Heavy Oil Thermal Cracking Research Articles

Study on the pathways of thermochemical sulfate reduction between sulfates and alkanes at low temperatures

To reduce the energy consumption of heavy oil thermal recovery, low-temperature hot water flooding is becoming popular. The occurrence of thermochemical sulfate reduction (TSR) reactions during the hot water flooding process generates H2S, which can corrode equipment and jeopardize personnel safety. Preventing and managing H2S requires studying TSR reactions. The study investigated the reactivity of SO42-, HSO4-, and [MgSO4]CIP in the TSR reaction during heavy oil low-temperature hot water flooding. The results indicated that during low-temperature hot water flooding, no significant thermal cracking of heavy oil occurs, only a minor aquathermolysis takes place, while the TSR reaction proceeds vigorously. The TSR reaction leads to increased yields of H2S, CH4, and CO2, as well as a higher S content in the heavy oil. Based on experimental results, numerical simulations of the reaction process between SO42- and CH4 were conducted using density functional theory and transition state theory. The results indicated that the reduction of SO42- to produce SO32- is the rate-limiting step in the entire reaction pathway between SO42- and CH4. Further analysis of the reaction barriers and chemical reaction rates of the three sulfates (SO42-, HSO4-, and [MgSO4]CIP) and C1-C5 alkanes was conducted based on the limiting step. Through macro and micro analysis, this study not only confirmed previous findings regarding the order of alkanes participating in TSR reactions from the perspective of microscopic molecular but also clarified the oxidation order of sulfate species under heavy oil low-temperature thermal water flooding conditions, with the sequence being HSO4- > [MgSO4]CIP>SO42-. This study provides a foundational understanding of TSR reactions during heavy oil low-temperature hot water flooding and is of significance for the prediction and management of H2S.

Optimization of Efficient Development Modes of Offshore Heavy Oil and Development Planning of Potential Reserves in China

Thermal recovery is still the most important means to increase heavy oil EOR. With the increase in the recovery factor and the difficulty of exploiting new exploration reserves, the efficient utilization of offshore heavy oil reserves has attracted much attention. However, due to the challenges of high development investments, high operating costs, platform safety factors, and high economic cumulative yield, the offshore heavy oil reserves of nearly 700 million tons have not been effectively utilized. In this paper, Chinese offshore heavy oil reserves were taken as the research object. The indoor one-dimensional experiments were carried out to optimize an applicable development method, and the superheated steam huff and puff was selected as the injection medium for high-speed and high-efficiency development of offshore heavy oil, which verified the great potential of the application of superheated steam in offshore heavy oil thermal recovery. A numerical simulation model for offshore heavy oil superheated steam injection development was established, and a dynamic model considering the thermal cracking of heavy oil was established through historical matching. Through the field numerical simulation models, the whole process development mode of a single sand body, thin interbedded reservoir superheated steam huff and puff turning to superheated steam flooding, and thick layer super heavy oil reservoir with bottom water sidetracking after superheated steam huff and puff for eight cycles was established. Through the numerical simulation method and grey correlation method, the main control factors of superheated steam development of different types of heavy oil reservoirs were determined, and the cumulative oil production charts of different types of reservoirs under the influence of the main control factors were built. The economic evaluation model of superheated steam development of offshore heavy oil was established. Combining multi-specialty of geological, reservoir engineering, drilling and completion, oceanographic engineering, economics, the economic limits of steam injection development under different reserve scales, and engineering conditions of offshore heavy oilfields were clarified. At last, we planned the economic production mode of undeveloped reserves and predicted the construction profile of superheated steam capacity of offshore heavy oil using the production charts and the economic charts. The research results clarify the great potential of thermal recovery development of offshore heavy oil, provide an important basis for the economic development of offshore heavy oil undeveloped reserves, and also provide an important decision for the sustainable and stable production of global heavy oil reservoirs.

