Best practices shared by aero users benefit frame owner/operators as well

The Western Turbine Users and CCJ are working together to expand the sharing of best practices and lessons learned among owner/operators of GE aero engines. WTUI VP Ed Jackson, plant manager of Missouri River Energy Services’ Exira Generating Station in Brayton, Iowa, says the organization’s mission is to help members better operate and maintain their plants, and a proactive best practices program supports this objective.

Jackson stressed the value of the joint program during the user organization’s annual meeting in Las Vegas, March 17-20, 2019, at the South Point Hotel and Spa. He encouraged attendees to support the initiative and explained how they would benefit from the experience. The latest fruits of that effort are the best practices profiled here, submitted by the 12 plants identified in the figure.    

Recall that CCJ launched the industry-wide Best Practices Awards program in late 2004. Its primary objective, says General Manager Scott Schwieger, is recognition of the valuable contributions made by owner/operator personnel to improve the safety and performance of generating facilities powered by gas turbines.

Industry focus today on safety and performance improvement—including starting reliability, fast starts, thermal performance, emissions reduction, and forced-outage reduction—is reflected in the lineup of proven solutions profiled below.

Outage Management

  • Edgewood Energy, BEST OF THE BEST

Performance Improvements

  • Energia del Valle de Mexico (EVM I)

  • Exira Station

  • Orange Grove Energy

Safety

  • Kearny

  • Edgewood

  • Lawrence

  • Greater Toronto Airport Authority (GTAA)

  • Worthington

  • Pinelawn

Operation and Maintenance

  • Orange Cogen

  • Channel Islands Cogen

  • Shoreham

Water Management

  • Exira Station

Posted in WTUI | Comments Off on Best practices shared by aero users benefit frame owner/operators as well

2019 Aeroderivative GT Best Practices: Outage Management

Edgewood Energy uses multiple service providers to reduce the cost of engine repairs

The standard approach for handling major gas-turbine repairs is to solicit bids from multiple vendors and select the one offering best value. NAES Corp Area Manager Kenneth Ford and O&M Manager John Lawton wanted to improve upon this process for an upcoming overhaul at the two-unit Edgewood Energy LLC peaking facility, one of several plants in J-Power USA Development Co’s Long Island (NY) portfolio. Their goal: Deliver greater value without negatively impacting work quality and outage duration.

First step was to explore the feasibility of using multiple service providers, each having one or more portions of the larger repair work scope. Some service providers declined to participate in this program, which required bidders to modify their previous proposals for the entire overhaul into quotations for specific aspects of the repair scope.

Vendors were asked to bid on the following work packages:

    • Depot-level overhaul of the low-pressure turbine.

    • New second-stage nozzle assembly for the high-pressure turbine.

    • Provide a replacement combustor and fuel nozzles, and perform all field service work.

Disaggregating the repairs into work packages with three different service providers produced a $350,000 saving compared to the lowest bid for the entire project. There was no significant change in outage duration using three vendors versus one.

However, plant staff put in extra man-hours, primarily for due diligence—including:

    • Repeated rounds of quotes, follow-up discussions, and clarifications necessary to clearly present the options and recommendations to site ownership.

    • Agreement on terms and conditions with the three service providers.

    • Extended discussions with site ownership for evaluating the risk versus reward of selecting three service providers instead of one.

Contractor oversight also added to staff man-hours because of the three entities involved.

With the multiple-vendor approach highly successful, the owner will consider it for upcoming work at its other Long Island facilities. Future bid specifications likely will ask service providers to quote both the entire work scope and specific repair packages.

Other aero best practices

Performance Improvements

Safety

Operation and Maintenance

Water Management

Posted in WTUI | Comments Off on 2019 Aeroderivative GT Best Practices: Outage Management

2019 Aeroderivative GT Best Practices: Performance Improvements

EVM I’s washable pre-filter reduces cost of gas-turbine operation

Dust clouds overwhelmed the inlet filters during the dry season at this LM6000PF-powered 3 × 0 peaking site in an agricultural area near Mexico City. Compounding the challenge at Energia del Valle de Mexico (EVM I) was dust from the construction of a new combined-cycle plant only three football fields away.

