Power Water Insights No

				Power Water Insights No. 6 February 10, 2012

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· “Hot Topic Hour” on February 16, 2012 is “Power Plant Cooling Towers and Cooling Water Issues”

“Hot Topic Hour” on February 16, 2012 is “Power Plant Cooling Towers and Cooling Water Issues”

Power plants utilize significant quantities of water mostly for cooling purposes while generating electrical energy. The most common method for cooling is flowing water withdrawn from a well, river, lake or ocean once through a heat exchanger and then discharging the water back into the source. Cooling towers that recirculate the water multiple times before discharging it are generally used only where water is scarce. This situation however is about to change and the use of open or closed recirculating cooling water systems may become necessary throughout the power industry.

Proposed rules on power plant water intake and discharge as well as an increasing scarcity of fresh water will drive this change. Although intake screens may be a solution to the proposed Section 316(b) Phase II Rule on water intake structures, many plant operators may select a much more expensive cooling tower as the best alternative considering the discharge rules. The EPA estimates that about 670 power plants will be affected by this rule. McIlvaine Company has estimated that 343 fossil plants and 42 nuclear plants would have to install cooling towers and recirculate 150,000 MGD after the final discharge rules are issued. The tighter air pollution rules recently finalized may also drive utilities to adopt cooling towers since the towers can help reduce emissions of SO₃ and particulates.

The adaption of a cooling tower is not done without other problems however. Maintaining water quality to prevent scale and fouling is one. Permitting issues other than those related to 316(b) that are unique to cooling towers is another.

The following speakers will address the latest cooling tower technology, maximizing exchange efficiency to improve efficiency and reduce evaporation loses, water maintenance issues, affect on other pollutants and other cooling water issues such as economic factors promoting or discouraging water conservation, alternative sources of water to reduce freshwater withdrawal and energy consumption for example municipal wastewater or gray water and reuse of plant wastewater, current and future regulatory compliance issues affecting power plant water intake, use and discharge and current and developing technologies to enhance water quality and reuse during all phases of the power generation process:

Mark Gerath, Technical Director, Water Resources, AECOM Environment, will discuss planning for the pending section 316(b) rule. His presentation will briefly summarize USEPA’s proposed 316(b) Rule published in 2011, including potential issues and challenges for compliance. Perceptions on likely changes in the final Rule expected this summer and strategies to facilitate compliance will also be discussed.

Larry Schimmoller, P.E., Global Technology Leader - Water Reuse at CH₂MHill, will review two case studies of using municipal reclaimed water for cooling water applications at power plants. Population growth, climate change, drought and dwindling water supplies have increased the beneficial use of municipal wastewater, including its application for cooling water at power plants. This presentation will discuss water quality considerations specific to reclaimed water use at power plants and will review two case studies of power plants using reclaimed municipal wastewater.

Ivan A. Cooper, P.E., B.C.E.E., Practice Leader at Golder Associates NC, Inc, will discuss water management issues at power plants. The use of open or closed recirculating cooling water systems may become necessary throughout the power industry. Proposed and new rules on power plant water intake and discharge as well as an increasing scarcity of fresh water will drive this change. However, the adaption of a cooling tower is not done without other problems. This presentation will describe some of the options available and the problems associated with them.

Trent Gathright, Product Manager, Power & Intakes at Energy Group-Americas, Ovivo USA, LLC, will discuss Intake Screens, Fish Handling, and general plant cooling water systems.

Matthew L. Haikalis, Technical Resource Engineer at Veolia Water Solutions & Technologies of Crown Solutions, will discuss water treatment for recirculating cooling water. Cooling water treatment demands can change when switching from a once-through system to a cooling tower system. These demands require significant thought when determining technologies that allow for optimal system control while managing economics, environmental impact and operational and maintenance requirements. Perhaps the most significant demand for cooling tower water treatment programs is the ability to control biofilm and microbiological activity, but also the cycling effect of a cooling tower effects scale control and corrosivity. Retention time of a tower compared to once-through cooling is also a significant factor.

To register for the Hot Topic Hour on February 16, 2012 at 10 a.m. (central time), click on:

The concept of co-locating municipal wastewater plants with coal plants looks better and better. As discussed in the Insights last week, there is nothing new about power plants using treated wastewater. What is new is starting with untreated wastewater. The more you analyze the option the better it looks. We will continue to report on insights from EUEC in future Insights, but here are some of the things we learned in stopping at the exhibitor stands.

Pictured below, from left to right are, Robert Pearson, Vice President, CH₂M HILL, Judith Chow, Research Professor, Desert Research Institute and Hollie Scott, Engineer, CH₂M HILL. CH₂M HILL is a global leader in full-service consulting, program management, design, construction and operations for public and private clients. With US$6.3 billion in revenue and more than 23,500 employees worldwide, they deliver innovative, practical, sustainable solutions to help clients develop and manage infrastructure and facilities that improve efficiency, safety and quality of life.

