Tuning unstable process of a superheated steam boiler through on-line efficiency modelling

This paper describes 2 mathematical models used to stabilize the behavior of the unstable loops of a superheated steam boiler operating on a constantly changing blast furnace gas fuel, and an on-line determination of the blast furnace gas calorific value. The superheated steam temperature loop, with dead times of 5-10 minutes, was modeled to obtain the shortest and most robust response time from the PID regulator. The overall efficiency of the system was computed on-line, and together with computing the losses on exhaust gases it allowed to determine the fuel calorific value, shortening the fuel change response and giving operator feedback.