Biomass conversion to hydrogen-rich synthesis fuels using water steam plasma

In this study, an experimental plasma-chemical reactor equipped with an arc discharge water steam plasma torch was used for biomass conversion to hydrogen-rich synthesis fuels. Glycerol and crushed wood were used as biomass sources. The effects of different conversion parameters including the water steam flow rate, treated material flow rate, and plasma torch power were studied. The experimentally obtained results were compared with the model based on the thermodynamic equilibrium. Additionally, the quantification of the plasma conversion system in terms of energy efficiency and specific energy requirement was performed. It has been found that the synthesis gas can be effectively produced from the biomass using water steam plasma.     

Steam Plasma Methane Reforming for Hydrogen Production

Reactions of methane with water and CO₂ in thermal plasma generated in a special plasma torch with a water-stabilized arc were investigated. Steam plasma with very high enthalpy and low mass flow rate was produced in a dc arc discharge which was in direct contact with water vortex surrounding the arc column. Composition of produced gas, energy balance of the process and its efficiency were determined from measured data. The output H₂/CO ratio could be adjusted by a choice of feed rates of input reactants in the range 1.1–3.4. Depending on experimental conditions the conversion of methane was up to 99.5%, the selectivity of H₂ was up to 99.9%, and minimum energy needed for production of 1 mol of hydrogen was 158 kJ/mol. Effect of conditions on process characteristics was studied. Comparison of measured data with results of theoretical computations confirmed that the reforming process produces gas with composition which is close to the one obtained from the thermodynamic equilibrium calculations. Relations between process enthalpy, composition of produced syngas and process characteristics were determined both theoretically and experimentally.     

Influence of the Shroud Gas Injection Configuration on the Characteristics of a DC Non-transferred Arc Plasma Torch

The characteristics of the plasma jet emanating from a dc non-transferred plasma torch is affected by many factors including arc current, type of gas, gas flow rate, gas injection configuration and torch geometry. The present work focuses on experimental investigation of the influence of shroud gas injection configuration on the I–V characteristics and electro-thermal efficiency of a dc non-transferred plasma torch operated in nitrogen at atmospheric pressure. The plasma gas is injected into the torch axially and shroud gas is injected through three different nozzles such as normal, sheath and twisted nozzles. The effects of flow rates of plasma/axial gas and arc current on I–V characteristics and electro-thermal efficiency of the torch holding different nozzles are investigated. The I–V characteristics and electro-thermal efficiency of the torch are found to be strongly influenced by the shroud gas injection configuration. The effect of arc current on arc voltage decreases with increasing the axial gas flow rate. At higher axial gas flow rate (>?45 lpm), the I–V characteristics of the plasma torch are similar irrespective of the nozzle used. The variation of electro-thermal efficiency with arc current is almost similar to that of arc voltage with arc current. As expected, the electro-thermal efficiency is increased when the axial gas flow rate is increased and at higher axial gas flow rate, it is not influenced by the arc current and shroud gas configuration. The plasma torch with normal nozzle may be better in the range of operating conditions used in this study.     

Tomographic Measurements of Temperature Fluctuations in an Air Plasma Cutting Torch

A tomographic optical system and method based on evaluations of plasma radiation in a wavelength range of 559–601 nm were used to acquire temperature distributions in an air plasma cutting torch in planes perpendicular to the arc axis with a time resolution of 1 μs. The derived frequency spectra and distributions of temperature fluctuations represented by standard deviations have shown significant variations in distributions of instabilities, depending on the time scales which are taken into account. The results confirmed the decisive role of arc current ripple modulation in the arc temperature fluctuations.     

Measurement of Temperature in the Steam Arcjet During Plasma Arc Cutting

Spectroscopic measurements were performed by observing the plasma inside the kerf during cutting of stainless steel using direct current electric arc. Experiments were carried out on the plasma torch operated with the plasma gas composed of the vaporized mixture of water and ethanol; arc current was 60 A and cutting speed 30 cm/min. Emission spectral lines of neutral iron were used to experimental evaluation of the temperature of plasma in the kerf and close under the cut plate. Complicated nature of the plasma inside the kerf, including presence of metallic vapours and departures from equilibrium, was taken into account. Hence relatively reliable results were obtained, from which it was possible to get insight into the energy balance and cutting performance of the torch. Temperature of the plasma in the kerf was substantially lower than at the nozzle exit of the torch; however the temperature drop along the kerf was small.     

