The concept of operation map is applied to a two-dimensional graph, which axes correspond to the input variables (oxygen/fuel ratio in x and steam/fuel ratio in y) where the main output variables evolution (temperature, efficiency and concentration of the main components of the gas) is plotted by using constant value lines.
Maximum and minimum values of the output variables determine the region or the window where the gasifier should be operated. Since there are two degrees of freedom, there are several ways to modify the value of an output variable and the choice of the best one depends on the other output variables. So that, a graph which shows all important variables is very useful to operate the gasifier in a safe and efficient way. In Fig. 5, an operation map built by using the model is shown. This map has been plotted by using information from a real operation period and by modifying oxygen and steam ratios. As it can be seen, when oxygen or steam increases, CO2 increases and CO decreases. When oxygen increases or steam decreases, temperature increases and H2 decreases. In a variable conversion model, when temperature decreases, fuel conversion decreases. As a result, CGE reaches a maximum and the other lines are curved.