Fire Hazards

Coal-Fired Power Plants: Additional Hazards Require Additional Solutions

coal-fired power plant fire hazards

Purpose: To explain the fire hazards that are found at coal-fired power plants.

Highlights:

  • What caused explosions at coal-fired power plants?

  • What are the hazards of coal dust?

  • What can you do to reduce the chances of coal-fired power plant fires?


Contributor:  Daryl Bessa, President of F.E. Moran Special Hazard Systems
Writer:  Sarah Block, Marketing Director of The Moran Group

Powder River Basin (PRB) coal has given coal-fired plants an environmentally conscious, inexpensive alternative to traditional bituminous coal since the 1980s. The lower NOx and SO2 in PRB coal reduced power plant emissions, decreasing pollution, and appeasing the 1990 Clean Air Act. At the same time, the low cost and availability made PRB coal not only a viable option, but a fuel of choice. While PRB coal was the predominant emission efficient energy source in 1990, in 2012, it no longer reins as the most environmentally friendly fuel. With the current government crack-down on coal-fired power plants, the existing plants will likely be the last.

Coal-fired power plants are extremely volatile. After all, there is a reason the industry saying is, "It isn't if a fire occurs, but when." With the prospect of aging coal-fired power plants and their propensity for combustion, it is essential to understand their fire hazards and insure the fire protection preparedness of coal-fired power plants with extensive fire protection solutions.

What Causes Coal-Fired Power Plant Explosions?

Throughout a twenty-five year (1980-2005) study of PRB coal-fired power plants, there were an average of 11 fires or explosions, 29 injuries, and 5 deaths per year. Another study conducted by the United States Department of Labor during the 1996-2009 time period noted 437 workplace coal power-related deaths, averaging 33 deaths per year in the United States. To understand what fire protection is necessary to guard against mishaps, it is crucial to first understand why explosions occur.



 

Coal Dust Hazards

For a fire to occur, the fire triangle needs to be present - oxygen, fuel, and heat. An explosion happens when two other elements are added to the equation - dispersion of dust and confinement of dust, as shown in diagram A. Oxygen and fuel cannot be avoided in a PRB coal-fired power plant, but the heat source can originate from several different sources. A common cause is the conveyor belt. As the coal is being transported from storage to use, the coal-dust begins to fall off the belt and accumulate. Once the dust accumulates to 1/32 of an inch, or about the breadth to leave a footprint, it becomes a fire hazard. NFPA 654 defines combustible dust as, "any finely divided solid material that is 420 microns or smaller in diameter and presents a fire or explosion hazard when dispersed and ignited in the air." If a conveyor belt is not in impeccable condition, and one moving part stops, the friction can create a heat source for combustion. Other causes of heat are friction through mixing operation, electrical shortage, tool usage, or storage bin transfer. The fire triangle is difficult to avoid.

explosion diagram

Diagram A 

Two additional elements are added to the fire triangle to create an explosion. The dispersion of dust happens naturally as the coal is being moved. The sub-bituminous coal is high in oxygen and moisture, making it more susceptible to deteriorate into powder than standard bituminous coal. It easily creates a dust and disperses over pipes, conveyor belts, floors, ceilings, and machinery. The confinement of coal dust happens just as easily. The dust spreads in unseen areas, like coal silos or chutes. A Kansas City coal-fired power plant witnessed this first hand when, on April 4, 2012, an explosion rocked the plant. Dust accumulated in a chute, completely unseen, and caused the fire. Often, it is the hidden dust that causes the devastation, carrying the explosion or causing secondary explosions throughout the plant.

Oil Fire Hazards

Coal dust is not the only cause of fires in a PRB Coal-Fired Power Plant. Both the turbine and transformer are insulated by oil, making them flammable. There are three different types of oil fires that can take place in or near the turbine or transformer: spray, pool, and three-dimensional. Spray fires happen when highly pressurized oil is released; 50% of the time, this fire happens because of malfunctioning bearings. If there is an unpressurized leak, plants could see a pool fire when the oil catches fire after it has accumulated on the floor or a three-dimensional fire if it catches fire while flowing downhill.

