Home » Articles » Energy Saver

Perspective: Energy Saver

Optimize Energy Costs, Part II

Alternative process heating methods could offer attractive pay-offs.

By Ven V. Venkatesan, Energy Columnist

Several process heating applications exist in most chemical plants. Fired heaters usually handle high-temperature heating requirements, while steam or hot oil take care of medium- and low-temperature heating needs. Plants designed during low-cost energy periods or those scaled-up from previous designs stand to benefit from alternative process heating methods.

For example, in a paraffin process plant, the raffinate feed was heated from 250°F to 390°F, using about 3,000 lb/hr of 350-psig steam. In this same unit, four fired heaters were in continuous service, releasing stack gases to atmosphere at temperatures ranging between 580°F and 868°F. Space limitations and large-scale structural modifications prevented attempts to install air preheaters. Hence, we recommended installing a raffinate preheating coil just above the convection of one of the heaters, and the idea was accepted immediately. The existing steam-heated raffinate exchanger was left in place for temporary use in the future. Such alternative heating methods utilizing waste heat streams generally have attractive payback periods.

Tuning the burners of fired heaters and boilers provides another opportunity to save energy . When multiple process units are located in the same site, some fired heaters in one plant are well tuned and well maintained, while others operate with very high excess air levels. The first and foremost activity is to tune the burners of a boiler or fired heater and develop the equipment's load versus excess air characteristics. Of the 200+ energy assessments I've completed, I've always found at least one fired heater or boiler that required burner tuning. This is the simplest of all energy savings opportunities that can be implemented without any capital requirement.

Identifying and fixing the root cause of the problem will likely offer additional spin-off benefits. In one of the process units in the same plant, engineers attempted to minimize the flash steam venting from a condensate receiver — or at least recover it for other use. Analysis revealed that medium-pressure steam intentionally was supplied to the condensate receiver to increase the suction head of a condensate pump that failed frequently. Further investigation disclosed the pump discharged into the boiler feed water supply line to the steam generators. The pump's discharge was modified and re-routed to the deaerator inlet line. Once the condensate pump's discharge pressure was reduced, the steam supply to the condensate tank stopped and the flash steam venting reduced significantly. Fixing the root cause of this energy waste problem not only decreased flash steam venting, but also increased the condensate pump's life cycle and performance.

Optimizing energy consumption in steam-powered vacuum systems can also generate savings. In one process plant, three-stage steam jet ejectors, with condensers between stages, provided the desired level of vacuum in the distillation columns. Though steam jet ejectors are more suitable than liquid ring vacuum pumps to maintain near-absolute vacuum, they're comparatively less efficient in the mild vacuum ranges. Because the required vacuum level is always achieved in stages, it's best to design with liquid ring vacuum pumps in the low-vacuum ranges and add steam jet ejectors in tandem for high-vacuum stages. In this plant, all steam jet ejector vacuum systems were modified to a combination vacuum system with water ring vacuum pump and steam jet ejector. This helped achieve energy savings of more than $200,000 annually.

Preheating the cold make-up water to the deaerators or steam boilers can also help save energy. Only some plants utilize this opportunity, mostly by recovering heat from the boiler blowdown water or wasted heat from stack gas. Many engineers consider only heat rejected from processes or stacks as a good preheating source. That isn't necessarily true — low-level heat rejected from equipment like air compressors and chillers can also be used to preheat cold make-up water.

In one chemical plant I visited in western Tennessee, my team suggested preheating the cold make-up water by cooling the plant's air compressors. The cold make-up water quantity and the air-compressor cooling water flow quantities were well-matched. Implementing this suggestion also helped eliminate the plant's air compressor cooling tower, which had posed chronic problems to its maintenance staff.

Energy-saving opportunities are endless, and by trimming down energy losses, plants can gain a lot more.

---

VEN V. VENKATESAN is Chemical Processing's Energy Columnist. You can e-mail him at VVenkatesan@putman.net

---

More From This Perspective

Optimize Energy Costs, Part II
01/25/2012
Alternative process heating methods could offer attractive pay-offs.

Optimize Energy Costs, Part I
12/20/2011
Several petrochemical examples highlight energy efficiency.

Save Energy in Water Systems, Part II
11/16/2011
Recover cold cash from cooling water systems.

Save Energy In Water Systems, Part I
10/13/2011
Plants often miss opportunities to more fully use hot water.

Don't Overwork Pumps and Fans, Part II
09/14/2011
Several opportunities exist to reduce a fan's energy use.

Don’t Overwork Pumps and Fans, Part I
08/22/2011
Four simple steps present opportunities to reduce energy use.

Recover Low Level Heat, Part II
07/27/2011
Additional innovative options exist to recover such heat

Recover Low Level Heat, Part I
06/03/2011
This two-part series highlights innovative concepts for recovering such heat

Optimize Your Compressed Air Systems
05/06/2011
Five simple steps could improve air compressor efficiency

Optimize Heat Exchangers
04/14/2011
Three parameters govern a heat exchanger's effectiveness.

Optimize Your Steam System, Part II
03/07/2011
A simple four-step process can improve steam efficiency.

Optimize Your Steam System, Part I
02/02/2011
A simple four-step approach can improve steam efficiency.

Take a Fresh Look at Your Process Heaters -- Part 2
01/06/2011
Three simple steps can help reduce stack temperature.

Take a Fresh Look at Your Process Heaters
11/30/2010
A simple four-step program can lead to significant savings.

Know the Basics of Energy Management
11/22/2010
Make energy management maintenance a routine part of your day.

