JP4742686B2 - Blowing synthetic resin into blast furnace - Google Patents

Description

  The present invention relates to a method for blowing a synthetic resin material into a blast furnace.

  In the blast furnace, iron ore, secondary raw materials, and coke as fuel are charged from the top of the furnace, air at approximately 1200 ° C is sent from the tuyere at the bottom of the furnace, and the coke that has descended to the tuyere is combusted. Gas is generated to produce hot metal. This coke requires about 500 kg per ton of pig iron. Since coking coal for producing this coke is more expensive than steaming coal, reducing the amount of coke used leads to cost reduction. Thus, gaseous fuel such as natural gas, liquid fuel such as heavy oil, and solid fuel such as pulverized coal are blown from the tuyere. Here, the amount of coke used is reduced by replacing it with blown fuel. In this replacement, it is considered important that the injected fuel burns in the raceway and is effectively used as heat. In particular, in the case of solid fuel, unburned materials that cannot be combusted are discharged into the furnace, and some are consumed by gasification reaction in the furnace, but unburned materials that cannot be consumed accumulate in the furnace and become gas. It can impede flow and lead to poor breathability.

  In recent years, methods for treating synthetic resin materials have become environmental problems, and many have been landfilled or incinerated, but there are problems of refractory damage to combustion furnaces due to lack of land and high heat. As a method for solving such a problem, there is a method in which a pulverized synthetic resin material is blown as a reducing material from the tuyere of the blast furnace, but at the time of blowing, a raceway is used to prevent unburned synthetic resin material from being discharged into the furnace. It is important to maintain high flammability in the way.

  As a technique for maintaining the combustibility of the synthetic resin material, for example, a method of controlling the position of the blowing lance is known in order to prevent the combustibility from being lowered in accordance with the change in the particle size of the synthetic resin material ( For example, see Patent Document 1. Hereinafter, described as “Prior Art 1”.

In addition, in order to achieve high combustion and gasification of the synthetic resin material, a method of controlling the particle size and strength of the synthetic resin material to an appropriate state is also known (see, for example, Patent Document 2; hereinafter referred to as “Prior Art 2”). .)
JP-A-9-202907 JP 2000-144221 A

  However, the above-described prior art has the following problems. In prior art 1, the longer the synthetic resin material having a larger particle diameter is blown, the longer the distance of the blowing lance from the tip of the tuyere, the higher the combustibility of the synthetic resin material. There is a limit to the distance that can be installed. Further, when the synthetic resin material is combusted and gasified in the blow pipe, the pressure loss in the blow pipe increases, which may adversely affect the operation due to the blowing limit.

  According to Prior Art 2, high-strength and large-diameter particles are combusted and gasified while staying in the raceway without splitting or collapsing in the middle, so that a high combustion / gasification rate can be achieved. However, as the amount of synthetic resin material blown per tuyere increases, the oxygen excess rate decreases, resulting in a gasification reaction being promoted instead of a combustion reaction with oxygen that is effectively utilized as a heat source. Therefore, even if it is a synthetic resin material whose strength and particle size are controlled to be in an appropriate state, if the amount of blowing is large, the raceway temperature will decrease and the consumption speed in the furnace will decrease. The accumulation of unburned powder in the furnace may deteriorate air permeability.

  Therefore, the object of the present invention is to solve such a problem of the prior art, and even when the amount of the synthetic resin material injected into the blast furnace increases without controlling the position of the synthetic resin material blowing lance, An object of the present invention is to provide a method for blowing a synthetic resin material into a blast furnace, which can maintain the flammability of the material and prevent deterioration in air permeability of the blast furnace.

The features of the present invention for solving such problems are as follows.
(A) In the blast furnace operation method of blowing synthetic resin material from tuyeres of a blast furnace, the accumulation amount of the powder which is unburned substances has not been consumed from blowing amount of the synthetic resin material blown from the tuyere synthetic resin material Subtract the volume ratio of the accumulated powder from the porosity of the initial packed bed. The pressure loss in the furnace is estimated using the void ratio corrected by the above, so that the estimated pressure loss is less than the pressure loss satisfying all the limit pressure loss determined by the blow-through and the limit pressure loss determined from the upper pressure limit of the equipment. The method of blowing a synthetic resin material into a blast furnace is characterized in that the number of tuyere of synthetic resin material is controlled.
(B) Estimating the pressure loss in the furnace using the amount of powder estimated from the mass balance of the unburned synthetic resin material blown from the tuyere at the lower part of the blast furnace. A method of blowing a synthetic resin material into a blast furnace as described in (a).

  According to the present invention, the combustibility of the synthetic resin material can be controlled, and the synthetic resin material can be consumed in the raceway without accumulating the unburned powder of the synthetic resin material in the furnace. Therefore, the pressure loss rise in the furnace can be prevented, and the operation can be continued while maintaining the blast furnace in a good state.

