JP5776675B2 - Agglomeration method of wet dust collection dust - Google Patents

Description

  The present invention collects dust contained in the exhaust gas of a vertical furnace by wet dust collection, agglomerates the wet dust collection dust, and recycles it as a raw material of the vertical furnace again. It relates to the formation method.

A method for collecting valuables by agglomerating dust contained in the exhaust gas of a vertical furnace and recycling it again into the vertical furnace has been studied for a long time.
As such, in order to obtain valuable materials by using dust agglomerates in a vertical furnace, the important thing is to carry out pulverization by impact during transportation before charging into the furnace or when charging into the furnace. Is to prevent. This is because the pulverized dust is again discharged as dust together with the exhaust gas from the top of the furnace, making it difficult to recover valuable materials.

  Much of the prior art is intended to reduce this dusting phenomenon by increasing the strength of the dust agglomerates. The dust agglomerated material increases the strength by increasing the amount of the binder or by using a hydraulic binder, and the curing time is lengthened. However, an increase in the amount of the binder leads to an increase in production cost, which is not preferable. In addition, since it is necessary to store the dust agglomerates for a long period of time to increase the curing time, there is a problem that the storage facility becomes large and the equipment cost increases.

  On the other hand, in patent document 1, in order that a dust agglomerate may have the intensity | strength suitable as a raw material of a vertical furnace, predetermined | prescribed quick lime or slaked lime is mix | blended with dusts, and a carbonaceous material as needed. When the powder is blended and the crushing strength per pellet is 20 kgf or more, it is cured in a carbon dioxide-containing gas stream, thereby enabling the dust agglomerate to develop strength in a short period of time.

  In addition, since the following Non-Patent Document 1 is cited in the [Mode for Carrying Out the Invention] described later, it is also described here.

JP-A-48-23613

Japan Chemical Engineering Association, 5th edition, Chemical Engineering Handbook, Maruzen, 1988

  However, in the method described in Patent Document 1, it has become possible for the dust agglomerates to develop strength in a short period of time, but in order to improve this strength, curing under a carbon dioxide atmosphere is required, Construction of a curing room that is cut off from the atmosphere is required, resulting in a significant increase in equipment costs.

  The present invention has been made in view of the circumstances as described above, and when the dust contained in the exhaust gas of the vertical furnace is agglomerated, an increase in production cost due to an increase in the amount of binder and a prolonged curing time, and Provided is a wet dust collection agglomeration method that can efficiently reduce the dust agglomeration phenomenon without increasing the cost of equipment due to an increase in the size of storage facilities or the construction of a curing room. It is for the purpose.

  The present inventors repeated various agglomeration tests of dust generated from a vertical furnace, particularly wet dust collection dust, and investigated the pulverization amount of the produced dust agglomerate to precipitate wet dust collection dust. By optimizing the amount of flocculant used in the process and optimizing the conditions for mixing the wet dust collection dust and hydraulic binder, the amount of powdering can be simplified (without the need for large capital investment) It was found that a dust agglomerated product with a small amount can be produced.

  Usually, dusts solidified (agglomerated) with a hydraulic binder undergo brittle fracture (breakage without plastic deformation in response to impact). For this reason, as described above, until now, the strength of dust agglomerates has been increased to avoid brittle fracture and prevent pulverization, and the amount of binder can be increased, the curing time can be extended, or a special curing method can be used. Etc. have been studied.

  On the other hand, the present inventors have come up with a method for suppressing powdering by imparting ductility to dust agglomerates to absorb impact energy by plastic deformation.

  FIG. 1 is a conceptual diagram for imparting ductility to a dust agglomerate.

  The dust agglomerated material is an aggregate of dust particles, but the conventional dust agglomerated material has joined the dust particles directly with a hydraulic binder. For this reason, the conventional dust agglomerated material is a rigid body, and is brittlely fractured and powdered with respect to external force.

