RU2507280C1 - Processing method of zinc-containing metallurgical waste - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: processing method of zinc-containing metallurgical waste involves mixing of waste with coke fines, pelletisation of charge and further performance of a Waelz process in a tube-type furnace. Besides, calcium hydroxide in the amount of 20-30% of silica content in the charge and coke fines with the size of less than 1 mm in the amount of 13-17% of the charge weight are added to the charge at mixing. Charge pelletisation is performed so that granules with the size of 2-4 mm and humidity of 10-12% are obtained. Waelz process treatment is performed at the temperature of 900-1000°C.

EFFECT: improving furnace capacity and reducing flow rate of coke fines of zinc-containing metallurgical waste, for example dusts of electric-arc furnaces.

2 cl, 1 dwg, 5 tbl, 5 ex

Description

The invention relates to ferrous metallurgy and can be used in the processing of zinc-containing wastes of ferrous metallurgy by Waelz.

Closest to the technical nature of the proposed method is a method of processing metallurgical waste, including mixing with a carbon reducing agent, pelletizing with bentonite and subsequent Waelz in a tube furnace. (“Steel”, No. 9, 2010, pp. 19-22).

The disadvantages of this method:

a) high consumption of carbonaceous reducing agent-400 kg / t of zinc-containing metallurgical waste, necessary:

- to maintain a high process temperature of 1150 ° C;

- for welts large granules more than 9 mm;

- for drying granules on the grate.

b) low productivity of the furnace (0.7 t / m ³ * day).

The purpose 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, the stage of mixing zinc-containing waste serves calcium hydroxide in an amount of 20 ÷ 30% of the silica content in the charge and coke breeze with a particle size of less than 1 mm in an amount of 13 ÷ 17% of the weight of the charge, pelletizing is carried out to obtain granules 2-4 mm in size and 10-12% humidity. The process is carried out at a temperature of 900-1000 ° C.

Figure 1 shows a hardware diagram of the processing of zinc-containing metallurgical waste. The scheme includes:

1 - tank for the preparation of pulp of calcium hydroxide;

2,3 - bins for zinc-containing metallurgical waste, solid carbon reducing agent with a particle size of less than 1 mm;

4 - reserve hopper, used to supply a corrective amount of solid carbon reducing agent with a particle size of 2 mm;

5 - mixer-pelletizer;

6 - Waelz kiln.

In a tank (1), calcium hydroxide pulp is prepared by stirring with water (Ca (OH) ₂ content is 180-220 g / dm ³ ).

Dusty zinc-containing metallurgical waste (fraction content - 1 mm-100%) is loaded into the hopper (2), and carbon-containing material (fraction content - 1 mm-100%) is loaded into the hopper (3). Then, from the bins (2,3), from the tank (1), the components are loaded into the mixer-pelletizer. The pelletizing process is carried out to obtain granules with a size of 2-4 mm and having a moisture content of 10-12%. The obtained granules are loaded into the oven. In addition, a solid carbonaceous reducing agent with a particle size of more than 2 mm can be fed into the furnace to adjust the Waelz process from the hopper (4).

The supply of calcium hydroxide pulp in an amount of 20-30% of the silica content in the mixture and coke breeze with a grain size of less than 1% in an amount of 13-17% allows to obtain durable granules 24 mm in size and having a moisture content of 10-12% without drying.

The use of the claimed amount of calcium hydroxide in combination with the claimed size of the mixture and its moisture content allows:

- reduce the temperature of Waelz from 1150-1250 ° C to 900-1000 ° C,

- to provide the necessary distillation and extraction of zinc and lead from pulverized waste (dust from an electric arc furnace).

Lowering the process temperature reduces the consumption of carbon-containing material without loss of zinc and lead with clinker.

The use of calcium hydroxide makes it possible to obtain granules that are durable and non-melting in the indicated temperature range. The formation of accretions, bedding of material in the furnace is excluded. At the same time, the productivity of the furnace increases from 0.65 t / m ³ * day. up to 1.1 t / m ³ * day.

The interval of the addition of calcium hydroxide 20-30% by weight of silica is determined by the need to bind the active component of silica to refractory calcium silicates and the need to obtain strong granules.