Typically, pre-filters were saturated with dust after only five weeks of service and the resulting high pressure drop across the air inlet, and significant compressor fouling, reduced power production by an average of 4% over the year. Plus, the final cartridge filters were being replaced every six months, instead of the planned annual change-out.  

Airborne dust also fouled inlet-chiller coils, making it virtually impossible to operate the performance-enhancement system continuously and efficiently.

A study by plant staff pointed to large particulates as a primary cause of rapid filter fouling. Evaluation of alternatives for extending the service lives of both the pre-filters and final filters focused on eliminating the problematic particles between 2 and 5 µm. A washable polyurethane Poret® foam blanket with 10 pores per inch, and supplied on a roll by manufacturer EMW filtertechnik, was selected as the pre-filter curtain. The expected material lifetime was three years based on a blanket washing interval of five months. Blanket cost per engine: $1000.

The foam blankets, which were installed by plant staff, had a pressure drop of 0.28 in. H2O right out of the box. Washing was recommended when the pressure drop increased to 0.5 in. By the end of the implementation period, the plant reported having achieved almost constant power output throughout the year at a higher capacity factor than was recorded in the previous 12 months.

Offline washing of the three units was more effective after installation of the foam blankets, with “great improvement” reported in compressor power and efficiency. The blankets also allowed staff to increase the interval between compressor washings from three months to six and to get longer life from both the pre-filters and final filters. Without the blankets it was necessary to replace the pre-filters every four months and the fine filters once or twice a year. Today, the pre-filters are changed out annually and the fine filters every two years.

Plant-wide controls upgrade at Exira makes for smoother, more reliable operation

A decade and a half after COD, Missouri River Energy Services’ Exira Station, a 3 × 0 LM6000PC-powered peaking facility, located in southwestern Iowa, found itself with obsolete control systems in a rapidly evolving industry requiring the latest technology to assure safe, reliable, and profitable operation.

Here’s an overview of the challenge:

    • Gas turbines were equipped with the OEM’s Mark VI controllers and Fanuc PLC sequencer. In addition to being obsolete, the Mark VI had levels of control that limited what MRES staff could access.

    • The PLC controlling the cooling tower and chilled water system required for performance-enhancing turbine inlet cooling prevented plant staff access because of licensing issues.

    • The BOP DCS, critical for simplified total plant control, was in need of upgrades to assure continuity of system support.

Add to this the need to upgrade the following: (1) chiller controls, (2) analog-type valve drivers to digital, (3) security cameras and software, (4) the plant network and the network connecting the plant to dispatch.

There were two primary goals for the project:

    • Upgrade the main obsolete control systems to something that would serve MRES well into the future.

    • Simplify the more than the dozen or so control systems at Exira to put them on one platform or to aggregate them into one system. Several benefits are obvious: facilitate maintenance and training, reduce spares, etc.

Work on the project started about two years before the physical effort began, with the development of a preliminary scope which was sent to various vendors for budget estimates that could be submitted to the board for consideration.

Project benefits. Today, Exira has all the main control systems—turbines, BOP DCS, and cooling tower/chilled water—on the same Rockwell Allen Bradley platform. Because all the systems are Allen Bradley, the interfaces among the systems are seamless, eliminating the server formerly used to translate the communications among all subsystems to get them to work together.

Controls upgrade, network redesign improve reliability of Orange Grove Energy

The controls network for Orange Grove Energy (OGE), a two-unit (LM6000) peaking facility located in Pala, Calif, was antiquated. Old software and a complex structure exposed the plant, owned by J-Power USA Development Co and operated by NAES Corp, to breakdowns and outages attributed to the lack of redundancy and knowledge on how to restore lost components.

OGE’s control room was home to eight displays and five stations equipped with a computer, keyboard, and mouse (figure). Additionally, there were another four HMI displays, keyboards, and computers at the facility for the OMTs.

