Case Studies - Institute of Clean Air Companies

Case Studies: Multi Pollutant Controls
Case Studies: VOC and HAPs Controls
Case Studies: Particulate Controls

Case Studies: Multi Pollutant Controls

Controlling NOx and VOCs from an Automotive Catalyst Manufacturer
Converting Urea to Ammonia On-Site

Controlling NOx and VOCs from an Automotive Catalyst Manufacturer

The Problem . . .
Engelhard, a manufacturer of automotive catalysts, included inorganic nitrate compounds in its formulations. Heat treating catalysts inside a high-temperature oven causes these compounds to decompose, producing NOx and other gaseous byproducts, including volatile organic compounds (VOCs). The NOx continuously emitted from the oven can reach concentrations of more than 20,000 ppm with VOC levels reaching 500 ppm. Thus, an emissions control strategy was needed.

The Solution . . .
Engelhard chose a combination SCR (Selective Catalytic Reduction) system from Durr Environmental. A scrubber was considered, but the NOx reduction would have been unacceptable given that the company required 99.9% NOx reductions. A scrubber would be limited to about 90 to 95% reduction at best. A SNCR (Selective Non Catalytic Reduction) process was another option, but the reductions would be limited to about 75% and the equipment would be quite a bit more expensive.

The exhaust temperature of this mixed gas stream operates at an average of 230 degrees C. The composition of the different oxidation states of NOx stays relatively constant at 30% nitrogen dioxide (NO2) and 70% nitric oxide (NO). Previous experience with a packed tower scrubber used a scrubber column packed with high surface area packing to affect intimate contact between the gas and absorbing liquid in a countercurrent flow pattern, resulting in a 60% maximum NOx destruction efficiency. The absorbing liquid was a dilute solution of sodium hydroxide. Since nitric oxide (NO) is insoluble, it must be oxidized to NO2 before diffusing across the mass transfer interface into the liquid phase in order to react with caustic soda and form sodium nitrate.

The combination NOx and VOC control used a single skid-mounted system, combining selective catalytic reduction (SCR) for the reduction of NOx and an oxidation catalyst for VOC removal. Most SCR catalyst systems used in the industry today reduce NOx from stationary power generating sources with lower NOx concentrations that operate 24 hours per day and 365 days per year. However, SCR technology is rapidly becoming a more popular option to reduce NOx from more complex chemical manufacturing processes because of its ability to reduce NOx to extremely low levels in the presence of other compounds and process flexibility to handle varying concentrations of NOx.

In a Durr combination system, the gas stream first passes through an oxidation catalyst to convert VOCs to carbon dioxide and water. Then it passes through a control system that modulates the ammonia flow added to the polluted gas stream. Ammonia regulated through a control valve mixes with ambient air pumped through a distribution manifold for uniform mixing with the NOx-containing gas before entering the SCR catalyst bed. Ensuring an even distribution of ammonia helped achieve optimal NOx destruction.

"This is the first time I know of that both VOC and NOx were treated in the same system to the high degree that this required," said Jim Griffin, Regional Sales Manager, Durr Environmental. "Prior systems sometimes treated the VOC or CO to about 50% reduction. Here we went to 99%+ reduction."

The Result . . .
The first of the two SCR/VOC systems installed at Engelhard continues to destroy NOx generated during the high-temperature treatment of automotive catalysts. The second system has been installed on another high temperature furnace. Both systems continue to maintain high NOx reduction capabilities with no major mechanical problems.

These abatement systems have allowed the catalyst manufacturer to stay within VOC and NOx emissions limits while proving to be easy to maintain and operate. They do not produce a secondary waste stream (low ammonia slip) and have lower capital costs compared to other available technologies considered.

