Hydrogen Generation Unit Research Articles

Sustainable Concept and Economic Evaluation of a Solar-Powered Hydrogen Generation Unit

Sustainable Concept and Economic Evaluation of a Solar-Powered Hydrogen Generation Unit

Carbon black and hydrogen production process analysis

The adoption of new environmentally responsible technologies, as well as, energy efficiency improvements in equipment and processes help to reduce CO2 rate emission into the atmosphere, contributing in delaying the consequences of intensive use of fossil fuels. For more effective actions, it is necessary to make the transition from the fossil-based to the renewable source economy. In this context, hydrogen fuel has a special role as clean vector of energy. Hydrogen has the potential to be decisive in mitigating greenhouse gas emissions, but fossil fuels high profitability due to global energy dependency actually drives the global economy.While renewable energy sources are not worldwide fully established, new technologies should be developed and used for the recovery of energetic streams nowadays wasted, to decarbonize hydrocarbons and to improve systems efficiency creating a path that can help nations and industries in the needed energy economy transition. Hydrogen gas can be generated by various methods from different sources such as coal and water. Currently, almost all of the hydrogen production is for industrial purpose and comes from the Steam Reforming, while the use of hydrogen in fuel cells is only incipient.The article analysis the plasma pyrolysis of hydrocarbons as a decarbonization option to contribute as a step towards hydrogen economy. It presents the Carbon Black and Hydrogen Process (CB&H Process) as an alternative option for hydrogen generation at large scale facility, suitable for supplying large amounts of high-purity carbon in elemental form. CB&H Process refers to a plant with hydrogen thermal plasma reactor able to decompose Hydrocarbons (HC's) into Hydrogen (H2) and Carbon Black (CB), a cleaner technology than its competing processes, capable of generating two products with high added value. Considering the Brazilian context in which more than 80% of the generated electricity comes from renewable sources, the use of electricity as one of the inputs in the process does not compromise the objective of reducing greenhouse gas emissions. It is important to consider that the use of renewable energy to produce two products derived from fossil fuels in a clean way represents integration of technologies into a more efficient system and an arrangement that contributes to the transition from fossil fuels to renewables.The economic viability of the CB&H process as a hydrogen generation unit (centralized) for refining applications also depends on the cost of hydrogen production by competing processes. Steam Methane Reforming (SMR) is a widespread method that produces twice the amount of hydrogen generated by natural gas plasma pyrolysis, but it emits CO2 gas and consumes water, while CB&H process produces solid carbon. For this reason, the paper seeks the carbon production cost by plasma pyrolysis as a breakeven point for large-scale hydrogen generation without water consumption and carbon dioxide emissions.

Design and thermodynamic modeling of a renewable energy based plant for hydrogen production and compression

In the examined paper, a solar and wind energy supported integrated cycle is designed to produce clean power and hydrogen with the basis of a sustainable and environmentally benign. The modeled study mainly comprises of four subsystems; a solar collector cycle which operates with Therminol VP1 working fluid, an organic Rankine cycle which runs with R744 fluid, a wind turbine as well as hydrogen generation and compression unit. The main target of this work is to investigate a thermodynamic evaluation of the integrated system based on the 1st and 2 nd laws of thermodynamics. Energetic and exergetic efficiencies, hydrogen and electricity generation rates, and irreversibility for the planned cycle and subsystems are investigated according to different parameters, for example, solar radiation flux, reference temperature, and wind speed. The obtained results demonstration that the whole energy and exergy performances of the modeled plant are 0.21 and 0.16. Additionally, the hydrogen generation rate is found as 0.001457 kg/s, and the highest irreversibility rate is shown in the heat exchanger subcomponents. Also, the net power production rate found to be 195.9 kW and 326.5 kW, respectively, with organic Rankine cycle and wind turbine. The final consequences obtained from this work show that the examined plant is an environmentally friendly option, which in terms of the system's performance and viable, for electrical power and hydrogen production using renewable energy sources.

