深井降温系统管道结垢微观机理

以深部矿井降温系统管道内壁出现的结垢问题为研究对象,首先采集管道水样进行水质全分析测试,确定管道内成垢性离子并建立化学及数学模型,其次采用第一性原理计算方法研究得到了深部矿井降温系统管道结垢微观机理。结果表明,深井降温系统管道内壁结垢过程包括Ca~(2+)和CO_3~(2-)的结合结晶及MgCO_3、CaSO_4转化为CaCO_3的转化;理论分析及第一性原理计算结果表明,深井降温系统管道内壁结垢的主要影响因素为成垢性离子(Ca~(2+)、HCO~-_3、Mg~(2+)和SO~(2-)_4,且Mg~(2+)和SO~(2-)_4的存在会抑制碳酸钙结垢的产生。该研究对于深部高温热害矿井的降温系统的结垢产生机制以及采取合理的防、除垢措施,保障良好的矿井降温效果和安全生产具有理论指导意义。     

换热器水系统结垢机理

换热器是煤化工生产过程中的重要设备,换热器的水系统在换热过程中易使设备腐蚀和结垢,造成换热器堵塞,本文只对水结垢机理作简要研究探讨。     

表面吸附的微观机理研究进展

介绍了表面吸附的微观机理研究进展 ,着重阐述了表面吸附的微观机理研究的理论基础、现代表面吸附的分析技术、现代理论研究方法 ,并指出了现代表面吸附研究的发展趋势。     

流动水系统中CaCO_3在换热表面上结垢机理的研究

设计了一种新的测垢实验装置,研究了模拟硬水CaCO_3在加热表面的结垢机理.提出了沉积-自由移去的结垢机制,并用湍流猝发理论结合Hasson的离子扩散模型,导出了碳酸钙结垢速率的数学模型,模型预测速率同实验数据吻合较好.     

换热器水系统结垢机理探讨

换热器是化工生产中的重要设备,换热器的水系统在换热过程中易使设备腐蚀和结垢,造成换热器堵塞,对换热器水系统结垢机理作简要探讨。     

气田高温回注水管道结垢机理研究

低温或常温气田回注水结垢的机理研究已经比较成熟,但对于气田高温回注水的结垢研究尚不够深入.气田高温回注水结垢受成垢离子种类和浓度、pH值、温度以及矿化度大小的影响.单一成垢离子和成垢离子浓度低以及pH值和温度下降都可以抑制水垢的生成,水的矿化度变大对水垢的生成有促进作用;而硫酸盐的存在对硫酸盐垢的形成有很大的促进作用....     

管道结垢机理及影响因素分析

油田管道结垢是国内外油田生产面临的普遍问题。针对油田结垢,从压力的影响、结晶动力学因素、流体动力学因素三大类因素入手,分析了管道结垢的影响机理。     

定边油田腐蚀结垢机理及治理

王崾先区块A区域注水始于2005年,注采时间长,大部分套管已有渗漏、破损,加之按照“就地脱水,就地回注”的原则,区域以地下水、处理后的油田产出水两种水源进行注水。经过多年的注水开发,逐渐显露出问题,根据生产现场反映区域内D集输站、上渠1399等注水站的供水管道、部分注水设备焊接处、注水井和油井井筒存在严重结垢和腐蚀现象,已严重影响到油田安全生产和注水系统的正常平稳运行。     

油田管道室内静态结垢模拟实验研究

目前油田注水设备及地面管线严重的结垢现象已经影响到油田正常的生产运行,而油田常见的结垢物主要为碳酸钙、硫酸钙等盐类垢,因此有必要对油田管道盐类垢的形成及影响因素进行分析。对4种常见的盐类垢进行了室内静态结垢实验,重点研究了结垢温度、作用时间以及管道材质对结垢速率的影响。实验结果表明:在40℃和80℃时,垢质晶体的形成速率较慢,而在60℃时,垢质晶体的形成速率较快,相同温度下,不同晶体类型的结垢速率也存在较大的差异;不同盐类垢均在8 h内的结垢速率最大,随着静置时间的延长结垢速率逐渐减小;钢制挂片表面的结垢量明显大于聚乙烯管道的结垢量,说明钢制挂片与介质发生的氧化反应对垢质的形成具有一定的促进作用。     

循环冷却水系统结垢量的计算

重碳酸盐的分解是造成循环冷却水系统结垢的主要原因.从重碳酸盐的分解深度入手,推导了循环水系统中结垢量的理论公式,以期能为水质控制和化学清洗提供一个可资借鉴的依据.     

Molecular and dissociative adsorption of a single water molecule on a β‐dicalcium silicate (100) surface explored by a DFT approach

The adsorption of water on a C₂S surface initiates belite to hydrate. In the present work, the adsorption behavior of single water molecule on a β‐C₂S (100) surface is explored using density functional theory (DFT) due to the lack of alternative approaches for direct observation. Four possible calcium atom sites on the β‐C₂S (100) surface slab are considered in our calculations. The results show that water can adsorb on the 2 five‐coordinated calcium sites only via molecular adsorption with adsorption energies of 0.59 and 0.85 eV, respectively, but can dissociate on the other 2 six‐coordinated calcium sites with higher adsorption energies of 0.96 and 0.99 eV, respectively. The energy barriers to the dissociative adsorption of water at the Ca(III) site(0.10 eV) is much lower than that at the Ca(IV) site, indicating that water prefers to adsorb and dissociate on Ca(III) sites. The dissociative adsorption of water causes more obvious surface calcium shifts and Si–O bond length increases than molecular adsorption. The dissociative adsorption of a water molecule changes the electron distribution, and the overlap between Ca 2p and O 2s orbitals leads to new Ca–O bond formations.     

