Abstract: A ball valve assembly for controlling flow of a mixture. The ball valve assembly includes a body with a cavity therein and a ball positioned in the cavity with a passage therethrough, and a low-pressure valve seat and a high-pressure valve seat for locating the ball therebetween. The ball is movable between an open position, in which flow of the mixture through the passage is permitted, and a closed position, in which flow of the mixture through the ball is substantially prevented. The low-pressure valve seat includes one or more scallops formed to permit movement of at least a portion of the solid particles past the low-pressure valve seat when the ball is in the open position.