Biomass granulation (straw, wood chips, rice husk, etc.) is a core link in new energy utilization, and high wear is the most prominent problem faced by granulator knives in this field. Straw contains silica, wood chips are often mixed with sand particles, and coupled with the high-fiber characteristics of the materials, ordinary granulator knives will quickly experience edge blunting, chipping, and other issues, seriously affecting production efficiency and costs. Due to its ultra-high hardness (HRA≥90) and wear resistance, tungsten carbide has become the preferred material for biomass granulator knives, but improper selection will still lead to "insufficient durability". Focusing on two mainstream biomass materials—straw and wood chips—this article uses plain language and clear tables to break down key selection points from the analysis of high-wear causes, tungsten carbide granulator knife selection parameters, and targeted solutions, helping industry practitioners accurately match needs and effectively handle high-wear working conditions.
1. First, Understand: Causes of High Wear in Straw and Wood Chips (Core Basis for Selection)
The high-wear characteristics of biomass materials are not caused by a single factor, but by the combined effect of material properties, impurities, structure, and other aspects. Only by clarifying the root causes can we select knives in a targeted manner:
1.1 Core Wear Factors (Clearly Presented in List)
- Silica and Sand Particle Abrasion: Straw (especially corn straw and wheat straw) contains 2-5% silica, and wood chips are often mixed with soil sand particles. Silica and sand particles have a hardness close to quartz (Mohs hardness 7), which will continuously grind the granulator knife edge, leading to rapid blunting;
- High-Fiber Tensile Wear: The fiber content of straw and wood chips is as high as 60-80%. During granulation, fibers will wrap around the edge and generate strong tensile force, exacerbating edge wear. At the same time, heat generated by fiber friction will cause material adhesion, further worsening the wear environment;
- Impact of Material Humidity Fluctuations: Biomass humidity (10-30%) varies greatly. High humidity causes materials to stick and block the machine, while low humidity makes materials dry and loose with stronger abrasiveness, requiring higher adaptability of granulator knives;
- Hard Spot Impact Wear: Wood chips may contain branch knots, and straw may have withered leaf stems and other hard spots. During granulation, these hard spots will cause instantaneous impact on the edge, leading to micro-chipping, which will reduce the service life of the knife over time.
1.2 Straw vs. Wood Chips: Differences in Wear Characteristics (Precise Distinction for Targeted Selection)
| Material Type | Core Wear Characteristics | Additional Challenges | Special Requirements for Granulator Knives |
|---|---|---|---|
| Straw (Corn/Wheat/Rice Straw) | High silica content (3-5%), strong abrasiveness, long and tough fibers | Easy to wrap, humidity-sensitive (prone to adhesion at high humidity) | High wear resistance, anti-winding, impact-resistant edge |
| Wood Chips (Hardwood/Softwood/Branch Fragments) | High sand particle impurity content (1-3%), presence of hard knots and spots, uniform but long-lasting abrasion | Frequent hard spot impacts, uneven material density | High hardness, impact resistance, wear-resistant and chip-resistant edge |
2. Core Selection Parameters of Tungsten Carbide Granulator Knives (Key to Handling High Wear)
Targeting the high-wear characteristics of biomass, the selection of tungsten carbide granulator knives should focus on three core dimensions: "material formula, edge structure, and knife body design", each with clear adaptation standards:
2.1 Material Formula: Balance Hardness and Toughness, Combining Wear Resistance and Impact Resistance
The material formula of tungsten carbide (cobalt content, grain size) directly determines wear resistance and impact resistance, which is the foundation for handling high wear:
| Selection Parameter | Recommended Configuration (Biomass-Specific) | Core Function | Not Recommended Configuration |
|---|---|---|---|
| Cobalt Content | 8-12% (corresponding grades: YG8/YG10/YG12) | Too low cobalt content (≤6%) results in insufficient toughness and easy chipping; too high (≥15%) reduces hardness and wear resistance; 8-12% balances wear resistance and impact resistance | YG6 (low cobalt, easy to chip), YG15 (high cobalt, insufficient wear resistance) |
