Fuel and CO2 Emission Reductions in Oil and Gas Refining Industry Thermal Oxidizers

Paper from the AFRC 2016 conference titled Fuel and CO2 Emission Reductions in Oil and Gas Refining Industry Thermal Oxidizers

There are many types of thermal oxidizers used in the oil and gas refining industry. This analysis will focus on thermal oxidizer applications that contain large quantities of inert gases contaminated with CO, hydrocarbons, and sulfur species. Thermal oxidizers generate CO2 in the process of destroying hazardous air pollutants (HAP), volatile organic compounds (VOC), and carbon monoxide. The fuel used in the thermal oxidizer burner is also a significant source of CO2 emissions. This analysis will evaluate methods to reduce CO2 emissions by selecting thermal oxidizer operating conditions (such as temperature and excess oxygen levels) and thermal oxidizer system configurations (such as direct fired systems, recuperative systems, and regenerative systems). Practical aspects and limitations of operating conditions and system configurations will also be evaluated relative to CO2 emission reductions.

Fuel and CO2 Emission Reductions in Oil and Gas Refining Industry Thermal Oxidizers American Flame Research Committee 2016 Industrial Combustion Symposium Nathan Petersen, Gernot Schwarting, Francisco Iglesias John Zink Company LLC Abstract There are many types of thermal oxidizers used in the oil and gas refining industry. This analysis will focus on thermal oxidizer applications that contain large quantities of inert gases contaminated with CO, hydrocarbons, and sulfur species. Thermal oxidizers generate CO2 in the process of destroying hazardous air pollutants (HAP), volatile organic compounds (VOC), and carbon monoxide. The fuel used in the thermal oxidizer burner is also a significant source of CO2 emissions. This analysis will evaluate methods to reduce CO2 emissions by selecting thermal oxidizer operating conditions (such as temperature and excess oxygen levels) and thermal oxidizer system configurations (such as direct fired systems, recuperative systems, and regenerative systems). Practical aspects and limitations of operating conditions and system configurations will also be evaluated relative to CO2 emission reductions. 1 Introduction Thermal oxidizers in the oil and gas refining industry are frequently designed to destroy a wide variety of gas and liquid waste streams. The carbon contained in these waste streams is inevitably transformed nearly completely to CO2 if the system is designed and operated properly. The waste gas may also contain large quantities of CO 2, which also contributes to the CO2 emissions discharged through the stack. Carbon emissions native to the waste stream entering a thermal oxidizer can only be reduced if captured before exiting the stack. Carbon dioxide captured from thermal oxidizer effluent gases is not common in industry and will not be addressed in this analysis. Many waste gases in oil and gas refining contain mostly inert species contaminated with species containing sulfur and carbon that must be oxidized before discharging to the atmosphere. The combustible species in these waste gases are well outside their flammability limits and must be heated above their auto-ignition temperature to be oxidized. Thermal oxidizers burn fuel such as natural gas to provide energy necessary to oxidize the species in the waste streams. The analysis in this paper will focus on these types of waste gases. Sulfur plant Tail Gas is a waste gas containing mostly inert species. A sample Tail Gas composition and flow that is representative of a 50 ton per day sulfur plant is shown in Table 1. Table 1: Sulfur Plant Tail Gas Composition Vol(%) H2S 500 ppm SO2 10 ppm H2O 5.3 N2 84.4 H2 3.8 CO2 6.4 CO 475 ppm COS 15 ppm CS2 traces Total Flow: 36,617 lb/hr Another typical waste gas stream generated during oil and gas refining occurs as a result of removing CO 2 and H2S from hydrocarbons with an amine scrubber. When the amine solution is regenerated, an off-gas containing the CO2, H2S and some hydrocarbons is sent to a thermal oxidizer for treatment before venting to the atmosphere. A typical composition of Amine Acid Gas for a typical