EE AND CO-WORKER WERE SEALING A HOLE ON THE 3RD STAGE EXPANSION JOINT ON THE 2ND FLOOR OF THE PREHEATER TOWER. CO-WORKER WAS CROUCHED ON ONE SIDE OF THE PIPE SCRAPING OFF THE OLD PATCH. EE WAS CROUCHED ON THE OTHER SIDE OF THE PIPING IN FRONT OF THE OPEN HOLE. HOT MATERIAL SPEWED FROM THECRACK IN THE PIPE AND STRUCK EE AROUND THE RT. EAR, FACE AND ARM. SMALL 2ND DEG. BURN ON EAR.