JP5487950B2 - Manufacturing method of high strength coke - Google Patents

Description

  The present invention relates to a method for producing high-strength coke by adjusting the amount of caking filler added to pulverized coal and coarse coal.

  In blast furnace operation, high-strength coke is required as a reducing material in order to ensure air permeability in the furnace and maintain stable operation. In order to produce high-strength coke, high-quality strong caking coal is required as coking coal. Many methods for producing high-strength coke using non-caking coal or non-caking coal as raw coal have been proposed (see Patent Documents 1 to 3).

  As a method of using low quality coal as raw coal for coke production, a method of classifying pulverized low quality coal into pulverized coal and coarse coal is known. In this method, a caking agent is added to pulverized coal and kneaded to form pulverized coal into particles or pseudo particles. The pulverized coal and pulverized coal that have been granulated or pseudo-particled and coarse coal are blended to form a blended coal and charged into a coke oven (see Patent Documents 4 to 7). A caking additive may also be added to the coarse coal.

  As the binder, coal-based binders (tar, pitch, etc.), petroleum-based binders, etc. are used. It greatly affects coal transportation (coal transportation) and coke oven operation. For example, if the amount of the caking additive added to the pulverized coal is small, the caking property of the pulverized coal cannot be sufficiently compensated, so that a desired coke strength cannot be obtained. As the amount of dust increases, the working environment deteriorates, and in terms of operation, the amount of carbon adhering to the coke oven wall increases, making the coke extrusion work difficult.

  That is, the selection of the binder and the setting of the addition amount are important not only in the coke strength but also in the working environment and the operation of the coke oven.

  Based on this importance, the present inventors first studied the correlation between the type of binder and the allowance for improving coke strength, and the caking filler (petroleum heavy residue) having a large allowance for improving coke strength. And proposed a method for producing high-strength coke (see Patent Documents 8 to 11).

The manufacturing method described above, (in DI ^0.99 _15, 84.5 or more) high strength because it can be stably produced coke, is useful.

  However, when applied to an actual machine, the amount of dust generated during transport of blended coal increases, the working environment deteriorates, and the amount of carbon adhering to the coke oven wall increases, making it difficult to extrude coke. However, there are still points to be improved in terms of work environment and operation.

JP 2003-226879 A JP 2006-283008 A JP 2007-002052 A JP-A-10-183136 Japanese Patent Laid-Open No. 11-116970 JP 2001-072982 A JP 2003-226879 A JP 2006-291190 A JP 2007-009016 A JP 2007-009030 A JP 2007-321076 A

  This invention makes it a subject to improve the point which should be improved in the said working environment side and the operation side of a coke oven, and it aims at providing the manufacturing method of the high strength coke which solves this subject.

  In the process of studying a technique for producing high-strength coke from low-quality blended coal, the present inventors have the same blending ratio of pulverized coal and coarse coal, and the same ratio of caking filler addition. It was discovered that even coal blends produced a non-negligible difference in coke strength.

  In the production of coke, since it is required to produce coke with as high strength as possible and no variation in strength, the present inventors have the same blending ratio of pulverized coal and coarse coal, and Moreover, even with blended coal having the same addition ratio of the caking filler, the inventors have intensively investigated the cause of the difference that cannot be ignored in coke strength.

  As a result, the following findings (x), (y), and (z) were obtained.

