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This revised AMO tip sheet on minimizing boiler blowdown provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.
This revised AMO tip sheet on recovering heat from boiler blowdown provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.
This revised AMO tip sheet is part of a series of tip sheets on how to optimize an industrial steam system.
This revised AMO tip sheet is part of a series of tip sheets on how to optimize an industrial steam system.
This revised AMO tip sheet on installing high-pressure boilers provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.
This revised AMO tip sheet on minimizing boiler short cycling losses provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.
Technology readiness levels (TRLs) of electrolysis systems have dramatically increased in recent years as the interest in clean hydrogen production and decarbonization of transportation, industrial and other sectors increases across the globe. This is especially true of high temperature steam electrolysis (HTSE) / solid oxide electrolysis cell (SOEC) systems which show promise of much higher system efficiencies than other more developed electrolysis technologies. This possibility of higher efficiencies of HTSE / SOEC systems has been previously assumed to be theoretically possible but in recent years it has become less theoretical and more realistic as an increasing amount of suppliers complete lab and pilot tests showing very promising results. Research in the areas of manufacturing techniques, material selection, electrode and electrolyte compositions, and balance of plant size and integration continues at a fast pace as an increasing number of suppliers both internationally and domestically become involved. The advantages of HTSE become more pronounced when HTSE is coupled with nuclear power plants (NPPs). This is because thermal energy produced by the nuclear reactor can be used in a series of heat transfer loops and heat exchangers to vaporize HTSE feedwater, which drastically improves the economics of the process. Idaho National Laboratory (INL) has been very involved in the research and modeling of HTSE systems for a number of years, in collaboration with other national laboratories, academia, and industry stakeholders both on the hydrogen production as well as the hydrogen demand side. The modeling completed over the years on a large variety of projects has led to a wealth of knowledge at INL including in the area of the technoeconomic assessment (TEA) of HTSE systems. TEAs include process modeling of the HTSE systems to calculate system energy requirements and equipment sizing, followed by estimation of capital and operating costs to enable calculation of the levelized cost of hydrogen (LCOH). The TEA work performed has produced incremental improvements and tuning of the methods, assumptions, models, and results of the analyses as well as providing some opportunities for validating these results. The purpose of this document is to record the current baseline HTSE analyses led by INL to show the current status of assumptions and costs of these systems. Given the rapid development of this technology, the variety of suppliers entering the space, and the increasing attention government and industry are giving to such systems, this document may be updated on a periodic basis with updated analysis and assumptions. This document compiles various analyses results and approaches completed over a period of years into a single document to be used as a baseline going forward. It represents what the INL HTSE analysis group assumes to be the internal best estimate of the current operation, costs, and landscape of the HTSE industry state of the art capability for current SOEC technology in an Nth-of-a-Kind (NOAK) plant, which in this study is defined as existence of the manufacturing capacity to support previous deployment of N = 100 count of 25 MWe modular HTSE blocks (with modular equipment component cost reductions specified as following a 95% learning curve). That said, this is a public document and as such so no proprietary data was used or included in this report. There may be HTSE suppliers that have performance specifications, and cost estimates, and test data that differ from the analysis presented in this document. This document is meant to be a best conservative estimate of the technology and not an absolute reference.
Radiation from large cylindrical gas volumes is studied as a means of simulating the flare in steam boiler furnaces. Calculations of heat exchange in a furnace by the zonal method and by simulation of the flare with cylindrical gas volumes are described. The latter method is more accurate and yields more reliable information on heat transfer processes taking place in furnaces.
The article is devoted to an analysis of the characteristics of the KGB-5M electric-spark plant developed by the authors for use in the formation of erosion- and abrasion-resistant protective-reinforcing coatings on the leading and trailing edges of the rotor blades of the steam turbines of thermal and atomic power stations. It is shown that an increase in the thickness of electric-spark coatings and the efficiency of the plant may be produced by decreasing the “stray” inductance of the external discharge circuit and through rational selection of new wear- and erosion-resistant synthetic materials. The results of metallographic investigations of coatings produced by the KGB-5M plant are presented. The KGB-5 plant, which consists of a low-voltage vessel and a high-voltage vessel, was developed to achieve electric safety in the formation of coatings in closed metallic vessels (for example, in the capacitor of a turbine).
