GB/T 40298-2021 English PDF (GBT40298-2021)

This document specifies the relevant content of the disposal and recycling of slag from hot dip galvanizing of steel, such as the composition of zinc slag, the recycling and disposal of zinc slag, the selection of recycling methods, the recycling process, and the requirements of resource conservation and environmental protection.

GB/T 40298-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.99
CCS H 34
Technical specification for disposal and recycling of
slag from hot dip galvanizing of steel
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 1, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 5
4 Composition of zinc slag... 5
5 Recycling and disposal of zinc slag ... 5
6 Selection of recycling methods ... 6
7 Recycling process ... 6
8 Resource conservation ... 9
9 Environmental protection ... 10
Technical specification for disposal and recycling of
slag from hot dip galvanizing of steel
1 Scope
This document specifies the relevant content of the disposal and recycling of slag from hot dip galvanizing of steel, such as the composition of zinc slag, the recycling and disposal of zinc slag, the selection of recycling methods, the recycling process, and the requirements of resource conservation and
environmental protection.
This document is applicable to the disposal and recycling of zinc slag from hot- dip galvanizing of steel. The disposal and recycling of zinc slag produced by steel’s hot-dipping Zn-Al, Al-Zn, etc., can refer to this document to implement. This document does not apply to the waste generated in the process of solvent hot dip galvanizing, such as waste fusing agent, fluxing agent, and dust collected by the dust collecting (removal) devices and the gas flue. It also does not apply to zinc sludge produced by chemical electro-galvanizing, and the zinc- containing waste slag that is classified as hazardous waste.
2 Normative references
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this standard.
GB/T 470 Zinc ingots
GB/T 1175 Casting zinc alloys
GB/T 3185 Zinc oxide (Indirect method)
GB 12348 Emission standard for industrial enterprises noise at boundary GB 31574 Emission standards of pollutants for secondary copper, aluminum, lead and zinc industry
and be prevented from chemical corrosion. The storage floor shall be hardened. 6 Selection of recycling methods
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 Recycling process
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.
Figure 3 -- Process flow for preparing zinc oxide powder by an
evaporation method
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 Resource conservation
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.