(X) In the process of transporting the blended coal to the coke oven, the caking filler on the pulverized coal side moves to the coarse coal side.
(Y) Due to the migration of the caking filler, the binder effect that suppresses dust generation on the pulverized coal side is insufficient, the amount of dust generation during conveyance of the blended coal increases, and the amount of carbon adhering to the coke oven wall increases. To increase.
(Z) The coke strength decreases due to a decrease in the caking property improving effect on the pulverized coal side.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) is classified the coal blend into fine coal and coarse coal, a method for producing high strength coke was charged into the coke oven and kneaded by adding caking filling material in the pulverized coal,
Obtaining the relationship between the concentration of the caking filler in the pulverized coal in the blended coal and the amount of carbon adhering to the coke oven wall, determining the upper limit CI of carbon adhering amount that can maintain the stable operation of the coke oven, From the relationship, determine the value AI of the caking filler concentration in pulverized coal corresponding to the carbon adhesion amount CI,
With the addition of caking filling material in the pulverized coal at a concentration above AI, the caking prosthetic material concentration of fines in the coal in the coke RoSo Nyutoki, so that the AI above, the type of caking prosthetic material and viscosity , The number of revolutions of the kneader when kneading the caking filler and pulverized coal, the kneading time between the caking filler and pulverized coal, the kneading temperature between the caking filler and pulverized coal, the kneading filler and kneading Adjusting at least one condition of the conveying time from the position where the pulverized coal and the coarse coal are mixed to the position where the pulverized coal and the coarse coal are charged into the coke oven. Coke production method.

  According to the present invention, the amount of dust generated during the transport of blended coal is reduced, and the amount of carbon adhering to the coke oven wall is reduced to constantly produce high-strength coke from low-quality raw coal. Can do.

It is a figure which shows the quantitative change of the caking filler in the coarse-grained coal in blended coal. It is a figure which shows qualitatively the relationship of the viscosity and temperature about three types of caking filler (x, y, z in a figure). It is a figure which shows the relationship between the transfer amount of a caking filler, and a viscosity. It is a figure which shows the relationship between the transfer amount of a caking filler, and a kneading | mixing state (The rotation speed of a kneader which kneads caking filler and pulverized coal, kneading time). It is a figure which shows the change of the transfer amount of caking filler when the distance from the mixing position of pulverized coal and coarse coal to a furnace charging position is changed. It is a figure which shows typically the actual machine line which implemented this invention. It is a figure which shows the relationship between the caking filler density | concentration in blended coal, and the quantity of carbon adhering to a coke oven wall (carbon adhesion amount). It is a figure which shows the relationship between specific volume (expansion rate) and the addition rate (%) of caking filler about coarse-grained coal and pulverized coal. It is a figure which shows the relationship between the viscosity and temperature about three types of caking filler (X, Y, Z in the figure).

  The present invention will be described.

  Conventionally, when pulverized coal and coarse coal were kneaded with the addition of caking filler, the caking filler was kept attached to the surface of pulverized coal, and the surface was coated with caking filler The pulverized coal and / or the pulverized coal particle group was uniformly distributed in the blended coal, and the blended coal was considered to be charged into the coke oven in the same state as during the kneading.

  However, as described above, as a result of the study by the present inventors, in the process of transporting the blended coal to the coke oven, the caking filler on the pulverized coal side moves to the coarse coal side, which is different from that during kneading. It was found that the blended coal was charged into the coke oven.

  The present inventors, for various types of coal, kneaded pulverized coal that is pseudo-particles by adding a required amount of caking filler, coarse coal without adding caking filler, or a required amount of caking Coarse coal was prepared by blending the coarse coal to which the material was added, and the quantitative change of the caking filler in the coarse coal before charging into the coke oven was investigated. The result is shown in FIG.

  From FIG. 1, before the blended coal is conveyed onto the charging vehicle after blending, the caking filler on the pulverized coal side moves to the coarse coal side, and the viscosity in the coarse coal is changed. It can be seen that the concentration of the binding filler increases.

  It can also be seen from FIG. 1 that when the type of caking filler is different, the amount of caking filler moving to the coarse coal side changes.

  These are important findings in the production of high-strength coke. The concentration of the caking filler in the pulverized coal is maintained at an optimum value, and pulverized coal kneaded with the caking filler and coarse coal are mixed. Even when blended, before the blended coal is transported to the charging car after blending, the caking filler in the pulverized coal moves to the coarse coal side and the blended coal is charged into the coke oven. This means that the concentration of the caking filler in the pulverized coal may be less than the optimum value.