  On the other hand, as shown in FIG. 1A, the present inventors do not collapse the dust aggregate 3 after forming the dust aggregate 3 by aggregating the dust particles 2 by the action of the aggregating agent. Then, the dust aggregates 3 were joined together by the hydraulic binder 4 to produce a dust agglomerated product 1 having ductility.

  FIG. 1B schematically shows a change when an external force is applied to the dust agglomerate 1. Aggregates (dust aggregates) 3 of dust particles 2 are not brittle and have ductility and are easily deformed. Therefore, the dust agglomerate 1 in which these dust aggregates 3 are joined by the hydraulic binder 4 also has ductility. For example, even if an external force is applied due to a drop or collision, the energy is absorbed as energy for plastic deformation, and powdering is reduced.

Therefore, in order to produce the dust agglomerate 1 as shown in FIG.
(A) Technology for making the dust aggregate 3 (b) Two techniques of joining the dust aggregates 3 with the hydraulic binder 4 are important.

  The present invention has been made based on the above idea and has the following features.

[1] Wet dust collection process for collecting dust contained in exhaust gas from vertical furnace as wet dust collection by a wet dust collector, and precipitating the wet dust collection dust obtained in the wet dust collection process A dust aggregate forming step of precipitating in a pond and adding a flocculant to form a dust aggregate, and a lump that agglomerates the dust aggregate obtained in the dust aggregate forming step using a hydraulic binder A method for agglomeration of wet dust collection dust, comprising:
In the dust aggregate forming step, a flocculant is added at 0.1 mass% or more and less than 0.5 mass% to form a dust aggregate,
In the agglomeration step, the agglomeration method of wet dust collection dust, wherein the dust agglomerate and the hydraulic binder are mixed and agglomerated in the presence of a predetermined amount of added water. .

  [2] The amount of added water is determined so that the slump value described in JIS A 1101 is 8 cm or more and 18 cm or less when mixing of the dust aggregate and the hydraulic binder is completed. The method for agglomerating wet dust collection dust according to 1).

  [3] The wet method according to [1] or [2], wherein in the agglomeration step, a predetermined amount of added water is mixed with the hydraulic binder and then mixed with the dust aggregate. Agglomeration method of dust collection dust.

  [4] The wet method according to [1] or [2], wherein in the agglomeration step, a predetermined amount of added water is mixed with the dust aggregate and then mixed with a hydraulic binder. Agglomeration method of dust collection dust.

  [5] The wet collection as described in [1] or [2], wherein in the agglomeration step, a dust aggregate, a hydraulic binder, and a predetermined amount of added water are mixed at a time. Agglomeration method of dust dust.

  In the present invention, when the dust contained in the exhaust gas of the vertical furnace is agglomerated, the manufacturing cost is increased due to an increase in the amount of binder and the curing time is prolonged, and the equipment cost is increased due to the enlargement of the storage facility and the construction of the curing room. The dust pulverization phenomenon of dust agglomerates can be efficiently reduced without incurring an increase in.

  That is, in the present invention, wet dust collection dust is precipitated with a flocculant in a sedimentation basin to form dust aggregates, and the dust aggregates are joined together with a hydraulic binder to produce a dust agglomerate. As a result, the dust agglomerates become ductile to external forces, and can efficiently prevent pulverization due to impact during transportation before charging into the furnace or charging into the furnace. .

It is a schematic diagram regarding the fine structure of the dust agglomerate in this invention. It is a flowchart for manufacturing the dust aggregate in this invention. It is a flowchart for agglomerating a dust aggregate using a hydraulic binder in the present invention. It is a flowchart showing the charging order of the raw material to a mixer at the time of agglomerating a dust aggregate using a hydraulic binder in this invention (Case 1). It is a flowchart showing the charging | discharging order of the raw material to a mixer at the time of agglomerating a dust aggregate using a hydraulic binder in this invention (Case2). It is a flowchart showing the charging | discharging order of the raw material to a mixer at the time of agglomerating a dust aggregate using a hydraulic binder in this invention (Case3). It is a figure showing an unsuitable flow as a charging order of the raw material to a mixer at the time of agglomerating a dust aggregate using a hydraulic binder (Case 4).

