Synthetic Ammonia Research Articles

Forecasting the Hydrogen Demand in China: A System Dynamics Approach

Many countries, including China, have implemented supporting policies to promote the commercialized application of green hydrogen and hydrogen fuel cells. In this study, a system dynamics (SD) model is proposed to study the evolution of hydrogen demand in China from the petroleum refining industry, the synthetic ammonia industry, and the vehicle market. In the model, the impact from the macro-environment, hydrogen fuel supply, and construction of hydrogen facilities is considered to combine in incentives for supporting policies. To further formulate the competitive relationship in the vehicle market, the Lotka–Volterra (LV) approach is adopted. The model is verified using published data from 2003 to 2017. The model is also used to forecast China’s hydrogen demand up to the year of 2030 under three different scenarios. Finally, some forward-looking guidance is provided to policy makers according to the forecasting results.

СТРУКТУРА ПРОИЗВОДСТВЕННОЙ СИСТЕМЫ РОССИЙСКОГО ХИМИЧЕСКОГО КОМПЛЕКСА: АНАЛИЗ ПРОШЕДШЕГО ПЯТИЛЕТИЯ

The authors monitored the organization of the production systems of the Russian chemical complex after half of the implementation period of the chemical industry development program until 2030. The results of 2021 were analyzed as indicators of the midpoint of the implementation of this program, which indicated the stability of the trends in the development of the complex. The article uses the results of the study «Expert and analytical support for assessing the state of the chemical complex of Russia and the performance targets for the implementation of the strategy for the development of the chemical and petrochemical complex for the period up to 2030» and the forecasts made by the authors at the initial stage of the program. It is shown that, despite the average utilization of the production capacities of the chemical complex by more than 80%, it is necessary to consider this indicator differentially by industry. The highest level of utilization was noted in the production of household chemicals and synthetic detergents, ammonia and methanol, and the lowest – in the production of chemical plant protection products and rubber products. It is concluded that the dynamics of the chemical complex of the Russian Federation demonstrates insufficient development of the direction associated with high processing of raw materials, therefore, it is advisable to increase the level of processing of raw materials in every possible way in the chemical industry, and to avoid strong dependence on fluctuations in world prices to focus on the domestic market, including innovative sectors of the economy and dual-use technologies.

Luigi Casale’s enterprise: Pioneer of global catalytic high-pressure industrial chemistry

The modern global synthetic ammonia industry owes its heritage to the Italian chemist Luigi Casale, who a century ago founded the forerunner of today's Casale S.A., of Lugano, Switzerland. Since the 1980s, Casale innovations have led in the energy-saving revamping of nitrogen plants, and in the introduction of related technologies, including novel catalysts.

Life cycle assessment of ammonia synthesis based on pulverized coal entrained flow gasification technology in China

The ammonia-synthesis industry has become a research hotspot, because its high energy consumption and CO2 emission exacerbate the current resource shortages and environmental pressures. However, the current research on life cycle assessment (LCA) of synthetic ammonia in China is limited. To fill gaps, this study analyzed the environmental performance of mainstream ammonia synthesis in China, i.e., pulverized coal entrained flow gasification (PEF) technology, based on LCA method. Results showed that the potential environmental impact on fossil depletion category was the main contributor to the overall environmental burden, which was primarily from coal mining and coal washing (85.3%). Global warming also had an indispensable impact on the overall environmental burden, and electricity was a dominant contributor with a proportion of 36.3%. Compared with anthracite fixed bed gasification (AFB) technology, PEF technology showed superiority in reducing the environmental burden, especially in the categories of global warming, freshwater ecotoxicity, and water depletion. Ammonia-synthesis routes based on the “green hydrogen” and “blue hydrogen” can greatly reduce carbon emission compared with the “grey hydrogen” route, with reduction ratios of 90.9% and 42.9%, respectively. Results further indicated that “green hydrogen” and “blue hydrogen” routes had huge prospects for environmental optimization in China's synthetic ammonia market. Green mining, underground coal washing technology, and renewable electricity substitution can effectively reduce the environmental burden throughout the entire life cycle of ammonia synthesis.

