A coating factory considering VOC control may consider introducing exhaust treatment equipment.

VOC stands for volatile organic compounds.
These can be understood as organic solvents in coating materials and thinners that evaporate into the air.

VOCs arise from coating booths, drying ovens, mixing areas, cleaning areas, and other locations.
VOC treatment may therefore be necessary for environmental measures, odor control, improved working conditions, and customer audits.

However, VOC treatment methods should not be selected casually.

“It is a well-known method, so it must be good.”
“It looks high-performing, so it must be good.”
“The equipment is inexpensive, so it must be good.”
“Other companies use it, so it must be good.”

Selecting a method in this way may result in a poor fit for the shop floor.

VOC treatment must be selected according to the exhaust conditions.

Exhaust airflow volume.
VOC concentration.
VOC composition.
Exhaust temperature.
Dust.
Tar.
Moisture.
Operating hours.
Variations in production volume.
Required treatment efficiency.
Running costs.

These determine which treatment method is suitable.

1. Select VOC treatment equipment by examining what the exhaust contains

There is something that must first be checked before selecting VOC treatment equipment.

It is what the exhaust to be treated actually contains.

Even within the same coating factory, exhaust properties differ by source.

Coating booth exhaust may have a large airflow volume and relatively low VOC concentration.
Drying oven exhaust may be hot and contain VOCs, odor components, and tar.
Cleaning area exhaust may release concentrated solvent odors for short periods.
Mixing area exhaust may mainly come from evaporation when containers are opened or materials mixed.

Selecting equipment without examining these differences makes effective treatment difficult.

VOC treatment should begin with exhaust composition rather than equipment names.

2. Greater exhaust airflow generally requires larger equipment

Exhaust airflow volume is particularly important when considering VOC treatment equipment.

It indicates how much air must be treated in a given time.

The greater the airflow volume, the larger the treatment equipment required.
Fans, ducts, treatment vessels, combustion chambers, adsorption towers, and other components also tend to become larger.
Equipment and electricity costs naturally increase.

Coating booth exhaust may require large airflow volumes for operator safety and mist removal.
However, VOC concentration may be relatively low.

Treating this low-concentration, high-volume exhaust directly requires large equipment and increases costs.

For such exhaust, measures before treatment are also important, such as combining treatment with a concentrator, reducing VOCs at the source, and improving transfer efficiency.

3. High- and low-concentration exhaust require different approaches

VOC treatment methods also vary with VOC concentration.

Thermal oxidation may be effective for high-VOC-concentration exhaust.
Because VOCs themselves include combustible components, high treatment efficiency may be easier to achieve under suitable conditions.

For low-concentration exhaust, on the other hand, thermal oxidation may require substantial supplementary fuel.
Operating costs then increase.

Activated carbon adsorption or concentration may also be considered for low-concentration exhaust.
However, adsorbent replacement frequency, disposal costs, and deterioration caused by dust or tar must also be checked.

A VOC treatment method therefore cannot be selected without checking concentration.

The important point is to examine exhaust airflow volume and VOC concentration together.

4. VOC composition changes which methods are suitable

VOCs are not a single substance.

Coating materials and thinners contain various solvents.
Examples include aromatic, ester, ketone, alcohol, and glycol solvents.

Their composition changes odor intensity, combustibility, ease of adsorption, and effects on catalysts.

Treatment methods also have different strengths and limitations.

Some components are readily adsorbed onto activated carbon, while others are not.
Some are suitable for catalysts, while others cause catalyst deterioration.
Some are suited to thermal oxidation, but fuel costs vary with exhaust concentration and temperature conditions.

It is therefore advisable to identify VOC composition as fully as possible before selecting treatment equipment.

Checking SDSs, reviewing coating material and thinner composition, and analyzing exhaust where necessary are important.

5. Dust and mist require pretreatment before treatment equipment

Coating factory exhaust may contain coating mist or dust in addition to VOCs.

If these enter VOC treatment equipment, they may cause equipment problems.

For example, mist or dust entering activated carbon adsorption equipment rapidly contaminates the carbon.
Coating mist or tar entering catalytic oxidation equipment may reduce catalyst performance.
In thermal oxidation equipment as well, contamination may accumulate in ducts or pretreatment sections.

The following pretreatment measures may be necessary before VOC treatment equipment.

• Filters
• Mist separators
• Dust removal equipment
• Tar removal
• Cooling
• Moisture removal
• Ensuring that ducts can be cleaned

VOC treatment equipment should not be considered on its own.
It must be designed as a system from exhaust inlet to outlet.

6. Tar is an important item when selecting treatment equipment

Tar-like components may be a problem in drying oven exhaust.

