Sulfur-impregnated activated carbon

Sulfur-impregnated activated carbons has been shown to be an effective sorbent for the removal of vapor-phase Hg< from CFPP and MWC flue gases [3,12,14,20-26]. This material has a large mercury adsorption capacity, but the addition of sulfur to activated carbon requires additional production cost. To avoid such processing steps, it may be possible to produce activated carbons from a precursor that already contains sulfur. 

The result also revealed that, for Hg° adsorption, an activated carbon derived from high-organic sulfur coal dod not benefit from a sulfur impregnation process at 600°C when compared with a sulfur-impregnated activated carbon prepared from... 

Mercury occurs in some natural gas streams and can result in severe corrosion of aluminum (e.g., brazed aluminum heat exchangers in LNG and turboexpander plants). The use of sulfur-impregnated activated carbon is a proven commercial process for removing the mercury, Sulfur is the active ingredient, securely fixing mercury, as sulfide, in the micro-porous structure of the carbon (Leeper, 1980). 

Molecular sieves have also found application for desulfurization of natural-gas feed to ammonia plants. Removal of all types of sulfur compounds ahead of these plants is desirable because sulfur acts as a temporary poi.son to steam-hydrocarbon reforming catalysts and a permanent poison to expensive low-temperature shift conversion catalysts. An installation employing a standard dual bed adsorption system has been described by Lee and Collins (1968). The authors also describe comparative tests of a molecular sieve and a commercial grade of impregnated activated carbon in a dual-bed mobile pilot unit. The test results indicated that the molecular sieve could treat 2 to 4 times as much gas per unit volume of adsorbent as the carbon. The commercial plant consistently provided gas to the primary reformer containing less than 0.3 ppm (vol) peak total sulfur from a feed gas averaging about 0.6 ppm... 

Some natural gases have also been found to contain mercury, which is a reformer catalyst poison when present in sufftciendy large amounts. Activated carbon beds impregnated with sulfur have been found to be effective in removing this metal. 

BMS A process for removing mercury from the effluent from the Castner-Kellner process. Chlorine is used to oxidize metallic mercury to the mercuric ion, and this is then adsorbed on activated carbon impregnated with proprietary sulfur compounds. Developed by Billingsfors Bruks, Sweden. 

Human adipose Addition of 13C-labeled standards to tissue followed by extraction with methylene chloride, acid-base washing, solvent exchange, treatment with silica gel impregnated with sulfuric acid, column chromatography using acidic silica gel, neutral alumina, and activated carbon addition of Relabeled standards. HRGC/HRMS (EPA Method 8290) 1 ppt No data EPA 1994c... 

Zeolites have also proven applicable for removal of nitrogen oxides (NO ) from wet nitric acid plant tail gas (59) by the UOP PURASIV N process (54). The removal of NO from flue gases can also be accomplished by adsorption. The Unitaka process utilizes activated carbon with a catalyst for reaction of NO, with ammonia, and activated carbon has been used to convert NO to N02, which is removed by scrubbing (58). Mercury is another pollutant that can be removed and recovered by TSA. Activated carbon impregnated with elemental sulfur is effective for removing Hg vapor from air and other gas streams the Hg can be recovered by ex situ thermal oxidation in a retort (60). The UOP PURASIV Hg process recovers Hg from clilor-alkali plant vent streams using more conventional TSA regeneration (54). Mordenite and clinoptilolite zeolites are used to remove HQ from Q2, clilorinated hydrocarbons, and reformer catalyst gas streams (61). Activated aluminas are also used for such applications, and for the adsorption of fluorine and boron—fluorine compounds from alkylation (qv) processes (50). 

Mercury is one of a number of toxic heavy metals that occur in trace amounts in fossil fuels, particularly coal, and are also present in waste materials. During the combustion of fuels or wastes in power plants and utility boilers, these metals can be released to the atmosphere unless remedial action is taken. Emissions from municipal waste incinerators can substantially add to the environmental audit of heavy metals, since domestic and industrial waste often contains many sources of heavy metals. Mercury vapor is particularly difficult to capture from combustion gas streams due to its volatility. Some processes under study for the removal of mercury from flue gas streams are based upon the injection of finely ground activated carbon. The efficiency of mercury sorption depends upon the mercury speciation and the gas temperature. The capture of elemental mercury can be enhanced by impregnating the activated carbon with sulfur, with the formation of less volatile mercuric sulfide [37] this technique has been applied to the removal of mercury from natural gas streams. One of the principal difficulties in removing Hg from flue gas streams is that the extent of adsorption is very low at the temperatures typically encountered, and it is often impractical to consider cooling these large volumes of gas. 

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