Thermal Cracking Process Research Articles

On the development of a polyolefin gasification modelling approach

Gasification is a promising alternative for polymeric waste valorization when mechanical recycling is unfeasible on account of its heterogeneity or partial contamination, or simply when it yields a product of lower quality than what the market requires. Apart from its application for electricity generation, the waste-derived syngas shows a great potential for chemical waste recycling for the synthesis of hydrogen, methane, natural gas or methanol. In spite of the effort devoted so far to the experimental demonstration of these processes to enable this technology to access commercial stage, it is still necessary to develop detailed models of the process that allow a precise prediction of the resulting syngas composition, as well as tar formation and global efficiency of the process. This research work presents the development of a polyolefin gasification model for fluidized bed reactors. The model details the behaviour of primary pyrolysis and homogeneous reactions of oxidation, steam reforming, aromatization and thermal cracking. To accomplish this, it adopts new modelling strategies for the definition of primary tar species in order to reflect their twofold nature (aliphatic and aromatic), as well as to describe kinetics and stoichiometry involved in thermal cracking processes of tar species. The model is able to successfully predict the generation, volume composition and heating value of the syngas, final tar generation and global efficiency of the process.

English

Nowadays, polyvinyl chloride (PVC) is the most usual plastic. Therefore, to make PVC, its monomer called vinyl chloride (VCM) must be produced first. It is a severely endothermic reaction that is done in an ethylene dichloride thermal cracking reactor within a temperature range of 680 to 758°K and pressure range of 2500000 Pascal. Thus, this cracking reaction changes into hydrochloric acid and VCM. In production unit, monomeric chloride has the main and principal role as the core of the process of thermal cracking that occurs in the furnace. Increased wall temperature causes boil gas mixture and pyrolysis reactions. Regarding simulation, the results showed that the number of pyrolysis produced composition with maximum concentration in the length of the reactor. This illustrated that these compositions participated in secondary reactions. Furthermore, by increasing the amount of coil outlet temperatures, the amount of formed coke will increase. If carbon tetrachloride is considered as the chlorine radicals, it has an important role as the motivator in the cracking procedures, radicals causing an enhancement in VCM production. Key words: Carbon tetrachloride, conversion factor, coke, coil outlet temperatures, thermal cracking.

Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

The thermal cracking process of oil sand bitumen was investigated via studying the thermal cracking behaviors and online-gas-releasing characteristics of its SARA fractions (saturates, aromatics, resins, asphaltenes) by using TG–FTIR. The results showed that the asphaltenes contributed the most to coke formation of oil sad bitumen according to its largest weighted coke yield compared with that of others. The online FTIR analysis for the gases evolved from the thermal cracking process of oil sand bitumen and its SARA fractions indicated that the gaseous products in the main reaction stage showed more complex composition than those in the volatilization stage, and predominantly consisted of CO2, CO, methane, ethylene, other light alkanes and olefins, light aromatics, and hydrogen sulfide. Moreover, the release behaviors of typical gaseous products (CO2, CO, methane, ethylene, and light aromatics) for oil sand bitumen and its SARA fractions were different due to the different composition and structure. The t...

Production and Characterization of Green gasoline Obtained by Thermal Catalytic Cracking of Crude Palm Oil (Elaeis guineensis, Jacq.) in a Pilot Plant

This study investigated the production and characterization of green gasoline obtained from crude palm oil (Elaeis guineensis, Jacq.), which was submitted at a process of thermal catalytic cracking in a pilot plant. The cracking reactions were carried out in a reactor of 143 L, operating in batch mode at 450ºC and atmospheric pressure, using 20% (w/w) sodium carbonate (Na2CO3) as catalyst. The organic product liquid (OLP) obtained in the cracking was submitted the distillation in laboratory scale using a column vigreux type. The results show that the yields in OLP obtained in the presence of Na2CO3 were of 65.86%, with acid value of 1.02 mg KOH/g and an elevated formation of gas residual. In relating to the green gasoline this presented a low kinematic viscosity value of 0,72 (mm2.s-1) and acid value of 1,11 mg KOH/g. GC–MS analysis indicated in chemical composition of the green gasoline a percentage of 52,78% of hydrocarbon, of these 15,78% are paraffinic compounds, 31,54% of olefin, 3,50% of naphthenic and 1,94% of aromatic compounds

