Advanced control solutions to increase efficiency of a furnace combustion process

In the present work the problem of the furnaces combustion optimization in petrochemical environment is presented. In particular, the paper is focused on the combustion efficiency that directly affects the operating costs of the plant. A preliminary study of the combustion process has been performed. A model of the system has been obtained by a black-box approach and limitations of the existing control architecture have been analyzed. A new control architecture, based on advanced PID control architecture, coupled “cross-limiting” control logics and Fuzzy logic has been developed and implemented in a Distributed Control System (DCS). The major benefits introduced by the new control system can be found in its reliability and in its robustness to compensate the measurable disturbances that affect the furnace. Moreover, the proposed control scheme has been proven to be effective in the reduction of the O₂ content in the exhaust of furnace gas as well as in the reduction of the fuel consumption. As a consequence of the O₂ reduction a reduction of the exhaust gas temperature has been achieved thus further increasing the furnace efficiency. The total efficiency increase has been estimated of about 2.2% with a significant energy saving of about 500 k€/year. Finally, the reduction of nitrogen oxide and carbon monoxide concentrations in the exhaust gases achieved by the new control strategy, allows minimizing the pollution emissions satisfying the actual national environmental requirements.