共查询到18条相似文献,搜索用时 78 毫秒
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聚氨酯包膜控释尿素制备工艺与养分释放特性研究 总被引:4,自引:0,他引:4
4,4'-二苯基甲烷二异氰酸酯(MDI)与植物油多元醇均匀喷涂在流化状态的尿素颗粒表面并发生化学反应,形成聚氨酯膜层。以侧喷流化床包膜工艺为基础,通过研究包膜量、反应温度、反应物比例等不同工艺条件下包膜尿素的养分释放性能,获得的生产聚氨酯包膜尿素的最佳工艺条件为反应温度75℃、MDI与植物油质量比1.0:1.0、反应时间20 min、催化剂用量0.40%(质量分数)、包膜比率为4.0%(质量分数),此包膜控释尿素的养分释放周期可达70 d。 相似文献
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采用静水溶出率法,在不损伤包膜的情况下,找出高温(50℃)静水浸提树脂包膜尿素与常温(25℃)静水浸提时间的相关系数。结果表明:通过50℃静水浸提来检测相应指标,可以有效缩短缓释肥料国家标准(GB/T23348-2009)和控释肥料行业标准(HG/T4215-2011)采用的25℃静水浸提检测所需的时间;树脂包膜尿素养分累积释放曲线相关系数均≥0.9900,呈极显著水平;检测时间只需8—10d,测量误差范围在2%-3%。 相似文献
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介绍了脲醛树脂包膜尿素的制备方法,研究了脲醛树脂及植物油用量对脲醛树脂包膜尿素氮初期溶出率的影响。结果表明,包膜量越多,包膜尿素氮的溶出率越低,但使用脲醛树脂直接包膜尿素的方法并不理想;先使用植物油在尿素颗粒的表面包一层油膜,再使用脲醛树脂包膜,可大幅度降低包膜尿素氮的溶出率,在使用1.0%的植物油后,树脂包膜量为15%时,氮的初期溶出率即可低于40%,大大降低包膜材料的使用量。 相似文献
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通过试验研究了脲醛缓释肥、脲醛缓释肥加尿素及尿素等6个养分投入量相同的处理对橡胶树胶水产量的影响.试验结果表明,施用脲醛缓释肥,提高了橡胶树胶水产量,以肥料中掺混60%脲醛缓释肥和40%普通尿素一次性施用效果最好,既降低了施用脲醛缓释肥的成本,又节省了劳动力. 相似文献
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Babar Azeem Zakaria Man Sayed Ameenuddin Irfan 《Chemical Engineering Communications》2018,205(10):1397-1414
To impede nitrogen loss due to leaching and NH3 volatilization, pristine urea particles are coated with synthetic polymers such as poly(acrylic acid) and polyethylene for the controlled release of nitrogen. However, due to nonbiodegradability and environmental and economic issues, these synthetic polymers are replaced with cheap, biodegradable, and green coating materials. In this study, borax-modified starch biopolymer is used to produce controlled release urea (CRU) in a tumbling fluidized bed. Central composite rotatable design is used to study the interactive effect of process parameters on time and kinetics of nitrogen release. Nitrogen release in distilled water is monitored by the UV–Vis spectrophotometer and soil burial test is used to observe release in soil. The optimum values of process parameters and response objectives generated by the analysis of variance are validated by triplicates of confirmation runs and the % error is reported as a precision indicator. A mathematical model is used to determine the diffusion coefficient of nitrogen release. Biopolymer-coated urea results in much better release performance when compared with starch-based CRU reported in the literature. The most influential process parameter both for time and kinetics of nitrogen release appears to be the coating time. Release time increases linearly with coating time and the diffusion coefficient decreases with increase in coating time. The kinetic study reveals that some of the samples followed non-Fickian diffusion and others followed Case-II transport during the release of nitrogen. 相似文献
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Factors affecting N release of urea from reactive layer coated urea 总被引:13,自引:0,他引:13
C. B. Christianson 《Nutrient Cycling in Agroecosystems》1988,16(3):273-284
An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to 56 days to study the effect of factors such as temperature, pH, soil moisture, and organic C additions on N release. The N release rate from RLCU was shown to be increased with increasing temperature and decreasing coating thickness. It was unaffected by the addition of lime to raise the pH or organic carbon sources to increase microbial activity. Although a slight effect of soil moisture was noted, it was not pronounced. Urea release tended to be in two stages — a constant diffusive stage in which, it is postulated, urea was still dissolving within the granule and diffusing to the soil at a constant rate and a slower logarithmic stage where the rate of release decreased with time. 相似文献
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