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a flowchart for producing the dust aggregate 3 in the embodiment of the present invention.

  The exhaust gas 6 discharged from the vertical furnace 5 is introduced into a wet dust collector (here, a cleaning dust collector) 7. As a result, the exhaust gas 6 is separated into solid and gas, the gas becomes clean exhaust gas 8, and the solid becomes slurry (wet dust collection dust) 9 (wet dust collection dust recovery step).

  The clean exhaust gas 8 is reused if it has value as energy, and if it has no value, it is diffused to the atmosphere after performing necessary treatments such as detoxification.

  Slurry (wet dust collection dust) 9 is introduced into a sedimentation basin 10 and is separated into solid and liquid. By adding a flocculant 11 to the sedimentation basin 10, a dust aggregate 3 is formed. The mud 12 discharged from the sedimentation basin 10 is a mixture (wet dust) of the dust aggregate 3 and excess water 14 and is introduced into the filtration device 13 and separated into the dust aggregate 3 and excess water 14 (dust Aggregate formation step).

  Here, there are no particular restrictions on the wet dust collector 7, the sedimentation basin 10, and the filtration device 13. For example, according to Non-Patent Document 1, wet dust collector 7 is page 781, sedimentation basin 10 is page 736, filtration. The device 13 may be appropriately selected from various devices described on page 714 that are suitable for each factory.

  FIG. 3 shows a flow for manufacturing the dust agglomerate 1 by joining and solidifying the dust aggregate 3 with the hydraulic binder 4 (agglomeration step). Note that this flow is merely an example and does not limit the present invention. For example, at least one type of dust aggregate 3 manufactured as shown in FIG. 2 may be used, but FIG. 3 shows a case where there are two types of dust aggregate 3 (with different component compositions, etc.).

  As shown in FIG. 3, two types of dust aggregates 3 are stored in the raw material yard as dust aggregates 3a and dust aggregates 3b, respectively. These are put into the storage tank B16 and the storage tank C17, respectively, so that a predetermined amount can be put into the mixer 21. Similarly, the hydraulic binder 4 is put in storage tank A15. Moreover, the additive 23 is put into the storage tank D18.

  The additive 23 is various powders generated at a factory, has a particle diameter of less than 1 mm, and particles do not form an aggregate. As an example, there are iron ore powders used as steel raw materials in steelworks, and in coking factories, etc., coke used as a heat source is pulverized. It has been found that when these additives are blended up to about 20 mass%, the present invention has no adverse effect and can be reused in the vertical furnace 5 as raw fuel.

  The dust aggregate 3, the hydraulic binder 4, and, if necessary, the additive 23 are put into the mixer 21 by the transport conveyor 19, and the added water 20 is added and mixed. Although there is no special restriction | limiting in the mixer 21, there exist restrictions in the injection | throwing-in order of the dust aggregate 3, the hydraulic binder 4, and the addition water 20, and it mentions later.

  The mixture after the raw materials (dust aggregate 3, hydraulic binder 4, added water 20, additive 23 if necessary) are mixed by the mixer 21 is placed in the curing place 22, and is cured for about 3 to 7 days. After solidification, the dust agglomerate 1 is produced by crushing and granulating as necessary. The produced dust agglomerate 1 is charged into the vertical furnace 5 as a fuel raw material.

  The amount of the added water 20 is preferably adjusted in advance so that the slump value of the mixture is measured in accordance with JIS A 1101 when the mixing of the raw materials is completed and the slump value is 8 to 18 cm. This is because when the slump value is 8 cm or more, high fluidity and stable placement can be achieved, and when the slump value is 18 cm or less, the water content is appropriate and the strength after curing can be ensured.

  The mixer 21 is not particularly limited, and many types can be used including those specified in JIS A 8603.

