The double-cone butt-welded structure is the mainstream design for pulverized coal filters in blast furnace coal injection systems at steel plants. Its design fully accommodates the requirements of pneumatic coal conveying: "low resistance, easy filtration, wear resistance, and easy maintenance." The core advantages can be summarized into four categories: optimized fluid dynamics, reliable structural strength, stable filtration efficiency, and convenient installation and maintenance, as detailed below:

 1. Excellent Fluid Dynamics Performance: Reduced Resistance and Minimized Coal Accumulation The structural form of the double-cone (typically composed of two inverted/upright cones butt-welded together) inherently optimizes the flow of air and pulverized coal, representing its most critical advantage. 

1. Smooth Airflow Transition, Reducing System Resistance ? Gradual Flow Channel Design: The filter inlet (typically connected to the main coal injection pipe) interfaces with the large-diameter end of the double-cone. As airflow enters the filter from the pipe, the flow channel cross-section first "gradually expands" (via the upper cone), then "gradually contracts" (via the lower cone) after passing through the filter element to the outlet pipe. This gradual flow channel avoids "local vortices" and "airflow impact" caused by abrupt structures like right angles or steps, significantly reducing system resistance (pressure loss is typically ≤5 kPa, much lower than the 10-15 kPa of flat or cylindrical filters). ? Adaptation to Pneumatic Conveying Conditions: Blast furnace coal injection systems require stable pulverized coal airflow (to avoid pressure fluctuations affecting coal injection rates). The smooth flow channel of the double-cone ensures uniform airflow velocity (inlet 20-25 m/s → filtration section 15-20 m/s → outlet 20-25 m/s) with no significant sudden changes, meeting the "low disturbance" requirement of dense-phase pneumatic conveying.

2. High Structural Strength and Wear Resistance: Suited for High-Pressure, High-Abrasion Conditions The working pressure of steel plant coal injection systems is typically 1.0-2.5 MPa, and pulverized coal (containing minor ash and impurities) continuously scours and wears the equipment's inner walls. The strength and wear resistance design of the double-cone butt-welded structure is highly targeted.

 1. Butt-Welding Process Enhances Overall Rigidity ? Advantages of Welded Structure: The upper and lower cones of the double-cone are connected by circumferential butt welds (rather than flanged joints), making the entire filter housing an "integrated rigid structure." This avoids risks associated with flanged connections, such as "bolt loosening" and "seal failure." Additionally, after non-destructive testing (e.g., UT, MT), the butt welds can withstand the system's pulsating pressure (pressure fluctuations during injection ≤10%) without cracking. ? Strong Material Adaptability: The housing typically uses Q235B or Q345R carbon steel. The "conical structure" of the double-cone inherently has a "pressure-resistant enhancement effect" (similar to pressure vessel head design). Under the same wall thickness, the pressure resistance of the conical structure is 15%-20% higher than that of a cylindrical shape, reducing material consumption and equipment weight.

 2. Optimized Wear Resistance ? Reinforced Scouring Surfaces: The scouring of pulverized coal airflow within the double-cone is concentrated in the "inlet cone section" and "around the filter elements." Local wear-resistant treatments (such as hardfacing with wear-resistant alloys or lining with alumina ceramic tiles) can be applied in these areas. The smooth curved surfaces of the double-cone facilitate even application of wear-resistant layers, avoiding issues of detachment in complex structures. ? Graded Wall Thickness Design: Some high-end filters employ a design with a "thickened wall in the inlet cone section" (2-3 mm thicker than other parts) to specifically resist the "initial scouring" at the coal inlet, extending the overall service life (under常規(guī) conditions, stable operation for 3-5 years, a 50% improvement over cylindrical filters).