  In the present invention, in the blast furnace operating method in which the synthetic resin material is blown from the tuyere of the blast furnace, the pressure loss in the furnace is obtained from the blowing amount of the synthetic resin material and the number of tuyere tuyere, and the pressure loss is an appropriate value below the reference value. The above-mentioned problem is solved by a method of blowing a synthetic resin material into a blast furnace, which controls the number of tuyere of the synthetic resin material.

  The pressure loss in the furnace is preferably determined using the amount of powder estimated from the powder mass balance in the lower part of the furnace. Estimate the amount of powder discharged from the raceway to the furnace lower packed bed for the powder that is unburned synthetic resin material blown from the blast furnace tuyeres. The pressure loss in the furnace is determined using the amount of body scattering and the consumption rate of powder at the lower part of the furnace, and the number of tuyere infused with the synthetic resin material is controlled so that the pressure loss becomes an appropriate value below the reference value.

  The synthetic resin material blown from the tuyere stays in the raceway and burns and gasifies, but unburnt synthetic resin material that cannot be consumed there accumulates in the furnace and deteriorates air permeability. Therefore, the present inventors set the appropriate number of blowing tuyeres according to the amount of synthetic resin blown, thereby controlling the combustion and gasification of the synthetic resin material per tuyere to be in an appropriate state. It was considered desirable to ensure that the pressure loss in the furnace was in an appropriate state without discharging the unburned resin powder of the resin material into the furnace. Therefore, the optimum number of tuyere was determined by the following method.

  Assuming that the unburned synthetic resin material is partly accumulated in the furnace when discharged from the raceway as a powder, and the accumulation rate changes according to the accumulation amount, the mass balance is as follows ( 1) It is represented by the formula.

F _in −F _out = dW _a / dt (1)
However,
F _in : Powder generation rate (discharge amount of powder from the raceway to the furnace lower packed bed) (kg / h),
F _out : powder scattering and consumption rate (kg / h),
W _a : Accumulated amount of powder (kg).

Here, F _in and F _out are expressed by the following equations (2) and (3), respectively.
F _in = W _p ω _c (1−η _c ) + W _p ω _ash (2)
F _out = kW _a (3)
However,
W _p : synthetic resin material blowing rate (kg / h),
ω _c : carbon fraction (−) in the synthetic resin material,
η _c : parameter (−) corresponding to the carbon combustion rate in the synthetic resin material,
ω _ash : Ash content in synthetic resin (kg)
k: A parameter (1 / h) related to the consumption of the synthetic resin material in the furnace.

When the expressions (2) and (3) are substituted into the expression (1), the powder accumulation amount W _a is expressed by a first-order differential equation with respect to time, and the following expression (4) is obtained by solving this.

W _a = (W _p ω _c (1−η _c ) + W _p ω _ash / k) × (1−e ^−kt ) + W ₀ × e ^−kt (4)
However,
W ₀ : Accumulated amount of powder (kg) in a steady state.

The volume ratio of the powder accumulation obtained here is calculated by calculating the volume ratio of the void in the furnace from the furnace volume and the density of the powder, and subtracting the volume ratio of the accumulated powder from the porosity of the initial packed bed. It was considered that the void ratio was a substantial void ratio in the furnace, and the pressure loss in the furnace was estimated using this value using the following formula (5) proposed by Ergun.
ΔP / ΔL = 150 {(1-ε) ² μu / ε ³ (Φd _p ) ² } +1.75 {(1-ε) ρu ² / ε ³ (Φd _p )} (5)
However,
ΔP: pressure loss in the furnace (Pa),
ΔL: distance (m) between two points of pressure measurement,
ε: substantial porosity in the furnace (−),
μ: fluid viscosity (Pa · s),
u: fluid velocity (m / s),
ρ: fluid density (kg / m ³ ),
Φ: shape factor of particles (−),
d _p : the average particle diameter (m) of the particles.

  It is determined whether or not the pressure loss in the furnace (furnace pressure loss) estimated by this method is within the appropriate range. If the estimated pressure drop in the furnace does not fall within the appropriate region, the furnace condition may become unstable. Therefore, the number of tuyeres of the synthetic resin material is increased so as to fall within the appropriate region, and the amount of the tuyeres per tuyere is decreased to lead to stabilization of the furnace condition. However, since the increase in the number of tuyere injecting synthetic resin is a factor that increases costs in terms of equipment and operating costs, it is desirable to blow in synthetic resin with the smallest number of tuyere within the appropriate range. . In addition, when increasing the number of tuyere, it is desirable to blow in such a manner that the arrangement is as uniform as possible in the circumferential direction in consideration of the circumferential balance of the blast furnace.

  Moreover, the appropriate region of the pressure loss in the furnace set here differs depending on the blast furnace. That is, a region below the pressure loss that satisfies all of the critical pressure loss determined by the critical pressure loss that blows through in the blast furnace, the critical pressure loss that is determined from the upper pressure limit of the equipment, etc. is set as the appropriate region.