Hollie is leading the water program in power. He has arranged for CH₂M Hill to present in our cooling tower water issues webinar next Thursday, February 16.

Pictured below, left to right, from AECOM, are Robert Iwanchuk, Manager, Air Quality Services, Environment and Michael Kincaid, Associate Principal. AECOM is a global provider of professional technical and management support services to a broad range of markets, including transportation, facilities, environmental, energy, water and government. AECOM offers a full range of environmental design and engineering disciplines.

Pictured below from GEA Heat Exchangers are Ferenc Horváth, Vice President, Balance of Plant Sales, Business Unit ACC/Heller and Geza Walter, Head of Research and Development. GEA EGI Contracting/Engineering Co., Ltd. is a major Hungarian contracting and engineering company. GEA EGI is part of the global GEA Group that operates in more than 50 countries worldwide. Their company belongs to the Heat Exchanger Segment of the corporation, more closely to its Business Unit Power. Power & Process Cooling and Balance of Plant systems make the backbone of GEA EGI’s contracting business.

The focus was on the Curcumix® dense slurry technology for handling flyash, bottom ash and FGD waste. One of the features is minimal water consumption and the production of solidified waste with very low leachate. A unit is installed at the Northside Generating Station of JEA and has been in operation since 2003. Installations in Romania and India are slated for startup this year. Power plants in Hungary and Romania have experience with this system dating back to 1991.

The San Antonio River can experience high water events that churn the meandering channel into a raging torrent. These incidents have until recently left in their wake a thick buildup of silt muck on the intake structure's floor of the CPS pump station that draws from the river to recharge Calaveras Lake.

A view of one of the mast-mounted mixers. The units can be adjusted for different angles of delivery, and raised up the pole for ease of maintenance.

Three-to four-foot deep buildup of sediment would cover the floors of the 36' x 20' x 50' intake's two pump chambers and block the suction bells of the 1500-HP vertical submersible pumps in each chamber which are 16 inches above the floor, according to Ron Christian with CPS Energy's Field Operations (as reported in Waterworld).

"The configuration of the trash grate and traveling screens only aggravated the buildup and the originally designed back flushing system lacked enough force to clear the mud from the pump suction bells. This became a chronic and critical problem, especially during summer months," he said.

A four-man crew often spent several days clearing the mud from the pits. Most often, their tool of choice was a large compressor unit that would power an air lance to loosen the sediment while flushing it out of the diversion structure. It was a tedious task inevitably repeated after nearly every high water event.

The problem was finally resolved when CPS Energy learned how another Texas utility's ingenuity had rectified a similar problem. During a meeting with that utility, CPS learned how it had dealt with an almost identical problem at the raw water pump station serving their power station. They stopped the silt settling problem by installing Flygt submersible shrouded mixers, manufactured by Xylem. The compact mixing units reliably stopped the sediment from settling and blocking the intake to the pumps.

Four, mast-mounted Xylem Flygt Model 4640 mixers were installed by a local contractor. “During the installation, the pump station's intake was closed off and the pits drained and cleared prior to receiving the shrouded axial impeller units," Christian said. "Two were mounted on masts with cables in each pit about one foot above the floor on opposite sides of the intake pump suction bells. The mixers can have their delivery angle reoriented 180 degrees off the wall line and the units rose up and down using their cables. The utility's personnel installed new water level sensors and mixer controls for automatic start/stop operation whenever river levels are 401-to 403-ASL and the river pumps not in service.

The intake chambers were flooded and stop logs removed," he said. "When the mixers were activated in the first pit early in 2008, even the small amount of sediment remaining on the floor was immediately churned up and flushed down river."

Following a series of high water events since, the Texas-scale problem caused by micron-size silt building up has been mitigated, saving man-hours once needed to clear the pits to help to insure a reliable source of makeup water from the river.

Selection of mixers for a water intake station (WIS) creates challenges even in the kind of mixer which can be used. Top entry type mixers are often difficult or even impossible to mount. Submersible mixers, because of their mounting flexibility, are often the only useable design.

Determining the size of a mixer required for a WIS presents more challenges. A WIS is not a well defined tank or basin – one side is open to the river. Also, depending on the river's flow, deposition of material on the station's ramp can range from some fine silt to massive amounts of silt and sand.

The key in making the mixer selection is to recognize that a shear stress must be applied to re-suspend the accumulated solids. The magnitude of the total mixer thrust required to achieve this shear stress is a function of the area to be cleared, the consistency of the settled solids and the desired time to achieve the removal of the solids.

Ecologix Environmental Systems, an Atlanta-based wastewater treatment company specializing in oil and gas, has designed a mobile integrated treatment system (ITS) for hydraulic fracturing that will treat up to 900 gallons per minute of frac flowback water.

