A stoker boiler heats liquid water at 200C to superheated steam at 4 MPa and 400C. Wood fuel which has an ultimate analysis (by mass on a dry basis) as 61.4% C, 5.79% H2, 25.31% O2, 1.09% N2, 1.41% S, and 5% ash (non-combustibles) is burned steadily with 50% excess air in the boiler. The fuel and air enter this boiler at standard conditions and the products of combustion in the smokestack are at 127C. Assume that sulfur dioxide has an enthalpy of formation of -297.1 MJ/kmol and an average specific heat capacity at constant pressure of 41.7 kJ/kmol-K. Write a balanced chemical equation for the combustion reaction and hence determine the air fuel- ratio. Prepare a 'mass balance diagram' for the boiler. Calculate the LHV (lower heating value) combustion efficiency and the quantity of steam generated per unit mass of fuel burned.