JP5817629B2 - Method for producing sintered ore using finely granulated carbon - Google Patents

Description

  The present invention relates to a method for producing sintered ore using finely granulated carbonaceous material.

In the production of sintered ore at an ironworks, nitrogen oxides (NOx) are generated in exhaust gas due to combustion of carbonaceous materials used as fuel. This reduction of NOx is an important issue in improving air pollution. As means for reducing the NOx, there is an exhaust gas denitration technique using ammonia as a reducing agent.
However, the exhaust gas denitration equipment according to the technology has a high construction cost, and the operation cost is high because ammonia is expensive. There is also a means to use anthracite with a low nitrogen content, but anthracite with a low nitrogen content has deteriorated in the mining environment due to resource depletion, and its use is limited.

  On the other hand, high-productivity is required for sintering machines in mass-production steelworks, and a method for producing sintered ore that enables both high productivity improvement effects and NOx suppression is desired. .

An invention is disclosed in which powder coke and anthracite are granulated using a special granulator such as a Malmerizer or Eirich mixer that utilizes centrifugal force to improve productivity and suppress NOx (Patent Document 1).
Moreover, invention of the method of curing for hardening after adding a hydraulic binder binder such as cement to a mixture of fine coke and fine coal and mixing and granulating is disclosed (Patent Document 2).
In addition, when the sintering raw material is granulated with a drum mixer, the raw material for sintering excluding the lime-based powder raw material and the solid fuel-based powder raw material is charged and granulated, and then the lime-based powder raw material and the solid fuel are downstream. A method of adding a system powder raw material and adhering / forming it to the exterior of the sintering raw material is disclosed (Patent Document 3).
In addition, the applicant of the present invention is a surface-coated carbon material in which a coating containing 36 mass% or more of Ca derived from a lime-based raw material is coated on the carbon material surface at a ratio of more than 2 mass% and less than 50 mass% with respect to the carbon material. Is disclosed as a sintered fuel in a blended coal (Patent Document 4).

JP-A-5-156271 JP-A-62-220590 JP 2003-138319 A International Publication No. 2011/129388

The invention described in Patent Document 1 granulates powdered coke and anthracite coal by centrifugal force using a special granulator, and there are restrictions on device selection.
The invention described in Patent Document 2 granulates coke breeze and fine coal, and uses a hydraulic binder and requires curing for hardening, which complicates the manufacturing process. The invention described in Patent Document 3 adds a lime-based powder raw material and a solid fuel-based powder raw material to the subsequent stage of the drum mixer, and aims to improve the cold strength and reducibility of the sintered ore. There is no description about NOx suppression.

  The invention described in Patent Document 4 is effective because it can achieve a NOx reduction effect and an improvement in productivity, but further improvement in productivity is desired.

  The objective of this invention is providing the manufacturing method of the sintered ore using the fine-powder granulated carbon material which enables coexistence of the high productivity improvement effect and NOx suppression.

The present inventors classify the carbonaceous material for the production of sintered ore, and the granulated carbonaceous material produced by mixing and granulating a lime source with a carbonaceous material of 1 mm or less, and other raw materials used in the sintering process It was found that by suppressing the contact, the productivity improvement of the sintering machine and the NOx reduction effect are exhibited.
The present invention is based on this new knowledge, and the gist thereof is as follows.

(1) Classifying carbonaceous materials for sinter ore production, obtaining a sieved carbonaceous material having a content of 1 mm or less of 73.0% by mass or more, and a sieved carbonaceous material,
Quick lime or slaked lime whose content of 1 mm or less is 70% by mass or more in the sieving carbon material is blended by 5% by mass or more and 50% or less by Ca with respect to the total of the sieving carbon material and the lime or slaked lime , Mixing and granulating to produce a fine granulated carbonaceous material,
For the total time of mixing and granulating raw materials including iron ore, return ore and auxiliary materials,
When a time exceeding 50% has elapsed since the start of granulation, the above-mentioned sieved carbon material and the above-mentioned finely granulated carbonaceous material are added, and the raw material including the iron ore, the return mineral and the auxiliary material, the sieve The manufacturing method of the sintered ore using the fine-powder granulated carbon material characterized by implementing the upper carbon material and the process of mixing and granulating the said granulated carbon material.
(2) The time of adding the above sieved carbon material and the finely granulated carbon material to the raw material containing iron ore, return ore and auxiliary material is the mixing and granulation of the raw material including iron ore, return ore and auxiliary material It is a point in time that exceeds 75% has elapsed since the start of the mixing and granulation with respect to the total time (1
The manufacturing method of the sintered ore using the fine-powder granulated carbon material as described in).

