| The inorganic solid particles(sodium nitrate,inorganic compound fertilizer,etc.)has the characteristics of caking during storage.The agglomeration of inorganic solid particles is because of the combined effect of both themselves factors and environmental factors.Dissolution and recrystallization on the surface of the particles result in the formation of the salt bridging between the intergranular contact points,which make the particles bond together and have no flowability.Then the particles change into hard lumps gradually.The agglomeration of inorganic solid particles go against its sales and usage.The effective method to solve the problem of agglomeration is to coat the inorganic solid particle with anticaking agent.Surfactant is usually composed of both hydrophilic polar groups and hydrophobic nonpolar groups.The hydrophilic groups of the surfactant can be adsorbed onto the surface of the inorganic salt particles with the hydrophobic groups toward the gas phase.Therefore,the surface of the solid particles adsorbed surfactant become hydrophobic,which hinder the enter of water from atmosphere and suppresses the deliquescence of granular products.Adsorbing surfactant can reduce the capillary attraction,change the crystallization behavior,reduce the interfacial energy,and restrain nucleation of crystal particles,which result in good anti-caking effect.This paper talk about the anti-caking properties and mechanisms of the surfactant for single component chemical sodium nitrate particles as well as multi-component compound fertilizer granules.Saturated solution method was used to adsorb the surfactant onto the surface of sodium nitrate particles.And the isothermal adsorption and research about anti-caking properties and mechanism have been done.By researching,the structure of the adsorbed layer of the surfactant on the surface of sodium nitrate particles and the anti-caking mechanism have been ascertained,and the anti-caking treatment process of the surfactant has been optimized.Based on the characteristics of the production process of compound fertilizer granules,we designed a new type of liquid compound fertilizer anti-caking agent.Appropriate coating process was selected to coat the surface of compound fertilizer granules with anti-caking agent.Subsequently,the anti-caking properties and mechanisms,as well as the production process have been studied.Specific studies and conclusions are as follows:1.Research about the adsorption isotherms of the surfactant SDBS,SDS,CTAB and TX10 on the surface of sodium nitrate particles shows that,the adsorption process of surfactant SDS and TX10 on the surface of sodium nitrate particles conforms to the Langmuir adsorption isotherm model.it is single molecular layer adsorption.Under experimental conditions,the maximum absorption capacity Qmax is 0.065 mmol/kg for SDS and 0.027 mmol/kg for TX10 respectively.The adsorption process of surfactant SDBS and CTAB on the surface of sodium nitrate particles more accord with the Freundlich adsorption isotherm model,is the multilayer adsorption.Calculation of the molecular chain cross-sectional area shows that average molecular chain cross-sectional area of the surfactant SDS,SDBS,CTAB,TX10 on the surface of sodium nitrate particles is greater than their limit molecule area.Compared to TX10,the average molecular chain cross-sectional area of SDS is more close to its limit molecular chain cross-sectional area,the SDS on the surface of sodium nitrate particles tends to single molecular layer adsorption.It shows that the tightness of the surfactant to arrange(membrane density)is SDS>TX10.The average molecular chain cross-sectional area of SDBS and CTAB is greater than their limit molecular chain cross-sectional area,and the adsorption of SDBS and CTAB on the surface of sodium nitrate particles is multilayer adsorption,so the tightness of the surfactant to arrange(membrane density)is low.2.Saturated solution method was employed to study the influence of different surfactant for the anti-caking properties of sodium nitrate particles.Surfactant was adsorbed onto the surface of sodium nitrate particles,which was confirmed by Fourier transform infrared spectroscopy(FT-IR).Through the measurement of XRD,it is found that the crystal type of sodium nitrate particles is not change with the addition of surfactant.The test of SEM shows that the addition of surfactant makes the sodium nitrate particle more uniform.And the fine particles is disappeared,the contact area between the particles is reduced.Which make the adhesion between particles blocked.Based on the determination of agglomeration rate and amount of moisture absorption for sodium nitrate particles adsorbed surfactant,it is found that the anticaking effect of surfactant for sodium nitrate particles is SDS>TX10>CTAB>SDBS,respectively.Research on the anti-caking properties of mixed surfactant for sodium nitrate particles shows that when the SDS and TX10 compound with the mole ratio is 1:1 it has best anti-caking properties for sodium nitrate particles.3.A kind of liquid compound fertilizer anti-caking agent based on biological oil and surfactant as an important component has been developed.The analysis of the coated effect and addition amount of the compound fertilizer granules shows that adding 0.3%liquid anti-caking agent of compound fertilizer,the liquid anti-caking agent could evenly coat onto compound fertilizer granules.The SEM observation shows that after treating with the liquid anti-caking agent,a dense wrap formed on particles surface to reduce the entrance of water from the surface and restrain deliquescence of particles to hinder the formation of the salt bridge and the compound fertilizer particles has anti-caking effect.Through measurement of oil/water/gas three phase contact angle for the liquid anti-caking agent and the diffusion rate of the liquid anti-caking agent on the surface of compound fertilizer particles,it can be seen that the greater of the three phase contact angle and the faster of diffusion rate,the better anticaking effect.When the quality ratio of each component of anti-caking agent is DDAC:TX10:MO =1:0.5:18.5,adding 0.3%anti-caking agent of compound fertilizer,the agglomeration rate of compound fertilizer particles fall from 31.4%(blank sample)to 2.6%.4.Based on the analysis of the industrial production and economic benefit for sodium nitrate and compound fertilizer anti-caking agent,it can be seen that the sodium nitrate anticaking agent consisted of different surfactants and liquid compound fertilizer anticaking agent which are low-cost and raw materials are easily to be obtained.The anticaking agents do not affect the property of the sodium nitrate and compound fertilizer.Furthermore,the anticaking agents are non-toxic and odorless with excellent anti-caking performance which can be put into production with reliable technology,feasible process,high product quality and remarkable benefit. |
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