An experimental and simulated investigation on pyrolysis of blended cyclohexane and benzene under supercritical pressure

The pyrolysis characteristics of blended cyclohexane and benzene mixture are investigated under supercritical pressure. The experimental results show that cyclohexane pyrolysis is greatly easier than thermal cracking of benzene, and the addition of cyclohexane can significantly promote the benzene pyrolysis, while the thermal cracking of cyclohexane itself is weakened by the addition of benzene. A simulation of the blended fuel is carried out by using Chemkin program, indicating that the chemical heat sink of cyclohexane pyrolysis can account for nearly 50% of its total heat absorption capacity, while benzene is inactive in thermal cracking process.

Evaluation of Adding Carbon Tetrachloride as Propulsion to the Thermal Cracking Reactor due to the Amount of Formed Coke in Different Coil Outlet Temperatures (COT)

Nowadays, polyvinyl chloride (PVC) was the most usual plastic. Thereby, to make polyvinyl chloride its monomer must be produced firstly that was called vinyl chloride (VCM). It was severely endothermic reaction that was done in an ethylene dichloride ethylene dichloride thermal cracking reactor within temperature range of 680-758°K and pressure range of 2500000 Pascal, thus this cracking reaction changed into hydrochloric acid and VCM. In production unit, monomeric chloride had the main and principal role as the core of the process of thermal cracking that occurs in the furnace. Increasing of wall temperature cause to boil gas mixture and causing pyrolysis reactions. Regarding to the simulation results showed that number of pyrolysis produced composition have maximum concentration in the length of reactor that illustrated these compositions participated in secondary reactions. Furthermore, by increasing the amount of coil outlet temperatures, the amount of formed coke will be increased. If Carbon tetrachloride considered as the chlorine radicals, it has an important role as the motivator in the cracking procedures, radicals causing an enhancement in VCM production.

Growth of Carbon Nanofibers in Phenolic Resin for Carbon-Contained Refractory Using Different Catalysts

Various phenolic resins modified with carbon nanofibers were prepared using Fe(NO3)3, Co(NO3)2, and Ni(NO3)3 as catalyst, respectively. The influences of different catalysts on the phase, microstructure evolution, and oxidation resistance of the modified phenolic resin were investigated by X-ray diffraction analysis, field-emission scanning electron microscopy, and thermal gravimetric analysis. The results showed that, compared with a single catalyst, the mixed catalysts (Co(NO3)2 : Fe(NO3)3 = 1 : 1) promoted the growth of the carbon nanofibers, which have the higher crystallinity, homogeneous dispersion, and nonagglomeration. These carbon nanofibers can effectively reduce carbon losses, increase char yield, and fill the holes in the thermal cracking process of phenolic resins.

Research of the thermal aging mechanism of polycarbonate and polyester film

Abstract Insulating paper is a traditional insulation material used for transformer insulation. Transformer development is not only limited to small sizes and large capacities, but also limited to insulation life as insulating paper cannot withstand high temperatures. Therefore, recent studies have focused on improving the performance of insulation paper and discovering better insulation materials. In this study, two types of polymeric materials, polycarbonate (PC) and polyester film (PET), were chosen for comparative analysis. In order to test whether these two materials could be used in oil-immersed transformers, the PC and PET were placed in transformer oil for thermal aging at 110°C and 130°C, respectively. The thermal cracking processes and fragmentation mechanisms of the PC, PET, and insulation paper were analyzed using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and atomic force microscopy (AFM), as well as their degrees of polymerization and surface morphologies. According to the test results, the initial thermal decomposition temperature of PC and PET are higher than insulation paper and exhibited a better thermal resistance. PC and PET have the potential to substitute insulation paper for large capacity power transformer.

