Kinetics of donor-vehicle coal liquefaction in a flow reactor

Development of the Exxon Donor Solvent process has necessitated studies to more clearly define the influence of liquefaction conditions on coal conversion. Process studies were conducted in a 22.7 kg/day (fifty-pound-per-day) integrated pilot plant. Illinois No. 6 coal was liquefied at temperatures from 644 to 756 K, pressures of 10 and 17 MPa, and a tenfold range of residence time. A kinetic model was developed in terms of an empirical classification of four reactive coal constituents. The reactive classes are an incorporation of concepts published in other coal-liquefaction kinetic studies. The effect of vehicle vaporization on actual residence time was used in evaluating the kinetic parameters for this study in a tubular flow reactor. The kinetic model accurately predicts distillation bottoms yields, which ranged from 41 to 72 wt % on coal. Material-balanced quadratic equations are presented for other liquefaction products.     

Complete conversion of brown coal into distillate

The conditions for complete conversion of Victorian brown coal were investigated with an iron–sulfur catalyst in a continuous reactor system consisting of three stirred tank reactors in series. The coal was found to be completely converted into distillate (b.p.<420°C) when the gas flow rate (GFR) through the reactors was increased and the slurry-feed rate was reduced at a temperature of 450°C and a pressure of 18.6 MPa. An analysis of the composition of the liquid in the reactors under liquefaction conditions confirmed that the increase in GFR markedly enhanced the stripping of the solvent fraction in the feed slurry and the lighter fraction derived from the coal, resulting in marked increases in the actual residence time (θ_RT) of the liquid consisting of the concentrated catalyst and heavy fraction. The stripping effect markedly enhanced liquefaction reactions, thus providing a higher distillate yield. However, the GFR effect was gradually saturated as the liquid remaining in the reactors (reactor liquid) became heavier with the increase in the GFR. The extension of nominal residence time (defined by the ratio of slurry-feed rate to reactor volume, θ_NT) from reduction of the slurry feed rate was found to be effective in extending the GFR effects under a high GFR condition, resulting in the complete conversion of the coal. In addition, the stripping of the solvent by the increased GFR was also found to be more enhanced at 18.6 MPa than that at 14.7 MPa although its vaporization was suppressed at a higher pressure. This is due to the heavy fraction in the reactor liquid being more hydrogenated over the concentrated catalyst at a higher hydrogen pressure. However, the dependencies of the conversion rate of the heavy fraction on θ_RT were almost the same for both 14.7 and 18.6 MPa. These results suggested that a complete conversion of the coal could be achieved at 14.7 MPa by using a heavier solvent.     

SOME ASPECTS OF DESIGN OF COMMERCIAL REACTORS FOR DIRECT COAL LIQUEFACTION

In recent years, a number of direct coal liquefaction processes have been developed. All processes use a slurry type reactor. Although for lab-scale reactors of large length-to-diameter ratio the use of highly sophisticated slurry reactor model may be justified, simple considerations can meaningfully elucidate the behavior of industrial reactors. A simple analysis shows that the coal liquefaction is controlled by intrinsic kinetics. Both gas and slurry phases can be assumed to be completely backmixed in large diameter reactors. A simple analysis of the thermal behavior revealed multiplicity for a fairly wide range of operating conditions. In most cases, the intermediate unstable steady state is close to the temperature observed in adiabatic coal liquefaction reactors (with and without quench). Due to the unstable character of the operation, point pathological phenomena like runaway may be possible and a close feedback control of the commercial reactor may be required.     

Liquid or slurry holdup in the flow of gas-liquid and gas-slurry mixtures in vertical tubes

In a support study for the development of the Synthoil coal liquefaction process, liquid (or slurry) holdups resulting from the flow of gas-liquid and gas-coal slurry mixtures in vertical tubes were measured. The effect of the viscosity of the liquid phase, the density of the gas phase, and the tube diameter on holdup values were investigated. The results showed that slurries of coal particles (up to 27.1 wt.%) in a white mineral oil behave as homogeneous Newtonian fluids. Therefore, the results obtained for the flow of gas-liquid mixtures are equally applicable to the flow of the type of gas-slurry mixtures that exist in the Synthoil coal liquefaction process.     

