Low Temperature Steam Research Articles

Modeling of low temperature steam reforming of flare gas to methane-rich fuel gas on Ni catalyst in different types of reactors

The results of mathematical modeling of fixed-bed catalytic reactors for low temperature low H2O/C steam reforming of propane-methane mixture and two real associated petroleum gases into methane-enriched fuel gas are reported. Three cases of practical interest were considered. In the first case, a lab-scale flow reactor, which is used for kinetic studies, was analyzed under assumption of constant wall/oven temperature. The possibility of noticeable hot and cold zones formation along the bed radius (4 mm) and length (33 mm) was predicted depending on the wall temperature and the ratios of H2O/C3H8 and C3H8/CH4. In the second case, a plant-scale adiabatic reactor was simulated, and the impossibility of conversion of flare gas with high C2+ fraction into fuel mixture with sufficiently high LHV (>31.8 MJ/m3) was predicted even if the post-removal of CO2 was assumed. In the third case, the advantages of a plant-scale tubular reactor against an adiabatic one were revealed for the reforming of “heavy” and “light” associated petroleum gas. The proposed bifunctional role of steam (first as a coolant, second as a reagent) increases the energy efficiency of tubular reformer due to recuperation of heat produced by reaction. The scheme with counter-current flows of reagent and coolant enabled to reduce twice the number of tubes in comparison with concurrent flow, but the catalyst temperature in the hot zone raised by 40°.

Effect of steam addition during carbonation, calcination or hydration on re-activation of CaO sorbent for CO2 capture

Calcium looping (CaL), based on cyclic carbonation/calcination using lime-based sorbents, is a promising technology for post-combustion CO2 capture. An important obstacle of this technology is the decay of sorbent over multiple cycles. Steam re-activation is a potential approach to improve the sorbent reactivity, however, the effects of both in-situ high-temperature steam (in carbonator or/and calcinator) and ex-situ low-temperature steam (steam hydration in hydrator) are still a matter of debate. Here, a bubbling fluidised bed reactor was used to investigate three steam addition options: steam addition during carbonation stage, or during calcination stage, or intermediate steam hydration after each CaL cycle. A CaO sorbent was tested under varying steam concentrations up to 40 vol.% for 10 CaL cycles (carbonation: 650 °C, calcination: 900 °C). Compared to the dry condition, steam addition during carbonation and intermediate steam hydration were both found effective for CaO re-activation. For the former, the improved sorbent reactivity was mainly attributed to an increased pore volume enhancing the extent of carbonation in kinetic regime; while for the latter, the formation of cracks accelerated the rate of diffusion. Nevertheless, decreasing the hydration temperature was detrimental to sorbent reactivity due to enhanced sintering upon cooling. In case of steam addition during calcination, the sorbent was affected negatively or positively depending on the concentration of steam. At higher steam concentrations (20, 40 vol.%), the sorbent reactivity was significantly decreased due to sintering associated with larger pores and lower surface areas. Overall, steam addition during carbonation was recommended for sorbent re-activation.

Energy Calculator for Solar Processing of Biomass with Application to Uganda

Rural areas of developing countries often have poor energy infrastructure and so rely on a very local supply. A local energy supply in rural Uganda frequently has problems such as limited accessibility, unreliability, a high expense, harmful to health and deforestation. By carbonizing waste biomass streams, available to those in rural areas of developing countries through a solar resource, it would be possible to create stable, reliable fuels with more consistent calorific values. An energy demand calculator is reported to assess the different energy demands of various thermochemical processes that can be used to create biofuel. The energy demand calculator then relates the energy required to the area of solar collector required for an integrated system. Pyrolysis was shown to require the least amount of energy to process 1 kg of biomass when compared to steam treatment and hydrothermal carbonization (HTC). This was due to the large amount of water required for steam treatment and HTC. A resource assessment of Uganda is reported, to which the energy demand calculator has been applied. Quantitative data are presented for agricultural residues, forestry residues, animal manure and aquatic weeds found within Uganda. In application to rural areas of Uganda, a linear Fresnel HTC integration shows to be the most practical fit. Integration with a low temperature steam treatment would require more solar input for less carbonization due to the energy required to vaporize liquid water.