The above η _c is a parameter corresponding to the combustion rate calculated from the mass balance in actual operation, and can be set as appropriate. For example, it can be obtained using the following equation (6).

η _c = 0.969− {0.0052−0.013 × ln (n / N)} × W _p (6)
However, n: Number of tuyere of synthetic resin material (−),
N: Total number of tuyere (−).

  Further, k is a constant, and an average value of values calculated using the formulas (4), (5), and (6) based on the actual values of the applied blast furnace was used.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of the present invention. In FIG. 1, 1 is a blast furnace, 2 is a tuyere, 3 is a lance, 4 is a blow pipe, 5 is a synthetic resin material storage hopper, and 6 is a synthetic resin. A material blowing tank, 7 is a compressed air supply device, and 8 is a distributor. The synthetic resin material is cut out from the synthetic resin material storage hopper 5 by the synthetic resin material blowing tank 6 and becomes a mixed fluid containing the synthetic resin material using the compressed air supplied from the compressed air supply device 7 as a carrier gas. The distributor 8 distributes the number of synthetic resin materials determined by using the method of the present invention to the number corresponding to the number of tuyere, and each of the mixed fluids is ejected from the lance 3 into the high-speed hot air of the blow pipe 4, It is blown into the blast furnace 1 through the mouth 2.

Examples of the present invention will be described below. For a blast furnace having an internal volume of 3223 m ³ and 34 tuyere, the pressure loss in the furnace was estimated from the amount of synthetic resin blown and the number of tuyere. The results are shown in FIG. According to FIG. 2, when the operation is performed with the upper limit (reference value) of the appropriate range of pressure loss being 150 kPa, for example, when performing a blowing operation of a synthetic resin material of 15 kg / t, the minimum blowing in which the pressure loss becomes an appropriate region It can be seen that the number of tuyere is eight.

  Using the above results, in the blast furnace where the synthetic resin material was blown at an average blowing ratio of 15 kg / t (equivalent to 130 kg / t per blowing tuyere) from four tuyere, the blowing feather of synthetic resin material The synthetic resin material was blown at an average blowing ratio of 15 kg / t (equivalent to 65 kg / t per blowing tuyere) with 8 nozzles. FIG. 3 shows the change over time in the furnace pressure loss.

  In FIG. 3, the portion from 0 to 30 days is a change over time in the pressure loss in the furnace when the synthetic resin material is blown from four tuyere, and in this case, after the pressure loss in the furnace gradually increases during the operation. A blow-through indicated by an arrow in FIG. 3 occurred. Therefore, in this case, it is thought that the powder discharged from the raceway deteriorated the air permeability in the furnace because the amount of the synthetic resin material per tuyere was large and the combustibility deteriorated.

  The 30th day and after shown in the graph of FIG. 3 is a case where the number of blowing tuyere is eight. In this case, the pressure loss in the furnace remained stable without any blow-through or slip, and the operation was stable. Therefore, in this case, it is considered that the synthetic resin material blown from the tuyere was consumed by combustion and gasification in the raceway without being discharged from the raceway as powder.

  From the above, it has been found that stable operation is possible by optimizing the number of synthetic resin materials blown in accordance with the amount of synthetic resin material blown using the method of the present invention.

It is the schematic which shows one Embodiment of this invention. It is a graph which shows the relationship between the pressure loss in a furnace, the blowing amount of a synthetic resin material, and the number of blowing tuyere. It is a graph which shows transition of furnace pressure loss.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Tuyere 3 Lance 4 Blow pipe 5 Synthetic resin material storage hopper 6 Synthetic resin material blowing tank 7 Compressed air supply device 8 Distributor

Claims (2)

In blast furnace operation method of blowing synthetic resin material from tuyeres of a blast furnace, the accumulation amount of material balance of the powder which is unburned substances has not been consumed from blowing amount of the synthetic resin material blown from the tuyere synthetic resin material It is corrected by subtracting the volume ratio occupied by the accumulated powder from the porosity of the initial packed bed, by determining the volume ratio of the accumulated powder amount in the void in the furnace from the furnace volume and the density of the powder. The pressure loss in the furnace is estimated using the porosity , and the estimated pressure loss becomes a critical pressure loss that blows through, and the synthetic resin so that it is less than the pressure loss that satisfies all the limit pressure loss determined from the upper pressure limit of the equipment. A method for blowing a synthetic resin material into a blast furnace, characterized in that the number of tuyere of the material is controlled. It is characterized by estimating the pressure loss in the furnace using the amount of powder estimated from the mass balance of the unburned synthetic resin material that was blown from the tuyeres in the lower part of the blast furnace and could not be consumed. The method for blowing a synthetic resin material into the blast furnace according to claim 1.

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