Located in Houston, the 150-acre campus of Texas Southern University (TSU) comprises more than 40 buildings. Hot water and—during winter months—steam heat is piped to the buildings from two central steam plants via underground tunnels. Recently, one of the plants was upgraded with the installation of four gas-fired LX-200 boilers from Miura.
"We were spending around $1.2 million annually on natural-gas consumption with our old fire-tube boilers, but that has dropped to about $400,000 since the Miura boilers were installed," Tim Rychlec, TSU's executive director of facilities and maintenance services, said. "Installation of the Miura boilers provides a 66-percent reduction in natural-gas usage, and it has also increased our overall steam production. We no longer have problems getting steam to any of the buildings on campus."
With a footprint smaller than that of traditional fire-tube boilers, Miura boilers are microprocessor-controlled for precise operation and employ a unique "once-through" fin-tube design that conserves fuel, saving an average of 20 percent annually on fuel costs over other boiler designs for typical installations. Additionally, Miura boilers emit less nitrogen oxide (NOx) and carbon dioxide (CO2) than conventional boilers. Low-NOx performance is achieved through reduced boiler-flame temperature, which lowers the number of excited nitrogen atoms available to bond with oxygen. With NOx emissions around one-quarter of those of traditional fire-tube boilers, Miura boilers comply with even the most stringent air-quality regulations. With regard to reduced CO2 emissions, Miura's technology leverages high operating efficiency to contribute significant carbon abatement with a payback.
Miura's technology produces boiler-horsepower outputs comparable to those of much larger units. In addition to reducing emissions and energy consumption, the boilers go from a cold start to full steam in less than 5 min. This on-demand steam-generation performance is easily scalable to large output-capacity applications through utilization of Miura’s modular MI controller system, which allows boilers to be staged on or off sequentially as needed to match load fluctuations, as opposed to consuming energy while idling in standby mode.
"Miura's on-demand steam capabilities are important to us," Rychlec said. "Last winter was the coldest we've had in quite a few years. We had a long stretch of below-zero temperatures and a lot of icing conditions, but every morning, we were able to start all four Miura boilers at once and warm our structures very quickly because of the on-demand steam feature, which made a huge difference. On the busiest days, we'll have three of the four Miuras running, and by the middle of the afternoon, it's pretty much staged down to one or two.
"The Miuras actually boil themselves down and rotate run time among the four of them so there is an even amount of run time on each," Rychlec continued, referencing the MI controller system, which sequentially turns the four steam boilers on or off to match prevailing load patterns. This achieves the highest possible in-service efficiency, a measure of overall boiler performance (regardless of load profile) taking into account all factors of boiler operation, including combustion efficiency, thermal efficiency, and fuel-to-steam efficiency.
"With the old fire-tube boilers, our steam pressure was usually somewhere between 90 and 40 lb," Rychlec said. "It would cycle back and forth, and the variations in steam pressure would sometimes cause problems with getting the condensation to come back. The Miura boilers, however, automatically cycle and enable us to control humidity and temperature in our buildings much more effectively. Now we set our steam at 70 lb, and it has run consistently at that pressure for the past year, with no deviation. We're even using less water because you don't need as many blowdowns."
Diagnostics and Automation
Control of the individual boilers is driven by the BL Micro Controller, which keeps track of multiple individual monitoring points. This advanced diagnostic system can identify any potential challenge to smooth operation and recommend a solution on an easy-to-read display. A "sliding-window feature" records events 4 sec before they occur for fast and effective troubleshooting. This system can be accessed via the Internet for remote monitoring and diagnostics.
"We have MOM (Miura Online Maintenance) tied to our campus automation system and can access the boilers remotely through a VPS (virtual private server) and secure VPN (virtual private network)," Rychlec said. "This has made things a lot better in our whole HVAC world. Temperatures are more stable inside classrooms and throughout the university. We can see how the buildings are doing, and we can even start a boiler if needed, which is pretty handy. It not only tells you if something is wrong, it tells you what to do, which has made our lives a lot easier by reducing our overall workload. Our maintenance is now just a couple of hours a month.
"We have more capacity than we will ever need, which is a good thing," Rychlec concluded. "The university is getting ready to add additional structures, but we won't have to upsize the Miura steam plant because we have more than enough capacity right now. Not only that, but we put four Miura boilers and a feed tank in the same footprint that just one of the old fire-tube boilers used to occupy. Now we have this huge extra space in our central plant that we can use for other things. Plus, the reliability of our Miura boilers allows our steam engineer to get more done."
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