The use of microwave technology to reduce the vast stockpile of scrap or waste tires has proven to be a viable and economical method to recycle scrap tires into a number of profitable and environmentally friendly products. Though the microwave theory is essentially the same in organic reduction and destruction applications, the excitation of organic molecules and the applicator design is distinctly different. Essentially, applications involving tires and plastics are referred to as a reduction cycle, as tires and plastics are reduced to their constituent molecules and simpler compounds. The application of microwaves in soil remediation, is referred to a destruction process, since the organic contaminants are destroyed in a set of irreversible reactions. Although the contaminants are reduced to smaller, safer, EPA-acceptable compounds, the original contaminants themselves are destroyed.
Since organic materials are combustible, a continuous, pressurized, nitrogen purge gas is always present in the Envirowave applicator to prevent combustion. Stainless Steel, Type 304, is the material of choice for the applicator design in order to achieve maximum corrosion resistance and strength.
The applicator is purged with nitrogen gas to displace any air. Nitrogen gas is provided by a nitrogen generator, containing a molecular sieve, at a purity of approximately 98%. In the event of a purge gas failure, the microwave high voltage system is shutdown, while standby nitrogen continues to purge the applicator throughout the magnetron cool down cycle. The cool down cycle allows the magnetrons to cool down to a quiescent level specified by the manufacturer, as well as providing time for the material to cool below normal reaction temperatures.
Due to this complexity, the reactions are continuously monitored by a gas chromatograph to identify both the products of reaction and to determine the endpoint of the microwave reduction cycle. The reduction cycle is designed as a batch process for reasons of simplicity.
Upon exit from the applicator, the gas stream, with its products of reaction developed from molecular excitation by microwave energy, will flow through a water-cooled condenser. The heavier organic liquids will separate from the lighter gases and form light distillate oils and diesel fuels. The liquid fuels may be used in a combustion chamber for power generation or delivered to a petrochemical plant for use as a feedstock in plastics or gasoline/oil refining. The gases may be used for combustion in a gas turbine for power generation or simply flared to atmosphere.
In the reduction cycle the gas vapors - after an appropriate residence time in the applicator - are drawn through a liquid scrubber to remove undesirable contaminants in gas stream, such as Hydrogen Sulfide. The liquid scrubber contains common chemicals used in water treatment plants, such as Sodium Hydroxide and Sodium Hypochlorite. The water from the scrubber, containing the reaction products removed from the gas stream, may be discharged into the sanitary sewer system and complies with EPA requirements regarding effluents.
Time and date-stamped data is provided continuously during operation to assure consistent by-products, as well as compliance with all applicable federal and state environmental regulations.
Controlled pyrolysis has been used traditionally in the destruction of waste tires. Pyrolytic reduction is defined as the result of externally-applied heat to achieve the thermal decomposition of organic compounds in a reduced oxygen atmosphere.
Pyrolytic tire reduction involves the following steps:
Combustion of tires directly in a cyclone furnace or rotary
kiln results in the following problems:
The Envirowave Microwave Tire Reduction Process is non-pyrolytic
- requiring no externally-
The patented Envirowave process accomplishes complete recovery of the base constituents of the tires, through microwave conversion into high BTU gas and fuel oil. The carbon/carbon black and steel are also recovered. The Envirowave process results in the direct conversion of shredded scrap tires into a gas process stream, suitable for combustion in a prime mover, with only pre-treatment and removal of any Hydrogen Sulfide which may be present. The fuel oil is consistent with No. 2 and No. 4 Diesel Fuels specifications.
In summary, the operative words illustrating the primary differences between pyrolytic and non-pyrolytic processes are the introduction of externally-applied heat sources. Envirowave microwave generators do not apply heat, but introduce excitation at the molecular level, resulting in the development of heat. Initiation of the Envirowave Tire Reduction Process requires absolutely no heat. Propagation of tire reduction occurs almost instantly after application of microwave energy, converting the solid rubber to a gaseous vapor. Termination of the process occurs only after removal of the microwave excitation source.
The strengths of the Envirowave Tire Reduction Process lie
in the unique ability to convert an
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