A quick and reliable algorithm is proposed to evaluate the feasibility of a double-feed reactive distillation column on the basis of the projection method (AIChE J. 2001, 47, 1333). A critical composition region is introduced where liquid seems to be more volatile than its equilibrated vapor in the projected space. If this critical composition region is spread along the entire binary edge of an upper feed and a top product in the original composition space, then a double-feed column cannot produce desired products. Otherwise, outside the critical composition region, single-stage calculations are carried out under potential pinch points to determine upper and lower bounds of the internal reflux ratio. If the permissible range of the reflux ratio near a pure product vertex overlaps with all the other permissible reflux ranges in one projected space, then a double-feed column can produce specified products.