Biomass gasification gas purification system and method and methanol production system and method

A methanol production method comprising:

• gasifying biomass so as to produce biomass gasification gas;
• removing dust in the biomass gasification gas;
• desulfurizing sulfur oxide components in the biomass gasification gas that has had the dust removed therefrom so as to produce desulfurized biomass gasification gas;
• reforming tar components in the desulfurized biomass gasification gas using a pre-reforming reactor, the pre-reforming reactor having a catalyst with an allowable catalyst temperature;
• feeding at least one of natural gas and steam to the pre-reforming reactor during said reforming of tar components;
• obtaining an equilibrium constant from partial pressures of CH4, H2O, CO and H2 at an outlet of the pre-reforming reactor;
• determining amounts of the natural gas and steam feeding to the pre-reforming reactor in said feeding at least one of natural gas and steam to the pre-reforming reactor so that the equilibrium constant that is obtained from the partial pressures of CH4, H2O, CO and H2 at the outlet of the pre-reforming reactor will be the equilibrium constant corresponding to the allowable catalyst temperature at the pre-reforming reactor;
• boosting biomass gasification gas that has been through the pre-reforming reactor to produce a boosted gas;
• and
• synthesizing methanol by using H2 gas and CO gas contained in the boosted gas.