Reformer Tubes Research Articles

Metallurgical developments in steam-methane reformer tube alloys

Metallurgical developments in steam-methane reformer tube alloys

Heat transfer analysis of a tube-in-tube steam reformer for the application of MGT-SOFC hybrid process

This work deals with the evaluation of a tube-in-tube reformer concept for the realization of the Micro Gas Turbine Solid Oxide Fuel Cell (MGT-SOFC) hybrid process using a semi-validated numerical model. Rigorous heat transfer analysis considering chemical reactions were performed for this concept. To validate the reforming kinetics and heat transfer mechanisms in a catalyst bed, experiments were conducted using a single reactor tube located in a temperature-controlled furnace. Different experimental conditions, such as furnace temperature and space velocity, were considered. A numerical model was replicated according to the single-tube reactor investigated and validated with the experimental results. The catalyst bed is considered as porous material with chemical reactions as internal source terms of species transport equations and energy transport equation. Since the heat transfer into the reformer tubes in the real operating environment is subject to different mechanisms (predominantly convection) than that in a furnace (predominantly thermal radiation), only the parameters on the side of the catalyst bed tuned by the single-tube experiment could be retained for the numerical model of the tube-in-tube concept, which leads to a semi-validated model. Based on this semi-validated model, the performance (such as temperature distribution, conversion rate of the products, etc.) and the applicability of a tube-in-tube reformer concept, considering the variation of boundary conditions, were investigated and evaluated.

Effects of geometries on flow characteristics and reforming performance of a steam-methane reformer

The effects of geometries on flow characteristics and reforming performance were studied in a 250-kW fuel cell reformer. A reformer system was numerically simulated using a simplified three-dimensional model domain with an appropriate user-defined function. The numerical results were compared with experimental data for validation. Outlet position was selected as a parameter for investigating the effects of geometry variation. The reference case has outlet at the bottom of the combustion furnace, and the outlet positions were changed from bottom to top. The numerical results show that the flow characteristics are quite different when the outlet position is changed. And the flow characteristics in the combustion furnace strongly affect the outlet temperature of reformer and reforming performance. Overall, flows of the corner sides were dominant, and the reformers which are located around the corner sides have relatively higher outlet temperatures and better reformer performances. Overall reformer performance and the flows in the combustion furnace can be predicted by measuring the outlet temperatures of reformer tubes. The effects of outlet position on the reformer performance are relatively lower than on the outlet temperatures of reformers.

Numerical Evaluation of Heat Transfer and Conversion Efficiency by Tube Design and Flow Configuration for a Compact Steam-Methane Reformer

In the chemical industry, hydrogen (H2) production through steam-methane reforming is a well-established process. With the growing demand for H-fueled vehicles and charging stations, there is a need for compact reformers with efficient heat transfer capabilities. In this study, computational fluid dynamics simulations were performed to evaluate the methane (CH4) conversion and heat transfer efficiency of various reformer designs. These designs include single, double, and triple tubes, each with parallel- and counter-flow configurations between the reformate feed and heat source. The findings revealed substantial disparities in methane conversion between the tube designs and flow configurations. Notably, the triple-tube design outperforms single and double tubes, exhibiting higher methane conversion and improved heat transfer efficiency. This superior performance is attributed to the larger wall area facing the heat source and additional heat recovery from the reformate flowing in the inner annulus. This led to the highest temperature at the catalyst exit among the cases, increasing methane conversion, and the lowest reformate temperature at the reformer tube exit, which is also beneficial for the subsequent water–gas shift reaction process. Installing external fins on the reformer tube provided a more effective enhancement of heat transfer than using internal fins in the catalyst section. Regardless of the tube design employed, the counter-flow configuration consistently enhanced the heat transfer efficiency, resulting in 4.6–11.9% higher methane conversion than the parallel-flow configuration. Consequently, the triple-tube design with the counter-flow configuration achieved the highest methane conversion, offering flexibility in the reformer design, including the potential for lower heat input and a reduced catalyst volume.

