Need to Know: Using Fluidized-Bed Technology

Nov. 25, 2005
to Clean Aluminum Castings

Removing mold and core sand from castings and managing the recovered sand is a tedious, expensive, and time-consuming task. The innovative Seghers Decor system uses fluidized-bed technology to remove the sand clinging to aluminum castings after shakeout and to recover it for re-use.

Seghers Keppel Technology Inc. is offering the casting-cleaning system to the foundry industry as an adaptation of its Fluid Clean technology, used in hundreds of installations in other industries worldwide. The result, the Marietta, GA, company claims, is “flexible, affordable and environmentally-friendly.” Seghers Keppel Technology is the American subsidiary of Keppel Seghers Group, headquartered in Belgium.

A system consists of a fluidized-bed reactor, an air-pollution control (APC) system, a material-feeding system, and a sand-recovery system.

The fluidized-bed reactor can be set between 750° and 950ºF. The casting, with mold and core sand adhering to it, is introduced via a load-basket/hoist system into the bed reactor and immersed into the hot sand mass. The heated, fluidized sand in the reactor gasifies the organic constituent that binds the mold and core sand.

In the post-combustion chamber, the off-gases from the organic binder are destroyed under the strongly oxidizing atmosphere. At the same time, inorganic compounds break down into inert solid particles that are carried out into the APC system. Separation of the inorganic solid particles is achieved in the cyclone portion of the APC system. Finally, an induced-draft fan exhausts all the cleaned gases through the stack in a way that meets all permit requirements.

The mold and core sand that remains is recovered into the fluidized-bed sand mass. Excess sand passes through an overflow weir and discharges through an exterior spout for removal and recovery.

Interestingly, the same system can be used simultaneously to heat treat large, complex aluminum castings to save time, and significantly reduce the build-up of internal stresses in the castings.

The unique configuration of heated sand mass along with the “flame-shield” post-combustion chamber allows for optimum control of each step of the de-coring and sand-recovery process, which results in extremely low emissions (CO, NOx, etc.). The APC uses a state-of-the-art cyclone to control particulate matter to local standards.

The fluidized-bed reactor can cope with very wide variations in the load composition. The system requires minimal labor to operate and can be equipped with an analog control panel or PLC.

The cycle times with the Decor process reportedly are shorter than with other technologies, and it is described as one of the few technologies that can recover the heat energy. This is a result of the fact that the sand bed functions as a natural heat accumulator.

More than 600 Seghers fluidized-bed installations have been installed worldwide for many different applications.

Keppel Seghers focuses its research and development activities is on development of advanced environmental technologies to solve a wide variety of environmental issues such as solid waste management, water and wastewater treatment and air pollution control.