Combined Steam Research Articles

Combined steam and dry reforming of methane for syngas production from biogas using bimodal pore catalysts

Three catalysts with bimodal pore structure: Ni/Al2O3, Ni/MgO-Al2O3, Ni/La2O3-Al2O3 were prepared by refluxed co-precipitation method and characterized by N2 adsorption-desorption, XRD, TPR, H2-TPD and CO2-TPD. For comparison, a Ni catalyst impregnated on commercial alumina was also prepared. The catalysts were tested in combined steam and dry reforming of methane (CSDRM) at atmospheric pressure, 600–700 °C and CH4:CO2:H2O = 1:0.48:0.8, for the preparation of synthesis gas with H2:CO ratio proper for methanol synthesis. The presence of both magnesium and lanthanum oxides contributes to a better dispersion and stabilization of Ni nanoparticles on the catalyst surface. The catalytic activity for CSDRM increases in the order Ni/Al2O3(r) < Ni/Al2O3 < Ni/La2O3-Al2O3 ≈ Ni/MgO-Al2O3. TPD methods revealed that the good performance of Ni/La2O3-Al2O3 is a consequence of its good properties for hydrogen adsorption, while the improved catalytic properties of Ni/MgO-Al2O3 reside in its good properties for CO2 adsorption. Synthesis gas with the H2:CO ratio between 2.3 and 2.5 was obtained for all the reaction conditions used in this work. The bimodal pore catalysts showed no deactivation during 6 h TOS. The analysis of used catalysts established the catalyst with the best stability as being Ni/La2O3-Al2O3.

The Demonstration of the Superiority of the Dual Ni-Based Catalytic System for the Adjustment of the H2/CO Ratio in Syngas for Green Fuel Technologies

A novel dual Ni-based catalytic process (DCP) to control the H2/CO ratio of 2 in the syngas product within one step at temperature &lt;700 °C was created and constructed. With the sequence of the catalysts located in the single reactor, the endothermic combined steam and CO2 reforming of methane (CSCRM) reaction and the exothermic ultra-high-temperature water–gas shift (UHT-WGS) reaction work continuously. During the process, the H2/CO ratio is raised suddenly at UHT-WGS after the syngas is produced from CSCRM, and CSCRM utilizes the heat released from UHT-WGS. Due to these features, DCP is more compact, enhances energy efficiency, and thus decreases the capital cost compared to reformers connecting with shift reactors. To prove this propose, the DCP tests were done in a fixed-bed reactor under various conditions (temperature = 500, 550, and 600 °C; the feed mixture (CH4, CO2, H2O, and N2) with H2O/(CH4 + CO2) ratio = 0.33, 0.53, and 0.67). According to the highest CH4 conversion (around 65%) with carbon tolerance, the recommended conditions for producing syngas with the H2/CO ratio of 2 as a feedstock of Fischer–Tropsch synthesis include the temperature of 600 °C and the H2O/(CH4 + CO2) ratio of 0.53.

An optimal hierarchical control scheme for smart generation units: An application to combined steam and electricity generation

Optimal management of thermal and energy grids with fluctuating demand and prices requires to orchestrate the generation units (GU) among all their operating modes. A hierarchical approach is proposed to control coupled energy nonlinear systems. The high level hybrid optimization defines the unit commitment, with the optimal transition strategy, and best production profiles. The low level dynamic model predictive control (MPC), receiving the set-points from the upper layer, safely governs the systems considering process constraints. To enhance the overall efficiency of the system, a method to optimal start-up the GU is here presented: a linear parameter-varying MPC computes the optimal trajectory in closed-loop by iteratively linearizing the system along the previous optimal solution. The introduction of an intermediate equilibrium state as additional decision variable permits the reduction of the optimization horizon, while a terminal cost term steers the system to the target set-point. Simulation results show the effectiveness of the proposed approach.

Promotional Effect of Iron on Nickel-Based Catalyst for Combined Steam-Carbon Dioxide Reformation of Methane.

