RU2496895C1 - Method of waelz process of zinc cakes - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method of Waelz process of zinc cakes involves mixing and pelletisation of zinc cakes together with solid carbon-containing material and Waelz process of pelletised material. With that, to the mixing stage there supplied is mixture of calcium- and magnesium-containing materials at content of magnesium oxide in mixture of 20-50% and ratio in the charge (CaO+MgO)/SiO₂=2÷4. Pelletisation of the mixture is performed together with solid carbon-containing material with fineness of less than 2 mm. Waelz process of pelletised material is performed with addition of carbon-containing material with fineness of more than 2 mm at the temperature of 1100°C. As carbon-containing material, wastes of coal and oil-processing industries are used.

EFFECT: increasing furnace capacity and reducing carbon-containing material consumption.

2 cl, 1 dwg, 5 tbl, 5 ex

Description

The invention relates to non-ferrous metallurgy and can be used in the processing of zinc cakes by Weltzing.

Closest to the technical nature of the proposed method is a method of Waelz zinc cakes, including rolling zinc cakes before drying with carbon-containing material together with coke breeze, and Waelz rolling material (SU 876761, C22B 19/38, publ. 30.10.1981).

The disadvantages of the calcareous method are the high fuel consumption (more than 400 kg / t cake), low productivity Waelz kiln (0.63 t / m ³ · day).

The technical result of the invention is to reduce the consumption of coke breeze, increasing the productivity of the furnace. This goal is achieved by the fact that in the known method of Waelz zinc cakes, including mixing, rolling together with solid carbon-containing material (coke breeze) at the mixing stage, a mixture of calcium and magnesium-containing materials is supplied with a content of magnesium oxide in the mixture of 20-50%, the ratio in the mixture (CaO + MgO) / SiO ₂ = 2 ÷ 4. Coating the mixture together with solid carbon-containing material with a particle size of less than 2 mm and welting with the addition of carbon-containing material with a particle size of + 2 mm at a temperature of 1100 ° C

In addition, waste from the coal and oil refining industries is used as a solid carbon-containing material.

Figure 1 shows the hardware diagram of the processing of zinc cakes. The scheme includes:

1 - filter press;

2, 3, 4, 5 - bins for zinc cake, a mixture of calcium and magnesium-containing materials, carbon-containing material with a particle size of less than 2 mm, recycled Waelzian dusts with a particle size of less than 1 mm;

6 - mixer granulator;

7 - Waelz kiln.

Zinc cake with a moisture content of less than 19% comes from the filter press 1 to hopper 2. Then zinc cake with a mixture of calcium and magnesium-containing materials (soda MgO 20-50%) from hopper 3, carbon-containing material (soda fractions less than 2 mm - 100%) from the hopper 4, the circulating dust of the Waelz kiln (particle size 100% less than 1 mm) from the hopper 5 is sent to the granulator-mixer. The mixed and granular material with a granule size of 2-5 mm is sent to the Waelz kiln for Waelz. Additionally, a solid carbon-containing material with a particle size of more than 2 mm can be fed into the furnace to adjust the Waelz process.

The supply of a mixture consisting of calcium and magnesium-containing components eliminates the formation of liquid phases in the furnace and the need to use expensive coke to absorb them, while the consumption of the carbon component of the charge is reduced by 30-40%, and it becomes possible to independently use the waste from the coal and oil refining industries.

When applying only one of the components, the above effect is not achieved:

A) since granules are readily destructible in the furnace, the yield of recycled material increases, followed by a decrease in the productivity of the Waelz kiln;

B) it is possible to obtain small granules (2-5 mm), which allow to increase the zinc stripping speed, reduce the Waelz temperature from 1250 ° C to 1100 ° C and, therefore, reduce the fuel component of the carbon-containing material.

The use of carbon-containing material with a particle size of less than 2 mm as an additive in granules increases the rate of reduction and subsequent distillation of zinc. In order to regulate the heat balance of the furnace, to exclude dust formation, solid carbon-containing material with a particle size of more than 2 mm is additionally fed into the furnace.

The lower grain size limit of solid carbon-containing material and granules (plus 2 mm) loaded into the Waelz kiln is calculated based on the physical properties of the material and the gas flow rate in the furnace.

Lowering the Waelz temperature during the processing of zinc cakes below 1100 ° C does not increase the positive effect.

