Study On Drum Coating Technique And Its Effect On Nutrients Release Characteristics Of Coated Fertilizer

In order to establish a high efficiency,low cost of drum coating process and technology,and replacement costs are relatively high and the efficiency is relatively low at the bottom of the spray fluidization coated craft and technology,based on the change of such factors as the ratio of coating materials,coating process parameters under the condition of drum process and bottom spray fluidization were used respectively to manufacture coated controlled release fertilizer coated process,and under the condition of same temperature compared two kinds of process of nutrient release characteristics of coated controlled release fertilizer,drum coating process and technology system research and evaluation of stability and reproducibility,for its application in the coated controlled release fertilizer industry to provide theory basis.The main research results and conclusions are as follows:1.The drum coating process has good stability and can produce coated controlled release fertilizers with excellent controlled release performance and stable product quality.The characteristic curve of nutrient release of coated fertilizer was of "S" type when it reached the national standard.Nutrient release includes three stages: slow release stage,fast release stage and trailing stage.2.For coated controlled-release fertilizers with an envelop thickness of 3%-6% and a fertilizer efficiency of 49d-165 d,the initial dissolution rate is between 0.01% and 0.60%,far less than the maximum value of 15% stipulated by national standards,and the differential dissolution rate is only between 0.01% and 1.33%.Increasing the envelop thickness can increase the envelop integrity and the fertilizer effect period of the coating fertilizer of drum coating process,which can reduce the initial dissolution rate and differential dissolution rate of the coating fertilizer,and at the same time extend the fertilizer effect period of the coating fertilizer,that is to say,increase the fertilizer retention capacity at the early stage of the coating fertilizer and extend the fertilizer supply period.The results also showed that the controlled release performance of coated fertilizer could be controlled by adjusting the technological parameters.3.Changing the ratio of film materials can change the length of the carbon chain in the film layer,the proportion of hydrophilic and hydrophobic groups,and further affect the membrane microstructure and the physical and chemical characteristics of the film layer,thus affecting the controlled release performance of the coated fertilizer.The optimum oil-solid ratio of vegetable oil and curing agent was 1:0.8.4.The Richards equation can accurately describe the nutrient release characteristics of the coated controlled release fertilizer.Therefore,the Richards equation of the nutrient release curve of the coated controlled release fertilizer can accurately predict the nutrient release rate and release period of the coated fertilizer.5.Training temperature 15 ℃ nutrient release characteristics of coated fertilizer of rotating drum has great influence,show the release speed,slow release period,quick release period,trailing period three stages are shortened,exploiting the period from the original 49d-165-d reduced to 6.81 d,43.00 d,but not significantly affect the type of nutrient release curve.However,the temperature dependence of drum coated fertilizers with different film thickness and film material ratio was different.The consistent rule was that the temperature dependence of drum coated fertilizers decreased with the increase of film thickness and the oil/solid ratio decreased with the decrease of temperature dependence.The effect of temperature on nutrient release rate is the result of multiple factors.6.Under the optimal envelop process parameters,the nutrient release characteristic curves of both drum and fluidized bed envelop fertilizers are of "S" type,both of which have extremely low initial dissolution rate and differential dissolution rate,and relatively lower initial dissolution rate and differential dissolution rate of drum envelop fertilizers.When the envelop thickness was equal to 4%,the effective period of drum envelop fertilizer was 117 d,which was significantly larger than that of fluidized bed process envelop fertilizer(85d).When the coating thickness reached 5%,there was no significant difference between the two treatments.7.For each ton of coated fertilizer produced,the efficiency of the rotary drum process is three times that of the bottom spray fluidized bed process,and the energy consumption is reduced by 25%.Drum process is an alternative to fluidized bed process because of its high efficiency,low energy consumption and small minimum membrane material consumption.