Ejector for preparing ammonia by urea pyrolysis

The utility model discloses an ejector for preparing ammonia by urea pyrolysis. The ejector comprises a liquid-phase main pipe provided with a plurality of liquid jet holes, a gas-phase main pipe which sleeves the periphery of the liquid-phase main pipe and is provided with a plurality of gas jet holes matched with the liquid jet holes, and a protection cover which allows flue gas in a boiler to pass, is arranged outside the gas-phase main pipe and covers the gas jet holes and the liquid jet holes in the protection cover, wherein the gas jet holes and the liquid jet holes are matched. According to the ejector, the protection cover and the high-temperature flue gas in the boiler are same in temperature, a urea solution ejected into the boiler not only is in contact with the high-temperature flue gas, but also is in direct contact with the high-temperature protection cover, and the ejected atomized urea solution is in contact with the high-temperature flue gas in the boiler and the high-temperature protection c