Boiler Blog | Nationwide Boiler Inc.

Routine maintenance on your boiler is a critical component for proper and efficient boiler operation. One of the main factors to improper maintenance that can also lead to boiler failure is not understanding the concept of blowdown. In this month’s Boiler Basics 101, we will be going over what blowdown is and how it will help improve your boiler’s health.

When boiler water turns to steam, solids from the water are left behind. The blowdown process involves partially draining the boiler to remove the sludge those solids create. If these are not removed, boiler performance will be reduced and ultimately, it can lead to boiler failure.

Industrial boilers have three types of blowdown procedures:

• Low Water Cutoff
  This blowdown procedure should take place after every shift. The water column must be kept clean to ensure the water level in the gauge glass accurately represents the water level in the boiler. Regular checks on the boiler verifies that the low water cutoff is operating correctly and cleans it out.

• Bottom Blowdown
  Bottom blowdown is done by manually opening a set of two valves that drains water out of the bottom of the boiler. The purpose of the bottom blowdown activity is to clean out solids that accumulate at the bottom of a firetube boiler or in the mud drum of a watertube boiler. Solids are pushed through a blowdown separator designed to take water from the boiler during blowdown and reduce it to atmospheric pressure for disposal. During this process, steam is rapidly separated from blowdown water and vented out the top of the blowdown separator. From there, the cooled blowdown solids can be safely removed from the boiler.

• Continuous Blowdown
  The purpose of the continuous blowdown is to help control the water quality in the boiler; the more impurities and the more chemical treatment required, the greater the amount of blowdown required. It is a procedure facilitated by a pipe entering the upper section of the boiler, typically located in the steam drum of a watertube boiler or the upper steaming portion of a firetube boiler.

The continuous blowdown process is generally automated and does not require much manual interaction, like with bottom blowdown. When operating continuous blowdown, adjust the valve to maintain the recommended boiler water dissolved solids level. This helps control the dissolved solids in boilers that are operated at a steady load.

It is important to consider proper blowdown procedures to keep the water piping clean and the boiler in working condition. If you would like to learn more about the different blowdown procedures, check out ABMA’s article outlining the steps for each type.

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

The removal of dissolved oxygen from boiler feedwater is absolutely necessary to protect your boiler equipment from severe corrosion. To ensure trouble-free boiler operation, a good deaerator is essential.

Deaerators in industrial steam systems are mechanical devices used to remove air and other dissolved gases from boiler feedwater in order to protect the system from corrosion. Dissolved oxygen in boiler feedwater will attach to the walls of metal piping and other metallic equipment and will form oxides (rust). It also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. A dissolved oxygen level of 5 parts per billion (PPB) or lower is needed to prevent corrosion in most high pressure boilers, accomplished by reducing the concentration of dissolved oxygen and carbon dioxide to a level where corrosion is minimized.

The two major types of deaerators are the tray type and the spray type. In both cases, the major portion of gas removal is accomplished by spraying cold makeup water into a steam environment.

Tray-type deaerating heaters release dissolved gases in the incoming water by reducing it to a fine spray as it cascades over several rows of trays. The steam that makes intimate contact with the water droplets then scrubs the dissolved gases by its counter-current flow. The steam heats the water to within 3-5º F of the steam saturation temperature and it should remove all but the very last traces of oxygen. The deaerated water then falls to the storage space below, where a steam blanket protects it from recontamination.

Nozzles and trays should be inspected regularly to insure that they are free of deposits and are in their proper position.

Spray-type deaerating heaters work on the same general philosophy as the tray-type, but differ in their operation. Spring-loaded nozzles located in the top of the unit spray the water into a steam atmosphere that heats it. The steam heats the water, and at the elevated temperature the solubility of oxygen is extremely low and most of the dissolved gases are removed from the system by venting. The spray will reduce the dissolved oxygen content to 20-50 ppb, while the scrubber or trays further reduce the oxygen content to approximately 7 ppb or less.

During normal operation, the vent valve must be open to maintain a continuous plume of vented vapors and steam at least 18 inches long. If this valve is throttled too much, air and non-condensable gases will accumulate in the deaerator. This is known as air blanketing and can be remedied by increasing the vent rate.

For optimum oxygen removal, the water in the storage section must be heated to within 5º F of the temperature of the steam at saturation conditions. From inlet to outlet, the water is deaerated in less than 10 seconds. Call us today is you have additional questions about deaerators and how important they are to your entire system.

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.

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.