FAQ: PROCESS

Question: If we treat 1 ton of used tires, how much electricity (total) will be generated from the syngas and how much of that electricity will be used to process the tires?

Answer: Based on 40% efficiency of conversion to electrical energy, tires will generate 3,480Kwh of electricity per ton of tires processed. The processing of tires requires 2000 Kwh of electricity. Therefore, the amount of excess electricity produced per ton of tires is 1480Kwh.

Question: What is the inner furnace pressure during actual operation and non-operation?

Answer: The system operates at a slight negative pressure whether processing waste or idling. This slight vacuum is created by a fan that moves the off-gas through the gas treatment system.

Question: During the process of putting waste into the PEM™ system, is there any danger? (For example, such as an explosion or leak or anything of that nature.)

Answer: The PEM™ system operates under a slight vacuum to avoid leaks of energetic gasses from the process chamber while waste is put into the PEM™ chamber. Also, the waste entry mechanism includes an "air-lock" type of device where nitrogen is injected to displace air. The waste entry system operates under a small positive pressure, provided by the flow of nitrogen, to provide added assurance that energetic gases will not escape from the PEM™ while the waste entry port is open for the introduction of waste into the PEM™. These and other controls on the system assure continued safe operation.

Question: How high is the temperature in the process vessel outside the plasma zone?

Answer: 1100 to 1400 degrees Celsius.

Question: How large is the plasma arc zone in a Model 4 PEM™ processing ash?

Answer: In a Model 4 PEM™, the plasma zone is typically about 45 cm in diameter.

Question: How far from the center of the plasma zone is the temperature high enough to melt fly ash?

Answer: About 22 cm. Note: these measurements do not apply to a PEM™ system of any other size. The plasma zones for larger capacity PEM™ systems are larger than in the Model 4 PEM™.

Question: When the waste entry port is open, what is the temperature of the inner furnace during that moment of time?

Answer: The system continues to operate at full power while waste is being introduced into the PEM™ chamber. The temperature at the core of the plasma arc is about 6000º to 10,000º Celsius. The PEM™ is designed to place the point of waste entry far enough above the plasma zone to assure a substantial reduction of the temperature at the point of entry. Also, the size of the plasma zone is controlled by the PEM™ control system to minimize the thermal effect on the refractory materials that surround the PEM™ chamber. The temperature at the point of entry can vary from 100º C to 400º C, depending upon the size of the PEM™ system and other variables such as the amount and type of waste that is already in the PEM™ and is undergoing transformation at or above the surface of the melt chamber.

Question:Is there any fly ash produced when waste is destroyed in the PEM™?

Answer: A small amount of particulate is carried into the gas cleaning system where it is removed from the syngas. In most systems, these solids can be cycled back into the process vessel.

Question: Is it possible to extract aluminum, which has a density of 2.7, from glass residue that has a density of 2 to 3?

Answer: No. most of the aluminum will remain in the glass. When aluminum is present in significant amounts, silicon metal will typically separate from the glass. Ferrous metals will separate from the glass if present in significant quantity.

Question: Can the metals captured by a PEM™ be separated by commercial recyclers or can such a mixture be used by an electric arc furnace to produce steel?

Answer: Yes. The value of this mixture of metals increases when the variety of metals present is minimized.

Question: Can the glassy residue be used as a substitute for the aggregate in concrete or other construction applications?

Answer: Yes. The glassy residue meets leachability requirements for protection of the environment and meets physical requirements for use as aggregate in many construction applications.

Question: Will it be safe to use the concrete in construction of buildings? Will it be affected by the acidity/alkalinity of the cement? Will it pose any safety problems?

Answer: The aggregate is essentially inert and will not be affected by the normal acidity/alkalinity of cement. It is possible to produce aggregate by crushing the vitrified residue or by fritting the glass by pouring it through water as it exits from the PEM™

Question: What is the temperature of the cooling water?

Answer: The cooling water system can be operated at about any temperature desired above the temperature of the supply water.

Question: How much boiled water can a PEM™ produce from the cooling water system per ton of municipal waste?

Answer: Only 18 pounds per hour. Operation of the cooling system at a temperature high enough to boil water is not recommended.

Question: How much boiled water can a PEM™ produce if the syngas is used to fire a boiler?

Answer: Conversion to steam is highly efficient. One ton of MSW will produce 1.6 tons of steam.

Question: Is the water from the gas scrubber system recirculated? If not, what is done with the scrubber water?

Answer: Water from the scrubber system is recirculated. However, in order to control the buildup of soluble solids, a controlled volume of water is removed from the scrubber while the PEM™ is processing ash. For a Model 4 PEM™ processing 2 tons of high chloride MSW incinerator fly ash per day, the volume of water released from the scrubber system will be approximately 200 liters per day.

Water removed from the scrubber system will typically contain 0.5% to 5% of halogenated salts, depending upon the concentration of halogen salts in the incinerator ash. These salts can be managed as soluble sodium salts or calcium salts.

Question: What is the composition of the scrubber water after use and does it require further treatment?

Answer: The scrubber water typically contains salts of chlorine and sulfur. Trace amounts of some volatile metals, such as mercury and cadmium may also be present. The scrubber system is designed to separate these metals in their elemental form from the scrubber water. The levels of salts and trace metals in the scrubber water are typically acceptable for release to private or municipal waste water treatment systems.

Question: After waste enters the PEM™, how long does it take until the residue from that waste comes out?

Answer: The processing of ash is a continuous operation. Molten glass residue will be removed from the PEM™ as long as waste is entering the PEM™. The vitrified material exits from the PEM™ about 1 hour after it enters the system.

Question: When no waste is being fed into the PEM™, do you turn off the electrical power?

Answer: The PEM™ system is electrically heated and operates in a non-oxidizing atmosphere. When no ash is being fed, the plasma heating mechanism is turned off. However, the joule heating of the melter is continued. This requires a very low amount of energy to maintain the glass in a molten state.

Question: How many hours of operation are required each day to process 2 tons of incinerator ash?

Answer: The Model 4 PEM™ can process 6 tons of ash per 24 hour day. Therefore, 2 tons of incinerator ash can be processed in 8 hours. In processing fly ash, an equal volume of bottom ash must be added.

Question: Does an operator need to be present at all times when the PEM™ is processing ash?

Answer: No. The system is highly automated and is equipped to signal a pager worn by the operator in the event that any operating parameter goes outside of the acceptable limits.

Question: How many hours does the operator need to be present?

Answer: The operator generally needs to be present for a total of 2 to 4 hours per 8 hour shift. Simplicity of operation and computer control minimize operator time and cost. However, the operator must be available at any time waste is being processed.

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