midstream processing operation is shown in Table 2. Note the high CO2 concentration native to the waste gas stream. Table 2: Amine Acid Gas Composition Vol(%) H2S 215 ppm CO2 90.2 H2O 9.5 CH4 0.27 C2H6 0.02 Other hydrocarbons traces Total Flow: 15,537 lb/hr 2 Systems designed to oxidize sulfur plant Tail Gas, Amine Acid Gas, and other mostly inert waste gases are designed with similar philosophy. The following analysis will focus on the sulfur plant Tail Gas application but most of these concepts can be similarly applied to other thermal oxidizer applications designed to oxidize endothermic waste gases. Thermal oxidizer temperature An appropriate temperature and residence time must be selected to achieve the desired levels of oxidation of the waste gases. Sometimes only H2S needs to be destroyed down to 10 ppmv or less (with suitable stack dispersion of unburned H2S and SO2) with no concerns of VOC or CO emissions. Thermal oxidizers operating at 1200°F with 1 second residence time and oxygen concentrations above 2 vol% typically achieve this result. The relationship between H2S emissions and residence time and operating temperature should be considered in selecting an appropriate combination of operating parameters. Different references of these relationships can be consulted to select a suitable combination (1, 2). Many current emission regulations also require limits of CO not to be exceeded (typically 50 to 100 ppmv). Carbon monoxide is more difficult to oxidize than H2S and requires higher operating temperatures with suitable residence times. Some simple global CO and VOC oxidation relationships have been developed that can be used to help evaluate CO burnout in thermal oxidizer flue gas (2,3,4). A simplified rule of thumb to ensure VOC destruction above 98% is to use a thermal oxidizer temperature of 1600°F with at least 0.75 seconds of residence time (5). Traditional John Zink Hamworthy Combustion thermal oxidizers typically operate with 1 second of residence time at 1500°F to meet most CO emission requirements in sulfur Tail Gas applications. Minimizing the thermal oxidizer temperature is very important to minimize the fuel and CO2 emissions. However, the temperature can't be reduced below what is required to meet CO and H2S emission limits. Figure 1 compares the burnout of H2S and CO at temperatures ranging from 1200°F to 1500°F. The curves in Figure 1 are based on the global reaction rate recommended for Tail Gas flue gases (2). The Tail Gas volume is typically diluted by approximately an equal volume of gas originating from the burner combustion products and excess combustion air. For simplicity, the initial H2S and CO concentrations are approximated as 250 ppmv in the calculations to represent the initial conditions of the thermal oxidizer flue gas treating the Sulfur Tail Gas shown in Table 1. The oxygen concentration is also approximated to be a constant 3 vol% (wet basis) in the calculations. 3 10000 H2S 1200°F 3 vol% O2 1000 100 10 CO 1000 100 10 1 1 0.0 0.5 10000 1.0 Residence Time (s) 1.5 0.0 2.0 0.5 1.0 Residence Time (s) 10000 H2S 1400°F 3 vol% O2 1000 100 10 1.5 2.0 H2S 1500°F 3 vol% O2 CO Concentration (ppmv) Concentration (ppmv) H2S 1300°F 3 vol% O2 CO Concentration (ppmv) Concentration (ppmv) 10000 CO 1000 100 10 1 1 0.0 0.5 1.0 Residence Time (s) 1.5 2.0 0.0 0.5 1.0 Residence Time (s) 1.5 2.0 Figure 1: Burnout of H2S and CO in perfectly mixed Sulfur Tail Gas thermal oxidizer flue gas at temperatures ranging from 1200°F to 1500°F The results in Figure 1 indicate that 1200°F is not sufficient to reduce the CO emissions below 50 ppmv within 2 seconds of residence time. At 1300°F the CO emissions decrease to 50 ppmv at 1.5 seconds of residence time. Further increases to the TO temperature reduce CO emissions even more quickly, but come at the expense of fuel usage and increased CO2 emissions. Table 3 shows the fuel firing (and associated CO2 emissions due to fuel burning) required to reach the thermal oxidizer temperatures ranging from 1200°F to 1500°F with 3 vol% O2 in the stack gas for the Tail Gas shown in Table 1. Table 3: Effect of Direct Fired T.O. Operating Temperature T.O. Temperature Fuel Firing CO2 Emissions From Fuel Reduction (°F) (MMBtu/hr) (ton/yr) (%) 1200 15.5 8,665 38 1300 18.3 10,240 27 1400 21.5 12,000 14 1500 25 14,000 0 The results in Table 3 are based on a representative 50 ton/day sulfur plant Tail Gas. Larger plants will have larger quantities of CO2 emissions and fuel firing rates proportional to the amount of Tail Gas that is processed in the thermal oxidizer. The reductions of fuel consumption and CO2 emissions noted in Table 3 are relative to a 4 "baseline" operating condition defined by 1500°F, 3 vol% O2. This was taken as the "baseline" operating condition for this paper since it represents the most common traditional John Zink Hamworthy Combustion operating condition for Tail Gas thermal oxidizers built using legacy technology. The reductions of fuel born CO2 emissions noted throughout this report are defined relative to this same baseline operating condition. The plots in Figure 1 have assumed perfect mixing and neglected the CO contributed to the flue gas from the burner. Reducing the thermal oxidizer temperature increases the tendency of the burner to contribute to the CO emissions. At low thermal oxidizer temperatures, such as 1200°F, it is possible the CO emissions in the stack exceed what was in the Tail Gas due to the burner producing large quantities of CO. The CO emissions generated from the burner depend on the burner and waste gas injector design along with the thermal oxidizer temperature and residence time. Upsets in the CO concentration of the incoming Tail Gas may also occur which also increase the load that must be burned. Figure 2 displays what CO burnout may look like in the thermal oxidizer with varying quantities of CO that may come from upsets in the Tail Gas composition and/or contributed from the burner assuming perfect mixing using global Tail Gas reaction kinetics parameters (2). Figure 2 illustrates the importance of the system design to minimize CO production from the burner if operating temperatures are to be reduced. CO Concentration (ppmv) 10000 1350°F 3 vol% O2 1000 250 ppmv 1000 ppmv 5000 ppmv 10000 ppmv 100 10 1 0.0 0.5 1.0 Residence Time (s) 1.5 2.0 Figure 2: Burnout of varying loads of CO in a Sulfur Tail Gas thermal oxidizer at 1350°F Excess O2 and Mixing The oxygen in the thermal oxidizer is supplied by fresh air and must be sufficient to oxidize both the burner fuel and combustible species in the waste gas. An excess of air (beyond what is needed based on stoichiometry) is supplied to the system to ensure thorough combustion. The increased excess air flow assists in increasing the reaction rates but perhaps more importantly ensures adequate O2 is available for reaction considering there will be non-perfect mixing. The fresh air added to the system adds to the heat load of the thermal oxidizer, which increases the burner firing and CO2 emissions of the system. Typically fresh air is added to reach 2 to 3 vol% O 2 in the stack gases of traditional John Zink Hamworthy Tail Combustion Gas thermal oxidizers. Operating with 2 vol% O2 in the stack requires good mixing of the air and Tail Gas. Operating below 2 vol% O 2 requires even better mixing. The design of the burner, waste gas injector, and thermal oxidizer vessel are critical to achieve very good mixing. Insufficient mixing will result in increased H2S and CO emissions proportional to the quantity of waste gas that has not encountered oxygen for sufficient residence time. It is important to consider the mixing delay when considering a suitable thermal oxidizer residence time. 5 Reducing the stack O2 content by a seemingly small quantity can have a substantial effect at increasing the system's fuel efficiency and reducing CO2 emissions. Table 4 shows firing rates and CO2 emissions generated by fuel firing to oxidizing the Tail Gas shown in Table 1 at 1500°F for various levels of excess oxygen in the stack gases. Table 4: Effect of Excess Oxygen in Direct Fired Thermal Oxidizer Stack O2 (vol%) Fuel Firing (MMBtu/hr) CO2 Emissions From Fuel (ton/yr) Reduction (%) 0 18.8 10,490 24.8 1 20.5 11,460 18 2 22.6 12,600 9.6 3 25 14,000 0 Heat Recovery Many times the effluent from the thermal oxidizer is discharged directly to the atmosphere. It is possible to recover energy from these