The invention relates to a recycling method for
phosgene in
tail gas generated in
calorescence reaction for synthesizing normal-
butyl isocyanate. The recycling method comprises the steps of continuously cooling and absorbing the
tail gas generated in the
calorescence reaction for synthesizing the normal-
butyl isocyanate through a low temperature
solvent, and condensing the
tail gas through a condenser, wherein the non-condensing gas directly enters a tail gas
processing system; preparing normal-butyl
acyl chloride from the
solvent containing the
phosgene with certain quality concentration through cold light reaction, metering the
phosgene-containing
solvent, shifting the solvent into a cold light kettle, dropwise adding n-
butylamine at -8 DEG C to -2 DEG C, after the dropwise adding, keeping the temperature for 1 hour so as to obtain the n-
butylamine acyl chloride; and resolving the n-
butylamine acyl chloride in a
calorescence reaction kettle to obtain the normal-
butyl isocyanate. The method provided by the invention has the advantages that the phosgene is utilized to the greatest extent, the load of the tail gas generated in the normal-butyl
isocyanate calorescence reaction in a tail gas
processing system and the alkali charge during tail gas
processing are reduced, the production cost of the product is reduced, and the purpose of saving and recycling resources is achieved.