Chlorine Flow Rate Research Articles

Comparative studies on simultaneous chlorination of LDPE and PP in paraffin

Polyolefin chlorination involves introducing chlorine atoms into the polymer chain which results in enhancement of specific properties of the respective polyolefin. Traditional chlorination is carried out in practice in the presence of toxic solvents which renders the process less environment friendly and highly energy intensive. The present study reports experimental investigations conducted on a potential alternative known as co-chlorination in which a polyolefin is chlorinated using paraffin as solvent. Unlike conventional solvents, paraffin also acts as a reactant and undergoes chlorination with the parent polyolefin. Low Density Polyethylene (LDPE) and Polypropylene (PP) were used as representative polyolefins in this study. Experiments were conducted at a temperature, chlorine flowrate, polyolefin concentration (in paraffin) and an agitation speed of 130 °C, 350 mL/min., 10 % and 400 rpm respectively. Comparative results based on chlorine content in the respective polyolefins post co-chlorination and product characterization using CHNS, FTIR and 1H NMR is presented.

Co-chlorination of low-density polyethylene in paraffin: An intensified green process alternative to conventional solvent-based chlorination

Abstract This study experimentally demonstrates the potential of co-chlorination as a green process alternative to conventional independent chlorination of polyolefins, which involves the use of non-environment-friendly solvents like carbon tetrachloride (CCl4). Low-density polyethylene (LDPE) was used as a representative polymer in this study and co-chlorinated with paraffin. Apart from being a reactant, the paraffin also acts as a solvent, thus eliminating the need for using CCl4 during the reaction. Test runs were first conducted to measure LDPE-paraffin solution viscosities at different LDPE concentrations to investigate the solubility of LDPE in paraffin. Co-chlorination experiments were then carried out covering a range of temperatures (100–130°C), chlorine flow rates (150–350 mL·min−1), LDPE concentrations in paraffin (10–30%) and agitation speeds (100–400 rpm). The chlorinated LDPE and paraffin products were subsequently characterized post separation using FTIR/1H NMR spectroscopy and differential scanning calorimetry. Specific properties of these two co-chlorinated products were compared with independently chlorinated LDPE and paraffin. The co-chlorinated products were found to compare well in terms of chlorine content and quality. A preliminary comparative study from a process perspective between co-chlorination and conventional chlorination of LDPE is also reported. The results obtained confirm the potential of co-chlorination as an environmentally friendly alternative.

Reducing Water Losses for Sustainable Urban Development

From the point of view of water supply systems, and in particular of distribution networks, the environmental, social and economic criteria have had a significant role in the selection of urban water development decisions. In this respect, the article addresses the issue of reducing water losses in drinking water supply systems. Thus, there are presented the methods and technologies used and studied, currently, for the detection of damages on the pipes of the distribution networks. Continuous monitoring of the pipeline network has become an integral part of drinking water supply systems. Remote data transmission and the use of professional software allows for accurate loss detection in places where the probability of loss is maximum. The relocation method has the benefit of economies of time and money. In most developed countries, the percentage of water loss is significant. The article makes a theoretical analysis on the application of non-revenue water loss solutions (NRW) in Timisoara, Romania. At various points in the drinking water distribution network, measuring points are installed to measure the pressure, residual chlorine concentration, flow rate and flow direction. Measurement panels installed in underground fireplaces and sensors mounted directly on pipes transmit the measured data from sensors directly to the dispatcher via the GPRS data service. In addition to this information, the measurement point also generates alarms in the event of a home flood, unauthorized access, or lack of power from the grid. The results of the analysis highlight the fact that the loss reduction is quantified in water savings with positive effects on the reduction of pressure on the existing networks.

