MMU系统防凝胶新配方可行性探讨

针对TEC流化床造粒技术附属MMU系统在生产实践中经常容易生成凝胶堵塞的问题,结合工艺相似并且十分成熟的脲醛树脂生产工艺,提出了一套既能防止凝胶产生,又能有效除尽游离甲醛的新配方。     

MMU系统反应机理分析和防凝胶结堵的改进

对TEC流化床造粒大颗粒尿素生产装置的单羟甲基脲(MMU)系统反应机理进行了分析.为防止MMU的聚合反应、减少反应液凝胶生成量、避免堵塞设备和管道,通过调整配料中甲醛与尿素的摩尔比,实现了MMU系统的平稳运行,满足了大颗粒尿素生产要求.     

浅析TEC大颗粒造粒工艺的3个核心问题

提出和剖析了TEC大颗粒尿素工艺中的3个核心问题:①尿素颗粒的成长时间对产品水含量的影响;②破碎机的负荷与辊间距调多大才能满足工艺生产要求;③MMU储槽中的溶液组分与凝胶结堵现象。结果表明,通过揭示3个核心问题与产品质量的内在关系,可采取相应措施,优化操作,提高产品质量。     

MMU装置防堵塞技改总结

介绍并分析了MMU(单羟甲基尿素)的合成机理,并对实际生产中遇到的易堵塞难题所采取的各种对策措施进行总结。     

加甲醛对尿素质量和尿素系统的影响初探

探索尿素装置中加入甲醛后尿素质量的改进和甲醛对尿素系统的影响以及甲醛对尿素系统的影响以及甲醛对尿系统的样品测定带来的干扰。     

三聚氰胺尾气循环至尿素合成系统

尿素制备三聚氰胺过程中产生的尾气主要含氮和二氧化碳，用甲铵溶液或尿素溶液对尾气进行二段吸收，然后返回到尿素合成系统。在第一段吸收过程中，用来吸收尾气的溶液量不足收全部尾气，将第一段吸收后的溶液和剩余的尾气分别压缩至溶液可以吸收全部尾气的压力，所生成的溶液返回到尿素装置的合成系统。     

甲醛对尿素质量和尿素系统的影响

探讨加入甲醛对尿素质量和尿素系统的影响以及甲醛对尿素系统的样品测定带来的干扰。     

提高尿素产品外观质量的技改措施

塔里木油田塔西南石化厂为解决尿素产品板结的问题,采用了在尿素中加入甲醛的技改方案。介绍了甲醛及其水溶液的理化性质;简述了在尿素中添加甲醛溶液的工艺原理和工艺流程。监测分析结果表明：控制尿素中甲醛含量在0.18%～0.3%之间时,尿素中总氮、水分、缩二脲含量无明显变化,而尿素颗粒强度明显提高,由未添加甲醛前的7.3 N提高到8.6 N。此外,尿素产品的粉尘量明显减少,尿素成品粒度由98%上升到98.5%。     

改变水溶性聚乙烯醇缩甲醛溶液粘度的方法

研究了改变水溶性聚乙烯醇缩甲醛溶液粘度的各种因素,包括未中和缩醛溶液及加一定量的尿素后,对产物粘度的影响,得出了提高低固含量水溶性聚乙烯醇缩醛溶液粘度的有效方法。     

我公司尿素造粒试验总结

淮化“18·30工程”尿素装置采用意大利斯拉姆公司生产工艺,日产尿素900t。该工程于1999年10月初步建成,具备吹扫及单体试车条件,12月18日,蒸发系统进行造粒试验,水解、解吸系统也同时进行化工试车。1　造粒方案的确定传统造粒方法:将成品尿素倒入尿液槽,再将冷凝液用尿液泵循环加热,以溶解尿素,制成60%～70%的尿素溶液。该方法缺点是将成品尿素倒入尿液槽,劳动强度大;尿液中混入的杂质多,特别是编织袋边丝带入系统使泵入口过滤器堵塞,也造成造粒喷头堵;尿素溶解时间长,造粒尿素中缩二脲含量高;尿素溶解过程中水解量大,氨味重,污染环境,投入…     

改性脲醛树脂用于水平井堵水的实验研究

陆粱油田大部分水平井已进人中高含水期,为稳油控水,提高采收率,介绍了一种可应用于水平井堵水的新型改性脲醛树脂,在分析其固化机理的基础上,通过性能影响实验和单管岩心流动实验评价了该堵剂体系的性能以及影响因素。改性脲醛树脂固化结果受温度影响大,低于40℃的条件下不能固化成韧性固体;通过调节剂控制固化时间,固化时间调节范围广;封堵强度高,注人性和耐冲刷性好,适宜于陆梁油田水平井堵水应用。     

13C‐NMR study on the structure of phenol‐urea‐formaldehyde resins prepared by methylolureas and phenol