  On the other hand, as described above, it is necessary to pay attention to the order in which the raw materials (dust 3, hydraulic binder, added water, additive if necessary) are added to the mixer, and a predetermined amount of added water was added. Later, that is, in the presence of a predetermined amount of added water, the dust aggregate and hydraulic binder need to be mixed. In other words, the dust aggregate and the hydraulic binder are not mixed in a state where a predetermined amount of added water is not present. Specifically, the three cases (Case 1, Case 2, and Case 3) shown in FIGS. 4, 5, and 6 are appropriate.

  Case 1 shown in FIG. 4 is a mixture of a hydraulic binder and a dust aggregate in which added water is added and mixed in the second stage of mixing after adding and mixing the added water to the hydraulic binder in the first stage of mixing. Are mixed (kneaded) while kneading. As described above, the amount of added water is preferably adjusted based on the slump value of the mixture at the end of the raw material mixing. As a result, in the mixer, the hydraulic binder to which the added water is first added / mixed becomes mortar (slurry) and has fluidity, so the friction with the dust aggregate to be mixed (kneaded) is small. Thus, the dust aggregates can be joined to each other by the hydraulic binder without destroying the aggregate structure of the dust aggregates. Therefore, the obtained dust agglomerate has ductility, and the amount of pulverization is suppressed. The additive described in FIG. 4 may or may not be up to the above-mentioned blending amount.

  Case 2 shown in FIG. 5 is a mixture of dust aggregate and hydraulic binder in which addition water is added and mixed in the second stage of mixing after adding and mixing the added water to the dust aggregate in the first stage of mixing. Are mixed (kneaded) while kneading. As described above, the amount of added water is preferably adjusted based on the slump value of the mixture at the end of the raw material mixing. As a result, in the mixer, the dust aggregate to which the added water is added and mixed first becomes a slurry and has fluidity, so that the friction with the hydraulic binder to be mixed (kneaded) is reduced and the dust aggregate is reduced. The dust aggregates can be joined to each other by the hydraulic binder without destroying the aggregate structure of the aggregates. Therefore, the obtained dust agglomerate has ductility, and the amount of pulverization is suppressed. The additive described in FIG. 5 may or may not be up to the above-described blending amount.

  Case 3 shown in FIG. 6 is a case where the dust aggregate, the hydraulic binder, and the added water are mixed (kneaded) at a time in the first stage mixing. That is, it is a case where any two of the dust aggregate, the hydraulic binder, and the added water are not mixed in advance. As described above, the amount of added water is preferably adjusted based on the slump value of the mixture after completion of the raw material mixing. As a result, the dust aggregate and the hydraulic binder have sufficient fluidity in the mixer, so that it is possible to join the dust aggregates with the hydraulic binder without destroying the aggregate structure of the dust aggregate. Become. Therefore, the obtained dust agglomerate has ductility, and the amount of pulverization is suppressed. The additives described in FIG. 6 may or may not be up to the above-mentioned blending amount.

  On the other hand, Case 4 shown in FIG. 7 shows a case where it is inappropriate as the order in which the raw materials are fed into the mixer. In this case, in the first stage mixing, the hydraulic binder and the dust aggregate are mixed (kneaded) while kneading, and then added water is added and mixed in the second stage mixing. In this case, at the time of kneading the dust aggregate and the hydraulic binder, the fluidity of the material (hydraulic binder, dust aggregate) is small, and the friction between the solid components of the material is large. As a result, the hydraulic binder is kneaded into the dust aggregate, the dust particles inside the dust aggregate are fixed to each other by the hydraulic binder, and the aggregate structure of the dust aggregate is destroyed. . Therefore, in this case, since the dust agglomerated material does not have ductility as shown in FIG. 1, the amount of pulverization increases due to brittle fracture.

  Next, in order to obtain a suitable range of the addition amount of the flocculant, samples in which the addition amount of the flocculant was variously changed were prepared, and a drop test was performed. The test was carried out by a method according to JIS M 8711 (Method for measuring drop strength of iron ore), and the 10 mm sieve under the sample after the test was used as the amount of powder. Moreover, the addition amount of the flocculant was calculated by the following formula (1).