| Grain Size | Medium-coarse grain (3-8μm) | Fine grain (≤2μm) has weak impact resistance and is prone to chipping due to hard spot impacts; medium-coarse grain improves edge wear resistance and impact resistance, adapting to biomass impurity impacts | Ultra-fine grain (≤1μm, insufficient impact resistance) |
| Material Density | ≥14.5g/cm³ | High density reduces internal pores in tungsten carbide, avoiding local wear caused by sand particle embedding and improving overall wear stability | ≤14.0g/cm³ (many pores, prone to wear) |
2.2 Edge Structure: Wear Resistance, Anti-Winding, and Impact Reduction
The edge is the part directly in contact with materials, and its structural design must specifically address the abrasion and winding problems of biomass:
- Edge Angle: 35-45° (35-40° for straw, 40-45° for wood chips). A larger angle enhances edge strength, reduces chipping from hard spot impacts, and lowers the probability of fiber winding;
- Edge Shape: Serrated edge (tooth pitch 3-5mm) + micro-chamfer (0.3-0.5mm). The serrated edge can quickly cut fibers to avoid winding, and the micro-chamfer disperses stress to improve impact resistance;
- Surface Treatment: Mirror polishing (Ra≤0.2μm) + nitriding treatment. Polishing reduces material adhesion, and nitriding treatment increases the surface hardness of the edge (HRA≥92) to enhance wear resistance.
2.3 Knife Body Design: Strengthen Structure to Adapt to High-Load Working Conditions
The knife body structure must provide sufficient support for the edge and adapt to the working characteristics of biomass granulators:
- Knife Body Thickness: ≥12mm (straw granulation) / ≥14mm (wood chip granulation). A thickened knife body improves overall rigidity, avoiding knife body deformation during high-load cutting;
- Tip Fixation Method: Embedded tip (welding + mechanical clamping). Biomass granulation has high impact loads; the embedded design is more impact-resistant than the integral type, and the tip can be replaced individually after wear, reducing maintenance costs;
- Chip Removal/Heat Dissipation Design: The knife body is equipped with chip removal grooves (width 5-8mm), and straw granulator knives are additionally equipped with heat dissipation grooves. Chip removal grooves can quickly discharge fiber debris, and heat dissipation grooves reduce frictional heat generation to minimize material adhesion.
3. Straw vs. Wood Chips: Targeted Selection Schemes (Direct Application, Pitfall Avoidance Guide)
Combined with the above analysis, exclusive selection schemes for the two types of materials are sorted out, covering core parameters, applicable scenarios, and expected effects for direct reference:
| Selection Dimension | Exclusive Scheme for Straw Granulation | Exclusive Scheme for Wood Chip Granulation |
|---|---|---|
| Tungsten Carbide Grade | YG8/YG10 (cobalt content 8-10%) | YG10/YG12 (cobalt content 10-12%) |
| Grain Size | Medium grain (3-5μm) | Medium-coarse grain (5-8μm) |
| Edge Structure | Serrated edge (tooth pitch 3-4mm) + 0.3mm micro-chamfer + mirror polishing | Serrated edge (tooth pitch 4-5mm) + 0.5mm micro-chamfer + nitriding treatment |
| Knife Body Structure | Thickness 12-14mm + chip removal grooves + heat dissipation grooves | Thickness 14-16mm + wide chip removal grooves + reinforced knife back |
| Tip Fixation Method | Welding + mechanical clamping (dual fixation) | Embedded tip (vacuum welding) |
| Adaptable Granulator Type | Flat-die granulator (low-speed, high-torque) | Ring-die/flat-die granulator (medium-high speed) |
| Core Adaptable Scenarios | Long-fiber materials such as corn/wheat straw and rice straw (humidity 15-25%) | Hardwood/softwood chips, branch fragments (impurity content ≤3%) |
| Expected Service Life | 600-900 hours (conventional working conditions) | 500-800 hours (conventional working conditions) |
| Key Optimization Points | Anti-winding, heat dissipation, resistance to silica abrasion | Resistance to hard spot impacts, sand particle abrasion, enhanced knife body rigidity |
Supplementary Notes:
- Adjustment for high-impurity scenarios: If the silica content of straw exceeds 5% or the sand particle content of wood chips exceeds 3%, upgrade to YG12 grade (high cobalt, high wear resistance) and thicken the edge to 2.5mm to further improve wear resistance;
- Adjustment for high-humidity scenarios: When humidity exceeds 25%, straw granulator knives can be added with PTFE anti-adhesion coating to reduce additional wear caused by material adhesion;
- Adaptation for low-output scenarios: For daily output <5 tons, conventional thickness knife bodies (10-12mm) can be selected to reduce procurement costs while ensuring basic durability.
