Addendum - November 1, 2019


True Costs of Power Plant Flow and Treat Products will be discussed at Power-Gen but also as a Continuing Process


McIlvaine is preparing tour guides relative to various flow and treat products at PowerGen in New Orleans,  November 18-21.  These are displayed at


This is part of a Silobuster Program to penetrate geographic, corporate, and technology silos. So, the guides will be equally useful at PowerGen India, PowerGen Asia, or PowerGen Europe. The segment relative to gas turbine inlet filter media will be utilized at a major filtration conference sponsored by the world’s largest non-woven media association. The silobuster programs are listed at You see among others one on coal-fired boiler flow and treat and another on gas turbine flow and treat


The purpose is to create access to the important silos of information which allow a purchaser to determine the true cost of a product or service. For a supplier with the lowest true cost product it is a whole new route to market Most Profitable Market Program.


Who funds these programs? Since the services are available free of charge to purchasers, the suppliers are the funders. Investments which would otherwise have gone to “sales leads” can be cost effectively diverted. Advertising can be coordinated so that it helps to validate a true cost claim. For example, when you click on the Power Engineering background article on HRSG corrosion control you also see an advertisement for Magnetrol level and flow control. This is an archive from February, so Magnetrol is obtaining long term benefit  from its advertisement.


The tour guides are designed to assist in purchasing related decisions. The decision makers are the people most sought after by suppliers. By providing networking with email and cell phone contacts of those interested in making purchasing decisions rather than just gaining background knowledge, the value of exhibiting is increased.


The value in supporting these silobuster initiatives is already being realized by some of the media and it is expected that others will follow. The McIlvaine Company charges suppliers modest fees to be involved in a silobuster program and counts on revenues from helping these companies pursue this new route to market for which individual purchase forecasts are the foundation.


Background documents relative to tour guide subjects have been published.  Here are the ones published in this Alert over the last two weeks.

True Cost of Limestone FGD Recycle Pumps

Woven Belts and Cloths for Coal Fired Power Plants

Here is background on additional subjects.

True Cost of Gas Turbine Inlet Filters


The McIlvaine Company is working with associations, media and suppliers to create true cost analyses of combust, flow and treat products and services. One such initiative is the “True Cost of Gas Turbine Inlet Filters.”


The true cost of a gas turbine inlet filter can be affected by a large number of factors. These factors are not constants but are changing. The filter purchaser is challenged to not only identify these factors but to keep up with the changes.


Large gas turbines are used to generate electricity by utilities. Smaller gas turbines, drive pumps and compressors in locations with extreme conditions such as desert dust, artic snow or sea spray on an oil rig. As turbines have become more efficient, they have become more susceptible to damage from contaminants in the combustion air. This ambient air from the surrounding environment can contain high dust loads. In California, with very tight emission standards, the particulate in the inlet air to the turbine can exceed emission limits. Thus, the gas turbine has to act as an air cleaning device.


The challenge for  gas turbine inlet fiber, media, and filter suppliers is to increase gas turbine availability in all environments with newer and more sensitive gas turbines. The newer turbine designs are negatively impacted by small particles. This has led to the use of HEPA filters with efficiencies classed as H10/E10 and higher. Studies show that turbine maintenance can be reduced with even higher efficiency E12-U17. One study showed that even if the cost of higher efficiency filtration were four times higher than lower efficiency filters, the true cost would be lower.


One can choose a system with non-cleanable filters. They are relatively inexpensive but require continuous filter replacement. By using a sequence of inefficient but inexpensive pre filters and a final high efficiency filter, the replacement cost can be minimized.


An alternative is to use a cleanable filter. Periodic air pulsing knocks off accumulated dust.  These systems are available from many suppliers if the F-9 efficiency is all that is desired.  Cleanable filters with H12 efficiency are available from only a few suppliers. On the other hand, there are many new developments which will expand the number of choices.


In terms of high efficiency dust capture mechanisms there is a choice between wet laid glass and synthetic nanofiber non-woven laminates or membranes. The traditional glass media for HEPA filtration has been used primarily in non-cleanable filters.


Quantifying the benefit is a balance between reduced fouling and increased pressure drop. The increased pressure drop can be estimated to restrict performance by approximately 0.4%, while cutting fouling provides a 1.2% improvement in output (empirical average). Therefore, the overall result is a potential efficiency improvement of 0.8%.


Alliance Pipeline believes that the E12 filters from Gore may allow Alliance to extend the interval between overhauls of its aero engines from 25,000 to as many as 50,000 hours (from three to six years).


