Best Management Practice : Steam Boiler Systems
Steam
boilers are commonly used in large heating systems, institutional
kitchens, or in facilities where large amounts of process steam are
used. This equipment consumes varying amounts of water depending on
system size and the amount of condensate returned.
Operations and Maintenance Options
To maintain water efficiency in operations and maintenance, federal agencies should do the following.
-
Develop and implement a routine inspection and maintenance program to
check steam traps and steam lines for leaks. Repair leaks and replace
faulty steam traps as soon as possible.
-
Develop and implement a boiler tuning program to be completed a minimum of once per operating year.
-
Provide proper insulation on steam and condensate return piping, as well as, on the central storage tank.
-
Blowdown is the periodic or continuous removal of water from a boiler
to remove accumulated dissolved solids and/or sludge. Proper control of
blowdown is critical to boiler operation. Insufficient blowdown may
lead to deposits or carryover. Excessive blowdown wastes water, energy,
and chemicals.
-
Obtain the services of a water treatment specialist to prevent system
scale and corrosion and to optimize cycles of concentration. Treatment
programs should include routine checks of boiler water chemistry.
-
Develop and implement routine inspections and maintenance programs on condensate pumps.
-
Regularly inspect both the water side and fire side of the boiler. If
needed, clean the tube surfaces to ensure optimal heat transfer thereby
maximizing system energy efficiency.
-
Employ an expansion flash tank to temper boiler blowdown rather than using cold water mixing.
-
Install meters on boiler system make-up lines.
-
Install meters on make-up lines to recirculating closed water loop heating systems so that leaks can be accounted for.
-
Consider summer shutdown, especially for those systems primarily used for space comfort heating.
Retrofit Options
The following retrofit options help federal agencies maintain water efficiency across facilities:
-
Install and maintain a condensate return system. Water use, chemical
use, and operating costs can be significantly reduced by capturing and
reusing steam system condensate. A condensate return system also lowers
energy costs as the condensate water is already hot and needs less
heating to produce steam than water from other make-up sources.
-
Install an automatic blowdown system based on boiler water quality to better manage the treatment of boiler make-up water.
-
Add an automatic chemical feed system controlled by make-up water flow or real-time monitoring of boiler chemical residuals.
-
To optimize cycles of concentration and reduce the frequency of
blowdown, an inert ion like silica or chloride can be measured in the
boiler and the concentration compared to the amount in the boiler
feedwater. For example, a boiler with a silica concentration of 100
parts per million (ppm) and a feedwater silica concentration of 10 ppm
is considered to be carrying 10 cycles of concentration. Monitoring the
ion continuously can allow better control and adjustment of the chemical
feed rate to optimize the number of blowdown cycles.
-
Blowdown heat exchangers are a useful technology to consider because
they allow some of the heat contained in the boiler blowdown to be
transferred to the boiler feed water. This also allows for the
production of low pressure steam, which can be returned to the steam
system or used in the de-aeration of boiler feed water.
Replacement Options
The following replacement options help federal agencies maintain water efficiency across facilities.
-
Replacement options vary depending on the size of the facility and
existing equipment. Consider performing an energy audit to reduce
heating loads and ensure that the system is sized appropriately.
Reducing the size of the boiler system can reduce water requirements.
-
Always purchase the most life cycle cost-effective boiler available for new installations or major renovations
-
Consider installing a small summer boiler, distributed system, or
heat-capture system for reheat or dehumidification requirements instead
of running a large boiler at part load. Also consider alternative
technologies such as heat pumps
-
Consult with experts in the field.
No comments:
Post a Comment