Hydrogen Fire Hazards

Hydrogen cools generators in coal-fired power plants. Hydrogen is an invisible threat with the capability to catch fire and/or explode. The gas is odorless, colorless, tasteless, and the flames are invisible. It will not be detected without the use of hydrogen sensors. Fire fighting should not commence until after the hydrogen source has been shut off. If hydrogen is still present, it is likely to re-ignite or explode.




What can I do to reduce the likelihood of an explosion?

The key to reducing the probability of a coal-fired power plant fire or explosion is preparation. Fires generate from several different sources: coal dust, oil, or hydrogen. It is necessary to be knowledgeable about fire ignition in order to avoid it. The main causes of plant fires and explosions are coal dust, equipment error, and human error. Training plant personnel on proper housekeeping and machinery maintenance along with proper fire protection will greatly reduce the chances of a fire or explosion.

Housekeeping

Without a stringent housekeeping regimen, even the most advanced fire suppression system will not be able to stop an explosion from happening. A documented housekeeping routine is necessary to reduce the odds of a fire or explosion. According to the Mine Safety and Health Administration, with a robust housekeeping schedule, the fuel source would be eradicated, eliminating secondary explosions. Secondary explosions have the largest death toll of all coal-fired power plant combustions.

Dust collectors alone will not adequately dispose of dust; in fact, 40% of fires and explosions were caused by the dust collectors. An effective option is to wet the dust to weigh it down so it does not float into hidden crevices. Because the dust is microscopic, microscopic water spray must be used. Plants should use a wash down system to keep coal dust at a minimum. Industry surveys have shown that plant personnel who have utilized wash down systems have been happy with the results.

During an outage, it is essential to clear dust completely from bunkers, silos, and conveyor belts. Idle dust can explode. When preparing for the outage, wash down all walls of the bunkers or silos to eliminate the source for explosions.

Carbon Dioxide

If dust cannot be completely cleared, another option is to pump carbon dioxide into a sealed bunker or silo. The carbon dioxide would eliminate the possibility of dust combustion by taking away its oxygen.

Design 


A bunker or silo should be designed as if a fire is imminent. Access points should be installed on several levels to allow for entrance of fire extinguishment tools. It is important for the water to directly contact the source of the fire in a bunker or silo. Another design choice that will reduce the chances of a fire or explosion is a cone shaped floor or a free flow bottom cone. Many bunkers or silos have a funnel-flow pattern that occurs when the walls inhibit the coal from flowing freely. Most coal will flow down the center, while the remaining coal that has accumulated on the sides will linger stagnantly. Stagnant coal can create a heat source. The key to reduce the likelihood of a bunker or silo fire is in the design.

What are my fire protection options?

Detection Devices

Several different detectors are needed throughout the facility, depending on the location. Silos, bunkers, and dust collectors are at a high risk for explosions due to the congregation of PRB dust. It is necessary to choose the correct detection device. Carbon monitors, infrared scanning, temperature scanning, or linear heat detectors are adequate options. Linear heat detectors, such as Protectowire, can detect heat along a length of space, instead of a singular spot. This works extremely well along conveyor belts, which are a major fire hazard because they easily create heat through movement or from idler or roller bearing failure.

Fire Suppression Systems

Sprinkler systems must be installed throughout a plant. The main fire culprits are silos, bunkers, conveyor belts, crusher buildings, dust collectors, coal pulverizers, turbines, generators, and transformers as seen in Diagram B. Hazard location will determine the best system type. Temperature controlled locations are best protected by a wet-pipe system. Non-temperature controlled areas need a dry-pipe system to avoid frozen pipes. Transformers and other areas where quick suppression is important and water damage is not a concern are effectively protected by deluge sprinkler systems.

coal-fired power plant hazards

Diagram B 

Three main suppressants dominate coal-fired power plants: water, CO2, foam and/or f500 solutions. It is essential in coal dust-related bunker/silo fires to use a piercing rod or inerting system to smother the fire at its source. In all other areas of a plant, various types of sprinkler systems will effectively suppress fires.

