ChemInform Abstract: Uptake of Chlorine Dioxide by Model Polar Stratospheric Cloud Surfaces: Ultrahigh-Vacuum Studies.

ChemInform ◽  
2010 ◽  
Vol 27 (26) ◽  
pp. no-no
Author(s):  
J. D. GRAHAM ◽  
J. T. ROBERTS ◽  
L. A. BROWN ◽  
V. VAIDA
Keyword(s):  
Chlorine Dioxide ◽  
Ultrahigh Vacuum ◽  
Polar Stratospheric Cloud

Uptake of Chlorine Dioxide by Model Polar Stratospheric Cloud Surfaces:  Ultrahigh-Vacuum Studies

1996 ◽  
Vol 100 (8) ◽  
pp. 3115-3120 ◽  
Author(s):  
James D. Graham ◽  
Jeffrey T. Roberts ◽  
Laura A. Brown ◽  
Veronica Vaida
Keyword(s):  
Chlorine Dioxide ◽  
Ultrahigh Vacuum ◽  
Polar Stratospheric Cloud

scholarly journals OClO as observed by TROPOMI: a comparison with meteorological parameters and polar stratospheric cloud observations

2022 ◽  
Vol 22 (1) ◽  
pp. 245-272
Author(s):  
Jānis Puķīte ◽  
Christian Borger ◽  
Steffen Dörner ◽  
Myojeong Gu ◽  
Thomas Wagner
Keyword(s):  
Chlorine Dioxide ◽  
Signal To Noise Ratio ◽  
Meteorological Data ◽  
Polar Vortex ◽  
Optical Absorption Spectroscopy ◽  
Orthogonal Polarization ◽  
Polar Regions ◽  
Polar Stratospheric Cloud ◽  
Lee Waves ◽  
A Minor

Abstract. Chlorine dioxide (OClO) is a by-product of the ozone-depleting halogen chemistry in the stratosphere. Although it is rapidly photolysed at low solar zenith angles (SZAs), it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation on chlorine oxide (ClO). Here, we compare slant column densities (SCDs) of chlorine dioxide (OClO) retrieved by means of differential optical absorption spectroscopy (DOAS) from spectra measured by the TROPOspheric Monitoring Instrument (TROPOMI) with meteorological data for both Antarctic and Arctic regions for the first three winters in each of the hemispheres (November 2017–October 2020). TROPOMI, a UV–Vis–NIR–SWIR instrument on board of the Sentinel-5P satellite, monitors the Earth's atmosphere in a near-polar orbit at an unprecedented spatial resolution and signal-to-noise ratio and provides daily global coverage at the Equator and thus even more frequent observations at polar regions. The observed OClO SCDs are generally well correlated with the meteorological conditions in the polar winter stratosphere; for example, the chlorine activation signal appears as a sharp gradient in the time series of the OClO SCDs once the temperature drops to values well below the nitric acid trihydrate (NAT) existence temperature (TNAT). Also a relation of enhanced OClO values at lee sides of mountains can be observed at the beginning of the winters, indicating a possible effect of lee waves on chlorine activation. The dataset is also compared with CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) polar stratospheric cloud (PSC) observations. In general, OClO SCDs coincide well with CALIOP measurements for which PSCs are detected. Very high OClO levels are observed for the northern hemispheric winter 2019/20, with an extraordinarily long period with a stable polar vortex being even close to the values found for southern hemispheric winters. An extraordinary winter in the Southern Hemisphere was also observed in 2019, with a minor sudden stratospheric warming at the beginning of September. In this winter, similar OClO values were measured in comparison to the previous (usual) winter till that event but with a OClO deactivation that was 1–2 weeks earlier.

Elemental chlorine-free bleaching of North American hardwood kraft pulps: Evaluation of oxidant-reinforced extraction variables on overall bleaching optimization

TAPPI Journal ◽  
2013 ◽  
Vol 12 (10) ◽  
pp. 33-41 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Response Surface ◽  
Chlorine Dioxide ◽  
North American ◽  
Yield Loss ◽  
Alkaline Extraction ◽  
Kraft Pulps ◽  
Pulp Bleaching ◽  
Response Surface Models ◽  
Elemental Chlorine ◽  
Surface Models

