The invention discloses a 
liquid ammonia evaporator and a 
liquid ammonia evaporation system for 
flue gas denitration, wherein the 
liquid ammonia evaporator comprises a heat exchange chamber and a stainless steel heat exchange 
pipe which is arranged in the heat exchange chamber; the heat exchange chamber consists of a lower heat exchange chamber and an upper heat exchange chamber; a denitrated 
flue gas inlet is arranged at the top of the lower heat exchange chamber and a denitrated 
flue gas outlet is arranged at the bottom of the lower heat exchange chamber; a hot air inlet is arranged at the bottom of the upper heat exchange chamber and a hot air outlet is arranged at the top of the upper heat exchange chamber; the stainless steel heat exchange 
pipe comprises a primary heat exchange 
pipe which is arranged in the lower heat exchange chamber and a secondary 
evaporator heat exchange pipe which is arranged in the upper heat exchange chamber; the pipe wall of the secondary evaporator heat exchange pipe consists of an inner wall and an outer wall; evenly distributed 
millimeter-level small holes are arranged on the inner wall; and evenly distributed micron-level 
micro holes are arranged on the outer wall, according to the liquid 
ammonia evaporator, the heat exchange efficiency of liquid 
ammonia is greatly improved and an 
ammonia evaporation supply 
system is simplified; and the liquid ammonia 
evaporation system has a compact structure and is capable of fully utilizing the 
waste heat of 
flue gas and the heat of preheated air.