NOVELTY - Purifying domestic garbage by thermal pyrolysis, involves: in pyrolysis gasification furnace, burning moisture-containing domestic garbage and oxygen to produce combustible gas containing e.g. carbon dioxide (CO2) and nitrogen (N2), smoke and slag and discharging flue gas; and recovering heat energy generated by flue gas having CO2, N2 and moisture to form medium-pressure steam, generating electricity by steam turbine and carrying out dust removing, deacidifying, removing heavy metal pollutant, and subjecting purified combustible gas to desulphurization and shift conversion reaction.    USE - For purifying domestic garbage by thermal pyrolysis in a pyrolysis gasification furnace, and converting the domestic garbage into a combustible gas by complete thermal pyrolysis, and synthesis of methanol and/or dimethyl ether and urea synthesis (claimed).    ADVANTAGE - The method can regulate the most optimum ratio of the synthetic biomass gas generating reaction components, to produce carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), nitrogen (N2), and further produce H2, ammonia (NH3) and a CO2 and urea; has heat efficiency of 30-40%; not only can realize domestic garbage, but also can realize zero discharge.    DETAILED DESCRIPTION - Purifying domestic garbage by thermal pyrolysis in a pyrolysis gasification furnace, and converting the domestic garbage into a combustible gas by complete thermal pyrolysis, and at the same time synthesis of methanol and/or dimethyl ether and urea synthesis through purifying and separating, and using electric power generation, where the method specifically involves: (1) thermal pyrolysis: in the pyrolysis gasification furnace, burning the moisture-containing domestic garbage and oxygen by a burner to produce a combustible gas containing carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), nitrogen (N2) and argon (Ar), smoke composed of CO2, N2, and moisture, and slag; allowing the combustible gas and slag to flow downwards and the smoke to flow upwards, and discharging the slag; discharging the flue gas reached the cleaning standard, through chimney and then further treating the combustible gas; (2) cooling: using a waste heat boiler for recovering the heat energy generated by the flue gas coming from the top of the pyrolysis gasification furnace, having a temperature of 400-500 degrees C and mainly composed of CO2, N2, and moisture in order to generate medium-pressure steam; generating electricity by a steam turbine or directly heating, and carrying out dust removing, deacidifying, and removing of the heavy metal pollutant; cooling to 60-70 degrees C and discharging through the chimney after reaching the standard; using a waste heat boiler or heat exchanger for recycling the heat energy of the combustible gas coming from the lower part of the pyrolysis gasification furnace, mainly composed of CO, CO2, H2, methane gas, N2, inert gas Ar, and possibly a small amount of hydrogen cyanide (HCN), halogen acid such as hydrochloric acid (HCl), hydrofluoric acid (HF), hydrogen sulfide (H2S), carbon monoxide sulfur (COS), an organic acid of the acidic substance and heavy metal pollutant, having a temperature of 160-200 degrees C in order to generate low-pressure steam for direct heating while decreasing the temperature to 35-45 degrees C; (3) dust removing: cooling the hot combustible gas stream and removing the dust from the combustible gas in lime-containing water in a venturi scrubber and a washing tower, where the washing water is good for reducing the thermal decomposition gasification process generating the HCN, HCl, HF, H2S, COS, organic acid substance and some heavy metal pollutant; using certain degree of lime washing water as the one of constituent of gasification agent in pyrolysis gasification furnace for gasification, and circulating the rest water to waste water treatment; (4) sulfur removal: subjecting the purified combustible gas to the desulphurization process, using or modifying the ADA method or a tannin or H/S method or KCA method of wet oxidation method desulfurizing technology, where the desulfurization efficiency can reach about 95%, and the content of the H2S is not greater than 30 mg/Nm3; and (5) conversion reaction: after desulfurizing, dividing the combustible gas into two parts, where one part of which is mixed with steam by segmentation method under catalyzing a shift conversion reaction condition, where the reaction equation is as given in the specification.