Technology-environment-economy assessment of high-quality utilization routes for coke oven gas

Coke oven gas (COG) is an important energy resource that rich in hydrogen and methane, which is conventionally used for industrial heating but is embarking on high-quality utilization routes to produce bulk energy and materials. Previous work emphasized the comparison of COG utilization with external competitors but has limited understanding of the internal competitiveness of different COG utilization routes, making it impossible to scientifically guide the high-quality utilization of COG. This study proposed a technology-environment-economy assessment framework to compare the competitiveness of six high-quality COG utilization routes called COG to electricity (COGTE), COG to methanol (COGTM), COG to hydrogen (COGTH), COG to synthetic natural gas (COGTSNG), COG to synthetic ammonia (COGTSA), and COG to olefins (COGTO). The framework employed the life cycle assessment method based on an economic functional unit to calculated individual indicators and used the entropy weight method to integrate these indicators to a comprehensive score. The results show that energy consumption, water consumption, and carbon emission are critical defects of COGTSNG, COGTM, and COGTE, respectively. Net present value rate, internal rate of return, and dynamic payback period are common but differentiated disadvantages of the five COG utilization routes other than COGTO with the current market price, which are the main factors of their weaker comprehensive competitiveness. COGTO is expected to be the most promising high-quality COG utilization route thanks to its excellent competitiveness, handsome market demand, and special policy preferences. In addition to COGTM, any of the other five COG utilization routes are likely to be most competitive when raw material and product prices fluctuate by 25%, which suggests that the investment should be tailored to local specific prices, demand, and policies.

Carbon defective carbon nitride with large specific surface area by hot oxygen etching for promoting photocatalytic performance

Defect engineering is an extremely powerful strategy for carbon nitride materials. In our paper, carbon defective-carbon nitride (V-g-C3N4) with a large specific surface area (555.3 m2 g−1) was prepared by multiple thermal and oxygen etching using urea as a precursor. The photocatalytic performance of the materials was evaluated by synthetic ammonia under visible light and full spectrum. Under visible light, V-g-C3N4 can produce 3.60 mmol/h/g of NH3, which is approximately ~ 3.24 times higher than that of g-C3N4. Under the sunlight, V-g-C3N4 can produce 21.35 mmol/h/g of NH3. Particularly, positron annihilation lifetime spectroscopy (PALS) was used to confirm the type of vacancies. The experimental results show that the method of multiple calcinations not only can successfully introduce the carbon vacancy into the polymerization network structure of carbon nitride, resulting in a large number of active sites are added for the reaction of ammonia synthesis, but also can expand the bandgap from 2.82 eV to 3.03 eV. In addition, After g-C3N4 was exposed to high temperature and weak oxygen three times, its structure became loose and porous, which also provides more active sites for the reaction. Herein, these findings provide a novel concept of introducing carbon vacancies to promote the efficiency of photocatalytic ammonia synthesis.

Using Atomically Dispersed Bimetallic Active Sites to Probe the Nitrate Reduction Mechanism to Ammonia

