Design of Blast Furnace System
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. In a blast furnace, fuel and ore are continuously supplied at the top while hot blast of heated pre-heated air is blast into the furnace through the bottom. This hot air or blast acts as a carrier, which carries the gaseous and solid materials down the heat gradient and out through the tuyeres at the base of the furnace. As the materials move down the heat gradient, the raw materials react with each other and the hot air to form a mixture of molten iron, slag and other materials, which are discharged into the casting area.
The blast furnace is a large and complex system with a range of components designed to create an efficient flow of materials and heat. A successful design requires careful consideration of all elements, including the furnace vessel, tuyeres, charging equipment, fuel and air, refractories, and cooling systems. All of these components must be carefully balanced to ensure a safe and reliable operation.
Furnace Vessel
The blast furnace is a large steel structure, which typically consists of a vertical shaft, lined with refractory layers, containing the furnace volume and the tuyeres. A cylindrical wall extending from the top of the furnace down to the tuyeres separates the interior from the external environment. The inside of the furnace is lined with refractory layers to protect the furnace shell from heat and to protect the walls from abrasion. The furnace vessel is also equipped with probes and thermocouples for measuring its internal temperature, pressure and oxygen levels.
Tuyeres
Tuyeres are small, angled pipes located at the base of the blast furnace that are used to inject hot air, or blast, into the furnace. The injection of hot air is the primary source of combustion and the main source of heat in the furnace, driving chemical reactions and keeping the temperature of the interior at the optimal level. The number and size of the tuyeres are determined by the furnace shape, size, materials and profile and vary depending on the process.
Charging Equipment
The charging equipment of the blast furnace is used to feed the raw materials into the furnace chamber. The most common type of charging equipment is a mechanized bell system, which uses a bell-shaped hopper to transport ore and fuel into the furnace chamber. Generally, the bell hopper is made of steel or ceramic to protect the furnace wall from corrosion, and to allow for easy maintenance.
Fuel and Air
Fuel and air are essential for a blast furnace to function and both must be supplied in carefully regulated amounts to ensure a safe and productive operation. Fuel is typically supplied as pulverized coal and injected into the furnace through separate tuyeres, while air is drawn in through the side wall of the furnace. Both the fuel and the air must be regulated carefully to provide enough oxygen for the smelting process while avoiding instability and excessive heat, which can damage the refractories.
Refractories
Refractory materials protect the furnace walls and the interior of the blast furnace from heat, wear and corrosion. Blast furnaces require multiple layers of refractory material, as each layer must be replaced or replaced periodically. The shape and placement of the layers must be carefully designed to ensure an efficient flow of materials, heat and gases while providing maximum protection to the furnace walls.
Cooling Systems
All blast furnaces must be cooled after each cycle, and in some cases the non-metallic parts of the furnace must be cooled even during the operation. The cooling systems for a blast furnace generally consist of air-cooled coils, water-cooled pipes, or cooling mists. Air-cooled coils are used for large furnaces, while water-cooled pipes are used for smaller furnaces. Cooling misters are also often used to cool the interior and the tuyeres.
In conclusion, the design of a blast furnace system is a complex and highly technical task that requires detailed consideration of a number of components and their interactions. The parts of the system must be carefully selected and designed, and the entire system must be properly balanced to ensure a safe and productive operation.
