Chlorine Pressure Research Articles

Electrode processes at the glass carbon/LiCl-CuCl-CuCl2 melt interface

The kinetics of the electrode processes occurring at the glass carbon/LiCl-CuCl-CuCl2\(\left( {N_{CuCl - CuCl_2 } = 0 - 7.5 mol \% } \right)\) melt interface is studied by the coulostatic method, single current pulse chronopotentiometry, and stationary voltammetry at a temperature of 950 K and the atmospheric pressure of chlorine over a melt. The exchange current densities in the molten mixtures are determined by the coulostatic method. These data are used to calculate the transfer coefficient (α = 0.54 ± 0.06) and the rate constant of the electrode reaction Cu2+ + e− ai Cu+ (kS = 0.26 ± 0.02 cm/s). The results of stationary voltammetry in the cathode potential region reveal pronounced limiting currents up to the precipitation of metallic copper on an electrode. The experimental data obtained by chronopotentiometry are used to find the transition times for various current densities over the entire concentration range under study. The dependences plotted in the iτ1/2 = f(i) coordinates suggest the presence of a chemical homogeneous reaction preceding the electrode process. The total value of the rate constants of the forward and back reactions is estimated to be ≈2. The copper mono- and dichloride concentrations are determined in the concentration range under study.

Intrinsic Kinetics of Chlorination of WO3 Particles With Cl2 Gas Between 973 K and 1223 K (700 °C and 950 °C)

Chlorination is one of the methods applied in extractive metallurgy for the treatment of minerals to obtain valuable metals, such as titanium and zirconium. The possibility of applying chlorination metallurgy to other metals such as tungsten was the major aim of this study. The kinetics of the chlorination of tungsten oxide (WO3) particles has been investigated by thermogravimetry between 973 K and 1223 K (700 °C and 950 °C) and for partial pressures of chlorine ranging from 15 to 70 kPa. The starting temperature for the reaction of WO3 with chlorine is determined to be about 920 K (647 °C). The influence of chlorine diffusion through the bulk gas phase and through the particle interstices in the overall rate was analyzed. In the absence of these two mass-transfer steps, a reaction order of 0.5 with respect to chlorine partial pressure, and an activation energy of 183 kJ/mol were determined. For tungsten oxide particles of less than 50-μm size, a complete rate expression has been obtained.

An equilibrium ab initio atomistic thermodynamics study of chlorine adsorption on the Cu(001) surface

The effect of chlorine (Cl) chemisorption on the energetics and atomic structure of the Cu(001) surface over a wide range of chlorine pressures and temperatures has been studied using equilibrium ab initio atomistic thermodynamics to elucidate the formation of cuprous chloride (CuCl) as part of the Deacon reaction on copper metal. The calculated surface free energies show that the 1/2 monolayer (ML) c(2 × 2)-Cl phase with chlorine atoms adsorbed at the hollow sites is the most stable structure for a wide range of Cl chemical potential, in agreement with experimental observations. It is also found that at very low pressure and exposure, but elevated temperature, the 1/9 ML and 1/4 ML phases become the most stable. By contrast, a high coverage of Cl does not lead to thermodynamically stable geometries. The subsurface adsorption of Cl atoms, however, dramatically increases the stability of the 1 ML and 2 ML adsorption configurations providing a possible pathway for the formation of the bulk-chloride surface phases in the kinetic regime.

