direct reduction iron technology in the popular companies

The technology of direct reduction of iron in many popular companies are different. Iron ore mining and iron production are carried out in two general ways, although there are other methods, including smelting reduction processes.

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The two methods are blast furnaces and direct reduction. The main differences between the two methods are the raw materials used, the type of regenerator, and the product produced.

The blast furnace product is the product of various methods for the direct reduction of molten pig iron and sponge iron (DRI: Direct Reduced Iron). Sponge iron is the original solid particle that becomes a porous sponge-like structure after regeneration.

There are two types of direct iron recovery methods: gas-based and coal-based. The basis of gas-based direct regeneration methods is the use of natural gas as a regeneration agent.

In these processes, natural gas is converted into reducing gas in a gas-producing reactor and used in a reduction furnace. In direct coal-based regeneration, non-coking coal is also used as a regeneration agent. This coal is converted into regeneration gas in the process. The gas-based process is used to produce more than 90% of sponge iron in a direct regeneration method.

Among the various methods of direct reduction of iron, the Midrex method has the most industrial application, so more than 60% of mushroom iron production is by the direct reduction method.

In the Midrex process, a shaft furnace or furnace is used to continuously regenerate solid iron oxide. The charge, including pellets and iron oxide lumps, moves down from the top of the furnace and is regenerated by hot regeneration gas (a mixture of hydrogen and carbon monoxide) flowing from the bottom to the top. The reduction of iron oxide occurs in reaction with H2 and CO.

The reducing gas in a gas shift reactor or Midrex process reformer is the reaction of natural gas (mainly methane) with the reduction furnace off-gas (mainly carbon dioxide and water vapor) and in the presence of a nickel catalyst.

After the reduction of the iron oxide in contact with the reducing gas, the reduced material passes through the cooling zone of the reduction furnace and is cooled by the cooling gas.

Finally, the sponge iron is taken at a temperature lower than 100 degrees Celsius and metal quality of approx. 92% from the bottom of the oven.

The production of iron is done by separating it from minerals. For this purpose, there are many (more than 100) methods depending on the progress of science and technology, available energy sources, types of iron ore, consumable regenerates, output, existing facilities, equipment, and investments, etc.

at the research and industrial level. Of course, the purpose of all these methods is the same, which is to reduce iron ore to separate the oxygen mixed with the iron using a reducing agent and the iron from impurities using flux or flux.

blast furnace

In this method, a blast furnace (BF: Blast Furnace) is used to produce pig iron. The output of the blast furnace is molten pig iron.

Pig iron from blast furnaces is usually sent to a basic oxygen furnace (BOF) for steelmaking. This steel production method is called BF-BOF.

This process is considered to be the most important crude steel production method in the world and about 60% of the world’s crude steel is produced by this method. Steel production at the Isfahan Steel Factory is also carried out using this process.

In blast furnaces, granulated iron ore is used in the form of coarse and fine grains after being made into agglomerates (lumps) or pellets. Coke is also used as a primary source of heat and regeneration. Spent coke is made from coal.

direct resuscitation

In this method, direct reduction (DR: Direct Reduction) of iron ore is used in various ways in drum furnaces, blast furnaces, fluid bed reactors, rotary furnaces, and the like.

In contrast to blast furnaces, the products produced by the direct reduction method are not melted, but initially in the form of solid pellets with a porous and spongy structure, called sponge iron or Direct Reduced Iron (DRI: Direct Reduced Iron).

Sponge iron obtained from the direct reduction process is used in electric furnace steelmaking (EC: Electric Furnaces).

Recovery of iron ore for the production of sponge iron is usually done through two gas-based methods or using non-coking coal.

In gas-based direct regeneration, natural gas is converted into regeneration gas in a reformer. During this process, the raw materials are introduced from the top of the furnace, and the regeneration gas is introduced from the middle of the furnace.

The raw material is regenerated in the furnace and leaves the tail of the furnace after cooling. In direct coal-based regeneration, the coal used cannot be converted into high-quality blast furnace coke due to its physical and chemical properties.

The ability to use non-coking coal results in smaller operating volumes, lower fixed and investment costs, less environmental pollution, and the ability to produce pig iron in smaller units compared to traditional blast furnace methods of pig iron production. These types of coal are converted to regeneration gas in direct regeneration methods.

direct reduction iron in popular companies

Since the establishment of the MIDREX technology factory in Qatar in 1978 to produce reduced iron, they have cooperated with well-known companies such as Kobe Steel and MIDREX Technology and have implemented a number of technical improvements in the process.

The largest MIDREX module with an annual capacity of 1.8 million tons started production in 2007. The MIDREX module and its associated meter have now reached a capacity comparable to a blast furnace.

Ironmaking using the MIDREX direct regeneration method, which we will call the MIDREX process from now on, uses natural gas to regenerate iron ore. The original process was developed by Midland-Ross and later changed to MIDREX Technologies, a wholly owned subsidiary of Kobe Steel. The first pilot plant was built in Toledo, Ohio in 1967. In 1969, Portland, Oregon built its first commercial plant with a capacity of 150,000 tons per year.