An Efficient Separation Method of Polysaccharides: Preparation of an Antitumor Polysaccharide APS-2 from Auricularia polytricha by Radial Flow Chromatography

Auricularia polytricha is an edible mushroom, quite popular in China. Modern pharmacology research indicate that A. polytricha polysaccharides possess antitumor and immunomodulatory activities. In this paper, an antitumor Auricularia polytricha polysaccharide (APS)-2 was purified by radial flow chromatography (RFC) in a column of 500 mL bed-volume (40 cm i.d × 15 cm) packed with DEAE52-cellulose anion ion-exchange resin. The optimal separation conditions were: sample flow-velocity 15–20 mL min^?1, sample volume 160–200 mL, and elution with distilled water and 0.2 M NaCl at a velocity of 35–45 mL min^?1. The yield and content of APS-2 obtained under these conditions were 182 mg g^?1 total polysaccharides and 98.35 %, respectively. The study provides guidelines for the separation and purification of polysaccharides using a radial flow chromatography column.     

An Efficient Separation Method of Polysaccharides: Preparation of an Antitumor Polysaccharide APS-2 from Auricularia polytricha by Radial Flow Chromatography

Auricularia polytricha is an edible mushroom, quite popular in China. Modern pharmacology research indicate that A. polytricha polysaccharides possess antitumor and immunomodulatory activities. In this paper, an antitumor Auricularia polytricha polysaccharide (APS)-2 was purified by radial flow chromatography (RFC) in a column of 500 mL bed-volume (40 cm i.d × 15 cm) packed with DEAE52-cellulose anion ion-exchange resin. The optimal separation conditions were: sample flow-velocity 15–20 mL min⁻¹, sample volume 160–200 mL, and elution with distilled water and 0.2 M NaCl at a velocity of 35–45 mL min⁻¹. The yield and content of APS-2 obtained under these conditions were 182 mg g⁻¹ total polysaccharides and 98.35 %, respectively. The study provides guidelines for the separation and purification of polysaccharides using a radial flow chromatography column.

     

Steam Plasma Treatment of Organic Substances for Hydrogen and Syngas Production

Gasification of several organic materials in steam plasma generated in a special plasma torch with a water-stabilized arc was investigated. Thermal plasma with very high enthalpy and low mass flow rate is produced in an arc discharge which is in direct contact with water. Biomass and several types of solid and liquid organic waste were gasified by plasma aided reactions of materials with water, carbon dioxide and oxygen. Composition of produced gas, energy balance of gasification process and gasification efficiency were determined from measured data. Synthesis gas with high content of hydrogen and carbon monoxide and very low content of carbon dioxide, light hydrocarbons and tar was obtained for all tested materials. Comparison of measured data with results of theoretical computations confirmed that steam plasma gasification produces syngas with composition which is close to the one obtained from thermodynamic equilibrium calculations.     

Fast GC with a Small Volume Column Oven and Low Power Heater

A new apparatus for fast gas chromatography separations is described. It consists of a small volume oven containing a coiled fused silica capillary column that is heated by a flow of hot air. The oven can be heated at rates of 10 °C s^?1 with a 300 W heater. Benchmark studies at various temperature programming rates are described. Retention time relative standard deviations increase with increasing heating rate, but are at most about 1% when an 8 °C s^?1 heating rate is employed. The small size of the column oven makes it possible for it to be attached to a commercial GC instrument through an opening provided for installation of a second injector.     

