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Boiler Basics 101: Deaerators & Feedwater Systems

Deaeration of boiler feed water is primarily known to remove dissolved oxygen from the water, however, there are four additional advantages of utilizing a deaerator: (1) carbon dioxide removal, (2) improved operation, (3) improved heat transfer, and (4) energy savings. In this month’s edition of Boiler Basics 101, we review the importance of including deaerators as part of your boiler plant.

Corrosion in boilers from dissolved gases leads to reduced heat transfer and efficiency losses. Both oxygen and carbon dioxide, if not removed from the water entering a boiler, will cause corrosion. Dissolved oxygen will attach to the metallic components of a steam system and form oxides, or rust, on boiler heat transfer surfaces. If carbon dioxide is present with the oxygen, the two gases together can be up to 40 percent more corrosive than if they were acting individually. Removing non-condensable gases and limiting or avoiding corrosion will greatly improve heat transfer.

Deaerators also serve the purpose of pre-heating the water before it enters the boiler. This process saves energy by recovering flash and exhaust steam from plant returns, energy that would normally be lost to the atmosphere, and utilizing it to pre-heat the feedwater. This recovered steam can account for 20 percent of the fuel typically required to provide heat for that process. Pre-heating the feedwater will also greatly reduce the chance of thermal shock caused by the expansion and contraction of heating surfaces and will ultimately improve the operation of your boiler.

Deaerators and atmospheric feedwater systems both have the same purpose and are made up of several individual devices including feed pumps, a corrosion resistant receiver tank, and a control panel. A deaerator does its job by mixing steam with soft water inside a pressurized tank, removing oxygen molecules which are then vented into the atmosphere. Atmospheric feedwater systems are non-pressurized and perform the same function while operating at a lower (atmospheric) pressure. A notable disadvantage of operating at a lower pressure is that a lesser amount of dissolved gases are removed. Although atmospheric systems are more cost effective, process requirements will dictate which system is ideal for your application.

Overall, if boiler feed water is not properly deaerated, corrosion will occur, and a boiler will operate less efficiently with a higher possibility of facing costly downtime and boiler repairs. Nationwide Boiler provides new deaerators and maintains a rental fleet of deaerating boiler feedwater systems for both low and high pressure applications. Our systems range in size for boilers 24,000 to 225,000 lb/hr, and are configured one of two ways: a skid-mounted deaerator with feed pump stand or complete mobile feedwater system including the deaerator, feed water pumps, water softener, and chemical feed system, all pre-piped and wired and installed inside of a trailer-mounted van.  

Be sure to check out our previous Boiler Basics 101 blogs and stay tuned for the next edition!

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Boiler Basics 101: Burners

The burner is the key equipment component for combustion control systems, providing the heat required for a boiler to convert water into steam. Ideally, a burner should achieve the highest degree of combustion efficiency with the lowest possible excess air. In this month’s edition of Boiler Basics 101, we will discuss the importance of burners and how they fit into the overall picture within the boiler system.

An industrial burner provides a basic function with a simple concept: it mixes fuel and air together to create combustion. Burners can be fired on various types of fuel but the most common utilized are natural gas, oil, propane and coal. In recent years, facilities have moved away from the use of coal to a more efficient and cleaner fuel like natural gas.

Regardless of the type of fuel used, the burner must perform five functions:

  1. Deliver fuel to the combustion chamber
  2. Deliver air to the combustion chamber
  3. Mix the fuel and air
  4. Ignite and burn the mixture
  5. Remove the products of combustion

Complete combustion occurs when all combustible elements and compounds of the fuel are entirely oxidized. However, with complete combustion comes harmful byproducts of combustion, including NOx and CO.

The amount of NOx and CO generated depends greatly on the burner design as well as the fuel fired. Burners with uncontrolled NOx may produce 60 ppm or more. Low NOx burners are the current standard and typically produce NOx of 30 ppm. Ultra-low NOx designs have been developed but are limited to firing on natural gas or propane. These types of burners will reduce NOx emissions to as low as 5 ppm to meet strict environmental requirements that are now common in certain parts of the country. If further NOx reduction is required, Nationwide Boiler’s CataStak™ SCR system can be utilized in conjunction with a low NOx burner.