Coke formation of heavy oil during thermal cracking: New insights into the effect of olefinic-bond-containing aromatics

The distributions of olefinic-bond-containing aromatic hydrocarbon (OAH) and the effect of OAH on coke formation during heavy oil thermal cracking have been rarely studied in the past. Here, the information of olefins in thermally cracked products derived from vacuum residue (VR) was investigated first, and then the effect of OAH on coke formation was elaborated by revealing the evolution characteristics of self/co-addition systems participated by representative OAH model compounds. The results found that OAHs were generated during VR thermal cracking, and they could participate in further reactions to promote coke formation. During thermal reaction, OAHs were more reactive for addition reactions than alkenes, and the reactivity of OAH increased roughly with the number of aromatic rings. Meanwhile, the higher concentration of OAH or the longer thermal reaction time or the higher thermal reaction temperature, the higher conversion of addition products, and the greater condensation degree of reaction products. OAHs participating in the larger structure molecule formation involves free radical addition reactions, which could occur between different OAHs as well as between OAHs and conventional aromatic molecules. More importantly, OAHs could form larger structure molecules by direct addition reaction of unsaturated double bond via non-free radical addition reaction, thus promoting fast coke formation.

Catalytic effects of Al2O3 nano-particles on thermal cracking of heavy oil during in-situ combustion process

In-situ combustion (ISC) is regarded as one of the most promising and economic alternative in the development of heavy oil reservoir. Maintaining high temperature oxidation (HTO) reaction with a high cracking efficiency at relatively low fuel consumption is deemed particularly crucial for the success of ISC process. In this work, Al2O3 nano-particles as a catalyst for achieving this during ISC is investigated in three parts. First, kinetic cell experiments with ramped temperature oxidation (RTO) process were conducted on the heaviest fraction of crude oil (residue) to obtain the apparent activation energy (Ea) fingerprints for oil-oxygen reactions with and without Al2O3. Second, thermogravimetric analysis-mass spectrometry-differential scanning calorimetry (TGA-MS-DSC) was used to detect pyrolysis products from the residue and characterize its dynamic change during the process, with SEM and EDS employed to observe the morphology and verify the condition of nano-particles afterwards. Third, combustion tube experiments were performed on the whole crude to analyze the distinction between combustion behavior with and without Al2O3. The results showed addition of Al2O3 catalyst resulted in: Ea decreased and oscillated visibly, temperature of fire front increased by 60.3–83.6 °C, speed of propagation was enhanced by 37.3%, residual coke remains in the quartz sand at the end of combustion tube experiment decreased by 24.8%, production efficiency increased by 13–64% with the reduction of COx production (12.3%) and oxygen consumption (26.9%). This shows a higher ultimate oil recovery is possible with higher upgraded oil percentage during a catalyst-assisted ISC process, which bodes well for future field application.

Balancing broad and deep searches in evolutionary computation via a parallel zoning search

Computational time and solution precision are two major concerns in evolutionary computation (EC). Although high-performance computing techniques have been applied to reduce the computational time of meta-heuristic algorithms, it does not mean that they can assist meta-heuristic algorithms in finding a high-quality solution. Moreover, most of meta-heuristic algorithms may belong to the “depth-first” search method, thus achieving a tradeoff between the broad search and the deep search is a crucial objective in the EC. To alleviate the above problems, a parallel zoning search (PZS) strategy is proposed in the current study. In the PZS, the entire search space is divided into many small search spaces for improving the broad search capability of algorithms and reducing the problem complexity. Subsequently, selected meta-heuristic algorithms considered as deep search algorithms are employed to find a satisfactory solution in each search region. The effectiveness of the PZS integrated into six differential evolution (DE) variants is demonstrated on two commonly used test suites, i.e., IEEE CEC2014 and BBOB2012. Results suggest that the PZS is a highly competitive approach to solve different types of optimization problems, especially on complex optimization problems. Finally, the PZS incorporated into six DE variants is used to estimate parameters of a heavy oil thermal cracking model. Results indicate that the PZS is an effective and efficient tool to help selected algorithms solve actual industrial optimization problems.