Olefins and Ethanol from Polyolefins: Analysis of Potential Chemical Recycling of Poly(ethylene) Mexican Case

Abstract Plastic solid waste (PSW) presents challenges and opportunities to society regardless of their sustainability awareness and technological advances. A special emphasis is paid on waste generated from polyolefin sources, which makes up a great percentage of our daily commodities’ plastic products. In Mexico 7.6 millions of tons of plastic in 2012 were wasted, which low density polyethylene LDPE, and high density polyethylene HDPE were the most abundant. Increasing cost, and decreasing space of landfills are forcing considerations of alternative options for PSW disposal. Years of research, study and testing have resulted in a number of treatment, recycling and recovery methods for plastics that can be economically, and environmentally viable. The following work studies the possibilities of polyethylene recycling. Nowadays, non-catalytic thermal cracking (Pyrolysis) is receiving renewed attention, due to the fact of added value on a crude oil barrel and its very valuable yielded products, but a fact remains that advanced thermo-chemical recycling of polyolefin still lacks the proper design, and kinetic background to target certain desired products and/or chemicals. On the other hand some research have shown a good performance that can be used in a real plant. ASPEN Plus is used to simulate a non-catalytic thermal cracking process. The process behavior of simulation is similar to the experimental data from other authors. Using gibbs free energy to identify the chemical equilibrium in system, its global minimization allows identifying the amount of substances present in the process. The simulation results demonstrate that it could be produced 49 % and 34 % wt of ethylene and propylene respectively from gas yield at 850 °C. Then scale the plant to produce ethylene and propylene from the pyrolysis and ethanol from a direct hydration of ethylene. Aspen Process Economics Analyzer is used in order to find the feasibility of the pyrolysis and ethanol production. The total sales/total production cost ratio obtained for the integrated process approaches was 2.55.

Bound cleavage at carboxyl group-glycerol backbone position in thermal cracking of the triglycerides in sunflower oil

Bound cleavage at carboxyl group-glycerol backbone position of triglyceride of sunflower oil during the thermal cracking reaction was studied. Required experiments were performed in a continuous tubular reactor at atmospheric pressure. Experimental results showed that cracking at each bond of OCOC depends on the temperature. At low process temperatures, decarboxylation was enhanced, while at high temperature more fatty acids were formed. When liquid products were fractionated into some light to heavy cuts, the distribution of fatty acids was observed. Concentration of COOH group in the cuts showed that at the cracking conditions, carboxylic acid head of fatty acids was more stable than their hydrocarbon chain, so the second bound cleavage step had been taken place along the hydrocarbon chain and lighter fatty acids were formed. As a result, a more accurate mechanism for thermal cracking of triglycerides is recommended. The presented mechanism would help the experimentalists to have an ccurate prediction of the products for thermal cracking process of triglycerides.

Kinetics and mechanisms of the catalytic thermal cracking of asphaltenes adsorbed on supported nanoparticles

The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content. The upgrading and recovery processes of these unconventional oils are typically water and energy intensive, which makes such processes costly and environmentally unfriendly. Nanoparticle catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ conditions. In this study, the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C7 asphaltenes was investigated using a thermogravimetric analyzer coupled with FTIR. The performance of catalytic thermal cracking of n-C7 asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support alone. For a fixed amount of adsorbed n-C7 asphaltenes (0.2 mg/m2), bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles, confirming their synergistic effects. The corrected Ozawa–Flynn–Wall equation (OFW) was used to estimate the effective activation energies of the catalytic process. The mechanism function, kinetic parameters, and transition state thermodynamic functions for the thermal cracking process of n-C7 asphaltenes in the presence and absence of nanoparticles are investigated.

