A mathematical model for the retorting of a large block of oil shale: effect of the internal temperature gradient

A mathematical model which incorporates the intrinsic kinetics of the decomposition of kerogen and carbonate minerals and the internal as well as external heat-transfer effects has been developed. This rigorous model is compared with the uniform-temperature model. The results indicate that at a heating rate of 1 °C/min and a mass velocity of gas of 0.0179 $\text{kg}\text{m}{}^2$ s, the uniform-temperature model gives about 10% error in the extent of conversion for particles of 6 cm in radius. As the particle size increases, the error becomes greater. Also, at higher heating rates or mass velocities the error is larger for the same particle size. The new model has been applied to the results of thermogravimetric experiments published in the literature. The comparison shows that the rigorous model describes the retorting of oil shale more accurately than the shrinking-core model or the uniform-temperature model.     

回转干馏炉内颗粒间传热特性的数值模拟

将离散元方法与颗粒热传导模型相结合,研究了页岩灰颗粒与油页岩颗粒在回转干馏炉内的混合传热过程,采用混合指数、颗粒平均温度和温度标准偏差作为评价混合传热效果的指标,分析了填充率、炉体转速、油页岩粒径及抄板形式对颗粒间混合传热特性的影响规律。结果表明,炉体转速和油页岩粒径是影响颗粒混合传热效果的主要因素,而填充率和抄板形式对混合传热效果的影响相对较小。当炉内未设抄板时,随着填充率和油页岩粒径的增大,颗粒间分层现象使混合传热效果变差,而随炉体转速的提高传热效果呈现出先增强后减弱的趋势;设抄板时,抄板形式对炉内颗粒间的混合起到不同程度的扰动作用,从而使传热效果得到显著改善。     

基于Aspen Plus的桦甸式油页岩干馏工艺系统模拟

引言油页岩是一种富含有机质、具有微细层理、可燃烧的细粒沉积岩,油页岩作为能源资源,既可以干馏炼油也可以燃烧发电。油页岩储量丰富,截至2005年底,37个国家油页岩探明总储量折算     

桦甸油页岩自热干馏

对油页岩干馏过程中能量输入过高的问题,研究了油页岩含氧低温载气干馏过程(N2-Air-R)。N2-Air-R过程是在氮气气氛下通过外加热将油页岩加热至一定温度,然后停止外加热并将氮气替代为150℃的空气,此后油页岩自热升温,不需外加热便可完成干馏。研究表明外加热到300℃时通入空气能达到最好的干馏效果。将N2-Air-R过程与其他两种干馏过程进行了比较:全程在空气气氛下采用外加热将温度加热到干馏终温550℃(Air-R);全程在氮气气氛下采用外加热将温度加热到干馏终温550℃(N2-R)。结果表明,N2-Air-R过程与其他干馏过程得到的页岩油成分相似,均为碳氢化合物,且沸程相近。最后通过研究三种干馏过程中半焦结构随温度的变化,讨论了N2-Air-R干馏过程与其他过程不同的原因。     

回转式油页岩干馏炉测温技术研究进展

介绍了油页岩低温干馏制油气的过程和工艺,阐明了干馏是一个复杂的物理传热和化学热解的过程,是整个页岩炼油中最关键的工艺,并介绍了目前国际上关于低温干馏反应炉的技术,其中包括Galoter技术、ToscoⅡ技术、LR技术以及ATP技术。分析了在油页岩反应炉中温度对产油率的影响,表明温度对整个反应炉的重要性,并进一步分析了温度对干馏所造成影响的原因,重点阐述了温度测量的重要性与技术方法。对回转式油页岩干馏炉的测温现状进行了综述,总结了目前常用的一些回转炉测温方法,针对回转式油页岩反应炉目前存在的问题,提出了在温度控制、系统检测、红外测温等方面的改进措施。     

小颗粒油页岩干馏技术探讨

主要介绍了国内、外小颗粒油页岩的处理技术,针对国内的三种加工工艺和国外的两种加工工艺所涉及到的五种炉型工艺进行比较,得出用回转炉处理小颗粒页岩的结论及用干馏瓦斯做外热式回转炉的燃料气、用外热式回转窑处理小颗粒页岩的设想。     

