Vertical combined urea synthesis reactor and system comprising same

The invention discloses a vertical combined urea synthesis reactor and a system comprising the same for co-producing and preparing urea with tail gas of a melamine device. The vertical combined urea synthesis reactor comprises an upper reaction section, a lower gas stripping section, a gas-liquid distributor and a gas rising cap, wherein the gas-liquid distributor and the gas rising cap are arranged between the reaction section and the gas stripping section; methylamine decomposition steam stripping, methylamine condensation, urea synthesis and synthesis tail gas washing are achieved in one device, materials between the sections flow through pressure difference and density difference, an auxiliary power device is not needed, the urea synthesis high-pressure system process is simplified, the device arrangement is more compact, the use amount of high-pressure pipelines is reduced, and the device investment is lower. Materials flow in the condensation section from bottom to top, the heat transfer coefficient and