Desulfurization and denitrification steam boiler

The utility model discloses a desulfurization and denitrification steam boiler. The boiler comprises a boiler body and a spraying pipe, the outer side of the boiler body is connected with an air inletpipe; a first preheating section is arranged on the outer side of the air inlet pipe; a second preheating section is arranged at the rear end of the air inlet pipe; a flue gas pipeline is arranged onthe side surface of the boiler body; a heat exchange pipeline is arranged on the outer side of the flue gas pipeline; a circulating water pump is connected to the rear end of the heat exchange pipeline, a spiral pipe is connected to the rear end of the flue gas pipeline, the spraying pipe is located on the inner side of the spraying tank, spraying holes are formed in the lower side of the spraying pipe, a water collecting tank is arranged at the lower end of the spiral pipe, a water outlet pipe is connected to the lower side of the water collecting tank, and a heat preservation layer is arranged on the outer side of t