Shot peening is currently utilized in coal-fired power plant components to mitigate scale exfoliation issues from steamside oxidation of austenitic stainless steel superheater and reheater tubing. To focus on commercially available material, this study exposed quarter-ring specimens cut from two different commercially shot peened type 304H tubes and exposed to 1 bar steam for up to 15,000 h at 550°, 600°, 625°, and 650 °C. Specimens were removed at increments to characterize the oxide thickness and microstructure. The shot peened inner surface generally retained a thin, protective Cr-rich scale with occasional Fe-rich oxide nodules at 550–625 °C. The increased oxidation resistance from shot peening began to degrade at 650 °C after as little as 5,000 h. Cut and polished faces of these specimens formed thick, Fe-rich oxides similar to polished 304H coupons. Surprisingly, the mechanically machined outer surface of the tube specimens performed similarly to the shot peened inner diameter, suggesting it had sufficient cold work to achieve a similar benefit. As a result, electron backscatter diffraction and Vickers-hardness measurements were used to characterize post-exposure changes in underlying microstructure and mechanical properties, respectively, imparted by shot peening.
A series of ZnO promoted Co/CeO2 catalysts were synthesized and characterized using XRD, TEM, H2-TPR, CO chemisorption, O2-TPO, IR-Py, and CO2-TPD. The effects of ZnO on the catalytic performances of Co/CeO2 were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co0 via enhanced oxygen mobility of the CeO2 support which decreased the activity of Co/CeO2 in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO2 exhibited minimum CO and CH4 selectivity and maximum CO2 selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO2 facilitated the oxidation of CHx and CO to form CO2; (2) increased ZnO coverage on CeO2 surface reduced the interaction between CHx/CO and Co/CeO2; and (3) suppressed CO adsorption on Co0 reduced CO oxidation rate to form CO2. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO2, which consequently affected the C2–C4 product distributions.
In this paper, the effects of slag composition (slag basicity CaO/SiO{sub 2} and FeO concentration) on the amounts of H{sub 2} gas generated and the magnetic spinel phase precipitated as a result of the reaction between synthetic steelmaking slag and steam at 1873 K (1600 °C) were studied by thermodynamic simulation (using Thermodynamic Package FactSage 7.0) and laboratory experiments. The thermodynamic calculation showed that, upon increasing slag basicity (CaO/SiO{sub 2}) from 1.0 to 2.5, for the reaction of 100 g of slags with 100 g of H{sub 2}O gas, the accumulated amount of the produced H{sub 2} gas increased from 0.17 to 0.27 g, while the amount of magnetic spinel phase first increased and then decreased, with the maximum precipitation of 16.71 g at the basicity of 1.5. When the FeO concentration increased from 15 to 30 pct for the slag with basicity of 2.0, the accumulated amount of the produced H{sub 2} gas increased from 0.17 to 0.28 g, and the amount of magnetic spinel phase increased from 5.88 to 10.59 g. The laboratory experiments were conducted in confocal laser scanning microscope to verify the reaction between 0.2 g of slag and 3.75 L of H{sub 2}O-Ar gas (P{sub H{sub 2O}} =0.2 atm). The results indicated that, for 100 g of slags, upon increasing slag basicity (CaO/SiO{sub 2}) from 1.0 to 2.5, both the produced H{sub 2} gas and magnetic spinel phase first increased and then decreased, with the maximum amounts being 0.09 g of gas and 37.00 g of magnetic spinel phase at the slag basicity of 1.50. For the FeO concentration increasing from 15 to 30 pct, the amounts of both the produced H{sub 2} gas and magnetic spinel phase increased from 0.04 to 0.10 g and from 18.00 to 27.00 g, respectively. The reaction rate between the molten CaO-SiO{sub 2}-FeO-MnO-Al{sub 2}O{sub 3}-MgO slag and the moisture (P{sub H{sub 2O}} =0.2 atm) increased with the increasing FeO activity in the slag. The dependence of the reaction rate (mol/cm{sup 2}/s) on FeO content can be expressed as r =(7.67(a{sub FeO})−2.99)×10{sup −7}.