Impact of Thermal Treatment on Asphaltene Functional Groups

The main objective of this study is to provide an in-depth analysis that reveals the impact of thermal treatment on the different functional groups that exist in asphaltene molecules. This contribution is important to further understand the nature of changes that take place in asphaltenes during distillation and thermal cracking processes. A slight increase was observed in the aromatic −CH groups, compared to aliphatic −CH groups, as crude oil is processed to atmospheric and vacuum residues. A slight decrease was also observed in the intensity ratio between methylene and methyl groups (CH2/CH3) with distillation, which suggests a decrease in the average length of alkyl side chains for asphaltene molecules. The Fourier transform infrared (FTIR) results also suggest the possibility of thiophenic compounds oxidation during the atmospheric and vacuum distillations. More obvious differences were noted between asphaltenes exposed to thermal cracking, separated from the pitch samples, and their parent asphaltene...

Thermal Conversion Regimes for Oilsands Bitumen

Thermal conversion of oilsands bitumen at 400 °C was investigated to gain a better understanding of temporal changes in liquid properties. The work approximated a mild thermal cracking (visbreaking) process with run-lengths extending into the coking region. Reaction progress could be divided into three main regimes: (I) stable visbreaking, (II) coking visbreaking, and (III) coking. In addition to observations anticipated from the literature, the work revealed aspects of the reaction progression that was not fully appreciated before. Stable visbreaking with minimal formation of coke had a “productive” period during which viscosity decreased, while asphaltenes content and gas yield were unchanged, followed by an “unproductive” period during which the viscosity, asphaltenes content, and gas yield all increased. After the onset of precipitation of solids, the solids (“coke”) yield increased and the asphaltenes content in the liquid decreased, but the viscosity increased. The origin of increased viscosity was ...

Tracing the Compositional Changes of Asphaltenes after Hydroconversion and Thermal Cracking Processes by High-Resolution Mass Spectrometry

With heavy crude oil refining on the rise, upgrading strategies are fundamental to yield high-value products. Hydroconversion and thermal cracking are well-established and widely used upgrading processes for heavy oils’ distillation cuts and residues. Recognizing molecular changes in these fractions after upgrading, particularly of asphaltenic compounds, is fundamental to understand and optimize the processes. In this work, we follow compositional changes in the asphaltene fraction of a Colombian heavy crude, after hydroconversion and thermal cracking, using high-resolution mass spectrometry. The liquid products from the upgrading processes were fractionated into maltenes and residual asphaltenes, with yields between 33% and 38% in maltenes from the original asphaltene feedstock. Contoured plots of double bond equivalents versus carbon number and van Krevelen diagrams show maltenic fractions exhibiting lower aromaticity, smaller molecular size, fewer heteroatomic species, and higher content of alkyl side ...

Characterization of organic matter fractions in an unconventional tight gas siltstone reservoir

This paper on core samples collected from the Triassic Montney Formation tight gas reservoir in the Western Canadian Sedimentary Basin (WCSB) illustrates that operationally-defined S1 and S2 hydrocarbon peaks from conventional Rock–Eval analysis may not adequately characterize the organic constituents of unconventional reservoir rocks. Modification of the thermal recipe for Rock–Eval analysis in conjunction with manual peak integration provides important information with significance for the evaluation of reservoir quality. An adapted method of the analysis, herein called the extended slow heating (ESH) cycle, was developed in which the heating rate was slowed to 10°C per minute over an extended temperature range (from 150 to 650°C). For Montney core samples within the wet gas window, this method provided quantitative distinctions between major organic matter (OM) components of the rock. We show that the traditional S1 and S2 peaks can now be quantitatively divided into three components: (S1ESH) free light oil (S2aESH) fluid-like hydrocarbon residue (FHR), and (S2bESH+residual carbon) solid bitumen (more refractory, consolidated bitumen/pyrobitumen).The majority of the total organic carbon (TOC) in the studied Montney core samples consists of solid bitumen that represents a former liquid oil phase which migrated into the larger paleo-intergranular pore spaces. Physicochemical changes to the oil led to the precipitation of asphaltene aggregates. Subsequent diagenetic and thermal cracking processes further consolidated these asphaltene aggregates into “lumps” of solid bitumen (or pyrobitumen at higher thermal maturity). Solid bitumen obstructs porosity and hinders fluid flow, and thus shows strong negative correlations with reservoir qualities such as porosity and pore throat size.Although the FHR fraction constitutes a small portion of the total rock mass and volume in Montney samples it has important implications for reservoir quality. This fraction represents a thin film of condensed, heavy molecular hydrocarbon residue covering surfaces of the present-time pore spaces and may represent the lighter component of the paleo-oil that migrated into tight interstices in the Montney reservoir. The FHR fraction potentially plays an important role in wettability alteration by creating hydrophobic matrix pore networks in portions of the reservoir that were not already filled with solid bitumen.

