Flue Gas Recirculation Method and System for Combustion Systems

A method of recirculation of flue gas for a combustion system, the combustion system comprising in sequence at least one pre-combustion drying zone, at least one combustion zone, and at least a first cooling zone, the method comprising the steps of

• (i) providing a plurality of exhaust gas outlets comprising at least one exhaust gas outlet provided respectively to each pre-combustion drying zone and each combustion zone to allow a gaseous flow selectively to and through each exhaust gas outlet;
• (ii) providing at least one cooling zone intake means to each cooling zone;
• (iii) providing at least one flue gas delivery means each having at least one recirculation intake means and at least one delivery outlet;
• (iv) selecting at least one exhaust gas outlet from the plurality of exhaust gas outlets, and connecting the selected exhaust gas outlet to one of the recirculation intake means;
• (v) selectively delivering at least part of the gaseous flow from each selected exhaust gas outlet as a recirculation flow to the flue gas delivery means;
• (vi) selectively delivering at least part of the recirculation flow through one of the delivery outlets to the selected cooling zone intake means;
• (vii) monitoring at least periodically the temperatures and pressures in each cooling zone receiving the recirculation flow to determine temperature and pressure values;
• and
• (iv) adjusting the recirculation flow in response to the determined temperature and pressure values.