The production of synthetic ammonia via nitrogen reduction is a critical step toward producing fertilizers, central the supporting global food security. To date, the energy-intensive and greenhouse gas-emitting Haber-Bosch process remains the only way to produce ammonia on industrial scale. Recently, significant research efforts have focused on identifying carbon- neutral and distributed pathways to synthesize ammonia, mainly via the electrochemical reduction of dinitrogen (N2).1 This approach, however, is limited by the low N2 solubility, competing hydrogen evolution reactions, and the stability of the N≡N triple bond. A promising alternative pathway to ammonia production is through the reduction of nitrate (NO3 -), a more kinetically and thermodynamically favorable nitrogen precursor. The reduction of nitrate to ammonia provides dual benefits as both a carbon-neutral pathway to ammonia and as a way of denitrification to remove all-too-prevalent and environmentally harmful nitrate contamination, while creating a useful product.2 Although there exists in the literature several works using metal catalysts for the nitrate reduction reaction (NTRR) to ammonia, only very recently have single atom catalysts (SAC) been applied to nitrate reduction.3 , 4 The NTRR is an 8e- transfer reaction, in which the exact electron transfer pathways, either a direct 8e- transfer or by 2 + 6e- pathway, in which a nitrite (NO2 -) intermediate is desorbed and reabsorbed. These processes are not well-studied on SACs. In this talk, we will present a series of atomically dispersed iron and molybdenum, mono and bi-metallic nitrogen doped carbon (M-N-C, M = Fe, Mo, FeMo) electrocatalysts for the NTRR. Our catalysts show potential for faradic efficiencies over 90%, while exhibiting outstanding stability over 48 hours of operation. Furthermore, our results suggest distinct NTRR mechanisms over Fe and Mo active sites, revealing new insights into preferred NTRR pathways over varying single atom sites. Such a detailed understanding of the NTRR electron transfer pathway will not only advance development of high performance, selective SACs, but stands to provide a new route to environmentally responsible ammonia synthesis. References (1) Choi, J.; Suryanto, B. H. R.; Wang, D.; Du, H. L.; Hodgetts, R. Y.; Ferrero Vallana, F. M.; MacFarlane, D. R.; Simonov, A. N. Identification and Elimination of False Positives in Electrochemical Nitrogen Reduction Studies. Nat. Commun. 2020, 11 (1).(2) van Langevelde, P. H.; Katsounaros, I.; Koper, M. T. M. Electrocatalytic Nitrate Reduction for Sustainable Ammonia Production. Joule 2021, 5 (2),(3) Zhu, T.; Chen, Q.; Liao, P.; Duan, W.; Liang, S.; Yan, Z.; Feng, C. Single-Atom Cu Catalysts for Enhanced Electrocatalytic Nitrate Reduction with Significant Alleviation of Nitrite Production. Small 2020, 16 (49).(4) Niu, H.; Zhang, Z.; Wang, X.; Wan, X.; Shao, C.; Guo, Y. Theoretical Insights into the Mechanism of Selective Nitrate-to-Ammonia Electroreduction on Single-Atom Catalysts. Adv. Funct. Mater. 2020, 2008533 (3), 1–8.. Figure 1

First Steps: Synthetic Ammonia in the United States

The synthetic ammonia industry, originally based on Fritz Haber's 1909 invention of a catalytic high-pressure method as scaled up by Carl Bosch at BASF, grew globally in the years following World War I, based on the processes of Brunner, Mond & Co. (Britain), Luigi Casale (Italy), Georges Claude (France), and Giacomo Fauser (Italy). The ammonia was mainly converted into ammonium sulphate fertilizer. There was less impetus in the United States for taking up these developments, because America relied on ammonium sulphate from its by-product coke ovens, sodium nitrate (Chilean nitrate) from South America, ammonia from coal gas works, and calcium cyanamide as manufactured by the American Cyanamid Company. Even when a synthetic ammonia industry started up in the United States, it was on a smaller scale than in Europe. However there emerged just before the Wall Street Crash two major producers of synthetic ammonia, Allied Chemical and Du Pont. This article presents a historical reconstruction of the early synthetic ammonia industry in the United States focusing on the 1920s, paying particular attention to Du Pont's success, which relied on the ammonia process of Casale. Standard accounts suggest that Du Pont acquired Casale technology as the result of a straightforward business acquisition. However, the situation, as shown here, was far more complex. Du Pont had to engage in aggresive litigation in order to acquire rights to the Casale process in 1927.

Novel ceramic hollow fibre membranes contactor derived from kaolin and zirconia for ammonia removal and recovery from synthetic ammonia

The adverse effects of ammonia found in wastewater streams lead to the development of advanced water treatment technology, i.e. membrane contactor (MC). In this study, single layer hollow fibre membrane (SLZK) and dual layer hollow fibre membrane (DLZK) were prepared from zirconia and kaolin and modified into hydrophobic membrane through simple grafting process via fluoroalkylsilane (FAS) agent. The properties of membranes such as morphology, surface roughness, mechanical strength, wettability and liquid entry pressure were analysed through scanning electron microscopy (SEM), atomic force microscopy (AFM), 3-point bending strength, contact angle and LEPw setup. Finally, the performance of the membranes was also investigated towards ammonia removal via membrane contactor system. Our findings showed that hydrophobicity properties significantly improved for both SLZK and DLZK membranes after grafting modification process as indicated by the increase of contact angle value from 5° and 1° to 132.7° and ~180.0° respectively. Based on the morphological analysis, the surface of DLZK showed more porous structure as compared to the SLZK. In addition, DLZK also displayed the highest mechanical strength and contact angle reading of 125 MPa and ~180° respectively. This suggests that the DLZK showed an excellent membrane contactor performance with highest value of mass transfer coefficient (3.77 x 10-5 ms-1) and almost complete removal of ammonia removal (91%). Overall, these results implied that dual layer ceramic membrane developed from kaolin and zirconia could provide the basis for the development of alternative ceramic membrane with excellent properties for membrane contactor system.