Coagulant addition amount (mass%) = coagulant addition rate (dry-t / hr) / dust generation rate (dry-t / hr) × 100 (1)
Here, the dust generation rate means the generation rate (collection rate) of wet dust collection dust.

  As a result, when the addition amount of the flocculant was less than 0.1 mass%, the amount of powder after the drop test (mass under sieve of 10 mm) became large. This is presumed that the aggregate of dust particles could not be made due to the small amount of the flocculant. On the other hand, when the addition amount of the flocculant exceeded 0.5 mass%, the amount of powder after the drop test (mass under sieve of 10 mm) started to gradually increase. This is presumably because the flocculant becomes surplus and the surplus flocculant is mixed with the hydraulic binder, so that the strength after hardening of the hydraulic binder is reduced and the bonding force between the dust aggregates is reduced. Therefore, it was concluded that the addition amount of the flocculant is preferably in the range of 0.1 mass% to 0.5 mass%.

  The above formula (1) is intended for the case where the wet dust collection dust and the flocculant are continuously charged. However, when the wet dust collection dust and the flocculant are batch charged, the following (2) ).

  Coagulant addition amount (mass%) = coagulant addition amount (dry-t) / dust generation amount (dry-t) × 100 (2)

  And the effect by this invention does not depend on the kind of flocculant in principle. Various types of flocculants were used in the test. Examples of inorganic flocculants include aluminum sulfate, sodium aluminate, iron sulfate, and iron chloride. Anionic polymer flocculants include sodium alginate, CMC sodium salt, and the like. Examples of the flocculant include a water-soluble aniline resin and polythiourea, and examples of the nonionic polymer flocculant include polyacrylamide and polyoxyethylene. As a result of the test, the preferred amount of flocculant was the same.

  However, these flocculants each have a pH value suitable for flocculation. Therefore, when using these flocculants, use flocculants that match the pH of the dust collection water at the factory, etc., or match the flocculants used. It is necessary to adjust either the pH value of the collected water.

  Examples of the present invention will be described.

  Table 1 shows the raw materials used in producing the dust agglomerates in this example.

  The dust in Table 1 was generated in a furnace (blast furnace, converter) in the steelworks. After exhaust gas containing dust was solid-gas separated in a cleaning dust collector (wet dust collector), the dust suspended in the dust collection water was concentrated in a thickener (precipitation pond) and dehydrated by a filter press. Even after dehydration, about 30-50 mass% of water remains and is called wet dust.

  This wet dust is obtained by collecting the collected water from a plurality of furnaces in one thickener and subjecting it to concentration and dehydration treatment. The composition is shown in Table 1 as an example. Of course, dust generated from a single furnace may be used.

  In this case, the additive in Table 1 is in the form of powder (100% by mass under a 1 mm sieve) generated during the conveyance of coke as a fuel. Usually, coke is used in a lump shape (approximately 30 mm to 150 mm in particle diameter), and it becomes difficult to use when it is in a powder form. Such a material was agglomerated at the same time as dust and tried to be used in a vertical furnace. In addition, the amount of powdery coke generated is not so large. Usually, a dust agglomerate is produced without addition, and when a certain amount has been accumulated, it is added and used.

  There are no particular restrictions on the hydraulic binders in Table 1, and various cements can be used. Here, Portland cement, which is generally widely used, was used.

  Table 2 shows the composition of each dust, additive, and hydraulic binder when producing dust agglomerate A (hereinafter agglomerated product A) and dust agglomerated product B (hereinafter agglomerated product B). ing. The amount of the hydraulic binder was fixed at 15 mass%, the agglomerate A was blended with 85 mass% of dust, the agglomerate B was dusted with 75 mass%, and the additive was 10 mass%.

  Next, the results of recycling the produced dust agglomerates (agglomerate A, agglomerate B) in a vertical furnace will be described. A dust agglomerate was charged simultaneously with the iron scrap in the process of producing pig iron by melting the iron scrap using the combustion heat of coke using a vertical furnace having an inner diameter of 3.4 m.

