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11.29.2006

Befesa. Sodium and potassium salt drying through the recovery of flue gases from a steam boiler

Within the constant enhancement and energy process efficiency program established for Befesa Escorias Salinas's factory in Valladolid, the project for the recovery or use of the residual gases from the boilers for drying the salt produced in the process has been integrated.

Up until now, this salt was treated in a rotary drum equipped with a natural gas burner. This burner generated gases at temperatures between 500 and 600oC that dried the salt by direct contact. The dry salt was evacuated from the equipment and the gases generated passed through a sleeve filter prior to being released into the atmosphere.

The new project eliminates the consumption of natural gas and uses the residual gases directly in one of the boilers that supplies steam to the crystallization plant for the salt that is going to be dried. The technique employed, given the characteristics of the gases available, has been by direct drying in a vibrating fluidized bed.

The gases are extracted directly from the stack and the fact that they are not sucked from the boiler is controlled at all times. The gases are run in under the bed of salt which, with the vibration and the fluidized effect produced in the particles, advances and dries out along the entire length of the unit. By controlling the residence time and volume of gases in function of the temperature of the gases supplied and the humidity of the salt, a compromise can be reached with the production capacity.

Under normal operating conditions, this process achieves a direct saving, through the saving of natural gas, of 2.5 euro per ton of dried salt.

Given the good results achieved, the installation has been enhanced even further and the equipment has recently been modified to help with the fluidization effect of the material. This has been done through the installation of a second pressure ventilator that draws air from the outside and introduces it into the final drying area.

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