Sulfur continued contamination

Sodium and potassium are restricted because they react with sulfur at elevated temperatures to corrode metals by hot corrosion or sulfurization. The hot-corrision mechanism is not fully understood however, it can be discussed in general terms. It is believed that the deposition of alkali sulfates (Na2S04) on the blade reduces the protective oxide layer. Corrosion results from the continual forming and removing of the oxide layer. Also, oxidation of the blades occurs when liquid vanadium is deposited on the blade. Fortunately, lead is not encountered very often. Its presence is primarily from contamination by leaded fuel or as a result of some refinery practice. Presently, there is no fuel treatment to counteract the presence of lead. 

In Mexico City, several air quality parameters are measured continuously by an Automated Monitoring Network operated by the Under Secretariat of Ecology. Carbon monoxide, particulate matter, sulfur dioxide, nitrogen oxide, and ozone are the contaminants exceeding Air Quality Standards. Emissions produced by 2.7 million vehicles and 35,000 commercial and industrial outfits are not easily dispersed in a Valley located at 2240 m and surrounded by two mountain chains which hinder air circulation. An Integral Program, recently established to alleviate pollution, is briefly described. 

Silverstein, J. L. et al., Loss Prev., 1981,14, 78 Nitrobenzene was washed with dilute (5%) sulfuric acid to remove amines, and became contaminated with some tarry emulsion that had formed. After distillation, the hot tarry acidic residue attacked the iron vessel with hydrogen evolution, and an explosion eventually occurred. It was later found that addition of the nitrobenzene to the diluted acid did not give emulsions, while the reversed addition did. A final wash with sodium carbonate solution was added to the process [1]. During hazard evaluation of a continuous adiabatic process for manufacture of nitrobenzene, it was found that the latter with 85% sulfuric acid gave a violent exotherm above 200° C, and with 69% acid a mild exotherm at 150- 170°C [2],... 

The sulfuric acid plant has boiler blowdown and cooling tower blowdown waste streams, which are uncontaminated. However, accidental spills of acid can and do occur, and when they do, the spills contaminate the blowdown streams. Therefore, neutralization facilities should be supplied for the blowdown waste streams (Table 15), which involves the installation of a reliable pH or conductivity continuous-monitoring unit on the plant effluent stream. The second part of the system is a retaining area through which non-contaminated effluent normally flows. The detection and alarm system, when activated, causes a plant shutdown that allows location of the failure and initiation of necessary repairs. Such a system, therefore, provides the continuous protection of natural drainage waters, as well as the means to correct a process disruption. 

Wet electrostatic precipitators (WESP) are used for removal of liquid contaminants such as sulfuric acid mist, aerosols, and particulate matter. The acid mist and aerosols are typically formed in a WGS by condensation of SO3. Unlike dry precipitators, wet precipitators do not require rapping to remove the dust. The collected mist and particulate matter form a liquid film that runs down a vertical collecting plate. In some cases, a continuous spray of liquid is used to prevent solids deposition on the collecting plates. 

The continually increasing demand for environmentally friendly industrial processes has also led to the development of techniques for recycling of the remaining 5-30% sulfate contained in the acidic wash water [2.55]. In modern processes, up to 99 % of sulfuric acid can be recovered and reused in production. In the chloride process, wastewater problems arise if the raw material contains < 90% Ti02. The metal chloride by products are sometimes disposed of in solution by the deep well method (e.g., at Du Pont). The metal chloride solutions are pumped via deep boreholes into porous geological strata. Special geological formations are necessary to avoid contamination of the groundwater by impurities. 

Dead spots and crevices - where equipment parts are not continuously wetted by oxygen-containing liquids - are prone to severe corrosion. Therefore, fabrication of this equipment should be done to avoid such vulnerable spots. An effort should also be made to reduce the potential for process contamination by corrosive agents such as sulfur (through oil in liquid NH3), H2S (along with C02) and chlorides (from cooling water)88. 

Lower temperatures. Loss of catalytic activity was found to be more severe during continuous sulfur addition, than when the system was pre-sulfided at a similar contamination level ... 

Procedure Into a suitable beaker, flask, ect., place 250 milliliters (8.5 fluid oz.) of cold water, and then add and dissolve 51 grams (1.8 oz.) of sodium hydroxide. Note sodium hydroxide generates excessive heat when dissolved in water so use caution. Thereafter, add in, in small portions at a time, 50 grams (1.7 oz.) of powdered sulfur, and stir the mixture vigorously during the addition. Note more sulfur may be added if desired. Thereafter, continue to stir the mixture for about 30 minutes. After 30 minutes the mixture is ready for use. Even though the mixture will be contaminated with sodium thiosulfate, it can be used directly in the reduction of nitro compounds. 

One final consideration when storing solid sulfur is the almost inevitable presence of sulfuric acid. Sulfur can become naturally contaminated with sulfuric acid through the presence of thiobacilli thiooxidans3 or continuous exposure to direct sunlight.4 Recent research has demonstrated the short-term effectiveness of certain bactericides in delaying bacterial colonization. Nevertheless, discrete pockets of weak (highly corrosive) sulfuric acid should always be presumed to exist within a sulfur storage pile. Hydrochloric acid, which may also be present when solid sulfur has been transported by vessel,5 must be neutralized to avoid potentially disastrous corrosion of downstream equipment. 

During operation, the electrolyte becomes more concentrated with copper, nickel, and arsenic and depleted with sulfuric acid. Floating slimes are composed of antimony arsenate, SbAsC>4, and bismuth arsenate, BiAsC>4. These can float to the cathode, causing contamination. Soluble impurities are removed from the electrolyte by continuously bleeding a portion of the electrolyte through a purification circuit. The impurity level in the anode determines the volume of electrolyte that must be removed for impurity control. Usually, the elements that control this bleed volume are either arsenic or nickel. The bleed volume is based on the quantity... 

The refinery blend contained a variety of light olefins, and contaminants (e.g., butadiene, oxygenates, sulfur) which are known to produce significant catalyst deactivation. These experiments were performed in a continuous, automated reaction/regeneration system... 

Decontamination of conventional wounds in a contaminated environment continues to be a major concern. Researchers have looked at the effect of bleach decontamination on damaged skin exposed to CWAs. Gold et al. (1994) evaluated the effects of water or diluted bleach (0.5%) as a wound decontaminant 2 min after hairless guinea pig was exposed to sulfur mustard. The study found that 0.5% hypochlorite and even water soaking for 5 min in a wound contaminated with sulfur mustard (20 mg/kg) cause greater necrosis than when no decontamination was carried out. This does not mean that the wound should not be decontaminated but rather that bleach soaking in the wound is not the route to decontaminant. 

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