**The core function and working principle of boiler Roots blower**
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**1、 Summary of core functions**
The Roots blower in the boiler system is a high-pressure gas conveying equipment that mainly undertakes three key tasks:
1. * * Combustion and oxygen supply * *: Forcefully deliver air to the furnace to ensure complete combustion of fuel
2. * * Material fluidization/conveying * *: Maintain bed material suspension or pneumatic conveying of coal powder/ash in fluidized bed boilers
3. * * Process gas circulation * *: supports the operation of environmental protection systems such as desulfurization and denitrification
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**2、 Specific application scenarios**
**1. Combustion and oxygen supply (blower)**
-Working principle:
By rotating the impeller, a constant flow of air is generated to overcome furnace resistance (usually 15-35kPa)
-Coal fired boiler: air-fuel ratio 1.2-1.5 (12-15m3 of air required per kg of coal)
-Gas boiler: gas distribution (natural gas: air ≈ 1:10)
-Advantages:
Flow is not affected by pressure fluctuations (volumetric principle)
More suitable for the dust environment of coal-fired boilers than centrifugal fans
**2. Fluidized air of fluidized bed boiler**
-* * Key Parameters * *:
|Parameters | Typical values | Adaptability of Roots blower|
|--------------|--------------------|--------------------|
|Fluidization wind speed | 0.8-1.5m/s | Precise adjustment through variable frequency control|
|Bed pressure | 8-15kPa | Pressure fluctuation<3|
-* * System Configuration * *:
```mermaid
flowchart LR
Roots blower → air preheater → air chamber → air distribution plate → quartz sand/limestone fluidization
```
**3. Pneumatic ash conveying system**
-* * Performance Characteristics * *:
-Transport concentration: 3-10kg ash/kg gas
-Wear resistant design: tungsten carbide spray coating on the surface of the impeller (hardness C ≥ 55)
-Explosion proof requirement: Ex tD IIIB T130 ℃ (coal powder explosion-proof)
**4. Environmental protection system supporting facilities**
-* * Application of desulfurization * *:
-Limestone slurry injection (pressure 25-40kPa)
-Oxidation fan (providing air for desulfurization tower)
-Flue Gas Recirculation (FGR):
-Reduce NOx emissions (cycle size 10-30)
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**3、 Comparative advantages with other fans**
|* * Features * * | Roots blower | Centrifugal blower | Screw compressor|
|----------------|----------------------|----------------------|----------------------|
|* * Traffic stability * * | ★★★★ (± 1) | ★★☆☆ (greatly affected by pressure) | ★★★☆☆|
|* * Dust resistant * * | ★★★☆ (pre filtration required) | ★☆☆☆ (impeller prone to wear) | ★★☆☆☆ (high oil filtration requirements)|
|* * Energy Efficiency * * | 65-75 | 80-88 | 75-82|
|* * Maintenance cost * * | Low (simple structure) | Medium | High (complex oil system)|
---
**4、 Key technical parameters for selection**
1. * * Traffic calculation**
-Coal fired boiler:
$$
Q=1.2 \ times \ text {fuel quantity} (kg/h) \ times \ text {air-fuel ratio} \ div 60
$$
*Example: A 20t/h boiler (air-fuel ratio 1.3) requires an air volume of approximately 26m3/min*
2. * * Pressure determination**
-Furnace resistance+pipeline loss+10 margin
-Fluidized bed boilers require additional calculation of bed material resistance
3. Temperature resistance requirements:
-Standard type: -20~120 ℃ (cast iron shell)
-High temperature type: ≤ 250 ℃ (requires water cooling jacket)
---
**5、 Typical system configuration**
**Coal fired boiler scheme * *:
```mermaid
flowchart LR
A Roots blower -->B Cyclone dust removal -->C Air preheater -->D Burner
B -->E [Bag Filter] -->A
```
**Key components * *:
-Explosion proof motor: Ex d Ⅱ B T4 (methane environment)
-* * Muffler * *: Impedance composite type (noise reduction 25dB (A))
-* * Filter * *: Accuracy of 5 μ m (pressure drop<300Pa)
---
**6、 Maintenance points**
1. * * Daily monitoring * *:
-Vibration value: ≤ 4.5mm/s (ISO 10816 standard)
-Bearing temperature: ≤ 95 ℃ (infrared temperature measurement)
2. * * Regular maintenance * *:
-Change gear oil every 2000 hours (ISO VG220)
-Clean the intake filter monthly
---
**7、 Economic analysis**
**Comparison of Total Cost of 75kW Models over 10 Years * *:
|* * Project * * | Roots blower | Centrifugal blower|
|---------------|---------------|---------------|
|Procurement cost | ¥ 85000 | ¥ 120000|
|Annual power consumption | 390000 kWh | 360000 kWh|
|Annual maintenance fee | ¥ 8000 | ¥ 15000|
|* * Total cost * * | ¥ 1.2 million | ¥ 1.5 million|
---
**8、 Selection suggestions**
**Recommended use * *:
-Fluidized bed boiler requiring constant flow rate
-Pneumatic ash conveying system (ash volume ＜ 30t/h)
-Blowing air for small and medium-sized boilers (≤ 35t/h)
**Not recommended * *:
-High flow conditions of gas boilers (>80m3/min)
-Containing highly corrosive gases (untreated SO flue gas)
**Practice: For 10-20t/h coal-fired boilers, choose a water-cooled three blade Roots blower (such as -150)+cyclone+bag type secondary filtration for comprehensive cost-effectiveness.