gases to offset fuel usage and CO2. The amount of energy that can be recovered from hot flue gas corresponds to the final discharge temperature and mass flow of the flue gas. Energy recovery efficiencies can be close to 100% if the flue gas is cooled down to ambient temperatures by heat absorption into the process utility fluid. There are practical limitations that limit the amount of heat that can be extracted from the flue gas. The heat exchange area may be impractical to reduce the flue gas temperature to very low temperatures. Avoiding condensing flue gases is also a special concern that limits the temperature reduction of the flue gas. Keeping the flue gas above condensation temperatures greatly reduces the potential of corrosion of the steel components. Flue gas temperatures are usually discharged above 250°F to avoid water condensation. Thermal oxidizer exhaust gases typically contain acid gas species, such as SOx. The dew point temperature of SOx is significantly higher than H2O, which favors keeping the exhaust gas at higher discharge temperatures to avoid corrosion issues with condensed acid. The surface temperature of metal components exposed to SOx is typically maintained above 350°F in order to inhibit corrosion. Figure 3 shows calculated SOx dewpoint temperature calculations based on the methods of Okkes (6). The dew points calculated in Figure 3 assume SO2/SO3 equilibrate at 1500°F in the flue gases resulting from Tail Gas combustion at 3 vol% O2. 6 SOx Dewpoint Temperature (F) 350 300 250 200 10 100 1000 Sulfur Concentration in Flue Gas (ppmv) 10000 Figure 3: SOx dewpoint temperatures in sulfur Tail Gas combustion products with varying loads of SOx Boilers and hot oil heaters are common heat recovery devices that are used to absorb much of the energy contained in the thermal oxidizer flue gas. The heat absorbed by these heat recovery devices offsets fuel use and CO2 emissions by reducing the loads of other fired equipment supplying heating for these plant utilities rather than a direct reduction within the boundary of the thermal oxidizer system. Table 5 shows the CO2 emissions that may be offset from other sources providing heating of steam or hot oil firing natural gas (assuming these other heat generating devices operate with 85% thermal efficiency). The incoming flue gas into the heat recovery device is assumed to be Tail Gas combustion products at 1500°F with 3 vol% O2 generated by a net heat release of 25 MMBtu/hr (burner) + 5.5 MMBtu/hr (Tail Gas) = 30.5 MMBtu/hr. Table 5: Effect of Waste Heat Recovery into Plant Utilities for 50 ton/day sulfur plant Tail Gas Thermal Oxidizer Stack Exhaust Temperature (°F) Heat Absorbed (MMBtu/hr) Heat Recovery Efficiency (%) CO2 Emissions Offset (ton/yr) 700 16.7 55 11,010 600 18.7 61 12,320 500 20.6 68 13,600 400 22.6 74 14,870 300 24.5 80 16,130 Waste heat recovery boilers are the most mechanically robust heat recovery device because the heat transfer surfaces are completely bathed in water, which allows the metal surface temperature to remain at a relatively constant temperature below maximum temperature limits of the metal. Hot oil heaters also benefit from having the cold side of the heat exchanger bathed in liquid. However, the oil may degrade or coke from high temperatures even though maximum metal temperature limits are not exceeded. Some plants may not have a need or benefit from hot oil or steam. Heat can alternatively be recovered from the flue gas by absorption into the incoming waste gas and/or combustion air. Recuperative thermal oxidizers are direct- 7 fired thermal oxidizer systems that pre-heat waste gas and/or combustion air using a gas/gas heat exchanger. Figure 4 shows a schematic of a recuperative thermal oxidizer pre-heating the Tail Gas. Exhaust Tail Gas Air Fuel Figure 4: Schematic of recuperative thermal oxidizer pre-heating Tail Gas Table 6 shows fuel and CO2 emission reductions as a result of recuperating heat into the combustion air. The results in Table 6 were based on a thermal oxidizer operating temperature of 1500°F with 3 vol% O2 while oxidizing the Tail Gas shown in Table 1. Table 6: Effect of Recuperating Heat into Combustion Air Air Pre-heat Temperature (°F) Stack