油页岩含氧低温载气干馏过程实验

油页岩干馏生产页岩油是油页岩的主要加工利用方式。为降低油页岩干馏所需热载气温度,以延长载气预热器使用寿命并实现节能操作,本文向热载气中掺入一定比例氧气,对含氧低温载气情况下的油页岩干馏过程进行了研究。测定了油页岩在含氧气体氛围中热解时的反应器床层升温特性,对气液相产物组成进行了分析并与无氧干馏产物进行了比较。结果表明,含氧低温载气干馏过程能够通过载气中的氧气与油页岩反应产生的热量使油页岩达到其干馏所需要的温度,页岩油收率及其成分与无氧高温载气干馏过程接近、而轻组分含量更高,并且含有更多的具有O—H键和C==O键官能团的化合物。本文研究结果为油页岩干馏生产页岩油提供了一种新的技术方法,具有较好的工业应用前景。     

The heat transfer coefficient between a particle and a bed (packed or fluidised) of much larger particles

The heat transfer coefficient has been measured for a heated phosphor-bronze sphere (diam. 2.0, 3.0 or 5.56 mm) added to a bed of larger particles, through which air at room temperature was passed. The bronze heat transfer sphere was attached to a very thin, flexible thermocouple and was heated in a flame to before being immersed in the bed. The cooling of the bronze sphere enabled the heat transfer coefficient, h, to be measured for a variety of U/U_mf, as well as diameters of both the particles in the bed and the heat transfer sphere. It was found that before the onset of fluidisation, h rose with U, but h reached a constant value for U?U_mf. These measurements indicate that in this situation (of a relatively small particle in a bed of larger particles) all the heat transfer is between the hot bronze sphere and the gas flowing over it. Consequently, a Nusselt number, based on the thermal conductivity of the gas, is easy to define and for U?U_mf (i.e. a packed bed), Nu is given by

     

Analysis the fry-drying process of oily sludge sample

Oily sludge is one of the hazardous materials if not properly treated. Thus, recovering oil from oily sludge could reduce environmental problems and have substantial commercial benefits. However, prior to oil recovery, dehydration is extremely necessary to effectively reduce energy consumption. Fry-drying is a novel dehydration method which characterized by low energy consumption and high drying efficiency. In this study, the spent lubricating oil of vehicle was used as frying medium, which enabled a drying operation that was environmental friendly and economically competitive. A modified Dean-Stark apparatus-II was designed to accurately and efficiently measure the water and oil contents of the fried sample. Considering the oil adsorption mechanism that occurred during the fry-drying of oily sludge, a suitable equation for the forced convective heat transfer coefficient (h) was established using the fundamental of energy balance. Results showed that the h change tendency and the calculated maximum value were distinct from previous food frying findings. Finally, the entire fry-drying process of oily sludge was divided into four periods according to the different sample drying rate change tendencies. The heat and mass transfer processes of each period were also analyzed.     

A refined methodology for evaluation of heat transfer coefficients in canned particulate fluids under rapid heating conditions

The conventional methodology was refined for calculating the heat transfer coefficients (U and h_fp) under rapid heating conditions. The conventional methodology of h_fp evaluation became unreliable and/or non-reproducible under rapid heating conditions such as those encountered during reciprocation thermal processing. This was due to fluctuations in gathered transient temperatures during rapid reciprocating motion and due to very short equilibration times (EQT) (heat-up time to 1 °C below operating temperature).In this method, U and h_fp were calculated employing temperature profiles predicted by using an average retort temperature (after the come-up period) and heat penetration parameters, instead of real data points from experimental temperature profile as used in conventional methodology. The method was validated for various reciprocation frequencies (0–3 Hz) and amplitudes (0–20 cm). Results revealed that the refined methodology was robust and produced reliable and consistent values of U and h_fp, under both slow and rapid heating conditions. Also, the heat transfer coefficient values, using the developed method, consistently matched the results and trends observed with conventional methods. A parameter sensitivity analysis was also conducted and the effects of perturbations of different parameters employed in the refined methodology were reported.     

Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (< 200 °C) and constant oil shale grade, both the relative dielectric constant (ε′) and imaginary permittivity (ε″) decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, ε′ decreases or remains constant with oil shale grade, while ε″ increases or shows no trend with oil shale grade. At higher temperatures (> 200 °C) and constant frequency, ε′ generally increases with temperature regardless of grade while ε″ fluctuates. At these temperatures, maximum values for both ε′ and ε″ differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools.     

