Central Ostrobothnia University of Applied Sciences
Department of Technology Kokkola
Chemical Engineering
BENS08K
Course: Conducting research and reporting
Topic: VOCs sources and removal techniques
Student’s name: Yan Chao & Qiao Zheng
Table of Contents
1. Introduction ................................................................................................................ 3
2. Sources of VOCs........................................................................................................ 3
3. Regulations to control VOCs ..................................................................................... 4
4. Removal techniques ................................................................................................... 5
4.1 Thermal oxidation ............................................................................................ 5
4.2 Catalytic oxidation ........................................................................................... 6
4.3 Comparison of thermal and catalytic oxidations ............................................. 7
5. Conclusions ................................................................................................................ 8
6. References .................................................................................................................. 8
1.Introduction
With the development of the technology, air pollution such as carbon monoxide,
nitrogen oxides, and volatile organic compounds has given rise to serious problem
nowadays. Volatile organic compounds have been recognized as a threat to our life
due to their significant effects. Volatile organic compounds are defined as organic air
pollutants emitted by chemical and petrochemical industries. They have a high vapor
pressure of 0.01 Kpa or more at the temperature of 293.5 K which causes a large
amount of molecules to evaporate from the compounds then enter the surrounding air.
It is a common type of industry emissions which will result in significant effects to
human health and environmental performance. The aim of this report is to carry out
the technique methods (thermal oxidation and catalyst oxidation) for removing the
VOCs emission. In this report, thermal oxidation and catalyst oxidation are compared
with each other and finally recommendation and conclusions are provided.
2. Sources of VOCs
The major sources of VOCs are petroleum chemicals, chemical solvents and vehicle
exhaust as well as combustion emissions. Chemicals are mainly released from
petroleum, the chemical industries, oil stations and other production or sales units.
Chemical solvents such as paint, interior, and interior decoration or other electrical
equipment may contain VOC emissions. In summary, the sources of VOC could be
listed as follow. (Wong 2007.)

