The prefiltration of gaseous emissions from an incinerator of radioactive solvents - the case of TBP

During the incineration of solvents containing tributylphosphate, a solution of calcium formate is injected to neutralize the phosphoric acids produced. Most of the combustion residues are then found in suspension in the form of calcium phosphate aerosols. The pilot installation at the Cadarache nuclear research centre was used to determine experimentally the main characteristics of these combustion residues. The mass median diameter was submicronic at a concentration around one gramme per cubic metre. The small particle size and high concentration mean that cleaning devices quickly become clogged. Attempts have therefore been made to design prefiltration techniques which are better suited to the incineration of TBP. The techniques studied include some rather novel devices such as the electrocyclone and polarized filters, as well as more conventional systems like the electrostatic filter and the cyclone. In the final analysis it would seem that the ideal prefiltration arrangement would incorporate a combination of processes. Under the experimental conditions, optimum filter efficiencies and minimum pressure were achieved with an electrostatic filter in conjunction with a bag filter. (author)