State of Aging Classification of Modified-HP Steel Tubes by Eddy Current Test Applying Machine Learning

In the petrochemical industry, steam reforming furnaces play a crucial role in large-scale hydrogen production. These furnaces are equipped with centrifugal cast HP-modified austenitic stainless-steel tubes, which are exposed to temperatures ranging from 600 to 1000ºC for extended periods. As a result, the wall temperature profile of these tubes exhibits a vertical gradient of distinct aging states, labelled as state I to VI in the literature, each characterized by specific microstructures. Given that the reformer tubes are expensive components of the furnace assembly, it is imperative to monitor their service life. Non-destructive testing is a vital tool for evaluating the structural integrity of industrial components. Hence, the objective of this study is to establish a real-time classification system for determining the aging states of HP-modified stainless-steel tubes using a non-destructive magnetic system and the machine learning technique Support Vector Machine (SVM). Two tubes, each measuring 12.6 meters in length, were removed from the same steam reforming furnace after 160,000 hours of service. The inspection was conducted using an eddy current hybrid probe adapted to an inspection vehicle, allowing for real-time data acquisition. The results demonstrated that the developed classification system was capable of accurately identifying the different aging states present along the studied tubes.

Maximal utilization of purge gas in methanol plants with improved primary furnace burners: A CFD study

The focus of this study is to achieve a better design of burners installed in petrochemical steam methane reformeing (SMR) furnaces. The initial design for the burners of the primary furnace in the Marjan petrochemical plant was problematic; hot spots occured on the side walls of the radiant chamber when the purge gas of the plant was added to the fuel stream. Three distinctive improvements have been recommended to alleviate this problem and provide higher combustion efficiency. These three suggestions include introducing pre-mixing of air and fuel streams, lowering the fuel nozzle velocity, and additional staggered nozzle holes to the base design to achieve more uniform flames. The non-premixed combustion computational fluid dynamics (CFD) simulations are conducted with ANSYS Fluent software on only one array of the burners, given the periodic boundary conditions at the two sides of each array. The resulting temperature and velocity distributions are obtained to compare the designs. The results indicate that a more uniform temperature distribution will be achievable by adding the staggered nozzle holes, which provide a heat flux of 7604 W/m2 and reduce the radiant wall’s average temperature by 0.598%. However, the combustion phenomenon occurs at its highest efficiency—99.998%—through the second design, where the fuel velocity is lowered at the nozzles. Although the first design with the pre-mixing of air and fuel performs more effectively in pushing flame towards the reformer tubes and reducing temperature variations along the radiant walls, the possibility of flash-back occurrence is high; so further safety actions must be taken into account. Eventually, the third design is chosen for implementation as economic analysis indicates that $10 million/year will be saved by lowering the amount of natural gas injected into the burners.

CFD simulation and optimization of turning different waste gases into energy in an industrial steam methane reformer

BackgroundOne of the most important processes of industrial hydrogen production is steam methane reforming (SMR). However, the biggest drawback of steam reformer processes is high energy consumption. In methanol production units, 40% of the energy consumed in the steam reformer is provided by methane burning. The best solution to reduce the consumption of methane gas is to use the waste gases of the units. InnovationTo boost the thermal performance of the furnace, as well as the reduction in natural gas utilization, the effects of the kinds of fuel in an industrial unit are investigated. Furthermore, the waste gas is studied to whether it can be used as fuel in an SMR or not. SignificanceCFD is one of the most powerful tools for simulation of the industrial by which a new unit can be set up or the performance of the old units can be developed. Additionally, the effect of diverse parameters on industrial processes can be examined, and the optimal operating conditions of the industrial unit can be found. MethodsIn this study for five different cases of fuel, the furnace of an industrial SMR unit, at the operating conditions, was simulated using Computational Fluid Dynamics, (CFD) and the results were validated by the industrial data. Moreover, regarding the higher thermal efficiency of the furnace and the lower consumption of natural gas, two cases called design, and the suggested modes, were investigated and suggested mode was proposed as the most suitable fuel. FindingBased on the results, removing purge gas and adding waste gases with lower hydrogen content are recommended. Compared with the operational fuel, the suggested mode decreases the flue gas temperature by 11.78 K and increases the temperature of the first row of the reformer tubes by about 4.17 K, while declining the natural gas molar flow rate by 32%. A 64% reduction in hydrogen content of the suggested mode leads to an increase 10% flame length and 14% enhancement of adsorbed radiative heat flux. Moreover, in the suggested mode it is possible to recycle the purge gas to the methanol synthesis reactor and enhance the methanol production to 1% which is 50 ton/day.

Investigation of Microstructure and Magnetic Properties of HP40-Nb Reformer Tubes

In this paper, the results of nondestructive evaluation, structure characteristics, and magnetic properties of HP-Nb steam reformer tubes of a direct reduction unit are presented. An eddy current testing technique based on a special normal probe was performed to estimate the service life of the outer surface of the reformer tubes at a frequency of 60 kHz. The magnetic properties were investigated by vibrating sample magnetometer testing. Microstructural transformations of reference samples were performed by an optical microscope equipped with image analysis software and scanning electron microscopes. With exposure to severe operational conditions in oxidizing atmospheres and high temperature, microstructural changes such as oxidation and transformation of M23C6 and M7C3 carbide in the carburization zone, and chromium depletion in the austenite matrix, can be intensified. The tubes were inspected on a point basis and the eddy current data were presented as an impedance map. The results of the eddy current testing and vibrating sample magnetometer showed that microstructural changes due to operational conditions affect the electromagnetic response of the tubes.

