In Japan, the latest gas treatment system for a coal-fired power station consists of a moving electrode type ESP, a DeSO_x system and a wet ESP. The gas temperature of the moving electrode type ESP is a cool 80 to 90°C. This system can reduce outlet dust concentration to less than 1 mg/m³N and outlet sulfuric acid mist to less than 0.1 ppm. At ICESP XI, Toshiaki Misaka, with others from Hitachi Plant Technologies, Co, Ltd., Tokyo, reviewed the operating costs for this type of ESP.

In 1979, Hitachi Plant Technologies developed the moving electrode system for ESPs. It prevents back corona by removing the collected dust using rotating brushes and movable collecting plates. The moving electrode system is effective for collecting high resistivity dust with high efficiency. It is compact compared with a conventional fixed electrode system and can also reduce electrical power consumption.

Figure 1 shows an illustration of a moving electrode type ESP. The first and second sections at the gas inlet side are fixed electrodes and the outlet section is the moving electrode system. The collecting plates of the moving electrode system are divided into strips, coupled with chains and are moved slowly by driving wheels. The discharge electrodes are installed between collecting plates at the collection zone. Dust is collected on the collecting plates by electrostatic forces. Dust attached to the collecting plate is transferred to the hopper before the dust layer becomes thick enough to cause back corona.

Figure 1. Overall structure of Moving Electrode Type Electrostatic Precipitator (MEEP)

The moving electrode system is equipped with brushes that sweep off dust from the movable collecting plate. Rotating brushes for dust removal are installed in the hopper. Since this area is a non-collection zone, it is free from gas flow or electricity. The collected dust is completely removed by the rotating brushes. Thus the collecting plates are kept clean at all times. In addition rapping reentrainment does not occur by brushing. This system maintains stable collection efficiency even when collecting high resistivity dust.

The moving electrode type ESP has various advantages compared to the fixed electrode type. It can decrease power consumption to 67 percent, reduce the installation area to 74 percent and it requires one less field. In the case of a retrofit of an existing ESP, a moving electrode type ESP is smaller than a fixed electrode type ESP. Therefore the requirement of higher performance can easily be met by adding the moving electrode type ESP in the area where the existing fixed electrode type ESP had been installed.

Figure 2 shows the latest installation list of the moving electrode type ESP, with a total of 57 units supplied as of 2008. Four new units are now under construction and the applications cover a wide variety of fields. There is an increasing demand for the use of the moving electrode type ESP for coal-fired boilers as outlet dust concentrations become more strictly regulated. Another increasing application is for sintering machine exhaust gas in iron works because the conventional fixed electrode type ESP cannot maintain stable collection efficiency due to high resistivity dust problems.

Figure 2 –Supply Record of Moving Electrode Type ESP

Until recently, moving electrode type ESPs have mainly been supplied in Japan. There are now various inquiries from foreign countries. In China, a moving electrode type ESP was supplied for the No. 5 coal-fired boiler of Changzhou Guangyuan Cogeneration Co., Ltd. in 2006. The ESP consists of two fixed electrode sections designed by Enelco Environment Technology Co. in China and one moving electrode section designed by Hitachi Plant Technologies Ltd. The measured performance data of this unit showed a collection efficiency of 98.89 percent. The second unit of a moving electrode type ESP for the No. 6 boiler has now started operation at the same site.

Cost comparisons of a moving electrode type ESP and a conventional fixed electrode type ESP were studied using actual operation results. In the case of the conventional fixed electrode type ESP, the total running cost over a span of 15 years is almost the same as that of the initial facility cost. Approximately 90 percent of the running cost is accounted for by the utility cost, which is used for the electric power required by the high voltage power supplied to the ESP. The moving electrode type ESP operates with less than 70 percent power consumption of the fixed electrode type ESP.

Maintenance and repair account for 7 to 12 percent of the running cost, and this is almost the same for both types of ESPs. However, the running cost of the moving electrode type ESP is only 68 percent that of the fixed electrode type ESP.

