The bottom and middle of the inner cavity of the washing device are respectively provided with a sieve plate. The sieve plate in the middle divides the inner cavity of the washing device into upper and lower cavities. The lower cavity is provided with a lower packing structure, the upper cavity is provided with an upper packing structure, and the packing structure of the upper cavity is also provided with a spray coil. The spray coil is connected with the external water inlet pipe, and the top of the washing device is provided with an air outlet It can make the gas and liquid contact evenly, separate the gas from the alkali mist, and purify the gas and recover the liquid at the same time