Factors affecting the performance and monitoring of a chlorine wash in preventing Escherichia coli O157:H7 cross-contamination during postharvest washing of cut lettuce

This study examined factors that may affect the performance of a produce wash in preventing E. coli O157:H7 cross-contamination. Fresh-cut romaine lettuce (8 or 20 g) inoculated with ca. 7 log CFU/g of E. coli O157:H7 expressing green fluorescence protein was washed with uninoculated cut lettuce (800 or 2000 g) in 40 L of water for 2 min. Washing trials were performed in both sterile tap water and spent wash water collected from a commercial leafy greens processing facility under different prewash free chlorine levels (0, 5, 20 and 30 ppm), water temperatures (3 and 20 °C), leaf-to-water ratios (1:20 and 1:50), and flow rates (fast, medium, and slow). Performance of the chlorine wash was greatly affected by free chlorine level and wash water quality. Temperature, lettuce-to-water ratio, or water flow rate did not appear to have a significant impact. A prewash free chlorine concentration of 10 or 20 ppm was effective in preventing E. coli O157:H7 cross-contamination when lettuce was washed in tap water in the two washing systems assembled; 30 ppm of chlorine was needed to prevent cross-contamination during washing in industry water. Small-scale (100 ml) inactivation studies were performed to examine the impact of organic and solid contents (with the addition of lettuce juice and play sand) on the antimicrobial efficacy of chlorinated water. Increases in organic matter resulted in greater depletion of chlorine and the presence of solids enabled the pathogen to better survive chlorination; both led to a lower antimicrobial efficacy observed. ORP did not correlate linearly with free chlorine. E. coli O157:H7 cross-contamination was observed when ORP exceeded 650 mV, indicating that a threshold level of 650 mV may not ensure the safety of produce wash water. Since effective chlorine level is highly influenced by wash water quality, monitoring of produce washing systems may best be performed by measuring wash water quality in conjunction with rapid measurement of free chlorine.

Online Monitoring of Wastewater Effluent Chlorination Using Oxidation Reduction Potential (ORP) vs. Residual Chlorine Measurement

Various control strategies are employed to insure that sufficient amount of chlorine has been applied to the wastewater effluent to achieve desired disinfection goals. In the commonly used control strategies, such Feed Back Control and Compound Loop Control, the combination of effluent flow rate, chlorine flow rate and chlorine residual are measured for dosing control with the chlorine residual used as a set point parameter. Recently Oxidation-Reduction Potential (ORP) has been employed as a control measurement and set point parameter for effluent chlorine dosing control as well. Theoretically, use of chlorine residual or ORP set point makes the chlorine dosing possible to simultaneously respond to changes in effluent flow rate and in process (such as fluctuating effluent ammonia levels), which cause variations in chlorine demand and thus the ORP or chlorine residual after the dose point. This would also potentially reduce chlorine feed requirements. Specific ORP or residual chlorine residual levels to ensure effective disinfection could be effectively monitored and maintained under changing effluent quality conditions. In addition, immediate detection of chlorine feed malfunction could be achieved when analyzers are employed at the chlorine dosing point.This title belongs to WERF Research Report SeriesISBN: 9781843397175 (eBook)

Use of On-line Water Quality Monitoring Data to Predict Bacteriological Failures

Variations in continuously monitored on-line water quality data were investigated to establish whether they could be linked to coliform detections at regulatory monitoring points. We focussed on chlorine residual, turbidity and flow rate at water treatment works (WTW)-A. Archived on-line monitoring data from WTW-A were analysed using cross-correlation and self-organising maps in MATLAB® to identify trends in the data running up to coliform detections. The results show that these tools could be developed to help manage WTWs to reduce the number of bacteriological failures. A fingerprint of WTW conditions relating to coliform failures was identified for this case study.

