Method for controlling the oxidation and calcination of waste foundry sands

A method for controlling the oxidation and calcination of waste foundry sands during a thermal reclamation process, the waste foundry sands having binders with a fuel content adhering thereto, the method comprising the steps of:

• passing the waste sands to a calcining chamber having a top, a floor and connecting sidewalls, the floor of the calcining chamber being provided with a plurality of vents the calcining chamber also being connected to a separate firebox capable of producing fluidizing hot gases for fluidizing the waste sands within the calcining chamber and forming a fluidized sand bed, the fluidizing hot gases being introduced to the calcining chamber by means of the floor vents;
• producing fluidizing hot gases by combustion means in the firebox, wherein the combustion means includes a burner, a source of primary combustion air for the burner and a source of secondary combustion air for the firebox;
• generating a first signal with a first signal generating means, wherein the first signal is representative of the temperature of the waste sands within the fluidized sand bed;
• generating a second signal with a second signal generating means, wherein the second signal is representative of the volume of available free oxygen in the fluidizing hot gases within the firebox, leaving the firebox and entering the calcining chamber through the floor vents;
• and
• using control means to precisely control the temperature of the waste sand s within the fluidized sand bed with respect to a preselected set point, wherein the control means follows a temperature control method comprising the steps of:
• analyzing the first and second signals generated by the first and second signal generating means,
• comparing the analyzed first and second signals with the preselected set point and
• adjusting the rate of waste sand feed to the calcining chamber and the quantity of supplementary fuel combusted in the firebox based on the comparison of the first and second signals with the preselected set point.