Semi coke tail gas temperature decreasing and purifying system

The invention discloses a semi coke tail gas temperature decreasing and purifying system which includes a spray column, a spiral forced-landing dehumidifier and a backwater temperature decreasing tank. The semi coke tail gas temperature decreasing and purifying system integrates temperature decreasing, washing, desulfuration and dehumidification. Impurities, such as sulfides, in coal gas are dissolved in water while the coal gas contacts with the water so that a desulfuration effect is achieved; particle substance is removed through the water so that a washing effect is achieved. Meanwhile, heat in the coal gas is absorbed by water and is discharged. In the spiral forced-landing dehumidifier, the water is discharged under gravity and forced-landing inertance. Meanwhile, the spray column and the spiral forced-landing dehumidifier have the effect of surface temperature decreasing. The water is in a gravity and cooling layer in the backwater temperature decreasing tank so that a cooling effect is achieved. Water, sulfides and impurities in processed tail gas is fully removed through the water. The coal gas is increased in calorific value and is reduced in consumption amount. Meanwhile, a waste discharge capacity is reduced.