The many factors and media choices impacting gas turbine inlet filter selection  have been discussed in a background document on display at


In the past the most efficient filters that were used on gas turbine inlets were rated F-9 with efficiency of more than 95% on particles 0.4 um diameter. The most penetrating particle size is about 0.2 um where the efficiency is much lower. Higher efficiency filters are rated based on the most penetrating particle size as follows:



HEPA Class

Retention (total)


> 85%


> 95%


> 99.5%


> 99.95%


> 99.995%


> 99.9995%


> 99.99995%


> 99.999995%


Membrane laminates such as used for dust collection can meet efficiencies up to E12.  The question is whether this is sufficient?


There are a number of new filter and media designs, which need to be evaluated. Mann & Hummel Vokes introduced the Aircube Pro Power S, which utilizes a new synthetic base media with much higher resistance to mechanical stress than glass fiber media and a stable high efficiency during operation. It is water and salt repellent while being extremely robust.

DHA Filter has introduced a cleanable HEPA filter for gas turbine inlets, which it will be displaying at Power-Gen.


Improving Limestone Scrubber Efficiency


U.S. and Indian FGD operators both are interested in higher SO2 removal efficiency. In the case of U.S. operators faced with operating higher cost old plants, the potential to cut pump-connected horsepower is appealing. For Indian operators there is the potential to reduce capital as well as operating costs. Three options involve scrubber design. scrubber chemicals, and optimization systems.

Relative to scrubber design there are the following choices


·          A spray tower with liquid flows as high as 100 gpm/1000 cfm and pressure loss of 3-6” w.g  (MET, Doosan, and many others)

·         A modified spray tower (MHPS)

·         A tray or rod deck scrubber with  flows less than 50 gpm/1000 cfm and pressure loss of 6-8” “ w.g. (B&W)

·         A sump scrubber with no liquid flow and pressure loss of 9-11” w.g


Where there is enough fan capacity a tray or rod deck can be added in a spray tower to increase efficiency.

Another alternative is to use dibasic acid or another chemical to enhance scrubber efficiency.  Some plants in Europe add lime during periods when higher efficiency is needed.


India is moving forward with approximately 100,000 MW of FGD systems. This will require 15-20  million of tons of limestone per year. SHI-FW has conducted a study which shows that because of the poor limestone a CFB scrubber is the best choice for many plants

This analysis  is based on a 300 MW plant with 0.6% sulfur. Limestone cost is 7 rs Crore /yr. ($989,000) based on 5 tons per hour and a cost of limestone at 1750 rs./ton ($ 24.50/ton) vs EPA cost estimates based on $30/ton. The tons/MW = 134.7.


Scrubber additives can improve the economics when using a poor-quality limestone. One answer is that if treatment chemicals can be justified for a 0.6% sulfur coal, they will be even more attractive for higher sulfur coals.
Here is the CEA specification for Indian Limestone.


Brad Buecker of Chemtreat has reviewed this analysis and concludes  “With regard to the analysis, the CaO range equates to a calcium carbonate (CaCO3) range of 82 to 91 percent.  A quick thought suggests that this might be an excellent application for ChemTreat’s DBA replacement product.  A general rule-of-thumb that I always followed is that limestones with 94% or greater CaCO3 concentration are usually quite reactive (if ground properly).  My gut feeling says that the stones outlined in the analysis could be significantly enhanced in reactivity using our FGD1105 product.”


Brad wrote an article in Power Engineering earlier this month where he provided further details:


“Many plants do not have access to such high-purity limestones. The stone may contain a significant concentration of dolomite (MgCO3∙CaCO3) or inert materials that inhibit reactivity. Thus, supplemental methods are needed to boost the reactions. A common method that has been used for years is addition of dibasic acid (DBA) to scrubber process streams, but new technology is improving upon this chemistry. Dibasic acid is a generic name for a blend of relatively short-chain dicarboxylic acids (two COOH functional groups), which add hydrogen ions (H+) to help in the dissociation of limestone, and then circulates through the process to continue assisting with SO2-absorption chemistry. However, the availability, cost, and even efficiency of DBA has placed limits on the chemical’s effectiveness. An alternative is available that is much more promising for wet FGD reactivity enhancement.”


 Personnel at the Longview Power Plant in Maidsville, West Virginia had faced constant problems with handling and feeding DBA to the wet-limestone scrubber of their 770 MW supercritical steam generator. For example, the product must be kept warm to prevent solidification. Exacerbating the issues were DBA delivery constraints, both from a distance perspective and that the tank volume had to be lowered to less than 10% before introduction of a fresh load. Combined, these factors affected scrubbing efficiency and SO2 removal, the latter of which is a critical aspect of scrubber operation. Violation of discharge permits can result in load restrictions or forced shutdowns.

