Methane (CH4), an important ingredient in the chemical and petrochemical industries, can come from natural gas as well as from solid hydrocarbons like

biomass or coal. For the latter source, the hydrocarbon is hydrogenated to produce synthetic gas, or substitute natural gas (SNG). The overall reaction for SNG production may be expressed as

C + 2H2 ^ CH4 — 74,800 kJ/kmol (1.14)

More details on these reactions are given in Chapters 5 and 9.

Symbols and Nomenclature

LHV = lower heating value of gas (kJ/mol)

Hc = combustion efficiency (-)

Hs = steam turbine efficiency (-)

Ha = efficiency of combustion and steam turbine (-)

Hg = gas turbine efficiency (-)

Hcc = combined efficiency of steam turbine and gas turbine (-)

Hb = overall efficiency, including gasification efficiency (-)

T1 = inlet steam temperature in the steam turbine (K)

T2 = exhaust steam temperature in the steam turbine (K)

Tgj = inlet temperature in the gas turbine (K)

Tg2 = exhaust temperature in the gas turbine (K)