Effect of the Catalyst Shapes and the Packed Bed Structure on the Efficiency of Steam Methane Reforming

One of the promising technologies for on-board hydrogen production is methane steam reforming in reactor with packed bed. The study of the effect of various catalytic packing arrangements on the steam methane reforming process is of considerable interest. The present article analyses the influence of catalyst shapes and packing arrangement on steam methane reforming reactions efficiency. The reformer tube contains several packings with a changing relative position; additionally, two forms of catalysts, a ball and a cylinder, are also used. The pressure drop depending on the packing location, methane conversion and hydrogen yield were analysed. It was found that the packing arrangement with spacing allows better distribution of the supplied heat. Due to the distance between the packing sections flow becomes more turbulent after each section, which intensifies the heat transfer and mixing of the mixture. The highest hydrogen yield is observed on catalytic packings located at a distance of 40 mm from each other and consisting of cylindrical catalysts. The most uniform pressure drop occurs at a packing arrangement without spacing. The increase in methane conversion observed with the increment in spacing distance, but the difference is insignificant. Therefore, the arrangement of catalysts with spacing can be used for the improvement of steam methane reforming process.

Creep life estimation of reformer alloy using θ-projection method - A neuro fuzzy approach

This paper deals with creep life assessment and deformation behavior of 11 years service exposed primary hydrogen reformer tube made up of HP40 grade of steel using the θ-projection method. Constant load creep tests have been performed at 870 °C under the stress range of 50–68 MPa. The generated creep data exhibit a significant amount of scatter under identical stresses. The existence of scatter in the creep deformation data leads to substantial amount of uncertainty in the estimation of θ-parameters and hence in the assessment of creep life. An adaptive neuro fuzzy based model is proposed to study the effect of variation of these parameters on creep life prediction. The model has been compared with the experimental findings.

Damage analysis of 800 series materials from reformer tube outlet components

To investigate the failure of 800 series materials from the furnace tube outlet components of the reformers, the test devices such as metallographic microscope, scanning electron microscope, carburizing detector and high temperature endurance testing machine were adopted. The failure mode and failure mechanism of 800 series materials for outlet components of reformer such as pig tail pipe, outlet pipe, stiffenerjoint and collection tube, which had been in service for 1–11 years from 7 petrochemical and chemical fertilizer enterprises were analyzed. The results suggest that the damage of 800 series materials from reformer outlet components in 7 petrochemical and chemical fertilizer enterprises mainly occurred on the base metal. The failure modes included bulging, cracking and fracture, and the principal failure mechanisms were creep and carburizing, respectively. The main factors affecting the failure of 800 series materials in the tube outlet components of reformer were discussed with respect to grain size, metal temperature and stress concentration. Consequently, multiple suggestions were given to avoid premature damage and failure of such components.

Failure Analysis of Two HP-Nb Heat-Resistant Tubes after 46,000 h Exposure to Reformer Service Conditions

This study presents a failure analysis in two reformer tubes used for hydrogen production in a petrochemical industry. These tubes (Tube A and Tube B) were made by the centrifugal casting of HP-Nb alloy in such a way that one contained titanium as a micro-element, and the other was free from titanium in its chemical composition. Although the two tubes were subjected to similar creep conditions, Tube A failed after only 46,000 h of operation against the design life of 100,000 h. SEM images showed initiation and growth of creep pores next to chromium carbide particles, as well as the formation of microcracks in Cr23C6 carbides. Pore initiation occurs as a result of grain boundary sliding and is strongly dependent on structural morphology. The tube containing titanium (Tube B) showed higher thermal stability and higher creep resistance than the tube without titanium (Tube A), which was due to the formation of finer and more discrete carbide particles. The final fracture of the tube without titanium (Tube A) occurred due to the coalescence of creep pores and the creation of grain boundary cracks.

