STABILITY OF A KILN STACK*

Mathematical proof is presented that the wind pressure on a round stack is two-thirds that of a square stack with the wind square to one side. A reconsideration is given of a stack section¹ where tension occurred, and a correction is presented. A convenient method and its application is also given for calculating the stability of a kiln stack upon the soil. The application of the “kern” theorem is discussed, using the kern for the worst condition, viz., with wind blowing diagonally against a square stack.     

CONCENTRATION OF FELDSPATHIC WASTE FROM A TITANIUM MINE NEAR ROSELAND,VIRGINIA *

The beneficiation of the feldspathic waste from a titanium mine near Roseland, Virginia, is discussed. This waste, which is mainly sodic plagioclase, quartz, and an iron-bearing mineral, gedrite, contains about 5.3% of Fe₂O₃. By magnetic concentration, 73% of the feed was recovered in a feldspar-quartz mixture with an iron content of 0.81% of Fe₂O₃. From this nonmagnetic product, between 85% and 90% of the feldspar with an iron content of 0.41 to 0.52% of Fe₂O₃ was recovered by agglomerate tabling and flotation. Examination of the feldspar concentrate, however, showed that iron stains and iron-bearing impurities of microscopic size in the feldspar prevented the separation of a feldspar concentrate with less than 0.36% of Fe₂O₃.