With a decrease of less than 20%, pellets melt with a partial loss of strength. With an increase of more than 30%, the strength of the granules decreases. The moisture interval of the granules is determined by the following factors:

- at a moisture content of less than 10%, granules with a strength of less than 2 kg / granule are obtained;

- at a moisture content of more than 12%, the granules are destroyed in the preparatory zone of the furnace. The iron content in Waelz oxide is increasing.

The consumption of coke breeze with a particle size of 1 mm in an amount of 13-17% is due to the requirements for the strength of the granules with the necessary zinc extraction.

An increase in the content of coke breeze reduces the strength of the granules, a decrease in the content decreases the degree of distillation of zinc, and increases the iron content in Waelz oxide.

An increase in the granule size of more than 4 mm leads to a decrease in the strength of the granules and is less than 2 kg / granule. Reducing the size of the granules less than 2 mm increases the iron content in Waelz oxide. The process temperature range of 900-1000 ° C is due to the requirements for zinc extraction (at a temperature of less than 900 ° C the degree of zinc stripping is sharply reduced) and the consumption of a carbon-containing reducing agent (at a temperature of more than 1000 ° C, the consumption of a carbon-containing reducing agent increases).

Example 1. The effect of calcium hydroxide additives.

To zinc-containing metallurgical waste (dust of an electric arc furnace, then EAF dust) composition,%:

Zinc - 19.3; lead - 1.9; silica oxide-6.8; add calcium hydroxide (Ca (OH) ₂ - 100%) in the form of pulp in the amount of 17; twenty; 23; 27; 30 and 33% by weight of silica. The content of calcium hydroxide in the pulp 200 g / DM ³ . In addition, we add solid carbon-containing material (coke) with a particle size of less than 1 mm (100%) in an amount of 15% by weight of the charge.

The resulting mixture was pelletized in a mixer-granulator to obtain granules of 2 ÷ 4 mm and a moisture content of 11.2%.

Granules with the addition of carbon-containing material with a particle size of 3 mm were loaded into a laboratory Waelz kiln and processed at a temperature of 950 ° C for 3 hours. The total coke consumption was 21% of the weight of the EAF dust, taking into account the corrective additive of coke breeze introduced into the furnace separately from the granules. The size of the specified coke breeze is 2 mm.

For comparison, an experiment was carried out on the prototype: without the addition of calcium hydroxide, with the addition of bentonite (5%) to the mixing stage, coke powder with a grain size of 3 mm in an amount of 15%. The resulting mixture was pelletized with water to a moisture content of 9%. Upon receipt of granules with a size of 10-20 mm, the granules were dried at T = 350 ° C. After drying, often cracked granules (mainly granules larger than 12 mm) were sieved. Hardened pellets were loaded into a laboratory Waelz kiln. The process was conducted in similar conditions to the proposed method.

The results of the experiments are given in table 1.

Table 1. The results of the experiments. The name of the method The consumption of Ca (OH) ₂ to the weight of silica,% The productivity of the furnace, t / m ³ * day. ^one The zinc content in clinker,% Material condition in the furnace Offered (21% carbon-containing material by weight of zinc-containing metallurgical waste) 17 0.9 1.3 Partial reflow twenty 1,0 0.5 Loose 23 1.05 0.1 Loose 27 1,2 0.1 Loose thirty 1,1 0.1 Loose 33 0.9 1.3 Partial fusion of disintegrating granules Known (21% carbon-containing material by weight of zinc-containing metallurgical waste) 0 0.45 5,4 Furnace Melt ¹ The furnace productivity is determined in tons of EAF dust attributed to 1 m ³ of the furnace’s working volume.

As can be seen from table 1., with a decrease in the consumption of calcium hydroxide to the silica content in the EAF dust to 17%, the material is partially melted in the furnace and the productivity decreases from 1.0 to 0.9 t / m ³ * day. The zinc content in clinker increases from 0.5 to 1.3%.

With an increase in the consumption of calcium hydroxide to the silica content in the EAF dust from 30 to 33%, a partial melting of the material occurs due to the partial destruction of the granules. The productivity of the furnace is reduced from 1.0 to 0.9 g / m ³ * day. The zinc content in clinker increases from 0.1 to 1.3%.

When conducting experiments on the prototype with the consumption of coke to the weight of zinc-containing waste (EAF dust) 21%, a positive effect is not achieved.