Auto-selection mechanism of differential evolution algorithm variants and its application

Each type of problems, such as unimodal/multimodal, linear/non-linear, convex/non-convex, and symmetrical/asymmetrical, has its own characteristics. Although various differential evolution (DE) variants have been proposed, several studies indicate that a DE variant may only exhibit high solution efficiency in solving a specific type of problems, but may perform poorly in others. Therefore, an important decision is made to automatically select a suitable DE variant among several chosen algorithms for solving a particular type of problems during the evolutionary process. To achieve this objective, an auto-selection mechanism (ASM) is introduced in this study. In the ASM, rankings attained using Friedman's test are adopted to assess the performances of DE variants. A learning strategy is employed to update the choice probabilities of DE variants, and an additional selection probability is used to alleviate the greedy selection issue. Three sets of benchmark test functions proposed in BBOB2012, IEEE CEC2005, and IEEE CEC2014 are used to evaluate the effectiveness of the ASM. The performance of the proposed algorithm is also compared with that of nine state-of-the-art DE variants and four non-DE algorithms. Statistical analysis results demonstrate that the ASM is an efficient and effective method that can take full advantages of multiple algorithms. Furthermore, the ASM is utilized to estimate the parameters of a heavy oil thermal cracking model. Experimental results indicate that the proposed algorithm outperforms the other compared algorithms in this case.

Narrow Fraction Model with Secondary Cracking for Low-Severity Thermal Cracking of Heavy Oil

Thermal reaction experiments of vacuum residuum were conducted in a micro-batch reactor at 410–480 °C. The product yield variation with time indicated that the secondary cracking reaction mainly oc...

Oxidation of Ethylene and Propene in the Presence of CO2 and H2O: Experimental and Detailed Kinetic Modeling Study

Ethylene and propene are major products of the thermal cracking of heavy oil. Under flameless combustion, they are oxidized in presence of large amounts of CO2 and H2O, which may affect their kinetics of oxidation. New experimental results for the kinetic of oxidation in a jet-stirred reactor (JSR) of ethylene and propene in the presence of CO2 and H2O were obtained (1 atm, 950–1450 K). Sonic probe sampling with online FTIR analyses and offline GC-TCD/FID analyses allowed the measurement of concentration profiles for the reactants and products. A detailed kinetic reaction mechanism was used to model the experiments. Good agreement with the data was obtained. Reaction paths analyses showed the important reactions influencing the kinetic of oxidation of the present fuel mixtures. Water tends to inhibit the combustion of the fuels, whereas CO2 has a small accelerating effect upon the oxidation of ethylene in fuel-rich conditions.

The Study of Molecular Modeling for Heavy Oil Thermal Cracking

AbstractThe tighter specifications for refining products have gradually led refineries to focus on the molecular modeling of petroleum processing. In this work, a systematic methodology is presented for the molecular modeling of heavy oil thermal cracking (HOTC). This research which is based on a microscopic understanding provides a basis to achieve better design, management, optimization, and control of HOTC. The molecular information of HOTC product streams is represented in the form of a MTHS (molecular type homologous series) matrix. From consideration of the complexity of structural isomers in heavy petroleum fractions, the heavy molecules in a homologous series are grouped to reduce the dimension of the MTHS matrix. Transformation correlations are developed to capture the molecular properties of each homologous series in the MTHS matrix and to interrelate the molecular composition and bulk properties of the product streams. The HOTC process model was built on the basis of the molecular representation provided by the MTHS matrix and the transformation correlations. Two case studies are illustrated for validation of the proposed model and methodology.

DNA computing based RNA genetic algorithm with applications in parameter estimation of chemical engineering processes

Based on RNA genetic operations and DNA sequence model under selection and mutation, an electronic RNA genetic algorithm (RNA-GA) with improved crossover and mutation operator is proposed. The proposed algorithm can be implemented on real biochemical reaction after simple transition, thus, the brute force method of DNA computing can be broken. The convergence analysis of the proposed algorithm shows that RNA-GA with elitist strategy can converge in probability to the global optimum. Comparisons of RNA-GA with standard genetic algorithm (SGA) for typical test functions show the advantages and efficiency of the proposed algorithm. As illustrations, the RNA-GA is implemented on parameter estimation of a heavy oil thermal cracking 3-lumping model and a fluid catalytic cracking unit (FCCU) main fractionator. In both cases, it is shown that the methodology is effective in parameter estimation of chemical processes.