The solution was to convert the entire OGE control system to virtual machines (VMs) running from a single Microsoft hypervisor. The VMs include balance of plant, CEMS, historian, engineering workstation, ADS, domain controller, and surveillance-camera server and workstation. To make the virtual system redundant, there are two workstations that use a remote desktop to control the VMs and two hypervisors that replicate the VMs between each other.

The two workstations can operate the plant concurrently and independently of one another. In the unlikely event that one of these VMs should fail, the VM can be recovered by either starting the replicated VM from the other hypervisor or restoring it from a nightly backup.

Orange Grove now depends less on hardware upgrades and maintenance since the VMs are running from a newer, more-robust server, reports Plant Manager John Hutson. This is a fully redundant system to minimize downtime and operate the plant from two different locations. As an added benefit, staff can access the VMs remotely for troubleshooting or plant operation. The control room workspace is much cleaner, less noisy, and requires less power and space since there is only one workstation, keyboard, and mouse—as opposed to five.

Other aero best practices

Outage Management

Safety

Operation and Maintenance

Water Management

Posted in WTUI | Comments Off on 2019 Aeroderivative GT Best Practices: Performance Improvements

2019 Aeroderivative GT Best Practices: Safety

How Kearny personnel leak-check an operating engine without entering the package

Personnel at PSEG Fossil’s Kearny Generating Station, a 10-unit peaking facility in central New Jersey managed by Peter Van Den Houten, strive to continually improve work practices to ensure the safety of plant and contractor personnel.

One recent example: An innovative application for GoPro cameras, to put “eyes” inside the engine package (photo). The compact camera system enables staff to capture photos and video under extreme conditions.

During post-maintenance testing or oil commissioning of the station’s peaking units, leak checks are a routine task, The ability to safely look for leaks has been greatly improved with the use of this camera system, developed in-house by the peaking team under the guidance of Al Van Hart, technical manager.

The GoPro cameras are seated on mag-base remote mounts, giving operators pan and tilt capability. The cameras can capture a live feed and send it to an operator outside the package in a safe environment. The camera’s mobility enables the operator to conduct a full set of leak checks without entering the package. Click the link to see the GoPro in action at https://vimeo.com/306229398.This has significantly improved the safety of those who perform this work.

Results. While some other peaking plants with LM6000 gas turbines use high-cost stationary cameras for leak detection, the PSEG team took the inspection task to the next level by using GoPro cameras with pan/tilt mounts to provide greater flexibility at a less cost.

Lifting hoist for Edgewood Energy’s water combination skid filter mitigates injury risk

Routine replacement of the combo skid suction filter for Edgewood’s LM6000s required a technician to work in an awkward position, with both arms extended at, or above, eye level. Additionally, the filter element, which is approximately 40 in. long, would need to be manually lifted out of the filter assembly and a new filter inserted. An exhausted filter, saturated with demineralized water, is estimated to weigh between 30 and 40 lb.

The challenge in this instance was to provide an ergonomically friendly solution that would make this routine task safer by eliminating the potential for injury caused by shoulder, back, and/or neck strain.

Plant personnel, including Chief Engineer Anthony Angieri and OMT Nicholas Post designed a simple lift system, utilizing a locally purchased manual winch. The winch provides a means of lifting the filter element out of the frame by utilizing its inherent mechanical advantage (photos). The lifting hoist has been a great success, with employees happy to have a simple and effective method to perform an unpopular task.

Custom platform, I-beam facilitate maintenance, improve safety at Lawrence

At Hoosier Energy’s Lawrence Generating Station, a peaking facility with six LM6000s, certain maintenance evolutions inside the gas-turbine packages required technicians to use an extension ladder. Example: The Kvaerner package does not have a deck at engine level so technicians had to use an extension ladder to work on the low-pressure compressor (LPC).

The ladder was lowered 4 ft from engine level so the footing could be safely secured to the package floor. This required the technician to don fall protection to complete both routine and non-routine LPC maintenance and created an ergonomically uncomfortable work environment.

Another challenge was to eliminate the rigging necessary to remove the LPC case. Rigging chains create a major safety hazard to the technicians and to the equipment. Chain-falls become a trip hazard and create several pinch points and hand traps. Chain-fall rigging requires extreme care while removing the LPC case in order to prevent airfoil damage.