Tar deposits form when heated coating constituents or volatile components cool and attach as sticky contamination.

Exhaust with substantial tar content requires care in treatment equipment selection.

Tar causes the following problems.

• Deposits inside ducts
• Clogged filters
• Rapid deterioration of activated carbon
• Catalyst contamination
• Reduced treatment efficiency
• The cleaning burden increases.
• Increased fire risks

For exhaust containing substantial tar, pretreatment, duct design, cleaning access openings, temperature control, and treatment method must be considered carefully.

For VOC treatment of drying oven exhaust, always check for tar as well as VOC concentration.

7. Activated carbon adsorption is often considered for low-concentration exhaust

Activated carbon adsorption is one VOC treatment method.

Activated carbon adsorbs VOCs and odor components.
It may be considered for relatively low-concentration exhaust or odor control.

An advantage is its relatively simple structure, which may make introduction easier.

However, there are also points of caution.

• Activated carbon eventually becomes saturated.
• Regular replacement is necessary.
• Replacement and disposal incur costs.
• High-temperature exhaust requires care.
• Dust or mist shortens service life.
• Ease of adsorption varies with composition.
• Fire risks must be considered.

Activated carbon adsorption may appear inexpensive.
However, frequent replacement makes running costs substantial.

Before introduction, check VOC concentration, airflow volume, composition, temperature, dust, and replacement interval.

8. Thermal oxidation may be effective for high-concentration exhaust

Thermal oxidation decomposes VOCs by combustion at high temperature.

It may be effective for exhaust with relatively high VOC concentration.
High treatment efficiency may also be achievable.

However, thermal oxidation incurs fuel costs.
Treating low-concentration exhaust may require substantial supplementary fuel.

The following points must also be checked for thermal oxidation.

• Exhaust airflow volume
• VOC concentration
• VOC composition
• Combustion temperature
• Fuel costs
• Safety management
• Dust and tar in the exhaust
• Potential for waste heat use
• Installation space
• Maintenance

Thermal oxidation is a powerful method, but unsuitable exhaust conditions can result in high operating costs.

9. Catalytic oxidation may allow treatment at lower temperatures

Catalytic oxidation uses a catalyst to decompose VOCs through combustion.

It may operate at lower temperatures than ordinary thermal oxidation and potentially save energy.

However, catalysts require care.

Catalysts may be affected by contamination or particular constituents.
Dust, mist, tar, and certain chemical components may reduce catalyst performance.

Check the following items for catalytic oxidation.

• VOC composition
• Presence of components affecting the catalyst
• Presence of dust or mist
• Presence of tar
• Need for pretreatment
• Catalyst replacement interval
• Operating temperature
• Maintenance costs

Catalytic oxidation is effective when conditions are suitable.
However, introducing it without checking exhaust composition may cause catalyst deterioration and reduced treatment performance.

10. RTOs are effective where heat recovery can be used

RTO stands for regenerative thermal oxidizer.

An RTO treats VOCs by combustion while recovering and reusing heat.
It may be considered for drying oven exhaust or VOC exhaust generated at a certain volume.

An advantage of an RTO is that heat recovery may reduce fuel consumption.

However, the equipment tends to be large and expensive to introduce.
If exhaust conditions are unsuitable, the expected energy savings may also be difficult to achieve.

Check the following items when considering an RTO.

• Exhaust airflow volume
• VOC concentration
• VOC composition
• Exhaust temperature
• Operating hours
• Stability of production volume
• Presence of tar or dust
• Need for pretreatment
• Installation space
• Fuel costs
• Maintenance costs

An RTO is a strong option when considering environmental measures and energy conservation together.
However, checking its suitability for the exhaust conditions is essential.

11. For absorption and scrubbers, examine compatibility with water or chemical solutions

Scrubbers may be used to treat VOCs or odors.

A scrubber brings exhaust into contact with water or a chemical solution to absorb or wash out components.

However, it is not effective for every VOC.
Benefits can be expected for components readily dissolved in water or treated by chemical solutions, but effectiveness may be limited for components that are poorly water-soluble.

Check the following points when considering a scrubber.

• Can the VOC components be readily treated with water or chemical solutions?
• Effectiveness against odor components
• Whether wastewater is generated
• Chemical consumption
• Sludge generation
• Mist dispersion
• Equipment corrosion
• Effects on wastewater treatment

A scrubber treats exhaust but may require management of the water or chemicals used afterward.

It is also necessary to check whether exhaust measures increase the wastewater treatment burden.

12. Combining treatment with concentration equipment

VOC concentrators may be used for low-concentration, high-volume exhaust.

This approach concentrates VOCs present at low levels in a large airflow into a comparatively smaller airflow before treatment.

