Possible Treatment Method
There are four different methods of treatment for VOC emissions. These methods are adsorption incineration condensation and absorption. Choosing the most adequate method of treatment varies depending on the contaminants concentrations of combustible particles the economical comparison and the requirements necessary.
Adsorption is a method where the contaminated gas is brought in contact with a solid that acts as a filter. The most common solid or industrial adsorbents are activated carbons due to their large surface area per weight ratio. Contaminates that are filtered out of the gas either enter the solid or reside on the surface of the particles.
Incineration is another method where the polluted gas will be combusted to burn. This method is often used to regulate the emission of organic compounds within a polluted gas. From experience within the waste water treatment field siloxanes are undesirable and when ignited they form a sand type of material. If siloxanes are in the gas and heated within process equipment this will cause major damage. Siloxanes are contained within biogas and flares are often implemented to resolve this issue. Abutec was the specific company that manufactured the siloxane flare implemented at the Blue Plains Advanced Waste Water Treatment Plant in Washington D.C. where I worked. Inadequate combustion will result in the release of pollutants smoke is often a common indicator of poor combustion. Below is an image of a similar model of Abutec siloxane flare.
Another method of controlling VOC emission rates is condensation. All gases can be either compressed or cooled to a temperature where they become liquid. Condensation is an application often used not just for air pollution. Many HVAC systems steam dump condensers and heat exchangers operated based off of the basic principles that involve condensation. Air or liquid heat exchange is utilized to cool a vapor stream to the point where it will condense. Principles of thermodynamics and heat exchange are utilized for more efficient heat exchange. The efficiency can range based on the design criterion and application of the system. Usually cooling systems rather than compression are utilized to achieve condensation due the economic benefits. Below is a deaerator similar in use to what I have experience with.
The fourth technique is absorption. Absorption is a technique where a gaseous pollutant is dissolved into a liquid. Water is commonly used. The only process equipment that I have worked with similar to this process is a deaerator which is a device that is widely used in the removal of oxygen and other dissolved gasses within the feed water for boilers. Also wet scrubbing could also possibly applicable in this category. The optimum process equipment that preforms absorption is designed to mix the pollutant as much as possible. Below is an image a wet scrubber similar to what was installed the combined heat and power job site.
The system that should be selected for the most efficient design is Adsorption. Due to the excess supply of activated carbon which is very commonly used as the media in the adsorption process. This media that removes many pollutants will need to be exchanged. This process would also be able to cater towards a smaller operation such as a 65 megawatt power plant. This method is also the most common economical and sustainable. During co-op there were several siloxane removal skids manufactured by Venture Engineering. These skids contained three different types of activated carbons which would need to be replaced after being expended. It is my assumption that these units were followed an adsorption process. The specific project that I worked on was the Combined Heat and Power Facility. This process used the digester gas from the anaerobic digestion process to generate power. The power was generated within a combustion turbine which contained a cogeneration aspect that also generated steam with heat from the exhaust gas. Below is an image of the construction on the turbine building. The large digesters can be seen in the very top left hand corner of the image as well.