Opposed multi-burner gasification technology: Recent process of fundamental research and industrial application

Opposed multi-burner (OMB) gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights. It has been widely used around the world, involving synthetic ammonia, methanol, ethylene glycol, coal liquefaction, hydrogen production and other fields. This paper summarizes the research and development process of OMB gasification technology from the perspective of the cold model experiment and process simulation, pilot-scale study and industrial demonstration. The latest progress of fundamental research in nozzle atomization and dispersion, mixing enhancement of impinging flow, multiscale reaction of different carbonaceous feedstocks, spectral characteristic of impinging flame and particle characteristics inside gasifier, and comprehensive gasification model are reviewed. The latest industrial application progress of ultra-large-scale OMB gasifier and radiant syngas cooler (RSC) combined with quenching chamber OMB gasifier are introduced, and the prospects for the future technical development are proposed as well.

Experimental and Theoretical Study of CO2 Solubility in Liquid CH4/H2 Mixtures at Cryogenic Temperatures

Methane-rich industrial byproducts, such as coke oven gas (COG) and synthetic ammonia exhaust tail gas, are often regarded as promising sources of unconventional natural gas. The design spec for liquefaction of these kinds of unconventional natural gas is quite different from that of conventional natural gas due to the presence of some special substances, such as hydrogen. In this work, CO2 solubility in liquid CH4/H2 mixtures is measured utilizing a static solid–liquid equilibrium (SLE) experimental apparatus. The experiments are carried out at cryogenic temperatures between 90 and 150 K in the pressure range of about 1.7–5.4 MPa. The results are compared with calculations based on the GERG-2008 and Peng–Robinson (PR) equations of state. It is found that, compared with the solubility of CO2 in pure methane, the existence of hydrogen makes CO2 solubility increase significantly between −160 and −145 °C and decrease significantly at temperatures above −140 °C. The results provide the basis for the CO2 purification system of the coke oven gas and synthetic natural gas liquefaction plant.

Biostimulation of sulfate-reducing bacteria used for treatment of hydrometallurgical waste by secondary metabolites of urea decomposition by Ochrobactrum sp. POC9: From genome to microbiome analysis

Sulfate-reducing bacteria (SRB) are key players in many passive and active systems dedicated to the treatment of hydrometallurgical leachates. One of the main factors reducing the efficiency and activity of SRB is the low pH and poor nutrients in leachates. We propose an innovative solution utilizing biogenic ammonia (B–NH3), produced by urea degrading bacteria, as a pretreatment agent for increasing the pH of the leachate and spontaneously stimulating SRB activity via bacterial secondary metabolites. The selected strain, Ochrobactrum sp. POC9, generated 984.7 mg/L of ammonia in 24 h and promotes an effective neutralization of B–NH3. The inferred metabolic traits indicated that the Ochrobactrum sp. POC9 can synthesize a group of vitamins B, and the production of various organic metabolites was confirmed by GC-MS analysis. These metabolites comprise alcohols, organic acids, and unsaturated hydrocarbons that may stimulate biological sulfate reduction. With the pretreatment of B–NH3, sulfate removal efficiency reached ~92.3% after 14 days of incubation, whereas SRB cell count and abundance were boosted (~107 cell counts and 88 OTUs of SRB) compared to synthetic ammonia (S–NH3) (~103 cell counts and 40 OTUs of SRB). The dominant SRB is Desulfovibrio in both S–NH3 and B–NH3 pretreated leachate, however, it belonged to two different clades. By reconstructing the ecological network, we found that B–NH3 not only directly increases SRB performance but also promotes other strains with positive correlations with SRB.