For More Information . . .
Jim Griffin
Regional Sales Manager
Durr Environmental
Phone: 214/668-5200
Email: jgriffin@de.durr-usa.com
http://www.durr.com

Converting Urea to Ammonia On-Site (Updated: July 2001)

The Problem . . .
Anhydrous and aqueous ammonia currently are the principal agents being used as reducing agents in selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) processes for converting nitrogen oxides (derived from the burning of fossil fuels) to inert nitrogen gas and water vapor. SCR and SNCR technologies are being deployed widely across the U.S. as part of control strategies to reduce acid rain and formation of ozone. Ammonia, however, is considered a toxic substance and authorities in some areas have placed restrictions on ammonia's use due to concerns about transporting it.

The Solution . . .
The Hamon Research-Cottrell and Wahlco system demonstrated at AES Alamitos Station to convert urea to ammonia at the site of the SCR is now in full commercial operation at AES Huntington Beach Station. Urea is a stable, non-volatile, environmentally benign material that is safe to transport, store, and handle.

In the system, known as Urea to Ammonia (U2A), dry urea is dissolved to form an aqueous solution which is fed to an inline reactor at a rate to produce the required ammonia by hydrolysis. Heat is applied to carry out the generation under controlled conditions to maintain a constant ammonia-gas supply pressure.

The process produces a gaseous mixture of ammonia, carbon dioxide, and water. It requires no storage of ammonia except for a small amount in the reactor at an active concentration of less than 2% -- significantly less than the 30% concentration of standard commercial aqueous ammonia. The process is automated, readily controlled and can replace existing ammonia supply systems. The only chemicals required are urea and water.

The Result . . .
The U2A system was successfully demonstrated by AES at its Los Alamitos, CA, facility in between October and December 2000. It demonstrated good turn-up and turn-down capabilities and was able to track the load changes as well as or better than AES's existing aqueous-ammonia system. Since the aqueous solution of urea was converted into ammonia on-site on demand, the risk of storing and handling large quantities of ammonia on-site or in-transport was reduced.

As a result of the AES Alamitos operation, the system was installed at AES Huntington Beach Station to serve the SCR on Units 1, 2, 3, and 4. Operation of the U2A on Units 1 and 2 went fully commercial during July 2001.

For More Information . . .
Hamon Research-Cottrell
Phone: 908/685-4000
Fax: 908/333-2150
http://www.research-cottrell-us.com


