How to make a boiler system simpler and more efficient
Learn how it is possible to remove components and achieve a simpler and yet more efficient system, using a boiler feed system as an example.
Many industrial applications have a much more complex design than what is necessary. In fact, a number of studies show that applying a more intelligent approach to application design can result in a simpler system that not only uses less components but also saves energy. In this tutorial, we’ll help you gain an understanding of how this is possible. Throughout, we’ll use a steam boiler feed system as an example.
First, let’s show a brief outline of a typical boiler system. The water level in the boiler is controlled by means of fixed speed pumps and a feed valve, and a by-pass loop allows water to return to the deaerator if there is enough water in the boiler and the valve is closed. As well as ensure a minimum required flow over the feed pumps. This operating system is very stable and indeed ensures a high steam quality, but there are a number of shortcomings, too.
For instance, the feed valve requires maintenance at least once a year, which obviously is an expense. In addition, the extra pressure needed to compensate for the pressure loss of 2-5 bars across the feed valve means that you’ll need bigger pumps to ensure efficient operation. This, in the end is not only a capital expenditure but also an operating expense due to the much higher energy consumption. Moreover, the by-pass loop obviously makes the initial investment higher but also adds to the operating expense. Fortunately, there’s a smarter and simpler mind-set to apply to this type of system.
If you replace the fixed speed pumps with variable speed pumps, the built-in control functionality in the pumps can control the level directly and make both the feed valve and the bypass loop redundant. The pumps simply receive the level signal from the boiler and automatically speed up and down depending on the steam consumption. Removing the feed valve and the by-pass – both of which are costly components – is a true win-win. And since there is now no longer a pressure loss from the feed valve you need to operate, a smaller pump is also often enough to deliver sufficient pressure to push water into the boiler.
In fact, the eliminated pressure loss in the valve and the saved components will quickly compensate for the cost of the new, smarter pumps.
Here, you can see a calculation of a typical load profile of industrial boiler system with two CR15-14 pumps – one of the pumps is in operation and one is in stand-by mode.
Now let’s take a look at the calculation of a traditional system and a new system. By adding up the total equipment costs… We can see that the additional equipment costs 640 euros. And by calculating the annual operating costs based on the load profile… the new system provides an annual saving of 3807 euros.
This results in a payback time of two months. And saves more than 28000kWh per year!
This allows us to chart the annual cost of operation. As shown here, the annual costs for maintenance and operation is half as high in the new smart system compared to the old system – clearly demonstrating the benefits of smart systems!
In closing, let’s take a closer look at a couple of the functionalities in an intelligent boiler feed system: Curve compensation, and the ability to stop at minimum speed.
Curve compensation ensures a more steady regulation. In a boiler feed system in which the system curve is very flat due to static pressure in the boiler, there is a risk that the pump control will be unstable in some pump types. Curve compensation helps us create a stable pump curve and is a crucial function in boiler feed applications among others.
An intelligent boiler feed system also has the ability to stop operation in periods where there is no consumption of steam. In contrast to typical boiler feed systems, in which pumps run at a constant speed, an intelligent boiler feed system will automatically stop operation if it has run at minimum speed for a certain amount of time. Ultimately, this results in significant savings.
In addition to the mentioned functionalities, intelligent boiler feed systems have a host of other functionalities, including duty/standby, duty/assist, set-point influence and many more.
So, we’ve established that intelligent boiler feed systems provide a much more energy-efficient solution than more complex traditional systems. By removing unnecessary components, you’re even creating a system that’s easier and cheaper to service – and so the obvious solution long-term.