Agglomeration and Deposition of Coke during Cracking of Petroleum Vacuum Residue

Hydrophobic fine solids can reduce the yield of toluene-insoluble coke in thermal cracking of heavy oils at short reaction times. In this work, fine carbon solids were used as additives in the coking of Arab heavy-vacuum residue (AHVR) in 1-methylnaphthalene (1-MN) to study the mechanism of this interaction. Both mesophase carbon and spherical graphite particles significantly reduced the coke yield compared with the case of no solid addition. Coke deposited on the surfaces of the two hydrophobic additives. This nucleation of coke deposition on the solid reduced the agglomeration of the coke, giving a better dispersion in the liquid. The highly dispersed coke phase on fine solids was more accessible for reactions with hydrogen-donor compounds in the oil phase, which in turn inhibited the initial rate of coke formation.

A computer aided tool for heavy oil thermal cracking process simulation

This work presents the model for the development of a computer aided tool for heavy oil thermal cracking process simulation. It is proposed a dual plug flow reactor representation for the light pyrolysis of petroleum distillation residues in coil-type reactors. The resulting reactor model consists of two parallel plug flows, one vapor and the other liquid, traveling at different speeds in a coil. Reaction is assumed to be the rate controlling process with equilibrium between the phases. Because of the pyrolysis reactions and pressure drop, vaporization takes place continuously along the coil so there is a decrease in the liquid hold-up. The model derived uses a heuristic lumping approach based on pilot plant data and the resulting pseudokinetic scheme presents a certain feed independence within the range of stocks available for the study. An industrial case study (delayed coking) is explored to provide insight into the problem of reconciling the kinetics of pyrolysis and carbonization for the upgrade of distillation residues.

Comprehensive Kinetic Models For the Aquathermolysis of Heavy Oils

Abstract Aquathermolysis experiments over the temperature range 360 to 422 ºC were performed on core samples taken from three large bitumen and heavy oil deposits found in Alberta: Athabasca, North Bodo, and Frisco Countess. The purpose of this work was to facilitate the development of comprehensive thermal cracking models for predicting gas and liquid phase product distributions under conditions anticipated during thermal recovery. Previous studies. have shown by material balance on oxygen that water is implicated in many of the chemical reactions leading to the formation of H2S and CO2, yet most of the reported thermal cracking studies have not included water. Additionally, experimental investigations in this area have, for the most part, not involved realistic time frames, and as such certain phenomena observed in this work have not been previously reported. The experiments conducted using Athabasca bitumen included runs with an initially previously oxidized oil sample (designed to simulate conditions preceding the arrival of the firefront during in situ combustion) and runs with a change in core mineralogy. Pre-oxidizing the oil was found to substantially increase the amount of H2 generated. Core mineralogy played an important role in the generation of CO2; and the amount of H2S produced was. dependent on oil composition, mineralogy, and time. Gas production was observed to be largely associated with the conversion of the heavy. oil and asphaltenes oil fractions. The cracking models developed in this work offer useful directional insight as to the effect of core mineralogy and oil composition on the kinetic parameters, and a much needed means of estimating the calorific value and acidic gas content of the produced gases during thermal recovery operations. Introduction The purpose of this work was to develop thermal cracking models capable of describing the liquid and gas phase compositional changes that occur during thermal recovery operations. Although rather extensive laboratory studies have been performed concerning the thermal cracking of heavy oils and bitumen, few in comparison have included water as part of the reactants. Laboratory studies(1, 2, 3) and field applications of thermal recovery processes(4) have demonstrated that appreciable amounts of gaseous environmental contaminants such as H2S and CO2 arecreated by the aquathermolysis (steam/oil reactions) of heavy oils. hese problems are all the more severe as the sulphur and oxygen content of the oil increases(5). It has also been demonstrated(2) that H2 and light saturated hydrocarbons are also produced by steam/oil reactions over the temperature range 200 to 300 ºC. Accordingly, casing gas produced from cyclic steam stimulation projects has sometimes been collected and condensed yielding between 0.015 and 1.5 m3 of condensate per well per day(6), with the noncondensible gas (which contains mostly methane) being used as a supplementary fuel for the steam generators. Thus, aside from the pollution aspect there is the potential to recover chemical energy from the effluent gases. In this paper we present thermal cracking models based on aquathermolysis experiments performed on core samples from three large bitumen and heavy oil deposits in Alberta: Athabasca, North Bodo, and Frisco Countess. The oils from these deposits have contrastingly different elemental compositions and API gravities. For the experiments involving Athabasca oil sands we report on three sets of tests: two involving significantly different core minera