In this study, the effect by Iron with nickel-based catalyst for the combined steam and carbon dioxide reforming of methane was investigated. Fe-promoted and un-promoted Ni-Mg-Ce/γ-Al2O3 catalysts were prepared by co-impregnation and evaluated in a quartz fixed-bed reactor at H₂O:CO₂:CH₄ ratios of 0.9:1:1 and a temperature of 1073 K under atmospheric pressure. The physicochemical properties of the catalysts were investigated by N₂ adsorption-desorption, XRD, H₂-TPR, CO₂-TPD, TGA and FE-SEM. The iron-supported catalysts showed improved resistance to carbon deposition and suppressed sintering of nickel. As a result, NMC-Fe(5) showed the lowest coke and high stability over 70 h among all other catalysts.

CO2 conversion through combined steam and CO2 reforming of methane reactions over Ni and Co catalysts

AbstractNi‐Co bimetallic and Ni or Co monometallic catalysts prepared for CO2 reforming of methane were tested with the stimulated biogas containing steam, CO2, CH4, H2, and CO. A mix of the prepared CO2 reforming catalyst and a commercial steam reforming catalyst was used in hopes of maximizing the CO2 conversion. Both CO2 reforming and steam reforming of CH4 occurred over the prepared Ni‐Co bimetallic and Ni or Co monometallic catalysts when the feed contained steam. However, CO2 reforming did not occur on the commercial steam reforming catalyst. There was a critical steam content limit above which the catalyst facilitated no more CO2 conversion but net CO2 production for steam reforming and water‐gas shift became the dominant reactions in the system. The Ni‐Co bimetallic catalyst can convert more than 70% of CO2 in a biogas feed that contains ~33 mol% of CH4, 21.5 mol% of CO2, 12 mol% of H2O, 3.5 mol% of H2, and 30 mol% of N2. The H2/CO ratio of the produced syngas was in the range of 1.8‐2. X‐ray absorption spectroscopy of the spent catalysts revealed that the metallic sites of Ni‐Co bimetallic, Ni and Co monometallic catalysts after the steam reforming of methane reaction with equimolar feed (CH4:H2O:N2 = 1:1:1) experienced severe oxidation, which led to the catalytic deactivation.

4E Analysis and Design of a Combined Cycle with a Geothermal Condensing System in Iranian Moghan Diesel Power Plant

Considering the new issues human society faces now, environmental issues, and climate change is one of the primary and most essential phenomena which have been caused by the unsustainable lifestyle of men over the last two centuries. Power and energy are some of the leading role players of today’s human lifestyle and one of the most effective in which the environment is affected. This article represents the results of research over the possibility of recovering waste heat and determination of design parameters of a waste heat steam generator for medium speed set of diesel generators, with the rated 42[Formula: see text]MW capacity and are used for power generation. The main goals of this study are to manage the waste heat of the engines and to help the severe water leakage of the power plant. In this paper, for managing the waste heat, a combined steam cycle is being designed for this process. This system added 19[Formula: see text]MW the overall electricity generation, and the exergy and energy efficiencies of the system are being increased by 29.2% and 32.8%. Moreover, finally, a geothermal condensing system (GCS) is designed to control the water shortages of the steam power unit condensing system. The GCS condensing system developed in this paper helps to reduce the water evaporation losses in the cooling water by more than 79% compared to the wet cooling towers.

Indicative energy technology assessment of hydrogen processing from biogenic municipal waste

An indicative appraisal has been undertaken of a combined Anaerobic Digestion and Steam Methane Reforming process to produce sustainable hydrogen from organic waste. The anaerobic digestion plant was based on the plant in Tilburg (The Netherlands), and was modelled from the kerbside organic waste collections through to methane production. Data on biogenic waste was obtained from a collection trial in a municipal area in the UK. This was scaled-up to match that of a Tilburg-like anaerobic digestion plant. The waste collection trials enabled the catchment area for an anaerobic digestion plant on a commercial scale to be estimated. A thermodynamic evaluation of the combined process included energy and exergy analysis in order to determine the efficiency of each process, as well as to identify the areas that lead to inefficiencies. The overall energy efficiency was 75% and the overall exergy efficiency was 60%. The main energy losses were associated with compressor inefficiencies. In contrast, the main exergy consumption was found to be due to the fermentation in the digestion tanks. Other hydrogen process efficiencies vary from 21% to 86%, with the higher efficiencies belonging to non-renewable processes. However, the sustainable hydrogen produced comes from entirely renewable sources (biogenic waste) and has the benefit of near-zero carbon emissions in contrast to fossil fuels. Finally, the case study included an indicative financial assessment of the collection to processing chain. A discounted payback period of less than 20 years was estimated with a modest annual charge for householders.