Performance analysis of an on-site hydrogen facility for fuel cell trains

Fuel cell technologies and hydrogen can represent a potential and powerful enabler for replacing traditional diesel vehicles, especially in railways. In this train of thought, the present paper aims to investigate a fuel cell hybrid powertrain for a regional route. The main powertrain components are numerically modeled and the railway operations are simulated. The results achieved, in terms of power demand, efficiency and hydrogen consumption, are discussed and they are useful for properly sizing the refueling system. As a matter of fact, the train will be fueled with compressed hydrogen, produced on-site at a hydrogen central depot, where a hydrogen refueling station is thought to be installed. The hydrogen generation unit is considered to be a PEM unit, operating at 353 K and 20 bar. The produced hydrogen is then compressed by mean of a volumetric compressor and then stored in hydrogen tank type II, at 350 bar. The dispensing scheduling is based on the daily hydrogen demand required by the fuel cell-based train route, according to the railway timetable. The system is indeed investigated from a technical point of view, proving the integration of such systems to represent a clean, sustainable, and flexible option.

Dynamic Bayesian network based approach for risk analysis of hydrogen generation unit leakage

Hydrogen leakage is a crucial risk for the hydrogen generation unit, which would lead to the potential fire and explosion accidents. Hydrogen leakage risk analysis is the essential alternative to ensure the safety of the hydrogen generation process. This paper presents a dynamic risk analysis methodology regarding the hydrogen leakage in the hydrogen generation unit by using the dynamic Bayesian network, which is employed to address the potential uncertainty and dynamic nature underlying the leakage risk of the hydrogen generation unit. A case study of hydrogen generation unit is carried out to demonstrate the applicability and advantage of the proposed methodology. Results indicate that the leakage probability of hydrogen generation unit can be significantly decreased within one year through equipment repair. Furthermore, the failure and repair rates of overflow alarm and pressure sensor are the most contributory factors to the hydrogen generation unit leakage. Finally, some active mitigative suggestions are presented to further reduce the leakage risk of the hydrogen generation unit.

Climate-energy-water nexus in Brazilian oil refineries

Oil refineries are major CO2 emitters and are usually located in water-stress sites. While some CO2 mitigation options can reduce water demand, others can increase it, and still others are neutral. By simulating two parametric models, one for all Brazilian refineries, and the other locally detailing the water balance of the country´s largest refinery, this study aimed to quantify the impacts of CO2 mitigation options on the water use of oil refineries. Findings show that, by pricing CO2 emissions up to 100 US$/tCO2, the list of mitigation options was able to abate 25% of the annual emissions in Brazilian refineries. A relevant share of this abatement derives from the implementation of carbon capture (CC) facilities in fluid catalytic cracking and hydrogen generation units. However, these CC facilities offset the co-benefits of other CO2 mitigation options that can reduce steam and cold-water requirements in refineries. In fact, for the largest Brazilian oil refinery, the implementation of all mitigation measures had almost no effect on its water balance. This means that CO2 abatement in refineries has no significant impact on water demand (no negative trade-off). However, this also means that the water stress in oil refineries should be dealt with measures not directly linked to CO2 abatement (no significant co-benefits).

Zero-energy penalty carbon capture and utilization for liquid fuel and power cogeneration with chemical looping combustion

Abstract The utilization of captured CO2 for fuel, chemicals and materials is currently a focus of significant research effort as a method that can simultaneously mitigate greenhouse gas effect while reduce fossil fuel depletion. In this work, CO2 source is provided by a desirable three-stage Fe-based chemical looping combustion power system that can achieve zero-energy-penalty CO2 capture while simultaneously obtain pure H2 source. The aim of this study is to present this designed process for the first time with demonstrating it as an energy-efficient and environmental-friendly CO2-to-liquid fuel pathway. Within this context, the liquid fuels energy output and carbon emissions are compared with different CO2 utilization ratios to the thermodynamic assessment, intending to disclose the insufficiency location within system. With conceivable improvements in an optimum condition, the fuel energy saving ratio and CO2 emission ratio of this process are projected to be 12.19% and 98.46%, respectively in relative to separate production system. The maximal exergy destruction, though projected to be located in chemical looping hydrogen generation unit (as represented by 37.56% of total exergy destruction), still has opportunities to reduce in some extent by elevating oxygen carries high-temperature resistance along with future research needs. Finally the sensitivity analysis is also projected to assess the strong influencing parameters that affect the system performance.

An Experience of Substitution for Imported Steam Reforming Catalysts

The performance of the Russian catalyst for steam conversion of hydrocarbons was monitored. The catalyst was produced at the Angarsk Plant for Catalysts and Organic Synthesis and operated in a hydrogen generation unit at the Syzran Refinery. The Russian catalyst was compared to the imported analog under the Rosneft program of import substitution. It was demonstrated under industrial conditions that the Russian catalyst is comparable in quality with the world standards.