Equilibrium conversion in Cu–Cl cycle multiphase processes of hydrogen production

This paper performs a thermodynamic equilibrium analysis of individual steps within the copper–chlorine (Cu–Cl) thermochemical cycle of hydrogen production. The cycle has a maximum temperature of 550 °C and it involves four reaction steps – producing hydrogen, copper, hydrogen chloride and oxygen – and a cupric chloride drying step. In this paper, the chemical reaction steps of the cycle are analyzed to determine the effects of process variables on chemical equilibrium conversion. It is found that the hydrogen production reaction can occur as a two-phase gas–solid system, rather than three phases. The optimal conditions for hydrogen production occur at a temperature below 400 °C, at atmospheric pressure. The study also found that the ideal condition to minimize excess steam, and completely consume any chlorine formed during the reaction, is a temperature of 400 °C, at atmospheric pressure. The operating conditions for complete consumption of chlorine were identified by the equilibrium partial pressure of chlorine formed, during decomposition of cupric chloride solid (CuCl 2), and the equilibrium partial pressure of chlorine from the reverse chlorine consumption reaction. Furthermore, the ideal condition for the copper oxychloride decomposition reaction is a temperature around 500 °C, atmospheric pressure, which minimizes cuprous chloride (CuCl) vaporization.

A Cooperative Effort: Take a Team Approach to Tackle Disinfectant Residual Problems

This article discusses an effort by the Pompano Beach (Florida) Utilities Department to improve disinfectant residual levels by using remote chlorine, pressure sensors and field sampling to analyze the situation. The supervisory control and data acquisition (SCADA) system for each lift station near an identified point was upgraded to send data on water system chlorine residual and pressure. The ability to see trends in disinfectant residual levels allowed utility personnel to better understand the effect of procedural changes or flushing activities that included the following: modifying ground storage tank (GST) operations; optimizing chlorine‐to‐ammonia ratios; managing excess capacity; flushing effectively; investigating forced‐flow flushing; and, proving to staff that long‐established habits can be changed only by proving the success of a new method.

The Kinetics of the Chlorination of Yttrium Oxide

The chlorination kinetics of Y2O3 with chlorine to produce YOCl was studied by thermogravimetry over a temperature range from 575 °C to 975 °C. The influence of convective mass transfer into the boundary layer surrounding the sample, gaseous diffusion into the sample pores, partial pressure of chlorine, and temperature on the reaction rate were analyzed in order to determine the rate-controlling step. The thermogravimetric and scanning electron microscopy (SEM) results showed that the process follows a model of nucleation and growth, and the process is chemically controlled for temperatures lower than 800 °C, with an activation energy (Ea) of 187 ± 3 kJ/mol. In the 850 °C to 975 °C range the reaction rate was affected by diffusion of Cl2 through the gas film surrounding the sample, with apparent Ea of 105 ± 11 kJ/mol. A global rate equation that includes these parameters has been developed $$ {\text{R}} = d\alpha /dt = 10^{5}\,{\text{kPa}}^{{ - 1}} {\cdot} \exp {\left( { - \frac{{187\;{\text{kJ}} {\cdot} {\text{mol}}^{{ - 1}} }} {{{\text{R}} {\cdot} T}}} \right)} {\cdot} p{\text{Cl}}_{2} {\cdot} 1.51 {\cdot} {\left( {1 - \alpha } \right)} {\cdot} {\left[ { - \ln {\left( {1 - \alpha } \right)}} \right]}^{{0.34}} $$

Techniques for controlling stage structure of metal chloride-GIC

Graphite intercalation compounds (GICs) are of interest to chemists and physicists because of their unusual properties. In recent years, much attention has been focused on the preparation and the properties of GICs and on their utilization. The present paper attempts to summarize recent experimental results relating to the novel methods to control precisely the stage structure of metal chloride-GICs. For vapor phase intercalation of AlCl3, the activity of halogens or CrO3 as additives was found to control the stage structure of obtained GICs. The extent of EuCl3 and TbCl3 intercalation could be controlled through adjustment of the pressure of chlorine: increasing pressure tends to increase the extent of intercalation. On the other hand the stage structure of CuCl2-GIC could be controlled by adjusting the pressure of argon gas in the reaction tube: argon gas tend to inhibit the extent of CuCl2 intercalation.