  Table 3 shows the composition of the raw fuel used. Here, scraps corresponding to H2 are mainly used among the scrap scrap standards established by the Japan Iron Source Association, which are widely used. This standard is related to the size of the scrap, and although there is no standard for the component, it contains impurities other than iron due to adhering earth and sand although it is a trace amount. Since these impurity concentrations are necessary for designing the slag component, Table 3 shows the estimated values for the composition other than iron. However, since the components vary depending on the lot, the components do not necessarily have to be the same. .

  The agglomerated product A and the agglomerated product B are obtained by mixing dust, additives, and a hydraulic binder with the composition shown in Table 2 as described above. However, the addition amount of the flocculant and the order in which the raw materials are charged into the mixer in the agglomeration step will be described later.

  These agglomerated material A and agglomerated material B were set in a yard (curing place) and then cured and solidified for 5 days. In use, they were granulated into a 50 mm agglomerate and used. Those having a lump size of less than 50 mm were again put in the mixer and reused. The size of the lump does not necessarily need to be 50 mm, but if the size is smaller than the size of the coke to be used, it tends to hinder the breathability of the furnace, so a larger size is better. However, if the lump size is increased, the amount returned to the mixer may increase, and it may be necessary to increase the mixer's capacity. Therefore, in light of the furnace air permeability and the capacity of the solidification equipment (agglomeration equipment), etc. Then, the size of the lump may be determined.

  And since the dust used here is ironworks generation | occurrence | production dust, a main component is iron. In many cases, iron is contained in the form of iron oxide, but it can be reduced and melted in a vertical furnace as an iron source and converted into molten iron.

  Also, it is not always necessary to produce dust from steelworks. For example, vertical furnaces are used in smelting processes such as manganese ore, chromium ore, and copper ore, and wet dust collectors are used for gas-solid separation of exhaust gas. Any factory can be applied.

  Further, Table 3 shows compositions of coke as a heat source, and silica and limestone used as a faux former (slag component modifier).

  Table 4 lists the inventive examples (Inventive Examples 1 to 4) and comparative examples (Comparative Examples 1 to 3).

  In Table 4, the number of blow-throughs and the coke ratio were used to represent the operation results of the vertical furnace. The blow-through phenomenon will be described. In a vertical furnace, coke is burned with air blown from the lower part of the furnace to produce a high-temperature reducing gas, and thereby scrap is dissolved or ore is reduced. Therefore, air permeability in the furnace is important because the gas flows from the lower part of the furnace to the upper part of the furnace. When the pressure loss increases due to accumulation of powder or the like in the furnace, the pressure in the furnace rises, but when the pressure reaches a certain level, the gas rise may be restarted explosively. In such a case, the contact time between the gas and the solid becomes extremely short, and the gas is discharged without sufficient heat transfer or reduction reaction from the high temperature gas to the solid. It causes defects and becomes a very inefficient phenomenon. In addition, there are concerns about mechanical damage to the furnace body due to an increase in pressure, and thermal adverse effects on various facilities due to the rapid ejection of high-temperature gas. Table 4 shows how many times this average phenomenon occurred on average per day. The smaller the coke ratio in Table 4, the better, but it showed a tendency to increase as the number of blow-throughs increased.

  Incidentally, t described in Table 4 indicates the generated hot metal ton.

  Examples of the present invention (Invention Examples 1 to 4) are examples of scrap melting operation in a vertical furnace when the present invention is applied.

  In the present invention example 1, the amount of brewing was 70 t / hr, and slap 940 kg / t and agglomerate A 100 kg / t were blended as iron sources. In order to adjust the slag component, 14.5 kg / t of auxiliary material silica and 30.4 kg / t of limestone were blended. In order to make a dust aggregate, 0.12 mass% of a flocculant was added to the sedimentation basin. Further, the raw material charging sequence to the mixer was set to Case 1 shown in FIG. 4 so that the hydraulic binder did not enter the dust aggregates when the raw materials were mixed. As a result, the dust agglomerates were ductile and the amount of pulverization could be kept low. Therefore, the air permeability of the furnace was kept good, the number of blow-throughs was 0 times / day, the furnace conditions were stable, and the coke ratio was also high. It was low.

