Calculating Boiler Blowdown Savings

by | Mar 27, 2009 | Industrial Energy & Onsite Utilities, Industry, Measurement Instrumentation | 0 comments

Boiler Blowdown Savings Calculator
I always like receiving goodies that I can pass along to the readers of this blog. This one, a boiler blowdown savings calculator, is from Emerson’s Jim Thompson. Jim is a manager in the Rosemount Analytical Liquid business.

Jim probably knew that I’m definitely not a boiler blowdown expert, so he was kind enough to point me to a great Boiler Blowdown Fact Sheet developed by the North Carolina Division of Pollution Prevention and Environmental Assistance.

For those like me who may have heard the term but not have known what it really meant, the fact sheet sums it up:

To avoid boiler problems, water must be periodically discharged or “blown down” from the boiler to control the concentrations of suspended and total dissolved solids in the boiler. Surface water blowdown is often done continuously to reduce the level of dissolved solids, and bottom blowdown is performed periodically to remove sludge from the bottom of the boiler.

It makes good economic sense to perform these blowdowns. You can reduce fuel consumption, use less chemical treatments, and reduce heat loss in the steam you are producing. Automated boiler blowdown operations can:

…save about 2 percent of a facility’s total energy use with an average simple payback of less than one year.

Jim pointed out that measurement of boiler feedwater conductivity is an indicator of the concentration of dissolved solids. Rosemount Analytical conductivity sensors, transmitters, and analyzers are used to measure for these dissolved solids. A blowdown system typically includes an automation system running the PID loop, a sample cooler and downstream conductivity sensor & transmitter as the loop input, and the blowdown control valve position as the loop output. Depending on the boiler application, conductivity, pH, dissolved oxygen and free chlorine may also be measured and controlled on the feedwater and makeup water lines.

The calculator uses the maximum recommended concentration limits according to the American Boiler Manufacturers Association (ABMA). Also, the American Society of Mechanical Engineers (ASME) has developed a best operating practices manual for boiler blowdown. The recommended practices are described in Sections VI and VII of the ASME Boiler and Pressure Vessel Code. The calculator helps you identify energy-saving opportunities by comparing your blowdown and makeup water treatment practices with the ASME practices.

If your process includes boilers, give the calculator a try to see if you have opportunities to improve efficiency and reduce ongoing maintenance costs.

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