Hydrogen Generation in an Annular Micro-Reactor: an Experimental Investigation of Water Splitting Reaction Using Aluminum in Presence of Potassium Hydroxide

2018 ◽  
Vol 17 (2) ◽  
Author(s):  
Shyam P. Tekade ◽  
Diwakar Z. Shende ◽  
Kailas L. Wasewar
Keyword(s):  
Water Splitting ◽  
Potassium Hydroxide ◽  
Hydrogen Generation ◽  
Energy Content ◽  
Average Rate ◽  
High Energy ◽  
Low Flow ◽  
Flow Rates ◽  
Metal Aluminum ◽  
Micro Reactor

Abstract Hydrogen is one of the important non-conventional energy sources because of its high energy content and non-polluting nature of combustions. The water splitting reaction is one of the significant methods for hydrogen generation from non-fossil feeds. In the present paper, the hydrogen generation has been experimentally investigated with water splitting reaction using metal aluminum in presence of potassium hydroxide as an activator under flow conditions. The rate of hydrogen generation was reported in the annular micro- reactor of 1 mm annulus using various flow rates of aqueous 0.5 N KOH ranging from 1 ml/min to 10 ml/min. The complete conversion of aluminum was observed at all the flow rates of aqueous KOH. The hydrogen generation rate was observed to depend on the flow rate of liquid reactant flowing through the reactor. At 1 ml/min of 0.5 N KOH, hydrogen generates at an average rate of 3.36 ml/min which increases to 10.70 ml/min at 10 ml/min of aqueous KOH. The Shrinking Core Model was modified for predicting the controlling mechanism. The rate of hydrogen generation was observed to follow different controlling mechanisms on various time intervals at low flow rates of aqueous KOH. It was observed that chemical reaction controls the overall rate of hydrogen generation at higher flow rates of aqueous KOH.

Hydrogen Generation in an Annular Micro-Reactor: An Experimental Investigation and Reaction Modelling by Shrinking Core Model (SCM)

2018 ◽  
Vol 16 (7) ◽  
Author(s):  
Shyam P. Tekade ◽  
Diwakar Z. Shende ◽  
Kailas L. Wasewar
Keyword(s):  
Experimental Investigation ◽  
Water Splitting ◽  
Hydrogen Generation ◽  
Energy Requirement ◽  
Reaction System ◽  
Core Model ◽  
Shrinking Core Model ◽  
Flow Rates ◽  
Metal Aluminum ◽  
Shrinking Core

Abstract Hydrogen can be one of the key elements as source of future energy requirement. Water splitting reaction is an important route for generation of hydrogen as maximum fraction of hydrogen constitute in water. The present work describes the experimental investigation for generation of hydrogen through water splitting reaction in flow conditions with the aid of metal aluminum and sodium hydroxide as an activator. The hydrogen generation through water splitting reaction at various concentrations of NaOH, viz. 0.5 N and 1 N and the flow rates ranging from 0.2 to 10 ml/min was studied. The yield of hydrogen generated is reported for each NaOH concentration and flow rate. The yield of hydrogen generated at all the considered concentrations and flow rates was found to be greater than 98 %. The shrinking core model has been modified and developed for predicting the conversion of aluminum in the reaction system as per the prevailing conditions and rate controlling mechanism. The RMSE value of predicted conversion of Al was found to be 0.0351 which signify that the model agrees well with the experimental data.

Hydrogen Generation Facilitates Sintering Atmospheres

2021 ◽  
Author(s):  
David Wolff
Keyword(s):  
Heat Conduction ◽  
Hydrogen Storage ◽  
Thermal Processing ◽  
Hydrogen Generation ◽  
Energy Content ◽  
High Energy ◽  
Pure Hydrogen ◽  
Post Processing ◽  
Hydrogen Supply ◽  
Processing Techniques

Abstract For annealing, brazing or sintering, furnace atmospheres help ensure that metals thermal processors obtain the results they need. Hydrogen-containing atmospheres are used to protect surfaces from oxidation, and to ensure satisfactory thermal processing results. Hydrogen-containing atmospheres make thermal processing more forgiving because the hydrogen improves heat conduction and actively cleans heated surfaces – reducing oxides and destroying surface impurities. For powder based fabrication such as P/M, MIM or binder-jet metal AM, the use of a hydrogen-containing thermal processing atmosphere ensures the highest possible density of the sintered parts without necessitating the use of post-processing techniques. Users of pure hydrogen or hydrogen-containing gas blend atmospheres often struggle with hydrogen supply options. Hydrogen storage may create compliance problems due to its flammability and high energy content. Hydrogen generation enables hydrogen use without hydrogen storage issues. Deployment of hydrogen generation can ease the addition of thermal processing atmospheres to new and existing processing facilities.