  In Invention Example 2, the amount of brewing was 70 t / hr, and slap was added at 940 kg / t and agglomerated product A was added at 100 kg / t as an iron source. In order to adjust the slag component, 14.7 kg / t of auxiliary material silica and 30.4 kg / t of limestone were blended. In order to make a dust aggregate, 0.35 mass% of a flocculant was added to the settling tank. In addition, the raw material charging sequence to the mixer was set to Case 2 shown in FIG. 5 so that the hydraulic binder did not enter the dust aggregates when the raw materials were mixed. As a result, the dust agglomerates were ductile and the amount of pulverization could be kept low. Therefore, the air permeability of the furnace was kept good, the number of blow-throughs was 0 times / day, the furnace conditions were stable, and the coke ratio was also high. It was low.

  In Example 3 of the present invention, the amount of brewing was 70 t / hr, and slap 940 kg / t and agglomerated product A 100 kg / t were blended as iron sources. In order to adjust the slag component, 14.6 kg / t of auxiliary silica and 30.4 kg / t of limestone were blended. In order to make a dust aggregate, 0.48 mass% of a flocculant was added to the sedimentation basin. Moreover, the raw material charging sequence into the mixer was set to Case 3 shown in FIG. 6 so that the hydraulic binder did not enter the dust aggregates when the raw materials were mixed. As a result, the dust agglomerates were ductile and the amount of pulverization could be kept low. Therefore, the air permeability of the furnace was kept good, the number of blow-throughs was 0 times / day, the furnace conditions were stable, and the coke ratio was also high. It was low.

  In Example 4 of the present invention, the amount of brewing was 70 t / hr, 945 kg / t of slap and 100 kg / t of agglomerate B were blended as iron sources. The amount of scrap used is slightly higher than in the other examples of the present invention because the agglomerate B has a slightly lower iron content than the agglomerate A. In order to adjust the slag component, 14.5 kg / t of auxiliary material silica and 30.4 kg / t of limestone were blended. In order to make a dust aggregate, 0.35 mass% of a flocculant was added to the settling tank. Moreover, the raw material charging sequence into the mixer was set to Case 3 shown in FIG. 6 so that the hydraulic binder did not enter the dust aggregates when the raw materials were mixed. As a result, the dust agglomerates were ductile and the amount of pulverization could be kept low. Therefore, the air permeability of the furnace was kept good, the number of blow-throughs was 0 times / day, the furnace conditions were stable, and the coke ratio was also high. It was low.

  On the other hand, a comparative example (comparative examples 1-3) is a scrap melting operation example by a vertical furnace when the present invention is not applied.

  Comparative Example 1 is an example where the amount of the flocculant added is insufficient. Since the blow-through phenomenon occurred frequently and the furnace condition deteriorated, the amount of brewing which was 70 t / hr in the inventive examples 1 to 4 decreased to 59 t / hr. As iron sources, 955 kg / t of slap and 100 kg / t of agglomerate A were blended. The amount of scrap used is slightly increased compared to Examples 1 to 4 of the present invention, but this is because the agglomerated material is pulverized and discharged along with the gas, resulting in a decrease in iron recovery rate. To do. Although 0.08 mass% of a flocculant was added to the settling basin, it was insufficient to make a dust agglomerate. As a result, the dust agglomerates did not have ductility and the amount of pulverization increased, so that the air permeability of the furnace deteriorated, the number of blow-throughs became 13 times / day, and the coke ratio also increased.