In general, the facility cost of a fixed electrode type ESP is initially cheaper by 10 percent compared to the moving electrode type ESP. The total cost including facility and running cost will, however, become the same as that of the moving electrode type ESP in 5 years. In 15 years, the total cost for the fixed electrode type ESP increases by 20 percent or more than that of the moving electrode type ESP. Thus, the moving electrode type ESP has an economical advantage over the fixed electrode type ESP.

In recent years, the power industry in India has been developing quickly. The total installed capacity, which was slightly more than 100,000 MW in 2001, is expected to reach around 215,000 MW in 2011. At ICESP XI, Lin Guoxin, Fujian Longking Co., Ltd., China, noted that this means an increase of about 6000 MW per year in India.

So far, 95 percent of the Indian coal-fired boilers are equipped with electrostatic precipitators. In 2005, the dust emission standard for 210 MW sized plants and above was 150 mg/Nm³. At that time, among the 83 coal-fired power plants, 27 plants, or about 32.5 percent, had emissions which did not meet the required standard. The current emission standard in India has since been raised. This shows that there is a substantial ESP market in India and at present, quite a number of Chinese enterprises are undertaking construction of coal-fired power plants there. As a result, Chinese environmental protection enterprises have also entered the Indian market. They must face the problem of how to solve the emission problems from firing Indian coal, which can generate ash that is difficult to collect.

For example, Balco Power Plant, which belongs to Bharat Aluminum Co., Ltd. is located at Korba in India. There are four units of 135 MW each, which were supplied in succession from 2005 to 2006. Due to the difference between the burned coal and the designed coal, the original ESP was unable to meet the required emission standard. In order to solve the issue, an SO₃ conditioning system was installed in March 2007. Although the emissions were reduced, in most cases they still exceeded the stipulated requirement.

The design SCA for the ESP at the Balco plant was 120 m²/m³/s of flue gas flow. This was far from the 180 m²/m³/s that should have been designed for the actual conditions. Inadequate SCA was the major reason for poor performance.

Flue gas conditioning (FGC) can enhance the performance of ESPs. Testing with SO₃ and NH₃ was conducted at the Balco plant. The test results showed that the outlet particle concentration was reduced by 50 percent when using SO₃ alone and by 65 percent when using both SO₃ and NH₃. Practice thus indicates that flue gas conditioning can improve the performance of an ESP collecting Indian coal ash. However, the improvement has a limit. It is necessary to have a certain minimum SCA before FGC can help to actually meet the emission requirements.

Fujian Longking began to study an ESP combined with a fabric filter in 2003. It consists of two parts in series, an ESP area at the front and a filter bag area at the rear. The structure is known as an Electrostatic Fabric Organic Integrated Precipitator (EFOIP).

In this process, dust is charged and most of it is collected in the front electrostatic precipitator area. The amount of dust entering the filter bag area is small in quantity but fine in size. As a result, the gas flow resistance in the filter bag area is largely reduced, the cleaning period is extended much longer, and the abrasion of the filter bags caused by scouring of coarse grain can be avoided. Practice indicates that the outlet particle concentration of EFOIP is less than 50 mg/Nm³ and the life of a filter bag is longer than four years. However, filter bags require a lot of maintenance.

Capital investment and operation costs depend on the mode of dust removal and precipitator size, as well as coal characteristics. For example, consider a 500-MW unit fired with typical Indian coal. Because of the typical Indian coal used in this project, with 0.25 percent sulfur content, high silica and a high inlet particle concentration of up to 97.7 g/Nm³, it is necessary to use an ESP with an SCA larger than 200 m²/m³/s of gas flow. This requires 4 parallel ESPs each with 2 chambers and 8 fields, with gas velocity lower than 0.65 m/s. If FGC plus the ESP is adopted, considering the limitation of SO₃ conditioning for achieving the 100 mg/Nm³ outlet requirement, the plant would need to use 6.5 fields of the above-mentioned ESP as the basic requirement. If EFOIP is adopted, it only needs to keep 2 fields of the above-mentioned ESP, and use 2.5 fields of space as the filter bag area. When compared with the above-mentioned ESP, an investment of 3.5 fields ESP can be saved. Therefore, the capital investment of EFOIP is the lowest and the ESP is the highest.