Assessment and Prediction of Complex Industrial Steam Network Operation by Combined Thermo-Hydrodynamic Modeling

Steam network operation stability and reliability is vital for any industrial branch. A combined steam network model comprising a balance and a coupled thermo-hydrodynamic model, including seasonal variations impact and system specificities, is presented. A balance model can readily be used by a refinery’s operators. The thermo-hydrodynamic model identifies system bottlenecks and cold spots and evaluates proposed operation and investment measures including heat loss reduction. A three-pressure levels refinery steam network served for model testing and validation. Balance model results reveal significant misbalance in steam production and consumption, reaching 30.5% in the low-pressure steam system, and heat balance differences in the range of 9.2% to 29.5% on individual pressure levels, attributable both to flow measurement accuracy issues and to heat losses. The thermo-hydrodynamic model results differ from the measured steam parameters by less than 5% (temperature) and by less than 4% (pressure), respectively, with the estimated operational insulation heat conductivity exceeding 0.08 W/m/K. Its comparison with that of 0.03 W/m/K for dry insulation material yields the need for pipelines re-insulation and a partial revamp of the steam network. The model is sufficiently general for any type of industry, pursuing the goal of cleaner and energy-efficient steam transport and consumption.

Hydrogen and/or syngas production through combined dry and steam reforming of biogas in a membrane reactor: A thermodynamic study

The possibility of valorizing biogas by producing pure H2 and/or syngas while minimizing the net CO2 emissions was analyzed, combining both dry and steam reforming of biogas. For this purpose, a multifunctional membrane reactor (MR) with a hydrogen permselective membrane was used. The MR, which allows obtaining ultra-pure hydrogen in the permeate side, is compared with a conventional reactor (CR). All analyses were performed from thermodynamic equilibrium calculations based on the Gibbs free energy minimization method. The temperature was varied up to 800 °C and 550 °C for the CR and the MR, respectively. The influence of water addition in the feed on the productivity of hydrogen and CO2 reduction was assessed as well. Results showed that the CR is more suitable to obtain syngas with high purity (only CO and H2) because it allows operating at very high temperatures. The syngas H2/CO ratio can be adjusted for further applications depending on the co-fed amount of water. However, in the permeate side of the MR high-purity hydrogen with a productivity of 73 mol per 100 mol of biogas fed can be obtained. This productivity is equivalent to an H2 production of 131 kg/h, assuming the biogas generation capacity of an existing landfill plant; still, by CO2 recycling, net CO2 emission can be reduced up to 50%.

Quantifying flexibility of industrial steam systems for ancillary services: a case study of an integrated pulp and paper mill

Due to the increasing use of intermittent renewable generation, the power grid requires more flexible resources to balance supply and demand of electricity. Steam systems with turbine-generators, which are widely used in industries, can be operated flexibly to support the power grid. Yet, the available amount of flexibility of industrial steam systems is still not clearly quantified. This study presents the method to quantify electricity generation flexibility of a typical industrial steam system with a steam turbine-generator and process heat demands. The proposed method is introduced based on a real case of an integrated pulp and paper mill in Austria. An integrated mathematical model representing the combined electricity and steam system is developed to simulate the behaviour of the on-site energy system to quantify the potential flexibility provision. Flexibility is represented as the maximum upward and downward changes in the imported electricity from the public power grid. The results demonstrate that it is possible to aggregate the flexibility of the industrial facility as a lookup table. Also, the results reflect key factors that limit the flexibility at different operating points of the turbine-generator.