Kinetic study on the chlorination of β-spodumene for lithium extraction with Cl2 gas

In this paper, the kinetics chlorination of β-spodumene for the extraction of lithium has been studied using gaseous chlorine as chlorinating agent. The effect of chlorine flow rate, temperature, mass of the sample, and partial pressure of Cl2 was investigated. The study of the effect of chlorine flow rate indicated that the chlorination of β-spodumene may be carried out in the presence of active chlorinating species The chlorine partial pressure was found to have an appreciable effect on the system reactivity. The temperature was found to be the most important variable affecting the reaction rate. The β-spodumene chlorination process by Cl2 was characterized by an apparent activation energy of about 359kJ/mol in the range from 1000 to 1100°C. Reaction was of non-catalytic gas–solid nature and experimental data fitted the sequential nucleation and growth model.

Chemical vapor deposition of rhenium on a gourd shaped graphite substrate

Chemical vapor deposition (CVD) of rhenium coatings on a gourd shaped graphite substrate is studied. Effects of deposition temperature, chlorine flow rate, total pressure and chlorination temperature on deposition rate, yield, morphology and texture of rhenium coating are investigated, respectively. Uniform rhenium coatings have been obtained by using proper combination of deposition conditions at an acceptable deposition rate and yield. The rhenium coatings consist of two sub-layers, i.e., an inner nucleation layer of fine equiaxed grains and an outer layer comprising oriented columnar grains. Although different surface morphologies have been observed, the grains of rhenium coatings are all <002> oriented. The tendency of the preferred orientation <002> is more significant with decreasing surface roughness of the coating.

Efficient pulsed chemical oxygen-iodine laser with instantaneous generation of atomic iodine by volumetric discharge

A pulsed chemical oxygen-iodine laser (COIL) using atomic iodine generated by volumetric discharge of CH3I is developed and tested. COIL with a gain length of 60 cm is energized by a square pipe-array jet singlet oxygen generator with basic hydrogen peroxide pumping circulations and operated at subsonic gas flow. Maximum output energy of 4.3 J, pulse duration of 50 μs, specific energy extraction from the active medium of 2.0 J/L, and the maximum chemical efficiency of 12.5% are achieved at a chlorine flow rate of 55 mmole/s.

Test bed for a high throughput supersonic chemical oxygen — iodine laser

The paper reports the development of a test bed for a chemical oxygen — iodine laser based on a high throughput jet flow singlet oxygen generator (JSOG). The system provides vertical singlet oxygen extraction followed by horizontal orientation of subsequent subsystems. This design enables the study of flow complexities and engineering aspects of a distributed weight system as an input for mobile and other platform-mounted systems developed for large scale power levels. The system under consideration is modular and consists of twin SOGs, plenum and supersonic nozzle modules, with the active medium produced in the laser cavity. The maximal chlorine flow rate for the laser is ∼1.5 mole s-1 achieving a typical chemical efficiency of about 18%.

Modelling of Chlorine Contact Tank and the Combined Applications of Linear Model Predictive Control and Computational Fluid Dynamics

A dynamic model is developed to present chlorine decay in chlorine contact tank, and a single-input single-output (SISO) model that presents both chlorine dosing and decay process is developed in Simulink of Matlab software with considerations of the process disturbances of temperature and stagnant flow in the tank. A computational fluid dynamics (CFD) model of chlorine transport and decay in the tank is also developed with the use of mixture multiphase model to present the chlorine mixing and decay models in the tank. To optimally control free chlorine residual (FCR) concentration in the SISO system, a linear model predictive control (LMPC) is designed using the SISO system and LMPC control algorithm. The LMPC control objective is to regulate the optimal mass flow rates of gaseous chlorine to control the chlorine decay process inputs/outputs within the constraints. The results on the LMPC simulation using reference data from a real water plant show that the LMPC can control the FCR concentration in the tank within the constraint by regulating the optimal mass flow rates of gaseous chlorine. Commercial CFD software, FluentTM, has been used in this study to simulate the FCR distribution in the CCT channel based on the LMPC result.