The material melts in the furnace. The productivity of the furnace decreases from 1.1 to 0.45 t / m ³ * days., And the zinc content in the clinker increases from 0.1 to 5.4%. Weltzing indices improve with increasing amount of carbon-containing material up to 40% by weight of EAF dust.

Example 2

The effect of moisture in the granules.

The experiments were carried out with the dust of the EAF (see example 1) with the addition of calcium hydroxide to the weight of silica 27%.

The moisture content of the mixture,% 9; 10; 11; 12; 13.

According to the prototype, the initial humidity was 9%, and after drying - 0%. The results of the experiments are given in table.2.

With a decrease in the moisture content of the granules less than 10%, their partial destruction and subsequent melting of the material occurs. At the same time, the iron content in Waelz oxide increases from 0.8 to 1.4%; and the zinc content in clinker increases from 0.1 to 1.3%. With an increase in humidity of more than 12%, partial melting of the material takes place, caused by the loss of strength of the granules. At the same time, the iron content in Waelz oxide increases from 0.8 to 1.6%, and the zinc content in clinker - from 0.1 to 5.4%.

When conducting experiments on the prototype, the strength of the granules is high, the iron content is within the normal range of 0.8%. However, due to the low degree of distillation of zinc and molten material in the furnace, losses of zinc with clinker increase from 0.1 to 5.3%.

Example 3

The effect of coarseness of coke breeze.

Pelletizing was carried out with EAF dusts (see examples 1,2) and coke breeze fineness less than 1 mm in quantity,%:

12; 13; fifteen; 17; 18 by weight of the charge.

According to the prototype, the size of coke breeze was 3 mm and consumption 15%. The results of the experiments are given in table.3.

Table 3. The results of the experiments. The name of the method Amount of coke breeze Pellet strength Iron content in Waelz oxide Zinc content in clinker Size of rolled up coke breeze, mm Material condition in the furnace Offered (21% carbon-containing material by weight of zinc-containing metallurgical waste) 12 2.6 0.7 1.3 <1 Partial reflow 13 2,4 0.8 0.1 <1 Loose fifteen 2,4 0.8 0.1 <1 Loose 17 2,3 0.8 0.1 <1 Loose eighteen 1.8 1,5 1.4 <1 Partial reflow Known (21% carbon-containing material by weight of zinc-containing metallurgical waste) fifteen 2.1 0.9 3,1 2 Reflow

With a decrease in the amount of coke breeze introduced into the granules, the strength of the granules does not decrease, however, there is a partial melting of the material and an increase in the zinc content in clinker from 0.1 to 1.3%. With an increase in the amount of coke breeze introduced into the granules, the strength of the granules decreases, melting occurs and the zinc content in the clinker increases from 0.1 to 1.4%.

When conducting experiments on the prototype, the granule size of more than 9 mm allows you to roll up coke breeze without a significant loss of strength. However, the zinc stripping rate decreases and the zinc content in the clinker rises from 0.1 to 3.1%.

Example 4

The effect of granule size.

Pelletizing was carried out with EAF dusts (see examples 1,2,3) to obtain granules of size, mm: 1, 2, 3, 4, 5. According to the prototype, the granule size was 9-10 mm.

The results of the experiments are given in table.4.

Table 4. The results of the experiments. The name of the method Granule size mm The iron content in Waelz oxide,% The zinc content in clinker,% The productivity of the furnace, t / m ³ * day. Material condition in the furnace Offered (21% carbon-containing material by weight of zinc-containing metallurgical waste) one 1.9 1,5 0.9 reflow 2 0.8 0.1 1,1 loose 3 0.8 od 1,1 loose four 0.8 0.3 1,0 loose 5 0.7 1.21 0.9 loose Known (21% carbon-containing material by weight of zinc-containing metallurgical waste) 10 0.7 4.4 0.4 loose

With a decrease in granule size of less than 1 mm, a partial melting of the material takes place, dust removal increases, which reduces the performance of the process:

- the productivity of the furnace decreases from 1.1 to 0.9 t / m ³ * day .;

- the iron content in Waelz oxide increases from 0.8 to 1.9%;

- the zinc content in the clinker increases from 0.1 to 1.5%.

