Reducing pollutant emissions is a significant challenge for all ironmaking plants. The key is to control the emissions from processes that generate large amounts of discharges.
From the initial design phase of a new project or the reconstruction of a blast furnace, it is crucial to carefully consider suitable solutions for high-emission processes.
The primary reason for poor environmental conditions in the blast furnace trough is insufficient dust removal capacity. Additionally, the sealing belt of the unloading car on the trough and the ventilation slot are often poorly maintained, leading to inadequate sealing. To meet ultra-low emission requirements, improve the filtering area of the dust collector and reduce the filtering air speed of existing bag filters.
The material screening equipment should be covered with an airtight cover, and the feeder, vibrating screen, weighing hopper, and dust removal pipe should be connected with soft joints. This ensures the entire screening operation is fully sealed. Alternatively, the loading inclined bridge should be fully enclosed, with no visible smoke or dust escaping from the dust-producing points of the blast furnace slots.
The exhaust gas from the equalized pressure discharge of the blast furnace roof tank should be recycled or purified to reduce dust emissions.
Blast furnace tapping dust, due to its characteristics and process operations, is a major focus and challenge for dust control in iron fields. The blast furnace tapping platform should be enclosed or semi-enclosed, with the iron and slag ditches covered. It is recommended to arrange the dust suction hood reasonably, optimize air volume distribution, and effectively seal dust-producing points. Using strong suction at the iron mouth and pre-furnace confinement can create a strong negative pressure field between the iron outlet and the dust suction hood, improving dust capture in the iron outlet area.
The design utilizes the wind outlet platform and columns should be set up on the tapping platform at the same time, enclosing all mud guns, iron opening machines, the front part of the main ditch, and the side near the blast furnace body.
The treatment of hot blast furnace flue gas is crucial for achieving ultra-low emissions, particularly controlling SO2 and NOx sources. Sulfur in the blast furnace gas mainly comes from coke, sinter ore, pellet ore, and blowing coal. It is recommended to strictly control the sulfur content rate of coke and blowing coal in the blast furnace. Dry quenching coke should be used and the sulfur content of the dry quenching coke should be less than 0.6%, blowing coal less than 0.4%, and the pellet is about 50% lower than the sulfur content in the sintered. Additionally, the blast furnace gas purification system should include a deacidification device, reducing H2S concentration after purification to less than 10 mg/m³. Suggested NOx control technologies include low-NOx combustion techniques such as graded combustion, flue gas recirculation, and flameless combustion.
When the hot stove vault temperature exceeds 1420°C, NOx generation increases rapidly. Enterprises, where individual hot stove flue gas NOx exceeds the standard, can consider adjusting the combustion mode. By controlling the temperature and air volume in the combustion zone, the oxygen concentration and temperature in the ignition zone can be reduced to halt NOx generation. Adopting the automatic burner control model of the hot blast stove allows temperature control of the vault based on program algorithms, accurately managing the air-fuel ratio and oxygen content in the flue gas, thereby facilitating low-NOx combustion.
During the water flushing granulation process, blast furnace slag produces a certain amount of slag cotton and steam flowing upward. Utilizing flue condensing steam, flue reheating technology, and flue dilution technology can reduce pollutant emissions during the slag flushing process.
Lumpy materials should be stored in closed silos or sheds, with dust reduction facilities such as spraying systems recommended in dry coal sheds. Dusting ash and other powdery materials should be conveyed in an airtight manner using pneumatic conveying equipment and tank trucks. Covering iron and torpedo tanks can reduce heat dissipation and effectively lower soot emissions.