  It is possible to provide a method for producing a sintered ore using a finely divided granulated carbon material that can achieve both a high productivity improvement effect and NOx suppression.

The figure which shows the relationship between NOx conversion rate and temperature. The figure which shows the relationship between a coke particle size and NOx generation amount. Explanatory drawing of the experimental process of this invention. Schematic of a sintering pot test apparatus.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows the relationship between the NOx conversion rate by coke combustion and temperature. The NOx conversion rate is a ratio (molar percentage) at which nitrogen atoms in the burned fuel are converted to NOx. Specifically, it is calculated by the following equation (1).

ηNO = 100 × NOx / ((CO + CO ₂ ) · N _CAKE / (C _LPG + C _CAKE + C _LS )) / 10000
... (Formula 1)
However, ηNO: NOx conversion rate (%), NOx: exhaust gas NOx (ppm)
CO: exhaust gas CO (%), CO ₂ : exhaust gas CO (%),
N _CAKE : N (mol) in coke, C _LPG : C (mol) in ignition gas,
C _CAKE : C (mol) in coke, C _LS : C (mol) in limestone.

NOx produced by sintering is mainly formed by oxidation of nitrogen in the carbonaceous material, and as shown in FIG. 1, it has been confirmed that it is easily produced at a low temperature of 1,000 ° C. or less. Therefore, in order to suppress NOx generation, it is important to burn the carbonaceous material as high as possible.
Moreover, the fine powder in the carbonaceous material burns at a low temperature and increases NOx. FIG. 2 shows the relationship between the carbonaceous material particle size and the NOx generation amount. NOx is corrected with O ₂ 15%. The fine powder in the carbonaceous material is considered to increase NOx because the combustion speed is high and combustion is completed at a low temperature. It is considered that the amount of NOx generated can be reduced if the fine carbonaceous material having a particle size of 1 mm or less can be removed.

  In this invention, the carbonaceous material for sinter production is classified, and the sieving carbon material whose content of 1 mm or less is 73.0 mass% or more and the remaining sieving carbon material are obtained. The reason why the content of 1 mm or less is 73.0% by mass or more is that when the content is less than 73.0% by mass, the productivity improvement effect when using the granulated carbon material is small. For carbon materials exceeding 1 mm, a state where there is no deposit on the surface is desirable from the viewpoint of combustion speed, so the upper limit of the content of 1 mm or less is not particularly limited for carbon materials used for granulated carbon materials, and the higher one is desirable. The maximum is 100% by mass.

The sieving carbon material having a content of 1 mm or less of 73.0% by mass or more is mixed and granulated with a Ca-containing raw material to produce a finely granulated carbon material.
Carbonaceous materials include coke, anthracite, and other fuels used for sinter ore production. Generally, powder coke generated at ironworks is used for sinter ore production. Since powder coke is produced by dry distillation of coal, the wettability of the surface is poor, and granulation is difficult only with powder coke. Therefore, there is a method of granulating by mixing with anthracite, pulverized coal or hydraulic binder (Patent Document 1 to Patent Document 3), and the present invention is characterized by using the Ca-containing raw material as a binder. And
Examples of the Ca-containing raw material include quick lime and slaked lime. Conventionally, Ca-containing raw materials are mixed with sintered raw materials such as iron ore to adjust the basicity of blast furnace slag and improve the productivity and quality of sintered ores. I came.

