Check out the press release for additional information.
Boiler Blog | Nationwide Boiler Inc.
Check out the press release for additional information.
Nationwide Boiler has been a proud member of the IDEA and we support the organization's goals of promoting energy efficiency and environmental quality through the advancement of district heating, district cooling and cogeneration.
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
|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!
Last month on the Boiler Blog, we focused on increased efficiency through the use of O2 trim. This is an easy, cost-effective addition to a boiler system with multiple added benefits. There are, however, additional ways to increase the efficiency of your steam plant even further. A Variable Frequency Drive (VFD) controls a motor’s speed by varying the frequency supplied to it, and VFD’s can help achieve significant electrical power savings when added to your boiler.
To illustrate the benefits of VFDs, take the power usage of the fan. A combustion air fan on a boiler typically uses a large amount of energy. For example, a 125,000 pph boiler can have a fan motor as large as 300 hp. While the actual power usage would typically be less than the rated size of the motor, when operating 24/7/365 at full load and assuming an electricity cost of 8 cents/KW, the cost of electricity can be upwards of $150,000 - just for the combustion air fan!
The use of VFDs will provide the most savings for boilers that have an average annual operational load of less than 100%. In fact, if your average boiler load throughout the year is 50%, or half load, you could save ⅞ th the fan power. This means that with the use of a VFD, the fan would require a fraction of the typical amount of energy used when running your boiler at full load. Generally speaking, if your boiler is operating at half load the fan will also operate at half speed. According to the fan laws, fan power is related to change in fan speed to the 3rd power. When operating the fan at half speed, the change in power is (½)3 or 1/8th the power! This is where the power savings would come from and why it would be most beneficial to utilize a VFD for scenarios where the boiler system operates more consistently at half load.
Let’s look further into the reason behind using 50% fan speed for 50% boiler load. When running your boiler at half load, the air flow requirement will also be reduced by half (assuming the burner excess air stays the same). Since the fan laws state that air flow changes linearly with fan speed, that means that at 50% fan speed (or RPM), the flow would be 50% of full load. For the static pressure requirement, the fan pressure is closely related to the square of the change in boiler load. So, at 50% load, the static pressure change would be (½)2 which also matches the fan laws which state change in fan speed changes fan static by the square. You’ll notice that if you multiply the flow and static changes together (i.e. ½ * (½)2) you get ⅛ th which is the same number for the power savings.
If a VFD is not being used, the alternate device is likely a line motor starter. With a motor starter, the fan is always running at full speed. At 50% load, the air flow is about half but the static pressure requirement typically increases due to the closing of the air dampers (which are used instead of a VFD to control the flow). That said, with a standard motor started, the overall fan power requirement stays about the same regardless of whether the boiler is operating at half or full load.
Stay tuned for our next Boiler Blog for additional educational topics, Nationwide Boiler news, and more!