Thermal and Chemical Nonequilibrium Effects in Free-Burning Arcs

Effects caused by thermal and chemical nonequilibrium in free-burning arcs in argon are presented and discussed. The results cover a range of arc currents between 100 and 200 A, interelectrode distance of 5–10 mm, and a variation of the electrode material and the shape of the cathode tip. The results obtained show that nonequilibrium in the near-electrode regions has a strong impact on the distributions of temperatures, electric conductivity and current density, and the arc voltage. Departure from chemical nonequilibrium in the vicinity of the cathode as a result of transport processes is indicated. Moreover, overpopulation of the atomic ground state close to the arc axis, under population of the excited states in the arc periphery with respect to the equilibrium values, axial dependence of the off-axis maximum of the radial emission coefficient of Ar I at 696.5 nm, and enhanced population of the Ar (1s₄) resonance level due to trapping of resonance radiation in the arc periphery are considered.     

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

The paper presents experimental results of reduction of cupric oxide (CuO) by low-temperature hydrogen plasma in a microwave-assisted plasma set-up. The experiments were carried out at low microwave powers in the range of 600–750 W and low hydrogen flow rates in the range of 0.833 × 10^?6 to 2.5 × 10^?6 m³ s^?1. In all the experiments for reduction of CuO with hydrogen plasma, an initial induction period was observed in the kinetic plots. The induction period decreases with increase in pressure or temperature. The induction period leads to the formation of active sites for adsorption of H₂. After the induction period, fast autocatalytic reduction takes place followed by a sluggish period towards the end. The reduction process proceeds in sequential steps through the formation of sub-oxides. The kinetic data fits the Avrami-Erofeev equation with ‘n’ value close to 3. The resultant activation energy measured during hydrogen plasma processing is around 75.64 kJ mol^?1. This is lower compared to activation energies measured by other methods of reduction indicating a clear advantage.     

The Effects of the Column Length on the Efficiency of Capillary Zwitterionic Organic Polymer Monolithic Columns in HILIC Chromatography

Organic polymer monolithic columns of different lengths have been prepared in 320 µm i.d. fused silica capillary by in situ radical polymerization of N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium betaine as a zwitterionic functional monomer and bisphenol A glycerolate dimethacrylate as a crosslinking monomer in the presence of porogenic solvents. The zwitterionic monolithic columns are intended for separations of polar compounds in hydrophilic interaction chromatography (HILIC). The effects of the capillary column length, from 115 to 175 mm, on separation efficiency, were investigated under HILIC conditions, using 95:5 acetonitrile in water as the mobile phase. The extra-column contributions to band broadening significantly decrease the efficiency (apparent height equivalent to a theoretical plate), especially for weakly retained samples, and increase with diminishing column length. The experimental height equivalents of theoretical plate, HETP, were corrected for the extra-column contributions, which were determined for a series of columns by extrapolation to zero column length. On a 175 mm long column, the column efficiency, HETP = 16.5 μm, measured at the optimum linear flow velocity of 0.5 mm s⁻¹, improved to HETP = 5 µm, after correction for extra-column contributions. For more strongly retained small polar compounds, interactions with zwitterionic groups and (or) water adsorbed inside the pores decrease the column efficiency at higher flow rates.

     

Electric Arc Fluctuations in DC Plasma Spray Torch

Direct current plasma torches for plasma spraying applications generate electric arc instabilities. The resulting fluctuations of input electrical power hamper a proper control of heat and momentum transfers to materials for coating deposition. This paper gives an overview of major issues about arc instabilities in conventional DC plasma torches. Evidences of arc fluctuations and their consequences on plasma properties and on material treatments are illustrated. Driving forces applied to the arc creating its motion are described and emphasis is put on the restrike mode that depends on the arc reattachment and the boundary layer properties around the arc column. Besides the arc root shown as a key region of instability, the Helmholtz oscillation is also described and accounts for the whole plasma torch domain that can generate pressure fluctuations coupled with voltage ones.     