神华上湾煤恒温阶段直接液化反应动力学

为考察神华上湾煤的直接液化性能及反应动力学,以加氢蒽油-洗油混合油作为溶剂、负载型FeOOH作为催化剂,在0.01 t·d^-1煤直接液化连续实验装置上考察了不同反应温度（435~465℃）、不同停留时间（7~110 min）下液化产品组成的演变规律。研究发现,随着煤的裂解及加氢反应的进行,煤及沥青类物质（PAA）收率不断减小,重质液化产物逐步向轻质液化产物转化。当反应温度为455℃、停留时间为90 min时,煤转化率为90.41%（质量分数（,油收率为61.28%（质量分数（。随着反应条件进一步苛刻,油收率下降。基于上湾煤直接液化反应特性及其产物收率变化规律建立了11集总煤直接液化反应动力学候选模型,以BFGS优化算法对实验数据搜索、选优,确定了动力学模型参数。检验结果表明所建立的动力学模型可用于恒温阶段直接液化行为的模拟计算。     

Pyrolysis of coal liquids

The pyrolysis of process recycle solvent derived from Western Kentucky coal via the SRC-II coal liquefaction process was investigated to ascertain the effect of residence time and temperature on the production of olefins. The study was made using an alonized transfer line reactor operating at temperatures of 650 and 730 °C, essentially atmospheric pressure, and residence times up to 0.13 s. A comparison is made with previously published results for the pyrolysis of hydrotreated COED light and heavy coal liquids (subsequently referred to as COED light and heavy oils, respectively) derived from Western Kentucky coal and steam pyrolysis of a hydrogenated fraction of SYNTHOIL derived from Western Kentucky coal. Results indicate that in each case the preferential pyrolysis of the saturate fraction occurs under convential pyrolysis conditions. Ethylene, propylene, and methane were the dominant gas products in all cases. The liquid pyrolysates from the COED oils and SRC-II recycle solvent had lower $\text{H}\text{C}$ ratios and heating values than their respective feedstocks. Mass spectroscopic analysis of the liquid pyrolysates in each case revealed the presence of polycyclic aromatics that were not present in the individual feedstocks. This trend which increased with temperature is indicative of cyclization and/or recombination of free radicals during pyrolysis. It is therefore surmized that the yields of light olefins from primary coal liquefaction products can be improved by partially hydrogenating them prior to pyrolysis. Alternatively, sufficient hydrogen can be provided in the vicinity of cracking to suppress retrogressive reactions which lead to the formation of coke. The pyrolysis of COED oils and SRC-II recycle solvent was found to follow first-order irreversible kinetics. The activation energy for the pyrolysis of the COED light and heavy oil was found to be 76.1 and 70.85 kJ g-mol^?1, respectively.     

催化裂化装置防结焦技术研究

从催化裂化工艺和实际生产出发,根据沉降器的结焦部位、焦块的形态和构成归纳出导致沉降器结焦的三大成因-湿催化剂粘附结焦、重组分油冷凝结焦和缩合反应结焦。原料油在催化剂上不能完全汽化形成湿催化剂,油浆中重组分在沉降器内以汽液两相形式存在,缩合反应生成液相的重组分,这些为结焦提供了物质基础。分析认为湿催化剂粘附结焦是提升管、旋分器料腿和沉降器内结焦的主要原因;重组分冷凝是旋分器升气管外壁、沉降器内和转油线结焦的主要原因。论述了包括原料性质、原料汽化率、油气停留时间、粗旋与顶旋的连接方式和设备的影响等五大影响沉降器结焦的主要因素,并总结提出避免或减缓沉降器结焦的措施。     

超临界水液化褐煤研究进展

超临界水直接液化褐煤是高湿低阶褐煤高效转化与资源化利用的一个重要的发展方向。阐述了超临界水液化制油的优势,总结了液化过程中的热解反应、脱杂反应、缩聚反应等关键反应;重点论述了操作条件(温度、停留时间、压力、溶剂等)对反应过程的影响机理;针对油品质的升级,总结了催化剂在液化油升级中的应用,分析了煤本身所含的铁系催化剂的催化特点,总结了贵金属在催化升级中的研究现状及部分过渡金属合金的高效催化特性;强调了煤与生物质共同液化的协同作用。对液化过程中存在的问题进行了总结,并展望了未来的工业放大应用。     

乙炔加氢制乙烯浆态床反应器的CFD模拟

对浆态床反应器中乙炔加氢制乙烯过程进行了模拟研究，采用TFM-PBM耦合方法描述浆态床内气相与浆态相的流动，并耦合乙炔加氢反应动力学建立流动-反应综合模型。通过小试实验对该模型进行验证，并将验证后的模型应用于浆态床中试装置中内构件作用机制与操作条件影响的模拟分析。结果表明，在浆态床反应器放大时，可通过设置竖管内构件，以破碎气泡，抑制气相径向运动，使乙炔加氢过程均匀、充分地进行。乙炔加氢制乙烯过程与气相停留时间和反应温度密切相关，在反应器放大中需严格控制温度，并可通过改变反应器内液位高度实现对气相停留时间的调控，从而可在保证乙炔充分转化的同时获得更高的乙烯选择性。     

