SU1504274A1 - Method of preparing sinter charge to sintering - Google Patents

Abstract

The invention relates to the preparation of raw materials for the production of iron and steel and can be used in agglomeration. The purpose of the invention is to increase the efficiency of sinter production. Iron ore materials and fuel are mixed and pelletized with lime feed and part of the fuel at the end of pelletizing, and soft or medium enriched quicklime with a specific surface ≥ 350 m ² / kg in an amount of 8-16 kg / ton of dry blend is rolled on the granules when they reach the process of pelletizing of particle size D _eq equal to 2.4-4.2 mm. After at least 0.1 h after the introduction of lime, a portion of the fuel is fed into the mixture and mixed with the latter in a mixing drum. This provides an increase in specific productivity, a reduction in fuel consumption and an increase in the strength of the agglomerate during sintering of a large-granular mixture with a high layer. 5 tab.

Description

The invention relates to the preparation of iron ore for the production of iron and steel.

The purpose of the invention is to increase the efficiency of sinter production.

The essence of the method lies in the fact that the charge after pelletizing to a well-defined particle size distribution is stabilized by the lime rolling. When slaking lime, a decrease in the moisture content of the charge and cementation of the surface of the granules occurs. As a result of these processes, lumpy activity (their production decreases sharply or even disappears

completely. Therefore, when mixed with the newly introduced fuel, the charge granules are neutral with respect to the fuel particles.

The process technology is implemented as follows.

In the batch compartment, all materials used at the sinter plant are metered, except for that part of the lime and fuel that is introduced into the charge after mixing and pelletizing. The parameters of the pelletizing mode - moisture content of the charge, the speed of rotation of the drum (tray), yrojr npc: you determine the basis of the condition of obtaining the pelletized charge with a large d.

SP

Hche

four

31504

 2.4-4.2 mm. When pelletizing, a grab-burned grab is introduced into the fir) or, at the extreme, medium-fired ground ground with a specific surface of 350 m / kg of non-burnt lime in the amount of 8-16 kg per 1 ton of the charge (dry). Lime is introduced by nakatgoan on the pre-pelleted mixture of particle size d, 2.4-4.2 mm. The fuel is introduced into the mixture after pelletizing and lime rolling in a stream on a conveyor belt and mixed in the mixer no less than 0.1 h after lime rolling.

The coarsening size of the charge is determined by sieve analysis of samples taken in the stream after the charge leaves the pelletizer. The lime is stopped by rolling, the granulation of the charge and, therefore, the results of the sieve ANALYSIS of the pelleted charge reflect its size before entering the lime.

The amount of free fuel in the coarse-grained charge is controlled by changing the mass ratio between the fuel introduced into the charge before pelleting (in the charge compartment) and the fuel that is introduced into the charge after grinding.

Lime rolling and subsequent charge holding for 0.1 h ensure the stabilization of the granulometric composition of the charge. By exposure is understood the absence of dynamic effects. This time the charge may be in flow, for example, on a belt conveyor.

The values of 2.4-4.2 mm reflect such a structure of the pelletized mixture, when the nature of the 15 position of the fuel particles takes on the role of an essential factor in the sintering process, as the most important characteristic of its texture. The minimum value of this parameter (d, | 2.4 mm) corresponds to the condition of efficient sintering of the charge with a layer height of 500 mm with a rarefaction of 7.8–8.0 kPa, which provides for existing gas-blowing means. The maximum size of the pelletized charge (1dtsd 4.2 mm) reflects the upper limit of the structural characteristics of the pelletized quiet, the conversion of which transforms the sintering mode into the firing mode.

The requirements for the quality of the lime-rolling Mopi, reflecting the firing mode and fineness, satisfy the condition of maximum hardening of the granules with a minimum shutter speed equal to O, 1 hour. This time the charge can be in the flow or in the bunker. If the conditions for lime quality are observed, this time is sufficient for the hydration of calcium oxide to quench to take on such dimensions when the mixture becomes stable, i.e. with repeated dynamic action, similar to a rotating drum, its particle size distribution remains almost unchanged.

Specifying the lower limit of the time interval between rolling known and mixing the charge with the newly introduced fuel is due to the fact that this value determines the cost of implementing the proposed method in practice: as the interval increases, special bunkers will be required, the capacity of which will be determined by the power of the traffic flows.

The parameters for the flow of rolled lime satisfy the swing range of the pelletized mixture by size. Favorable results on the rate of slaking of lime and the hardening of pellets of the pelleted charge are achieved at a certain water ratio, the absolute value of which depends not only on the quality of lime, but also on the composition of the charge. The increase in size of the pelletized mixture is associated with an increase in its humidity. Therefore, it is advisable to associate the consumption of lime with the size of the pelletized charge. The experiments established the relationship between the amount of lime to be crushed and the size of the pelletized mixture, which satisfies the condition for the minimum duration of lime ingot while maintaining the high strength of the granules (the intervals reflect a change in the composition of the mixture in the amount of finely divided concentrates from 50 to 85) (see Table 1).

