GB/T 40298-2021Technical specification for disposal and recycling of slag from hot dip galvanizing of steel (English PDF)

6.1 Production of zinc alloy ingots for casting

When using zinc slag to produce the raw material ingots for zinc alloy castings in accordance with the requirements of GB/T 1175, it is advisable to use liquating and refining treatment; remove most of the oxidized impurities, iron-aluminum and iron-zinc compounds in the zinc slag; and produce a zinc alloy melt with low impurities. The impurity content shall meet the requirements of GB/T 1175.

6.2 Production of zinc ingots

When using zinc slag to produce high-purity zinc ingots in accordance with the requirements of GB/T 470, it is advisable to use zinc alloy melt after liquating and refining treatment; carry out further distillation treatment; collect and condense the zinc vapor to produce high-purity zinc ingots. The purity shall meet the requirements of GB/T 470.

6.3 Production of zinc oxide powder

When using zinc slag to produce zinc oxide powder according to the requirements of GB/T 3185, it is advisable to use the zinc alloy melt after liquating and refining treatment, and do further evaporation treatment in the aerobic state to produce zinc oxide powder. The purity shall meet the requirements of GB/T 3185.

7.1 Liquating and refining treatment

The zinc slag's liquating and refining treatment methods are as follows.

a) Melt and heat zinc slag to 580 °C ~ 600 °C by a liquating-refining furnace; introduce the refining gas for refining treatment. The oxides and iron-aluminum impurities in the zinc slag will float up to become top slag; remove the top slag from the melt and do further processing later. The iron-zinc compounds in the zinc slag will settle to become bottom slag, which remains at the bottom of the furnace; then separate it from the melt for further processing. The zinc alloy melt in the middle will have low impurity content.

7.4 Treatment of bottom slag from refining and residues from distillation and evaporation

The main components of bottom slag from refining and residues from distillation and evaporation are zinc, aluminum, iron, etc. They shall be processed by high-temperature distillation in a vacuum electric furnace. Heat it up to 1000 °C ~ 1050 °C in a vacuum state; make the zinc be evaporated into vapor; cool it in a vacuum state to form a zinc liquid; then treat it according to 7.2 or 7.3.

The high-temperature distillation residue is aluminum-iron alloy. Detect the alloy, after the impurity content meets the requirements (Zn<=3.5% and Pb<=0.5%), cool and cast it into ingots, which can be used as the raw materials of steel-making deoxidizer.

8.1 Zinc's total recovery rate

The total recovery rate of zinc shall reach more than 88%.

8.2 Water recycling rate

Adopt a reasonable water treatment system, the water recycling rate shall reach more than 95%.

8.3 Energy consumption

Select the type of energy under the premise of fully considering energy conservation. It is necessary to select high-efficiency thermal insulation materials, energy-saving fans, energy-saving pumps, and some supporting facilities, such as waste heat recovery and utilization, comprehensive flue gas treatment.

In the preparation of low-purity zinc alloy ingots by liquating and refining treatment, the comprehensive energy consumption shall be less than 30 kgce/t.

The comprehensive energy consumption in high-purity zinc ingots preparation with vacuum distillation method shall be lower than 1000 kgce/t. The comprehensive energy consumption of the preparation of zinc oxide by atmospheric distillation shall be lower than 800 kgce/t. […]