Hydrocarbon Processing Issue 04 | Page 6

O 2 ENRICHED OXYGEN IN COMBUSTION AND OXIDATION CONTROL In a traditional combustion process, oxygen (O 2 ) is supplied to the combustion reaction in the form of atmospheric air. The O 2 contained within the air combines with hydrogen and carbon from the fuel source, forming water and carbon dioxide in a process that releases heat. THE SERVOMEX SOLUTION SERVOMEX SUPPLIES THE EFFECTIVE GAS ANALYSIS SYSTEM FOR MONITORING ENRICHED O 2 IN THE COMBUSTION PROCESS. SERVOTOUGH OxyExact 2200 in a three-analyzer voting system ENERGY SAVINGS FROM O 2 INJECTION Air is composed of approximately 21% O 2 , 78% nitrogen (N 2 ), and 1% other gases. During combustion, the chemically inert N 2 in the air dilutes the O 2 , carrying away some of the energy in the hot combustion exhaust gas. %O 2 AIR %O 2 100% O 2 The efficiency of the process is dependent on both the exhaust gas temperature and the percentage of the O 2 in the combustion air. SERVOPRO MultiExact 4100 Performance studies conducted by the US Department of Energy, using O 2 levels at 100%, have shown a fuel consumption reduction between 10-20%, alongside NOx reductions of 90%. Theoretical studies have postulated that fuel savings of 42% over conventional systems may be possible using O 2 at 95%. This uses three SERVOTOUGH OxyExact 2200 process O 2 analyzers in a voting system, located between the air/O 2 mixing system and the furnace. At levels above 25%, flammability is increased significantly, which may impact upon plant safety. For this reason, many processes limit the O 2 enrichment to between 22-25%, which is still sufficient to achieve significant fuel savings. Energy Tips - Process Heating. September 2005 In a three-analyzer voting system, the process depends on the measurement made by the majority of analyzers. So, if only one analyzer reports a significant change in O 2 levels, it is “outvoted” by the other two, and no action is taken. However, if two analyzers detect a change, their reading is held as correct and action is taken – in this case to adjust the O 2 mix accordingly to return it to the correct concentration. BENEFITS OF OXYGEN-ENRICHED COMBUSTION Increased efficiency: Lower emissions: Improved stability: Increased productivity: Flue gas heat losses are reduced Reduced levels of NOx, carbon monoxide and hydrocarbons Higher O 2 results in more stable combustion and higher temperatures, leading to better heat transfer The heat generated is increased for the same amount of fuel P06 %O 2 EITHER OPTION Increasing the O 2 level in the combustion air to a level above 21% reduces this energy loss, potentially increasing the efficiency of the combustion process. Typically, liquid O 2 is used to increase the O 2 concentration in the combustion air before it enters the furnace. Accurate monitoring is required to ensure that the O 2 concentration remains within the specified limits, to obtain the optimum balance between safety and efficiency. %O 2 Voting systems allow problems with analyzers to be detected early without endangering the process. If two analyzers return the same measurement and the third varies, it may suggest a problem that can be investigated and corrected before the process is affected. It also provides a greater degree of safety, since using a single analyzer would make it more difficult to detect measurement variations, allowing incorrect measurements to go unnoticed for longer. The OxyExact 2200 uses an intelligent three-enclosure system that enables simplified, versatile sampling of up to 100% O 2 , with no requirement for pre- sample drying. It is certified for the use of enriched O 2 in Zone 1 hazardous areas. High-precision Paramagnetic sensing technology provides the accurate performance required for optimum process control, while the robust design ensures reliable operation in demanding conditions. depleting Paramagnetic technology as the OxyExact 2200s, except for safe areas only. The advanced communications offered by the MultiExact 4100s provide easy integration into voting and control systems. SERVOPRO MultiExact 4100 SERVOTOUGH OxyExact 2200 Servomex has also recently installed SERVOPRO MultiExact 4100 analyzers at a site using oxygen-enriched air for combustion. These provide accurate O 2 analysis using the same digital non- Find out more at: servomex.expert/mag-2200 P07