Centrifugal bubble O2 (1Δ) gas generator with a total pressure of 100 Torr

A centrifugal bubbling singlet-oxygen gas generator is developed in which chlorine with helium are injected into the rotating layer of the alkali solution of hydrogen peroxide through cylindrical nozzles directed at an angle of 30° to the bubbler surface. The concentrations of water vapour and O2 (1Δ) and the gas temperature were determined by using the multichannel recording of the emission bands of oxygen at 634, 703, 762 and 1268 nm. For the chlorine and helium flow rates of 60 and 90 mmol s-1, respectively, the specific chlorine load of 3.2 mmol cm-2, a total pressure of 100 Torr in the working region of the gas generator and the oxygen partial pressure of 36 Torr, the chlorine utilisation was 90% and the content of O2 (1Δ) was ≈60%. For the ratio of the flow rates of chlorine and the alkali solution of hydrogen peroxide equal to 1 mol L-1, the water vapour content was ≈25%. The chemical efficiency of the oxygen—iodine laser with this gas generator achieved 23% for the specific power of 12.7 W cm per 1 cm3 s-1 per pass of the solution through the gas generator.

Multikilowatt chemical oxygen-iodine laser with chemical generation of molecular iodine

A multikilowatt chemical oxygen-iodine laser (COIL) using molecular iodine generated chemically as the iodine source was developed and tested. The COIL, with a gain length of 26.5cm, was energized by a square pipe-array jet singlet oxygen generator (JSOG), with a nozzle bank having a designed Mach number of 2.5. The JSOG, operating without a primary buffer gas, has a much better operation stability during basic hydrogen peroxide pumping circulations. Iodine injectors/nozzles made of polyimide were used. An output power of 7.8kW and a chemical efficiency of 24.5% were achieved with a chlorine flow rate of 353mmole∕s.

Singlet oxygen generator based on the reaction of chlorine with filament-guided jets of basic hydrogen peroxide

The chlorine utilization efficiency and singlet oxygen concentration are determined as functions of the chlorine flow rate, the base concentration, and the flow rate and temperature of basic hydrogen peroxide in a singlet oxygen generator based on the reaction of chlorine with filament-guided descending basic hydrogen peroxide jets. The effluent gas, without aerosol entrainment, contains about 10% residual chlorine and more than 60% singlet oxygen.

Microcontaminants in Pentachlorophenol Synthesis. 3. Effect of Temperature and Chlorine Flow Rate at End of Run

Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) are undesired byproducts that form as microcontaminants during the synthesis of pentachlorophenol. In temperature-programmed, laboratory-scale synthesis, most of the microcontaminant toxicity forms near the end of the run and while the molten pentachlorophenol product cools and solidifies. Terminating the chlorine feed to the reactor before the end of the run, where some tetrachlorophenol remains, prevented the formation of microcontaminants in high concentrations in the final product. Therefore, it appears that the microcontaminant-forming reactions that occur near the end of the run are inhibited by creating chlorine starvation conditions in the reaction system. In a commercial implementation of this strategy, it may also be beneficial to purge the reactor contents with an inert gas after stopping the chlorine flow to remove the residual chlorine.

Chemically assisted ion beam etching of GaAs by argon and chlorine gases: Experimental and simulation investigations

A two-dimensional chemically assisted ion beam etching model (CAIBE) has been developed in connection with the experiment. The effects of the chlorine flow rate and the GaAs substrate temperature have been studied. For a low Cl2 flow rate (QCl2&amp;lt;2sccm), the simulation results show that the GaAs etching rate is mainly controlled by the physical etch process. Over this value, the ion assisted mechanism becomes preponderant. In the case of the band etch through the mask, the increase of the Cl2 flow rate and the temperature contribute to the improvement of the etching anisotropy and elimination of microtrenching. A good agreement between the simulations and the experiments concerning the etching rate and the etch profiles through the mask versus the flow rate and temperature have been obtained.

