Blast furnace coal injection process flow

The blast furnace coal injection process is a method used in iron and steelmaking to replace a portion of the coke traditionally used in the blast furnace with coal. This process offers benefits such as increased productivity, reduced coke consumption, and improved environmental conditions by reducing emissions. Here is a simplified flow of the blast furnace coal injection process:

1. Coal Preparation:

- The coal used for injection is typically a low-ash, low-sulfur bituminous coal. It needs to be prepared to the correct size, usually between 30 to 70 mesh (0.074 to 0.200 mm).

- The coal is cleaned to remove impurities, such as ash and sulfur, which could be detrimental to the iron and steel production process.

2. Coal Injection:

- The prepared coal is then dried and ground to a fine powder. The powder is injected into the blast furnace through nozzles located in the tuyeres, which are the openings at the bottom of the furnace through which the hot blast air is blown.

- The coal powder is injected at a rate that ensures complete combustion and efficient replacement of coke. The injection rate and pressure are carefully controlled to optimize the process.

3. Combustion and Reduction:

- As the coal powder mixes with the hot blast air, it combusts to produce carbon monoxide (CO) and carbon dioxide (CO2), which are essential for the reduction of iron ore to iron.

- The injected coal acts as a reducing agent, reacting with the oxygen in the blast air to form CO, which then reacts with the iron ore to extract the iron metal.

4. Melting and Slag Formation:

- The reduction reactions in the blast furnace generate heat, which melts the iron ore and any additional iron-bearing materials, such as scrap.

- The melted iron, known as molten iron or iron bath, collects in the hearth at the bottom of the furnace.

- Simultaneously, a slag, composed of non-ferrous impurities, forms and floats on top of the molten iron. The slag is periodically removed from the furnace through a slag tap.

5. Iron and Steel Production:

- The molten iron is periodically drawn off from the bottom of the furnace through a tap hole and is further processed to produce steel.

- The steel can be cast into ingots, billets, or continuous casting strands, depending on the desired end product.

6. By-Products Recovery:

- The gases produced during the coal injection process, which include CO and CO2, as well as other pollutants, are captured and treated to minimize environmental impact.

- The off-gas from the blast furnace can be used to generate electricity or heat, or it can be processed to remove pollutants before being released into the atmosphere.

7. Maintenance and Environmental Control:

- Regular maintenance of the coal injection system is necessary to ensure reliable operation and to prevent equipment failure.

- Environmental controls, such as dust suppression systems and gas treatment facilities, are in place to mitigate the impact of the process on the environment.

The coal injection process is a complex integration of mineral processing, combustion engineering, and blast furnace operations. It requires precise control and monitoring to ensure optimal performance and product quality.