As for operating costs, considering power consumption, sulfur consumption and maintenance costs, the three modes of dust removal are comparable. Large maintenance for the filter bags and troubles of replacement are the disadvantages of EFOIP. However, EFOIP can assure performance of dust removal on economic terms.

Akron’s FirstEnergy Corp. faced a federal court mandate to clean up or shut down the R.E. Burger Power Plant, reports Bob Downing at Ohio.com. Last April the company chose to switch the plant to biomass, perhaps with some coal burned, too.

The utility had faced a $330-million bill to install scrubbers at the Burger plant to comply with a consent decree with the U.S. Justice Dept. In 2005, FirstEnergy had agreed to spend $1.1 billion to install scrubbers at its W.E. Sammis Power Plant. It also committed to cleaning, repowering or closing Burger and two other coal-burning plants to reduce sulfur dioxide emissions. The new consent decree on the Burger fuel switch was finalized in August 2009 in U.S. District Court in Columbus, OH.

That order affects Burger Units 4 and 5, which were built in 1944. They do not have scrubbers but do have electrostatic precipitators. The decree does not cover the other units at Burger:  a coal-fired peaking plant and three oil-fired peaking units. The consent decree makes the Burger plant the first coal-fired utility power plant in the U.S. to reduce its greenhouse-gas emissions under a Clean Air Act consent decree, the U.S. Justice Dept. said. Burning mostly biomass, Burger will produce lower emissions overall than if the plant were retrofitted with a scrubber. After its first year, the plant’s air emissions are expected to drop by 14,000 tons a year for SO₂, by as much as 14,000 tons for NO_x and by as much as 700 tons for soot. The plant’s carbon dioxide emissions are expected to drop from 1.7 million tons a year to 400,000 tons, a decline of 76 percent.

Building resumed in late October at the projected multi-million dollar Aspen Power Biomass Plant under construction in North Lufkin, TX reports ktre.com. Aspen Power had some legal hurdles after its air quality permit was set aside which halted construction last March. A settlement has now been reached.

A press release from Aspen Power stated, “Aspen’s originally-proposed emission controls were found by a Texas administrative law judge to result in emissions compliant with all applicable air quality standards. In order to resolve ongoing litigation and challenges to its permit application, Aspen agreed to the additional controls, including the installation of selective catalytic reduction technology to further reduce nitrogen oxide emissions. Aspen also agreed to add catalytic oxidation and to enlarge its electrostatic precipitator to further reduce organic and particulate emissions.”

Aspen Power is a renewable 50-MW energy project. It will burn clean wood debris generated by timber harvesting, sawmill and municipal maintenance/storm cleanup activities. The plant is scheduled to open in 2010.

Siemens has developed a new mobile testing unit for electrostatic precipitators, helping plant operators make more informed decisions on how to optimize ESP performance.

When retrofitted with modern power electronics, ESPs can become up to 30 percent more efficient due to a smoother direct current supply. Additionally, the new control systems can be restarted more quickly following a dielectric breakdown. Traditionally, plant operators had to replace the plant’s electronics in order to explore the potential for this optimization. This resulted in plant downtime. The new Siemens mobile testing unit eliminates this need, allowing cheaper and easier testing of modernization potential.

According to Siemens, in a few days, the mobile installation can provide the information needed to decide if a new electronics system alone is sufficient to optimize the filter or if more extensive changes to the plant are required.

Often the performance of existing ESPs can be improved by utilizing appropriate upgrading technologies. At ICESP XI, Tuomas Timonen, Alstom Power Service, Environmental Product Group, Vaxjo, Sweden, with others, stated that for existing ESP upgrade applications, some technologies may be better suited than others. This can be for reasons of layout and cost, process integration, age and design of the plant and the emission levels required. The most appropriate solution can be selected after detailed inspection and assessment of the present electrical, mechanical and gas distribution status as well as process conditions.

