Blast furnace takes steel plate as shell, and the shell is lined with refractory bricks. Blast furnace body is divided into throat, shaft, waist, belly and hearth from top to bottom. With the advantages of good technical and economic indicators, simple process, large output, high labor production efficiency and low energy consumption, the iron produced by this method accounts for the vast majority of the world's total iron output.

In the process of blast furnace production, iron ore, coke and slag-making flux (limestone) are loaded from the top of the furnace, and preheated air is blown in along the furnace circumference from the tuyere located at the lower part of the furnace. Carbon in coke at high temperature (some blast furnaces also inject auxiliary fuels such as pulverized coal, heavy oil and natural gas). ) burns with oxygen blown into the air to generate carbon monoxide and hydrogen, and the oxygen in the iron ore is removed in the process of rising in the furnace, thus reducing to obtain iron. The molten iron is discharged from the taphole. Unreduced impurities in iron ore combine with fluxes such as limestone to form slag, which is discharged from the slag outlet. The generated gas is discharged from the top of the furnace and used as fuel for hot blast stoves, heating furnaces, coke ovens and boilers after dust removal. The main products of blast furnace smelting are pig iron, as well as by-products blast furnace slag and blast furnace gas.

2. What is the principle of blast furnace ironmaking production?

In the development of blast furnace ironmaking technology, it is concluded that the influence of smelting intensity on focal ratio will increase with the continuous improvement of smelting intensity, and the output will gradually decrease after a slight delay.

This law reflects the complex heat and mass transfer phenomenon between two gases and burden in blast furnace. Blast furnace ironworkers should master this law and use it to guide production, that is, according to specific production conditions, determine the smelting intensity value suitable for the lowest coke ratio, so as to make the blast furnace smooth, stable and high-yield.

However, the smelting conditions of blast furnace can be changed. With the progress of ironmaking technology, such as strengthening concentrate, adopting reasonable burden structure, adopting high-pressure operation and comprehensive blast technology, and reforming equipment, the operating conditions of blast furnace can be greatly improved. Under advanced operating conditions, the suitable smelting intensity can be further improved, while the minimum coke ratio is further reduced and the output is further improved.

This is the reason why countries all over the world have continuously improved smelting conditions for decades to improve smelting intensity, reduce coke ratio and increase output.

3. Complete understanding of blast furnace ironmaking knowledge

Ironmaking equipment is called blast furnace, also known as blast furnace. It is shaped like a tube. The method of ironmaking is to add ore, coke and limestone from the top of the furnace, and introduce pressurized air into the furnace from the bottom. When coke burns, ore, limestone and coke react together to form molten iron and slag.

There are several areas in the blast furnace. The bottom of the furnace is the place where molten iron is filled, which is called the hearth. The upper part of the furnace is called the belly, and the upper part of the belly is called the furnace body (sometimes subdivided). There is a charging device at the top of the furnace shaft, and the burden (i.e. ore, coke and limestone) enters the furnace from here. In the upper part of the furnace, dozens of blowpipes are arranged around the furnace, which are connected with the tuyere of the furnace, and preheated air and fuel (such as oil or natural gas) injected into the furnace are injected into the furnace through these pipes. At this time, the preheated air entering the furnace can reach a high temperature of 900 to 1250 degrees Celsius. After entering the furnace, this high-temperature gas will react violently with coke to generate coal gas (carbon monoxide), and at the same time, it will rise along the furnace, reaching 1650 degrees Celsius, so that the burden will become molten iron and slag. The belly is the hottest part of the blast furnace, because it is the place where air and coke react violently (that is, burn). In order to protect the furnace whose shell is steel plate from burning out, people build refractories in the furnace. A cold water circulation system and a water spraying device are also embedded in the furnace wall. The molten iron produced by ore is gathered in the furnace, and the furnace is provided with a tapping hole for tapping molten iron and a slag tapping hole for tapping slag. Because the slag is lighter than molten iron and floats on the molten iron, the slag outlet is above the taphole. The large blast furnace has several tapholes and slag outlets. Look at the schematic.

