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Air vs. Steam Atomization Part 3 – The Atomization Process

Posted on July 24th, 2017 by in Chemical Manufacturing Excellence

Air-Steam-Atomization-3

Liquid hazardous waste needs to be in contact with oxygen at a high temperature in order to combust and be destroyed. These liquids are typically injected into the hot gas stream through spray nozzles that are designed to transform the liquid stream into droplets that are more easily combusted. The spray nozzles commonly utilize steam to heat the liquid and mechanically cause the droplets in the spray pattern to form and easily travel in the hot gas to locate oxygen molecules for combustion. In general, better atomization results in better combustion.

This sounds good (and has been good enough for years) but consider that using steam atomization causes steam molecules to surround the droplets that are formed by the spray nozzle. The droplets must then remove themselves from this localized steam environment to find oxygen for combustion.

On the other hand, it is possible to atomize the waste with (preferably hot) compressed air. The compressed air may not be as hot as steam but it surrounds the droplets with a localized oxygen-rich environment so combustion can occur almost immediately. In addition, the atomization air provides a more oxygen-rich environment near the droplets than is found in the hot gas that the burner generates. In other words, atomizing with air concentrates the oxygen where it is needed better than the incinerator burner itself. Equal masses of steam or air are required to atomize a given amount of liquid waste.

From a combustion perspective, atomizing stream is not consumed in the incineration process but it is maintained at a high temperature during the residence time. On the other hand, atomizing air is consumed in the incineration process. Therefore assuming that a stack oxygen sensor is used to trim the combustion air in the burner, the mass flow though the incinerator will be lower when atomizing with air. You may recall that reducing the mass flow through the incinerator will increase residence time which tends to improve waste destruction. It also can increase incinerator capacity by increasing the amount of liquid waste that can be incinerated with the same residence time.

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All opinions shared in this post are the author’s own.

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