August 2016 - Power Air Quality Insights 264

New Webinars for PacifiCorp On Front End Optimization and Back End NO_x Reduction Are Slated for The End of the Month

The next article summarizes the conclusions at the end of the PacifiCorp webinar on August 2. Since that time there have been further discussions and the tentative conclusion that raising the air heater exit temperature and adding Sorbacal ahead of the baghouse will result in an installation to cost effectively remove NO_x. The other requirement is initial NO_x reduction in the furnace through optimization and SNCR. Two more webinars will be held on the project. On September 1, there will be a discussion of the back end options. On September 8, the front end options will be discussed. In each case, participants will be advised to view new information added to Power Plant Air Quality Decisions (PPAQD).

There is the belief that NO_x leaving the furnace can be reduced to as low as 0.l lb./MMBtu. On the other hand, maybe the exit quantity would be 0.22 lbs./MMBtu. Since .07 lbs./MMBtu is the exhaust limit, the removal efficiency for the catalytic filter will have to be 30-70 percent. Doosan, Siemens, Emersion and GE have all made presentations relative to reducing NO_x leaving the boiler to as low as 0.1 lbs./MMBtu. In order to further determine the likelihood of this reduction, we have asked for case histories and white papers. We have already posted additional sever papers from Emerson and one from GE. Siemens is supplying several papers. We may make some phone calls to find out the current status of these installations. We are soliciting names of people and locations so we can make these calls. Results of the calls will be posted. In some cases, where confidentiality is desired, we will just provide a generic plant name such as a “large plant in the Midwest.”

Relative to the back end and urea/ammonia/H202 injection we need recommendations on where and which chemical should be injected. If both SNCR and catalytic filters are used, there will be ammonia slip from the SNCR. Where should the additional reagent be injected? Where should the Sorbacal be injected? Is there any reason to consider SBS instead of hydrated lime? Bob Crynack believes the addition of H202 along with the urea will increase removal efficiency. This needs to be further pursued. More information on the projected temperature vs. efficiency on the catalytic filters will be provided by FLS.

There may be other options that have been missed in the three previous webinars. If you believe there are other technologies which should be considered, please send your information to Bob McIlvaine at rmcilvaine@mcilvainecompany.com.

Catalytic Filters – Last Thursday most of the attendees including McIlvaine heard information which was being released for the first time relative to the performance of catalytic filters on NO_x removal. Some insights on use of H202 as a reducing agent were also new to almost all the listeners.

The previous sessions had established that optimization along with SNCR, combustion modifications and possibly reburn would achieve front end emissions of 0.22 to 0.15 lbs/MMBtu. McIlvaine was optimistic that this session would demonstrate that all that would be required on the back end would be to insert catalytic bags to replace the existing sets. F.L. Smidth, W.L Gore and others raised a serious obstacle when we found out that the maximum temperature at the baghouse entrance would be 275°F. This raises maintenance as well as efficiency concerns.

The maintenance concern is that at 275°F, there will be formation of ammonium bisulfate and plugging of the bags. Unfortunately, URS sodium bisulfite proponents were not on the call but presentations at previous webinars have shown that bag plugging can be reduced with the injection of SBS at the inlet to the air heater. The primary role is keeping the air heater clean but the injection seemed to reduce downstream bag plugging.

This brings up a point relative to alternatives. SNCR is likely to play a key role under any combination of technologies. This means that the bags will be subjected to ABS under any scheme. Would it be worse when the catalytic bags are used as compared to the FLS bags already in place. Ken Johnson of Pentair was on the call and indicated his willingness to pursue these issues. Bag cleaning will be a challenge under all the scenarios. Pentair has solved problems with their pulsing systems at other plants, so their input will be welcome.

Lime injection ahead of the bag filters would also very likely solve the problem. Lhoist, Mississippi Lime and others can provide insights on this. A radical option would be to remove both NO_x and acid gases in the bag filter and eliminate the downstream lime scrubbers. But then the question of solid waste disposal would have to be addressed.