When Kobe Steel began building a 400,000-ton-a-year factory in Qatar in 1978, the process had not yet blossomed. Kobe Steel has drastically changed the design by using the company’s technology that harnesses the power of the blast furnace to make the new process sustainable. On the other hand, MIDREX Technologies has made several improvements to its factories established in different countries. All these changes were integrated in the early 1980s, almost completing the process.

When KOBE Steel partnered with MIDREX Technologies in 1984, the maximum production capacity was 600,000 tons per year. Subsequent optimizations by Kobe Steel in collaboration with MIDREX Technologies have significantly increased production capacity. Production capacity in 2007 reached 1.8 million tons, equivalent to a small blast furnace.

The MIDREX process produces directly reduced iron, which we will call DRI from now on. The process regenerates iron ore using reformed gas produced from natural gas.

direct reduction iron in popular companies

DRI is mainly used as a feedstock for electric arc furnaces or electric arc furnaces and as a source of clean iron to replace scrap iron.

After the oxygen was removed, pores remained in the DRI. If these holes are filled with water, they can cause reoxidation of ambient oxygen, generating heat and sometimes a fire. This problem makes it difficult for products to be transported by sea or stored in the open for long periods.

To solve this problem, Kobe Steel invented a technology that compresses DRI into small iron ingots or briquettes at temperatures around 700 degrees Celsius.

DRI has a density of about 3.4 to 3.6 tons per ton. cubic meters, while briquettes have a density of 5 to 5.5 tons per cubic meter.

The above reoxidation problem limits the site selection of plants for direct reduced iron production near steel mills. Hot briquetting technology addresses this siting limitation, making it possible to build scaled-down iron production facilities in sources such as natural gas and iron ore. and cheaper energy is available.

This product called HBI (Hot Briquette Iron) (Hot Briquette Iron) can be exported by ship to steel mills and plate mills in other countries, in this way this technology increases the number of MIDREX’s possible mills around the world, they can be found in Made there, can the low more.

Iron ore piles or pellets produced by direct reduction are dumped as raw material from the top of the shaft furnace. Iron ore is reduced in the furnace (oxygen is taken from iron oxide) and the reduced iron is discharged from the bottom of the furnace.

The regeneration gas is blown out almost from the center of the shaft furnace, regenerates the raw material above the nozzle and is discharged from the furnace top.

direct reduction iron in popular companies

Cooling gas in the lower part of the oven cools the DRI. Both inlet and outlet are dynamically sealed with sealing gas, which can realize continuous supply of raw materials and continuous discharge of DRI.

The exhaust gas (Top Gas) discharged from the top of the furnace is cleaned and cooled by a wet scrubber and then returned for reuse. The upper gas containing CO2 and H2O is pressurized by a compressor, mixed with natural gas and sent to the reformer. The furnace is equipped with hundreds of reforming tubes filled with nickel catalysts.

The mixture of overhead gas and natural gas is changed through these lines to produce regeneration gas including carbon monoxide and hydrogen.

The steel industry accounts for around 21% of the industry’s total energy consumption. The two main methods of steelmaking, blast furnace and electric arc furnace, account for the majority of energy consumption.

Compared to electric arc furnaces, blast furnaces consume about four times the energy of arc furnaces, and most of this energy is used to produce raw materials and coke.

On the other hand, much more polluting gases such as CO, SO2, and NO2 enter the environment in blast furnace and converter processes than in arc furnaces; therefore, it is not surprising that steelmaking using the arc furnace method has grown significantly in recent years. years.

Until about 1970, arc furnaces used mainly cast iron and steel. Today, most arc furnaces are designed to produce high-quality steel with small amounts of harmful elements. The lack of quality has caused steel producers to look for suitable alternatives.

In recent years, in most countries where natural gas is relatively cheap, iron ore has been produced from gas, reduction, and sponge iron from partial oxidation of natural gas, and there are several methods of direct reduction.

A number of researchers have investigated the possibility of using sponge iron in electric furnaces for steel production, with reports of up to 100% successful use of these materials in electric arc furnaces.

Traditional steelmaking methods, including blast furnaces and converters, are suitable and economical for producing steel on a large scale.

direct reduction iron in popular companies

Since sponge iron is easy to use, especially in small smelting and casting workshops, which are very common in our country, and does not require a large investment like traditional steel production methods, it seems very reasonable and necessary to use direct recycling methods to prepare raw materials Raw.

The modern era of direct regeneration began with the development of HYL technology in Mexico in the 1950s, followed by the development of the Midrex process in the 1970s.

Today, there are thousands of direct recycling units worldwide, ranging from a small capacity (10,000 tons per year in India) to more than 2 million tons per year globally. Global production reaches more than 70 million tons per year.

There are many methods of direct recovery of iron ore in the world, the most important of which are the Midrex and HYL methods. Iran is one of the largest producers of sponge iron in the world using the Midrex method.

Midrex iron sponge is an active product with many problems with storage and export. The method of hot briquetting of sponge iron is one of the new technologies introduced to protect the sponge iron, which is convenient for storage and transportation.

According to reports, in 2012 Iran exported 31,000 tons of sponge iron to the rest of the world. There is a large amount of sponge iron in China, and by making briquettes, it will be possible to enter the domestic and world consumer market.

In this study, issues related to the melting and performance of this product in smelting furnaces will be examined and compared with the performance of sponge iron and hot briquettes to illustrate the status and value of this intermediate iron product.

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