There is no doubt that there is a large ESP retrofit/rehabilitation market for a variety of reasons. First, the number of power plants approaching 40 years of age (a nominal life time) in the next decade will be large. Second, the imposition of tougher emission requirements will force change. It is estimated, based on experience, that roughly 20 percent of plants in the 40-year-age bracket will be rehabilitated and this represents approximately 20 GW/year. In the last two years, the trend toward plant upgrades has increased significantly. Alstom has globally executed more than one hundred ESP upgrades in coal, oil and bio-fired power plants as well as iron and steel, cement, pulp and paper industry and waste-to-energy plants.

The basis of operation and maintenance is an awareness of the operating situation of the air pollution control equipment. Regular mechanical and electrical inspections are recommended to determine the actual condition of the equipment, in order to maintain optimum efficiency. Analysis is necessary to determine the best type and the best time to repair or replace parts to minimize service interruption. A process of continual inspections in numerous locations allows performance comparisons, detection of trends and possibly advance notice of a failure.

For an ESP with good flow, mechanical and electrical conditions, there are several ways to improve particulate collection efficiency. There are a series of upgrade techniques ranging from transformer/rectifier (T/R) control, high voltage power supply Switched Integrated Rectifiers (SIR), flue gas conditioning, more efficient ESP design and field extensions. The most suitable technique is chosen based on the actual conditions, outage opportunity and economical aspects. The cost for different upgrading techniques differs significantly.

Alstom has developed a new generation of high voltage power supplies, called SIRs. The upgrade of conventional T/Rs to SIRs will usually result in a significant ESP performance improvement. This is due to a higher power input possible at operations that were limited by voltage or sparks. For example, a South African coal-fired boiler (2 x 315 MW electrical) ESP 4 T/R was upgraded with four SIR sets. The main challenges were high space charge combined with high resistivity flyash. Before the upgrade, dust emission levels were around 35 mg/Nm³. After the upgrade and extensive tuning the dust emission level dropped to 25 mg/Nm³.

Increasingly, operators are interested in advanced control system and optimization software solutions. Optimization software as part of an overall air pollution control plan has been shown to not only improve environmental compliance, but to also provide a number of financial benefits for users, such as a decrease in overall operating costs, an increase in equipment life time and even the ability to manage valuable air pollution trading credits. Based on process experience in particulate control, Alstom developed the Electrostatic Precipitator Optimizing of Charges (EPOQ) control algorithm. The control algorithm is a self-adapting expert software, with the main aim of minimizing emissions.

Another upgrade possibility is a control and monitoring system that offers opportunity for continuous process supervision. Regular monitoring and fine-tuning of the air pollution control equipment can guarantee the lowest possible emissions and energy consumption. Analysis of operating data allows maintenance measures to be implemented in a planned and optimal manner and also produces a rapid advance warning if the operating conditions should deviate from the norm.

To further innovate in the service area, Alstom offers a new, long-term service option that may solve many operating problems. This long-term agreement is backed by a complete performance guarantee for operating economy and emission levels. The agreement is based on a longer period of time (for example, 10 years) to give the customer complete control over the cost of their air pollution control equipment, without any surprises caused by extended downtime or faults in the design.

Today’s power generators and industrial producers need to operate their plants more cost-effectively while complying with more stringent environmental regulations. Challenges such as emissions compliance have caused operators to look for ways to help existing plants do what once seemed impossible — to simultaneously produce more power and products, increase profitability and yet become more environmentally friendly.

One of the many challenges facing the U.S. electric generation industry is reconciling the dual imperatives of profitable business practices and strong workplace safety. The dedicated staff at Ameren’s Hutsonville Power Station, located in Hutsonville, IL, have successfully worked together to increase their facility’s efficiency while looking out for their fellow workers, writes Angela Neville in Power.