CFD modeling of the flow dynamics and gasification in the combustor and gasifier of a dual fluidized bed pilot plant

Numerical simulation of the dense gas-solid reactive flow in a pilot-scale dual fluidized bed for biomass gasification is conducted with large eddy simulation coupled with multiphase particle-in-cell approach. After validating the numerical results with the experimental data, the hydrodynamics of different components operating under different flow regimes are explored. The results show that dense bottom and dilute upper exist in the combustor, while the elutriation of fine particles appears in the freeboard of gasifier. Strong swirling flow together with the fishtailing phenomenon of gas phase appear in the cyclone. Gas density is large in the lower part of combustor, and decreases along the horizontal direction. Large thermal conductivity and specific heat capacity of gas phase exist in the gasifier due to the large mass fraction of low-temperature steam. Biomass inlet results in a large mass fraction of gaseous species in the right part of gasifier. The size distribution of heat carrier negligibly affects the gas thermal property in the lower part of both the combustor and gasifier.

Novel post combustion CO2 capture in the coal-fired power plant employing a transcritical CO2 power generation and low temperature steam upgraded by an absorption heat transformer

This paper deals with a double effect heat transformer-aided carbon dioxide capture unit with transcritical carbon dioxide power generation for a coal-fired steam power plant. In the proposed system a double absorption heat transformer is used to upgrade low energy level steam into high-level and drive carbon dioxide capture unit. Also, a transcritical carbon dioxide power generation that is utilized captured carbon dioxide to generate power and compensate a portion of the required electrical energy of the carbon dioxide capture unit. This system avoids extracting high-grade temperature steam extracted from high-pressure stage of steam turbine and hence overall thermal efficiency of power plant increases compared to the reference systems. Comprehensive thermodynamic and economic evaluations are conducted to reveal the feasibility of the presented system. The results show that the evaporator temperature has the highest effect on net power output. An increase of 10 K in the evaporator temperature from 80 °C to 90 °C, leads to a reduction of 4.9% in generated power. However, a 50% increase in carbon dioxide capture rate from 40% to 90%, leads to a rise of 23.4% in the exergy destruction rate. Moreover, the payback period is approximately 4 years and 6 months.

Steam reforming of polystyrene at a low temperature for high H2/CO gas with bimetallic Ni-Fe/ZrO2 catalyst

Recovery of chemicals and fuels from unrecyclable waste plastics at high temperatures (>800 °C) has received much research attention. Thermodynamic equilibrium calculation suggests that it is possible to perform the low-temperature steam reforming of polystyrene. In this study, we synthesized a Ni-Fe bimetallic catalyst for the low-temperature (500 °C) steam reforming of polystyrene. XRD characterization showed that Ni-Fe alloy was formed in the catalyst. Compared to conventional Ni catalysts, the Ni-Fe bimetallic catalysts can significantly increase the H2/CO ratio in the produced gas with high gas production yield. The online gas analysis revealed that H2, CO, and CO2 were formed in the same temperature range. H2 and CO were formed simultaneously through steam reforming reactions, and CO2 was formed through water-gas shift reaction. New morphologies of carbon deposition on the catalyst surface were found, suggesting that wax could be condensed on the catalyst surface at a low temperature.

Исследование влияния низкотемпературной плазмы и паровой стерилизации на свойства трековых мембран из полиэтилентерефталата

Исследование влияния низкотемпературной плазмы и паровой стерилизации на свойства трековых мембран из полиэтилентерефталата

Immunoadsorption in ABO-incompatible kidney transplantation in adult and pediatric patients with follow-up on graft and patient survival: First series from India.