SIMULATION AND ANALYSIS OF A HYDROGEN GENERATION UNIT

High Purity Grade Hydrogen is an important compound used in oil refineries due to its capacity for withdrawing sulfur impurities from fuels. This feedstock is commonly produced in Hydrogen Generation Units through a Steam Methane Reforming process. Due to the high-grade requirements in Hydrotreament processes, a hydrogen purification step is mandatory, often conducted in batteries of adsorption columns, known as Pressure Swing Adsorption (PSA). The main objective of this paper is to present the simulation of a Hydrogen Generation Unit, focusing on the PSA process modeling approach. ASPEN PLUS™ was utilized in conjunction with MATLAB® to model the whole process. The link between both simulators was established through VBA (Visual Basic for Applications) macros developed in Excel. This two-way connection did not affect the results obtained by the simulation of the whole process unit, as it was carried out successfully and was able to represent the global mass and energy balances satisfactory, obtaining hydrogen with 99.8% purity.

Catalysis for efficient low-temperature hydrogen production and storage

Hydrogen, an energy-intensive and clean power source, has been treated as an ideal energy carrier to replace the coal and oil based global energy system for the more sustainable economic development. Especially, with the increasing finical support from worldwide in the researching of renewable energy both for the public and military using. Generally, hydrogen cycling includes three steps: (1) the continuously large scale hydrogen generation; (2) the safe and efficient hydrogen storage and transportation; (3) the efficient conversion of hydrogen to electricity or other forms of energy. For the using of hydrogen, a representative example is polymer electrolyte membrane fuel cells (PEMFCs) which has been widely studied. However, the bottle-neck for the bursting of hydrogen economy besides the effective using of hydrogen lies in the efficient generation and safe storage of hydrogen. Recently, our research group developed α-molybdenum carbide (α-MoC) supported Au and Pt catalysts for the low temperature water-gas shift (WGS) reaction and aqueous-phase reforming of methanol, respectively, both were essential reactions for industrial hydrogen generation. The WGS reaction (where carbon monoxide plus water yields hydrogen and carbon dioxide) is an important process for hydrogen generation and carbon monoxide removal in various energy-related chemical operations. This equilibrium-limited reaction is favored at a low working temperature. However, the reported catalysts by now always show unsatisfied performance under low operating temperatures and no catalysts ever reported reaching the activity of 0.1 molCO molmetal−1 s−1 below 150°C. Meanwhile, potential application in fuel cells also requires a WGS catalyst to be highly active, stable, and energy-efficient to match the working temperature of on-site hydrogen generation and consumption units. Concerning this problem, we synthesized layered gold clusters on a molybdenum carbide (Au/α-MoC) substrate to create an interfacial catalyst system for the ultralow-temperature WGS reaction. Water was activated over α-MoC at 30°C, whereas carbon monoxide adsorbed on adjacent Au sites was apt to react with surface hydroxyl groups formed from water splitting, leading to a high WGS activity reaching 1.05 molCO molmetal−1 s−1 under 120°C which is one order of magnitude higher than the early reported catalysts. Beside the Au/α-MoC for robust WGS reaction, we also developed highly distributed single atom Pt supported by molybdenum carbide (Pt/α-MoC) for aqueous-phase reforming of methanol. With the reforming of methanol and water, hydrogen with a high gravimetric density of 18.8% by weight can be in situ released. The average turnover frequency of Pt/α-MoC can reach 18046 mol of hydrogen per mole of platinum per hour at 190°C, which is two order of magnitude higher than the traditional catalysts. Based on the X-ray absorption fine structure (XAFS) and single atom resolution electron microscopy characterization results, Pt was determined to be atomic dispersed over α-MoC support at the low metal loadings, which maximized the exposure of Pt atom. Based on reaction mechanism investigation and DFT calculation, Pt/α-MoC was proved to be a bifunctional catalyst, with α-MoC support dissociating the O−H bond of H2O and methanol at low temperature, atomic dispersion of Pt scissoring C−H bond of CH3OH. The effectively reforming of intermediates with surface hydroxyls generate CO2 at the interface of Pt/α-MoC. The excellent performance of our catalytic system provide a new strategy for the efficient low-temperature hydrogen production and storage. In this short perspective, we introduce the new findings by our group and also summarize the recently developed representative catalysts involving the low temperature water-gas shift reaction and aqueous-phase reforming of methanol. We hope it can provide a reference for the future designing of catalysts in the field of hydrogen production and storage.

