250kW Rotary Kiln Furnace
Rotary kiln furnaces can be used for a variety of different processes. The principle fields of application of indirectly heated rotary tube furnaces are the heat treatment of powdered, granular or crushed bulk materials. The rotary kiln used has a power rating of 250kW and has been used for the gasification and pyrolysis of sewerage sludge. This along with various metal heat treatments can be investigated with this rig. The kiln itself consists of a rotating metal tube, located within a refractory lined combustion chamber. The heated length of the furnace is 1.8m long and 0.6m diameter. The kiln is provided with three gas burners along the tube length, temperature controllers regulate the gas flow to these burners, thus controlling the burner operation.. The combustion air is supplied and controlled by a centrifugal air fan. The flue gases pass around the rotary shell and out of the combustion chamber through a chimney stack mounted on the top of the combustion chamber of the kiln.
The pyrolysis chamber within the rotating tube heats the feedstock intensely, thereby releasing the complex hydrocarbons. The complex hydrocarbons are then broken down into smaller chained hydrocarbons. The pyrolysis process produces a hydrocarbon gas (syngas gas), condensable hydrocarbons and a solid char. The rotary kiln facilitates a natural rotation providing agitation of the feedstock at high temperatures and allowing for a more complete conversion of all the feedstock to syngas. Product temperatures up to 1000°C are possible. Contrary to traditional gasifiers, it sits horizontally and at a slight slope, allowing for a gravitational flow that moves the feedstock through the system. The kiln can be inclined over the range of 0-2.5degrees and at rotational speeds up to n rpm and therefore control the residence time from entry to exit. The bed material within the rotating reactor tube is gently churned and processed towards the discharge end by vanes within the reactor’s wall. The char is discharged from the outlet of the kiln into the char/gas separator. The char settles to the bottom of the solid separator and is collected and removed via an ash bin. The produced syngas is drawn into a condenser at approximately 800°C where the condensable gases and any tar can be collected. The remaining non-condensable gases are then drawn out through the condenser at approximately 80°C into a thermal oxidiser.