The impact of hot galvanising on ecology

Gradina Cink applies BAT (Best Available Techniques) in its operations. BAT represents the most effective and advanced techniques, processes and practices that are available and economically feasible to reduce emissions of pollutants, protect natural resources and preserve the environment, taking into account technical, economic and other relevant factors.

BAT is developed and updated based on the latest developments in technology and scientific research.

Our company takes care of knowledge and information sharing among employees. For this reason, the management continuously holds training sessions, and those in occupational health and safety and ecology are crucial.

Hot galvanised elements are protected against corrosion. The hot galvanising process applies a layer of zinc to the metal surface, so corrosion will first appear on the zinc instead of the steel. This is called zinc sacrifice, and the zinc becomes the sacrificial metal that will corrode before the metal underneath can corrode.

It extends the life of metal elements and prevents their deterioration. This affects the global reduction in the production of steel and steel elements, as well as the total reduction of other resources, the reduction of emissions of harmful substances into the environment, and the consumption of energy used in obtaining and processing steel.

Waste is generated as hard zinc and zinc ash during the galvanising process. However, these waste materials are recycled, and zinc is extracted from them and reused. Recycled zinc is used for various purposes in construction, electronics, automotive, pharmaceutical and other industries.

When immersing the elements in the zinc melt, various particles are released into the air as a result of combustion. For this reason, a purification device is used – a white smoke filter. This device is extremely efficient and removes contaminating elements from the air, from powdery substances to gaseous inorganic compounds. Contaminant contents in the form of fine powder are waste and, as such, are handed over to authorised companies with technologies for their storage and processing. The white smoke filter installed in our factory uses a special filtration technology, which purifies the air to a significantly lower level of particles than that prescribed by law.

Chemical preparation is a phase that precedes the process of immersion in molten zinc. The elements are degreased, cleaned and prepared by immersion in a flux solution. The chemical preparation phase takes place in tubs in a closed chamber, and each tub has independent suction lines that prevent air pollution and protect employees’ health. Vapours from the chemical preparation phase are taken to the purification device – a wet scrubber. The wet scrubber is a device that uses a stream of water, and with the help of liquid dispersion, the acidic vapours fall and are retained in the liquid at the bottom of the device. When the amount of particles in the water of the purifier reaches a certain level, the contaminated water is used to replenish the level of individual tubs as part of chemical preparation. Thus, the acidic vapours remaining in the purifier liquid do not represent waste liquid but are recirculated in the process.

Every step and process in our plant, which follows the hot galvanising service, is monitored with the help of the state-of-the-art program and additional software tools. This minimises human factor errors, as a unique software system enables monitoring.

It is also worth mentioning that no wastewater is generated during all stages of the hot galvanising process. After the end of their useful life, new liquids are formed through the chemical preparation of the elements, and the used liquids and resulting sludge are shipped to authorised operators. Most of this waste is recycled, and acids are regenerated by special methods and systems.