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 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.