The right burner design, along with proper combustion controls, will maximize the efficiencies of your boiler system. And as a representative of Webster Combustion, Nationwide Boiler and Pacific Combustion Engineering can help in the proper selection of your new or retrofit burner.

Be sure to check out our next Boiler Basics 101 blog to continue learning about various boiler-related topics.

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Boiler Basics 101: Evolution of the CataStak

With air emission regulations constantly changing, Nationwide Boiler has had to adopt new ways to keep up with more stringent standards. For instance, in 1995, Nationwide became the first rental boiler company to convert their fleet of watertube boilers to low NOx levels of 30 ppm. The company’s method of choice to reduce NOx emissions further led to the creation of the CataStak™, which was developed in the late 90s and since then has proven to reduce NOx emissions by as much as 99%. In addition, it can be supplied for new equipment or as a retrofit on an existing system. What were the early days of the CataStak like? What steps did it take to get to where it is now? Let’s find out in this edition of Boiler Basics 101.

It all began when Nationwide Boiler chose Selective Catalytic Reduction, or SCR technology, to be their solution to NOx compliance. They determined that SCR was the best alternative due to its reliability, ease of operation, high efficiency, and its ability to reduce emissions to single digit NOx levels. In 1999, Nationwide Boiler became the first rental boiler company to conduct an SCR field demonstration on a package watertube boiler and followed by utilizing the system heavily in their rental fleet. The enormous success of rental SCR systems suggested to company management that a market existed for a field-retrofit system for package boilers - later to be branded and trademarked in 2001 as the CataStak™ SCR System.

Fast forward to the year 2004, Nationwide began offering the CataStak for new and existing package watertube boilers to meet sub 9 ppm NOx levels. After witnessing its continual growth, Nationwide Boiler introduced a new business unit, Nationwide Environmental Solutions (NES). NES was formed with a focus on lowering overall industrial greenhouse gas emissions and increasing the operational efficiency of fired equipment. This allowed Nationwide to continually raise the bar in providing reliable solutions to meet market demand.

Nationwide later developed the urea-based CataStak as a solution for customers adverse to the stringent handling requirements of ammonia. The system utilizes common diesel exhaust fluid (DEF), a safe and readily available 32.5% liquid urea solution. It was first demonstrated on a package firetube boiler in 2011 and has since been expanded to be utilized on watertube boilers and other fired equipment. Initially, the system was offered only for permanent applications but in 2018, Nationwide became the first rental boiler supplier to provide urea-based SCR systems on a boiler rental project. The company now has a fleet of urea-based SCR systems to support the rental market.

The CataStak has come a long way and has now been installed in over 180 applications. These installations range from temporary to permanent package boilers, fired heaters, gas turbines, and heat recovery steam generators. With all of these accomplishments, the CataStak has become the standard for compliance assurance, reliability and product quality. CataStak SCR systems lead the industry with the best track record in terms of performance, and source test results often exceed current local, regional and national emissions requirements.

If you’re interested in learning more about the CataStak, our website has all the details you need to get started. And be sure to check out the previous and future Boiler Basics 101 blogs to continue learning about various boiler-related topics.

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Protect Your Rental Equipment This Winter

As we enter the heart of the winter season, it’s important to remember that cold weather conditions have the potential to cause freeze damage to any boiler installed outdoors. In particular, the protection of non-enclosed rental boilers and equipment installed outdoors is imperative to avoid damage. Rental boilers and equipment come in various designs and configurations, and each unique type will require different forms of freeze damage protection. Knowing the type of equipment will help determine the right steps on how to prevent damage.  

 Here are the most common types of rental boilers: 

  - Mobile Boiler Rooms
  - Mobile Steam Plants
  - Trailer-Mounted Boilers
  - Skid-Mounted Boilers
  - Mobile Feedwater Systems
  - Skid-Mounted Deaerators and Other Auxiliary Equipment

Just remember that any lines without a constant flow of water will freeze and must be properly protected from the cold. Always make sound engineering judgment calls to avoid the repercussions of freeze damage. If you have a temporary boiler and want to learn more about the proper ways to avoid freeze damage, read the recent issue of Process HeatingNationwide Boiler was featured and our Marketing Manager, Chelsey Ryker goes over the specifics of boiler protection for each model.

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