CN107779534B - Process for treating zinc-containing and iron dust and mud in iron and steel plant by shaft furnace method - Google Patents

Abstract

The invention relates to a shaft furnace method for processing zinc and iron dust sludge in iron and steel plants, and belongs to the field of iron and steel metallurgy. It is characterized in that all the dust sludge in the sintering, blast furnace, converter, electric furnace and steel rolling processes of the iron and steel plant is processed by briquetting, and directly used as the raw material of the shaft furnace to smelt molten iron without sintering. This process integrates the respective advantages of rotary hearth furnace, oxycup shaft furnace and DK small blast furnace. The improvement of oxycup shaft furnace process makes up for the shortcomings of oxycup shaft furnace, reduces smelting cost, reduces environmental pollution and increases smelting efficiency. . This process can process all the dust sludge in the sintering, blast furnace, converter, electric furnace and steel rolling process of the iron and steel plant, and fully recover the iron, carbon, zinc and other valuable elements in the dust sludge, and the main products are molten iron, crude zinc and high calorific value gas.

Description

A shaft furnace method for processing zinc and iron dust sludge in iron and steel plants

technical field

The invention relates to a process for processing zinc and iron dust sludge in iron and steel plants, in particular to a shaft furnace method for processing zinc and iron dust sludge in iron and steel plants.

Background technique

The dust in iron and steel plants mainly comes from the dust removal process of sintering, pelletizing, blast furnace, converter and rolling, etc. Generally, the content of TFe is 30-70%, and it also contains a certain content of carbon and valuable elements. In traditional blast furnace-converter steel In the production process, the amount of dust generated is about 8-12% of the crude steel output, which is very large. Therefore, the recycling of steel plant dust has great economic and social benefits. Zinc, lead, alkali metals and other harmful elements contained in dust sludge limit its recycling and utilization. Disposing of dust sludge through landfill not only occupies valuable land resources, but also pollutes the environment and wastes mineral resources. In order to avoid secondary pollution caused by dust and sludge discharge and external sales, many iron and steel enterprises reluctantly carry out dust remixing and sintering or pelletizing process to achieve internal recycling, but this has resulted in the deterioration of raw material quality, and harmful elements such as alkali metals and zinc. Enrichment in the steel process and many other issues.

At present, the widely used dust and sludge treatment processes in the world include three processes: rotary hearth furnace, OxyCup and DK. These processes can handle dust and sludge to a certain extent, but there are also areas that need to be improved. Here is a comparison of the advantages and disadvantages of the three processes:

Table 1 Comparison of Rotary Hearth Furnace, OxyCup and DK Process

The main product of the rotary hearth furnace is metalized pellets, but the product has high sulfur content, low production efficiency, large investment and large floor space; the OxyCup process product is molten iron, which can treat a wide range of dust and sludge, but the equipment has a short operating cycle and maintenance work. Large quantity; DK process is simple to operate, and the application is relatively mature. The product is molten iron, but it needs to be sintered, which brings high pollution and high energy consumption. Due to the shortcomings of the above three processes.

SUMMARY OF THE INVENTION

The purpose of the invention is to solve the problem that the main product of the traditional rotary hearth furnace has high sulfur content, low production efficiency, large investment and large floor space; the OxyCup process product is molten iron, the equipment operation period is short and the maintenance workload is large; problems such as high pollution and high energy consumption. The shaft furnace method of the present invention is indirect reduction, and the product is molten iron.

A shaft furnace processing method for zinc and iron dust sludge in an iron and steel plant, which is characterized in that all dust sludge in the sintering, blast furnace, converter, electric furnace, and steel rolling processes of the iron and steel plant is processed by briquetting, and directly used as the raw material of the shaft furnace without sintering Smelting molten iron into the furnace, the specific process steps are as follows:

(1) Cloth: A bell-type cloth is used, and the composition of the charge is: dust sludge mass, coke, and flux, and the proportions are 76%, 23%, and 1% respectively. The top of the shaft furnace and the shaft of the shaft furnace are made of traditional bell-shaped cloth, and the opening of the furnace body is used as the outlet of the flue gas of the shaft furnace.

(2) Blast: The air volume entering the furnace is 1630m ³ /t, and the air temperature is about 1000-1200℃.

(3) Pulverized coal injection: the injection volume is 30kg/t.