Phenol‐urea‐formaldehyde (PUF) resins were synthesized by reacting mixture of methylolureas (MMU), phenol, and formaldehyde. The structure of PUF cocondensed resins at different stages of reaction were analyzed by liquid ¹³C nuclear magnetic resonance (NMR) spectroscopy. The liquid ¹³C‐NMR analysis indicated that methylolureas had the dominant content in MMU with the reaction between urea and formaldehyde under the alkaline condition. The PUF cocondensed resins had no free formaldehyde. methylolureas were well incorporated into the cocondensed resins by reacting with phenolic units to form cocondensed methylene bridges. The second formaldehyde influenced the further reaction and the structure of the PUF resins. The resins with the prepared method of PUFB possessed relatively high degree of polymerization and low proportion of unreacted methylol groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fast advancement and hardening acceleration of low‐condensation alkaline PF resins by esters and copolymerized urea

Low‐condensation phenol‐formaldehyde (PF) resins coreacted under alkaline conditions with up to 42% molar urea on phenol during resin preparation yielded PUF resins capable of faster hardening times than equivalent pure PF resins prepared under identical conditions and presented better performance than the latter. The water resistance of the PUF resins prepared seemed comparable to pure PF resins when used as adhesives for wood particleboard. Part of the urea was found by ¹³C‐NMR to be copolymerized to yield the alkaline PUF resin; whereas, especially at the higher levels of urea addition, unreacted urea was still present in the resin. Increase of the initial formaldehyde to phenol molar ratio decreased considerably the proportion of unreacted urea and increased the proportion of PUF resin. A coreaction scheme of phenolic and aminoplastic methylol groups with reactive phenol and urea sites based on previous model compounds work has been proposed, copolymerized urea functioning as a prebranching molecule in the forming, hardened resin network. The PUF resins prepared were capable of further noticeable curing acceleration by addition of ester accelerators; namely, glycerol triacetate (triacetin), to reach gel times as fast as those characteristic of catalyzed aminoplastic resins, but at wet strength values characteristic of exterior PF resins. Synergy between the relative amounts of copolymerized urea and ester accelerator was very noticeable at the lower levels of the two parameters, but this effect decreased in intensity toward the higher percentages of urea and triacetin. ¹³C‐NMR assignements of the relevant peaks of the PUF resins are reported and compared with what has been reported in the literature for mixed, coreacted model compounds and pure PF and urea‐formaldehyde (UF) resins. The relative performance of the different PUF resins prepared was checked under different conditions by thermomechanical analysis (TMA) and by preparation of wood particleboard, and the capability of the accelerated PUF resins to achieve press times as fast as those of aminoplastic (UF and others) resins was confirmed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 359–378, 1999     

环保型脲醛树脂胶粘剂的低温合成

本文根据尿素与甲醛加成一缩合反应机理，通过控制脲醛树脂生产过程中尿素与甲醛的摩尔比，加入聚乙烯醇改进其初粘性，加入三聚氰胺改进其耐水性并加入甲醛捕捉剂降低产品中的游离甲醛含量。采用二次缩聚工艺，控制脲醛比pH值以及反应温度来减少脲醛树脂中游离甲醛的含量。在较强酸度、低温度条件下实现了树脂的合成，减少了能源消耗。     

交联魔芋葡甘聚糖水凝胶包裹尿素的缓释效果

以魔芋粉为原料，经三级醇溶去杂工艺，得纯化魔芋葡甘聚糖；以环氧氯丙烷为交联剂，制备出交联魔芋葡甘聚糖水凝胶；交联魔芋葡甘聚糖水凝胶于尿素水溶液中强力搅拌，抽滤，制得包裹尿素的交联魔芋葡甘聚糖水凝胶。试验了交联魔芋葡甘聚糖水凝胶对尿素的包裹率；以及包裹尿素的交联魔芋葡甘聚糖水凝胶缓释尿素的效果。结果表明，交联魔芋葡甘聚糖水凝胶对尿素缓释效果良好。     

Solubility of metallic-salt in acid nutrients in acid fertilizer solutions of urea phosphate,urea sulfate and urea nitrate

Solubilities of individual metallic-salt micronutrients were determined at 0°C in saturated acid fertilizer solutions of urea phosphate, urea sulfate, and urea nitrate. By using the acid pH mechanism, less expensive metallic salts can be used with drip irrigation applications to supply specific micronutrient needs to crops.Solubility of the sulfates of Cu, Fe, Mn, and Zn varied with each acid solution. Solubility of the above sources in the urea sulfate solutions also varied with the amount of sulfate in solution. The solubility of molybdenum decreased with the acidic conditions of the urea nitrate acid solution but appeared to increase for the urea phosphate and urea sulfate acid solutions. Boron was only slightly soluble in all the acid solutions.     

过氧化尿素降解甲醛的研究

用过氧化尿素固体粉末降解密闭储气瓶中的甲醛,通过正交实验,研究了过氧化尿素用量、降解温度以及降解时间与降解甲醛能力的关系。结果表明,用过氧化尿素降解体积为1L储气瓶中的甲醛气体,适宜条件为:过氧化尿素用量为0.5g,反应温度为35℃,降解时间为36h时,甲醛的降解效果好,降解率达到79.41%。同时分析了用过氧化尿素降解甲醛的原理。