Concentration may allow equipment such as thermal oxidizers or RTOs to be used efficiently.

However, concentration equipment also has points of caution.

• Compatibility with VOC composition
• Deterioration caused by dust or mist
• Need for pretreatment
• Concentration ratio
• Operating control
• Maintenance
• Installation costs
• Installation space

Concentration equipment is a strong option for low-concentration, high-volume exhaust, but it must be designed according to what the exhaust contains.

13. Examine the running costs of VOC treatment equipment

VOC treatment equipment should not be judged solely by installation cost.

Various running costs arise after introduction.

• Electricity costs
• Fuel costs
• Adsorbent replacement costs
• Catalyst replacement costs
• Filter replacement costs
• Chemical costs
• Sludge and waste disposal costs
• Cleaning costs
• Inspection costs
• Spare parts costs
• Costs of responding to shutdowns

Costs for consumables such as activated carbon and catalysts, in particular, vary greatly with replacement intervals.

High dust or tar content in the exhaust also affects equipment life and replacement intervals.

VOC treatment equipment should be assessed by long-term total cost rather than purchase price.

14. Common challenges in selecting VOC treatment methods in Vietnamese factories

Vietnamese factories often face the following challenges in selecting VOC treatment methods.

Exhaust airflow volume is not accurately known.
VOC concentration is not measured.
VOC composition is not checked.
Odor control and VOC control are confused.
Coating booth and drying oven exhaust are treated in the same way.
Dust and tar pretreatment are overlooked.
The method is selected solely by installation cost.
Running costs are not estimated.
Adsorbent and catalyst replacement frequency is not checked.
Changes in exhaust conditions after coating material changes are not considered.

Under these conditions, introducing VOC treatment equipment may fail to deliver the expected effects.

VOC control must begin by understanding the actual exhaust conditions.

15. Items to check when selecting a VOC treatment method

The following items provide a practical basis for selecting a VOC treatment method.

1. Sources

Identify whether the exhaust comes from coating booths, drying ovens, cleaning areas, mixing areas, or other sources.

2. Exhaust airflow volume

Establish the volume of air to be treated.

3. VOC concentration

Check whether concentration is low, high, or highly variable.

4. VOC composition

Check suitability for adsorption, thermal oxidation, or catalytic treatment.

5. Exhaust temperature

Check whether the exhaust is hot or at ambient temperature.

6. Dust and mist

Check whether pretreatment is necessary.

7. Tar

Check this particularly for drying oven exhaust.

8. Moisture

Check effects on adsorbents and catalysts.

9. Operating hours

Check whether operation is continuous or intermittent.

10. Cost

Check both installation and running costs.

16. The value CoatureVietnam sees in VOC treatment method selection

CoatureVietnam does not regard VOC treatment as an equipment issue alone.

VOCs arise from coating materials, thinners, application methods, drying ovens, booths, cleaning, mixing, exhaust, and working methods.

Before selecting a treatment method, CoatureVietnam therefore first considers whether generation can be reduced at the source.

Improve transfer efficiency.
Reduce cleaning thinner consumption.
Improve container management.
Consider low-VOC coatings.
Consider the potential to switch to waterborne or powder coating.
Control drying oven exhaust appropriately.
Then select the necessary treatment equipment.

This order is important.

CoatureVietnam examines VOC treatment from the following perspectives.

• Material: Coating materials, thinners, and cleaning solvents
• Method: Application methods, cleaning methods, and container management
• Machine: Booths, drying ovens, and exhaust treatment equipment
• Man: Operator practices and training
• Management: Regulatory compliance, customer audits, investment decisions, and running costs

This puts into practice the principle CoatureVietnam values:
“Coating the Future with Science and Care”.

Science means checking VOC concentration, composition, airflow volume, temperature, dust, and tar to select the optimal treatment method.
Care means creating conditions in which the factory can operate with confidence without burdening operators or the surrounding environment.

Conclusion

Do not select VOC treatment methods by equipment name.

Activated carbon adsorption.
Thermal oxidation.
Catalytic oxidation.
RTOs.
Scrubbers.
Concentrators.

Each method has its own characteristics, strengths, and limitations.

The important point is to select according to exhaust conditions.

Exhaust airflow volume.
VOC concentration.
VOC composition.
Exhaust temperature.
Dust.
Mist.
Tar.
Moisture.
Operating hours.
Running costs.

Only after checking these can the appropriate treatment method be identified.

VOC control also goes beyond installing treatment equipment.
Reducing generation at the source, improving transfer efficiency, reviewing cleaning work, and considering low-VOC materials are important as well.

CoatureVietnam treats VOC control as a topic connecting coating materials, equipment, operation, and environmental measures, and proposes practical improvements suited to Vietnamese factories.