In the aggregate, all the parameters governing the lime nourishment condition (quality and quantity), together with an indication of the time interval between lime rolling and mixing with the fuel, ensure stabilization of the granulometric composition of the pelletized mixture. This circumstance is the main one, which is responsible for obtaining a qualitatively new texture of a pelleted Gaich, when the fuel is in the charge in the form of free particles, it plays the role of independent structural elements. The amount of free fuel is regulated in accordance with the requirements of the sintering process technology. In fact, this textural property of the pelletized mixture is an additional factor controlling the technological process by affecting the carbon burning behavior of the fuel, the more the fuel is in a free state, the greater is the completeness of chemical combustion of carbon. The positive role of this phenomenon is not negated by the economic side of sinter production. No less important is the reduction of carbon monoxide emissions into the atmosphere.

Experiments have shown that the use of the method of preparing the gaicht for sintering increases the amount of carbon in the fuel that burns to 45–55 to 85% or more. As a result, the amount of CO emitted into the atmosphere with waste gases is reduced by 54-88%.

The main advantage of the proposed method is that it allows one to master the technology of sintering the charge with a layer of 500 mm and higher with existing gas-blowing means. Taken together, this provides a significant improvement in all the major technical and economic indicators of the sinter production. Their quantitative assessment was determined on the basis of laboratory experiments.

Examples of specific implementation method.

Experiments were performed in the laboratory.

The ore part of the mixture consisted of oxidized ores and fine-grained concentrates — products of wet magnetic enrichment of ferruginous quartz- ses, with a ratio (by weight) of 0.3: 0.7.

The fluxes consisted of a mixture of lime, dolomite and lime. The flux consumption met the condition for the preparation of sinter with a basicity of 1.40. The lime consumption in relation to the charge was constant - 3.0% (by weight).

Two types of lime were used: before mixing, lime, non-ground (-15 mm), hardly absorbable (CaO, 78%) was injected into the mixture; specially prepared lime for rolling.

A mixture of Coxic and anthracite in the ratio

0 0.6: 0.4.

The composition of the mixture was responsible for obtaining the agglomerate of the following chemical composition, wt.%: Fe 32.40; FeO 9.70; SiOj 8.70; CaO 12.18; 3.21;

5 1.64; In 1.40.

Drafting the mixture. Before mixing and pelletizing, all components were injected into the mixture, except for a part of lime and fuel, which were added

0 in charge after pelletizing.

The mixture was mixed in two stages. —At the first stage, all components of the mixture were mixed, except for that part of lime and fuel,

5 which were intended to be added after pelletizing. In the second stage, the pelleted mixture was mixed with rolled lime and the newly introduced fuel. The control parameter is 0 hp with the time interval between lime rolling and secondary mixing. In the experiments, the magnitude of this interval (time of charge loading with lime rolled) varied within 0.083–1 h. Mixing was carried out on a plate granulator. . Batching of the charge, as well as mixing, was carried out with dish-shaped granules - torus. Pelting duration

The temperatures varied within the range of 0.05-0.1 hours. Before the start of the inlet, the mixture was moistened to 7.8–9.5%, depending on the required size of the pelletizing mixture.

five

Numbing lime produced

by panting on the lumping mixture for 60-90 s until the end of the pelletizing and continued for 40-70 s depending on the amount of lime to be applied. Three types of lime were used for rolling: milled (m.o.), medium-calcined (sr.) And strongly burned (s.o.). The specific surface varied from 340 to 500.

The amount of lime being rolled varied between 7.5 and 16.5 kg / ton of charge (dry).

0

The amount of free fuel in the coarse-granulated charge was controlled by changing the ratio between the fuel introduced into the mixture before mixing and the fuel introduced into the mixture after cutting lime.

The sintering of the mixture was carried out on a bowl with a diameter of 300 mm at a vacuum of 7.8 kPa. Fuel ignition produced a mixture of blast furnace and coke oven gas with a calorific value of 7100 - 7300 kJ / m.

The equivalent diameter calculated by the formula

.t

ei

 t,

where m m is the mass of the sample, kg;

- mass of class 1, kg;

d. - average particle diameter (granules) of class i, mm; n is the number of classes (the charge was divided into 7 classes: 0-0.5; 0.5-1; 1-2; 2-3; 3-5; 5-10 and 10 mm). In the presented experiments, the charge was monitored in three places: before lime (nd,), after rolling lime (d; ir5) z, and after mixing with fuel (d,) ,. This made it possible to assess the dynamics of change in the structure of the charge at various stages of its preparation for specularization.

The amount of free fuel in the pelletized mixture was determined by centrifuging the charge in bromoform solution with a density of about 1.8 g / cm.

The indicator of the complete chemical combustion of carbon fuel was taken as the coefficient for using carbon fuel, calculated by the formula

  "2C- CO-qC- CO

CO - thermal

where qC - C0, j and qC effects from the combustion of 1 kg of carbon fuel to CO and CO, respectively 34.0 and 10.34 MJ;

С-COj, 1C- СО - coefficients reflecting the amount of carbon in the fuel that burns to COj and CO, fractions.