Effect of System Variables on Heat Transfer to Canned Particulate Non-Newtonian Fluids During End-Over-End Rotation

Apparent heat transfer coefficients h_ap and U_a were evaluated to quantify the heat transfer process with particulates in high viscosity non-Newtonian fluids in end-over-end thermal processing. An orthogonal array L16 experiment was used to examine the significances of system factors on h_ap and U_a values with plastic particles in CMC aqueous solutions. The variance analysis showed that rotation speed, liquid viscosity, retort temperature, particle material and particle concentration were significant factors (P < 0.05) for h_ap and U_a. The effects of can size was also significant for h_ap. A central composite rotatable design (CCRD) experiment and two full factorial experiments were carried out to study the effects of those significant factors on h_ap and U_a values. Results showed that with the decrease of liquid viscosity and the increase of rotation speed, particle density and retort temperature, h_ap and U_a values increased. With the increase of can size h_ap values decreased. With the particle concentration increasing h_ap and U_a values firstly increased and then decreased with further increase in particle concentration.     

油页岩有氧干馏过程的机理研究

常规的油页岩无氧干馏技术具有高能输入的缺点,因此本课题组发展了低能输入且无需高温热载体的有氧干馏技术。利用热重分析技术(TG-DTA),并结合拉曼和红外(FT-IR)等表征技术,研究了桦甸油页岩在不同过程中的分解特性。结果表明:在无氧条件下油页岩的热失重显著低于在有氧条件下的热失重,归于在无氧过程中产生大量的不能生成页岩油的残余碳。残余的碳与氧很容易发生反应并能放出大量热量,残余的碳与氧气反应释放出的热量高达油页岩总热值的35%,这部分热量远远高于油页岩热解所需的热量。最后,根据以上的分析结果,提出了油页岩有氧干馏过程可能的反应机理。     

Structural and quantitative evolution of organic matters in oil shale during two different retorting processes

In this study, traditional strongly endothermic anaerobic retorting (AR) and relatively novel self-heating retorting (SHR) processes for oil shale (OS) were investigated and compared in detail. These studies mainly involve the structural and quantitative evolution of organic matters in OS during retorting, including varieties of crystallite parameters, carbon framework structure, amounts of various structural carbons and toxic polycyclic aromatic hydrocarbons, and so on. The obtained results well elucidate some reaction pathways in AR and SHR as well as certain differences between the two retorting processes. Moreover, based on our former work that verifies SHR greatly simplifies retorting operation by in situ generating heat to replace external heat carrier/provision, this study further demonstrates that SHR also alleviates the environmental effect of organic toxic residues as compared to AR. The present study provides some critical results not only for penetrating the reaction mechanism but also for assessing or controlling the environmental impact of both retorting processes.     

Trace metal composition of Green River retorted shale oil

Crude shale oils from an aboveground and two in-situ retorting processes were characterized for 26 trace element constituents. The shale oils were pyrolysed from Green River Formation oil shale by pilot plant or semiworks-sized facilities. Trace elements were resolved into those predominantly associated with suspended shale fines or emulsified water, and those more intimately associated with the shale oil matrix. The abundance of the metals As, Co, Fe, Hg, Mo, Ni, Sb, Se, V and Zn were quantified in whole and fractionated shale oil samples; the possible chemical nature of several metals is discussed. Based on the shale oils examined, the following observations were noted: the shale oils contained moderately high levels of Fe (33–63 ppm) and As (9.3–29 ppm), and lower quantities of Co, Mo, Ni, Se and Zn (≈1–10 ppm); most trace metals were associated with asphaltene or resin components; relative to reported mean values for petroleum, the As, Co, Fe, Mo and Se were more prevalent in Green River shale oil; in-situ retorting processes appeared to introduce Mo into the product shale oil.     