Exhaust Temperature (°F) Fired Duty (MMBtu/hr) CO2 Emissions due to Fuel (ton/yr) Reduction (%) 100 1500 25.0 14,000 0 800 1250 16.7 9,355 33.2 1000 1187 15.0 8,386 40.1 1200 1125 13.4 7,518 46.3 1400 1029 12.0 6,733 51.9 Increasing the air preheat temperature reduces the fuel firing which also reduces the incoming air flow required to maintain 3 vol% O2 in the stack gases. The mass flow of air limits the fuel reduction to slightly more than 50% if heat is exclusively recuperated into the combustion air. Preheating the combustion air will increase NOx concentration since the peak flame temperatures will be higher. However, the total mass flow of NOx discharged from the stack will be less since the burner firing rate is lower. The relationship of NOx emissions relative to air preheat temperatures in a recuperative thermal oxidizer has previously been shown by Johnson (7). Heat can also be recuperated into the waste gas. Table 7 shows fuel emission reductions as a result of recuperating heat into the Tail Gas. The results in Table 7 were based on a thermal oxidizer operating temperature of 1500°F with 3 vol% O2 while oxidizing the Tail Gas shown in Table 1. 8 Table 7: Effect of Recuperating Heat into Tail Gas Tail Gas Pre-heat Temperature (°F) Stack Exhaust Temperature (°F) Fired Duty (MMBtu/hr) CO2 Emissions due to Fuel (ton/yr) Reduction (%) 100 1500 25.0 14,000 0 800 1107 13.2 7,411 47.1 1000 951 9.7 5,434 61.2 1200 766 6.1 3,400 75.7 1400 541 2.4 1,316 90.6 Table 7 shows Tail Gas pre-heat temperatures 1000°F and above, which is above the auto-ignition temperatures of many combustible species. If oxygen is present in the waste gas it will react with the combustibles inside the heat exchanger, which may damage the equipment. Even if oxygen is not present there may be undesirable reactions in the waste gas, such as coking of hydrocarbons, when the pre-heat temperatures are high. Heat can be recuperated into both the combustion air and waste gas simultaneously. This is preferably done in separate heat exchangers due to concerns of internal burning damaging the equipment. Table 8 shows the impact of using two heat exchangers to pre-heat both the combustion air (to 800°F) and Tail Gas (to various temperatures). Table 8: Effect of Recuperating Heat into Combustion Air (to 800°F) and Tail Gas Tail Gas Pre-heat Temperature (°F) Stack Exhaust Temperature (°F) Fired Duty (MMBtu/hr) CO2 Emissions due to Fuel (ton/yr) Reduction (%) 800 793 7.6 4,270 69.5 1000 647 4.9 2,740 80.4 1200 478 2.1 1,180 91.6 1300 382 0.7 380 97.3 Theoretically, the burner heat release can be reduced to very low rates in recuperative thermal oxidizers. Some practical challenges that limit the amount of heat recovery that can be obtained with gas/gas heat exchangers are temperature limits of the heat exchanger, size of the heat exchanger, and turndown range of the burner and fans. Gas/gas heat exchangers are not as robust as boilers since they inherently have large thermal gradients that create larger thermal and mechanical stresses on the structure. The heat exchanger must always have some flow through the "cold" side to ensure the equipment isn't damaged from the hot thermal oxidizer gases. Recuperating heat into the combustion air can be advantageous since it is always flowing when the unit is in operation (even at startup). Process conditions resulting in exothermic compositions of waste gas can damage the recuperative heat exchangers. The temperatures resulting from the exothermic heat release coupled with the heat recovery are likely to exceed the temperature limits of any metal heat exchanger. The system may need to be designed with a bypass around the heat recovery if the process is known to have exothermic upsets in the waste gas. 9 Recuperative heat recovery systems can be very reliable when they are operated within their design parameters, while offering high heat recovery efficiencies. John Zink Hamworthy Combustion has designed and supplied a Tail Gas Incinerator with recuperative heat recovery for a refinery in Germany which has been in successful operation for nearly 20 years. Systems that recover heat by alternating flows of incoming waste gas and exhaust gases across