Analysis of biomass hydrothermal liquefaction and biocrude-oil upgrading for renewable jet fuel production: The impact of reaction conditions on production costs and GHG emissions performance

This paper shows a detailed analysis of a biomass HTL process by considering changes in three main reaction variables (i.e. catalysts (water, Na2CO3(aq.), and Fe(aq.)), temperature (280–340 °C), and catalysts/biomass mass ratio (0–0.33 kg catalysts/kg biomass)), and by assessing their influence on the techno-economic and GHG emissions performance. This analysis is based on Aspen Plus® simulations, process economics and life-cycle GHG assessment on SimaPro (using Ecoinvent 2.2). Results showed that the lowest production cost for biocrude oil is achieved when HTL is performed at 340 °C with Fe as catalyst (450 €/tbiocrude-oil or 13.6 €/GJbiocrude-oil). At these conditions, the biocrude oil produced has an oxygen content of 16.6 wt% and a LHV of 33.1 MJ/kgbiocrude-oil. When the hydrotreatment and hydrogen generation units are included, the total production costs was 1040 €/tupgraded-oil or 0.8 €/Lupgraded-oil. After fractionation, the estimated production cost was 1086 €/tbiojet-fuel or 25.1 €/GJbiojet-fuel. This value is twice the commercial price of fossil jet fuel. However, the allocated life cycle GHG emissions for renewable jet fuel were estimated at 13.1 kgCO2-eq./GJbiojet-fuel, representing only 15% the GHG emission of fossil jet fuel and therefore, indicating a significant potential on GHG emission reduction.

Carbon capture potential and costs in Brazil

This article estimates carbon capture potentials and costs of energy and industrial facilities in Brazil. These estimates are important for an emerging economy whose energy- and process-related CO2 emissions are expected to grow over time. The Brazilian case is emblematic due to the prospects for carbon capture in biomass processing facilities, such as ethanol distilleries with nearby petroleum sedimentary basins (enhanced oil recovery – EOR – potential through CO2 injection), and for increasing petroleum production and the potential role for carbon capture in industrial plants. Findings show that capture costs are lower for petroleum platforms and hydrogen generation units in oil refineries or ammonia plants. In platforms, CO2 capture should be performed for economic reasons, regardless of environmental concerns. Capture in ethanol distilleries may also occur at reduced costs and become viable, given the additional revenue associated the use of the captured CO2 for EOR in mature oil fields in the country. For the other evaluated sectors, carbon capture is also available but at costs exceeding 30 US$/tCO2 and, in some cases, reaching approximately 100 US$/tCO2. Potentials, on the other hand, can get up to 28 MtCO2/year captured in the oil and gas sector and 47 MtCO2/year in the cement sector.

Thermodynamic analysis of a combined chemical looping-based trigeneration system

Energy and exergy analyses of a newly developed three-reactor chemical looping hydrogen generation process are performed for trigeneration of power, hydrogen, and heating. The present integrated system consists of an (a) air separation unit (ASU), (b) gasification sub-system, (c) chemical looping hydrogen generation unit in connection with SOFC assisted gas turbine (CLHG-SOFC/GT), (d) an extended heat recovery steam generation unit (HRSG) to supply heat for Steam cycle, organic Rankine cycle and space heating, (e) a two stage steam Rankine cycle (SRC) for power generation with reheat and regeneration, and (f) an organic Rankine cycle (ORC) to produce power. The gasified coal is separated and purified in quench chamber and syngas cleaner; CO2 and H2 are generated from fuel and steam reactors of chemical looping unit, and both are then compressed after separated from water and ready for transportation. A specified amount of H2 produced from steam reactor is also used to produce electricity with SOFC/GT. A comprehensive parametric study is performed, and the effects of multi-generation and system integration, environmental conditions, and system parameter variations on overall efficiencies are investigated. Overall electrical, hydrogen, energy and exergy efficiencies are comparatively determined for different cases. Overall energy and exergy efficiencies of proposed system are found to be 56.9% and 45.05%, respectively, with a total exergy destruction rate of 15,421kW. The highest exergy destruction occurs in the gasifier and CLHG due to high temperature chemical processes.

