Stirred tank reactor

The invention discloses a stirred tank reactor and aims at improving a stirring turbine in the stirred tank reactor by using a four-layer combination stirring turbine. The stirring turbine comprises a first layer turbine, a second layer turbine, a third layer turbine and a fourth layer turbine which are arranged from the middle to the bottom of a stirring shaft sequentially. The first layer turbine is an upward axial flow turbine, the second layer turbine is a disk type turbine, the third layer turbine is an upward axial flow turbine, and the fourth layer turbine is a radial flow turbine. Radial circulation close to a liquid level, radial circulation close to a middle area of a stirred tank and radial circulation in a bottom area of the stirred tank are formed, so that circulation quantity inside the stirred tank is big and mixing time is short. Poor mixing area does not exist, and solid containing rate and gas containing rate are evenly distributed. A mass transfer condition of air and liquid is good, and single transfer efficiency is high. Entrainment quantity of sizing is greatly reduced, fouling of a heat exchanger is reduced, and service life is long. Operation cost is lowered, and production cost is saved.