Thermal Cracking Unit Research Articles

Techno-economic evaluation of post-combustion carbon capture based on chemical absorption for the thermal cracking furnace in ethylene manufacturing

As the core unit of an ethylene production plant, thermal cracking furnace generates a large amount of CO2 emissions. To reduce the CO2 emissions, post-combustion carbon capture based on chemical absorption using monoethanolamine (MEA) solvent is used to capture CO2 from the thermal cracking furnace. The computational fluid dynamics (CFD) method was used to simulate the operation of a 60kt/a thermal cracking furnace to obtain the flow rate and composition of the flue gas. A carbon capture plant model was developed using Aspen Plus® and validated using the pilot plant test data from Technology Centre Mongstad (TCM) in Norway. Scale-up of the capture plant model was carried out to match the flue gas flow rate of the thermal cracking furnace. Two integration cases of the carbon capture plant and the industrial thermal cracking unit were carried out. The results show that the excess heat of the gasoline fractionator can be used to provide heat for the carbon capture plant without affecting ethylene production. The economic evaluation was conducted based on the two case studies. Results show that the cost of CO2 capture can be reduced from $80.03/tonne (without heat integration) to $70.41/tonne with heat integration. When considering the impact of carbon credits on capture costs, the cost will be further reduced to $50.41/tonne.

Process modelling and simulation of bitumen partial upgrading: Analysis of solvent deasphalting‐thermal cracking configuration

AbstractIn this study, we investigate a process for partial upgrading of Canadian oil sands bitumen by means of modelling and simulation. In continuation of our previous study focused on a different process configuration for partial upgrading, the process scheme analyzed in this work consists of a solvent deasphalting step to reject asphaltenes from bitumen, a thermal cracking of the deasphalted product step, and a hydrotreating step to saturate the olefins generated by thermal cracking. The model was built using commercial simulation software, incorporating customized models for the solvent deasphalting and thermal cracking units. Trends in partial upgrader product yields and quality are examined under two operating scenarios: one where the thermal cracker operates in once‐through mode and the other where the heavy portion of the thermal cracker product is recycled. Both scenarios were observed to have difficulties in achieving the product quality targets set for partial upgrading (density <0.9400 g/cm3 at 15.6°C and viscosity <350 cSt at 7°C) without any diluent addition. A key factor that significantly impacts final product yield and quality in this partial upgrading process is the formation of new asphaltenes during thermal cracking.

Investigation of mango (Mangifera odorate) sap and starch as organic adhesive of bio-briquette

Rice husk and coconut shell waste is potential biomass found in Palembang that has not been utilized properly. Besides being used for primary purposes, biomass can be used for energy sources like renewable energy. Biomass residues can be obtained from the pyrolysis process with thermal cracking units (UTC) and used as bio-briquettes. Bio-briquette is prepared from a mixture of pyrolysis residues of coconut shell and rice husk with a mass ratio of 2:1 using a combination of adhesive mucilage (mango sap) and paste (starch). The adhesive is prepared by dissolving the starch in water, then mixing it into melted mango sap. The mass ratio of the sap and starch is 1:1 (w/w), while the ratio of the mixture of adhesive and water is 1:10. Based on the ATR-FTIR characterization, it showed that the C = C strain group and the C-H bending group appeared at 2800 cm−1, which was confirmed by its appearance at 800 cm−1 in the fingerprint area. Then, appears peak in the area of 1300 cm−1, indicating the presence of a nitro group, which is assumed to have come from mango sap. Measurements of the briquette physicochemical properties such as moisture content, ash content volatile matter, and fixed carbon were measured using the proximate analysis method. Furthermore, the addition of coconut shells in producing bio briquettes from rice husks increased the calorific value by 7.305 MJ kg−1. So that, bio-briquette is an effective as an alternative energy source to replace fossil fuel for household purposes.

