2675
Upgrading Carbon from ASR-Char by Froth Flotation: Model
Development and Implementation
Gjergj Dodbiba, Yutaro Takaya, Ade Hidayat, Kazumi Otake
Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Japan
ABSTRACT: This study investigates froth flotation to recover hydrophilic carbon-containing particles from
automobile shredder residue char (ASR-char). Froth flotation, one of the main mineral processing methods, is
often used in many mineral processing plants. Currently, flotation conditions are optimized using any of the
reported kinetics models and experiments. Kinetic models have been developed to simulate the relationship
between the flotation time and the recovery of the valuable component in the concentrate. However, the grade
at an arbitrary time cannot be derived from the reported kinetic model. Therefore, this research aims to develop
a new kinetic model that can simulate the grade of valuable components in the concentrate. In addition,
flotation experiments were conducted to acquire the data to be input and then verify the proposed kinetic
model. Three different-sized fractions of ASR-char were prepared and used as test samples for the investigation.
This study found that the new kinetic model can simulate the relationship between the flotation time and the
grade of carbon in the concentrate. The results suggested maintaining a relatively short flotation time ensures
a high-grade carbon product. The main advantage of the developed model is that it can evaluate the flotation
efficiency from the viewpoint of the recovery and the grade of the valuables in the concentrate.
Keywords: Flotation, Kinetics model, Grade, Char
INTRODUCTION
In the scrap processing industry, automobiles, home appli-
ances, and other obsolete equipment are generally subject
to physical separation to recover ferrous and non-ferrous
materials for recycling. Recent improvements in scrap pro-
cessing technologies have been made, including thermal
treatment, particularly carbonization, which is commonly
practiced in Japan (Sakai et al., 2014). A carbonization
treatment process can recover a considerable amount of
material and energy from scrap materials. However, unfor-
tunately, some recycling facilities in Japan are troubled by
the amount of carbon-containing solid residue produced,
known as the automobile shredder residue char (ASR-
char) (Forton et al., 2006). ASR-char is a heterogeneous
mixture of carbon and other materials such as metals, glass,
etc. ASR-char is usually sent to the landfill without further
treatment. The reason is that the particle size of the ASR-
char is small (generally less than 1 mm), and its high ash
content makes it challenging to utilize the char as a solid
fuel (Kurose et al., 2006 Santini et al., 2015).
In this study, the ASR-char has been treated by
froth flotation to separate the hydrophilic ash from the
hydrophobic particles (i.e., carbon-containing particles).
Generally speaking, froth flotation is a beneficiation tech-
nique for recovering valuable concentrates from various
ores (Laskowski, 2001). It utilizes the difference in sur-
face characteristics of mineral particles to recover valuable
Upgrading Carbon from ASR-Char by Froth Flotation: Model
Development and Implementation
Gjergj Dodbiba, Yutaro Takaya, Ade Hidayat, Kazumi Otake
Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, Japan
ABSTRACT: This study investigates froth flotation to recover hydrophilic carbon-containing particles from
automobile shredder residue char (ASR-char). Froth flotation, one of the main mineral processing methods, is
often used in many mineral processing plants. Currently, flotation conditions are optimized using any of the
reported kinetics models and experiments. Kinetic models have been developed to simulate the relationship
between the flotation time and the recovery of the valuable component in the concentrate. However, the grade
at an arbitrary time cannot be derived from the reported kinetic model. Therefore, this research aims to develop
a new kinetic model that can simulate the grade of valuable components in the concentrate. In addition,
flotation experiments were conducted to acquire the data to be input and then verify the proposed kinetic
model. Three different-sized fractions of ASR-char were prepared and used as test samples for the investigation.
This study found that the new kinetic model can simulate the relationship between the flotation time and the
grade of carbon in the concentrate. The results suggested maintaining a relatively short flotation time ensures
a high-grade carbon product. The main advantage of the developed model is that it can evaluate the flotation
efficiency from the viewpoint of the recovery and the grade of the valuables in the concentrate.
Keywords: Flotation, Kinetics model, Grade, Char
INTRODUCTION
In the scrap processing industry, automobiles, home appli-
ances, and other obsolete equipment are generally subject
to physical separation to recover ferrous and non-ferrous
materials for recycling. Recent improvements in scrap pro-
cessing technologies have been made, including thermal
treatment, particularly carbonization, which is commonly
practiced in Japan (Sakai et al., 2014). A carbonization
treatment process can recover a considerable amount of
material and energy from scrap materials. However, unfor-
tunately, some recycling facilities in Japan are troubled by
the amount of carbon-containing solid residue produced,
known as the automobile shredder residue char (ASR-
char) (Forton et al., 2006). ASR-char is a heterogeneous
mixture of carbon and other materials such as metals, glass,
etc. ASR-char is usually sent to the landfill without further
treatment. The reason is that the particle size of the ASR-
char is small (generally less than 1 mm), and its high ash
content makes it challenging to utilize the char as a solid
fuel (Kurose et al., 2006 Santini et al., 2015).
In this study, the ASR-char has been treated by
froth flotation to separate the hydrophilic ash from the
hydrophobic particles (i.e., carbon-containing particles).
Generally speaking, froth flotation is a beneficiation tech-
nique for recovering valuable concentrates from various
ores (Laskowski, 2001). It utilizes the difference in sur-
face characteristics of mineral particles to recover valuable