Patent 4242084 Air pollution control and heat recovery system for industrial ovens

Patent 4242084

Air Pollution Control & Heat Recovery System for Industrial Ovens

This patent was developed for a brand new 55 gallon drum manufacturing plant.

Epcon had the responsibility to design and build 5 (five) Paint Curing Ovens; two (2) Three-Stage Heated Washlines; four (4) Dry-Off Ovens; and a Thermal Oxidizer.  This ingenious solution for air pollution abatement and heat recovery, utilized a single Thermal Oxidizer, by combining all the equipment into a single system.

Solvent-laden controlled exhaust from five (5) Ovens pass through a two-stage heat exchanger, built as part of the Thermal Oxidizer.  The preheated exhaust gases go through the Thermal Oxidizer’s combustion chamber where the VOC’s are destroyed to 99 % plus, and the heat is released to preheat the incoming exhaust. Secondary heat recovery is to generate high pressure hot water, at 270 °F for 6 stages of two (2) Washlines.  Heat Exchangers are used in the holding tanks and they heat the water to 140 – 150 °F. Hot clean exhaust, goes to Four (4) Burnerless Dryers.  And, the final exhaust goes to atmosphere.

A system of air pollution control and heat recovery is provided for an arrangement of industrial ovens, especially for drum manufacture. A plurality of paint bake ovens of various capacities, lengths and heat input are provided for multi-stage processing in the manufacture of drums. A supply of high temperature water is provided for multi-stage cleaning and rinsing in the manufacturing operation. The combined exhaust from all of the ovens at 25% LEL is preheated in a heat exchanger and then all of the combustible components are burnt off by passing through the flames of an incinerator grid burner. The effluent from the burner first passes through the heat exchanger to preheat the oven exhaust gases and then through hot water coils to provide all of the necessary hot water for the system. High pressure hot water (275 °F) is provided in this heat exchange operation. The hot gasses from the last heat exchanger, completely free of combustible contaminates, are mixed with fresh air to supply hot air for the dryers used in the process. There is a substantially complete recovery of heat and the gasses discharged to atmosphere meet air quality standards.

The reason for the patent is there is only one (1) Thermal Oxidizer for five (5) Ovens, versus five (5) Thermal Oxidizers. Tremendous Capital Cost Savings in not having to put in separate, individual Thermal Oxidizers and eliminating multiple burners, gas trains, and controls. In addition, compressive heat recovery, which resulted in big savings in fuel consumption.

Overall, there is only 1MBTU gas consumption, so approximate consumption-related savings of approximately 47MBTUs.  

Preheat Exchanger saves approximately 4MBTUs per hour.

Free hot water is generated for the washlines, with a cost savings of approximately 12MBTUs.

Free hot air to the four (4) dryers.  Gas savings of approximately 6MBTUs.

Air Pollution compliance benefit of the system at 98%+ DRE (destruction and removal efficiency) has been achieved year after year.

The system operated successfully for approximately 35 years before modifications. This patent was a cornerstone for Epcon’s future success in the industry, but was also expanded upon and utilized in other applications, achieving great results.

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