Converter Refractory Hot Gunning Machine (Semi-Dry Gunning): A Key Equipment for Prolonging Converter Service Life
In the iron and steel smelting process, the converter— 作为 the core equipment for steelmaking—operates under harsh conditions of high temperature, severe erosion, and strong scouring for a long time, leading to extremely fast wear of the furnace lining refractories (referred to as "refractories" for short). Once local spalling or excessive erosion of refractories occurs, it not only shortens the converter's service life but also may cause major safety accidents such as molten steel leakage, directly affecting production continuity and economic benefits. Traditional converter cold repair or shutdown brick relaying methods have problems such as long maintenance cycles, high costs, and significant resource waste, making them difficult to meet the needs of modern iron and steel enterprises for "high efficiency, low consumption, and continuous production."
Against this background, the semi-dry gunning technology has become the mainstream solution for converter refractory maintenance due to its advantages of "rapid repair, hot-state operation, and high material utilization rate." The supporting converter refractory hot gunning machine (semi-dry type) has thus become the core equipment to implement this technology. This article comprehensively analyzes the semi-dry gunning type converter refractory hot gunning machine from aspects of working principle, core advantages, technical parameters, application scenarios, and maintenance key points.
I. Core Technology: Princip
le and Advantages of Semi-Dry Gunning
Different from wet (slurry-like) and dry (pure powder-like) gunning technologies, the core of semi-dry gunning lies in rapidly mixing refractory powder with a small amount of water (usually 8%-15% of the powder mass) in a dedicated mixing device to form "moist but non-agglomerated" semi-dry material pellets. These pellets are then injected at high speed to the damaged parts of the converter lining using compressed air. Upon contacting the high-temperature furnace lining surface, the pellets quickly dehydrate and sinter, forming a strong bonding layer with the original refractories, thereby achieving immediate repair of eroded or spalled areas.
Compared with traditional gunning technologies, semi-dry gunning has three core advantages:
High bonding strength and long-lasting repair effect: The semi-dry pellets have low water content, so there is no obvious "moisture evaporation gap" after being injected onto the high-temperature lining. The interface bonding strength with the base refractories after sintering can reach over 15MPa, significantly higher than that of wet gunning (usually 8-10MPa).
High material utilization rate and no secondary pollution: The semi-dry pellets have uniform particle size (usually 0.1-1mm) and strong directionality under the action of compressed air (pressure: 0.6-0.8MPa), with a rebound rate of only 5%-8% (wet gunning has a rebound rate of about 15%-20%). This not only reduces refractory consumption costs but also minimizes dust pollution under the furnace.
Hot-state operation without affecting production rhythm: The equipment can complete gunning within the "interval time" (usually 15-20 minutes) after the converter taps and before charging the next heat, without the need for shutdown and cooling. This avoids production interruptions caused by cold repairs, reducing the downtime of a single converter by more than 300 hours per year.
II. Structure and Working Process of Converter Refractory Hot Gunning Machine (Semi-Dry Type)
The semi-dry converter refractory hot gunning machine usually consists of five major components: the feeding system, mixing system, injection system, control system, and mobile device. These systems work in coordination to ensure efficient and stable gunning.
1. Core Structure Analysis
Feeding system: Includes a refractory powder silo, screw feeder, and compressed air storage tank.
Mixing system: Uses a twin-shaft agitator mixer.
Injection system: Composed of a gunning lance and flexible delivery pipe. The gunning lance can be operated by a robotic arm or manually to cover all areas of the converter lining (including the furnace mouth, furnace body, and furnace bottom).
Control system: Real-time displays parameters such as feed rate, water volume, air pressure, and gunning time. It also presets gunning process formulas for different parts (e.g., furnace mouth slag line, furnace body hot spots). Operators only need to select the corresponding mode to start the operation, lowering the operational threshold.
III. Equipment Selection and Technical Parameter Reference
Converters of different tonnages (e.g., 120t, 200t, 300t) have significantly different performance requirements for gunning machines. Enterprises should focus on three key indicators during selection: gunning capacity, operation efficiency, and adaptability. The following are reference parameters for typical specifications:
Note: During selection, additional consideration should be given to the converter mouth diameter (e.g., approximately 2.8m for 120t converters and 4.0m for 300t converters) to ensure the gunning lance can cover the entire lining area.
IV. Application Scenarios and Economic Benefits
The semi-dry converter refractory hot gunning machine is widely used in daily lining maintenance, especially in the following scenarios:
Slag line area repair: The slag line is severely eroded by molten slag and requires frequent maintenance.
Furnace mouth maintenance: The furnace mouth is long-term scoured by high-temperature flue gas and abraded by splashing molten steel, easily leading to "mouth expansion." Semi-dry gunning can quickly restore the furnace mouth shape, avoiding flue gas leakage and heat loss caused by an excessively large mouth.
Emergency repair of sudden damage: If local spalling occurs on the converter lining, the hot gunning machine can complete repairs within 1-2 operation intervals, preventing damage expansion and the risk of molten steel leakage.
V. Equipment Maintenance and Operational Key Points
To ensure the long-term stable operation of the semi-dry gunning machine, daily maintenance and standardized operation are essential:
1. Daily Maintenance Key Points
Daily inspection: Clean residual powder in the silo; check the wear of the screw feeder blades (replace if wear exceeds 3mm); check the water volume of the gunning lance water jacket (ensure inlet pressure ≥0.3MPa) to prevent overheating and deformation of the lance tip.
Weekly maintenance: Disassemble the mixer shafts, clean agglomerated material on the shafts; check the wear of the delivery pipe inner wall (replace if wall thickness <5mm) to avoid pellet blockage during delivery.
Monthly maintenance: Calibrate the water volume sensor and feed rate metering device to ensure parameter accuracy; replace the compressed air filter element to prevent impurities from entering the injection system and affecting air pressure stability.
In conclusion, as a "key guardian" for prolonging converter service life, the semi-dry converter refractory hot gunning machine not only significantly reduces enterprise production costs and improves production efficiency but also provides important support for the green and low-carbon development of the iron and steel industry. It is an indispensable core equipment in modern steelmaking workshops.
le and Advantages of Semi-Dry Gunning