  Since the caking filler is for supplementing caking properties of pulverized coal, a decrease in caking filler causes a reduction in caking properties. As a result, coke strength is reduced. Furthermore, the binder effect which suppresses dust generation is insufficient, the amount of dust generated during the transport of blended coal increases, and the amount of carbon adhering to the coke oven wall increases.

  The present invention is based on the “transfer phenomenon of caking filler” found by the present inventors, and when the caking filler is added to pulverized coal and kneaded, It is characterized in that the amount is added in an increased amount.

  By increasing the amount of the caking filler added to the pulverized coal, even if the increased amount is transferred to the coarse coal during the transfer of the blended coal, the dust generation during the transfer can be suppressed. However, if the amount of the caking filler is increased too much, when the blended coal is charged into the coke oven, uneven distribution of the caking filler in the blended coal becomes significant, resulting in a difference in coke strength. Therefore, it is preferable to suppress the amount of caking filler from the pulverized coal side to the coarse coal side as much as possible.

  Moreover, when the caking filler is added to the coarse coal and kneaded, the caking filler in the pulverized coal is transferred to the coarse coal side before charging the blended coal into the coke oven. The caking filler may be added at a reduced amount. By reducing the amount of the caking filler, uneven distribution of the caking filler in the blended coal can be eliminated.

  According to the inventors' investigation, the amount of caking filler from the pulverized coal side to the coarse coal side is determined by the type of caking filler, the temperature at the time of addition, the kneading state, and the pulverized coal and coarse coal. Although it changes depending on the distance or time from blending of granular coal to furnace charging, the caking filler is less likely to migrate as the viscosity of the caking filler increases (a) and (b) pulverized coal and coarse coal. The lower the coal blending temperature after blending, the harder it is to move, and (c) the harder the transition is as the blended state of pulverized coal and caking filler is better (the pulverized coal and caking filler are sufficiently kneaded). On the other hand, (d) the larger the distance or time from blending pulverized coal and coarse coal to charging the furnace, the greater the amount.

  FIG. 2 shows the relationship between viscosity and temperature for three types of caking fillers (x, y, z in the figure). Thus, the viscosity varies depending on the type of caking filler, and decreases with increasing temperature. Using these caking filler materials, the relationship between the migration amount of the caking filler material and the viscosity, and the relationship between the migration amount of the caking filler material and the kneading time were investigated.

  FIG. 3 shows the relationship between the amount of migration of the caking filler and the viscosity, and FIG. 4 shows the amount of migration of the caking filler and the kneading state (the number of rotations of the kneader for kneading the caking filler and pulverized coal, The relationship with kneading time is shown.

  When the number of rotations of the kneader is increased and the caking filler and pulverized coal are kneaded for a long time, the caking filler and pulverized coal form a dense mixed state, so that the caking filler that tends to migrate decreases, The amount of transition to the coarse coal side decreases.

  FIG. 5 shows a change in the amount of migration of the caking filler when the distance from the blending position of pulverized coal and coarse coal to the furnace charging position is changed. Naturally, as the distance increases, the amount of caking filler increases.

  In this way, the amount of caking filler material transferred depends on the type of caking filler material, temperature, and kneading conditions (kneading time, kneader rotation speed, etc.), and further, the mixing position of pulverized coal and coarse coal It depends on the distance to the charging position (distance between blending and furnace charging) and is not uniquely determined. However, the caking filler added to each of the caking filler, pulverized coal and coarse coal is kneaded. The addition amount (%) of is estimated as follows.

  When blending pulverized coal: F% and coarse coal: (100-F)%, when the blended coal is charged into the coke oven, the optimum addition rate of the caking filler carried by the pulverized coal is A1%, The optimum addition rate of the caking filler carried by the coarse coal is B1%.

  In addition, A1% and B1% are values satisfying F × A1 + (100−F) × B1 = 100 × C when the addition rate of the caking filler to the blended coal is limited to C%, When there is no limitation on the addition ratio, the addition ratio is such that the effect of improving the coke strength DI is saturated.

