JPH0718313A - Operation of vertical furnace - Google Patents

Abstract

PURPOSE:To keep ventilation satisfactory in condition and to stably operate a furnace by adjusting grain diameter of fine powder, gas flowing rate, grain diameter of a packing layer, blowing rate of the fine powder, etc., in a vertical furnace and controlling the reducing value of a space ratio to the control value of below. CONSTITUTION:Into the vertical furnace 1 packed with the grains 4, the fine powder 6 from a fine powder blowing part 3 is blown together with the gas from a gas blowing part 2 to allow to react the grain 4 and fine powder 6 with gas. At this time, a holding up quantity rhok of the fine powder in the furnace is estimated by using the equation rhok=(mu<2>/4.436X10<-11>rhog.g)(Ug/ g-Dg)<1/2>)<-3.74>*(Dk/D<p>)<2.08>(Gko/Gg)<0.97>*10<7.9> (wherein, mu: gas viscosity, rhog: gas density, g: gravity acceleration, Ug: gas flowing velocity, Dp: grain diameter of grains in the packing layer, Dk: grain diameter of fine powder, Gko: mass velocity of the fine powder, Gg: mass velocity of the gas). Successively, the reduction DELTAepsilon of the space ratio is calculated by using the equation DELTAepsilon=epsilono(rhok/rhoko) (wherein, rhoko: the hold up quantity of the fine powder, epsilono: the space ratio of the packing layer). This DELTAepsilon is controlled to the control value alpha or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention predicts the retention amount of fine powder in a furnace in a vertical furnace in which gas and fine powder flow through a packed bed filled with particles, and controls the retention amount. Thus, the present invention relates to a method of maintaining the reaction of particles, gas and fine powder in the furnace smoothly, and operating the vertical furnace in a stable state. The present technology can be applied to a blast furnace, a gas generation furnace, a shaft furnace for iron oxide reduction, and the like.

[0002]

2. Description of the Related Art In an industrial furnace in which gas and fine powder flow through a packed tower, fine powder stays in the furnace depending on the operating conditions. Accumulation of fine powder deteriorates the air permeability in the furnace, which in turn inhibits the temperature rise in the packed bed and lowers the reaction efficiency by causing a localized drift of the gas flow, so the amount of retention is controlled to an appropriate level. It becomes important to do. When the fine powder stays extremely, the gas flow rate at that time,
If the amount of air blown in and the particle size of the fine powder are continuously maintained, fluidization of the filled particles may occur, which may lead to blowout, or the operation may be stopped.

Taking a blast furnace as an example, in recent years the amount of pulverized coal blown into the blast furnace has increased, and along with this, unburned char that does not burn in the raceway, which is the combustion zone of the blast furnace, rises with gas above. In addition, the coke powder generated by combustion or abrasion in the raceway part also exhibits the same behavior. The fine powder from the raceway flows as a solid-gas two-phase flow in the packed bed, but the movement and accumulation behavior of the fine powder depends on the particle size of the coke particles forming the packed bed, the gas flow rate, and the particle size and amount of the fine powder. It can be different.

If the accumulation amount (hold-up) of the pulverized coal in the packed bed can be estimated when the operating conditions of the furnace are given, appropriate action can be taken against abnormal ventilation, and the stability of the blast furnace can be improved. Although effective for operation, it is difficult to estimate this holdup with the conventional technology.
Further, for example, reduction of iron oxide in a reducing shaft furnace filled with pitch coke and blowing fine coal and air from the tuyere to flow CO through the gas generating furnace to generate CO and a reducing gas blown from the lower part of the iron oxide packed bed. The same problem as described above also occurs in fine powder generated by pulverization or abrasion between particles.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention maintains good ventilation in the furnace even when a large amount of fine powder is blown into the furnace, so that the inside of the furnace is always maintained. It is an object of the present invention to provide a method for operating a vertical furnace, which maintains an active state, thereby allowing gas and solids to flow smoothly and stably operating the furnace.