(4) Smelting: The smelting time is 3-5h, and the smelting temperature is 1100-1250℃.

(5) Release from the furnace: molten iron and slag are obtained by smelting. After the slag and iron are separated, the molten iron can be used for converter steelmaking or production of cast iron. Non-burning bricks, slag cotton, etc.

(6) Exhaust: The dust-laden flue gas from the shaft furnace can be purified by the gas dust collector to obtain zinc-rich flue gas, which is used as the raw material for the zinc-making industry.

Further, the opening of the furnace body is used as the flue gas outlet of the shaft furnace, the ratio of the height of the furnace top to the height of the shaft furnace is 1; 3, the height-diameter ratio of the shaft furnace is 8:3, and the opening of the furnace body is used as the flue gas outlet of the shaft furnace. , The discharge port of the shaft furnace is located at 4/5-5/6 of the furnace body, and the blower port is located at 15cm-50cm at the upper end of the discharge port.

Further, the preparation of the dust sludge briquette is to mix the dust sludge with a certain amount of cement binder and pulverized coal, and after several times of machine mixing, briquetting is carried out, and the powder is pressed into a diameter by vibrating and punching by a brick press. About 70-110mm agglomerates, after 3 days of curing, the dust sludge cold consolidation agglomerates can be obtained.

Further, the fixed carbon content of the coke powder or coal powder should be greater than 85%, generally between 85% and 90%.

Further, the total iron content of the final briquette must be greater than 35%, generally between 35% and 40%.

The specific invention of the shaft furnace:

(1) Shaft furnace top and furnace body

The top of the shaft furnace adopts traditional bell cloth, and the opening of the furnace body is used as the flue gas outlet of the shaft furnace. Due to the high temperature environment in the top gas trap, all zinc and most of the alkali metals are discharged with the flue gas, and will be discharged in the subsequent The washing system is filtered and collected to form a zinc-rich mud cake; the cold briquette on the top of the furnace has a high sealing performance, so only a single-bell furnace top device is installed on the furnace top. Compared with the traditional blast furnace, the design of the furnace top is not complicated, and there is no strict sealing, and the collected flue gas can be treated to obtain zinc-rich dust sludge.

(2) Dust sludge briquetting workshop

Compared with the DK process, the production of dust cold-consolidated briquette instead of traditional sinter reduces energy consumption and reduces pollution. Table 2 shows the physical and chemical composition of different dusts of Baosteel. Although the chemical compositions of different dusts and sludges are different, the shaft furnaces can all be treated uniformly. Table 3 shows the main chemical components of the coke powder. The fixed carbon content of the coke powder (or coal powder) used should be greater than 85%, generally between 85% and 90%. Mix dust sludge, coal powder, cement and water in a certain proportion, wherein the proportions of dust sludge, coke powder (or coal powder), cement and water are respectively 70-80%, 10-12%, 7-9%, 7 -9%, briquetting after mixing to make dust sludge cold consolidation briquette. The total iron content of the final briquette must be greater than 35%, generally between 35%-40%, and the diameter of the briquette is 70-110mm.

Table 2 Chemical composition of different dusts, wt%

Table 3 Chemical composition of coke powder, wt%

The briquetting workshop is composed of raw material workshop, batching workshop, transportation system, dust storage bin, mixing tower, brick making system and maintenance workshop. The briquetting workshop mainly includes the following parts:

1) Raw material workshop (wet material storage, finished carbon brick storage and transportation)

2) Raw material batching and transportation system

3) Dry powder (dust dust) storage bin and pneumatic conveying system

4) Stirring tower and brick making system (receive the pre-determined material mixture and stir to produce a uniformly distributed mixture)

5) Powder transportation system (belt conveyor, underground corridor)

6) Carbon brick curing workshop (carbon bricks are cured for 3 days between curing and curing)

7) Finished carbon bricks, coke and additives transportation system (belt conveyor, large inclination belt conveyor, receiving pit, corridor and transfer station)

(3) Ingredients of raw materials into the furnace

Due to the low grade of iron entering the furnace and the large amount of slag, although the coke ratio of the shaft furnace is higher than that of the ordinary blast furnace, which is 400kg/tHM and reaches 600kg/tHM iron, because this process does not require sintering, the energy consumption of sintering can be saved by about 50kg /tHM. The dust sludge used in each process is 450,000 tons of dust sludge. Cement is used as a binder, and it is pressed into hexagonal prisms with a size of 50-110mm by a ball-pressing device, which can produce about 500,000 dust sludge agglomerates. ton, according to the alkalinity of dust sludge agglomerates, it is necessary to add a certain amount of silica as a flux into the furnace. The shaft furnace products are molten iron and slag. The composition of molten iron is similar to that of traditional blast furnace molten iron. It can be directly used in converter steelmaking production. The amount of molten slag is 448.05kg/tHM. Can be used for building materials or cement production. The shaft furnace material balance table is shown in Table 3.

