This article's table of contents introduction:
- The "Boiler" Context (Waste Heat Recovery)
- The "Cement Kiln" Context (Rotary Kiln)
- The "Coal Mill / Pulverizer" Context (Boiler inside the Mill)
- Key Technical Specifications for a Cement Plant FD Fan (Typical)
- Common Problems with Cement Plant FD Fans
- Summary: Which fan is the "Forced Draught Fan"?
It appears you are looking for information on Forced Draft (FD) Fans specifically in the context of Cement Plants and Industrial Rotary Kilns.
While "Forced Draught Fan" is a standard term in power plant boilers, in a cement plant, the fan that supplies combustion air to the rotary kiln is typically referred to as the Kiln ID Fan or Main Burner Fan, or more generally as the Primary Air Fan and Secondary Air Fan.
However, if you are looking at a Waste Heat Recovery Boiler (WHRB) on a cement kiln, or a Coal Mill supplying the kiln, a true Forced Draft (FD) Fan is used.
Here is a breakdown of the forced draught fan roles in a cement plant and industrial rotary kiln context, covering the typical configurations:
The "Boiler" Context (Waste Heat Recovery)
If your question refers to a Waste Heat Recovery Boiler (WHRB) attached to the cement kiln exhaust:
- Role: The FD fan supplies combustion air to the auxiliary burner in the WHRB. (The kiln itself provides the primary hot gas).
- Location: At the inlet of the WHRB's burner (or duct burner).
- Why: To ensure proper combustion of supplementary fuel (if needed) when kiln exhaust is too low to maintain boiler steam output.
- Difference: In a standard power plant boiler, the FD fan pushes air through the air heater into the furnace. In a WHRB, the FD fan pushes air into a small combustion chamber integrated into the gas duct.
The "Cement Kiln" Context (Rotary Kiln)
In a standard cement rotary kiln, the primary fan supplying air to the main burner is NOT called an FD fan in the power plant sense. Instead, it is part of a specific system:
- Primary Air Fan:
- Role: Provides the high-pressure air needed to push pulverized coal (or alternative fuel) into the kiln burner pipe and shape the flame.
- Location: At the kiln hood (the lower end of the rotary kiln).
- Characteristic: High pressure (1000–2000 mmWC), low volume.
- Cooler Fans (Secondary Air Supply):
- Role: These are centrifugal fans that blow ambient air into the grate cooler. This air cools the clinker but ~70% of this air becomes "secondary air" (combustion air) for the kiln.
- Location: Under the clinker cooler grate.
- Function: They are the real forced draught for the kiln's flame, but they are called "Cooler Fans" or "Under-Grate Fans."
The "Coal Mill / Pulverizer" Context (Boiler inside the Mill)
- Role: The Coal Mill FD Fan (or Primary Air Fan) supplies hot air to the mill to dry and transport the coal powder to the kiln burner.
- Characteristic: Hot air (300–400°C), high volume, moderate pressure.
Key Technical Specifications for a Cement Plant FD Fan (Typical)
If you are procuring or troubleshooting a fan for a cement kiln or its auxiliary boiler, look for these parameters:
| Parameter | Typical Value | Notes |
|---|---|---|
| Flow Rate | 50,000 – 300,000 m³/hr | Depends on kiln size (1000 – 10000 TPD) |
| Static Pressure | 800 – 1500 mmWC | Lower than power plant ID fans |
| Temperature | 20°C (Ambient) up to 350°C (Hot air) | FD fans usually handle clean, cool air (20-40°C). Hot air fans need special materials. |
| Gas Type | Clean air (FD) or Dust-laden air (Primary) | FD fans handle clean air. Primary air fans handle air + coal dust. |
| Material | Carbon steel (Ambient) / Corten steel (Hot) | Hot air fans need expansion joints and bearing cooling. |
Common Problems with Cement Plant FD Fans
- Vibration:
- Cause: Dust build-up on impeller blades (especially for hot air fans pulling from the cooler).
- Solution: Regular cleaning or online washing systems.
- Erosion / Wear:
- Cause: If handling primary air with coal particles or if there is carryover from the cooler.
- Solution: Hard-facing (welding) of blades or use of liner plates.
- High Temperature Trip:
- Cause: If the kiln backfires or if hot gas ingresses back into the fan duct.
- Solution: Damper interlocking and temperature sensors.
Summary: Which fan is the "Forced Draught Fan"?
- In a Dedicated Boiler (WHRB): The FD Fan pushes air into the boiler's furnace.
- In a Cement Kiln: The Primary Air Fan and Cooler Under-Grate Fans collectively serve as the "forced draught" for the kiln, but they are not called FD fans in standard cement terminology. The main fan that pulls gases through the kiln is the Kiln ID Fan (Induced Draught).
If you need to order a replacement fan, please specify:
- Application: (e.g., "Primary air for 5000 TPD kiln" or "FD fan for WHR boiler.")
- Gas Type: (Clean ambient air, hot air, or air + coal dust).
- Temperature: (Max operating and trip temperature).
Would you like a technical datasheet template for specifying such a fan?