DMF的力场构建及乙腈-甲醇-DMF三元体系的汽液相平衡模拟

采用量子化学和Gibbs系综Monte Carlo模拟相结合的方法,对TraPPE-UA力场中缺失的N,N-二甲基甲酰胺（DMF）力场参数进行了补充,为含DMF多元体系的汽液相平衡模拟奠定了基础。采用新构建的力场参数,在NVT-Gibbs系综中计算了DMF的汽液相平衡性质,结果表明该力场能准确计算出DMF的饱和液相密度、蒸气压、沸点、临界值和蒸发焓。在NPT-Gibbs系综中,采用TraPPE-UA力场分别计算了乙腈-甲醇、DMF-甲醇、DMF-乙腈二元混合物的汽液相平衡性质,并与实验值进行了比较。模拟结果与实验值较为吻合,验证了力场模型的可靠性。最后在NPT-Gibbs系综中采用TraPPE-UA力场对乙腈-甲醇-DMF三元体系的汽液相平衡数据进行了预测,为设计和优化乙腈和甲醇的萃取分离过程提供了基础数据。     

Hydrothermal dewatering of lower rank coals. 1. Effects of process conditions on the properties of dried product

The hydrothermal dewatering of a Loy Yang Low Ash Victorian brown coal has been studied under a wide range of process conditions. The intra-particle porosity (<1 μm pore radius) determined by mercury porosimetry of the resulting dried products, a proxy for the maximum solids concentration of coal-water slurries, is reported as a function of reaction time, processing temperature, autoclave size and configuration and slurry concentration. Of these variables only the process temperature had a significant influence on the product intra-particle porosity, which decreased with increasing temperature. Other product variables were affected by a wider range of process conditions; increase in temperature and residence time and decrease in slurry concentration led to marked increase in loss of organic material to waste water, and the elemental composition of the product changed significantly with e.g. residence time. Drying of coal samples of particle sizes >50 μm gave products of constant intra-particle porosity but smaller coal particles gave products with higher intra-particle porosities as a result of agglomeration. Milling of the coal reduced the porosity of the dried coal at constant particle size.     

煤液化残渣制浆研究

对某煤液化残渣进行湿法成浆性实验研究,通过对煤液化残渣料浆在表观黏度、稳定性和流变特性方面的考察,认为在选取合适的添加剂和添加剂加入量的条件下,具备合理粒度分布的煤液化残渣能够制备出高质量分数符合湿法气流床气化工艺要求的料浆。     

1,2-环氧环己烷和1,2-二氯乙烷二元体系汽液平衡数据的测定与关联(英文)

Vapor-liquid equilibrium data (T, x, y) of binary system 1,2-epoxycyclohexane + 1,2-dichloroethane were determined experimentally by using a modified ROSE-Williams equilibrium vaporization system at 101.33 kPa. The results show that this binary system does not have azeotropic point. The vapor-liquid equilibrium data are in thermodynamic consistency. The binary interaction parameters in the Wilson equation are presented with the correlation of vapor-liquid equilibrium data. The measurements of liquid phase composition and bubble point temperature are well represented by the Wilson equation. Values of vapor molecular fractions and activity coefficients from the Wilson equation are presented. This work provides important engineering data for the separation of 1,2-dichloroethane and 1,2-epoxycyclohexane .     

煤液化油的基本热力学性质测定方法的分析

分析了煤液化油的一些基本热力学性质:比热、蒸汽压、气-液相平衡常数和蒸发焓等,并参考石油基本热力学性质的各种测定方法及关联式计算法,探索研究了煤液化油基本热力学性质的测定方法和关联式计算法,特别是对煤液化油比热、蒸汽压的测定、气-液相平衡常数的计算及蒸发焓的估算作了详尽的讨论.最后得出了测定煤液化油这些热力学性质的适宜方法.简要概括了煤液化油馏分临界性质参数的计算.     

