Updated: July 2002

1. Outline of system

This equipment has three heat storing towers filled with ceramic heat storing material and the combustion room with burner on top of them. There is a control valve for gas passage in the lower part of each heat storing tower.
Each heat storing tower has the pre-heating process, radiation process and purge process, each of which is selected by the timer. In the pre-heating process, the VOC gas is pre-heated by passing it through the heat storing material which stores heat from the exhaust gas in the radiation process.
Then, the solvent and VOC are combusted, oxidized and decomposed in the combustion room. In the radiation process, the exhaust gas from the combustion room gives heat to the heat storing material, and discharged to the atmosphere from the chimney. In the purge process, the uncombusted gas pooled at the lower part of the heat storing tower in the pre-heating process is replaced with the exhaust gas from the combustion room so that any smell may be prevented when the pre-heating process is switched to the radiation process.
The burner installed in the combustion room is used in the initial temp rise, or in case the decomposition temp (800ºC-900ºC) cannot be obtained only by the heat generated by solvent and VOC in the raw gas.

2. Characteristics

1) High performance
The solvent and VOC are oxidized and decomposed at the high temp 800ºC-900ºC in the combustion room, so most part can be eliminated. This can be regarded as the best way to treat the solvent of multi-components and VOC gas.
2) High efficiency & low NOx
Since the heat recovery rate is as high as 85%-95%, it doesn't need so much amount of combustion fuel as compared with other method (direct combustion system, catalytic combustion system). Even if the solvent (VOC) concentration is 1000 ppm or lower, self-burning is available.
Since less of combustion fuel , less of NOx is generated.
3) High-concentration treatment is available.
In case any highly concentrated solvent/VOC exceeding self-burning area is treated in the RTO, the inside of the combustion room may be heated to a temp above 1000ºC, possibly damaging the units. In this case, a direct bypass line from the combustion room to the chimney helps exhaust gas bypass the heat storing material to prevent the inside of the combustion room from being heated abnormally. There is another way to prevent abnormal temp rise by sucking atmospheric air. By each of these ways or by their combination, it is possible to control the inside of the combustion room into normal temp.
4) Countermeasures for substances of high boiling point
Various impurities that may be used for raw materials could be trapped in the raw gas. These substances could come flying as mist at high boiling point, and could be deposited on the units (mainly at the lower part of heat storing material and control valve), thus eventually causing the system to fail in operation. For the countermeasures, the following methods are available. We apply each of the methods or any combination of them to maintain a lasting and stable operation.
- Select heat storing materials in a way that the gas passage may not be clogged even when any impurity sticks.
- Adopt "Bake out"(the tar-burning cycle) so that any stuck impurities can be removed.
- Let the high-temp exhaust gas return to the raw gas line to prevent any impurity from becoming mist, and from sticking to anything.
5) Others
Ceramic wool is used for fire-resistant material in this equipment, it is free of cracks in the event of sudden thermal changes as compared with the conventional castor, and can be used for a longer time with no repair.
The switching control valve is selected so strictly that it may be used for a long time with less work for maintenance/repair.

3. Performance

1) Treating capacity
Up to 1000m³/H - 6000m³/H can be dealt with the 3-tower type. For more, increase the number of towers or units.
2) Performance
- VOC Removal rate -99%
- Thermal recovery rate 85-95%

4. Applicability and objectives

Solvents and VOC are used in various industries of painting, printing, tape, rubber, paper, packing and texture, and the fields related to electronics. Various solvents are used for various purposes. All of these exhaust gases from production system can be treated by this equipment.
This is also used as the deodorizers at the night soil treatment plant and sewage water treatment plant.

5. Others

If coupled with any solvent gas (VOC) thickener for the lower concentration gas than starting self-burning and a large-volume exhaust gas, the gas volume will be reduced, and if the solvent concentration is raised, economic treatment is available.