When the addition rate of the caking filler added at the time of kneading is A ′% in the case of pulverized coal, and B ′% in the case of coarse coal,
F × A ′ + (100−F) × B ′ = F × A1 + (100−F) × B1
Is established.

  The amount of ΔAB in the caking filler shifts from pulverized coal to coarse coal, and the addition rate of caking filler in the pulverized coal at the time of charging into the coke oven decreases from A '% to A1%, coke oven The addition rate of the caking filler in the coarse coal during charging increases from B ′% to B1%.

  If A1% and B1% at the time of coke oven charging are determined, and the transfer amount ΔAB of caking filler that moves from pulverized coal to coarse coal is determined, set A '% and B'% at the time of kneading. Can do.

  Next, how to obtain the optimum addition rate of the caking filler added to the blended coal will be described.

(I) Added only to pulverized coal (F%) (reduction of carbon adhesion)
When caking filler is added only to pulverized coal and mainly controls the amount of carbon adhering, first, the concentration of caking filler in the blended coal and the amount of carbon adhering to the coke oven wall (carbon adhering amount) Seeking a relationship. Normally, the concentration of the caking filler in the blended coal and the carbon adhesion amount are in the relationship shown in FIG.

  The upper limit CI of the carbon adhesion amount that can maintain the stable operation of the coke oven is determined, and the caking filler concentration AI in the blended coal corresponding to the carbon adhesion amount CI is obtained from the relationship shown in FIG. Since the caking filler is not added to the coarse coal, the concentration AI is the addition rate of the caking filler added to the pulverized coal.

(Ii) Addition to pulverized coal (F%) and coarse coal ([100-F]%) (improvement of coke strength)
When the caking filler is added to pulverized coal and coarse coal, and the carbon adhering amount is suppressed and the coke strength is improved, first, as shown in FIG. The relationship between the specific volume (expansion rate) and the caking filler addition rate (%) is determined.

  From the above relationship, the specific volume (expansion rate) is the same as the specific volume (expansion rate) V1 of coarse coal when no caking filler is added, and the caking filler addition rate to pulverized coal A3 is obtained, F × A3 is calculated, and compared with 100 × C (C: addition rate of caking filler added to blended coal).

(Ii-1) In the case of F × A3> 100 × C A3 is obtained so that F × A3 = 100 × C. The obtained A3 is the ideal addition rate AI. The caking filler is added only to pulverized coal at the ideal addition rate AI. Even if the caking filler added only to pulverized coal shifts to coarse coal during transportation of blended coal, sufficient caking filler remains in the pulverized coal. It is possible to suppress carbon adhesion to the coke oven wall.

(Ii-2) In the case of F × A3 ≦ 100 × C: A4 and B4 are obtained so that F × A4 + (100−F) × B4 = 100 × C (see FIG. 8). The obtained A4 and B4 are an ideal addition rate AI and an ideal addition rate BI, respectively. The caking filler is added to pulverized coal at the ideal addition rate AI, and the caking filler is added to the coarse coal at the ideal addition rate BI.

  Next, how to determine the migration amount of the caking filler will be described.

The present inventors defined the following formulas (1), (2), and (3) in order to determine the migration amount of the caking filler.
D = k × (F / d _f ) × {(100−F) / d _c } (1)
dQ = W × D × (ΔC / logμ) (2)
dA = (dQ × 100 × 100) / (W × F) (3)

here,
D: Coefficient taking into account the effect of contact area between pulverized coal and coarse coal (1 / h)
k: Coefficient F: Ratio of pulverized coal (%)
d _f : Average particle size (mm) of kneaded pulverized coal
d _c: Sotsubusumi average particle size (mm)
dQ: Transfer amount of caking filler (t / h)
W: Conveying speed of blended coal (t / h)
ΔC: Difference between the caking filler concentration of pulverized coal and the caking filler concentration of coarse coal at time t (%)
μ: Viscosity of caking filler at temperature K (cp)
K: Temperature of blended coal and caking filler at time t (° C)
dA: Change in caking filler concentration of pulverized coal at time t (%)

  The above formulas (1) to (3) will be described. Based on the premise that the migration amount dQ of the caking filler is proportional to the surface area of the pulverized coal and the surface area of the coarse coal, the proportionality coefficient D is defined by the above formula (1).

