Chlorine removal

The presence of chlorides in the feed gas can cause the zinc oxide to sinter as they are absorbed to form zinc chloride. Any hydrogen chloride formed in the hydrodesitlfurizer can be removed from the gas by installing a bed of alkalized alitmina in front of the zinc oxide. After this treatment the natural gas usitally contains less than O.lmg chlorine per cubic meter. An average of about 10-12 wt% chloride can be absorbed before the alkalized alumina is saturated. Platformer hydrogen containing up to 2 ppm HCl is commonly treated in this way. Only a relatively small bed of absorbent is required at a space velocity of 10,000-15,000 h.  

Zinc oxide has been used to remove sitUur compounds from hydrocarbons since the 1930s, when the steam reforming process was first introduced. When a zinc oxide composition is specially prepared to have a high surface area and high degree of porosity, it can absorb more than 20 wt% sulfur in a single bed. It was the preferred choice in the early days, because the partial pressirre of hydrogen sulfide at equilibriitm imder reaction conditions, particularly in the presence of water vapour, is very small compared to that of the bog iron ore used previously to purify water gas/producer gas. 

Thus six atoms of iron will produce nine molecules of water compared with six atoms of zinc, which only produce six. Furthermore iron sulfide can release hydrogen sulfide by reaction with hydrogen and steam during plant start-up or shut-down conditions. In practice, therefore, when iron oxide is used it is always followed by a guard bed of zinc oxide. 

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Soft drinks Potable water treatment, sterilization with chlorine Chlorine removal and adsorption of dissolved organic materials... 

Concern has been expressed about the possible formation of dioxins and furans. However, measurements during experiments indicated that the emissions of dioxins and furans were not significantly elevated. Dioxin emissions with or without plastic input appeared to be about a factor of 100 below the standard of 0.1 ng/Nm TEQ TCCD (toxicity equivalent in relation to the toxic dioxin TCCD) (a.7). This might be due to the benefit of the strongly reducing atmosphere and the high temperature of 2100 °C. In total, until now the conclusion has been that at current PVC levels in MSW, pretreatment for chlorine removal is unnecessary. 

Thus, the enhancements in chlorine removal from W diads compared to EV diads and from m-W diads compared to r-W diads observed in the (n-Bu)3SnH reduction of DCP, TCH, and PVC are consistent with the free-radical chain reaction mechanism. Inductive effects produced by neighboring 7-Cl s tend to favor the reduction of W diads relative to EV diads and steric interactions resulting from different preferred conformations in each isomer favor the removal of Cl from m-W diads relative to r-W diads. 

The results for the chlorine and sulfur content before and after the base treatment are listed in Table 1. As one can see, the least amount of chlorine removed after the base treatment of the resins was recorded for the precursor of catalyst A. Precursors of polysulfonated resins D and E released a larger fraction of the incorporated chlorine during the base treatment step, thus producing the... 

Thus a spent scrubbing solution is obtained that contains equimolar quantities of NaOCl and NaCl. The chlorine-containing vent streams may contain also and variously C02, HC1 and other components naturally occurring in atmospheric streams. Clearly the C02 and HC1 have the potential to reduce the capacity of the caustic stream for chlorine removal. 

This equation illustrates that the residence time will always be somewhat less than the process with the fastest turnover time. In the cases of sodium and chlorine, removal of the cyclic seasalt component significantly increases the computed MORTs for these elements. 

Table 1 Sodium Consumption Per Chlorine Removed Required to Completely Dechlorinate Model Compounds in Liquid NH3 at Room Temperature...

The filters are backwashed occasionally to remove any suspended solids that may have accumulated on the surface of the bed. Backwashing does not remove material adsorbed in the pores of the carbon. Although a few installations regenerate their carbon using thermal, steam, solvent extraction, or other techniques, most applications see replacement of carbon when exhausted. Typical "life" of carbon used for TOC removal is 6 -12 months. For chlorine removal, the typical "life" is 12 - 18 months. 