Study of the dynamic and static behavior of de vortex plasma torches: Part II: Well-tye cathode

This work was devoted to the study of the dynamic and static behavior of de vortex plasma torch with a well-type cathode (power level below 100 kW). The dynamic behavior of the torch was characterized by the fulctuations of arc voltage and current, plasma jet radiation, and acoustic pressure. Characteristic frequencies of the arc root movement inside the torch were observed. By numerical simulation (with the numerical codeMelodie, it was shown that the position of the erosion diameter) of the axial velocity along the cathode channel near the wall. The static behavior of the torch was inverstigated for different cathode designs. The variations of voltage U with arc current I, gas flow rate G nature of the gas and cathode design were represented by semiempirical relationships established between dimensionless numbers. By dimensional analysis, the behavior of this torch was compared with that of two powerful torches: the Aerospatiale and the Plasma Energy Corporation torches.     

Effect of Cathode Nozzle Geometry and Process Parameters on the Energy Distribution for an Argon Transferred Arc

The influence of two nozzle geometries and three process parameters (arc current, arc length and plasma sheath gas flow rate) on the energy distribution for an argon transferred arc is investigated. Measurements are reported for a straight bore cylindrical and for a convergent nozzle, with arc currents of 100 A and 200 A and electrode gaps of 10 mm and 20 mm. These correspond to typical operating parameters generally used in plasma transferred arc cutting and welding operations. The experimental set up consisted of three principal components: the cathode-torch assembly, the external, water-cooled anode, and the reactor chamber. For each set of measurements the power delivered to each system component was measured through calorimetric means, as function of the arc’s operating conditions. The results obtained from this study show that the shape of the cathode torch nozzle has an important influence on arc behaviour and on the energy distribution between the different system components. A convergent nozzle results in higher arc voltages, and consequently, in higher powers being generated in the discharge for the same applied arc current, when compared to the case of a straight bore nozzle. This effect is attributed to the fluidynamic constriction of the arc root attachment, and the consequential increase in the arc voltage and thus, in the Joule heating. The experimental data so obtained is compared with the predictions of a numerical model for the electric arc, based on the solution of the Navier–Stokes and Maxwell equations, using the commercial code FLUENT©. The original code was enhanced with dedicated subroutines to account for the strong temperature dependence of the thermodynamic and transport properties under plasma conditions. The computational domain includes the heat conduction within the solid electrodes and the arc-electrode interactions, in order to be able to calculate the heat distribution in the overall system. The level of agreement achieved between the experimental data and the model predictions confirms the suitability of the proposed, “relatively simple” model as a tool to use for the design and optimization of transferred arc processes and related devices. This conclusion was further supported by spectroscopic measurements of the temperature profiles present in the arc column and image analysis of the intensity distribution within the arc, under the same operating conditions.     

SPE and LC–ESI–MS for Quantitative Analysis of Mitiglinide in Human Plasma in a Bioequivalence Study

Liquid chromatography–electrospray ionization mass spectrometry has been used for rapid, selective, and sensitive quantitative analysis of mitiglinide in human plasma. Sample pretreatment involved solid-phase extraction from plasma with gliclazide as internal standard. Separation was performed on a C₁₈ column (150 × 2.0 mm) with 71:29 (v/v) acetonitrile–water (containing 0.1% formic acid and 0.2 mmol L^?1 ammonium acetate) as mobile phase at a flow rate of 0.2 mL min^?1. The method was validated then successfully applied to a clinical bioequivalence study of mitiglinide in 20 healthy volunteers after oral administration.     

High Speed Video Camera and Electrical Signal Analyses of Arcs Behavior in a 3-Phase AC Arc Plasma Torch

A 3-phase AC plasma torch has been developed and aims at overcoming some limits of the classical DC torches in terms of efficiency, cost and reliability. However, the arc behavior in 3-phase plasma torch remains poorly explored. This paper is dedicated to the high speed video camera at 100,000 frames per second and electrical signal analyses of arcs behavior in a 3-phase AC arc plasma torch. First, a reference case at 150 A, in nitrogen as working gas, has been deeply analyzed. Afterwards, a parametric study based on current and inter-electrode gap has been carried out. Results show that only one arc can exist at a given time and arcs rotate by switching from a pair of electrodes to another one, following the maximal electrical gap potential. However, a particular “abnormal” arc behavior was sometimes observed. Indeed, the arc motion within the inter-electrode gap increases the heat exchange and stabilizes the 3-phase discharge whereas the system is unbalanced when the arc is in the periphery. The analysis highlights that the arc motion is strongly influenced by the electrode jet velocity and repulsive Lorentz forces. The parametric study shows that the current increases both jet velocity and arc discharge stability. Elsewhere, the increase of the inter-electrode gap can also stabilizes the electrical 3-phase arc discharge. Furthermore, the correlation between arc motion and current waveform is highlighted. This work is likely to open the way toward a better understanding of 3-phase discharges in the perspective of their further optimization.     

