The present invention relates to a method and apparatus for preparing
hydrazodicarbonamide using urea as starting material economically and
environmentally desirably. The apparatus includes a pyrolysis furnace to
obtain biuret and ammonia by pyrolyzing urea; a recrystallization reactor
to purify the biuret obtained from the pyrolysis furnace; a first reactor
to obtain an metal monohalobiuret salt by reacting the biuret with metal
hypohalogen compound or with halogen and base; a second reactor to
synthesize the hydrazodicarbonamide by reacting the monohalobiuret metal
salt with ammonia; and an ammonia evaporator to separate the excess
ammonia from hydrazodicarbonamide and to supply the separated ammonia to
an ammonia concentrator.