Technique method for double-line production of polypropylene

The invention relates to a technique method for production of polypropylene, which comprises the following steps: adding propylene into two liquid-phase reactors for reaction with the pressure being 3.5MPa and the temperature being minus 5 DEG C; adding titanium catalysts, triethyl aluminum and diphenyl dimethoxy silane into a gas-phase reactor for reaction, with the aluminum-titanium being 100-160mol/mol, the aluminum-silicon ratio being 10-30mol/mol, the temperature being 69-70 DEG C, the pressure being 3.3-3.5MPa, the sera concentration being 130-200g/L, the material level being 30-70 percent; and the pressure reaches 2.6-3.0MPa and the material level reaches 25-45 percent, spraying circulating quenching liquid containing propylene and propane to the powder bed of the gas-phase reactor through the internal circulation of the gas-phase reactor, and sending the gas phase into a scrubbing system to remove impurities through the external circulation of the gas-phase reactor. The method can flexibly adjust the production capacity and the product quality, efficiently utilize the equipment, increase the reaction time, enhance the catalyst activity, enlarge the energy consumption adjusting room, and improve the reactor safety.