ceramic media are referred to as regenerative thermal oxidizers (RTO). The incoming gases absorb the residual heat left in the ceramic from the hot exhaust gases from the previous regeneration cycle. A combustion chamber with a burner located between the incoming and outgoing ceramic media adds heat as necessary to reach the desired temperature. The outgoing gases are cooled by the ceramic media previously exposed to the incoming gases and are discharged at relatively cool temperatures. Tail Gas does not contain oxygen so fresh air must be mixed in before entering the ceramic media. Figure 5 shows a schematic of a regenerative thermal oxidizer. Exhaust Air Fuel Ceramic Packing Beds Tail Gas + Air Switching Valves Figure 5: Schematic of regenerative thermal oxidizer (RTO) Table 9 shows fuel and CO2 emissions as a result of absorbing heat into a mixture of Tail Gas and combustion air with an RTO. The results in Table 9 were based on an RTO combustion chamber operating temperature of 1500°F with 3 vol% O2 while oxidizing the Tail Gas shown in Table 1. Table 9: Effect of Heat Recovery Using Regenerative Thermal Oxidizer Tail Gas/Air Pre-heat Temperature (°F) Stack Exhaust Temperature (°F) Fired Duty (MMBtu/hr) CO2 Emissions due to Fuel (ton/yr) Reduction (%) 800 793 7.6 4,270 69.5 1000 623 3.9 2,190 84.4 1200 420 0.6 310 97.8 1300 306 0 0 100 Table 9 shows calculations that appear to be steady-state conditions. The RTO process is dynamic in nature and the actual pre-heat temperatures and stack temperatures will vary as the beds are cycled. 10 The heat recovery efficiency of the RTO allows it to operate with very low fuel consumption rates and practically no fuel is needed if the waste gas contains sufficient heating value to offset the system heat losses. In some operational cases additional air for cooling or a hot bypass might be needed if the waste gas heat release is higher than the heat losses through the refractory. The surface area to volume ratio of the ceramic media is very high, making it possible to achieve very high heat recovery efficiency, provided the regeneration cycles are switched frequently enough to maintain low exit temperatures. Another effect of operating with very high heat recovery efficiency is that the cycling valves along with the inlet and outlet ducts operate over a relatively narrow range of cooler temperatures. Alternating the flow directions through the beds creates a potential for some waste gas to bypass the oxidation process when the valves cycle. This can be addressed by using a third bed in the cycling process. The third bed allows the waste gas to be purged from a bed for one cycle before becoming the heat recovery/exhaust bed. The cycling valves need to be leak free, regardless of the number of beds used, to prevent waste gas by-passing to the stack. For applications containing SOx in the exhaust gas, the regenerative heat recovery system needs to be designed so that the flue gas temperature will not drop below the acid due point in order to minimize corrosion. The RTO process is generally the most energy efficient for thermally treating waste gas streams with low heating values and is frequently used to treat air contaminated with VOC. John Zink Hamworthy Combustion has also supplied RTO process designs for sulfur plant Tail Gas applications. Case Study John Zink Hamworthy Combustion has recently supplied a refining customer in the Middle East with a Tail Gas thermal oxidizer designed using TriLoTM technology. An isometric drawing of this system is shown in Figure 6. TriLoTM technology is an optimized system where the burner generates low levels of NOx and CO along with Tail Gas injection methods resulting in very efficient mixing. As a result of this technology, thermal oxidizer operating temperatures can be reduced while complying with the customer's emission requirements. The operating conditions for this system are shown in Table 10. Figure 6: Isometric view of a TriLoTM sulfur plant Tail Gas thermal oxidizer system 11 Table 10: Operating Conditions of TriLoTM Tail Gas Thermal Oxidizer Temperature 1200°F NOx < 30 ppmvd CO < 200 ppmvd H2S < 0.2 ppmvd O2 3 vol%, d Fuel Firing 284 MMBtu/hr The system shown in Figure 6 