SMM Exclusive: Overview Of The Current Status And Prospects Of China’s Aluminium Ash Industry

Aluminium Ash Industry Overview

1.1 Definition and classification of aluminium ash

Aluminium ash, in a narrow sense, specifically refers to the infusible inclusions, oxides, additives and reactants that chemically react with the additives floating on the surface of the aluminium melt during aluminium smelting, aluminium alloy and secondary aluminium processing and production. In a broad sense, aluminium ash also refers to all solid waste related to electrolytic cell overhaul waste and flue gas dust collection ash from aluminium smelters. As an important solid waste in the aluminium industry, its compositions are very complex, mainly composing of Al, Cl, Na, and N, among other elements.

Aluminium ash is produced in all processes, including aluminium electrolysis, aluminium processing, and recycled aluminium processing. Its sources can be divided into three types: aluminium ash in the aluminium electrolytic smelting process, aluminium ash in the aluminium alloy casting process and aluminium ash in the processing of recycled aluminium.

According to the processing process of aluminium ash, it can be divided into primary aluminium ash and secondary aluminium ash. Primary aluminium ash is aluminium ash with metal aluminium extraction value. It mainly comes from primary aluminium, aluminium processing and recycled aluminium industries. It is generally gray-white. The main components are metal aluminium, alumina and some salts added during the smelting process. Its metal content is relatively high, between 20% and 70%. Among them, the primary aluminium ash content produced by electrolytic aluminium accounts for the highest proportion.

Secondary aluminium ash is the residue after extracting metallic aluminium from primary aluminium ash using physical or chemical methods. It is generally gray-black and mainly comes from electrolytic aluminium, recycled aluminium and independent aluminium ash processing companies. Compared with primary aluminium ash, the composition of secondary aluminium ash is relatively complex, and the content of metallic aluminium is lower, generally less than 15%, and the aluminium content is usually between 5% and 10%.

Sources and main chemical components of aluminium ash (unit: wt%)

Data source: SMM

1.2 Aluminium Ash Industry Value Chain

The entire process of the aluminium ash industry chain includes the production of upstream aluminium ash, the processing and terminal application of downstream aluminium ash, etc.

There are many ingredients that can be used in aluminium ash, such as metallic aluminium, alumina, fluoride salts, silica, calcium oxide and other substances. Therefore, resource utilization based on the property differences of different substances in aluminium ash is an important manifestation of maintaining or even increasing the value of aluminium ash. For example, secondary aluminium ash rich in alumina and fluoride salts can be processed to produce calcium aluminate powder and special cement. Secondary aluminium ash containing a certain amount of alumina, silica, etc. can be processed and used as Raw materials for the production of cement. Secondary aluminium ash containing aluminium hydroxide can be used as raw materials for processing water purification agents, etc.

Overview of China’s aluminium ash market

According to SMM statistics, China's primary aluminium ash production is expected to be 2.4 million mt in 2022. Affected by changes in the "solid waste to hazardous waste" policy, China's effective primary aluminium ash processing capacity dropped significantly in 2021, and a large amount of primary aluminium ash cannot be processed in a timely manner. As a result, the output of secondary aluminium ash dropped significantly.

The problem of aluminium ash treatment can be solved in the following ways: On one hand, companies currently equipped with primary aluminium ash treatment are adding secondary aluminium ash treatment capacity or plan to do so. By continuing the process, they will establish a complete solution to the harmless treatment of primary and secondary aluminium ash which is a full-process solution for resource utilization. On the other hand, the considerable potential value of aluminium ash has also attracted new companies to join. However, at present, hazardous waste treatment in domestic aluminium industry is still in its primary development stage. Mature aluminium ash treatment technologies and processes still need time to be perfected, and the resource utilization of aluminium ash has a long way to go.