Direct metabolic effects of isoproterenol and propranolol in ischemic myocardium of the dog

1980 ◽  
Vol 239 (4) ◽  
pp. H469-H469
Author(s):  
Michael Goodlett ◽  
Kyran Dowling ◽  
Lynne J. Eddy ◽  
James M. Downey
Keyword(s):  
High Energy ◽  
Ischemic Myocardium ◽  
The Other ◽  
Energy Utilization ◽  
Metabolic Effects ◽  
Low Flow ◽  
High Energy Phosphate ◽  
Drug Induced ◽  
Flow Rates ◽  
Induced Changes

The effect of either isoproterenol or propranolol on the metabolism of ischemic myocardium was examined. To ensure that all changes were due to changes in metabolism and not drug-induced changes in residual flow to the ischemic regions, we devised a preparation in which two coronary branches on the same heart were simultaneously perfused at a low flow rate. Microsphere measurements verified that the two ischemic regions were receiving identical blood flow rates. One branch received an infusion of 0.9% NaCl and the other received the drug. After 1 h both regions were biopsied and the high-energy phosphate levels in each region were determined. ATP and phosphocreatine each fell to about 50% of their starting values in the 0.9% NaCl-treated regions, and isoproterenol did not further depress the high-energy phosphate concentrations. Propranolol, on the other hand, significantly preserved the high-energy phosphate concentrations. We conclude that although isoproterenol seemed incapable of accelerating energy utilization in ischemic myocardium, propranolol is apparently capable of reducing it.

Potassium Hydroxide Activated Hydrogen Generation Using Aluminum in Water Splitting Reaction

2018 ◽  
Vol 17 (3) ◽  
Author(s):  
Shyam P. Tekade ◽  
Diwakar Z. Shende ◽  
Kailas L. Wasewar
Keyword(s):  
Water Splitting ◽  
Potassium Hydroxide ◽  
Hydrogen Generation ◽  
Foil Thickness ◽  
Aluminum Particles ◽  
Controlling Mechanism ◽  
Different Temperatures ◽  
Shrinking Core ◽  
Alkaline Activator ◽  
Experimental Runs

Abstract The water splitting reaction using aluminum represents one of the best methods for on-demand hydrogen requirements. The present paper describes the hydrogen generation in water splitting reaction using aluminum in presence of potassium hydroxide as an alkaline activator. The effect of concentration of KOH, temperature, and shape of aluminum particles on the hydrogen generation in water splitting reaction was experimentally studied using various concentrations of aqueous KOH viz. 0.25 N, 0.50 N, 0.75 N and 1.0 N, at different temperatures of 30 °C, 40 °C, and 50 °C for Al powder (diameter: 200 mesh) and Al foil (thickness: 11 microns). The complete conversion of Al was recorded for all the experimental runs. The average hydrogen generation rate was found to vary between 3.40 ml/min to 21 ml/min per 0.1 g aluminum under considered concentrations and temperatures. The shrinking core model was applied to the experimental data for predicting the rate controlling mechanism.

Photosynthetic water splitting by the Mn4Ca2+OX catalyst of photosystem II: its structure, robustness and mechanism

2017 ◽  
Vol 50 ◽  
Author(s):  
James Barber
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
Energy Content ◽  
Metal Cluster ◽  
High Energy ◽  
Reaction Centre ◽  
Light Reaction ◽  
Terminal Electron Acceptor ◽  
Lipid Environment ◽  
Reducing Equivalents