Optimization of H2 Production in a Hydrogen Generation Unit

This article presents the results of the use of advanced process control algorithm to optimize the H2 production of Henrique Lage Refinery (REVAP) located in the state of São Paulo, Brazil. The control methodology is applied to the second Hydrogen Generation Unit (HGU) of the Refinery and consists of optimizing its production in order to guarantee the hydrogen supply for the refinery's header without production loss. The designed controller had the support of dynamic simulation for disturbances modelling and identification which contributed for the improvement of the control strategy. The results in this paper represents the application of the control methodology in the real plant.

The quantitative risk assessment of a hydrogen generation unit

The safety of hydrogen generation process is a major concern. This paper discusses the quantitative analyzes of the risk imposed on neighborhood from the operation of a hydrogen generator using natural gas reforming process. For this purpose, after hazard identification, the frequency of scenarios was estimated using generic data. Quantitative risk assessment was applied for consequence modeling and risk estimation. The results revealed that, jet fire caused by a full bore rupture in Desulphurization reactor has the highest fatality (26person) and affects the largest area of 5102 m2. The lethality radius, maximum radiation and safe distance of this incident were 140 m, 370 kW/m2 and 225 m respectively. A full bore rupture in Reformer can lead to the most dangerous flash fire. In this incident the concentration of released material in LFL zone (area of 1483.17 m2) and ½ LEL zone (area of 1970.74 m2) were 61,125 ppm and 40,000 ppm respectively. QRA is a credible method to assess the risks of hydrogen generation process.

Root Cause Analysis of Failure in Hot and Cold Mixing Point in Hydrogen Generation Unit (HGU) due to Thermal Fatigue Phenonmenon

In a Process unit there are several streams that are exchanging heat to optimize the unit operation. In the HGU at IOCL, Guwahati refinery repetitive failures were observed in a 2" 0, SS 304 pipe at this hot and cold mixing point. The investigation revealed that the two streams were handling fluid at a temperature of 40°C and 160°C, the difference being 120°C. These huge temperature differences lead to thermal gradient across the wall thickness of the pipe and also along the length of the pipe surface in the flow direction. The inner surface of the pipe seeing a higher temperature than the outer surface and therefore more expansion at inner surface. Due to this thermal fatigue phenomenon and hindered expansion severe stresses were observed at the inner surface of pipe leading to crack initiation and further propagation across the wall thickness. As a temporary measure the joint was replaced with identical pipe with higher thickness (schedule), and as a permanent solution it was suggested to replace the mixing point with an injection "Quill" design to avert the huge thermal gradient.

Root Cause Analysis of Failure in Hot and Cold Mixing Point in Hydrogen Generation Unit (HGU) due to Thermal Fatigue Phenonmenon

Root Cause Analysis of Failure in Hot and Cold Mixing Point in Hydrogen Generation Unit (HGU) due to Thermal Fatigue Phenonmenon

자열개질기의 운용조건에 따른 열유동 수치해석

The study is to analyze the chemical and heat-flow reactions in the hydrogen generation unit(autothermal reformer), using computational numerical tools. Autothermal reformer(ATR) is involved in complex chemical reaction, mass and heat transfer due to exothermic and endothermic reactions. Therefore it is necessary to reveal the effects of various operation parameters and geometries on the ATR performance by using numerical analysis. Numerical analysis needs to dominant chemical reactions that includes Full Combustion(FC) reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction and Direct Steam Reforming(DSR) reaction. The objective of the study is to improve theoretically the reformer design capability for the goal of high hydrogen production in the autothermal reformer using methane. Hydrogen production reached maximum in a certain value of Oxygen to Carbon Ratio(OCR) or Steam to Carbon Ratio(SCR). When the longitudinal distance to dimeter ratio(L/D) is increased, hydrogen production increases.

Exergy and industrial ecology: an application to an integrated energy system

Exergy analysis can help integrate separate technologies following the principles of industrial ecology. An application of exergy analysis to calculate depletion numbers, which relate exergy destruction and total exergy use, is demonstrated for a gas turbine cycle combined with a hydrogen generation unit. The design includes a Solid Oxide Fuel Cell (SOFC) with internal natural gas reforming and a Membrane Reactor (MR) in place of a combustion chamber. The depletion number for the separate technologies is found to be more than two times greater than for the combined system, implying the latter is more environmentally benign and like an ecosystem.