The plant safety committee, including Matthew O’Hara, lead O&M technician, discussed options and decided that a custom diamond-plate platform would eliminate the need for an extension ladder and fall protection (Fig 1). It also would allow technicians to work safely from an ergonomically friendly position.

Plant Manager Robert VanDenburgh’s operations team discussed options and concluded installing an I-beam above the LPC case would allow technicians to remove the case without extensive rigging (Fig 2). One technician can comfortably work from the installed platform to complete the LPC case removal without the dangers associated with ladders and rigging.

Results:

    • The custom platform installed in the LPC work area eliminated the fall hazard. The LPC now can be accessed without the need for an extension ladder or fall protection. Plus, ergonomics of this work environment have been improved dramatically.

    • The I-beam installed above LPC aft of the VBV ductwork allows for safe and level case lifts without need for extensive rigging.

Instrument relocation promotes safe, easy access to vital data at Toronto plant

The 2 × 1 combined-cycle cogeneration plant serving the Greater Toronto Airport Authority (GTAA) has two gas compressors, one for each of the plant’s LM6000s. Proper operation of the compressors is critical for achieving high engine availability.

Each compressor is equipped with a lubricator cycle-count display. It’s important for cycle count to be relatively constant too ensure against excess oil which could mix in with the natural gas being compressed. The display was in a location difficult for personnel to access and take readings. Plus, ever-present oil mist made for a slippery deck.

The safety hazard was exposed when an operator slipped and lost his balance while gathering data, hurting his back in the process. The injury was not a major one, but the incident provoked a thought process to mitigate this risk.

Plant Manager Don Tiffney’s staff initiated measures to ensure that the area is maintained clean and also installed anti-skid strips on the floor. But this was a temporary solution. Next step was for O&M Manager Socrates Furtado’s team to examine the feasibility of relocating the cycle-count display away from the unit in a location more accessible to operators. Personnel installed a limit switch next to the lubricator and wired it to a new cycle-count display mounted on the main panel, as shown in the photo.

Relocation of the display mitigated the risk of injury to operators during their shift rounds. Also, the new location prevented oil mist from depositing on the display, making it easy to view the parameter displayed.

Mitigating hazards associated with inspection of air-inlet chiller coils at Worthington

Hoosier Energy’s 174-MW Worthington Generating Station relies on four 1800-ton chillers during summer peak operations to provide 40F water to the air inlet houses of its four LM6000s, thereby ensuring top gas-turbine performance.

To protect against freeze-up during the winter, 40% glycol is added to the chilled-water loop; a small boiler maintains loop temperature at 54F. The warm glycol/water mixture circulates through the inlet coils, heating inlet air to maintain the optimal temperature for efficient generation.

Periodic coil inspections required removal of the upper panels on the filter house which can be accomplished only from the top of the structure. This dictated an aerial lift and fall protection. The aerial lift created a safety hazard and fall protection increased the time required to complete inspections.

Among the challenges facing plant personnel were the following:

    • How to eliminate the need for an aerial lift.

    • How to engineer out the need for fall protection.

    • How to remove the access panels without need for a pry bar.

    • How to decrease the amount of time needed to complete coil inspections.

Plant Manager Robert VanDenburgh’s operations team concluded that the safest way to access the coils was to install a fixed ladder to the top of the filter house. The team also decided to install a guardrail on top of the filter house package to remove the fall hazard. Plus, handles were installed on each of the four coil cover plates to eliminate the need for a pry bar. The handles eliminate pinch points and hand traps which will allow the technician to remove the coil plates with increased safety and greater ease.

Results:

    • By installing ladders and guardrails, the fall hazard associated with the coil inspections has been eliminated. Plus, the amount of time needed to perform inspections also has been reduced.

    • Because many inspections are conducted during cold weather conditions, minimizing exposure to the elements also created a safer work environment. Installing handles to the coil access plates completely eliminated pinch points and hand traps, adding another layer of safety to this task.

    • Plant personnel created a much safer work environment while reducing the time needed to complete inspections. The safety improvements have enabled an increase in inspection intervals, thereby boosting gas-turbine performance.