[0006]

Means for Solving the Problems The present invention is to solve the above-mentioned problems. The holdup amount ρ _k of fine powder in a vertical furnace is estimated by using the equation (1), and then the equation (2) is calculated. The decrease Δε in the porosity is calculated by using, and if Δε is a control value α of 0.08 or more, the particle diameter D _{k of} the fine powder, the gas flow rate U _g , the particle diameter D _{p of} the packed bed, and the fine powder injection By adjusting any one or two or more of the quantities G _k0, the equation (2) is calculated again using ρ _k calculated from the equation (1), and Δε is set to α by repeating the adjustment and calculation. It is a control method for a vertical furnace characterized by the following control.

Ρ _k = (μ ² /4.436×10 ^-11 ρ _g · g) (U _g / g · D _p ) ^1/2 ) ^-3.74 * (D _k / D _p ) ^2.08 (G _k0 / G _g ) ^0.97 * 10 ^7.9 (1) Δε = ε ₀ · (ρ _k / ρ _k0 ) ... (2) where ρ _k : Hold-up amount of fine powder (kg / m ³ −
bed) μ: Gas viscosity (kg / m · s) ρ _g : Gas density (kg / m ³ ) g: Gravitational acceleration (m / s ² ) U _g : Gas flow velocity (m / s) D _p : Packing Particle diameter of layer (m) D _k : Particle diameter of fine powder (m) G _k0 : Average mass velocity (blowing amount) of fine powder in the furnace (kg /
m ² · s) G _g : Average mass velocity of gas in the furnace (kg / m ² · s) Δε: Reduction of void ratio (−) ρ _k0 : Hold-up amount of fine powder when the space is completely filled (kg) / M ³ -bed) ε ₀ : Porosity of packed bed without fine powder (= 0.45)
(-)

[0008]

The feature of the present invention is that the hold-up amount of the fine powder in the packed bed is deeply related to the particle size of the coke particles or the like constituting the packed bed, the flow velocity of the gas, the particle size and the amount of the fine powder according to the model experiment, In addition, they have found the quantitative relationship between them. That is, the holdup ρ _k of the fine powder in the vertical furnace is estimated by using the equation (1), and then the decrease Δε in the porosity is calculated by using the equation (2). If the Δε is equal to or more than a certain control value α of 0.08 or more, any one or more of the fine powder particle diameter D _k , the gas flow rate U _g , the packed bed particle diameter D _p , and the fine powder blowing amount G _k0. Is adjusted to calculate (2) again using ρ _k calculated from (1), and by repeating this, Δε is controlled to be equal to or less than α. Here, the fine powder is defined as a powder of 500 μm or less.

The increase in the holdup of the fine powder is arranged as a phenomenon in which the space in the packed bed is filled with the fine powder. When the space of the packed bed is kept in a healthy state, its porosity ε ₀ is 0.4.
It is in the vicinity of 5. If this fine powder fills the space and exists,
The decrease in porosity Δε can be expressed as in the above equation (2). On the other hand, according to the model experiment, when the porosity of the packed bed was decreased by 0.1 due to the retention of the fine powder, the gas flow velocity, the blowing amount, and the particle size of the fine powder were kept fluidized at that time when the packed particle was fluidized. Eventually, it became clear that it was a blowout.

This phenomenon will be explained by taking a blast furnace as an example.
If the void ratio epsilon ₀ = 0.45 vicinity of the space filling layer when the space of the coke packed layer was kept in a healthy state fines were completely filled, its weight [rho _k0 is the 225 kg / m ³ -bed Become. According to the equation (1) derived from the model experiment, the average particle flow rate U _{g of the} lower part of the blast furnace with the fine powder particle diameter D _k = 80 μm
= 0.8 m / s, the hold-up of fine powder is ρ _k =
It becomes 50 kg / m ³ -bed. The decrease Δε in the porosity at this time is Δε = 0.45 × (50/225) = 0.1 from the equation (2), and the packed bed porosity ε at this time is as follows. ε = ε ₀ −Δε = 0.45−0.1 = 0.35

If ρ _k = 50 kg / m ³ -bed or more, this packed bed will be fluidized or blown by fine powder. That is, in this case, it is necessary to manage ρ _k to be equal to or less than this value (= 50) by the equation (1). ρ _k
The following are examples of control means for lowering. (1) Decrease the fine powder particle diameter D _k . (2) Lower the gas flow rate U _g . (3) Increase the particle diameter D _p of the packed bed. (4) The amount of fine powder blown is reduced to reduce the average mass velocity G _k0 in the furnace.