This study was performed to elucidate the influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbons over CeO{sub 2}-Al{sub 2}O{sub 3} supported Ni and Rh catalysts at 800 C. The characteristics of the carbon deposits on the used catalysts after the reactions without and with sulfur were investigated by temperature-programmed oxidation (TPO), transmission electron microscopy (TEM), scanning transmission X-ray microscopy (STXM), temperature-programmed hydrogenation (TPH), X-ray absorption near edge structure (XANES), and scanning electron microscopy (SEM). Though abundant carbon deposits can accumulate on the pure CeO{sub 2}-Al{sub 2}O{sub 3} support due to fuel thermal cracking, the addition of Ni or Rh metal greatly reduced the carbon deposition in the sulfur-free reaction. The presence of sulfur increased the carbon deposition on both catalysts, which has a much more significant impact for the Ni catalyst. Carbon XANES study on the used catalysts revealed that graphitic carbon was dominant in the presence of sulfur, while oxidized carbon species (quinone-like carbon, carboxyl and carbonate) prevailed without sulfur. Meanwhile, the formation of carboxyl and carbonate more dramatically dropped on the Ni catalyst than that on the Rh catalyst. Our results strongly suggest that (I) the presence of sulfur can suppress carbon gasification and promote the formation of graphitic carbon on reforming catalysts due mainly to its poisoning effect on metals, and (II) Rh catalyst possesses stronger capability to maintain carbon gasification activity than Ni catalyst in the presence of sulfur.
Bulk metallic nickel is a poor catalyst for the reforming of oxygenates being deactivated by the deposition of coke. In contrast, Ni-ceria is an active system for the catalytic extraction of H2 from the ethanol steam reforming reaction (ESR, C 2 H 5 OH + 3H 2 O ↔ 2CO 2 + 6H 2 ). Numerous studies, with model (well-defined crystal surfaces) and technical (high surface area powders) catalysts, have been devoted to understand the fundamental role of each catalyst component, the performance of adjacent sites in the metal-oxide interface, and the complex mechanistic steps that convert two oxygenated reactants (ethanol and H 2 O) into H 2 . The size and low loading of Ni on ceria facilitate metal-oxide support interactions that probably enhance the reactivity of the system. To establish the precise role of both Ni and Ce is challenging. However it is clear that both Ni and Ce are associated with the dissociation of H 2 O (OH + H), while ceria readily adsorbs and partially dissociates ethanol (i.e. ethoxy formation). The most difficult step of Csingle bondC bond dissociation likely occurs only on Ni or at the Ni-Ce interface. H 2 O and OH remain as important agents for the prevention of excess C build up during the C—H/C—C dissociation process. Often, deactivation upon C build up, is a direct result of Ni sintering and decoupling of the Ni-Ce interactions. One strategy to maintain good activity and stability is to protect the Ni-Ce interaction, and this can be achieved through the use of solid solutions (Ce 1–x Ni x O 2–y ) or by employing stabilizing agents such as W (Ni x W y Ce z O 2 ). In this study, we present and discuss the most recent work for the ESR reaction and show the important role of ceria which participates directly in the reaction and also enhances catalytic activity through metal-support interactions.
Ni-based catalysts for CH 4 steam reforming require fine-tuning to withstand deactivation under dynamic operation conditions relevant to emerging H 2 -driven technologies. This study investigates the impact of the Mg:Al ratio and Pt presence in catalyst composition on the activity and stability of industrially relevant Ni-based mono- and bimetallic catalysts during simulated daily start-up and shut-down cycles in various gas atmospheres. The evolution of the catalyst structure during extensive testing procedures was investigated in detail by complementary electron microscopy, in situ/operando XAS and XRD. The results obtained revealed that catalyst deactivation is promoted at high Mg:Al ratios and especially affects the monometallic catalysts. By converting CH 4 at lower temperatures, Pt regulates the extent of Ni oxidation and its incorporation into MgO lattice. Further prevention of catalyst deactivation was achieved by optimizing the reactor shut-down procedure to minimize the simultaneous exposure to high temperatures and H 2 O vapors. By flushing the reactor with N 2 only around the reaction extinction temperature, a fraction of Ni species is maintained in metallic state, which is beneficial for the long-term activity and reaction operation economy.