Integrated hydrogen liquefaction processes with LNG production by two-stage helium reverse Brayton cycles taking industrial by-products as feedstock gas

Hydrogen-rich industrial by-products, such as coke oven gas (COG) and synthetic ammonia exhaust tail gas, are often simply utilized as fuel gas, or even not utilized at all in many cases. An innovative and efficient utilization method is proposed and investigated in this paper. Aiming to coproduce liquid hydrogen and liquefied natural gas (LNG), three helium reverse Brayton cycles are constructed, optimized, analyzed and compared. The LN-He-1 process is constructed with reference to conventional industrial hydrogen liquefaction processes, but with different feedstock gas. The LN-He-2 and N–He processes, which are an improvement on the basis of LN-He-1. A combination of distillation and flash is utilized to reduce the separation load. Analysis of load variation, power consumption, exergy, heat transfer and turbomachinery efficiencies are carried out. For different feedstock gas compositions, the specific power consumptions of LN-He-1, LN-He-2 and N–He processes are within 26.45–54.78 kWh/kmol (feedstock gas), 26.32–53.78 kWh/kmol (feedstock gas) and 21.94–50.42 kWh/kmol (feedstock gas), respectively. The exergy efficiencies are between 13.0% and 66.5%.

Main group metal elements for ambient-condition electrochemical nitrogen reduction

Electrocatalytic N2 reduction under ambient-condition is considered to be the most appealing strategy to the conventional Haber-Bosch process for synthetic ammonia to alleviate greenhouse emissions and reduce environmental pollution, mainly powered by renewable energy. Recent years, rapid advances have been gained in this attractive research field, and numerous electrocatalysts have been exploited. However, its conversion efficiency is still far behind the requirement of industrial applications owing to the breakage of the N≡N triple bond, which is an energetically challenging kinetically complex multistep reaction and the strong competing reaction of hydrogen evolution reaction. Recently, main group metal-based catalysts have been demonstrated promising application prospect for ammonia production, significantly boosting their further application in this field. However, a comprehensive review of main group metal-based catalysts towards electrochemical ammonia production applications is still lacking. In this review, the fundamentals of N2 reduction, such as the reaction pathways, the reaction potential and the challenges of N2 reduction have been comprehensively discussed. And then, the role, mechanism, and effect of each main group element-based catalysts used for N2 reduction (Li, K, Al, Ga, Sn, Sb, Bi, and their compounds) are systematically summarized. Finally, several state-of-the-art strategies to promote their NRR catalytic performance, as well as the existing problems and prospects are put forward. This review is expected to guide the design and establishment of more efficient electrocatalytic N2 reduction systems based on main group metal elements in the future.

Understanding the key role of vanadium in p-type BiVO4 for photoelectrochemical N2 fixation

The photoelectrochemical N2 reduction reaction (PEC NRR) is extremely charming to the synthetic ammonia (NH3), for its mild operating conditions and low carbon footprint. Taking account of the strong chemical inertness of N2 and competitive hydrogen evolution reaction, it is necessary to explore a robust and stable photoelectrocatalyst. Herein, a robust p-type BiVO4 (p-BiVO4) photocathode is firstly reported for NRR under ambient conditions. Interestingly, V sites are proved as the mainly ideal active center for N2 adsorption/activation based on the density functional theory (DFT) calculations. The ammonia evolution rate (VNH3:11.6 × 10−8 mol h−1 cm−2) and Faradaic efficiency (16.2%) were obtained at −0.1 V vs. RHE in 0.1 M Li2SO4 solution, outperforming most of the photoelectrocatalysts reported thus far. Moreover, the 1H nuclear magnetic resonance result confirmed that the source of N was completely from the feeding N2 gas. This work provided a new opportunity to tap the V-based photocathode in the field of PEC NRR.

Metal-Free C3N4 with plentiful nitrogen vacancy and increased specific surface area for electrocatalytic nitrogen reduction

As a substitute for synthetic ammonia under mild condition, electrocatalytic nitrogen reduction reaction (NRR) provides a hopeful approach for the development of ammonia. Nevertheless, the current development of NRR electrocatalysts is far from enough and a systematic research is needed to gain a better improvement. This article presents that 2D C3N4-NV with a large specific surface area and abundant nitrogen vacancies is prepared by a simple and feasible method, and used as a metal-free catalyst for electrocatalytic NRR. Experiment result and density functional theory (DFT) calculation reveal that nitrogen vacancies in 2D C3N4-NV can act as an efficient active site for catalytic NRR, which is conducive to capturing and activating N2, lowering Gibbs free energy (ΔG) in reaction and inhibiting hydrogen evolution reaction (HER) at the same time. In addition, the larger specific surface area also makes more active site exposed, which is good for the contact between the electrolyte and the active site, thus enhancing its NRR activity. The electrocatalyst shows an excellent catalytic activity for NRR in 0.1 M HCl, including Faradaic efficiency of 10.96%, NH3 yields of 17.85 μg h−1mgcat.−1, and good stability (over 20 h).