Last May, along with the 2009 Electric Power Conference and Exhibition held in Rosemont, IL, the PRB Coal User’s Group (PRBCUG) recognized two (one large, one small) PRB Coal Plants of the Year. Bob Taylor, former PRBCUG chairman, presented the Small Plant of the Year Award to members of the Hutsonville staff.

Greg Musch, the production superintendant in Hutsonville, described the operations of the 162-MW intermediate-load, PRB coal-fired plant. “The first unit at Hutsonville went online in 1940, followed by the second in 1941,” he said. “Later, the 80-MW Unit 3 went online in January 1953, and the 82-MW Unit 4 went online in May 1954. Units 3 and 4 are GE turbines/CE tangential-fired boilers. In 1981, Units 1 and 2 were retired.”

The first delivery of PRB coal occurred in September 2004. A blend of 25 percent PRB and 75 percent bituminous coal was used after the Illinois Environmental Protection agency (IEPA) permit requirements were met. The sulfur emission credit price escalation was one of the main driving factors. Currently, the plant uses 100 percent PRB coal.

The total cost of the PRB transition included $6.9 million for in-plant adaptations and $4.5 million for coal yard upgrades. Total conversion time was four years.

Musch elaborated on the new fuel-handling challenges that plant employees faced. The first challenge was controlling dust while still utilizing existing coal-handling conveyors, transitions and coal-crushing equipment. The use of surfactants, water spray, sealed conveyor transitions, electrical system modifications and an aggressive cleaning schedule permitted the safe handling of PRB fuel.

Musch also pointed out that after the plant began using PRB coal, the boiler area required more frequent use of sootblowers. Flyash also tended to accumulate and eventually built up large snowdrifts of flyash that reduced boiler airflow capability. Therefore, boiler wall blowers and long lance sootblowers were added to the backpass horizontal tube bank sections as well as the ESP inlet and outlet turning vanes.

Due to the properties of PRB flyash, annual explosive cleaning is now required to clean the backpass horizontal tube bank sections of the boiler. Changes to the plant’s regular housekeeping duties were also necessary as a result of switching to PRB coal. These included the launch of a new, more aggressive and accountable cleaning schedule and weekly inspections by an outside corporate safety professional.

As more power plants follow the example of award-winning facilities like Hutsonville, the trend toward smarter ways of handling jobsite risks should produce improved results for workplace safety.

Staff at the Rockport Power Plant in southern Indiana have turned many difficult challenges into opportunities for improvement. Therefore, states Angela Neville, writing in Power,  it is not a surprise that the Rockport Plant, operated by Indiana Michigan Power, a branch of American Electric Power, was recognized as the Large Plant of the Year at the 2009 Powder River Basin Coal Users’ Group (PRBCUG) Awards Banquet.

This plant, like many other represented in the PRBCUG, wasn’t designed for PRB coal, explained Bob Taylor, former PRBCUG chairman. “A fatality from a dust explosion and numerous other experiences caused them to aggressively learn about the characteristics of PRB coals and implement actions for continuous improvements and proactive approaches to protecting people,” he said.

At one time, the Rockport Plant had the worst safety and health record in the company’s fleet. It also had more fires than most. The engagement and involvement of all employees turned the plant into one of the better performers.

Groundbreaking for the Rockport Plant occurred on August 29, 1977. It was built as a sister plant to several others that were designed to burn bituminous coal. However, before startup, a switch was made to burn lower-cost PRB coal, even though few in the company had any experience with this lower-sulfur but harder-to-handle coal. Unit 1 was placed into commercial operation on December 10, 1984. Unit 2 followed in December 1989. These were the fifth and sixth 1300-MW units built by AEP.

One of the advantages, besides lower coal costs, of using PRB coal is that it helps the Rockport Plant reduce air emissions. PRB coal is low in sulfur content, which is good for meeting the SO₂ limit, and high in moisture, which helps the plant meet its NO_x targets. The plant also uses activated carbon injection to control mercury emissions.

Challenges to using PRB coal included the staff learning the requirements for handling and burning PRB coal. It can self-combust if it is not compacted on the storage pile properly. Dust and slagging can also present problems.