Cu-based layered double hydroxides (LDHs) are widely recognized as effective catalysts for low-temperature methanol steam reforming, yet achieving high hydrogen productivity together with near-complete suppression of CO formation remains challenging. Here, we report the synthesis and evaluation of a series of CuZnGa LDH-derived catalysts and Ce-modified analogues prepared via an aqueous miscible organic method, which enables high metal dispersion and precise structural control. The optimized CuZnGa catalyst exhibits a hydrogen production rate of 16.9 µmol H 2 ·g cat −1 ·s −1 at 180 °C with an H 2 /CO ratio exceeding 3500, outperforming many state-of-the-art low-temperature systems. Importantly, the incorporation of small amounts of Ce further suppresses CO formation while maintaining high hydrogen productivity. Combined spectroscopic characterization and density functional theory calculations reveal that Ce is incorporated into the LDH lattice by substituting Ga 3+ sites up to a critical threshold, beyond which highly dispersed CeO x species are formed. These species provide mobile lattice oxygen that participates in a Mars-van Krevelen-type pathway, selectively oxidizing CO and suppressing the reverse water-gas shift reaction. This study establishes a clear relationship between Ce speciation, oxygen mobility, and catalytic selectivity in LDH-derived systems. The resulting catalysts demonstrate the potential of interface-engineered Cu-based materials for efficient low-temperature hydrogen production with minimal CO contamination.
Operating proton conducting solid oxide fuel cells (H-SOFCs) with hydrocarbon as fuel remains a challenge because of the instability of the anode and electrolyte materials in a CO 2 /H 2 O-containing atmosphere and the catalytic activity and coking resistance of the anode for direct oxidation of hydrocarbons. Therefore, in this paper, the steam reforming of methane (SRM, an endothermic process) is integrated into the H-SOFCs (fuel cell process, an exothermic process) for internally converting hydrocarbon to hydrogen and increasing energy efficiency of H-SOFCs. Moreover, a proton-conducting zirconate oxide (BaZr 0.8 Y 0.2 O 3 , BZY), which is stable in a CO 2 /H 2 O-containing atmosphere, is applied as an electrolyte and anode material of H-SOFCs. The operation of BZY-based H-SOFCs with internal SRM is assessed by thermodynamic calculation and experiments for the first time. The catalytic activity and coking resistance of the Ni-BZY anode for SRM are investigated thermodynamically and experimentally. Finally, the results demonstrate that the Ni-BZY anode possesses reasonable catalytic activity as well as good coking resistance for SRM at a temperature as low as 550 °C. Then, the electrochemical performance and durability of H-SOFCs operated with internal SRM are comprehensively studied from 550 °C to 700 °C.
Modern heat recovery steam generators (HRSGs) operate at elevated temperatures, leading to the formation of oxides inside the tubes of heat exchangers (HXs). This oxide growth reduces the heat recovery efficiency. Moreover, after reaching a certain critical thickness, some oxide scales detach from the tube surface (exfoliation), causing erosion damage to the components downstream. Predicting the metal temperature distribution and associated oxide thickness in the HXs of an HRSG can aid in mitigating these problems. Here, a computational fluid dynamics (CFD) model was developed within the commercial code STAR-CCM+ for the prediction of fluid flow, conjugate heat transfer, and associated oxidation in HRSGs. Moreover, a new Porous Media Model (PMM) method was developed to model the fin effect on the heat transfer in HX, which can substantially reduce the prohibitive computational costs of fin meshes. The developed CFD model was used to conduct a high-fidelity simulation of a real-scale HRSG to investigate flow, heat transfer, and oxide growth. The calculated oxide thickness on different tubes can be used to identify HX regions that require oxide-resistant coatings to prevent exfoliation and ensuing damages. Furthermore, this CFD framework can serve as a reference for future studies that intend to model and investigate high-temperature oxidation in HXs used for any applications.