Calcining method and apparatus

Claim 1

A LIME KILN COMPRISING A SUBSTANTIALLY VERTICAL SHAFT HAVING AN UPPER STONE INLET, EXHAUST MEANS IN THE UPPER PORTION OF THE SHAFT BELOW SAID STONE INLET FOR WITHDRAWING SUBSTANTIALLY ALL SPENT GASES FROM THE UPPER PORTION OF THE KILN AND DETERMINING THE LOWER END OF A STORAGE ZONE AND THE UPPER END OF A PREHEATING ZONE, SAID SHAFT HAVING A LOWER LIME OUTLET WITH FUEL-FREE AIR INLET MEANS CONNECTED THEREWITH AND DETERMINING THE LOWER END OF A LIME COOLING ZONE, FUEL INJECTION MEANS CONNECTED WITH THE SHAFT AT A LEVEL ABOVE SAID AIR INLET MEANS AND DETERMINING THE LOWER END OF A FIRST COMBUSTION ZONE, A PLURALITY OF AIR INJECTION MEANS AT SPACED LEVELS ABOVE SAID FUEL INJECTION MEANS, SAID SPACED AIR INJECTION MEANS DETERMINING A SECOND COMBUSTION ZONE BETWEEN THEIR LEVELS AND THE BOTTOM OF A THIRD COMBUSTION ZONE ABOVE THEM, MEANS FOR ABSTRACTING SOME AIR FROM THE SHAFT AT A LEVEL BETWEEN SAID AIR INLET MEANS AND FUEL INJECTION MEANS AND FOR DELIVERING THE ABSTRACTED AIR TO SAID PLURALITY OF AIR INJECTION MEANS FOR USE AS SECONDARY COMBUSTION AIR FOR THE FUEL, THE REMAINING UNABSTRACTED AIR BEING DRAWN UPWARDLY THROUGH THE SHAFT BY SAID EXHAUST MEANS TO FUNCTION AS PRIMARY AIR FOR COMBUSTION OF THE FUEL, WHEREBY A FUEL-FREE CALCINATION FINISHING ZONE IS ESTABLISHED IN THE COOLING ZONE BELOW SAID FUEL INJECTION MEANS, AND WHEREBY FIRST, SECOND AND THIRD CALCINING ZONES SUBJECT TO AIR-FUEL COMBUSTION ARE ESTABLISHED IN DESCENDING ORDER BELOW SAID PREHEATING ZONE.