The above four options are restricted by the conditions under which they are placed, that is, the production amount, the conditions for blowing fine powder, the conditions for blowing air (gas blowing), etc., so that the priority order changes depending on the situation. Regarding U _g , in the case of a shaft furnace or a gas generating furnace, the gas flow velocity distribution in the radial direction does not pose a problem, but in the case of a blast furnace, since the distribution of ventilation resistance in the radial direction is generated, it is possible to obtain an accurate value in the blast furnace. It is difficult to grasp the figures. Therefore, here, the average gas velocity of the hearth or the average of the hearth is applied.

The present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing the system of the present invention, and 1 is a vertical furnace in which gas and fine powder move in packed bed particles, such as a blast furnace, a gas generation furnace, and a shaft furnace. Reference numeral 2 is a gas blowing portion, and 3 is a fine powder blowing portion, which is blown with a fine powder particle diameter D _k . 4 is a packing particle, and a granular coke having an average particle diameter D _p , iron oxide, or pitch coke forms a fixed layer or a moving layer.
5 is a part for discharging particles. In the case of blast furnaces and gas generating furnaces, this part does not exist because particles are extinguished by combustion.

Reference numeral 6 represents fine powder retained in the packed bed at a retention amount ρ _k . As fine powder, coke powder, iron oxide powder,
Chars, fluxes, etc. that have been transformed from pulverized coal. The retention mode of the fine powder consists of both a dynamic holdup moving through the packed bed and a static holdup stopped by being promoted by the packed bed.

The gas is moving from the bottom to the top at the sectional average velocity U _g of the furnace, and the fine powder is moving together with the gas at the sectional average mass velocity G _k0 . As for the fine powder particle diameter D _k, the particle diameter corresponding to the inside of the furnace is applied to the fine powder particle diameter D _{k which} changes due to combustion.

FIG. 2 is an explanatory view showing the outline of the present invention.
The operation factors that influence the _holdup of the fine powder are the fine powder blowing amount G _k0 , the gas flow rate U _g , the particle diameter D _p of the packed bed, and the fine powder particle diameter D _k , and 11 is a mechanism for adjusting the fine powder blowing amount G _k0 .
Reference numeral 12 is an adjusting mechanism of the gas flow rate U _g , 13 is an adjusting mechanism of the particle diameter D _p of the packed bed, and 14 is an adjusting mechanism of the fine powder particle diameter D _k . Reference numeral 15 is a fine powder holdup ρ _k calculation mechanism, which is calculated from equation (1) using the physical properties of the gas and the operating parameters 11, 12, 13, and 14. Reference numeral 16 denotes a calculation mechanism for obtaining the porosity reduction Δε of the packed bed, which is calculated from the fine powder holdup ρ _{k of} 15 using the equation (2).

Reference numeral 17 is a value α for which the reduction Δε of the porosity is set.
A judgment mechanism, a status display mechanism, and an alarm generation mechanism that determine whether or not the value exceeds. Usually this α is 0.1
Is set, but since this value changes depending on the case, it is defined as a certain value of 0.08 or more. When it is less than 0.08, it is considered that the porosity ε is kept in a normal state in which the gas smoothly flows through. Each parameter value and judgment status are monitored. If the determined Δε is less than or equal to α, an instruction to continue the operation is given, and if α or more is given, an alarm is issued and the optimum action type and action amount are instructed.

The fine powder blowing amount 11 is controlled, for example, by a flow rate control mechanism of the powder cut out from the hopper, the gas flow velocity 12 is controlled by, for example, the rotation speed of the blower, and the packed bed particle diameter 13 is controlled by, for example, the average particle size of the coke charged. The adjustment and control of the fine powder particle diameter 14 can be realized by, for example, controlling the crushed particle size of the crusher.

[0019]

EXAMPLES Examples of the present invention will be shown below. FIG. 3 shows an example of controlling holdup of fine powder in a blast furnace. As a background, there is a need to increase the amount of pulverized coal injected.

In step (1), the amount of pulverized coal blown per t of pig iron was 60 kg / t. At this time, the average mass velocity G _k0 in the furnace is 0.027, the calculated holdup value ρ _k = 35.5 kg / m ³ -bed, and Δε =
It was 0.071. Since the control value α was 1.0, it means that the operation was on the safe side.