This investigation evaluates how higher reaction temperatures or oxidant reinforcement of caustic extraction affects chlorine dioxide consumption during elemental chlorine-free bleaching of North American hardwood pulps. Bleaching data from the published literature were used to develop statistical response surface models for chlorine dioxide delignification and brightening sequences for a variety of hardwood pulps. The effects of higher (EO) temperature and of peroxide reinforcement were estimated from observations reported in the literature. The addition of peroxide to an (EO) stage roughly displaces 0.6 to 1.2 kg chlorine dioxide per kilogram peroxide used in elemental chlorine-free (ECF) bleach sequences. Increasing the (EO) temperature by Δ20°C (e.g., 70°C to 90°C) lowers the overall chlorine dioxide demand by 0.4 to 1.5 kg. Unlike what is observed for ECF softwood bleaching, the presented findings suggest that hot oxidant-reinforced extraction stages result in somewhat higher bleaching costs when compared to milder alkaline extraction stages for hardwoods. The substitution of an (EOP) in place of (EO) resulted in small changes to the overall bleaching cost. The models employed in this study did not take into account pulp bleaching shrinkage (yield loss), to simplify the calculations.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

Optimization of elemental chlorine-free bleaching for a softwood kraft pulp • part 2: economic analysis of chemical and steam consumption

TAPPI Journal ◽  
2010 ◽  
Vol 9 (9) ◽  
pp. 47-53 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Chlorine Dioxide ◽  
Previous Investigation ◽  
Kraft Pulp ◽  
Energy Costs ◽  
Alkaline Extraction ◽  
Stage Versus ◽  
Kraft Pulps ◽  
Steam Consumption ◽  
Elemental Chlorine ◽  
Softwood Kraft Pulp

Our previous investigation [1] re-analyzed the data from Basta and co-workers (1992 TAPPI Pulping Conference) to demonstrate how oxidative alkaline extraction can be augmented and how these changes affect chlorine dioxide consumption with elemental chlorine-free (ECF) sequences. The current study manipulates extraction delignification variables to curtail bleaching costs with a conventional U.S. Southern softwood kraft pulp. The economic advantages of ~0.35% to 0.65% H2O2 peroxide reinforcement in a 70°C (EOP)-stage versus 90°C (EO)-stage are predisposed to the brightness targets, to short or long bleach sequences, and to mill energy costs. Minimized bleaching costs are generally realized when a 90°C (EO) is employed in D0(EO)D1 bleaching, whereas a 70°C (EOP) is economically advantageous for D0(EOP)D1E2D2 bleaching. The findings we disclose here help to clarify previous ECF optimization studies of conventional softwood kraft pulps.

Bleaching optimization at WestRock mill in Covington, Virginia

TAPPI Journal ◽  
2016 ◽  
Vol 15 (9) ◽  
pp. 581-586 ◽  
Author(s):  
RICARDO B. SANTOS ◽  
PETER W. HART ◽  
DOUGLAS C. PRYKE ◽  
JOHN VANDERHEIDE
Keyword(s):  
Hydrogen Peroxide ◽  
Sodium Hydroxide ◽  
Chlorine Dioxide ◽  
Capital Expenditures ◽  
Equipment Repair ◽  
Optimization Program ◽  
Hardwood Pulp ◽  
Improved Performance

The WestRock mill in Covington, VA, USA, initiated a long term diagnostic and optimization program for all three of its bleaching lines. Benchmarking studies were used to help identify optimization opportunities. Capital expenditures for mixing improvement, filtrate changes, equipment repair, other equipment changes, and species changes were outside the scope of this work. This focus of this paper is the B line, producing southern hardwood pulp in a D(EP)DD sequence at 88% GE brightness. The benchmarking study and optimization work identified the following opportunities for improved performance: nonoptimal addition of caustic and hydrogen peroxide to the (EP) stage, carryover of D0 filtrate to the (EP) stage, and carryover of (EP) filtrate to the D1 stage. As a result of actions the mill undertook to address these opportunities, D0 kappa factor decreased about 5%, sodium hydroxide consumption in the (EP) stage decreased about 35%, chlorine dioxide consumption in the D1 stage decreased about 25%, and overall bleaching cost decreased about 15%.

TIMETAL 35A

Alloy Digest ◽  
2001 ◽  
Vol 50 (11) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
High Temperature ◽  
Nitric Acid ◽  
Physical Properties ◽  
Chlorine Dioxide ◽  
Heat Treating ◽  
Bend Strength ◽  
Temperature Performance ◽  
Sodium And Potassium

Abstract Titanium shows outstanding resistance to seawater and marine atmospheres. It is also resistant to attack by hot metallic chloride solutions, sodium and potassium hypochlorite, and chlorine dioxide. The metal is resistant to attack by hot nitric acid at concentrations up to 80% and is not attacked by sulfuric acid. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength as well as fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: TI-122. Producer or source: Timet.

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