Biogenic processes

Mobile sources

Stationary sources, such as
 Solvent evaporation and utilization
 Manufacturing processes of organic chemicals
 Gasoline marketing
 Loading losses of storage tanks
 Food industry
 Coating processes
VOCs take part in the chemical reaction of nitrogen oxides to form ozone under the
sunlight and heat condition. Ozone leads to deterioration of air quality and it is the
major component of summer smog. VOCs have significant effects to human health,
and the influences can be classified into three types. One type is sensory stimulation.
The second type is skin irritation and other systemic toxicity which result in eye
mucosa irritation, nasal mucosa irritation. VOC could easily transfer through the
blood to brain which leads to the suppression of central nervous system and result in
headache, uncomfortable and fatigue feelings. The third type is genotoxicity and
carcinogencity. The common types of VOCs are acetone, benzene, formaldehyde,
heptanes, hexane, methyl chloride, styrene and toluene. (United States Environmental
Protection Agency 2011).
3. Regulations to control VOCs
Because VOCs have significant effects on human health, some countries have
established laws and regulations to control VOC contents. EU Directive 1999/13/EC
restricts the usages of VOCs for certain activities and equipments installations.
2004/42/EC directive restricts the amount usage of VOCs in paints, interior
decoration and interior volatile organic solvents. The total contents of volatile organic
compounds indoor air must be lower than 300 ug/m3. In U.S. 40 CFR 63 Subpart II
limits the usage of paints, adhesives, solvents and volatile organic compounds in glue
and the total contents of VOCs must be less than 0.5 mg/m3. Japan has requested the
total VOCs indoor levels must below 400 ug/m3. In China, we demand the total
amount of VOCs indoor air concentration less than 0.6mg/m3 (8 hours). In the year of
2002 January 1st, we have established the standard named “GB 18582-2001 interior
decoration materials, interior wall paint harmful substances limitations”. (Khan 2000.)
4. Removal techniques
There are a variety range of techniques for removing the VOCs. They are classified
into two different grounds based on the different working methods: (1) processing and
equipment modification. (2) add-on-control techniques which involves thermal
oxidation, catalytic oxidation. The first group is the effective method used in changed
operating conditons or raw materials for minimizing VOCs emissions and the second
group is mainly achieved by regulating emissions. (Khan 2000.)
4.1 Thermal oxidation
The thermal oxidation system, fume incinerators, designed for oxidizing combustible
materials with the presence of oxygen to heating up the system temperature above the
autoignition point and resulting in combustion reaction. Normally, the system
removes VOCs percentages approximately 95% to 99% which VOC concentrations
are from 100 ppm to 2000 ppm. In performing this method, the combust VOCs are
incinerated in the temperatures ranges from 1300 to 1800 F. The real processing
efficiency and rate varies depending on the concentration of the materials, the type of
the materials and the amount of oxygen and processing temperature. Additional
heating and pressure are needed for combustion zone due to the difficulty of
incinerated compounds. Regenerative and recuperative techniques are two common
types of energy recovery systems which use the combustion exhaust stream for
heating up the system. The heart of system is thermal incinerator which is made of
ceramic beds to capture the heat during the combustion reaction (see Graph 1). If the
system temperatures reach the combustion temperature, the heat exchanger will
transfer the exhaust gas into specific situation (cold air). In order to keep the system
temperature, the incoming gas steam is delivered into heated bed during the same time.
(Khan 2000.)
Graph 1. A thermal oxidizer may incorporate recuperative or regenerative energy
recovery (Edward 2002)
4.2 Catalytic oxidation
Catalytic oxidation systems are quite similar to combustion systems. The catalyst is
used to reduce the combustion energy requirements. It is designed for removing the
VOCs compound from the range 90% to 95% which contains the concentrations from
100 ppm to 2000 ppm. The processing temperate is the main difference compared
with thermal oxidation and it is about 700-900 F. The incoming gas stream is heated
in the pre-heater and then delivered into monolithic support structure with coated by
the catalyst. The function of catalyst is to produce secondary combustion wastes.
(Khan 2000.)
Graph 2. Catalytic oxidizer operates at low temperature than thermal oxidizers
4.3 Comparison of thermal and catalytic oxidations
The comparison between thermal oxidations and catalytic oxidation concerns about
the percentage of destruction VOCs compounds, the VOC concentrations, the
moisture content, processing temperature and the holding capacity (as table 1shows).
Table 1. The comparison between thermal oxidation and catalytic oxidation (Khan
2000)
Techniques
VOC content(ppm)
Thermal oxidation
100-2000
Catalytic oxidation
100-2000
Destruction(%)
95%-99%
90%-95%
Capacity range (cfm)
Temperature(F)
1000-500,00
700-1000
1000-10000
350-500
5. Conclusions
Due to the environmental concern from the public, the VOCs act as the important
industrial emissions, resulted in significant effects to human health as well as
environmental performance. There are a variety range of technique methods for
removing the VOCs compounds. In this report thermal oxidation systems and catalyst
oxidations have been compared with each other. Thermal or catalyst oxidations are all
common types of methods to destruct the VOCs or they can bring the advantage of
energy gain from economy point of view. On the other hand, there are still some
limitations for designing the systems due to specific operations requested as well as
furthering processes for the toxic compounds. Finally, it is concluded that catalyst
oxidation seems to be promising technology for VOC removal overcoming the
shortcoming of limitations. In the future, more potent technology are hoped to be
developed for removing VOCs with the considerations of good efficiency and lower
cost.
6. References
Faisal I. & Aloke, 2000. Removal of Volatile Organic Compounds from polluted air.
Journal of Loss Prevention in the Process Industries 13, 527–545.
Edward & Bakerl. 2000. Reduce VOC and HAP emissions. Practical Solutions for
Reducting Volatile Organic Compounds and Hazardous Air Pollutants. Centre for
waste reduction technologies, New York,(NK) 2001.