BACKGROUND:There are no published reports on desensitization protocol for ABO-incompatible kidney transplants using Immuno-Adsorption (IA) plasmapheresis from India. IA offers certain advantages including processing of larger plasma volumes, quicker reduction of isoagglutinin titers and no requirement of replacement fluids.AIMS AND OBJECTIVES:Authors' center evaluated success of desensitization protocol, and graft/patient outcomes when IA procedures were performed for desensitization in adult and pediatric ABO-incompatible kidney transplant patients.METHODS:Patients undergoing ABO-incompatible kidney transplant with use of IA were evaluated at tertiary care center in north India. Patient records for 2-years were collated from hospital information system (HIS) and procedure forms.RESULTS:Sixteen IA procedures were performed in five patients who underwent successful ABO-incompatible kidney transplant. Initial isoagglutinin IgG titer ranged from 32-512. Mean number of IA procedures performed to achieve the desired pre-transplant IgG titer ≤8 was 3.2. New IA column was used for each patient (and re-used for the same patient, if needed, after sterilization with Low temperature steam of formaldehyde). Mean plasma volume processed during each IA procedure was 4.5 times. No adverse events were observed during any IA procedure. All patients achieved successful desensitization. All patients continue to do well clinically with mean follow-up period of 8.8 months. Although IA was expensive, it offered advantages like specificity, larger plasma volume processing with desired reduction in titer, no 'replacement fluid' requirements and no adverse events in present case series.CONCLUSION:IA plasmapheresis was universally successful in decreasing the ABO-isoagglutinin titers to desired level in all prospective ABO incompatible kidney transplant patients.

Tar content and composition during a low-temperature steam gasification of rice husks

The research work extends our recent empirical knowledge on the rice husks, a carbonaceous solid material. This solid biofuel option was characterized with a potential net heating value of 16–17 MJ/kg, significant high ash deformation temperature recorded above 1450 °C, capable and considerable for thermochemical conversion systems. An experimental performance on a dual fluidized bed steam gasifier using rice husks pellets was carried out at a low temperature between 600 and 650 °C and fuel power of 100 kWth. Pure steam was used as a gasification agent in fluidization at a steam to fuel ratio of 1.2 kg/kg on dry basis. Calcite with mainly CaCO3 in composition was used as bed material for the reactor. Tar content and composition in the product gas stream were analyzed with a gas chromatograph coupled with mass spectrometer (GC–MS). Significant high amounts of total GC–MS tar components (without benzene, ethylbenzene, and xylene) and gravimetric tar (higher molecular tar) were detected at 29.44 and 17.82 g/m3 on dry basis. Benzene content was, respectively, presented on a value of 9 g/m3 on dry basis. Obtained products consisted of relevant amount of phenol and heterocyclic aromatic tars (class 2). The specific composition of common and additional analytes presented in GS–MS tar was summarized for better understanding of tar formation and reduction phenomena of rice husk gasification.

Bio-CH4 from palm empty fruit bunch via pyrolysis-direct methanation: Full plant model and experiments with bio-oil surrogate

Abstract A promising, cleaner alternative process of thermochemical conversion of lignocellulosic biomass to biomethane is proposed and rigorously investigated via modelling and experiments for the first time. Using a conventional nickel on calcium aluminate catalyst, operated in bench scale at 1 atm, 400 °C, and with a feed molar steam to carbon ratio of 2, the Low Temperature Steam Reforming of acetic acid, representing a single compound bio-oil surrogate, achieves a promising 81.9% fuel carbon conversion to gases with a methane yield of 15.7 wt% of the feed. This compares to 21 wt% methane yield at equilibrium, thus demonstrating encouraging first time performance and scope for future catalyst optimisation. A comprehensive Aspen Plus model is developed for the first time for an industrial plant producing biomethane from palm empty fruit bunch (50 wt% initial moisture), an under-used agro-industrial waste produced in vast amounts in South-East Asia and Sub-Saharan Africa. Dependency on external heating is completely eliminated by heat recovered from combusting 25% of the gas product. Based on the simulation results of the autothermal plant, a final gas product consisting of 99.2 wt% of CH4 and 0.8 wt% of H2 is predicted with a plant thermal efficiency of 80.6%, i.e., comparable to modelled efficiencies found in the literature for wood gasification to biomethane plants that generate syngas as a necessary intermediate.