In the step (2), it was planned to operate at a pulverized coal injection rate (PCR) per 100 t of pig iron = 100 kg / t. When the amount of pulverized coal _injected increases, the hold-up increases due to an increase in G _k0 , Δε exceeds the control value α = 0.1, and Δε = 0.117 was calculated. Therefore, in step (3), the pulverized coal particle size D _The operation of lowering _k from 80 μm to 60 μm was performed. Δε decreased to 0.068,
It became possible to operate on the safe side.

In step (4), the production of the blast furnace was forced to be reduced, and the average gas flow rate U _g was changed from 1.00 m / s to 0.95.
It decreased to m / s. Δε is 0.11 due to the decrease in U _g
It rose to 1 and exceeded the control value. Therefore, in this case, when the pulverized coal injection amount (PCR) per pig iron t was reduced from 100 kg / t to 80 kg / t in step (5), G _k0 changed from 0.0457 to 0.0366, and the safety side was reached. Moved to.

The above-mentioned procedures are shown for the sake of easy understanding, and in reality, since these procedures are performed as pre-prediction-control, Δε is α when controlled by the present invention.
It does not exceed the control value of and can always operate on the safe side.

For the packed particle diameter D _p , the rate of increase of D _p is 1
It has an effect of reducing Δε by 10% with respect to 0%. Δε
Has risen to 0.109, the average coke grain size has been increased to 45
When changed from mm to 50 mm, Δε is 0.9
It dropped to 8. The effect of D _p is small as a direct effect within the control range of the operation, but has a secondary effect as a means for controlling the gas flow velocity distribution in the radial direction.

[0025]

EFFECTS OF THE INVENTION According to the method of the present invention, the fine powder retention behavior of a vertical furnace can be quantitatively grasped, and excessive retention of fine powder can be prevented by controlling the decrease in porosity Δε. is there. As a result, the fluidization or blow-through of the packed bed can be grasped in advance as the air permeability deteriorates.
This is an innovative technology in that it can prevent delay in action.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a system of the present invention.

FIG. 2 is a block diagram showing the principle of the present invention.

FIG. 3 is a graph showing an example in which holdup control is performed in a blast furnace according to the present invention.

[Explanation of symbols]

 1 Vertical furnace 2 Gas blowing part 3 Fine powder blowing part 4 Filled particles 5 Particle discharging part 6 Fine powder

Claims (1)

[Claims] 1. A holdup amount ρ _k of fine powder in a vertical furnace.
Is calculated using the equation (1), and then the decrease Δε in the porosity is calculated using the equation (2). If the Δε is a control value α of 0.08 or more, the particle diameter D _{k of the} fine powder is calculated. , Gas velocity U
_g , the particle diameter D _p of the packed bed, and the fine powder blowing amount G _k0 are adjusted one or more kinds, and the formula (2) is calculated again using ρ _k calculated from the formula (1), A method for controlling a vertical furnace, wherein Δε is controlled to be equal to or less than α by repeating the adjustment and calculation. ρ _k = (μ ² /4.436×10 ^-11 ρ _g · g) (U _g / g · D _p ) ^1/2 ) ^-3.74 * (D _k / D _p ) ^2.08 (G _k0 / G _g ). ^0.97 * 10 ^7.9 (1) Δε = ε ₀ · (ρ _k / ρ _k0 ) …… (2) where ρ _k : Hold-up amount of fine powder (kg / m ³ −
bed) μ: Gas viscosity (kg / m · s) ρ _g : Gas density (kg / m ³ ) g: Gravitational acceleration (m / s ² ) U _g : Gas flow velocity (m / s) D _p : Packing Particle diameter of layer (m) D _k : Particle diameter of fine powder (m) G _k0 : Average mass velocity (blowing amount) of fine powder in the furnace (kg /
m ² · s) G _g : Average mass velocity of gas in the furnace (kg / m ² · s) Δε: Reduction of void ratio (−) ρ _k0 : Hold-up amount of fine powder when the space is completely filled (kg) / M ³ -bed) ε ₀ : Porosity of packed bed without fine powder (= 0.45)
(-)