Recovery of Fluorine from Stack Gases

Abstract

Substantially all of the fluorine that is present in the stack gas from fused tricalcium phosphate furnaces, nodulizing kilns, and calcium metaphosphate furnaces is in the form of hydrogen fluoride (HF). A considerable portion of the fluorine in the gases evolved from superphosphate manufacture is in the form of silicon tetrafluoride (SiF4) (1). Conclusive information is not at hand regarding the form of the fluorine compounds from other processes.

Disposal of Fluorine.

“…A 4-foot depth of limestone was required to remove 96% of the fluorine and a 9-foot depth was required for complete recovery of the fluorine at velocities of 0.6 to 1.5 feet/ second (37). In another study (34), with a fluorine breakthrough defined at 200 ppm F 2 , the capacity to dispose o£ fluorine was only 0.045 g F/g limestone (12% theoretical).…”

“…Sorption of halogen gases from air using limestone has been reported (36,37). A 4-foot depth of limestone was required to remove 96% of the fluorine and a 9-foot depth was required for complete recovery of the fluorine at velocities of 0.6 to 1.5 feet/ second (37).…”

Atmospheric Pollution, Spanish Moss and Filter Paper Exposures for Detection of Air-Borne Fluorides

“…Means for fluorine acquired by filter papers placed in each pair of ventilated buckets. 4 Whatman No. 2, 12.5-cm.…”

Fate and Effects of Hydrofluoric Acid Added to Four Tennessee Soils in 4-Year Lysimeter Study

“…When integrated with plant responses obtained in earlier pot culture experiments, the findings indicate that the fertility of a soil will not be impaired by hydrofluoric acid that may come to it from the atmosphere. Hydrofluoric emissions occur in the thermal production of orthoand metaphosphate fertilizers and in the preparatory nodulization of rock phosphate charges for reduction in electric furnaces (9). The emitted acid undergoes dispersion in the gaseous phase, as mists and as droplets, according to height of release, topography, atmos-pheric moisture, and meteorological conditions.…”