Is Your Boiler the Best It Can Be?

Few energy devices are as universally used in industrial plants as are boilers. Because they are seen as a mature technology, boilers often don’t receive the regular attention given other industrial equipment. Yet because it is the largest single energy consuming device in the plant, the industrial boiler should be at the center of interest in most energy efficiency improvement plans.

04/01/2010


 

 

Few energy devices are as universally used in industrial plants as are boilers. Because they are seen as a mature technology, boilers often don’t receive the regular attention given other industrial equipment. Yet because it is the largest single energy consuming device in the plant, the industrial boiler should be at the center of interest in most energy efficiency improvement plans. At a minimum, you should bring your existing boiler plant up to date with today’s technology. It may be that a boiler replacement will pay for itself in short order.

 

A Major Energy User

The U.S. Department of Energy (DOE) suggests that plant owners begin by determining the efficiency of the steam generation system, based on steam energy output to fuel input. DOE says, “Steam generation needs to be measured with accurate, well maintained and calibrated flow measurement devices and reconciled with a rigorous steam balance.”

 

DOE also recommends that owners optimize excess combustion air to improve steam generation efficiency. An oft-stated rule of thumb is that boiler efficiency can be increased 1% for each 15% reduction in excess air or 40°F reduction in stack gas temperature. To achieve these improvements, better boiler controls are often needed. Older boilers typically have mechanical linkages that easily drift out of calibration, and are, under the best conditions, imprecise. Modern controls use digital sensing and direct-drive mechanisms to allow burners to meet tight performance standards and remain accurate, even with changing fuel, air and furnace conditions.

 

Keeping Boiler Surfaces Clean

Another critical aspect to boiler efficiency is maintaining clean fire-side and water-side boiler heat transfer surfaces. A good deposit control program is necessary to do this. It is important to perform boiler blowdowns regularly to reduce dissolved solids in the system. Follow boiler manufacturer and feedwater additives provider recommendations to optimize these blowdowns.

 

The significance of boiler water-side scale was emphasized in a presentation at a recent Energy Solutions Center’s Technology Marketing Assessment Forum by Jason Smith from Miura Boiler, one of the world’s largest boiler manufacturers. Smith noted that just a 1/32" inch deposit of scale on boiler tubes causes a 10% reduction in boiler efficiency. He further pointed out that such an increased level of scale on all U.S. boilers would cause a waste of $81 billion in fuel costs, and an additional 405 million excess tons of carbon dioxide emissions. The case for appropriate feedwater treatment and adequate blowdowns is obvious.

 

Newer boilers are designed to minimize fire-side deposits. One of the main advantages of natural gas is that the potential for these deposits is minimal to begin with. Optimizing fuel-air ratios further reduces fire-side problems.

 

Heat Recovery Essential Today

As fuel prices have increased, it has become increasingly important to recover energy that would otherwise be wasted. Economizers can be added in the boiler’s exhaust gas stream to recover heat that would otherwise be lost to the atmosphere. This heat can be used to preheat boiler makeup water or feedwater. Heat recovery from boiler blowdown equipment is also a practical way of recovering heat that would otherwise go down the drain. Downstream of the boiler, more energy can be conserved by adjusting or replacing steam traps, and by improving condensate return systems.

 

Condition of Existing Boiler Critical

According to Steve Connor, Marketing Services Director at Cleaver-Brooks, the decision whether to retrofit or replace a boiler can be complex. He points out, “The most important consideration is the condition of the existing boiler, especially the pressure vessel %%MDASSML%% shell, furnace and tubes.” He explains, “If during the annual inspection wherein the waterside and fireside surfaces are revealed, it doesn’t show signs of heavy scaling, pitting, cracking or stress, the pressure vessel is most probably in good shape and in a position to deliver many more years of dependable life.”

 

Summertime Presents a Challenge

Connor points out that often even if a boiler performs well through the efficiency analysis, there still may be losses due to improper sizing. He indicates that this often results from a boiler being oversized in summer months of the year, or at times when some process steam is needed but major industrial processes are shut down. “During these times, the boiler 'loafs’ along in low-fire most of the time, cycling several times an hour. This is extremely inefficient operation and drives up radiation and convection losses as a percent of input while increasing excess air levels, reducing combustion efficiency.” In cases like this, the best solution may be the addition of a small “summertime” boiler, sized for these reduced load conditions.

 

Smith from Miura explains that the penalties from part-load operation can be significant, especially with older boilers with inadequate designs for high-turndown operation. Even the most modern boilers decline in efficiency in high-turndown situations. The solution may be multiple boilers. Smith notes that a group of smaller high-efficiency boilers with modern controls can operate as a single boiler with no turndown penalty, with boilers being quickly brought online as needed.

