尿素生产中尿液的不稳定流动对尿素一分塔的影响

介绍了水溶液全循环法尿素生产系统中,一分塔的精馏段由泡罩塔盘改为规整填料后出现的一系列问题,针对尿液的不稳定流动造成一分塔规整填料严重腐蚀的原因,进行分析并提出整改和预防措施。     

Relationships between ammonia volatilization and nitrogen fertilizer application rate,intake and excretion of herbage nitrogen by cattle on grazed swards

Grazed pastures emit ammonia (NH₃) into the atmosphere; the size of the NH₃ loss appears to be related to nitrogen (N) application rate.The micrometeorological mass balance method was used to measure NH₃ volatilization from rotationally grazed swards on three plots in the autumn of 1989 and throughout the 1990 growing season. The aim of the research was to derive a mathematical relationship between NH₃ volatilization and N application rate, which would vary between soil type and weather conditions. In both years the plots received a total of 250, 400 or 550 kg N ha^–1 as calcium ammonium nitrate (CAN) split over 6 to 8 dressings. The number of grazing cycles ranged from 7 to 9 for the three N plots.In the last two grazing cycles of 1989, NH₃ losses were 3.8, 12.0 and 14.7 kg N ha^–1 for the 250N, 400N and 550N plots, which was equivalent to 5.3%, 13.9% and 14.4% of the amount of N excreted on the sward, respectively. In 1990, NH₃ losses were 9.1, 27.0 and 32.8 kg N ha^–1 for the 250N, 400N and 550N plots, which was equivalent to 3.3%, 6.9% and 6.9% of the N excreted, respectively. Differences in urine composition between the plots were relatively small. Rainfall and sward management affected the size of the NH₃ volatilization rate. Volatilization of NH₃ was related to N excretion and N application rate.A calculation procedure is given to enable the estimation of NH₃ volatilization from N application rate. Adjustments can be made for grazing efficiency, grazing selectivity, N retention in milk and liveweight gain, concentrate N intake and milking duration. Losses of NH₃ increase progressively with an increase in N application rate until herbage yield reaches a maximum at an application rate of about 500 kg N ha^–1 yr^–1.     

尿素嵌入法制备纤维素氨基甲酸酯的研究

探讨了尿素嵌入法制备纤维素氨基甲酸酯(CC)的生产工艺。指出:选用聚合度为450~625、α-纤维素含量大于90/的纤维素浆粕,用14/~16/的氢氧化钠溶液,于40~50℃条件下活化处理30~40min后,与尿素以1∶2~3的比例混合,在137℃的二甲苯体系中反应2~3h,便可得到含氮量为2.4/~3.5/的纤维素氨基甲酸酯产物。该产物在氢氧化钠溶液中可形成良好的稳定溶液,过滤性好,可直接用于纺丝。     

三聚氰胺的绿色生产技术

由尿素合成三聚氰胺的反应有副反应存在 ,能生成缩二脲、三聚氰酸一酰胺、三聚氰酸二酰胺和蜜勒胺等副产物。利用水溶液中的三聚氰胺在高温高压下可以完全分解的性质 ,采用国外最新开发的OAT专利技术 ,将废水中夹带的少量工艺产品和聚合物废料转化回收 ,可提高原料的利用率 ,消除水污染     

尿素合成塔腐蚀在线监测

简要介绍了尿素合成塔腐蚀在线监测技术、监测仪及其安装、使用情况。     

低压开车法在CO2气提法尿素装置的应用

介绍了低压开车法在改进型CO2气提法尿素装置中的实际应用，总结了低压开车法的优点，论述了低压投料的技术要点和措施，给出了开车过程曲线及技术数据。     

D.s.c. investigation of the states of water in poly(vinyl alcohol-co-itaconic acid) membranes

The state of water in water-swollen poly(vinyl alcohol-co-itaconic acid) membranes, having various water contents from 0.31 to 0.83, was investigated by d.s.c. measurements and compared with those in water-swollen poly(vinyl alcohol) membranes. The amount of freezing water in the membranes was estimated by use of a relationship between the phase transition temperature and the enthalpy of the crystallization of supercooled water. The melting temperature of the water in the membranes immersed in urea and NaCl 0–2 mol l^?1 aqueous solutions was also determined by d.s.c. analysis. The present study proposes a method for estimating the solubilities of urea and NaCl in both of the freezing and the non-freezing water using the melting point depression of the freezing water in the membranes immersed in the solute solution.     

聚碳酸酯厚壁制品的注射成型

通过分析聚碳酸酯的工艺特性,针对特定的厚壁注塑制品,在材料的选择上要考虑熔体流动速率、含水量等;在设备的选择上要考虑螺杆形式、压缩比、长径比等方面;在模具的设计上要考虑采用的浇口形式、大小、脱模斜度、排气、模具预热及冷却等;在注塑工艺上可通过调整料筒温度、注射压力、速度、模温等来设置合理的工艺参数。通过以上一些措施,可以使特定的厚壁制品达到要求。     

氨汽提合成塔腐蚀控制探讨

分析尿素合成塔腐蚀机理、类型,并提出防腐蚀的控制方法。     

秸秆黄腐酸包膜尿素在水稻上的应用效果

在石灰性土壤上进行田间小区试验，结果表明，秸秆黄腐酸包膜尿素能满足水稻生长最大效率期对营养的要求，有利于有效穗的分化，提高结实率。等氮量试验平均增产9．6％，等重量试验平均增产7．4％。