The ratio (CaO + MgO) / SiO ₂ = 2 ÷ 4 in the granules allows to minimize the formation of liquid phases in the granules and increase the rate of sublimation of zinc. Reducing the ratio to less than 2 does not completely eliminate the melting. An increase in the additive of more than 4 reduces the hourly productivity of the Weltz-oxide furnace.

As a solid carbon-containing material that replaces coke, coal industry wastes can be used, for example, anthracite with a carbon content of less than 75%; refinery industry wastes - petroleum coke (carbon soda - less than 75%); secondary coke breeze obtained by magnetic separation of clinker from Weltz (carbon soda 55-60%).

Example 1

The effect of additives mixtures of calcium and magnesium materials

To zinc cake composition,%:

zinc - 20.2, lead - 1.9, iron - 25.3, silicon oxide - 7.1 added calcium-containing material - limestone (soda. CaO-56%) and magnesium-containing material - waste from the production of magnesite (soda. MgO-70%). The content of magnesium oxide in the mixture was 35% in an amount providing a ratio of (CaO + MgO) / SiO ₂ equal to 1.0, 2.0, 3.0, 4.0, and 5.0; solid carbon-containing material (neftekoks) with a particle size of (-1) mm in an amount of 20% by weight of cake; circulating dust from Waelz zinc cakes (fraction - 1 mm). The mixture was poured on a granulator-mixer to obtain granules 3 mm in size.

Granules with the addition of 5% (by weight of cake) carbon-containing material with a grain size of 3 mm were loaded into a laboratory Waelz kiln and processed at a temperature of 1100 ° for 2 hours. The total consumption of carbon-containing material was 25% by weight of zinc cake.

For comparison, experiments were carried out on the prototype: without the addition of a mixture containing calcium and magnesium, but with the addition to the stage of mixing and rolling of carbon-containing material, not divided into fractions, plus and minus - 2 mm in the amount of 25% and 40% by weight of zinc cake, as well as circulating dust from Waelz zinc cakes.

Then the material was loaded into the furnace, where it was processed under the conditions similar to the proposed method. The results of the experiments are shown in table 1.

Table 1 The name of the method The addition of a mixture of calcium and magnesium-containing materials to the ratio (CaO + MgO) / SiO ₂ The productivity of the furnace, t / m ³ · day ¹ Clinker composition,% Material condition in the furnace zinc carbon Offered (25% carbon-containing material by weight of zinc cake) one 0.44 3,1 5,4 Partial melting 2 0.89 0.8 3.9 Loose 3 0.96 0.6 3,5 Loose four 0.96 0.4 3,1 Loose 5 0.92 1.3 2.9 Loose Known (25% carbon-containing material by weight of zinc cake) 0 0.21 5.2 6.7 Melts Known (40% carbon-containing material by weight of zinc cake) 0 0.63 1,2 10.0 Loose ¹ The furnace productivity is determined in tons of recycled zinc cake, referred to 1 m ³ of the furnace’s working volume per day.

As can be seen from table 1, when a mixture of calcium and magnesium-containing materials is added to zinc cake, the furnace productivity increases from 0.21 t / m ³ per day to 0.96 t / m ³ · day. The zinc content in the clinker is reduced to 0.4%, the material in the furnace does not melt, it becomes loose, it is welded. The decrease in the ratio (CaO + MgO) / SiO ₂ less than 2 leads to partial melting, lower productivity and increase the zinc content in the slag. An increase in the additive of more than 4 does not increase the positive effect, but due to the need for the consumption of carbon-containing material for heating calcium and magnesium-containing material, the zinc content in the clinker increases and productivity decreases.

When conducting an experiment on the prototype, a positive effect is not achieved with a carbon-containing material consumption of 25% by weight of zinc cake, the Waelz index is improved by increasing the amount of carbon-containing material to 40% by weight of zinc cake and replacing petroleum coke with metallurgical (more expensive) coke.

Example 2

Effect of magnesium oxide in a mixture of calcium and magnesium-containing materials

The experiments were carried out under conditions (see Example 1). The content of magnesium oxide in the mixture was,%: 10; twenty; thirty; fifty; 60.

table 2 The content of magnesium oxide in a mixture of calcium and magnesium-containing materials The productivity of the furnace, t / m ³ · day The amount of working material,% to the loading of granules 0 0.87 12 10 0.9 8 twenty 0.94 5 thirty 0.96 3 fifty 0.96 3 60 0.88 10

From the above data in table 2 shows that when using only calcium-containing material, the output of the circulating material increases from 3-5% to 12% due to the destruction of the granules in the furnace. This reduces performance. A similar phenomenon is observed when the content of magnesium oxide in the mixture exceeds 50%. The optimal range of magnesium oxide in a mixture of calcium and magnesium materials is 20-50%.