The second concern is efficiency. At 275°F, a three layer FLS bag might only have a 50 percent NO_x removal efficiency or maybe even lower. Nadia Jorgensen, sales manager for catalytic filters for FLS, promised to review the efficiency curves and respond with some predictions for removal at 275°F. An alternative would be to raise the gas temperature. The plants which have opted for tail-end SCR have justified a very large increase in gas temperature. Here the need may be only for a 275°F rise. PacifiCorp indicated this would not be easy but would be doable.

One thing to check is air heater leakage. Is the 275°F a function of 10 percent air in leakage into the air heater? If so, then the temperature can be raised with air heater modifications. Air volume to the baghouse would be reduced and the catalytic filter would be a great choice. We will check with Arvos and Howden for their opinions on the air heater in leakage. Both were in a previous PacifiCorp webinar. We will also check with Howden on fan implications (volume is a function of temperature).

It would all be a matter of economics. Raising the gas temperature entering the baghouse means less transfer of heat in the air pre heater and a fractional percent decrease in plant efficiency. On the other hand, an SCR would add 8-10 in. pressure drop to the system and also reduce plant efficiency. The capital cost of the SCR would be far greater than the catalytic bag filter replacement and some minor air heater modifications. If the solution is reducing air heater leakage, then the economics for the catalytic filter are even more attractive.

H202 and Ozone - Bob Crynack cited his considerable experience with FMC to conclude that H202 to oxidize the NO_x to a soluble NO₂ and downstream capture in the lime scrubbers was not very promising, but that injection in the furnace along with urea would substantially enhance SNCR. He believes this could be a cost effective route for PacifiCorp. FMC has sold the division involved in this. We will contact the new owners and gather more information.

DuPont indicated that their Lotox system which adds ozone ahead of the scrubbers would likely be a good solution. They make this observation based on a number of refinery and industrial installations, so we will seek more information from them and also from Linde who is the licensor.

In-Duct SCR - Fuel Tech submitted additional slides to validate the performance of a small layer of catalyst. Combined with SNCR this approach should yield sufficiently high NO_x removal. More input on this approach will be sought.

In-furnace Reduction - The Castle Light presentation focused on replacing the burners with entrained gasifiers. The NO_x reduction is substantial. The negative would be a significant capital investment. One question we will pursue with Keith Moore is whether the use of calcium sulfite as a catalyst for NO_x reduction in the burners can be implemented without the whole entrained gasifier installation.

McIlvaine will continue to pursue the in-furnace and back-end options. Future webinars are planned. Coordination with PacifiCorp will be pursued. Smaller groups to pursue individual options will be encouraged. Optimization is an example.

Siemens, Doosan, Emerson, and GE all recommended in furnace approaches. Each has a different approach. The next step will be to understand the differences. On a broad basis there seems to be a difference in whether to rely on changing parameters to affect the results or changing the results empirically, which in turn changes the parameters. With neural networks which can learn from various damper settings, the settings can be optimized. This has the same result of centering the fire ball which is alternatively done with tunable diode laser measuring tools and then burner air damper adjustments.

How do each of the suppliers characterize their reliance on actual on line instrumentation, OFA, EGR, reburn, models, and learning systems. This first step can be followed by more insights on actual experience in similar boiler designs with similar coals.

The recording of this session and the power point presentations are available in 44I Power Plant Air Quality Decisions (Power Plant Decisions Orchard). This is free of charge to utilities. Since you are receiving this Alert you are undoubtedly a subscriber to the 42EI Utility Upgrade Tracking System. If so, the 44I is only $800/yr plus $80/yr for additional users.

Old coal-fired power plants in Europe and the U.S. must invest in technology to meet new emission standards, but must do so with a modest investment. New coal-fired power plants being built in Asia and certain other countries are tasked with obtaining high conversion efficiencies which are achieved with operation at high temperatures and pressures. The result is that coal-fired power plants, whether they are new or old, have difficult decisions to make. 44I Power Plant Air Quality Decisions (PPAQD) which includes information on all coal-fired power plant products and services provides power plants and their suppliers with Decision Guides to include the latest developments presented in a format so that the benefits of each option are compared.

PPAQD provides a powerful new tool both for the plant operators and suppliers. For example, in the last three weeks there has been a specific analysis of NO_x control options for a utility which is facing a $700 million investment to comply with regional haze rules. The major options are to install SCR or to initiate a series of projects which in combination will achieve the needed NO_x reduction. The combination options include:

These options have been reviewed in webinars with a large number of utility people in attendance to hear presentations by GE, Siemens, Emerson, Fuel Tech, FLS, AECOM and others.

