Q5 Is the system safe?

Isn't it dangerous if combustible gas leaks?

Unless airtightness is maintained in moving parts and other locations where combustible gas exists, gas leakage can occur.

A feature of our fluidized-bed gasification and melting system configuration is that the gasifier and melting furnace use no moving parts. When there are no moving parts, airtightness is maintained and there is no gas leakage in such locations. Our system also uses an airtight structure for the feed inlet, which prevents gas leakage or air infiltration into the furnace.

Other measures taken are:

• Negative-pressure control in the furnace to prevent leakage of pyrolysis gas
• In the event of a gas leakage, a combustible gas detector placed nearby the gasifier detects any leakage, an alarm will be sounded to alert workers, and the feeder and other equipment will shut down; also, sufficient space around the gasifier allows ventilation

Can't combustible gas cause an explosion?

An explosion is a rapid combustion reaction that occurs when certain concentrations of combustible gas and oxygen are exceeded and there is an ignition source. It is therefore vital to ensure:(1) No occurrence of rapid combustion; and (2) Proper management of the concentrations of combustible gas and oxygen. Our fluidized-bed gasification and melting system is a safe system that has thorough safety measures in place and is structurally designed so that explosions do not occurs.

(1)Avoiding rapid combustion

• Partial combustion takes place in the sand layer within the gasifier, so an ignition source constantly exists. This ignition source provides a continuous, gentle combustion of the combustible gas so that no explosive rapid combustion occurs.
• The furnace top refractory surface temperature of the melting furnace is maintained at a certain temperature or higher as an ignition source. As with the gasifier, this ignition source creates a continuous, gentle combustion of the combustible gas so that no explosive rapid combustion occurs.

(2) Preventing gas explosions through management of the concentration of combustible gas and oxygen

• When the temperature of the sand layer is high, there is rapid progress in the pyrolytic decomposition of the combustibles, which tends to generate combustible gas in high concentration. The use of automatic control to keep the sand layer temperature between 500 and 600 ˚C prevents the rapid generation of combustible gas to keep the concentration of combustible gas in the furnace constantly below the explosion limit.

Gas Leakage and Explosion Prevention Measures