A heat transfer study for a partially immersed refractory rod in a plasma

The thermal behavior of a tungsten rod partially immersed in a plasma flame is analyzed. The longitudinal temperature profiles are obtained by numerical solution of the heat balance equation. Results show that a heat transfer model consisting of pure natural convection up to the plasma outer edge and forced convection inside the plasma, fails to predict temperatures at the hot tip of the rod. In order to make the experimental and calculated profiles to converge, one has to consider modifications in the mechanical and thermal conditions of the surrounding medium due to the presence of the rod in the plasma. This leads to the use, in the “cold” gas zone, of particular values of heat transfer coefficient h and of a parameter T_x which is defined only at the immediate boundary of the rod. The latter are given in the form of variations along the axis of the rod. This perturbation effect decreases with the rod diameter. Allowance is made for the variation of the thermal properties of the solid.     

Results of mathematical modeling of oil shale retorting in an aboveground,external-combustion,moving-bed retort

Our one-dimensional mathematical model for simulating the chemical reactions and physical processes in oil shale retorting was applied to the indirect mode of operating an aboveground retort in which externally heated recycle gas provides the heat required for the retorting process. Countercurrent to the hot gas flow, a moving bed of shale is pushed upward through an expanding conical reactor, as in the Union B retort. The model was applied to a hypothetical set of commercial-scale conditions in order to identify key operating or design parameters. Variations in recycle-gas temperature and flow rate, shale flow rate, shale grade, water content, particle size distribution, bed porosity, uniformity of bed porosity, and retort dimensions were studied. The results of these calculations help identify the relative importance of the different process parameters in terms of oil yield, pressure drop, exit temperature of gas and shale, fuel consumed in heating the recycle gas, compressor power, condenser cooling load, and reactor size.     

Results of mathematical modeling of oil shale retorting in an aboveground,internal combustion retort

The one-dimensional mathematical model developed at the Lawrence Livermore National Laboratory to simulate the detailed chemical reaction kinetics involved in modified in-situ retorting of oil shale has been applied to simulate aboveground retorting in a moving, packed-bed retort. Application of the model to simulate such a retort was made for the internal combustion mode of operation, using typical operating conditions of the Paraho semiworks retort. Comparison with the semiworks experimental data revealed the general accuracy of the model in calculating retort temperature profiles, oil yield, off-gas composition, and outlet shale composition. The model was also applied to a hypothetical set of commercial-scale conditions in order to identify key operating or design parameters. These parameter studies predicted that the oil yield and the overall process performance could be markedly improved by increasing the recycle gas flux, decreasing the inlet-air flux, and relocating the inlet-air distributors. A process flowsheet was developed for the complete retorting system.     

Thermal degradation of shale oils: 1. Kinetics of vapour phase oil degradation

As vertical modified in-situ retorts (VMIS) have been scaled up and tested, the overall oil yield has declined and is generally lower than that observed in an above-ground process. This reduced oil yield could adversely affect the economics of VMIS retorting. Diminished yields are attributed to a combination of factors associated with scale-up such as in complete rubblization, wide particle size distributions (large blocks of shale), and poor flow distributions. Additionally, oil losses can occur by comparatively long exposure of the oil vapours to high temperatures, by exposure to successive condensation and revaporization of the oil as it travels down the retort, and finally by long time thermal exposure of the condensed oil retained in the bottom portion of large VMIS retorts. To study such vapour phase degradation of shale oil using oil produced from Occidental Petroleum's No. 6 VMIS retort, a tubular continuous flow reactor, with an on-line gas chromatograph for gas composition monitoring was used to study thermal degradation of shale oil under retorting conditions. Oil and a combination of gases including steam were metered into the preheater and then the vapours passed into a quartz tubular reactor where the temperature and residence time of the gaseous mixture were controlled. Complete mass balances were performed giving the weight fraction of oil converted to noncondensable hydrocarbon gases and coke. This experimental design is novel because high temperature thermal degradation of shale oil was studied for the first time under steady state flow conditions with carefully controlled residence time and temperature. A range of temperatures (425–625 °C) and residence times (2–10 s) were used in a series of factorial-designed experiments (3²) to accurately determine the effects of these variables. Results of the study showed that the addition of steam to the carrier gas did not reduce oil degradation losses but did react with the coke thereby changing the product gas composition and quantity. A first-order oil degradation rate expression was used to model the rate of oil loss. The calculated activation energy was 17.3 kcal mol^?1. Chemical analyses of the product liquids and gases confirmed previously reported findings that the oil loss indices (alkene/alkane, ethylene/ethane, naphthalene/(C₁₁ + C₁₂), and gas/coke) increase with increasing oil degradation.