Correction of Hemodynamics with Hypertonic Sodium Chloride Solution in Critical Conditions

Objective: to assess the capabilities of small-volume hypertonic infusion in the context of early goal-directed therapy for critical conditions in surgical patients. Subjects and methods. Twenty-nine patients (SAPS II 47.5±6.81 scores) operated on for generalized peritonitis (n=24) or severe concomitant injury with damages to chest and/or abdominal organs (n=5) who had the clinical and laboratory signs of a systemic inflammatory reaction were intravenously injected 4 ml/kg of 7.5% of hypertonic sodium chloride solution (HS) and colloidal solution, followed by infusion and, if indicated, inotropic maintenance of hemodynamics for 6 hours in order to achieve the goal vales of mean blood pressure (BP), central venous pressure (CVP), central venous blood oxygen saturation (ScvO2), and diuresis. Plasma concentrations of sodium, chlorine, and lactate, acid-base balance, and osmotic blood pressure were monitored. Results. The patients were found to have infusion therapy-refractory critical arterial hypotension, low ScvO2, and oliguria before small-volume circulation maintenance. In all the patients, HS infusion originally caused a rapid rise in BP up to the goal value, with its further colloid infusion maintenance requiring additional dopamine infusion in 12 patients and red blood cell transfusion in 3. This could stabilize over 6 hours BP at the required level in 25 patients, in 9 of whom CVP only approximated the goal value. All the patients were found to have a significant increase in ScvO2 up to an average of 68% in response to HP infusion after 30—60 minutes; in 14 out of them ScvO2 exceeded 70%. By hour 6, ScvO2 stabilized at its goal level in 23 (79%) examinees. Administration of HS caused a significantly increased diuresis. In patients with recovered renal function, the observed hypernatremia, hyperchloremia with hyperchloremic acidosis were transient. Conclusion. The results of the study show it possible to include small-volume hypertonic infusion at the starting stage of early goal-directed therapy, the net result of which will be determined by the recovery of water-electrolyte homeostasis.

Chlorination of Zinc Oxide between 723 and 973 K

The kinetics of the chlorination of zinc oxide has been studied by thermogravimetry between 723 and 973 K. The starting temperature for the reaction of ZnO with chlorine is determined at about 498 K. The influence of gaseous flow rate, sample mass, temperature, and chlorine partial pressure in the reaction rate is analyzed. It is established that the reaction occurs under mixed control, being pore diffusion coupled with chemical reaction as the rate controlling step. An apparent reaction order of 0.5 with respect to chlorine partial pressure was determined. A kinetic model for the chlorination reaction of porous solids under mixed control determined an intrinsic reaction order of zero with respect to partial pressure of chlorine and an intrinsic activation energy of 249 kJ mol−1.

High temperature behavior of electrostatic precipitator ash from municipal solid waste combustors

Municipal solid waste (MSW) flue gas residues require further treatment prior to disposal or reuse, and vitrification is one of the main solidification–stabilization processes. This paper investigates the high temperature behavior of MSW flue gas residues, performed in laboratory experiments up to 1400 °C, and coupled with thermogravimetric analyses, X-ray diffraction, chemical and electron microprobe analyses. Melting temperatures of electrostatic precipitator (ESP) ash are in the range of 1202–1272 °C, whereas semi-dry scrubber residues melt between 1900 and 2300 °C. We show that the mean liquidus temperature of flue gas residues can be simply evaluated from their CaO content, by using the CaO SiO 2 Al 2O 3 ternary diagram. For ESP ash, the liquidus phase is a Zn-rich aluminous spinel, followed by anorthite at 1225 °C, and melilite at 1190 °C. The total mass loss reaches 18 wt.% at 1300 °C. Moreover, 90% of evaporation takes place below 1000 °C, linked to evaporation of C, Cl, S, Na, K, and of the toxic metals Hg, Cd, Pb, Cu. Due to the high partial pressure of chlorine during heating, chloride is the most probable form of evaporation for Cd, Pb, and Cu. However, most of Zn, Cr, Ni, Sb and Sn remain in the vitrified product.