An integral part of finding a solution to fire protection is choosing a company with experience and expertise to implement a comprehensive system. Fire protection providers must have the design capability to plan custom solutions for site obstructions and plant nuances. Each fire susceptible location of a plant must have a fixed sprinkler system that is designed specifically for that area. High value - high risk facilities are vastly more complicated than other industries; a fire protection solution provider should be experienced in providing fire protection for plant environments to ensure solutions that are suitable for the specific application. With proper housekeeping schedules, diligence, and fire suppression systems, the safety of people, plant, and production is greatly increased.

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Storing Flammable Liquids: How to Make the Complexities of NFPA 30 Simple

flammable liquid

Contributor: Andy Aleksich, Senior Designer of F.E. Moran Special Hazard Systems
Writer:  Sarah Block, Marketing Director of The Moran Group

On November 22, 2006, a malevolent explosion turned the town of Danvers, MA upside down. The explosion started in a chemical manufacturing plant, destroying it. The subsequent fires had far-reaching effects; it destroyed twenty-four homes, six business, and dozens of boats at a nearby marina. At least ten residents were hospitalized as a direct result of the explosion, and over 300 residents in the nearby neighborhood were evacuated. This disaster spurred the residents of Danvers, MA to establish community groups' Safe Area for Everyone (SAFE) and re-established the Local Emergency Planning Committee (LEPC). The U.S. Chemical Safety and Hazard Investigation Board (CSB) determined that the explosion was fueled by escaped vapor from a 2,000-gallon tank of highly flammable liquid. The ensuing fire blazed for seventeen hours.

It was discovered that although it is required for chemical plants that store flammable liquid to be inspected every year by the local fire department, the Danvers plant had not been inspected for four years. Additionally, the facility was not storing the flammable liquid in compliance with OSHA, Massachusetts fire code, or NFPA requirements. However, because the Massachusetts fire code does not require the application of NFPA 30 retroactively, the plant was not directly non-compliant. The chemical plant had a foam/water fire sprinkler system. This type of system is meant to work in conjunction with a fire alarm box that contacts the fire department. However, the chemical plant did not have a fire alarm box, so the fire department was not notified, allowing the conflagration to continue for seventeen hours. The CSB recommended the city of Danvers adapt the NFPA 30 code. Had they taken the advice, the chemical plant would have been in direct violation. They are not the only ones. Everyday facilities are cited for violating this code. Why are NFPA 30 violations so prevalent?

 

Insurance Underwriters are Focusing on NFPA 30

Currently, insurance underwriters are paying close attention to NFPA 30, Flammable and Combustible Liquids. In recent years, many plants have received written recommendations by risk management audits to revise the way flammable liquids and chemicals are being stored. Plants have the difficult task of combining the requirements from the NFPA, local authorities, and insurers into one fire protection solution. In some cases, one authority has precedence over another in one aspect of fire protection, but not all. For example, if a fire protection solution has been designed, developed, and tested by an approved testing facility, but does not meet NFPA requirement, if the authority having jurisdiction (AHJ) approves, it becomes compliant with NFPA. The complexity of NFPA 30 often results in unintentional non-compliancy.

NFPA 30 is Complex

To give this code perspective, we will compare it to NFPA 13, The Standard for Installation of Sprinkler Systems. NFPA 13 is a code used for every type of Fire Sprinkler System solution.
In this code, there are 26 chapters. In NFPA 30, which has a much smaller population of users, there are 29 chapters, 14 annexes, 1 chart, and 1 form.

To determine each fire protection need, according to NFPA 30, facilities must answer a series of questions before coming to a conclusion. For example, to find out how high a facility can store flammable liquids in vertical stacks, facilities must research and answer the following questions:

1. Is it a liquid (fluidity, viscosity, water-miscible)?
2. What type of liquid is it (flammable, combustible, flash points, boiling points, etc)?
3. What is the liquid classification (IA, IB, II, III, IIIA, IIIB)?
4. What type of occupancy is the liquid stored in (healthcare facility, industrial, processing plant, liquid storage warehouse, etc)?
5. What type of container is the liquid stored in (drums, portable tanks, relieving, non-relieving, immediate bulk containers, etc)?
6. Is there an automatic sprinkler system protecting the space (design flow rate, density, foam/water, etc)?
7. What is the container arrangement (palletized, rack, maximum allowable quantity, etc)?

