Investigation Of Intermixture's Physicochemical Property In The Production Process Of Compound Fertilizers

With the flying development of chemurgy and fertilizer, compound fertilizers hasbecome the main force of the fertilizers industry. The production technology ofcompound fertilizers has drived to maturity stage after several decads' development,while, there are still several hard nuts to crack. Started from settling the disadvantagesof intermixture in the production process of compound fertilizers, the subjectresearched the critical relative humidity(CRH) of intermixture and the kinetics ofbiuret's generation mainly.The CRH is a important index of the hygroscopic of fertilizers. Started from thechemical congruence among single fertilizers, the subject researched the CRH ofintermixture in the production process of compound fertilizer which was affected byfertilizer formula, ambient temperature and mineral addition agent. From the resultsof investigation we can observed that the CRHs of intermixture has the same trendwith P₂O₅:K₂O when N's percentage composition was changless, has the same trendwith N:K₂O when P₂O₅'s percentage composition was changless, has the same trendwith N:P₂O₅when K₂O's percentage composition was changless at 30℃. From theCRH of intermixture of different fertilizer formulas at different temperature we know,not only the CRHs of intermixture reduce with the temperature's rise, but also thedepressed extent of CRHs of every fertilizer formulas reduce with the temperature'srise, whatever the N:P₂O₅:K₂O. Compared the CRHs of intermixtures whichcomprise mineral addition agent or not, the result indicates that the CRHs ofintermixtures which comprise mineral addition agent still reduce with thetemperature's rise, and the CRHs of intermixtures which comprise mineral additionagent less than that which not comprise mineral addition agent.Biuret generates from heated urea. When urea was heated temperture abovemelting point, two urea molecules become one biuret molecule and one ammoniamolecule by condensation reaction. Excessive biuret in compound fertilizer is harmfulto farm crops. The chlorophyl in crops will be damaged if crops absorb in biuret fromfertilizers, the photosynthesis and the growth of crops will be affected severely.In this thesis, we researched the generates of biuret in the production process ofcompound fertilizer mainly, the results can be divided into two parts as follows:1. the experimental research of biuret was generated. Four influencing factors: the concentration of urea's solution, reaction temperature, reaction time, amount ofwater of intermixture all has something to do with the generation of biuret in theproduction process of compound fertilizers. We can find from investigation results,the output of biuret rise with the reaction temperature's rise in the production process;the longer reaction time, the heavier output of biuret at the same reaction temperature;under the same heat up condition, the higher reaction temperature, the heavier outputof biuret; the much amount of water of intermixture, the heavier output of biuret at thesame reaction temperature.2. The kinetic investigation of biuret's generate. Kinetic curves have beendrawn up at 120℃, 130℃, 140℃and 150℃. From the curve and data we observedthat the reaction of biuret's generate belongs to liquid phase molecular reaction, it alsobelongs to organic homogeneous condensation chain reaction. We can get the kineticequations from these curves at different reaction temperature in different reaction timeas follows:120℃y = 0.703+0.00565x130℃j;=0.7244+0.00634x140℃y = 0.7585 + 0.0105x150℃y =0.8088 + 0.0151xCombining the four zero order reaction's kinetic equations with the Arrheniusequation, we calculated the activation energy of zero order reaction as follows:E_a=47.66kJ/molThe results show that the zero order reaction stage is controled by chemical reactions.