How pet cremation incinerators work
A pet cremation incinerator is a compact two-chamber unit, typically handling 50 to 500 kg per cycle, fired on diesel, LPG or natural gas. Animals are placed on the hearth of the primary chamber, which runs at about 650 to 850°C, either one animal at a time for individual cremation or several together. The gas passes to a secondary chamber held at 850 to 1,000°C with a residence time of one to two seconds. Animal carcasses are 60 to 70% water with variable fat, so heat release and gas volume change sharply as fat ignites. Many small units discharge hot gas to a self-supporting chimney, using a dilution air inlet or an ID fan for draft; larger units add a heat exchanger or quench and a scrubber.
Where the FD fan sits
- Inlet
- FD fan
- Air header
- Primary hearth air
- Secondary chamber air
The fan is mounted on the incinerator frame and feeds air pipes to ports in the primary chamber and to nozzles in the secondary chamber. On packaged units it is often a single compact fan with two branches and manual or motorised dampers. Pressure required is about 80 to 200 mmWC, enough to push air through the ports and nozzles and mix it into the gas in each chamber.
Air at the FD fan
| Air temperature at the fan | Ambient, 25 to 45°C |
| Dust | Clean air |
| Pressure at the fan outlet | Typically 80 to 200 mmWC |
| Air demand | Rises sharply during fat ignition |
| Burner air | Usually from packaged burner blowers |
| 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 pet cremation incinerators
| Blade form | Backward curved, compact |
| Material of construction | Mild steel, painted |
| Drive and arrangement | Direct drive |
| Bearings and cooling | Standard bearings |
| Flow control | Variable speed drive or motorised dampers controlled from chamber temperature |
| Also specified | Inlet guard and low noise motor |
What this FD fan has to cope with
Smoke during fat ignition
When fat ignites, volatile release and oxygen demand jump within a minute. Without extra secondary air the afterburner runs short of oxygen and the chimney smokes, even though the burner is firing correctly. A fan with spare capacity above the average demand, and fast control from secondary chamber temperature or oxygen, keeps combustion complete through the flare-up.
Overheating the primary chamber
Too much primary air during a fat flare-up feeds the fire on the hearth and drives the chamber beyond its refractory limit, cracking the hearth over time. Reducing primary air while increasing secondary air controls the burn without smoke, so separate control of the two branches, rather than one fixed damper setting, matters on a pet cremator.
Air ports blocked by ash
Hearth air ports can block with ash, bone fragments and melted fat residue, starving the burn on one side of the hearth and lengthening the cycle. A fan with pressure margin keeps air flowing through partly blocked ports, and ports placed where the operator can reach them for cleaning between cycles keep the air distribution even.
Energy and control
Pet cremation is a batch process with frequent charging and short peaks. A speed controlled fan that follows chamber temperature avoids running at full air through the long burnout and cool-down periods, saving fuel that would otherwise heat excess air. The fan power is small, but the fuel effect of over-airing a small chamber is significant.
ID fan and FD fan in pet cremation incinerators
| ID fan | FD fan | |
|---|---|---|
| Position | After dilution or quench, at the chimney | On the incinerator frame |
| What it handles | Hot flue gas, dry or saturated | Ambient air |
| Temperature at the fan | 250 to 350°C dry, 55 to 75°C wet | Ambient |
| Main design concern | Fat flare-up temperature and bearing heat | Fast secondary air response |
| Control | Chamber draft and dilution | Chamber temperature |
See also the Induced Draft (ID) Fan for pet cremation incinerators.
Questions buyers ask
What does the combustion air fan on a pet cremator do?
The combustion air fan on a pet cremator supplies controlled air to the primary hearth to burn the carcass and to the secondary chamber to burn the smoke and odour. It works alongside the burner blowers and is adjusted through the cycle, giving more secondary air during fat ignition and less air overall during burnout.
Why does a pet cremator smoke when fat burns?
Fat ignites quickly and releases volatiles faster than the secondary air can burn them in the afterburner. Supplying more secondary air and less primary air at that moment, from a properly sized combustion air fan with fast control, keeps the chimney clear. Charging smaller loads or spreading fatty carcasses across cycles also helps.
How big is the air fan on a small pet incinerator?
It is usually a small fan, often a few hundred to a couple of thousand cubic metres per hour, but it should be sized for the peak air demand when fat ignites, not just the average over the cycle. Pressure is typically 80 to 200 mmWC, depending on the nozzle design and the air piping.
Information needed to quote an FD fan for pet cremation 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 branches. Number of air ports and nozzles in the primary and secondary chambers.
- Control. Temperature or oxygen based control, or fixed dampers.
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.