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本文提出用尿素作为pⅡ调节剂,加快硫酸亚铁单液法调剖剂中亚铁离子在地层温度下的沉淀,增大沉淀率,提高封堵效能。岩芯流动试验结果表明,15%FeSO4.7II 2O/5%尿素调剖剂体系的封堵能力比不含尿素的体系增大近一倍。 相似文献
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反应烧结法制备MgAlON的合成机理及烧结行为的研究 总被引:2,自引:1,他引:1
通过对以Al2 O3、MgO和AlN为起始原料 ,在氮气气氛中反应烧结合成MgAlON材料合成机理的研究发现 :在 12 0 0℃以前 ,MgO与Al2 O3反应生成镁铝尖晶石 ,此后 ,随着温度的升高 ,Al2O3不断向所形成的尖晶石中固溶 ;在 130 0℃以前 ,AlN基本上不参与反应 ,而在更高的温度下 ,AlN开始向尖晶石中固溶形成MgAlON ,约在 15 5 0℃时形成单一的MgAlON相。用热膨胀仪检测了试样的线变化率随温度和时间的变化 ,用最小二乘法回归分析了试样线变化率的实验数据 ,并根据烧结理论对MgAlON材料烧结初期的动力学进行了探讨。结果表明 ,MgAlON材料烧结初期的烧结机理以体积扩散为主 相似文献
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A series of experiments introduced interruptions to the execution phase of simple Tower of London problems and found that the opportunity for preparation before the break in task reduced the time cost at resumption. Retrieval of the suspended goal was facilitated when participants were given the opportunity to encode retrieval cues during an "interruption lag" (the brief time before engaging in the interrupting task) but was impeded when these visual cues were subsequently altered following interruption. The results provide useful support for the goal-activation model (E. M. Altmann & G. J. Trafton, 2002), which assumes that context--at the points of both goal suspension and goal retrieval--is critical to efficient interruption recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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潘锦华 《特种铸造及有色合金》2005,25(11):689-691
介绍了五台山铜塔铸造工艺,由于其结构特殊,故采用了3种工艺分别铸造而成:细砂湿模造型、树脂砂毁模贴皮造型和熔模铸造.介绍了铜塔表面化学着色技术.铜塔铸造工艺对其他相似艺术铸品具有一定的借鉴价值. 相似文献
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针对尿素合成塔的腐蚀问题,详细介绍了从投产使用到现在该设备的腐蚀现状.并从不同角度进行详细分析,提出了解决问题的办法及日常运行中应注意的问题. 相似文献
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The crystal structure of urea-polyethylene complex in the hexagonal form, obtained by one of our preparation methods, is analysed by X-ray power diffractometry. In this analysis, the fixed molecular parameters of urea are used, and three models with respect to rotational disorder of the guest polyethylene molecule are assumed. It is shown that the host lattice structure constructed by urea molecules is essentially the same as that of urea-n-paraffin complex. Effects of the disorder structure of the guest on X-ray scattering of the complex are presented. However, there is a difficulty in identifying the disorder structure by X-ray analysis. With the aid of a potential energy calculation between the hexagonal urea tunnel and the guest molecule, a rotational disorder model is preferred. 相似文献
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Catherine J. Watson 《Nutrient Cycling in Agroecosystems》1990,24(1):1-10
Urea can be an inefficient N source due to rapid hydrolysis by soil urease leading to NH3 volatilization. The current study investigated the effect of the urease inhibitor phenylphosphorodiamidate (PPD) incorporated at two concentrations (0.5% and 1% w/w) within the fertilizer granule on NH3 volatilization from surface applied urea. The daily rates of NH3 loss from 20 soils of widely differing properties from Northern Ireland were measured over 14 days using ventilated enclosures under simulated spring conditions. Cumulative loss rates were calculated and fitted to a logistic model from which total NH3 loss (Amax) and the time to maximum rate of loss (Tmax) were determined. Stepwise multiple linear regression analysis related the effectiveness of PPD in reducing NH3 volatilization from urea to soil properties.The total cumulative loss of ammonia from unamended urea varied from 0.37 to 29.2% depending on soil type. Ammonia volatilization appeared to be greatest on a soil with a high pH (R2 = 0.65), a low titratable acidity (TA) (R2 = 0.63) and a soil that was drying out (R2 = 0.50). Soil pH was negatively correlated with TA (r = –0.826, P < 0.001) suggesting that soils with a low TA may have received recent lime. Including cation exchange capacity (CEC) and % N as well as pH-KCl in the multiple linear regression equation explained 86% of the variance.The effectiveness of PPD in reducing Amax varied between 0% to 91% depending on soil type, the average over all 20 soils being 30 and 36% for 0.5% and 1% PPD respectively. The most important soil properties influencing the effectiveness of the urease inhibitor were soil pH-H2O and TA accounting for 33% and 29% of the variance respectively. PPD was less effective on a soil with a high pH and low TA. These were the soil conditions that led to high NH3 volatilization from unamended urea and may explain why PPD had limited success in reducing ammonia loss on these soils. Multiple linear regression analysis indicated that 75% of the variation in the % inhibition of NH3 loss by PPD could be significantly accounted for by pH-H2O, initial soil NO
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-N concentration, % moisture content and % moisture loss.The delay in Tmax by PPD ranged from 0.19 to 7.93 days, the average over all 20 soils being 2.5 and 2.8 days for 0.5% and 1% PPD respectively. TA, % moisture content, urease activity and CEC were soil properties that significantly explained 83% of the variation in the % delay in Tmax by PPD in multiple linear regression analysis. However, none of these soil properties were significant on their own. As urea hydrolysis occurs rapidly in soil, delaying Tmax under field conditions would increase the chance of rain falling to move the urea below the soil surface and reduce NH3 volatilization. A urease inhibitor should be more effective than PPD on soils with a high pH and low TA to be successful in reducing high NH3 losses. 相似文献
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机械松衬尿素合成塔衬里的修复白玲,唐联生,向均,江伟(成都化肥厂)关键词尿素合成塔,衬里,检修成都化肥厂尿素合成塔如图1所示,外筒采用多层15MnVgC板包扎而成,总厚度88mm,衬里是机械松衬6mm厚0Cr17Mn13Mo2N钢板,现在已使用10年... 相似文献