An Introduction to VOCs Virtually every consumer product that is seen has some kind of coating to make it either more attractive or more durable. The commonality between most printing, painting, and adhesive coating industrial processes is that they use solvent-based liquids. A layer of a liquid is applied, and as the solvent evaporates, the coating dries into the form we see on the packaging of products. There are many such industrial processes ranging from automobile paint booths to the manufacture of bottle caps. When a solvent-based fluid dries, the evaporated solvent disperses into the environmental air. This is evidenced by the distinctive smell in such facilities. However, the neighboring residents and the EPA (not to mention the various sorts of wild critters in that area) are not fond of these substances being released into the environment. The purpose of our oxidizer product lines is to remove these fumes before they are released from the industrial plant. The reliability of an oxidizer is very important because EPA regulations prevent our customers from running their process if the oxidizer is not functioning. Another term used to describe generic solvent fumes is volatile organic compound (VOC). Volatile- Evaporating readily at normal temperatures and pressures Organic- Chemical make-up centered on carbon atoms Compound- A substance that is made up of two or more elements There are thousands of different VOCs that are used in industry ranging from the relatively simple (Methane, CH4) to more chemically complex (Isopropyl Nectate, CH3COOCH(CH3)2). Each has its own properties and uses, but the commonality is that they all need to be removed from an industrial exhaust before it can be released into the environment. An Introduction to Oxidation Oxidation is one of the most common chemical reactions that occurs not only in industry, but in our day-to-day lives. It is a chemical reaction that occurs between an organic compound and oxygen to form smaller, more stable compounds. Since the process involves large molecules being broken and rearranged into smaller molecules, oxidation reactions convert chemical energy into heat energy. One commonly seen example of an oxidation reaction is what occurs between iron and the oxygen in water. The new substance created is iron oxide – also known as rust. It is too small to notice and occurs over a long period of time, but a little bit of heat is released when rusting occurs. Another example is the act of living organisms that breathe. Our lungs are designed to carry out a simple form of oxidation. We inhale oxygen rich air, which interacts with the iron in our blood (turning it red). As the iron + oxygen forms into iron oxide, we exhale carbon dioxide and water vapor. The same kind of reaction can occur with VOCs, except that the reaction takes place much faster. By adding a little bit of heat to get the reaction going, you can make oxidation happen very quickly. If it happens fast enough, a significant amount of heat is released also. When oxidation happens quickly like this, we call it combustion. As anyone who has used a gas grill can tell you, once you get the reaction going, the heat produced is enough to keep the reaction going for as long as you have enough oxygen (from the air) and fuel (in this case propane). Regardless of whether it is a VOC in an oxidizer, coal in a power plant boiler, or the act of exhaling, the chemical reaction is virtually the same. That is why on a cold day you will see a cloud of white water vapor coming from the stack of a factory or power plant. In truth, they are not really "smoke-stacks" anymore, nearly as much as they are "water-vapor-stacks". The important thing to note in considering our oxidizer product lines is that they are designed to take a VOC (which is harmful to the environment) and convert it into carbon dioxide and water vapor (which are not harmful to the environment). Energy Balancing and Oxidizer Design In the most general terms, an oxidizer is a piece of equipment that provides enough heat and oxygen to carry out a sustained oxidation reaction on a VOC. Most oxidizer applications inherently contain enough oxygen, so the name of the game in designing an oxidizer is to provide the required amount of heat energy by the most economical method. The heat energy to sustain an oxidation reaction can come from any of three sources: heat content of the VOC, heat content of the fuel, and heat recovery. The methods that are used to provide the heat are what differentiates one type of oxidizer from another, and are selected based on the type of process and the cost of available fuel. The simplest type of oxidizer is called the Flare Stack. This type is used in applications that have a very high heat content in the VOC. No heat exchanger is required because the VOC provides the majority of the heat to sustain combustion. The lack of a heat exchanger is not a problem because the heat that can be generated from the VOC makes up for the difference. For a flare stack, the heat diagram would look like this: However, many industrial processes do not have the high heat content that is required to make a flare stack cost efficient. These are the applications that The Air Preheater Company focuses on. Since fuel is a cost for the oxidizer, our goal is to design equipment that makes up for the VOC content with heat recovery rather than added fuel. All oxidizers, that Air Preheater designs, have a heat exchanger. For example, a process with 30% LEL does not contain enough heat for the VOC to sustain the oxidation reaction by itself, but nevertheless the VOC content is significant. Therefore, we would design a heat exchanger to recover just as much heat as to make up the difference. Based on the heat content of the VOC, a 50% efficient heat exchanger might be acceptable.  This would be ideal for the Recuperative Cor-Pak® Oxidizer. If the heat content of the VOC is negligible, it is desirable for the oxidizer to recover as much heat from the combustion as possible. This calls for a very high efficiency heat exchanger. For example, in an application with 3½% LEL, it would be ideal to supply an oxidizer with a 95% efficiency heat exchanger. The heat recovered from the process would be enough to turn off the fuel valve as long as the VOC provides its meager heat.  This type of application would be ideal for the Regenerative TechNO-VOC™ Oxidizer. Thus, the design of an oxidizer is not based on the maximum possible heat recovery, but on the amount of heat recovery required to make up the difference between the VOC heat content and the heat required for oxidation. › Locate a Salesperson