Accordingly, the plant staff began full-scale testing and then subsequent application of an alternative, specially-formulated organic acid blend with the product name of FGD1105 (patent pending).  Almost immediately upon chemical addition, SO2 emissions dropped by approxi- mately 35% to 40%, such that even at full load one of the scrubber’s five recycle pumps could be, and was, removed from service. Stack SO2 emissions only slightly increased from 120 lb./hr. to 200 lb./hr. following the pump reduction. This action alone reduced auxiliary power consumption by 3 MW, at a projected annual benefit of approximately $700,000. As a test, the plant staff removed a second recycle pump from service and found that SO2 removal was still more efficient than in the period prior to the FGD1105 addition. According to Chad Hufnagel, Longview’s Plant Manager, the ability to operate with 3 recycle pumps instead of 4 or 5 has provided additionally flexibility for recycle pump maintenance strategy, as well as offering additional net revenue opportunity with improved unit efficiency.


Therefore, the cost saving is more than $700,000/yr. less the cost of the additive. There are other questions to pursue such as changes to wastewater treatment costs. This analysis is based on a spray tower. If a tray tower or rod deck scrubber is used, then the saving would have to be in fan rather than pump horsepower. Another question to be answered is the parasitic cost of power for the average Indian plant vs. that in the U.S.


The McIlvaine Coal Fired Power Plant Decisions has a number of relevant papers. They include  INVISTA DBA Dibasic Acid - The McIlvaine Company


There are a number of suppliers of DBA around the world. They include


·         Cathay Industrial Biotech

·         Palmary Chemical

·         Henan Junheng Industrial Group Biotechnology

·         Evonik

·         Invista

·         Zibo Guangtong Chemical



FGD Scrubber Monitoring and Control:  The use of the right chemicals is only part of the true cost reduction. Monitoring and control of parameters is equally important. The CEMS system should be used for process monitoring. In the case above the system could operate with 3, 4, or 5 pumps depending on the reactivity of the limestone. However varying sulfur levels in the incoming coal provide another variable. If SO2 is measured prior to the scrubber as well as at the stack the right balance between efficiency and energy consumption can be determined.


The measurement of liquids is also important. Brad Buecker addressed this subject in an older Power Engineering article. He pointed out that it is important to constantly measure the alkalinity in the scrubber module or modules, as too much alkalinity will waste reagent while lean alkalinity will impair SO2 removal. The technique universally employed in wet scrubbers is pH monitoring. These measurements must be continuous, with control of reagent feed rates based upon the readings. For the lab staff, grab-sample pH analyses are very important to make sure that the in-line probes/monitors are accurate.


The slurry circulating pumps can only handle so much mass before electrical requirements are exceeded. Like pH, scrubbers are equipped with continuous density monitors, typically utilizing radioactive detectors. Again, the lab staff needs to monitor density on a grab sample basis to ensure the accuracy of the continuous instruments.


Control of solids chemistry offers interesting challenges and is extremely critical to operation. Experience has shown that operation in either a completely oxidized state (no calcium sulfite-sulfate hemihydrate in the scrubbing slurry) or a completely un-oxidized state (no gypsum in the slurry) minimizes scaling in the scrubber. Scale buildups can be extremely problematic, as deposit formation on scrubber internals and subsequent gas flow restrictions may cause unit de-rates and even forced outages if gas flow is severely restricted.

The technique that has proven itself very well for scrubber solids analysis is thermogravimetry. A thermogravimetric analyzer (TGA) is a quantitative not a qualitative instrument, so the operator needs to have a good idea of the primary constituents in the sample before analysis. If the sample compounds decompose at distinct and separate temperatures, it becomes easy to calculate the concentration of the original materials. Wet-limestone scrubber byproducts lend themselves well to this technique.


The plant can vary the number of pumps in operation. An  optimization system enables the plant to use the minimum number of pumps required to keep the outlet SO2 lower than limits. This also reduces the amount of limestone slurry required, but the major contributor to cost savings is cutting energy use by removing one or more recirculation pumps from service based on the input SO2 value. One optimization system available was described by  Toshihiko Fujii of Yokogawa Electric Corp. in a recent Power Magazine article.


FGD control is normally implemented by the distributed control system through the regulation of limestone slurry flow. The limestone slurry flow is controlled based on the pH value as measured by an analyzer installed in the absorber. Typically, the pH value must be controlled to ensure proper performance of the desulfurization process in the absorber, therefore the limestone slurry flow is controlled to maintain the proper pH value. For this control scheme, other indices such as the FGD inlet and outlet SO2 are not used, and all recirculation pumps are operated regardless of the inlet SO2 value, with slurry flow regulated by the control valve.


