Chapter 9, Problem 9.64P

Methane at 25°C is burned in a boiler furnace with 10.0% excess air preheated to 100°C. Ninety percent of the methane fed is consumed, the product gas contains 10.0 mol CO₂/mol CO, and the combustion products leave the furnace at 400°C.

(a) Calculate the heat transferred from the furnace, $-\stackrel{\dot{}}{Q}\left(kW\right)$, for a basis of 100 mol CH₄fed/s. (The greater the value of $-\stackrel{\dot{}}{Q}$. the more steam is produced in the boiler.)

(b) Would the following changes increase or decrease the rate of steam production? (Assume the fuel feed rate and fractional conversion of methane remain constant.) Briefly explain your answers, (i) Increasing the temperature of the inlet air; (ii) increasing the percent excess air for a given stack gas temperature; (iii) increasing the selectivity of CO₂to CO formation in the furnace; and (iv) increasing the stack gas temperature.