Pinelawn’s safety mod for easier filling of LM6000 hydraulic start reservoir

The challenge was to find a safer way to add fluid to the gas-turbine hydraulic starter reservoir, which is located under a system radiator and tucked away in the corner of its auxiliary enclosure. The original design situated the fill port in a cramped and hard-to-reach location, thus creating the potential for staff injury as a result of strain or from a slip/trip/fall.

Plant Manager Kenneth Ford’s team at this 1 × 1 combined cycle looked at several solutions, but in consideration of the challenging enclosure configuration, decided to relocate the fill port by simply adding several short lengths of piping. It is now in an easy-to-reach location and at a greater vertical height thus creating a much-improved ergonomic work environment.

Relocating the fill port has reduced the chance of injury from awkward body positioning. The modification generated very positive feedback from the site O&M personnel who recognize the importance of a safe workplace.

Other aero best practices

Outage Management

Performance Improvements

Operation and Maintenance

Water Management

Posted in WTUI | Comments Off on 2019 Aeroderivative GT Best Practices: Safety

2019 Aeroderivative GT Best Practices: O&M

Low-cost thermal imaging camera assists Orange Cogen’s operators during rounds

Orange Cogeneration, a 2 × 1 LM6000-powered combined cycle owned by Northern Star Generation and operated by Consolidated Asset Management Services LLC (CAMS), exports power to the local utility and sells steam from its condensing/extraction steam turbine to an orange-juice plant and an ethanol plant across the street for process use. Plant reliability is of critical importance.

Like many plants today, the Bartow (Fla) facility owns a thermal camera for use by technicians in troubleshooting and inspecting various mechanical and electrical issues that present symptoms as thermal gradients. These cameras are precise and can measure very high temperatures, but they are also expensive and cannot be treated roughly by inexperienced or less-than-fully-trained users.

Plant Manager Allen Czerkiewicz’s team found a small plug-in thermal camera, made by FLIR® Systems Inc, that does not have the full capabilities of the company’s more sophisticated models but offers a wide usable range of detection and is relatively inexpensive (photos).

Although designed for attachment to a smart phone, Orange Cogen’s CAMS staff has mated it to an Android tablet which allows a very large display. Also incorporated into the plant’s assembly is a rugged tablet case that has a built-in strap allowing secure one-handed operation. The complete setup cost less than $650, allowing the purchase of multiple devices to outfit the operations staff.

Using the camera on normal rounds, operators have found hot spots in the HRSG outer casings, motor bearings that have begun to get hotter than expected, as well as electrical contacts that have become hotter than neighboring phases because of higher electrical resistance. This device also allows the easy capture and sharing of pictures of these identified issues so that follow up with the more advanced unit, if required, can be quickly made.

Best of all, although the thermal imaging system appears to be rugged and the plant has not encountered any issues in operation, management is comfortable knowing that if the unit gets damaged, it will not be too significant a financial burden if replacement is required.

Having this preventive-maintenance tool handy for the operations staff allows personnel to get ahead of any issues that show themselves through thermal variances and gives an improved predictive approach to Orange Cogen’s maintenance activities.

Continuous blowdown realignment at Channel Islands Cogen saves water, chemicals

The Channel Islands Power Cogeneration Facility, a 30-MW 1 × 1 combined cycle in Camarillo, Calif, operated for 30 years under a baseload power purchase agreement with the local utility. In April 2018, owner California State University began operating under a dispatch-style PPA.

The change in operating profile required the NAES Corp O&M staff to keep the HP and IP drums warm to meet startup times specified in the new PPA. Heat is provided by a sparging system which injects steam at the bottom of the steam-drum risers, thereby developing a natural-circulation pattern to sustain chemical mixing. The use of sparging steam increases drum water levels over time. Operators managed drum levels by venting steam from the tops of the drums and by opening the bottom drains when necessary.

The process of adding and draining water dilutes the boiler chemicals necessary to protect drum internals. Continuous injection was required to maintain chemistry levels within the baseload target ranges.