Increasing production of gasoline and diesel fuel in medium and small refineries to meet the needs of Iraqi market

Iraq is considered one of the countries exporters of oil in the world, but the output of motors fuels from the refined crude oil less than (45 wt %), which is associated with the lack of Iraqi refineries with secondary processes.Iraq consist of five big capacity crude oil refineries which include (atmospheric crude distillation, hydrotreating, catalytic reforming and isomerization) and produce high quality motors fuel, in addition five medium and five small in capacity crude oil refineries include only atmospheric crude distillation which produce low quality raw products (light and heavy naphtha, light gasoil and reduced crude).The total capacity of Iraqi oil in the last years changed from 28 to 35 million ton/year. Most of our refineries include old equipment, but in spite of the annual maintenance for these refineries the motor fuels products could not able to cover all the Iraqi requirements of motor fuels 27 million ton/year.In these refineries produce reduced crude (fuel oil) in large quantity and because of this, Iraq imports gasoline fuel (30 wt%) of its requirements and LPG (17 wt%) of its requirements.This situation impose on us to increase the output products quantity from the Iraqi crude oil by development the medium and small capacity refineries via installation thermal processes units instead of vacuum distillation units, by this actual research we will find that the deep of refinery will increase from 54 to 70 wt%, and production of motor fuel will change from 45 to 68 wt%.Purpose of the work: development of the flowchart which is applied in Iraqi small capacity refineries (1.3 – 1.4 million Ton/year) by installation thermal cracking units to produce maximum allowable yield and quality of motors fuels.This research depends on actual experiments which are done by me in Ufa state petroleum technological university on actual crude oil and reduced crude brought from Iraqi‘s refineries from the oil fields Basrah (Zubair) and Kirkuk.

Development and assessment of concentrated solar energy driven ammonia synthesis from liquefied natural gas

The proposed system targets the production of carbon dioxide-free hydrogen from liquefied natural gas through a solar-driven catalytic thermal cracking process integrated into the ammonia synthesis unit. The catalytic material is being regenerated in an adjacent vessel by burning the deposited coke. As a result, pure carbon dioxide stream is obtained and can be used directly in urea synthesis, sequestration or other related applications. It is expected that the system will reduce the amount of fossil fuel consumption in the ammonia synthesis and mitigate the associated environmental impacts. The energetic and exergetic analyses are carried out to assess the performance of the developed system and to identify the optimum operating conditions. At an operating temperature of 900 °C of thermocatalytic cracking, the optimum pressure for optimal production of hydrogen is determined to be 23.8 bar. The corresponding overall energy and exergy efficiencies are calculated as 35.8% and 37.4%, respectively. At the same conditions, the energy and exergy efficiencies of the thermal cracking unit reach 61.8% and 59.3%, respectively. Several parametric studies are conducted to evaluate the effects of operating conditions at the cracker, irradiance day-night ratio, and consideration of CO2 for transport and sequestration activities on the overall performance and production of the system. Ammonia production can reach 974 Metric Tons per Day (MTPD) and 893 MTPD considering operating conditions of 900 °C and 800 °C, and inlet LNG flow rate of 688 MTPD and 630 MTPD, respectively.

Model predictive control of vinyl chloride monomer process by Aspen Plus Dynamics and MATLAB/Simulink co-simulation approach

Characteristics of a vinyl chloride monomer (VCM) process is complex and nonlinear due to interactions between units in a reaction-separation network, multiple process streams, and multiple control loops involved. A fluctuation of the thermal cracking unit could result in a difficulty in maintaining downstream units at the setpoints. In this work, an approach to develop a model predictive control (MPC) for the VCM process by deploying a co-simulation between MATLAB/Simulink and Aspen Plus Dynamics is presented. The co-simulation provides more capability and comfortability to design the MPC controller, and evaluate controllability. The VCM process consisting of thermal cracking, quench and distillation is modelled by Aspen Plus Dynamics. The MPC is developed by integrating the concept of plant-wide control and subsystem partitioning. To reduce the burden of mathematical modeling, the MATLAB system identification toolbox is used to develop a multivariable linear model for the MPC controller by reconciling dynamics data from the VCM plant model. Performances of the developed MPC is evaluated under the regulatory test of the EDC feed disturbance. By comparison with the multiple single-input-single-output proportional-integral controllers through the efficiency indexes—an integral squared error, an overshoot and a settling time. Simulation results supported that the MPC controller outperforms proportional-integral controllers.

