Improving steam system efficiency

Systematic plant improvements

04/16/2013


Installation of a ConDex condensing economizer at California packaging plant reduced fuel consumption at the plant by 10% by using waste heat to provide process hot water for plant processes. Courtesy: Combustion & Energy Systems Ltd.Steam system efficiency sometimes doesn’t get the attention it deserves. Perhaps it’s because the boiler plant is hidden in a lower level mechanical room. Perhaps it’s because today’s gas-fired steam systems run unobtrusively, without the need for constant attendance. But these systems are often the largest energy user in industrial facilities and deserve at least as much attention as lighting or window leaks.

Natural gas-fired boilers are clean and have high inherent efficiency because of the ideal nature of the fuel. Yet a systematic approach to saving energy at the boiler plant and through the system can yield significant additional energy savings, not to mention improved reliability and lowered greenhouse gas emissions. A major improvement can often be made by addition of a boiler economizer. Starting with the most basic, what steps should be taken to make your steam plant more efficient? 

Find the Leaks

A first step is to find steam and condensate leaks. Puddles on the mechanical room floor or elsewhere in the plant are often signs of leaky steam traps or valve packing, or problems in the condensate return system. You don’t need special equipment to find these problem areas. Trace them to the source and fix them. Hot spots along steam and condensate lines are also obvious indications of either steam leaks or inadequate insulation.

If you have a trained infrared sensor team and the right equipment, they can find these hot spots. Alternatively, help is available from infrared specialists. A single large uninsulated valve could be costing your company hundreds or even thousands of energy budget dollars each year. Custom insulation companies make removable 

covers for pipes and fittings that are efficient and easy to replace after service work.

Condensate Return Systems

In older plants, condensate return lines were often incomplete and these are seldom adequately inspected or kept in repair. With today’s tight energy budgets, this is unacceptable. You need to study the entire condensate system and extend return lines throughout the plant. Just as importantly, plan to inspect the entire system with regularity. Failure rates of steam traps and valve packings make such systematic inspection essential. By taking advantage of improved condensate return you not only salvage the heat from the condensate, but also reduce your costs for makeup water treatment and feedwater pre-heating. 

Boiler Blowdown Heat Recovery

If you are not currently salvaging waste heat from your boiler blowdown system, this should be considered.  Blowdown heat recovery is particularly effective for higher-pressure industrial boilers. Recovered heat is often used for preheating makeup water, feedwater, or for building potable water systems. Package heat recovery systems are available for a wide range of blowdown systems sizes. This chart illustrates potential heat recovery values. 

Boiler Blowdown Heat Recovery Potential

Based on a steam production rate of 100,000 pounds per hour, 60°F makeup water, and 90% heat recovery. Illustration from DOE/EERE Energy Tips, Steam

Boiler Burner Review

Even if your boiler is in excellent condition, it can’t perform efficiently without a high-efficiency burner in peak operating trim. Some owners are improving the efficiency of their boiler by replacing older burners that have slack mechanical controls with newer models that feature precise digital controls and fuel-air mixture feedback devices. Not only does this reduce the need for constant combustion recalibration, but it also permits the boiler to operate with an optimum mixture at all firing levels.

You’ll probably want an industrial boiler specialist to evaluate the burner-boiler operation. Provide this consultant with a complete profile of your varying steam and hot water requirements throughout the week and throughout the year. The payback on a burner replacement can be remarkably short – sometimes just a few months. Don’t postpone this decision. 


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