Thermal Cracking of Virgin and Waste Plastics of PP and LDPE in a Semibatch Reactor under Atmospheric Pressure

Study of the decomposition kinetics, pyrolysis products, and even reaction mechanisms plays an important role for the development of polymer recycling. In the present research, the kinetics of virgin and waste polypropylene (PP) and low-density polyethylene (LDPE) were studied by a modified Coats–Redfern method. Afterward, thermal cracking of them in a semibatch reactor under atmospheric pressure in nitrogen has been investigated. Both virgin and waste plastics are decomposed at 420–460 °C, and the products have been characterized using GC, FT-IR, 1H NMR, and GC-MS. The reaction path and the degradation mechanism for the thermal cracking of polymer in this study were also discussed. The lower activation energy of waste PP and LDPE indicates that waste plastics degrade at lower initial temperature and may favor mild conditions. Due to the short residence time, the higher gaseous and liquid yields were obtained for virgin PP and LDPE. A large amount of residues for waste polymer indicates that it is a favorable way to degrade waste plastics in a semibatch reactor without further separation. Chain scission reactions are the predominant degradation mechanism in this thermal cracking process. The significant content of unsaturated hydrocarbons in PP thermal cracking products shows the intramolecular hydrogen transfer and β-scission reactions are predominant. In the case of LDPE, intermolecular hydrogen transfer and β-disproportionate reactions also occur. For thermal cracking polymer in a semibatch reactor under atmospheric pressure, the high yields of gasoline (C6–C12) and diesel (C13–C22) fraction in liquid products confirm that it is a desirable way to realize waste plastics recovery.

An efficient treatment of ultra-heavy asphaltic crude oil using electron beam technology

Abstract Electron beam technology, as a promising energy-efficient process, is used as a new treatment for ultra-heavy asphaltic petroleum fluids. Over the past few decades, heavy oil resources have been recognized to be among the most abundant sources of energy. However, extraction, transportation, and processing problems of these fluids still remain to be a challenge in the petroleum industry. The contribution of these hydrocarbon resources to the energy market has been impacted by the fact that the conventional upgrading and visbreaking methods demand a considerable energy investment. In this paper, we coupled electron beam irradiation with conventional thermal processing methods to find an energy-efficient way of improving unfavorable properties of heavy asphaltic hydrocarbons. Electron irradiation was observed to improve the viscosity reduction process by a factor of 30% compared to thermal treatment. Energy transfer process becomes more efficient in radiation-induced reactions, which results in an intensified cracking process. The role of complex asphaltene structures on radiation thermal cracking was investigated by using hydrocarbons with high and low asphaltene content. Our results showed that in samples with high asphaltene content, electron radiation impacts the reaction mechanism of the thermal cracking process. In fact, high energy electrons interact with aromatic structures of asphaltene molecules, resulting in products with a different hydrocarbon component distribution and time-stability properties, as opposed to the simple thermal cracking case. On the other hand, experiments showed thermal and radiation thermal cracking processes follow a similar reaction mechanism for hydrocarbons of low asphaltene content.