With an increase in granule size of more than 4 mm, process indicators are reduced due to a decrease in the rate of zinc stripping:

- the zinc content in clinker increases from 0.3 to 1.4%;

- the productivity of the furnace drops from 1.1 to 0.9 t / m ³ * day.

When conducting experiments on the prototype with a grain size of 10 mm compared with the claimed method, the productivity of the furnace decreases from 1.1 to 0.4 t / m ³ * day., And the zinc content in the clinker increases from 0.1 to 0.4%.

Example 5

The effect of process temperature.

The EAF dusts of the composition (see Example 1) were poured into granules with a size of 3 mm, with a calcium hydroxide content of 25% by weight of silica in the mixture, and with the addition of coke fines to granules with a grain size of less than 1 mm in an amount of 15% of the weight of the mixture. The granules had a moisture content of 11%. To the obtained granules were added carbon-containing material in an amount providing a total coke content of 21% by weight of EAF dust. The mixture was processed in a laboratory Waelz furnace at a temperature of, ° C: 890; 900; 950; 1000; 1010 for 3 hours.

For comparison, an experiment was performed on the prototype (see example 1). The results of the experiments are given in table.5.

Table 5. The results of the experiments. The name of the method Temperature in the furnace, ^° С The productivity of the furnace, t / m ³ * day. Zinc content in clinker Coke breeze consumption, kg / t EAF dust Material condition in the furnace Offered (21% carbon-containing material by weight of zinc-containing metallurgical waste) 890 0.9 1.4 210 Loose 900 1,0 0.7 210 Loose 950 1,1 0.1 210 Loose 1000 1,1 0.1 210 loose 1010 0.9 1,0 210 Partial reflow Known (21% carbon-containing material by weight of zinc-containing metallurgical waste) 1150 0.7 1,1 400 loose 950 0.3 6.1 400 loose

Lowering the temperature of the process from 900 to 890 ° C reduces the productivity of the furnace from (1.1 ÷ 4.0) to 0.9 t / m ³ * day. and increases the carbon content in the clinker from (0.1 ÷ 0.7) to 1.4%.

An increase in the process temperature does not increase the positive effect (at a consumption of coke breeze of 210 kg / ton of EAF dust), at the same time it leads to partial reflow of the material, and also reduces the productivity of the furnace from 1.1 to 0.9 and increases the zinc content in clinker from 0 , 1 to 1.0%.

When conducting experiments on the prototype, the consumption of coke breeze increases from 210 to 400 kg / t of EAF dust, while the process indicators are lower than in the claimed method, namely, the productivity of the furnace decreases from 1.1 to 0.7 t / m ³ * day. , the zinc content in clinker increases from 0.1 to 1.1%. In this case, it is necessary to increase the process temperature from 900-1000 ° C to 1150 ° C. By lowering the process temperature to the claimed productivity of the furnace decreases to 0.3 t / m ³ * day., And the zinc content in the clinker increases to 6.1%.

Thus, the experiments showed that in the proposed method at the stage of mixing with zinc-containing metallurgical waste, for example, dust of electric arc furnaces (EAF), the addition of calcium hydroxide should be 20-30% of the silica content in the charge, coke breeze introduced into the granules should be smaller than 1 mm, and its amount should be 13-17%, while the granules should have a size of 2-4 mm and a moisture content of 10 ÷ 12%.

Under these conditions, the Waelz process can be carried out at a temperature of 900-1000 ° C.

Using the proposed method in comparison with the known method of processing zinc-containing metallurgical waste will allow:

- increase the productivity of the furnace from 0.7 to 1.1 t / m ³ * day .;

- reduce the consumption of carbonaceous reducing agent from 400 kg / t of zinc-containing metallurgical waste to 210 kg / t of these wastes;

- eliminate the expensive process of drying granules;

- simplify the flow chart.

Claims (2)

1. A method of processing zinc-containing metallurgical waste, including mixing with coke breeze, pelletizing the mixture and subsequent Waelz in a tube furnace, characterized in that when mixed, calcium hydroxide in the amount of 20-30% of the silica content in the charge and coke breeze with a particle size less than 1 mm in the amount of 13-17% of the weight of the mixture, and pelletizing the mixture is carried out to obtain granules with a size of 2-4 mm and a moisture content of 10-12%. 2. The method according to claim 1, characterized in that the Waelz lead at a temperature of 900-1000 ° C.