The role of plasma in syngas tar cracking

Gasification of biomass and municipal solid waste is a technology that has been proposed as a dual-purpose solution for mitigating environmental impacts as well as for producing syngas, a very useful intermediary product for energy valorization and organic synthesis. However, the presence of pollutants, notably tar, hampers this raw syngas (producer syngas) to be used in high-efficient energy applications such as jet engines and fuel cells or in Fischer-Tropsch synthesis, limiting its economic value. For reducing tar, a lot of scientific and technical effort has been devoted. In this paper, the state of the art of plasma tar removal from syngas is done, focusing on the use of plasma in tandem with existing technologies, underlining its advantages and the remaining challenges. The most promising ways to get a syngas with very low tar levels using plasma seem to be (i) tandem tar cleaning techniques (e.g. secondary plasma enhanced catalytic unit) and (ii) secondary thermal plasma cracking units.

Investigation of propane addition to the feed stream of a commercial ethane thermal cracker as supplementary feedstock

Abstract With the aim of investigating the solutions of ethane shortage in a commercial ethylene plant, addition of propane as supplementary feedstock and increasing steam to hydrocarbon ratio were proposed as possible strategies. These strategies were proposed to compensate for the ethane shortage in the thermal cracking unit of the commercial plant. Run length, ethylene yield, and propylene yield were considered as the determining factors to appraise the strategies. The major contribution of present work would be the investigation of effect of feed shift on the run length of the steam cracker. Regarding this, five different cases were investigated in real plant condition. To include all the aspects of process, a mathematical model with reasonable assumptions was developed and then validated against the real plant data. Based on the obtained results, increasing propane concentration leads to increase in propylene yield and decrease in ethylene yield. Besides, run length of process was obtained to be longer in the cases with higher propane content in the feed stream.

Effects of binary vacuum residue blending ratios on the product yields in a delayed coking process

ABSTRACTBlending of different hydrocarbon cuts is a common procedure in refining processes such as thermal cracking units. Blending could affect the products properties considerably. In this work, four binary blends of Iranian vacuum residues are prepared and thermally cracked at 500°C for 2 h in a batch atmospheric delayed coking reactor. Product yields have been defined for different blending ratios. Results show that the yields of liquid products have considerable deviations compared to the simple mixing rule. These deviations could be positive or negative compared to the simple mixing rule. The deviations could also be justified by SARA (saturate, aromatic, resin, asphaltene) analysis of blends. A new method has been proposed to predict the sign of deviation based on metals and sulfur contents.

Preparation of Light Fuel Fractions from Heavy Vacuum Gas Oil by Thermal Cracking Reaction

This work deals with thermal cracking of heavy vacuum gas oil which produced from the top of vacuum distillation unit at Al- DURA refinery, by continuous process. An experimental laboratory plant scale was constructed in laboratories of chemical engineering department, Al-Nahrain University and Baghdad University. The thermal cracking process was carried out at temperature ranges between 460-560oC and atmospheric pressure with liquid hourly space velocity (LHSV) equal to 15hr-1.The liquid product from thermal cracking unit was distilled by atmospheric distillation device according to ASTM D-86 in order to achieve two fractions, below 220oC as a gasoline fraction and above 220oC as light cycle oil (LCO).The first fraction which was below 220oC was fractionated to light fractions (gasoline, kerosene and gas oil) by atmospheric distillation device. The fractions (gasoline, kerosene and gas oil) were distilled by atmospheric distillation device in order to obtained distillation curve for these fractions. Physical properties were recorded for these cuts to compare it with standard property test, in order to studying the possibilities of industrial uses. The maximum conversion of heavy vacuum gas oil was obtained by this process equal to 82 wt. % of feed at 540oC.

Fouling Management of Thermal Cracking Units

ABSTRACTVisbreakers and other thermal cracking units are thermal process units in crude oil refineries that upgrade heavy petroleum, usually residual oils produced from atmospheric or vacuum distillation of crude oil. The associated process streams of these units consist of heavy hydrocarbons with very high viscosities and impurities, resulting in fouling of the heat exchangers used to cool or heat these streams. This paper presents a practical fouling analysis for thermal cracking units in a refinery in Germany. Fouling management at this refinery was initiated as part of the refinery energy-saving program. Following similar analysis of the refinery's crude preheat trains, heat exchanger networks associated in the thermal cracking units were modeled by entering the plant monitoring data, network topology, and heat exchanger geometries into a commercial heat exchanger network simulator, SmartPM. Fouling behaviors of vacuum residue streams and thermal cracker residue streams were identified and quantified. Both chemical reaction fouling and particulate fouling mechanisms were identified to be responsible for the fouling in these streams. Dynamic fouling models were fitted and used to predict fouling of these heavy petroleum streams, which fouled on both the shell and tube sides of the shell-and-tube heat exchangers.