A comprehensive CFD simulation of an industrial-scale side-fired steam methane reformer to enhance hydrogen production

The present work deals with the CFD simulation of steam methane reforming (SMR) with a view to design and improve the SMR technology. Numerical simulations have been devoted to accurately modeling the primary reformer tube used in major petrochemical industries by employing the kinetic mechanism, standard k-Ɛ turbulence models, and discrete ordinates (DO) radiation model. The developed model has been validated with the available modeling studies on industrial steam methane reforming in the operating condition. Moreover, the effects of some key parameters such as surface heat flux, reformer tube length, reformer tube diameter, steam-to-carbon ratio (S/C), and feed flow rate on the performance of industrial tube reformer have been investigated. Using a suitable sensitivity analysis, the optimal values of these parameters are recommended for the optimal performance of the reformer tube in order to increase hydrogen production in the industrial reformer. Numerical results show that considering the optimal values including surface heat flux of 95 kW·m2, reformer tube length of 11 m, reformer tube diameter of 0.172 m, S/C = 1.6 and feed flow rate of 0.34 kg·s−1 leads to an increase of about 20% in hydrogen production compared to petrochemical industrial data.

Energetic, GHG, and economic analyses of electrified steam methane reforming using conventional reformer tubes

A concept for electrified Steam Methane Reforming (eSMR) based on reformer tubes is proposed as a pathway for hydrogen decarbonization. The proposed concept applies radiant heating elements to a conventional gas-fired reformer. A thermochemical model and a techno-economic framework are developed to evaluate process performance at various conditions and the economic potential of the proposed concept. A baseline scenario with feedstock and electricity priced respectively at $4/MMBtu and $0.04/kWh, and assuming 2% of fugitive methane emissions and 50 gCO2eq/kWh, results in an LCOH of $1.53/kgH2 and a decarbonization cost of $38/tonCO2. The techno-economic results demonstrate that the proposed eSMR process leads to lower LCOH than mainstream alternatives over a wide range of energy prices. The study shows that reformer tube electrification is both economically viable and technically feasible, and therefore has the potential to decarbonize hydrogen production at a low cost.

Gas-phase aluminizing of HP40Nb steel used in reformer tubes: Synthesis, characterization, and its implications for the microstructure and high-temperature creep resistance of the base alloy

This study investigates the microstructure and creep behavior of gas-phase aluminized High-Performance (HP40Nb) steel. Microstructures of coated and base alloy were examined by electron and optical microscopes. Gas-phase aluminizing of HP steel resulted in the formation of a top AlNi layer over an interdiffusion zone (IDZ) on the base alloy. Results also showed that there were hardly any cavities or discontinuities formed in top layer and IDZ during the aluminizing process. The creep test results showed that the gas-phase aluminized steel had significantly a higher minimum creep rate and consequently a shorter time-to-rupture, as compared to uncoated HP40Nb steel. Microscopic examinations revealed that the main reason for the fracture of the steel after the creep test was formation of micro-cavities in the vicinity of carbides and growth of micro-cracks along the grain boundaries and alongside inter-dendritic areas. Also, fractography analysis showed that a quasi-cleavage fracture had occurred for both coated and uncoated steel. The implication of gas-phase aluminizing on creep resistance of coated HP40Nb steel, and its interrelation between the microstructure and observed mechanical properties are discussed and explained through the paper.

Steam Methane Reforming with Chemical-Looping Combustion: Scaling of Fluidized-Bed-Heated Reformer Tubes

The combination of chemical-looping combustion (CLC) and steam methane reforming (SMR) bears the potential for quantitative and energy-efficient CO2 capture along with hydrogen production from natural gas. A 2-dimensional axisymmetric model of a SMR tube was used to estimate the possibility to adapt the tube dimensions to better fit into fluidized-bed heat exchangers. A constant surrounding fluidized-bed temperature was set as the boundary condition. There are two phenomena that affect the reactor performance: the effective heat-transfer rate from the fluidized bed to and through the tube wall and onward to and into the catalyst bed on the one hand and the effective reaction rates of the governing chemical reactions on the other hand. Literature models were used for the heat-transfer description assuming a state-of-the-art reforming catalyst and classical SMR kinetics were formulated. The simulation results show a temperature decrease toward the tube center in steady state operation. The gas phase composition at the tube outlet reflects the radial temperature distribution as the chemical equilibrium is approached well. Simulations with smaller tube diameters indicate that the necessary tube length for equivalent gas conversion is significantly reduced. In a 1/2-scale setting with 63 mm inner diameter (ID) of the tube instead of 126 mm ID in full scale, the necessary tube length is only 6.0 m instead of 12.5 m, and in a 1/4-scale setting with 31.5 mm ID, the necessary tube length is only 3.3 m. A temperature increase of the fluidized bed from 900 to 950 and 1000 °C may reduce the necessary tube length in the 1/4 scale from 3.3 to 2.6 and 2.2 m, respectively. These indications are promising with respect to the possibilities for fluidized-bed immersed reformer tube dimensioning and arrangement. More detailed reactor design studies will be necessary to judge the industrial feasibility of the CLC-SMR combination.