For each different liquid storage fire protection solution - sprinklers, detection, and a wide-array of physical storage requirements - several questions must be researched and answered. This can be extremely burdensome for facility staff with a variety of responsibilities.

Solution

With a combination of fire protection professionals and NFPA 30 provided charts and forms, it is possible to apply this extremely complicated code. If a facility chooses to take on this task independently, it is recommended to utilize figures 16.4.1(a), 16.4.1(b), and 16.4.1(c) (see below) from NFPA 30 to determine the correct section of chapter 16 to apply to the facility's fire protection solution.

 

However, even with the use of charts, many sections of the code have numerous exceptions and refer to the Authority Having Jurisdiction (AHJ) as the point of reference.

It is advised that facilities do not attempt to apply the complicated NFPA 30 code on their own. Hire a fire protection solution provider that has a relationship with the AHJ and underwriters who can provide their expertise to ensure code compliancy. With the help of one simple seven question form (see below) and a fire protection solution provider, facilities can feel certain their buildings are code compliant.

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Solar Power's Secret Fire Hazards

solar power plant

Contributor:  Daryl Bessa, President of F.E. Moran Special Hazard Systems
Writer:  Sarah Block, Marketing Director of The Moran Group

The sun beams enough energy in one hour to power the entire world for one year. However, the world is still in the beginning stages of adopting this renewable energy source. There are many aspects of solar power that are misunderstood. A major misconception is the idea that solar power plants have no inherent fire risk. The majority of large scale solar power plants are concentrated solar power plants (CSP), which use solar energy to power conventional steam turbines. Therefore, CSP plants have the same fire hazards as many conventional power plants. With the push to "green" energy, CSP plants are gaining popularity. Currently, 1,000MW of energy from concentrated solar power is under construction (cleantechnica.com); enough to power 200,000 homes. With the rapid growth of this form of energy, how do we keep it protected from fire?

 

Converting the Sun into Power

Harnessing the sun's energy into usable electricity is one of the cleanest forms of power. It is a renewable source of energy that will faithfully rise each morning. The process of converting the sun's rays into power is relatively simple, but can create fire hazards that must be protected.

CSP plants use a series of lenses, mirrors, or heliostats and tracking systems to condense sunlight into a narrow beam of light. Solar plants have numerous options for technology that condenses the sunlight into a beam: Concentrating Linear Fresnel Reflector, Stirling Dish, Linear Parabolic Reflector/Parabolic Troughs, Solar Dish, or Solar Power Tunnel. The intense beam of light created is then used to provide heat to power a conventional steam turbine.

The concentrated beam of sunlight is used as a heat source to warm the heat transfer fluid, molten salt, or steam generator to power the steam turbine. The steam turbine is connected to a generator, which produces the energy.

Because concentrated solar power plants are a combination of solar energy and steam energy, the same fire hazards are present as in many other power plants.

Hidden Fire Hazards in a Solar Power Plant

Solar power: the words themselves give the illusion of safe energy. However, CSP plants share several of the fire hazards that many standard plants possess. Lube oil systems, transformers, turbine bearings, switchgears, and other areas of concern associated with conventional plants should be considered.

In an HTF type plant, the solar field has its own fire hazards. The concentrated sunlight created from the solar field is used to bring the heat transfer fluid to a high temperature. The heat transfer fluid flows from the solar field to a standard steam turbine. The heat transfer fluid is generally a form of oil and can be very flammable. The heat transfer fluid introduces a fire hazard to the solar field. The heat transfer fluid pump and pipe racks can be protected with deluge systems and linear heat detection.