AbstractThe biological energy cycle of our planet is driven by photosynthesis whereby sunlight is absorbed by chlorophyll and other accessory pigments. The excitation energy is then efficiently transferred to a reaction centre where charge separation occurs in a few picoseconds. In the case of photosystem II (PSII), the energy of the charge transfer state is used to split water into oxygen and reducing equivalents. This is accomplished by the relatively low energy content of four photons of visible light. PSII is a large multi-subunit membrane protein complex embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Four high energy electrons, together with four protons (4H+), are used to reduce plastoquinone (PQ), the terminal electron acceptor of PSII, to plastoquinol (PQH2). PQH2 passes its reducing equivalents to an electron transfer chain which feeds into photosystem I (PSI) where they gain additional reducing potential from a second light reaction which is necessary to drive CO2 reduction. The catalytic centre of PSII consists of a cluster of four Mn ions and a Ca2+ linked by oxo bonds. In addition, there are seven amino acid ligands. In this Article, I discuss the structure of this metal cluster, its stability and the probability that an acid-base (nucleophilic-electrophilic) mechanism catalyses the water splitting reaction on the surface of the metal-cluster. Evidence for this mechanism is presented from studies on water splitting catalysts consisting of organo-complexes of ruthenium and manganese and also by comparison with the enzymology of carbon monoxide dehydrogenase (CODH). Finally the relevance of our understanding of PSII is discussed in terms of artificial photosynthesis with emphasis on inorganic water splitting catalysts as oxygen generating photoelectrodes.

Vascular washout reduces Ca2+ overload and improves function of reperfused ischemic hearts

1990 ◽  
Vol 258 (2) ◽  
pp. H354-H361
Author(s):  
M. Tani ◽  
J. R. Neely
Keyword(s):  
Contractile Function ◽  
Fold Increase ◽  
High Energy ◽  
Low Flow ◽  
High Energy Phosphate ◽  
Flow Rates ◽  
Flow Perfusion ◽  
Lactate Levels ◽  
Developed Pressure ◽  
Zero Flow

Relationships between myocardial Ca2+ uptake, recovery of ventricular function, and restoration of tissue metabolites were determined during 30 min of reperfusion following ischemic and anoxic perfusion with either zero or low coronary flow, zero flow with intermittent perfusion, and low-flow perfusion without substrates. When zero-flow ischemia was maintained for 30 or 40 min, tissue lactate levels increased approximately 100-fold; with reperfusion of these hearts, developed pressure recovered to only 70 and 40% of preischemic function, respectively, and Ca2+ uptake increased by 7- and 15-fold. In contrast, 30 min of low-flow (1 ml/min) anoxic perfusion resulted in accumulation of less lactate (15-fold increase), less reperfusion Ca2+ uptake, and recovery of developed pressure to the preanoxic level. Omission of energy substrates during the low-flow anoxic perfusion caused a reduced recovery of heart rate with lower high-energy phosphate levels and increased Ca2+ uptake, but contractile function recovered to the same extent as in low-flow perfusion with substrate. Even very low flow rates (0.06-0.16 ml/min) of oxygen-deficient perfusate increased high-energy phosphate content and contractile function and decreased Ca2+ uptake. Intermittent perfusion with either oxygenated or anoxic buffer between four 10-min episodes of ischemia reduced lactate accumulation, maintained function, and left Ca2+ uptake essentially unchanged. Recovery of developed pressure during reperfusion was negatively correlated with the amount of lactate that accumulated during ischemia or anoxia and with reperfusion Ca2+ uptake, regardless of the duration or type of ischemia or anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Towards the Hydrogen Economy—A Review of the Parameters That Influence the Efficiency of Alkaline Water Electrolyzers

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3193
Author(s):  
Ana L. Santos ◽  
Maria-João Cebola ◽  
Diogo M. F. Santos
Keyword(s):  
Energy Content ◽  
Water Electrolysis ◽  
High Energy ◽  
Operating Conditions ◽  
Energy Sources ◽  
Alkaline Water Electrolysis ◽  
Alkaline Water ◽  
New Energy ◽  
Recent Developments ◽  
Cell Components

Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide, researchers and companies are continuously working on this matter, taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content, but a somewhat elusive one for being a gas with low molecular weight. This review examines the current electrolysis processes for obtaining hydrogen, with an emphasis on alkaline water electrolysis. This process is far from being new, but research shows that there is still plenty of room for improvement. The efficiency of an electrolyzer mainly relates to the overpotential and resistances in the cell. This work shows that the path to better electrolyzer efficiency is through the optimization of the cell components and operating conditions. Following a brief introduction to the thermodynamics and kinetics of water electrolysis, the most recent developments on several parameters (e.g., electrocatalysts, electrolyte composition, separator, interelectrode distance) are highlighted.

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