The production of blast furnace is continuous, and once it is ignited, it will continue to burn without special circumstances (usually, the time from blast furnace opening to shutdown can reach more than ten years). Coke, ore and limestone will be gradually installed in the furnace body. Coke is ignited at the bottom of the furnace, and then burned violently by hot air, so that the ore melts into molten iron, and the ash of coke forms slag with limestone and iron slag. The hot gas rises from the combustion zone, heats the burden newly added into the furnace, and then is led out from the gas pipeline at the top of the furnace. According to the size of blast furnace, tapping times and frequencies are different, generally 6~ 12 times/day and night. The large blast furnace has 2~5 tapholes, which tap iron in turn. Each tapping interval is 30~60 minutes. The released molten iron will flow into the ladle, and then it will be transported to the steelmaking plant for steelmaking, or cast pig iron nearby. When tapping, open the tap hole with an electric drill to make the molten iron flow into the ladle along the iron ditch. After the molten iron is discharged from the furnace, a machine called a clay gun is used to blow mud, and the mud blocking the taphole is blown into and out of the taphole to seal the outlet. After tapping, slag will be discharged after a while. Slag is packed in a special slag tank, and then transported away after loading. Because the blast furnace is in continuous operation, the furnace will still burn violently when slag is discharged below. When the slag is almost exhausted, the burden burning above the slag will also reach the slag outlet. At this time, the scene will be very spectacular-a flame will be ejected from the slag outlet. At this time, the slag outlet will be blocked. Usually, a blast furnace has two slag outlets. Some modern giant blast furnaces have reduced the amount of slag, so they no longer set a slag outlet, let the slag flow out of the taphole with the molten iron, and then clean the slag. The place where blast furnace tapping and slag scraping are also called blast furnace tapping yard, which is the busiest place of blast furnace. In fact, the scenes that we usually see on movies and TV are all taken in the blast furnace tapping yard. Most ladle and slag ladle are transported by train, so there are always trains and tracks next to the blast furnace.

/kloc-before the 0/8th century, people used coal or charcoal instead of coke to make iron. At that time, the blast furnace was also very small. By the beginning of the 20th century, large blast furnaces in America could only produce several hundred tons of iron every day. /kloc-in the middle of the 0/9th century, people invented the method of blowing hot air into the blast furnace instead of cold air. At the beginning of the 20th century, blast furnace blower was innovated and blast furnace ironmaking developed rapidly. Modern blast furnaces are mostly 20 to 30 meters in height and 6 to 14 meters in true diameter, and can produce pig iron 100 to 1000 tons every day.

In the past, there was no cooling equipment on the wall of small blast furnace, and the blast furnace was cooled with water in 65438+60' s. There are many cooling methods, and the cooling methods adopted are different due to the different temperatures in different areas of the blast furnace. Some places use water tanks, some places spray water, some places ventilate and so on. The water that takes away the heat of the blast furnace is cooled and then reused.

At this point, we have a general understanding of blast furnace and ironmaking. In fact, the blast furnace is only a device for smelting, and there are many auxiliary system facilities related to it. Let's learn about these devices.

4. What are the safety features of blast furnace ironmaking production?

The safety features of blast furnace ironmaking production are as follows: (1) The ironmaking process is a continuous high-temperature physical and chemical change process, and the whole process is accompanied by high temperature, dust and toxic gases; The process of slag tapping and tapping is closely related to high temperature melt and blast furnace gas.

(2) A lot of smoke, harmful gas and noise escape during the operation, which pollutes the environment and worsens the working conditions. (3) More electromechanical equipment, overweight transportation equipment and high-pressure systems such as high-pressure water, high-pressure oxygen and high-pressure air are needed in the operation process.

(4) There are many and complicated accessory equipment systems, and the coordination requirements between them are strict. (5) The labor intensity of the operators in front of the furnace is relatively high.

In short, ironmaking production is characterized by labor-intensive, labor-intensive, high temperature, noise and dust hazards, many gas areas, many inflammable and explosive places, vertical and horizontal roads and railways, three-dimensional cross operation, close coordination between upper and lower processes, and many and complicated equipment.

5. blast furnace ironmaking knowledge: what is the full wind blocking rate?

There are four main assessment indicators for tapping operations:

(1) punctuality attack rate. In order to maintain the stable and continuous production of blast furnace, it is necessary to tap iron at a specified time. The calculation formula is: on-time tapping rate = on-time tapping times/actual tapping times * 100%.

(2) The difference of tapping quantity or the uniformity of tapping. The difference between the actual iron output and the theoretical iron output is the iron output difference.