  The migration rate of the caking filler at time t is proportional to the concentration difference between (i) the caking filler concentration of pulverized coal and the caking filler concentration of coarse coal (the greater the concentration difference, the faster the migration rate). ), And (ii) the amount of transfer (t / h) of the caking filler material is assumed to be inversely proportional to the logarithm of the viscosity of the caking filler material (the higher the viscosity, the slower the transfer speed). It defined with Formula (2).

  Since the concentration of the caking filler in the pulverized coal affects the carbon adhesion amount, the above formula (2) is used to change the concentration of the caking filler in the pulverized coal at time t (%): dA It was defined in (3).

How to determine the amount of migration of the actual caking filler will be described. First, the above-described shift amount when the caking filler z shown in FIG. 9 is used is obtained. The procedure is as follows.
(1) K is obtained by actual measurement.
(2) The viscosity of the caking filler at the temperature K is determined from the relationship between the viscosity of the caking filler and the temperature shown in FIG.

(3) Set the following initial conditions.
k: Coefficient F: Ratio of pulverized coal (%)
d _f : Average particle size (mm) of kneaded pulverized coal
d _c: Sotsubusumi average particle size (mm)
C: caking filler addition rate of blended coal (%)
A0: caking filler addition rate of pulverized coal (%)

(4) Based on the initial value (mixing position), dQ and then dA are calculated to obtain “A (A1)” at the next position.
(5) Repeat to obtain A (= A1) at the blended coal charging position.

  (6-1) Addition only to pulverized coal (F%) (suppression of carbon adhesion) In the case of (i) above, if A1 ≥ AI (target value), transport and installation of blended coal under this condition To enter.

  (6-2) Addition to pulverized coal (F%) and coarse coal ([100-F]%) (improving coke strength) In the case of (ii) above, (ii-1) A1 = AI (target value) ), The blended coal is transported and charged under these conditions. (Ii-2) If A1 ≠ AI (target value), A0 is adjusted so that A1 = AI (target value). Until (4) to (6) are repeated.

  Table 1 shows a calculation example.

A method for determining the amount of migration of the caking filler when the kneading conditions are changed will be described. The particle size of the pseudo particles at the kneader exit may be used. That is, the d _f a particle size of pseudo particles, calculated according to Determination of migration of the caking prosthetic material.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
The present invention was implemented on an actual machine line schematically shown in FIG. After drying the coal blend X in the dryer 1, in classifier 2 to the pulverized coal X ₀ and coarse coal X ₁ binary classification. The pulverized coal X ₀ is collected by the pulverized coal collector 3, kneaded by the kneading filler b whose viscosity is adjusted by the caking filler viscosity controller 5, and then kneaded by the kneader 4, and then the temperature controller. 8 adjusts the temperature.

The coarse coal X ₁ is kneaded by the kneading filler b whose viscosity is adjusted by the caking filler viscosity controller 7 and the kneader 6, and then the temperature is adjusted by the temperature controller 8.

The kneaded pulverized coal X ₀ b and the kneaded coarse coal X ₁ b after temperature adjustment are blended at the blending position M to become blended coal Xb, which is conveyed to the charging device 9 and charged into the coke oven 10 from there. Is done.

  Additive ratio for blended coal caking filler C = 3%, pulverized coal ratio F = 20%, added ratio of caking coal caking filler during kneading A ′ = 15%, caking supplement for coarse coal during kneading The material addition rate B '= 0%, and the type of caking filler added to the pulverized coal, kneading temperature, kneader rotation speed, kneading time, and transport time are changed to compensate for caking coal caking during furnace charging. A material addition rate A1 and a coarse coal caking filler addition rate B1 at the time of furnace charging were determined.

