Using LowNOx FLU-ACE to Remove Nitrogen Oxides

The LowNOx FLU-ACE provides all of the benefits of the other FLU-ACE products, while economically removing nitrogen oxides air pollutants by 90% from any waste gas stream.

The Thermal Energy's LowNOx process is a two step process, with the first step as the gas phase chemical reaction of nitrogen monoxide as NO into nitrogen dioxide as NO2 through a compact gas reactor, and with the second step as the FLU-ACE tower for removing 98% of the nitrogen dioxide as NO2, which is absorbed and dissolved into the water as nitrates, which are non-hazardous and can be recycled as a commercial fertilizer.

This process allows the NO-to-NO2 reactor to adapt to upgrade any existing wet scrubber system APC technology into a Low NOx - APC system. Although conventional wet scrubber technology is not as efficient as the FLU-ACE for removing the NO2 in the second step, other wet scrubbers will perform adequately and therefore, offer an immediate market opportunity. The existing wet scrubber manufacturers already established in the market, are potential LowNOx process licensing candidates and some will be potential joint venture or strategic alliance partners.

The LowNOx FLU-ACE technology achieves 90% NOx removal at a lower cost than some methods of selective catalytic reduction (SCR) and silective non-catalytic reduction (or SNCR) techniques. Other advantages are that the LowNOx FLU-ACE does not produce hazardous byproducts; does not adversely affect the energy efficiency and operating cost; and does not suffer from an "ammonia slip" concern.

The LowNOx FLU-ACE technology has been approved for patent by the European patent office and is patent pending in 42 countries (including U.S.A., Europe, & Japan). Patents are being issued on an individual country basis over the next year.

LowNOx Process and LowNOx FLU-ACE vs. Other NOx Control Technologies

The global NOx or nitrogen oxide air pollution emission problem is the current focus of the new U.S., EC, and Japan Environment Protection Agency (EPA) regulations.

The U.S. EPA just announced on Sept. 24, 1998, the "Final NOx Rule" for the 22 North East U.S. states and the District of Columbia, which requires a 28% reduction in NOx emissions (or 1.1 million tons per year) to be achieved by the year 2003. As discussed on page 23, this new U.S. EPA NOx Rule may cost the North Eastern U.S. region more than $28 billion USD in order to meet the regulation by way of applying the competing SCR and SNCR NOx reduction technologies.

The LowNOx process and LowNOx FLU-ACE technology are revolutionary in their approach to achieving 90% reduction of NOx emissions, and have a several large competitive advantages over the SNCR and SCR technologies, including the achievement of the higher 90% NOx reduction at 30% to 50% lower cost per ton of NOx removed than SNCR and SCR.

Competing SNCR NOx Control Technology

SNCR is the abbreviation for Selective Non Catalytic Reduction of NOx method into nitrogen and water. There are two types of SNCR NOx process: the first technique known as Ammonia-based SNCR as it utilizes ammonia (NH3) injected into the flue gas at 1,600°F to 2,000°F, and the second technique known as Urea-based SNCR as it utilizes urea (NH2CONH2) as the reducing agent injected into the flue gas at 1,650°F to 2,100°F. The ammonia-based SNCR technique was developed and patented by Exxon Research and Engineering Company, and is known as Thermal DeNOx. Alternatively, the Urea-based SNCR technique was originally developed by the Electric Power Institute (EPRI, Palo Alto, CA), and is known as NOxOUT, and is offered by Nalco Fuel Tech, Inc. and its licensees (i.e.: Foster Wheeler, Wheelabrator Air Pollution Control, Research Cottrell, Todd Combustion, RJM Corporation, and several others internationally).

Both SNCR technologies have proven to reduce NOx emissions between 30% and 80%, depending upon the both the fuel (i.e., natural gas, fuel oil, refinery grade oil, coal, wood, and municipal solid waste) being combusted, and the type of combustion equipment (i.e., furnace, boiler, etc.) being retrofitted.

However, in addition to the high cost, the disadvantages of SNCR are:

a. the high temperature range required;
b. large amount of space required to adapt injection nozzles and to accommodate enough residence time to complete the reduction chemical reaction at the high temperatures; and
c. the undesirable excess ammonia and urea reagent "slip" which takes place due to incomplete chemical reaction.

Although the emission of excess urea is not that severe, the emission of the excess ammonia (toxic) from Thermal DeNOx is an environmental containment concern.

Competing SCR NOx Control Technology

The SCR process or Selective Catalytic Reduction of NOx method, takes advantage of the selectivity of ammonia (NH3) to reduce NOx to nitrogen and water at a lower temperature in the presence of a catalytic surface. Two catalyst formulations are denoted:

1. "base metal" including oxides of titanium, molybdenum, tungsten, and vanadium; and
2. "zeolites" which are alumina-silicate-based.

Although there are several different formulations of catalyst material, and the specific catalyst structure or bed designs and sizes vary depending upon the application, the basic principle of operation is the same.