(3) High-pressure all-wind plugging rate. Blocking the taphole with high pressure and full air volume is not only beneficial to smooth running, but also beneficial to maintaining the formation of mud bags at the taphole. The calculation formula is (only the full wind plugging rate is calculated for atmospheric blast furnace): high-pressure full wind plugging rate = times of high-pressure full wind plugging taphole/actual tapping times * 100%.

(4) The qualified rate of taphole depth. In order to ensure the safety of taphole, each blast furnace has a range of taphole depth that must be maintained. Every time the taphole is opened, the measured depth meets the requirements. The calculation formula is: taphole depth qualified rate = depth qualified times/actual tapping times * 100%.

6. Who can talk about the blast furnace reaction of cast iron?

Main reactions: 2Fe2O3+3C= high temperature = 4Fe+3CO2↑ and CaCO3= high temperature = Cao+co2cao+SiO2 = casio3c+CO2 = 2co. The operating principle of blast furnace ironmaking is based on concentrate.

The influence rate of concentrate technology level on blast furnace ironmaking production is about 70%, the influence rate of equipment is about 10%, the influence rate of blast furnace operation technology is about 10%, the influence rate of comprehensive management level is about 5%, and the influence rate of external factors is about 5%. 1 the connotation of blast furnace concentrate technology includes: "high, cooked, clean, small, uniform, stable, less and good".

"High" means that the iron grade of the ore charged into the furnace is relatively high; The drum strength of sintering, pelletizing and coke should be high; Sinter has a high alkalinity (generally 1.8~2.0). High-grade ore is the core of concentrate technology.

With the increase of ore grade 1%, the blast furnace fuel ratio will decrease 1.5%, the blast furnace output will increase by 2.5%, and the amount of iron slag per ton will decrease by 30kg, allowing the blast furnace to inject more 15kg/t pulverized coal. "Cooked" means that the proportion of clinker in blast furnace raw materials is high.

Clinker refers to sinter and pellets. With the continuous progress of blast furnace ironmaking production technology, it is not emphasized that the clinker ratio is very high.

Some enterprises have put about 20% of high-grade natural lump ore into the furnace. "Net" means "small" in the raw fuel, and "small" means that the particle size of the charging raw materials should be smaller.

The practice of blast furnace ironmaking shows that the optimum strength particle size is: sinter 25~40㎜, coke 20~40㎜, hematite and limonite are easy to reduce 8~20㎜. For small and medium-sized blast furnaces, the particle size of raw fuel is allowed to be smaller.

"Uniform" means that the particle size of blast furnace burden should be uniform. Putting the burden with different particle sizes into the furnace in stages can reduce the filling property of the burden, improve the permeability of the burden, and save coke and increase production.

"Stable" means that the chemical composition and physical properties of the raw fuel to be fed into the furnace should be stable and the fluctuation range should be small. At present, the unstable performance of raw materials for blast furnace ironmaking in China is the main factor affecting the normal production of blast furnace.

Ensuring the reasonable storage capacity of the raw material yard (ensuring that the proportion of ore blending changes little) and establishing a neutralization mixing yard are effective means to improve the structural stability of the burden. "Less" means less harmful impurities in iron ore and coke.

In particular, the contents of S and P should be strictly controlled, and the contents of elements such As En, Pb, Cu, As, K, Na, F and Ti(TiO2) should be well controlled. "Good" means that the metallurgical properties of iron ore are better.

Metallurgical performance means that the reduction degree of iron ore should be greater than 60%; The reduction pulverization rate of iron ore should be low; The softening point of ore under load should be high and the softening temperature range should be narrow; The droplet characteristics of ore need high temperature and narrow range. The influence of coke quality on blast furnace ironmaking should be highly valued. The influence rate of coke quality change on blast furnace ironmaking production index is 35%, which accounts for half of the influence rate of concentrate technology level.

Coke plays the role of burden skeleton in blast furnace, and it is also a reducing agent in smelting process. It is the main source of heat income from blast furnace ironmaking (about 60%~80%) and the supplier of carbon in pig iron. Especially under the condition of high coal injection ratio, the coke ratio is significantly reduced, which makes the skeleton effect of coke on the burden more obvious.

At this time, the good quality of coke plays a very key role in improving the permeability of charge and slag iron. Large blast furnace adopts the charging system of large ore batch, which makes the coke layer in the furnace thicker (up to 300~500㎜) and forms a good coke window, which plays a good role in the smooth production of blast furnace.

