Boiler Blog | Nationwide Boiler Inc.

Playing off our last topic, some might argue that there is another boiler type, or classification, to consider. In today’s article, we will discuss the difference between saturated and superheated steam boilers, and the applications that they are most commonly used for.

Let’s begin by talking about the science behind these two types of steam. Simply put, when water is heated to its boiling point, it will begin to vaporize and saturated steam is produced. Superheated steam occurs when the water is continually heated to temperatures beyond the boiling point, without any increase in pressure. Also known as dry steam, superheated steam has a much lower density and produces zero condensate.

As with the other types of boilers previously discussed, saturated and superheated steam boilers each have their own unique advantages and disadvantages and are better geared for certain applications over others. Saturated steam has a high density and is an excellent heating source. Commonly utilized in food processing, sterilization, district heating, and pulp & paper processing, saturated steam has the following advantages: 

• Produces fast and even heating due to latent heat transfer
• The temperature can quickly be established through the control of pressure
• Has a high heat transfer coefficient, which requires a smaller heat transfer surface and in turn, allows for reduced initial
• equipment costs

Superheated steam is not typically utilized in heat transfer applications. However, due to its dry composition and ability to cool while remaining in the same physical state, it can be extremely versatile and is most commonly utilized in refineries, for generating electricity, and for powering turbines.

Superheated steam is ideal for powering turbines for the following reasons:

• The dry steam allows for steam-driven equipment to function effectively and efficiently (while condensate from wet steamwould negatively affect performance of the equipment)
• Improves thermal efficiency and work capabilities of turbines
• Contains zero condensate, minimizing the risk of corrosion and erosion damage

With a low heat transfer coefficient that is equivalent to that of air, superheated steam has more energy and can work harder than saturated steam, but the heat content is less useful. In addition, boilers that are built to produce superheated steam require more expensive components on the boiler system, in comparison to a saturated steam boiler. Therefore, it is extremely important to do your homework ahead of time to determine which type of steam is best suited for your particular application.

Did you know that Nationwide Boiler maintains a fleet of both saturated and superheated steam boilers for rent and for sale? In fact, we own the World’s Largest 125,000 lb/hr saturated steam mobile boiler, and the World’s Largest 110,000 lb/hr superheated steam mobile boiler!  Visit our website at nationwideboiler.com to learn more.

Within the RECLAIM standards, Rule 1146 outlines specific guidelines for boilers, steam generators, and process heaters that have a heat input of 5 mmBtu/hr or greater, that are utilized in all industrial, institutional, and commercial operations. This rule has changed several times, and at the end of 2018, another revision to the rule was adopted. All Group 1 units (>/= 75MMBTu/hr) as well as Group II units (20 - 75 MMBTu/hr) with an existing permit limit greater than 2 ppm must comply with a 5 ppm NOx limit. In addition, facilities that qualify must be in compliance by 2022 – 2023. The table below outlines all equipment and current limits based on category and heat input.

If your facility falls into the RECLAIM bubble, Nationwide Boiler can assist in bringing your stationary equipment up to current standards to comply with the latest rules and regulations. Our CataStak™ SCR system is proven to reduce NOx emissions to as low as 2.5 ppm on boilers, fired heaters, and other demanding applications. Imagine what we can do for your facility to get you in compliance with RECLAIM!

Stay tuned for part 2, where we will outline specific rules and regulations within the SJVAPCD.

Combustion equipment safety is essential for the daily operation of facilities and safety of plant personnel. Safety protocols and mechanisms in industrial plants have improved drastically in the last century, but incidents still occur far too frequently. Because boiler systems are inherently dangerous, safety must be factored into the design of not just the boiler, but also the burner, combustion control, and the overall operation of the system.

The burner management system (BMS) is just one of many safety devices built into a boiler system, designed to control the combustion process from beginning to end in a safe and reliable manner. It monitors high and low gas pressure, the combustion air fan, combustion air, and water levels, in addition to monitoring safety devices and controlling the sequence of lighting the burner. If any issues arise related to pressure or water level, it will initiate closure of the shut-off valves. To automate these processes, PLC-based controls are often used as a BMS. PLC based BMS gives you much more flexibility, the ability to use analog input signals as limits, limit voting and the versatility to have almost unlimited safety limits.

A Programmable Logic Controller (PLC) is a robust computer utilized for industrial automation. Although a PLC doesn’t physically look like a typical computer, it incorporates the very same technology seen in computers and smart devices that we use every day. The PLC receives information from connected sensors or input devices, processes the data, and triggers outputs based on pre-programmed parameters. It consists of a power supply, a CPU (central processing unit), input and output cards, and communication cards. A programming device (often a laptop computer) is utilized for writing programs into the PLC and HMI (human machine interface) which provides a visual model of the system as a whole.

Compared to traditional technologies, a PLC-based system is easier to troubleshoot, more reliable, more cost-effective, and much more versatile. In addition, PLC-based controls provide added levels of safety for the burner management system and overall operation of your boiler. PLCs are built in compliance with NFPA 85 and SIL2 requirements at minimum and can be configured to meet SIL3 standards as well. Therefore, we are seeing boiler control panels being built or updated to PLC-based systems more than ever.

Pacific Combustion Engineering has extensive knowledge and experience in the design, build, and programming of PLC-based combustion control systems. If you are in the market for an upgrade or brand-new panel that incorporates PLC, give us a call and we will design a system that fits your unique process needs.

The price of fuel is constantly fluctuating and with it comes creative ways to be more economical. Finding methods to be more energy efficient is never a waste of time. In the boiler room, efficiency improvements can be found by many sources, however, a common option for energy savings includes the use of an economizer. What is an economizer? The economizer is a fabricated assembly of finned tubing that captures waste heat extracted from the boiler’s stack flue gases; the exhaust that leaves the boiler stack (or “flue”).

It’s all about the principle of Heat Transfer. While low temperature water, or feedwater, enters a boiler system, high temperature flue gas exits. An economizer captures heat from the flue gas that would typically go to waste, and utilizes it to preheat the feedwater. By doing this, an economizer is able to increase thermal efficiency by decreasing the energy required to heat the water to steam. This will typically result in a reduction of 1% in fuel cost per 10 degree rise in feedwater temperature. Overall, an economizer can be a major cost savings for boiler owners and will easily provide a quick return on investment.

The economizers’ simple technology and static parts provide longevity and low maintenance, and they are available in multiple designs and configurations. Conventional economizers are cylindrical or rectangular and come in a range of sizes for both firetube and watertube boilers. Rectangular designs are more commonly used for larger industrial watertube boilers, and can be configured for vertical or horizontal gas flows, finned or bare tube design, and other additional options if needed. A condensing economizer can improve waste heat recovery even further by cooling the flue gas below its dew point, reclaiming both sensible heat from the flue gas and latent heat by condensing the flue gas water vapor.

When determining whether an economizer is ideal for your boiler equipment, the location of the economizer into stack is important. To ensure the most thermal recovery during the process, you need to make sure the economizer is installed as close to the furnace breach as possible. This will help avoid thermal loss and cooling.

At Nationwide Boiler, we offer our EconoStak economizer as an optional addition (or a standard addition in some cases) on our fleet of watertube rental boilers. The EconoStak consists of the economizer as well as all of the associated piping and structural supports required for very efficient and safe operation. In addition, we are a West Coast representative for E-Tech Heat Recovery Systems, a leading provider of economizers for new, replacement, and retrofit applications.

Contact Nationwide Boiler today to see if an economizer is the right option for you, and be sure to check out our previous Boiler Basics 101 blogs. We review various topics each month, so stay tuned for the next edition!