Highly Active Catalysts Based on the Rh4(CO)12 Cluster Supported on Ce0.5Zr0.5 and Zr Oxides for Low-Temperature Methane Steam Reforming

Syngas and Hydrogen productions from methane are industrially carried out at high temperatures (900 °C). Nevertheless, low-temperature steam reforming can be an alternative for small-scale plants. In these conditions, the process can also be coupled with systems that increase the overall efficiency such as hydrogen purification with membranes, microreactors or enhanced reforming with CO2 capture. However, at low temperature, in order to get conversion values close to the equilibrium ones, very active catalysts are needed. For this purpose, the Rh4(CO)12 cluster was synthetized and deposited over Ce0.5Zr0.5O2 and ZrO2 supports, prepared by microemulsion, and tested in low-temperature steam methane reforming reactions under different conditions. The catalysts were active at 750 °C at low Rh loadings (0.05%) and outperformed an analogous Rh-impregnated catalyst. At higher Rh concentrations (0.6%), the Rh cluster deposited on Ce0.5Zr0.5 oxide reached conversions close to the equilibrium values and good stability over long reaction time, demonstrating that active phases derived from Rh carbonyl clusters can be used to catalyze steam reforming reactions. Conversely, the same catalyst suffered from a fast deactivation at 500 °C, likely related to the oxidation of the Rh phase due to the oxygen-mobility properties of Ce. Indeed, at 500 °C the Rh-based ZrO2-supported catalyst was able to provide stable results with higher conversions. The effects of different pretreatments were also investigated: at 500 °C, the catalysts subjected to thermal treatment, both under N2 and H2, proved to be more active than those without the H2 treatment. In general, this work highlights the possibility of using Rh carbonyl-cluster-derived supported catalysts in methane reforming reactions and, at low temperature, it showed deactivation phenomena related to the presence of reducible supports.

Low-temperature-steam activation of phosphorus in biochar derived from enhanced biological phosphorus removal (EBPR) sludge

The property and release behavior of phosphorus in biochar derived from enhanced biological phosphorus removal sludge (EBPR sludge) were investigated. A low-temperature-steam (LTS) activation method was developed to increase the P availability in the biochar. The results demonstrate that the P content in the biochar is comparable to that in typical P fertilizers. The biochar contained a considerable portion of fast-release P. Polyphosphates (poly-P) were the predominant P species in the biochar. LTS greatly improved P availability in biochar produced at 700 °C by hydrolyzing insoluble poly-P to soluble pyro-P and ortho-P. In addition, the presence of Ca2+ could greatly reduce the P-release from biochar produced at lower temperature, e.g. 400 °C, due to that Ca2+ could facilitate the precipitation/adsorption of orthophosohates/pyrophosphates released from the low temperature biochars. Such phenomena was not observed with high temperature biochar, as the soluble poly-P released from 700 °C biochar could complex with Ca2+ rather than precipitated with it. Other environmental conditions, i.e., environmental pH, ionic strength of the soil porewater, and presence of low-molecular-weight acid, only had minor or negligible effects on the P-release of most studied biochars. This study concludes that LTS-activated-700 °C biochar could be a promising P fertilizer given its high, rapid, and unaffected P-release under various environmentally relevant conditions.

Electric and mechanical detection of changes in heated apple flesh

The relationships between cell membrane damage by heating and textural parameters of apples were investigated. We determined changes in mass, volume, electrical impedance, mechanical properties, and juiciness of apple tissues after low-temperature steam heating at 40, 60, and 80 °C. The electrical indicator LTO was calculated from Cole-Cole plots using electrical impedance spectroscopy of apple tissues. Juiciness was estimated by measuring electrolyte release in cellular fluids during compression tests. At each temperature, the change in mass was very small compared to the sample volume. The LTO showed cell membrane damage of apples at 60 and 80 °C, which declined the mechanical properties, but increased juiciness. We showed that cell membrane damage affected the mechanical properties and juiciness of the heated apples. The LTO can be useful for estimation of changes in the mechanical properties and juiciness of apples during heat processing.