连续内环流三相反应器局部流动特性

在φ200 mm×2500 mm连续内环流三相反应器内,考察了空气 水 玻璃珠体系反应器内局部流动参数随操作条件的变化规律。结果表明,导流筒内截面平均气含率随表观气速的增大而增大,较之气液两相流,在低固含率时,加入固体对气含率影响不明显,而在较高固含率下,气含率有明显降低,但固体再增加时对气含率变化影响不大。在较低表观气速下,进料浆速对导流筒内气含率轴向分布趋势有一定的影响,但在较高表观气速下影响不大,导流筒内的气含率大于环隙内的气含率且随气速增大差别更加明显,浆相连续有利于气相分散并增大环隙内的气含率。导流筒内循环浆速径向分布呈抛物状,中心高、近壁处低,受进料浆速和入口固含率影响都不大。浆相循环强度最低为20,高可达180。固含率轴、径向分布受表观气速和进料浆速的影响,固含率轴、径向分布基本均匀,随进料浆速增加,反应器内固含率降低。     

Performance,mixing and kinetics study in the flotation column reactor using coal

ABSTRACT

A flotation column has been designed and characterized with respect to gas velocity, slurry velocity, frother concentration, gas holdup, bubble surface area flux for the study of the mixing property, liquid phase residence time distribution, flotation recovery and rate constant. The study was performed using coal as solid. A strategy of integrating chemical kinetics into the flotation process to test the floatability behaviour of coal and to estimate floatability parameter of coal has been developed. The results indicate that the coal floatability parameter is 3.05 × 10^?4. A relationship between gas holdup and bubble surface area flux was developed.     

Kinetics of coal liquefaction during heating-up and isothermal stages

Direct liquefaction of Shenhua bituminous coal was carried out in a 500 ml autoclave with iron catalyst and coal liquefaction cycle-oil as solvent at initial hydrogen of 8.0 MPa, residence time of 0–90 min. To investigate the liquefaction kinetics, a model for heating-up and isothermal stages was developed to estimate the rate constants of both stages. In the model, the coal was divided into three parts, easy reactive part, hard reactive part and unreactive part, and four kinetic constants were used to describe the reaction mechanism. The results showed that the model is valid for both heating-up and isothermal stages of liquefaction perfectly. The rate-controlled process for coal liquefaction is the reaction of preasphaltene plus asphaltene (PAA) to oil plus gas (O + G). The upper-limiting conversion of isothermal stage was estimated by the kinetic calculation.     

工业醇类煤沥青水浆制备磨矿动力学研究

对两种工业醇类煤沥青水浆的制备进行磨矿试验研究,结果表明甲醇煤沥青水浆的磨矿效果略好于乙醇煤沥青水浆;建立了乙醇煤沥青水浆和甲醇煤沥青水浆磨矿动力学方程式,分别为R(t)=100exp[-(-1.3564+0.43454.lnd).t(-0.42203+0.195241.lnd)]和R(t)=100exp[-(-0.02975+0.02908.d0.67972).t(-0.12083+0.13259.lnd)],据此可以求出任意磨矿时刻待磨粒级的分布率R(t)。     

氢气在无催化煤液化中的反应机理

采用平衡液相取样法气体溶解度测定装置测定了氢气在萘中的溶解规律,并采用间歇式微型反应釜研究了氢气在无催化煤液化中的反应机理.结果表明:1)氢气在萘中的溶解随着温度和压力的升高而增加,溶解速率先快后慢,在5min时达到最大溶解量的76.21%左右,直到30min达到平衡;2)在萘溶剂的无催化煤液化反应中,氢气的溶解不是控制步骤,溶解氢参与液化反应的速度才是控制步骤;3)在较短时间的萘溶剂无催化煤液化时,氢气在萘溶剂中的预溶解提高了无催化煤液化的总转化率,其主要原因是部分预溶氢提前活化,使得煤液化反应初期活性氢增加;4)在较长时间的萘溶剂无催化煤液化时,预溶氢对总转化率的提高很小,但促进了液化产物的进一步裂解加氢轻质化.     

Effect of processing conditions on organics in wastewater from hydrothermal dewatering of low-rank coal

A study was carried out into the effects of processing conditions on the nature and amounts of organics released into wastewater from hydrothermal dewatering (HTD) of low-rank coal. Processing conditions examined included temperature, residence time, water to coal ratio in the slurry, slurry loading, and coal lithotype. High temperature and pressure treatments of low-rank coal slurries were used to simulate the HTD process. It was found that the extent of extraction of organics during HTD processing depended on the coal lithotype and increased with increasing temperature, residence time, and the proportions of steam and water present during processing. For a constant residence time, the concentration of organics in the wastewater increased exponentially with temperature over the temperature range 250-350 °C. A maximum level of approximately 7 g/l (expressed as TOC) of organics was observed following processing at 350 °C. Hot filtration of the coal slurry produced a higher organics loading compared to that found in wastewater obtained at low temperature.