Stripping specificity

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

The acacia trees produce gum arable only under adverse conditions, lack of moisture, poor nutrition, and hot temperatures. Gum arable is produced at wounded surfaces of the acacia trees. The wounds are generally produced deUberately in cultivated trees by stripping bark during the dry season. The gum is collected by hand over a period of several weeks with average yields of 250 grams per tree per year. Cmde exudates are hand sorted and exported before processing and milling to various specifications. 

In addition, the following ASTM Standard Specifications are for the Nb—lOHf—ITi—IZr alloy known commercially as C103 B652-92 Niobium—Hafnium AHoy Ingots B654-92 Niobium—Hafnium AHoy Foil, Sheet, Strip, and Plate B655-92 Niobium—Hafnium AHoy Bar, Rod, and Wine. 

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

Specifications for the principal LPG products are summarized in Table 4. Detailed specifications and test methods for LPG are pubHshed by the Gas Processor s Association (GPA) (3) and ASTM (4). The ASTM specification for special-duty propane and GPA specification for propane HD-5 apply to propane that is intended primarily for engine fuel. Because most domestic U.S. LPG is handled through copper tubing, which could fail if corroded, all products must pass the copper strip corrosion test. A test value of No. 1 represents a LPG noncorrosive to the copper. 

Both mono- and disodium phosphates are prepared commercially by neutralization of phosphoric acid using sodium carbonate or hydroxide. Crystals of a specific hydrate can then be obtained by evaporation of the resultant solution within the temperature range over which the hydrate is stable. For the preparation of trisodium phosphate, sodium hydroxide must be used to reach the high end pH because CO2 cannot be stripped readily from the solution above a pH of near 8. 

Because the ore quaUty is variable, large open-pit mining areas are first identified by general exploration specific mining strips are later identified by further exploration and testing. Surface mining methods are used. The overburden is drilled, blasted, and removed, and the waste from a given strip is dumped into a previously worked-out strip. After removal of the overburden, the exposed caUche is drilled, blasted, and loaded into 80-metric ton tmcks that dehver the ore to a transfer rail station for transportation to the plants. 

Process water streams from vinyl chloride manufacture are typically steam-stripped to remove volatile organics, neutralized, and then treated in an activated sludge system to remove any nonvolatile organics. If fluidized-bed oxychlorination is used, the process wastewater may also contain suspended catalyst fines and dissolved metals. The former can easily be removed by sedimentation, and the latter by precipitation. Depending on the specific catalyst formulation and outfall limitations, tertiary treatment may be needed to reduce dissolved metals to acceptable levels. 

Attack on metals can be a function of fuel components as well as of water and oxygen. Organic acids react with cadmium plating and 2inc coatings. Traces of H2S and free sulfur react with silver used in older piston pumps and with copper used in bearings and brass fittings. Specification limits by copper and silver strip corrosion tests are requited for fuels to forestall these reactions. 

Unreacted phosgene is removed from the cmde chloroformates by vacuum stripping or gas purging. Chloroformates of lower primary alcohols are distillable however, heavy-metal contamination should be avoided. As stated earlier, chloroformates generating a stable carbonium ion on decomposition, ie, secondary or tertiary chloroformates or henzylic chloroformates, are especially unstable in the presence of heavy metals and more specifically Lewis acids and, hence, should be distilled at as low a temperature and high vacuum as possible. 

Solvent extraction in batch or continuous systems is used to recover most of the residual oil from the presscake. Heptane, hexane, or a mixture of these solvents is used to recover the oil. The solvent-extracted presscake is steam stripped to recover solvent and a residual meal known as castor pomace, containing 1% residual oil. The solvent extracted oil is also processed for solvent recovery (qv). The oil from the extraction procedure is darker than the mechanically pressed oil and has a higher free fatty acid content. It is sometimes referred to as a No. 3 castor oil and is used for blending with higher quaUty oils that are well above No. 1 specifications. 

Sodium chlorite has also been used for treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans. Chlorine dioxide from chlorite is also useful for microbial and slime control in paper mills and alkaline paper machine systems (164,165). The use of sodium chlorite in textile bleaching and stripping is well known. Cotton is not degraded by sodium chlorite because the oxidation reactions are specific for the hemiceUulose and lignin components of the fibers. 

Eor use in paint strippers, one of its first appHcations, methylene chloride is blended with other chemical components to maximi2e its effectiveness against specific coatings. Typical additives include alcohols, acids, amines or ammonium hydroxide, detergents, and paraffin wax. Paint stripping formulations without methylene chloride have not as yet been shown to be as effective as those with methylene chloride. 

---