O2在-CH2-CH2OH基团上的化学吸附

煤炭自燃是煤表面与氧气发生吸附进而发生化学反应的结果,在定义煤表面的基础上,应用量子化学理论和方法,研究煤表面中的-CH2-CH2OH基团对氧分子的化学吸附过程,无论吸附单氧分子或是多氧分子,氧分子的O-O键都被拉长并断裂,氧原子与-CH2-CH2OH基团的C原子或H原子形成了新的化学键.吸附能随着吸附氧分子数的增加而增大,呈二次函数关系.     

CO2在La2O3(011)表面吸附和活化的DFT计算

运用广义梯度密度泛函理论方法(density functional theory,DFT),结合周期性平板模型,研究了CO2在La2O3(011)表面的吸附和活化,计算了CO2吸附的吸附能和Mulliken电荷数.结果表明,CO2在La2O3(011)表面吸附形成6种平衡构型,分别为CO2-η1、CO2-η2、CO2-...     

循环冷却水系统的黏附速率预测模型的研究

结垢是循环冷却水系统中常见的水质故障,人们常用水质判断指数来判断循环冷却水水质的结垢趋势。通过对某石化公司循环冷却水系统生产运行数据的分析,选取了对黏附速率影响较大的水质参数,借助神经网络的非线性映射、泛化及容错能力,基于BP神经网络建立了黏附速率的预测模型。利用该模型对循环冷却水系统一定周期黏附速率的预测结果较好,说明该方法可行,具有很好的应用前景。     

氧气厂低温冷却水系统结垢原因及解决方法

简述了氧气厂低温冷却水系统流程.通过对补充水水质、低温水系统流程、工艺控制条件等的研究,分析了低温水系统结垢原因,并提出了具体的解决方法.     

High‐throughput and comprehensive prediction of H2 adsorption in metal‐organic frameworks under various conditions

High‐throughput prediction of H₂ adsorption in metal‐organic framework (MOF) materials has been extended from a few specific conditions to the whole T, p space. The prediction is based on a classical density functional theory and has been implemented over 712 MOFs in 441 different conditions covering a wide range. Some testing materials show excellent behavior at low temperatures and obvious improvement at high temperatures compared to conventional MOFs. The structures of the best MOFs at high and low temperatures are totally different. Linear and nonlinear correlations between the two Langmuir parameters have been found at high and low temperatures, respectively. According to the analysis of the excess uptake, we found that the saturated pressure increases along with temperature in the low temperature region but decreases in the high temperature region. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2951–2957, 2015     

电厂循环冷却水系统极高浓缩倍数运行工程实践

对高效水质稳定剂配方在极高浓缩倍数下运行进行工程验证,从腐蚀速率、菌落总数、污垢沉积率、凝汽器端差和真空度变化等指标,以及实际机组检查来评定实际运行效果。结果表明,在以河水为补充水源,浓缩倍数为13的条件下运行,碳钢腐蚀速率为0.031 0 mm/a,304不锈钢腐蚀速率为0~0.000 4 mm/a,铜的腐蚀速率为0~0.000 4 mm/a,菌落总数为1 100 CFU/m L,均小于GB 50050—2007《工业循环冷却水处理设计规范》的要求;污垢沉积速率除1次超标外,其余为2~10 mg/(cm2·月);凝汽器端差等主机参数稳定,机组内部实际检查结果没有异常。循环冷却水系统在极高浓缩倍数下运行,有较好的节水效益。     

Elucidating energy scaling between atomic and molecular adsorbates in the presence of solvent

Condensed phase reactions have recently attracted increased interest, but principles for efficiently screening and designing catalyst materials through computations are lacking. In this study, we examine the applicability of energy correlations between adsorbed surface species, which have been instrumental in accelerating the computational design of catalyst materials in gas-phase contexts, in various representations of a condensed phase reaction environment. We perform detailed density functional theory calculations of the adsorption of atomic and molecular species in the presence of various representations of solvent species. Our results show that the well-known scaling in the gas phase context is preserved, with scaling slopes unaffected by the adsorbate-liquid interactions. Moreover, these results hold when changing surface structure, solvent identity, and even in highly disordered environments. We envision the establishment of an energy scaling framework for condensed phase reactions to accelerate catalyst discovery and design in those contexts.     

Understanding the adsorption of calcium sulfate on tetracalcium aluminoferrite and tricalcium aluminate surfaces

Calcium sulfate (CaSO₄), an essential retarder in cement, retards the hydration of tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF) phases. However, its retarding mechanism remains unclear. This paper focused on the adsorption of CaSO_4f on C₄AF and C₃A surfaces based on isothermal calorimetry, the measurement of the ionic concentrations in a diluted system, and density functional theory to enhance the understanding of the retardation mechanism. The results showed that the retarding effect of CaSO₄ on C₄AF was stronger than that on C₃A due to the slower CaSO₄ consumption rate, lower driving force for CaSO₄ adsorption, and surface coverage of Fe(OH)₃ gel. The adsorption of CaSO₄ hindered Ca dissolution more markedly on C₄AF than C₃A, which was pronounced on Fe-free C₄AF surfaces. The adsorption of CaSO₄ weakened the affinity of water on C₄AF and C₃A surfaces, lowering the driving force for H₂O adsorption. The adsorption of H₂O and CaSO₄ promoted the dissolution of Al on the [AlO₆] octahedral surface of C₄AF, which may be responsible for the maintenance of a higher Al concentration in the solution. Based on the above results, the adsorption of CaSO₄ on initial C₄AF and C₃A hydration was explained.