Therefore, the present invention uses a part of conventionally used Ca-containing raw materials as a binder for granulation of powder coke, which is difficult to granulate.
The Ca-containing raw material has a particle size of 1 mm or less and 70% by mass or more, and the mixing ratio is 5% to 50% in Ca with respect to the total mass of the carbonaceous material and the Ca-containing raw material.
If the Ca-containing raw material has a large particle size and the content of 1 mm or less does not satisfy 70% by mass or more, the effect as a binder for powder coke granulation is not exhibited. Moreover, if the addition ratio of the Ca-containing raw material is less than 5% by mass with Ca, the effect as a binder cannot be exhibited, and if it exceeds 50% by mass, it is sufficient, and if it exceeds this, it becomes economically disadvantageous.

The sieving carbon material generated by classifying the carbon material is mixed and granulated together with the finely granulated carbon material and raw materials including iron ore, return mineral and auxiliary materials.
In the present invention, the sieving carbon material and the finely granulated carbon material are added after being mixed and granulated. That is, before mixing and granulation of raw materials including iron ore, return ore and auxiliary raw materials are completed, sieving carbonaceous materials and fine granulated carbonaceous materials are mixed, granulated iron ore, return ores and auxiliary raw materials. Is added to the raw material containing, and then all the blended raw materials are mixed and granulated.

  The reason why the fine granulated carbon material is added afterwards is to prevent the fine granulated carbon material from being destroyed. In other words, when the fine granulated carbon material is added from the start of mixing / granulation of raw materials including iron ore, return minerals and auxiliary raw materials, the sieving charcoal is generated by rolling during mixing and granulation of these raw materials. This is because the pseudo particles formed from the material and the Ca-containing raw material are destroyed.

  The reason why the above sieving carbon material is added afterwards is to increase the combustibility of the carbon material and increase the productivity of the sintered production. In other words, when sieving coal is added from the start of mixing and granulation of raw materials including iron ore, return ore, and auxiliary materials, fine iron ore adheres to the surface of sieving coal, Reduce flammability. As a result, the combustibility of the carbonaceous material is deteriorated, and the productivity of the sintered production is lowered.

At the time when the sieving carbon material and the finely granulated carbon material are added later, the raw material including the iron ore, the return mineral and the auxiliary material, the sieving carbon material and the finely granulated carbon material are mixed and granulated. It is preferable that a time exceeding 50% has elapsed since the start of the mixing / granulation with respect to the total time, and it is more preferable that a time of 75% or more has elapsed.
The inventor obtained the optimum point at the time of post-adding the sieve carbonaceous material and the fine granulated carbonaceous material by a sintering experiment shown in the examples.

Next, examples of the present invention will be described, but the present invention is not limited thereto.
FIG. 3 shows an explanatory diagram of an example of the experimental process of the present invention. A pot firing test of sintered ore was carried out using powdered coke as the carbonaceous material and quick lime or slaked lime as the Ca-containing raw material. The Ca-containing raw material is quick lime with a ratio of 1 mm or less of 70% by mass, quick lime with a ratio of 1 mm or less of 37% by mass, or slaked lime with a ratio of 1 mm or less of 100% by mass (hereinafter collectively referred to as a CaO source). Using.

A CaO source was added to the under-sieve coke and mixed and granulated using a universal kneader and a drum granulator to produce finely granulated coke in advance. In this example, quick lime is used as the CaO source, and the addition amount thereof is 30.8% by mass with respect to the total amount of the under sieve coke and the CaO source, the mixing time is 180 seconds, and the granulation time is 180 seconds.
The above-mentioned finely granulated coke produced in advance at the time of adding 7.5% by weight of water to the raw material including iron ore, return mineral and auxiliary materials, and mixing for 60 seconds using a drum mixer having a diameter of 1 m and granulating for 220 seconds; The sieved coke after classification was added to the drum mixer. The raw material containing iron ore, return ore and auxiliary materials, fine granulated coke and sieve coke were further granulated for 20 seconds to prepare a blended raw material for a pot firing test. In this example, the timing of adding finely granulated coke and classified coke after sieving to the raw material containing iron ore, return ore and auxiliary materials is the mixing and granulation of raw materials including iron ore, return ore and auxiliary materials. This is the time when 93% (20 / (60 + 220 + 20)) time has elapsed from the start to the total time from the start to the end of mixing and granulation.