Two-ply 16GS+08X13 steel column stress-strain state analysis with metal delamination taken into account

Columns are the main mass transfer equipment used in oil refining processes. In this regard, in order to save expensive materials, two-ply steel columns became widely used. Currently, the determination of residual life of such columns is based on standard methods of strength calculations for vessels and apparatuses. However, the existing methods of strength calculations are based on a simplified representation of the column apparatus at various stages of calculation and do not provide a comprehensive picture of its stress-strain state (SSS) taking into account geometrical features and the fact that the shell is double-layer. It is known that SSS of equipment produces considerable influence on the processes of damage accumulation during operation. One of the most prevalent defects in the shell of two-ply steel columns is delamination between the main layer and cladding layers due to the formation of a decarburized layer in the process of continuous operation. The column stress-strain state was analyzed in this paper with the use of ANSYS software implementing the finite element method, considering as follows: the size and location of manholes and nozzles; dead load and operating parameters; the results of investigations of two-ply 16GS+08X13 steel column mechanical properties in the as delivered condition and after continuous operation at a thermal cracking unit; double-layer shell. It is established that the maximum stresses in the most loaded bottom of the column with a nominal wall thickness in a double-layer model reach 228 MPa, which is almost 80 MPa higher than the stress values obtained for a single-layer model. The dependence of maximum stress values on the size of delamination defect is determined with the defect being located in the most loaded and the least loaded zones of the column bottom for the metal being in the as delivered condition and after continuous operation.

Comparison of Soft-Sensor Design Methods for Industrial Plants Using Small Data Sets

This paper analyzes a number of strategies that are devoted to improving the generalization capabilities of neural-network-based soft sensors when only small data sets are available. The aim of this paper is to search for a strategy that is able to cope with the problem of scarcity of experimental data, which often arises in industrial applications. The strategies that are considered are based on the manipulation of experimental training data sets to increase their diversity either by injecting noise into the available data or by using the bootstrap resampling approach. A new method, which is based on an aggregation of neural models, trained on different training data sets, which are obtained by noise injection and bootstrap resampling, is proposed in this paper. The methods considered were compared in an industrial case study regarding the design of a backup soft sensor for a thermal cracking unit, working in a refinery in Sicily, Italy. The results of the case study show that all the methods considered produced an improvement in the estimation capability of the models. The best performance was obtained by using the method proposed by the authors.

Modeling elementary reactions in coke formation from first principles

Theoretical calculations are presented on elementary reactions which are important during coke formation in a thermal cracking unit. This process is known to proceed through a free radical chain mechanism. The elementary reaction steps that lead to the growth of the coke surface can be divided into five classes of reversible reactions: hydrogen abstraction, substitution, gas phase olefin addition to radical surface species, gas phase radical addition to olefinic bonds and cyclization. To identify the elementary reaction classes that determine the coking rate, all microscopic routes that start from benzene and lead to naphthalene have been investigated. It is found that initial creation of surface radicals, either by hydrogen abstraction or substitution and subsequent hydrogen abstractions, determines the global coking rate. The influence of the local polyaromatic structure on the kinetics of the hydrogen abstraction reactions is determined by performing calculations on a large set of polyaromatic hydrocarbons (PAHs). On basis of the BDE values six types of possible reactive sites at the coke surface can be distinguished. For the initial hydrogen abstraction the local polyaromatic structure strongly influences the reaction kinetics and abstraction is preferred from less congested sites of the polyaromatic.

