Abstract: There will be a lot of by-product salt slag when producing hydrazine hydrate by urea method.However,the salt slag contains lots of impurities,which have not been effectively utilized.A new reasonable way of utilizing hydrazine hydrate by-product salt slag was introduced,i.e.seperate the salt and alkali in the by-product by saline wash,and alkaline liquor and solid sodium chloride could be obtained; and then utilizing Na₂CO₃ and NaOH in the liquor to produce sodium fluoride (NaF).This process not only recycled the sodium chloride and alkali in the salt slag and by-produced white carbon black,but also solved the problem of environmental pollution.Influences of various factors on product quality and recovery were also studied and the optimum processing conditions were obtained as follows:1) make sodium fluosilicate into a suspension and heated to about 60 ℃,then gradually dropping the liquor at the speed of 15~20 L/min;2) mass fraction of sodium carbonate in the liquor should be controlled at 20%~25% with a reaction temperature at 85~90 ℃;3) mass fraction of sodium chloride impurity in the liquor should be controlled at 15%~20%. 

Key words: hydrazine hydrate, salt slag, sodium fluosilicate, NaF