by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
Flexo Sustainable : Year End 2011
necessary to generate the required treatment temperatures. This is because the oxidation of VOCs is an exothermic reac- tion where heat and energy is released. SELF-SUSTAINING SYSTEMS If there is enough fuel value in the VOCs, an oxidizer doesn’t need auxiliary natural gas to maintain its operating tempera- ture. That type of system is said to be self-sustaining. In these cases, the fans moving the process exhaust through the oxi- dizer system are the only producer of Energy Input CO2. Regenerative Thermal Oxidizers (RTOs) have been replac- ing other technologies because of the lower auxiliary fuel con- sumption requirement and subsequent lower CO2 emissions. For example, an RTO operating with 10,000 SCFM of process flow containing 75 lbs/hr of Isopropyl alcohol will generate the following: • About 165 lbs/hr of Process Exhaust CO2 • About 5 lbs/hr of Energy Input CO2 By increasing the ceramic heat recovery media of the RTO in this example, the operator can even eliminate the 5 lbs. of CO2 from energy input, making the oxidizer system truly self- sustaining. Conversion from a catalytic oxidizer used in the past, to more efficient RTOs, would reduce the CO2 emissions by more than 500 tons per year. Intuitively, oxidizers—with their high chamber tempera- tures—would seem to come with a large Energy Input CO2 penalty, however, a properly designed oxidizer system can in fact be the best choice of technology to limit this additional quantity of CO2 from energy input into the treatment process. In addition to minimizing Energy Input CO2 emissions, oxi- dizer designers have realized that other CO2 reductions can be made. The following application is just such a case. DIRECT HEAT RECOVERY Back in 2008, a major food can producing company presented an opportunity to treat the exhaust stream from a coating process of 20,000 SCFM with up to 400 lbs/hour of various VOCs. The fuel value in this quantity of VOCs is ap- proximately 6.0 MM BTU/hr. In the past, this exhaust stream would typically have been treated with a thermal recupera- tive oxidizer with approximately 35 percent internal thermal energy recovery. The reason that such a low energy recovery was often used was that the plant desired oxidizer stack gases hot enough to put back into their process ovens. This method of direct heat recovery from a thermal oxidizer stack was forward-thinking in its time and was able to reduce the number of process burners required as well, further reducing maintenance costs. For such an operation, the typical breakdown of energy required—and CO2 released— would be: Oven energy input: 12.0 MM BTU/hr Oxidizer energy loss at 35percent TER: 6.0 MM BTU/hr Heat Release from VOCs: <6.0 MM BTU/hr> Net Energy Input into system: 12.0 MM BTU/hr CO2 generated per hour: 1400 lb/hour CO2 Instead of going the typical route, a Regenerative Thermal Oxidizer (RTO) with 95 percent thermal energy recovery (TER) was used. Such a high TER translates to much lower stack gas temperatures—too low in fact for those gases to be re- cycled into the process ovens. To overcome this issue Anguil designed a custom heat recovery system for the can manu- facturer that utilized a smaller amount of gases taken at very high temperatures directly from the oxidation chamber. In this way, the heat recovery of the entire system did not have to be derated just to get the desired direct heat recovery tempera- ture in the exhaust stack. Because of the high TER of the custom RTO, the breakdown of energy required for the entire system became: Oven energy input: 12.0 MM BTU/hr Oxidizer energy loss at 95 percent TER: 1.5 MM BTU/hr Heat Release from VOCs: <6.0 MM BTU/hr> Net Energy Input into system: 7.5 MM BTU/hr CO2 generated per hour: 875 lb/hour CO2 CO2 reduction: ~ 37 percent This equates to a yearly reduction in CO2 of approximately 2300 tons! While the quantity of Process Exhaust CO2 remained un- changed, the unique design of the RTO and energy recovery system truly changed the CO2 equation for this facility. n About the Author: Jeff Kudronowicz is the application engi- neering manager for Anguil Environmental Systems. He is a chemical engineer with more than 25 years of experience in the air pollution control industry. Jeff ’s role at Anguil involves equipment selection, pricing and technical sales support. He is charged with conceptualizing the assembly of various industrial applications that require thermal and catalytic oxidizers, concentrator systems, cyclones and acid-gas scrub- bers. Jeff is also responsible for implementing and maintain- ing product standards for the company. 1 of 4 Wicket Ovens: Industrial ovens and dryers are often sources of process greenhouse gas emissions. www.flexomag.com year-end 2011 Sustainable FLEXO 9