The above-prepared raw material for a pot firing test was filled in a sintering pot test apparatus, and a firing test was performed. A schematic view of the sintering pot test apparatus used for the implementation is shown in FIG.
The sintering pot test apparatus includes an ignition furnace 1, a sintering pot 2, an air box 3, a blower 4, and an analyzer 5. The diameter of the sintering pot 2 is 300 mm and the bed height is 600 mm. The sintering pot 2 is filled with a blended raw material to be a test body, ignited in the ignition furnace 1 and heated. At the same time, the blower 4 is activated for 90 seconds after ignition and firing is performed under a constant suction negative pressure of 12 kPa. The exhaust gas generated in the sintering pan 2 was discharged through the wind box 3 and analyzed for NOx by the analyzer 5.

Table 1 shows the particle size distribution of the powder coke used in this test. Table 2 shows the composition of the raw materials used in this test. In Table 2, “CaO granulated” means that when powder coke is classified using sieves of different sizes and granulated coke is granulated with a CaO source, and when the powder coke is not classified, the total amount of powder coke is CaO. When granulated at the source. “No CaO granulation” refers to a case where powdered coke is mixed and granulated with a CaO source together with raw materials including iron ore, return ore and auxiliary materials without classifying the powder coke.
Table 3 lists the test results as examples or comparative examples. Table 4 shows the particle size distribution of the sieving coke used for CaO granulation.

In Examples 1 to 8 and Comparative Examples 1 to 12, sieving coke was granulated using quick lime having a ratio of 1 mm or less of 70% by mass as a CaO source. In Comparative Example 17, quick lime having a ratio of 1 mm or less of 37% by mass was used as the CaO source, and in Example 9, slaked lime having a ratio of 1 mm or less of 100% by mass was used as the CaO source.
(Example 1 to Example 8)
In Example 1, 66.7% by mass (Ca; 47.6% by mass) of a CaO source was added to 0.25 mm or less sieving coke prepared by pre-classification, and then mixed and granulated to obtain a fine powder. Granulated coke was created. When 93% of the total mixing and granulation time of the blended raw material passed, sieved coke and fine granulated coke were added to the blended raw material, and the remaining granulation was performed. The production rate was good at 36.7 t / d / m ² , and NOx was also low at 150 ppm.
In Example 2, when 75% of the total mixing and granulation time of the blended raw materials had elapsed with respect to Example 1, sieving coke and fine granulated coke were added, and the remaining granulation was performed. Both production rate and NOx were good.
In Example 3, compared to Example 1 and Example 2, when the total mixing and granulation time of 55% has elapsed, sieving coke and fine granulated coke are added, and the remaining granulation is performed. Did. Both production rate and NOx were good.
In Example 4, Example 5, and Example 6, 30.8% by mass (Ca; 22.0% by mass) of a CaO source was added to 1.0 mm or less sieving coke prepared by pre-classification, Finely granulated coke was prepared by mixing and granulating. When 95%, 75%, and 55% of the total mixing and granulation time of the blended raw materials passed, sieved coke and granulated coke were added, and the remaining granulation was performed. Both production rate and NOx were good.
In Example 7 and Example 8, the CaO source was 27.2% by mass (Ca; 19.4% by mass) with respect to the under-sieve coke having a ratio of 1.0 mm or less prepared by pre-classification and having a ratio of 73.5% by mass. Add, mix and granulate to make fine granulated coke. When 75% and 55% of the total mixing and granulation time of the blended raw materials had elapsed, sieved coke and granulated coke were added, and the remaining granulation was performed. Both production rate and NOx were good.
From the results of Examples 1 to 8, it was found that the Ca content of fine granulated coke should be 50% by mass or less.

Example 9
Instead of quick lime 30.8% by mass (Ca; 22.0% by mass) as the CaO source of Example 5, in Example 9, 40.7% by mass of slaked lime (Ca; 22.0% by weight) was used. As a result, both the production rate and NOx were good.
From this, it turned out that both quicklime and slaked lime are suitable as a CaO source.

(Comparative Examples 1 to 4)
Compared to Examples 1 to 6, the addition of sieving coke and finely granulated coke is performed at the time when the total time of mixing and granulation of the blended raw materials is 50% or when 0% has elapsed (mixing and granulation start and At the same time). The production rate was low and NOx was high. From this, it was found that the addition of sieve coke and fine granulated coke is preferably over 50% of the total time of mixing and granulation of the blended raw materials, and more preferably 75% or more.

