Patent 4240787 Drying oven with heat reclamation and air pollution control system

Patent 4240787

Drying Oven with Heat Reclamation & Air Pollution Control System

This patent was developed for a drill pipe and line pipe coating industry.

Drill pipe, line pipe and all sorts of other pipes are lined (coated) internally or externally, with either phenolic coating or some rust presentation coatings, depending upon the use of the pipe. Mostly the coatings are applied for corrosion protection or easy flow of fluids, minimizing the friction inside the pipe.

Phenolic coating is applied internally, in three stages; with all three stages consisting of application of coating, and curing. The second stage is a duplicate of the first stage:  coating and curing.  And, likewise the third stage.

In a sequence of ovens, the exhaust from one oven is circulated to the next at a high linear velocity, but low volume (at 25% LEL) and heated to a high temperature (1400° F) by in-line incineration of the fumes. The low volume, high velocity, high temperature gasses are mixed with a high volume, low velocity, low temperature exhaust collected from the end of that oven. This incineration and mixing and recirculation of gasses is repeated in each succeeding oven and no gasses are exhausted to atmosphere until the last oven. In the last oven, in sequence, a burner is provided to incinerate fumes recirculated at one end of the oven and the exhaust goes to atmosphere through an incinerator/heat exchanger where the reclaimed heat is supplied to outside air being fed to support combustion in the incinerator at one end of the last oven.

Instead of going to a dedicated Thermal Oxidizer, the exhaust is recycled into the next stage combustion chamber, where approximately 95% of hydrocarbons are destroyed.  Likewise, from the second stage to the third stage, approximately 95% of hydrocarbons are destroyed.  The third and final stage has a Recuperative Thermal Oxidizer, which destroys the hydrocarbons at 99+%

Epcon has utilized the application of this patent in many systems that it has built over the years.


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