Improving ESP Efficiency was the Hot Topic on January 28

Five experts were able to address questions from a very knowledgeable audience in the 2-hour Hot Topic session yesterday. How do you define efficiency? Is it based on discrete particles or on totals including condensibles such as sulfuric acid mist? Even the division line between metal particles and acid vapor is blurred. What about selenium and mercury which are vapors at ESP temperatures? If you are judging efficiency based on opacity, how different are the conclusions than if it is based on mg/m³? Is efficiency based on tons per year in versus tons per year out, or on a three hour test sometime during the year?

In one 2-hour session it was possible to shed a little light on this complex subject.

Yougen Kong, P.E., Ph.D., Technical Development Manager at Solvay Chemicals, Inc., explained that trona is a better alternative to SO₃ for conditioning electrostatic precipitators. Using SO₃ to condition the flue gas of boilers burning low-sulfur coal is going to be less attractive with mercury control; SO₃ inhibits the mercury removal by either flyash or powdered activated carbon (PAC). A better alternative is to inject trona into the flue gas upstream of a hot-side or cold-side ESP.  It can lower the resistivity of the flyash and solve the problem of back corona due to “sodium depletion” on hot-side ESPs. In addition, the added trona can remove SO₃ and thus improve mercury removal. The trona addition system is simple and its capital cost is much lower than that of an SO₃ production and injection system.

In the question and answer period, Yougen observed that the selenium removal was substantially higher with the trona injection. Bob McIlvaine postulated that this could be the “tail wagging the dog.”  If a utility plant is facing a big expense to remove selenium from its wastewater then maybe the trona injection can be justified on this aspect alone. Coincidently one of the utilities participating in the session volunteered that it had both successfully piloted trona and was facing a selenium discharge problem in its FGD wastewater. So it seems that this is a valid and important advantage of trona injection.

Harry Wheeler, Environmental Services Operations, Alstom Power, discussed how the performance of existing ESPs can be enhanced by utilizing multiple techniques. PM removal efficiency within the confines of a box can improve by changing electrode geometry (plate spacing), internals like discharge electrodes, rapping system as well as by replacing conventional T/R sets with high frequency power supplies and advanced controllers. Although fabric filters are more widely used in greenfield power plants as the PM collector with activated carbon systems for mercury control, proven technology is now available to achieve a high rate of mercury removal keeping the existing ESP as the PM collector.

Harry, in answering a question on wide plate spacing, observed that the wide plates are more forgiving. A ½ inch misalignment at 18 inches is not nearly as significant as ½ inch at 9 inches spacing. Alstom’s experience with biomass co-firing leads them to believe it will not cause particulate problems which cannot be addressed.

Paul Leanza, Senior Technical Engineer for Post Combustion Control Equipment at Pollution Control Services, Inc., focused on the precipitator’s ability to achieve the future PM_2.5 regulations. The majority of existing ESPs are not operating under their original design basis. Many existing ESPs have not been upgraded with modern operating philosophies or equipment. Taking a holistic approach in evaluating the precipitator in its current operating parameters permits a viable plan to go forward, as the operating parameters have been modified as additional post-combustion control equipment like SO₂, SO₃, NO_x, and Hg control have been incorporated over the last 15 years.

Paul’s comment that even the re-design of the outlet box on an ESP will change the flow characteristics was seconded by Harry Wheeler. Paul also pointed out that the SCR can help or hurt precipitator operations. It is likely to change the inlet flow distribution. The right amount of ammonia slip can help whereas an excess will result in emission problems.

Helmut Herder, Vice-President, Environmental Technology Division of NWL, described how and why use of the Power Plus SMPS improves the collection efficiency of an ESP while using less power (KVA input). When asked how the yearly emissions in tons compares after SMPS is installed, Helmut stated that the high reliability of Power Plus makes it efficient throughout the campaign. He showed graphs pointing to the higher percent reduction of small particles (PM_2.5) with Power Plus.

Jonathan (Jon) Barr, Vice-President Sales & Marketing, ADA-ES (ADA Environmental Solutions LLC), addressed the problems with coal-fired power plants which use SO₃ to improve the performance of their ESPs with PRB coal. If these plants are required to control mercury emissions and use activated carbon, the SO₃ can reduce the carbon's effectiveness and reduce the efficiency of the mercury removal. ADA has a patented flue gas conditioning chemical that is an effective SO₃ replacement and does not interfere with activated carbon's ability to adsorb mercury.

The capital costs of the system are low. Chemical costs are somewhat higher than molten sulfur but when one compares the combination of molten sulfur plus excess carbon vs. the ADA approach, the total life cycle cost for the ADA approach is quite favorable.

The Bios, abstracts and photos can be viewed as follows: BIOS, PHOTOS, ABSTRACTS - JANUARY 28, 2010.htm

The individual slides are located in our Particulate Decision Tree as follows:

Jonathan Barr – ADA-ES

Particulate Continuing Decision Process For: Products

Flue Gas Conditioning as an SO₃ Replacement with Mercury Control, presented by Jonathan Barr - ADA-ES. Hot Topic Hour January 28, 2010.

http://www.mcilvainecompany.com/Particulate_Decision_Tree/subscriber/Tree/DescriptionTextLinks/Jon Barr - ADA - 1-28-10.pdf

Yougen Kong – Solvay Chemicals

Particulate Continuing Decision Process For: Products

 A Better Alternative to SO₃ for conditioning Electrostatic Precipitators, presented by Yougen Kong - Solvay Chemicals, Inc. Hot Topic Hour January 28, 2010.

http://www.mcilvainecompany.com/Particulate_Decision_Tree/subscriber/Tree/DescriptionTextLinks/Yougen Kong - Solvay Chemicals - 01-28-2010.pdf

Helmut Heider - NWL

Particulate Continuing Decision Process For: NWL

Electrostatic Precipitators PowerPlus SMPS Solutions, presented by Helmut Heider, NWL. Hot Topic Hour January 28, 2010.

http://www.mcilvainecompany.com/Particulate_Decision_Tree/subscriber/Tree/DescriptionTextLinks/Helmut Herder - NWL - 1-28-10.pdf
 

Harry Wheeler and Tapan Mukherjee – Alstom Power

Particulate Continuing Decision Process For: Options

Methods Utilized to Improve Precipitator Performance, presented by Tapan Mukherjee and Harry Wheeler - Alstom. Hot Topic Hour January 28, 2010.

http://www.mcilvainecompany.com/Particulate_Decision_Tree/subscriber/Tree/DescriptionTextLinks/Tapan Mukherjee - Alstom Power - Jan. 28, 2010.pdf

Paul Leanza - Pollution Control Services (PCS)

Particulate Continuing Decision Process For: Options

Evaluate Existing ESP, presented by Paul Leanza, PCS. Hot Topic Hour January 28, 2010.

http://www.mcilvainecompany.com/Particulate_Decision_Tree/subscriber/Tree/DescriptionTextLinks/Paul Leanza - Pollution Control Services 01-28-10.pdf