i am currently designing a superheater as a shell and tube heat exchanger. i have done my energy balance around my superheater. The only componentent in my superheater right now is steam (h2O). I have calculated my Q.

Note: saturated steam is being converted to superheated steam from 300K to 800K.

I need to calculated the amount of fuel/ mass flowrate of fuel I need to combust to achieve this. i will be combusting ch4. im not sure how to go about this. Can you please guide me, thank you.