(Comparative Example 5 to Comparative Example 8)
Comparative Example 5 to Comparative Example 8 classified powder coke with respect to Examples 1 to 8 by a sieve having a mesh size of 3 mm. The CaO source was added to 22.2 mass% (Ca; 15.9 mass%) with respect to the under-sieving coke, and mixed and granulated to prepare fine granulated coke. Comparative Example 5 and Comparative Example 6 were cases where 93% and 75% of the total time of mixing and granulation of the blended raw materials were added when sieving coke and granulated coke were added, and both had low production rates. Comparative Example 7 and Comparative Example 8 are cases in which 50% of the total time of mixing and granulation of the blended raw materials and 0% elapsed when sieving coke and granulated coke are added, both of which have low production rates and NOx it was high.
In the particle size distribution of the under sieve coke shown in Table 4, the ratio of 1 mm or less of under sieve coke is 73.5% by mass in Example 7 and Example 8, whereas in Comparative Example 5 and Comparative Example 6, 72. 2% by mass. From this, it was found that the ratio of the particle size of 1 mm or less in the under sieve coke is preferably 73.0% by mass or more.

(Comparative Example 9 to Comparative Example 12)
This is a case where the surface is coated with CaO without classifying the powder coke. Comparative Examples 9 and 10 are examples in which the coated coke was added when 93% and 75% of the total time of mixing and granulation of the blended raw materials had elapsed. This is an invention proposed by the present applicant according to Patent Document 4, and both the production rate and NOx are good, but the productivity is slightly inferior to the present invention. Comparative Example 11 and Comparative Example 12 were cases where the addition of the coated coke was 50% or less of the total time of mixing and granulation of the blended raw materials. In both cases, the production rate was low and the NOx was also high.

(Comparative Examples 13 to 16)
This is a case where the powdered coke is mixed and granulated with the entire blended raw material without classification and without mixing and granulating CaO with the powdered coke. In both cases, the production rate was low and the NOx was also high.

(Comparative Example 17)
The comparative example 17 is a case where the ratio of 1 mm or less of a CaO source is reduced. In Example 4, instead of the ratio of quick lime of 1 mm or less of 70%, Comparative Example 17 was 37% by mass. As a result, in Comparative Example 17, the production rate was low and NOx was also high. From this, it was found that the ratio of 1 mm or less of the CaO source is desirably 70% or more.

  The present invention can be used for the production of sintered ore using a finely granulated carbon material that can achieve both high productivity improvement effects and NOx suppression.

  DESCRIPTION OF SYMBOLS 1 ... Ignition furnace, 2 ... Sintering pan, 3 ... Wind box, 4 ... Blower, 5 ... Analyzer.

Claims (2)

Classifying the carbonaceous material for sinter ore production, obtaining a sieved carbonaceous material having a content of 1 mm or less of 73.0% by mass or more, and a sieved carbonaceous material,
Quick lime or slaked lime whose content of 1 mm or less is 70% by mass or more in the sieving carbon material is blended by 5% by mass or more and 50% or less by Ca with respect to the total of the sieving carbon material and the lime or slaked lime , Mixing and granulating to produce a fine granulated carbonaceous material,
For the total time of mixing and granulating raw materials including iron ore, return ore and auxiliary materials,
When a time exceeding 50% has elapsed since the start of granulation, the above-mentioned sieved carbon material and the above-mentioned finely granulated carbonaceous material are added, and the raw material including the iron ore, the return mineral and the auxiliary material, the sieve The manufacturing method of the sintered ore using the fine-powder granulated carbon material characterized by implementing the upper carbon material and the process of mixing and granulating the said granulated carbon material. The time at which the sieving carbon material and the finely granulated carbon material are added to the raw material containing iron ore, return ore and auxiliary materials is the total time of mixing and granulating the raw materials including iron ore, return ore and auxiliary materials Against
The time when more than 75% has elapsed since the start of granulation,
The manufacturing method of the sintered ore using the fine-powder granulated carbon | charcoal material of description.