Chemical recovery unit

Claim 1

A CHEMICAL RECOVERY UNIT HAVING AN UPRIGHT FURNACE INTO WHICH BLACK RESIDUAL LIQUOR PRODUCED FROM KRAFT PULPING PROCESS IS INTRODUCED FOR BURNING AND SMELTING, SAID FURNACE HAVING THE INNER SURFACE OF ITS UPRIGHT WALLS LINED WITH STEAM GENERATING TUBES FORMING PART OF A STEAM GENERATING SYSTEM OPERATIVE TO GENERATE STEAM OF AT LEAST 900 POUNDS PER SQUARE INCH, THESE WALLS HAVING PRIMARY AIR INDUCTION PORTS THEREIN SPACED SOMEWHAT ABOVE THE FURNACE BOTTOM FOR DIRECTING AIR INWARDLY TOWARD A PILE OF SMELT AND BURNABLES ON THE BOTTOM OF THE FURNACE, SAID STEAM GENERATING TUBES AT THE REGION BELOW SAID PORTS HAVING SECURED TO THEIR SURFACE THAT IS DIRECTED INWARDLY OF THE FURNACE A STAINLESS STEEL METALLIC SHEET-LIKE MEANS GENERALLY CONFORMING TO SAID TUBE SURFACE, SAID METALLIC MEANS HAVING NUMEROUS RELATIVELY CLOSELY SPACED OPENINGS DISPERSED THROUGHOUT ITS AREA WITH A PORTION OF THIS MEANS BEING RETAINED IN SPACED RELATION FROM THE TUBES SUCH THAT A REFRACTORY IN A SEMIFLUID STATE MAY BE RECEIVED THEREBETWEEN, SAID METALLIC MEANS BEING WELDED TO THE TUBE AT NUMBEROUS LOCATIONS THROUGHOUT THE AREA OF SAID MEANS AND A LAYER OF REFRACTORY MATERIAL DISPOSED OVER AND ABOUT SAID METALLIC MEANS SUCH THAT THE METALLIC MEANS IS EMBEDDED THEREIN, WHEREBY THE METALLIC MEANS RETAINS SAID LAYER OF REFRACTORY MATRIAL IN PLACE INTERMEDIATE SAID TUBE REGION AND THE INTERIOR OF THE FURNACE.