The invention relates to a purification method of hydrocyanic acid. In the method, a purification
raw material adopts 1-10% by weight of hydrocyanic
acid water solution. The purification method comprises the following steps of: preheating the purification
raw material to 40-60 DEG C, then introducing into a rectifying
tower, adding a
polymerization inhibitor, and performing
distillation under the conditions that the
tower top pressure is 10-90KPa negative pressure, the
tower top temperature is 0-25 DEG C, the tower kettle pressure is 20-95KPa negative pressure, the tower kettle temperature is 60-100 DEG C and the
reflux ratio is 3-15 so as to realize refining and purification of the hydrocyanic acid. The whole device comprises a
vacuum pump which is connected with a
reflux tank for operating and used for maintaining the negative pressure in the tower, and the trace hydrocyanic acid contained in
exhaust gas of the
vacuum pump is sent to an incinerator for
incineration treatment. According to the purification method disclosed by the invention, the
pressure difference between the tower top and the tower kettle is reduced, the
operation temperature is reduced, the
corrosion of all the devices can be avoided or reduced, and the
polymerization of the hydrocyanic acid is further eliminated, thus the quality of a hydrocyanic acid product and the yield thereof are further improved; and the purification method has the characteristics that the purification method is more economic, energy-saving, environment-friendly and
safer.