The heat transfer fluid flows until it reaches the heat exchanger which can be another potential problem area. The steam turbine uses lube oil to keep it moving smoothly. Fires can ignite within the turbine underfloor, exciter, lube oil piping, or the turbine bearings. It is recommended that a robust fire protection system is installed in this area. An automatic sprinkler, foam-water sprinkler, or deluge system is appropriate for the turbine area. An early warning detection system will ensure that the plant personnel are given adequate notice of a fire ignition. A fire protection solution provider will be able to provide custom recommendations based on the plant's particular hazards.

solar power plant

 

The next step in solar energy generation is the generator, which produces the energy. The generator contains lube oil, and/or hydrogen which can fuel a fire from the slightest spark. To protect a generator, a pre-action sprinkler system or inert gas system is ideal. They reduce the likelihood of an accidental discharge while protecting delicate equipment.

Cooling towers are often thought of as fire resistant because they are usually wet; however, cooling towers contain hidden dry areas and are completely dry during maintenance. Cooling towers are made from combustible materials. The heat source in a cooling tower fire can come from outside sources, such as a fire from another part of the plant that has spread or internal sources, such as maintenance welding, overheated bearings, or electrical failures. A concern within cooling towers is the accelerated corrosion of piping, including fire protection pipes. Plants must take this into consideration and adjust the inspection, testing, and maintenance schedule for this part of the plant.

Concentrated solar power plants provide a clean, renewable form of energy throughout the world. However, inherent fire hazards may be overlooked within this form of energy generation. Plants must protect the valuable assets, people, and production with a proper fire protection solution. Work with an experienced fire protection solution provider to ensure all fire hazards are adequately protected with robust fire sprinklers and detection systems.

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Converting Power Plant Fuel Sources: what hazards will arise?

biomass fire protection

Contributor:  Daryl Bessa, President of F.E. Moran Special Hazard Systems
Writer:  Sarah Block, Marketing Director of The Moran Group

Followers of the power industry are well aware of the EPA regulations pushing coal power into the history books. Because of this, many plants are converting fuel sources. There are several options for fueling plants: solar, biofuel, combined-cycle - but the fuel of the moment is natural gas. With its current minimal cost and clean burning, it is a fuel that government regulators and plant managers can agree on. However, the process of converting fuels can be hazardous. There are numerous fire protection considerations that need to be made before, during, and after the conversion.

The Process of Converting Fuels

When a plant converts from one fuel source to another - for the purpose of this article, we will use the example of coal to natural gas, as this is the most common conversion -, the equipment needs to be changed and the boiler has to be converted from coal burning to gas burning. Conveyors and silos are no longer needed, but they may still be on the premises. If so, they may still contain residual coal dust that can cause spontaneous combustion. If a silo remains on the property for storage or another use, it needs to be protected with fire sprinklers. A fire or explosion in these shuttered areas could easily damage other working parts of the plant.

New piping, additional compressors, and valves will be added to convert to natural gas; the new equipment needs to be protected from fire during and after construction. A natural gas pipeline purge will take place during the conversion, and this could cause a massive fire or explosion. Kleen Energy is a prime example of what can happen when a mistake takes place during a pipeline purge. On February 7, 2010 in Middletown, CT an explosion occurred, spurred by the purging of a natural gas pipeline. Six people were killed and over fifty people were injured. A tragic event such as this can take place during construction with any number of workers on site, which is why completing the fire protection first is essential to workplace safety.

Protecting Plant Personnel

Workplace safety is a hot button topic. Safety issues and the lack of protecting employees has been a trending story in the news. How do we protect contractors during a fuel conversion from fire? Contractors must be aware of fire hazards and pre-plan to mitigate them. For example, in the case of Kleen Energy, employees were unaware a gas pipeline purge would be taking place that fateful day. That didn't allow employees to create a Job Safety Analysis (JSA) to determine possible safety risks and ways to avoid them.

Contractors should also be aware of fire protocol. If a fire takes place, it is necessary that all personnel on the site knows how they should react: who should the contractors notify? Where should they go as a muster area? How do you react if a co-worker is injured by the fire? All personnel should be aware of a fire plan.

 

Lastly, fire protection should be installed as soon as possible. Fires take place more often during construction or maintenance than when the plant is operating, so employees and property must be protected at all times. There will be new fire hazards associated with the conversion, and it is the job of the plant to protect those involved.

By thoroughly planning the fuel conversion, plants can adequately protect the personnel, plant, and productivity.

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