Pyrolysis of Aromatics and Polar Compounds Fractions of Deasphalted Oils in the Presence of Saturated Model Compounds.

To obtain an insight into behavior of saturated components in thermal cracking of heavy oils, Curie-point pyrolysis of mixtures of aromatics (A) and polar compounds (P) fractions (A+P) of deasphalted oils (DAO) (i.e. DAO samples not containing saturates fraction) prepared from an Arabian mixture (AL/AM) and Minas crude was examined in the presence of three kinds of saturated model compounds, triacontane, squalane, and cholestane. It was found that the naphthenic compound, cholestane, can considerably reduce coke yields from both oil samples, whereas the other two compounds showed essentially no effect. Possible role of naphthenic compounds in the thermal treatment of heavy oils was also discussed, based on the results of the pyrolysis of cholestane. In addition, pyrolysis of asphaltenes from the two crudes, in the presence of the saturates fraction of AL/AM-DAO, which contained a relatively large amount of naphthenic compounds, was also examined.

Heavy-oil cracking: The case for nonhomogenous kinetics

The thermal cracking of heavy oils has been modelled on the basis of combinations of first-order reactions in order to describe the behaviour of pseudocomponents with time and temperature of reaction. An alternative formulation uses the concept of a time-varying rate constant of the form[Formula: see text]where β is the rate constant and γ is an exponent that has values of 0 < γ ≤ 1.0. This was used to derive a transform of temperature and time that we have called the reaction ordinate Rω, which enables the correlation of extensive kinetic data sets by means of three constants: β, γ, and the mean activation energy Ea. We demonstrate this correlation for two sets of published data. The values of γ were less than unity and are interpreted in terms of the Kohlrausch function, leading to the hypothesis of a continuous distribution of activation energies in the system. This form of correlation is similar to that of the continuous-time random-walk relaxation phenomena that has been explained in many ways including fractal time, and thus we propose that this is indirect evidence for the nonhomogenous nature of heavy-oil-cracking kinetics.

Selective thermal cracking of heavy oils. Part 4. Thermal cracking of kuwait atmospheric residue in the presence of hydrogen and nickel supported catalysts.

Selective thermal cracking of heavy oils. Part 4. Thermal cracking of kuwait atmospheric residue in the presence of hydrogen and nickel supported catalysts.

Selective thermal cracking of heavy oils. Part 3. Thermal cracking of Kuwait atmospheric residue in the presence of hydrogen and metal supported .BETA."-Al2O3 catalyst.

強塩基性物質β"-Al2O3にNi, Mo, Co等の水素化能を有する金属を担持した触媒を用い, 反応圧75kg/cm2, 反応温度435°Cの条件でクウェート常圧残油の分解を行い, 担持金属が反応特性に与える影響を検討した。本分解法では, コーク収率が著しく低いことを除き, 生成物分布は同レベルの分解率を持つ無触媒系のそれとほぼ同一であり, 分解は熱的に進行していることが示唆された。触媒は事実上ラジカルの水素化安定化のみを行い, 反応特性は主として触媒の水素化能によって支配され, 触媒の水素化能が高い系ほど転化率, コーク収率は低下した。

Selective thermal cracking of heavy oil. (Part 5). Selective thermal cracking of Kuwait atmospheric residue using CO shift reaction.