Free chlorine removal—LTV Light oxidation of free chlorine in water. Available in the Electronic Technical Library of Hanovia Ltd., London, England, www. hanovia.co.uk, 2006. 

Table 19.7 Chlorine removal step [9]. (Reproduced by permission of the American Chemical ...

Shiraga and Uddin [6] carried out thermal and catalytic degradation of mixed plastic containing PVC. The solid acid catalyst employed in this study is silica-alumina with a chlorine sorbent such as goethite hydrated Iron Oxide FeO (OH). The dechlorination ability effects of contact mode, liquid phase contact, (LP) or vapor phase contact (VP) were studied. Dechlorination results show that the vapor phase contact was more effective for chlorine removal. 

Observations of these reactions in the natural environment indicate that they take place on the order of years per chlorine removed for aryl halides in sediments (Brown et al., 1987 Adriaens et al., 1999 Fu et al., 2001 Gaus et al., 2002), and months to years for alkyl halides or pesticides in groundwater (Potter and Carpenter, 1995 Wiedemeier et al., 1999 Skubal et al., 2001). Accurate calculations account for the metabolic rates measured in sediments or soils (Henrichs and Reeburgh, 1987 Schlesinger, 1991 Murphy and Schramke, 1998). For example, Fu et al. (2001) estimated the rate of cometabolic dioxin dechlorination in estuarine Passaic River sediments at 3-8 pg of diCDD per gram sediment per year, based on sediment respiration rates, and the ratios of dioxin dechlorination as compared to methane production, which represented the dominant TEAP under which these reactions occurred. 

Phenylcyclohexylchloroarsine, (C8H5)(C6lIn)AsCl. — A solution of 80 grams of dicpcfohexylphenylarsine in 600 e.c. of petroleum ether is treated with chlorine. Removal of the solvent yields the trichloride, which decomposes at 167° C., and from the decomposition products 50 grams (73 per cent.) of the chloroarsine are isolated on fractionation. It boils at 183° to 184° C. at 15 mm. 

Kralingen, Netherlands [83] Surface water Meuse River Coagulation Sedimentation Ozonation Dual layer filtration Carbon filtration Safety chlorination Protection against periodic taste/odor and toxic substances Removal of THM s produced by chlorination Removal of matter produced by or unsuccessfully removed by ozonation Particle size 0.8 mm Bed deptli 4 m Bed diameter 6 m Volume per filter 116 m" Contact time 12 min. 

Choisy-le-Roi, France [8 ] Surface water Seine River Ozonation (1) Coagulation/flocculation Sedimentation Sand filtration GAC filtration Ozonation (2) Post chlorination Removal of taste Removal of organics which might form toxic chloro-compounds during post chlorination Two columns Contact time 15 miri. Vol per filter 117 m Filter velocity 9 m/hr Organics removal improved by 40%... 

In summary, results from the test series indicated that, for a flow rate of up to 100 gpm for EBMUD water, one Dechlor tablet maintained the residual chlorine concentration below the detection limit for 45 min. An increase in the number of tablets increased the residual chlorine removal efficiency. However, an increase in flow rate to 450 gpm resulted in an increase in residual chlorine concentrations to above detection (and compliance) limits within 25 min, even in the presence of 16 tablets. Results also indicated that, when the flow rate was decreased (to 50 gpm) and the number of tablets increased (to 28), the DO concentration decreased significantly. 

Chlorination removed the HgCF3 giving Ru(CO)2(Cl)(PPh3)2(CF3), and treatment with CH3CN displaced the CO trans to the CF3. The CF3 can be converted to CO with HC104, but the more interesting reaction is... 

The influence of geometrical factors, the specific reactorload and the feedstock properties on the fuel gas production including the amount of tarry components will be analysed. No atttention will be paid to the possibility of in situ sulphur or chlorine removal. Earlier attempts to predict the product gas composition were based on thermodynamic models i.e. a combination of mass and energy balances assuming for one or more reactions chemical equilibrium at an empirically determined temperature e.g. outlet temperature. 

Positions of Chlorines Removed by Each Dechlorination Process... 

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