In addition, the coke oven operation status (dust generation, carbon adhesion to the furnace wall, coke extrudability) at that time was evaluated by ○ ×, and coke strength (DI ¹⁵⁰ ₁₅ ) was measured. The results are shown in Table 2.

  In Comparative Example 1, since a large amount of the caking filler transferred from the pulverized coal to the coarse coal side from the time of kneading to the time of charging the coke oven, the addition rate A1 of the caking coal caking filler at the time of charging the coke oven is It was 9.7%. Under these conditions, in order to achieve stable coke oven operating conditions, the target value of A1 is 10% or more, there is a lot of dust generation, a large amount of carbon adheres to the furnace wall, and the coke extrudability is also good. The coke oven operation was not good.

  On the other hand, in all the examples, A1 was 10% or more, and the coke oven operation state was good.

  In Example 1, as a result of changing the type of caking filler to caking filler material y having a lower viscosity than caking filler material z of Comparative Example 1, the caking furnace was charged with pulverized coal caking filler. The addition rate A1 could be 12.9% above the target value.

  In Example 2, the kneading temperature of the caking filler z was lowered from 80 ° C. in Comparative Example 1 to 40 ° C., and the viscosity of the caking filler z during kneading was increased. The carbonized caking filler addition rate A1 could be 11.9% above the target value.

  In Example 3, as a result of increasing the kneader rotation speed from 30 rpm of Comparative Example 1 to 50 rpm in kneading of the caking filler z, the kneadability was improved. As a result, the caking furnace caking furnace caking furnace was used. The addition rate A1 could be 10.3% above the target value.

  In Example 4, the kneading time at the time of kneading of the caking filler z was increased from 1 min to 2 min in Comparative Example 1 to improve the kneading performance. As a result, the addition ratio of caking coal caking filler at the time of charging in the coke oven was increased. A1 could be 10.7% above the target value.

  In Example 5, as a result of shortening the time from kneading of the caking filler z to charging the coke oven from 2h to 1h in Comparative Example 1 by increasing the conveying speed, the anti-fine powder when charging the coke oven was reduced. The addition rate A1 of the carbon caking filler was able to be 11.0% above the target value.

  As described above, according to the present invention, troubles in operation can be avoided, and high-strength coke can be constantly produced from low-quality coal blends. Therefore, the present invention has great applicability in the coke manufacturing industry and the steel industry.

DESCRIPTION OF SYMBOLS 1 Dryer 2 Classifier 3 Pulverized coal collector 4, 6 Kneading machine 5, 7 Condensation filler viscosity controller 8 Temperature controller 9 Charger 10 Coke oven b Condensation filler X Blended coal X ₀ Pulverized coal X ₁ Coarse coal X ₀ b Kneaded pulverized coal X ₁ b Kneaded coarse coal Xb Blended coal M Mixing position

Claims (1)

And classified the coal blend into fine coal and coarse coal, a method for producing high strength coke was charged into the coke oven and kneaded by adding caking filling material in the pulverized coal,
Obtaining the relationship between the concentration of the caking filler in the pulverized coal in the blended coal and the amount of carbon adhering to the coke oven wall, determining the upper limit CI of carbon adhering amount that can maintain the stable operation of the coke oven, From the relationship, determine the value AI of the caking filler concentration in pulverized coal corresponding to the carbon adhesion amount CI,
With the addition of caking filling material in the pulverized coal at a concentration above AI, the caking prosthetic material concentration of fines in the coal in the coke RoSo Nyutoki, so that the AI above, the type of caking prosthetic material and viscosity , The number of revolutions of the kneader when kneading the caking filler and pulverized coal, the kneading time between the caking filler and pulverized coal, the kneading temperature between the caking filler and pulverized coal, the kneading filler and kneading Adjusting at least one condition of the conveying time from the position where the pulverized coal and the coarse coal are mixed to the position where the pulverized coal and the coarse coal are charged into the coke oven. Coke production method.

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