Copper Recovery From Ammonia Solutions Through Electro-Electrodialysis (EED).

Alkaline leaching with highly selective ammoniacal complexing agents is an interesting alternative for the treatment of copper concentrates. This treatment is beneficial for copper recovery because it allows the formation of soluble amines complexes, with cupric tetramine () being the most stable. In order to suppress the unit operation of solvent extraction (SX) and move directly to the electrochemical process, an electro-electrodialysis (EED) process using ion exchange membranes to obtain copper is proposed. The study contemplates the operation with synthetic ammonia solutions containing copper at different concentrations and current density under standard conditions of pressure and temperature. The presented data demonstrate that the concentration of copper in the solution and the excess of ammonia are inversely related to the efficiency of the current and the voltage of the cell, whereas an increase in current density causes an increase in current efficiency, contrary to what happens in sulfuric systems.

Molecular dynamics study at N2/H2O-rGO interfaces for nitrogen reduction reaction

It is an emerging trend to develop synthetic ammonia via nitrogen reduction reaction(NRR) by using simple, economical and efficient catalysts under mild conditions. Due to the intrinsic rich-functional groups of the surface, its versatile tailorability and the true stability among all the two-dimensional materials, reduced graphene oxide (rGO) is drawing a rising attention of researchers to the NRR application. However, due to the hydrophobicity of C and hydrophilicity of oxygen-containing groups of rGO, the interface dynamics between rGO surface and N2 and H2O molecules, which are two basic precursors for catalytic NRR are still unclear up to date. Herein, we propose to explore this problem by constructing a hierarchical model for rGO-N2/H2O interface interaction and conducting molecular dynamics (MD) simulation at ambient conditions. We find a way to tune the function groups to maximize the adsorption of N2 and H2O molecules at the same time. H2O molecules are more likely to form hydrogen bonds with oxygen-containing groups of rGO in the near range. While in the remote region, N2 molecules tend to form non-bonding interactions with pure C atoms without oxygen-containing groups of rGO. These results will provide theoretical guidance for NRR based on rGO and rGO based materials.

Development of Electrocatalysts for Efficient Nitrogen Reduction Reaction under Ambient Condition

AbstractAs one of the most important chemicals and an energy carrier, synthetic ammonia has been widely studied to meet the increasing demand. Among various strategies, electrochemical nitrogen reduction reaction (e‐NRR) is a promising way because of its green nature and easy set‐up on large‐scale. However, its practical application is extremely limited because of the very‐low production rate, which is strongly dependent on the electrocatalysts used. Therefore, searching novel efficient electrocatalysts for e‐NRR is essential to promote the technology. In this review, it highlights the insights on the mechanism for the NH3 electrochemical synthesis, recommend a reliable protocol for the ammonia detection, and systematically summarize the recent development on novel electrocatalysts, including noble metal‐based materials, single‐metal‐atom catalysts, non‐noble metal, and their compounds, and metal‐free materials, for efficient e‐NRR in both experimental and theoretical studies. Various strategies to improve the catalytic performance by increasing exposed active sites or tuning electronic structures, including surface control, defect engineering, and hybridization, are carefully discussed. Finally, perspectives and challenges are outlined. It can be expected that this review provides insightful guidance on the development of advanced catalytic systems to produce ammonia through N2 reduction.

Failure analysis of high-temperature reformer tube of Incoloy 800H in synthetic ammonia installation

Failure analysis was conducted for a cracked Incoloy 800H reformer tube serviced at 580℃ in an ammonia installation based on the microstructure observation, fracture analysis, mechanical properties testing and finite element analysis. Results showed that the stress relaxation cracking (SRC) during operation was the primary cause of the repeated cracking, and the assembling malposition had a significant impact on the SRC by raising local stress. The larger the malposition was restrained, the earlier the cracking time was. A method for estimating the failure time due to malposition was proposed, which could be used to determine the malposition criteria during fabrication. In addition, the aged Incoloy 800H tube was much more sensitive to the SRC than virgin material since the ductility of the material decreased obviously after about 5 years’ service at high temperature. This work confirms that “free-stress deflection angle” method is of choice to reduce SRC in case large malposition cannot be avoided.