“Efficient and affordable water treatment is one of the biggest operational challenges with hydro-fracking, and there is a need for new treatment methods that are environmentally compliant and economically viable,” said Eli Gruber, CEO of Ecologix. “The mobility and treatment capacity of this system is an industry-breakthrough that will change the way frac water is treated.”

Ecologix Mobile ITS is a completely self-contained system that can be easily transported and set-up for operation onsite. Using dissolved air flotation technology, the system has the capacity to treat frac flowback water at a rate of nearly 900 gallons per minute. Such rapid treatment capability reduces the burden on equipment and logistics required when using traditional treatment methods and thus could significantly reduce operational costs.

Ecologix re-designed the ITS to also allow the water to be re-used for future drilling, with closed-loop capabilities in the near future. “With increasing environmental scrutiny associated with hydro-fracking, we designed the system to treat the water so that it could be used for industrial recycle and re-use, rather than discharged into ground wells,” said Gruber. “This treatment method is both environmentally-sustainable and affordable, which is just what the industry needs to continue fracking operations in the future.”

The system removes essentially all suspended solids, fats, oils and greases from wastewater, produced water and frac water.

Algae’s biomass, once refined, can be used for animal feed and its lipid oil for blended petroleum based fuels. DAF Corporation’s FC Maximizer clarifier is a hybrid DAF clarifier perfectly designed to feed and harvest algae. According to the company “this DAF Maximizer clarifier is a very cost-effective algae harvesting machine sold in the marketplace. It feeds and harvests algae with removal efficiencies reaching 99 percent. Everyone knows algae feeds on carbon dioxide and sunlight. Our unique DAF clarifier design allows you to pipe back its clean carbon dioxide enriched nutrient discharge water into your growing pond for enhanced growth and production. A side stream of carbon dioxide laden water from our AMT is consistently delivering its fine micron bubbles into the processing clarifier tank. Trillions of CO₂ micro bubbles all equal sized, rise to the surface in the Maximizer tank with NO coarse air bubbles. This process creates a dense fine algae float mat that is removed by the FC Maximizer variable speed, two-blade rotating scoop. Its unique design gently dips into the surface float and scoops up the algae and lipid oil, discharging it into the clarifier piping system for processing.”

“Algae’s biomass once refined can be used for animal feed or its lipid oil for blended petroleum based fuels. Our DAF FC Maximizer clarifier is a very cost-effective way to harvest algae. It can also feed algae. Part of our DAF clarifier system is the AMT air dissolving system. It can be used to nourish algae with a side stream of CO₂ as a nutrient. It’s very unique in design. This side stream of carbon dioxide with laden water and compressed air from this AMT is injected into the DAF clarifier as fine micron bubbles. These micron bubbles rise to the surface of the water in the tank at a rate 10” to 12” per minute. Hundreds of millions of all equal sized, fine micron bubbles entrap themselves in the suspended solids or algae bloom in the DAF Maximizer tank. Parallel with this process, on the DAF’s open tank top rim is a rotating stainless steel tank carriage that supports the fixed and rotating tank internal parts. A stainless steel, variable speed, two-blade rotating scoop is attached to it. This unique design gently dips and scoops up the dense fine float mat and discharges it into a discharge pipe.”

The market for filters which remove medium size particles from liquids will rise from $6 billion last year to over $7 billion in 2015. The biggest market growth will be in East Asia where the revenues will exceed $2.7 billion in 2015. This is the latest forecast in Liquid Filtration and Media World Markets published by the McIlvaine Company (www.mcilvainecompany.com).

This forecast does not include reverse osmosis, microfiltration and ultrafiltration which remove smaller particles. It does not include screens which remove very large particles. It covers the removal of particles from 1-50 microns. It does not include cartridges which are used for liquids with very low solids content. It does include gravity media filters, automatic backwash filters, filter presses, gravity belt filters, drum filters, belt filter presses and bag filters. The bag filters are the only segment which is not self cleaning.

Large numbers of belt filter presses are being sold to dewater sludge in Asian municipal wastewater treatment plants. Gravity media filters are widely used to purify water as it is extracted from rivers and streams. Filter presses find many uses in the chemical industry where they are used to separate products. Drum filters are used for product separation in the mining industry. Gravity belt filters are used to wash gypsum formed in coal-fired power plant scrubber systems. Bag filters are used in many industries where they compete with cartridges.

Automatic backwash filters have enjoyed the largest percentage growth in recent years. Originally, these filters were fitted with screens which could not remove particles smaller than 50 microns. The development of sintered metal allowed designs which can now remove particles as small as 5 microns. These filters find widespread use for purification of the side stream in cooling tower systems.

Major international suppliers include, Siemens, Ovivo, Xylem, Veolia, Amiad and Andritz. There are many media suppliers who manufacture the cloths and bags. They include Clear Edge, Sefar, National Filter Media and GKD.