A Study on Thermo-catalytic Degradation for Production of Clean Transport Fuel and Reducing Plastic Wastes

Both the landfilling and incineration processes of plastic waste management system are identified as sources of pollutant gas emitters. Reprocessing is also uneconomical in comparison to the virgin plastic products in terms of commercial values due to polymeric contamination. This article studies the thermo-catalytic conversion processes waste plastics. The reaction conditions and the quantification of types of catalysts used for the conversion processes influenced the quality of the resultant hydrocarbons. Obtaining higher yield of conversion and transport grade fuel require more investigation to adapt this technical process as one of the effective alternative resources for fuel production. Thermo-catalytic process resolves the problem of halogen contents in the PVC type plastics by converting them into residues with the use of NaHCO3 and AgNO3 which capture chlorine type products from the gaseous hydrocarbons. Addition of catalysts in the convenient reactor reduces the requirement of higher temperature operations like thermal cracking processes and produces more liquefied products. It has been observed that, the aromatic plastic contents should be observed during the conversion process to obtain fuels based on allowable aromatic contents according to the fuel standards and emission regulations implemented in respective regions. The temperature of the process need to be controlled as per the boiling points of the mixture contents to avoid formation of vapor in the reactor which could causes sticky adherence to the reactor walls. A continuous liquid fractionating distillation process can reduce the formation of light gases in the yield. It was also found that the mixture of LDPE, HDPE, PP and PS yield 87.19% fuel with 20 wt% ZnO catalyst at 200 – 400°C in a steel reactor. These fuels can be used directly in the automotive engines or can be retreated in the refineries to divide into gasoline and diesel fuels as per carbon chains. Since the plastic feedstocks do not contain any sulfur components the produced fuel can be treated as clean enough. Thus the fuels produced from this process can be considered as one of the potential alternative resources of fuel production resulting into an effective reduction of plastic wastes in a country.

A Mesostructure-based Damage Model for Thermal Cracking Analysis and Application in Granite at Elevated Temperatures

Thermal stress within rock subjected to thermal load is induced due to the different expansion rates of mineral grains, resulting in the initiation of new inter-granular cracking and failure at elevated temperatures. The heterogeneity resulting from each constituent of rock should be taken into account in the study of rock thermal cracking, which may aid the better understanding of the thermal cracking mechanisms in rock. In this paper, a mesostructure-based numerical model for the analysis of rock thermal cracking is proposed on the basis of elastic damage mechanics and thermal–elastic theory. In the proposed model, digital image processing (DIP) techniques are employed to characterize the morphology of the minerals in the actual rock structure to build a numerical specimen for the rock. In addition, the damage accumulation induced by thermal (T) and mechanical (M) loads is considered to modify the elastic modulus, strength and thermal properties of individual elements with the intensity of damage. The proposed model is implemented in the well-established rock failure process analysis (RFPA) code, and a DIP-based RFPA for the analysis of thermally induced stress and cracking of rock (abbreviated as RFPA-DTM) is developed. The model is then validated by comparing the simulated results with the well-known analytical solutions. Finally, taking an image from a granite specimen as an example, the proposed model is used to study the thermal cracking process of the granite at elevated temperatures and the effects of temperature on the physical–mechanical behaviors of the granite are discussed. It is found that thermal cracks mostly initiate at the location of mineral grain boundaries and propagate along them to form locally closed polygons at the elevated temperatures. Moreover, the effects of temperature on the uniaxial compressive strength and elastic modulus of the granite are quite different. The uniaxial compressive strength decreases consistently with increasing temperature, but there exists a threshold temperature for elastic modulus which starts to decrease as the temperature increases after it exceeds the threshold.

Prediction of products yield at the thermal cracking of vegetable oil

Abstract According to previous studies on the pyrolysis of vegetable oils, it resulted that the thermal cracking process is prone to produce large yields of ethylene, propylene, hydrogen and methane, comparable with the gas proceeding from the steam cracking of naphtha, but at much lower process temperature, this ensuring important energy savings. The studies are performed on very different raw materials and different reaction conditions, that being why at this moment it is very difficult to predict the products yield. This paper uses an analytical semiempirical model (ASEM) developed at the University of Florida, by applying it to a different raw material. The ASEM model fits very well to our experimental data, obtained at higher temperature but some parameters have to be adjusted. In the end we confirm a set of systemic parameters to be used for the prediction of main products yield proceeding from vegetable oil in an extended range of temperatures.