クウェート常圧残油を原料とし, ガス流通式小型反応器を用いて, ニッケル, コバルト, モリブデンなどの金属担持アルカリ担体触媒存在下, (CO-H2O) 雰囲気中で, 全圧力50～75kg/cm2G, 温度420°C, H2O送入量4～8g/hr, CO送入量7～8l/hrの範囲の反応条件で熱分解反応を行った。その結果, COシフト反応が進行し, かなりの水素が発生し, そのうち60～80%が重質油の水素化に消費された。触媒存在下では, 無触媒下での熱分解に比べ, 中間留分選択率は増加し, ガスおよびコーク選択率は減少すること, および触媒存在下においても, CO圧力, H2O送入量によって生成物分布が変わることが判明した。生成留出油中には, ナフサ中25～30%, 灯油中6～15%, 軽油中8～12%のオレフィンが含有され, 触媒の有無によって大きな違いは認められなかった。また, これらの反応条件下では, 触媒の有無, 種類によらず脱硫率は低かった。本反応系の諸特徴は熱反応の中間体である遊離基が触媒によって水素化されるとして説明された。

Influence cinétique et chimique d'alcènes sur la pyrolyse d'alcanes: mise au point et nouveaux résultats

On the basis of previously reported, as well as new, experimental results, a review is presented of the kinetic and chemical influences of alkenes on the pyrolysis of alkanes. The results confirm that the addition of free H• atoms to the double bonds of alkenes is not sufficient to explain their inhibiting influence on the pyrolysis of alkanes. On the contrary, our results show that the processes of addition can account for the chemical effects of added alkenes on the pyrolysis of alkanes, namely, the modifications brought to the nature and the ratio of the products formed during the reaction. The results presented here confirm that the addition of alkyl free radicals to the double bond of alkenes does not lead to important chemical effects. The previously reported experimental results (pyrolysis of ethane in the presence of ethylene or propene, the pyrolysis of 2,2-dimethylbutane in the presence of propene, isobutene, or two isopentenes), completed by our new results (pyrolysis of ethane in the presence of isobutene, pyrolysis of isobutane in the presence of ethylene, of propene, of trans-2-butene, or of 2-methyl-2-butene), can lead to very simple general rules, on the basis of which it is possible to explain the results and to predict the modifications (relating to the nature of the products and to their ratios) that will result from the addition of an alkene during the pyrolysis of an alkane at a temperature of 500 °C (773 K). Aside from their fundamental aspects, these observations and their mechanistic consequences could be useful for the preparation of models for these thermal reactions, especially for the simplification of complex models. These observations also explain certain facts observed in industry and can help in solving some of the problems associated with the thermal cracking of heavy oils.

Thermal cracking and gasification of combustible materials in fluidized bed reactors.

At first, the author explains how the bubbling bed model has been conceived, developed and utilized for research and development of fluidized bed reactors. Referring to the Kunii-Kunugi Process for thermal cracking of heavy oils which uses a circulation system of coke particles, it is emphasized that a number of the results of the fundamental investigation have been well utilized throughout the development of the new process. The circulation system of fluidized solids has been applied for industrialization of Pyrox Process, which gasifies the solid waste materials. Judging the successful operation of the preceding two processes, the above circulation system could be well utilized for large scale carbonization-gasification process, which may be suitable to be constructed on an off-shore artificial island for a coal conversion center in the future. For small scale gasification of biomass or the other type of combustible materials, on the other hand, circulation of particles within a vessel is much preferable, one example of which is given in the text. At present, the author maintains that there are sound theoretical background for a rational prediction of gas and/or solids conversion in ordinary fluidized bed reactor.