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Boiler Basics 101: Economizers for Increased Efficiency

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.

BOILER EFFICIENCY COMPARISON
  Combustion Efficiency at
4% Excess Oxygen
Stack Gas
Temperature
 Boiler  78% to 83% 350F to 355F
 Boiler with Standard Economizer  84% to 86%  250F to 300F
 Boiler with Condensing Economizer  92% to 95%  80F to 150F


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!

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Guest — aadax industry
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Monday, 09 December 2019 08:15
Guest — Emma
Nice blog. It will surely help beginners update their knowledge. The efforts you have put in to create the posts are quite interes... Read More
Tuesday, 10 March 2020 08:02
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6 Tips for Improved Efficiency & Reduced NOx Emissions

75,000pph Rental Boiler with Urea-Based SCR System for Single Digit NOx

Nationwide Boiler's Director of Environmental Solutions, Sean McMenamin, provided content for this month's issue of Process Heating Magazine. The topic of discussion this time around is reducing NOx emissions and improving overall boiler efficiency.

Sean has provided six tips to ensure the highest possible thermal efficiency, and lowest possible NOx output. This includes:

1. Reducing Stack Gas Temperature to Increase Efficiency
2. Managing Excess Air Levels for Optimum Performance
3. Utilizing Flue Gas Recirculation (FGR) to Reduce NOx Emissions
4. Selective Catalytic Reduction for Ultra-Low NOx Performance
5. Combining Economizers & SCR Systems for Emissions & Efficiency Gains
6. Monitoring Emissions & Efficiency Performance

For additional details related to these tips and tricks for reducing NOx and increasing efficiency, check out the full article in Process Heating's September 2018 issue!

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Guest — Nisha Sabnis
Excellent blog post. I already bookmark it. Your content is the very depth informative tips regarding improves efficiency and redu... Read More
Friday, 16 November 2018 12:34
Guest — Siya Sharma
Awesome Tips! I am learning so many things from your blog.I found your post full of new information which help us . The blog you ... Read More
Wednesday, 16 January 2019 06:05
Guest — Sang15512
Thanks for the info!
Monday, 24 August 2020 09:25
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See The DataStak Demo at Power-Gen!

Nationwide Boiler's newest innovative product - the DataStak Emissions and Efficiency Monitoring System - was highlighted in the latest issue of Today's Boiler Magazine. See the article here: goo.gl/3n2W4v

The DataStak provides boiler operators with information related to the emissions output and efficiency of their boiler systems. In today's marketplace, this data is not just something that most energy and facility engineers want to know, but many need to know this information for reporting purposes.

We designed the DataStak system to provide real-time, unified data at your fingertips, from one convenient, on-site source. It is more than just a combustion or NOx analyzer. The DataStak is a cost effective, packaged emissions and efficiency monitoring system with O2, NOx, CO, and CO2 measurements, in addition to real time boiler efficiency, fuel usage and carbon footprint calculations.

Representatives from Natiownide Boiler are in Las Vegas, NV this week for Power-Gen, the largest power generation event of the year. Experience the power of the DataStak, live and in-person at the show! Visit us at booth #6019 to learn how the DataStak can help you stay informed on how your boiler is performing.

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Guest — Nia Nelson
Energy efficient appliances are a necessity these days. Everyone should inculcate the habit of using only the energy efficient ap... Read More
Tuesday, 18 December 2018 08:06
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Minimizing Boiler Blowdown and Decreasing Costs



Even with the best pretreatment programs, boiler feedwater often contains some degree of impurities, such as suspended and dissolved solids. The impurities can remain and accumulate inside the boiler as the boiler operation continue, leading to carryover of boiler water into the steam, causing damage to piping, steam traps and even process equipment. The increasing concentration of suspended solids can form sludge, which impairs boiler efficiency and heat transfer capability.

One way to improve efficiency is to review your blowdown practices. This includes the use of an automatic blowdown control system by regulating water volume discharged in relation to the amount of dissolved solids present.  This system maintains proper water chemistry within acceptable limits, while minimizing blowdown and reducing energy losses. Cost savings come from the significant reduction in the consumption, disposal, treatment, and heating of water.

The U.S. Department of Energy's Industrial Technologies Program calculated annual cost savings associated with the installation of an automatic blowdown control system that reduced blowdown rate from 8% to 6%. The example below assumes a continuously operating natural gas-fired, 150 psig, and 100,000 lb/hr steam boiler. Makeup water temperature of 60 degrees, with boiler efficiency of 83%, with fuel valued at $3.00 MMBTU was used, and the total water, sewage and treatment costs are $0.004 per gallon.

The annual cost savings in the example above equals:

Boiler Feedwater:

Initial = 100,000 / (1-0.08) = 108,695 lbs/hr

Final = 100,000 / (1-0.060 = 106,383 lbs/hr

Makeup Water Savings = Initial - Final, or 108,695 lbs/hr - 106,383 lbs/hr = 2,312 lbs/hr

Enthalpy of boiler water = 338.5 Btu/lb; for makeup water at 60 degrees = 28 Btu/lb

Thermal Energy Savings = 338.5 - 28= 310.0 Btu/lb

Annual Fuel Savings = 2,312 lbs/hr x 8760 hrs/yr x 310.5 Btu/lb x $3.00/MMBtu / 0.82 x 106 = $23,007

Annual Water and Chemical Savings = 2,312 lbs/hr x 8760 hrs/yr x $0.004/gal / 8.34 lbs/gal = $9,714

Annual Cost Savings = $23,007 + $9,714 = $32,721
If you need additional information about feedwater systems or other ways you can decrease costs, contact Nationwide Boiler today and we are happy to discuss ways to improve your bottom line: 1-800-227-1966.

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