Which of the following is NOT a method of controlling superheater temperature?

Controlling superheater temperature is critical in steam engineering to ensure efficient operation and prevent overheating. Among the methods listed, pressure modulation is not typically used for this specific purpose.

Attemperation involves injecting water into the superheater or downstream of it to cool the steam slightly and thus control the temperature. This method is effective because it directly addresses the steam's temperature by adding a specific amount of cooler water.

Flue gas bypass refers to allowing some of the flue gases to bypass the superheater. By controlling the amount of gas flowing through the superheater, a more stable temperature can be maintained, reducing the risk of overheating.

Flue gas recirculation, on the other hand, involves reintroducing some of the flue gases back into the combustion process, which can help control the overall temperature of the gases entering the superheater and thus indirectly influence superheater temperature.

Pressure modulation, while a valuable tool in other aspects of steam system management, does not directly modify the temperature of the superheated steam in the context of controlling superheater temperatures, making it the least relevant technique among the options provided.