Table 3 shaft furnace material balance table

(4) shaft furnace gas

Although the coke ratio is higher than that of ordinary blast furnaces, the calorific value of the gas is very high, the calorific value of the gas is about 7000kJ/m ³ , and the CO content of the gas reaches about 54%. Therefore, the shaft furnace can be used as a gas generator. The shaft furnace gas composition and calorific value are shown in Table 4 and Table 5.

Table 4 shaft furnace top gas composition

Table 5 Comparison of calorific value of various coal gas, kJ/m ³

(5) Cast iron form

The shaft furnace has a short smelting cycle, a high utilization factor, and a large amount of iron per unit time. Therefore, the shaft furnace adopts the conventional blast furnace tapping form, which is different from the siphon tapping of the OxyCup process.

(6) Wind temperature

The air temperature of the shaft furnace is relatively high, and the air temperature can reach about 1000 to 1200 °C, while the OxyCup shaft furnace process is only about 600 °C. High air temperature can firstly increase the output; secondly, as the air temperature increases, the heat brought into the hearth by the hot air increases, and at the same time, the burning coke reduces the amount of gas generated, so that the coke ratio can be reduced; finally, the heat carried by the gas decreases, making the furnace Cylinder temperature increases, shaft and top temperatures decrease.

Figure 1 shows the overall temperature distribution of the shaft furnace when the air volume is 1727.91m ³ /h simulated by Fluent. It can be seen from Figure 1 that the temperature distribution of the new melting furnace is reasonable, the size of the formed swirl zone is suitable, and the size of the dust and sludge agglomerates is reasonable. The softening temperature range is 1150-1300°C, which is very narrow and forms a thin layer of reflow zone. This will facilitate the rise of gas flow and the fall of charge, making the gas flow distribution more reasonable.

(7) Pulverized coal injection

Due to the high air temperature, pulverized coal can be injected. The expensive metallurgical coke is replaced by coal, which reduces the coke ratio and greatly reduces the cost of blast furnace ironmaking. At the same time, blast furnace coal injection can be used as a means to adjust the furnace conditions. Secondly, the blast furnace coal injection can improve the working state of the hearth and make the blast furnace run smoothly. Finally, conditions can be created for the blast furnace to increase air temperature and oxygen-enriched blast.

The invention designs a technical prototype of the shaft furnace method for efficient dust and sludge treatment, digests and absorbs the advantages of the rotary hearth furnace, OxyCup and DK processes, and makes up for the shortcomings of the three processes. The new melting furnace method has no need for sintering process, raw fuel Wide applicability and other advantages. The main products are molten iron, crude zinc and gas. The molten iron can be directly smelted into the converter, the crude zinc can be directly recovered, and the gas has a high calorific value and can be used as a good fuel.

Description of drawings

Figure 1 is the cloud diagram of the overall temperature field of the shaft furnace,

Fig. 2 is a shaft furnace process flow diagram,

Figure 3 is a schematic diagram of a shaft furnace body.

Detailed ways

The invention takes the dust and sludge of the iron and steel plant as the main raw material, adds a certain amount of pulverized coal, cement, flux and water, mixes evenly, and passes through a vibrating briquetting machine to make the dust and sludge cold-solidified agglomerates. After curing, it enters the shaft furnace, and finally obtains crude zinc, molten iron and gas with high calorific value. The specific implementation is as follows:

Embodiment 1:

(1) Collect blast furnace bag ash, converter mud, gas mud, rolling scrap and other wastes in a centralized manner.