The carbon burning pattern of the fuel is determined by the content of CO and CO resulting from the combustion of the carbon of the fuel. The latter were determined by calculation based on an analysis of the composition of the exhaust gases.

As technical and economic criteria for evaluating the effectiveness of the proposed method, we used conventional indicators reflecting the specific productivity of the sintering plant and the quality of the sinter. The latter was assessed according to GOST 15137-77, the terms of which provide for the assessment of the simplicity of the output of cells. +5 mm and cl. -0.5 mm.

In tab. 2 shows the encryption of benchmarks and key technological parameters reflecting the conditions of the experiments.

In tab. 3 shows the experiments, illustrating the value of the parameter - size pelletized mixture. Here, experience I reflects the conditions of the usual technology of preparation of the charge, when not

2 "2C- CO-qC- CO

100%

0

five

0

five

0

five

fuel and lime are applied. Experience 2 reflects the conditions of preparation of the charge, claimed in the prototype. The conditions of experiments 6 and 7 correspond to the limiting values of d, and

The max values 4 and 8 of this parameter are outside the limits defined by the claims (2.3 mm in experiment 4 and 4.3 mm in experiment 8).

In tab. Table 4 shows the experiments illustrating the effect on the sintering indices of the amount of lime to be limeed. Experiments 6 and 10, as in the table. 2. They perform the role of basic in relation to sintering conditions at a layer height of 300 and 600 mm.

I

In tab. 5 shows experiments illustrating the effect of the quality of rolled lime. Experiment 10 was taken as the base case. Experiments 18 and 19 reflect the influence of the quality parameters of lime below the limiting values: in experiment 18, highly calcined lime was used for nakatashan, and in experiment 19, with a low specific surface area of 340. In the 17 dp run, medium calcined lime was used. Experiments 19, 20 and 21 allow us to trace the effect on the effectiveness of the predicted method for increasing the grinding fineness of the lime to be applied.

1504

expressed in increasing its specific surface area.

In tab. 6 shows experiments illustrating the effect of exposure to a pelleted batch with knurled lime before mixing with the fuel. Experiment indicators 10 are accepted for the initial version. Experience 22 satisfies the conditions under which the holding time is less than the regulated value — 0.083 h. In experiments 23, 24 and 25, this time is respectively 0.117 0.5 and 1 h.

As follows from the results of the experiments, the method provides for obtaining a coarse-grained mixture with an adjustable amount of free fuel, which makes it possible to sinter the mixture with a high layer of 500 mm or more. In aggregate, this is reflected in the improvement of technical and economic indicators. Depending on the height of the layer and the amount of free fuel in the pelleted charge, the economic efficiency of the proposed method is as follows (as compared with the prototype):

Increase specific

productive-

Table

Controlled parameters of experiments to determine the effectiveness of the proposed method for producing a large-granular mixture with a controlled amount of free fuel

1 Layer height

2C content in charge

3Humidity of the batch

A (d ,,),

ten

STI,%

Reduced fuel consumption,% Increased mechanical strength of the agglomerate,%: cl. +5 mm

according to class -0.5 mm formula from

22 - 34 18.7

10 - 13

13 - 15 gains

A method for producing a coarse-grained agglomeration mixture, which includes mixing and pelletizing of metered materials with rolling lime pellets and portions of fuel fed to the charge mixture, characterized in that, in order to increase the efficiency of sinter production, the mixture is pelletized to a grain size corresponding to d, e 2 , 4–4.2 mm, and soft or mediumly burnt quicklime with a specific surface of 350 m / kg in the amount of 8–16 kg / t of the charge (dry) is rolled on them, and part of the fuel is introduced into the pelletized shea Htu after at least 0, 1 hour after the rolling of lime and mixed with the mixture in a mixing drum.

Table 1

mm%

mm.5 (nd, L

6 (d ,.)

Quality of lime:

7In firing mode

8po the specific surface

9Number of lime rolled

10 Amount of fuel entered after lime

11 Exposure duration of charge with knurled lime

12Number of free fuel in charge

13Cost of use of carbon fuel (kg)

14Leaveout

15 Vertical sintering speed

16Specific performance Agglomerate strength

17X (Cl. +5 mm)

18X (Cl. -0.5 mm)

mm mm

m Vxr

kg / t of charge (dry)

% of total consumption

% of total

%

% of sinter mm / min t / (h)

%%

table 3

T p b l and c a 6

Claims (1)

13-15 A method for producing a coarse-grained agglomeration charge, comprising mixing and pelletizing the metered materials by rolling lime on pelletized granules and parts of the fuel supplied to the mixture, characterized in that, in order to increase the efficiency of the agglomeration production, the mixture is pelletized to the granule size corresponding to d, _ke = 2, 4-4,2 mm and rolled on them gently sredneobozhzhennuyu or burnt lime with a specific surface of 350 m ^ ⁴ / kg in an amount of 8-16 kg / ton charge (dry), and the portion of fuel injected in the pelletized charge After about 0.1 hours at least after rolling and lime is mixed with the charge in a mixing drum.