operates at reduced thermal oxidizer temperatures compared to a traditional operating temperature of 1500°F, which would require approximately 458 MMBtu/hr of fuel firing. The reduced operating temperature saves approximately 174 MMBtu/hr of fuel, which reduces the CO 2 emissions by approximately 97,470 ton/yr from this system. This thermal oxidizer is also equipped with a waste heat boiler that cools the stack gases to approximately 700°F, which absorbs approximately192 MMBtu/hr of heat from the flue gas. Assuming a separate boiler operates with 85% thermal efficiency, 226 MMBtu/hr of fuel firing is saved from that boiler, which reduces the CO2 emissions from the plant by another 126,600 ton/yr. A total of 224,070 ton/yr of CO2 is not emitted to the atmosphere, and 400 MMBtu/hr of fuel is conserved as a result of this specialized thermal oxidizer design compared to a traditional direct fired thermal oxidizer with no heat recovery. Conclusions Reducing operating temperature and/or stack O2 concentrations will increase the fuel efficiency and reduce CO 2 emissions on any endothermic gas thermal oxidizer by a substantial amount. However, reducing temperature and stack O2 may also reduce the destruction efficiency of the thermal oxidizer below acceptable limits. Therefore, a careful balance of the different objectives must be applied to obtain the optimal solution. Reductions of the operating temperature and stack O2 concentration require very good mixing to realize the anticipated reaction rates. Improvements to mixing on existing systems can be achieved with the installation of refractory chokes or vector walls. Installation of forced draft burners and different waste gas injectors can also be very effective to improve mixing. These modifications also have high potential to also reduce CO generation from the burner. Computational fluid dynamic modeling is an additional tool that can be used to identify sources of mixing mal-distribution in the system and to optimize remedies to improve the mixing on existing systems. Heat recovery is the most effective way to save fuel and reduce CO2 emissions since the thermal oxidation process liberates significant energy that generates very high temperatures. Boilers are the most mechanically robust heat recovery devices and can be equipped on most thermal oxidizer systems if steam is needed in the facility. Regenerative thermal oxidizers have the highest heat recovery efficiencies and are most suitable for processes that have endothermic waste gas conditions. John Zink Hamworthy combustion offers field services, engineering studies, replacement parts and computational fluid dynamics modeling that can be used to recommend operating conditions or retrofitting existing systems. John 12 Zink Hamworthy Combustion also supplies direct fired thermal oxidizers (using the TriLoTM technology) with and without heat recovery (boilers, hot oil heaters), recuperative thermal oxidizers (gas/gas heat exchangers), and regenerative thermal oxidizers (RTO) for many endothermic waste gas thermal oxidation applications. 13 References: 1. Engineering Data Book Volume II, 12th ed., Gas Processors Suppliers Association, Tulsa, Oklahoma, Chapter 22, 2004. 2. Dowling, N.I.; Huang, M.; Clark, P.D.: "The Chemistry and Kinetics of Claus Tail Gas Incineration - Improving Incinerator Efficiency" Brimstone 2008 Sulphur Recovery Symposium, Vail, Colorado. 3. Barnes, R.H.; Saxton, M.J.; Barrett, R.E.; Levy, A: "Chemical Aspects of Afterburner Systems" U.S. Environmental Protection Agency, Report No. EPA-600/7-79-096, U.S. Government Printing Office, Washington, DC, 1979. 4. de Nevers, N.: Air Pollution Control Engineering, 2 nd ed., Waveland Press, Inc., Long Grove, Illinois, Chapter 10, 2010. 5. "Air Pollution Control Technology Fact Sheet", U.S. Environmental Protection Agency, Report No. EPA452/F-03-022 6. 7. Okkes, A.G.: "Get Acid Dew Point of Flue Gas", Hydrocarbon Processing, Vol 7 (1987). Johnson, B.C.; McQuigg, K.: "The Effects of Operating Conditions on Emissions from a Fume Incinerator" Proceedings of the 1994 International Incineration Conference. Houston, Texas. © 2016 John Zink Company LLC. 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