A vertical ring shaft kiln comprising • a vertical burning region having an intermediate sintering zone (Z 3 ) defined by a first wall and an opposite second wall , • a gap between the first wall and the second wall having a length (L) in a predetermined distance wherein the first wall and second wall are formed in a ring shape one inside the other, • a support wall connects the bottom part of the first wall and an opposite bottom part of the second wall with an outlet , • a number of burners having outer nozzles provided at the first wall and having inner nozzles provided the second wall to develop a flame in adjustable manner throughout the length (L) by injecting fuel and oxygen/air inside the sintering zone (Z3), characterized by further comprising • outer and inner auxiliary nozzles provided at a distance from the corresponding inner and outer nozzles to inject oxygen/air inside the sintering zone (Z3), • a number of heat sensors disposed at the outer side of the first wall providing actual heat change information at the first wall , • a detection unit producing a thermal map of the sintering zone (Z 3 ) to find over burned or unburned spots comparing a detected heat value (t d ) with the homogenous heat pattern previously set by a threshold heat value (t t ), • a control unit in connection with the detection unit , which providing a homogenous heating pattern at the unburned or over burned spots by changing the vertical flow speed (v f ) or by activating the neighboring corresponding burner or auxiliary nozzle, • a roller crusher provided at the outlet of the vertical burning region and fed by the sintered material thus determining the vertical flow speed (vf). • a vertical burning region having an intermediate sintering zone (Z 3 ) defined by a first wall and an opposite second wall , • a gap between the first wall and the second wall having a length (L) in a predetermined distance wherein the first wall and second wall are formed in a ring shape one inside the other, • a support wall connects the bottom part of the first wall and an opposite bottom part of the second wall with an outlet , • a number of burners having outer nozzles provided at the first wall and having inner nozzles provided the second wall to develop a flame in adjustable manner throughout the length (L) by injecting fuel and oxygen/air inside the sintering zone (Z3), • outer and inner auxiliary nozzles provided at a distance from the corresponding inner and outer nozzles to inject oxygen/air inside the sintering zone (Z3), • a number of heat sensors disposed at the outer side of the first wall providing actual heat change information at the first wall , • a detection unit producing a thermal map of the sintering zone (Z 3 ) to find over burned or unburned spots comparing a detected heat value (t d ) with the homogenous heat pattern previously set by a threshold heat value (t t ), • a control unit in connection with the detection unit , which providing a homogenous heating pattern at the unburned or over burned spots by changing the vertical flow speed (v f ) or by activating the neighboring corresponding burner or auxiliary nozzle, • a roller crusher provided at the outlet of the vertical burning region and fed by the sintered material thus determining the vertical flow speed (vf). <EOS>