-16 EP EP19830402210 patent/EP0141890B1/en not_active Expired
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Publication number | Publication date |
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DE3371412D1 (en) | 1987-06-11 |
EP0141890A1 (en) | 1985-05-22 |
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