Catalytic steam gasification of sawdust char on K-based composite catalyst at high pressure and low temperature

The effects of temperature, pressure, steam ratio and K-based composite catalysts on the pressurized steam gasification of sawdust char were studied and the physicochemical structure of composite catalysts was characterized in detail. The results indicated that steam promoted the production of hydrogen but suppressed that of CH4. The generation of CH4 required high pressure, low temperature and suitable steam atmosphere. The composite catalysts reduced the reaction temperature and increased the carbon conversion, theirs catalytic performance ranked in descending order was KCe > KCo > KFe > KNi, where KCe showed perfect catalytic performance, which mainly determined by the ability to activate carbon during pressurized steam gasification of char. KFe and KCo were more conducive to water-gas-shift reaction, while KNi had the better performance on gasification reaction. The transformation paths of the composite catalysts were as follows: Ce(NO3)3·6H2O → CeO2, Co(NO3)2·6H2O → CoO/Co3O4 → Co → CoO, Fe(NO3)3·9H2O → Fe2O3 → FeO → Fe3O4 and Ni(NO3)2·6H2O → NiO → Ni.

Syngas production with thermo-chemically recuperated gas expansion systems: An exergy analysis and energy integration study

In spite of the large degree of energy integration in the modern syngas production units, the highly endothermic reactions of steam methane reforming and the combined steam and power generation still require a huge amount of energy that is typically supplied by an expensive natural gas-fired furnace at very high temperatures. Since normally only half of the energy supplied by the furnace is used to carry out the reforming reactions, the remaining heat recovery must be performed in a separate convection train (HRCT). Additionally, the high temperature effluent of the secondary reformer is generally cooled down by producing low temperature steam, increasing the process irreversibility and the losses associated to the excessive amount of condensate. Thus, in this paper, the advantages of introducing a chemically recuperated gas turbine (CRGT) concept to simultaneously carry out the endothermic chemical reactions and recover the exergy available from the autothermal reformer effluent are discussed. In this way, higher temperatures and higher conversions can be attained with lower driving forces. The power required by the air compression as well as other ancillary systems (e.g. air separation unit, carbon capture system, boiler feedwater pumps and recompressor) can also be supplied, while the exergy of the exhaust gases from the turbine is used more efficiently than in typical steam generation systems. Thus, more compact and integrated syngas production plants can be envisaged. Moreover, by introducing more advanced cogeneration features such as air enrichment, process gas reheating and incremental levels of pressures in the reaction-driven components, energy savings together with drastically reduced atmospheric CO2 emissions and irreversibility can be achieved in the frontend syngas production section. As a result, the average specific exergy destruction and exergy fuel consumption of the proposed CRGT-based configurations are, respectively, 12.0% and 2.7% lower, whereas the specific atmospheric CO2 emissions are cut down up to 25%, when compared to the conventional syngas production process.

Demonstration Plant of the Kawasaki CO2 Capture (KCC) System with Solid Sorbent for Coal-Fired Power Station

In a Kawasaki CO2 capture (KCC) system, CO2 in an exhaust gas is captured using a solid sorbent system with low-temperature steam. Because this system reuses the waste heat, it conserves energy in comparison with other conventional technologies. While a moving bed system makes it possible to apply the KCC technology to a large-scale plant, technology development at a large test facility is necessary. Therefore, this study investigates the application of the solid sorbent developed by Research Institute of Innovative Technology for the Earth (RITE) to the KCC moving-bed system for practical use. This study also evaluates the performance of the solid sorbent in a bench-scale test plant and preliminarily examines the installation at a 40 t-CO2/d-scaled pilot test plant to identify technological challenges at coal-fired power stations.

