How poultry waste incinerators work
Poultry waste incinerators handle farm mortalities, hatchery waste such as unhatched eggs, shells and dead chicks, and processing plant offal and feathers. Small farm units are batch-loaded two-chamber incinerators. Larger units at hatcheries and processing plants are often continuously fed by ram or screw into a primary chamber at about 800°C, with a secondary chamber at about 1,000°C. The waste is wet and fatty, and eggshell adds calcium carbonate, so the ash is lime-rich. Feathers and down are light and entrained easily. Gas leaves the secondary chamber, is cooled in a heat exchanger or by tempering air, passes a cyclone and sometimes a bag filter, and the ID fan delivers it to the stack. A combustion air blower supplies both chambers.
Where the FD fan sits
- Inlet screen
- FD fan
- Air header
- Primary chamber ports
- Secondary air nozzles
- Chambers
The blower sits beside the incinerator and feeds a header with branches to the primary and secondary chambers. Air to the primary chamber is spread across many low-velocity ports so that it does not lift the light waste, while secondary air enters through fewer higher-velocity nozzles for mixing. The blower works against typically 120 to 300 mmWC. Its inlet is screened and placed away from poultry houses and waste handling.
Air at the FD fan
| Air temperature at the fan | Ambient, 25 to 45°C |
| Air at the chambers | Ambient; preheated in some heat recovery designs |
| Dust | Feathers, dust and odour in farm air; inlet screen needed |
| Pressure at the fan outlet | Typically 120 to 300 mmWC |
| Air split | Primary chamber sub-stoichiometric; secondary chamber excess air |
| Density at the design temperature | About 1.13 kg/m³ at 40°C, 94% of standard air. Pressure developed and power drawn scale with density, so the fan is selected at this condition and the motor is checked at the coldest operating or start-up condition. |
FD Fan selection for poultry waste incinerators
| Blade form | Backward curved, compact |
| Material of construction | Mild steel, painted or galvanised for farm humidity and ammonia |
| Drive and arrangement | Direct mounted on the motor shaft |
| Bearings and cooling | Motor bearings |
| Flow control | Branch dampers and variable speed drive on chamber temperatures |
| Also specified | Inlet screen and air pressure switch interlock |
What this FD fan has to cope with
Feather lift from high primary air
High air velocity in the primary chamber carries feathers and ash out before they burn. Spreading primary air over more ports and controlling it to the gasification need limit carry-over.
Ammonia and humidity corrosion
Farm air contains ammonia and moisture from the poultry houses, and both corrode unprotected steel inside and outside the fan. Galvanised or coated construction, and an air intake taken from a clean, dry area away from the houses and manure stores, extend fan life considerably.
Inlet blockage
Feathers, down and dust from waste handling collect on inlet screens and reduce airflow, which leads to incomplete combustion and smoke. A generous screen area, an intake located away from the feed hopper and a simple daily cleaning routine prevent this.
Energy and control
The combustion air blower is small, but the air split between the chambers has a direct effect on support fuel use and on how much ash and feather char reaches the ID fan. Keeping primary air low for gasification and controlling secondary air on oxygen avoids overcooling the chambers. A variable speed drive suits continuously fed units, where the feed rate follows the farm or plant waste through the day.
ID fan and FD fan in poultry waste incinerators
| ID fan | FD fan | |
|---|---|---|
| Position | After heat exchanger and cyclone | Beside the incinerator, feeding both chambers |
| What it handles | Hot gas with feather char and lime-rich ash | Ambient combustion air |
| Temperature at the fan | 200 to 260°C, up to 350°C upset | Ambient, 25 to 45°C |
| Main design concern | Dust and sticky deposits | Low primary velocity to limit carry-over |
| Control | Primary chamber pressure | Chamber temperatures and oxygen |
See also the Induced Draft (ID) Fan for poultry waste incinerators.
Questions buyers ask
How is combustion air supplied in a poultry incinerator?
A blower supplies limited air to the primary chamber, where waste dries and gasifies, and excess air to the secondary chamber, where gases burn completely. Burners have their own integral blowers.
Why is low air velocity needed in the primary chamber?
Feathers and fine ash lift very easily. High air velocity carries them out of the primary chamber before they burn, which raises particulate emissions and adds to the deposits that build up on the cyclone and the ID fan.
What material is used for the combustion air blower on a poultry farm?
Galvanised or coated mild steel is common, because farm air contains ammonia and humidity that corrode bare steel. The blower handles ambient air only, so heat or acid resistance is not needed; the ID fan is where those matter.
Information needed to quote an FD fan for poultry waste incinerators
- Duty point. Combustion air quantity in m³/h or kg/h and the static pressure at the fan outlet, with the margins you want.
- Air condition. Site ambient temperature range and altitude, and whether the fan takes ambient air or air already heated.
- System. Boiler or furnace capacity and fuel, resistance of the air heater, windbox, grate or burner, and the existing fan curve or nameplate if this is a replacement.
- Mechanical. Drive arrangement, flow control (damper, inlet vanes or variable speed drive), noise limit, rotation and discharge orientation.
- Air ports. Primary and secondary air port layout and design flows.
- Site air. Location of the air intake relative to poultry houses and waste handling.
Built and tested in Chennai
Adroit Fantech Engineers has designed and manufactured industrial fans at Ayanambakkam, Chennai since 2004. Each impeller, casing and shaft is built for the gas and temperature it will see, performance tested as per IS 4894 or BS 848 Part I, and balanced to grade G 6.3 or G 2.5 as per ISO 21940-11, with the records supplied with the fan. We also replace rotors and retrofit existing fans of any make.