Precise Depth Control of Silicon Etching Using Chlorine Atomic Layer Etching

In this study, the atomic layer etching (ALE) of Si was carried out using Cl2 adsorption followed by Ar+ ion beam irradiation with a low energy Ar+ ion beam generated by an inductively coupled plasma ion gun. A saturated silicon etch rate due to chlorine ALE could be obtained when the Ar+ ion acceleration voltage of the ion gun was in the range of 70 to 90 V, as a result of the preferential etching of silicon chloride formed during the chlorine adsorption period by the Ar+ ions while the silicon sputter etch rate remains insignificant. This was attributed to the differences in the silicon-to-silicon and silicon-to-silicon chloride binding energies. The saturated silicon etch rate by ALE was dependent on the chlorine flow rate, i.e. the surface coverage of chlorine and the Ar+ ion irradiation time. In this experiment, a silicon etch rate of 1.36 Å/cycle, which is a (100) silicon monolayer per cycle, could be obtained by flowing more than 10 sccm chlorine gas followed by bombarding the surface by Ar+ ions with an acceleration voltage of 70 V for more than 40 seconds. Under this condition, when a 30 nm scale silicon etch profile was examined after 200 cycles, a silicon etch profile with no undercut could be obtained.

Molybdenum Gate Technology for Ultrathin-Body MOSFETs and FinFETs

Damage-free sputter deposition and highly selective dry-etch processes have been developed for molybdenum (Mo) metal gate technology, for application to fully depleted silicon-on-insulator ( devices such as the ultrathin body (UTB) MOSFET and double-gate FinFET. A plasma charge trap effectively eliminates high-energy particle bombardment during Mo sputtering; hence the gate-dielectric integrity (TDDB, Q/sub BD/) is significantly improved and the field-effect mobility in Mo-gated MOSFETs follows the universal mobility curve. The effects of etch process parameters such as chlorine (Cl/sub 2/) and oxygen (O/sub 2/) gas flow rate, and source and bias radio frequence powers, were investigated in order to optimize the Mo etch rate and selectivity to SiO/sub 2/. A highly selective etch process was successfully applied to pattern Mo gate electrodes for UTB MOSFETs and FinFETs without leaving any residue or stringers. Measured electrical characteristics and physical analysis results are discussed.

Reaction Pathways in Pentachlorophenol Synthesis. 1. Temperature-Programmed Reaction

Pentachlorophenol, a wood preservative for nonresidential applications, contains parts per million levels of dibenzodioxins and dibenzofurans with six or more chlorine atoms. There is interest in reducing the levels of these microcontaminants in pentachlorophenol. We conducted pentachlorophenol synthesis reactions in the laboratory to demonstrate the ability to mimic the commercially practiced temperature-programmed synthesis and to identify an operating region where mass-transfer limitations were effectively eliminated. The laboratory system was operated in a temperature-programmed fashion and produced pentachlorophenol with a yield and microcontaminant content similar to those of the commercially produced material. The experiments also revealed a stirring rate, number of gas spargers, and chlorine flow rate that enabled the laboratory-scale reaction to proceed in the kinetics-controlled regime. Results indicated that microcontaminant formation was low until near the end of the run where the microcontami...

Chemical oxygen-iodine laser using a new method of atomic iodine generation

The chemical oxygen-iodine laser (COIL) with a new chemical method of atomic iodine production was investigated. In this system, iodine atoms are formed in the COIL cavity by the fast chemical reaction of hydrogen iodide with chlorine atoms that are also produced chemically. It was found that, in the absence of singlet oxygen, the ground state atomic iodine can be produced with a high yield (80%-100%). In gas containing singlet oxygen, a gain on 3-4 electronic transition in iodine atom was achieved (0.35% cm/sup -1/). Both the concentration of atomic iodine and the gain depend substantially on the ratio of reacting gases and the penetration of secondary gases into the primary gas flow. In laser experiments, effects of the flow rate of reacting gases and their penetration on the laser output power were found. The output power of 310 W was attained at chlorine flow rate of 27 mmol/spl middot/s/sup -1/ corresponding to chemical efficiency of 12.7%. This was the first time the gain and laser output power were achieved in the COIL with atomic iodine generated by the proposed method.