| Regenerative thermal oxidizer's (RTOs) are used to | | | | can be adjusted for by allowing necessary operating |
| control many various types of air pollution compounds | | | | flexibility in the design of the RTO system such as the |
| which are emitted by a wide variety of industrial | | | | additional dilution air, hot air by-pass systems and |
| processes. Regenerative thermal oxidizer's are widely | | | | proper LEL monitoring. |
| accepted and RTO technology has been successful | | | | Particulates in your process stream are another |
| with most installations, operating trouble-free for | | | | matter. Particles in the gas stream are the biggest |
| extended periods. In some cases, however, operation | | | | threat to efficient RTO operation as it can lead to bed |
| has been troublesome. | | | | plugging and/or media degradation and account for a |
| RTO Understanding | | | | large amount of RTO fires. Among all of the plant |
| Regenerative thermal oxidation technology is a method | | | | processes, starch facilities, water treatment facilities, |
| of capturing and retaining the temperature needed to | | | | rendering, biomass dryers and coffee roasters are |
| oxidize the plant air pollution. The pollutant is injected | | | | particularly prone to such problems because of the |
| into a heat recovery chamber which contains ceramic | | | | many ways their processes can generate particles. |
| media, by Injecting the process stream through the inlet | | | | Source of Particles and Effects to the RTO System |
| heat recovery chamber, the emission stream is | | | | Coarse particles are particles greater than five |
| preheated to a temperature near or at the combustion | | | | microns. Their root is completely mechanical from such |
| chamber temperature. In low VOC applications a fuel | | | | as actions as tumbling or pneumatic action. |
| burner maintains the temperature to approximately | | | | Characteristically particles of this origin impact or plug |
| 1,450 degrees Fahrenheit for complete oxidation. | | | | the cold face surface of the ceramic media bed. If left |
| Upon leaving the combustion chamber, the waste | | | | unabated, this can also become a fire safety hazard. |
| stream enters the outlet heat recovery chamber. The | | | | Fine particles have a diameter less than one micron. |
| waste stream passes through the outlet heat transfer | | | | Which are exclusively caused by the thermal |
| ceramic media bed, where the heat energy from the | | | | processes. Particles are formed when the process |
| inlet heat recovery and the combustion chamber is | | | | stream vapor cools and then condenses. The particle |
| transferred to the ceramic heat exchange media. | | | | may be solid or liquid in nature depending on its |
| Lastly, the cleaned process stream leaves the RTO | | | | chemical properties; some examples are oils and |
| system through outlet valves to the exhaust stack. | | | | resins, while others that are generated thermally are |
| This process reversal allows the RTO to recover up | | | | metal oxides. |
| to 95 percent of the BTU value generated in the | | | | Fine particles are derived from the evaporation of |
| combustion chamber which greatly minimizes the | | | | organic material and the cooling within the ceramic bed |
| supplemental fuel costs. A correctly designed and | | | | prior to the exhaust manifolds has the potential to plug |
| engineered RTO unit can operate continuous without | | | | the ceramic media. Particles in the process stream |
| downtime or significant amount maintenance. | | | | which are considered fine and which are considered |
| Process Stream | | | | chemically reactive also cause ceramic media plugging. |
| A valuable tool is to understand the importance of | | | | They also tend to react with the heat exchange |
| process stream that defines the RTO operation. Most | | | | media. Examples of chemically active fine particles are |
| all process streams have some particulate matter in | | | | the oxides of sodium and potassium. These react with |
| an emissions stream. The quantity may be insignificant | | | | the ceramic media at elevated temperatures and |
| as in ambient air, but it is always present. | | | | cause the media to become brittle with breaking and |
| The VOC concentration in the process stream varies, | | | | bed plugging. |
| but process upset conditions due to excessive VOC, | | | | |