Mineral oils: processes and products – Asphalts – tars – pitches and resins; making – treating and... – Chemical modification of asphalt – tar – pitch or resin
Reexamination Certificate
1999-05-24
2001-06-12
Myers, Helane E. (Department: 1764)
Mineral oils: processes and products
Asphalts, tars, pitches and resins; making, treating and...
Chemical modification of asphalt, tar, pitch or resin
C208S045000
Reexamination Certificate
active
06245217
ABSTRACT:
The present invention relates in general to the field of pollution abatement equipment. Specifically, the present invention pertains to a regenerative thermal oxidation system for reducing atmospheric emissions of volatile, organic compounds associated with the manufacture, shipping and storage of asphalt materials.
BACKGROUND OF THE INVENTION
Asphalts are well known and widely used in a variety of products. While asphalts are primarily composed of high molecular weight hydrocarbons, they invariably contain minor amounts of low molecular weight hydrocarbons exhibiting substantial volatility. As such, the manufacture, storage and transportation of asphalt materials present opportunities for escape of such volatile, organic components (VOCs) into the atmosphere, as well as the accumulation of highly explosive vapors in storage facilities and processing equipment.
In view of the environmental and safety hazards such VOCs present, methods to control their accumulation and emission have been developed. Typically, these involve drawing the vapors into a flame incinerator where they are combusted. Unfortunately, the incineration of such VOCs by a flame burner is expensive, and the temperatures reached in such incinerators often favor the formation of undesirable nitrous oxides.
Although regenerative thermal oxidizers (RTOs) are well known and used in various industries for the treatment of effluent gas streams to reduce VOCs, their usefulness in conjunction with the manufacture, storage and transportation of asphalt has not previously been fully appreciated due, at least in part, to the failure of commercially available RTO devices to accommodate the relatively high content of condensable vapors or blowing distillate oil (BD oil) entrained in the gas stream drawn off from such operations. When asphalt vapors are introduced directly into an RTO unit, the BD oil contained in such streams quickly forms a layer of coke on the heat transfer elements of the RTO unit which reduces its effectiveness. As such, the frequent cleaning and/or replacement of the heat transfer elements in such units has previously rendered their use in conjunction with the manufacture of asphalt uneconomical. Although advances in this regard have been made by incorporating a cyclone separator upstream of the RTO unit to remove BD oils, such as in the BIOTOX systems commercially available from BIOTHERMICA, the performance of such separators at low or varying flow rates, or for removing particles of varying sizes, is less than optimum. Accordingly, a need exists for a RTO system capable of effectively removing the condensable oils and oxidizing the VOC's contained in asphalt vapors over a wide range of particle sizes and flow rates. This need is met by the invention described herein.
SUMMARY OF THE INVENTION
The present invention provides a regenerative thermal oxidation system especially adapted to reduce the VOC content of vapors associated with the manufacture, storage and transportation of asphalt. The RTO system comprises a separator to remove BD oils from the vapors, and an RTO unit to oxidize the VOCs contained in the vapors. The system is capable of effective operation at over widely varying flow rates which makes it ideally suited to intermittent use as may be encountered in connection with a truck loading station or a portable unit. Moreover, the separation unit of the system advantageously removes entrained or condensed oils from the vapor stream effectively over a wide range of particle sizes, which reduces fouling of the heat transfer elements of the RTO unit and reduces the formation of sulfur dioxide. Additionally, the RTO unit may be electrically powered, which reduces the nitrous oxide emissions below the levels typically encountered with flame incinerators.
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patent: 5573656 (1996-11-01), Santos
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Guy Drouin, Jean Gravel and Valya Papadopoullos, “VOC and COC Emission Control By Regenerative Thermal Oxidation”, Jun. 23,-28, 1996, pp. 1-10.
Biotox Regeneratie Oxidation Process, BPCO, EMCO Division, Ville LaSalle (Quebec) Canada, Process Data Sheets.
Sophie Kneisel, “R&D Equals Profits In Biotox Equation”,Consulting Engineer, Nov./Dec. 1994.
Carney Kenneth E.
Jenne Richard A.
Dottavio James J.
Eckert Inger H.
Myers Helane E.
Owens Corning Fiberglas Technology
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