Study of Chlorine-Oxygen Exchange Reaction in NaCl-2CsCl

Formal equilibrium constant for reaction of oxide ion formation and coefficient of oxide ion activity was determined in molten NaCl-2CsCl and at temperature range 823-923K using oxygen sensor and different partial pressure of chlorine and oxygen.

Ａｒ‐Ｃｌ２‐Ｏ２雰囲気におけるＰｂＯ‐ＰｂＣｌ２の塩化および蒸発挙動

It is quite important to know the reactivity and behavior of Pb contained in steelmaking dust, or bottom ash and fly ash generated from municipal solid waste incineration process with chlorine. In the present study, chlorination and evaporation kinetics of PbO-PbCl2 melt have been investigated in Ar-Cl2-O2 atmosphere from 1023 to 1123K. The weight of PbO specimen increased first and then decreased in Ar-Cl2-O2 stream during experiments, which phenomena mean that produced PbCl2 by PbO chlorination formed liquid oxychloride phase of PbO-PbCl2 system and then PbCl2 evaporated. Increase of partial pressure of chlorine increased the initial chlorination rate, however no effect on the latter evaporation rate was observed. Decrease of maximal weight gain of specimen and the slight increase of evaporation rate were observed with increasing partial pressure of oxygen. Apparent activation energies of chlorination and evaporation of PbO-PbCl2 melt in the steady state were 35 kJ/mol and 156 kJ/mol, respectively. Evaporation rate of PbO-PbCl2 was also investigated at 1073K in Ar-O2 atmosphere, however the change of evaporation rate with changing partial pressure of oxygen was within experimental error. Measured evaporation rate strongly depended on the composition of melt. Composition dependency of evaporation rate estimated from the activity of PbCl2 for the PbO-PbCl2 system generally represented the same trend, however the measured evaporation rate was larger than estimated one in the whole composition range. This result indicates that the formation of oxychloride melt affects the evaporation rate. Chlorination mechanisms and removal efficiency of Pb by chlorination have been discussed based on the present results.

Corrosion behavior of three iron-based model alloys in reducing atmospheres containing HCl and H 2S at 600 °C

The corrosion of three Fe– xCr alloys ( x = 8, 12, 18 wt.%) was examined at 600 °C in reducing atmospheres containing HCl and H 2S with two different H 2S contents and compared with the behavior of the same materials in H 2S–free H 2–CO 2 and H 2–HCl–CO 2 mixtures producing similar oxygen and chlorine pressures. Exposure to the low-H 2S gas mixture had only a reduced effect on the behavior of Fe–8Cr and Fe–18Cr, but increased significantly the corrosion rate of Fe–12Cr. Increasing the H 2S level accelerated the corrosion of all the alloys, but particularly that of Fe–18Cr. In both cases only minor amounts of sulfur and chlorine were present close to the alloy/scale interface. An increase of the Cr content reduced the corrosion rate in both H 2S gas mixtures, especially in the range 8–12 wt.% Cr, due to a larger volume fraction of Cr 2O 3 in the scale. The results have been discussed on the basis of the thermodynamic stability diagrams of the Fe–O–Cl–S and Cr–O–Cl–S systems.

Chlorination kinetics of ZnO with Ar-Cl2-O2 gas and the effect of oxychloride formation

The chlorination rate of ZnO with Ar-Cl2-O2 gas was measured from 1023 K to 1273 K and the effects of temperature and partial pressures of chlorine and oxygen were investigated. The rate-determining step of chlorination was considered to be the dissociation of intermediate between ZnO and Cl2 from linear relationship between reciprocal values of reaction rate and partial pressure of chlorine. The activation energy of chlorination was 58.2±2.5 kJ/mol. This comparatively low activation energy as a chemically controlled reaction was consistent with estimated rate-determining step of the dissociation of unstable compound. Increasing the partial pressure of oxygen slightly increased the chlorination rate, and this effect is considered to be caused by the increase in the formation rate of zinc oxychloride. To clarify the formation of zinc oxychloride, the equilibrium between Ar-Cl2-O2 gas and ZnO was investigated by the transpiration method at 1073 K. Calculated partial pressures of ZnOCl from experimental results were in the same order with or one order of magnitude larger than those estimated from reported Gibbs energy of formation of ZnOCl. Zinc oxychloride formation in ZnO chlorination must be taken into consideration as well as ZnCl2 and Zn2Cl4 formation.

