Pickle liquor

Use closed-loop systems for pickling regenerate and recover acids from spent pickling liquor using resin bed, retorting, or other regeneration methods such as vacuum crystallization of sulfuric acid baths. 

Tankwater, Bright dip acid (phosphoric), Cyanide rinse hath, Pickle Liquor, Sodium AJuminate Liquor, N.S.S.C. Liquor, Kraft Liquor, Soda Liquor, Sulfite Liquor, Stillage, Corn Syrup, Gelatin, Salt, Soybean Oil, Steepwater, Sugar, Whey, Mercerizing Caustic, Nylon Salt, Rayon Spin Bath, and Sodium Sulfate. 

California Steel Industries, Inc., located in Fontana, CA, reclaimed wastes to increase profits and address water use issues. The facility, a steel mill, is situated in an area that does not have a ready supply of process water. Also, the offsite recycling facility used to dispose of spent process pickle liquor was soon to become unavailable. As a result of these concerns, the company constructed an onsite recycling facility designed to recover ferrous chloride for resale and to reuse water and hydrogen chloride for use in steel processing operations. Environmental benefits include the recovery and resale of 20 to 25 t/d of ferrous chloride, 13,440 L/d of hydrogen chloride, and 49,200 L/d of water. In addition, corporate liability was minimized because spent liquor was no longer sent to a disposal facility. 

Cleaned steel products (e.g., sheets, plates, bars, pipe) Process wastewater containing mill scale, oils, other pollutants, and low levels of metals Wastewater sludge Air pollution control (APC) dust Spent pickle liquor (K062)... 

Spent pickle liquor rinse water sludge... 

Reuse minimal K062, Spent pickle liquor Hazardous components lead, nickel, chromium Total generation about 6 million t/yr Reuse some recycled... 

Pickling done before coating may use a mildly acidic bath such spent liquor is not considered hazardous. Waste pickle liquor flows typically range between 10 and 20 gal/t of pickled product. Rinsewater flows may range from less than 70 gal/t for bar products to more than 1000 gal/t for certain flat-rolled products. The principal pollutants in rinsewater include TSS, dissolved iron, and metals. For carbon steel operations, the principal metals are lead and zinc for specialty and stainless steels the metals include chromium and nickel.15... 

Spent pickle liquor in the acid pickling wastewaters is listed as hazardous waste K062, regulated under RCRA, as it contains considerable residual acidity and high concentrations of dissolved iron salts.2 Exhausted pickling baths are mainly composed of nitrate (150 to 180 g/L), fluoride (60 to 80 g/L), iron (III) (30 to 45 g/L), chromium (III) (5 to 10 g/L), and nickel (II) (3 to 5 g/L). 

Spent pickle liquor is considered a hazardous waste (K062) because it contains considerable residual acidity and high concentrations of dissolved iron salts. For example, spent pickle liquor and waste acid from the production of stainless steel is considered hazardous. The hazardous constituents in K062 are lead, nickel, and hexavalent chromium. Waste pickle liquor sludge generated by lime stabilization of spent pickle liquor is not considered hazardous unless it exhibits one or more of the characteristics of hazardous waste. An estimated 6 million tons of spent pickle liquor are generated annually in the U.S.1... 

Flydrochloric acid regeneration. This process is used to treat the spent pickle liquor containing free hydrochloric acid, ferrous chloride, and water that is obtained from steel finishing operations. The liquor is concentrated by heating to remove some of the water, followed by thermal decomposition in a roaster at temperatures (925 to 1050°C) sufficient for complete evaporation of water and decomposition of ferrous chloride into iron oxide (ferric oxide, Fe203) and hydrogen chloride (HC1) gas.19 The iron oxide is separated for offsite recovery or... 

The spent pickling liquor is called waste pickling liquor (WPL), which must be properly treated for disposal or reuse. Wastewaters from pickling include acidic rinse waters, metallic salts, and waste acid. WPL is considered a hazardous waste by the U.S. Environmental Protection Agency (U.S. EPA). 

Lime or alkaline substances are used to neutralize the waste pickle liquor. In addition, 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS),... 

Through the late 1980s, spent pickle liquor was traditionally land disposed by steel manufacturers after lime neutralization. The lime neutralization process raises the pH of the spent acid and makes heavy metals in the sludge less likely to leach into the environment. Today, however, some of the spent pickle liquor can be recycled or regenerated on-site by steel manufacturers.5... 

The waste pickle liquor, rinse water discharges, and fume scrubber effluent can be combined in an equalization tank for subsequent treatment. Basically, three methods are used to treat the WPL ... 

All pipes and fittings are transported to the pickling process in which an overhead crane is used to lower them into an acidic pickle liquor solution that chemically cleans and etches the black oxide surface layer resulting in a clean, rust-resistant pipe. 

An acid regeneration system has been installed to regenerate spent pickle liquor for reuse on-site. 

Waste pickle liquors from these operations can often be of use to sanitary waste treatment systems for phosphate control and sludge conditioning. Some industrial firms can use spent process waste from pickling operation. Iron in the waste is used as a coagulant in wastewater treatment systems.1415... 

The above equation constitutes the theoretical or stoichiometric amount of liquid hydrochloric acid needed to pickle 1 ton of steel. Stoichiometric means as per chemical formula, using absolutely pure materials with no losses.16 In practice, it is not possible to use up all the acid in the pickle tank if pickling is to be complete in any acceptable time. Depending on the pickling equipment, between 70% and 80% of the free acid will be used up in dissolving the scale, and 20-30% will remain as free acid in the spent pickle liquor.16... 

In a steel product manufacturing plant involving acid pickling operation, disposal of hazardous metal sludge is the most expensive engineering task, and treatment of pickling liquor and rinse water is the second most expensive engineering task. 

Mahmoud, M. H. H. Barakat, M. A. Utilization of spent copper-pickle liquor for recovery of metal values. Renew. Energy 2001, 23, 651-662. 

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