VOCs Abatement System

 

Overview

"In VOCs treatment, the combustion type refers to the highly reliable VOCs treatment type that enables the combustion of organic substances in great definition, satisfies three requirements of ‘Oxidation temperature’, ‘ Residence time’, and ’Complete mixture', and enables over 98% purification efficiency as well as the destruction to clean gases. By maintaining the combustion conditions of over 750℃ of temperature and over 0.5 second of residence time, it is possible to remove over 98% of VOC gas under stable operation. However, it bears a problem in terms of operation cost due to high fuel consumption requirement from high combustion temperature, unless any proper alternative waste heat recovery plan is provided. The heat exchange type in heat recovery process shows only 40~65% in terms of economic efficiency, which still leaves a problem of fuel cost increase and further may result in side effects such as increase in NOx generation due to high fuel consumption. The regenerative Thermal Oxidizer (RTO/RCO), by adopting direct heat exchange through heat media, is a highly economical combustion device that increases the heat recovery efficiency up to 98% while greatly reducing the fuel requirement and therefore features high energy reduction and anti-NOx generation effect."

 

The fundamentals of Regenerative Thermal Oxidation Device

"The regenerative thermal oxidizer is equipped with more than two regeneration chambers where the replacement and exchange of gas flowrate is operated. In the center of the device, combustion chamber is equipped with and the regeneration chamber is filled with ceramic heat media.In figure A, the odorous gas is heated up to approx. 800℃ while passing through regeneration chamber in left.

The odorous substance is thermal destructed and the purified high-temperature gas flows in to right generation chamber to deliver the temperature to heat media while cooling off itself and finally is discharged to air.

Following to this process, the odorous gas becomes status B and then flows in to the right regeneration chamber and is heated from the heat media, then is heated again up to approx. 800℃ in combustion chamber. The heated gas flows in the left regeneration chamber to cool off the heat media and then is finally exhausted stack. This operation is automatically controlled to destruct VOCs."

 

 

Process

" The most important function of the combustion device in regeneration chamber is to enable VOC substance to achieve optimal destruction efficiency from combustion, along with other important factors as high heat recovery efficiency for minimized fuel consumption in operation. The advantageous combustion device type is 2-Chamber type which provides 95% of destruction efficiency and over 95% heat recovery efficiency. However, due to the necessity of simultaneous switching at damper in converting the flow of in-flowed gas, a certain portion of incombusted gases are leaked through the outlet at that point and subsequently result in only 95% of destruction efficiency but not 99.99%."

" As an improvement to this current problem, 3-Chamber type combustion device which is added with 1 more heat media chamber is capable of achieving over 99.99% of destruction efficiency. However, this improved type requires higher cost, it is desirable consider such factors as inflow conceatration of applicable gas, the object value of discharge concentration and facility investment cost when selecting the appropriate type of combustion device. We have developed Rotary 1-Can RTO and commercialized 2 years ago which compensates defects of 3-Chamber RTO by providing high destruction efficiency of over 99%, less facility investment cost and easy operation and maintenance."

 

Features of Regenerative Thermal Oxidation Type

"The system retains following features when compared with heat recovery type devices applying Recuperative Thermal Oxidation type. used of heat exchager”

 

1) High heat recovery efficiency and economic fuel consumption.
- The recuperative combustion type required increased fuel consumption for higher combustion temperature, however with the regenerative thermal oxidation type, the fuel consumption remains almost the same even when the combustion temperature set higher.

 

2) Stable operation and long service life
- Most VOCs components are completely thermal destructed through direct combustion at high temperature between 750 ~ 950℃ . Further, the temperature at combustion chamber remains stable against the changes in gas amount, or VOCs component’s concentration, which provides stable combustion. Moreover, as it does not adopts any metal materials in hot zone, the system offers anti-damage from the thermal oxidation, the long service life and consequently lower maintenance cost.

 

3) Simple structure and relatively low pressure drop.
- The simple and anti-failure driving system constructed with only damper or valve as well as the highly heat transferable HoneyComb type regeneration chamber allow less pressure drop and subsequently lower utility cost.

 

4) Low NOx generating device.
- Because the system requires low fuel consumption, it generates very little Fuel NOx, and the VOCs destruction by the regeneration chamber of hot zone processed with diffusion combustion without generating any local high temperature seldom occurs Thermal NOx.

 

5) Counteracts to gases with VOCs component such as Halogen.
- The heat media is constructed with corrosion resistant ceramic materials to counteract the VOC components including Halogen Ion (CI, Br…)."

 

Regenerative Thermal Oxidizer comparison by type

"The regenerative thermal oxidation types currently commercialized include 1-Can, 2-Chamber, 3-Chamber types depending on the regeneration chamber (otherwise referred to as Chamber, Can, and Tower) of which major features are as follows."

 

Device type comparison

Classification 2-Chamber RTO/RCO 3-Chamber RTO/RCO 1-Chamber RTO/RCO
Development history Before 3-Chamber RTO Before 1-Can RTO Late 1990’s
Features In, Out switch type direction conversion In,Out switch type direction conversion and additional Purge function 12-Section Rotary Valve Type, consecutive performance of In, Out, and Purge
Damper type Slide, Butterfly, Poppet, etc. Slide, Butterfly, Poppet, etc. 12-Section Rotary Valve
Merits and defects 1) Simple structure.
2) Low device cost.
3) Easy maintenance and operation.
4) Low destruction efficiency.
(approximately 95%)
5) No PURGE function.
6) VOC is partially discharged during damper switching.
7) Back pressure is generated during damper switching
1) High device cost.
2) Too much dead space.
(approximately 30%)
3) Complicated structure.
4) Large installation area.
5) Complicated maintenance and operation.
6) High destruction efficiency.
(approximately 99%)
1) Less expensive than 3-Chamber.
2) High destruction efficiency.
(approximately 99%)
3) Simple structure and small installation area.
4) Little dead space.
(approximately 17%)
5) Easy maintenance and operation.
6) Discharging gas maintains even conceatration.
7) Smooth gas flow.
8) Back pressure is not generated.
BAKE-OUT Possible. Possible. Possible.
PURGE SYSTEM Impossible. Possible. Possible.
Initial investment Low High Medium