Combined steam and CO2 reforming of methane (CSCRM) over Ni–Pd/Al2O3 catalyst for syngas formation

In order to syngas formation, combined steam and carbon dioxide reforming of methane (CSCRM) used in the presence of Ni–Pd/Al2O3 catalysts, which were synthesized by the sol-gel method. Al2O3 supported Ni–Pd catalyst exhibited the appropriate surface area of 176.2 m2/g and high dispersion of NiO phase with an average crystallite size of 11 nm, which was detected on catalyst surface utilizing transmission electron microscopy (TEM). The influence of three independent operating parameters including reaction temperature in the range of 500–1000 °C; (CO2 + H2O)/CH4 ratio, in the range of 1–3 and CO2/H2O ratio; in the range of 1–3, were investigated on the responses (i.e., CH4 conversion, H2 yield, CO yield, amount of coke formation on the catalyst surface and H2/CO ratio) in CSCRM by using response surface methodology–central composite design (RSM-CCD) method. The obtained results from ANOVA and the proposed quadratic models could fine forecast the responses. It was seen that the total methane conversion and CO yield was almost accessible at temperatures higher than 850 °C. Moreover, the CO2/H2O ratio exhibited no significant effect on the CH4 conversion, H2 yield and CO yield of Ni–Pd/Al2O3 catalysts in CSCRM reaction. However, the high CO2/H2O ratio in inlet feed led to the syngas formation with a low H2/CO ratio. The results revealed that lower CO2/H2O ratio and higher temperature as well as higher (CO2 + H2O)/CH4 ratio help to decrease the coke formation.

Syngas production via combined dry and steam reforming of methane over Ni-Ce/ZSM-5 catalyst

Recently, dry reforming of methane (DRM) has drawn more attention because of its environmental benefit and effective utilization of energy. The main focus of this area relies on the aspect of improvement of catalytic properties of catalysts used in DRM. This paper aims to develop an ideal Ni-Ce/ZSM-5 catalyst and to find out the optimum reaction conditions to achieve the best performance. In order to overcome some shortcomings of DRM, steam was introduced in the reaction system to generate steam reforming of methane (SRM) simultaneously. Ni-Ce/ZSM-5 catalysts were prepared by the impregnation method, and different catalytic reaction conditions were investigated. It is found that these condition parameters affect the catalytic performance in varying degrees. By adjusting these parameters properly, the Ni-Ce/ZSM-5 catalyst possesses an outstanding ability to convert CH4 and CO2 into syngas with highest conversion up to 99% and 94%. In addition, it was proved that the catalyst prepared had great stability as well under the determined reaction conditions. During 40 h of long reaction, the catalyst maintained high activity and did not show obvious deactivation. The conversion of CH4 and CO2 remained 95% and 85% respectively and the ratio of syngas was close to 1. Moreover, the catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), specific surface area and pore size analysis, TG analysis and H2-TPR analysis. The result of the characterization clarified the structure and composition of the catalysts and gave a better explanation of the catalytic performance.

Improving the thermal efficiency of a T-GDI engine using hydrogen from combined steam and partial oxidation exhaust gas reforming of gasoline under low-load stoichiometric conditions

Hydrogen (H2) addition is known to have features of increasing the laminar burning velocity (Di Sarli and Di Benedetto, 2007), the resistance of the flame to strain-induced extinction (Di Sarli and Di Benedetto, 2012, 2013), and also enlarging the operating window of stable combustion (Di Sarli, 2014). We experimentally investigated how to improve the thermal efficiency of a turbo gasoline direct injection (T-GDI) engine using H2 from combined steam and partial oxidation exhaust gas gasoline reforming under low-load stoichiometric conditions. During real driving, 4 and 6 bar brake mean effective pressure (BMEP) at 2,000 rpm are frequently used. Our experimental results show that reformed H2 improves the brake thermal efficiency (BTE) of T-GDI engines operating at 4 and 6 bar BMEP. Furthermore, the combustion speed (increasing heat release rate) and stability (reducing cyclic variation) were enhanced by reformed H2, making more heavy exhaust gas recirculation (EGR) operation. Combining steam and partial oxidation exhaust gas gasoline reforming with extra air injection to a reformer had a large effect on the fuel conversion efficiency of the reformer as the engine load decreased. Therefore, the BTE of the T-GDI engine with combined steam and partial oxidation reforming achieved further improvement over steam reforming only at 4 bar BMEP. Nitrogen oxide (NOX) emissions increased with reformed H2. However, on the basis of the improved combustion stability achieved using reformed H2, NOX emissions could be reduced further by using a higher EGR rate while enhancing the BTE.