		Case Studies Resources Case Studies: Multi Pollutant Controls Case Studies: VOC and HAPs Controls Case Studies: Particulate Controls Case Studies: Multi Pollutant Controls Controlling NOx and VOCs from an Automotive Catalyst Manufacturer Converting Urea to Ammonia On-Site Controlling NOx and VOCs from an Automotive Catalyst Manufacturer The Problem . . . Engelhard, a manufacturer of automotive catalysts, included inorganic nitrate compounds in its formulations. Heat treating catalysts inside a high-temperature oven causes these compounds to decompose, producing NOx and other gaseous byproducts, including volatile organic compounds (VOCs). The NOx continuously emitted from the oven can reach concentrations of more than 20,000 ppm with VOC levels reaching 500 ppm. Thus, an emissions control strategy was needed. The Solution . . . Engelhard chose a combination SCR (Selective Catalytic Reduction) system from Durr Environmental. A scrubber was considered, but the NOx reduction would have been unacceptable given that the company required 99.9% NOx reductions. A scrubber would be limited to about 90 to 95% reduction at best. A SNCR (Selective Non Catalytic Reduction) process was another option, but the reductions would be limited to about 75% and the equipment would be quite a bit more expensive. The exhaust temperature of this mixed gas stream operates at an average of 230 degrees C. The composition of the different oxidation states of NOx stays relatively constant at 30% nitrogen dioxide (NO2) and 70% nitric oxide (NO). Previous experience with a packed tower scrubber used a scrubber column packed with high surface area packing to affect intimate contact between the gas and absorbing liquid in a countercurrent flow pattern, resulting in a 60% maximum NOx destruction efficiency. The absorbing liquid was a dilute solution of sodium hydroxide. Since nitric oxide (NO) is insoluble, it must be oxidized to NO2 before diffusing across the mass transfer interface into the liquid phase in order to react with caustic soda and form sodium nitrate. The combination NOx and VOC control used a single skid-mounted system, combining selective catalytic reduction (SCR) for the reduction of NOx and an oxidation catalyst for VOC removal. Most SCR catalyst systems used in the industry today reduce NOx from stationary power generating sources with lower NOx concentrations that operate 24 hours per day and 365 days per year. However, SCR technology is rapidly becoming a more popular option to reduce NOx from more complex chemical manufacturing processes because of its ability to reduce NOx to extremely low levels in the presence of other compounds and process flexibility to handle varying concentrations of NOx. In a Durr combination system, the gas stream first passes through an oxidation catalyst to convert VOCs to carbon dioxide and water. Then it passes through a control system that modulates the ammonia flow added to the polluted gas stream. Ammonia regulated through a control valve mixes with ambient air pumped through a distribution manifold for uniform mixing with the NOx-containing gas before entering the SCR catalyst bed. Ensuring an even distribution of ammonia helped achieve optimal NOx destruction. "This is the first time I know of that both VOC and NOx were treated in the same system to the high degree that this required," said Jim Griffin, Regional Sales Manager, Durr Environmental. "Prior systems sometimes treated the VOC or CO to about 50% reduction. Here we went to 99%+ reduction." The Result . . . The first of the two SCR/VOC systems installed at Engelhard continues to destroy NOx generated during the high-temperature treatment of automotive catalysts. The second system has been installed on another high temperature furnace. Both systems continue to maintain high NOx reduction capabilities with no major mechanical problems. These abatement systems have allowed the catalyst manufacturer to stay within VOC and NOx emissions limits while proving to be easy to maintain and operate. They do not produce a secondary waste stream (low ammonia slip) and have lower capital costs compared to other available technologies considered. For More Information . . . Jim Griffin Regional Sales Manager Durr Environmental Phone: 214/668-5200 Email: jgriffin@de.durr-usa.com http://www.durr.com Converting Urea to Ammonia On-Site (Updated: July 2001) The Problem . . . Anhydrous and aqueous ammonia currently are the principal agents being used as reducing agents in selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) processes for converting nitrogen oxides (derived from the burning of fossil fuels) to inert nitrogen gas and water vapor. SCR and SNCR technologies are being deployed widely across the U.S. as part of control strategies to reduce acid rain and formation of ozone. Ammonia, however, is considered a toxic substance and authorities in some areas have placed restrictions on ammonia's use due to concerns about transporting it. The Solution . . . The Hamon Research-Cottrell and Wahlco system demonstrated at AES Alamitos Station to convert urea to ammonia at the site of the SCR is now in full commercial operation at AES Huntington Beach Station. Urea is a stable, non-volatile, environmentally benign material that is safe to transport, store, and handle. In the system, known as Urea to Ammonia (U2A), dry urea is dissolved to form an aqueous solution which is fed to an inline reactor at a rate to produce the required ammonia by hydrolysis. Heat is applied to carry out the generation under controlled conditions to maintain a constant ammonia-gas supply pressure. The process produces a gaseous mixture of ammonia, carbon dioxide, and water. It requires no storage of ammonia except for a small amount in the reactor at an active concentration of less than 2% -- significantly less than the 30% concentration of standard commercial aqueous ammonia. The process is automated, readily controlled and can replace existing ammonia supply systems. The only chemicals required are urea and water. The Result . . . The U2A system was successfully demonstrated by AES at its Los Alamitos, CA, facility in between October and December 2000. It demonstrated good turn-up and turn-down capabilities and was able to track the load changes as well as or better than AES's existing aqueous-ammonia system. Since the aqueous solution of urea was converted into ammonia on-site on demand, the risk of storing and handling large quantities of ammonia on-site or in-transport was reduced. As a result of the AES Alamitos operation, the system was installed at AES Huntington Beach Station to serve the SCR on Units 1, 2, 3, and 4. Operation of the U2A on Units 1 and 2 went fully commercial during July 2001. For More Information . . . Hamon Research-Cottrell Phone: 908/685-4000 Fax: 908/333-2150 http://www.research-cottrell-us.com Home \| Back to Top \| Printer-friendly version