 

Boiler Cost Dwarfed by Fuel Cost

Where the existing boiler has reached the end of its useful life with poor pressure vessel conditions and overall poor performance, replacement is the logical step. Connor points out that boilers on average consume four times their cost in fuel every year, so selection of the replacement boiler needs to be well thought out. Industrial users must consider operational requirements, physical conditions of the facility, and financial values.

 

Hospitals, though actually institutional energy users rather than industrial users, face many of the same decisions as industry because their need for steam is continuous but variable throughout the day and throughout the year. Thus, their decision process is instructive. Rockville General Hospital in Connecticut is a 233,000 square foot facility that had recently gone through a consolidation process and was looking to improve its competitive position without adversely affecting patients. The hospital’s engineering director, John Lombardi, and HVAC engineer, Scott Roman, looked at improving the efficiency of the facility’s steam generation.

 

Changing Facility Requirements

Overall steam requirements had declined due to outsourcing of some of the facility’s laundry and sterilization needs. They chose to retain one of the hospital’s existing firetube boilers as a standby unit, and they supplemented this unit with a new Optimized Cleaver-Brooks firetube boiler with a high-turndown modulating burner with electronic controls and parallel positioning actuators for precise air and fuel metering.

 

The new unit also included an advanced stack economizer for heating feedwater and a second condensing stage for preheating cold makeup water. Because this second stage captures the latent energy in the flue gas, it helps the boiler offer up to 90% fuel-to-steam efficiency. In addition to boosting boiler efficiency from 75% or less to more than 90%, the new system delivers NOx emissions of less than 9 ppm and an annual reduction in CO2 emissions of approximately 600,000 lbs.

 

Making the Right Decision

Using this hospital as an example, Cleaver-Brooks’ Connor stresses, “Looking at a boiler’s in-service efficiency potential and coupling it with basic engineering knowledge will lead to the best solution for any process or heating application. It’s a matter of putting the right shoe on the right foot or, in Rockville’s case, putting the right boiler type, properly sized and configured, in the proper place to do the job.”

 

 

 

More Info.
Clayton Industries Boilers
www.claytonindustries.com
Cleaver Brooks Boilers
www.cleaver-brooks.com
DOE %%MDASSML%% Improving Boiler Efficiency
www1.eere.energy.gov/industry/bestpractices/pdfs/steam4_boiler_efficiency.pdf
Energy Solutions Center %%MDASSML%% Access to Boiler Information
www.CleanBoiler.org
Fulton Boiler Company
www.fulton.com
Hurst Boilers
www.hurstboiler.com
Miura Boilers
www.miuraboiler.com
Superior Boiler Works
www.superiorboiler.com
Unilux Boilers
www.uniluxboilers.com

 

 

 



Top Plant
The Top Plant program honors outstanding manufacturing facilities in North America.
Product of the Year
The Product of the Year program recognizes products newly released in the manufacturing industries.
System Integrator of the Year
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
June 2018
2018 Lubrication Guide, Motor and maintenance management, Control system migration
May 2018
Electrical standards, robots and Lean manufacturing, and how an aluminum packaging plant is helping community growth.
April 2018
2017 Product of the Year winners, retrofitting a press, IMTS and Hannover Messe preview, natural refrigerants, testing steam traps
June 2018
Machine learning, produced water benefits, programming cavity pumps
April 2018
ROVs, rigs, and the real time; wellsite valve manifolds; AI on a chip; analytics use for pipelines
February 2018
Focus on power systems, process safety, electrical and power systems, edge computing in the oil & gas industry
Spring 2018
Burners for heat-treating furnaces, CHP, dryers, gas humidification, and more
April 2018
Implementing a DCS, stepper motors, intelligent motion control, remote monitoring of irrigation systems
February 2018
Setting internal automation standards

Annual Salary Survey

After two years of economic concerns, manufacturing leaders once again have homed in on the single biggest issue facing their operations:

It's the workers—or more specifically, the lack of workers.

The 2017 Plant Engineering Salary Survey looks at not just what plant managers make, but what they think. As they look across their plants today, plant managers say they don’t have the operational depth to take on the new technologies and new challenges of global manufacturing.

Read more: 2017 Salary Survey

The Maintenance and Reliability Coach's blog
Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
One Voice for Manufacturing
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Maintenance and Reliability Professionals Blog
The Society for Maintenance and Reliability Professionals an organization devoted...
Machine Safety
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
Research Analyst Blog
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Marshall on Maintenance
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
Lachance on CMMS
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
Electrical Safety Update
This digital report explains how plant engineers need to take greater care when it comes to electrical safety incidents on the plant floor.
Maintenance & Safety
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
IIoT: Machines, Equipment, & Asset Management
Articles in this digital report highlight technologies that enable Industrial Internet of Things, IIoT-related products and strategies.
Randy Steele
Maintenance Manager; California Oils Corp.
Matthew J. Woo, PE, RCDD, LEED AP BD+C
Associate, Electrical Engineering; Wood Harbinger
Randy Oliver
Control Systems Engineer; Robert Bosch Corp.
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me