  Comparative Example 2 is an example when the amount of the flocculant added becomes excessive. Since the blow-through phenomenon occurred frequently and the furnace conditions deteriorated, the output amount in the inventive examples 1 to 4 decreased from 70 t / hr to 62 t / hr. As an iron source, 954 kg / t of slap and 100 kg / t of agglomerate A were blended. The amount of scrap used is slightly increased compared to Examples 1 to 4 of the present invention, but this is because the agglomerated material is pulverized and discharged along with the gas, resulting in a decrease in iron recovery rate. To do. Although 0.55 mass% of the flocculant was added to the sedimentation basin, the amount was excessive, and the excess flocculant mixed with the hydraulic binder, which had an adverse effect on the hardening of the hydraulic binder (the bonding force between the dust aggregates). This is thought to have caused a decline. As a result, the amount of dust agglomerated powder was increased, so that the air permeability of the furnace deteriorated, the number of blow-throughs became 5 times / day, and the coke ratio also increased.

  The comparative example 3 is an example in the case where the starting order of the raw materials to the mixer is inappropriate. Since the blow-through phenomenon occurred frequently and the furnace condition deteriorated, the amount of brewing which was 70 t / hr in the inventive examples 1 to 4 decreased to 58 t / hr. As iron sources, 955 kg / t of slap and 100 kg / t of agglomerate A were blended. The amount of scrap used is slightly increased compared to Examples 1 to 4 of the present invention, but this is because the agglomerated material is pulverized and discharged along with the gas, resulting in a decrease in iron recovery rate. To do. It was an appropriate amount to add 0.35 mass% of the flocculant to the settling basin, but since the raw material charging sequence to the mixer was Case 4, as shown in FIG. 7, the hydraulic binder entered the dust aggregate when mixing the raw materials. It was a condition that would occur. As a result, the dust agglomerated material did not have ductility, brittle fracture and powdering amount increased, the furnace air permeability deteriorated, the number of blow-throughs became 12 times / day, and the coke ratio also increased.

DESCRIPTION OF SYMBOLS 1 Dust agglomerate 2 Dust particle 3 Dust aggregate 4 Hydraulic binder 5 Vertical furnace 6 Exhaust gas 7 Wet dust collector (cleaning dust collector)
8 Clean exhaust gas 9 Slurry 10 Sedimentation basin 11 Flocculant 12 Mud 13 Filtration device 14 Excess water 15 Storage tank A
16 Storage tank B
17 Storage C
18 Storage D
19 Transport conveyor 20 Additive water 21 Mixer 22 Curing place 23 Additive

Claims (5)

A wet dust collection process for collecting dust contained in the exhaust gas of a vertical furnace as wet dust collection dust by a wet dust collector, and the wet dust collection dust obtained in the wet dust collection process in the sedimentation basin A dust aggregate forming step of forming a dust aggregate by adding an aggregating agent while precipitating, and an agglomeration step of agglomerating the dust aggregate obtained in the dust aggregate forming step using a hydraulic binder A method of agglomerating wet dust collection dust comprising:
In the dust aggregate forming step, a flocculant is added at 0.1 mass% or more and less than 0.5 mass% to form a dust aggregate,
In the agglomeration step, the agglomeration method of wet dust collection dust, wherein the dust agglomerate and the hydraulic binder are mixed and agglomerated in the presence of a predetermined amount of added water. .   The amount of added water is determined so that the slump value described in JIS A 1101 is 8 cm or more and 18 cm or less when mixing of the dust aggregate and the hydraulic binder is completed. A method of agglomerating wet dust collection dust.   The agglomeration of wet dust collection dust according to claim 1 or 2, wherein in the agglomeration step, a predetermined amount of added water is mixed with the hydraulic binder and then mixed with the dust aggregate. Method.   3. The agglomeration of wet dust collection dust according to claim 1 or 2, wherein in the agglomeration step, a predetermined amount of added water is mixed with the dust aggregate and then mixed with a hydraulic binder. Method.   The agglomeration of wet dust collection dust according to claim 1 or 2, wherein in the agglomeration step, a dust aggregate, a hydraulic binder, and a predetermined amount of added water are mixed at a time. Method.