Gas Technology: Vertical tubeless boilers can be a solution
Modern vertical tubeless boilers offer rapid startup, high efficiency and a small footprint to save space in the crowded boiler room. They can be used for either steam or hot water. The earliest designs were simply a cylindrical furnace surrounded by an outer tank of water. Combustion gases made a quick trip through the furnace, gave up what heat they could through the walls of the vessel, and were exhausted. These boilers were necessarily inefficient and slow to heat up. Today’s tubeless designs are a great departure from this primitive system.
Nearly Complete Heat Extraction
Designers of today’s vertical tubeless designs have taken this basic concept and reworked it to vastly increase efficiency and shorten startup cycles. The key has been to take the exhaust from the internal vessel and pass it through multiple heat exchange surfaces also surrounded by water. This results in nearly complete extraction of the heat of combustion.
An example is the Cyclone 4VT tubeless boiler by Hurst, which features a long exhaust path through four passes in the water vessel. An additional pass of the exhaust gas is used to dry the steam product, thereby reducing scaling. This boiler is available in 12 sizes ranging from 6 bhp to 100 bhp, producing steam quantities ranging from 207 to 3450 lbs/hr at 15 to 250 psig.
Small Footprint a Popular Feature
According to Chad Fletcher from Hurst, there are several significant advantages to this boiler over other compact boiler types. “They have a smaller footprint due to the vertical design and a much larger capacity boiler can be put into the same space as a scotch boiler. They are faster to come from cold to full steam. Finally, they are completely packaged at the factory with the feed tank and blowdown tank prepped and prewired there. Installation on the jobsite becomes as simple as electricity, feedwater, blowdown and steam connections.”
He notes that they can be installed either as standalones or in combination with existing boiler equipment. “You often see these units as standalone pony boilers or backups for summer. You will find large systems like hospitals with multiple large boilers using these package units for steam for laundry, kitchens, etc. when the demand for steam is small and there is no reason to fire up a large unit during non-peak hours in these places.”
Efficiency of the modern vertical tubeless boiler is outstanding. Fletcher indicates that efficiencies from 79% to 83% are typical. “It will depend on fuel and firing conditions.” Fletcher points out that rapid startup and quick response to changing loads is an important feature. “Their ability to handle large swing loads in start-and-stop situations is critical.”
In addition to the steam boiler, Hurst also offers a 4VT Cyclone hot water boiler for situations where hot water only is needed. It delivers hot water at a standard pressure of 30 psi, with optional delivery up to 160 psi, 250° F. Like the steam boiler it offers rapid response from a cold start and the ability to meet fluctuating hot water demands.
Time to Take a Look
Whether your interest is in replacing an old, inefficient boiler or adding steam or hot water capacity to your plant without expanding the boiler room, the tubeless vertical approach is worth considering. You may find its efficiency pays for the upgrade quickly, without requiring difficult plant modifications or boiler room expansions.
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Fulton Boiler Works, Inc.
Hurst Boiler Co.
Lattner Boiler Co.