Pretreatment Technology Of ADC Foaming Agent

ADC (Azodicarbonamide) foaming agent wastewater consisted of high concentration of NH4+-N and complex components, which is large quantity and hardly to treat. Air or steam stripping are often used to deal with this water in industry, whereas, the wastewater is not only rich in NH4+-N, but also have a lot of urea, hydrazine hydrate and other nitrogen-containing organic compounds, which are relatively stable under alkaline conditions and difficulty to remove, so it's unable to meet emissions standards. Air or steam stripping process need to adjust to pH value of 11 or above, large alkali consumption and high costs.Sodium hypochlorite can break up organic matter to small molecules with strong oxidation and have advantages of extensive sources and low prices. Therefore, it was regarded as an oxidation to decomposed urea and hydrazine hydrate in ADC wastewater in this paper. The effect of sodium hypochlorite dosage, reaction temperature, pH value, stirring speed, reaction time, air quantity on the removal of urea and hydrazine hydrate were investigated respectively. In order to reduce cost, the thesis adopted two-step dosing alkaline, with CaO and NaOH in the regulation of pH value. The results show that:(1) The dosage of sodium hypochlorite have the greatest impact on removal rate of urea and hydrazine hydrate. When the dosing coefficient a is 4.29 g-g-1, both removal rate can reach to 95%.(2) When the reaction temperature is 40℃, the removal effect of urea and hydrazine hydrate are best.(3) pH value and stirring speed have little effect on the urea and hydrazine hydrate removal respectively.(4) Reaction between urea and sodium hypochlorite can meet the removal requirements in 20min, but reaction of hydrazine hydrate with sodium hypochlorite can complete within a few minutes.(5) Bubbling agitation can increase urea removal rate by 8%, but have little effect on the removal of hydrazine hydrate.(6) CaO and NaOH adjusted pH values to 13 commonly, the lowest calcium content in solution, at the same time the quantity of NaOH reduce by 38%.