Removal of Zn and Pb from Fe2O3–ZnFe2O4–ZnO–PbO Mixture by Selective Chlorination and Evaporation Reactions

Selective chlorination and evaporation reactions could become one of the useful methods for the treatment of steelmaking dust containing zinc and lead. In the present study, chlorination rate of Fe2O3–ZnFe2O4–ZnO–PbO mixture with Ar–Cl2–O2 gas (PCl2=0.5×104 to 2.0×104 Pa, PO2=1.0×104 to 5.1×104 Pa) has been measured at 1 073 K by gravimetry and the effects of partial pressures of chlorine and oxygen on the chlorination and evaporation rates have been investigated. Zinc oxide and lead oxide contained in the oxide mixture were selectively chlorinated and zinc and lead chlorides evaporated to gas phase, while iron oxide remained as oxide in a chlorinated residue. By chlorinating with Ar–Cl2 gas, over 99% of zinc and lead could be removed from oxide mixture and approximately 3% of iron has been lost by chlorination and evaporation reactions simultaneously. To decrease the loss of iron oxide and improve the efficiency of selective chlorination and evaporation reactions, chlorination by using Ar–Cl2–O2 gas has been conducted and the enrichment of oxygen gas effectively depressed the chlorination of iron oxide, while the removal efficiency of zinc and lead was maintained.

Chlorination Kinetics of ZnFe<SUB>2</SUB>O<SUB>4</SUB> with Ar-Cl<SUB>2</SUB>-O<SUB>2</SUB> Gas

Chlorination rate of ZnFe2O4 with Ar-Cl2-O2 gas was measured at 1023 to 1123 K by gravimetry. The effects of temperature, partial pressures of chlorine and oxygen on the rate were investigated. Zinc oxide contained in ZnFe2O4 specimen was selectively chlorinated and evaporated in gas, while iron oxide remained as oxide in a chlorinated residue. Chlorination rate increased with increasing partial pressure of chlorine. On the other hand, chlorination rate slightly decreased with increasing partial pressure of oxygen and chlorination of iron oxide was prevented. Since the order of chlorination rate with respect to partial pressure of chlorine was approximately 0.5, the rate-determining step of chlorination is considered to be the dissociative adsorption of chlorine gas on the surface of solid ZnFe2O4. Decrease of chlorination rate with the increase of partial pressure of oxygen could be explained by the occupation of adsorption sites of chlorine atoms by oxygen and the chlorination rate was expressed as functions of partial pressures of chlorine and oxygen as r=k·(P_Cl2^1/2/1+K_OP_O2^1/2) The activation energy of chlorination was 35.1±2.2 kJ/mol which is relatively small compared to that of ZnO chlorination reaction (58.2 kJ/mol). It is considered that this low activation energy is due to the weak adsorption of chlorine atom on the adsorption site.

