The efficiency of cold gas is actually only 23%

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I recently used Aspen Plus to conduct gasification simulations, and the input parameters and simulation results are as follows: Coal feed rate: 87,500 kg/hr; HHV: 25.52 MJ/kg; 9,781.6 Btu/lb (1 kg = 2.2046 lb; unit conversion note). The composition and parameters of the resulting gas are as follows: Temperature: 1,401.7°C; Pressure: 28 kg/sq cm; Vapor fraction: 1; Mole flow rate: 7,067.961 kmol/hr; Mass flow rate: 16,561.2105 kg/hr; Enthalpy: -491.207 MMBtu/hr. The mole percentages are as follows: CO: 0.59%, CO2: 0.088%, H2: 0.197%, CH4: 8.2×10^-6%, O2: 0.001%, N2: 0.035%, Ar: 3.00×10^-6%, H2S: 0.002%, COS: 2.07×10^-4%, NH3: 2.30×10^-5%, H2O: 0.087%. I will first explain my calculation method, and I hope experts can provide feedback: Cold gas efficiency = Heat value of the gas / Heat value of the coal (high calorific values are used here; it’s not clear whether the Enthalpy value in the gas parameters refers to the high calorific value). For the heat value of the gas, I have used the Enthalpy value itself； 491.207 MMBtu/hr. Denominator: heat value of coal, q=25.52 MJ/kg; HHV per 1 kg = m*q = 87500*25.52 = 2232743.275 MJ/hr (total heat value). HHV in MMBtu/hr = 2116.143754 MMBtu/hr (the unit for the total heat value has been changed). Thus, the efficiency of cold gas is 491.207/2116.143 = 23%. Personally, I think there must be an issue with the heat value of the gas as calculated by the simulation; otherwise, the efficiency of cold gas couldn’t be so low ； (2) My approach is incorrect; I hope experts can explain it in detail