DEMONSTRATION ON THERMAL TREATMENT OF ASBESTOS-CONTAINING
DISASTER WASTE FOR SAFE DISPOSAL AND ENERGY RECOVERY
Y. Kodera1*, K. Sakamoto2 and H. Sekiguchi3
1National Institute of Advanced Industrial Science & Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569 Japan
2Street Design Corporation, 6-9-30 Shimo-odanaka, Nakahara-ku, Kawasaki, Kanagawa 211-0041 Japan
3Tokyo Instute of Technology (Tokyo Tech), 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 Japan*e-mail: y-kodera@aist.go.jp; phone +81-29-861-8045, fax +81-29-861-8434
Abstract
A new treatment process was demonstrated to show the effective treatment of asbestos and energy recovery from wood
wastes at 5-ton/day scale in Kamaishi city, one of the most serious disaster area in the Great East Japan Earthquake.
The treatment facility consists of two core systems, a carbonizing furnace (Furnace No.1) and a fixed-bed steam
gasification furnace (Furnace No.2). The wastes contain asbestos with inorganic building materials, a flux for melting
asbestos, wood and plastics (mainly polyethylene). Asbestos-containing wastes were treated in Furnace No.1 at about
850 °C for the residence time about 15 min under partial-combustion conditions. Wood wastes gave charcoal withformation of hot flue gas. The resulting charcoal was gasified in Furnace No.2 to give water gas in the presence of superheated steam at about 900 °C, which was given in a heat exchanger of the flue gas from the Furnace No.1. Asbestos
with a flux was converted into a harmless powder and charcoal was converted into water gas, which was further used in adiesel engine to generate electricity.
Keywords: asbestos, carbonization, steam gasification, wood, waste

1. Introduction
Landfill has been a conventional disposal method ofasbestos-containing demolition wastes. Huge amountsof landfill capacity are already consumed in the disaster.
Considering the risk of asbestos emission from landfill
sites, some companies developed thermal transformationof needle-shape crystalline of asbestos into harmless
form usually under 1200 to 1500 °C. Some researchersand companies also reported a melting process at thelower temperature ranges using a flux containing alkaline
compounds.
Here we demonstrated a new energy-saving process for
melting asbestos by using combustion heat of wood andplastics in a first furnace. This process is also used for
producing a flammable gas in a second furnace by thestream gasification of charcoal, which was obtained
through partial combustion in the first furnace. Materialbalance and energy balance were calculated to compare
other types of thermal treatment such as pyrolysis.

2. Materials and Methods
Three types of wastes were used as a feed (Table 1).
Table 1. Sample components. (wt%)
Inorgatic Combustible
Moisturecontents
components
Wood
5.95
79.45
14.60
Building
60.87
22.46
16.67
materialPlastics
2.10
96.91
1.00
SampleThe asbestos contents of wastes of building material isshown in Table 2.
Table 2. Asbestos in building materials. (wt%)
Chrysotile
AmositeCrocidolite
Tremolite/Actinolite
11.0
18.0
15.5
1.4
Figure 1 shows a schematic diagram of the facility forasbestos treatment and energy recovery of the wastes.
Operation procedure is as follows:
1) Waste samples were shredded in a shredder
equipped with an air-tight shield.
2) In a carbonization furnace (Furnace No.1),
preloaded wood sample was ignited and the internal
temperature was maintained at about 850 °C under
the controlled air supply.
3) After mixed with a flux, the mixed samples of wood,building material and plastics were transferred to thefurnace No.1 through a screw feeder.
4) A solid residue of charcoal and ash from asbestoscontaining building material was continuously
discharged from Furnace No. 1 through a screwconveyer.
5) The solid residue was transferred to a fixed-bed
gasifier (Furnace No.2) that was heated at about
900 °C under the flow of super-heated steam.
6) The resulting water gas was supplied to a dualfueled engine to generate electricity.

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

FuelFuel

SteamCleaner
HEFluxPowerGenerator

AirFurnace
No.1

Waste

ElectricityFurnace
No.2

HESolidresidue

HC: heat exchanger

FilterFluegas

Dust

Figure 1. Schematic diagram of a treatment facility of disaster wastes

3. Results and Discussion
Each input materials are converted into the products inFurnace No.1 as Eqs. 1 through 3.
wood ➞ charcoal + combustion flue gas + steam (1)building material + flux ➞ ash(2)plastics ➞ combustion flue gas(3)Moisture in building material and plastics also gives
steam. Conversion of asbestos in the building material
into harmless ash proceeds under the conditions of thetemperature range over 850 °C and a reaction period ofabout 15 min. A screw conveyer for taking solid residue
out of Furnace No.1 were controlled to satisfy theconversion conditions with monitoring the temperaturesin the furnace.
Typical results of the demonstration were summarized inTables 3.
Table 3. Material balance of Furnace No.1 and 2
Input
OutputComponent
Rate,kg/h Component
Rate,kg/hWood
100.0
Solid residue
30.2
Building
22.9(ash andmaterialcharcoal)
Plastics (PE)
22.0
Flux
5.0
Water gas
43.7
Air from
999.6
Cumbustion
3,217.0
blowersflue gas
Steam
30.0
Intaken air
2,100.0
Total
3,279.5
Total
3,290.9
Asbestos in the building material were transformed into
harmless ash, which was confirmed by microscopic

analysis. In the analysis, no asbestos fiber was found in3000 samples. And asbestos was not found also in
combustion flue gas.
Solid residue containing charcoal (30.0 kg/h) and ash(15.3 kg/h) was supplied to Furnace No.2 through ascrew conveyer attached to Furnace No.1, and treatedunder a stream of super-heated steam at 900 °C. Hotflue gas from Furnace No.1 was used a heat source togenerate super-heated steam and for heating Furnace
No.2.
Water gas (54.4 kg/h) was obtained, and was supplied toa power generator. The gas composition was shown in
Table 4.
Table 4. Composition of water gas from Furnace No.2
Component
Content, volume %Hydrogen24.6
Carbon monoxide
5.9Nitrogen
41.4
Oxygen1.0Methane
0.3
The high Nitrogen content was probably due to thecombustion flue gas intaken from Furnace No.1 througha screw conveyer.

4. Conclusions
Disaster wastes containing building material withasbestos, wood and plastics were treated in two furnaces.
Volume reduction of wastes was achieved through partial
combustion followed by steam gasification. Asbestos
was converted into harmless power during live charcoalburning. No asbestos was found in solid residue and fluegas.

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013