Optimization of inlet temperature for deactivating LTWGS reactor performance

AbstractAn industrial Cu‐based low‐temperature water‐gas shift (LTWGS) reactor, subject to deactivation by irreversible chlorine adsorption, has been modeled and optimized. Both the chlorine adsorption kinetics and deactivation kinetics were assumed first order to chlorine partial pressure, and the rate constants were considered independent of temperature. The Efficient Production (EP) method has been used to compute the reactor production until the outlet CO conversion decays below a permissible minimum level. Two alternative strategies for the inlet temperature have been used to maximize the EP: constant and time‐variable. Compared to the EP obtained for the optimum constant inlet temperatures, EP resulting from the use of the optimum time‐variable inlet temperature sequence were higher, affording important energy savings. Furthermore, a sensitivity study with respect to most influential operational variables, such as inlet total flow rate, steam‐to‐gas ratio, pressure, and concentrations of chlorine, hydrogen, carbon monoxide, and inert content, was carried out. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Plutonium Precipitation in the MOX Co-deposition Tests for the Oxide Electrowinning Process

MOX deposition tests were continued in 2002 at RIAR, to increase the Pu concentration in the MOX deposit. The objective was achieved but a significant amount of PuO2 precipitates was found. This phenomenon was investigated by evaluating a hypothetical quantity named “Quasi Equilibrium (Q.E.) concentration” of plutonyls in the melt and their solubility. It was found that the oxygen pressure was too high in the 2002 tests, which made the Q.E. concentration too high and the chlorine pressure was too low, which reduced the solubility of plutonyls in the melt. It may be necessary to increase the oxygen pressure to obtain MOX deposit with Pu concentration higher than 30%, but the pressure must be limited depending on the chlorine pressure to avoid the Pu precipitation.

Roughness and damage of a GaAs surface after chemically assisted ion beam etching with Cl 2/Ar +

The surface roughness and the near surface damage of semiconductor structures after etching are important criteria for applications in the field of opto- and micro-electronics. The chemically assisted ion beam etching (CAIBE) causes a surface roughness higher than that for ion beam etching (rms < 0.2 nm) but lower than that for chemical dry etching (rms > 5 nm). Compared to the roughness an inverse behaviour is observed for the damage of the near surface region. Physical processes like sputtering, implantation or diffusion cause heavy damage. The higher the chemical assistance of the physical ion etching, achieved at a high chlorine pressure or a high surface temperature, the higher the etch rate and the lower the damage. For the CAIBE process an average damage depth of about 200 nm was measured. The damage was evaluated by photoluminescence spectroscopy measurements on a multi quantum well structure of Al 0.35Ga 0.65As/GaAs after bevel etching of the surface to improve the depth resolution of the damage measurements.

Chlorination and Evaporation Behaviors of PbO-PbCl2 System in Ar-Cl2-O2 Atmosphere

It is quite important to know the reactivity and behavior of Pb contained in steelmaking dust, or bottom ash and fly ash generated from municipal solid waste incineration process with chlorine. In the present study, chlorination and evaporation kinetics of PbO-PbCl2 melt have been investigated in Ar-Cl2-O2 atmosphere from 1023 to 1123 K. The weight of PbO specimen increased first and then decreased in Ar-Cl2-O2 stream during experiments, which phenomena mean that produced PbCl2 by PbO chlorination formed liquid oxychloride phase of PbO-PbCl2 system and then PbCl2 evaporated. Increase of partial pressure of chlorine increased the initial chlorination rate, however no effect on the latter evaporation rate was observed. Decrease of maximal weight gain of specimen and the slight increase of evaporation rate were observed with increasing partial pressure of oxygen. Activation energies of chlorination and evaporation of PbO-PbCl2 melt in the steady state were 35 kJ/mol and 156 kJ/mol, respectively. Evaporation rate of PbO-PbCl2 was also investigated at 1073 K in Ar-O2 atmosphere, however the change of evaporation rate with changing partial pressure of oxygen was within experimental error. Measured evaporation rate strongly depended on the composition of melt. Composition dependency of evaporation rate estimated from the activity of PbCl2 for the PbO-PbCl2 system generally represented the same trend, however the measured evaporation rate was larger than estimated one in the whole composition range. This result indicates that the formation of oxychloride melt affects the evaporation rate. Chlorination mechanisms and removal efficiency of Pb by chlorination have been discussed based on the present results.