Online Model-Based Process Safety Concepts in Polymerization

Summary: To safeguard runaway reactions in industrial scale, qualified methods have to be used. While mechanical safety devices are usually installed, their design may be problematic as the runaway kinetics must be known. This may not be the case for many processes due to the required flexibility and possible unanticipated deviations from recipes. It is shown that runaway kinetics can be very fast and can lead to high conversions. Therefore, a method is proposed that does not depend on kinetics but limits the amounts of unreacted monomer in the reactor by monitoring the conversion and by quantitatively determining the hazardous potential. If a potential violation is observed, feeds to the reactor are interrupted.     

核反应堆压力容器模拟钢中富Cu原子团簇的析出与嵌入原子势计算

利用原子探针层析技术(APT)和热处理时效方法,研究了合金元素Ni对核反应堆压力容器模拟钢中富Cu原子团簇析出的影响.实验结果表明,添加合金元素Ni(0.84wt%)的样品中析出富Cu原子团簇的数量密度高于不添加Ni的样品,富Cu原子团簇内以及团簇和基体界面处都有Ni元素的富集现象,这说明合金元素Ni会促使富Cu原子团簇的析出.从多体势的角度出发,利用嵌入原子势理论,基于纯金属元素Fe,Cu,Ni的多体势参数,建立了Fe-Cu二元和Fe-Cu-Ni三元体系的嵌入原子多体势.计算结果表明,当模拟合金中存在1at%Ni时有利于富Cu原子团簇的析出,这与实验结果相符.     

Mesoporous Silica Supported Multiple Single‐Site Catalysts and Polyethylene Reactor Blends with Tailor‐Made Trimodal and Ultra‐Broad Molecular Weight Distributions

A ternary blend of the bisiminopyridine chromium (III) (Cr‐ 1 ) with the bisiminopyridine iron (II) (Fe‐ 2 ) post‐metallocenes with the quinolylsilylcyclopentadienyl chromium (III) halfsandwich complex (Cr‐ 3 ) was supported on mesoporous silica to produce novel multiple single‐site catalysts and polyethylene reactor blends with tailor‐made molecular weight distributions (MWDs). The preferred cosupporting sequence of this ternary blend on MAO‐treated silica was Fe‐ 2 followed by Cr‐ 1 and Cr‐ 3 . Cosupporting does not impair the single‐site nature of the blend components producing polyethylene fractions with = 10⁴ g · mol⁻¹ on Cr‐ 1 , = 3 × 10⁵ g · mol⁻¹ on Fe‐ 2 , and = 3 × 10⁶ g · mol⁻¹ on Cr‐ 3 . As a function of the Fe‐ 2 /Cr‐ 1 /Cr‐ 2 mixing ratio it is possible to control the weight ratio of these three polyethylenes without affecting the individual average molecular weights and narrow polydispersities of the three polyethylene fractions. Tailor‐made polyethylene reactor blends with ultra‐broad MWD and polydispersities varying between 10 and 420 were obtained. When the molar ratio of Fe‐ 2 /Cr‐ 1 was constant, the ultra‐high molecular polyethylene (UHMWPE, > 10⁶ g · mol⁻¹) content was varied between 8 and 16 wt.‐% as a function of the Cr‐ 3 content without impairing the blend ratio of the other two polyethylene fractions and without sacrificing melt processability. When the molar ratio Fe‐ 2 /Cr‐ 3 was constant, it was possible to selectively increase the content of the low molecular weight fraction by additional cosupporting of Cr‐ 1 . Due to the intimate mixing of low and ultra‐high molecular weight polyethylenes (UHMPEs) produced on cosupported single‐site catalysts a wide range of melt processable polyethylene reactor blends was obtained.

     

Knotted Picture of Unitary Transformation Applied to Single Particle Quantum State

This paper introduces the unified expression of four Bell bases and uses the composition operation in knot theory to obtain the knotted picture of unitary operators based on Pauli operators, and gives the knotted expressions of 12 inversion relations between the four Bell bases.     

Knotted Topological Phase Singularities of Electromagnetic Field

In this paper, knotted objects （RS vortices） in the theory of topological phase singularity in electromagnetic field have been investigated in details. By using the Duan＇s topological current theory, we rewrite the topological current form of RS vortices and use this topological current we reveal that the Hopf invariant of RS vortices is just the sum of the linking and self-linking numbers of the knotted RS vortices. Furthermore, the conservation of the Hopf invariant in the splitting, the mergence and the intersection processes of knotted RS vortices is also discussed.     