Currently, the Rockport Plant is making another improvement to deal more safely with PRB coal’s volatile properties. It is replacing the old baghouse-style dust collectors with wet extraction-style dust collectors. These will eliminate much of the danger of fires and/or explosions. This new improvement also reduces the compressed air usage in the coal yard by eliminating any need for compressed air that is required on a baghouse-style collector.

Plant Manager Pat Hale attributes the success of the Rockport Plant first and foremost to the large number of talented and competent employees. Also, they have continued to make improvements to equipment, materials and processes that have made the unit operate much better and have improved safety.

Cloud Chamber Scrubber (CCS) technology, offered by Tri-Mer^® Corp., is sometimes confused with electrostatic precipitation (ESP) because both use electric charge. Aside from this similarity, the technologies are strikingly different. CCS uses charged droplets. Wet ESPs work by charging the particles in a gas stream, causing them to migrate through an electrostatic gradient to collectors, usually tubes or plates, where they are washed by a continuous film of water into a sump.

In contrast, CCS technology charges only the collector (that is, the water droplets) and moves the collectors to the particles. When a particle passes within 20 microns, the droplet charge induces a dipole force on the particle, which causes the particle to move the short distance to the droplet for capture and collection. The charged droplet “cloud” is able to handle even heavy particle loading with high efficiency.

For more information on CCS, visit www.tri-mer.com.

MemPro Ceramics Corp. is a global supplier of ceramic nanofibers. Ongoing collaboration with the University of Akron in Ohio is at the foundation of the technology developed to date. The company’s website is www.mempro.com, and the nCAT fiber technology is summarized at:  www.ceramicnanofibers.com.

MemPro Ceramics has received notice that the National Science Foundation (NSF) has awarded the company a $147,000-grant to continue the development of innovative ceramic nanofiber technology. The grant brings the total amount that the company has received from NSF to $847,000. The current grant will be used to expand the company’s technical options to reduce harmful exhaust from fuel-burning engines. MemPro has patented catalyst technology that provides low cost pollution control to fuel burning engines of all sizes. In 2008 the company received $500,000 from NSF to develop its NOXFOX™ brand of catalytic filters to meet 2011/2011 EPA small spark-ignition (SI) standards. The standards are aimed at reducing the harmful health effects of emissions from fuel-burning engines.

The new grant will allow research on ceramic nanofiber technology for larger engines, biofuels synthesis, new battery technologies and removal of hydrogen sulfides from natural gas streams. The company is currently scaling up production of its nCATfiber™ materials, which are based on ceramic nanofibers laden with catalyst metals like platinum, palladium and rhodium. MemPro’s technology minimizes the amount of these metals compared with other technologies and in some cases provides a completely recyclable product.

MemPro has been conducting engine testing on nCATfiber materials at its testing facility in Broomfield, CO, under the guidance of Chief Technology Officer, Dr. Gary Carlson. According to Dr. Carlson, “The new grant allows us to expand into larger markets such as the automotive and petrochemical industries. Support from NSF has been valuable during our expansion.”

As a cement company and a major player in the manufacturing industry, Holcim Philippines gauges its performance by balancing business operations with environmental conservation. The company advocates energy-efficient use of building materials, housing and infrastructure. Holcim Philippines chief operating officer, Ian Thackwray, in businessmirror.com, said the company works actively with local government units (LGUs) and industrial companies in promoting solid waste management to ensure refuse is put into productive and environment-friendly use in their cement manufacturing processes.

Thackwray explained that Holcim’s co-processing technology makes use of nonrecyclable and nonbiodegradable municipal wastes such as plastics which usually end up in dumpsites. These can pose health and environmental hazards in many rivers and waterways. He explained that co-processing waste materials has been implemented successfully in the U.S. and several European countries, and that Holcin has developed the capability and know-how to replicate this in the Philippines.

The firm has also invested in equipment to monitor emissions and keep the air clean. Its cement plants are equipped with continuous emission monitoring systems. It also maintains baghouse filters and ESPs in all of its plants.