Updated: July 2002

1. Purpose

The concentration of emitted organic solvents vapor in the plants or atmosphere such as toluene, xylene and ketones is, in many cases, diluted (most working environment are 50-200 ppm or lower), the capital investment for changing into non-polluted air including catalytic incinerators is never the least expensive.
The system enables to achieve a substantially reduced total cost including running cost by effectively concentrating the diluted solvent vapor and minimizing the stream which is required for subsequent treatment. (For instance, the above mentioned catalytic incinerators)

2. Outline and Features

Fig-1: Honeycomb rotor

Fig-1 shows its outlined mechanism. The diluted solvent vapor (contaminated air) which is sucked in, is directed to the honeycomb-structured rotor to be adsorbed by activated carbon, one of its material, or hydrophobic zeolite. The purified stream is mostly exhausted into the air as non-hazardous air, except in printing works where it is returned to the working environment to economize the air conditioning cost.
On the other hand, the adsorbed solvent is sent to the regeneration area (concentration area) along a rotating rotor where smaller amount of ambient air, heated up to 110ºC, (usually amounting to 1/5 to 1/15 of the treating steam) to desorb the solvent. Thus, a greater volume of exhaust stream with low concentration is compressed into smaller volume of high concentrated stream, which reduces a maximum of 80% (calculated by Daikin) of an initial cost of required subsequent equipment, and as high as 90% when it comes to the running cost.

[Concentration Ratio]
A concentration ratio means the ratio of treating gas volume against air volume for concentration. The latter is usually determined by selecting a lower concentration of the two described below.
1) A 1/5 concentration of LEL (lower explosion limit) of the vapor solvent.
2) A concentration of the solvent burning itself in the catalytic incinerator.

[Zeolite]
Recently, zeolite collects a lot of attention as effective new material for a honeycomb-structured rotor, though activated carbon has been mostly used so far. The reason being that zeolite resolves the most detrimental problem of ignition that activated carbon could not in spite of its superb feature of adsorption. The development of hydrophobic zeolite has made it possible to progress the extent of availability including security and use it easily.
In addition, adopting zeolite enables to deal with low boiling solvents such as lower alcohol. Furthermore, it is expected to apply zeolite to effectively reduce certain kind of odors that occur in daily life.

3. Applications and Measuring Results

Table-1 illustrates measuring results of the system installed at a printing factory and machinery producing works. Though two systems have different ratios of the concentration, they are both good examples to demonstrate reduced compactness of the equipment with substantial reduction of an initial investment cost as well as running cost.
Photograph-1 shows a combined installation of the system (HONEYDACS) and catalytic incinerator (CATADACS).

Table-1: Measuring results of existing factories

4. Fluidized Organic Solvent Recovery System

The system aims for recycling directly recovered organic vapor solvents, not by means of catalytic incinerator. The carrier gas used for desorption is N2 gas which has no concern for possible ignition. The recovered solvents have such a high quality that they can be utilized as they are. The system is, therefore, introduced here because it is reviewing in terms of recycling the resources as well as atmospheric protection.