Low-temperature steam conversion of flare gases for various applications

The present work aims at studying low-temperature steam conversion of model flare gas mixtures containing C2H6-C5H12 in methane excess over industrial Ni-based catalyst. It is shown that at 250–350 °C and H2O/CC2+ molar ratio of 0.7–1.0, steam conversion can be applied to convert C2+-hydrocarbons into CH4, CO2 and H2, which results in the lowering net calorific value, the Wobbe index and dew point temperature of the gas obtained. However, complete conversion is not necessary for certain applications. In these cases, kinetically controlled partial conversion of ethane and propane enables one to obtain methane-rich mixtures with desired calorific properties for various applications. This idea has been experimentally verified. Kinetic study of C2H6-C5H12 low-temperature steam conversion has been performed. A simple macrokinetic model, which included irreversible first-order kinetics for C2H6-C5H12 steam conversion and quasi-equilibrium mode for CO2 methanation, has been suggested. The model adequately describes the experimental data on the conversion of model flare gas mixtures at various temperatures and flow rates and has been applied to predict the reaction conditions which would allow one to obtain methane-rich mixtures with the desired properties for various applications.

Low-Temperature Steam Reforming of Natural Gas after LPG-Enrichment with MFI Membranes

Low-temperature hydrogen production from natural gas via steam reforming requires novel processing concepts as well as stable catalysts. A process using zeolite membranes of the type MFI (Mobile FIve) was used to enrich natural gas with liquefied petroleum gas (LPG) alkanes (in particular, propane and n-butane), in order to improve the hydrogen production from this mixture at a reduced temperature. For this purpose, a catalyst precursor based on Rh single-sites (1 mol% Rh) on alumina was transformed in situ to a Rh1/Al2O3 catalyst possessing better performance capabilities compared with commercial catalysts. A wet raw natural gas (57.6 vol% CH4) was fully reformed at 650 °C, with 1 bar absolute pressure over the Rh1/Al2O3 at a steam to carbon ratio S/C = 4, yielding 74.7% H2. However, at 350 °C only 21 vol% H2 was obtained under these conditions. The second mixture, enriched with LPG, was obtained from the raw gas after the membrane process and contained only 25.2 vol% CH4. From this second mixture, 47 vol% H2 was generated at 350 °C after steam reforming over the Rh1/Al2O3 catalyst at S/C = 4. At S/C = 1 conversion was suppressed for both gas mixtures. Single alkane reforming of C2–C4 showed different sensitivity for side reactions, e.g., methanation between 350 and 650 °C. These results contribute to ongoing research in the field of low-temperature hydrogen release from natural gas alkanes for fuel cell applications as well as for pre-reforming processes.

Low Temperature Steam Methane Reforming Over Ni Based Catalytic Membrane Prepared by Electroless Palladium Plating

A Pd/Ni-YSZ porous membrane with different palladium loadings and hydrazine as a reducing reagent was prepared by electroless plating and evaluated for the steam methane reforming activity. The steam-reforming activity of a Ni-YSZ porous membrane was greatly increased by the deposition of 4 g/L palladium in the low-temperature range (600 °C). With an increasing amount of reducing reagent, the Pd clusters were well dispersed on the Ni-YSZ surface and were uniform in size (∼500 nm). The Pd/Ni-YSZ catalytic porous membrane prepared by 1 of Pd/hydrazine ratio possessed an abundant amount of metallic Pd. The optimal palladium loadings and Pd/hydrazine ratio increased the catalytic activity in both the steam-reforming reaction and the Pd dispersion.

Process Intensification by Exploiting Diluted 2nd Generation Bio-ethanol in the Low-Temperature Steam Reforming Process

Second generation bioethanol, obtained by the fermentation of lignocellulosic biomass, which is not competitive with the food and feed field, is one of the most interesting promising biofuels, already available in semi-commercial amount. Steam reforming of bioethanol has been used here for sustainable hydrogen and syngas production. Differently purified second generation bioethanol feeds, directly supplied by an industrial plant, for the steam reforming process, assessing the influence of impurities and catalyst formulation. Ni/La2O3, Ni/ZrO2 and Ni/CaO–ZrO2 prepared by Flame Spray Pyrolysis were used as catalysts. Catalytic performance at high and low temperature was evaluated in order to investigate a broad range of temperature, which is one of the most critical condition in term of catalyst activity and deactivation, besides energy saving. The possible effect of impurities contained in less purified feedstocks is also discussed. Stable performance up to 100 h-on-stream was attained even under stressing reaction conditions.