Plant Manager Jeff Smith’s staff began looking for ways to recapture the water from the blowdown/venting process. In reviewing the system configuration, investigation of the continuous blowdown system (CBS) showed that during baseload operation it was designed to recover some steam. After further discussion, this question arose: Could water be directed to the deaerator (DA) rather than just the steam?

During the baseload operating period, continuous blowdown valves rarely were used; most sat idle. Most years they only were operated during annual valve maintenance. The blowdown control valves and associated manual valves were checked to verify full working capability. After a little maintenance, the system was cleared for use.

Starting with the IP drum, the system was tested to prove the concept of pushing the water from that drum to the DA. It took a couple of tries to get it to work because IP drum pressure was not high enough to overcome the water-column head pressure and DA steam pressure. After a couple of adjustments (closing the drum vent and boosting sparging-steam pressure), water could be moved into the DA via the steam path.

The chemical supplier was contacted to discuss the possibility of shifting control ranges for phosphate, pH, and O-alkalinity under the new operating profile. Plant personnel were told they could reduce the phosphate range from 10-20 ppm to 1-2 ppm. pH also would adjust slightly.

During warm standby, the chemistry levels were low enough to assume that there would be little to no chemical deposition in the feedwater system. Values were in the ppb range because of their dilution in the feedwater system. This would allow the minute amount of chemicals in the steam drums to flow through the DA to the standby boiler feedwater pumps (BFP) and finally into the standby boilers.

During the first few days of September, the standby BFP discharge conductivity was monitored; no change was noted. The chemistry levels in the drums of the standby boilers remained steady. The amount of chemicals transported out of the HP and IP drums did not significantly affect standby-boiler drum chemistry over the short term.

The chemical supplier also recommended that the plant monitor iron levels in the HP and IP drums. Silica typically was monitored to protect steam-turbine blades. Chemistry protocols were adjusted to check for iron when in warm standby and for silica when operating. Three months of iron sampling gave no indication of issues with the warm-standby chemistry protocol. Iron levels in the HP and IP drums are consistent with historical iron levels throughout the condensate and feedwater systems.

Fig 1 shows how the CBS works during baseload operation. Hot water moves from the HP drum to the IP drum to the flash tank (green circuit). Here the thermal drain trap holds the hot water, allowing it to steam off. Steam is routed to the deaerator (blue); water is released to drain (yellow) when the thermal drain trap cycles. In this operating profile, the control valves on the steam drums were programmed to operate based on conductivity levels in the drums.

Fig 2 illustrates the alternative operating condition for the CBS. The thermal drain trap (red) is isolated from the drain line. Hot water moves from the HP drum to the IP drum to the flash tank to the deaerator (green). For this operating profile the control valves were reprogrammed to operate based on drum level. No water or chemicals are routed to the drain.

Fig 3 shows the water path from the DA to the standby BFW pumps to the standby boilers (green). A detailed review of the water flow path shows that there are no system components—such as attemperators—that could be impacted by the introduction of low levels of phosphates.

Both May and September were zero-dispatch months. During May the plant was maintained in warm standby utilizing venting and blowdown operating profile described in Fig 1; September used the repurposed CBS described in Fig 2.

Results. The table compares operating parameters and chemical consumption for warm standby operation using the venting/blowdown scheme (May) and the repurposed CBS (September). The latter approach offers clear savings in water and chemicals.

Lighting upgrade makes Shoreham’s liquid fuel unloading area safer

High-pressure sodium lighting in the fuel-oil (FO) offloading area at Shoreham was dim, and existing light fixtures were heavy and prone to failure. Whenever one did fail, it was a challenging task requiring complete removal of the fixture from the underside of the roof in order to replace any failed components (starter, ballast, wiring, etc) The frequency with which these older, heavier fixtures were failing at the two-unit (LM6000) peaking facility owned by J-Power USA Development Co suggested that a more permanent solution was necessary.

The NAES Corp O&M staff engaged a vendor whose core business is to provide LED retrofit assemblies for most commercially available standard lighting fixtures. The aim was to replace the existing fixtures with LED retrofits that offer a much lower profile, thus preventing the bases from being impacted by the wind (the most common cause of failure of the older style models).

