The invention relates to a 
flue gas desulphurization and denitration method as well as its apparatus, and especially relates to a desulphurization and denitration 
technology system for 
flue gas from large-scale mobile facilities such as ships. The method comprises the following steps: 
flue gas is passed through a 
heat pipe exchanger and a 
heat pump in order for increasing temperature of 
flue gas, and 
flue gas is selectively passed through an electric heater for heating to the temperature of 340-350 DEG C, an 
urea solution is used for preparing 
ammonia gas in a 
hydrolysis reactor, 
ammonia gas is diluted by partial high temperature 
flue gas at an outlet of a SCR reactor and then mixed for injecting flue gas which is undenitrated, the mixed flue gas enters into the SCR reactor for a flue gas denitration reaction, the flue gas after denitration is passed through the 
heat exchanger, the 
heat pump and the 
hydrolysis reactor and cooled, and then enters into a desulfurization 
tower, flue gas after desulphurization is directly discharged into 
atmosphere, and an absorption liquid adds alkali and 
seawater for regeneration and cycle usage. In the method, the 
heat exchanger and the 
heat pump are used for recovering 
waste heat of flue gas, and the 
energy consumption is greatly reduced. The 
ammonia production method through 
hydrolysis is capable of increasing the mixing degree of ammonia and flue gas, so that denitration efficiency can be further increased.