The optimization system typically consists of three functions: enhanced regulatory control, model-based prediction, and process value prediction. The system uses these three functions to continuously determine the minimum required number of recirculation pumps in operation, and to calculate the setpoint for the limestone slurry flow PID (proportional-integral-derivative) control loop.


A 700-MW coal-fired power plant in Japan implemented the optimization system. This plant runs about 300 days per year at baseload and is not in operation for the other 65 days of the year. The energy savings realized by running only the required number of recirculation pumps was 12.4% of the unit’s total house load, equating to about $900,000 in energy savings per year based on market conditions in Japan. Another benefit was reduced pump run times, which resulted in lower pump maintenance costs and extended pump life. A third benefit was less limestone usage.


HRSG Corrosion Control


Last week we reported on this in the Alert. Flow accelerated corrosion (FAC) can cause iron loss in steam piping and lead to lethal accidents. As a result, programs are necessary to reduce metal loss and to monitor the loss which does occur. A team from Danaher analyzed the problem in a Power Engineering article appearing in January 2019.


We cited the use of fine particle on line monitoring. But here is more detail on the iron measurement instrumentation:


Hach TU5400 Nephelometer


Using advanced laser optics and signal processing, the instrument detects increased concentrations of submicron-sized particles that are a precursor to larger particles. This allows for early filter deterioration detection that meets or exceeds that of particle counters all with the day-to-day convenience, simplicity, and reliability of a Hach turbidimeter. Operators can detect impending filter breakthrough, delineate filter ripening, and maximize effective filter run time. The Hach TU5400 Laser Nephelometer can detect to 0.0001 NTU, providing operators with confidence in their turbidity measurement.


The TU5400 sensor can be used with any of Hach's sc Digital Controllers. Each sc controller accepts from two to eight sensors. Multiple controllers can be networked to accommodate many more sensors and parameters, reducing the cost per measuring point. Just plug in any Hach "plug and play" digital sensor and it's ready to use without software configuration. "Plug and Play" connectivity means there's no complicated wiring or set up. The TU5400 Nephelometer controller system now can manage multiple digital sensors.


Level and Flow Control are also important: Magnetrol level and flow control are used in a number of ways to optimize corrosion control. This includes the ammonia storage tank, improving heat rate efficiency through feedwater heater level control and optimizing makeup water treatment, energy management, steam generation cycle, condensate and waste heat recovery.


Turbine Bypass Valves Background Data Now Available


The turbine bypass system is a very important component of power stations, and of a difficult service too. Although it does not operate continuously, when it is required to operate it has to be fast and reliable. Its main job is called steam conditioning. It means pressure reduction and desuperheating of steam that has been produced by the boiler but, due to transient or unexpected conditions, cannot flow through the turbine.


The percentage of total steam handled by the turbine bypass system depends on plant design philosophy. Capacity usually ranges between 30% up to 100% of the maximum continuous rating (MCR) boiler steam flow. The high-pressure turbine bypass system provides an alternate flow path at the high-pressure side of the turbine, taking the steam from the turbine inlet to the reheater inlet section. This bypass system permits stable operation of the boiler when the turbine trips off line or during start-up operations. Steam flowing through the high-pressure bypass control valve is throttled and cooled to a temperature slightly above the HP turbine exhaust temperature, by spraying feed water at the outlet of the bypass control valve. This flow is then combined with high pressure exhaust steam and passes through the reheater.


The low-pressure turbine bypass system presents a flow path around the LP turbine, taking steam from the reheater outlet and conditioning it to be fed into the condenser. For condenser protection, high pressure and temperature drops are taken by valve throttling and by the addition of large amounts of desuperheating spray water, preventing superheated steam from reaching the condenser.


These are critical valves and also expensive. The initial cost can exceed $100,000 per valve. Operational and maintenance costs can be substantial. Problems and variables include



Plug valve sticking


Optimal bypass % range

Reaction time

Materials for LP vs. HP vs. new conditions, such as cycling or ultrasupercritical conditions

Multi-stage pressure reduction to reduce trim wear

Stellite delamination

Flow accelerated corrosion

Maximizing power output


There are a few relevant speeches and some exhibitors, such as Emerson and SPX, which manufacture turbine bypass valves. Other suppliers, such as BHGE, will be participating in the networking resulting from the tour guide. The stand and networking details  have been provided and will be updated.


In addition, two background documents have now been added:


Turbine  Bypass Valve Suppliers


Turbine Bypass  Technology and Applications


These documents will be expanded prior to the conference and then on a continuing basis.


The Guide to True Cost of Gas Turbine Inlet Filters will be used to facilitate discussions at a number of events in the coming months. It will be used along with a tour guide on the subject at the  PowerGen exhibition in November.