Chrome treatment

Chromate versus Non-Chrome Treatment of Refinery Cooling Tower Effluents... 

This problem can easily be solved by using stabilized aluminum pigments. Pigments inhibited with phosphoorganic compounds, chrome treatments or by organic or inorganic encapsulation are commercially available. Further possibilities are published in Ref [5.183]. 

CfiHsNjOs. Red needles m.p. 168-169°C. Soluble in dilute acids and alkalis. Prepared by reduction of picric acid with sodium hydrogen sulphide, ft is used for the preparation of azodyes, which can be after-chromed by treatment with metallic salts owing to the presence of a hydroxyl group ortho to the amino-group. 

Chrome-complexed fluorochemicals, as weU as fluoropolymers, are widely used products. The compositions are proprietary. Fluorochemicals provide a high degree of water repeUency as weU as repeUency to aqueous stains, oUs, grease, and oilhorne stains. TraditionaUy, treatments are appUed duting a dmm process ia which about 30 min are required for flUl penetration of the leather to occur. Products are also avaUable for appUcation with sprayiag equipment and roU coaters. 

Mordant Dyes. MetaUizable azo dyes are appHed to wool by the method used for acid dyes and then treated with metal salts such as sodium chromate [7775-11-5] sodium dichromate [10588-01-9] and chromium fluoride [1488-42-5] to form the metal complex in situ. This treatment usually produces a bathochromic shift ia shade, decreases the solubUity of the coloring matter, and yields dyeiags with improved fastness properties. The chromium salts can be appHed to the substrate before dyeiag (chrome-mordant or chrome-bottom method), together with the dye ia a single bath procedure (metachrome process), or as a treatment after dyeiag (afterchrome process). 

Treatment of Industrial Wastes. The alkaline nature and inexpensive price of lime make it ideal for treatment of acid waste Hquors (6), including waste pickle Hquids from steel plants, wastes from metal plating operations, eg, chrome and copper plating, acid wastes from chemical and explosives plants, and acid mine wastewaters. 

Ohio, high carbon ferrochromium is leached with a hot solution of reduced anolyte plus chrome alum mother Hquor and makeup sulfuric acid. The slurry is then cooled to 80°C by the addition of cold mother Hquor from the ferrous ammonium sulfate circuit, and the undissolved soHds, mostiy siHca, are separated by filtration. The chromium in the filtrate is then converted to the nonalum form by conditioning treatment for several hours at elevated temperature. 

The metal obtained by this process contains less iron and oxygen than that from the chrome alum electrolyte. The gas content is 0.02 wt % O, 0.0025 wt % N, and 0.009 wt % H. If desired, the hydrogen content can be lowered still further by a dehydrogenation treatment. 

Environment Water treatment was chrome-zinc for the first 6 years and orthophosphate for the next 5 years. Free residual chlorine 0.1-0.3 ppm filtered orthophosphate 10-17 ppm, 6-8 cycles calcium <200 ppm, 200°F (93°C), pressure 50 psi (0.3 MPa). 

This means that parts must be ordered in advance for the turnaround and other work must be planned so that the whole operation may proceed smoothly and without holdups that could have been foreseen. This usually means close collaboration with the manufacturer or consultant and the OEM (or specialty service shop) so that handling facilities, service men, parts, cleaning facilities, inspection facilities, chrome plating and/or metaliz-ing facilities, balancing facilities, and some cases even heat treatment facilities, are available and will be open for production at the proper time required. This is the planning, which must be done in detail before the shutdown with sufficient lead-time available in order to have replacement parts available at the job site. 

Shafts are made of material ranging from medium carbon to low alloy steel and are usually heat treated. Shafts were originally made of forgings for the compressors in process service. But because of the availability ot high quality material, hot rolled bar stock has been used for shafts up to S inches in diameter. Bar stock shafts are given the same heat treatment and quality control as forgings. Many of the process users prefer a low alloy, chrome-moly-nickel material for shafting, particularly for compressors in critical service. 

Rotor material in all cases is low alloy steel with an appropriate heat treatment to match the stresses imposed by the blades and rotor weight The rotor is generally manufactured from a forging with the material being a chrome-molybdenum alloy such as AISI 4140 or AISI 4340. 

Yourfacility is involved in chrome plating of metal parts, which produces an aqueous plating waste that is treated on-site to recover chromium sludge. The effluent from the on-site treatment plant, which contains chromium compounds (a listed toxic chemical), is piped to a POTW. The chromium sludge is transferred to an off-site, private ly owned firm tor the recovery of the chromium. 

Like the analogous chrome alums they find use as mordants in dying processes. The sulfate is the cheapest salt of Fe and forms no less than 6 different hydrates (12, 10, 9, 7, 6 and 3 mols of H2O of which 9H2O is the most common) it is widely used as a coagulent in the treatment not only of potable water but also of sewage and industrial effluents. 

The chemical supplier can also identify any regulated pollutants in the facility s treatment chemicals and offer available substitutes. The federally regulated pollutants are cyanide, chrome, copper, nickel, zinc, lead, cadmium, and silver. Local and/or state authorities may regulate other substances, such as tin, ammonia, and phosphate. The current status of cyanide and noncyanide substitute plating processes is shown in Table 9.11... 

As a result of variation shown in toxicity, the evaluation of technologies applicable for discharge control, and treatment by some compounds within the industrial chemicals, the SIC 281 groups are further subdivided into 11 subcategories.23 They are aluminum fluoride, chlor-alkali, chrome pigments, copper sulfate, hydrofluoric acid, hydrogen cyanide, nickel sulfate, sodium bisulfate, sodium... 

Some other types of treatment processes can be employed in the chrome pigment industry in order to achieve safer industrial practices in terms of pollution. Processes such as ion exchange, biological oxidation, and use of glass for filtration before settling have potential application in this industry. 

FIGURE 22.7 General wastewater treatment process flow diagram at a typical chrome pigment plant. 

Mordant dyes are notoriously troublesome from the viewpoint of colour matching because the hue of the chromium complex usually differs greatly from that of the unmetallised parent dye (section 5.4.1). If other metal ions are present in the treatment bath or on the fibre during chroming, the colour obtained is likely to differ from that of the pure chromium complex. Certain important chrome dyes, including Cl Mordant Black 11 (3.29) and Black 17 (3.30), are particularly sensitive to traces of iron or copper. The hue of the black dyeings obtained is redder in the presence of copper and browner with iron contamination. The fastness to light and wet treatments may also prove inferior under these conditions. Even certain 1 2 metal-complex acid dyes show similar effects in the presence of these impurities,... 

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