Acid regeneration, flux regeneration, and acid neutralization systems represent the logical completion of a hot-dip galvanizing plant. With them, it is possible to significantly improve both the environmental impact and the production efficiency of the galvanizing line. The industry needs to renew its image, and the logic of environmental respect is the main path to enhancing social reputation.
Another remarkable advantage of introducing regeneration and neutralization units within your company pertains to significant cost savings achieved through the reduction of disposals.

Similarly, in the case of the regeneration of spent acids, the resulting production of ferrous sulfates, potent soil fertilizers, serves as an excellent example of a circular economy. The added value brought by the decrease in the ecological footprint allows galvanizing to emerge in certified paths of nature preservation; therefore, these units cannot be missing in modern plants.

Spent flux regeneration units

This process involves recycling the fluxing solution in a closed-circuit reprocessing unit. By adding hydrogen peroxide and ammonia, the iron in the solution is separated as non-hazardous iron hydroxide sludge, which can be easily disposed of in authorized solid waste dumps. The fluxing tank solution undergoes a sequence of steps, including oxidizing, neutralizing, sludge settling, and filter press to clear it.

The pH of the solution is automatically monitored and adjusted with the appropriate alkaline reagent. Simultaneously, redox levels are checked to dose the correct amount of hydrogen peroxide for iron oxidation, resulting in precipitation of ferric hydroxide in the sludge settling tank.
The filter press separates solid sludge from clear flux solution, which is returned to the fluxing tank for pretreatment operations. This unit works automatically, with periodic manual unloading of the sludge from the filter press.

Highlights

Control of iron content
Iron content in the fluxing solution is kept under 5g/l (0.667oz/gal) concentration.

Zinc saving
By reducing the iron content in the flux, less dross and ash are produced leading to a lower zinc consumption.

Enhanced quality
A cleaner zinc bath leads to an improved quality of finished products.

Versatile

Spent acid regeneration units

The acid regeneration unit recovers hydrochloric acid from spent acid and pickling solutions. Differently from common regeneration processes, sulfuric acid is used as reagent. The regenerated acid is free of contaminants such as sulfates, iron, and zinc. The evaporation unit of the equipment operates under a strong vacuum.

The by-product of the regeneration process is ferrous sulfate, potent soil fertilizer agent, which is produced as a solid crystal and separated through a filter press. This technology can handle a significant presence of zinc chloride in the spent pickling acid. The equipment is designed to work with storage tanks for both spent and regenerated acids.

Highlights

Sulfuric acid based cycle
H2SO4 is used as reagent for HCl recovery.

Great efficacy
Up to 95÷97% of hydrochloric acid in spent pickling solutions can be regenerated. HCl is recovered at 19÷21% concentration.

Green by-products
The reaction mainly generates hydrate FeSO4 (ferrous sulfate), a soil fertilizing agent.

Positive economic balance

Acid neutralization and water recycling units

The wastewater treatment process involves collecting and blending rinsing waters from tanks, neutralizing its acidic level adding them the right amount of spent acid and soda. The system operates even without the rinsing waters flow.

Afterward, oxidation converts certain compounds, settling separates solids, and filtration produces semi-solid sludge. This plant can handle waste liquors from galvanizing, recycling rinsing waters, and maintaining pH levels. It operates automatically and requires occasional manual sludge removal.

Highlights

Treatment of used hydrochloric acid
Primary scope is the treatment of the exhausted solution of HCl acid from pickling destined to disposal.

Versatile
The plant is capable to treat spent acid with different concentrations of dissolved iron and free acidity (typically: 130÷170g/l or 17,37÷22,71oz/gal of iron and 50÷30g/l or 4÷6.6oz/gal of free acidity).

Reliable
By means of the neutralization plant, iron and other metals dissolved in acid precipitate in hydroxide form; soda is used to neutralize the acidity, reaching the right pH for the hydroxide compound to precipitate.

Water production
Produced water, with high salt content, can be used or treated differently.