Example 3

The effect of the feed on the rolling of a solid carbon-containing material with a particle size of less than 2 mm

The experiments were carried out under conditions (see Example 1).

A carbon-containing material with a grain size of 0.5 mm; 1 mm; 2 mm; 3 mm; 4 mm.

Table 3 The name of the method The size of the carbon-containing material supplied for rolling, mm The productivity of the furnace, t / m ³ · day. The carbon content in clinker,% Proposed 0.5 0.98 3.3 one 0.97 3.3 2 0.96 3,5 Famous 3 0.82 12 four 0.75 fifteen

From the data shown in table 3, it is seen that an increase in the size of the carbon-containing material supplied for rolling reduces the productivity of the furnace from (0.96-0.98) t / m ³ · day to (0.75-0.82) t / m ³ · days due to a decrease in the rate of distillation of zinc. At the same time, the degree of carbon use in granules is reduced, and the carbon content in clinker increases to 12-15%.

Example 4

The effect on the Weltzentzie of the additive - carbon-containing material with a particle size of more than 2 mm

The experiments were carried out under conditions (see Example 1).

A solid carbon-containing material with a particle size of 2 mm, 3 mm, and 4 mm was additionally fed into the Waelz furnace.

Table 4 The name of the method The size of the carbon-containing material supplied to the furnace, mm Consumption of solid carbon-containing material (by weight of cake,%) The formation on the walls of the furnace flooring Proposed 2 mm 25 Not formed Famous 3 mm 40 A thickness of 100 mm is formed 4 mm 40 A thickness of 170 mm is formed

From the data shown in table 4, it can be seen that an increase in the size of the solid carbon-containing material supplied to the welting from 2 mm to 3-4 mm reduces the degree of absorption of the liquid phases by the specified material and, in this case, build-up occurs in the furnace.

To absorb liquid phases, it is necessary to increase the consumption of solid carbon-containing material from 25% to 40% by weight of cake.

Example 5 Effect of Weltz temperature.

The experiments were carried out under conditions (see Example 1). The Waelz process was conducted at temperatures of 1000 ° C; 1100 ° C; 1200 ° C.

Table 5 The name of the method Waelz process temperature, ° C The consumption of solid reducing agent, to the weight of cake,% Productivity Waelz kiln, t / m ³ · day Proposed 1000 25 0.9 1100 25 0.96 Famous 1200 40 0.86

An increase in the Waelz temperature increases the fuel component of the carbon-containing material, increasing its consumption from 25% to 40% by weight of the cake. In this case, there is a decrease in furnace productivity from 0.96 to 0.86 t / m ³ · day.

Lowering the Waelz temperature without reducing the consumption of solid containing material reduces the productivity of the furnace from 0.96 to 0.9 t / m ³ · day.

Thus, the experiments showed that in the proposed method, the addition of calcium and magnesium-containing material to zinc cake should provide the ratio (CaO + Mgo) / SiO ₂ = 2 ÷ 4.

When the content of magnesium oxide in the mixture is 20-50%, a carbon-containing material with a particle size of less than 2 mm should be fed to the pelletizing step, and carbon-containing material with a particle size of more than 2 mm should be used as an additive to the obtained granules during Wielding. The process of welting rolled material is carried out at a temperature of 1100 ° C. The use of the proposed method compared to the known method of Waelz zinc cakes allows you to:

- increase the productivity of the furnace from 0.63 to 0.96 t / m ³ · day;

- reduce the consumption of carbon-containing material from 400 to 250 kg / t cake;

- use waste from coal and oil refining industries as carbon-containing material.

Claims (2)

1. A method of rolling zinc cakes, including mixing, rolling zinc cakes together with solid carbon-containing material and rolling of rounded material, characterized in that a mixture of calcium and magnesium-containing materials is supplied to the mixing stage with a content of magnesium oxide in the mixture of 20-50% and a ratio of the mixture (CaO + MgO) / SiO ₂ = 2 ÷ 4, the mixture is pelletized together with solid carbon-containing material with a particle size of less than 2 mm and the Weltz is rolled with an addition of carbon-containing material with a particle size of more than 2 mm at temperature 1100 ° C. 2. The method according to claim 1, characterized in that the waste material from the coal and oil refining industries is used as the carbon-containing material.