Sherco Unit 1 is a 750 MW unit with overfired air and low NO_x burners. A NO_x control program was initiated in 2014. The goal was to reduce and maintain NO_x emissions from a shared stack to below 0.15 lb/MMBtu over a 30 day rolling average starting January, 2015. At the start of the project, the goal was not being met. The penalty is that if the NO_x is not maintained below the 0.15 lb/MMBtu average, the units must be derated to achieve the goal. Emissions are measured in a shared stack from two 730 MW T-fired units with no SCRs. CO constraint is that CO emissions must be maintained below 400 ppm.

Some of the problems centered around poor coal fineness and distribution. All seven mills were retrofitted with Loesche dynamic classifiers with the goal of achieving 75 percent through 200 mesh and 99.9 percent through 50 mesh. The company also installed a Neuco Combustion Opt system which provides closed loop optimization of fuel and air biases in the boiler as frequently as very minute. The result was a 10 percent NO_x reduction and achievement of the goals.

Power Plant Air Quality Decisions Aids Power Plants in Making Environmental Decisions

A utility had to quickly address ways to reduce air pollution on four large boilers based on an EPA disapproval of the State plan. The utility opted to use the free Power Plant Air Quality Decisions (PPAQD) to help make the decision. This included access to a comprehensive intelligence system with decisively classified options plus recorded webinars.

Because of the potential size of the investment ($700 million), McIlvaine elected to conduct three focused webinars to help the utility apply the system. Suppliers contributed new information for the system which has proved to be very useful. This information was reviewed during the sessions in a crowd decision making mode. The decision options were then revised to reflect new alternatives and new values for existing routes.

The utility has not yet made a final decision on the solution, but at this point, the most likely choice is one that no one would have predicted at the start of the process. One reason is that some of the application knowledge has been limited to the cement, glass and waste-to-energy applications and was not known to the power industry. In addition, some of the processes, when applied to other pollutants, have proved successful in coal-fired power. So this was the first time it was realized that they were equally applicable to the target pollutant. The third reason was that new developments make this option much more attractive.

The staff of the utility has impressive resumes and knowledge of air pollution control equal to any power generator. The fact that a large U.S. utility can benefit from the system leads to the conclusion that any small power plant or offshore power plant will derive even more benefit from use of the system.

The world’s relevant information is doubling every few years while an individual’s ability to assimilate it remains fixed. Systems such as Power Plant Air Quality Decisions become increasingly necessary.

DATE	HOT TOPIC HOUR AND DECISION GUIDE SCHEDULE *The opportunity to interact on important issues*
August 25, 2016 10:00am CDT *Markets*	Oil, Gas, Refining - Supply and demand; impact on flow control and treatment products; regional impacts e.g. subsea in North Atlantic vs. shale in the US vs. Oil Sands in Canada.
September 1, 2016 11:30am CDT	PacifiCorp Webinar 4 on back end NOx removal - Review of options from webinar 3 to determine suitability of catalytic filters, Sorbocal injection for ABS control, H202 with SNCR, in duct catalyst, raising air heater temperature and fan adjustments.
September 8, 2016 11:30am CDT	PacifiCorp Webinar 5 on front end NOx reduction - Review of options for NOx reduction including combustion modifications, reburn, SNCR, and optimization with review of previous presentations of Emerson, Doosan, Siemens and GE. A number of case histories, now being posted to PPAQD, will also be reviewed. Summaries of phone calls to end users may also be included.
TBA *Markets*	Food - Analysis of 12 separate applications within food and beverage with analysis of valve, pump, compressor, filter, analyzer and chemical options; impact of new technologies such as forward osmosis.
TBA *Markets*	Municipal Wastewater - Quality of pumps, valves, filters, and analyzers in Chinese and Asian plants; new pollutant challenges; water purification for reuse.
TBA *Markets*	Mobile Emissions -Reduction in CO, VOCs, and particulate in fuels, oils, and air used in on and off road vehicles; impact of RDE and failure of NO_x traps and the crisis in Europe created by the focus on clean diesel.