Systematics and modelling representations of LPG thermal cracking for olefin production

Pyrolysis of hydrocarbons is an important commercial process for the production of ethylene, propylene and 1,3 butadiene. These low molecular weight olefins are among the most important base chemicals for the petrochemical industries for polymer production. A simulation program of the reaction kinetics and coke formation inside the coils of a thermal cracking unit can provide information on the effects of operating conditions on the product distribution. The aim of this study was to develop a mechanistic reaction model for the pyrolysis of LPG that can be used to predict the yields of the major products from a given LPG sample with commercial indices. A complete reaction network, using a rigorous kinetic model, for the decomposition of the LPG feed has been developed, which is used for the simulation of industrial LPG crackers. This model has been adapted using industrial data for the pyrolysis yields of LPG. The present paper attends on the asymptotic coking mechanism and describes the development of a kinetic coking model in the pyrolysis of LPG. Detailed and accurate information about the product distribution, growth of coke layer, the evolution of the tube skin temperatures can be obtained from this simulation. Simulations of this kind can be used to optimize the furnace operation. They can be used as a guide for the adaptation of the operating variables aiming at prolonging the run length of the furnace. The reactor model, as well as kinetic scheme, is tested in an industrial cracking furnace.

Kinetic Modeling and Simulation of the Selective Hydrogenation of the C3-Cut of a Thermal Cracking Unit

The kinetics of the gas phase selective hydrogenation of methyl acetylene (MA) and propadiene (PD) over a Pd/alumina catalyst were investigated in a fixed bed tubular reactor at temperatures 60−80 °C and a pressure of 20 bar. Hougen−Watson type kinetic equations were derived. The formation of higher oligomers slowly deactivated the catalyst. The effect of the deactivating agent on the rates of the main reactions as well as on the deactivating agent formation itself was expressed in terms of a deactivation function multiplying the corresponding rates at zero deactivation. Finally, the kinetic model was plugged into the reactor model to simulate an industrial adiabatic reactor.

Reactivity and aromaticity of polyaromatics in radical cyclization reactions

AbstractTheoretical ab initio calculations are presented on cyclization reactions of polyaromatics that occur by a radical mechanism. Such processes are one of the elementary steps for polyaromatic hydrocarbon formation in thermal cracking units and during soot formation. Ring closure can take place at various sites of the polyaromatic surface. It is the aim of this study to obtain insight into the influence of the local structure on the reactivity of the polyaromatics. Aromaticity is a determining factor for the reactivity and can be probed by various magnetic properties such as the diamagnetic susceptibilities, proton chemical shifts, and nucear‐independent chemical shifts. A correlation is established between the magnetic properties and activation energy of the studied reactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

Ab initio study on elementary radical reactions in coke formation

AbstractAb initio calculations are presented on radical reactions that occur during the formation of coke in a thermal cracking unit. Kinetic parameters for the addition reaction of the ethylbenzene radical to ethene and the subsequent cyclization of the butylbenzene radical are calculated by means of Transition State Theory and Density Functional Theory. Special care is taken to correctly treat the internal rotations to predict accurate values of the preexponential factor. The influence of the local structure of the coke matrix on the kinetic parameters is tested by calculating kinetic parameters of clusters consisting of more than one benzene ring. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003

Exhaustive Refining of Crude Oil Feedstock: Visbreaking of Residues

The quality of the high-viscosity residues changed significantly after reconstruction of the vacuum units (VU) on the AVT units at Ryazan' Oil Refinery Open Joint-Stock Company (see Table 1). A visbreaking unit based on the TK-1, type 15/5 thermal cracking unit in operation since 1961 was constructed for processing these residues. A mixture of vacuum and atmospheric resids was used as the feedstock for the TK-1.

Stability of cracked naphthas from thermal and catalytic processes and their additive response. Part I. Evaluation of stability and additive response

Olefinic naphthas derived from fluid catalytic cracking (FCC) or thermal cracking units are increasingly being used in high-octane motor gasoline with growing concern for resulting fuel quality. Hindered phenols and substituted arylamines are the two classes of antioxidants generally used for improving the stability of gasoline. The olefin types in cracked naphthas depend strongly on the process from which they are derived and hence are expected to show different responses with different antioxidants. However, systematic information on this aspect of antioxidant action is non-existent in the literature. Using two representative commercial antioxidants from each class with representative naphthas (FCC, visbreaking and coker), it was found that phenolic antioxidants gave a better response with thermally cracked naphthas. With amine-type antioxidants no clear preference could be observed.