**In depth analysis of the applicability of Roots blowers for boilers**
---
**1、 The core role of Roots blower in boiler system**
1. * * Key application scenarios**
-* * Coal fired boiler * *: Fly ash circulation, coal powder transportation (pressure 9.8-49kPa)
-Gas boiler: Combustion air pressurization (flow rate 5-50m3/min)
-Fluidized bed boiler: Bed material fluidization (requiring constant flow characteristics)
-* * desulfurization system * *: limestone slurry transportation (anti-corrosion design)
2. * * Performance advantages**
-* * Stable flow rate * *: Volumetric principle, flow fluctuation ＜ ± 2 (better than centrifugal fan)
-Load resistance variation: When the outlet pressure fluctuates within 49kPa, the flow rate remains constant
-* * Low sensitivity * *: better dust tolerance than screw compressors (clearance 0.15-0.3mm)
---
**2、 Comparison of boiler operating condition adaptability**
|* * Parameters * * | Roots blower | Centrifugal blower | Screw compressor|
|----------------|-----------------------|-----------------------|-----------------------|
|* * Flow regulation * * | Only adjustable through speed/bypass | Valve adjustable (30-) | Infinite speed regulation (20-)|
|* * Energy Efficiency Ratio * * | Medium (65-75) | High (80-88) | High (75-82)|
|* * Dust resistance * * | ★★★☆☆ (pre filtration required) | ★☆☆☆ (impeller prone to wear) | ★★☆☆☆ (precision rotor requires protection)|
|* * Maintenance cost * * | Low (simple structure) | Medium | High (complex oil system)|
---
**3、 Key technical points for selection**
1. * * Traffic calculation**
-Coal fired boiler:
$$
Q=1.2 \ times \ text {fuel quantity} (kg/h) \ times \ text {air-fuel ratio} \ times 10 ^ {-3}
$$
*Example: A 10t/h coal-fired boiler (with an air-fuel ratio of 1.2) requires an air volume of 14.4m3/min*
2. * * Pressure determination**
-Consider * * air duct resistance * *+* * bed pressure (fluidized bed) * *+* * margin (10)**
-Typical values:
|Boiler type | Pressure range (kPa)|
|---------------|----------------|
|Chain grate | 15-25|
|Circulating fluidized bed | 35-49|
3. Temperature resistant design**
-Standard type: -20 ℃~120 ℃ (shell cast iron HT250)
-High temperature type: ≤ 250 ℃ (requires water cooling jacket+graphite seal)
---
**4、 Special plan for dust and corrosion prevention**
1. * * Level 3 protection system**
```mermaid
flowchart LR
A [intake] -->B [cyclone separator] -->C [bag filter] -->D [anti-corrosion coating fan]
```
-* * Cyclone separator * *: removes particles ≥ 20 μ m (efficiency 90)
-Bag filter with an accuracy of 5 μ m (pressure drop<300Pa)
-* * Coating protection * *:
-Normal working condition: epoxy resin (temperature resistance of 150 ℃)
-Flue gas desulfurization: PTFE lining (resistant to pH 1-14)
2. * * Electrostatic protection**
-Impeller grounding resistance ＜ 10 Ω
-Surface resistance of filter material 10-10 Ω (anti-static filter bag)
---
**5、 Energy Efficiency Optimization Strategy**
1. * * Variable frequency control**
-Energy saving calculation:
$$
P_2 = P_1 \times \left(\frac{n_2}{n_1}\right)^3
$$
*Reduce speed by 20 → save energy by 48.8*
2. * * Heat recovery system * * (applicable for exhaust temperature>80 ℃)
-Installing a gas to gas heat exchanger can recover 30-50% of thermal energy
---
**6、 Typical faults and prevention**
|* * Fault phenomenon * * | Root cause | Solution|
|---------------|------------------------|-----------------------------|
|Excessive vibration | Dust accumulation on impeller (dynamic balance failure) | Monthly cleaning+dynamic balance (G2.5 level)|
|Bearing overheating | Sealing failure (dust ingress) | Switching to labyrinth seal+grease lubrication (L-CKD)|
|Flow rate decrease | Filter blockage (pressure difference>500Pa) | Install pressure difference alarm+automatic blowback|
---
**7、 Economic analysis (taking 75kW model as an example)**
|* * Project * * | Roots blower | Centrifugal blower|
|---------------|------------------|------------------|
|Procurement cost | ¥ 85000 | ¥ 120000|
|Annual maintenance fee | ￥ 8000 | ￥ 15000|
|10-year total cost | ¥ 165000 | ¥ 270000|
|* * Energy saving potential * * | After frequency conversion renovation ↓ 25 | Limited frequency conversion effect|
---
**8、 Selection Conclusion**
1. * * Recommended usage scenarios**
-Boiler systems that require constant flow conveying, such as fluidized beds and pneumatic ash conveying
-Dust concentration * * ＜ 200mg/m3 * * (requires filtration)
-Pressure requirement * * ＜ 58.8kPa * * (overpressure requires multi-stage series connection)
2. * * Not recommended for use**
-High flow conditions of gas boilers (low energy efficiency when>100m3/min)
-Containing highly corrosive gases (such as desulfurized SO flue gas)
**Practical suggestion * *:
For coal-fired boilers with a capacity of 10-35t/h, a water-cooled three blade Roots blower (such as CSR series)+cyclone+bag type secondary filtration is selected to achieve comprehensive benefits. After configuring the frequency converter, it can maintain operation in the 30-80 load range.