Исследование процесса сушки шиповника в поле действия ультразвука

Introduction. Rose hips are rich in macro- and micronutrients. Unfortunately, heat treatment destroys most nutrients. Ultrasonic technologies make it possible to reduce the drying time and lower the temperature regime. The research objective was to adjust ultrasound technology to rose hip production in order to reduce the loss of vitamins and improve the quality indicators of the dried product.&#x0D; Study objects and methods. The research featured rose hips of the Rosa canina species collected in the south of Kazakhstan. This subspecies of wild rose is poor in vitamin C. Nevertheless, this shrub is extremely common in Russia and other countries of the Commonwealth of Independent States. The raw material was dried according to standard methods. One group of samples was treated with ultrasound, while the other served as control. Both groups underwent a sensory evaluation and were tested for moisture and vitamin C.&#x0D; Results and discussion. The rose hips were dried in a combination steam oven with a built-in ultrasonic wave generator. The research revealed the following optimal parameters of the ultrasound drying process: frequency of ultrasonic vibrations – 22 kHz, processing time – 2.5 h, temperature in the combination steam oven – +56°C, initial moisture content – 30%. The resulting product met the requirements of State Standard. The loss of moisture was 57%. According to State Standard 1994-93, the initial moisture content should be 15% or less. Time decreased from 360 min to 160 min, and the initial moisture was 13%. The experiment confirmed the initial hypothesis that ultrasonic treatment improves the drying process by improving quality indicators and preserving vitamin C in raw materials using.&#x0D; Conclusion. Ultrasound treatment during moisture removal from rose hips provides a resource-saving technology that fulfills an economically and socially important function.

The analysis and solution of contact rubbing fault for low pressure rotor of gas-steam combined cycle turbine unit

The contact rubbing fault mechanism for low pressure rotor of gas-steam combined cycle steam turbine unit is analyzed deeply in this paper. It is include that the high start and stop frequency of the gas turbine, the special operation mode of the long-time turning and the high designed turbine turning speed are the main reasons for the axial displacement to the inlet side of the fir-tree root and the contact rubbing fault of the low pressure rotor . At the same time, this paper presents a solution to the problem of contact rubbing fault of low-pressure turbine rotor, and analyzes the dynamic stress and vibration frequency of the new blade after technical improvement. The results show that the stress of root and groove of the new blade and the vibration frequency of the new blade can meet the requirements of safe and stable operation of the unit.

Hydrogen and/or syngas production by combined steam and dry reforming of methane on nickel catalysts

Two alumina supported Ni catalysts with pore sizes of 5.4 nm and 9 nm were synthetized, characterized and tested in the Combined Steam and Dry Reforming of Methane (CSDRM) for the production of hydrogen rich gases or syngas. The reaction mixture was designed to simulate the composition of real clean biogas, the addition of water being made in order to have molar ratios of H2O:CO2 corresponding to 2.5:1, 7.5:1 and 12.5:1. Structural and functional characterization of catalysts revealed that Ni/Al2O3 with larger pore size shows better characteristics: higher surface area, lower Ni crystallite sizes, higher proportion of stronger catalytic sites for hydrogen adsorption, and higher capacity to adsorb CO2. At all studied temperatures, for a CH4:CO2:H2O molar ratio of 1:0.48:1.2, a (H2+CO) mixture with H2:CO ratio around 2.5 is obtained. For the production of hydrogen rich gases, the optimum conditions are: CH4:CO2:H2O = 1:0.48:6.1 and 600 °C. No catalyst deactivation was observed after 24 h time on stream for both studied catalysts, and no carbon deposition was revealed on the used catalysts surface regardless the reaction conditions.

Multi-objective design optimization of a multi-generation energy system based on geothermal and solar energy

In this paper, a multi-generation system based on geothermal energy and parabolic trough solar collectors is proposed for the simultaneous generation of power, cooling, freshwater, hydrogen, and heat. Power is generated by a combined steam Rankine cycle and an organic Rankine cycle. Ten different refrigerants are used for the organic Rankine cycle, among which R123 has the best performance. In addition, four fluids are used as the geothermal fluid, among which Therminol 59 has recorded the best performance. Solar intensity, geothermal mass flow rate, geothermal fluid temperature, and steam turbine inlet pressure have proven to be the most prominent parameters affecting the exergy efficiency and cost. After analyzing the proposed system from the energy, exergy and exergoeconomic points of view, a multi-objective-optimization-genetic-algorithm is applied for improving the performance of the system. In order to apply the multi-objective optimization, Engineering Equation Solver and MATLAB software are linked together by the Dynamic Data Exchange method. According to the obtained results. The results show that the exergy efficiency of the system and the total unit cost respectively reach to 29.95% and 129.7 $/GJ at the optimum point.