Train Your Plant Manager on Energy Efficiency
10/20/2010
Present your energy program in a way the plant manager can quickly comprehend.

Train Your Project Manager on Energy Efficiency
09/07/2010
Treating energy saving measures as project add-ons can help.

Train Your Operators on Energy Efficiency
08/09/2010
Provide them with the right information and listen to their ideas.

Energy Saver -- Educate Your Peers
07/07/2010
Train your technical specialist on energy efficiency.

Beware of Energy Mishaps
06/09/2010
Webinar speakers identify common energy program mistakes.

How's Your Motor Running?
05/11/2010
Try optimization to help reduce motor energy expenses.

Energy Saver: Take the Heat Off Your Bottom Line
04/07/2010
It's time to find cool ways to cut summertime energy costs.

Innovations Promise Better Energy Efficiency
03/09/2010
Five developing technologies may profoundly impact plant practices.

Turn Waste Energy Into Cash
02/10/2010
Make the Energy Independence and Security Act pay off for you.

New Energy Efficiency Standards Are Coming
01/13/2010
Government, industry and academia team up on program.

Respond Right to Reduced Rates
12/08/2009
Maintaining energy efficiency helps keep operating costs in check.

Energy Saver: Improve Batch Processing
11/05/2009
A number of steps can lead to better energy efficiency at the outset.

Save Cold Cash
10/08/2009
Here are a few tips to keep your winter energy bills under control.

It’s Time to Answer The E(nergy)-Mail
09/03/2009
Readers provide their input on content of recent columns.

Simplify Your Energy Message
08/04/2009
Money loss calculators can spur better operator response to wasted energy.

Not All Carbon Dioxide Is Created Equal
07/07/2009
Put biomass to use to help reduce your plant’s carbon footprint.

Energy Saver: Don’t Get Heated Up by a Hot Stack
06/09/2009
Consider several projects to lower temperatures and recover energy.

Energy Saver: Put Energy into Environmental Projects
05/13/2009
Taking a broader look at such projects can improve their prospects.

Find the Hidden Gems
04/15/2009
Good practices can reduce energy waste in your utility systems.

Energy Saver: Conduct Your Own Furnace Survey
03/24/2009
Calculate heat loss in every step to help prioritize efforts.

Energy Saver: Do Your Own Steam Survey
02/17/2009
Finding energy wasters yourself can save a lot of money.

It’s Time to Review Your Plant Energy Systems
01/16/2009
Annual checkups help ensure components keep running smoothly.

Consider Three Ways to Energy Efficiency
12/11/2008
Now’s the time to make radical changes in funding energy projects

Capture More Savings on an Ongoing Basis
11/19/2008
Advanced controls can help to maximize sustainable energy efforts.

Make Your Energy Savings Permanent
10/14/2008
Here are five ways to create sustainable energy programs.

Group Blazes the Trail to Achieving Energy Efficiency
10/10/2008
Texas pilot study may lead to plant certification program

Innovative Fixes for Saving Energy in Plants
08/07/2008
Some uncommon practices can help reduce plant costs

Energy Saver: Thinking small yields big payback
06/17/2008
Take advantage of power cost and receive cheap heat for your process

Some training courses are worth the price
06/02/2008
Learn to use energy tools to make your plant more efficient

Energy Saver: Avoid fouled exchangers
05/23/2008
Fixing common efficiency problems will improve heat recovery

Are you getting the most from your exchange?
03/13/2008
Use a pinch study to gain better understanding of your heating and cooling sources.

It’s time for a design check
02/13/2008
Pay closer attention to energy efficiency and impose standards.

Resolve to trim that excess air
02/05/2008
Five excess air heater good practices can lead the way to peak performance.

Put energy into people issues
10/30/2007
It’s time for a little industrial energy waste amnesty, says Christopher Russell, contributing editor, in this month's Energy Saver column.

Say farewell to the old energy paradigm
10/01/2007
Controlling costs in today’s market requires a different approach, says Christopher Russell, contributing editor, in this month's Energy Saver column.

Tackle organizational obstacles
08/28/2007
For energy cost control, aptitude plus operational style equals results, advises Contributing Editor Christopher Russell, in this month's Energy Saver column.

Survey results reveal cost reduction strategies
08/20/2007
Learn what large companies do to manage their energy costs in this month's Energy Saver column by Contributing Editor Christopher Russell.

Face energy challenges like a frontiersman
07/24/2007
Be both a hunter and a farmer of energy management, advises Contributing Editor Christopher Russell, in this month's Energy Saver column.

Build your portfolio
05/16/2007
Is energy efficiency an engineering project or a management process? Contributing Editor Christopher Russell answers that question in this month's Energy Saver column.

Defeat barriers to energy cost control
04/24/2007
Use communications and incentives to overcome “The Competitor Within", advises Christopher Russell in this month's Energy Saver column.

Energy management boosts competitiveness
03/28/2007
Energy Saver columnist Christopher Russell advises that you consider all the motives and rewards for managing plant-wide energy consumption.

Use a portfolio approach to energy management
03/01/2007
A business plan for industrial energy management is remarkably similar to financial planning, says Christopher Russell in his Energy Saver column.

Use a multifaceted approach to manage your energy costs
02/12/2007
One or two tools alone won’t allow you to maximize results, but this list of six common tools will help, according the Christopher Russell in this month's Energy Saver column.

Take the right first step to manage your energy costs
12/18/2006
Conducting an energy assessment provides a business plan for improvements and is the first step to managing energy costs, according to Chemical Processing's energy columnist Christopher Russell.