Rapid LC-APCI-MS-MS Method for Simultaneous Determination of Phenacetin and Its Metabolite Paracetamol in Rabbit Plasma

A highly sensitive liquid chromatographic-atmospheric pressure chemical ionization-tandem mass spectrometric method is developed to quantitate phenacetin and its metabolite paracetamol in rabbit plasma. The analytes and internal standard oxazepam are extracted from plasma by liquid–liquid extraction using ethyl acetate, and separated on a Zorbax SB-C₁₈ column (2.1 mm × 150 mm, 5 μm) using acetonitrile–0.1% formic acid in water (40:60 v/v) at a flow of 0.4 mL min^?1. Detection is carried out by multiple reaction monitoring on a ion-trap LC-MS-MS system with an atmospheric pressure chemical ionization interface. The assay is linear over the range 4–1,600 ng mL^?1 for phenacetin and 3–2,000 ng mL^?1 for paracetamol, with a lower limit of quantitation of 4 ng mL^?1 for phenacetin and 3 ng mL^?1 for paracetamol. Intra- and inter-day precision are less than 7.1% and the accuracy are in the range 97.3–103.5%. The validated method is successfully used to analyze the drug in samples of rabbit plasma for pharmacokinetic study.     

Comparative PIV and LDA studies of Newtonian and non-Newtonian flows in an agitated tank

The paper presents results of an experimental study of the fluid velocity field in a stirred tank equipped with a Prochem Maxflo T (PMT) type impeller which was rotating at a constant frequency of N = 4.1 or 8.2 s^?1 inducing transitional (Re = 499 or 1307) or turbulent (Re = 2.43 × 10⁴) flow of the fluid. The experiments were performed for a Newtonian fluid (water) and a non-Newtonian fluid (0.2 wt% aqueous solution of carboxymethyl cellulose, CMC) exhibiting mild viscoelastic properties. Measurements were carried out using laser light scattering on tracer particles which follow the flow (2-D PIV). For both the water and the CMC solution one primary and two secondary circulation loops were observed within the fluid volume; however, the secondary loops were characterized by much lower intensity. The applied PMT-type impeller produced in the Newtonian fluid an axial primary flow, whilst in the non-Newtonian fluid the flow was more radial. The results obtained in the form of the local mean velocity components were in satisfactory agreement with the literature data from LDA. Distribution of the shear rate in the studied system was also analyzed. For the non-Newtonian fluid an area was computed where the elastic force dominates over the viscous one. The area was nearly matching the region occupied by the primary circulation loop.     

A Simple and Sensitive LC Method for Quantification of Cefteram in Human Plasma

A simple and sensitive liquid chromatographic method was developed for quantification of cefteram in human plasma. Amoxicillin was used as an internal standard. The present method used protein precipitation for extraction of cefteram from human plasma. Separation was carried out on a reversed-phase C₁₈ column. The column effluent was monitored by UV detection at 262 nm. The mobile phase was a mixture of methanol and water containing 0.3% v/v triethylamine and 0.6% v/v glacial acetic acid (35:65:0.3:0.6 v/v) at a flow rate of 0.30 mL min^?1. The column temperature was 20 °C. This method was linear over the range of 47.5–4,750.0 ng mL^?1 with determination coefficient greater than 0.99. The mean extraction recovery of cefteram and IS was ≥76.82 and ≥76.49%, respectively, and the method was found to be precise, accurate, and specific during the study. The method was successfully applied for a pharmacokinetic study of cefteram in human.