Due to the high blast furnace charge column and high charge compression rate, coke quality evaluation not only meets the requirements of M40, M 10, ash content, sulfur content and other indicators, but also increases the requirements of coke thermal reaction performance indicators, such as post-reaction strength (CSR), reactivity index (CRI) and other indicators. The quality of coke used in large blast furnaces in developed countries is generally better than that in China, which is one of the important reasons for the development of blast furnace indicators abroad.

The M40 of coke used in large blast furnaces abroad is generally more than 85%, and the M 10 is less than 6.5%. Using advanced technology, technology and equipment to achieve high efficiency of blast furnace means high utilization coefficient and low energy consumption. Improving the ore grade is an effective means to achieve high utilization rate.

Realizing reasonable burden structure can improve ore grade. At present, the proportion of pellets in the material structure of blast furnace smelting in China is low (the average of key iron and steel enterprises in China is 1 1%).

The iron grade of pellets can reach 60%~66%, while the sinter grade is above 58%. Therefore, China should strive to improve the production capacity of pellets and increase the proportion of pellets to more than 20%.

It is suggested that belt roaster and grate-kiln production equipment should be actively used to produce pellets. The quality of pellets produced by this equipment is better than that of shaft furnace.

Author: indu12007-12-109: 47 Reply to this statement-. Using bell-less top equipment can realize reasonable distribution, improve the utilization rate of CO2 in gas (CO2 content in gas can be increased by 0.5%, and fuel consumption can be reduced 10kg/t), thus reducing fuel consumption; But also can effectively control the development of the air flow edge, thereby prolonging the service life of the blast furnace. China has successfully developed various types of bell-less furnace top equipment, which is applied to large blast furnaces, and the cost is also lower than 50% of imported ones.

We should vigorously promote domestic equipment and support the development of China's manufacturing industry. Actively promoting the differential pressure power generation technology of blast furnace top gas (TRT) can recover 30% of blast furnace blower energy and reduce the energy consumption of ironmaking process1~18kgce/t.

A blast furnace with a top gas pressure greater than 120kpa should be equipped with TRT device, and its power generation varies with the top gas pressure. Generally, each ton of pig iron can generate 20 ~ 40kW. Dry dust removal can increase power generation by about 30%.

Due to the increase of gas temperature 10℃, the output of power generation turbine can be increased by 3%. Coal injection into blast furnace is the central link of structural adjustment of ironmaking system, and it is also the general trend of ironmaking technology development at home and abroad.

Injecting pulverized coal into blast furnace can not only save coke and alleviate the contradiction of insufficient total coke in China, but also reduce the environmental pollution caused by coke production process, and at the same time save energy (energy consumption in coking process is 144.4 kgce/t, and energy consumption in pulverized coal process is 20-35 kgce/t), and reduce the ironmaking cost (the price ratio of 1 ton pulverized coal is lower than 65438+ in 500 yuan).

7. Non-blast furnace ironmaking production process

There are three kinds of gas-based direct reduction equipment in operation at present.

The first type is shaft furnace, represented by MIDREX process. The shaft furnace process occupies most of the direct reduction production capacity.

The second is the reaction tank, and the only process using the reaction tank is the HYL method. The reactor adopts the backward intermittent production mode of fixed bed, so it is gradually being eliminated, but the sponge iron produced by HYL method still accounts for more than 7% of the total output until 1997.

The third type is fluidized bed, and the only representative one at present is FIOR method. The output share of 1997 is 1%. In coal-based direct reduction, only rotary kiln process has considerable production capacity.

The typical rotary kiln process is SL-RN method. Carbon-containing pellets are used in converter process, which is still in the development and research stage.

External heating reaction tank, also known as stuffy tank, is a technological process in which mineral powder and reducing agent are put into the reaction tank and reduced by external heating. Foreign countries generally use this process to produce iron powder for powder metallurgy, and the heating is carried out in tunnel kiln.

In recent years, many local and private enterprises in China have used this method for small-scale sponge iron production. Heating usually uses existing equipment and is not limited to tunnel kiln.

Electrothermal direct reduction consumes a lot of electricity and has been discontinued at present. There are still a few processes with small production capacity whose positions are not clear in this classification, such as KINGLOR-METOR method.

This method is heated by gas outside the shaft furnace and reduced by coal inside the shaft furnace, and the consumption of natural gas converted into heat is roughly equivalent to that of coal.