RF properties of 700 MHz, <Emphasis Type="Italic">β</Emphasis> = 0.42 elliptical cavity for high current proton acceleration

BARC is developing a technology for the accelerator-driven subcritical system (ADSS) that will be mainly utilized for the transmutation of nuclear waste and enrichment of U²³³. Design and development of superconducting medium velocity cavity has been taken up as a part of the accelerator-driven subcritical system project. We have studied RF properties of 700 MHz, β = 0.42 single cell elliptical cavity for possible use in high current proton acceleration. The cavity shape optimization studies have been done using SUPERFISH code. A calculation has been done to find out the velocity range over which this cavity can accelerate protons efficiently and to select the number of cells/cavity. The cavity’s peak electric and magnetic fields, power dissipation P _c , quality factor Q and effective shunt impedance ZT ² were calculated for various cavity dimensions using these codes. Based on these analyses a list of design parameters for the inner cell of the cavity has been suggested for possible use in high current proton accelerator.      

钾助剂对F-T合成铁基催化剂浆态床反应性能的影响

 采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了不同K助剂含量的系列微球形Fe/Cu/K/SiO2催化剂(K/Fe质量比为0.010～0.058),采用低H2/CO比的合成气于典型的工业反应条件下(523～533 K, 1.5 MPa, H2/CO=0.67)进行了长期的浆态相F-T合成(FTS)反应性能评价. 结果表明: K助剂的添加可增大催化剂活性,提高C5+、总的烯烃、有机含氧化合物及CO2的选择性,并促进水煤气变换反应,但过高的K含量易使催化剂反应稳定性变差. 适中的K含量为K/Fe＝0.030,该K含量催化剂的660 h浆态床FTS反应性能评价结果显示,该催化剂具有较高的催化活性和C5+选择性,产物分布较合理,长期运行稳定性好,反应后卸载下的催化剂形貌观测表明该催化剂还具有较好的抗磨损性能. 除K助剂的化学效应起主导作用外,催化剂的织构性质尤其是孔结构可能对催化剂的催化性能也有一定的影响,并引起K/Fe＝0.045时铁基催化剂对FTS产物选择性和水煤气变换反应活性的部分调变.     

Large-eddy simulation of MILD combustion using partially stirred reactor approach

Subgrid-scale (SGS) parameterization and method for calculating filtered reaction rate are critical components of an accurate large-eddy simulation (LES) of turbulent flames. In this study, we integrate gradient-type structural SGS models with a partially stirred reactor approach by using detailed chemical kinetics to simulate a turbulent methane/hydrogen jet flame under moderate or intense low-oxygen dilution (MILD) conditions. The study examines two oxygen dilution levels. The framework is assessed through a systematic and comprehensive comparison of temperature, and mass fractions of major and minor species with experimental data and other reference simulation results. Overall, the statistics of the combustion field show excellent agreement with measurements at different axial locations, and a significant improvement compared to some previous simulations. It suggests that the proposed nonlinear LES framework is able to accurately model MILD combustion with reasonable computational cost.     

CuI/2,2'-联吡啶/2,2,6,6-四甲基哌啶氧化物催化氧化醇生成腈的工艺

以高压反应釜为反应装置,采用CuI/Bipy(2,2'-联吡啶)/TEMPO(2,2,6,6-四甲基哌啶氧化物)催化体系,以氨水作氮源,分子氧作氧化剂,对醇催化氧化生成相应腈的方法进行了优化。 以苯甲醇的催化氧化反应为模型反应,考察了催化剂及其用量、溶剂、反应温度以及时间对催化性能的影响。 实验表明:在高压釜中,120 ℃、40×10⁵ Pa的氮氧混合气(φ(O₂)=8%)条件下,将催化剂摩尔分数降低至1%(脂肪醇催化剂摩尔分数为5%),反应时间缩短至8 h时,催化效果最佳。同时,该反应系统对于不同的芳香醇和脂肪醇的氧化均取得了90%以上的转化率和90%以上的产品收率。     

Study of material agglomeration during nozzle injection of multiviscosity liquid into a fluidized bed reactor by the electric conductance method

Fluidized bed agglomeration is an important and challenging problem for thermal cracking in fluid cokers. A low coker temperature can be problematic because the bitumen is injected into the fluidized bed with a different viscosity, resulting in formation of agglomerates of varying sizes, which slows the cracking reactions. In the present study, the bed material agglomeration process during nozzle injection of multiviscosity liquid was investigated in a fluidized bed operated at different mass ratios of the atomization gas to the liquid jets (GLR = 1%–3.5%) and gas velocities (3.9U_mf and 5.9U_mf) based on a conductance method using a water–sand system to simulate the hot bitumen–coke system at room temperature. During the tests of liquid-jet dispersion throughout the bed, different agglomeration stages are observed at both gas velocities. The critical amount of tert-butanol in the liquid jets that could lead to severe agglomeration of the bed materials (poor fluidization) at GLR = 1% is about 10 wt% at the low fluidizing gas velocity (3.9U_mf) and 18 wt% at the high gas velocity (5.9U_mf). This study provides a new approach for on-line monitoring of bed agglomeration during liquid injection to guarantee perfect contact between the atomized liquid and the bed particles.