(2) Mix the dust mud, coke powder (or coal powder), cement and water according to the proportions of 74%, 10%, 8% and 8% respectively, and briquette after several times of machine mixing, and vibrate through the brick press. Stamping makes the powder pressed into agglomerates with a diameter of about 70mm, and after 3 days of curing, the cold-consolidated agglomerates of dust and sludge can be obtained.

(3) The dust sludge agglomerates and a certain proportion of coke and flux are put into the shaft furnace for smelting, the smelting temperature is 1200 ℃, and the smelting cycle is 4 hours.

(4) The molten iron and slag are obtained by smelting. After the slag and iron are separated, the molten iron can be used for converter steelmaking or cast iron production. Bricks, slag cotton, etc.

(5) The dust-laden flue gas from the shaft furnace can be purified by the gas dust collector to obtain zinc-rich flue gas, which is used as the raw material for the zinc-making industry.

(6) The CO content in the gas can reach more than 50%, which belongs to the high calorific value gas and can be used for power generation or return to the hot blast stove process.

Embodiment 2:

Mix the dust mud with a certain amount of cement binder and pulverized coal. After several times of machine mixing, briquetting is carried out. The powder is pressed into clumps with a diameter of about 90mm by vibrating and punching by a brick press, and then 3 days of curing. The cold solidified mass of dust sludge can be obtained. Others are the same as the first embodiment.

Embodiment three:

The dust sludge agglomerates and a certain proportion of coke and flux are put into the shaft furnace for smelting, the smelting temperature is 1100℃, and the smelting cycle is 5h. Others are the same as the first embodiment.

Claims (3)

1. A process for treating zinc-containing and iron dust and mud in a steel plant by a shaft furnace is characterized in that all dust and mud in the working procedures of sintering, blast furnace, converter, electric furnace and steel rolling in the steel plant are briquetted and directly used as raw materials of the shaft furnace to smelt molten iron without sintering, and the process comprises the following specific process steps:

(1) material distribution: adopts bell-shaped burden distribution, and comprises the following components: the dust and mud block mass, the coke and the flux are respectively 76 percent, 23 percent and 1 percent, the furnace top of the shaft furnace and the furnace body of the shaft furnace adopt the traditional bell-type material distribution, and the hole of the furnace body is used as a smoke outlet of the shaft furnace;

(2) air blowing: the air volume in the furnace is as follows: 1630m³The air temperature is 1000-1200 ℃;

(3) coal powder injection: the blowing amount is 30 kg/t;

(4) smelting: the smelting time is 3-5h, and the smelting temperature is 1150-1250 ℃;

(5) discharging: smelting to obtain molten iron and molten slag, separating the slag from the iron, using the molten iron for converter steelmaking or cast iron production, and performing water quenching on the molten slag to obtain water slag which is used as a raw material for producing cement or directly used for producing baking-free bricks and slag wool;

(6) exhausting: the dust-containing flue gas from the shaft furnace is purified by a gas dust collector to obtain zinc-rich smoke dust which is used as a raw material in the zinc production industry;

the dust-mud agglomerate is prepared by mixing dust mud, coke powder or coal powder, cement and water according to a certain proportion, wherein the proportion ranges of the dust mud, the coke powder or coal powder, the cement and the water are respectively 70-80%, 10-12%, 8-10% and 8-10%; then, the mixture is pressed into blocks after being mixed for a plurality of times by a machine, the powder is pressed into blocks with the diameter of 70-110mm by a brick press through vibration and stamping, and the dust and mud blocks can be obtained after 3 days of maintenance;

the furnace body is provided with a hole as a smoke outlet of the shaft furnace, the ratio of the height of the furnace top to the height of the shaft furnace of the furnace body is 1: 3, the height-diameter ratio of the shaft furnace is 8: 3, the open hole of the furnace body is used as a smoke outlet of the shaft furnace, the discharge port of the shaft furnace is positioned between 4/5 and 5/6 of the furnace body, and the blast hole is positioned between 15cm and 50cm at the upper end of the discharge port.

2. The process for treating zinc-containing and iron dust and sludge in a steel plant by using the shaft furnace as claimed in claim 1, wherein the fixed carbon content of the coke powder or the pulverized coal is between 85 and 90 percent.

3. The process for treating zinc-and iron-containing dust and sludge in a steel and iron plant through a shaft furnace according to claim 1, wherein the total iron content of the finally obtained dust and sludge agglomerate is between 35 and 40 percent.

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