Gaseous ammonia is injected with a carrier gas, typically steam or compressed air, into the flue gas upstream of the catalyst. The ammonia/flue gas mixture enters the catalyst, where it is distributed evenly through or across the catalyst bed. The flue gas then leaves the catalytic reactor and continues to the exit stack or air preheater. The SCR technology is capable of achieving similar NOx reductions as Thermal DeNOx SNCR; however, SCR utilizes a much smaller amount of ammonia due to the positive impact of the lower reaction temperature and the selective catalyst. Hence, the ammonia "slip" is much lower from SCR than SNCR.

SCR operates most efficiently at temperatures between 575°F and 800°F, and when the flue gas is relatively free of particulate matter, which tends to contaminate or "poison" the catalytic surfaces.

Typically, the catalytic reactor is located ahead of the air heater, to take advantage of the temperature regime.

Sometimes, however, the reactor may be placed just ahead of the stack and downstream of the particulate collection devices, e.g. electrostatic precipitators (ESPs), to avoid catalyst contamination.

In most cases, however, reactor placement just before the stack requires reheating of the flue gas to meet the catalyst reaction temperature requirements, which in turn adversely increases the cost of the SCR system. In addition, because catalysts lose their effectiveness over time due to contamination or clogging of catalyst pores, they must be replaced periodically. On large boilers and flue gas applications, it has been reported that catalyst replacement would be necessary between every one to five years, depending on the application and the level of contaminants in the fuel (ref. U.S. EPA, Research Triangle, NC).

In summary, SCR technologies have proven to reduce NOx emissions between 53% and 90%, depending upon both the fuel (i.e., natural gas, fuel oil, refinery grade oil, coal, wood, and municipal solid waste) being combusted, and the type of combustion equipment (i.e., furnace, boiler, etc.) being retrofitted.

However, in addition to the high cost, the disadvantages of SCR include:

a. the high temperature range required;
b. large amount of space required to adapt injection nozzles and to accommodate enough residence time to complete the reduction chemical reaction at the high temperatures;
c. requires additional space, installation cost, and downtime to accommodate the catalyst beds or reactor;
d. high operating and maintenance cost associated with catalyst bed replacement every one to five years;
e. solid waste disposal cost associated with spent catalyst; and
f. potential for undesirable excess ammonia "slip" which takes place due to incomplete chemical reaction.

Although the emission of the excess ammonia (toxic) from SCR is less than from the SNCR Thermal process; however, the ammonia "slip" is an environmental containment concern.

Other disadvantages or limitations of SCR cited by the U.S. EPA for application to the coal and fuel oil fired power utility boilers in the North East region stem from the fact that SCR has proven to work best on boilers burning low sulfur (<1%) and low ash coals and fuel oils. The use of SCR for high sulfur coal will result in high boiler maintenance as few of the units control SO2. Only 25% of the coal fired utility boilers in the U.S. North East region are fired with coal of sulfur content less than 1%, and are considered to be candidates for SCR.

However, 2/3 of the natural gas and fuel oil fired utility boilers in the NE U.S. region were operated with fuel oil containing less than 1% sulfur, and are considered candidates for SCR.

LowNOx process and LowNOx FLU-ACE technology Superiority

In addition to having a 30% to 50% lower cost per ton of NOx removed than the competing SNCR and SCR NOx reduction technologies, the LowNOx process and LowNOx FLU-ACE technology do not suffer from any of the disadvantages (as listed above) associated with the SNCR and SCR technologies. The LowNOx process does not utilize any catalyst, and utilizes the total opposite chemical reaction with NOx compared to SNCR and SCR. The LowNOx process utilizes an oxidation chemical reaction of nitrogen monoxide with ozone to produce nitrogen dioxide (NO2), as opposed to the reduction chemical reactions used by SNCR and SCR to strip the oxygen from the NO and NO2.

As described before, the LowNOx process is a simple phosphorus additive atomization and injection process into the flue gas; which initially creates ozone, which then reacts with nitrogen monoxide to produce nitrogen dioxide, and then the NO2 is easily removed by 90% through a standard wet scrubber or removed by 98% through a FLU-ACE condensing & reactive scrubber.

Also, the LowNOx FLU-ACE technology will consistently achieve 80% to 90% NOx reductions (which is higher removal than both SNCR and SCR for fossil fuels) no matter which fuel (coal, oil, gas, wood, etc..) is being combusted.

LowNOx Process in Front of Existing WFGD Scrubber Creates Cost Effective Combined DeNOx & DeSOx System

In the cases where a Wet Flue Gas Desulfurization Scrubber (WFGD) is already in place on a coal fired power boiler; only the LowNOx process needs to be installed prior to the WFGD scrubber, in order to achieve combined 90% DeNOx and DeSOx removal. Applying the LowNOx process without a FLU-ACE condensing scrubber unit, will be an extra 30% less expensive or more NOx reduction cost effective, at an estimated cost effectiveness range of $800 to $1200 USD per ton (corresponding to PC wall fired boiler sizes of 750 mmBtu/hr and 250 mmBtu/hr input coal firing rate).

In comparison to SCR, for the same coal fired boiler size range at only 80% NOx removal, the corresponding SCR cost effectiveness range is $3000 to $4800 USD per. Therefore, the LowNOx process installed in series in front of an existing WFGD on a coal fired power boiler, would be 65% to 75% less expensive than SCR, and would achieve a higher NOx removal efficiency at 90%.