Improvement Of Biurea Production By Urea And Waste Water Resources

Biurea is an important intermediate of azobisformamide foaming agent (ADC), as well as the besteffect of military fire retarding agent. Domestic mainly uses the method of urea production, plenty of wasteliquid generated in the process, mainly as NH3-N, COD, Cl-, SO2-4, Na+, SS and other small amounts ofsubstances. The waste liquid constituents more complex phase, which enterprise cannot effectively dealwith because of the high processing costs; If we direct emission without handle, it can cause seriouspollution to the environment. Therefore, wastewater treatment technology is a long-term failure to solve theproblem, which directly impact on the development and survival of ADC industry.In this paper, we pretreat the biurea wastewater by the traditional method of urea production, degradeammonia and organic nitrogen with ultrasound-stripping method and ozone oxidation method in turn. Dueto the composition of salt is complicated, it cannot be effectively separated, and thus we improve theprocess, using hydrochloric acid instead of sulfuric acid to prepare biurea. For the salt-water system afterimproving process, phase diagram was drawn, through analysis and calculations, the salts were recycled,the results were as follows:(1) using the method of ultrasound-stripping to remove industrial biurea wastewater, mainly examinesthe factors influencing the removal rate of a ammonia nitrogen,including wastewater pH, temperature,aeration, aeration gas type, ultrasonic power. The experimental results showed that: controlling the pHvalue of10, stripping temperature is30℃, aeration rate1.0L·min-1, the ultrasonic power is400W,ammonia nitrogen removal rate reached more than92%, removal rate of CODCr reached18%. Then usingozone oxidation process for secondary treatment, effects of pH, temperature and flow rate of ozone werestudied to remove ammonia and organic nitrogen in wastewater. The experimental results showed that:controlling the pH value of10, the temperature of20℃, ozone flow3.0L·min-1, ammonia and organicnitrogen removal rate reached91%and95%respectively. After two technical processing, the totalammonia and organic nitrogen removal rate reached99%and97%.(2) Improving the synthetic process with hydrochloric acid instead of sulfuric acid synthesi to producebiurea. under the condition of acid, factors that affect product yield were stuied, incluing the pH value, ratio of hydrazine and urea, reaction temperature, reaction time, acid addition order. Results show that: when pHvalue of3~5, ratio of urea dosage amount and theoretical amount is1.4:1.0, when heated to105℃andmaintain the temperature10h, biurea yield can reach97%. It has well repeatability and high product yield,the melting point of biurea under optimum conditions was determined, and infrared spectra was analysised,it showed that the purity of the product is high.(3) The ternary solid liquid equilibrium of salt water system Na+,NH4+//Cl--H2O was studied using wetslag method, solubility data of NaCl and NH4Cl in water was measured, and then we draw the phasediagram. By analyzing and calculating the phase diagram, the salt resource were recycled after processimprovement, the purity of NaCl reached95%, which can be used as a raw material within companies. Thepurity of NH4Cl reached92%, which nitrogen content is more than24%, which completely satisfy therequirements of agricultural ammonium chloride (GB/T2946-2946). On the one hand, it reduce theenvironmental pollution caused by waste water, on the other hand, the waste reasonable used, accordingwiththe idea of green production..