Tuning combined steam and dry reforming of methane for “metgas” production: A thermodynamic approach and state-of-the-art catalysts

Nowadays, combined steam and dry reforming of methane (CSDRM) is viewed as a new alternative for the production of high-quality syngas (termed as “metgas”, H2:CO of 2.0) suitable for subsequent synthesis of methanol, considered as a promising renewable energy vector to substitute fossil fuel resources. Adequate operation conditions (molar feed composition, temperature and pressure) are required for the sole production of “metgas” while achieving high CH4, CO2 and H2O conversion levels. In this work, thermodynamic equilibrium analysis of CSDRM has been performed using Gibbs free energy minimization where; (i) the effect of temperature (range: 200–1000 °C), (ii) feed composition (stoichiometric ratio as compared to a feed under excess steam or excess carbon dioxide), (iii) pressure (range: 1–20 bar) and, (iv) the presence of a gaseous diluent on coke yields, reactivity levels and selectivity towards “metgas” were investigated. Running CSDRM at a temperature of at least 800 °C, a pressure of 1 bar and under a feed composition where CO2+H2O/CH4 is around 1.0, are optimum conditions for the theoretical production of “metgas” while minimizing C(s) formation for longer experimental catalytic runs. A second part of this work presents a review of the recent progresses in the design of (principally) Ni-based catalysts along with some mechanistic and kinetic modeling aspects for the targeted CSDRM reaction. As compared to noble metals, their high availability, low cost and good intrinsic activity levels are main reasons for increasing research dedications in understanding deactivation potentials and providing amelioration strategies for further development. Deactivation causes and main orientations towards designing deactivation-resistant supported Ni nanoparticles are clearly addressed and analyzed. Reported procedures based on salient catalytic features (i.e., acidity/basicity character, redox properties, oxygen mobility, metal-support interaction) and recently employed innovative tactics (such as confinement within mesoporous systems, stabilization through core shell structures or on carbide surfaces) are highlighted and their impact on Ni0 reactivity and stability are discussed. The final aspect of this review encloses the major directions and trends for improving synthesis/preparation designs of Ni-based catalysts for the sake of upgrading their usage into industrially oriented combined reforming operations.

Degradation analysis of a combined cycle heat recovery steam generator under full and part load conditions

In this paper, a theoretical model is proposed to simulate the performance and determine the degradation percentages of a Heat Recovery Steam Generator (HRSG) components at different operating loads and conditions. In addition, a new criterion is developed to determine the actual operational load of the HRSG based on the actual test performance (ATP) measured variables. The proposed model and the load determining criteria are applied to two-year collected data. After applying modeling procedure and load determining criteria, 10 readings were obtained for each operational month (January and August) every year for each operational loads of (100%, 75%, and 50%). The degradation analysis is carried out based on the actual power plant logged data; this distinguishes this research from the other studies in the same field. The results show that the degradation rate increases with time and with the operational load. On the other hand, there was no significant effect observed on the degradation rate by ambient conditions. Overall, the results indicate that the maximum degradation of the HRSG components was in the low-pressure stage of the HRSG at the full load and reached −6.73%, while the maximum overall degradation of the HRSG reached −6.02% at the full load.

The fault analysis for low pressure last stage blade of the deep load changing gas-steam combined cycle steam turbine unit

In this paper, the causes of the abrasion at the fir-tree type blade root of low pressure last stage which are loosely assembled and the axial movement of the blade root to the intake side of gas-steam combined cycle steam turbine unit are deeply analyzed, which are caused by the special operating conditions of long-term turning and the high-speed setting of turning gear of the deep peak load changing units. At the same time, through the analysis of the fracture of the broken blade, the damage of the top shroud and the vibration data of the accident process, it is concluded that the abrasion at the blade root results in loosening of the blade, the violent striking between the loose blades during the high-speed turning process, results in the damage of the top shroud and the blade. Under the action of centrifugal force of rated speed condition, a break first occurs, and the broken debris falls between the last rotor blade and the static blade, which causes severe impact damage to the blade body, thereby causing secondary tearing of the blade.