Abstract: A baffle employs a particular arrangement of baffle plates in a three dimensional configuration to aerodynamically separate popcorn ash particles from a flue gas flow. The baffle is attached to the rear wall of an economizer outlet flue back pass and is placed just below the economizer gas outlet. The baffle is designed to be uniquely shaped in three dimensions to redirect the large popcorn ash particles towards the deepest parts of the hoppers, which increases the fraction of the ash particles that are captured in the hoppers and decreases the potential for plugging in downstream equipment. The baffle is comprised of several triangular plates, usually three plates for every hopper. Each group of three plates is placed such that they appear to be three sides of an inverted pyramid. The open, fourth side of each of these pyramid shapes is on the side of the baffle closest to the front wall.