4. Selection Pitfall Avoidance Guide: These Wrong Practices Will Exacerbate Wear
4.1 Common Selection Mistakes (Clearly Listed to Avoid Pitfalls)
- Mistake 1: Blindly pursuing high hardness and selecting low-cobalt grades (e.g., YG6) → Insufficient toughness, prone to edge chipping from straw stems and wood chip knots;
- Mistake 2: Edge angle too small (≤30°) → Sharp edge but insufficient strength, prone to edge rolling and chipping after long-term grinding;
- Mistake 3: Selecting integral tungsten carbide granulator knives → Biomass granulation has high impact, and the integral type has weak impact resistance, prone to knife body fracture;
- Mistake 4: Neglecting surface treatment → Knives without polishing/nitriding treatment have severe material adhesion, exacerbating wear and blockage.
4.2 Installation and Maintenance Notes (Key to Extending Service Life)
- Installation Gap: Control the gap between the granulator knife and fixed knife at 0.2-0.4mm. Excessively large gaps cause excessive fiber tension, while excessively small gaps increase frictional wear;
- Daily Maintenance: Clean residual fibers and impurities on the edge after daily operation, check edge wear weekly, and perform precision grinding (maintaining the original angle) when slight blunting occurs;
- Material Pretreatment: Crush straw to ≤5mm before granulation to remove hard stems; screen wood chips to remove large sand particles before granulation, reducing impurity abrasion.
5. Typical Application Cases (Intuitive Reference to Verify Selection Effects)
| Application Scenario | Material Type | Working Conditions (Humidity/Impurity) | Selection Scheme | Usage Effect |
|---|---|---|---|---|
| Corn Straw Biomass Fuel Granulation | Corn Straw | Humidity 20%, silica content 4% | YG8 grade, medium grain, serrated edge + heat dissipation grooves | Service life 850 hours, no chipping, 60% reduction in blockage frequency |
| Hardwood Chip Pellet Processing | Oak Wood Chips | Humidity 15%, sand particle content 2% | YG12 grade, medium-coarse grain, reinforced knife back | Service life 720 hours, uniform edge blunting, no fracture |
| Mixed Biomass (Straw + Wood Chips) Granulation | Wheat Straw + Pine Wood Chips | Humidity 18%, impurity content 3% | YG10 grade, medium grain, wide chip removal grooves | Service life 680 hours, adapts to mixed material characteristics, uniform wear |
Conclusion: Core of Biomass Granulator Knife Selection – Balancing "Wear Resistance + Impact Resistance + Anti-Winding"
To handle the high-wear working conditions of straw and wood chips, the selection of tungsten carbide granulator knives does not require complex calculations. The core is to grasp three key points: "material formula balances hardness and toughness, edge structure resists wear and winding, and knife body design strengthens support". Straw granulation focuses on anti-winding and heat dissipation, while wood chip granulation emphasizes resistance to hard spot impacts and sand particle abrasion.
As a tungsten carbide industry practitioner, we can provide customized granulator knife solutions based on the characteristics of different biomass materials—from tungsten carbide grade adjustment, edge structure design to knife body strengthening, fully adapting to high-wear working conditions. If you need precise selection advice based on specific materials (e.g., special straw, high-impurity wood chips), granulator parameters, or output requirements, please contact us to help improve biomass granulation efficiency and reduce knife replacement costs!