Comparison between 1D and 2D numerical models of a multi-tubular packed-bed reactor for methanol steam reforming

The hydrogen-rich gas produced in-situ by methanol steam reforming (MSR) reactions significantly affects the performance and endurance of the high-temperature polymer electrolyte membrane (HT-PEM) fuel cell stack. A numerical study of MSR reactions over a commercial CuO/ZnO/Al2O3 catalyst coupling with the heat and mass transfer phenomena in a co-current packed-bed reactor is conducted. The simulation results of a 1D and a 2D pseudo-homogeneous reactor model are compared, which indicates the importance of radial gradients in the catalyst bed. The effects of geometry and operating parameters on the steady-state performance of the reactor are investigated. The simulation results show that the increases in the inlet temperature of burner gas and the tube diameter significantly increase the non-uniformity of radial temperature distributions in reformer tubes. Hot spots are formed near the tube wall in the entrance region. The hot-spot temperature in the catalyst bed rises with the increase in the inlet temperature of burner gas. Moreover, the difference in simulation results between the 1D and 2D models is shown to be primarily influenced by the tube diameter. With a methanol conversion approaching 100% or a relatively small tube diameter, the simplified 1D model can be used instead of the 2D model to estimate the reactor performance.

PREDIKSI SISA UMUR PAKAI TUBE REFORMER JENIS HP MODIFIED

ABSTRACT
 Tube reformer modified HP type (23Cr-35Ni Nb) is an important component in the fertilizer industry in the primary reformer. Tube reformer is produced in centrifugal casting method that has the hard characteristic, put up with high temperature, pressure and resistance corrosion. It is because it has a large amount of nickel (Ni) and chrome (Cr) elements so that it can hamper the corrosion. The tube reformer has been operated on for 15 years. Based on technical data modified HP tube reformer has 11,4 years of design life and one of the tubes had been burst in beneath, so it needs to decide how long the remaining life assessment of the modified HP reformer tube is. The aim of the research is in order to know how to last long the remaining life assessment of the tube reformer HP modified used, so it can plan to fix/change with a new tube. In order to support the research, it needs some tests such as metallography, hardness test, tensile test, chemical composition, and creep test. According to API 530, to measure how last the remaining life assessment of tube reformer based on creep test which is accelerated by using LMP method can get 52488,35 hours or 5,99 years. The remaining life based on microstructure damage related to the classification diagram of tube wall damage according to L May in C level (or 50 %) is 50,000 hours or 5,77 years.
 Keywords: Centrifugal casting, tube reformer HP modified, creep test, Larson Miller parameter, remaining life assessment.

Failure Analysis of a Cracked Hydrogen Reformer Tube

Failure Analysis of a Cracked Hydrogen Reformer Tube

Energy intensity in applying low-temperature chemical looping in steam reforming

An energy analysis of methanol production via low-temperature chemical looping steam reforming was performed based on the process design; the potential benefits in reducing fuel consumption and excess heat generation were analysed. The feasibility of performing chemical looping reforming at temperatures lower than the conventional 900 °C is linked with the on-going development of a suitable oxygen carrier through the supercritical method. Pinch analyses were performed on designs that operate at three different reforming temperatures, namely 900, 500, and 300 °C, with either a high or a low heat transfer assumption within the reforming furnace. The results show that notable benefits are expected if the heat transfer from the combustion gases to the reformer tube contents improves along with lowering the reforming temperature. This ‘optimistic scenario’ resulted in an ≈ 41% decrease in excess heat generation and an ≈ 55% decrease in fuel consumption, as the reforming temperature decreased from 900° to 300°C. However, in the ‘pessimistic scenario’, where heat transfer does not improve despite the reforming temperature lowering, fuel consumption and excess heat generation remained almost constant when the reforming temperature was lowered from 900° to 300°C. In reality, heat transfer within the reforming furnace could behave somewhere between the low and high heat-transfer assumptions. The benefits of lowering the reforming temperature thus depend on several process and equipment design factors, including the temperature driving force, heat transfer area, and pinch approach temperature. An ill-designed reforming furnace, represented by the low heat-transfer scenarios, could result in no significant improvements despite the lowering of the reforming temperature; whereas well-designed equipment, represented by the high heat-transfer scenarios, could bring a significant improvement in energy consumption and waste heat generation.