Cost also was an important consideration because replacement parts for the existing light fixtures were proving more and more expensive, and harder to come by.

Good results. Since replacing all the fixtures within the FO offload area with LED retrofit kits, there has not been any unexpected maintenance, says Plant Manager Kenneth Ford. The low profile of these lights secures tightly to the box mounts, so wind is no longer a factor. Plus, the area is dramatically brighter, providing much safer walking and working surfaces for plant staff.

From a financial view, the LED retrofit kits, on average, were less than half the cost of replacement incandescent fixtures.

Other aero best practices

Outage Management

Performance Improvements

Safety

Water Management

Posted in WTUI | Comments Off on 2019 Aeroderivative GT Best Practices: O&M

2019 Aeroderivative GT Best Practices: Water Management

New rules on waste-water discharges dictate conversion of Exira Station to ZLD

Stricter limits on waste-water discharges imposed as part of the NPDES permit renewal process made it impossible for Exira Station to consistently comply with the new rules as the facility was originally designed and operated. Challenges faced by the owner, Western Minnesota Municipal Power Agency, and the operator, Missouri River Energy Services, included the following:

    • The allowed concentration of copper in drinking water was 60 times greater than the new discharge limit.

    • Trace constituents in rainwater—such as iron, copper, zinc, and lead—can exceed the new standards.

    • Makeup, both withdrawn from plant wells and supplied by the regional water (potable) provider, is unsuitable for direct discharge.

Background facts:

    • Simple-cycle peaking plant with three LM6000PC gas turbines.

    • Inlet chillers/cooling tower.

    • Demin water for NOx suppression.

    • Makeup water from wells (10% to 25% of total); potable water from regional provider (90% to 75%).

Plant management decided that the optimal solution strategy was to eliminate the discharge of waste water from the plant. Their options:

    • Redesign the waste-water system to collect cooling-tower blowdown and water from plant drains and containment berms and haul it offsite for disposal.

    • Evaporate the liquid and dispose of the solids.

    • Recycle all waste water.

The last alternative was selected. A recycle-water treatment system was installed. As shown in the diagram, it consists of an underground collection tank for blowdown, plant drains, etc, and a high-efficiency filtration system that recycles processed water back to the raw-water storage (makeup) tank. Filter backwash is retained for offsite disposal.

Critical to the success of the ZLD concept employed is the relatively small amount of makeup required for the cooling tower compared to that needed for NOx control. This differential assures the dilution of blowdown required for economical operation of the demin system.

Here are some typical summertime (June through September) round numbers to put all this in perspective:

    • Raw water storage tank (makeup) capacity, 510,000 gal.

    • Total water use (includes blowdown), 44,000 gal/day.

    • Demin-water consumption, 31,000 gal/day.

    • Cooling-tower blowdown, 5000 gal/day (conductivity of 3000 µS/cm).

    • Raw-water conductivity, 600 µS/cm.

    • Conductivity of water in the storage tank (mixed raw water and blowdown), 850 µS/cm.

    • Recycle-water treatment system throughput, 50 gpm.

Results. The cooling tower was designed for four cycles of concentration in summer but was limited to less than two cycles to keep all of the monitored parameters below the required NPDES limits. Negative impacts of fewer cycles: Excessive blowdown (increased makeup) and inability to maintain inhibitor/dispersant chemical levels at optimal levels to protect piping and equipment.

Conversion to ZLD restored the original as-designed capability, thereby reducing blowdown (and makeup) and improving the effectiveness of cooling-water chemicals. Plus, collection of all drains means rainwater gathered from the berms also flows to the makeup tank (via the recycle-water treatment system). This reduces the consumption of water from wells and the regional provider. Burns & McDonnell provided engineering services for the conversion to ZLD.

Finally, because the plant doesn’t discharge, there’s no need for sampling and analysis, and no violations, reported Plant Manager Ed Jackson

Other aero best practices

Outage Management

Performance Improvements

Safety

Operation and Maintenance

Posted in WTUI | Comments Off on 2019 Aeroderivative GT Best Practices: Water Management